For hydrogen production units with medium-pressure gas fed into PSA systems, what are the required levels of methane and carbon monoxide?
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Why is this indicator needed? What about the methane content at the converter outlet and the medium-temperature carbon monoxide content?
Firstly, the amount of adsorbent for these two gases is limited, and it cannot deviate too much from the designed level, otherwise it will affect the purity of hydrogen. Secondly, the amounts of methane and carbon monoxide result from waste of raw materials due to low conversion and transformation rates.
I agree with the opinion from the first floor: it will increase the load on the adsorption tower, resulting in hydrogen of substandard quality. The amount of adsorbent available is limited, so the adsorption capacity is insufficient. Methane and carbon monoxide fail to meet the specifications, with low conversion and transformation rates
The methane content at the converter outlet is controlled at 4.5%, while the CO content at the medium conversion outlet is controlled at 3%. It is mainly related to the functions of conversion furnaces and medium-shift reactors. Conversion refers to the process of turning methane into hydrogen; if its concentration is high, is that acceptable? Medium-shift reaction involves converting CO into CO2. If there is no need to control either of these processes. There’s no need to build conversion furnaces and medium converters; theory needs to be strengthened.
If these two indicators are not well controlled, it will put a lot of pressure on PSA later on. . . . .
CO and methane molecules are too small; the normal adsorption layer is an activated carbon layer. If their concentration is too high, they will move on to the molecular sieve layer or even penetrate the molecular sieve and reach the product. It is more difficult to separate them in the molecular sieve area than in the activated carbon area.
The teacher on the 2nd floor said it very well – we need to take into account not only the adsorption properties of the adsorbent but also the conversion efficiency and the rate of change of efficiency of the device
I agree with what was said on floor 7: CO is relatively difficult to adsorb; specialized activated carbon adsorbents must be used for this purpose. 5A molecular sieves have a strong adsorption capacity for methane, but their desorption ability is weak. Failing to control the parameters can cause impurities to penetrate the adsorption layer
Mainly, the methane content after conversion and the carbon monoxide content after medium transformation are controlled at <5% and <3%, respectively.