The issue of the quality of medium-pressure steam produced as a by-product of ammonia synthesis
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As the title suggests, for the medium-pressure steam generated as a by-product in the ammonia synthesis unit of ammonia plants, what are the advantages and disadvantages of saturated steam compared to superheated steam? How to choose? It would be best to have specific data for comparative analysis.
This is related to the steam balance of each company, so there’s no clear answer I guess. Furthermore, from the perspective of thermal balance, it is necessary to consider what synthesis process is being used; as long as the heat required for preheating the gas entering the synthesis tower is met, the more heat that can be recovered, the better.
It is the commonly used low-pressure ammonia synthesis, employing the Cassali process.
The by-product steam usually has low pressure; saturated steam is sufficient for use as a heat source. If it is to be used as a steam turbine power source, for example at a temperature of 450 degrees, overheating is usually required through other equipment; it is not practical to achieve overheating directly in the synthesis process.
What’s the logic? Many people do this.
To the best of my knowledge, the steam generated as a by-product in the Cassali process is mostly saturated or superheated steam at 2.5–4.5 MPa, which is compatible with the company’s steam network. It produces saturated steam, with a slightly higher heat recovery efficiency; when superheated steam is produced, the heat recovery efficiency decreases. Approximately 0.9–1.0 tons of steam are generated per ton of ammonia.
Don’t you think that using steam under such pressure to generate electricity means that these small generators are almost obsolete by now?
I don’t understand; there’s no need to generate electricity. Isn’t it appropriate to use medium-pressure superheated steam in production to drive the turbines?
To generate superheated steam, additional equipment is required. As a high-temperature and high-pressure system, adding such equipment means increased investment, more work for connecting the systems, higher system circulation resistance, and elevated operating costs. As for steam power generation, it’s not impossible; if saturated steam can be used in a balanced manner within the plant, the energy efficiency will be higher than that of power generation. In my opinion, there’s really no need to generate electricity ； If the heat balance cannot be maintained, generating electricity could be considered