Oxygen consumption in fixed-bed atmospheric gas production

In fixed-bed gas generation at atmospheric pressure, air is used as the gasifying agent; in gas generation using pure oxygen, oxygen serves as the gasifying agent. The oxygen consumption for producing 1,000 cubic meters of crude gas is around 220 units. Gas production per furnace in the case of pure oxygen usage is high, reaching 13,000 NM3/h. The concentrations of CO and H2 are over 80%, while the CO2 concentration is above 15%.

We have been in operation for several months: H2 at 48%, CO at 28–30%, and CO2 at 21%. Scabs often form inside the furnace, and the maximum flow rate of oxygen per stream is 1500 Nm3/h. Based on the composition of the gas, is the amount of steam used too high? Those who have operated fixed-bed pure oxygen furnaces, please share any suggestions. Thank you.

First, let’s address the original poster’s question. For 100,000 cubic meters of semi-water gas, as stated in the second floor’s response, the oxygen consumption of a fixed-bed reactor under normal pressure is indeed the lowest among all types of reactors. Assuming an effective gas content of 80% (CO + H2), the amount of pure oxygen required is approximately 17,600 Nm3/h; this necessitates the use of a cryogenic air separation unit with a capacity of 20,000 Nm3/h. If air is used, that would be 83,800 Nm3/h of air. One of the key reasons why constant-pressure fixed-bed reactors are used so widely and for such a long time in China is their low cost of operation; the oxygen used as a gasification agent is free, and steam can be produced and utilized internally, which means that the gasification agent is essentially free. If it is changed to a pure oxygen continuous fixed-bed system with atmospheric pressure, then it has little prospect. The energy consumption of batch fixed-bed reactors at atmospheric pressure is extremely high, with the largest portion of this energy being used for compressing gas. Although switching to continuous fixed-bed reactors using pure oxygen at atmospheric pressure increases the gasification rate, reduces the number of gasification furnaces needed, and eliminates the need for gas storage tanks, the complex processes involved in the entire system remain unchanged; the amount of compression work required for the gas still remains the same. What’s more, oxygen, which is used as a gasification agent, now comes at a cost – its price is 0.45 yuan per cubic meter. All attempts by Jinmei’s subsidiaries to convert batch gasification furnaces into continuous fixed-bed reactors using pure oxygen failed, and the new air separation units that were installed remained unused. The way forward for fixed-bed reactors lies still in pressurization. Let’s talk about the issue on the 3rd floor again. In the constant-pressure fixed-bed reactor, the effective gas components are not particularly prominent, but the CO2 content is a bit high. The concentration of useful gas components is low, while the CO2 content is high; moreover, scabs often form inside the furnace. The first thing that comes to mind is that the steam-to-oxygen ratio is too low, meaning there isn’t enough steam. I’m not sure what the current steam-to-oxygen ratio is – if it’s less than 1, then it’s indeed too low. You might want to try increasing the steam-to-oxygen ratio and see what happens. If the oxygen-to-gas ratio is relatively high, then you need to consider issues such as the layer height and even the height-to-diameter ratio. Of course, easy scarring is not caused solely by a low oxygen-to-carbon ratio; other factors include the use of coal with high caking properties, problems with the air distribution across the grate, and localized overheating.

Thank you, moderator! ~When we do the calculations, it’s not very clear either. .