Study On Sintering Characteristics Of Straw Pulp Black Liquor In The Process Of Alkali Recovery In Fluidized Bed

In today’s society,the demand for paper is growing with the rapid economicdevelopment.Papermaking consumes a very large amount of water,and the pulpingprocess will produce black liquor which can causing serious environmentalpollution.Black liquor treatment has been the problems we need to be resolved,especially in the black liquor of straw pulp.It has characteristics of highviscosity,low lignin content, high silica content, hemicellulose and high chlorinecontent,which lead to its treatment very difficult.In a variety of black liquortreatments, fluidized bed combustion technology is most suitable.It can burn lowcalorific value material,the investment is lower,it has high alkali recovery rate anddoes not cause secondary pollution.This paper uses the fluidized bed combustiontechnology to deal with black liquor of straw pulp.The effect of soak dechlorinationof grass fiber materials and the combustion characteristic of black liquor of strawpulp in fluidized bed is investigated in the paper.Let the wheat straw and rice straw soak for48hours in boiled deionized water,then we can conclude that rice straw and wheat straw in the percentage of chlorinewere0.69%and1.62%. Comparative tests are made in different time andtemperature, the change trends of leaching speed and the highest leaching rate ofchlorine(rice straw is79.5%,wheat straw is88.51%) are gained.The combustion test of black liquor was carried out in bench-scale fluidizedbed with sodium-based zeolite, aluminum-based zeolite and calcium-based zeoliteas bed materials.We can conclude that the type of bed material, operatingtemperature,and calcium carbonate as an additive impact of black liquor onsintering characteristics.And the bed material particle size variation withtemperature were analyzed.The combustion test showed that calcium-based zeoliteis the most suitable bed material and CaCO3could effectively suppress thesintering.Under800℃,the alkali recovery test was carried out with calcium-basedzeolite as bed materials.We can conclude that alkali recovery rate is76.02%andoptimal quality of calcium carbonate is19.5percent of black liquor solids.