化工设计大赛_清华大学队_摘要

222H O H O333H O2CH OHCH OCH ligh ole st fin −−+⎯⎯⎯→2H O33CH OCH higher olefins+alkanes+aromatics−⎯⎯⎯→SummaryShared Electron Team: WANG Xiaoxue, GU Tian, WANG Jing, HAN Kehang, CAO ChenxiAbstractThe Shared Electron Team from Tsinghua University has designed a 600 kt/a MTO plant for a integrated enterprise of coal chemical industry. Using the methanol produced from upper stream plants, our olefin factory can provide ethylene and propylene to downstream polyolefin unit. Up to now, we have accomplished the feasibility study report, the preliminary design specification with addendums, the 3D modeling of the whole plant.BackgroundChina is a country which features in “lack of oil, deficient in natural gas, while relatively rich in coal”. The market of light olefins (e.g. ethylene and propylene) is considerably promising in China, while the domestic self supply rate is only about 50%, meaning that we have to import large amount of oil as raw material to fulfill the needs of light olefins. In response to the oil price shocks, we find that methanol has the best potential for replacing petroleum on a widespread basis. Using methanol to produce light olefins (Methanol To Olefins, or MTO) is very likely to help relieve the crisis of oil, and is becoming a brand new way to get ethylene and propylene.Technology Introduction1.Raw Material Route(Main reaction)(Side reaction)Reactions require SAPO-34 zeolite catalyst. MTO process doesn’t require pure methanol, thus itis safe to use crude methanol from upper stream plant.2.Process Description•Reaction & Pre-separation UnitAfter three-stage heated, the methanol gas flows into MTO fluidized bed reactor, contacts the SAPO-34 catalyst and gets converted at 450℃, 0.22MPa. The product gas then is separated by two stage cyclone separators set insideand the third-stage cyclone separator set outside to separate catalysts particles and recover catalysts. Side-by-side type reactor and regenerator will be used. Catalyst can recycle via U-tubes between the reactor and the regenerator, thus the process fulfills the requirement of continuously reaction and regeneration.1!Figure 1. Reactor and RegeneratorProduct gas leaving the third-stage cyclone goes through quench/water-washing tower MT-0101 to cool down ，then goes to the stripper MT-0102 to recover light hydrocarbon products from quench water. Clean water got from the stripper can be reused in the system.Gas from the stripper gets pressed by two stage compressors to a pressure of 0.47MPa and water washed in PT-0101. After compressed to 1.10MPa, Product gas gets caustic washed in PT-0102 and desiccated in PR-0101, then flows into olefins separation unit.•Olefins Separation UnitWe designed a Front-end Depropanization & Front-end Hydrogenation & Propane Washing Process in our olefins separation unit in order to prevent deep-cooling.Dry product gas goes through high and low pressure depropanizers, debutanizer, acetylene hydrogenation reactor, pre-distillation & absorption columns, deethanizer, ethylene tower and propylene tower (from ST-0101 to ST-0204) to be refined.Simulation results from Aspen Plus indicates that we are able to refine the product gas to get polymer grade ethylene and propylene from tops of ethylene tower and propylene tower.2共有電子Figure 2. Reaction and Cooling/Stripping FlowsheetFigure 3. Compressing, Water Wash, Caustic Wash and Desiccation Flowsheet3.Process Features•Recycling of process water.Most of the quench water is recycled back to the quench tower after heat-exchange, the rest is purified after stripping and used in water-washing tower.•High yield of light hydrocarbons.Light hydrocarbons dissolved in quench and water-washing procedures can be recovered, the yield of product is greater than 99.5%.•Front-end depropanization process.Total energy consumption is comparatively low. The reboiler’s risk of coking is remarkably reduced.