Study On Production Of Cement Clinker By Adding Lead-zinc Tailings And Solidification Of Heavy Metals

Tens millions tons of tailings have been accumulated in a certain lead-zinc mining area, heavy metals and other harmful substances from these tailings might permeated into surface water and groundwater, this has become a heavy threat to the water safety of Xiangjiang river. In this paper, combined with the geographical advantages that the lead-zinc mining area was adjacent to cement plant, the lead-zinc tailings was used as raw materials instead of quartz mining and nonferrous ash, researched the preparation of cement clinker. The aim of this paper was to solve the pollution problems of heavy metals in a certain lead-zinc mining area, and provide materials to cement plants through resourcing by tailings.The tests were conducted under the following conditions:the tailings additions of0-18.0%and the temperature of1300℃,1350℃and1400℃The burn-ability of raw meal was tested by the glycerol alcohol method; the compressive strength and flexural strength were measured according to cement mortar strength detection method (ISO). Mineral composition, chemical composition and microstructure of clinkers were characterized by using XRD and SEM. The heavy metals content in clinker was analyzed by method of atomic fluorescence spectrometry and atomic absorption spectrometry. The tests results show that:(1) At1350℃, when the additions of lead-zinc tailings was15.0%-18.0%, the f-CaO content in clinker was less than1.0%, which indicated that the added lead-zinc tailings could improve the burn-ability of raw material, and the calcination temperature could be decreased by50℃(2) When calcination temperature was1350℃and additions of lead-zinc tailings was12.25%,15.0%and16%, the portland cement could be produced in accordance with GB175-2007, the content of C3S reached a maximum of49.2%, the compressive strength of cement in28d was53.99MPa. When the calcination temperature arrived at1400℃and additions of lead-zinc tailings was15.0%, the cement strength exceeded the requirement of42.5R standard; When additions of lead-zinc tailings were16.0%, the cement strength exceeded the requirement of42.5standard.(3) Through XRD and SEM, the clinker was mainly composed of C3S, C2S, C3A and C4AF, and the distribution of each content was reasonable. The content of silicate minerals of clinker calcined at1400℃was higher than which calcined at1350℃. The size of C3S particles was much larger, while the C2S particles were round and filled in the gaps of C3S particles.(4) During the process of calcination, the average curing rate of heavy metals such as Zn, As, Cd and Pb was89.76%,83.62%,73.20%and15.19%respectively. The leaching toxicities of those mentioned heavy metals in clinker were much lower than the state standard of GB5085.3-2007, which met the requirement of innocuous production.