Water Treatment Issue(s) Nothing is Impossible…
BOILER CHEMICAL TREATMENT Posted on January 25, 2011 | 2 Comments
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[email protected] TREATMENT KIMIAWI PADA SISTEM BOILER Fungsi utama boiler adalah mentransfer energi dari bentuk gas panas yang diciptakan melalui bahan bakar hingga mengubah air menjadi uap. Uap panas atau air panas kemudian digunakan pada proses produksi. Air umpan seringkali mengandung unsur pengotor, yang menggangu kinerja & efisiensi pada sistem boiler. Aditif kimia dapat digunakan untuk mengatasi masalah yang diakibatkan oleh unsur pengotor tersebut. Untuk meningkatkan kualitas air umpan, dan uap yang baik, bahan kimiawi dapat di-injeksikan secara langsung ke air umpan yang digunakan. Keuntungan treatment secara kimiawi. • Meningkatkan kinerja boiler; • Menghemat bahan bakar dan biaya perawatan menjadi lebih murah; • Menurunkan waktu downtime mesin; dan • Melindungi aset produksi dari kerusakan dan meningkatkan daya pakai alat produksi. TREATMENT KIMIAWI UNTUK BOILER TIPE WATER-TUBE Air umpan terdiri atas air baku (make-up water) dan air kondensat (uap balik). Air baku umumnya mengandung pengotor, yang menyebabkan deposit pada boiler. Zat pengotor yang umum dijumpai termasuk alkalinitas, silika, besi, oksigen terlarut, kalsium & magnesium (hardness). Blowdown, secara periodik ataupun otomatis adalah proses pembuangan air pada boiler, untuk membatasi konsentrasi zat pengotor dan mineral-2 lain yang terkandung pada air boiler. Blowdown penting sebagai penunjang treatment kimiawi. Masalah-Masalah yang disebabkan oleh Zat Pengotor pada Boiler
Kerak. adalah deposit mineral yang biasa terjadi. Kerak adalah padatan terjadi akibat reaksi dari zat pengotor dan permukaan pipa logam. Kerak berperan sebagai insulator memperlambat transfer panas, yang menyebabkan efisiensi menurun dan pemakaian bahan bakar jadi meningkat. Efek yang lebih serius adalah overheating dan penyebab kerusakaan pada pipa-2 boiler. Korosi. Korosi disebabkan oleh kandungan oksigen terlarut pada air umpan. Reaksi oksidasi menjadi semakin agresif bila mendapat energi panas menciptakan korosi pada permukaan logam. Kerusakaan akibat korosi dapat terjadi pada drum boiler, header, dan pipa-2 kondensat. Asam. adalah juga penyebab korosi pada logam. Air dikatakan asam bila pH air umpan berada dibawah kisaran 8,5. Alkali karbonat diubah menjadi CO2 oleh panas dan tekanan pada boiler. CO2 terbawa sepanjang uap air diproduksi. Ketika uap air mengembun, CO2 menjadi larut dalam air membentuk asam karbonat (H2CO3) dan secara langsung menurunkan pH pada air kondensat. Asam tersebut juga akan merusak pipa kondensat. PERSYARATAN TREATMENT KIMIA BOILER Produk Treatment. Faktanya adalah biasanya program treatment memerlukan prosentase relatif kecil dari keseluruhan biaya operasi pada boiler. Akan tetapi, kinerja treatment yang buruk menyebabkan efek domino yang meningkatkan biaya operasi maupun pemeliharaan boiler. Untuk hasil terbaik, seluruh chemical untuk treatment internal harus digunakan secara kontinyu dengan dosis yang cukup. Chemicals dapat diumpan langsung ke tangki air umpan. Kimia tertentu boleh dicampur penggunaannya pada waktu bersamaan. Posisi injeksi chemical biasanya diletakkan lebih tinggi dari posisi sirkuit boiler. Untuk posisi feeder chemical dibawah pompa air umpan, pompa harus disesuaikan dengan tekanan boiler.
