Study On The Desulphurization And Utilization Of Ashes Form CFB Boiler Combustion Fujian Anthracite

Coal is the dominant energy resource in FuJian province among which about 98.3%is anthracite.The physical properties,e.g.,tough structure,poor reaction ability,low DT temperature and strong thermal fragmentation,etc,make its ignition and burnout very difficult.The circulating fluidized bed(CFB) boiler has so many advantages including fuel flexibility,high combustion efficiency,low pollutant emissions that it has been the first choice for burning FuJian anthracite recently.So far the main problem for the combustion of Fujian anthracite in CFB boiler is the low desulphurization efficiency.The main reason is that a reliable theory is not available for the desulfurization of FuJian anthracite in CFB boiler.In addaition,there is not a clear understand of the property of the ash from CFB when Fujian anthracite is burnt with desulphrization agent and the utilization of the ash is limited.So,the study on desulphrization of Fujian anthracite and the utilization of its desulphrization ash is very important to improve the desulphurization efficiency and the redource utilization of the desulphurization ashes.This thesis is mainly to report the author's research work on the desulphurization characteristics of FuJian anthracite during combustion in CFB boiler.Experiments were carried out by mechnism experiment about the characteristics of calcination and sulfur fixation and industrial trials of the desulphurization in pilot CFB boiler.It's found that calcination time and calcining temperature significant effect on specific surface area of limestone;during the process desulfurization reaction,the utilization ratio of limestone was very low.The blocking problem for porosity of limestone was analyzed through the calcination and sulfur fixation experiment through a bench scale CFB boiler,This will offer the reference for improving the utilization ration of limestone.Then the industrial trials of the desulphurization in a 75t/h commercial CFB boiler at a thermal power plant were conducted to illustrate the dynamic distribution of SO₂ emission and the bed temperature vs.the input of limestone.The effect of different Ca/S ratio and bed temperature on the desulphurization efficiency was studied and the optimal Ca/S ratio and desulphurization temperature were obtained for FuJian anthracite.it was found that SO₂ emission concentration and the bed temperature varied significantly after adding limestone in CFB boiler;the desulfurization efficiency increased with increasing of Ca/S;the optimum desulphurization temperature was 900～950℃.those results will provided important reference for industrial application of CFB boiler combustion FuJian anthracite.The second part of the thesis is the experimental research on the utilization of the desulphurization ashes of FuJian anthracite.The basic characteristics of the desulphurization ashes of FuJian anthracite were checked by experimental test,including theparticle size distribution,carbon content,aperture and specific surface area,composition,etc.The results showed that the carbon content in the desulphurization ashes was very high.The change of CaO and SO₃ content was obvious in the ash before and after desulphurization.Based on this result,the effect of desulphurization ashes on cement performance was tested when it was used as cement component according to the national standard for cement production and test, i.e.,GB/T17671-2001 and GB/T17671-1999 respectively.It's found that the volume stability of cement blending desulphurization ashes unqualified.and mortar strength of blending cement decreased.Finally the characteristics of hydration reaction was study,this will provide some guidance for the redource utilization of desulphurization ashes.