CHEMICAL TREATMENT IN BOILER SYSTEM
The main function of a boiler is to transfer energy from the form of hot gas created through fuel to convert water to steam. Hot steam or hot water is then used in the production process. Feed water often contains impurities, which interfere with performance & efficiency in boiler systems. Chemical additives can be used to overcome problems caused by these impurities. To improve the quality of feed water, and good steam, chemicals can be injected directly into the feed water used.
Benefits of chemical treatment.
• Improve boiler performance;
• Save fuel and lower maintenance costs;
• Reducing engine downtime; and
• Protect production assets from damage and increase the usability of production equipment.
CHEMICAL TREATMENT FOR WATER-TUBE TYPE BOILERS
Feed water consists of raw water (make-up water) and condensate water (back steam). Raw water generally contains impurities, which cause deposits in the boiler. Common impurities include alkalinity, silica, iron, dissolved oxygen, calcium & magnesium (hardness). Blowdown, periodically or automatically, is the process of removing water from a boiler, to limit the concentration of impurities and other minerals contained in boiler water. Blowdown is important as a support for chemical treatment.
Problems caused by impurities in the boiler
Crust. is an ordinary mineral deposit. Crust is a solid due to the reaction of impurities and the surface of metal pipes. Crust acts as an insulator to slow down heat transfer, which causes decreased efficiency and increased fuel consumption. A more serious effect is overheating and causing damage to the boiler pipes.
Corrosion. Corrosion is caused by dissolved oxygen content in feed water. Oxidation reactions become more aggressive when getting heat energy creates corrosion on metal surfaces. Damage due to corrosion can occur on boiler drums, headers and condensate pipes.
Acid. is also a cause of corrosion in metals. Water is said to be acidic if the pH of feed water is below the 8.5 range. Alkaline carbonate is converted to CO2 by heat and pressure in the boiler. CO2 is carried as long as water vapor is produced. When water vapor condenses, CO2 dissolves in water to form carbonic acid (H2CO3) and directly lowers the pH of the condensate water. The acid will also damage the condensate pipe.
BOILER CHEMICAL TREATMENT REQUIREMENTS
Treatment Products. The fact is that treatment programs usually require a relatively small percentage of the overall operating costs of the boiler. However, poor treatment performance causes a domino effect that increases operating costs and boiler maintenance. For best results, all chemicals for internal treatment must be used continuously with adequate doses. Chemicals can be fed directly into the feed water tank. Certain chemicals may be mixed for use at the same time. The chemical injection position is usually placed higher than the boiler circuit position. For the chemical feeder position under the feed water pump, the pump must be adjusted to the boiler pressure.
Basic Boiler Schema . As shown in the figure, the steam generation system consists of 3 main components; deaerator, boiler, and condensate system. Oxygen scavenger is fed to the deaerator tank. internal treatment is fed to the feed water pump or drum boiler.
Chemical Treatment
Lime Softening and Soda Ash . Lime is mixed with raw water to precipitate calcium, magnesium, and silica in water. Soda ash is mixed to precipitate non-bicarbonate hardness. This process occurs in the clarifier tank followed by an ion exchange process through demineralization. Both of these chemicals are in liquid form, also granular.
Oxygen Scavengers. deaerator removes oxygen in feed water; however, trace oxygen is still present and causes corrosion problems. Oxygen scavengers are mixed in feed water. A common form of oxygen scavenger is sodium sulfite. Sodium sulfite is cheap, effective and easily measured in water.
Sulfite without catalyst (Oxygen Scavenger)
Sodium sulfite without a catalyst can be mixed with other chemical agents. Location of sulfite injection between the feed water tank (economize tank and boiler. If only sulfite is used, then the following basic equipment is needed:
- Chemical injection pump
- Pipes, flaps, fittings, filters made of stainless steel or PVC
- flowmeter
- Pressure gauge
- Electrical panel
- Mixer or mixer
Sulfite is generally in liquid form, characterized by acid, which will create corrosive properties of the material used. HDPE sulfite tank.
