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2017 Donghua Technology - Shaanxi Drum Cup The 11th National College Student Chemical Design CompetitionQilu Petrochemical 800,000 tons / year FCC plant renewable flue gas desulfurization projectAbstractDesign unitNorthwestern University School of Chemical EngineeringDesign teamLiu guang yi caiMember nameLi Wenxuan Lin Bo Gu Jiahua Liu Mingyue Ye FengMentorZhao Binran Chen Liyu Liu Enzhou Hao Qingqing Chu Yazhi1. Abstract of ProjectThis project is the deep desulfurization and recycling of the renewable flue gas of the 800,000 tons / year catalytic cracking unit of Shengli Refinery in Qilu Petrochemical Group of Shandong Province. It is located in Qilu Chemical Industrial Park, Linzi District, Zibo City, Shandong Province.The project utilizes the sulfur-containing waste gas from the FCC unit to improve the reaction of the sulfur-containing solid, by filtration, evaporation, crystallization, drying and so on by using the NaOH solution as the absorbent by the turbulent Venturi desulfurization and dust removal technology developed by Sinopec Ningbo Engineering Company Separation process operation, the final purity of 99% sodium pentahydrate sodium sulfate crystals 6560t / a.2. Product ProgramThe product program of this project is based on the national industry policy and development plan and determined, and fully consider the domestic market prospects and capacity. The project for the environmental protection project, the FCC renewable flue gas dust, desulfurization purification, compliance of the exhaust emissions. Absorption of sodium bisulfite obtained by neutralization reaction, the reduction reaction to be sodium thiosulfate. There are no other by-products.Tab. 2-1 Comparison of several product solutionsProduct solutionsNA2S2O3(NH4)2SO4MgSO4CaSO4H2CO3ProcesscomplexeasiereasiereasiercomplexRaw material costslowlowhighlowlowProduct marketbetterbetterbetterPoorPoorProduct pricehighlowhighlowlowTab.2.2 Product scaleNoproduct nameunitQuantitypurity /wt%1Na2S2O35H20Million tons / year656099Tab.2.3 National standard for industrial sodium pentahydrate sodium sulfate crystalsprojectindexExcellent productFirst gradeSodium thiosulfate content /% 99.098.0Water insoluble matter /% 0.0010.003Sulfide (taking Na2S as an example)/% 0.0010.003iron（Fe）/% 0.0020.003PH (200 g / L solution) /% 6.5-9.56.5-9.53. Process DesignThis project uses sodium desulfurization process for flue gas desulfurization, sodium desulfurization process has many other processes do not have the characteristics. Sodium hydroxide solution is a good alkaline absorbent, from the absorption of chemical mechanism analysis, SO2 absorption is acid and alkali neutralization reaction, sodium alkaline stronger than other absorbers; and from the absorption of physical mechanism analysis, SO2 Is a gas-solid reaction, sodium absorption of SO2 is a gas-liquid or gas-gas reaction, so, relative to other desulfurization, the reaction rate is fast, reflecting the complete, high utilization of absorbent, can do a high desulfurization efficiency. Sodium desulfurization efficiency is high, to meet the various regions of the environmental requirements of enterprises.Process Overview:Flue gas after the first booster fan into the dust tower, the dust to dust, dust removal efficiency of up to 90%, the flue gas temperature down to 60 , most of the smoke in the sulfur dioxide and a small amount of sulfur dioxide is removed ; Absorption liquid into the microfiltration equipment to remove the solid impurities, the liquid into the desulfurization tower top of the demister, the other part into the cooling into the dust after the cold tower.Flue gas from the dust from the cold tower out into the desulfurization tower, and sodium hydroxide solution contact reaction, desulfurization efficiency of 80% or more; after the reaction solution and the circulating absorption of liquid mixture, through the circulating pump again with the flue gas contact reaction, desulfurization The efficiency of more than 70%, the flue gas and then through the top of the absorption tower to remove the slurry removed by the slurry droplets, from the flue lead to the chimney into the follow-up process, the total desulfurization rate of up to 96%.After the reaction of the salt slurry into the sodium sulfite reactor and sodium hydroxide solution for neutralization reaction, the solution of bisulfite ions into all the sulfite ions, three-effect evaporation of sodium sulfite solution concentrated into the sodium thiosulfate reaction The reactor was reacted with sulfur to obtain sodium thiosulfate. The reactor was a loop reactor, and the solution of sodium thiosulfate was subjected to double-effect evaporation. The mixture was cooled into the continuous cooling of the crystallizer to obtain high purity (99%) of sodium pentahydrate crystals.4. Innovative instructionsA. Countercurrent turbulent dust removal desulfurization technologyCountercurrent turbulent desulfurization desulfurization technology to take the stage of the flue gas purification process, the use of multi-layer nozzle sprayed dense water curtain to purify the flue gas, the pressure drop is low, it has the following characteristics:(1) does not produce fogGas and liquid reverse contact, while the flue gas into the desulfurization tower (T0102) before, has been in the vice tower (T0101) was cooled to saturation temperature, into the main tower after the first tower spray, do further cooling desulfurization dust, after treatment Of the flue gas into the main tower of the second level, in this large amount of water spray, to further remove the flue gas entrained in the water vapor, to achieve the effect of removing water vapor.