The influence of rotary valve distribution systems on the energetic efficiency of regenerative thermal oxidizers (RTO)

On–off valve systems, commonly used in regenerative thermal oxidizer (RTO) plants, generate, during the opening time, a mass flow rate (MFR) which is constant. On the contrary, rotary valve systems, which are increasingly adopted in RTO plants, are characterized by variable MFR profiles. In this work, the energy requirements of two RTO systems, equipped with on–off or rotary valves, were determined using a home‐developed numerical code. Energy performances were evaluated by calculating the thermal efficiency and pressure drop within structured or random packed bed RTO systems, at the same mean MFR. The results demonstrated that thermal efficiency was only moderately influenced by the valve system, and is slightly lower for the RTO with on–off valve. On the other hand, the study revealed that energy requirements of all RTO systems were basically unaffected by cycle duration, allowing valve rotational velocity to be freely set to maximize for other technical requirements. On the contrary, pressure drop was greatly influenced by the valve type and increased as variability in MFR function augmented. Moreover, the type of regenerator, structured or random packed bed, affected differently the total energy requirements (basically pumping energy plus auxiliary fuel). Energy requirements of structured and random regenerators were comparable only when volatile organic compounds concentration was lower than typical values encountered in the industrial practise. In other cases, structured regenerators RTO were more competitive. Finally, structured regenerators are usually the best choice when rotating valve distribution systems are adopted. Copyright © 2007 John Wiley & Sons, Ltd.     

Numerical evaluation of the energetic performances of structured and random packed beds in regenerative thermal oxidizers

Regenerative thermal oxidizers (RTO) can be conveniently used to control volatile organic components (VOC) emissions, because of their thermal efficiency and cost effectiveness.In the RTO technology, beds of inert material are used in order to heat the polluted air by cooling burnt gases, through a sequence of cyclic operations which cut the fuel requirements.A computational 1D unsteady model, able to account for both structured and random packed bed regenerators, is developed and applied to realistic plant conditions. Process thermal efficiency and gas pressure drop are calculated as functions of the system geometry and operating parameters.The code can be usefully employed in the analysis and design of RTO systems and in order to choose the more suitable type of regenerator, structured or random packed bed (even considering various particle shapes).Energetic performances of both random and structured regenerators were compared, showing that the first ones exhibit a little higher thermal efficiency but also an elevated pressure drop, at a same value of exchange surface per unit volume of the bed. Random packed bed regenerators resulted less attractive from the energetic point of view and their usage is advisable if their lower cost satisfy economical requirements.     

Development and exergoeconomic evaluation of a SOFC-GT driven multi-generation system to supply residential demands: Electricity,fresh water and hydrogen

In this study, a novel multi-generation system is proposed by integrating a solid oxide fuel cell (SOFC)-gas turbine (GT) with multi-effect desalination (MED), organic flash cycle (OFC) and polymer electrolyte membrane electrolyzer (PEME) for simultaneous production of electricity, fresh water and hydrogen. A comprehensive exergoeconomic analysis and optimization are conducted to find the best design parameters considering exergy efficiency and total unit cost of products as objective functions. The results show that the exergy efficiency and the total unit cost of products in the optimal condition are 59.4% and 23.6 $/GJ, respectively, which offers an increase of 2% compared to exergy efficiency of SOFC-GT system. Moreover, the system is capable of producing 2.5 MW of electricity by the SOFC-GT system, 5.6 m³/h of fresh water by MED unit, and 1.8 kg/h of hydrogen by the PEME. The associated cost for producing electricity, fresh water and hydrogen are 3.4 cent/kWh, 37.8 cent/m³, and 1.7 $/kg, respectively. A comparison between the results of the proposed system and those reported in other related papers are presented. The diagram of the exergy flow is also plotted for the exact determination of the exergy flow rate in each component, and also, location and value of exergy destruction. Finally, the capability of the proposed system for a case study of Iran is examined.     

Thermal Performance of a Phase Change Material‐Based Latent Heat Thermal Storage Unit

An experimental analysis is presented to establish the thermal performance of a latent heat thermal storage (LHTS) unit. Paraffin is used as the phase change material (PCM) on the shell side of the shell and tube‐type LHTS unit while water is used as the heat transfer fluid (HTF) flowing through the inner tube. The fluid inlet temperature and the mass flow rate of HTF are varied and the temperature distribution of paraffin in the shell side is measured along the radial and axial direction during melting and solidification process. The total melting time is established for different mass flow rates and fluid inlet temperature of HTF. The motion of the solid–liquid interface of the PCM with time along axial and radial direction of the test unit is critically evaluated. The experimental results indicate that the melting front moves from top to bottom along the axial direction while the solidification front moves only in the radial direction. The total melting time of PCM increases as the mass flow rate and inlet temperature of HTF decreases. A correlation is proposed for the dimensionless melting time in terms of Reynolds number and Stefan number of HTF. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21120     