Sulfite with catalyst (Oxygen Scavenger)
Sulfite with catalyst MUST be used independently without other chemicals mixed and fed continuously. The water used also MUST be pure water (demineralized water). Generally this type is fed to water tanks.
Hydrazine (Oxygen Scavenger)
Hydrazine may be used with other chemical agents except those of an organic type, amine compound and nitrate type. But it is very good if used independently. Hidrazine usually uses a closed bait system because it is quite dangerous if exposed to exposure to humans.
Organic Oxygen Scavengers
Organic compounds can also be used such as hydroquinone and ascorbic acid (vitamin C). Should be fed independently and continuously.
Neutralizing Amines
Neutralizing amines are chemical types of strong bases that are able to neutralize carbonic acid which usually forms in the condensate. Which includes this type include: morpholine, diethyleminoethanal (DEAE) and cyclohexylamine. Neutralizing amines do not protect from corrosion due to oxygen but only inhibit the activity of oxygen because of its strong alkaline nature.
Filming Amines
Filming amines is a type of chemical that forms a thin layer on a condensate pipe with the aim of protecting it from corrosive activity both due to oxygen and acid. Some types include: octadecylamine (ODA) and ethoxylated soya amine (ESA). The combination of these two types is commonly used.
Internal Treatment Chemicals
There are three major classifications of chemicals used in internal treatment: phosphates, chelants, and polymers. These chemicals may be fed separately or in combination; in most balanced treatment programs, two or three chemicals are fed together. The preferred feed point varies with the chemical specified. For example, when caustic soda is used to maintain boiler water alkalinity, it is fed directly to the boiler drum. When caustic is used to adjust the feedwater pH, it is normally injected into the storage section of the deaerating heater.
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 boiler shutdown routine. Phosphates are usually fed directly into the steam drum of the boiler, although they may be fed to the feedwater line under certain conditions. Treatments containing orthophosphate may produce calcium phosphate feed line deposits; therefore, they should not be fed through the boiler feed line. Orthophosphate should be fed directly to the steam drum boiler through a chemical feed line.
Polyphosphates must not be fed to the boiler feedwater line when economizers, heat exchangers, or stage heaters are part of the boiler system. If the preboiler system does not include such equipment, polyphosphates may be fed to the feedwater piping provided that total hardness does not exceed 2 ppm. In all cases, feed rates are based on feedwater hardness levels. Phosphates should be fed neat or diluted with condensate or high-purity water.
polyphosphates may be fed to the feedwater piping provided that total hardness does not exceed 2 ppm. In all cases, feed rates are based on feedwater hardness levels.
Phosphates should be fed neat or diluted with condensate or high-purity water. polyphosphates may be fed to the feedwater piping provided that total hardness does not exceed 2 ppm. In all cases, feed rates are based on feedwater hardness levels. Phosphates should be fed neat or diluted with condensate or high-purity water.Mild steel tanks, fittings, and feed lines are appropriate. If acidic phosphate solutions are fed, stainless steel is recommended.
Chelants
Nitrilotriacetic acid (NTA) and ethylenediamine tetraacetic acid (EDTA) are the most commonly used chelants. Chelants combine with hardness in water to form soluble compounds. The compounds can then be eliminated by blowdown.
- • Chelants treatment is not recommended for feedwater with high hardness concentration
- • Chelants should not be fed if the feedwater contains a significant level of oxygen.
- • Chelants should never be fed directly into a boiler
The preferred feed location for chelants is downstream of the feedwater pump. All chelant treatments must be fed to the boiler feedwater line by means of a stainless steel injection nozzle at a point beyond the discharge of the boiler feed pumps. If heat exchangers or stage heaters are present in the boiler feed line, the injection point should be at their discharge. Care should be exercised in the selection of metals for high-temperature injection quills.
At feed solution strength and elevated temperatures, mild chelating agents can corrode and copper alloys; therefore, 304 or 316 stainless steel is recommended for all feed equipment. Equipment specifications are the same as those for regular sulfite. Chelant products may be fed neat or diluted with condensate. Chelant feed rates must be carefully controlled based on feedwater hardness, because misapplication can have serious consequences.
