7Silica Membentuk deposit pada boiler/waterside Terbentuk sebagai magnesium silicate atau silicic acidSelective silica carryoverTidak dapat dikontrol secara mekanikal dengan steam separator
8Selective Silica Carryover Silica terlarut pada steamDikontrol dengan pembatasan kandungan silica pada air boilerDikontrol dengan pembatasan tekanan operasi boilerDikontrol dengan mempertahankan kontrol pH yang tinggi
9Bentuk Kerak Besi/Iron Kerak besi biasanya ditemukan dalam boiler sebagai salah satu atau lebih bentuk berikut:Bentuk kompleks dengan calciumBentuk kompleks dengan phosphateHematite Fe2O3Magnetite Fe3O4
13Problem Kerak Boiler tube failure Disebabkan karena pengurangan heat transfer dan tube overheatingUnder-deposit corrosionDisebabkan karena konsentrasi tinggi dari bahan bersifat korosif concentration of corrosive agents (dapat berupa NaOH)
14Apa yang dapat dilakukan untuk mencegah kerak/deposit Kontrol secara ketat terhadap kualitas air umpan (sesuai dengan batas kontrol)Mengaplikasikan internal treatment
15Internal Treatment Options Presipitasi kontaminanPelarutan (solubilize) kontaminanPendispersian (disperse) kontaminanSoluble contaminants are blowdown more easily than suspended contaminantsMetal oxides are generally suspended material in the boiler water and must be dispersed to be removed by the blowdown
16Program Internal Treatment Secara Umum/Konvensional Coagulation programsOrganic sludge conditionersPhosphate residual programsPhosphate-Polymer ProgramsChelates & Chelate / Polymer programsAll-Polymer programCoagulation treatment programs were commonly used in the past ( ). Today, modern, inexpensive pretreatment technology has made their use almost obsolete.Phosphate residual programs are best suited for feedwaters that are consistently below 60 ppm hardness, have low magnesium, and have silica content greater than one-third the magnesium content.Organic sludge conditioners:Tannins are particularly effective in conditioning sludge containing a high percentage of calcium carbonate. Normal application is treating high hardness feedwater for boilers operating below 400 psig (30kg/cm2); tannins are rarely used today.Lignins are stable at temperatures as high as 315 C and are effective in conditioning phosphate sludges as well as iron oxide.Starches are used when high feedwater silica levels result in abnormal quantities of silica-type chemical reaction products (sludges) Starches can also be used when oil contamination is a continuing problem.Polymers can be used alone or in combination with chelates or phosphates. Certain polymers have the capability of dispersing iron and silicates while sequestering calcium and magnesium.Phosphate-Polymer Programsare well suited to boilers with feedwater hardness levels of up to 3 ppm, and where concentrating mechanisms are suspect. They mormally give better results than conventional phosphate organic programs.Chelates&Chelate/Polymer Programs must be fed continuously into dearated feedwater. The presence of any oxygen increases the potential for corrosion by the chelating agent. Therefore, an oxygen must be fed ahead of the feed point of the chelating agent.All-Polymer programs (Transport-Plus) contain nochelates, phosphates, or phosphonate and require no supplemental dispersant to be effective. They offer superior performance over any other currently available programs.
17Historical Overview of Nalco’s Internal Treatment Programs Soda ash, Sodium Aluminate, and PhosphatesChelationSynthetic organic polymersTransport-PlusSoda ash, sodium aluminate, and phosphates, used with natural organics such as tannins or lignins, were among the first precipitating programs developed. These programs are used with higher hardness feedwaters, boilers then tend to be dirtier than the newer programs. Precipitating programs were not designed for iron control.Chelation as a means of hardness control through solubilization was the next type of program developed. Two chelates are generally used, nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic acid (EDTA). This program offers superior cleanliness over phosphate programs, however it had a major weakness, the potential for corrosion if overfed or fed to a system containing dissolved oxygen.Synthetic organic polymers aided chelation programs, but they could not alter chelate’s corrosive nature.Transport-Plus was developed to offer the cleanliness of chelates without the potential for boiler corrosion, even if overfed.
