Design of a small solar-powered desalination system

A design is presented for a solar/thermal system configured to power a reverse osmosis (RO) desalination unit to produce 7000 gallons of fresh water in an eight hour period. A field of line-focus tracking solar collectors is used to heat a high pressure liquid-vapor water storage tank supplying two compound reciprocating steam engines, one direct-connected to the RO high-pressure pump and the other to an electric generator for auxiliary power. An auxiliary heating loop with an oil-fired boiler is also used to supply the steam engines.The system operates in either all-solar, all-oil, or mixed solar/oil modes. Primary operating mode is assumed to be a mixed solar/oil mode in which the oil-fired boiler is used only to prevent shutdown of the RO system during the course of a partly sunny day. In this mode, the RO system does not come on line in the morning until the solar collector field has brought the high-pressure storage tank to a point near maximum operating pressure. Thereafter, the oil-fired boiler comes on automatically whenever the storage tank is drawn down to a pressure near minimum full-power operation (due to inadequate or intermittent insolation) and remains on, supplying the steam engines, until the solar collectors have again brought the storage tank to the high-pressure cutoff.In the all-solar mode, the system continues to operate at reduced power as storage tank pressure drops below the point at which the oil-fired boiler would otherwise come on. A portion of the RO system is shut down to maintain pressure in the remainder.The all-oil mode is used whenever fresh water is required during non-sunny periods, or to increase fresh water production in sunny periods.     

复合热源太阳能热泵热水系统性能模拟

提出了一种复合热源太阳能热泵热水系统,通过阀门切换,可以根据不同的天气状况改变运行模式,以空气和太阳辐射作为热源制取生活用水。针对设计的150 L热水系统建立了数学模型,对不同运行模式下的性能进行了计算机模拟分析,分析了太阳辐射强度及环境温度对系统性能的影响,并计算了系统的全年运行状况。从模拟结果可以看出,热泵串联集热器模式（HP+SC）比集热器串联热泵模式（SC+HP）耗时稍长,但COP更高,各月总热效率前者略高于后者。COP及总热效率均随太阳辐射强度及环境温度的升高而升高。在4～10月的晴朗天气下,应尽量优先采用集热器模式（SC）,仅在完全没有太阳辐射时才使用热泵模式（HP）。     

太阳能热泵供暖技术综述

回顾了国内外太阳能热泵的发展过程,介绍了太阳能热泵地板辐射采暖系统主要设备太阳能集热器、蓄热设备、地板采暖系统、控制系统、运行方式的组成和结构形式,论述了太阳能热泵的技术原理和特点以及在供暖方面的应用等。针对当前太阳能热泵供暖系统有待解决的问题进行了分析和探讨,结果表明把热泵技术与太阳能热利用技术结合可提高太阳能集热器效率和热泵系统性能,同时能解决全天候供热问题。     

CO2 methanation: Optimal start‐up control of a fixed‐bed reactor for power‐to‐gas applications

Utilizing volatile renewable energy sources (e.g., solar, wind) for chemical production systems requires a deeper understanding of their dynamic operation modes. Taking the example of a methanation reactor in the context of power‐to‐gas applications, a dynamic optimization approach is used to identify control trajectories for a time optimal reactor start‐up avoiding distinct hot spot formation. For the optimization, we develop a dynamic, two‐dimensional model of a fixed‐bed tube reactor for carbon dioxide methanation which is based on the reaction scheme of the underlying exothermic Sabatier reaction mechanism. While controlling dynamic hot spot formation inside the catalyst bed, we prove the applicability of our methodology and investigate the feasibility of dynamic carbon dioxide methanation. © 2016 American Institute of Chemical Engineers AIChE J, 63: 23–31, 2017     

太阳能-热泵复合供能系统

为最大限度利用可再生能源,将太阳能PV/T集热器与热泵相结合组成太阳能-热泵复合供能系统,通过不同阀门之间的相互切换,可实现多种运行模式以满足人们对生活热水、采暖或制冷的需求。实验主要针对单空气源热泵制热、PV/T与水源热泵联合制热及PV/T与双热源热泵联合制热3种运行工况进行研究,分别从室内温度、制热量、热泵COP、集热效率、发电效率等方面对系统进行实验研究与理论分析,实验结果表明,3种运行工况下热泵COP分别为2.26、3.4和2.61,平均室内温度分别为15.3、18.8和16.5℃,基本能满足冬季采暖负荷要求。系统可充分利用太阳能与热泵各自的优势,实现能源节约,为太阳能和热泵在建筑中联合运行模式提供部分参考价值。     

