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The low-pressure shift converter in Chongqing Jianfeng Chemical’s 300,000 tons/year ammonia synthesis plant, operated using the Braun process, has achieved its best performance ever. Author/Source: Sichuan Shutai Technology & Chemical Co., Ltd. Date: 2020-02-03. Clicks: 159. By replacing the catalyst model used in the low-pressure shift converter (SCST-231-53), Chongqing Jianfeng Chemical was able to reduce the CO content at the outlet of this converter to below 0.2% under full-load operation – the actual value reached 0.17%. This achievement sets a new standard for achieving further energy savings and reducing consumption in low-water, low-carbon processes, while also ensuring safe, stable, long-term, full-capacity, and optimal operation. Chongqing Jianfeng Chemical Co., Ltd. is a holding subsidiary of Chongqing Jianfeng Industrial Group Co., Ltd., and is part of the Chongqing Chemical and Pharmaceutical Group. The company owns two sets of natural gas-based ammonia synthesis plants. The first plant was put into operation in 1993, with an annual production capacity of 300,000 tons of ammonia and 520,000 tons of urea; it utilizes the Braun ammonia synthesis process from the United States and the Snam urea process from Italy. The second-phase plant has a capacity of 450,000 tons of synthetic ammonia per year, along with 800,000 tons of urea per year; it utilizes the KBR synthetic ammonia process from the United States and the Stamicarbon urea process from the Netherlands. It was put into operation in May 2012. Since its commissioning, the company has maintained meticulous management, stable operation, and achieved excellent results. For its low-temperature conversion reactors, it has used the B206-1 low-temperature conversion catalyst from Sinopec Nanhua Catalyst Factory, as well as the B205-1 low-temperature conversion catalyst from Clariant Huajin (formerly known as German Southern Chemicals and Panjin Liaohe Catalyst Factory, among others). In November 2019, the company’s first-phase plant with an annual capacity of 300,000 tons of synthetic ammonia underwent a major maintenance campaign, during which the low-temperature catalyst was replaced; the volume of catalyst used in this process was 47 m3. Before making the replacement, the performance of low-temperature shift catalysts in the 540,000 tons per year synthetic ammonia production units of \"Inner Mongolia Chemical Industry Company\", the 300,000 tons per year synthetic ammonia production unit of \"Xinjiang Tianyun Chemical (Qixiashan, Nanjing)\", and the two 300,000 tons per year synthetic ammonia production units of \"Inner Mongolia United Chemical\" was evaluated. It was found that the SCST-231-53 low-temperature shift catalysts used in these Kellogg process units performed better than previous catalysts, and it was likely that they would also yield good results in the Braun process; therefore, it was decided to use this model of catalyst. This product has been operating at full capacity for over a month now; the CO carbon content at the low-temperature conversion outlet has dropped from 0.22% during the same period in the past to 0.17%. The conversion rate has reached 93.4%, and the pressure difference has decreased from 40–50 kPa during that same period to around 21.5 kPa. This represents the best performance ever since the plant started operation in 1993, indicating a new breakthrough in the technology used for low-temperature conversion catalysts in China. The catalyst began temperature-induced reduction on November 22, 2019, using low-hydrogen dry gas reduction. During the reduction process, it must be carried out strictly in accordance with the pre-established plan, and the reduction temperature shall not exceed 200°C to maintain the catalyst’s activity at low temperatures. The reduction process was completed on November 26, 2019, and it was successfully integrated into the system on November 29. Currently, the operating load of this device is 103%; the natural gas flow rate is 30,006 Nm3/h, the water-to-carbon ratio in the conversion process is 2.7. The inlet temperature of the low-temperature shift reactor is around 206°C, and after adjustments it has remained at around 193°C. The peak temperature is 212°C, the pressure is 2.9 MPa, the pressure difference is 21.5 KPa, the steam-to-gas ratio in the low-temperature shift process is 0.33. The carbon monoxide content at the inlet of the low-temperature shift reactor is 2.69%, while it remains stable at around 0.17% at the outlet. From 2000 to 2018, this system used a B205-1 low-temperature shift catalyst. At the beginning of its operation, the water-to-carbon conversion ratio was 2.7, the steam-to-gas ratio in the low-temperature shift reactor was 0.33, the inlet temperature of the reactor was 195°C, the peak temperature was 213°C, the carbon monoxide content at the inlet was around 2.7%, while the CO content at the outlet was around 0.22%. The pressure difference was 40–50 kPa. Compared to the operation of the device and the low-temperature catalysts used in the past, this time: 1. The pressure difference has decreased by more than 50% on a year-on-year basis, and it remains relatively stable with almost no fluctuations ； 2. The CO content at the outlet of the low-temperature converter remains stable at around 0.17%, a decrease of 0.05% compared to the previous level. This allows for an increase in synthetic ammonia production by 6.5 tons per day, generating annual economic benefits of 5.85 million yuan. It also reduces consumption and enables normal operation at higher loads. It can be concluded that the SCST-231-53 low-variation catalyst offers significant advantages when used in energy-saving low-water-carbon Braun processes, KBR processes, and AMV processes; it enables the outlet CO concentration to be reduced to near-equilibrium levels, providing an important guarantee for energy savings, cost reduction, and increased production. It is applicable to both Kellogg and low-water-carbon energy-saving process units, such as Chongqing Jianfeng Chemical’s First Fertilizer Plant, Jinxi Natural Gas Chemical Plant, Sichuan Tianhua Company, and Wushihua’s Second Fertilizer Plant that use the Braun process ； KBR process units: Chongqing Jianfeng Chemical’s Second Fertilizer Plant, Hainan Fudao Phase II, China National Petroleum Corporation’s Daqing Petrochemical Complex, China National Petroleum Corporation’s Tarim Large-scale Fertilizer Plant, etc ； AMV process units: Hainan Fudao Phase I, Zhongyuan Dahua, etc.