At a pressure of 3300 kilograms, what material are the pipes inside the EVA reaction dam made of?

With a reaction pressure of 3300 kilograms, how thick must this pipe be?

Currently, there are mainly four production processes for EVA products at home and abroad: high-pressure continuous bulk polymerization； Medium-pressure suspension polymerization ； solution polymerization ； Emulsion polymerization. Among them, high-pressure bulk polymerization is the most common method; most EVA resins available on the market are produced using this high-pressure continuous bulk polymerization process, with a VA content of 5%-40%. 1. Continuous bulk polymerization under high pressure: The continuous bulk polymerization process under high pressure typically uses autoclave reactors or tubular reactors, and its principle is similar to that of the low-density polyethylene (LDPE) production process. Among them, the tubular polymerization process can produce EVA with a VA content of less than 30%, and the one-pass conversion rate in the tubular reactor is 25%-35%. Typical processes for tubular polymerization include the BASF tubular process, the Lmhausem/Ruhrehemie tubular process, the Russian tubular process, the Sumitomo Chemical tubular process, and the VEB Leuna-Werke tubular process, among others. The batch polymerization process can produce EVA with a VA content of less than 40%, and the single-pass conversion rate in the batch reactor is 10%-20%. Typical processes for batch polymerization include the batch methods used by DuPont, USI, and others.

Successful Commissioning of Lianyungang’s 100,000-ton Batch Process EVA Plant – Publisher: Wang Na, Publication Date: 2017-05-26. Following the successful commissioning of the 200,000-ton/year tubular process EVA plant, early on May 16th, the 100,000-ton/year batch process EVA plant was also commissioned successfully in one go, producing qualified products. This also marks the successful operation of the entire EVA project facility. The Jiangsu Sierbang EVA project commenced construction in June 2014. During the construction period, there were zero major safety incidents or major quality issues, with a first-pass welding success rate of 97.8% ； A total of 63,388.8㎡ of concrete work was completed for civil engineering purposes, 103,800㎡ of road construction was carried out, 14,863 tons of steel structures were installed, 1,029 sets of moving and stationary equipment were put in place, 623,456 inches of piping was installed, 4,975 high-pressure pipelines were constructed, 22,999㎡ of areas were protected against fire involving steel structures, and a total of 147,803㎡ was covered with insulation materials for equipment and pipelines. Before November 2015, the EVA facility was in the civil construction phase, with the main focus on the construction of large-volume concrete structures such as the reaction dam and compressors; while ensuring the completion of these key elements, other foundation constructions were also carried out simultaneously. To ensure the completion of the construction on schedule, the project team increased its workforce, with over 500 people employed during the peak period of civil engineering work. Starting in October 2015, the site gradually entered the installation phase, with a focus on large-scale construction of steel structures and prefabrication of pipes. Within three months, 12,000 tons of steel structures and pipes with a total diameter of 200,000 inches were installed, creating favorable conditions for the intensive pipe installation work that followed the holiday period. Regarding the equipment, due to the large number of compression units and the difficulty in installation, the project team has assigned experts to ensure strict oversight in terms of construction progress, quality, and safety. In March 2016, the project team began organizing the construction of high-pressure pipelines. Since these pipelines with pressures of 500, 1600, and 3600 kilograms were being constructed for the first time by our company, the project team attached great importance to this task and arranged for relevant personnel to go to Yangba to receive training; they were only allowed to start working after completing the training organized by foreign experts. The technical staff and construction teams overcame various difficulties in the construction process, learned from their experiences, quickly mastered the requirements and characteristics of high-pressure pipeline installation, and successfully completed the construction of these pipelines. In February 2016, the owner organized a \"100-Day Intensive Work\" campaign. To meet the owner’s high standards, the project team increased its workforce, with over 1,300 people on site during the peak construction period. During the construction process, the project team organized tasks scientifically and made comprehensive plans, strictly following the established control points. Monthly and weekly plans were developed in reverse order, with thorough evaluations and strict compliance ensured. Construction was carried out by focusing on the critical path, thereby ensuring efficiency while also paying close attention to quality and safety; as a result, the set control point targets were successfully achieved. After the Spring Festival in 2017, the project team began to assist the owner with related finalization tasks such as purging, airtightness testing, and commissioning. On March 13, the tubular EVA unit was successfully commissioned, and on May 16, the batch-process EVA unit was also commissioned successfully, producing qualified products. Thus, the construction of the 300,000-ton EVA plant has been successfully completed. Compared to other EVA plants in China, the EVA plant operated by Jiangsu Sierbang operates under higher pressures and requires more advanced technology. The successful operation of this plant demonstrates our company’s extensive experience in construction management as well as its high level of technical expertise; as a result, the project team has received high praise from the client and the supervisors.

