Experimental Study On Resource Utilization Of Sintering Plant FGD Ashes

The production of iron and steel requires large amounts of fuel and ore in its thermal process,while releases large amounts of air pollutants.Among them,the volume of SO2 emissions from sintering process accounted for from 50%to 70%in the production system of iron and steel enterprises.So controlling SO2 emissions of sintering process has become an important measure to reduce iron and steel industry pollution emissions.In recent years,the semi-dry flue gas desulfurization process has been widely used in sintering flue gas desulphurization in China,as its advantages of less investment,less land occupation and no waste water discharge.However,the semi-dry flue gas desulfurization process also produces a large number of desulfurization ashes.At present,only a small part of desulfurization ashes was used at home and abroad,the vast majority was abandoned.It if not be rationally used,will result in secondary pollution and occupation of land.Therefore,resource utilizationthe of semi-dry desulfurization ashes has become an environmental problem that urgent need to address.The sintering flue gas desulfurization ashes of the experiment are from the factory in anshan.We need to treat the synthetic wastewater by them,and through the liquid-liquid and gas-liquid carbonization way to prepare calcium carbonate respectively.This article studied the characteristics of reaction process that desulfurization ashes and chrome contained wastewater,and studied the characteristics of precipitation process,optimizes technological parameters,determines the appropriate technological conditions.The removal rate of hexavalent chromium in chrome contained wastewater was mainly studied in the experiment of treating chrome contained wastewater by desulfurization ashes.The influence factors such as the initial pH of wastewater,the dosage of desulfurization ashes,vibration speed and reaction time were discussed.Based on the results of one-factor-at-a-time(OFAT)experiment,Box-Behnken Design(BBD)according to the principles of response surface methodology(RSM)was carried out to optimize the removal rate of hexavalent chromium.A quadratic polynomial model assessing the effects of the four independent variables on the removal rate of hexavalent chromium had been developed.According to the analysis of variance(ANOVA),the model was significant and there was no lack of fit.Model analysis was performed with the help of software and the optimum values of the four factors were obtained which was initial pH=1.08,dosage of sintering flue gas desulfurization residue of 0.05 g/mg Cr(VI),vibration speed of 191 r/min,reaction time of 25 min.And the removal rate of hexavalent chromium of 98.64%was achieved.Compared with the removal rate of hexavalent chromium under optimum conditions of OFAT experiment,there was a increase of 0.44%.The effects of ultrasonic power?different additives?Ca2+concentration?reaction temperature and n(Ca2+):n(NH4HCO3)on the morphology and particle size of CaCO3 were studied in the experiment of the liquid-liquid preparation of calcium carbonate.The optimum conditions were obtained as follows:ultrasonic power of 240 W,the additive was citric acid,the concentration of Ca2+was 0.57 mol/L,carbonization temperature was 15?,n(Ca2+):n(NH4HCO3)=1:1.Cube calcium carbonate was prepared with mean diameter 1?m and homogeneity of particle size.The product reached the standard of industrial precipitated CaCO3(GB/T2226-2000).The effects of excessive NH4Cl?reaction temperature?Ca2+concentration?different additives?additive dosage and carbon dioxide flow on the morphology and particle size of CaCO3 were studied in the gas-liquid preparation of calcium carbonate.The optimum conditions were obtained as follows:excessive NH4Cl of 30%,carbonization temperature was 15?,the concentration of Ca2+was 1.00 mol/L,the additive was sodium polyphosphate,the dosage of additive was 3%of calcium carbonate,adding the flow rate of CO2 was 400 mL/min.Spherical calcium carbonate was prepared with diameter less than 100 nm.The product reached the standard of industrial precipitated CaCO3(GB/T2226-2000).