Structural Optimization Design And Performance Analysis Of High Efficiency And Low Emission Regenerative Gasification Combustion System

In recent years,northern China has been continuously attacked by haze-fog in winter for the large-scale central heating.The direct combustion of coal inevitably leads to a large number of SOx,NOx and smoke emission,and the alternative use of clean and renewable energy for coal is the only way to solve the above problems.The combination of gasification technology and high temperature air combustion technology(HTAC)is an effective way to popularize renewable energy and achieve multiple ways of coal utilization.Therefore,a regenerative gasification combustion system was designed.The system mainly consisted of two parts:updraft gasifier and regenerative combustion system.In this study,the structural optimization design and performance analysis of the whole combustion system was completed,including the use of the drawing software ProE for 3D modeling and the use of Excel to complete the thermal calculation.The gasifier was designed with primary and secondary gasification agents in the intake system.At the same time,the grate was designed as a rotatable double layer grate,which ensured the uniformity of the gasification process and improved the gasification efficiency and syngas quality.In addition,this grate can effectively alleviate the problem of biomass ash coking at the bottom of the gasifier.This gasifier was independently applied in a non-ferrous metal smelting enterprise in Qingdao.Practice proved that after replacing the burning engine,the gasifier completely solved the corrosion problem of the alkali metals in the biomass to the graphite-SiC crucible.Further XRD(X-ray diffraction)and SEM-EDX(scanning electron microscopy and energy dispersive X-ray)analysis of the crucibles showed that the corrosion mechanism of the graphite-SiC crucible for the biomass gasifier is high temperature oxidation corrosion,while the corrosion mechanism of the biomass burning engine on the graphite-SiC crucible was further alkali metal corrosion on the basis of high temperature oxidation corrosion.The updraft gasifier with the biomass as fuel has a unique filter retention effection to the volatile alkali metals.It is the key to solve the problem of dust plugging and corrosion in the direct combustion process of the solid fuel.The regenerative combustion system included three parts:honeycomb ceramic regenerator,regenerative low NOx burner combined with flue gas recirculation and hot water boiler.The syngas generated from the updraft gasifier was introduced into the horizontal flue of the combustion system to burn.In the middle of the horizontal flue,a certain proportion of the flue gas was diverted upward and then mixed with the combustion air again after the cooling through three stages of system tubes(second,third and fourth lubes).This part of the flue gas not only solved the problem of imbalance of water equivalence ratio of regenerator.Moreover,the mixing of diffused flue gas and combustion air can inhibit the generation of thermal NOx by decreasing the oxygen content in combustion air.The honeycomb type ceramic heat storage device was arranged symmetrically on both sides of the system.The burner was arranged at the syngas outlet above the regenerator,and the periodic switch of the flue gas/combustion air was realized through the reversing valve.For this new type of gasification combustion system,a complete thermal calculation method was put forward based on the thermal calculation method of traditional boiler,and the thermal calculation tables including system heat balance,fule part,tube part and regenerator part were completed by Excel software.The checking calculation results showed that the error of thermal calculation of each part of the system was within a reasonable range.Finally,the variable load analysis of the regenerative combustion system was carried out.The system still maintained high thermal efficiency at low load operating state,but considering the influence of the dew point of flue gas,the load regulation range of the system was small.In short,this paper proposes an integrated solution for a high efficiency and low emission regenerative gasification combustion system in response to the increasingly serious environmental and energy crisis in recent years in China,which provides new ideas for changing China's energy structure and environmental issues,and provides a technical reference for the real engineering application of gasification technology and high temperature air combustion technology.