【Major Chemical Equipment】091 – Domestic circulating heat exchange and separation unit
Thread Content
The past decade has been a period of rapid development in China’s chemical industry, marked by the emergence of many new processes, products, and equipment. There has also been significant progress in China’s chemical processing equipment, which has contributed to the swift advancement of the petrochemical sector. Here, we have compiled some of the achievements and breakthroughs made by Chinese equipment manufacturers in terms of larger-scale production and greater use of domestic equipment. We invite everyone to share their insights and discuss these topics together; let’s cheer for Made in China and support the development of chemical processing equipment! *********************************** The circulating heat exchange separator is a high-end device in the coal chemical industry, whose core technology is monopolized by foreign countries. At the beginning of the project, Shanghai Lanbin assembled a high-caliber development team composed of scientists and engineers of different age groups. Under the leadership of technical leader Comrade Zhang Yanfeng, they faced challenges head-on. Over the course of more than two years, despite repeated experimental failures, they never lost heart and ultimately overcame numerous world-class technical difficulties, including those related to anti-clogging heat transfer design, the reliability of key components, and the manufacturing processes for super-large structures. As a result, a domestically produced circulating heat exchange separator was developed and put into industrial use.
Application scenarios of the circulating heat exchange separator: The process flow of the circulating heat exchange separator is shown in Figure 1. The circulating heat exchange separator is suitable for coal-to-oil Fischer-Tropsch synthesis units. The high-temperature oil and gas generated by the Fischer-Tropsch reaction exchange heat with the low-temperature circulating gas in the heat exchange module of the circulating heat exchange separator, after which they proceed to the separation module for gas-liquid separation. The separated oil and gas mixture is collected along the inner wall of the shell and sent to the oil and gas air cooler via the oil and gas outlet. The liquid phase heavy oil obtained as a result of separation is sent to the stripping tower through the liquid collection tank and downcomer at the bottom of the separation module. The recycled gas, after heat exchange in the heat exchange module of the circulating heat exchange separator, enters the Fischer-Tropsch reactor.
More people are welcome to participate in the relevant discussions. Click on the blue link to access it: The 【HaiChuan Equipment Guessing Game】 series is being updated continuously in 2022; all fans are invited to join actively! https://bbs.hcbbs.com/thread-2079686-1-1.html (Source: Huahai Chuanliu – Haichuan Chemical Industry Forum) Summary post on the series 【Major Equipment in the Chemical Equipment Industry】 https://bbs.hcbbs.com/thread-3312079-1-1.html (Source: Huahai Chuanliu – Haichuan Chemical Industry Forum) Summary post discussing the components of cracking furnace equipment for 【Ethylene Cracking】 https://bbs.hcbbs.com/thread-3308724-1-1.html (Source: Huahai Chuanliu – Haichuan Chemical Industry Forum)
Application Examples of Domestic Circulating Heat Exchange Separators 2.1 Configuration Overview **The FTO synthesis unit of the oil product synthesis plant in the 4 million tons/year coal indirect liquefaction project operated by Energy Group Ningxia Coal Industry Co., Ltd. consists of 8 series; series 1 to 6 use imported circulating heat exchange separators, while series 7 and 8 employ domestic circulating heat exchange separators. 2.2 Design parameters: The medium flowing through the plate stack of the cyclic heat exchange and separation unit in the FTO synthesis section of the oil product synthesis plant for the 4 million tons per year coal indirect liquefaction project is high-temperature oil and gas. The total mass flow rate is 797,618 kg/h, the operating temperature is 270/1254 K, the operating pressure is 2.75 MPa, and the allowable pressure drop is 50 kPa ； The shell-side fluid is circulating gas, with a total mass flow rate of 797,948 kg/h. The operating temperature is 80/2199, the operating pressure is 3.1 MPa, and the allowable pressure drop is 50 kPa. The shell side design pressure is 3.5 MPa, and the design temperature is 270°C ； ； The design pressure for the plate process is 3.5 MPa, and the design temperature is 300
2.3 Material selection for equipment: In the Fischer-Tropsch synthesis unit, the oil and gas stream flowing through the plate side of the circulating heat exchange separator operates at high temperatures and contains organic acids, CO2, and H2. The circulating gas stream on the shell side also contains CO2 and H2. Both the plate side and the shell side are subject to high-temperature conditions as well as hydrogen-corrosive environments. The available materials for the pressure-bearing components are chromium-molybdenum steel and austenitic stainless steel. Based on the design requirements of the cyclic heat exchange separator and the Nelson curve, as well as considering the material costs, the equipment shell is made of 15CrMoR+304L composite steel plates, while the heat transfer plates and separation elements are made of stainless steel S30408.