Polymeric Dispersants. In most applications, polymeric dispersants are provided in a combined product formulation with chelants and / or phosphates. Dilution and feed recommendations for chelants should be followed for chelant-dispersant and chelant-phosphate-dispersant programs. Dilution and feed recommendations for phosphates should be followed for phosphate-dispersant programs. These combination programs typically have the best results with respect to boiler cleanliness.
Neutralizing Amines
Neutralizing amines are high pH chemicals that 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 attacks; however, it helps keep oxygen less reactive by maintaining an alkaline pH.
Neutralizing amines may be fed to the storage section of the deaerating heater, directly to the boiler with the internal treatment chemicals, or into the main steam header. Some steam distribution systems may require more than one feed point to allow proper distribution. An injection quill is required for feeding into a steam distribution line. Neutralizing amines are usually fed based on condensate systems pH and measured corrosion rates.
These amines may be fed neat, diluted with condensate or demineralized water, or mixed in low
concentrations with the internal treatment chemicals. A standard packaged pump skid and tank can be used for feeding.
Filming Amines
Filming amines are various chemicals that form a protective layer on the condensate piping to protect it from both oxygen and acid attacks. The two most common filming amines are octadecylamine (ODA) and ethoxylated soya amine (ESA). Combining neutralizing and filming amines is a successful alternative to protect against both acid and oxygen attacks.
The filming amines should be continuously fed into steam headers at points that permit proper
distribution. A single feed point is satisfactory for some systems. In every case, the steam distribution should be investigated and feed points established to ensure that all parts of the system receive proper treatment. Filming amines must be mixed with condensate or demineralized water. Water containing dissolved solids cannot be used, because the solids would contaminate the steam and could produce unstable amine emulsions.
The use of stainless steel tanks is recommended. Equipment specifications are the same as those for regular sulfite, except that a vapor-type injection nozzle or quill is required.
Computerized Boiler Chemical Feed Systems
Computerized boiler chemical feed systems are being used to improve program results and cut operating costs. These systems can be used to feed oxygen scavengers, amines, and internal treatment chemicals. A typical system incorporates a metering pump, feed verification equipment, and a microprocessor-based controller. These systems are often linked to personal computers, which are used to monitor program results, feed rates, system status, and plant operating conditions. Trend graphs and management reports can then be produced to provide documentation of program results and help in troubleshooting.
In many cases, these systems can be programmed to feed boiler treatment chemicals according to complex customized algorithms. For example, the chelant feed can be adjusted automatically, based on an analyzer or operator hardness test results, boiler feedwater flow, and minimum / maximum allowable product feed rates. Thus, chemical feed precisely matches system demand, virtually eliminating the possibility of underfeed or overfeed. Feed verification is another important facet of some computerized feed systems. The actual output of the pump is continuously measured and compared to a computer-calculated setpoint.
If the output doesn’t match the set point, the speed or stroke length is automatically adjusted. The benefits of this technology include the elimination of time-consuming drawdown measurements, the ability to feed most chemicals directly from bulk tanks, precise chemical residual control, and minimal manpower requirements. virtually eliminating the possibility of underfeed or overfeed. Feed verification is another important facet of some computerized feed systems. The actual output of the pump is continuously measured and compared to a computer-calculated setpoint. If the output doesn’t match the set point, the speed or stroke length is automatically adjusted.
The benefits of this technology include the elimination of time-consuming drawdown measurements, the ability to feed most chemicals directly from bulk tanks, precise chemical residual control, and minimal manpower requirements. virtually eliminating the possibility of underfeed or overfeed. Feed verification is another important facet of some computerized feed systems. The actual output of the pump is continuously measured and compared to a computer-calculated setpoint. If the output doesn’t match the set point, the speed or stroke length is automatically adjusted. The benefits of this technology include the elimination of time-consuming drawdown measurements, the ability to feed most chemicals directly from bulk tanks, precise chemical residual control, and minimal manpower requirements.
Statements and suggestions here are based on the best information and practices known to
us. However, it should not be assumed either that information is complete on the subjects covered or that all possible situations, safety measures, precautions, etc. have been included. These statements and suggestions are not intended to reflect provincial, municipal or insurance requirements or national safety codes; where applicable, those sources must be considered directly.