20Perlakuan secara Koagulasi (Coagulation Treatments) Calcium hardness dipresipitasikan sebagai Calcium Carbonate.Magnesium hardness dipresipitasikan sebagai Magnesium Hidroksida atau Magnesium SilicateThe principles and mechanisms of coagulation programs have been well defined and tested over the years. Essentially, a coagulation program preferentially precipitates feedwater calcium hardness as calcium carbonate, while the feedwater magnesium hardness is preferentially precipitated as magnesium hydroxide or magnesium silicate. Feedwater calcium in either the bicarbonate or sulfate form is preferentially precipitated as calcium carbonate. Calcium sulfate scale can be completely inhibited by maintaining enough soda ash (Na2CO3) to completely react with the expected calcium sulfate levels entering the boiler via the feedwater.Maintaining a CO3-2 to SO4-2 ratio of greater than 0.01 in the boiler water will assure that the proper reaction takes place and that no calcium sulfate scale will form. A properly applied coagulation program further ensures this preferential reaction by incorporating a small amount of phosphate. The phosphate can react with calcium sulfate to preferentially precipitate tricalcium phosphate.Feedwater magnesium, either the bicarbonate or chloride form, is preferentially precipitated as magnesium hydroxide or magnesium silicate.Once the preferred precipitation reactions occur, the precipitated sludge must be conditioned so that it is free flowing and non-adherent. The addition of specific organic materials will control the crystal growth of the precipitated CaCO3 and Mg(OH)2. The controlled crystal growth allows the formation of large, flocculated suspended solids that can be easily removed by normal blowdown procedures.In summary, coagulation programs preferentially precipitate the feedwater calcium and magnesium hardness. The precipitated species are conditioned in the boiler water by organic chemicals that permit them to agglomerate and flow freely without adhering to the boiler metal surface. The conditioned sludge (reaction products) is then easily removed by blowdown.
21Aplikasi Program Koagulasi: Program Koagulasi dapat diaplikasikan bila;Tekanan operasi boiler < 350 psigHardness feedwater/air umpan > 60 ppmAlkalinity air boiler < 500 ppmA coagulation program is best suited for low-pressure boilers (no greater than 350 psig; 24.5 kg/cm2) where the feedwater hardness is greater than 60 ppm. Because of the low-pressure, high feedwater hardness limitations, coagulation programs are rarely used today.To treat a feedwater with high sodium bicarbonate alkalinity, where alkalinity reduction is required to avoid exceeding the 500 ppm maximum "P" alkalinity, it is best to reduce the feedwater alkalinity externally using dealkalization or other conventional methods. Rarely, direct addition of sulfuric acid to the feedwater is used to reduce alkalinity. This method is dangerous, and requires exact control with automatic monitoring equipment.
22Program Koagulasi Kekurangan: Kebaikan: Dapat diaplikasikan untuk air umpan dengan kandungan hardness yang tinggi.Kekurangan:Cycle operasi boiler rendahTDS air boiler tinggiJumlah blowdown banyak – pembuangan panas (wastes heat)Pembentukan kerakThe main advantage of a coagulation program is its application in boilers that have extremely high feedwater hardness (60 ppm or greater). This program permits a plant to operate a boiler using high feedwater hardness without having to purchase pretreatment (softening) systems. On the other hand, the large amounts of TDS and suspended solids limit the cycles of concentration that may be carried; thus more blowdown is required. Increased blowdown is quite expensive in terms of energy and water lost. In addition, this type of program is more susceptible to scale formation.Coagulation treatment programs were commonly used in the past ( ). Today, modern, inexpensive pretreatment technology has made their use almost obsolete.The best solution to boiler scale is proper softening of the makeup water followed by a good chemical control program. Occasionally, this cannot be done, and for these situations, a coagulation program may be the best choice.By far the most common treatment technologies in use today utilize pre-softening to reduce residual hardness in the makeup to very low levels.
23Calcium dipresitasikan sebagai calcium phosphate Program PhosphateCalcium dipresitasikan sebagai calcium phosphateMagnesium dipresitasikan sebagai magnesium hydrosidaTricalcium phosphate has an extremely low solubility. Hence, when properly controlled, the addition of phosphate to boiler water removes calcium so completely and efficiently that calcium sulfate, calcium carbonate, and calcium silicate scales can be prevented. In the presence of sufficient alkalinity, the actual phosphate precipitate formed is hydroxyapatite, which is a less sticky, more readily conditioned reaction product than tricalcium phosphate.Although phosphates can also precipitate magnesium as magnesium phosphate, proper boiler chemistry will preferentially precipitate magnesium as a less adherent and more easily conditioned magnesium hydroxide or magnesium silicate. The hydroxide can come from added sodium hydroxide, for waters low in alkalinity, or from the decomposition of naturally occurring carbonate and bicarbonate alkalinity.
