摘要
综合治理SO_2的污染问题具有十分重要的意义。本文在快速水合脱硫剂的基础上,本着提高脱硫剂的固硫反应速度和粉煤灰对含钙细颗粒担载效果的目的,研究了快速水合脱硫剂的制备过程,并在此基础上提出了改进的脱硫剂制备方法,同时研究了石灰块制备浆液的输送过程。
石灰块的水合过程是决定脱硫剂在短时间内达到较高钙利用率的关键过程,其决定因素是Ca(OH)_2在水溶液中的粒径分布。为了实现Ca(OH)_2颗粒在水溶液中的细粉化,本文研究了不同水合制备条件下浆液中Ca(OH)_2的粒径分布规律,包括改变原料石灰产地、原料石灰尺寸和液固质量百分比,发现Ca(OH)_2在水溶液中发生严重的团聚现象。本文同时讨论了添加分散剂对浆液中Ca(OH)_2粒径分布的影响,研究结果表明六偏磷酸钠对减轻团聚有一定的作用。
另外,本文利用中试规模的浆液制备与输送系统,开展了石灰块水合制备的新式脱硫剂浆液和工业上采用的建材粉脱硫剂浆液的输送特性研究。研究结果表明,新式脱硫剂浆液的粒径小于工业脱硫剂浆液的粒径,不同的取样位置和输送速度对两种浆液的粒径分布基本没有影响。在相同的浓度下,新式脱硫剂浆液的阻力与工业脱硫剂相当,新式脱硫剂浆液放置100小时后,尽管其输送阻力增大,但仍能正常运行。
增强粉煤灰对含钙细颗粒的担载能力,减轻脱硫剂的磨耗剥落是提高快速水合脱硫剂在循环流化床中钙利用率的有效措施。本文利用振筛方法研究了不同粉煤灰粒径和粉煤灰改性方法对粉煤灰担载效果的影响。研究结果表明,粉煤灰的粒径越大,其担载效果越好,所制备脱硫剂经过振筛实验后仍能保持较高的固硫能力。通过火法、碱法和酸法改变粉煤灰的表面形态后,所制备脱硫剂的担载能力增强,并且脱硫剂振筛前后的固硫能力比原始粉煤灰脱硫剂有所提高。通过表面阳离子活性剂改变粉煤灰的表面电位后,未能增强粉煤灰对含钙细颗粒的担载能力,且所制得脱硫剂的固硫能力有所下降。
It is very important to control SO_2 pollution in China. In order to improve the sorbent activity and the adhesion between the fine Ca(OH)_2 particles and the fly ash particles, the sorbent preparation process was investigated for rapidly hydrated sorbent. The preparation mechanism was analyzed and the improved preparation method was proposed. In addition, the transportation process of a new sorbent slurry made by lime was investigated.
As for rapidly hydrated sorbent, the key point of realizing high desulfurization efficiency in short time is the lime hydration process, which is determined seriously by the Ca(OH)_2 particle size distribution in the sorbent slurry. To improve the Ca(OH)_2 particle distribution with reduced particle size in water, various preparation parameters were investigated, including the lime composition, lime size and the liquid-solid ratio. The results show that Ca(OH)_2 particles agglomerate in water. Furthermore, the effect of dispersant on the Ca(OH)_2 particle size in water was investigated. The results show that sodium hexametaphosphate can reduce Ca(OH)_2 agglomeration in water.
The particle size distributions and transportation characteristic of the new sorbent slurry made by lime and industrial sorbent slurry have been studied in a pilot-scale slurry preparation and transportation system. The results show that the particle size of the new sorbent was smaller than that of industrial sorbent. Transportation velocity and different measurement positions had little effects on the particle size distribution of both sorbent slurries. The transportation resistance of the new sorbent slurry was almost equivalent with the industrial sorbent slurry for the same slurry concentration. After the new sorbent was kept static for 100 hours, the slurry can still be successfully transportation although the transportation resistance increased.
It is an effective method to improve the calcium utility of rapidly hydrated sorbent in circulating fluidized beds by enhancing the adhesion between the fine Ca(OH)_2 particles and the fly ash particles and reducing the attrition rate of the sorbent. Vairous fly ash particle sizes and modification methods were investigated to enhance the ability of fly ash carrying fine particle by sieving experiment.
The results show that a bigger particle size of calcium sorbent had a lower attrition rate and remained high sulfur dioxide removal ability after sieving experiment. Fly ash modified through fire, alkali and acid methods changed the fly ash surface morphology and the sorbent prepared by these modified fly ash had lower attrition rate and higher sulfur dioxide removal ability than the original fly ash. However, fly ash modified through cationic surfactants to change its surface electric properties had no effect on the adhesion ability between the fine Ca(OH)_2 particles and the fly ash particles while the sulfur dioxide removal ability of sorbent made from this modified fly ash sorbent greatly reduced.
引文
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