Since the conditions of use are beyond our control, Hayward Gordon makes no guarantee of results and assumes no liability in connection with the information contained herein. When dealing with installation, operation or maintenance of specific pumps, the Hayward Gordon manuals and instructions are advised that the product should be followed carefully.
BOILER SYSTEM CHEMICAL 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. Feedwater boilers often contain impurities, which impairs boiler operations and efficiency. Chemical additives can be used to correct the problems caused by these impurities. To improve feedwater quality, and steam purity, these chemicals can be injected directly into the feedwater or steam. 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 the 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 the boiler water and to control the buildup of dissolved solid levels in the boiler.
Blowdown is essential in addition to chemical treatments. List of Problems Caused By Impurities in Water 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 metal tubes, on the water-side tube surface. Scale acts as an insulator that reduces heat transfer, causes a decrease in boiler efficiency and excessive fuel consumption. More serious effects are overheating of tubes and potential tube failures (equipment damage).
Oxygen Attack Oxygen attack is the most common cause of corrosion inside boilers. Dissolved oxygen in feedwater can be very aggressive when heated and reacts with the boiler’s internal surface to corrosive components on the metal surface. Oxygen attack can cause further damage to steam drums, mud dams, boiler headers and condensate piping. Acid Attack Acid attack is another common cause 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.
BOILER SYSTEM CHEMICAL TREATMENTS AND FEED EQUIPMENT REQUIREMENTS
Product Feed Considerations An often-overlooked fact is that the water treatment program usually represents a small percentage of the overall costs of a boiler operation. However, poor treatment or equipment performance can create domino effects increasing operating and maintenance costs. For best results, all chemicals for internal treatment of a steam generating facility must be fed continuously and at proper injection points. Chemicals may be fed directly from the storage tank (neat) or may be diluted in a day tank with high-purity water. Certain chemicals may be mixed together and fed from the same day tank. Chemical feed points are usually selected as far upstream in the boiler water circuit as possible.
For chemical feeds beyond the feedwater pump or into the steam drum, the pump must be matched to the boiler pressure. For high-pressure boilers, proper pump selection is critical. The Basic Boiler System Schematic As shown in the figure, a steam generating system includes three major components for which treatment is required: the deaerator, the boiler, and the condensate system. Oxygen scavengers are usually fed to the storage section of the deaerator. The boiler internal treatment is fed to the suction or discharge feedwater pump, or to the steam drum. Condensate system feed points also vary, according to the chemical and the objective of treatment. Typical feed points include the steam header or other remote steam lines.
Chemical Treatments Lime Softening and Soda Ash Lime 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. Both hydrated lime and soda ash can be purchased as a liquid, a slurry or in a dry granular form. Specialized handling and preparation systems are required for dry storage and makedown.
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. Uncatalyzed sodium sulfite (Oxygen Scavenger) may be mixed with other chemicals.
The preferred location for sulfite injection is a point in the storage section of the deaerating heater where the sulfite will mix with the discharge from the deaerating section. If sulfite is fed alone, the following basic equipment is needed: • skid mounted dual metering pumps (duty / stand-by) with stainless steel wet end / trim • pulsation dampener • stainless steel relief valve • stainless steel check valve • stainless steel Y-strainer • stainless steel tubing valves, and fittings • flowmeter • calibration cylinder • pressure gauge with diaphragm seals • electrical junction boxes • dilution water line c / w static mixer (optional) • drip pan (optional) •
In all cases, an injection quill should be used. Sulfite shipped as liquid concentrate is usually acidic and, when fed neat, corrodes stainless steel tanks at the liquid level. Sulfite storage tanks must be fiberglass, or polyethylene. Lines may be PVC or 316 stainless steel. Catalyzed sulfite (Oxygen Scavenger) Catalyzed sulfite must be fed alone and continuously.
Mixing of catalyzed sulfite with any other chemical impairs the catalyst. For the same reason, catalyzed sulfite must be diluted with only condensate or demineralized water.
