CYCLOHEXYLAMINE

Cyclohexylamine is used in the manufacturing of chemical intermediates, insecticide intermediates, rubber accelerators, water treatment chemicals and corrosion inhibitors.Cyclohexylamine is a primary aliphatic amine consisting of cyclohexane carrying an amino substituent.
Cyclohexylamine is a colorless organic liquid having a substituent of an amine group. Cyclohexylamine is used in low-pressure boilers where the condensate works for a longer period of time.
Cyclohexanamine; Aminocyclohexane; CHA; Cyclohexylamine; Hexahydrobenzenamine; Aminohexahydrobenzene; Hexahydroaniline; 1-Aminocyclohexane; 1-Cyclohexylamine;

EC / List no.: 203-629-0
CAS no.: 108-91-8
Mol. formula: C6H13N

Cyclohexylamine is used especially for the industrial water treatment, for the production of cure accelerator, for the manufacturing of synthetic sweeteners and in a rubber industry for the production of vulcanisation accelerators. Cyclohexylamine is typically used as an intermediate in synthesis for different herbicides, antioxidants and pharmaceuticals.

Synonyms: Aminocyclohexane
Aminohexahydrobenzene
Cyclohexanamine
Hexahydroaniline

Cyclohexylamine is used as an intermediate in synthesis of other organic compounds.
It is the precursor to sulfenamide-based reagents used as accelerators for vulcanization and is a building block for pharmaceuticals.

Formula: C6H11NH2 / C6H13N
Molecular mass: 99.2
Boiling point: 134.5°C
Melting point: -17.7°C
Relative density (water = 1): 0.86
Solubility in water: miscible
Vapour pressure, kPa at 20°C: 1.4
Relative vapour density (air = 1): 3.42
Relative density of the vapour/air-mixture at 20°C (air = 1): 1.03
Flash point: 28°C c.c.
Auto-ignition temperature: 293°C
Explosive limits, vol% in air: 1.5-9.4
Octanol/water partition coefficient as log Pow: 1.4
Viscosity: 2.10 Pa*s at 20°C

APPLICATION AREAS
Cyclohexylamine is used especially for the industrial water treatment, for the production of cure accelerator, for the manufacturing of synthetic sweeteners and in a rubber industry for the production of vulcanisation accelerators.

SEGMENTS
Agriculture
Catalysis and Chemicals Processing
Chemical synthesis
Dyestuffs, pigments and optical brighteners
Food industry and auxiliaries
Hardener and crosslinking agents for polymers
Industrial Water Treatment
Lubricants and oils
Manufacturing of diabetics
Manufacturing of herbicides and pesticides
Manufacturing of insecticides / acaricides
Manufacturing of pharmaceutical agents
Manufacturing of sweeteners
Manufacturing of textile dyestuffs
Petroleum
Polymer auxiliaries
Polymers, Polymerisation initiator
Specialities, Stabilizers for explosives

Cyclohexylamine appears as a clear colorless to yellow liquid with an odor of ammonia. Flash point 90°F.
Irritates the eyes and respiratory system. Skin contact may cause burns. Less dense than water. Vapors heavier than air.
Toxic oxides of nitrogen produced during combustion.

Cyclohexylamine is a primary aliphatic amine consisting of cyclohexane carrying an amino substituent.
It has a role as a human xenobiotic metabolite and a mouse metabolite. It is a conjugate base of a cyclohexylammonium.

Cyclohexylamine
Cyclohexylamine is a colorless organic liquid having a substituent of an amine group.
Cyclohexylamine is used in low-pressure boilers where the condensate works for a longer period of time.
It can remain along with condensate steam at various steam pressures which cannot be done with other neutralizing amines.
It is a metabolite of cyclamate and has been found to be useful in production of other organic compounds.

On the basis of end user demands and desires, industrial Cyclohexylamine can be utilized for various respective applications for various respective industries like agriculture, rubber, food, oil, pharma, petroleum and textile industries.

Key Features and Benefits
Condensate line treatment
Prevent of carbon dioxide corrosion
Prevents formation of carbonic acid in boiler steam system
Completely volatile
Versatile applications

Application Areas
Agriculture
Manufacture of Herbicides, Insecticides, Pesticides
Catalysis & Chemicals Processing
Chemical Synthesis Reactions
Dyes, Pigments, Textiles
Hardener & Cross Linking Polymers
Industrial Water Treatment
Polymer Auxiliaries
Lubricants & Oils
Petroleum
Stabilizers for Explosives
Polymerization Initiator

Cyclohexylamine Market size has foreseen dynamic growth owing to its increased usage as a corrosion inhibitor for boiler water treatment plants and low corrosion inhibitor in oil field production where high alkalinity is preferred.
It is also used in manufacturing of several synthetic chemicals which include acid gas absorbents, dry cleaning soaps, emulsifying agents, plasticizers and insecticides.
It is also used in rubber industry for manufacturing of vulcanization accelerators.
Moreover, increasing use in making synthetic sweeteners and for industrial water treatments will further augment the industry growth.
Some other amines, especially morpholine is replacing the product demand in water boiler treatment may act as a restraint for industrial cyclohexylamine market over the forecasted period of time.
Cyclohexylamine generally is found from wood plant of toddalia asiatica. It is a strong base and a flammable liquid.
It is manufactured by the catalyst hydrogenation of aniline at high pressure and temperature by the reduction of nitrocyclohexane or by the ammonolysis of cyclohexanol.
It is colourless or yellowish colour liquid with odour of ammonia or fish. It is also referred as Hexahydroaniline, Aminohexahydrobenzene, Aminocyclohexane and Cyclohexanamine.
The product has a melting and boiling plant at 17.7 ºC and 134.5 ºC respectively.
Like all other amines it has a weak base when compared to other strong bases including NaOH and has a stronger base than aniline, which differs only in than its ring in aromatic.
It also has some health hazardous effects including toxic and caustic.
It also cause irritation in eyes and also there is possible risk of impaired fertility.
On the basis of its application, industrial cyclohexylamine market can be segmented into artificial sweeteners, corrosion inhibitors, accelerators in rubber industry, water treatment industry.
It is also used in manufacturing several synthetic chemicals, including acid gas absorbents, dry cleaning soaps, dyes, emulsifying agents, plasticizers and insecticides.
Among these, water treatment industry hold a major share in application segment. Upsurge in use of rubber in various end uses is likely to drive the product market over the estimated years.
Industrial cyclohexylamine market can be divided on the basis of end user industry into agriculture, chemical, dyes & pigments, rubber, food, oil, pharmaceutical, petroleum and textile industries.
Amongst, chemical synthesis and rubber industry holds a maximum portion in end user industry segment and is considered to remain the same during the forecasted years.
North America industrial cyclohexylamine market will witness significant growth due to presence of substantial number of industries in the region.
Rising research & development activities in the region will provide positive outlook to the industry growth.
Upsurge in chemical and pharmaceutical industries will be the key reasons for propelling the future growth.
Boom in shale gas & oil in the U.S. may have a positive effect on the industry market.
Europe industrial cyclohexylamine market is the second biggest market and the region will observe the same strong trend over the estimated years.
Rise in automotive industries has raised the demand for tyres, thereby impelling the industry demand. Propagating textile and chemical sector in the region will further enhance the market.
Asia Pacific industrial cyclohexylamine market is the fastest growing region owing to rapid industrialization & urbanization and expanding textile & pharmaceutical industries.
Increasing number of water treatment plants owing to growing population will boost the industry demand.
Also, upsurge in chemical activities in various countries in the region will support the market.

Cyclohexylamine is an organic compound, belonging to the aliphatic amine class.
It is a colorless liquid, although, like many amines, samples are often colored due to contaminants.
It has a fishy odor and is miscible with water.
Like other amines, it is a weak base, compared to strong bases such as NaOH, but it is a stronger base than its aromatic analog, aniline.

Preparation
Cyclohexylamine is produced by two routes, the main one being the complete hydrogenation of aniline using some cobalt- or nickel-based catalysts:

C6H5NH2 + 3 H2 → C6H11NH2
It is also prepared by alkylation of ammonia using cyclohexanol.
It is a useful intermediate in the production of many other organic compounds (e.g cyclamate)

Applications
Cyclohexylamine is used as an intermediate in synthesis of other organic compounds.
It is the precursor to sulfenamide-based reagents used as accelerators for vulcanization.
It is a building block for pharmaceuticals (e.g., mucolytics, analgesics, and bronchodilators).
The amine itself is an effective corrosion inhibitor. Some sweeteners are derived from this amine, notably cyclamate.
The herbicide hexazinone and the anesthetic hexylcaine are derived from cyclohexylamine
CAS Number: 108-91-8
IUPAC name: Cyclohexanamine
Other names
Aminocyclohexane
Aminohexahydrobenzene
Hexahydroaniline
Hexahydrobenzenamine

Cyclohexylamine is a colorless organic liquid having a substituent of an amine group.
Cyclohexylamine is used in low-pressure boilers where the condensate works for a longer period of time. It can remain along with condensate steam at various steam pressures which cannot be done with other neutralizing amines.
It is a metabolite of cyclamate and has been found to be useful in production of other organic compounds.