24Phosphate Technology Ortho phosphates Mono-, di-, tri- sodium phosphatesPoly PhosphatesSodium hexa meta phosphateSodium hepta meta phosphateSodium tripoly phosphateTetra sodium pyro-phosphatePhosphate residual programs are acceptable where makeup hardness is less than 60 ppm. Numerous chemicals can furnish the phosphate radical necessary for internal softening treatment; compounds of the orthophosphate ion, PO4-3 (mono-, di-, and trisodiurn phosphates), are the most widely used. Other phosphate ions are meta (PO3-) and pyro(P2O7-4). Some of these salts are called polyphosphates because they form inorganic polymers. Among these are the glassy sodium polyphosphates (hexa- and heptametaphosphate) and crystalline sodium polyphosphates such as sodium tripolyphosphate and tetrasodium pyrophosphate. The meta- and pyrophosphates can be described as molecularly dehydrated phosphates. When added to water, these phosphates 're-hydrate" (at a rate that is temperature-dependent) to the orthophosphate form from which they were derived.Although this discussion of phosphates is rather limited, it is a reminder that the precipitation of tricalcium phosphate (or hydroxyapatite) in the boiler can occur only when the phosphate in use has been converted to trisodium orthophosphate by heat and reaction with boiler alkalinity. This is true for all phosphate treatment for calcium scale control.This slide is not an all inclusive list of phosphate types in use: there are others. However, all are classed as ortho or poly phosphates.
25Phosphate Technology Titik Injeksi Ortho phosphate Diinjeksikan lansung ke drum boilerPoly phosphateDiinjeksikan ke line air umpan
26Phosphate Technology Kelebihan Mudah dimonitor dan dikontrol Tidak memerlukan air umpan dengan kemurnian tinggiDapat diaplikasikan pada boiler tekanan tinggiDikenal luasMemiliki perizinan FDA dan USDAFluktuasi hardness air umpan dapat ditanganiResidual PO4 tidak bersifat korosifPO4 residual yang tinggi - buffer untuk ekskursiBiaya relatif murah1. Easy to monitor and control - test equipment is cheap, easy to use and readily available. Testing is easy for operators to use with accuracy.2. Do not require "ultrapure" feedwater: program can tolerate some hardness3. Can be used at high pressure up to about 1200 psig, but use is normally with pressures below 600 psig4. Well understood and accepted by industry. These programs have been in use for some years, and considerable experience exists with their use.5. Many types of phosphate can be FDA/USDA approved6. Can handle fluctuations in feedwater hardness, but this should not be construed as a license to ignore the requirement for good control of pretreatment softening equipment.7. Residual PO4 is noncorrosive to boiler metal.8. Carry large PO4 residuals, so there is more room for feedwater quality excursions should they “accidentally” occur.9. Less expensive ingredients mean overall lower program cost compared to some other technologies.
27Phosphate Technology Kekurangan Menghasilkan presipitasi/endapan pada sistemKelebihan alkalinity dapat menyebabkan korosiMemerlukan lebih banyak blowdownJika demikian, lebih banyak panas hilang dan lebihbanyak pemakaian bahan kimiaKemungkinan dapat menyebabkan terjadi kerakUmumnya diaplikasikan bersama sludge dispersant1 . Precipitates of calcium carbonate and magnesium hydroxide can result in scaling and deposition, BTU losses, tube overheating and failure2. Excess alkalinity can result in caustic corrosion in some units. In units with severe concentrating mechanism, especially when combined with high heat flux, there can be a high localized concentration on caustic soda which can cause caustic gauging3. May require more blowdown (lower boiler water concentrations); this results in greater BTU, chemical, and water losses4. Causes suspended solids, therefore supplemental dispersant is necessary
29Sludge ConditioningPadatan Calcium Phosphate dan Magnesium Hydroxide yang tidak terlarut terbentuk (Sludge)Particulate Iron Oxide kembali ke kondensatPadatan mengendap pada permukaan panas boilerTransfer panas tidak seimbang, dapat beresiko pipa pecah
31Pengaplikasian Sludge Conditioners Produk Starch OrganicJika Mg:SiO2 ratio < 2Jika minyak mengkontaminasi air boilerDalam pabrik pengolahan makananProduk Lignin OrganicUntuk mengkondisi Calcium Phosphate & Iron Oxide
32Titik Injeksi Sludge Conditioners Tangki DeaeratorJalur air umpan boilerLansung ke steam drum
34Chelants Melarutkan ion logam Membentuk senyawa kompleks yang sangat larutIon-ion bersaing (PO4, SiO2, OH) mengurangi efetivitas
