Add carbon dioxide before conversion
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Our company adds liquid carbon dioxide before the conversion process, but the hydrogen-to-carbon ratio remains around 2.4 even after conversion. So, does adding carbon dioxide change the value of the vaporization ratio, thereby allowing adjustment of the levels of CO, CO2, and H2 in the fresh gas after conversion?
This is a matter of the amount of carbon replenished; large compressors, large vaporizers, and large heat exchangers are designed to ensure an adequate amount of carbon replenishment as well as a proper hydrogen-carbon balance. The steam-to-char ratio can only adjust the carbon-carbon ratio of the syngas; it is the oxygen ratio that determines the composition of the fresh gas.
Do you mean that in the combustion reaction in the upper section of the converter, the oxygen supply according to the equation H2+0.5O2=H2O determines the hydrogen-to-carbon ratio in the fresh gas? Wouldn’t this lead to a waste of H2? We also have the process of producing liquid ammonia by stripping hydrogen from the off-gases later on. I would like to ask whether, after carbon supplementation, it is necessary to change the previous adjustment parameters for each step in the methanol production process
To calculate the increased methanol production after carbon supplementation, it is appropriate to use the total carbon conversion rate of CO2.
It’s simple: add oxygen until a favorable conversion rate for methane is achieved; at this point, the oxygen-to-carbon ratio determines the main components of the gas. The added steam can only be used as a reaction and protective medium.
In the catalytic conversion of methane in pure oxygen, CO2 acts as an inert gas. The thermodynamic temperature at which CO2 reacts with methane is around 1200°C, while the maximum temperature in the conversion furnace does not exceed 1100°C; therefore, only water vapor participates in the methane reformation process. However, the presence of CO2 inhibits further reactions between CO and H2O as well as the high-temperature dissociation of CO, thereby increasing the relative yield of CO. Yet, there is no significant improvement in the hydrogen-to-carbon ratio