Key Features and Benefits
Condensate line treatment
Prevent of carbon dioxide corrosion
Prevents formation of carbonic acid in boiler steam system
Completely volatile
Versatile applications

Cyclohexylamine is a kind of transparent and colorless liquid with a strong fishy taste and ammonia-like smelling.
Cyclohexylamine is flammable with a relative molecular mass being 99.18, the relative density being 0.8191, the melting point being-17.7 ℃, boiling point being 134.5 ℃, 118.9 ℃ (6.67 × 104Pa), 102.5 ℃ (4.00 × 104Pa), 72.0 ℃ (1.33 × 104Pa), 56.0 ℃ (6.67 × 103Pa), 45.1 ℃ (4.00 × 103Pa), 41.3 ℃ (3.33 × 103Pa ), 36.4 ℃ (2.67 × 103Pa), 30.5 ℃ (1.99 × 103Pa), 25.0 ℃ (1.17 × 103Pa), the refractive index being 1.4372, the flash point being 32 ℃ and the ignition point being 265 ℃.
Cyclohexylamine is soluble in water and can be miscible with common organic solvents such as ethanol, ethyl ether, acetone, ethyl acetate, chloroform, heptane, benzene and the like.
Cyclohexylamine can be evaporated together with the steam and can absorb the carbon dioxide in the air to form a white crystalline carbonate.
It can form azeotrope with water with the co-boiling point being 96.4 ℃ and water content being 55.8%.
Its aqueous solution is alkaline. The pH of 0.01% aqueous solution of 0.01% is 10.5.
Its steam can form explosive mixture with air.
This product is toxic and irritating to the skin and mucous membranes, causing gangrene; inhaling its vapors has a narcotic effect but without causing blood poisoning.

Rat oral administration: LD50: 710 mg/kg.
The maximal allowable concentration in workplace is 10 × 10-6.
Heating cyclohexylamine together with hydrogen iodide in a sealed tube at 200 ℃ can generate methyl cyclopentane.

Heating cyclohexylamine together with dimethyl sulfate in ether generate methyl cyclohexane and a small amount of dimethyl cyclohexylamine as well.
Its hydrochloride can have reaction with sodium nitrite salt to generate cyclohexanol.
Its reaction with excess amount of ammonia and zinc chloride can generate 2-methyl-pyridine.

Preparation: they finished product of cyclohexylamine can produced through catalyzing the reduction action of aniline at a high temperature and high pressure (with nickel or cobalt as the catalyst); it can also be produced by taking the cyclohexanol and cyclohexanone as the raw material produced from catalytic reduction of phenol, and further go through amination action with ammonia to prepare it.
In industry, cyclohexylamine is mainly used as the thiazole vulcanization accelerator of rubber as well as being used as the tank cleaning agent, dyeing auxiliaries and surfactants.

The main purpose
Cyclohexylamine can be used as the raw materials of surfactants for production of alkylbenzene sulfonate for being used as emulsifier and foaming agent;
Cyclohexylamine can be used as the raw materials of making perfume for production of cyclohexyl allyl propionate;
Cyclohexylamine can be used as the raw materials of production of dye such as being used for production of Acidic Blue 62, disperse fluorescent yellow, fluorescent yellow dispersion H5GL, weak acid blue BRN, Disperse Blue 6 and dye additives;
Cyclohexylamine can be used as the raw material of food additives sweeteners; cyclohexylamine can also be used to produce cyclohexylamine sulfonate salts and Sodium Cyclamate; the later one is a sweeter which is 30 times as sweet as sucrose.
The Ministry of health of China has approved it for being applied to pickles, sauces, wine preparation, cakes, biscuits, bread, frozen drinks, beverage with the maximum allowable amount being 0.65g /kg.
Cyclohexylamine can be used as the raw materials of pesticide such as insecticide “propargite” for fruit tree production, herbicides “WilBur” and bactericidal agent;
Cyclohexylamine can be used in the preparation of the additives used in petroleum products, the treatment agent of boiler feed water and corrosion remover;
Cyclohexylamine can be used as the raw material for production of thiazole vulcanization accelerator of rubber CZ; this kind of vulcanization accelerator has an excellent efficacy which is especially suitable for SBR and FDA rubber.
Cyclohexylamine can be used as a rust inhibitor for producing anti-rust paper;
Cyclohexylamine can be used as a tank cleaning agent;
Cyclohexylamine can be use as antifreeze agent;
Cyclohexylamine can be used as Antistatic agents (Textile auxiliaries), latex agglutination agents and additives for petroleum products;
Owing to the alkalinity of the cyclohexylamine aqueous solution, it can be used as the absorber for removing carbon dioxide and sulfur dioxide.

Chemical Properties
It is colorless liquid with an unpleasant odor.
It is miscible with various kinds of organic solvents.

Uses
It can be used as the vulcanization accelerator of rubber; and also used as the raw material of synthetic fibers, dyes, and gaseous-phase corrosion inhibitor.
It can be used for the manufacture of dyes, softener VS and drugs such as Antiradon, thio-TEPA and solaziquone; it can also be used in medicine, pesticides.
Cyclohexylamine is the intermediate of herbicides “Hexazinone” as well as the intermediate of rubber accelerators, oil additives, and corrosion inhibitors.
This product can be used for the preparation of cyclohexanol, cyclohexanone, caprolactam, cellulose acetate and nylon 6 and the like.
Cyclohexylamine itself is a solvent and can be used in resins, paints, fat, and paraffin oils.

It can also be used for making desulfurization agent, rubber antioxidant, vulcanization accelerator, chemical auxiliaries of plastics and textile, the treatment agent of boiler feed water, metal corrosion inhibitors, emulsifiers, preservatives, anti-static agents, latex coagulants, oil additives , fungicides, pesticides and dye intermediates.
The sulfonate salt of cyclohexylamine can be used as artificial sweeteners for being applied to foods, beverages and pharmaceuticals.
It can be used in organic synthesis, plastic synthesis, also used as a preservative and acid gas absorbent.
It can be used for the production of water treatment chemicals, artificial sweeteners, and the intermediate of rubber processing chemicals and agrochemicals.
It can be used as acidic gas absorbent for organic synthesis.

Production method
It is derived from the catalyzed hydrogenation of aniline. The process can be divided into normal pressure method and reduced pressure method.
In addition, other routes such as the catalytic aminolysis of either cyclohexane or cyclohexanol, the reduction of nitro cyclohexane, and the catalyzed aminolysis of cyclohexanone can also be applied for produce cyclohexylamine.
The preparation method is using aniline as raw materials and going through catalytic hydrogenation.
Mix the aniline vapor and hydrogen gas and pour into the catalytic reactor; carry out the hydrogenation reaction at 130 to 170 ℃ in the presence of a cobalt catalyst with the finished product obtained after cooling and further distillation.

Category
Flammable liquid
Toxicity grading
highly toxic
Acute toxicity
Oral-rat LD50: 156 mg/kg; Oral-Mouse LD50: 224 mg/kg
Irritation data
Skin-rabbit 2 mg/24 hours Mild; Eyes-Rabbit 0.05 mg/24 hours, severe.
Hazardous characteristics of explosive
Being mixed with air can be explosive.
Flammability and hazard characteristics
it is flammable in case of fire, heat, and oxidants with combustion producing toxic fumes of nitrogen oxides.

Storage characteristics
Treasury: ventilation, low-temperature and drying; store it separately with oxidants and acids.
Extinguishing agent
Dry powder, dry sand, carbon dioxide, foam, 1211 fire extinguishing agent.
Professional standards
TWA 40 mg/m3

Chemical Properties
clear liquid

Chemical Properties
Cyclohexylamine is a colorless to yellow liq- uid (amines, primary aromatic). It has an unpleasant fishy odor.

Chemical Properties
Cyclohexylamine is a derivative of ammonia in which one of the hydrogen atoms has been replaced with a six-carbon, saturated ring.
It is a very strong base and forms salts with all acids, including carbon dioxide which it rapidly absorbs from the air.
It undergoes the usual reaction of aliphatic amines with carbon disulfide to form dithiocarbamates.
Cyclohexylamine reacts with long-chain fatty acids to form soaps (Carswell and Morrill 1937).
With nitrous acid, it forms cyclohexanol with the release of nitrogen (Schweizer 1978).
Cyclohexylamine reacts with organic compounds containing an active halogen atom, acid anhydrides, and alkylene oxides to replace one or both hydrogens on the nitrogen atom.
Cyclohexylamine attacks all copper alloys and lead. When hot, it attacks aluminum very slowly.

Uses
In organic synthesis, manufacture of insecticides, plasticizers, corrosion inhibitors, rubber chemicals, dyestuffs, emulsifying agents, dry-cleaning soaps, acid gas absorbents.

Uses
Cyclohexylamine is used in the manufactureof a number of products, including plasticizers, drycleaning soaps, insecticides, andemulsifying agents.
It is also used as a corrosion inhibitor and in organic synthesis.

Uses
Production of rubber processing chemicals; corrosion inhibitor in boiler feed water; production of insecticides, plasticizers, and dry cleaning soaps; a metabolite of the sweetener cyclamate

Definition
ChEBI: A primary aliphatic amine consisting of cyclohexane carrying an amino substituent.

Production Methods
Cyclohexylamine is produced by the reaction of ammonia and cyclohexanol at elevated temperature and pressure in the presence of a silica-alumina catalyst (SRI 1985).
It is also prepared by a similar process of catalytic hydrogenation of aniline at elevated temperature and pressure.
Fractionation of the product of this reaction yields CHA, aniline, and a high-boiling residue containing n-phenylcyclohexylamine and dicyclohexylamine.

General Description
A clear colorless to yellow liquid with an odor of ammonia. Flash point 90°F. Irritates the eyes and respiratory system. Skin contact may cause burns. Less dense than water.
Vapors heavier than air. Toxic oxides of nitrogen produced during combustion.

Air & Water Reactions
Highly flammable. Sensitive to air and light.
Soluble in water.

Reactivity Profile
Cyclohexylamine neutralizes acids in exothermic reactions to form salts plus water. May be incompatible with isocyanates, halogenated organics, peroxides, phenols (acidic), epoxides, anhydrides, and acid halides.
Flammable gaseous hydrogen may be generated in combination with strong reducing agents, such as hydrides.

Health Hazard
Cyclohexylamine is a severe irritant to theeyes, skin, and respiratory passage.
Skincontact can produce burns and sensitization;contact of the pure liquid or its concentratedsolutions with the eyes may cause loss ofvision.
The acute oral and dermal toxicity ofcyclohexylamine was moderate in test sub jects.
The toxic effects include nausea, vom iting, and degenerative changes in the brain,liver, and kidney. Inhalation of its vaporsat high concentrations may cause a narcoticeffect.
LD50 value, oral (rats): 156 mg/kg
LD50 value, skin (rabbits): 277 mg/klg

Fire Hazard
When heated to decomposition, Cyclohexylamine emits highly toxic fumes.
Vapor may travel a considerable distance to source of ignition and flash back.
Toxic oxides of nitrogen are produced during combustion.
Nitric acid; reacts vigorously with oxiding materials.
Stable, avoid physical damage, storage with oxidizing material.

