Methanation of chemical process exhaust gases
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1. Chemical process exhaust gases contain 0.3-0.5% CO; the CO content can vary to some extent, with a maximum of 0.8% and a minimum of 0.1%； The CO2 content is less than 100 ppm, and the oxygen level after purification is ≤0.1%. Is it feasible to consider methanation? 2. If the methanation process is used, what are the reaction temperature and pressure? 3. Is the general requirement for sulfur using a catalyst 0.1 ppm or lower?
This requires a comprehensive analysis: what is your total gas volume, what are the other components in the exhaust gases, and what are their concentrations?
The total gas flow rate is approximately 50,000 cubic meters per hour; the other components are hydrogen and nitrogen
Let me answer and we can discuss it together. 1. It’s feasible, but there’s one issue: what product do you want to produce after methanation? Whether it is better to use natural gas or to directly recover hydrogen through pressure swing adsorption of the raw material – which option offers better cost-effectiveness – can only be determined by developing a specific plan. 2. As for the methanation reaction itself, pressure is not a determining factor; currently, the maximum temperature that methanation catalysts can withstand is said to be 850 degrees, though it is usually around 500-600 degrees. Since the carbon content in your case is very low, the increase in temperature will not be significant. 3. The sulfur content here is already sufficient to meet the requirements of methanation catalysts
Is the methane produced by your exhaust emissions sufficient to cover the cost of the catalyst?
Poster: 1: CO2 can be added to the gas to adjust the H/C ratio in methanation； 2: A desulfurization unit must be installed to ensure that the total sulfur content before entering the methanation unit is less than 0.1PPM ； 3: The methanation processes currently in use in China, whether domestic or imported, generally operate at around 3.0; the reaction temperature varies depending on the composition of the materials involved ；
The total volume of chemical plant exhaust gas is approximately 50,000 cubic meters per hour; it contains 0.3–0.5% CO, with this concentration varying to some extent – it can reach up to 0.8% at its maximum and as low as 0.1% at its minimum； The CO2 content is less than 100 ppm, and the oxygen level after purification is ≤0.1%. The other components are hydrogen and nitrogen. The carbon content in the gas is very low, so methanation is theoretically feasible; however, carbon needs to be added to adjust the hydrogen-to-carbon ratio, which requires a large amount of hydrogen to produce methane – 4 molecules of hydrogen are needed to produce one molecule of methane – and this approach may not be economically viable. It is more economical to consider extracting hydrogen from these exhaust gases as a product.
I may not have explained it clearly; the main idea here is to use hydrogen that has been purified for ammonia synthesis, replacing PSA purification with methanation in order to reduce hydrogen waste and also minimize nitrogen loss.
Methanation is a very common method for syngas purification, and it is entirely feasible.