【Ten Years of Rapid Development in Chemical Processing Equipment】Domestically produced gas quenching heat exchangers for reaction gases, 1980–2017
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Witnessing the decade-long rapid development of chemical processing equipment, I admire the prosperity and strength of modern China. Wishing everyone a happy New Year, and may their families enjoy peace and health. I hope this contribution will encourage more people to participate; with your involvement, Haichuan becomes even better. Everyone is welcome to join in the discussions on this forum. ------------------------------------------------------------------ In November 2017, the domestically produced equipment developed by Maoming Gravity Company – the Shaanxi Yanchang reaction oil and gas quenching heat exchanger – was completed and shipped off, destined for Yan’an, Shaanxi, a sacred site of the revolutionary movement. The successful development of the rapid cooling heat exchanger for reaction oil and gas in Shaanxi Yanchang marks another crucial step forward in the localization of equipment in China, filling a gap in the manufacture of similar products domestically. To date, this type of device is being produced in the country for the first time, and it is also only the third of its kind in the world. The extended reaction oil and gas quenching heat exchanger was manufactured by Maoming Gravity Company for Shaanxi Yanchang Petroleum Yan’an Energy Chemical Co., Ltd. It is used in the comprehensive utilization project of oil and gas resources in a 400,000 tons per year light oil processing facility, and belongs to the category of oil and gas quenching equipment. Leveraging its technical strengths, Gravity Company took the initiative to undertake the task of advancing the localization of emergency cooling heat exchangers for reaction gases and oils. Faced with various complex domestic and international challenges, the company established specialized R&D teams that have successively completed multiple key research projects.
The production of oval tubes is the core of manufacturing this reactive gas-oil quenching heat exchanger. These flat-round tubes are 4.1 meters in length; they consist of 42 pieces in 8 different specifications. Their material is 13CrMo4-5, and they are characterized by being hard and brittle, prone to cracking when heated, which makes manufacturing them difficult. In the past, it had to be imported, as there were very few manufacturers abroad capable of producing it; it was already quite difficult to make ones that were 1 meter long. Lacking any prior experience, the skilled craftsmen faced the challenges head-on, conducting repeated experiments to determine the scientific parameters involved. They developed a mature manufacturing process and ultimately overcame the technical difficulties; the flat circular tubes they produced had smooth transitions without any wrinkles. After testing their mechanical properties, all specifications met or exceeded those specified in the drawings, earning high praise from renowned experts.
Tasks such as tube arrangement, stacking, welding of the joint boxes, and installation of anti-backflow sleeves at the medium inlet are all important quality control points in the manufacturing process. The total weight of this equipment is nearly 200 tons, with 452 heat exchange tubes in total, arranged in 21 rows; each row contains up to 28 heat exchange tubes. The dimensions of the tube array are 10,350×4,100 millimeters. Due to shrinkage during welding, it is particularly important to prevent the accumulation of errors during assembly. The gravity craftsmen conducted numerous simulation tests, ranging from the exploration of technical solutions and the determination of welding material parameters to the analysis of heat treatment data, gradually reaching one technical milestone after another. After meticulous work by the skilled craftsmen, at the beginning of October 2017, the extended reaction oil and gas quenching heat exchanger was finally unveiled to the Chinese public. The total length of its tubes as well as its diagonal dimensions were kept within a range of plus or minus 3 millimeters, while its flatness was maintained within 2 millimeters. All the technically demanding requirements regarding concentricity and other parameters were also met as specified in the design drawings. The expert acceptance panel, composed of users and contractors, gave high praise to Gravity Manufacturing.
At 11:00 on October 19, 2018, the 400,000 tons per year light oil processing unit (ACO) of the Yanneng Chemical Project, which was EPC-general contracted by Beijing Engineering Company, successfully produced qualified ethylene and propylene products. Thus, the main process chain of this device – including conversion, quenching, compression, cold separation, hot separation, and oxidation of waste alkali – has been established, marking a partial success.
The ACO unit at Yan’an Energy Chemical Company is the first hydrocarbon catalytic cracking unit of its kind in China. It utilizes catalytic reaction technology to produce high-value products such as ethylene and propylene at low temperatures, offering significant advantages in terms of energy savings and emission reduction compared to the traditional high-temperature steam cracking process. The ACO unit utilizes KBR’s advanced catalytic cracking technology for olefin production; it is characterized by a high level of technical complexity, intricate process flows, and difficulties in operation. Since its first trial run in October 2018, factors such as changes in the properties of the feedstock, poor catalyst selectivity, and coking in the reaction gas quenchers, coupled with the lack of existing operational experience, have prevented the unit from achieving the yield levels specified in its initial design. This has had a serious impact on the company’s material balance and economic performance. Short operation cycles and low yields of dienes have always been the two major challenges preventing our plant from achieving full production capacity and performance standards; this has also become one of the key projects that the company is focusing on addressing.
In the face of the bottleneck issues encountered during the operation of the plant, Yan’an Energy Chemical Company took coordinated action and made informed decisions; it promptly established a technical task force and held numerous discussions with design institutes and patent holders. As a result, various technical improvements were implemented, such as adding an additional oil quencher after the reaction gas oil quencher, which extended the plant’s operating cycle from 50 days to 213 days. On this basis, the feed load to the conversion unit was gradually increased. Under high-load operating conditions, the reaction pressure was adjusted to reduce the residence time of the process gas in the reaction gas quenching heat exchanger, thereby slowing down the coking rate of this heat exchanger and laying a solid foundation for increasing the yield of dienes. Since the beginning of this year, the light oil processing center has taken the ‘Three Comparisons and Three Improvements’ initiative as a driving force, focusing closely on the main goal of achieving full production capacity and standards. During the major maintenance period, improvements were made to the riser feed system and the cracking furnace system, and new catalysts were installed, which effectively increased the stability of the plant’s operation. The yield of dienes rose from 48% to over 55%. After the start of the major maintenance on the unit, the center continuously explored the composition of the raw materials based on the unit’s operating conditions, and by taking into account the yield of dienes, it adjusted the operational parameters in a timely manner. Ultimately, operational parameters suitable for the actual composition of the raw materials were determined, which enabled further optimization of the unit’s operation and an increase in the yield of dienes.
The Yan’an Coal, Oil and Gas Resources Comprehensive Utilization Project is invested and constructed by Shaanxi Yanchang Petroleum Group. It is an integrated upstream and downstream project that uses coal, light oil, and natural gas as primary raw materials, with methanol deep-processing units and light oil processing units as its core components. The project covers an area of 3,500 mu, with an estimated total investment of 21.6 billion yuan. The project mainly involves the construction of 8 main production units, including ones for manufacturing 1.8 million tons per year of methanol, 600,000 tons per year of methanol derivatives, 400,000 tons per year of light oil products, 450,000 tons per year of polyethylene, 250,000 tons per year of polypropylene, 200,000 tons per year of butanol, 80,000 tons per year of dipropyl heptanol, and 50,000 tons per year of EPDM rubber, along with the supporting utility systems. Construction of the project began on September 11, 2015; the installation was successfully completed by the end of 2017, and single-unit testing started in the first half of 2018. On September 2, the MTO and olefin separation unit were successfully started up for the first time!