What is the approximate ratio of methanated hydrocarbons to methane in the production of LNG from coke oven gas?
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What is the approximate ratio of methanated hydrocarbons to methane in the production of LNG from coke oven gas? As far as I know, this ratio is very important; a high carbon ratio can lead to an uncontrolled release of reaction heat, resulting in overheating!
Calculate it yourself. A 1% CO methanation temperature increase is roughly 70–72 degrees, while a 1% CO2 methanation temperature increase is about 60 degrees. It depends on the properties of your catalyst; control the concentration of the feed material. After the three stages of reaction are complete, generally more than 12% hydrogen remains
Or use a different algorithm: one CO molecule consumes three hydrogen molecules, while one CO2 molecule consumes four hydrogen molecules. In coke oven gas, the ratio of CO to CO2 is generally 2:1; therefore, the hydrogen required for the reaction should be five times the volume of CO. In addition, there is hydrogen consumed during the hydrogenation of olefins and the conversion of alkanes in coke oven gas, as well as hydrogen required for the conversion of organic sulfur into inorganic sulfur. Moreover, an excess of hydrogen is needed to ensure the conversion rate of carbon. The hydrogen content in the gas after the reaction should be greater than 12%, and the minimum ratio can also be calculated based on this
If your gas source is coke oven gas and there are no other gas sources available, then the H/C ratio can range between 3.01 and 4.05. If this ratio falls below 2.9, overheating will occur, as you mentioned (under the assumption that the cycle gas and inlet temperature remain constant). If the only gas source is coke oven gas, you should check the designed gas composition as well as the actual gas composition in use; in such cases, the ratio will tend to be closer to 4.05 rather than the optimal value of 3.01. Additionally, you can refer to the PDP provided by your methanation technology supplier, as it covers all possible scenarios.