How to choose the conversion process in the ammonia process technology program

The effective components of ammonia syngas are hydrogen and nitrogen, of which the ratio of hydrogen to nitrogen is about three. Coal as the raw material for the production of crude gas, all contain CO, CO2, CH4, and sulfide and other impurities, and the content of carbon monoxide is higher, the purpose of the transformation is mainly to transform carbon monoxide in the semi-aqueous gas and water vapor into carbon dioxide and hydrogen, and then through the decarbonization section of carbon dioxide removal, so that the composition of the gas to meet the requirements of ammonia synthesis.

The selection of the conversion process is closely related to the gasification process and the subsequent purification process. As the transformation reaction is exothermic, the lower the reaction temperature, the more favorable for the reaction, the steam required for the reaction is an important part of the production cost, so the selection of the process should be conducive to saving steam, reducing energy consumption, and improving the production capacity of the equipment.

In order to achieve the purpose of conversion, there are two processes available: non-sulfur-resistant medium-temperature conversion using iron catalysts and sulfur-resistant low-temperature conversion using cobalt and molybdenum catalysts.

At present, domestic small and medium-sized ammonia synthesis enterprises mostly adopt the traditional medium-variable and low-variable process, full low-variable process and medium-low-low process. The full low-temperature transformation is a new transformation process developed on the medium-temperature string low-temperature process relative to the medium-temperature transformation. It adopts cobalt-molybdenum sulfur-resistant conversion catalyst with excellent low-temperature activity, and the hot spot temperature of one section of the reaction is reduced by 100~200°C compared with that of medium-temperature conversion, which significantly reduces the steam-to-gas ratio required for the conversion reaction and saves a large amount of steam consumption. At the same time, due to the decline in reaction temperature and conversion rate of the conversion reaction, the gas volume is relatively smaller, lowering the system resistance and reducing the consumption of compression power. This process relaxes the index of primary desulfurization, thus reducing the cost of desulfurization. In addition, the drop in operating temperature also reduces the material requirements for the converter furnace and improves the equipment maintenance conditions. In short, under the same operating conditions and working conditions, its equipment capacity and energy-saving effect are better than that of medium string low and medium low low process.

At present, the domestic ammonia synthesis plant using pressurized gasification process are used in sulfur-resistant low change process. This process can make full use of the temperature of the gasification outlet process gas and the large amount of water vapor contained therein, thus eliminating the need for additional steam, and on the other hand, also reduces the pressure of the steam network of the whole plant. The sulfur-tolerant catalyst has a strong organic sulfur conversion capability, and the high activity of the catalyst reduces catalyst loading.