word20131-設(shè)計(jì)文檔0-Abstract

Luoyang Petrochemicals annual output of 200,000 tons of VAC project AbstractCATALOG1. Project Description12. Product & Raw material13. Process Design34. Energy-saving Design45. Equipment design66. Clean production127. Site selection and layout138. Security environment analysis159. Economic Benefit Analysis1510. Project Summary17 Zhejiang University of Technology Pray 6 Team 1/11. Project DescriptionThis project is a supporting subproject based on the natural gas chemical project of Sinopec Luoyang Petrochemical Co., Ltd. It plans to use the acetylene and acetic acid supplied by Luoyang Petrochemical as raw materials for the resource utilization of isobutylene. The project uses 390 million m3 of natural gas per year, with an annual output of 207,135 tons of vinyl acetate (VAC) and a by-product of 922.53 tons of crotonaldehyde. It is built on the open space reserved for development on the east side of Luoyang Petrochemical Industrial Zone. The team in the process design, taking into account economic benefits and clean production, clear thinking, highlights, mainly reflected in the following aspects: Using acetylene and acetic acid from the main plant as raw materials to produce vinyl acetate by high-efficiency reaction. In the process, four cycles of acetic acid and acetylene and two small cycles of soft water are realized to improve atomic utilization;The heat pump rectification technology, double-effect rectification, pinch analysis and heat integration technology are used to optimize the process to improve efficiency and reduce energy consumption.The azeotropic distillation is used to achieve high-efficiency separation of the binary azeotrope system, reducing pollution, and detailed treatment of the subsequent three wastes;The use of the dividing wall technology to improve the degree of product separation, the new packing technology to improve the separation efficiency, the new heat exchanger to increase efficiency and energy saving, the new gas-liquid separator to optimize the system operation, the new magnetic pump to reduce the consumption of the section2. Product & Raw materialThe project is designed to produce 207,135 tons of vinyl acetate per year. The raw materials are acetylene and acetic acid produced from Luoyang Petrochemical Natural Gas Chemical Project. The production process of this project is green and environmentally friendly, and it has created a huge economic benefit.Table 1 Luoyang Petrochemical acetylene composition and propertiescomponentcontent（wt/%）componentcontent（wt/%）Acetylene 99.7carbon dioxide 60010-6Carbon monoxide20010-6Nitrogen, Argon 210010-6Propadiene 40010-6Oxygen 21010-6Table 2 Luoyang Petrochemical acetic acid composition and propertiescomponentcontent（wt/%）componentcontent（wt/%）acetic acid 98.5Water 0.8Formic acid 0.30Acetaldehyde 0.10Evaporation residue0.03Fe 0.0004In order to maximize the economic benefits and at the same time take into account the principle of green environmental protection, the process also produces crotonaldehyde by-product in addition to the main production of vinyl acetate. According to the investigation of this project, both types of by-products can be sold locally, which greatly reduces the cost of sales and transportation, and also improves sales efficiency.Table 3 Project main and side product listSerial numberProductsSpecifications(%)outputremarks1VAC99.85207135main product2Crotonaldehyde99.23922.53by-productFigure 1 The total integration map of the project3. Process DesignThe project is demonstrated by product selection and process plan. The project selects natural gas acetylene technology developed by Borden and Blawkeox in the United States and acetaldehyde oxidation to acetic acid technology. The general plant uses German BASF partial oxidation technology to prepare acetylene, and uses British BPs methanol low pressure carbonylation synthesis technology to prepare acetic acid. The process flow consisting of vinyl acetate synthesis section, vinyl acetate refining section, acetaldehyde oxidation section and acetic acid recovery section was 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.Figure2 process flow diagram In the vinyl acetate synthesis section, the raw materials acetylene and acetic acid from the main plant are preheated by evaporation in the evaporation tower, sent to the reactor for synthesis, and the reaction mixture is sent to the vinyl acetate refining section for purification. After absorption, an unabsorbed acetylene gas and a product mixture are obtained. The unabsorbed acetylene gas is purified and returned to the evaporation column as a recycle gas. After separating and refining the product mixture, the gas mixture of acetaldehyde and acetylene is sent to the acetaldehyde oxidation section. After absorption, dehydration and oxidation, the product mixture is returned to the vinyl acetate refining section; the vinyl acetate crude product is After dehydration, the finished vinyl acetate is obtained; the acetic acid mixed solution is sent to the acetic acid recovery section, and the crotonaldehyde by-product and the acetic acid are recovered by azeotropic, dehydration, refining and the like, and the purified acetic acid is returned to the evaporation tower and the absorption tower for recycling.In the end, the project received 207,135 tons of vinyl acetate and 922.53tons of by-product crotonaldehyde.4. 