To protect the entire boiler system, including any economizers, catalyzed sulfite should be fed to the storage section of the deaerating heater. Caustic soda may be used to adjust the pH of the day tank solution; therefore, a mild steel tank cannot be used. Materials of construction for feed equipment are the same as those required for regular sulfite. Hydrazine (Oxygen Scavenger) Hydrazine is compatible with all boiler water treatment chemicals except organics, amines, and nitrates. However, it is good engineering practice to feed hydrazine alone. It is usually fed continuously into the storage section of the deaerating heater. Because of the handling and exposure concerns associated with hydrazine, closed storage and feed systems have become standard. Materials of construction are the same as those specified for sulfite.
Organic Oxygen Scavengers Many organic compounds are available, including hydroquinone and ascorbic acid. Some are catalyzed. Most should be fed alone. Like sulfite, organic oxygen scavengers are usually fed continuously into the storage section of the deaerating heater. Materials of construction are the same as those specified for sulfite. Neutralizing Amines Neutralizing amines are high pH chemicals that 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 attacks; however, it helps keep oxygen less reactive by maintaining an alkaline pH. Neutralizing amines may be fed to the storage section of the deaerating heater, directly to the boiler with the internal treatment chemicals, or into the main steam header. Some steam distribution systems may require more than one feed point to allow proper distribution. An injection quill is required for feeding into a steam distribution line.
Neutralizing amines are usually fed based on condensate systems pH and measured corrosion rates. These amines may be fed neat, diluted with condensate or demineralized water, or mixed in low concentrations with the internal treatment chemicals. A standard packaged pump skid and tank can be used for feeding. 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 two most common filming amines are octadecylamine (ODA) and ethoxylated soya amine (ESA).
Combining neutralizing and filming amines is a successful alternative to protect against both acid and oxygen attacks. The filming amines should be continuously fed into steam headers at points that permit proper distribution. A single feed point is satisfactory for some systems. In every case, the steam distribution should be investigated and feed points established to ensure that all parts of the system receive proper treatment. Filming amines must be mixed with condensate or demineralized water. Water containing dissolved solids cannot be used, because the solids would contaminate the steam and could produce unstable amine emulsions.
The use of stainless steel tanks is recommended. Equipment specifications are the same as those for regular sulfite, except that a vapor-type injection nozzle or quill is required. Internal Treatment Chemicals There are three major classifications of chemicals used in internal treatment: phosphates, chelants, and polymers. These chemicals may be fed separately or in combination; in most balanced treatment programs, two or three chemicals are fed together. The preferred feed point varies with the chemical specified. For example, when caustic soda is used to maintain boiler water alkalinity, it is fed directly to the boiler drum.
When caustic is used to adjust the feedwater pH, it is normally injected into the storage section of the deaerating heater. Phosphate Mono-, di- 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 boiler shutdown routine.
Phosphates are usually fed directly into the steam drum of the boiler, although they may be fed to the feedwater line under certain conditions. Treatments containing orthophosphate may produce calcium phosphate feed line deposits; therefore, they should not be fed through the boiler feed line. Orthophosphate should be fed directly to the steam drum boiler through a chemical feed line. Polyphosphates must not be fed to the boiler feedwater line when economizers, heat exchangers, or stage heaters are part of the boiler system. If the preboiler system does not include such equipment, polyphosphates may be fed to the feedwater piping provided that total hardness does not exceed 2 ppm.
In all cases, feed rates are based on feedwater hardness levels. Phosphates should be fed neat or diluted with condensate or high-purity water. Mild steel tanks, fittings, and feed lines are appropriate. If acidic phosphate solutions are fed, stainless steel is recommended. Chelants Nitrilotriacetic acid (NTA) and ethylenediamine tetraacetic acid (EDTA) are the most commonly used chelants. Chelants combine with hardness in water to form soluble compounds.
The compounds can then be eliminated by blowdown. • Chelants treatment is not recommended for feedwater with high hardness concentration • Chelants should not be fed if the feedwater contains a significant level of oxygen. • Chelants should never be fed directly into a boiler The preferred feed location for chelants is downstream of the feedwater pump. All chelant treatments must be fed to the boiler feedwater line by means of a stainless steel injection nozzle at a point beyond the discharge of the boiler feed pumps. If heat exchangers or stage heaters are present in the boiler feed line, the injection point should be at their discharge. Care should be exercised in the selection of metals for high-temperature injection quills.