Industrial uses
The primary use of cyclohexylamine is as a corrosion inhibitor in boiler water treatment and in oil field applications (HSDB 1989).
It is also a chemical intermediate for rubber processing chemicals, dyes (acid blue 62, former use), cyclamate artificial sweeteners and herbicides and a processing agent for nylon fiber production (SRI 1985).
Windholz et al (1983) reports its use in the manufacture of insecticides, plasticizers, emulsifying agents, dry-cleaning soaps, and acid gas absorbents.

Potential Exposure
CHA is used in making dyes, chemicals, dry cleaning chemicals; insecticides, plasticizers, rubber chemicals; and as a chemical intermediate in the production of cyclamate sweeteners. Used in water treat- ment and as a boiler feedwater additive.
It is also used in rubber production to retard degradation.

Metabolism
Cyclamate is metabolized to cyclohexylamine by the gut flora in the rat (Renwick and Williams 1969; Bickel et al 1974; Tesoriero and Roxon 1975) and is excreted in the urine after cyclamate ingestion by rats, rabbits, dogs, monkeys, and humans (Asahina et al 1971; Coulston et al 1977; Kojima and Ichibagase 1968; Leahy et al 1967; Oser et al 1968). There is individual variation in the ability to biotransform cyclamate to cyclohexylamine, probably due to the presence or absence of the necessary bacteria. Bacteria exposed to cyclamate seem to acquire the ability to convert cyclamate. Those individuals that do produce cyclohexylamine have been categorized by researchers as convertors. Rhesus monkeys fed cyclamate for eight years converted 0.5% of the dose to cyclohexylamine which in turn was metabolized to cyclohexanone and cyclohexanol to the extent of 1-2% (Coulston et al 1977).
Generally, cyclohexylamine is readily absorbed and rapidly excreted from the body. After administration to rats, cyclohexylamine appears in body tissues with the highest concentrations in the lungs, spleen, liver, adrenals, heart, gastrointes- tinal tract and kidneys (Estep and Wiegand 1967 as reported by Bopp et al 1986).
After oral administration (0.2 g/kg) to rabbits, cyclohexylamine gave rise to unchanged cyclohexylamine and 7V-hydroxycyclohexylamine in the urine (Elliott et al 1968). When [14C]-labelled cyclohexylamine was administered, 68% of the radioactivity was recovered in the urine after 60 h. A small amount (0.5%) was eliminated in the breath and 45% of the administered dose was shown to be excreted in the urine as unconjugated cyclohexylamine, 0.2% as JV-hydroxycyclohexylamine in conjugated form, and 2.5% as cyclohexanone oxime. The authors postulated the latter metabolite to be an artifact formed from the glucuronide of TV-hydroxy cyclohexylamine during the hydrolysis procedure.
In contrast to rabbits, man, as well as rats and guinea pigs, excrete 90% or more of a dose of [14C]-labelled cyclohexylamine unchanged in the urine (Renwick and Williams 1972). Small amounts of radioactivity were found in the feces, 1% or less in man, rat and rabbit, and 4-7% in the guinea pig. Only 4-5% of the dose was metabolized in 24 h in the rat and guinea pig and 1-2% in man. The metabolites identified indicated that in rats, the metabolism of cyclohexylamine was mainly through hydroxylation of the cyclohexane ring, in man by deamination and in guinea pigs and rabbits by ring hydroxylation and deamination. The metabolites to cyclohexylamine were excreted in both free and conjugated forms.
When cyclohexylamine was administered orally to healthy adult humans at doses of 2.5, 5, and 10 mg/kg body weight, 86-95% of the dose was excreted in the urine in 48 h as unchanged cyclohexylamine (Eichelbaum et al 1974). Dose dependency was shown by the plasma half-lives which ranged from 3.5 to 4.8 h. A study by Roberts and Renwick (1985) showed other species and strain differences in metabolism of cyclohexylamine. After administration of [14C]- cyclohexylamine (35-500 mg/kg) to male mice and rats, 80% of the dose was excreted in the urine 24 h after dosing. In Wistar rats, 14-19% of the 14C was present as 3- and 4-aminocyclohexanols, while in the DA strain rat, aminocyclohexanols accounted for only 1-2% of the activity, and in mouse, <1%. Dose or route of administration did not significantly affect metabolism.
When [14C]-cyclohexylamine hydrochloride was administered to pregnant rhesus monkeys by infusion into the antecubital vein, maternal and fetal levels of radioactivity were virtually identical over a period of 6 h (Pitkin et al 1969) indicating that cyclohexylamine freely crosses the hemochorial placenta.
Rabbit liver microsomes have been shown to deaminate cyclohexylamine to cyclohexanone in the presence of NADPH and molecular oxygen (Kurebayashi et al 1979). The hexanone was then reduced to the alcohol (approximately 75% of the deaminated product). Carbon monoxide, SKF 525A, metyrapone, potassium cyanide and mercuric chloride inhibited the deamination. These results suggest that the deamination is catalyzed by a microsomal cytochrome P-450 monooxygenase system.

Shipping
UN2357 Cyclohexylamine, Hazard class: 8; Labels: 8-Corrosive material, 3-Flammable liquid.

Purification Methods
Dry the amine with CaCl2 or LiAlH4, then distil it from BaO, KOH or Na, under N2.
Also purify it by conversion to the hydrochloride (which is crystallised several times from water), then liberation of the amine with alkali and fractional distillation under N2.
The hydrochloride has m 205-207o (dioxane/EtOH). [Lycan et al. Org Synth Coll Vol II 319 1943, Beilstein 12 III 10, 12 IV 8.]

Incompatibilities
May form explosive mixture with air.
Cyclohexylamine is a strong base: it reacts violently with acid.
Contact with strong oxidizers may cause fire and explosion hazard.
Incompatible with organic anhydrides; isocyanates, vinyl acetate; acrylates, substituted allyls; alkylene oxides; epichlorohydrin, ketones, aldehydes, alco- hols, glycols, phenols, cresols, caprolactum solution; lead. Corrosive to copper alloys, zinc, or galvanized steel.

Waste Disposal
Incineration; incinerator equipped with a scrubber or thermal unit to reduce nitrogen oxides emissions.
Cyclohexylamine Preparation Products And Raw materials

Raw materials
Ethanolamine Cyclohexane NITROCYCLOHEXANE Aniline Cyclohexanol Cyclohexanone

CYCLOHEXYLAMINE
Cyclohexanamine
108-91-8
Aminocyclohexane
Hexahydroaniline
Hexahydrobenzenamine
Aminohexahydrobenzene
Cyclohexyl amine
1-Cyclohexylamine
1-Aminocyclohexane
Aniline, hexahydro-
Benzenamine, hexahydro-
Aminocylcohexane
Cyclohexylamines
cyclohexyl-amine
UNII-I6GH4W7AEG
1-AMINO-CYCLOHEXANE
CCRIS 3645
HSDB 918
cyclohexaneamine
Cyclohexylamine.HCl
EINECS 203-629-0
UN2357
I6GH4W7AEG
BRN 0471175
Cyclohexylamin
Cyclohexylamine [UN2357] [Corrosive]
DSSTox_GSID_23996
CAS-108-91-8
HAI
cylohexylamine
cyclohexylarnine
cyclo-hexylamine
cyclohexane-amine
n-cyclohexylamine
cyclohexanyl amine
Hexahydro-Aniline
monocyclohexylamine
4-Cyclohexylamine
Cyclohexylamine,(S)
Hexahydro-Benzenamine
Cyclohexanamine, 9CI
CyNH2
ACMC-1BUGG
Cyclohexylamine, 99.5%
$l^{1}-azanylcyclohexane
bmse000451
EC 203-629-0

Chemical formula: C6H13N
Molar mass: 99.17
Appearance: clear to yellowish liquid
Odor: strong, fishy, amine odor
Density: 0.8647 g/cm3
Melting point: −17.7 °C
Boiling point: 134.5 °C
Solubility in water: Miscible
Solubility: very soluble in ethanol, oil
miscible in ethers, acetone, esters, alcohol, ketones
Vapor pressure: 11 mmHg (20° C)
Acidity (pKa): 10.64[3]
Refractive index (nD): 1.4565

It is corrosive.
Cyclohexylamine is listed as an extremely hazardous substance as defined by Section 302 of the U.S. Emergency Planning and Community Right-to-Know Act.
It has been used as a flushing aid in the printing ink industry.

