What are the advantages of using CO2 gas as a coal transport gas compared to using nitrogen as a coal transport gas?
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I read a report stating that the gasification unit for certain fertilizer SHELL powder was originally designed to produce synthetic ammonia, using nitrogen as the gas carrier for transporting coal; the purity of the ethylene glycol produced was not sufficient to meet the required standards, which became a bottleneck preventing the plant from increasing its production capacity. This project involves partially modifying the nitrogen-based coal powder transportation system of the original pulverized coal gasification unit, by using CO2 gas for transportation, in order to increase production capacity and generate economic benefits. I’m seeking advice here: what are the advantages of using CO2 as a gas for transporting coal, compared to using nitrogen as such a gas?
Is it Hubei Fertilizer Factory? The advantage of using CO2 for pneumatic conveying over N2 is that there is no reaction between N2 and H2 to produce ammonia, which is beneficial for downstream low-temperature methanol washing and gas purification. The downside is that the content of useful gases in the raw gas is relatively lower
That’s right; the news was about this factory. The principle behind it is to avoid the formation of ammonia nitrogen compounds, thereby increasing the purity of the gas
It mainly depends on the subsequent products: if nitrogen is used as a raw material, it is best to use nitrogen; if nitrogen turns into an inert gas later on, then carbon dioxide should be used. However, a system for producing or supplying carbon dioxide must be available at the time of initial operation.
The advantage is definitely that using CO2 is better; as a carrier gas, CO2 can increase the yield of useful gas, result in less off-gas, and thus reduce losses of useful gas. It also plays a role in reducing CO2 emissions
Nitrogen is used for ammonia synthesis, while CO2 is used for methanol production; during the gasification process, C + CO2 → CO, and CO2 + H2 → CO + H2O. This helps to increase the carbon conversion rate. However, when CO2 is used as a carrier gas, it contains water since it is obtained through low-temperature methanol washing. As a result, poor heating in the coal feed line can lead to blockages and shutdowns of the system
Nitrogen is more expensive; using carbon dioxide, I think, means producing and using it on-site, and it can also increase the effective gas yield – at the very least, it helps to reduce the amount of carbon dioxide generated. However, generally nitrogen is used for driving the process, and carbon dioxide is switched in once the low-temperature methanol washing unit is operating normally. The use of nitrogen inevitably leads to a reaction between nitrogen and hydrogen, which increases the requirements for handling ammonia in the steam stripping section of the low-temperature methanol washing unit.
This can reduce processing energy consumption and lower the emissions of ammonia nitrogen compounds
It can be said that way, but carbon dioxide also has its disadvantages, as mentioned on floor 6.
But when CO2 is used as the carrier gas, since it is obtained through low-temperature methanol washing, it inevitably contains water; as a result, problems such as fluctuations in the heating system along the coal pipeline, blockages, and plant shutdowns can occur. So, could a dehydration unit be added to the pipeline?