蓄热式热氧化技术在煤制气低温甲醇洗尾气治理中的应用

通过蓄热式热氧化(RTO)技术在煤制气低温甲醇洗尾气治理项目中的实际应用,证明采用RTO技术处理低温甲醇洗尾气可稳定可靠地达到GB 31571—2015《石油化学工业污染物排放标准》的排放要求,且NO_x排放值极低,说明RTO技术能够有效控制高温氧化过程中NO_x的生成;RTO技术可实现极高的热回收效率,从而通过余热回收利用副产蒸汽,实现项目的正收益。     

Performance evaluation of a solar thermal energy storage system using nanoparticle-enhanced phase change material

This paper presents a numerical investigation on the thermal performance of a solar latent heat storage unit composed of rectangular slabs combined with a flat-plate solar collector. The rectangular slabs of the storage unit are vertically arranged and filled with phase change material (PCM: RT50) dispersed with high conductive nanoparticles (Al₂O₃). A heat transfer fluid (HTF: water) goes flow in the solar collector and receives solar thermal energy form the absorber area, then circulates between the slabs to transfer heat by forced convection to nanoparticle-enhanced phase change material (NEPCM). A numerical model based on the finite volume method and the conservation equations was developed to model the heat transfer and flow processes in the storage unit. The developed model was validated by comparing the obtained results with the experimental, numerical and theoretical results published in the literature. The thermal performance of the investigated latent heat storage unit combined with the solar collector was evaluated under the meteorological data of a representative day of the month of July in Marrakesh city, Morocco. The effect of the dispersion of high conductive nanoparticles on the thermal behavior and storage performance was also evaluated and compared with the case of base PCM without additives.     

Mathematical Model for Fluid Flow and Heat Transfer in the Cooling Shaft of Coke Dry Quenching Unit

IntroductionCoke Dry Quenching (CDQ) unit is a regenerativesystem whose thermal fUnchon is to cool off the red hotcoke with the circulahng gas and at the same time tOtransfer energy from the incandescent coke to watervapor fOr electricity generation. In comParison toconventional Coke Wet Quenching (CWQ) system, CDQenables not only energy savings, but also environmentalprotection. Further advantage is the imProved quality ofcoke. TherefOre, CDQ technology is becoming theconunon practi…     

Turbulent flow in the distribution header of a PEM fuel cell stack

A numerical investigation of the flowfield in a model distribution header manifold of a polymer electrolyte membrane fuel cell stack is conducted. The computational model simulates two segments of an experimental setup of a pair of model headers which replicate the headers of a fuel cell stack. The model headers consist of an inlet and outlet sections connected with a plate containing an array of holes that replicate the unit cells. The flow structures in the outlet header are rather complex and are the result of the superposition of a series of impinging jets in a confined space in the presence of crossflow. The flow from each hole, which represents an individual cell outlet, enters the outlet header as a jet stream and is subjected to a crossflow. Large Eddy Simulations (LES) are performed for a portion of the outlet header to investigate the complex turbulent flow and related structures under different crossflow conditions, and are complemented by Particle Image Velocimetry (PIV) measurements. The LES results show that two large vortical structures are formed in the header cross-section, with a high-speed round jet from the cell outlet holes forcing a diversion of the crossflow, dividing it into two separate branches. Investigation of the flow restructuring after a blockage of one of the jets is performed. Simulation results using a slot opening for the jet show flow instabilities. The results of this study highlight the unsteady and highly turbulent nature of the flow in the header and provide a characterization of the complex three-dimensional structure of the flow. The flowfield and flow structures may impact the overall pressure drop along the header and the effective cross-sectional area for the flow leaving the header. The observations and insights obtained from the LES simulation and PIV measurements point to the need to further investigate the impact on flow sharing in a stack of the flowfield development in the outlet header.     

