Research On High-performance Ceramsite Prepared By Cold Rolled Stainless Steel Dewatering Sludge

Stainless steel cold-rolled processing of dehydrated sludge is a byproduct solid waste of stainless steel processing characterized content with high Ca and low Si/Al, and has some heavy metal elements such as Cr﹑Ni,so it is classified as an hazardous waste. If not to be treated properly, this sludge would infect the environment seriously. These solid wastes with a large amount of deposition, such as coal gangue and fly-ash, need large area farmland for stack, and this way of simple stack is a severe pollution with environment. Therefore, it is significant for improving the relation of resource, energy and environment and promoting the sustainable development of the society that to exploit an effective reusing method of these wastes.The main purpose of this paper is searching for a recycling way of the sludge that coal gangue and fly-ash are chosen as the adjustment to produce ceramsite used in building area. Two directions are researched:one direction is to choose the sludge, coal gangue and some clay as the raw materials to produce lightweight inflation ceramsite, then take the bulk density, water absorption and mechanical strength as reference points, chiefly search for the influence of the experimental terms to ceramsite firing inflation, including composition of raw material, sintering temperature and time, it is found that gangue and sludge can be made into lightweight inflation aggregate with bulk density as0.64g/cm, water absorption as2.3%and crushing strength as2.60kp when it is produced by sludge30wt%, gangue60wt%, clay10wt%as raw material, sintering at1060℃for l0min; the other is to choose the sludge, fly-ash and some clay as the raw materials to develop high strength low water-absorption ceramsite, then determine the mechanism of every technological parameter influencing on ceramsite production, the ceramsite is prepared lastly with crushing strength as5.05kp,water absorption as3.7%and bulk density as0.93g/cm3when the optimum parameters are fly ash70wt%,sludge20wt%,clay10wt%as raw material, preheating temperature of400℃,preheating time of30min, sintering temperature of1125℃and preservation time of15min.The largest amount of sludge allocated in inflation light and high-strength ceramsite are respective30wt%and20wt%under the sintering temperature1060℃and1125℃which are evidently lower than ordinary ceramsite and energy-saving.Then some samples are carried out the leaching experiment of heavy metal toxicity on basis of the corresponding national standard, the results demonstrate that the two directions can solidify the toxic elements Cr,Ni very well with the dissolution values much lower than the limited values of national standard, verifying the method environmentally-friend.However, for developing the sludge ceramsite in practice, the sludge contains high Ca and low Si/Al, in which the flux content is overmuch, especially short fluxing agent.This adverse feature is remarkably bad for the sintering range, causing the sintering process control more difficult that should be taken seriously on the utilization of the hazardous waste.