Design of a thermally integrated bioethanol-fueled solid oxide fuel cell system integrated with a distillation column

Solid oxide fuel cell systems integrated with a distillation column (SOFC-DIS) have been investigated in this study. The MER (maximum energy recovery) network for SOFC-DIS system under the base conditions (C_EtOH = 25%, EtOH recovery = 80%, V = 0.7 V, fuel utilization = 80%, T_SOFC = 1200 K) yields Q_Cmin = 73.4 and Q_Hmin = 0 kW. To enhance the performance of SOFC-DIS, utilization of internal useful heat sources from within the system (e.g. condenser duty and hot water from the bottom of the distillation column) and a cathode recirculation have been considered in this study. The utilization of condenser duty for preheating the incoming bioethanol and cathode recirculation for SOFC-DIS system were chosen and implemented to the SOFC-DIS (CondBio-CathRec). Different MER designs were investigated. The obtained MER network of CondBio-CathRec configuration shows the lower minimum cold utility (Q_Cmin) of 55.9 kW and total cost index than that of the base case. A heat exchanger loop and utility path were also investigated. It was found that eliminate the high temperature distillate heat exchanger can lower the total cost index. The recommended network is that the hot effluent gas is heat exchanged with the anode heat exchanger, the external reformer, the air heat exchanger, the distillate heat exchanger and the reboiler, respectively. The corresponding performances of this design are 40.8%, 54.3%, 0.221 W cm⁻² for overall electrical efficiency, Combine Heat and Power (CHP) efficiency and power density, respectively. The effect of operating conditions on composite curves on the design of heat exchanger network was investigated. The obtained composite curves can be divided into two groups: the threshold case and the pinch case. It was found that the pinch case which T_SOFC = 1173 K yields higher total cost index than the CondBio-CathRec at the base conditions. It was also found that the pinch case can become a threshold case by adjusting split fraction or operating at lower fuel utilization. The total cost index of the threshold cases is lower than that of the pinch case. Moreover, it was found that some conditions can give lower total cost index than that of the CondBio-CathRec at the base conditions.     

Dynamic optimization of cryogenic distillation operation for hydrogen isotope separation in fusion power plant

Stable operation of a hydrogen isotope separation system is one of the most important issues in the sustainable operation of fusion power plants. Owing to the present limitation in retention time of fusion reaction, fusion reactors are run in repeated batch operations, causing large fluctuating flows in the system. Hence, to reliably produce required products, counteractive operational strategies must be devised. To this end, we perform dynamic optimization in this paper to derive an optimal control policy that can minimize the tritium inventory and satisfy the product quality specifications. In addition, a rigorous dynamic model for packed columns is developed to simulate realistic behaviors of cryogenic distillation. We demonstrate that the optimization results yield vital operational strategies, such as operation mode switching, without any expertise provided.     

Transient analysis of heat pump assisted distillation systems. 1 The heat pump

A simple algorithm to simulate the transient behaviour of a vapour compression heat pump is described. Individual models are developed for various components of the heat pump such as compressor, evaporator, condenser and expansion valve. The components are simulated separately and are combined to form the total system. The compressor is a hermetically sealed, reciprocating piston type with adiabatic compression, the evaporator and condenser are coiled copper tubes, and the expansion valve is assumed to be adiabatic. The transport and thermodynamic properties of the refrigerant used are obtained from empirical equations. The total system is viewed in a simplified manner in order to apply the results of this transient analysis to the behaviour of a chemical process operation, namely, distillation.     

IGCC电站空分系统精馏塔的分段简化模型

针对IGCC电站空分系统精馏塔的逐板模型维数高、计算速度慢的缺点,用分段建模法建立了精馏塔的简化模型。该模型具有物理意义明确、通用性强、计算速度快且结果精确等特点,为进一步实现IGCC电站空分系统的动、静态仿真以及在线优化控制奠定了基础。     

Design scenarios for integrated renewable energy systems

The wide variety of renewable energy resources and their highly site-specific and variable nature, coupled with different types and qualities of energy needs, pose a challenging problem to the designers of integrated renewable energy systems (IRES). This paper discusses some typical design scenarios and the formulation of designs using the knowledge-based design tool IRES-KB with the aid of KAPPA-PC development tools. A remote village with no electrical grid connection is chosen for this study since renewables are most likely to make their greatest impact in such locations. The versatility of IRES-KB is brought out in the discussion of the results     

Exergy analysis of a MSF distillation plant

In this paper, a large MSF distillation plant in the gulf area is analyzed thermodynamically using actual plant operation data. Exergy flow rates are evaluated throughout the plant, and the exergy flow diagram is prepared. The rates of exergy destruction and their percentages are indicated on the diagram so that the locations of highest exergy destruction can easily be identified. The highest exergy destruction (77.7%) occurs within the MSF unit, as expected, and this can be reduced by increasing the number of flashing stages. The exergy destruction in the pumps and motors account for 5.3% of the total, and this also can be reduced by using high efficiency motors and pumps. The plant is determined to have a second law efficiency of just 4.2%, which is very low. This indicates that there are major opportunities in the plant to reduce exergy destruction and, thus, the amount of electric and thermal energy supplied, making the operation of the plant more cost effective.     