直燃式焚化炉的节能改造

当前覆铜板行业所使用的废气焚化炉有直燃式废气焚化炉和蓄热式废气焚化炉。蓄热式废气焚化炉的蓄热陶瓷体能够将燃烧机的热量储存起来,当蓄热陶瓷体的温度超过有机废气的着火点时,即使燃烧机不点火,炙热的蓄热陶瓷体也能点燃有机废气。介绍了直燃式（TO）焚化炉和燃气蓄热（RTO）焚化炉的原理和特点,广东深鑫电子材料有限公司的直燃式焚化炉改造为燃气蓄热（RTO）焚化炉,工程应用表明,可以降低燃油消耗,降低生产成本。     

Performance of a second generation solar cooling unit

This paper describes the performance of a 1.5 ton solar-operated absorption refrigeration unit operating with a 14 m² flat-plate solar collector system and containing five heat exchangers: the generator, the absorber, the condenser, the solution heat exchanger (all of these being of shell-and-tube type) and finally the evaporator, which is of the fin-and-tube type. One circulation pump is used for solution flow and another for the hot water flow. The condenser and the absorber are both cooled by city mains water. This particular unit, called the second generation unit, is compared with an earlier, first-generation unit (FGU), i.e. a low-cost, locally manufactured unit of 0.5 ton capacity. The results are based on the observed operation of the unit during hours of sufficient solar irradiance in April and May, the beginning of the air-conditioning season in Jordan. The variation of both the generator and evaporator temperatures during the test period are reported. Also reported is the performance of the unit as measured by the actual and theoretical (ideal) coefficients of performance, both of these being functions of the temperatures and solar irradiance. The maximum values obtained for both actual and theoretical coefficients of performance were 0.85 and 2.7, respectively. These values are within the range of values published in literature, and higher than those obtained by the FGU.     

Optimal working conditions of various city gate stations for power and hydrogen production based on energy and eco-exergy analysis

In this study, the feasibility of producing power and hydrogen from the waste heat of different City Gate Stations (CGSs) is investigated to select the optimal working conditions. A thermodynamic model is developed for a proposed system combined of the CGS station, the Rankin cycle and the extended hydrogen production cycle. Initially, six CGS stations are simulated based on energy, exergy-economic and environmental analysis and then a comparative study is conducted between different stations. The results of numerical modeling show that the Mashhad-old station with 5315 kW and 31.062 ton/year has the highest amount of power and hydrogen production among other stations, respectively. It is also observed that, it is more economic to increase the input gas pressure in order to increase the production rate. In addition, optimal working conditions are determined based on the two important optimization factors of the hydrogen production rate and SUCP (sum unit cost of the product) using genetic algorithm optimization technique. The results of multi-objective optimization indicate that Gonbad, Gorgan and Mashhad-old stations, where the inlet gas mass flow rate is in the range of 8–9 kg/s, are the optimum stations.     

第四代DLE燃烧室流场特性研究

参照西门子的第四代干式低污染(Dry Low Emissions,DLE)燃烧室,设计了模型燃烧室,通过激光粒子图像速度仪(Particle Image Velocimetry,PIV)测量技术,对燃烧室头部出口流场进行了实验研究,分析了头部结构变化和入口空气流量变化对流场特性的影响。研究结果表明:两个主旋流器的旋流方向组合对燃烧室头部出口的流场特性有着很大影响;预混室RPL (Rich-Pilot-Lean)段的流量变化主要影响旋流器中轴线附近的轴向回流速度;入口空气流量变化对流场的影响主要表现在速度值上,但对速度变化趋势没有太大的影响。     

Improving farm efficiency of interacting vertical‐axis wind turbines through wake deflection using pitched struts

This work presents a numerical study of the obtained performance and the resulting flow field between two interacting large scale vertical‐axis wind turbines (VAWTs), under the influence of a deflected wake through the struts pitching of the upwind turbine. The configuration consists of two VAWTs aligned in the direction of the incoming flow in which a wide range of fixed struts pitching angles in the upwind turbine have been investigated. The main goal is to evaluate the influence of the wake deflection on the turbines performance while they are operating at their optimal tip speed ratio (TSR), and to reproduce the most relevant phenomena involved in the flow pattern of the interacting wake. Arrangements with cross‐stream offsets have also been tested for quantifying the contribution of this modification into the overall performance. For this purpose, an actuator line model (ALM) has been implemented using the open‐source CFD library OpenFOAM in order to solve the governing equations and to calculate the resulting flow. The Large eddy simulation (LES) approach is considered to reproduce the turbulence flow effects. A preliminary study to identify the optimal TSR of the interacting downwind turbine has been investigated.     

