Study On The Co-combustion And Pollutant Emission Characteristics Of Coal Gangue And Coal Slime In O₂/CO₂

With the increase of coal mining and washing,the stocks of low calorific coal gangue and coal slime are increasing year by year.They are the main solid wastes,which are mainly used for power generation in China.In order to alleviate the CO₂ emissions,more and more scholars begin to pay close attention to the oxy-fuel combustion.As a new type of clean combustion technology,O₂/CO₂ combustion technology not only can effectively capture CO₂,but also reduce NO_X and SO₂ emissions in the process of combustion.In this paper,the combustion characteristics and release of SO₂ and NO_X during the combustion have been investigated with the aid of TG-DTG and Testo350.The main conclusions are as follows:（1）The coal gangue and coal slime were selected from Pingshuo.The combustion characteristics of coal gangue and slime and the mixture samples of them were studied by the thermal weight analyzer.The influences of temperature,mixing ratio,heating rate and oxygen concentration on combustion characteristics were investigated.The study shows that the combustion performance of coal gangue can be optimized by the addition of coal slime in the air and O₂/CO₂ atmosphere,but there is no synergism between them.In the atmosphere of O₂/CO₂,with the increase of the heating rate,the weight loss curve moves to the high temperature region.The increase of oxygen concentration can effectively reduce the ignition temperature and promote combustion.（2）The emission characteristics of SO₂ in the combustion process of coal gangue and slime are also analyzed by tube furnace and flue gas analyzer.The influence of temperature,blending ratio and oxygen concentration on SO₂ emission characteristics is investigated.The results show that the emission content of SO₂ is significantly reduced with the increase of the blending ratio of coal slime.During co-combustion of coal gangue and coal slime,with the increase of temperature,the SO₂ content increases,and two release peaks of SO₂ appear above 800℃;In the range of oxygen concentration selected in the experiment,with the increase of oxygen concentration,the release peak of SO₂ in gas increases,and the amount of SO₂ and the conversion rate also increase.（3）During co-combustion in O₂/CO₂,NO emission is lower;with the increase of coal slime blending ratio,NO peak concentration is gradually increasing,which may be caused by the relatively high content of volatile N.With the increase of temperature,the concentration of NO gradually increases;with the increase of O₂ concentration,the concentration of NO also gradually increases,and the time of NO release is slightly advanced,and it is basically all released at 250s.This study reveals the combustion characteristics of coal gangue and coal slime and pollutant emission characteristics in O₂/CO₂.It provides theoretical basis for oxy-fuel combustion in CFB and it has the scientific significance to solve the problem of low calorific value of coal storage.