基于定型结构相变储热模块小区供热的智慧控制系统

研究了基于定型结构相变储热模块小区供热的智慧控制系统,对定型结构相变储热模块及供热系统进行了描述。结合冬季供热的负荷系数随室外环境温度的变化规律,提出小区供热的智慧控制系统及其内涵。结合城市小区供热的示范工程,智慧供热系统与传统二种操作模式进行对比,分别降低供热设备运行费用24%、32%。基于定型结构相变储热模块供热系统,因为使用低谷电或可再生能源用电,使用智慧控制系统后,运行费用降低明显。智慧供热系统与传统两种操作模式进行对比,分别降低供热设备运行费用70%、73.3%。因此,基于定型结构相变储热模块小区供热,采用智慧供热系统对于运行费用降低具有非常重要的意义。     

热泵和太阳能在电镀废液处理与回用中的应用

介绍了一种新型的电镀化工废液蒸发浓缩回用系统。该系统采用专利技术的聚丙烯减压蒸发器,以高温水源热泵和太阳能集热系统作为加热能源,实现能源和物料的全循环回收。比较了该系统与燃油、燃煤锅炉以及电加热系统的能耗,分析了某电镀厂采用该系统处理氰化镀铜、氰化镀银、氰化镀金及镀镍废液一个月所取得的效益。实践证明,该系统运行成本低、无污染,产生的经济效益明显。     

Numerical model of an inflatable solar collector

The main objective of this paper is to present a mathematical model to simulate the operation of an inflatable solar air heat collector for grain dryers. The solar collector exhibits a semicylindrical shape when air is injected into the confined space between the walls of the two covers. The mathematical model of the collector is obtained by applying the law of conservation of energy on the four main parts of the collector, absorber plate, two covers, and air that flows inside the equipment. To improve the accuracy of the model, the solar collector was divided into N control volumes, with each one containing the four parts, in such a way that one system with 4N differential equations is obtained. The unknown quantities of this system are the temperatures of the absorber plate, air, and walls of both covers in each control volume. The results allow us to conclude that the collector performance strongly depends on several entrance variables of the model (the air flow and air temperature at the collector entrance) and geometric equipment parameters (the collector length, internal radiation at the inner surface of the cover, and space between both covers). Therefore, the model can be used for optimizing the solar collector.     

化工过程多回路PID控制系统模式切换参数自整定

化工过程一般为多变量系统,但其主要控制方案为分散多回路PID常规控制。由于多变量系统内部存在不同程度的耦合作用,各控制回路之间存在相互影响,当其他回路进行手动/自动模式切换时,本回路等效被控对象将会发生突变,导致本回路的原有控制参数不能适应等效被控对象的变化,造成控制性能下降,甚至闭环系统不稳定。为避免这种情况的发生,从整个系统的角度研究控制回路模式切换时的稳定性,采用多变量频域Nyquist阵列设计法。基于对角优势下正Nyquist稳定性判据,从Gershgorin圆边界点的角度定量分析各个控制回路在模式切换前后的稳定性变化程度,从而确定各回路控制器增益的调整方向及程度,实现各回路的控制器参数在控制回路模式切换瞬间的自动整定,尽可能抵消控制回路模式切换对整个系统的扰动,保证整个系统的闭环稳定性。以Shell公司重油分馏塔的多回路PID控制系统为例,将3个PID控制回路依次投用时,根据Gershgorin圆边界点进行控制参数的自整定,闭环系统仍能保持一定的控制性能,否则闭环系统将不稳定。     

Thermodynamic analysis and optimization of RWGS processes for solar syngas production from CO2

Process systems were investigated for syngas production from CO₂ and renewable energy (solar) by the reverse water‐gas shift (RWGS) and the reverse water‐gas shift chemical looping (RWGS‐CL) process. Thermodynamic analysis and optimization was performed to maximize the solar‐to‐syngas (StS) efficiency η_StS. Special emphasis was laid on product gas separation. For RWGS‐CL, maximum StS efficiencies of 14.2 and 14.4% were achieved without and with heat integration, respectively. The StS efficiency is dictated by the low overall efficiency of H₂ production. RWGS‐CL is most beneficial for the production of pure CO, where the StS efficiency is one percent point higher compared to that of the RWGS process with heat integration. Heat integration leads to significant reductions in external heat demand since most of the gas phase process heat can be integrated. The StS efficiencies for RWGS and RWGS‐CL achieve the same level as the reported values for solar thermochemical syngas production. © 2016 American Institute of Chemical Engineers AIChE J, 63: 15–22, 2017     

