What is an appropriate level of methane content in the synthetic cycle gas?
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When the methane content in the synthetic cycle gas reaches 20%, the ammonia content at the outlet is not lower than that when the methane content is 10%.
This post was last edited by 654262293 on 2010-8-20 at 12:39. Our methane content is around 8%, while the ammonia value is approximately 12.85. When methane levels increase, the ammonia value decreases, and this effect is quite noticeable.
This issue depends on the duration of use of the ammonia synthesis catalyst and the production load; at the beginning of catalyst use, the methane content threshold can be set relatively high.
This post was last edited by 654262293 on 2010-8-20 at 12:40. When the methane content is kept around 8%, and under conditions of low system load, good catalyst activity, and low pressure, the inert gas level can be maintained between 15-20%; otherwise, it can be kept below 10-15%. If a hydrogen recovery unit is available, 15% or less is optimal.
The level of methane in the synthetic ammonia cycle gas is related to factors such as the process chosen for ammonia synthesis, operating conditions, and the CO2 content in the exhaust gas from the decarburization absorption tower. Under normal circumstances, the methane in the cycle gas produced under high pressure with an operating pressure of 26–30 MPa is slightly higher, estimated to be around 20% as mentioned by the original poster ； The cycle gas methane from low-pressure synthesis, with an operating pressure of around 15 MPa, has a lower value, generally around 10%.
We keep it around 14%.
This post was last edited by 654262293 on 2010-8-20 at 12:42. Inert gases do not participate in reactions nor do they poison catalysts; however, their presence reduces the partial pressures of hydrogen and nitrogen, which in turn lowers the rate of ammonia production. The higher the content of inert gases, the greater the decrease in ammonia production rate. Additionally, since inert gases do not participate in the reaction, they carry away heat from the reactor as they pass through it, resulting in a drop in the temperature of the catalyst layer; this also causes the compressor and the recycler to perform unnecessary work. The level of inert gas content should be controlled based on catalyst activity. When the system pressure is low, it can be set a bit higher; when the system pressure is high, it should be set a bit lower.
There is a theory that methane acts as a catalyst in the synthesis tower. ! ! ! ! ! ! ! ! ! !
Our target range is 10%-16%, which is generally determined based on the production load and the pressure in the synthesis tower; a lower value is used when the load is high. When the load is 100,000 NM3/H, methane levels are kept around 11%
Is that really the case? I think it depends on the specific design. The process package we use from CASALE has an inert gas content of no more than 1%. And if methane plays a catalytic role in the synthesis tower, then less venting is required for that methanation synthesis tower. I’d like to know the theoretical basis for this claim
This post was last edited by Chemical Gas Purification on 2010-9-24 at 17:44. The level of methane control is determined based on the design pressure, the duration of catalyst use, and the composition of the fresh gas. The poster observed that when the methane content in the synthetic cycle gas reached 20%, the ammonia content at the outlet was not lower than it was when the methane content was 10%; however, they did not take into account the amount of gas that was vented from the system – that is, the venting of these valuable gas components!