Regarding the removal of argon using liquid nitrogen washing
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Our facility is a coal-based synthetic ammonia plant, and the operating procedures are as follows: this plant uses the process of refining raw gas with low-temperature liquid nitrogen. It is carried out in two steps: First, high-boiling-point impurities such as CO2 and CH3OH remaining in the feed gas after methanol washing can be removed through molecular sieve adsorption, thereby preventing their freezing at low temperatures from affecting cryogenic equipment. Secondly, due to the large difference in boiling points between H2 and CO, CH4, Ar, and N2, as well as the fact that the boiling points of CO and CH4 are higher than those of H2 and N2, CO, CH4, and Ar are condensed by liquid nitrogen and dissolved in it, thereby achieving gas purification. Our refrigeration system is designed to handle 757 m3 of off-gas, of which 0.9% is argon and 65% is hydrogen. We plan to wash this gas with ammonia and then feed it back into the system via a compressor for further reaction. The operating procedures state that argon should be removed, but the process engineer says that liquid nitrogen washing cannot remove argon. Therefore, I’m seeking advice from everyone here! ! !
I still don’t understand the question; I only see that the engineer’s opinion differs from what the operating procedures stipulate. As for this discrepancy, it still needs to be resolved by the person who created it; the engineers should be able to explain it clearly. Under the same pressure, liquid nitrogen should be able to condense the argon component into it. I’m not very familiar with your process, just for reference.
I mainly want to ask whether liquid nitrogen washing can remove argon. We plan to recover some of the vent gas (which is normally burned in a flare during normal operation); the flow rate is 757 m3/h, and the argon content is 0.9%. Can liquid nitrogen washing be used to remove this argon? Prevent argon buildup.
In theory, it’s possible, but is there a way to account for it? Since liquid nitrogen is a secondary energy source, corresponding equipment is required, and the properties of other components must also be taken into account to determine whether they are suitable for remaining uncondensed at low temperatures. At the same time, there is also an oxygen component, which makes it quite complex. It’s best to send the process; explaining it with pictures will be more intuitive.
We are an ammonia synthesis plant, and our design includes a liquid nitrogen washing unit; no additional equipment is needed. I’ve also checked other sources, and it is possible to remove argon using this method.
This post was last edited by Dedication on 2020-12-4 at 12:54. Please explain your process for venting gas. If the gas is washed with liquid nitrogen and released under stable pressure during operation, now in order to recover the hydrogen contained within, the vented gas is sent back for liquid nitrogen washing. 1: How is it sent back? Equipment 2 requires pressurization: Since it can’t be cleaned normally, if it’s sent back, it still won’t be cleanable; that’s the limited capacity of the equipment. 3: Taking everything into consideration, such as the amount of gas that needs to be released, and whether it’s worth using equipment for hydrogen recovery – like Prisen’s system – whether the costs can be covered I took another look at the post posted by the original poster; it’s a person who enjoys learning and delving into details, working in mechanical equipment fields, and studying both mechanical, electrical, and instrumentation aspects as well as manufacturing processes. The numbers 50/80 seem quite friendly
Our syngas comes after being washed with liquid nitrogen; I checked the operating procedures and found that argon can be removed. 1. A reciprocating compressor is sufficient; the investment can be recouped within half a year. 2. The flow rate of the vent gas is low, and passing it through a reciprocating compressor before sending it to liquid nitrogen washing has almost no impact on it; with a design capacity of 150,000 cubic meters, the vent gas volume is less than 1,000 cubic meters. 3. We directly recover the hydrogen and nitrogen after ammonia washing, without the need for any additional equipment; thus the cost is low, but the annual profit is around several million yuan
It is recommended to analyze the gases in the synthesis circuit, as there are differences between the design data and the actual operating data； Regarding whether to install a hydrogen-ammonia recovery unit, if the enterprise already has existing chemical equipment that can be reused, that is an option; but if not, a new unit will need to be purchased. It is recommended to carry out thorough preliminary work and conduct a comprehensive analysis to determine whether it is the gasification, purification, or refining system that is causing changes in the gas composition. It is best to optimize the previous system to address the issue.
The synthesized off-gas returns to the purification process, and in addition to considering argon, the effects of ammonia and water vapor must also be taken into account. It is best to use the hydrogen extraction method: the pressurized gas is washed with ammonia, hydrogen is extracted, the hydrogen is sent to the inlet of the demethanization/synthesis compressor, and the waste gas is sent to the flare. The economic costs need to be carefully calculated
We pass through the ammonia scrubber, then use a compressor to increase the pressure before entering the transformed ammonia scrubber, and subsequently entering the low-methane section; therefore, argon is the main factor to consider.