Heat pump assisted distillation. VII: A feasibility study on heat transformer assisted distillation systems

The problems in matching a heat driven heat transformer to a distillation process in heat pump assisted distillation are discussed. The performance of such a system is a function of the temperature difference across the distillation column. Plots are given of the calculated coefficients of performance against the temperatures of the top and bottom products. In addition plots are given of the calculated coefficients of performance against the generator temperature when the generator is independently heated. The percentage of energy saved is also plotted against coefficient of performance.     

Energy saving opportunities in heat integrated beverage plant retrofit

This paper presents practical applications of mathematical programming for energy integration in a large beverage plant. The opportunities of heat integration between batch operations were analysed by a mixed integer linear programming (MILP) model, which was slightly modified by considering specific industrial circumstances. The feasibility of combined electricity, heating and cooling production was studied using a simplified MILP model, developed for the selection of an optimal polygeneration system. The superstructure includes cogeneration systems with different prime movers (steam turbine and gas turbine), and a trigeneration system with a back-pressure steam turbine. The proposed heat integration scheme and the selected cogeneration system may improve a company’s economic performance and reduce its environmental impact.     

Heat pump assisted distillation. VI: Classified references for heat pump assisted distillation systems from 1945 to February 1986

More than one hundred and fifty references for heat pump assisted distillation systems have been listed and classified under the following categories: heat pump assisted distillation (1) with an external working fluid, (2) using one of the distillation components as the working fluid, (3) overall assessments and (4) experimental data.     

Heat pump assisted distillation. V: A feasibility study on absorption heat pump assisted distillation systems

The problems in matching a heat driven absorption heat pump to a distillation process in heat pump assisted distillation are discussed. The performance of an absorption system is a function of the temperatures in the evaporator, the condenser, the absorber and the generator and the ratio of the mass flow rate in the secondary circuit to the mass flow rate in the primary circuit. In absorption systems design choices are limited by the Gibbs phase rule. Plots are given of the coefficient of performance against the temperatures of the top and bottom products and also against the energy saved.     

Dynamic simulation of a cryogenic batch distillation process for hydrogen isotopes separation

The operational flexibility of cryogenic batch distillation may propel its application in the Isotope Separation System of the fusion reactor. The batch distillation, unlike continuous distillation, is not a steady-state process. In order to obtain improved separation efficiency, a reasonable dynamic model of batch distillation should be developed. In this paper, dynamic simulations of the batch distillation separation process of a hydrogen-deuterium mixture were performed utilizing Aspen Plus and Aspen Dynamics. The validity of the established simulation model was firstly verified by our experimental results. Following that, two dynamic control structures, i.e., composition control and temperature control, were added to improve the recovery efficiency of batch distillation light component products. In comparison with the distillation without dynamic control structure, the distillation with composition control and temperature control can improve the H₂ recovery ratio by 5.45% and 5.09%, respectively.     

Low light conditions modelling for building integrated photovoltaic (BIPV) systems

The low irradiance efficiency of photovoltaic modules is important to the optimization of BIPV systems. When photovoltaic modules are integrated into a building, architectural design considerations compete with maximizing photovoltaic energy production. As a result, BIPV arrays are often not facing south and are frequently mounted vertically. Under these conditions, a greater portion of the total sunlight striking the array is diffuse or at high angles of incidence. In northern latitudes a significant amount of the total yearly energy is produced at low light levels.A grid-connected array of BIPV modules integrated into the BCIT Technology Centre building in Burnaby, B.C. was used for assessing the accuracy of an energy performance model developed for BIPV systems. The BIPV system uses AC modules and a computerized data acquisition system for monitoring the performance of modules and inverters. The performance model was developed from analysis of the open circuit voltage, maximum power point voltage and maximum power point current of the individual modules comprising the BIPV array.The algorithm for calculating power output of the photovoltaic array is derived from the ideal diode equation using the single diode model of a photovoltaic cell. An empirically derived parameter modifies the equation. Once the parameters for different module technologies are established, it is possible to compare their annual performance in a BIPV system.     

