【Ten Years of Great Development in Chemical Technology】The World’s First 60,000-Ton Dedicated Continuous Polymerization Plant for PBST from 2021 to 2032
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Over the past decade, chemical technology has seen significant development; let’s praise the prosperity and strength of modern China. By sharing our ideas, we can encourage more people to participate and make the discussions more lively. Hainan becomes even better with your involvement – we welcome everyone to join in the forum discussions. In August, when the fragrance of rice fills the air, in August 2021, the office of the Management Committee of Hainan Yangpu Economic Development Zone publicly released a draft of the Environmental Impact Assessment Report for the 60,000 tons per year PBST continuous polymerization project. Public information indicates that this project utilizes the PBST copolyester polymerization process technology and equipment independently developed by Sinopec Beijing Research Institute of Chemical Technology (abbreviated as \"BEIRI\") and China Textile Science Research Institute (abbreviated as \"CTSR\"); these are the first engineering devices of domestic origin developed through independent research. The key technologies of this process are the continuous polymerization technology of the PBST device and the THF recovery technology. This project involves the construction of a new 60,000 tons/year PBST polyester continuous polymerization plant, as well as systems for storage and transportation, utility facilities, and accompanying environmental protection measures. The plant is equipped with two production lines: one with a capacity of 20,000 tons/year and another with a capacity of 40,000 tons/year. Project investment: The total investment in the project amounts to 528,679,200 yuan, with 45,750,800 yuan allocated to environmental protection measures, accounting for 8.65% of the total project investment. The 20,000 tons per year production line of this project mainly produces film bag material and injection-molded materials with a melt index of around 5–10, while the 40,000 tons per year production line focuses on film bag material and foamed materials, aiming for a melt index of 5. The two production lines of this project can produce PBAT and PBT products in a cross-manufacturing manner, with a total capacity of ≤60,000 tons per year; in addition, 0.66 10,000 tons/year of **furan (THF) is generated as a by-product. Since the beginning of 2004, the North China Institute of Chemical Technology has been conducting research on the polymerization of PBST using rare earth compounds as catalysts, and has completed polymerization tests at various scales, including pilot-scale, laboratory-scale, pilot plant-scale, and industrial production scale. Meanwhile, based on the molecular structure design of PBST, shape memory materials, room-temperature moldable fracture fixation materials, 3D printing wires, and others have been developed. This technology has already been implemented at Hainan Refining & Chemical Co., where a plant with an annual production capacity of 60,000 tons is under construction. Delivery of the plant is expected by the end of 2023; it will be the first dedicated continuous polymerization plant for PBST both in China and abroad.
Process technology selection: The technical features of the PBST copolyester polymerization process developed independently by the Beijing Institute of Chemical Technology and the China Textile Research Institute are process optimization and short residence time; this project adopts a five-reactor production setup along with optimized process parameters. The main raw materials include terephthalic acid (PTA), 1,4-butanediol (BDO), succinic acid (SA), catalysts, and additives, all of which are added to the system simultaneously. This approach offers advantages such as simple operation, easy control, low levels of by-products, and high product quality. In particular, when PBST polyester chips are produced through continuous manufacturing, the production process is stable and the overall performance of the products is excellent. By working together with the excellent teams at Beihua Institute in terms of material structure design and development, product processing and application, polymer physics characterization, and plastic standardization, it is possible to produce PBST products with Sinopec’s unique specifications, thereby leading and shaping the industry market. This approach helps to address the current issues in the degradable plastics market, such as poor product performance, lack of distinct features, mismatched prices, and weak competitiveness.
1) The plant is planned to be designed using a continuous five-reactor process, comprising two vertical esterification reactors with stirring mechanisms, one pre-polycondensation reactor, one basket-type final polycondensation reactor for film formation, and one horizontal viscosity-increasing polycondensation reactor. The esterification reactor operates under a slight negative pressure ； All three polycondensation reactors operate under negative pressure, and their vacuum generation systems are provided by a vacuum pumping system powered by butanediol. 2) Taking into account the process characteristics of negative-pressure esterification, two negative-pressure esterification reactors are used to carry out the reaction under certain conditions such as temperature, pressure, and residence time. Negative pressure conditions facilitate the rapid completion of the esterification reaction at low temperatures, effectively reducing side reactions. 3) By adjusting the appropriate material residence time, i.e., the devolatilization space, based on the fluidity of the material, it is ensured that low-temperature polycondensation takes place under high-vacuum conditions; this allows small molecules to be rapidly removed from the material within the reactor, thereby reducing the occurrence of side reactions. A vertical pre-shrinking reactor is used. 4) To ensure the evaporation rate and time, maintain a plug flow of the material, and prevent high-temperature material from remaining and affecting product quality. A horizontal final condensation reactor is used. 5) To promote the devolatilization of materials and ensure further reaction of highly viscous materials. A horizontal shaft-type viscosity-increasing reactor was selected. 6) The complete process for the PBST continuous polymerization production line utilizes a multi-point online addition system to enhance flexibility; additive injection ports are provided in both the oligomer pipeline and the prepolymer pipeline, allowing additives with different functions to be added to the system as needed, thereby producing functional PBST products. An online addition system is installed in the high-viscosity melt pipeline; some high-viscosity modifiers can be added to this pipeline through the injection port, and after being mixed evenly by a dynamic mixer, they are granulated. 7) High-efficiency separation technology is employed to recover the by-product THF, with a recovery purity of ≥99.8%. 8) The design of the complete set of equipment gives priority to clean production, including waste gas recovery from the installations, wastewater treatment and reuse of treated water, as well as collection of solid waste. 9) The complete set of equipment will make rational use of energy, recycling all recoverable energy sources; by employing various energy-saving measures, it will effectively reduce the energy consumption of the system, thereby minimizing the operating costs of the products. 10) The complete set of equipment will also be designed with intelligent features. 11) The complete equipment technology features flexibility; it not only meets the production needs of PBST but also those of a range of products such as PBT, PBS, and PBAT.