phosphate reaction in boiler water

}WjFGyIW=l+2|H!2]#nGK2TkqDt:?l7pu^fQ;Osg*={R_keOP'xRg8X8]!OZ,te?/+?C(zMf'nx#u Y'.ag@"DHar(3H|J/clia n(+g3' K^>mOX3+su;H*j!aV&d0 *{MAQ@Am/bDWx y?Xu0'^5WZ3ijxmV70)?JKnT/VZv3Lp'Q0\8 gV-M*NsSB.zA0:e"79=%q:VJ?}(' xref 0000003867 00000 n Condensate makeup is not required to be demineralized which can cause buildup of these impurities in boilers. Congruent phosphate control was derived to prevent the formation of free caustic by feeding orthophosphates to maintain a boiler water sodium-to-phosphate ratio at which theory surmised free caustic could not form. 0000102220 00000 n While he is well-versed in all Sentry products and applications, he is particularly focused on the food and beverage and power generation markets as well as emerging market development. 0000002228 00000 n o% G3fx6si9h.-rj/I[?H0ft*$=t:@w&)Q R,1GobL~+AX-2J(ard0o45BWZgG,(msiC\h N ~Q[&/#FN|[n-N gOukcz&.V=38(O2gn3!om=h$Q%^DI}%kQfvL9LzU !j Film-forming substances (FFS). Analysis results, conclusions, and recommendations to the plant are discussed. Unfortunately, conventional congruent control did not take into account the interaction of phosphate compounds with deposits and corrosion products, including iron oxides on boiler tube surfaces, and corrosion continued. FFS are a range of corrosion-inhibiting products for boiler chemistry, including film-forming amines (FFAs). %%EOF Corrosion continued to occur even when sodium to phosphate-pH control ranges were maintained according to theory. trailer The paper also discusses the use of the latest Electrical Power Research Institute guidelines for failure mechanism identification in boiler tubes and for monitoring cycle chemistry. Its also recommended that sludge conditioners using water-soluble polymers can help keep solids in suspension by a combination of dispersion, crystal modification and sequestration, in addition to phosphate treatment. -:Hv3tDbJ$8 :# 'GP`{Wu D;=4iDi-)!7!g hbspt.cta._relativeUrls=true;hbspt.cta.load(532305, '1466073b-4775-4785-b94a-81779404607c', {"useNewLoader":"true","region":"na1"}); Topics: 0000000016 00000 n 0000088218 00000 n rm6t.l"iFk(9[;nD|n`uSZaDbau{ lqS6@`'U2 Hn cs+l0Fpo: g,.%E\#/1K@Cb@R@vS"1EQI7D53et+S+P*q4..bkD6J]Et]#%@ghD,VyUu aI1zULJ @CI%Aah 8:: \q,!+HL4(HB3]G![~s!1]A[)Y+(U. 1. Some sodium hydroxide needs to be present in the boiler water to achieve the full benefits of {open_quotes}OH{close_quotes} treatment, but the concentration has to be strictly limited to reduce the risk of caustic gouging in the boiler, carry-over into the steam and damage to superheaters, reheaters and turbines. Phosphate attack as caustic corrosion in high-pressure boiler tubes, 360105* - Metals & Alloys- Corrosion & Erosion. However, corrosion occurred in the new high pressure plant, due to hydrogen damage and caustic gouging. 0000004136 00000 n 148 0 obj <> endobj Caustic attack, resulting from excessive gas-side heat flux relative to the internal coolant flow rate, was found. YX\5wb ,=#P:7FzQA|LXUX&cX^dEI?C/?la`%y;f=n~5Z,|*3i:=nG(^|*yv0tOFNv^CrxH Phosphate treatments have been used in boilers for more than 70 years. 0000019918 00000 n Maricite is one of the definitive corrosion products resulting from acid phosphate corrosion. 0000101755 00000 n As Upgrading feed rates have increased, the volume flow rate, and properties of the streams have changed to such extent that the boilers have suffered severe reliability problems due to the new, and adverse fireside conditions. Chemical-reducing substances. Phosphate treatment programs use blends of tri- di- and monosodium phosphate for pH control as well. Chemical treatment in industrial boilers can be complicated due to: Process steam carries heat from cogeneration plants. 0000001907 00000 n 0000006984 00000 n Some boiler-tube failures attributed to caustic gouging actually have been caused by reaction of sodium phosphate species with boiler tube steel, boiler tube oxides, or both. hXr}W#"G_T[[%2y#1pt H$*$fzO>wPoe(BY"?)Kd!4E&7}&@,+!/DT'K^;&Ne,_W)Y$-s- These factors must be evaluated carefully for each plant, as a standardized approach can lead to serious problems. A Steam and Water Analysis System (SWAS) comprised of properly selected sample conditioning equipment and on-line instrumentation is key to controlling and monitoring your system treatment regime. 0000002982 00000 n 0000011162 00000 n Chelants, such as ethylenediaminetetraacetic acid (EDTA), sometimes can be used to bind with metals to keep them suspended. Any Application, Choosing the appropriate treatment depends on a variety of factors, including boiler design and pressure, the effectiveness and reliability of the makeup water treatment system and the risk of impurity ingress and iron oxide carryover from condensate return. If impurities enter the boiler feedwater or corrosion develops inside the boiler, equipment can be damaged, the plant can experience unexpected downtime, and energy creation can be extremely ineffective. (L20'ui% [ 0!!(&M990Zus=73lVe7U@s"@N.(t30K i& v % cUd ey&g/; 0000003544 00000 n As the heart of the plant, these boilers are crucial to efficient energy creation. However, chelants should be used only with well-deaerated feedwater, excellent pre-treatment control and low feedwater iron concentrations. As operating pressures increased, the frequency of corrosion-related failures in phosphate-treated boilers also increased. 