蓄热式氧化炉在处理SBS生产废气中的应用

本方案主要是采用蓄热式氧化炉(简称RTO)处理SBS生产过程中产生的有机废气,通过把有机废气加热分解成CO2和H2O。相比传统的有机废气处理工艺,RTO处理有机废气效率高,污染物排放少,同时,节省了燃料的消耗。     

The integration of Price Responsive Demand into Regional Transmission Organization (RTO) wholesale power markets and system operations

A number of states and utilities are pursuing demand response based on dynamic and time-differentiated retail prices and utility investments in Advanced Metering Infrastructure (AMI), often as part of Smart Grid initiatives. These developments could produce large amounts of Price Responsive Demand, demand that predictably responds to changes in wholesale prices. Price Responsive Demand could provide significant reliability and economic benefits. However, existing RTO tariffs present potential barriers to the development of Price Responsive Demand. Effectively integrating Price Responsive Demand into RTO markets and operations will require changes in demand forecasting, scarcity pricing reform, synchronization of scarcity pricing with capacity markets, tracking voluntary hedging by price responsive loads, and a non-discriminatory approach in curtailments in capacity emergencies. The article describes changes in RTO policies and systems needed incorporate Price Responsive Demand.     

Parametrical analysis of the design and performance of a solar heat pipe thermoelectric generator unit

This paper describes a solar heat pipe thermoelectric generator (SHP-TEG) unit comprising an evacuated double-skin glass tube, a finned heat pipe and a TEG module. The system takes the advantage of heat pipe to convert the absorbed solar irradiation to a high heat flux to meet the TEG operating requirement. An analytical model of the SHP-TEG unit is presented for the condition of constant solar irradiation, which may lead to different performance characteristics and optimal design parameters compared with the condition of constant temperature difference usually dealt with in other studies. The analytical model presents the complex influence of basic parameters such as solar irradiation, cooling water temperature, thermoelement length and cross-section area and number of thermoelements, etc. on the maximum power output and conversion efficiency of the SHP-TEG. Simulation based on the analytical model has been carried out to study the performance and design optimization of the SHP-TEG.     

满足车用国Ⅳ排放标准的EGR与DOC技术的应用研究

为实现车用柴油机大流量废气再循环,研制了氧化催化转化器(DOC)后处理器与大流量冷却式废气再循环(L-CEGR)系统组成的排放控制新技术配置,并在11L车用发动机上进行了试验。试验结果表明:采用电控可变几何涡轮增压器(VGT)为主件的L-CEGR系统使NOx排放下降28.6%;采用160MPa高压喷射和进气优化后,PM排放降低74.4%,铂含量为0.55g/unit的DOC能使PM排放降低20%;柴油机各项排放指标均达到国Ⅳ标准,也符合NO2排放限值要求;L-CEGR与160MPa高压喷射等技术相结合,使发动机加权平均燃油消耗率降低3.5%。     

干熄炉内传热和流体流动的数学模型

干熄焦工艺具有节能和环保双重效益，其基本原理是利用循环惰性气体冷却焦炭。根据多孔介质理论，采用非达西流和非局域热平衡方法，建立了干熄炉内流体流动和传热的数学模型，并采用基于非正交同位网格的SIMPLE方法求解对流扩散方程，通过数值求值，得到了干熄炉内气体速度，压降以及气体和焦炭的温度分布规律，计算结果表明熄焦过程解决焦炭温度偏析的关键是改善布料时焦炭粒度分布的均匀性。     

On the influence of the anodic porous transport layer on PEM electrolysis performance at high current densities

In this study, the influence of the anodic porous transport layer (PTL) on the performance of a proton exchange membrane (PEM) electrolysis laboratory test cell was investigated up to a current density of 5 A*cm⁻². Operation parameters such as water volume flow rate (0.2–0.8 l*min⁻¹), temperature (40–80 °C) and pressure (1–30 barg) have been varied to study their influence on the polarisation curve. Special attention has been paid to the appearance of mass transport losses (MTL) and their dependency on the operation parameters. Two stack designs that are commercially in use - one with and one without flow channels underneath the PTL - were tested and evaluated. Fundamental differences in performance have been observed between the two cell designs. Operation parameters only show impact on performance for the configuration without flow channels. Here, MTL were observed in several cases already for current densities around and above 1.0 A*cm⁻². An increase in pressure, temperature or water flow rate reduces MTL for these configurations.     

Particle swarm optimization for redundant building cooling heating and power system

An optimal and redundant building cooling heating and power (BCHP) system can yield economical savings, but more importantly can save energy as well as reduce the emission of pollutants. This paper presents the energy flow analysis of the conventional separation production (SP) system and the redundant BCHP system. Four decision variables (the capacity of power generation unit (PGU), the capacity of heat storage tank, the on–off coefficient of PGU and the ratio of electric cooling to cool load) to be optimized are selected in consideration of the design and the operation strategy of BCHP system. An objective function to simultaneously measure the energetic, economical and environmental benefits achieved by BCHP system in comparison to SP system is constructed and maximized. Particle swarm optimization algorithm (PSOA) is employed to search the optimal solutions. A case study of BCHP system with thermal storage unit and hybrid cooling system is presented to ascertain the feasibility and validity of the optimization method.