(2) is not easy to plugFirst, the wet spray process of the unique nozzle and spray the system makes the system has a strong self-cleaning capacity, so that equipment is not easy to plug; In addition, the spray liquid for the sodium hydroxide solution, less impurities, it is not easy to plug the equipment.(3) system stability, impact resistanceAs the wet scrubbing process has a higher gas-to-water ratio, a large amount of spray water can withstand unstable impacts of abnormal operation and contaminant concentrations.(4) The system is equipped with a booster fan to overcome the resistance generated by the desulfurization system.(5) the main tower for the three-tier structure, the internal use of granite material, to overcome the FCC desulfurization in the abrasion, corrosion, high temperature problems, to ensure the safe and stable operation of equipment to extend the service life of equipment.(6) desulfurization cycle liquid to take outside the tower, the tower outside the way of cooling. The circulatory system replenishes lye, process water and partially recycled liquid. Thus realizing the circulating liquid cooling and waste water treatment.B. Circulating tubular reactorThe tubular reactor is a reactor with zero backmixing. The reactor feed is a sulfur solid and sodium sulfite solution, which is a solid-liquid phase reaction. If this reactor is used alone, although the problem of sulfur solids floating on the liquid surface is solved, there is no effective mixing area Not big. The two reactors are designed to be used together. Under the reaction conditions, a continuous tubular reactor with a stirrer was used to achieve the greatest degree of reaction of sulfur solids with sodium sulfite.The use of such reactors has the advantage that:(1) to achieve solid-liquid phase reaction, driven by the stirring paddle, can make the sulfur solid in the sodium sulfite solution dispersed evenly, to avoid the concentration of the reactor uneven.(2) In the tubular reactor, the reaction solution containing the sulfur solid flows continuously in the tube to solve the problem that the sulfur solid floats on the surface of the water.(3) further increase the solubility of sulfur solids by increasing the reaction temperature. The reactor temperature distribution is determined.In order to further improve the performance of the reactor, the design of the tubular reactor, plus the elbow to reduce the volume of the tubular reactor, while the reaction material can be part of the material, the other part of the reactor discharge.Both sides of the elbow on both sides of the use of mechanical mixing, jacket heat exchange, used to strengthen the flow of sulfur solid in the solution, the timely removal of reaction heat.C. continuous cooling crystallization technologyThe design of the project has chosen a new type of cooling crystallization process, the main equipment for the Olso mold, thus solving the problem of uneven water crystal sodium thiosulfate crystal.For more information, please refer to the Innovative Note.5. Energy-saving designA. Multi-effect evaporation technologyEach evaporator is referred to as a first effect, the first effect of the incoming steam, the first effect of the steam using the first effect, and so on. Because the steam for the effect of the next use, to improve the utilization of raw steam, save the amount of steam.In the pretreatment and reaction workshop, it is necessary to evaporate and concentrate the sodium sulfite solution from the desulfurization tower to near saturation, and the amount of water to be distilled off is 1 ton / hr. From an industrial point of view, the amount of water is not large, but taking into account the equipment for a long time to work, to 8400 hours, the total annual energy consumption is greater. So the use of energy-saving three-effect evaporation. Through Aspen simulation, you can get the use of three-effect evaporation than single-effect evaporation to save the amount of steam 300kg / h.According to the same principle, in the product refining workshop Olso mold before the sodium thiosulfate concentration system, take the two-effect evaporation.B. Heat exchange network optimizationIn this project, there are more public utilities involved. In order to make full use of energy, this project uses the Aspen Energy Analyzer software, according to the pinch design method, combined with the actual situation, the flow of shares matching, designed an optimal hot and cold flow matching program. The initial heat transfer network is first designed automatically and then compared with the total cost of the heat exchanger and the number of heat exchangers to obtain the optimal heat transfer network. See the Aspen flow simulation source file.Tab. 4-1 automatically design the best heat transfer schemeTab. 