Calculation of synthetic circulation volume
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I’m involved in the design of methanol synthesis; could someone with expertise please explain how the flow rate of the gas in the methanol synthesis cycle is calculated? What age is appropriate? Thank you very much; could you give an example?
There is no theoretical value for the gas flow rate in the methanol synthesis cycle; it mainly depends on the performance of the catalyst, and we can determine it by analyzing the gases exiting the synthesis process. Generally, based on experience, the ratio of recycled gas to fresh gas is around 7:1.
Agree to 7:1; our fresh gas volume is around 140,000, while the recycled gas volume is around 920,000 to 960,000
The cycle ratio for monolcohol production should be kept between 5.5 and 6; 7, as mentioned above, would be considered quite high
It mainly depends on the specific conditions of the equipment. It’s only a little past 2 o’clock here right now
I believe that due to differences in specific process conditions such as synthetic pressure and reactor type, the synthetic circulation volume varies; however, the option that is best suited for a particular situation is certainly the best one. Moreover, each process has its most appropriate circulation ratio.
So, could someone upstairs give a few examples? I think around 4 should be sufficient.
The gas flow rate in the methanol synthesis cycle depends primarily on the performance of the catalyst; we can determine it by analyzing the gases entering and leaving the synthesis process. In our company, at East China University of Science and Technology, the technical cycle ratio is around 5.5. Also, as mentioned on the fifth floor, “it mainly depends on the specific conditions of the equipment.” “It’s only a little after 2 o’clock here right now,” and they don’t mention the value of (H2–CO2)/(CO+CO2) = 2. I find that a circulation ratio of 2 to be a bit strange; could you explain the specific process?
The determination of the recycle ratio is related to factors such as the type of synthesis tower, the quality of the feed gas, and the synthesis pressure; there is no universal rule for it. If the recycle ratio is too low, the reaction may be too intense, making temperature control difficult and ensuring carbon efficiency impossible. On the other hand, if the recycle ratio is too high, it increases power consumption, system resistance, and the investment required for equipment and pipelines. For the production of ordinary monohydrates, if the hydrogen-to-carbon ratio in the feed gas is kept within the normal range (2.05–2.25) and the content of inert gases is not high, it depends on whether the reactor is air-cooled or water-cooled. For air-cooled reactors, the recycle ratio is generally not less than 5; whereas for cold-quench reactors with lower efficiency, the recycle ratio indeed needs to be above 7. If the reactor is of the water-cooled type, the circulation ratio can be appropriately reduced, provided that the reactor’s design enables effective heat transfer under high CO conditions at the inlet, and high-activity and high-heat-resistant catalysts are used to ensure that the overall conversion rate of the active components remains satisfactory even at a lower circulation ratio. Especially in large methanol plants, the recycle ratio has been reduced to around 2 in many cases, but there are yet no operational examples. For some devices with special characteristics, such as those with a high content of inert gases or a hydrogen-to-carbon ratio that deviates significantly from the aforementioned range, it is even more necessary to determine the optimal circulation ratio through full-process simulation calculations.
The figure for this one should be for a plant with a capacity of 400,000 tons; the cycle ratio seems to be a bit high
Our system has a fresh gas flow rate of 140,000, and a recycled gas flow rate of 700,000; it is a water-cooled reactor
The circulation ratio is related to the composition of the feed gas and the heat transfer mode and capacity of the reactor. The reactor has strong heat transfer capacity; what’s the harm in using a slightly lower circulation ratio?
The circulation ratio is generally between 5:1 and 10:1. If the recycle ratio is too low, side reactions may increase.
7:1? Is it a bit too big? Our 300,000 units of methanol reached only around 650,000 at its peak
The fresh gas flow rate for 300,000 tons of methanol is estimated to be around 100,000 tons, while the recycle gas flow rate is 650,000 tons; thus, the recycle ratio is at least over 6.