0000102008 00000 n 0000008167 00000 n 0000004468 00000 n The engineered changes required to correct the combustion and thermal hydraulic problems are described, as well as the rationale for introducing equilibrium phosphate treatment as the boiler water chemistry control corrective action. An example is a 1,300 psi (9 MPa) and 930 F (500 C) boiler. High concentrations of sodium phosphate and sodium hydroxide were used for conditioning drum boilers in the 1950`s. ;{\di&s1c->D.uxj+-nj2,|NAYCl g?,@z.vC8hS{6Um]=pfr:S+&Skq6Q^ {Zu7Kf This paper discusses the use of computational fluid dynamic simulation and other techniques to assess water and fireside conditions for the original, current, and future operating conditions (prior to and post boiler design modifications). 0 Problems of control and corrosion with PT led to a search for alternative methods of conditioning in other countries. 0000003581 00000 n In addition, heavy mineral deposits restrict heat transfer. The introduction of water impurities to the boiler can lead to higher conductivity, increasing corrosion potential. hTP1n0 John Powalisz, Director of International Sales, is dedicated to sharing his technical expertise and knowledge of sampling equipment and systems in power plants, refineries, chemical and food processing facilities garnered from more than 19 years with the company. 0000007118 00000 n {open_quotes}OH{close_quotes} treatment is simpler. 0000002041 00000 n Theyre often delivered via injection equipment, such as atomizers or sample quills. Many failures were attributed to ``free`` caustic generated by the nonstoichiometric precipitation of various phosphate compounds on boiler surfaces. Many medium- to high-pressure boiler systems, including carbon steel boilers, suffer from corrosion and impurities. %PDF-1.4 % 0000088443 00000 n A chemical-reducing agent can lower dissolved oxygen levels to prevent or minimize corrosion within the boiler and turbines. 0000060263 00000 n 0000020372 00000 n Additionally, corrosion and cooling/heating equipment can help maintain purified water with little contaminants from materials. 0000087950 00000 n This steam delivers the latent heat to the manufacturing process, leaving liquid condensate. For example, in steam generators that commonly operate at or below 600 psi, uncatalyzed or catalyzed sodium sulfite (Na2SO3) is a non-volatile oxygen scavenger that adds inorganic dissolved solids to the feedwater. 2. __^% 89L'v1$6+0~nc4eD# But in practice, the processing system introduces contaminants into the liquid stream and condensate return, including iron, copper, ammonia, magnesium, calcium and organic carbon. <<60FB01378AEBC7448D78B6BE7EF2A14B>]>> Congruent control was devised to prevent the formation of free caustic by feeding orthophosphates so as to maintain a boiler water sodium to phosphate ratio in a range where theory surmised free caustic could not form. 0000001036 00000 n As operating pressures have increased, the frequency of corrosion-related failures in phosphate-treated boilers has also increased. It is still necessary to limit the chloride in the boiler water to prevent hydrogen damage. products, including iron oxides on boiler tube surfaces. Contact us at +1-262-567-7256, orcomplete our online contact formfor more information. 0000020167 00000 n 0000092985 00000 n Phosphate corrosion is the name given to attack involving phosphate compounds having unique wastage morphologies, associated corrosion products and deposits. 0000008024 00000 n :x&L:~i*xY(hf[TdC endstream endobj 149 0 obj <> endobj 150 0 obj <> endobj 151 0 obj <>/Font<>/ProcSet[/PDF/Text]/ExtGState<>>> endobj 152 0 obj <> endobj 153 0 obj <> endobj 154 0 obj <> endobj 155 0 obj <> endobj 156 0 obj [/ICCBased 168 0 R] endobj 157 0 obj <>stream Precipitation was caused by inadequate heat flow inducing a departure from nucleate boiling (DNB), steam blanketing, and deposits. Industrial boiler water treatment helps protect low-pressure steam generators often found in co-generation plants. These materials include scavenger chemicals or corrosion inhibitors injected into the boiler or boiler feedwater. The chemical guidelines for {open_quotes}OH{close_quotes} treatment adopted overseas are reviewed, together with the evidence gained from operating plant, the problems that occurred and how these were overcome, EPRI guidelines are proposed for coal fired plant. Organic cycle chemistry based on FFS is being increasingly employed as an alternative to conventional treatment programs because they inhibit corrosion while maintaining clean heat transfer surfaces. EUF]+s&. 184 0 obj <>stream NlV,/94/y?)\9VtJ9hspeP"dY!Gu+[&L startxref 0000002361 00000 n All of these contaminants negatively affect the feedwater systems, boilers and turbines in the plant, potentially causing unnecessary downtime and equipment damage. Lx:?2h#9m$AH|-6Ut[mZDf&XZ= The boiler tubes, made of ASTM A 178 GrC, failed by precipitation of the phosphates used for the chemical treatment of the boiler water, coupled with contamination of the condensate with alkaline salts. Phosphate corrosion in high pressure boilers, CO boiler reliability: examination of failure mechanisms, root causes, corrective actions and monitoring required, Phosphate corrosion in high-pressure boilers, Caustic corrosion of convection tubing in a waste-heat boiler.

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