1-Aminocyclohexane
1-Cyclohexylamine
Aminocyclohexane
Aminohexahydrobenzene
Aniline, hexahydro-
Benzenamine, hexahydro-
CHA
CHA (pl)
ciclo-hexilamina (pt)
cicloesilammina (it)
ciclohexilamina (es)
ciclohexilamină (ro)
cikloheksilamin (sl)
cikloheksilaminas (lt)
cikloheksilamīns (lv)
ciklohexil-amin (hu)
cikoheksilamin (hr)
cyclohexylamin (da)
Cyclohexylamin (de)
cyclohexylamine (fr)
cyclohexylamine (nl)
cykloheksylamin (no)
cykloheksyloamina (pl)
cyklohexylamin (cs)
cyklohexylamin (sv)
cyklohexylamín (sk)
sykloheksyyliamiini (fi)
tsükloheksüülamiin (et)
ċikloeżilammina (mt)
κυκλοεξυλαμίνη (el)
циклохексиламин (bg)

CAS names
Cyclohexanamine
Other
IUPAC names
cyclohexamine

Cyclohexanamine
cyclohexanamine
Cyclohexylamin
Cyclohexylamine
cyclohexylamine
Cyclohexylamine
cyclohexylamine
N-ethyl-1- phenylcyclohexan-1-amine

Trade names
1-AMINOCYCLOHEXAN
AMINOHEXAHYDROBENZOL
CHA
CYCLOHEXANAMIN
CYCLOHEXYLAMIN
CYCLOHEXYLAMINE
Cyclohexylamine
cyclohexylamine
HEXAHYDROANILIN

108-91-8 [RN]
1-Aminocyclohexane
1-AMINO-CYCLOHEXANE
1-Cyclohexylamine
203-629-0 [EINECS]
Aminocyclohexane
aminohexahydrobenzene
Aniline, hexahydro-
Benzenamine, hexahydro-
Cyclohexanamin [German] [ACD/IUPAC Name]
Cyclohexanamine [French] [ACD/Index Name] [ACD/IUPAC Name]
cyclohexyl amine
Cyclohexylamine [Wiki]
GX0700000
Hexahydroaniline
I6GH4W7AEG
Magenta-GlcA [Trade name]
N-Cyclohexylamine
[108-91-8]
1219805-96-5 [RN]
143247-75-0 [RN]
157973-60-9 [RN]
26227-54-3 [RN]
4-12-00-00008 (Beilstein Handbook Reference) [Beilstein]
6850-39-1 [RN]
Aminocyclohexane, Cyclohexanamine
Aminocylcohexane
ANL
CHA
ciclo-hexilamina [Portuguese]
cyclohexanamine [ACD/Index Name] [ACD/IUPAC Name]
Cyclohexanamine, 9CI
Cyclohexanamine-D11
Cyclohexylamine [UN2357] [Corrosive]
Cyclohexylamine [UN2357] [Corrosive]
Cyclohexylamine 1000 Ã‚Âµg/mL in Methanol
Cyclohexylamine 1000 Âµg/mL in Methanol
Cyclohexylamine 1000 ï¿½g/mL in Methanol
Cyclohexylamine Solution, 1,000 mg/L, 1 ml (RM, ISO GUIDE 34)
CYCLOHEXYLAMINE, 99%
cyclohexylammonium
CYCLOHEXYLAMMONIUM ION
EINECS 203-629-0
HAI
Hexahydro-Aniline
Hexahydro-Benzenamine
HEXAHYDROBENZENAMINE
http://www.hmdb.ca/metabolites/HMDB0031404
https://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:15773
InChI=1/C6H13N/c7-6-4-2-1-3-5-6/h6H,1-5,7H
ST5213819
trans-2-aminocyclohexane

1-Aminocyclohexane
1-Cyclohexylamine
Aminocyclohexane
Aminohexahydrobenzene
Aniline, hexahydro-
Benzenamine, hexahydro-
CHA

Applications
Intermediate used in the production of:

Corrosion inhibitors
Pharmaceuticals
Rubber chemicals

-Replacement costs for underground steam/condensate systems are high.
There is also a high cost associated with reduced efficiency while systems are corroding.
The use of neutralizing amines, notably DEAE,morpholine, and cyclohexylamine, play a large role in the curtailment of condensate corrosion.
This note describes the use and properties of these amines and provides information to simplify the choosing of an appropriate neutralizing amine to give the most economical and effective results in different systems.

Condensate return line corrosion prevention is an important aspect of boiler water chemistry.
Replacement costs for underground steam/condensate systems are expensive, not to mention the cost of the energy lost in the form of heat in the condensate that is wasted while the corroding system is failing.
Also, high makeup rates, due to loss of condensate, often lead to difficulty in maintaining proper boiler water chemistry.
Damage to the boilers themselves from scale and corrosion can also occur.
Corrosion of return line systems is more common in installations having extensive return systems, such as central energy plants.

Condensate piping corrosion is usually caused by the presence of carbon dioxide, oxygen, or potable water contamination in returning condensate.
Oxygen can enter return lines through leaky traps, pumps, valves, and fittings or with boiler feedwater if not completely deaerated and treated with sodium sulfite.
Pitting of return piping is indicative of corrosion caused by oxygen or potable water contamination.
Corrosion due to oxygen can be prevented by properly treating boiler water and sealing leaks in the system.
Corrosion due to contamination can be prevented by stopping leakages of mineralized water into the return system, generally through leaking hot water heater tubes.

Carbon dioxide in condensate originates from boiler makeup water alkalinity.
Carbon dioxide causes corrosion in the form of grooving or channeling along the bottom of the condensate return pipe.
Since all boiler plants use feedwater with at least some alkalinity, corrosion due to carbon dioxide is a serious and common term of condensate corrosion

Carbon dioxide is produced in boilers because boiler water temperatures cause feedwater alkalinity in the form of bicarbonate to break down into hydroxide and carbondioxide

The hydroxide remains in the boiler water and raises the causticity and pH levels.
The carbon dioxide is a gas and leaves the boiler with steam, eventually dissolving in condensed steam.
Carbon dioxide dissolved in water is acidic, forming carbonic acid.

Carbonic acid, like any other acid, is corrosive.
Condensate corrosion due to carbon dioxide can be prevented by minimizing the amount of carbon dioxide produced in the boiler and by treating the residual with “neutralizing” amines, a family of volatile alkaline liquids

Diethylaminoethanol, morpholine, and cyclohexylamine are the three most widely used neutralizing amines.
Historically, only morpholine and cyclohexylamine have been authorized for use in boiler plants.
Once carbon dioxide is produced in the boiler, its corrosive ettects can be minimized by the addition of these amines to neutralize the eftect of carbon dioxide by raising condensate pH to a minimum ot 7.
The amines are generally fed separately from other chemicals into the boiler steam drum and go over with steam and dissolve in the condensate.

Each of these amines will not work equally well in all systems.
Optimum results are obtained by choosing the appropriate amine on a system by system basis.
The following is a description of DEAE, then morpholine and cyclohexylamine and finally a neutralizing amine selection chart.

Diethylaminoethanol (DEAE) is a currently available and widely used amine.
DEAE has a vapor-liquid distribution of 1.7.
This is equivalent to 1.7 parts in steam to every one part in condensate.
This means that DEAE will have a relatively uniform distribution throughout return condensate.
This makes DEAE ideal for the protection of moderate length systems in between the range of either morpholine or cyclohexylamine used separately.
The boiling point of DEAE is 32b OF but it forms an azeotrope (a liquid mixture having a constant minimum boiling point) with water to boil at 21U OF thus enabling DEAE to be used in low pressure systems, especially those having high feedwater bicarbonate and carbonate alkalinity.
Morpholine is not suitable for low pressure systems because of its high boiling point and cyclohexylamine may cause problems in systems with high teedwater alkalinity (above 7b ppm).

High feedwater of alkalinity produces a high level of carbon dioxide amines.
The solubility of amines and carbon dioxide together is limited.
They form bicarbonate salts, the least soluble of which is cyclohexylamine bicarbonate.
When carbon dioxide and cyclohexylamine are present in high amounts, cyclohexylamine bicarbonate deposits out.
The likely area for formation of deposits is in low flow areas at the far end of the return system.
This problem can be avoided by reducing “feedwater alkalinity (dealkalization) or by using DEAE in place of cyclohexylamine in systems with high feedwater alkalinity.

Morpholine.
Morpholine has a low vapor-liquid distribution ratio of 0.4.
This is equivalent to U.4 part in the steam to 1.U part in condensate.
Since more morpholine tends to be present in the liquid phase (condensate), it will drop out of steam early making it suitable for protection of short to moderate length condensate return systems.
However, since the boiling point of morpholine is 264 F, it can only be used in high pressure systems, at least lb psig but best above 5b psig.
Because of its high boiling point, very little morpholine is lost in deaerators from returning condensate.

Cyclohexylamine.
Cyclohexylamine has a high vapor-liquid distribution ratio ot 4.7.
It is best suited tor protection ot the far reaches ot long systems.
In very long systems, it is necessary to also treat with morpholine to protect parts ot the system close to the boiler.
Cyclohexylamine boils at 273 F but forms an azeotrope with water to boil at 2U5 F.
Thus it can be used in low pressure steam systems.
Cyclohexylamine also provides good protection in systems without deaerators.
However, cyclohexylamine should not be used in systems with a feedwater bicarbonate and carbonate alkalinity of x ppm or higher, as explained previously.
In addition, care should be used when feedwater alkalinity is above xx ppm.

Morpholine/Cyclohexylamine.
A mixture of morpholine and cyclohexylamine can also be used to provide full protection in medium and large systems.
Morpholine will protect the near ends of the system and cyclohexylamine will protect the tar sections.
The optimum ratio ot each amine in the mixture is determined by performing condensate pH surveys.
One can start with a mixture ratio ot I part cyclohexylamine to 3 parts morpholine (2b/75 percent).
The condensate pH survey is then conducted by taking condensate samples from representative locations in the return system.
It samples from far sections have a lower pH than other samples, increase the amount of cyclohexylamine in the mixture and vice-versa.
Another pH survey should be conducted whenever the ratio is changed.
Eventually, samples taken from points throughout the system should be within the optimum pH range ot 7.b to 8.0 or slightly higher.

Chemical Feeding. Feeding of neutralizing amines, including DEAE, is preferably done by means of continuous feed pumps to keep their concentration in the boiler and condensate at a fairly constant level.
They can be fed directly into the boiler steam drum or main steam header.

The use of neutralizing amines is an important part of good boiler water treatment.
The first step is to select the proper amine to use in each boiler.
Proper application of the amine will then provide a large measure of protection against corrosion in condensate return systems.

Carbon dioxide (CO2) can enter steam systems through boiler water or process leaks.
When steam containing CO2 condenses, the CO2 combines with available hydrogen to form carbonic acid.
While carbonic acid is a mild organic acid, if allowed to accumulate and concentrate, it can lower condensate pH enough to cause channeling corrosion of steel condensate lines.

