Study On The Gas-solid Two-phase Flow Characteristics In The Ender Pulverized Coal Gasifier

Ender pulverized coal gasification technology is one of the fluidized-bed gasification technologies.Because of its characteristics of strong gasification capability,wide coal adaptability,and stable operation,Ender pulverized coal gasification technology is widely used in small and medium-sized chemical companies.The gas-solid two-phase flow process within fluidized bed is relatively complicated,and there is significant influence on the gas-solid two-phase heat and mass transfer,particle combustion efficiency,etc.Therefore,studying the gas-solid two-phase flow in the furnace has comprehensive understanding of the Ender pulverized coal gasification technology.This paper aims at the Ender pulverized coal gasifier with a gas production volume of 20000Nm3/h in a chemical plant as the research object.The gas-solid two-phase flow process of the 1:15 modeling test bench is built.The PV6-D is used to measure the test benches of different structures.The test results showed that the distribution of flow field in the furnace with variable structure is more uniform.The Fluent software is used to carry out numerical simulation of gas-solid two-phase flow characteristics on test stands of different structures,in order to provide theoretical guidance for industrial operations.(1)The numerical simulation of original structure modeling test bench.The effects of nozzle velocity and initial layer height on the velocity and concentration fields of the gas-solid two-phase in the furnace were studied.Numerical simulation results show: the radial flow structure in the furnace is a ring-core structure where the upflow of low-concentration particles in the spout region and the downflow of high-concentration particles in the annular region coexist.In the horizontal direction,the tangential velocity of gas and particles is symmetrical about the center line of the furnace,and the movement direction on both sides of the centerline is opposite,but the value of velocity is basically the same.When the nozzle gasification rate increases from60m/s to 90m/s,the axial velocity increase of the particles in the central spray zone is significantly greater than that of the axial velocity of the particles in the annular zone;the gas-phase and particle tangential velocity increase;The volume concentration of the particles in the spray zone is maintained around 0.05m3/m3;the volume concentration of the particles in the ring gap varied greatly(0.55-0.41 m3/m3);Particles flow rate in the furnace becomes faster.When the initial layer height increased from 90 mm to 120 mm,the axial velocity of the particles in the spray zone and the annular zone decreased;The gas tangential velocity;The tangential velocity of the particles decreases,and the particle volume concentration change little in the spray zone(0.07-0.1m3/m3),which varies greatly in the gap region(0.51-0.57 m3/m3);The squirt area narrows;The gaparea widens.The flow rate of particles in the furnace is suppressed.(2)The numerical simulation of variable structure modeling test benches.The nozzle is changed to uniform 60onozzle arrangement.The effects of nozzle velocity,initial layer height and particle diameter on the velocity and concentration fields of the gas-solid two-phase in the furnace are investigated.The numerical simulation results show that the radial flow structure in the furnace is a ring-core structure where the upflow of low-concentration particles in the spout region and the downflow of high-concentration particles in the annular region coexist.The Ender furnace with the change of nozzle structure is the multi-nozzle spouted bed.Compared with the original structure,the axial velocity of the particles of spray zone in the variable structure is relatively high.There is no significant difference in the ring gap area,so the particle flow is accelerated.The spray zone widens and the annulus area narrows,which results in more particles being carried away by the gas,which will reduce the carbon conversion rate in the furnace to a certain extent.When change the velocity of the nozzle gasification rate and the height of initial material layer,there is the same effect on the gas-solid two-phase distribution of the velocity and concentration in the varied structure as the gas-solid two-phase distribution of the velocity and concentration in the original structure.The difference is that the influence amplitude is inconsistent.When the particle size increase,the axial velocity of particles in the spray zone reduce from2.48m/s to 1.57m/s,and the axial velocity of particles in the annulus region change little;the particle volume concentration gradually increased;The squirt area narrows;The gap area widens.When the particle size increases,the flow rate of particles in the furnace is suppressed.