Word 20032 设计文档集0-Abstract

Tianjin Tian-tie rolling two540,000 Nm3 / h flue treatment project Abstract1. Project DescriptionThis project aims to build a flue treatment branch factory for Tianjin Tian-tie rolling two steel co., LTD. in Tianjin Beichen chemical industrial park. A set of flue treatment plant with a throughput capacity of 540,000 Nm3 / h was built, including de-nitration using SCR catalytic reduction process, desulphurization using ammonia method and epoxy propane continuous catalytic propylene carbonate process. As a result, SO2 and CO2 in this process is recovered and utilized to produce ammonium sulfate of 35,700 t/a and propylene carbonate of 58,500 t/a. The design aims recycling utilization of raw materials and adoption new technology of energy saving, and thus reduces demand for the raw materials and energy losses, respectively. The designed is comprehensively considered on both economic efficiency and clean production and thus reduces the negative impact of the system on environment. Reasonable management scheme on discharge of the pollutants was also proposed. The design with clear thought line and outstanding bright spot are outlined as follows. Figure 1-1 Design highlights2. Product & Raw materialThis project was proposed for Tianjin Tiantie group to treat and recycle a throughput capacity of 540,000 Nm3 / h flue gas. Exhaust gas of sintering machine originated from general factory is sent in pipelines to the branch factory which is constituted of de-nitration, desulfurization and de-carbonization processes. CO2 and SO2 in the flue gas were recycled to product ammonium sulfate of classy article with annual output of 35700 tons and propylene carbonate (PC) of 99.5% with annual output of 58,500 tons, respectively. The flue gas composition of the general plant is obtained and the results are shown in Figure 2-1.Figure 2-1 Composition of flue gas2.1 Product plan: Table 2-1 product planProduct name(NH4)2SO4PCExecution standardGB535-1995ISO 9001:2000SpecificationsClass articleTop quality goodsProduction35.7kt/a58.5kt/a2.2. Process DesignAfter product selection and process comparison, the process of de-nitration, desulfurization, and de-carburization in sequence was determined. Nitrogen oxides was removed using SCR catalytic reduction process, and SO2 was removed using ammonia desulphurization process. A part of CO2 was absorbed using methyl diethanolamine (MDEA) from flue gas and used to produce propylene carbonate (PC). Liquid ammonia and aqueous ammonia were provided by Tianjin-tiantie coking co., LTD. and both propylene oxide (PO) and methyl MDEA were bought from other manufacturers. The whole process is divided into flue gas treatment section and product preparation section. The flue gas processing section is constituted of de-nitration, desulfurization, decarburization. The product preparation section is divided into propylene carbonate (PC) synthesis and the preparation of ammonium sulfate. The whole process was simulated and optimized in steady state using Aspen Plus.The process flow diagram is shown in Figure 2-2, and the whole process is detailedly described in Chapter IV of the chemical process system in the preliminary design specification.Figure 2-2 Process flow diagramFlue gas from the general factory was first sent to dust remover to remove dust, then was delivered into the de-nitration device, which adopted SCR catalytic reduction process. Under ammonia, nitrogen oxides were reduced and N2 and H2O were produced in the catalytic process. After de-nitration, flue gas was piped by blower to desulfurization tower and desulfurized using ammonia desulphurization technology. In this unit weak acid absorption liquid (ammonium sulfite) was sprayed by the nozzle from the top to the bottom of the tower, and counter contacted with flue gas flow. As a result, SO2 in flue gas was absorbed and absorption liquid was saturated and pumped to the outer tower for oxidation reaction. Air forced oxidation technology was used in the oxidation reaction in the oxidizer. Oxidation product was sent back to concentration section of desulfurization tower and cooled flue gas, and thus oxidation product was primarily concentrated with the utilization of flue gas heat. The concentrated adsorption liquid was sent to the product processing section and produced ammonium sulfate products after double-effect evaporation and drying process. After desulphurization, flue gas was sent to decarburization section. In the section some of the CO2 in flue gas was absorbed by MDEA. Desorbed CO2 and propylene oxide was mixed and continuously catalytically synthesized PC. This project turns losses into profits. Water integration and centralized treatment were used to reduce emissions of pollutants, reducing environmental pollution greatly. The whole process simulation is shown in