Study On The Preparation Mechanism And Technology Development Of Highly Effective Sorbent

It is very important to control SO₂ 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.