Distributed model predictive control of switched nonlinear systems with scheduled mode transitions

A method for the design of distributed model predictive control (DMPC) systems for a class of switched nonlinear systems for which the mode transitions take place according to a prescribed switching schedule is presented. Under appropriate stabilizability assumptions on the existence of a set of feedback controllers that can stabilize the closed‐loop switched, nonlinear system, a cooperative DMPC architecture using Lyapunov‐based model predictive control (MPC) in which the distributed controllers carry out their calculations in parallel and communicate in an iterative fashion to compute their control actions is designed. The proposed DMPC design is applied to a nonlinear chemical process network with scheduled mode transitions and its performance and computational efficiency properties in comparison to a centralized MPC architecture are evaluated through simulations. © 2013 American Institute of Chemical Engineers AIChE J, 59:860‐871, 2013     

Kinetics of Isothermal Ethanol Adsorption onto a Carbon Molecular Sieve under Conventional and Microwave Heating

The isothermal kinetics of ethanol adsorption from aqueous solution onto a zeolite type carbon molecular sieve (CMS‐3A) under conventional heating (CH) and microwave heating (MWH) was investigated. The adsorption kinetics is described by the model of a phase‐boundary controlled reaction for both heating modes. The activation energy (E_a) for the adsorption process under MWH is lower than under CH while the preexponential factor (lnA) is higher. Ethanol adsorption is a kinetically complex process whose complexity changes with the mode of heating. The established decrease in E_a and increase in lnA under MWH compared to CH is explained with the increase in the ground vibrational level of the – OH twisting vibrations in the ethanol molecule and with the decrease in its anharmonicity factor which is caused by the selective resonant transfer of energy from CMS‐3A to the OH oscillators.     

直冷式乏风热泵系统在小保当煤矿的应用分析

为实现煤矿企业清洁能源供热,针对煤矿生产矿井排出的乏风余热,采用目前国际先进的直冷式深焓取热乏风热泵系统供热技术替代传统的锅炉供热,解决我国北方煤矿企业冬季有防冻要求的进风井口供热需求。本文以小保当煤矿矿井乏风余热供热系统项目为例,阐述了直冷式深焓取热乏风热泵系统的间壁式（间接换式）乏风换热、乏风取热机组集尘及结霜原理;采用乏风取热机组清洗除尘和防结霜除霜解决方法,并与天然气锅炉、电锅炉两种供热方案进行对比,分析计算了三种方案的项目投资和系统运行费用,论述了各方案的优势和不足。分析表明,煤矿企业采用矿井乏风余热资源,利用直冷式深焓取热乏风热泵供热系统替代传统锅炉供热,技术可行,且具有更好的经济效益和应用效果。     

Test results from a solar boiler for saline water distillation

In this paper the performance of a low temperature, 50–70 C, solar boiler is presented. The boiler consisted of a double-glazed flat-plate solar collector, a flash chamber, a water cooled surface condenser, a circulating pump, and a temperature-controlled preheater to simulate constant temperature thermal storage. Data were obtained on this boiler from October 1980 to May 1981. During this period, the instantaneous total incident solar radiation at noon, as measured by a pyranometer in the plane of the collector ranged from 0.7 to 1.0 kWm^-2 and the diurnal total incident solar radiation ranged from 13 to 29 MJ m^-2day^-1. At these conditions the instantaneous efficiency of the collector ranged from 30 to 55 percent while the diurnal efficiency ranged from 20 to 44 percent.The results show that the performance of the solar collector was the dominant factor in determining the performance of this boiler. They also show that low temperature steam, 50 to 70 C, from such boilers can be produced to drive multieffect distillation systems using high performance evaporators for desalting saline water.     

Dynamic real‐time optimization and control of a hybrid energy system

A proactive energy management strategy for a stand‐alone hybrid renewable energy system is presented. The study was motivated by the system built in Lambton College (Sarnia, Ontario, Canada) which includes photovoltaic arrays, wind turbine, battery, electrolyzers, hydrogen storage tanks, and fuel cells. The control architecture consists of two levels of hierarchy: (1) optimal predictive scheduling at the supervisory level and (2) local controllers for each of the system units. A “day‐ahead” approach is followed at the supervisory level and a bidirectional communication between the supervisory, proactive control, and the low‐level control layer is established. The proposed energy management strategy accounts for external (i.e., weather and demand) and internal disturbances. The efficacy of the proposed strategy is demonstrated through case studies. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2546–2556, 2014     

