0_特等奖_浙江大学-VIVO

1 PROJECT PRECIS PRECIS VIVO Team: GUO Yunlong*, LIN Nan, YU Chenjian, CUI Xiaohong, ZHAO Junjie The VIVO Team from Zhejiang University has designed a conjoint project of 90,000t/yr CO2 capture and microalgae cultivation for Dalian Songmudao Chemical Industry Park. We use ameliorated MEA&MDEA as the main absorbent to capture more than 80% of the CO2 from the flue gas of the heat-engine plant in the industry park. 90,000 tons per year of CO2 is divided into two parts: 20,000 tons supplies the Microalgae Cultivation Section; the rest 70,000 tons to be sold goes directly to storage tanks. In this project, we combine traditional chemical engineering with the advanced biochemical engineering, and realize circular economy by capturing CO2 and producing high value-added Chlorella product. Therefore it is very promising both for environment protection and for economic benefits. With a rising level of greenhouse gas threatening the existence of mankind, we, as a new generation of responsible chemical engineers, are urged to think about how to reach an optimized economical development with a reduced emission of Carbon Dioxide (CO2). Now Carbon Dioxide Capture, Storage and Utilization (CCS&U) is such a concept that endeavors to reduce CO2 level and leads a circular economy. Support by both government and industries, researchers have devised many methods to capture CO2 in large amount, although few of which can be put into practice. Therefore, how to maximize the capture and utilization while minimize the cost is the key issue in this project. Figure 1 Flow Chart of CO2 Capture Process 2 PROJECT PRECIS A. Selection of Absorbent Chemical absorption is a worthwhile selection among all the other technologies, especially for power flue gases. Therefore chemical absorption was chosen in this project. Among methods of chemical absorption, absorption with amine stands out with fast absorption rate, higher efficiency and some other advantages. In our project, we use compound amine to absorb CO2, which contains 15.6% (molar fraction) monoethanolamine (MEA) + 4.2% methyldiethanolamine (MDEA) + 80% water and some other additives. MEA serves as major absorbent and MDEA as an activating additive, which increases the unit absorption of CO2 while decreases the unit energy consumption in absorbent regeneration. B. CO2 Capture Process Section Description This section is mainly made up of three parts, namely absorption section, regeneration section and absorbent mixing section. In absorption section, CO2 and MEA come into mass&heat transfer from the top and the bottom of an absorption tower and react inside (CO2 absorption rate is 80%). The rich fluid is heated to steam state at 80℃ by rich-poor fluid heat exchanger. In regeneration section, the operating condition under normal pressure can lower the cost of equipment and operation. The top condensation is partially gas and liquid, which is supposed to separate the main gas product, carbon dioxide. The capture rate of 11.4t CO2 per hour ensures a capture of 90,000t CO2 in total per year (the plant works 330 days per year). In the mixing section, since most of absorbent is recycled, five fluids are mixed here, which are fluids of two flashes, poor fluid, complementary water and MEA. C. Process Advantages and Innovation 1) The concentration of MEA and MEDA in the absolvent has been optimized. It promotes the unit absorption of CO2 while decreases the unit energy consumption of absorbent regeneration. Our replenishment of MEA is 9g/hr, namely 0.79g/1t CO2, which is only 1/5 of the MEA consumption of Sichuan Tiancheng Group, who also use MEA and MDEA as the main absorbent but with a different composition. 2) The CO2 capture process is simple, with only a few facilities, thus it can easily achieve a stable operation for a long time, which is of vital significance to industrial production. By optimizing the operating parameters in this process, we have greatly lowered the unit cost of CO2 capture. D. Energy Saving With the help of ASPEN Energy Analyzer V7.1 and the pinch theory, we learned the heat exchange duty of the whole plant and optimized heat exchange net. Taking into consideration of all factors, such as cost of equipment and operation, climate and plant layout and significant features of the process, for example the microalgae cultivation section of our plant needs low grade energy to keep the temperature of tower steady, we designed our heat exchange net. Through this heat integration energy consumption can be reduced by over 20%. 3 PROJECT PRECIS In this process, mixed gas severs as the carbon source, which consists of captured CO2 from absorbing section and fresh air. With such mixed gas, Chlorella, a common single-celled green alga, can be cultivated at 35~40℃ in a relatively high density. Consequently, the amount of CO2 utilized in this section approaches 20,000 tons per year with a production of 2557 tons of microalgae biomass per year. This will no doubt create considerable profit because of its wide application feedstuff and tonics. A. Program Feathers 1) Innovative design of dense Chlorella cultivation with CO2-rich mixed gas; 2) Realization continuous production of Chlorella cultivation. B. Elaboration of This Process 1) Cultivation Step In the cultivation step, the mixed gas of captured CO2 (20%) and fresh air serves as cultivation gas for a semi-continuous process of cultivation. When the concentration of microalgae reaches 1g/L, the fluid would be pumped into the Carbon-Fix Tower I. 2) Carbon Sequestration Step CO2 in this step is enriched to 45% under normal pressure with replenishment of Captured CO2 and it is recycled in these two carbon-fix towers. In Tower I microalgae grow smoothly in a range from 1.5g/L to 3g/L, while in Tower II the concentration jumps to 5g/L. When the concentration of microalgae reaches the set values, the fluid can be pumped from Tower I to Tower II and then processed with separation and desiccation. Figure 2 Flow Chart of Microalgae Cultivation Process C. Reactor Design Process 1) Carbon-fix Tower Table 1 Technological Parameters Technological parameters Final value Mixed gas flow 1283.14m3/h CO2 flow 577.41m 3/h Air flow 686.64m3/h Liquid(Chlorella) flow 4.28m3/h Length of the column tube 200m Tube diameter 1000mm Chlorella primary weight 235.545kg 4 PROJECT PRECIS In the carbon-fix tower, tubes, gas distributors and gas flow ports are devised. Inner small protuberances of the tubes are designed to maintain turbulent flow for a better mixture of gas-liquid phases. 