Design recommendations for heat discharge systems in walls

When the design of an in-wall heat discharge system (HDS) is inappropriate, the heat stored in the system is not completely discharged into the environment, therefore an excess flow of heat is transferred to the space where the internal temperature is to be modified. This study presents the results obtained by modifying the design conditions of an HDS, the purpose being to prevent the design of the system from contributing to the overheating of the controlled space. Considered in the design modifications was: the separation between the plates that form the air channel, height and width of the system, dimensions of the opening of the air channel intake and the heat storing capacity of the storage plate. After making these variations to the analytic model, this study concludes that it is advisable to increase both the width of the system and the opening of the air channel intake, thus allowing for a greater flow of ventilation air within the system without overheating either the heat storage plate or the interior of the controlled space.     

Design and performance evaluation of a waste-to-energy plant integrated with a combined cycle

In this paper, a waste-to-energy (WTE) system integrated with a gas fuelled combined cycle is considered. The plant is designed as a possible future option for thermal utilization of urban wastes in the northern part of the Turin Province, Italy. The plant should provide electricity (about 160 MW at maximum electric load) to the grid and heat to a district heating network (about 50 MW at maximum thermal load). This kind of plants is particularly interesting because of the high net electric efficiency (about 46%) that is possible to achieve, compared with the equivalent global efficiency of the separate plants (about +7% waste utilization efficiency with respect to conventional plants), and the complex design that is required.     

镁熔坨综合余热回收窑设计

经过电弧炉熔炼后的镁熔坨含有大量的余热资源,但科学、有效地回收这部分余热仍是镁熔坨余热回收的难点问题。在总结分析已有的镁熔坨余热回收技术的基础上,设计了一种镁熔坨综合余热回收窑,在预热物料段利用往复炉排预热物料,循环水段利用冷却水管获得热水供暖,镁熔坨的余热回收率达39%。     

Transient analysis of heat pump assisted distillation systems. 2 Column and system dynamics

A model to simulate the transient behaviour of a heat pump assisted distillation column is presented. The packed bed distillation column is treated as a distributed parameter system with time and space as independent parameters. The column modelling using appropriate basic equations, their application to binary systems, the solution scheme to the model equations and the distillation column simulation algorithm are described. The heat pump simulation algorithm is then coupled with this algorithm and the column transient behaviour with and without heat pump assist is obtained. The results are compared with earlier steady state data in the literature.     

户外通讯机用柜空调热管一体机的设计

移动通讯是人们生活不可或缺的一部分,数据传输速度也在不断提升。国内通讯营运商对户外通讯基柜建设投入是空前的,户外通讯机柜空调装机数量巨大,能源消耗严重,因此,户外通讯机柜空调节能减排显得至关重要。本空调热管一体机设计能有效降低户外机柜空调能耗,节能率达到42%～75%,对旧通讯机柜空调改造及新建站点的节能优化有很好的推广价值。     

考虑风光不确定性的分布式能源集成虚拟电厂收益-风险均衡模型

文章将风电场、光伏发电、小水电站等分布式能源聚合为虚拟电厂,并考虑价格型需求响应负荷及激励型需求响应负荷,以运营收益最大化为目标,综合考虑负荷供需平衡约束、机组运行约束以及旋转备用约束等,构建虚拟电厂常规调度优化模型,利用条件风险价值法(CVaR)和鲁棒随机优化理论构造虚拟电厂风险规避优化模型。最后,以独立微电网作为实例对象,验证了模型能够在最大化经济效益的同时,最大化利用清洁能源,合理控制运营风险,实现虚拟电厂最优化运营。     

Design and analysis of a solar tower power plant integrated with thermal energy storage system for cogeneration

In the current study, a solar tower–based energy system integrated with a thermal energy storage option is offered to supply both the electricity and freshwater through distillation and reverse osmosis technologies. A high‐temperature thermal energy storage subsystem using molten salt is considered for the effective and efficient operation of the integrated system. The molten salt is heated up to 565°C through passing the solar tower. The thermal energy storage tanks are designed to store heat up to 12 hours. The temperature variations in the storage tanks are studied and compared accordingly for evaluation. The effect of operating temperatures on the freshwater production and overall system efficiency is determined. About 24.46 MW electricity is generated in the steam turbine under sunny conditions. Furthermore, the storage subsystem stores heat during sunny hours to utilize later in cloudy hours and night time. The produced power decreases to 20.17 MW in discharging hours due to temperature decrease in the tank. The electricity generated by the system is then used to produce freshwater through the reverse osmosis units and also to supply electricity for the residential use. A total flowrate of 240.02 kg/s freshwater is obtained by distillation and reverse osmosis subsystems.     

一种基于排取热量平衡的地源热泵系统设计方法

地源热泵空调系统作为一种高效节能的空调系统,正得到日益广泛的应用.然而,由于建筑物的冷负荷及其运行时间往往大于供暖负荷及其运行时间,设计过程中往往取最不利情况下的负荷计算结果作为设计依据,排取热量的不平衡导致地温变化,最终影响空调运行性能.针对于此,提出了一种基于排取热量平衡的地源热泵系统设计方法.