Figure 2-3.Figure 2-3 The whole flowsheet3. Energy-saving DesignIn this project, the amount of utilities are required. For making full use of energy, heat exchanger network was designed by using Aspen Energy Analyzer software based on the pinch point design method. Combining the actual situation, heat and cold streams were matched, and a matching scheme of the optimal cold and heat flow unit was designed. At the same time, the optimized heat exchanger network was returned to process simulation step and the optimal results were obtained by comparison and analysis. These details are depicted in Aspen source file of the whole process simulation.Figure 3-1 Heat exchanger network before optimizationFigure 3-2 Heat exchanger network after optimizationComparison of utility usage before and after optimizationFigure 3-3 Comparison of utilities before and after optimizationAfter optimization of the heat exchanger network using the Aspen Energy Analyzer, we design these heat exchangers using EDR software in details, and the design results are shown in the typical equipment design specification.3.2 HighlightsIn this project, a variety of innovative technologies were proposed and utilized. Based on theory combined with practice, ammonia escape is controlled in ammonia desulphurization and the desulfurization efficiency is improved. These process was simulated by using Aspen software. The simulation results are in good agreement with the industrial data and thus it has high credibility. Outline of the innovation is as shown as follows. Figure 3-4 highlightsThe process simulation of double effect evaporation is shown in Figure 3-5 and the comparison of HP stream usage is shown in Figure 3-6. Considering crystal precipitation along with evaporation process, cross-flow operation was adopted in double-effect evaporation, which was more advantageous to crystal precipitation. The first evaporator was heated using low pressure steam, and the next evaporator was heated directly with the secondary steam, in order to maintain evaporation efficiency and reduce the usage of utilities at the same time.Figure 3-5 Simulation of double effect evaporation Figure 3-6 Comparison of HP-stream usage after using double effect evaporationThe process simulation of hydraulic turbine is shown in Figure 3-5 and the power consumption with turbine or not is shown in Figure 3-6.Figure 3-5 Hydraulic turbine simulation Figure 3-6 Comparison of power consumption after using hydraulic turbine The analysis of saving energy is described detailed in Chapter IV of Chemical process system in the preliminary design specification.4. Equipment DesignBecause of large flue gas flow, gas disturbance in the traditional de-nitration reactor was serious, and the catalytic reduction efficiency decreased, resulting in the unsteady removal efficiency. Therefore, our team utilized baffles in the reactor, and the baffles could keep the flue gas with constant velocity, making the distribution of the flue gas flow through the catalyst reasonable.Figure 4-1 Diagram of reactor structure Table 4-1 Model parameters of de-nitration reactorThe entrance sizeCatalyst sizeNumber of catalyst layers(including spare)Direct current plate heightSpacing of direct currentExport size2m7.5m8m7m3600mm100mm4m7.5mThe simulation process and result analysis of the baffle Firstly, the simulation results of the reactor without baffle were obtained, as shown in Figure 4-2. As seen in the figure, there are many eddies in the reactor, the velocity near the left side is near zero, and the velocity at the right side is 20 m/s. Flow velocity distribution without baffle is not reasonable.Figure 4-2 Flow velocity distribution without baffleIn order to obtain reasonable simulation flow field, baffle was setup at the channel bend and on the upside of the catalyst to adjust the velocity distribution. After many trials, a better flow field distribution was obtained. The reactor with baffles is called as the advanced reactor. The convergence of the residual curve is completed by improving the grid files and adjusting simulation process parameters. Finally, the velocity distribution of the catalyst layer was obtained. With the addition of baffles, flow charts of velocity distribution and velocity streamline distribution are shown in Figure 4-3 and Figure 4-4, respectively.Figure 4-3 Flow velocity distribution with baffleFigure 4-4 Velocity streamline distribution with baffleIt is found that the internal velocity distribution of the reactor have been improved well, as shown in Figure 4-3 and Figure 4-4. The velocity is kept between 4m/s and 6 m/s, and the distribution of velocity field is much reasonable. The improvement of structure and the setting up of baffle ensures the uniform velocity distribution in the SCR de-nitration system. There is no eddy flow in the