35Chelant yang Umum EDTA (Ethylene diamine tetracetic acid) Memiliki 6 sisi logam kompleks termasuk atom nitrogen dan oksigenNTA(Nitrilo triacetic acid)Memiliki 4 sisi logam kompleks
36Perbandingan Kedua Jenis Chelant NTA lebih stabil secara thermal900 psig max. untuk NTA,600 psig max. untuk EDTABiaya NTA lebih murah dari pada EDTAEDTA memkompleks Magnesium lebih baik dari pada NTAEDTA memkompleks besi lebih baik dari pada NTAEDTA memiliki perizinan FDA
37Aplikasi ChelantsHarus diinjeksikan secara kontinu pada jalur air umpan memakai injection quill & piping stainless steelTidak boleh ada oksigenKonsentrasi residual pada air boiler harus dijaga di bawah 10 ppm sebagai CaCO3 untuk meminimalkan korosiAkurasi kontrol pemakaian diperlukan
38Chelant Control Ranges Boiler Pressure Chelant Residualpsig (Bar) ppm as CaCO3400 (30)( )( )
39Kelebihan Chelant Tidak terbentuk endapan Permukaan perpindahan panas lebih bersihFrekwensi acid cleaning lebih sedikitTerkadang dapat mengurangi jumlah blowdown
40Kekurangan Chelant Biaya lebih mahal Memerlukan kontrol yang sangat ketat terhadap mutu air umpanLebih sulit untuk test kontrolResidual berlebih bersifat korosifIon-ion yang bersaing dapat bersifat korosif
41Program Phosphate-Polymer Mempresipitasikan hardness dan besiPolymer mendispersikan sludge hasil reaksi, untuk menghindari pengendapan pada pipaBoiler lebih bersih daripada program phosphate konvensional
42Aplikasi Program Phosphate-Polymer Hardness air umpan lebih rendah dari 3 ppmSoftener atau air baku dengan hardness rendah
43Program Phosphate-Polymer KelebihanPerizinan FDA/USDADapat diaplikasikan pada air umpan dengan T.hardness tinggi.Boiler lebih bersihLebih mudah ditest/dikontrol.Tidak mahal.Tidak bersifat korosifDisadvantageRequires much stricter control of feedwater hardness and chemical program
44Program Phosphate-Polymer KekuranganMemerlukan kontrol yang ketat terhadap hardness air umpan dan residual bahan kimia
45Program All-Organic Polymer All-polymer program, polymeric blendTidak mengandung chelant atau phophate, tidak memerlukan tambahan dispersanBerfungsi dengan melarutkan Calcium & Magnesium dan mendispersi besi dan partikulat lainnyaTidak bersifat agresif terhadap metal boiler
46Program All-Organic Polymer Diinjeksikan ke tangki deaerator untuk boiler bertekanan < 600 psig dan menggunakan air softenerProgram/dosis injeksi berdasarkan batas atas kontrol untuk hardness dan besi, bukan nilai rata-rataKekurangan dosis (<20% dari yang diperlukan) dapat membentuk deposit Calcium Acrylate pada boiler
47Program All-Organic Polymer Tidak bersifat korosif untuk internal boilerMemberikan hasil boiler yang lebih bersih - clean boilers – meningkatkan heat transferTransport 100% of hardnessTidak bersifat volatil – aman untuk turbinHardness air boiler dapat ditestTest produk sederhana/mudahProgram passivasi yang baik
48Program All-Organic Polymer Pengaplikasian terbatas untuk tekanan boiler <1000 psigMemerlukan air umpan dengan hardness rendahBeberapa formulasi mengkontribusikan ammonia ke steam
49Definisi Korosi 2 e- + 1/2 O2 + H2O <---> 2OH- Korosi adalah proses elektrokimia, dimana metal (teroksidasi) kembali ke bentuk alamiahnya (natural state).Sell Korosi (corrosion cell) : anoda, katoda dan elektrolit harus ada2 e- + 1/2 O2 + H2O <---> 2OH-2OH- + Fe <---> Fe(OH) e-Cathodic (reduction) half cell reactionAnodic (oxidation) half cell reaction
50Korosi pada Boiler Tipe korosi Korosi akibat oksigen/oxygen corrosion Konsentrasi alkalinity/alkalinity concentrationKorosi akibat caustic/caustic corrosionKorosi akibat asam/Acid corrosionKorosi akibat chelant/Chelant corrosionErosi/korosiCorrosion can occur throughout a boiler system. The most common causes of corrosion are the shown on this slide.Different kinds of corrosion are found in different parts of the boiler. Corrosion in boiler systems is not a simple matter to define because the various chemistries involved are often interrelated and complex.Corrosion of boiler metal is generally considered to be one of two types: general corrosion or localized corrosion. General corrosion is a uniform attack of the metal surface resulting in a slow, even wastage of the boiler metal. General corrosion does not normally result in enough metal loss to cause tube or wall thinning and subsequent tube failures.Localized corrosion results in a fairly rapid and severe metal loss in a small, localized area. Such corrosion results in gouge or pitting attack that can cause tube failures in a very short time. The concentrating corrosion mechanism ( such as may be found under iron oxide deposits) is an example of severe, localized corrosion.
