1-Abstract1-设计文档-Word2010Abstract

CNOOC and Shell Petrochemical Project with an Annual Output of 200,000 Tons of Vinyl Acetate AbstractCatalog1.Project Description12. Product & Raw material23. Process Design34. Energy-saving Design55. Equipment design76. Clean production127. Site selection and layout138. Security environment analysis159. Economic Benefit Analysis1510. Project Summary17Guizhou University Leap Chemical Plant 1/11. Project DescriptionWith the rapid development of Chinas oil industry, China has become the worlds largest producer and consumer of VAC. The demand for VAC is increasing day by day. Vinyl acetate is a bulk chemical with an annual consumption of millions of tons and has a production history of more than 55 years in China. The existing production technology is mature and stable, which also means that there is much room for improvement in the application of advanced technology. Therefore, it has become a social issue to be solved urgently to be able to produce VAC in a reasonable, safe, green, efficient and environmentally friendly manner.In view of the above background, the project, to design a chemical production plant with an annual output of 200,000 tons of vinyl acetate for Huizhou Daya Bay Economic and Technological Development Zone , based on the concept of cleanness, safety and environmental protection.This project is a supporting sub-project based on 1.66 million tons of ethylene from CNOOC and Shell petrochemical company limited. It is planned to produce vinyl acetate from ethylene supplied by CNOOC and Shell Petrochemicals and methanol supplied by the Yongji Chemical. This project uses 172,811.2 tons of ethylene annually, produces 200,000 tons of methyl vinyl acetate (VAC) annually, and produces 45,275.75 tons of acetic acid by-product, which is built on the reserved development space on the southwest side of Huizhou Daya Bay Economic and Technological Development Zone. In the process design, we took into account both economic benefits and clean production, with clear thinking and outstanding highlights, which are mainly reflected in the following aspects: Acetic acid, one of the sources of VAC raw materials, was innovatively produced by low-pressure carbonylation of methanol, and supported Ni-Mo-La/AC green catalyst was used. Three major cycles of methanol, carbon monoxide and ethylene are realized in the process flow to improve the utilization rate of raw materials.The environment-friendly vapor-phase oxidation of ethylene was used to produce VAC, and a new fixed-bed reactor was used. To a certain extent, it improves the efficiency of heat exchange, effectively avoids the occurrence of flying temperature, reduces the amount of heat carrier, and reduces the operation cost of the device.A number of energy-saving technologies such as heat pump distillation, boiling distillation, splint analysis and thermal integration technology were adopted to optimize the process, improve efficiency and reduce energy consumption. And realize the resourcing treatment of Waste water, Exhaust gas and Residue.Pressure swing adsorption was used to treat carbon monoxide, and multi-column separation was carried out to improve the separation effect.Using a new type of heat exchange element-twisted tube to improve heat transfer efficiency; A new type of energy-saving shielded pump is adopted to replace the conventional shielded pump with high energy consumption in the past.2. Product & Raw materialThe project is designed to produce vinyl acetate by ethylene gas phase oxidation. Its raw materials are ethylene from CNOOC and Shell Petrochemicals and methanol supplied by Yongji Chemical, a company in the park. The production process of this project is green and environment-friendly, with high atomic economy and great economic benefits.Table 1 Quality standard of raw materialsnumberName纯度年需求量1Methanol99.85104975.7 t2CO10016614808 Nm33Ethylene100172811.2 t4O21008742456 Nm3 In order to maximize the realization of economic benefits, and in line with the principle of green environmental protection, in addition to the main production VAC, the co-production of Acetic acid. the main and by-products can be sold locally, which greatly reduces the cost of sales and transportation and improves the sales efficiency.Table 2 Main and Deputy Products of the ProjectNumberProductsSpecificationsOutputRemarks1VAC99.85200,000 tmain product2Acetic acid99.9945275.75tby-product3. Process DesignAfter product selection and process scheme demonstration, the project adopts methanol low-pressure carbonylation process and ethylene gas phase oxidation process. The process flow consisting of acetic acid synthesis section, VAC synthesis section and VAC refining section is designed to realize the steady-state simulation and optimization of the whole process. The process flow is shown in Figure 1. For details, see Chapter 4, Chemical Process and System of Preliminary Design Specification.Figure 1 Process flow diagramThe gases extracted from the circulating gas compressor and the supplemental ethylene are preheated by the gas from the reactor through the second heat exchanger and enter the lower part of the acetic acid evaporator.In acetic acid evaporator, the feed s gas countercurrent contact with acetic acid from the upper part, saturated by acetic acid, It comes out from the top of the acetic acid evaporator and is heated by superheated steam to a slightly higher reaction temperature and enters the oxygen mixer, evenly and rapidly meet the oxygen to a Required concentration of oxygen. in case of explosions, local oxygen is strictly prevented for excessive.The raw gas derived from the oxygen mixer is added with a spray-like potassium carbonate solution in the middle of the piping and enters the string fixed bed reactor. The tube is filled with palladium - gold catalyst, the hot water with medium