CIESC Journal ›› 2017, Vol. 68 ›› Issue (12): 4615-4624.DOI: 10.11949/j.issn.0438-1157.20170627

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Limestone calcination kinetics in simultaneous calcination and sulfation under CFB conditions

CHEN Liang, WANG Ziming, WANG Chunbo   

  1. School of Energy, Power and Mechanical Engineering, North China Electric Power University, Baoding 071003, Hebei, China
  • Received:2017-05-16 Revised:2017-09-27 Online:2017-12-05 Published:2017-12-05
  • Supported by:

    supported by the National Key Research and Development Program of China (2016YFB0600701) and the Fundamental Research Funds for the Central Universities (2016XS105).

流化床锅炉内石灰石同时煅烧/硫化反应中煅烧动力学特性

陈亮, 王子铭, 王春波   

  1. 华北电力大学能源动力与机械工程学院, 河北 保定 071003
  • 通讯作者: 王春波
  • 基金资助:

    国家重点研发计划项目(2016YFB0600701);中央高校基本科研业务费专项资金项目(2016XS105)。

Abstract:

The interaction of limestone calcination and sulfation in simultaneous calcination/sulfation under circulating fluidized bed furnace conditions was studied by constant-temperature thermogravimetric setup. The sulfation reaction took place simultaneously with calcination and CaSO4 was formed in the particles when SO2 was present. Compared to pure calcination condition, the mass loss rate of limestone calcined in the presence of SO2 was lower but the final mass was higher. Limestone calcination was slowed down by SO2 presence and the calcination rate decreased with increase of SO2 concentration within the range of 0-0.3%. A probable mechanism was proposed that CaSO4 formation by SO2 sulfation with CaO of limestone particles upon calcination may fill or plug pores in CaO layer, impede CO2 transfer, and hinder calcination reaction. The mechanism of SO2 inhibition on limestone calcination was supported by product pore structure analysis and calculation that some pores were plugged and effective CO2 diffusion coefficient in pores was reduced. However, the calcination rate of limestone was increased with particle size decreased from 0.4-0.45 mm to 0.2-0.25 mm, no matter whether there was SO2 or not. Temperature also largely affected calcination, SO2 impeding effect was less pronounced at 880℃ than at 850℃, which was probably due to reduced pore plug of CaSO4 at 880℃.

Key words: calcination, sulfation, limestone, reaction kinetics, circulating fluidized bed, diffusion

摘要:

采用恒温热重实验台研究了循环流化床内石灰石同时煅烧硫化反应中煅烧反应与硫化反应的相互作用。当煅烧环境中存在SO2时,煅烧反应与硫化反应同时发生,并在颗粒中生成CaSO4。与纯煅烧工况相比,在含有SO2的气氛中煅烧石灰石时,颗粒的质量下降速率降低,而煅烧终质量升高。SO2的存在能够降低石灰石的煅烧速率,而且在0~0.3%的范围内,SO2浓度越高,煅烧越慢。对该现象提出以下机理:当煅烧过程中存在SO2时,SO2会与正在煅烧的石灰石颗粒的CaO层发生硫化反应生成CaSO4,所生成的CaSO4会堵塞颗粒的孔隙,增加CO2的扩散阻力,进而减慢煅烧反应速率。对煅烧产物孔结构的测试和计算表明在同时煅烧硫化中部分孔隙被堵塞、封闭,孔内CO2有效扩散系数下降,证明所提出的机理能够合理解释SO2对石灰石煅烧的减缓作用。随着粒径由0.4~0.45 mm减小到0.2~0.25 mm,无论反应环境是否存在SO2,石灰石的煅烧速率均加快。温度对煅烧速率有明显的影响,850℃下SO2对石灰石煅烧速率的减缓程度大于880℃,这可能是由于880℃下CaSO4对颗粒孔隙的堵塞作用下降导致的。

关键词: 煅烧, 硫化, 石灰石, 反应动力学, 循环流化床, 扩散

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