51Korosi Akibat OksigenOksigen yang terlarut di air merupakan materi dasar terjadinya reaksi di katoda
52Korosi Akibat OksigenANODE: Natural Metal Electrically Charged Metal ElectronsFe0 Fe e-CATHODE: Electrons Oxygen Water Charged Ion2e /2 O2 + H2O 2(OH-)Hydroxyl Ions FormCorrosion ProductsHydroxide or OxideOH-O2Metal Ions DissolveOxygen corrosion is an electrochemical process. Iron dissolves at the anodes, releasing electrons that are subsequently consumed by oxygen at the cathode. Pits occur where metal leaves the surface.Above picture misrepresents the pitting process slightly for clarity. - The actual accumulation or tubercle formed from corrosion products usually covers the pit rather than being located adjacent to it.High flow rates will increase the corrosion rate because the reactants are brought in contact faster and corrosion products are also scoured away faster.ActiveAnodicAreaLess Active Cathodic AreaElectron flow
53Korosi akibat Oksigen/Oxygen Corrosion Dapat terjadi pada sepanjang sistemMekanisme sama seperti sel korosi akibat oksigenMekanisme korosi dipengaruhi oleh:Konsentrasi oksigenTemperaturpHOxygen corrosion can be found throughout the boiler cycle from the deaerator to the final condensate system. The basic chemical mechanism is the same as that found in most waters where oxygen exists in the presence of iron. It produces a very severe localized corrosion.Three variables affect the corrosivity of oxygen: oxygen concentration, temperature, and pH. As the temperature or oxygen concentration increase, the corrosion rate accelerates. pH and oxygen corrosion are inversely related: as the pH increases, the oxygen becomes less corrosive. This is one reason that alkaline conditions are preferable for boiler waters.
55Bahan kimia : Oxygen Scavenger Korosi Akibat OksigenBahan kimia : Oxygen Scavenger
56Oxygen Scavenger yang Umum Dipakai SulfiteHydrazineHydroquinoneDEHA (Diethyhydroxylamine)MEKO (Methylethylketoxime)CarbohydrazideErythorbic acidChemical scavengers are reducing agents that react directly with dissolved oxygen. The reaction products are removed through boiler blowdown or system venting. Chemical oxygen removal is the last opportunity to prevent oxygen from entering the boiler. Nalco offers four types of oxygen scavengers that are:-SulfiteHydrazineELIMIN-OXSUR-GARD
57ONDEO Nalco’s Oxygen Scavengers Sulfite/Catalyzed SulfiteCarbohydrazide (Elimin-Ox)Erythorbic acid (SUR-GARD)ONDEO Nalco PatentsNalco offers four types of oxygen scavengers that are:-Sulfite/ Catalyzed sulfiteELIMIN-OXSUR-GARD
58Sodium Sulfite - Inorganic Oxygen Scavenger 2Na2SO3 + O > 2Na2SO48,6 ppm per 1 ppm oxygen terlarutPada temperatur kamar sodium sulfite mengurangi oxygen sebesar 30 % dalam 10 menitPada temp.> 120 oC, masih dibutuhkan waktu reaksi lebih dari 30 detikDi atas 150 °C ,oxygen mengkorosi permukaan metal/besi lebih cepat dari pada waktu reaksi sulfite dengan oksigenSodium sulfite is used to remove dissolved oxygen from the boiler feedwater. Oxygen removal reduces the potential for corrosion in the feedwater and boiler system.When operating properly, spray and tray type deaerators are capable of mechanically reducing the level of dissolved oxygen to less than 7 ppb. However, even at trace levels, dissolved oxygen is extremely corrosive and must be removed. Sodium sulfite reacts with, “scavenges”, the dissolved oxygen, and forms harmless products that are removed through boiler blowdown.Sodium sulfite (Na2SO3) is a reducing agent that chemically scavenges dissolved oxygen by reacting directly with it.Since the presence of dissolved oxygen helps drive the corrosion cell, its removal can shut down the corrosion mechanism.Reducing oxygen corrosion will help control boiler water iron levels and the insulating corrosion products that result.Catalyzed sulfite is preferred to uncatalyzed sulfite because of the very short reaction times available in boiler feedwater systems.Catalyzed Sulfite ( dengan katalis Cobalt Salt ) lebih baik
59Kelebihan Sulfite Reaksi cepat Lebih murah Lebih mudah dianalisa Perizinan FDA/USDAOverfeed of catalyzed sodium sulfite will:1. Result in excessive energy loss due to the increased blowdown caused by high levels of dissolved solids;2. Significantly increase the cost of the treatment program.Underfeed of catalyzed sodium sulfite will result in serious corrosion.