At feed solution strength and elevated temperatures, mild chelating agents can corrode and copper alloys; therefore, 304 or 316 stainless steel is recommended for all feed equipment. Equipment specifications are the same as those for regular sulfite. Chelant products may be fed neat or diluted with condensate. Chelant feed rates must be carefully controlled based on feedwater hardness, because misapplication can have serious consequences. Polymeric Dispersants. In most applications, polymeric dispersants are provided in a combined product formulation with chelants and / or phosphates.
Dilution and feed recommendations for chelants should be followed for chelant-dispersant and chelant-phosphate-dispersant programs. Dilution and feed recommendations for phosphates should be followed for phosphate-dispersant programs. These combination programs typically have the best results with respect to boiler cleanliness. Neutralizing Amines Neutralizing amines are high pH chemicals that neutralize the carbonic acid formed in the condensate (acid attack). The three most commonly used neutralizing amines are morpholine, diethyleminoethanal (DEAE) and cyclohexylamine.
amines cannot protect against oxygen attacks; however, it helps keep oxygen less reactive by maintaining an alkaline pH. Neutralizing amines may be fed to the storage section of the deaerating heater, directly to the boiler with the internal treatment chemicals, or into the main steam header. Some steam distribution systems may require more than one feed point to allow proper distribution. An injection quill is required for feeding into a steam distribution line. Neutralizing amines are usually fed based on condensate systems pH and measured corrosion rates. These amines may be fed neat, diluted with condensate or demineralized water, or mixed in low concentrations with the internal treatment chemicals.
A standard packaged pump skid and tank can be used for feeding. 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 two most common filming amines are octadecylamine (ODA) and ethoxylated soya amine (ESA). Combining neutralizing and filming amines is a successful alternative to protect against both acid and oxygen attacks.
The filming amines should be continuously fed into steam headers at points that permit proper distribution. A single feed point is satisfactory for some systems. In every case, the steam distribution should be investigated and feed points established to ensure that all parts of the system receive proper treatment. Filming amines must be mixed with condensate or demineralized water. Water containing dissolved solids cannot be used, because the solids would contaminate the steam and could produce unstable amine emulsions. The use of stainless steel tanks is recommended.
Equipment specifications are the same as those for regular sulfite, except that a vapor-type injection nozzle or quill is required. Computerized Boiler Chemical Feed Systems Computerized boiler chemical feed systems are being used to improve program results and cut operating costs. These systems can be used to feed oxygen scavengers, amines, and internal treatment chemicals. A typical system incorporates a metering pump, feed verification equipment, and a microprocessor-based controller.
These systems are often linked to personal computers, which are used to monitor program results, feed rates, system status, and plant operating conditions. Trend graphs and management reports can then be produced to provide documentation of program results and help in troubleshooting. In many cases, these systems can be programmed to feed boiler treatment chemicals according to complex customized algorithms. For example, chelant feed can be adjusted automatically, based on analyzer or operator hardness test results, boiler feedwater flow, and minimum / maximum allowable product feed rates. Thus, chemical feed precisely matches system demand, virtually eliminating the possibility of underfeed or overfeed.
Feed verification is another important facet of some computerized feed systems. The actual output of the pump is continuously measured and compared to a computer-calculated setpoint. If the output doesn’t match the set point, the speed or stroke length is automatically adjusted. The benefits of this technology include the elimination of time-consuming drawdown measurements, the ability to feed most chemicals directly from bulk tanks, precise chemical residual control, and minimal manpower requirements.
Statements and suggestions here are based on the best information and practices known to us. However, it should not be assumed either that information is complete on the subjects covered or that all possible situations, safety measures, precautions, etc. have been included. These statements and suggestions are not intended to reflect provincial, municipal or insurance requirements or national safety codes; where applicable, those sources must be considered directly. Since the conditions of use are beyond our control, Hayward Gordon makes no guarantee of results and assumes no liability in connection with the information contained herein.