Neutralizing amines such as cyclohexylamine (CHA), diethylethanolamine (DEEA)—also known as diethylamino-ethanol (DEAE)—and triethanolamine (TEA) are used to prevent this corrosion.

These chemicals, sometimes referred to as “volatilizing amines,” are applied to the steam header or the boiler feedwater.
When the boiler water is converted to steam, the amines are carried with it throughout the steam system.
When the steam condenses back to its liquid phase, the amines also return to their aqueous phase, neutralizing condensate acidity and preventing corrosion.

Return Line Treatments
Corrosion can also occur in condensate return lines. Corrosion can be caused by oxygen in the steam or carbon dioxide which leads to the production of carbonic acid.
Oxygen should ideally have been dealt with by the treatment of the feed water but any remaining can be removed using steam volatile oxygen scavengers.
Carbon dioxide corrosion can be controlled by pre-treatment techniques or by the addition of steam volatile neutralising and filming amines.
Filming amines are generally dosed into the steam lines and form a protective film on the surface of the condensate lines.
Neutralising amines enter the condensate lines with the steam and neutralise the carbonic acid thereby raising the pH.

Neutralizing Amine Chemistry
There are several different neutralizing amine components typically used in the treatment of boiler feedwater and/or condensate. Neutralizing amines each have different chemical properties, and it is important to understand the differences so that the correct components can be applied. Neutralizing amines typically applied in power plant systems are cyclohexylamine (CHA), methoxypropylamine (MPA), monoethanolamine (ETA), and morpholine.

Neutralizing amines are weak bases that are typically classified in terms of their “neutralizing capacity,” “basicity,” and “distribution ratio.” The neutralizing capacity is a measure of how much amine it takes to neutralize a given amount of acid. Usually it is expressed as the ppm of CO2 (or carbonic acid) neutralized per ppm of neutralizing amine. Once the acid has been neutralized, each amine has a different ability to boost pH, which is accomplished by the hydrolysis of the amine to form hydroxyl (OH-) ions.

Distribution ratio refers to the volatility of the amine, which is one factor that helps determine how each amine component will partition between the liquid and steam phases. The distribution ratio of a particular amine also influences how much amine is recycled throughout the system, and how much amine will be lost from the system via boiler blowdown and steam venting.

While neutralizing amine chemistry may appear to be relatively straightforward, it is in fact quite complex. For example, the distribution ratio for a given amine is actually a function of pressure, temperature and pH. This means if you feed more or less neutralizing amine in a given system and affect the pH, the distribution of the amine between the liquid and steam phases will change as well.

In addition, the chemistry of neutralization is actually based on equilibrium chemistry of weak acids and weak bases. In many cases, there are multiple neutralizing amine components and acid components present so it becomes even more difficult to predict the amine distribution and pH profile across the system without using sophisticated computerized modeling techniques or without performing extensive empirical in-plant analyses.

The thermal stability of the neutralizing amine must also be considered when designing a treatment program to control FAC. Most amines degrade to some degree in an aqueous, alkaline, high temperature environment to form carbon dioxide, organic acids and ammonia. Morpholine, CHA, ETA, and MPA are considered the most thermally stable amines and are routinely employed in high-pressure power plant applications.

Modern boiler plants produce steam for use in various applications, including electrical generation, manufacturing processes, sterilization of surgical instruments, space heating and humidification.
In a number of these applications, the potential for contamination of the product or process from boiler water additives is a major issue.
These applications include humidification, sterilization, and manufacturing processes where steam contacts food or food products.

Among the various chemicals used in boiler water treatment, of particular concern are amines, which are used to prevent carbonic acid corrosion in the steam condensate system.
The most commonly used type, neutralizing amines, are volatile compounds that leave the boiler with the steam and are present to prevent corrosion in condensate receivers and return piping.
While neutralizing amines are safe to use, their use in certain processes is regulated.

In systems in which treated steam contacts food or food packaging, the Food and Drug Administration (FDA) allows only the neutralizing amines morpholine, diethylaminoethanol (DEAE) or cyclohexylamine to be used.
Further, the FDA limits the allowable level of each in treated steam to 10 parts per million (ppm) of morpholine, 15 ppm of DEAE, and 10 ppm of cyclohexylamine.

In addition, FDA allows 25 ppm total amine when any or all are used in combination, provided that individual limits are not exceeded

Low and medium pressure boilers must be protected from scale deposition and corrosion to promote optimum energy efficiency and prolong the useful life of the plant equipment.

The definition of low and medium pressure is somewhat discretionary. For the purposes of this discussion, low pressure shall apply to boilers up to 150 psig. These boilers are typically used in space heating applications where the percentage of return condensate is high. Medium pressure boilers fall in the range of 150 to 650 psig. These are typically power generating plants where process steam is required. The makeup demand is greater in medium boiler plants due to steam consumption and loss.

In either case, the water treatment requirements can be met with basic chemicals. However, in the specialty chemical market, the various brand names and proprietary formulations create some confusion as to the best practice for boiler water treatment. This article will clear away some of the clutter by presenting a basic approach to providing effective chemical treatment for low and medium pressure boilers.

The basic boiler water treatment chemicals can be broken down into five (5) groups:

Oxygen scavengers
Scale-control agents
Alkalinity builders
Sludge dispersants
Condensate treatment
OXYGEN SCAVENGERS

Residual dissolved oxygen in the boiler promotes pitting-type corrosion that is an insidious, highly localized form of attack. If left unchecked, the propagation of the pit ultimately leads to tube failure. Boiler makeup can contain up to 10 ppm dissolved oxygen depending on the temperature. The first line of defense is removal by mechanical deaeration. This reduces the oxygen concentration to 7 parts per billion. The remaining oxygen is removed by chemical scavengers fed to the feedwater storage section of the deaerator.

Sodium sulfite Na2SO3 is the most commonly used and fastest acting oxygen scavenger. Available as a 90% active powder or less-concentrated liquid, sodium sulfite reacts rapidly with residual dissolved oxygen to form harmless sodium sulfate. Eight (8) parts of sodium sulfite are required to react with one (1) part of dissolved oxygen. An excess residual of 20 to 50 ppm of sodium sulfite are carried in the boiler to protect against oxygen ingress. Sulfite is available in a catalyzed version to enhance its reaction at lower temperatures, but uncatalyzed sulfite is acceptable for use at boiler saturation temperature and pressure.

Although very effective as an oxygen scavenger, sulfite does not readily react with boiler metal to promote the formation of a protective black iron magnetite surface. Black iron magnetite is a more passive (corrosion resistant) form of iron as compared to red iron hematite.

Hydrazine is often used as an oxygen scavenger in higher pressure boilers since it does not add dissolved solids to the boiler water. It also has the advantage of converting red iron oxide (hematite) into black iron oxide (magnetite). One part of hydrazine is required to react with 1 part of dissolved oxygen. An excess residual of 1 to 3 ppm is typically carried in the boiler to protect against oxygen intrusion and maintain the protective magnetite film.

Hydrazine has been classified as a potential carcinogen, hence its use has been in decline. Several hydrazine alternatives have been developed, however, that offer the advantage of being a metal passivator without the health and safety concerns associated with hydrazine.

Hydrazine alternatives fall into two (2) categories: volatile and non-volatile. In addition to reacting with oxygen in the pre-boiler and boiler, volatile scavengers carry with the steam into the condensate system where they further react with dissolved oxygen. Non-volatile scavengers such as sulfite and hydrazine do not.

The class of volatile oxygen scavengers include carbohydrazide, methylethylketoxime (MEKO), hydroquinone and diethylhydroxylamine (DEHA). These chemicals react much slower with dissolved oxygen as compared to sodium sulfite. However, they offer the benefit of promoting a black iron magnetite surface. They also react with dissolved oxygen in the condensate. Because of their volatile nature, these products are not used in boilers where the steam comes into contact with food or pharmaceutical products.

Sodium erythorbate is a non-volatile oxygen scavenger that can be used as an alternative to sodium sulfite and hydrazine. It has the advantage of being a metal passivator like hydrazine. However, since it appears on the Generally Recognized as Safe (GRAS) list of food additives, it does not pose the same health and safety concerns as hydrazine and the other alternatives. The theoretical dosage of erythorbate is 11 ppm per ppm dissolved oxygen.

SCALE CONTROL AGENTS

Hardness (calcium and magnesium) and iron in feedwater can react in the boiler to produce an insulating deposit on heat transfer surfaces. Scale deposits are also a fundamental cause of overheating and stress boiler tube failures.

The first line of defense in preventing unwanted boiler deposits is softening the boiler makeup by ion exchange or hot lime softening. Ion exchange softeners essentially remove all hardness and iron from the boiler makeup. Chemical treatment is required, however, to react with residual hardness and provide a safeguard against hardness leakage.

Various chemicals are used to prevent the formation of scale and baked-on sludge deposits. These include sodium phosphate, chelating agents like EDTA, and synthetic polymers.

Two forms of sodium phosphate find application in low and medium pressure boilers; disodium phosphate (NaHPO4 having a 49% P2O5 content) and sodium metaphosphate (NaPO3 having a 69% P2O5 content). Both react under boiler conditions to produce orthophosphate (o-PO4). PO4 readily reacts with calcium hardness and alkalinity to form an insoluble sludge of hydroxyapatite. The boiler sludge produced by this reaction is effectively removed by routine surface and bottom blowdown. Magnesium hardness reacts with silica and hydroxide alkalinity to yield an insoluble sludge. In general, boiler blowdown is controlled such that the suspended solids produced by these precipitation reactions do not exceed 500 ppm.

As an alternative to precipitating treatment programs, chelating agents are often used to keep calcium and magnesium soluble thereby avoiding the formation of an insoluble sludge. Ethylenediaminetetraacetic acid (EDTA) reacts with calcium, magnesium, iron and copper such that precipitation does not occur. It also reacts to a lesser extent with boiler metal surfaces and may remove some magnetite, hence overfeeding of chelants should be avoided. Four (4) parts of EDTA are required per ppm metal ion. EDTA is available as a powder and a 35% solution.

