Investigation Of MILD Pulverized Coal Gasification By Parallel Jets

China is a country with a large energy consumption.The consumption of coal in primary energy is ranked first and will be maintained for a long time.It is of great significance how to cleanly use coal.Coal gasification and reuse is one of the promising clean and efficient ways to use coal.In this paper,the concept of Mild combustion is used to carry out research on the Mild gasification of pulverized coal.Mild combustion comes from high-temperature air combustion.Through recent research,it has been found that Mild combustion has many advantages,such as low pollution,stable combustion,and even uniform temperature distribution,and it has the characteristics of fuel flexibility.Studies have shown that gaseous fuels,liquid fuels,and solid fuels can achieve Mild combustion under proper conditions.Mild gasification of pulverized coal is more challenging than Mild pulverized coal combustion.The ratio of air and pulverized coal is smaller in Mild gasification,that means it is more difficult to organize the flow filed through air.This thesis carried out the following work based on the previous research of the research group:First of all,I have improved the existing test rigs,and carried out the exploration of Mild gasification experiments under different working conditions.Through analysing the problems in the existing programs,I laid the foundation for the next plan,and deepened the understanding of Mild gasification.Through experimental research,it has been found that when the existing gasifier is tested,the large heat dissipation results in a low gasification temperature in the gasifier.The overall carbon conversion rate is low.For the gasifier is placed horizontally,the bottom of the gasifier can easily accumulate slag,affecting the flow organization.Based on the idea of parallel jet entrainment to form a large back-flow,the influence of pulverized coal transport methods and nozzle layout schemes,horizontal or vertical erection of gasifier on the flow field structure,concentration distribution of pulverized coal,etc.were carried out based on the existing work.Using numerical simulation to explore feasible flow field organization.The addition of gravity makes the average residence time of the particles greatly reduced,and when the furnace is placed horizontally,a large number of pulverized coal particles will fall on the furnace wall.In comparison,the vertical placement of the furnace is better.The farther the secondary air nozzle is from the center of the furnace,the larger the recirculation zone and the more uniform distribution of the pulverized coal.For the pulverized coal is divided into three feeds into the furnace,the concentration distribution of pulverized coal is more uniform than the pulverized coal injected in the central of furnace.The Mild gasification of pulverized coal,compared with Mild pulverized coal combustion,releases less heat and the gasification demand has a relatively high temperature.How to ensure the high temperature of the gasifier and it can be used for a long time is very important.Therefore,this thesis redesigned the pulverized coal Mild combustion and gasification furnace and analyzed the design scheme.The furnace refractories were selected to have a thickness of 150 mm,a thickness of 192 mm for the insulating material,and an outer diameter of 1524 mm for the steel shell.At this time,the amount of heat dissipated in the coal heat release was 6.5%.Through the research on the above content,the deficiency of the existing test rig was found and the corresponding solution was proposed.An optimized gasification nozzle scheme and a lower heat-dissipation furnace design have been designed to provide reference for the continued development of pulverized coal gasification.