The issue of CO content in the output of synthetic ammonia glycol
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Our company’s ammonia synthesis process is as follows: shift reaction — PSA-CO2 — medium-pressure methanol (without a recycle pump, uniform-temperature internals, copper catalyst, 12 MPa) — high-pressure methanol (without a recycle pump, uniform-temperature internals, copper catalyst, 22 MPa) — methanation — ammonia synthesis. The company now wants to shut down one of the systems, either the medium-pressure methanol or the high-pressure methanol system. In my opinion, the equilibrium concentrations of CO and CO2 after medium-pressure methanolization should be higher than those under high-pressure methanolization; furthermore, the generation of large amounts of methane after methanation is detrimental to the synthesis system. But I don’t know how to calculate it, or what the relevant empirical values are. Please help, thank you.
If one methanol production unit is shut down, it is necessary to reduce the CO content at the exit of the conversion process in order to lessen the load on the subsequent systems. The CO and CO2 contents in the gas flowing after the methanol production stage will definitely be higher as a result of the shutdown of one unit, which in turn increases the load on the methanation process. The methane content in the gas fed into the ammonia synthesis process also increases accordingly; this represents an increase in the amount of inert gases, thereby having an impact on the ammonia production volume.
Thank you, moderator. The CO level at the outlet of the methanol conversion system when using a parking cover will definitely decrease; it might be based on the scenario where the electric furnace is not in use. My question is: if only the medium-alcohol system is used, could the CO concentration at the outlet become too high, thereby affecting production?
How much CO control are you adjusting at the outlet now? How much should CO2 emissions from decarbonization be controlled? What are the CO values for the two methanol export streams respectively?
The CO content at the outlet of the converter is less than 1.5%, and the CO2 content at the PSA outlet is less than 2%. There is no analysis table for CO and CO2 at the outlet of medium-alcohol; at the outlet of high-alcohol, CO+CO2 is generally below 100 ppm. A portion of the medium-alcohol system goes through a bypass.
Reduce the CO output at the outlet to below 1%; it would be even better if it could be reduced further. Shutting down one methanol unit will have an impact on the subsequent systems, but it is estimated that this impact can be overcome.
Are there any requirements for the CO2 level at the PSA pressure swing adsorption outlet?
The lower, the better. I wonder if there is any headroom in your PSA?
There are no automatic instruments for manual sampling and analysis. Compare the crude alcohol production of the other two systems. If it is necessary to shut down one of them, it is recommended to shut down the medium-pressure alcohol system; this makes it easier to isolate and protect the system. With one less pressure level, operating the compressor becomes simpler, and it is easier to maintain the conditions at the outlet of the high-pressure system. The high-pressure section of the compressor requires a certain amount of headroom