60Kekurangan Sulfite Menambah solid/padatan ke air boiler Kemungkinan dapat menambah jumlah blowdownTidak ada efek passivasi pada metal boilerTidak sesuai untuk boiler dengan tekanan operasi > 600 psi (40 bar)Terurai menjadi H2S & SO2Overfeed of catalyzed sodium sulfite will:1. Result in excessive energy loss due to the increased blowdown caused by high levels of dissolved solids;2. Significantly increase the cost of the treatment program.Underfeed of catalyzed sodium sulfite will result in serious corrosion.
61Elimin-Ox Oxygen Scavenger Bersifat volatil/tidak menambah solid Mempasivasi permukaan metalElimin-Ox is an all-volatile oxygen scavenger developed in response to concerns associated with handling hydrazine.Elimin-Ox is used to both remove dissolved oxygen, as well as enhance metal passivation.Oxygen removal reduces the potential for corrosion in the feedwater and boiler system.
62Reaksi Elimin-Ox Elimin-Ox * + 2O2 2N2 + 3H2O + CO2** + 2O2 2N2 + 4H2O + 2N2H4 + CO2**Elimin-Ox helps complete the deaeration process by chemically removing the trace levels of dissolved oxygen remaining after mechanical deaeration.At low temperatures (<150oC) Elimin-Ox reacts directly with dissolved oxygen.At higher temperatures (>150oC) Elimin-Ox forms hydrazine which reacts directly with oxygen as follows:N2H4 + O2 ---> H2O + N22NH3 + N2 + H2>205 C* As Carbohydrazide** Maximum 29 ppb/ppm Elimin-Ox Fed
63Sur-Gard Non-volatile Oxygen Scavenger Menghilangkan Dissolved Oxygen Mengurangi potensi korosiBereaksi dengan oksigen secara kimiawiMempasivasi permukaan metalFood Grade ApprovalSUR-GARD is a non-volatile oxygen scavenger.SUR-GARD is used to both remove dissolved oxygen, as well as enhance metal passivation.Oxygen removal reduces the potential for corrosion in the feedwater and boiler system.SUR-GARD helps complete the deaeration process by chemically removing the trace levels of dissolved oxygen remaining after mechanical deaeration.SUR-GARD also helps prevent corrosion by passivating the metal surfaces in the feedwater section of the boiler system.
64Surgard, Eliminox - Organic Oxygen Scavengers KelebihanTidak menambah solid/padatan ke air boiler, sehingga tidak menaikkan jumlah blowdown.Mempasivasi permukaan metal, sehingga dapat melindungi dari korosi.Surgard sudah diizinkan FDA/USDAKekuranganReaksi lebih lambatLebih mahal
65Hydrazine N2H4 + O2 ---> 2 N2 + 2H2O toxic material - safe storage and handling issues become paramountN2H4 + O > 2 N H2O3 N2H4 ---> 4 NH3 + N2at temp. > 390°F (200°C)
66C6H4(OH)2 + 1/2O2 ---> C6H4O2 + H2O Hydroquinonereacts quickly with oxygen at room temperaturedecomposition -> acetates, CO2, and H2Osome toxicity issuesC6H4(OH) /2O2 ---> C6H4O2 + H2O
67Diethylhydroxylamine volatile neutralizing aminehydroquinone may be added to increase low temp. scavenging ratedecomposition > 148°C (300°F) is rapid (seconds)acetic acid, CO2, acetaldehyde, ethylamine, low mwt organics, and NH3 at temperatures above 275°C4 (CH3CH2)2NOH O2 ---> 8 CH3COO H+ + 2N H2O
68Condensate System Pre-Treatment Process Process Process DEAERATORProcessProcessThe steam/condensate system extends from the boiler all the way back to the deaerator.Blowdown flash tankLow pressure steamFlashtankCondensateReceiver
69Condensate Corrosion Destroys capital equipment repair, maintenance, loss of efficiencyCan affect end productsif condensate contacts final productsWill lead to increased boiler deposits of corrosion products (metal oxides)
70Primary Causes of Condensate Corrosion Carbon dioxideOxygenAmmoniaAbove are the primary corrodents in condensate.Specific systems may also need to deal with miscellaneous other contaminants:organic acidsSO2/H2S from sulfite decomposition or process contamination
71Condensate Corrosion Carbonic acid corrosion dissolved carbon dioxide and the resulting carbonic acid, is the most common source of condensate corrosionCO2 + H2O <---> H2CO3 <---> H+ + HCO3-Fe + 2 H HCO > Fe(HCO3)2 + H2
72Condensate CO2 Corrosion Sources of CO2thermal decomposition of carbonate alkalinity in the boilerin-leakage of air into the condensate system2 NaHCO3 ---> Na2CO3 + CO2 + H2ONa2CO3 + H2O <---> 2 NaOH + CO2
73Condensate CO2 & O2 Carbonic acid and oxygen in the presence of oxygen 2 cathodic reactions are possibleoxygen may react with other corrosion products2 Fe + O2 + 4H+ ---> 2 Fe H2O4 Fe+2 + O2 + 4H+ ---> 4 Fe H2O4 Fe(HCO3)2 + O2 ---> 2 Fe2O3 + 4H2O + 8 CO2
74Chemical Condensate Treatment Neutralizing aminesFilming aminesACT ProgramChemical treatment programs for steam/condensate systems come in three varieties.No matter which treatment program is used, it has to be able to distribute through the steam/condensate system to the point of condensation.