2) Semi-continuous Culture Reactor In this stirring reactor, there is an 8-hole (diameter 10cm) circle distributor (diameter 1m). Baffles are used to break bubbles; a stirring speed of more than 250rpm prevents algae from depositing. Figure 4 Flow Chart of Control Systems A. Objectives Guarantee the continuous and stable operation of the whole process under normal conditions and the fast response to abnormal conditions during emergencies. B. Single Loop PID Controllers Single loop PID controllers are tuned to ensure that process parameters and product specifications generally meet our requirements. Such single loop PID control schemes include control of water mass fraction of lean solvent flowing into the absorption tower, outlet temperature of rich solvent from the heat exchanger, level of the reboiler of the stripper tower, temperature and pH of the reactors where microalgae grow, etc. C. Advanced Process Control Since the above single loop PID controllers do not work well when dealing with complex disturbances, immeasurable parameters and constraint conditions, advanced process control strategy, specifically Model Predictive Control, is designed for control of CO2 concentration in outlet gas of the absorption tower. Model prediction, online-optimization, and modification according to feedback to controllers ensure the ratio of the flow rate of inlet flue gas to the flow rate of inlet lean solvent is controlled Figure 3 The Illustration of Carbon-fix Tower 5 PROJECT PRECIS Dalian Songmudao Chemical Industry Park Bohai Gulf within desired range and thus CO2concentration in outlet gas is satisfactory. D. Protective Measures in Emergency There are two typical types of protective measures in emergency. One is to stop the processes whatever dangers appear, while the other one takes various constraint conditions and their logical relationships into consideration and when some parameters are about to run beyond the safe range, another control loop is ready to replace the control loop working under normal conditions. Since the former strategy is apt to economic loss and fierce fluctuation of the whole process, we choose the later one in which shutdowns are not necessarily geared every time. E. Future Developments For further improvement in the future, we highly recommend concepts from optimization, mathematical analysis and nonlinear dynamics be integrated into our process design, control and operation, the result of which will lead to powerful synergies among these tasks, better performance of the process and improvements in profitability, efficiency and environmental impact. We plan to build our plant in Dalian Songmudao Chemical Industry Park (DSCIP), Liaoning Province. Neighboring the Bohai Gulf, the DSCIP possesses superiority of location, along with amenities of transportation and comfort of nice weather. Gathering of corporations in the park invigorates this area in form of industrial chain. Support from research institutes and local government also boosts the development of DSCIP. Our project will be successful here since we concord with the circular economy in this industry park. Our Plant, covering an area of 25,994 square meters, consists of the administration quarter, the production area, the auxiliary production area and the storage tank farm. The layout strictly meets the criteria of chemical industry in all aspects, such as safety, environment, transportation and future development. Some tools that we used in designing this plant include Auto CAD, Sketch Up, SmartPlant 3D and Artlantis for rendering. Finally we will present you a visual touring in our plant. Figure 5 Geographical Location of Dalian Songmudao Chemical Industry Park Figure 6 Layout of the Plant 6 PROJECT PRECIS We refer to chemical common data processing which is used in economic analysis, and utilize Aspen Process Economic Analyzer for help. Cash flow, investment cost estimates, risk assessment and feasibility analysis have all been calculated. The prominent profit indicates the splendid future of our project. Table 2 Financial Analysis Overview Serial Number Item Value 1 CO2 project scale 90 thousand tons/year 2 Device lifetime 10 years 3 Raw material consumption 0.123 million Yuan/year 4 Plant area 25994m2 5 Employees 73 6 Total investment costs 430.19 million Yuan 7 Annual earnings 153.47 million Yuan/year 8 Expenditure 83.40 million Yuan/year 9 ROI 27.60% 10 Investment tax rate 58.74% 11 Invest return rate 25.10% 12 Payback period 8.06 years 13 NPV 285.66 Yuan In this project, we have completed the demonstrative report of feasibility, the preliminary design specification, 2D&3D design of our plant. We optimized the fomular of MEA-MDEA absorbent process control design, which increases the unit absorption of CO2 while decreases the unit energy consumption in absorbent regeneration. Economic evaluation and other essential works we should do referring to the related national and industrial design specifications. Also, we designed an efficient heat exchange net, saving more than 20% of energy. Moreover, we utilized the captured CO2 for profitable production by innovatively realizing the semi-continuous microalgae cultivation. Among these works, the process was simulated and optimized for countless times with the help of Aspen V7.1. 2D&3D design were finished with a vast of tools, such as AutoCAD, Sketch Up, SmartPlant 3D and Artlantis. A reasonable economic evaluation is done with the help of Aspen Economic Analyzer and Matlab. With this conjoint project of 90,000t/yr CO2 capture and microalgae cultivation, our VIVO team from Zhejiang University has historically hewed a stone of hope out of the challenging mountain of CCS&U. *Please consult the documents we hand in for more details. Figure 7 Risk and Uncertainty Analysis