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 Aspen Energy Analyzer V9.0 software, according to the pinch design method, combined with the actual situation, the stream matching, designed an optimal cold and hot stream matching program. At the same time, the optimized heat exchange network is returned to the process simulation and PID drawing, and the final solution is obtained through comparative analysis. See the Aspen process simulation source file and PID drawing for details. The plant heat exchanger network matching scheme is shown in Figure 2.Figure 3 heat exchanger netword matching schemeAfter heat integration to optimize the heat exchanger network, a total of 55.65MW for cold engineering and 46.76MW for thermal engineering are required, which is 50.34MW compared with before optimization. Heat pump distillationFigure 4 Heat pump distillation Table 4 Before and after heat Simulation flow chart pump distillation energy useThe use of heat pump rectification in the heat pump coarse separation tower has the advantages of simple equipment, low investment, good separation effect and low operating cost. After Aspen comparison simulation, the total energy consumption of heat pump distillation is saved by 90.47%. Double-effect distillationThrough double-effect rectification, the acetic acid recovery process is improved, and the total energy consumption is reduced from 37971.9kw to 32181.9kW and 5787.8kW. Figure 4 double-effect distillation Table 4 Energy consumption before and simulation Flow chart after the use of double-effect distillation Separate and refined towerThe energy consumption from the original two-column process is 18,273.99kw, the heat consumption is 3,1174.1kw, and the energy consumption and energy saving of a single dividing wall distillation tower is 11.6%. Figure 5 Split wall tower Table 5 Energy consumption before and flow chart Split wall column extractive distillation5. Equipment designIn the design process of this project, the equipment such as the dividing wall tower and the methacrolein synthesis reactor were designed in detail, and the heat exchanger, pump, compressor and other equipment were selected. See Typical Equipment Design and Selection and Reactor Design Specification for details. New gas distributorThe diameter of the gas inlet pipe is smaller than the diameter of the reactor. If the reaction gas is directly injected into the large-diameter reactor from the small-diameter gas inlet, the gas velocity is too large in the vicinity of the gas inlet, and the energy of the gas is mainly kinetic energy. The static pressure energy is very small, and the distribution of the gas entering the reactor in the radial direction of the reactor is very unfavorable, thereby tending to cause the reaction gas to be unevenly distributed after entering the reactor, thereby affecting the conversion rate and selectivity of the reaction. Therefore, it is very important to arrange the gas distribution device at the inlet of the reaction gas.According to the patent CN202893325U, the reactor adopts a novel gas distributor, which has the characteristics of simple structure, uniform gas distribution, small pressure drop, convenient manufacture and installation, and the like. The new gas distributor structure is shown in the following figure, including an enlarged diameter steady flow section and a spherical head. The first end of the expanded diameter steady flow section is connected to the head of the reactor through a flange, and the second end is connected to the spherical head, and the distribution hole is uniformly arranged in the circumferential direction.Figure 6 Schematic diagram of gas distributor structure Ring distributorSince the reactor uses water-steam as the heat transfer medium, the uniform distribution and uniform collection of the inlet and outlet of the heat transfer medium have a great influence on the heat transfer effect. The conventional annular distributor adopts the method of uniformly opening the inner side wall of the annular passage, but does not consider that the velocity distribution and the static pressure distribution in the annular passage are not uniform, and there is a vortex inside the passage, so that the fluid distribution is uneven. Therefore, according to the research of Bai Yu, Yu Zhongfeng et al. (CFD simulation study of variable mass flow in annular distributor), the lower annular distributor of the reactor opens a hole along the inner side wall of the annular passage, and the diameter of the hole gradually decreases; The annular distributor is uniformly bored along the circumference of the inner side wall of the annular passage.Figure 7 Schematic diagram of the annular distributor structure Circular annular baffle baffleSince the reactor has a large diameter and a large number of tubes, a flow dead zone is easily generated. Therefore, in order to increase the flow rate of the heat transfer medium, enhance the degree of turbulence of the shell-side fluid, and improve the heat transfer effect, a baffle plate needs to be added to the shell side of the reactor. The traditional reactor adopts a bow baffle, but for the special water-steam heat transfer medium of the reactor, the volume of the fluid increases after the water vaporization becomes water vapor, and the bow baffle often cannot satisfy the water-steam. The requirement for uniform distribution of phases. According to the patent CN202893318U, the process adopts a disc-circular baffle, and the center resection rate gradually increases along the axial direction of the reactor, which can better adapt to the flow condition of the fluid volume after the water vaporization becomes water vapor. Figure 8 Baffle distribution diagram New type of oxygen distributorThe oxidation of acetaldehyde is a gas-liquid two-phase reaction, so the distribution of oxygen in the liquid is particularly