脉冲袋式除尘器在集中供热系统25t/h锅炉中的应用

简要叙述集中供热系统25t/h锅炉为了烟气除尘排放、节能减排达标,根据锅炉的实际情况采用袋式除尘方案。主要讲述脉冲袋式除尘器的工作原理、设备设计构造部分,设备安装空载运行、喷涂、重载运行等内容。根据环保部门的检测结果,给予集中供热系统25t/h锅炉的除尘方法提供可靠的设计思路和方案,做好"节能减排、环境保护"工作。     

On‐line optimizing control of bulk polymerization of methyl methacrylate: Some experimental results for heater failure

An experimental unit has been assembled to carry out on‐line optimizing control of the bulk polymerization of methyl methacrylate (MMA). A rheometer‐reactor assembly is used. Temperature and viscosity measurements are used to describe the state of the system. The polymerization is carried out under an off‐line computed optimal temperature history, T_op(t). A planned disturbance (heating system failure) is introduced at time t₁. This disturbance leads to a fall in the temperature of the reaction mass. A new optimal temperature history, T_reop(t), is re‐computed on‐line and is implemented on the reaction mass at time t₂, when the heating is resumed. This procedure helps ‘save the batch’. A genetic algorithm is used to compute this reoptimized temperature history in a short period of ～2 min of real time. The feasibility of the on‐line optimizing control scheme has been demonstrated experimentally. Replicable results for the viscosity history, η(t), of the polymerizing mass under several non‐isothermal conditions have been obtained. These experimental results are quite trustworthy, even though the model predictions are only in approximate agreement with them, perhaps because of the extreme sensitivity of results to the values of the model parameters. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2350–2360, 2002     

Low‐order optimal regulation of parabolic PDEs with time‐dependent domain

Observer and optimal boundary control design for the objective of output tracking of a linear distributed parameter system given by a two‐dimensional (2‐D) parabolic partial differential equation with time‐varying domain is realized in this work. The transformation of boundary actuation to distributed control setting allows to represent the system's model in a standard evolutionary form. By exploring dynamical model evolution and generating data, a set of time‐varying empirical eigenfunctions that capture the dominant dynamics of the distributed system is found. This basis is used in Galerkin's method to accurately represent the distributed system as a finite‐dimensional plant in terms of a linear time‐varying system. This reduced‐order model enables synthesis of a linear optimal output tracking controller, as well as design of a state observer. Finally, numerical results are prepared for the optimal output tracking of a 2‐D model of the temperature distribution in Czochralski crystal growth process which has nontrivial geometry. © 2014 American Institute of Chemical Engineers AIChE J, 61: 494–502, 2015     

寒冷地区CO2空气源热泵供暖运行性能分析

CO₂空气源热泵能够在寒冷地区低温环境下稳定运行,可望在建筑供暖领域推广应用。为客观、合理地评价CO₂空气源热泵供暖的运行性能,搭建了寒冷地区超临界CO₂空气源热泵供暖系统。根据室外环境温度和供暖热负荷将供暖期划分为5个不同的阶段,分阶段调整CO₂空气源热泵供暖运行参数。测试结果表明,CO₂空气源热泵能够满足寒冷地区供暖需求,且供暖系统在供暖季的平均性能系数可达2.236,同时供暖房间具有较好的舒适度。以燃煤锅炉、燃气锅炉为参照,采用等效电方法对比分析了三种热源供暖的能源利用效率及CO₂排放量。对比分析结果表明,在考虑能源品位之后,CO₂空气源热泵供暖的能源利用效率高于燃气锅炉供暖,略低于燃煤锅炉供暖。受燃料含碳量的影响,CO₂空气源热泵供暖的CO₂排放量虽然高于燃气锅炉供暖,但比燃煤锅炉供暖减少20.89%。     

基于不确定蒸汽需求和设备故障的锅炉系统随机规划设计

公用工程系统中锅炉系统设计不仅要考虑锅炉应对发生的故障的可靠性,还要保证系统具有一定应对蒸汽需求的波动的可操作性。本研究针对满足不确定蒸汽需求和考虑设备故障的锅炉系统设计,提出基于数学规划法的设计模型：对生产过程波动引起的不确定蒸汽需求以概率表达,采用Markov模型分析锅炉故障,表达为以一定概率发生的不确定参数。优化模型采用二阶段随机规划策略对蒸汽需求不确定波动和锅炉故障实现引起的约束违背进行补偿,以降低不确定变量对目标函数和约束条件的影响。以年总费用最小为目标,建立混合整数线性模型（MILP）,实现锅炉系统配置,设备模式确定以及应对蒸汽需求波动和设备故障发生的补偿操作的优化设计。