Reaction mechanism in the gasifier

A high oxygen-to-coal ratio results in a decrease in the effective gas components.

In fact, the effective gas components depend on what your downstream product is; if it is synthetic ammonia, then a higher hydrogen content is preferable； If it is urea, then a higher content of CO2 is preferable ； If the main product is methanol, then the CO:H2 ratio is adjusted to 1:2.2 in the conversion step ； If the main product is acetic acid, it is better to control CO. The composition of the syngas is related to the type of coal selected, the oxygen-to-coal ratio, the type of furnace, and the residence time in the reaction chamber (which affects the carbon conversion rate).

An increase in the oxygen-to-coal ratio results in more coal undergoing combustion, leading to an increased heat release. This raises the temperature of the gasifier, providing more heat for the endothermic gasification reaction, which is beneficial for such reactions. Therefore, the carbon conversion rate, cold gas efficiency, and gas production increase, while CO2 and specific oxygen consumption as well as specific coal consumption decrease. As the oxygen-to-coal ratio increases further, the carbon conversion rate increases only slightly. Meanwhile, the excess oxygen entering the gasifier leads to an increase in CO2, which reduces the efficiency of cold gas production and the gas yield, while increasing the specific oxygen consumption and specific coal consumption. Therefore, there should be an optimal value for the oxygen-to-coal ratio; it is generally considered that an atomic ratio of oxygen to carbon around 1.0 is suitable. The composition of the synthetic gas is related to the concentration of the water-coal slurry, the oxygen-to-coal ratio, the reaction temperature, and the reaction pressure

An increase in the oxygen-to-coal ratio raises the temperature inside the furnace, increases the levels of carbon monoxide and hydrogen in the gas, enhances the conversion rate of carbon, facilitating its complete combustion, and also increases the carbon dioxide content in the gas

The reactions within the gasification furnace are very complex, and there are many factors that influence them; it is not possible to generalize. For example, the volume of the furnace chamber and its length-to-diameter ratio can both affect the reactions that take place inside.

When the furnace temperature exceeds the oxygen-to-coal ratio, the composition of the effective gases decreases accordingly, while carbon dioxide increases, as does methane!

In fact, the gasification reaction can be simply understood (although the actual reaction is very complex) as a process of oxygen-deficient combustion; it takes place in a reducing atmosphere with a high oxygen content, which in turn results in a high level of carbon dioxide and a low amount of available gas.

The gasification reactions mainly include: the CO2 reduction reaction: C+CO2→2CO-Q; the complete combustion of carbon: C+O2→CO2+Q; the heterogeneous water-gas reaction: C+H2O→H2+CO-Q and C+2H2O→2H2+CO2-Q; the methane conversion reaction: CH4+H2O→3H2+CO-Q; and the reverse transformation reaction: H2+CO2→H2O+CO-Q. Generally, as the gasification temperature increases (that is, as the oxygen-to-coal ratio rises), the level of CO2 first decreases and then increases. At very low temperatures, the exothermic reaction of complete combustion of carbon: C+O2→CO2+Q occurs more frequently, while the other endothermic reactions occur less often. However, as the temperature rises, the endothermic reaction that produces CO becomes more active, and CO2 levels start to decrease. At very high temperatures with an abundance of O2, a situation similar to extreme peroxides can occur, during which C and CO are completely converted into CO2; as a result, CO2 levels increase later on

1. Pyrolysis and combustion of volatile components: When the coal slurry is mixed with oxygen and injected into the vaporization furnace, the water in the slurry rapidly turns into water vapor, while the coal powder undergoes dry distillation and thermal pyrolysis. 2 Combustion and gasification: On one hand, coal coke reacts with the remaining oxygen to produce gases such as CO2 and CO, releasing heat; on the other hand, it reacts with water vapor and CO2 to produce H2 and CO. 3 Gasification: There is almost no O2 in the reactants; mainly coal coke, methane, etc. react with water vapor and CO2 to produce H2 and CO. 1) Volatile matter combustion and gasification reactions: CmHn + (m+4)O2 → mCO2 + 2H2O; CmHn + 2O2 → mCO + 2H2; CmHn + mH2O → mCO + (m+2)H2; CmHn + mCO2 → 2mCO + 2H2. 2) Carbon combustion and gasification reactions: C + O2 → CO2; C + 2O2 → CO; C + H2O → CO + H2. 3) Equilibrium reactions of water gas: C + CO2 → 2CO; CO + H2O → CO2 + H2

Agree with what was said on floor 4: too much oxygen leads to more carbon dioxide production, so it should be an oxygen-deficient reaction. . .

Slurry concentration, good atomization performance of the burner, an appropriate oxygen-coal ratio at T4+ (30~50), and a furnace temperature that ensures proper control of liquid slag discharge :)