important. If the distribution is not good, the degree of oxidation will be uneven, thereby increasing the occurrence of side reactions and reducing the yield of acetic acid. In order to improve the distribution in the reactor, the project adopts a new type of oxygen distributor improved by Hunan Xiangwei Co., Ltd. The new oxygen distributor consists of two rings. As shown, oxygen enters the feed tube and is connected to the oxygen distributor via an oxygen manifold. The gas enters the liquid phase through small holes throughout the distributor. Due to the action of the two rings, the gas distribution in the tower is uniform, and the gas-liquid contact is good, which is beneficial to reduce the occurrence of side reactions and increase the yield of acetic acid.Figure 9 New type of oxygen distributor shape diagram High efficient flow-guided sieve trayIn the rectification system of this project, there are mainly vinyl acetate, acetic acid, water, acetylene, acetaldehyde, crotonaldehyde and other substances. Since vinyl acetate is an easy-to-self-polymer, it is prone to self-polymerization in the vicinity of the feeding plate and on several trays above the tower. The plugging phenomenon occurs over time and cannot be operated normally for a long time.The vinyl acetate dehydration tower can not solve the problems of plugging tower and liquid flooding well by using the traditional sieve plate. By consulting the data, the sieve plate is efficiently guided on the basis of the ordinary sieve plate, and a bubbling promoter is arranged in the inlet region of the liquid phase, and a louver guide hole is added on the tray. This improvement increases the effective bubbling area, changing the tray operation from a bubbling type to a jetting type, and evenly distributing the gas while reducing the liquid level gradient, thereby reducing the pressure drop of the dry plate and reducing the entrainment of the mist. The mass transfer efficiency is improved.Figure 10 Structure diagram of high efficient flow-guided sieve trayThe high-efficiency guide screen is 50%100% larger than the traditional tray, the separation efficiency is 20%40%, the tower pressure is reduced, and the weight is light. The cost is about 40% of that of the bubble tray, 60% of the valve tray, and the plugging resistance is good. It is especially suitable for the rectification of special systems such as high viscosity, easy self-polymerization and solid particles. Helical coiled tube heat exchangerIn the vinyl acetate synthesis section of this project, a large amount of heat is released from the 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 all 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 tends to foul in the tube, which seriously affects the heat exchange and causes the life of the heat exchanger to decrease and the energy consumption to increase. In view of the above problems, the project adopts the helical coiled tube heat exchanger with high heat transfer efficiency, low energy consumption, low operating cost, low fouling tendency and small space occupation in the vinyl acetate synthesis section. The winding core body, the casing and the center tube are composed, and the detailed structure is as follows：Figure 11 Structure diagram of helical coiled tube heat exchanger New type of CQB-N fluoroplastic magnetic pumpDue to the corrosive nature of the raw materials and absorbent acetic acid of this project, in order to implement the concept of green energy conservation, the pump used in this project decided to adopt the new type of CQB-N fluoroplastic magnetic pump through market research.The new type of CQB-N fluoroplastic magnetic pump uses modern magnetic mechanics principle to realize contactless indirect transmission using permanent magnets. When the motor drives the outer rotor ( the outer magnetic steel) to rotate, the magnetic field wire passes through the isolating sleeve to drive the inner rotor ( the inner magnetic steel) and the impeller to rotate synchronously, and the medium is completely enclosed in the stationary isolation sleeve, thus achieving the purpose of leak-free pumping medium. The static seal is used to replace the dynamic seal, so that the overcurrent component of the pump is in a sealed state, completely solving the phenomenon of bubble, poping, dripping and leaking which cannot be avoided by the mechanical seal transmission pump, which is an ideal choice to eliminate environmental pollution and create energy-saving, environmentally friendly, safe and leak-free factories.Figure 12 new type of CQB-N fluoroplastic magnetic pump6. Clean productionThis project is a clean production process for producing vinyl acetate and by-product crotonaldehyde by utilizing Chinas abundant natural gas resources, mainly as follows: Using domestic abundant natural gas resources, as the raw material for the production of vinyl acetate in our factory, the production process is green and environmentally friendly, and the atomic economy is high, which can create huge economic benefits. The process route carries out four major cycles of acetic acid and acetylene, and the two small cycles of soft water of the process not only improve the atom utilization rate, but also reduce the three wastes.3 Using high-efficiency reaction and separation technology, the acetic acid mixture is separated and refined, which reduces the discharge of mixed acid, improves the recycling rate of acetic acid, and expands the economic benefits.The project uses zinc acetate/activated carbon catalyst in the vinyl acetate synthesis reaction to ensure low pollution and even no pollution, and achieve environmental