Study On Combustion Characteristics Of Semi-coke In Fluidized Bed

In recent years,China’s restrictive policies in the fields of iron and calcium carbide have led to a long period of overproduction of the semi-coke.A serious backlog of semi-coke powder has affected regional economic development.As solid residue of coal gasification,the semi-coke has targeted the removal of harmful components such as sulfur,chlorine,phosphorus,and mercury in the coal,so the semi-coke resource has the potential to become a kind of clean fuel.However,during the production of the semi-coke,a large amount of volatile of precipitated from the coal,which resulted in the incombustibility of burning.So the semi-coke used in the industrial pulverized coal furnace and the civilian heating furna ce was poor.According to the background,the study on the combustion characteristics of semi-coke in a fluidized bed was carried out.First,industrial analysis,elemental analysis,and thermogravimetric analysis were used to study the characteristics of semi-coke fuels,combustion characteristics and weight loss characteristics.It was found that semi-coke is a kind of low-sulfur,low-nitrogen coal with low volatile and high fixed carbon.The reaction capacity and combustion stability are between lignite and bituminous coal,and the burnout characteristics are close to that of bituminous coal.The semi-coke combustion kinetic models were calculated by Coats-Redfern Kissinger,and Flynn-Wall-Ozawa which obtain the most mechanism function,preexponential factor,and activation energy.Secondly,the effects of different combustion temperatures,excess air coefficient,and blending ratios on the emission characteristics of the semi-coke were carried out in fluifized bed.The results showed that higher combusti on temperature promote the formation of SO₂ and NOx.The increase of temperature has an inhibitory effect on emissions of CO;the emission of SO₂,NOx,and CO generally increase with higher excess air coefficient;mixed-burned lignite causes a decrease in emission of NOx,and a increase in emission of SO₂ and CO.Finally,semi-coke powder was applied to a 14 MW circulating fluidized bed boiler in order to study the emission concentration of semi-coke under different operating conditions.Verify the feasibility of the flue gas recycling method to reduce the emission of pollutants,which can lay a solid foundation for the industrialized application of semi-coke.The results show that: the recirculation of flue gas can reduce the emission of SO₂ and NOx,and increase the emission concentration of CO.The flue gas purification system has a clear effect on pollutants purification.