Study On The Disposal Technology Of Hazardous Wastes Containing Heavy Metal With Cement Industry

The disposal technic of the hazardous waste is a very serious and urgent problem faced by the whole world.As this disposal of the hazardous waste containing heavy metal(HM)is special and hazardous,unproper technics and facility would be inefficient and lead to secondary pollution.Traditional technics all have limitations and demerits.With the giant scale of cement industry,alkaline and high-temperatured calcination circumstance and clinker solidification,precalcining cement technic comparatively have some advantages in the dispose of the hazardous waste containing HM.On the base of synthetically analysis of different waste disposal technics,the thesis clarifies the feasibility and advantages of precalcining cement technic in the disposal of the hazardous waste containing HM,studies the reaction mechanism between HM and clinker phase and the change of the existing conformation of HM.The thesis also studies the heavy metal stabilization mechanism and proportion,the change of clinker phase,and the security lixivium of HM in the cement clinker.The thesis draws following conclusions;(1)Compared with other technics,while disposing hazardous waste containing HM precalcining cement technic is much more clean and thorough.(2)With the increacing of the adulteration proportion of HM,the calcination of cement raw material is improved distinctly.PbO and Cr₂O₃ could decrease f-CaO but has a optimal adulteration proportion.Improvement effect of MnO₂,CuO,Ni₂O₃,SnO₂ and CO₂O₃ is very remarkable.A small quantity of CuO and NiO could markedly improve the quality of cement clinker,while the effect would almost be changeless with the increace of adulteration proportion.(3)The ionic radius of HM could influence the clinker sintering,formation of mineral phases and liquid-phase and the clinker Strength;With the augment of the ionic radius of HM,the burnability of cement raw material, the formation of C₃S and the clinker Strength is gradually increasing.According to the study of SEM and XRD test result,the adulteration of some kind of HM might be disadvantageous for the formation of liquid-phase.But with the augment of the ionic radius of HM,it might gradually improve and even increase the formation of liquid-phase.The liquid-phase of clinker adulterated with MnO2,C0203 or Cr₂O₃ is much more than that without those HM.While the liquid-phase of clinker adulterated with V₂O₅ or Ni₂O₃ is much less than that without those HM.(4)Under the situation of laboratory,the HM incorporation proportion of which the single-adulteration proportion is 1.0%respectively is;Mn 81.2%,Cr 67.3%,Co 72.8%, Ni 58.5%,Cu 61.0%,Zn 65.9%,Cd52.7%,Pb 63.1%,As 78.4%,V80.4%.While the disposal proportion of the multiple-adulteration HM respectively is;Mn 86.0%,Cr 87.7%, Co91.4%,Ni 89.5%,Cu 80.9%,Zn 81.1%,Cd75.1%,Pb 79.6%,As 88.3%,V87.6%.(5)The leaching quantity of HM in clinker has relations with the kind of HM,while not with the quantity in raw material.The leaching quantity of HM in clinker is bally tiny,wich means the HM has entered the stable alkaline inner space of clinker through physical package,chemical adsorption and crystallization process.When adjust the leaching liquor to be acidic,the leaching quantity of HM would increase greatly,which convincingly testifies the good HM disposal effect of cement clinker.(6)The incorporation of heavy metals to different clinker minerals is selective;Zn is concentrated in the interphase of clinker;As,Co,Cu and Ni is mainly incorporated by C₃A and C₄AF,but also partly in C3S and C₂S;Cd and Pb can not be separated clearly from interphase and C₃S and C2S,they are equably distributed in those mean clinker minerals.(7)When the raw cement material adulterated with sludge,battery,phosphor and printing ink at the proportion of 2.0%,the incorporation proportion of riM is all above 99%. In actual situation,the air circumstance in precalcining cement kiln is alkaline,close and negative-pressured,which is advantageous for the incorporation of riM in the waste.(8)When the raw cement material adulterated with sludge,battery,phosphor and printing ink at the proportion of 2.0%,the lixiviation proportion of HM in the waste is far below the national criterion.Combining the precalcining cement industry and the diposal process of domestic waste and hazardous waste containing HM,we would create an ecological united industry. So we could dispose the hazardous waste contenning HM more effectively,and partly substitute some cement material at the same time.And this would definitly be the development direction of ecological cement industry.