interior, and the flow velocity is smooth. These characteristics meet the requirements of flow velocity and direction of flue gas in SCR system.5. Plant location &LayoutUnder the guidance of long-term planning, the plant site was chosen close to the main plant and selling market according to the concrete circumstances of this project. In detail, the plant was determined to build in Beichen chemical industrial park, as a branch factory for tian-tie two steel rolling workshop for desulphurization. Beichen area is located in the north of Tianjin city, where water and land transportation is convenient, indicating obvious regional advantages. The terrain is low, flat, west-high and east-low. Except for the geographical environment factors, the air mass alternation is the dominant factor for temperature change. Because of backing on the Eurasian and facing the Pacific Ocean, it possesses maritime climate in summer, but in most of the time per a year is controlled by the northwest continental air mass, showing cold winter and heat summer.Figure 5-1 Site selection of the plant5.1 Plant layoutThe plant layout was designed according to the requirements of the design specifications listed. The whole plant is rectangular, with a span of 271.3 m and a north-south direction of 137.8 m. The total area of the plant is 37385.1 m2. The whole factory is constituted of four parts of living area, auxiliary production area, production area and storage and transportation area.Figure 5-2 Plant layout5.2. 3D layout In the project the equipment layout was drawn using AutoCAD, where the location of equipments was determined to facilitate production. The three-dimensional plant layout was also designed. These design results are shown in Figure 5-3 to Figure 5-4, and are depicted detailedly in source files of 3d layout and piping of workshop and 3d plant layout.Figure 5-3 3D layout of workshopFigure 5-4 3D piping diagram of workshop Figure 5-5 3D plant layout6. Analysis of safety and environmentIn this project, Risk System software was used to identify major hazards from epoxy propane and liquid ammonia storage tank area and terminal material source was analyzed combing the physical property of materials. According to the results of source identification, pool fire accident model, boiling liquid expanding vapor explosion prediction, and vapor cloud explosion prediction were all applied to analyze the damage scope of accidents. In addition, ALOHA software was used to simulate the steam cloud explosion accident, BLEVE accident, pool fire accident and poisoning accident of storage tanks. Noise System software was applied to evaluate the noises of the site and its surroundings. The environmental impact assessment was carried out by using Screen3Mod atmospheric estimation and EIAW water quality evaluation and prediction. HAZOP analysis software and Dow chemical fire and explosion hazard index evaluation were also adopted to predict the risk from major hazards. After these prediction and assessment, A control system combining SIS, DCS with ESD were installed to realize the stability control of equipments and systems.Environment safetyFigure 6-1 Safety and environment design7.Project economic analysis The economic and technical analysis of our factory followed relevant economic indicators and analysis methods. With fully understanding trends of market price, the investment, profit and cash flow of the whole plant were calculated and explained detailedly by using Aspen Economic Analyzer. The total investment of our factory is 233.65 million yuan, an annual profit is 12.691million yuan and an investment recovery period is 8.42 years. The results show that the project is economical feasible and thus the factory has high economic benefits.Table7-1 Comprehensive economic and technical indicatorsNumberProject nameunitValueFirstScalekt/a94.2SecondSolutions1(NH4)2SO4kt/a35.7 2PCkt/a58.5 Thirdworking daysdays333 FourthMain raw and auxiliary materials1NH3kt/a9.3 2MDEAkt/a0.0053 3POkt/a37.2 4H2Okt/a173.7 5DKCZERONOXRm3/a19.17 6KI/-Al2O3t/a3.90 7Airkt/a238.0 FifthUtility consumption1electricitykWh3.7681072MP-steamt/a4268.48483Cooling waterkt/a2813.94Coke oven gast/a716SixthThree wastes emissions 1Waste waterkt/a40.622Waste gaskt/a614.833Solid wastest/a19.236SeventhProject capacityperson137EighthGross floor aream257280.61Building aream27046.62Road aream210156.33Green aream25881.7NinthTotal investment10 thousand 233651Construction investment10 thousand 18093.42working capita10 thousand 5271.6TenthTotal annual sales revenue10 thousand 63433.1ElevenAnnual total cost10 thousand 44970.9TwelveAnnual profit10 thousand 12692.1ThirteenAnnual sales tax and additional10 thousand 3540.3FourteenAnnual income tax10 thousand 2239.8FifteenFinancial evaluation index1ROI%312Investment interest rate%38.93Investment payback periodyears8.4