資源回收廠焚化爐爐管腐蝕問題探討

Investigation of Boiler Wall Tube Corrosion in Waste Incineration Plants

蘇俊吉(Chun-Chi Su) ； 陳孟宏(Meng-Hun Chen) ； 呂國旭(Goa-Shee. Leu)

《石油季刊》 54卷2期 (2018/06) Pp. 43-55

摘要

利用焚燒技術來處理固體廢棄物是國際的潮流，一般稱為固體廢棄物焚化廠(Solid Waste Iincinerators，SWI)，也有稱為廢棄物能源廠(Waste-to-Energy Plants, WTE)，垃圾焚化廠所燃燒的固體廢棄物種類多樣化，和一般燃煤、燃油或燃氣之鍋爐比較，焚燒後所產生的煙氣成分也相形複雜，常造成焚化爐內部相關組件腐蝕，文獻指出70%廢棄物焚化廠停爐原因和高溫腐蝕有關，因高溫腐蝕損傷所需的維修費用占整體維修預算33%左右，約占10%年度營業額，本文藉由分析破管洩漏之水牆管和過熱蒸氣管，來探討垃圾焚化廠鍋爐管之腐蝕機制，進而提出防蝕管理方案，分析結果顯示垃圾焚燒廠鍋爐管破管洩漏主要為高溫氯化腐蝕，造成外壁減薄所致，此外燃燒後之煙氣含鹼基金屬鹽(K/Na)以及重金屬(Zn/Pb)氯化物和氯化鐵(FeCl_3)之混合物構成低熔點共晶化合物，導致發生熔融氯鹽腐蝕，進而加速腐蝕速率，氯來源主要為焚燒含PVC之工業廢棄物和含NaCl之家庭廢棄物，在高溫分解和反應所產生的鹽酸(HCl)和氯氣(Cl_2)等產物。改善建議方案包括(1)降低工廠事業廢棄物焚燒量，以降低氯含量、(2)調整操作條件為富氧操作，以降低鹼基氯鹽的形成和沉積、(3)材質提升為含高鉻和鉬元素之鎳基合金，例如Alloy 625已被證實應用在垃圾焚燒廠水牆管有優異之抗蝕性和(4)強化吹灰效果，降低爐管外壁之飛灰沉積量，進而減緩高溫氯化腐蝕以及熔融氯鹽腐蝕；改善方案應考量破管洩漏所產生停產相關損失和維修成本來進行整體壽命循環成本(Life Cycle Cost，LCC)之經濟效益評估作最適化選擇。

關鍵字

廢棄焚化廠 ； 水牆管 ； 高溫氯腐蝕

並列摘要

Utilization of waste incineration technology for disposal of municipal solid waste has become more prevalent in many countries. It was commonly known as solid waste incinerators (SWI), also known as waste-to-energy plants (WTE). The types of solid wastes that are burned are diversified comparing with the boilers that burn coal, oil or gas. The components of flue gas generated after incineration are complicated that often cause corrosion for internal components of incinerator. According to the literature, 70% of waste incineration plants have been shut down due to high temperature corrosion. Maintenance costs due to high temperature corrosion damage account for about 33% of the overall maintenance budget, accounting for about 10% of annual turnover. In This paper, the corrosion mechanism of boiler tubes in waste incineration plants was investigated by analyzing the broken waterwall tubes and superheater tubes and then an anti-corrosion management solution were proposed. The analysis results showed that the leakage of the broken pipe was mainly caused by high-temperature chlorine corrosion resulting in thinning of the outer wall. In addition, The mixture contained chlorides of alkali metals salts(K/Na)、heavy metal (Zn/Pb) and ferric chloride (FeCl_3) for the flue gas after combustion forms a low melting eutectic compound. The compound resulted the occurrence of the molten chloride salt corrosion and then accelerated corrosion rate. Chlorine is mainly produced by the incineration of industrial waste containing PVC and domestic waste containing NaCl. The production of hydrochloric acid (HCl) and chlorine (Cl_2) were due to pyrolysis and reaction of PVC and NaCl. The recommendations for remedies includes (1)stopping the incineration of industrial waste containing PVC to reduce the chlorine content, (2) adjusting the operating conditions for rich-oxygen to reduce the formation and deposition of alkali metals chlorine salts, (3) upgrading the material to contain high chromium and molybdenum nickel based alloys. For example, alloy 625 have been proven to have excellent corrosion resistance for water-wall tubes in waste incineration plants and (4) enhanced soot blowing effectiveness to reduce the amount of ash fly deposits on the outside of the tubes, thereby slowing the high temperature chlorination corrosion and molten chloride salt corrosion. The optimal choose of above solutions should consider the life cycle cost(LCC) to assess the economic benefits associated with the production-related losses and maintenance costs caused by the leakage of the broken tubes.

並列關鍵字

Waste-to-Energy Plants ； Waterwall Tube ； High Temperature Chlorine Corrosion