75Neutralizing Amines Neutralizes carbonic acid and increases pH Effective against other acidsNeutralizing amines react with all acids.It is not uncommon to see amine usage increase in an account for, seemingly, no good reason. Often, some kind of organic contamination has occurred. This can be something as simple as a cleaner leaking into a condensate system. When these organics break down in the boiler, volatile organic acids are formed which leave with the steam, condense in the condensate system and depress pH. A neutralizing amine will neutralize these acids the same way carbonic acid is neutralized.
76RNH2 + H2CO3 ---> (RNH3)+ + (HCO3)- Neutralizing AminesNeutralization of carbonic or other acidsBasicity or pKacyclohexylamine 10.6diethylaminoethanolmorpholineRNH2 + H2CO > (RNH3)+ + (HCO3)-pKa is a function of solution temperaturekeep pH above 8.8
77Simple Acid/Base Neutralization Amine hydrolysis in water:R-NH H2O « R-NH OH-Neut. amine water Neut. amine hydroxideCO2 hydrolysis in water:CO H2O « H2CO3 « H HCO3-carbon dioxide water carbonic acid bicarbonateNet reaction:R-NH H2CO3 « R-NH HCO3-Neut. Amin carbonic acid Neut. amine bicarbonateNeutralizing amines react with CO2 by means of a simple acid/base neutralization reaction.The amine hydrolyzes in water to generate a captive OH- (hydroxide).Likewise, the CO2 hydrolyzes in water to generate carbonic acid. Carbonic acid is very unstable in water and quickly dissociates to H+ (acid molecule) and bicarbonate.The net result of the two reactions is amine bicarbonate.When feeding only neutralizing amines, we typically feed for a slight excess of amine. The OH- generated then serves to raise the pH.
78Optimum pH Control Increases copper corrosion Increases mild steel corrosionNeutralizing amines do not directly address corrosion caused by oxygen. However, copper and iron corrosion product solubilities are very low at a pH of approx As a result, corrosion products precipitate and form a semi-protective layer at the surface. This also decreases oxygen diffusion rate to the metal surface, again limiting the corrosion rate.An all-neutralizing amine program is not the best choice in high alkalinity waters because it can easily be cost prohibitive.Most systems will require a blend of several amines to assure proper protection of the entire system.8.08.59. 2Optimum pH
79a blend of amines is typically required Neutralizing Aminesa blend of amines is typically requiredAmine AAmine BNeutralizing amines can be characterized by following:The V/L ratio which is the amount of amine in the vapor or steam vs the amount in the liquid or condensate. This characteristic determines how well the amine distributes through the system.The molecular weight and basicity affect the amine’s strength. These characteristics determine how many kgs of amine are required to neutralize or treat a kg of CO2.We usually feed blends of amines to obtain the desirable characteristics required to treat an extensive, complicated condensate system.Prefer VapourPrefer Water
80Disadvantages Not effective against oxygen corrosion Expensive in high alkalinity systemsDistribution can cause problemsa blend of amines is typically requiredDifficult to testNeutralizing amines do not directly address corrosion caused by oxygen. However, copper and iron corrosion product solubilities are very low at a pH of approximately As a result, corrosion products precipitate and form a semi-protective layer at the surface. This also decreases the oxygen diffusion rate to the metal surface, again limiting the corrosion rate.An all-neutralizing amine program is not the best choice in high alkalinity waters because it can be cost prohibitive. (1 molecule of amine for every molecule of CO2.)All systems will benefit from a blend of several amines to assure protection of the entire system.