Various long chain synthetic organic polymers are beneficial in the treatment of boiler feedwater for the prevention of scale deposits. The polymers are best described as “weak” or “modified” chelants in that they chemically tie up impurities in the feedwater to prevent their deposition in the boiler. In these applications, the polymers replace phosphate and EDTA as the primary scale control agent.

ALKALINITY BUILDERS

Maintenance of sufficient boiler alkalinity is required to enhance the precipitation reactions with calcium and magnesium hardness plus help in the formation of a passive metal surface. With a phosphate treatment program, hydroxide (OH) alkalinity is required to insure that calcium reacts to form calcium phosphate hydroxide (hydroxyapatite) and that magnesium reacts to form magnesium hydroxide (brucite, aka milk of magnesia).

The most common alkalinity builder is sodium hydroxide (NaOH, aka caustic soda). This is available as a 98% flake form having a 76% Na2O content. More commonly, it is obtained as a 50% active liquid or in more dilute liquid versions depending on the source of supply.

Alternatively, sodium carbonate (Na2CO3, aka soda ash) may be used. This product is available as a 99% active powder having a 58% Na2O content. Soda ash reacts under boiler temperature and pressure to produce sodium hydroxide and free carbon dioxide. This has the disadvantage of increasing the carbon dioxide content of the steam, which, in turn, results in the formation of corrosive carbonic acid in the condensate. For this reason, most low and medium pressure boiler applications favor the use of liquid sodium (or potassium) hydroxide as the alkalinity builder.

No definitive, universally-agreed-upon range for excess caustic (OH) alkalinity exists. Excessively high OH alkalinity should be avoided as this has been shown to adversely affect steam purity and increase the tendency for caustic attack of boiler metal in the form of embrittlement and gouging. In general, experience suggests that a range of 85 to 300 ppm OH alkalinity is typical for boilers operating in the low and medium pressure ranges.

SLUDGE DISPERSENTS

Various boiler additives have been used to reduce the tendency of boiler precipitants to settle out or bake on to generating tubes. Early on, boiler operators applied natural substances like potato starch and tannin/lignin extracts from tree bark. These natural additives are still used today with some success. However, with the development of more chemically refined synthetic polymers, the use of natural organic dispersants continues to decline.

Synthetic polymers are often used in conjunction with phosphate and chelant programs to react with boiler sludge in order to keep it fluid, dispersed and easily removed by surface and bottom blowdown. The first boiler polymers were long chain polyacrylic acid (AA) and polymethacrylate (PMA) molecules. Many other polymeric boiler additives have since been developed including maleic acid, sodium glucoheptonate ,

2-acrylamido-2-methyl propane sulfonic acid (AMPS), and various co-polymers and ter-polymers of AA/AMPS. Not all polymers are suitable for use in food and dairy plants, however. Those that are permissible for such use are listed in the Code of Federal Regulations, 21CFR173.310.

Polymer dosages vary depending on the type of chemical used. In general, the dosage of active polymer falls within the 10 to 20 ppm range. Over-dosing polymers should be avoided as this adversely affects their dispersant performance.

STEAM CONDENSATE TREATMENT

Carbon dioxide that volatilizes with the steam due to the thermal decomposition of carbonate alkalinity in the feedwater dissolves into the condensate to form carbonic acid, which is corrosive. Volatile neutralizing amines are frequently required to neutralize this acid to cause an upward adjustment in pH.

The first step in minimizing problems caused by volatile gases like carbon dioxide is to reduce the bicarbonate and carbonate alkalinity in the boiler makeup. This can be done by ion exchange dealkalization or demineralization. Although dealkalization of boiler makeup is a common practice in high pressure boiler installations, many low and medium pressure boilers operate on soft water makeup. The natural bicarbonate alkalinity is not removed in a sodium exchange water softener. And, as mentioned previously, chemical additives such as sodium carbonate (soda ash), which may be used as an alkalinity builder in the boiler, add to the carbon dioxide potential of the steam.

Neutralizing amines are used alone or in combination to adjust and maintain the condensate pH to within an alkaline range of 7.5 to 8.5. Generally, pH does not adversely affect the corrosion rate of steel above a pH of 6.0. Using neutralizing amines to maintain the pH above 6.0 provides additional protection from pH excursions.

The most common neutralizing amines are morpholine, diethylaminoethanol (DEAE), and cyclohexylamine. Each has a different distribution ratio between the steam/condensate phases. Some trial and error is required to determine the optimum type and amount of neutralizing amine required. Amines are best applied by injection with a quill into the main steam header, but they can also be applied directly to the boiler where they distill off into the steam phase.

In some applications, such as in food and dairy plants, the use of steam condensate treatment is restricted or prohibited. Sorbitol anhydride esters have been recently approved by the FDA for use in treating steam condensate in food plants up to a dosage of 15 ppm in the steam. Other restrictions on amine usage may apply where clean steam is required for pharmaceutical, humidification, sterilization or other manufacturing processes.

SUMMARY

Operating low and medium pressure boiler plants at maximum efficiency requires careful control over the boiler water chemistry. This includes protecting the boiler from oxygen-pitting type corrosion, preventing scale deposits on heat transfer surfaces and protecting the steam condensate system from corrosion.

These goals are best achieved by the application of basic water treatment chemicals.

Sodium sulfite for oxygen scavenging
Sodium phosphate for reaction with calcium hardness
Sodium EDTA if a non-precipitating chemical program is desired
Sodium hydroxide for reaction with magnesium hardness and to adjust boiler alkalinity
Polymeric dispersants such as polyacrylate, polymethacrylate and various co- and ter- polymers
Neutralizing amines including morpholine, DEAE, and cyclohexylamine.

Film-Forming Amines in Steam/Water Cycles –structure, properties, and influence on corrosion and deposition processes

This neutralizing amine has generally been used for low pressure operations with long condensate returns.
Pure cyclohexylamine will boil at 273° F.
This corresponds to a minimum boiler pressure of 30 psig.
The boiling point of the neutralizing amines are not the only criteria for evaluating their effectiveness.
Cyclohexylamine goes through a mechanical function called the formation of an azeotropic mixture.
The azeotropic point of a cyclohexylamine mixture has a boiling point of 207° F.
Cyclohexylamine has one of the highest steam distribution ratios.
The steam distribution ratio of an amine is defined as the ratio of the amine contained in the steam vs. the amount of amine contained in the condensate at that pressure.
This means that more cyclohexylamine will stay with the steam as pressures are reduced.
Cyclohexylamine will carry out to the far reaches of the condensate system.

Cyclohexylamine has a high potential for formation of an amine carbonate in condensate systems.
When used in steam humidification systems it is possible for odor problems to occur.

Diethylaminoethanol (DEAE)

DEAE is probably the most widely used neutralizing amine today.
While the boiling point of DEAE is higher than other amines (325° F) it also forms an azeoptropic mixture which is approximately 210° F.
The steam distribution ratio falls midway between morpholine and cyclohexylamine.
DEAE provides good general coverage to low pressure as well as higher pressure systems.
DEAE does not form an amine carbonate like other neutralizing amines.

Morpholine

Morpholine has one of the lowest boiling points of all amines.
The boiling point of morpholine is 262° F which corresponds to about a minimum boiler pressure of 22 psig.
Morpholine does not form an azeotropic mixture so a low boiling point is necessary.
The steam distribution ratio for morpholine is the lowest of all amines.
Morpholine will have more amine in the water phase than in the steam.
For this reason where low pressures are involved we would not find sufficient amounts of amine remaining in the steam for complete coverage.
Morpholine is also a very effective neutralizer up to a pH of 7.0.
Its effectiveness drops off in trying to raise the condensate pH to a 8.0 to 8.5 range.
Morpholine also has a slight tendency to form an amine carbonate.

Dimethylamino-2-Propanol (DMA-2P)

DMA-2P is a lesser known amine than the first three discussed.
DMA-2P has a low boiling point of about 253° F.
This amine also forms an azeotropic mixture which has a boiling point of 207° F.
DMA-2P has a very high distribution ratio even higher than cyclohexylamine.
DMA-2P will protect the far reaches of long distance low pressure systems.
DMA-2P will not form an amine carbonate in the condensate return system.

Ammonia

Ammonium hydroxide is used as a neutralizing amine in situations where live steam contacts a food product.
This type of amine is the only product acceptable in dairy plant systems.
Ammonia has a very high distribution ratio even higher than cyclohexylamine and DMA-2-P.
Ammonia should not be fed into the feedwater or D.A. tank because of loss through the tanks vent.
Ammonia is also very corrosive to copper and copper alloys.

Octadecylamine
Octadecylamine is not a volatilizing amine.
It will not volatilize in a boiler below 425 psig.
ODA therefore must be injected into the steam header via a vapor steam injection nozzle.
When injected into the steam header it exists as a dispersion in the steam.
Octadeyclamine is not soluble in water so when it falls out of the steam solution it lays down the passivating mechanism.
A monomolecular film is formed when the hydrophobic ends of the amine molecule attach to the metal surfaces.
This monomolecular film repels water creating a barrier between corrosive condensate and the metals.
Excessive feed or too rapid of feed will cause the system to plug iron oxides removed from the metals.
Incomplete film formation will cause localized corrosion. Extreme care and monitoring are required when using ODA.

Ethoxylated Soya Amine
Ethoxylated soya amine is another type of film forming amine.
The major difference between ODA and this type amine is that ODA has one hydrophilic attachment where the soya amine has three.
This increases the solubility of the molecule resulting in a lower sludging tendency.
The soya amine is therefore easier to apply and maintain.
Again extreme care and monitoring are required when using this amine.

Cyclohexylamine is a neutralizing corrosion inhibitor that is effective in neutralizing carbonic acids in low pressure condensate systems where other amines are limited.
A favorable liquid-vapor distribution ratio assures protection at the far ends of extensive systems.

