Study On Cement Production With Calcium Carbide Sludge

Calcium carbide sludge is a sort of industrial waste which is difficult to utilize. It is an effective approach to use calcium carbide sludge as one of raw materials for cement production. Firstly, physical property and chemical composition of calcium carbide sludge were all-around analysed. In order to solve the difficulty of calcium carbide sludge dehydration, flocculation experiment was done through adding flocculant to improve dehydration performance of calcium carbide sludge. Secondly, by substituting calcium carbide sludge for limestone as calcareous raw material to calcine cement clinker, effect of calcium carbide sludge batching on clinker calcination was studied, and then cement convention performance was determined. Finally, effect of calcium carbide sludge as composite material was studied focusing on alkali-activated effect in slag cement. Corresponding mechanism analysis was researched with modern testing method.Primary chemical composition of calcium carbide sludge is calcium hydroxide, and its content reaches as high as 87.81%. Dehydration of calcium carbide sludge is difficult because of its high viscosity and poor flowability. Through some flocculation treatment experiments, dehydration performance of calcium carbide sludge is studied by using polyacrylamide(PAM) as flocculant. As the results of test, PAM is a perfect flocculant that can remarkably improve dehydration performance of calcium carbide sludge. The best concentration and dosage of PAM are 0.08% and 90mg/L respectively. In aspect of operation characteristics, the best agitation is 200r/min for 30s in quick process followed by slow process at 20r/min for 3 min.By substituting calcium carbide sludge for limestone, raw material had fairly good burnability and cement clinker had high quality. With the addition of calcium carbide sludge increasing, f-CaO of the sample fell off, both apparent activation energy of clinker formation reaction and sinter temperature decreased. Reaction went easily and burnability improved a lot. Compared with clinker producing by limestone, clinker which used calcium carbide sludge as raw material had the identical mineral composition, and Alite formed well. With the addition of calcium carbide sludge increasing, water requirement of cement standard consistency increased, setting time became shortly and strength also presented a trend to increase in general. The various function indexes of cement measured up with national standards.As composite material of slag cement, calcium carbide sludge played alkali-activated effect on the slag. It could increase concentration of Ca(OH)₂ in fluid phase and shorten induction period of cement. It could also promote hydration of slag, and generate a lot of AFt, AFm and C-S-H gel. The suitable ratio of crystal to gel could improve early strength of cement bacause AFt, C-S-H gel, Ca(OH)₂ and AFm were mingled with each other closely. The addition content of calcium carbide sludge should not be too large, otherwise concentration of Ca(OH)₂ in fluid phase was too high, and a large number of Ca(OH)₂ megacrysts appeared harmful to strength development.