The low-temperature shift reactor of Chongqing Jianfeng Chemical’s 300,000 tons/year ammonia synthesis plant operating under the Braun process has achieved a record-high performance level

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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: 377. 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 being 0.17%. This achievement sets a new benchmark for further energy savings and reduced 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 operates two natural gas-based ammonia synthesis plants. The first phase of the plant was completed and put into operation in 1993, with a capacity of 300,000 tons of ammonia per year, along with a urea production capacity of 520,000 tons per year. 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 low-voltage transformation processes, it has used the B206-1 low-voltage catalyst from Sinopec Nanhua Catalyst Factory, as well as the B205-1 low-voltage catalyst from Clariant Huajin (formerly known as German Southern Chemicals and Panjin Liaohe Catalyst Factory, among others). In November 2019, a major overhaul was carried out on the company’s first-phase plant with a capacity of 300,000 tons of synthetic ammonia per year; during this process, the low-temperature shift catalyst was replaced. The volume of catalyst loaded 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. The product has been operating at full capacity for over a month now. The CO content at the outlet of the low-temperature shift reactor has decreased from 0.22% during the same period last year to 0.17%; the shift conversion rate has reached 93.4%. The pressure drop has also dropped from 40–50 kPa in the previous period to around 21.5 kPa. This represents the best operating performance since the plant was put into service in 1993, signifying a new breakthrough in the application technology of domestic low-temperature shift catalysts. The catalyst began temperature-raised reduction on November 22, 2019, using the low-hydrogen dry gas reduction method. 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 restoration 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 been maintained 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 previously, in this case: 1. The pressure difference has decreased by more than 50% on an annual 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-activation catalyst offers significant advantages when used in energy-saving, low-water and low-carbon Braun processes, KBR processes, and AMV processes; it enables the outlet CO concentration to be reduced to near-equilibrium levels, thereby 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; examples include Chongqing Jianfeng Chemical’s No. 1 Fertilizer Plant using the Braun process, Jinxi Natural Gas Chemical Plant, Sichuan Tianhua Company, and Urumqi Petrochemical’s No. 2 Fertilizer Plant ； 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 Fertilizer Plant, etc ； AMV process units: Hainan Fudao Phase I, Zhongyuan Dahuahua, etc.