Studies On The Mixing Characteristics Of The Gasification Agent And Raw Syngas With The Fly Ash Gasification Burner

As an advanced gasification technology,the technology of the raw syngas with fly ash entrained flow gasifier can solve the problem of high combustible content of fly ash in the raw syngas of fluidized bed fundamentally.By the mean of secondary gasification of fly ash,this technology can synergistically realize the removal of fly ash from raw syngas and the gasification of fly ash.As an independent post-treatment technology for syngas,it can couple with fluidized bed gasifier under different furnace types and different treatment capacity,which is economical and practical,and has high development prospects.The mixing and flow characteristics of the gasification agent and raw syngas with the fly ash gasification burner are of great significance to the design of new fly ash gasification burner and the development of the raw syngas with fly ash entrained flow gasifier.In a domestic chemical plant,a single raw syngas with fly ash entrained flow gasifier,which has the syngas production of 80000Nm~3/h,is currently in the stage of test and commissioning.In order to solve the problem of slag plugging in the burner of this gasifier during operation,Harbin University of Technology proposed a new and efficient burner for the gasification of fly ash.In this paper,a single-phase cold test rig for the fly ash gasification burner with a ratio of 1:2.5 to the prototype was built.Through the use of thermocouples and IFA300 constant temperature hot wire anemometer,the effects of jet angle and external gasification agent velocity on cross-jet mixing characteristics and flow characteristics between external gasification agent and raw syngas with fly ash gasification burner were researched,which would provide theoretical guidance for its industrial application.Through the mixing and flow tests of fly ash gasification burner,it could be seen that the jet trajectory of external gasification agent showed diffusion of trumpet shape in the process of cross-mixing of external gasification agent and raw syngas.The intensity of mixing between external gasification agent and raw syngas declined with the mixing process and the mixing speed decreased accordingly.At the initial stage of mixing,the velocity decreased rapidly,and there was a backflow area near the upper boundary of the external gasification agent jet.Under the condition of the same external gasification agent speed,the single-phase mixing test showed that the initial mixing position between external gasification agent and raw syngas was advanced from Y=20 mm(Y was the distance from the position to the burner outlet along the direction of the jet)to Y=0 mm with the increase of jet angle from 50°to 90°.When the jet angle increased from 50°to 70°,the critical combustion concentration area ratio and the maximum axial mixing velocity at each cross-section increased greatly,and the difference of the maximum radial mixing velocity was small.When the jet angle increased from 70°to 90°,the difference between critical combustion concentration area ratio and axial maximum mixing velocity was small,and the radial maximum mixing velocity decreased greatly.Under the condition of external gasification agent speed with 75m/s,the critical combustion concentration area ratios at the cross section of Y=70 mm at the jet angle of 50°,70°and 90°were 19.46%,31.27%and 36.99%respectively,and the maximum axial mixing velocity peaks were 3.13,8.31 and 7.32,respectively.The single-phase flow test showed that with the increase of the jet angle,the undershoot depth of the external gasification agent jet center at the same Y section increased,and the peak relative velocities of the external gasification agent flow were at Y=20mm,Y=10mm and Y=0mm,respectively.The central trajectory of the external gasification agent jet was closer to the burner outlet.When the jet angle was 90°,the mixture of raw syngas and external gasification agent occurred at the burner nozzle,which was easy to burn the burner.With the comprehensive consideration,the recommended angle of jet was 75°.Under the condition of the same jet angle,single-phase mixing test showed that with the increase of external gasification agent speed from 30m/s to 90m/s,the initial position of reaction between external gasification agent and raw syngas remained unchanged,and the ratio of critical combustion concentration area at each cross-section increased first and then decreased.When the gasification agent speed was 75m/s,the ratio of critical combustion concentration area was the largest.When the jet angle was 70°,the critical combustion concentration area ratio was 31.27%at the cross section of Y=70mm.Along the direction of raw syngas jet,the axial maximum mixing velocity increased first and then decreased,while the radial maximum mixing velocity decreased gradually.When the angle of the jet was 70°,the axial maximum mixing velocity peaks(8.31 and 8.42)of the gasification agent at 75 m/s and 90 m/s were much larger than those at other angles.The single-phase flow test showed that with the increase of gasification agent speed from 30 m/s to 90 m/s,the undershoot depth increased at the same Y section,and the trajectory of the external gasification agent jet center was closer to the outlet of the gasification burner.Based on the above tests,the speed of external gasification agent was recommended to be 75m/s.