CIESC Journal ›› 2020, Vol. 71 ›› Issue (7): 3313-3321.DOI: 10.11949/0438-1157.20191566

• Energy and environmental engineering • Previous Articles     Next Articles

Effect of calcium phosphate monobasic on ash fusion and sintering characteristics of cornstalk

Youjian ZHU1(),Xianxian ZHANG1,Yiming CHEN1,Xuehong WU1,Haiping YANG2,Hanping CHEN2()   

  1. 1.Energy and Power Engineering Institute, Zhengzhou University of Light Industry, Zhengzhou 450002, Henan, China
    2.State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074, Hubei, China
  • Received:2019-12-23 Revised:2020-03-22 Online:2020-07-05 Published:2020-07-05
  • Contact: Hanping CHEN

磷酸二氢钙对玉米秆灰熔融烧结特性的影响研究

朱有健1(),张显显1,陈奕名1,吴学红1,杨海平2,陈汉平2()   

  1. 1.郑州轻工业大学能源与动力工程学院,河南 郑州 450002
    2.华中科技大学煤燃烧国家重点实验室,湖北 武汉 430074
  • 通讯作者: 陈汉平
  • 作者简介:朱有健(1987—),男,博士,讲师,yjzhu01@hotmail.com
  • 基金资助:
    国家自然科学基金项目(51706210);河南省教育厅项目(16A470003)

Abstract:

Agricultural straw usually contains high alkali metals, which can easily cause high temperature melting and sintering of the boiler during the combustion process and affect the normal operation of the boiler. In this work, the effect of a phosphate additive, Ca(H2PO4)·H2O (calcium phosphate monobasic, CPM), on ash sintering characteristic of a typical agricultural biomass cornstalks was investigated by using standard ash fusion measurement and ash sintering test at 700—1000℃. Meanwhile, the reaction behavior and the possible reaction products from the calcination of calcium phosphate monobasic and potassium salts at elevated temperature were investigated. The results showed that, during the heat treatment at elevated temperatures, temperature and mixing ratios of CPM and potassium salts had significant influence on reaction products. Meanwhile, when the mixture of CPM is excessive, in addition to the two reactions, there is high temperature decomposition reaction of CPM and secondary reaction between the reaction products. The reaction of CPM and potassium salts started at 300℃, with mainly Ca2P2O7, Ca(PO3)2, KCa(PO3)3 at 300—600℃ and mainly K2CaP2O7 at 700—900℃. Thermal decomposition of CPM and secondary reactions between the resultant products occurred when the P/K molar ratio was larger than 1, in addition to the reaction between CPM and K salts. In addition, it was found that K2CO3 has a higher reactivity with CPM compared to KCl. The addition of CPM in cornstalk significantly increased the ash fusion temperature and reduced the sintering degree by forming high melting phosphates mainly Ca9MgK(PO4)7 and CaKPO4. These results can provide theoretical guidance for the application of phosphorus-based additives in alleviating ash fusion and sintering issues during agricultural biomass combustion.

Key words: combustion, cornstalk, fusion and sintering, calcium phosphate monobasic

摘要:

农业秸秆通常含有较高的碱金属,在燃烧过程中易造成锅炉高温熔融烧结问题,影响锅炉正常运行。使用灰熔点测试仪并结合灰样烧结度测试研究磷酸二氢钙添加剂对玉米秆灰熔融烧结特性的影响规律。此外,使用固定床管式炉研究了磷酸二氢钙与两种不同钾盐之间的反应特性。结果表明燃烧温度和磷酸二氢钙与钾盐混合比例对反应产物影响显著。在碱金属盐过量时,磷酸二氢钙与碱金属盐在温度高于300℃时开始反应,300~600℃产物以Ca2P2O7、Ca(PO32、KCa(PO33为主,700~900℃反应产物主要为K2CaP2O7。当磷酸二氢钙过量时,除磷酸二氢钙与钾盐的反应外同时存在磷酸二氢钙的高温分解反应以及反应产物间的二次反应。此外,研究发现磷酸二氢钙与K2CO3的反应活性显著高于KCl。在玉米秆中添加磷酸二氢钙后可在灰分中形成高熔点的Ca9MgK(PO47和CaKPO4,显著提高生物质灰的熔融温度并在实验温度范围内有效缓解玉米秆的熔融烧结。研究成果可为磷基添加剂在缓解生物质锅炉灰熔融烧结中的应用提供理论指导。

关键词: 燃烧, 玉米秆, 灰熔融烧结, 磷酸二氢钙

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