鍋爐水汽系統(tǒng)的腐蝕與防護(hù)

1、會(huì)計(jì)學(xué)1鍋爐水汽系統(tǒng)的腐蝕與防護(hù)鍋爐水汽系統(tǒng)的腐蝕與防護(hù)第1頁(yè)/共58頁(yè)2凝汽式發(fā)電廠水汽系統(tǒng)流程凝汽式發(fā)電廠水汽系統(tǒng)流程第2頁(yè)/共58頁(yè)3第3頁(yè)/共58頁(yè)4第4頁(yè)/共58頁(yè)5第5頁(yè)/共58頁(yè)6第6頁(yè)/共58頁(yè)7第7頁(yè)/共58頁(yè)8在水側(cè)沉積物中蒸汽的蒸濃效應(yīng)在水側(cè)沉積物中蒸汽的蒸濃效應(yīng)第8頁(yè)/共58頁(yè)9第9頁(yè)/共58頁(yè)10第10頁(yè)/共58頁(yè)11鋼在水溶液中的腐蝕速度與鋼在水溶液中的腐蝕速度與pH值的關(guān)系值的關(guān)系第11頁(yè)/共58頁(yè)12低碳鋼第12頁(yè)/共58頁(yè)13第13頁(yè)/共58頁(yè)14Fe2+ + 2OH-Fe+ 2 e-Fe(OH)2H2OOH-+H+2H+H22 e +With dissolv

2、ed oxygen :4 e- + O2 + 2 H2O 4 OH-OH- 2 e-Anodic reaction陽(yáng)極反應(yīng)Cathodic reaction陰極反應(yīng)第14頁(yè)/共58頁(yè)15第15頁(yè)/共58頁(yè)16Iron corrosion product release from carbon steel in boiler feedwater.第16頁(yè)/共58頁(yè)17 Average copper release as a function of pH shows optimum pH in range of 8.8 to 9.2 for different copper-based alloy

3、s (Courtesy of EPRI)The best pH for protection of copper alloys is somewhat lower than the optimum level for carbon steel. For systems that contain both metals, the condensate and feedwater pH is often maintained between 8.8 and 9.2 for corrosion protection of both metals. The optimum pH varies from

4、 system to system and depends on many factors, including the alloy used. To elevate pH, neutralizing amines should be used instead of ammonia, which(氨水） (especially in the presence of oxygen) accelerates copper alloy corrosion rates. Also, amines form protective films on copper oxide surfaces that i

5、nhibit corrosion.銅的腐蝕與銅的腐蝕與pH值的關(guān)系值的關(guān)系第17頁(yè)/共58頁(yè)18 第18頁(yè)/共58頁(yè)19第19頁(yè)/共58頁(yè)20第20頁(yè)/共58頁(yè)21第21頁(yè)/共58頁(yè)22第22頁(yè)/共58頁(yè)23第23頁(yè)/共58頁(yè)24 堿腐蝕通常是散亂地發(fā)生在熱負(fù)荷高的水冷壁上堿腐蝕通常是散亂地發(fā)生在熱負(fù)荷高的水冷壁上。腐蝕損壞的爐管數(shù)在。腐蝕損壞的爐管數(shù)在10%以?xún)?nèi)，主要以?xún)?nèi)，主要由于爐水局由于爐水局部濃縮產(chǎn)生的濃堿所致。部濃縮產(chǎn)生的濃堿所致。 堿腐蝕造成管壁減薄，且有腐蝕坑。蝕坑的深度堿腐蝕造成管壁減薄，且有腐蝕坑。蝕坑的深度通常為通常為24mm（爐管壁厚（爐管壁厚56mm）。）。被腐蝕爐管的

6、被腐蝕爐管的機(jī)械性能、金相組織均正常，屬延性損壞。機(jī)械性能、金相組織均正常，屬延性損壞。當(dāng)管壁當(dāng)管壁減薄到一定程度時(shí)，在應(yīng)力作用下發(fā)生破裂，即鍋減薄到一定程度時(shí)，在應(yīng)力作用下發(fā)生破裂，即鍋爐爆管。爐爆管。 爐水爐水pH值越高，堿腐蝕的危險(xiǎn)性越大，爐水的酚值越高，堿腐蝕的危險(xiǎn)性越大，爐水的酚酞堿度與總堿度的比值越大，產(chǎn)生堿腐蝕的傾向越酞堿度與總堿度的比值越大，產(chǎn)生堿腐蝕的傾向越大大。 沉積物下堿腐蝕沉積物下堿腐蝕第24頁(yè)/共58頁(yè)25游離游離NaOHNaOH第25頁(yè)/共58頁(yè)26第26頁(yè)/共58頁(yè)27It is possible to have 100,000 ppm of caustic be

7、neath the deposit while the bulk water contains only about 5-10 ppm of caustic 第27頁(yè)/共58頁(yè)28第28頁(yè)/共58頁(yè)29沉積物下堿腐蝕機(jī)理第29頁(yè)/共58頁(yè)30堿性腐蝕示意圖堿性腐蝕示意圖第30頁(yè)/共58頁(yè)31腐蝕創(chuàng)削 第31頁(yè)/共58頁(yè)32Caustic stress corrosion cracking (embrittlement，脆變) of a boiler tube. Photomicrograph shows intercrystalline cracking（晶間裂紋）.第32頁(yè)/共58頁(yè)33第3

8、3頁(yè)/共58頁(yè)34第34頁(yè)/共58頁(yè)35第35頁(yè)/共58頁(yè)36第36頁(yè)/共58頁(yè)37第37頁(yè)/共58頁(yè)38第38頁(yè)/共58頁(yè)39第39頁(yè)/共58頁(yè)40第40頁(yè)/共58頁(yè)41第41頁(yè)/共58頁(yè)42Bracket,支架第42頁(yè)/共58頁(yè)43第43頁(yè)/共58頁(yè)44Vulnerable，易受損的Susceptible，易受影響的第44頁(yè)/共58頁(yè)45Erosion-corrosion（侵蝕腐蝕） of condenser tube wall. Erosion-corrosion of stainless alloy pump impeller.Impeller lasted 2 years in ox

9、idizing conditions; after switch to reducing conditions, it lasted 3 weeks! 第45頁(yè)/共58頁(yè)46 Boiler corrosion cause-and-effect diagram shows major types and causes of corrosion.downtime 停機(jī)in-leakage，漏入第46頁(yè)/共58頁(yè)47第47頁(yè)/共58頁(yè)48第48頁(yè)/共58頁(yè)49罪魁禍?zhǔn)椎?9頁(yè)/共58頁(yè)50第50頁(yè)/共58頁(yè)51第51頁(yè)/共58頁(yè)52第52頁(yè)/共58頁(yè)53在水側(cè)沉積物中蒸汽的蒸濃效應(yīng)在水側(cè)沉積物中蒸汽的蒸濃效應(yīng)第53頁(yè)/共58頁(yè)54第54頁(yè)/共58頁(yè)55鋼在水溶液中的腐蝕速度與鋼在水溶液中的腐蝕速度與pH值的關(guān)系值的關(guān)系第55頁(yè)/共58頁(yè)56第56頁(yè)/共58頁(yè)5