pressure runs between the tubes, and the raw gas contacts and reacts with the catalyst at a given temperature and pressure.The heat after reacting is absorbed by the hot water between the tubes and vaporizes to produce medium pressure steam.The products, including VAC, CO2, water and other by-products, as well as unreacted ethylene, acetic acid, oxygen and inert gases, are derived from the bottom of the reactor.The product is cooled to about 60 C step by step and enters the absorption tower. The top of the tower is sprayed with cold acetic acid. The VAC gas in the reaction is captured. Most of the unreacted raw materials from the top of the tower are pressurized by compressors and re-participating the reaction, A small part of the gas is recycled and refined, and CO2 is removed for purification.VAC, water and unreacted acetic acid are sent to the primary distillation column as reaction liquid, and acetic acid is separated for recycling.The steam from the top of the tower is condensed and sent to the degassing tank for pressure reduction and removal of ethylene and other gases dissolved in the reactions liquid. The gas is also recycled. The degassed reaction solution is treated by stripping and dehydration and then sent to rectification and purification.A small amount of circulating gas from the acetic acid separation tower, containing 15% 30% CO2, enters into the washing tower first, and then is washed with acetic acid in the middle of the tower, and a small amount of VAC is removed. A small amount of water is sprayed on the top of the tower to wash away the acetic acid contained in the gas, so as to avoid consuming too much potassium carbonate in the CO2 absorption tower. After washing, part of the circulating gas is emptied to prevent the accumulation of inert gas, while the rest enters the CO2 absorption tower and countercurrent contacts with 30% potassium carbonate solution under the conditions of 0.6 0.8Mpa and 100 120 to remove CO2 in the gas. After absorbing and treating the gas, the CO2 content drops to about 0.019%. After condensing and drying, the water is removed, and then it is recycled into the compressor for recycling.The liquid of reaction is divided into two layers in the degassing tank. Most is water in the lower layer, and a small amount of vinyl acetate is recovered in the Steam Tower.The upper liquid is coarse vinyl acetate containing water, which is sent to dehydrating tower for dehydration, and then dehydrating light distillation tower for removing low-boiling substances, and then dehydrating heavy distillation tower, and then to condensing the steam at the top of the tower to obtain high-quality vinyl acetate products of polymerization level, and finally to the product storage tank.The polymerization ability of pure ethylene acetate is very strong, and it can be slowly polymerized at room temperature, and the resulting polymer can easily block the pipeline, affecting normal operation. Therefore, in the case of pure ethylene acetate storage or heat, poly-blocking agents must be added, such as hydroquinone, dianiline, ammonium acetate, etc4. Energy-saving Design Heat exchange netword optimizationIn this project, the amount of design public works is large. In order to make full use of energy, the project uses the Aspen Energy Analyzer software to match the flow pattern according to the pinch design method and the actual situation, and designs an optimal cold-heat stream matching scheme. See the Aspen process simulation source file and PID drawing for details. The whole plant heat exchanger network matching scheme is shown in Figure 2.Figure 2 heat exchanger netword matching schemeAfter optimizing the heat exchange network through thermal integration, a total of 42.44MW of cold utilities and 34.28MW of heat utilities are required,which saves 62.06MW of energy compared with that before optimization. Heat pump distillationFigure 3 Heat pump distillation Simulation flow chart Using heat pump distillation in VAC refining tower has the advantages of simple equipment, little investment, good separation effect and low operating cost. After Aspen comparison simulation, the total energy consumption of heat pump distillation was 4730815 Watt, which saved 85.77 %. Heat pump distillation saves 100 % heat consumption and saves 78.79 % cold consumption.The use of heat pump distillation in VAC refining tower has the advantages of simple equipment, little investment, good separation effect and low operating cost. After Aspen comparison simulation, the total energy consumption of heat pump distillation was 4730815 Watt, which saved 85.77 %. Heat pump distillation saves 100 % heat consumption and saves 78.79 % cold consumption.Table3 Before and after heat pump distillation energy use项目普通精馏热泵精馏Cold utilities（Watt）2827951599792Hot utilities（Watt）26880690Compressor power consumption（Watt）0181692Pump power consumption（Watt）03721Total energy consumption（Watt）55160207852055. Equipment designIn the design process of this project, the tower, vinyl acetate synthesis reactor and other equipment were designed in detail, and the heat exchanger, pump, compressor and other equipment were selected. See Typical Equipment Design and Selection and Reactor Design Instructions for details. New tubular reactorThe vinyl acetate reactor in this project adopts an isothermal tubular fixed bed reactor, in which the catalyst is filled. Condensate water is passed through the shell to remove the heat generated by the reaction in time and control the reaction temperature. The fixed bed has fixed catalyst particles, less backmixing, high average concentration of reactants and fast reaction rate, which can overcome the shortcomings of fluidized bed. In addition, the fluid flow in the fixed bed is close to the push flow, which is conducive to achieving higher conversion rate and selectivity. Larger production