Morpholine has a low steam distribution ratio best suited for high-pressure systems.
Morpholine provides corrosion protection in steam plants and efficiently recycles steam back to boiler.

DEAE (Diethylaminoethanol) provides corrosion control in steam condensate systems in industrial and utility plants.
It protects areas where condensate first forms. Suitable for use in low pressure and high.

The Facts about Neutralizing Amines in Steam Systems
Neutralizing Amines are added to steam systems to neutralize carbonic acid and raise the pH of the condensate.
They are added in direct proportion to the amount of carbon dioxide in the steam.
Excess amounts of neutralizing amines may be required to raise the condensate pH to the desired pH control range.
Typically, a condensate pH of 7.4 – 9.0 provides effective protection in most systems.
In systems that contain no copper or aluminum alloys, the higher pH values will improve mild steel corrosion control.

Volatility of amines used for water treatment in steam generating systems

The relative volatilities of cyclohexylamine and morpholine in dilute aqueous solution have been measured in the temperature range 150 to 300-C at the corresponding equilibrium vapour pressure of the solution.
Cyclohexylamine strongly prefers the steam phase while
morpholine has a relatively volatility close to that of water.

In both cases an azeotrope of the anline and water, with a vapour pressure higher than that of either component, must exist; however, with morpholine and water azeotrope formation only occurs above 175°C.
The concentration dependence of the distribution between the steam and solution phases of both amines is explained in terms of their partial ionization in solution

Chemical Inhibitors
There are two basic chemical inhibitors that are used for minimising corrosion in condensate systems—neutralising amines and filming amines.
Neutralising amines are volatile, alkaline chemicals that increase the condensate pH level.
They offer protection against carbonic acid attack, but do not completely prevent oxygen corrosion.
Filming amines form a barrier between the metal and the condensate, thus preventing both carbonic acid and oxygen attack.
The choice between neutralising and filming amines, or both, depends on the particular operating conditions.
That is, if there is air leakage into steam condensate lines, generally filming amines are better suited, whereas in tight systems with low fresh water make-up, neutralising amines are usually more practical.

Neutralising Amines
The most common neutralising amines are listed in Table 1 below.
Each one functions by neutralisation, and is effective only in controlling corrosion caused by low pH.
Neutralising amines volatise from the boiler water, carry-over with the steam, and dissolve in the condensate where they react with carbonic acid to form amine carbonate or amine bicarbonate.
Excessive amine carbonate/bicarbonate concentrations may result in their precipitation.
However, in most cases the amine carbonates/bicarbonates dissolve in the condensate and are returned to the boiler where heat causes them to break down into amine and carbon dioxide, and the cycle is repeated.
The amine vapour/liquid distribution ratio (DR)—defined as the ratio of the amount of amine in the steam to the amount of amine in the condensate—is used to determine which amine, or groups of amine, that is best suited for a particular condensate system.

The amine DR’s are listed in Table 1 below.
Table 1: Distribution Ratios of Neutralising Amines
Amine Vapour/Liquid
Distribution
Ratio
(at 0 psig)
Vapour/Liquid
Distribution
Ratio
(at 600 psig)
Ammonia 10.0/1.0 4.2/1.0
Cyclohexylamine 4.0/1.0 6.6/1.0
Diethylaminoethanol
(DEAE)
1.7/1.0 3.8/1.0
Dimethylaminoethanol
(DMAE)
1.0/1.0 1.9/1.0
Morpholine 0.4/1.0 1.3/1.0

Since the object of volatile amine treatment is to neutralise the carbonic acid that is formed in the condensate, it is important to note that only that portion of the amine that dissolves in the condensate is capable of complying with this objective.
The amine in the steam phase does not neutralise acid in the condensate.
Therefore, if most of the steam condenses early in the system, morpholine with its low DR of 0.4/1.0 (i.e., 0.4 part morpholine in the steam; 1.0 part morpholine in the condensate) would be the amine of choice because of its higher concentration in the condensate.
Cyclohexylamine with its higher DR of 4.0/1.0 would be more effective for longer far reaching condensate systems due to its higher concentration in the steam phase.
Similarly, DEAE or DMAE would be the amine of choice for moderately sized condensate systems because of their intermediate DR’s.
In complex steam systems, the prevention of deposits from excessive amine carbonate/bicarbonate concentrations may be best accomplished by feeding a mixture of amines.

The volatility of neutralising amines dictates that they should be purchased at a concentration that is in keeping with due regard to the fire hazard associated with their low flash point temperatures (i.e., 40% for morpholine & cyclohexlyamine).
They are usually added to the boiler feedwater, along with the boiler water scale & corrosion inhibitors, and continuous injection is required.
The primary means for controlling neutralising amines is by adding sufficient amine to maintain condensate pH levels within the range of 8.5-9.5 pH for systems without steam humidification and 8.0-8.5 pH in systems where a portion of the steam is used for space humidification.

However, control can also involve the monitoring of condensate iron concentrations, the use of corrosion coupons, and visual examination.
Whichever method(s) is used, it is important to monitor as many condensate streams as possible.

Filming Amines
The most common filming amine is octadecylamine (ODA).
It is a large molecule that has both hydrophilic—water attracting—and hydrophobic—water repelling— ends in its structure.
Bonding at the hydrophilic end forms an adherent nonwettable organic film on the metal surface, thus preventing contact between that surface and the corrosive condensate.
The monomolecular film thus formed inhibits attack from both oxygen and carbonic acid.
A clean surface is required for filming amines to work properly because the presence of deposits on the metal surface inhibits film formation; therefore, either areas under the deposits are not protected, or the deposits are undercut and sloughed off, thus resulting in blockage of steam traps and valves in the condensate system.
Because high velocities could potentially erode the protective film, a continuous amine feed directly to the main steam supply at a typical concentration of 1-3 ppm is required.
The control of filming amines is accomplished by monitoring condensate iron concentrations, the use of corrosion coupons, and visual examination.
Whichever method(s) is used, it is important to monitor as many condensate streams as possible.

CHARACTERISTICS OF NEUTRALIZING AMINES
In order to maintain a safe indoor air quality (IAQ), design engineers and owners should be knowledgeable about the chemical additive properties with respect to their purpose, use and toxicity as each has different properties, toxicities, advantages and disadvantages.
Neutralizing amines are organic compounds that behave as weak bases and have a strong, characteristic, fishy or ammonia-like odor.
They are classified by their (1) neutralizing capacity– a measure of how much amine it takes to neutralize a given amount of acid, expressed as the parts per million (ppm) of carbonic acid neutralized per ppm of neutralizing amine; (2) alkalinity or pH and (3) vapor/liquid distribution ratio (V/L) defined as the tendency of the chemical compound to condense with the steam condensate.
For neutralizing amines, the V/L represents the amines interaction between the liquid and steam phases and the pressure, temperature and pH of the steam/condensate environment.
The higher the ratio the more likely the amine will stay with the steam in a distribution system, while an amine with a lower ratio will condense earlier depending on its chemical properties and the variables of pressure, temperature and pH.
A higher ratio product therefore is a better choice for a larger/longer system while a lower ratio product is best for a smaller system.
The neutralizing amines are corrosive in and of themselves before they chemically react with an acid to neutralize that acid and they must be handled judiciously.
Although there are alternatives to using neutralizing amines in certain situations, the use of neutralizing amines remains the method of choice in many facilities because of its reasonable cost and general ease of use and monitoring.

Neutralizing amines each have different chemical properties so that a combination of appropriate amines may be necessary to address the corrosion effects on different segments of the system.
In addition to selecting a neutralizing amine or combination of amines based on these characteristics the cost, consumption rate, length of the condensate lines, amount of carbon dioxide generated in the boiler and thermal stability must be considered as well.
Because of the complexity of combined amine additive interactions and the systems for which they are selected, sophisticated computerized modeling techniques may be used to predict the amine distribution and pH profile across the system.

The most commonly used neutralizing amines in boiler systems are,cyclohexylamine (CHA), diethylaminoethanol (DEAE), morpholine, ammonia methoxypropylamine (MPA), monoethanolamine (ETA) because, used individually or in combination, they are capable of preventing corrosion in systems of various lengths, and it is fairly easy to control their indoor air concentrations well below accepted exposure limits through the use of standard operating procedures and practices.
Of these, CHA, DEAE and morpholine are the most commonly used neutralizing amines in steam boiler humidification systems in health care facilities.
This is primarily because they have been approved by the FDA for use in food processing applications or in other words, for ingestion.
The USDA permits the use of the amines in meat plants.
As described in the section ‘Regulation of Neutralizing Amines’, FDA, OSHA, and ACGIH exposure limits are significantly higher than any levels that have been found in the classic exposure case studies reported in the literature.
Since no Federal government regulations exist governing the use of amines in direct steam humidification systems (other than in the food industry in which all the existing standards and guidelines are based on ingestion) the water treatment industry tends to follow FDA limits for amine levels in steam used for direct steam humidification systems.
However, lacking better or more current scientifically based criteria, this is all the guidance currently available to manufacturers and regulators.

Cyclohexylamine
Cyclohexylamine (CHA), a colorless to yellow liquid with a strong fishy odor, is used primarily for boiler water treatment in low pressure systems (50 down to 5 psi) and also for systems with long condensate systems where it is used in combination with other neutralizing amines.
It has a high vapor–liquid distribution ratio of 4.7:1 (i.e., cyclohexylamine will place 4.7 times the material in the vapor phase as in the water phase).
CHA is unique among the neutralizing amines approved for steam boiler systems in that it will stay with the steam as pressure is reduced.
Cyclohexylamine is a mutagen and a corrosive chemical that can be an acute and chronic irritant to the lungs, skin, and eyes. Inhalation exposure can cause dizziness, lightheadedness, anxiety, nausea and vomiting.
It is also a flammable liquid and a fire hazard.