81Filming Amines Long chain amines that absorb onto the metal surface Function at the lower pH range of 6.5 to 9.0O2CO2O2O2CO2O2CONDENSATEO2O2CO2O2CO2O2O2Filming amines build a protective barrier layer between the metal surface and the aggressive condensateNeutralizing amines are typically fed in conjunction with neutralizing amines, since the pH must be between 6.5 to 9.0 for film formation to occur. The ideal pH (optimum corrosion protection) occurs in the pH range 7.5 to 8.0.CO2O2O2CO2CO2CO2O2CO2Metallic wallProtective filming amine layer
82A filmed metal surface promotes dropwise condensation
83Filming Amines Protect against acids, O2, and ammonia Dosage dependent on surface area and not contaminant concentrationCost effective in high CO2 systemsBecause filming amines do function by formation of a barrier layer, they are effective against most condensate contaminants; i.e acids, oxygen, and ammonia.They also effectively protect against air-in-leakage.They are cost effective for high alkalinity and low % condensate return.
84Filming Amines Limitations/Considerations Film formation takes timepH control still necessaryOverfeed may cause sticky deposits and “gunk” ball formationShould be fed after turbines and condensate polishersWill clean up old depositsBut if they were so wonderful, everyone would be using filming amines. And they’re not. Filming amines do have several significant drawbacks as shown above.Note following in addition to above:pH > 9 causes the film to strippH<6.5 causes the amine not to filmFilmers have very low V/L ratios and can have problems distributing throughout the system.
85Advanced Condensate Treatment (ACT) ACT is an innovative condensate corrosion program that uses new technology to prevent operational problems.
86Innovative ApproachBrand New Approach!Instead of neutralizing carbonic acid or using a filming amine,Nalco researchers discovered safe emulsifiers which provide a barrier to corrosion in the condensate system.
87So Safe, it is in the stuff you eat ... Nalco’ ACT program is made from food grade materials used in many food products.The ACT program has received U.S. FDA clearance under 21 CFR Part 173 for Secondary Direct Food Additives Permitted in Food for Human Consumption; Boiler Water Additives.
88Provides Safe Corrosion Barrier to Metal Surfaces no filmer
89It serves the regulatory needs It serves the safety needs ACT ProgramIt serves the regulatory needsIt serves the safety needsIt serves the technical needsIt serves the economic needsUnder ordinary circumstances, only facility managers and engineering staffs concern themselves with the implications of improper boiler water treatment. With respect to regulatory issues and condensate treatment, wider awareness is important. An amine-related problem certainly affects more than the engineering staff. It also affects all people working around the plants. The symptoms of exposure to amines are nausea, vomiting, dizziness and the like. Amines can be introduced inhalation, ingestion, absorption through the skin and skin and eye contact. Obviously, the higher the level of exposure, the more serious the potential risk. In worst cases, exposure to amines can cause liver and kidney damage and a variety of respiratory problems.Less often, concern is raised not because someone has been exposed to a high concentration of amines, but because of the application of the steam treated with amines. The areas of concern are:1. Food Processing Plants regulated by the Food & Drug Administration (FDA)2. Meat, Poultry and egg processing plants regulated by the USDA3. Hospitals where the steam is used for the preparation of food, sterilization of surgical instruments or direct humidification of room air4. Offices and other types of buildings where steam is used for heat or humidification.Reportable quantities - In some states in the USA and some countries, there have been restriction limited the amount of hazardous chemicals in the system or even limit amount of spilled chemical.ACT fills in the technical gaps which conventional amines treatment cannot succeed.Our customers want to buy products that work, deliver REAL value and provide a quantifiable ROI!
90Benefits Effective against carbonic acid Effective against oxygen corrosionEffective against erosion corrosionEasy to test forDosage dependent on surface area and not contaminant concentrationCost effective in high CO2 systemsOperate at lower pH and not alter pHWe know there is technical gap that the existing amine products cannot fill in. Here are some properties that ACT can add more value.When feed is interrupted, typical neutralizing amine cannot adequately protect the system due to a rapid drop of pH. The typical filming amine protection is also decrease while the film move off.In some applications or industries, it does not allow the contamination of nitrogen with some system for example refining.Unlike typical filming amine, ACT does not bond to itself that can cause gunk ball.ACT, unlike typical filming amine, has no cleaning property that remove the corrosion products before filming on to the surface.
91Disadvantages Must be fed to the steam header Not volatile Same as other filmers, ACT needs to be fed directly to steam header.It is not volatile, therefore, flash steam areas require satellite feed