Basical Research On Using Co-pyrolysis Semi-coke Of Lignite And Pine As Alternative Fuel For Cement Kiln

Coal resources are an important part of China's energy resources,of which low-rank coal reserves account for 55%of national coal resource reserves.Lignite is the most typical type of low-rank coal.It has a low degree of coalification,low calorific value,and high moisture content,which leads low energy conversion efficiency and pollutes the environment.The efficient and clean use of lignite is particularly important for sustainable development.Co-pyrolysis of lignite and biomass has become a hot topic at home and abroad.The cement industry is the most important basic raw material industry in China,and its mainstream technology has long used bituminous coal as fuel.With the rapid development of China's cement industry,the increasing shortage of high-quality bituminous coal in the cement industry and the rising price of coal.The search for alternative fuels is imminent.The application of low-rank coal and biomass to cement kilns can not only reduce the consumption of high-quality coal resources,but also provide a new way for the efficient use of low-rank coal and biomass.This project uses Yunnan lignite?HM?and pine?SM?as raw materials,and discusses the effect of co-pyrolysis process on the yield and properties of semi-cokes.FTIR characterization and thermogravimetric analysis were performed on the pyrolysis products to explore the coordinating role in the co-pyrolysis process and optimize the pyrolysis process.The effects of process conditions such as final pyrolysis temperature,raw material ratio,and particle size on the co-pyrolysis semi-cokes burn-out rate were investigated using rapid combustion experiments.Based on thermal weight loss experiments,multiple combustion characteristics indexes were introduced to analyze the slow combustion process of pyrolysis semi-cokes.The relationship between the combustion characteristics of pyrolysis semi-cokes and the amount of pine was explored.Mix the optimal semi-coke,bituminous coal,and lignite to explore the optimal blending ratio of fuel.This project mainly has the following research conclusions:?1?The co-pyrolysis tar yield obtained with the 40%-pine blending ratio reached a maximum of 19.88%,and reached a maximum positive deviation from the theoretical weighted value.The semi-coke calorific value obtained under this condition also reached a maximum of 33.687 MJ·kg^-1.FTIR characterization of co-pyrolysis semi-coke and tar,thermogravimetric analysis of raw materials both indicate that there is a synergistic effect during co-pyrolysis.The addition of pine had varying degrees of impact on the properties,surface morphology,total sulfur content,and alkali metal content of co-pyrolysis semi-cokes.?2?In the rapid combustion experiment,the co-pyrolysis semi-cokes burnout rate is positively related to the fuel ratio of the sample and the pine blending ratio.And the optimal particle size is 150-240 mesh.The results of thermal weight loss experiments show that:Compared with the corresponding indexes of the lignite pyrolysis semi-coke,the flammability index C,the ignition stability index R_W,the burnout index C_b,and the comprehensive combustion characteristic index S_N of the co-pyrolysis semi-cokes mixed with pine are all increased significantly.?3?The optimal co-pyrolysis semi-coke?SHJD?was obtained at the 40%blend ratio of pine,the particle size of 150-240 mesh and the final pyrolysis temperature of 450?.The moisture,ash,volatile matter,calorific value,and total sulfur content of the semi-coke SHJD all meet the requirements for coal used in cement kilns.The fast combustion burn-off rate of SHJD is 94.02%,which is 7.71%higher than that of lignite semi-coke BJC.The optimal fuel blending scheme is bituminous coal:lignite:optimal semi-coke=50%:0%:50%.