Morpholine
Morpholine is the amine of choice for direct sterilization systems and short run systems.
It must be blended with either DEAE or CHA for use in longer systems since it drops out of the steam early.
It has a low boiling point and low distribution ration (0.4 parts morpholine in the steam; 1.0 part morpholine in the condensate).
There are no data available on levels of morpholine in ambient and residential indoor air and in drinking water.

Diethylaminoethanol (DEAE)
Diethylaminoethanol (DEAE), a colorless liquid with a nause ating, ammonia like odor, has a vapor–liquid distribution ratio of 1.7, which is between cyclohexylamine and morpholine.
It is a good choice in a medium length system where either morpholine or cyclohexylamine used separately would not provide complete protection.
DEAE is not effective in low pressure systems because of its high boiling point.
DEAE can be compared to morpholine as a primary irritant.

Other neutralizing amines sometimes used for corrosion inhibition include: methoxypropylamine
(MOPA) used primarily in the oil industry in anticorrosion of petroleum lines; dimethylpropylamine (DMPA) used mainly in the foundry industry, as a tertiary amine catalyst for the production of sand cores (cold box process); monoethanolamine (MEA), similar to morpholine, is used for corrosion control in steam cycles of power plants, including power plants with pressurized water reactors.
It is sometimes selected because it does not accumulate in steam generators (boilers) and crevices due to its volatility, but rather distributes relatively uniformly throughout the entire steam cycle

A system with a number of different types of runs of varying length could mean that a blended amine program will be needed.

It could also require the use of remote pumping stations.

The system could take a short run to a low pressure turbine, then a medium length run for a process and then a series of long runs that go through pressure reducing stations.

In this case, a blend of three neutralizing amine would be required.

Cyclohexylamine for the long run and for the reducing station, DEAE for the medium run and Morpholine for the short run turbine line.
By using a 35% solution of each of these amines and varying the amount of each amine in the mix tank, you will be able to come up with a blend that will work for that particular system.
After you have determined how many runs there are, you need to determine the length of the runs.
This will determine if one or more amines will be needed in this system.

Cyclohexylamine will stay
in the condensate system over long runs and in low pressure situations.

DEAE is a good medium range amine, but does not have the ability to pass over the long runs and through pressure reducing stations below 15 psi.

Morpholine is used for short runs and will have to be blended with one or both of the other neutralizing amines if the system is more than a short run.

It is important at this point to realize that DEAE as a 25% or 50% solution is the most widely used neutralizing amine.

DEAE will adequately protect the return line system in most middle market water treatment accounts.

Its success is also its vulnerability.

In many accounts,Diethylaminoethanol is being fed where there is one long run and some low pressure reducing stations.

In these cases, the largest part of the system is protected, but a small section is not. One
condensate return line run has a pH of 8.2 and the other has a pH or 6.8.

In these cases,Cyclohexylamine needs to be blended in with the DEAE.
The new combination product now protects both the long and the medium runs of the system.

The total alkalinity of the raw water and the quantity of raw water will determine the use rate of the neutralizing amine.
1 ppm of 35% neutralizing amine is required for every ppm of total alkalinity in the feed water.
Multiply this times the millions of pounds of feed water and you can establish the feed rate in pounds for the neutralizing amine.
Use this check to see if the present amine program is being under or over fed.
The feed rate could point out where the real problem is.
In a pump and gravity system, a condensate receiver that is open to the air can pull oxygen into the condensate lines.
The account now has severe pitting in some of the lines and not in others.
The use of a blend of a neutralizing amine and a filming amine will help this condition.
Sealing the receiver is what really needs to be done.

Cyclohexylamine CAS-no.: 108-91-8
2-Amino-2-methylpropanol CAS-no.: 124-68-5
2-Diethylaminoethanol CAS-no.: 180-37-8
Morpholine CAS-no.: 110-91-8
3-Methylpropylamine CAS-no.: 5332-73-0
• Other film forming products (FFP): Commercially available products with film forming properties which do not contain film forming amines.

Film forming amines are solid or paste-like materials and they are sparingly soluble in water.
They are applied as solutions, emulsions, or suspensions in water and can be blended with alkalizing substances, such as ammonia, alkalizing amines, sodium hydroxide, or phosphate.

The dosage can be as a single component or as a blend of different substances.
The objectives of a FFA treatment include:
• Corrosion reduction in continuous operation;
• Minimization of corrosion product transport;
• Formation of clean, smooth heat transfer surfaces;
• Corrosion protection during shutdown/layup.
The formation of hard scales such as calcium carbonate or silicates due to poor water purity cannot be prevented, and it is currently not clear whether they can be (partially) removed with a FFA/FFAP treatment.

The primary function of a boiler is to transfer heat from hot gases generated by the combustion of fuel into water until it becomes hot or turns to steam.
The steam or hot water can then be used in building or facility processes.

Except for a small number of specialty models, boilers generally fit into one of the two common categories:
fire-tube boilers and water-tube boilers.

Fire-tube boilers pass hot combustion gases through tubes submerged in water.
Water-tube boilers, on the other hand, circulate water inside the tubes in a closed vessel filled with hot combustions gases.
In either category the boiler feedwater and fuel often contain impurities, which impairs boiler operation and efficiency.

Chemical additives can be used to correct the problems caused by these impurities.
To improve feedwater quality, fuel oil condition, and steam purity, these chemicals can be injected directly into the feedwater, steam or fuel oil.

This fact sheet discusses the potential problems associated with the impurities in the feedwater and fuel and the chemical treatment programs available.
Benefits of Chemical Treatments
• Increase boiler efficiency;
• Reduce fuel, operating and maintenance costs;
• Minimize maintenance and downtime; and
• Protect equipment from corrosion and extend equipment lifetime.

Chemical Treatments for Waterside of Boiler Tubes
The feedwater is composed of makeup water (usually city water from outside boiler room/ process)
and condensate (condensed steam returning to the boiler).
The feedwater normally contains impurities,which can cause deposits and other related problems inside the boiler.
Common impurities in water include alkalinity, silica, iron, dissolved oxygen and calcium and magnesium (hardness).
Blowdown, a periodic or continuous water removal process, is used to limit the concentration of impurities in boiler water and to control the buildup of dissolved solid levels in the boiler.
Blowdown is essential in addition to chemical treatments.

Boiler Waterside Fouling
Scale is one of the most common deposit related problems.
Scale is a buildup of solid material from the reactions between the impurities in water and tube metal, on the water-side tube surface.
Scale acts as an insulator that reduces heat transfer, causing a decrease in boiler efficiency and excessive fuel consumption.
More serious effects are overheating of tubes and potential tube failure (equipment damage).
Fuel wasted due to scale may be approximately 2-5 percent depending on the scale thickness.
Oxygen attack is the most common causes of corrosion inside boilers.
Dissolved oxygen in feedwater can become very aggressive when heated and reacts with the boiler’s internal surface to form corrosive components on the metal surface.
Oxygen attack can cause further damage to steam drums, mud dams, boiler headers and condensate piping.

Acid attack is another common causes of corrosion.
Acid attack happens when the pH of feedwater drops below 8.5.
The carbonate alkalinity in the water is converted to carbon dioxide gas (CO2) by the heat and pressure of the boilers.
CO2 is carried over in the steam.
When the steam condenses, CO2 dissolves in water to form carbonic acid (H2CO3) and reduces the pH of the condensate returning to the boilers.
Acid attack may also impact condensate return piping throughout the facility.

Chemical Treatments

• Lime Softening and Soda Ash
Quick or slaked lime (usually calcium hydroxide) is added to hard water to precipitate the calcium, magnesium and, to some extent, the silica in the water.
Soda ash is added to precipitate non-bicarbonate hardness.
The process typically takes place in a clarifier followed by a hydrogen cycle cation exchange and a hydroxide cycle anion exchange demineralization.

• Phosphate
Mono-, di- or trisodium phosphate and sodium polyphosphate can be added to treat boiler feedwater.
Phosphate buffers the water to minimize pH fluctuation.
It also precipitates calcium or magnesium into a soft deposit rather than a hard scale.
Additionally, it helps to promote the protective layer on boiler metal surfaces.
However, phosphate forms sludge as it reacts with hardness; blowdown or other procedures should be established to remove the sludge during a routine boiler shutdown.

• Chelates
Nitrilotriacetic acid (NTA) and ethylenediamine tetraacetic acid (EDTA) are the most commonly used chelates.
Chelates combine with hardness in water to form soluble compounds.
The compounds can then be eliminated by blowdown.
The preferred feed location for chelates is downstream of the feedwater pump.
A stainless steel injection quill is required.
However, chelates treatment is not recommended for feedwater with high hardness concentration.

• Polymers
Most polymers used in feedwater treatment are synthetic.
They act like chelates but are not as effective.
Some polymers are effective in controlling hardness deposits, while others are helpful in controlling iron deposits.
Polymers are often combined with chelates for the most effective treatment.

• Oxygen Scavengers
A deaerator removes most of the oxygen in feedwater; however, trace amounts are still present and can cause corrosion-related problems.
Oxygen scavengers are added to the feedwater, preferably in the storage tank of the feedwater, to remove the trace mount of oxygen escaped from the deaerator.
The most commonly used oxygen scavenger is sodium sulfite.
Sodium sulfite is cheap, effective and can be easily measured in water.

• Neutralizing Amines
Neutralizing amines are high pH chemicals that can be fed directly to the feedwater or the steam header to neutralize the carbonic acid formed in the condensate (acid attack).
The three most commonly used neutralizing amines are morpholine, diethyleminoethanal (DEAE) and cyclohexylamine.
Neutralizing amines cannot protect against oxygen attack; however, it helps keep oxygen less reactive by maintaining an alkaline pH.

• Filming Amines
Filming amines are various chemicals that form a protective layer on the condensate piping to protect it from both oxygen and acid attack.
The filming amines should be continuously fed into the steam header with an injection quill based on steam flow.
The two most common filming amines are octadecylamine (ODA) and ethoxylated soya amine (ESA).
Combining neutralizing and filming amine is a successful alternative to protect against both acid and oxygen attack.

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March 25, 2022

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