2.4 Equipment Structure The domestically produced circulating heat exchange and separation unit (Figure 2) is arranged vertically, with the upper part serving as the heat exchange module and the lower part as the separation modules #6-7$. The heat exchange module and the separation module are located within a cylindrical pressure vessel, in separate chambers, without affecting each other. The heat exchange module uses a plate-shell type heat exchanger #8-15$, with heat transfer elements that are purely counterflow, straight-channel corrugated plates; the fully welded plate bundle is installed within a pressure-resistant shell. Expansion joints are installed on the connection pipes at the upper and lower ends of the plate bundle to absorb the expansion difference between the plate bundle and the shell. The housing is equipped with a pair of equipment flanges, which can be opened during inspection and maintenance to remove the plate bundle. The separation module is located at the outlet of the lower plate side in the heat exchange module, and the separation elements are TP plates #16$, arranged around the central tube. The separator module housing is expanded to reduce the flow velocity of oil and gas; the oil and gas diffuse radially within the TP plate and separate axially. The separated oil and gas are sent to the air cooler via the gas phase outlet at the top of the separation module, while the heavy oil is collected in the liquid collection tank and then exits the circulating heat exchange and separation unit through the downcomer and the liquid phase outlet.
2.5 Application Results In December 2016, domestic circulating heat exchange separators were put into use in series 7–8 of the Fischer-Tropsch synthesis unit of the oil product synthesis plant in a 4 million tons/year coal indirect liquefaction project. In August 2017, industrial operation testing and on-site calibration were carried out on this equipment; the calibration results are shown in Table 1. As can be seen from Table 1, at a load of 101%, the actual heat transfer coefficient of the domestically produced circulating heat exchange separator is 691.4 W/(m²·K), which is 1% higher than the designed value; thus, the equipment exhibits good heat transfer performance. The total pressure drop across the plate and shell sides is 80 kPa, which is 6% lower than the designed value, indicating good resistance performance of the equipment. The mass flow rate of the heavy oil at the outlet is 12.74 t/h, which is 6.2% higher than the designed value, reflecting high separation efficiency of the equipment. To date, the domestically produced circulating heat exchange separators have been in operation for nearly 3 years, having withstood harsh operating conditions such as startups and shutdowns. The equipment is safe and reliable, with all performance parameters meeting the expected standards, thereby fully satisfying the requirements for high-load operation of the Fischer-Tropsch synthesis unit and ensuring safe, stable, long-term, optimal operation of the facility. By comparing the operational data of the domestic circulating heat exchange separators of series 7–8 in the Fischer-Tropsch synthesis unit with those of the imported equipment of series 1–6 in the same unit, the results are shown in Table 2. In Table 2, the temperature difference across the heat exchanger and between the oil and gas streams indicates heat transfer performance; the gas production volume in the reactor reflects the amount of steam generated as a by-product of the reaction, while the unit steam consumption per cycle (under standard conditions) indicates the steam consumption by the compressor.
As can be seen from Table 2, under the 100% load operating condition of the Fischer-Tropsch synthesis unit (with a purified gas flow rate of 3.5×108 m3/h under standard conditions), the temperature difference between the cold and hot fluid sides of the domestically produced circulating heat exchange separator is higher than that of the imported equipment. The increase in the temperature of the purified gas entering the reactor effectively accelerates the Fischer-Tropsch synthesis reaction within the reactor, increasing the amount of heat released during the reaction as well as the amount of steam generated as a by-product. A lower exit temperature on the hot fluid side helps to reduce the load on the oil-gas-air cooler and thus lowers power consumption. The pressure drop across the hot fluid side of the domestically produced equipment is also lower than that of the imported equipment. With the domestically produced circulating heat exchange separator, the average steam consumption for the circulating gas compressor in the Fischer-Tropsch synthesis unit is 67.7 kg/km3 under standard conditions, whereas it is 81 kg/km3 when using imported equipment; this represents a 16.4% reduction in steam consumption. The comparison of pressure drops shows that the plate-type flow channel design of the domestically produced circulating heat exchange separator, along with its resistance to clogging, are superior to those of the imported equipment. 3 Conclusion At present, the 2 domestically developed circulating heat exchange and separation units manufactured by Gansu Lanke Petrochemical High-Tech Equipment Co., Ltd. have been put into industrial use in the FTO synthesis unit of the oil product synthesis facility of **Energy Group Ningxia Coal Industry Co., Ltd.’s 4 million tons per year coal indirect liquefaction project; another unit has already had a supply contract signed with Shanxi Lu’an Coal-Based Synthetic Oil Co., Ltd. Compared with the traditional layout schemes in which heat exchangers and oil-gas separators are placed separately, the circulating heat exchange and separation unit offers advantages such as a compact structure, reduced space requirement for equipment installation, lower equipment weight, simpler external connection piping, better coordination in the heat exchange and separation process, and easier unified control and management. Compared with imported circulating heat exchange separators, domestic circulating heat exchange separators are cheaper, have higher heat transfer efficiency, and better flow resistance, making them worthy of widespread adoption.