Skema Dasar Boiler. Seperti pada gambar, sistem pembangkitan uap terdiri atas 3 komponen utama; deaerator, boiler, dan sistem kondensat. Oxygen scavenger diumpankan pada tangki deaerator. treatment internal diumpankan pada pompa air umpan atau drum boiler. Treatment Kimiawi Lime Softening dan Soda Ash. Lime dicampurkan ada air baku untuk mengendapkan kalsium, magnesium, dan silika pada air. Soda ash dicampurkan untuk mengendapkan hardness non-bicarbonate. Proses ini terjadi pada tangki clarifier diikuti oleh proses pertukaran ion melalui demineralization. Kedua bahan kimiawi ini dalam bentuk cair, juga granular. Oxygen Scavengers. deaerator menghilangkan oksigen pada air umpan; akan tetapi, oksigen yang masih trace masih ada dan menyebabkan masalah korosi. Oxygen scavengers dicampurkan pada air umpan. Bentuk umum oxygen scavenger adalah sodium sulfite. Sodium sulfite murah, efektif, dan mudah diukur kandungannya pada air. Sulfite Tanpa Katalis (Oxygen Scavenger) Sodium sulfite tanpa katalis dapat dicampurkan dengan agen kimiawi lainnya. Lokasi injeksi sulfite diantara tangki air umpan (economize tank dan boiler. Jika hanya sulfite yang digunakan, maka diperlukan peralatan dasar sebagai berikut: Pompa injeksi kimia Pipa2, kelep, fitting, saringan yg terbuat dr stainless steel atau PVC flowmeter Alat ukur tekanan Panel kelistrikan Alat pengaduk atau mixer Sulfite umumnya dalam bentuk cairan, berkarakter asam, dimana akan membuat sifat korosif terhadap bahan yg digunakan. Tangki sulfite HDPE. Sulfite dengan katalis (Oxygen Scavenger) Sulfite dengan katalis HARUS digunakan secara mandiri tanpa dicampur kimia lain dan diumpan secara sinambung. Air yang digunakan juga HARUS air murni (demineralized water). Umumnya jenis ini diumpan pada tangki air. Hydrazine (Oxygen Scavenger) Hydrazine boleh digunakan bersama agen kimia lainnya kecuali yang bertipe organik, senyawa amine dan jenis nitrat. Akan tetapi sangat baik bila digunakan secara mandiri. Hidrazine biasanya menggunakan sistem umpan tertutup karena cukup berbahaya jika terkena paparan terhadap manusia. Oxygen Scavengers Organik Senyawa organik juga dapat digunakan seperti hydroquinone dan asam askorbat (vitamin C). Sebaiknya diumpan secara mandiri dan bersinambung. Neutralizing Amines Neutralizing amines ialah jenis kimiawi basa kuat yg mampu menetralisir asam karbonat yg biasanya terbentuk pada kondensat. Yg termasuk jenis ini diantaranya: morpholine, diethyleminoethanal (DEAE) and cyclohexylamine. Neutralizing amines tidak melindungi dari korosi akibat oksigen tetapi hanya menghambat aktivitas oksigen tersebut karena sifat basa kuatnya. Filming Amines Filming amines adalah jenis kimia yg membentuk lapisan tipis pada pipa kondensat dengan tujuan melindungi dari aktivitas korosif baik akibat oksigen maupun asam. Beberapa jenis diantaranya: octadecylamine (ODA) and ethoxylated soya amine (ESA). Kombinasi kedua jenis tersebut umum digunakan. Internal Treatment Chemicals There are three major classifications of chemicals used in internal treatment: phosphates, chelants, and polymers. These chemicals may be fed either 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 routine boiler shutdown. 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 boiler steam drum 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 preboiler 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 hightemperature injection quills. At feed solution strength and elevated temperatures, chelating agents can corrode mild steel 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 attack; 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 system 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 amine is a successful alternative to protect against both acid and oxygen attack. 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 herein are based upon 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 circumstances, 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 pertaining to that product should be followed carefully. Tel: +62 (21) 6457-334 Fax: +62 (21) 6456-256 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. Boiler feedwater often contains impurities, which impairs boiler operation 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 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. 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 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). Oxygen Attack 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 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 feed 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. 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 feedwater pump suction or discharge, 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. Sulfite (Oxygen Scavenger) Uncatalyzed sodium sulfite 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 preboiler 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 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 attack; 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 system 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 amine is a successful alternative to protect against both acid and oxygen attack. 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 either 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 routine boiler shutdown. 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 boiler steam drum 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 preboiler 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, chelating agents can corrode mild steel 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 chelantphosphate-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 attack; 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 system 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 amine is a successful alternative to protect against both acid and oxygen attack. 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 computercalculated 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 herein are based upon 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 circumstances, 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.
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This entry was posted in Water Treatment Articles. Bookmark the permalink. 2 RESPONSES TO “BOILER CHEMICAL TREATMENT”
syafii | October 22, 2012 at 9:23 am | Reply bang….knp ya sebagian dr artikel ini berbahasa inggris….mohon kalau bisa semua menggunakan bhs.indonesia…biar org awam seperti saya bisa memahami…tentunya juga bisa sangat berguna dlm pekerjaan saya ….demikian bang….terima kasih….
yohanes | November 27, 2015 at 2:14 pm | Reply ane bingung.. kok jadi inggris ya pembahasan setengah dibawahnya,,, cape deh..
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