Oxygen-enriched coal gasification uses combustion-supporting air with an oxygen content of 23%-19% to be sent to the gas generator for combustion. It is different from traditional steam.——Compared with the mixed gas produced from air, oxygen-enriched gas uses a mixture of oxygen-rich air and steam as the gasification agent, which increases the concentration of oxygen in the gasification agent. As the concentration of oxygen in the gasification agent increases, the content of the combustible part (CO and H2) in the gas component increases, and the concentration of the inert component decreases relatively. The oxidation reaction of carbon intensifies, and the furnace temperature rises accordingly, which accelerates the gasification reaction speed, increases the calorific value of the gas, and also improves the gasification efficiency and gasification intensity.
When using oxygen-enriched air to produce coal gas, it is necessary to increase the supply of water vapor in order to reduce the temperature of the oxide layer. Because, under the conditions of the oxide layer, the reaction speed of H2+1/2O2 = H2O is incomparably higher than the reaction speed of C+H2O = H2+CO, so the water vapor passing through the oxide layer does not interact with the carbon in the fuel, and is an inert substance like nitrogen. It moves the sensible zone from the oxide layer to the reduction layer, raising the temperature of the reduction layer. In order to prevent the high operating temperature and the high temperature of the gas leaving the furnace from increasing heat loss, causing the slag to melt and affecting the permeability and forward flow of the charge, it is necessary to increase the amount of water vapor supplied in the blast. The endothermic reaction of carbon and water vapor is used to reduce the temperature of the gasification layer. Add a lot of water vapor to the gasification agent, and the gas produced at this time is called steam—Oxygen-enriched gas is a mixture of carbon gasification products with oxygen and water vapor.
Oxygen-rich oxidation process analysis:
A. The temperature of the fuel layer rises and the calorific value of the gas increases.
The content of the active ingredients (H2 + CO) in the mixed gas generator mainly depends on the progress of the CO2 reduction reaction and the steam decomposition reaction, that is,
C + CO2 = 2CO – 162.4 MJ/mol
C +H2O = CO + H2 – 118.8 MJ/mol
The above two reactions are endothermic reactions, so the increase in furnace temperature is conducive to the increase in the equilibrium concentration of H2. and CO. Moreover, under the normal operating temperature of the generator, the reaction rates of the above two reactions are within the kinetic control zone, and the gasification temperature can be adjusted and controlled by blast air and saturation temperature. When using oxygen-enriched oxidation, as the oxygen concentration in the gasifying agent increases, the reaction temperature increases. As long as the amount of steam is increased, the operation can be performed within a safe temperature range. At this time, the calorific value of the gas increases from the original 5930 to 6393 KJ/m3.
B. The gasification reaction speed is accelerated and the gasification intensity is increased.
The gasification reaction rate depends on the complete oxidation reaction of carbon. This is a reaction controlled by external diffusion, which increases the concentration of oxygen in the gasification agent, that is, a mixture of oxygen-rich air and steam is used as the gasification agent. At this time, due to the increase in the oxygen concentration in the gasification agent, the concentration of inert components, that is, a mixture of oxygen-rich air and steam is used as the gasification agent. At this time, due to the increase in the oxygen concentration in the gasification agent, the concentration of the inert component decreases relatively. The oxidation reaction of carbon intensifies, and the furnace temperature rises accordingly, which speeds up the oxidation reaction and increases the heat released per unit time accordingly, thus providing sufficient heat for the reduction reaction. It can increase the amount of gasified carbon per unit time and unit furnace cross section, which means increasing the gasification intensity and reducing the carbon content of the ash.
Benefits of oxygen-enriched oxidation:
1. The carbon content of ash and slag is significantly reduced and the carbon conversion rate is greatly improved.
2. The calorific value of gas quality is significantly improved,
3. Gasification efficiency is effectively improved
4. Applicable to a wider range of coal types
