Weekly Topic for Ammonia Production: What issues should be considered in the oxygen-enriched continuous gasification of briquetted coal?

I’m also looking forward to the moderator’s post; upvote! I hope those who have practical experience in this area can offer some guidance :)

Looking forward to it; I hope experts can offer a lot of guidance.

Those from Sanming, Fujian, should have a say – why isn’t anyone coming?

Reply to 1# Yan Qiusheng: The main advantages of the oxygen-enriched continuous gasification process are: (1) Compared with intermittent gasification, coal briquette consumption can be reduced by 20%. (2) Environmental pollution caused by purge gas release is virtually eliminated (oxygen-enriched continuous gasification without a purge phase), resulting in significant environmental benefits. (3) The production capacity per furnace is high. Compared with intermittent gasification, the gas production per furnace of the same furnace type can be doubled. (4) The conversion rate of carbon is high; the mass fraction of residual carbon in the ash can be reduced to 7%–12%, and the impurities carried away in the gas are significantly decreased. (5) The process is simple, the furnace operation is stable, it is easy to operate, and the maintenance workload is low. Since the gasification process is a simple top-blowing operation without the multi-stage switching of intermittent gasification, it is relatively easy to operate. With no valves that need to be switched frequently, the amount of maintenance work is reduced, resulting in lower maintenance costs. (6) High steam decomposition rate; compared to batch gasification, the steam decomposition rate can be increased by 10%. (7) Due to the use of continuous gasification, the gas composition remains stable, which is particularly beneficial for the stability of the entire production system. (8) High heat utilization rate, with the ability to generate medium-pressure steam as a by-product. The main drawbacks of the oxygen-enriched continuous gasification process are: (1) Although it is a continuous gasification process, it remains at atmospheric pressure, and thus it cannot overcome the problems of low carbon conversion efficiency and high energy consumption. (2) Although the investment is lower compared to pressurized gasification, compared to fixed-bed batch gasification, this process requires oxygen and the installation of an air separation unit, resulting in higher investment costs. Moreover, the cost of producing oxygen increases the cost of the final product; this is the main factor restricting the development of oxygen-enriched continuous gasification. Although there are views currently suggesting that the use of PSA pressure swing adsorption oxygen production technology can reduce investment and costs, if the nitrogen generation process in subsequent stages is taken into account, a new pressure swing adsorption nitrogen production unit is still required; overall, its investment and costs remain higher than those of batch gasification. (3) An excessive oxygen content in gas poses significant hazards. In the gas produced by oxygen-enriched continuous gasification, the oxygen content is relatively low, with a volume fraction of generally only 0.2%. However, due to the high oxygen content in oxygen-enriched air, incomplete gasification can lead to a rapid increase in oxygen levels in the gas, posing significant safety risks for subsequent processing stages. Currently, to control the oxygen content during the production process, the measure taken is to raise the outlet temperature of the gas furnace to above 550°C; this measure, in turn, leads to increased consumption of raw coal. (4) The carbon dioxide content in the gas is high. In the gas produced by oxygen-enriched continuous gasification, the volume fraction of carbon dioxide can reach 15% to 20%; the main consequences of this are increased power consumption in compressors, higher steam consumption in the conversion stage, and increased load on the decarburization stage. To address this drawback, as long as it is thoroughly considered during the design phase, it will not have much impact on production; it merely results in higher energy consumption during production. (5) The methane content in the gas is high. The volume fraction of methane in the gas produced by oxygen-enriched continuous gasification is >2%. For large nitrogen fertilizer manufacturers, the liquid nitrogen washing process can be used for removal; however, small and medium-sized nitrogen fertilizer companies currently do not have very effective methods for removing methane, and they can only address this issue by increasing the amount of air released during synthesis. This results in increased power consumption in the synthesis section. At the same time, the high methane content also means that oxygen-enriched continuous gasification is not suitable for the co-alkanol process with a high alcohol-to-ammonia ratio. (6) The gas contains organic compounds such as benzene and naphthalene. Although the content of organic compounds such as benzene and naphthalene in the gas produced by oxygen-enriched continuous gasification is low, their hazards are significant; moreover, these hazards are not apparent at the beginning of production, but they gradually become evident over time as accumulation occurs. Its main manifestations are as follows. ①It affects the regeneration systems in the desulfurization and modified desulfurization units, making it difficult for sulfur foam to form ； ②Affects the decarbonization system. If PSA decarburization is used, it can cause poisoning of the adsorbent; whereas carbon propene decarburization or NHD decarburization can result in excessive levels of benzene and naphthalene in the carbon dioxide gas, affecting the urea production plant. ③Prolonged exposure will affect the lifespan of the catalysts in the synthesis section. At present, small and medium-sized nitrogen fertilizer manufacturers do not yet have very effective purification processes for organic substances such as benzene and naphthalene. Although some research institutions have proposed using the benzene and naphthalene removal processes from natural gas purification to treat water gas, this is still in the research stage, with no practical production examples yet. (7) Oxygen-enriched continuous gasification is not suitable for the production of monohydric alcohols. Since the oxygen-enriched volume fraction used in the oxygen-enriched continuous gasification process is only 50%–60%, the nitrogen volume fraction in the water gas remains above 10%; such water gas cannot be used at all for the production of monohydric alcohols. Currently, there are also suggestions that carbon dioxide from the decarbonization unit and pure oxygen can be combined to form oxygen-enriched air to be used as a gasification agent. But doing this **results in increased oxygen consumption, increased compression work, and higher costs. At the same time, the purity requirement for carbon dioxide is also high.