capacity can be obtained with smaller amount of catalyst and smaller reactor volume. The structure is simple, the mechanical abrasion of the catalyst is small, is suitable for noble metal catalysts; The operation of the reactor is convenient and the operation elasticity is large.To sum up, the vinyl acetate reaction process has a large thermal effect, the catalyst is not easy to deactivate, the catalyst particles are small, the price is expensive, and backmixing is not conducive to the reaction system, so the reactor type is selected as a tubular fixed bed reactor.Tubular fixed bed reactor has the following advantages: small backmixing, effective dissolution of fluid and catalyst, and higher selectivity when the reaction is accompanied by series side reactions; mechanical loss of catalyst; the structure is simple, and its investment and operation cost are between the adiabatic fixed bed and the fluidized bed; Compared with common fixed beds, tubular fixed beds are easier to control the heat transfer process. Therefore, tubular fixed bed is an ideal reaction equipment for methacrolein reaction. Fig. 3 New fixed-bed reactor New type of shield pumpIn order to implement the concept of green energy conservation, the pump used in this project decided to adopt a new energy-saving shield pump through market research. This series of pumps was produced by Shanghai Hanuo Pump Valve Co., Ltd., which replaced the conventional high-energy conventional shield pump products.The conventional shielded motor is 10% lower in efficiency and lower in power factor than the same motor with the same power. However, the magnetic circuit of the series of pumps is a radial structure with simple structure and less magnetic leakage. Due to space constraints, this special magnetic isolation method is adopted to reduce the size of the magnetic isolation bridge to increase the magnetic resistance and reduce the leakage magnetic flux. Small, using less NdFeB permanent magnets can provide the air gap magnetic density required for the motor. The design improves the overall efficiency of the pump, and utilizes Hastelloy and NdFeB permanent magnet materials to make the motor have high efficiency, high power factor, high power density, strong overload capability, low temperature rise, low noise, and long-term high temperature operation. High reliability, no leakage, explosion-proof, corrosion-resistant, etc., and stable operation at 200 C. Figure 7 IMC series continuous continuous lining fluorine magnetic pump New Methanol Explosion-proof PumpExplosion-proof pumps are generally used to transport flammable and explosive media or explosive dangerous places. Explosion-proof materials such as aluminium alloy and stainless steel are required for the pump body. The explosion-proof pump produced by Shanghai Upper Stone Machinery has the advantages of simple structure, stable performance, high speed, small volume, light weight, high efficiency, large flow, easy operation and maintenance.The explosion-proof methanol pump of Shanghai Shangshi Machinery Manufacturing Co., Ltd. is a single-stage single-suction centrifugal pump, which is used to transport liquor, alcohol or ethanol, methanol and other liquids without solid suspended particles. (Changing impeller can transport crystalline methanol containing small particles). It has a wide temperature range, and the temperature of the medium being transported is 39 69 C. Pump inlet pressure is not more than 0.7 MPa, widely used in chemical, petroleum, alcohol, metallurgy, synthetic fibers, food, medicine and other sectors. Explosion-proof methanol pump is suitable for conveying flow range of 2-2000 m/h, equipped with explosion-proof motor. According to different media, the material of the parts can be made of 1Cr18Ni9Ti, 0Cr18Ni9, 304L, SUS316L, Cr18Ni12Mo2Ti and other materials according to customers requirements.Fig. 5 Methanol pump “Twisted tube” useIn the metformin synthesis section of this project, a large amount of heat is released due to the oxidation reaction, and the temperature of the mixed gas exiting the reactor is high, and the heat is used step by step. The heat exchangers involved are gas-gas phase heat exchangers. The total heat transfer coefficient of the gas-gas phase heat exchanger is low, resulting in a large heat exchange area, an increase in equipment costs, and an increase in floor space. Moreover, the fluid is easy to foul in the tube, which seriously affects the heat exchange and causes the heat exchanger life to decrease and the energy consumption to increase. In view of the above problems, the project uses a heat transfer element that can simultaneously improve the heat transfer efficiency of the shell side and tube length Figure 9 Schematic diagram of twisted tube bundleof the heat exchanger in the methacrolein synthesis section heat exchanger - twisted tube, the working principle is as follows：The twisted tube is made by flattening and twisting a common round tube. The cross section is elliptical, the two ends are still circular in cross section, and the elliptical section is continuously twisted to form a spiral flow path, which is rotated 360 degrees each time through a lead section; A point support is formed at the shaft, and a support is formed every 60 degrees of rotation, and a support point is six support points, and the space between the tube bundles is a spiral flow path. The fluid in the twisted tube rotates and flows, forming a secondary flow in the cross section; the self-supporting structure is formed at the long axis of the shell section, and the flow path is also spiral. The shell-side fluid rotates while flowing longitudinally, which enhances heat transfer and reduces pressure. Loss, in addition, the longitudinal flow also avoids fluid-induced tube bundle vibration. High efficiency gas-liquid separatorn order to achieve bette