•Pre-distillation & propane washing unit.Replacing the traditional demethanation column, we successfully avoids the use of deep-cooling equipments, with the lowest temperature of only -40℃. Thus, we solely need a propylene refrigeration system, without ethylene and methane systems, which can enormously save energy as well as equipment and operation cost.Energy Saving1.Heat IntegrationThe whole MTO process produces more heat than consumes. This feature makes it possible to reduce heat utility. Based on deep analysis on streams, we used Aspen Pinch to match the heat and cold streams, and finished the heat integration.Figure 4. Olefins Separation FlowsheetThe energy analysis indicated that the energy-saving rates of total heating and cooling are 83.4% and 72.3% respectively, compared with absolute heat exchange amount.2.Propylene Refrigeration System and Heat Pump TechnologyWe designed a propylene refrigeration system to o ffer cold capacity to overhead condensers, as well as mid-streams in the separation unit, with the temperature varying from -40℃ to 11℃. Our design can also o ffer heat to some of the reboilers as a heat pump. After comparing with three stage compressors system, we choose four-stage compressors system as our refrigeration recycling process, which is able to o ffer cold capacity at four di fferent temperatures ( -50℃，-35℃，-10℃ and 22℃) with a total power cost of 15315 kW.Plant Design and Workshop Design1.Plant Site Selection!!DTMIN: 10.0 (Duty based)Case: HEN3 OF MTOFigure 5. Enthalpy-Temperature Curves Figure 6. Heat Exchange NetworkFigure 7. Propylene Refrigeration System2We chose Yuheng industrial area, Yulin City, Shanxi Province as our plant site. Yulin is famous for its coal mines. Also, there is large amount of undeveloped land resources, abundant water supply and highly-developed transport network. In a word, the city of Yulin is very suitable to develop coal chemical industry. In the industrial area sits a good many coal chemical plants, so basic facilities there are highly developed.2.Plant DesignThe whole plant is divided into production area, auxiliary production area, tank area and o fficework/living area. The total area of the plant is 132000 m .Figure 8. Total Plant Design3.Workshop DesignWe designed olefins preliminary separation workshop and finished 3D piping in details, including the piping of 4 distillation columns, 1 absorption column, 1 acetylene converter, heat-exchangers, intermediate storage tanks and pumps.Figure 9. Olefins Preliminary Separation Workshop 3D PipingTechnical and Economic IndexRegarding to the state relevant policies and the design result of the whole factory, we finished the financial analysis of this plant. The result indicates a brilliant future of this project.Table 1. Technical and Economic Index FormNo.ItemUnitAmountRemarks1Production Capabilitykt/a300 eachEthylene /Propylene!!!!!!!!!!!!!!!!!!2Operation Time per Year hours/a80003Material ConsumptionMethanol kt/a50Calculated as Pure 4Public utilityFresh Water kt/a1424Electric Power kWh/a170736Steam kt/a327.15Employees person21026Plant Area m1320007Total Investment Million yuan2331.038Construction Fund Million yuan2018.33Construction-period Interest Excluded 9Working Capital Thousand yuan24220010Yearly Total Cost Thousand yuan542130011Yearly Total in Come Thousand yuan484180Post-tax12Payback Period of Loan year7Construction-period Included13Profit Ratio%27.7Investment14Profits and Taxes Ratio%39.0Investment15Internal Rate of Return%10Total ; IRR16Net Present Value Thousand yuan211760NPV17Payback Period year8Construction-period Included18Break Even Point%15.7BEP ConclusionAdopting the SAPO-34 catalyst in the reaction unit, this reaction is carried out in fast turbulent fluidized bed. “Front-end depropanization and Front-end Hydrogenation & propane washing” technology is used in separation unit, which helps us avoid the application of deep cooling equipments and use propylene cryogen only.The equipment cost and compressor power are greatly saved thanks to the special design. We find the optimal design of heat exchanger network, and calculate and design the propylene refrigeration system.We finished feasibility study, the compared different process and made our selection. We also have finished the imitation of the whole process by using Aspen Plus, processed the heat integration by using Aspen Pinch, and finished the PFD and PID by using AutoCAD, and the ichnography of plant layouts by using SketchUp for 3D design. Please consult the documents we hand in for more details.。