Some issues in the carbon monoxide conversion section of ammonia synthesis
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I am a senior student currently working on the design of the carbon monoxide shift unit for ammonia synthesis. I have encountered some issues during this process, and I have written them down here in the hope of discussing them with everyone. In the materials reviewed, the oxidation of heavy oil involves a reaction between oil and oxygen to produce feed gas, and the feed gas contains very little nitrogen. Isn’t there a process that involves a direct reaction between air and heavy oil, with no nitrogen added during the synthesis stage?
Partial oxidation of heavy oil requires oxygen to drive the reaction and provide heat. If air is used, first, such a vigorous reaction cannot be achieved as the reaction temperature is not high enough; second, an excess of air must be added, and the excess nitrogen needs to be removed in subsequent stages.
It is recommended that the original poster change the direction of their graduation thesis; new ammonia production plants using oil-based feedstocks are no longer being built, and most of the existing plants have changed their processes. So your current topic is a bit far removed from practice; it is recommended that you work on ammonia production from natural gas or coal. As for HTS or LTS issues, simply doing the design isn’t too complicated.
Heavy oil can also be oxidized using oxygen-enriched air; the oxygen content in such air is 50–52%. Compared to oxidation with pure oxygen, the furnace temperature remains more stable and the process is more adaptable. The downside is a 6% increase in fuel consumption. The biggest drawbacks are an 20% increase in gas volume, limited equipment capacity, higher investment costs, and increased electricity consumption. Air vaporization is out of the question – it’s simply not economical. The person on the third floor is right; basically all of the original oil-based types, regardless of size, were replaced, as the cost was too high. It seems that you are not just involved in the design of transformation processes.
In the gasification section, the oxidation process of either heavy oil or coal must take place at specific high temperatures (usually between 1250 and 1350 degrees). At these temperatures, carbon is converted to CO most effectively, with fewer hydrocarbons such as CH4. (In the case of 9 gasification reaction equilibria, in chemical process design, it is first necessary to find theoretical support, on which basis the most moderate temperatures and practically suitable pressures can be determined.)
OP, you can work together with the air separation design team; that way, less nitrogen will be added to the system:::::::::::