Study On The Flow And Combustion Gasification Characteristics Of The Atmospheric Four-nozzles Pulverized Coal Gasifier With High Speed Circulating Gasification Agent

At present,most of the gasification furnaces used by small and medium-sized coal chemical industries in China are fixed-bed gasifiers,which have high requirements for coal quality,low carbon conversion efficiency.Although the pressurized entrained-flow gasification unit has superior performance,it is expensive to invest,it is difficult to apply to chemical industries.The atmospheric pulverized coal gasification technology has the characteristics of low cost of investment,high carbon conversion efficiency.It is suitable for the small and medium-sized coal chemical upgrading.Based on this demand of a large number of small and medium-sized chemical plants in China,It has been taken the lead in proposing the gasification technology for atmospheric entrained-flow gasifier with high-speed circulating with four-nozzles and has been applied in industry.The object of this article is the industrial demonstration project of the technology.The Wulashan Fertilizer Plant has been applied of the entrained gasifier with gas generation of 30000 Nm3/h.According to the single-phase cold modelling criteria,the structure and operating parameters of the cold test bench were determined,and a cold bench with a prototype ratio of 1:8 was built.The single-phase flow field in the gasifier can be divided into six flow areas,namely the upper back-mixed area,the upper refraction area,the horizontal jet area,and the center.The round zone,the lower refraction zone and the lower back-mixed zone;the gas in the lower refraction zone and the back-mix zone of the furnace along the height of the gasifier,the mixing intensity gradually increases,and the gas exchange volume in the vicinity of the nozzle can reach 5 times the furnace bottom zone.As the horizontal deflection angle of the gasifier nozzle increases from 4° to 12°,the diameter of the circle increases from 74 mm to 126 mm.Changing the load will have a significant impact on the tangential velocity of the gas stream.When the gasifier load is increased to 120% of the design load,the lower region of the gasifier is significantly affected.The tangential velocity on the same section can reach the maximum of the design load tangential velocity.1.8 times.Under the design load,in the single-phase flow field in the furnace,the tangential velocity is stable at the theoretical value?the ratio of the ratio of the actual load to the design load and the tangential velocity of the flow field under the design load?,the flow condition is similar to the design load.The numerical simulation was used to study The reaction of coal and gasification agent mainly occurs at the edge of the jet.The high temperature zone of the gasifier is mainly concentrated in the upper part of the gasifier and near the circumference of the nozzle.The cross section of the nozzle forms a central negative pressure zone,and the minimum temperature is about 1100 K.The concentrations of CO₂ and water vapor at the burner gasification flame are relatively concentrated,and CO and H₂ are concentrated in areas other than the nozzle.As the horizontal deflection angle of the nozzle increases,the distance between the high temperature area and the wall surface decreases.As the gasifier load increases from 60% design load to 120% design load,the combustion reaction zone in the furnace expands,the gasification reaction zone at the edge of the combustion reaction zone to move down,the high concentration range of CO and H₂ decreases,while combustion The CO₂ and H₂ O enrichment regions increase.Furnace outlet flue gas temperature increased from 1593 K to 1724 K,CO concentration increased from 56.41% to 60.56%,CO₂ concentration gradually decreased from 13.72% to 10.66%,H₂ concentration increased from 14.70% to 18.62%.