For the selection of the process route, the production process of EVA employs high-pressure polymerization. The high-pressure polymerization process can be divided into two types based on the design of the reactor: batch reactors and tubular reactors. The former are high-pressure batch reactors equipped with agitators, whose length-to-diameter ratio ranges from 2:1 to 20:1 ； Another type is a tubular reactor with a length/diameter ratio greater than 12,000:1, having an inner diameter of 25–64 mm and a length of 0.5–1.5 km. The production processes for the batch and tubular methods are generally similar. The process unit of an industrial EVA plant usually consists of five parts: raw material compression, an initiator preparation and comonomer injection system, a polymerization reaction system, a separation system (to separate the polymer from unreacted ethylene), and an extrusion granulation and post-treatment system (including degassing, mixing, storage, packaging, etc.). The autoclave reaction process is more suitable for producing resin with a multi-branched structure, which is used for extrusion coatings. The tubular reaction process is suitable for producing resins with a narrow molecular weight distribution; such resins are more suitable for insulation coatings in wires and cables, and exhibit excellent performance in membrane applications. Currently, the volume of batch reactors ranges from 0.75 to 3.0 m3, the average reaction temperature is between 150 and 300°C, the reaction pressure is 110 to 200 MpaG, and the conversion rate lies between 15% and 23%. In EVA copolymer products, the VA content can exceed 40%. Typically, the plant scale is 50,000 to 100,000 tons per year, with the maximum annual production capacity for a single EVA line being 145,000 tons per year. The VA content in EVA produced by the tubular method can reach 28%. The capacity of newly built plants is generally over 200,000 tons per year, with the current maximum capacity for a single production line being 450,000 tons per year. Based on factors such as product output and specifications, this project plans to adopt the tubular process to produce high-end EVA products with a medium VA content. Compared to the batch process, the main advantages of the continuous process are as follows: ① The total production capacity is higher than that of the batch process, with the maximum capacity per unit line reaching 450,000 tons per year. ② The VA content in EVA products is generally no more than 20%; in some manufacturing processes it can reach 28%, with a maximum of 30%. Such materials are mainly used in film materials, cables, and photovoltaic applications. ③ The reaction temperature and pressure are higher than those in the batch method. ④ The investment and operating costs per unit of product are low.

Introduction to the process principle: Ethylene polymers are composed of long chains of carbon atoms that are interconnected, with each carbon atom carrying two hydrogen atoms; in other words, they are made up of numerous -(CH2)- units. A polymerization reaction carried out using a single monomer is called homopolymerization, and the resulting polymer is known as a homopolymer. The low-density polyethylene product (LDPE) in this project belongs to the category of homopolymers ； A polymerization reaction in which two or more monomers participate together is called a copolymerization reaction, and the polymer formed is known as a copolymer. The main product of this project, ethylene-vinyl acetate copolymer resin (EVA), belongs to the category of copolymers.

Process flow analysis: This unit mainly consists of the following process units: ethylene compression, regulator/copolymer injection, initiator preparation and injection, polymerization, high-pressure and low-pressure separation and recycling systems, extrusion and granulation systems, hot water systems, post-treatment systems (degassing, pneumatic conveying), as well as systems for the collection of VA and the purification of exhaust gases.