4-2 Manual design of heat exchange networkC. Steam condensate utilizationThree-effect evaporation used in the steam is 0.6Mpa low-pressure steam, steam condensed into liquid, the temperature is still high, at 159 , heat can be recycled. The hot water was used to heat the sodium sulfite solution into the reactor (R0202), saving 200 kg of low pressure steam per hour.D. Process water recyclingDust removal and cooling tower produced by the process of large amount of water, dust content is relatively low, directly discharged into the wastewater treatment system will cause waste of resources. Here, we used a membrane separator, the use of micro-filter device on the dust from the cold tower produced by the process of water treatment. After the microfiltration treatment of water, one into the desulfurization tower desulfurization tower, another share after cooling and then re-cycle dust recovery tower.6. Site selection and layoutA. Site selectionThe project site is located in Zibo City Linzi District - Qilu Chemical Industry Zone, the industrial park overall planning area of 607,200 square kilometers, the project covers an area of 65,000 square meters.Tab. Qilu Chemical Industrial Park LocationShandong Qilu Chemical Industrial Park and the park Qilu Petrochemical for the smooth implementation of the project provides a wealth of raw materials, convenient transportation facilities to ensure that during the development of this project, raw materials and products can be smooth, fast and efficient transport out. At the same time relying on the plant Qilu Chemical Group strong advanced production level, advocate clean production, circular economy concept for the construction of the project provides a good guarantee, and the formation of the location advantages for the product to provide a sufficient market.After the analysis of the nature of the entire process of dangerous goods, according to the actual process, personnel operation, maintenance and repair, safe and sound production and other factors on the plant layout. Taking into account the inherent risk of the process and the load of the building, according to the standard of building materials and fire resistance to choose, become the plant layout of the important basis for safe production. Tab. 6-2 Total layout planB. Three-dimensional layoutUsing AutoCAD to draw the equipment layout, the device was positioned, according to the device layout using 3D MAX on the whole device for three-dimensional layout, the use of PDMS layout shop piping, the effect is as ollows: Tab. 6-3 Workshop 3D renderingsTab. 6-4 Workshop three - dimensional piping diagram7. Environmental safety assessmentThrough the use of RiskSystem environmental risk assessment software, the risk analysis of the raw materials and tank areas of the plant area is carried out. Then, the meteorological conditions, the distribution of the residential area and the characteristics of the project are analyzed, and the hazards and risks after the accident are predicted. Environmental Impact Assessment (ERA) and Environmental Impact Assessment (EIA) provide the basis for the risk decision and management of the project and provide the basis for the design and construction of the project.Risk assessment of major hazard sources by HAZOP analysis software.8. Economic evaluationThe whole plant comprehensive technical and economic indicators are as follows:Tab. 8-1 Major technical and economic indicatorsNoproject nameunitQuantityRemarks1Processing capacity / scaleTreatment of flue gasNm3/h155869Maximum (design)Sulfur dioxidet/a3140Soott/a6462Product solutions2.1ProductNa2S2O35H20t/a65603Year operation timeh84004Main raw materials fuel consumption consumption4.130% NaOHt/a88204.2St/a10085Power consumption5.1Water t/h11.55.2ElectricitykWh55000005.3steam（0.6MPa）t/h1.56Waste discharge6.1Waste watert/h2.7Production wastewatert/h1.86.2Exhaust gasDischarge desulfurization flue gasNm3/h137206Wet flue gas after desulfurization6.3Solid WasteDesulfurization waste residuet/a1615 water 60%7Traffic volume7.1Import volumet/a88207.2Shipped outt/a83608Device capacitypeople399Total area9.1Plant areaHa6.59.2Investment intensityMillion yuan / ha5839.3Green rate%13.910Energy consumption per unit of productKg standard oil / t products550511financial indicator11.1Total investment in the projectMillion yuan350012.2Annual sales revenueMillion yuan393612.3Cost and expenseMillion yuan1814.98212.4ProfitMillion yuan99.5612.5TaxMillion yuan436.2712.6Loan repayment periodYear312.7Total investment rate of return%4.6412.8Internal rate of return on funds%6.3612.9Breakeven point%829. Summary of the projectThe project to safe production, energy saving, resource utilization for the design concept and objectives of the initial design. The desulfurization scheme of sodium hydroxide solution as desulfurization absorber was determined by reviewing literature and market research. With the technology mature and reliable, to meet the environmental requirements, investment savings, the second pollutant treatment method is simple and so on principles, desulfurization and dust removal process selected to improve the Sinopec Ningbo Engineering Company developed t