Study On Mixing And Flow Characteristics Of Full Mixing Burner’s Outlets Of Jet Flows In Fly Ash Gasifier

Widely used in the fluidized bed gasification technology of the modern coal chemical industry,due to the low operating temperature,there is more fly ash in the crude synthesis gas with higher combustible content.The existing process for removing fly ash from crude syngas has great drawbacks.Also fly ash removal and utilization are separate,resulting in waste of resources.In order to solve the above problems,the fly ash air bed gasification technology was developed.A fly ash air bed gasifier with a crude gas treatment capacity of 80,000 Nm3/h has been built.The actual operation results verify that the technology can effectively reduce the content of fly ash in the crude syngas and the content of combustibles in the fly ash,but the problem of serious clogging of solid slags in the burner nozzle.The research group of Professor Li Zhengqi of Harbin Institute of Technol ogy proposed a gasifier and crude synthesis gas fully mixed gasification burner.They built 1:2.5 single burner single-phase cold-flow model test bench,using the thermocouple and hot wire anemometer to measure the mixing and flow characteristics of the cross-jet of gasifier and crude syngas at the exit area of the burner at different nozzle diameters and outlet wind speeds.At the same time,the numerical simulation method was used to establish a three-dimensional mathematical model on the test bench to obtain the cold flow field at the outlet of the burner.The technical parameter combination of the burner was obtained to provide technical support for industrial operation.Under the same velocity of the gasifier nozzle,with the increase of the inner diameter of the nozzle,the lower flushing depth of the gasifier increases,the area of the jet area affecting the rough syngas jet increases significantly,and the deflection amplitude of the flow also increases.The larger the inner diameter,the greater the maximum relative velocity ratio,and the flow velocity decays more slowly.When the outlet wind speed is 60m/s,within the measurement range of X=0mm-120 mm,the critical combustion concentration area ratio between the quantized gasifier and the crude syngas combustion area increases from 0 to 47.39% at the condition with an inner diameter of 13 mm.The maximum critical combustion concentration area ratio is 1.31 times and 1.25 times of the conditions with an inner diameter of 10 mm and 16 mm.The maximum mixing velocity,which represents the mixing degree of the cross jet,has the axial peak value of 2.44,3.53 and 3.08 respectively under the operating conditions with the inner diameter of 10 mm,13mm and 16 mm,and the underflushing depth of gasification agent reaches around 44 mm,52mm and 72 mm respectively.The cold flow field obtained by numerical simulation is basically consistent with the hot-wire measurement results.In summary,the recommended inner diameter of the gasification agent nozzle is 13 mm.Under the same inner diameter of gasifier nozzle,the maximum relative velocity ratio tends to increase first and then decrease rapidly.With the increase of outlet wind speed,the lower flushing depth of gasifier increases,the airflow deflection amplitude increases,the maximum relative velocity ratio is also large,and the velocity attenuation is relatively slow.When the inner diameter of the nozzle is 13 mm and the outlet wind speed is 60m/s,the maximum critical combustion concentration area ratio is 1.24 times and 1.08 times of 35m/s and 85m/s.As a whole,when the outlet wind speed is 60m/s,the maximum axial and radial mixing velocities are larger than the other two working conditions.At the outlet wind speed of 35m/s,60m/s and 85m/s,the blanking depth of gasification agent under working conditions respectively reaches 36 mm,52mm and 68 mm.In summary,the recommended outlet velocity of the gasification agent nozzle is 60m/s.