Technical and Economic Aspects and Experience from 6 Years of Operating the Technology Using the Waste Heat from the Exhaust Gases of Heat Sources and 3 Years of Operating a Heating Plant in an Autonomous, Island Regime

This article is focused on technical and economic evaluation of more than 6-years experiences of operating the Waste Heat Recovery technology—the manner and system of flue gas processing generated in the combustion process in heat & power plants, cogeneration units, etc., which burn the gaseous fuel, primarily natural gas, or methane, biogas, geothermal gas, or other gaseous mixtures containing hydrogen. The solution proposes a more effective and non-traditional use of gaseous fuel for heating, the flue gases of which are processed in order to extract additional utilisable heat, with potential elimination of CO2 from them. Deploying of the heating plant in an island regime (OFF-GRID) enables definition of the benefits brought by the 3 years of operational experience and presents visions for the future offering the possibility to utilise the support energy services at the municipal as well as regional level.

Characteristics of gaseous product from municipal solid waste gasification with hot blast furnace slag

Possibility of combustible gas production from municipal solid waste （MSW） using hot blast furnace （BF） slag has been studied.The objective of this work is to generate combustible gas from MSW using heated BF slag.In this experiment,the thermal stability of the MSW was analyzed by thermogravimetric analysis,and effects of temperature,gasifying agent （air,N2,steam） and BF slag on the gas products were investigated at 600？900 ？C.The thermogravimetric analysis indicates that the weight loss of MSW includes four stages：evaporation of the moisture,combustion of volatile materials,burning of carbon residue and burnout of ash.The contents of the combustible gas increase with increasing temperature,and the lower calorific value （LCV） increases rapidly at 600？900 ？C.It is found that volume fraction of CO,H2 and CH4 at different atmospheres increases in the order N2〈air〈steam.It is believed that BF slag acts as the catalyst and the heat carrier,which promotes the gasification reactivity of MSW.

Experiment Study on the Exhaust-Gas Heat Exchanger for Small and Medium-Sized Marine Diesel Engine

This paper aims to design a special exchanger to recover the exhaust gas heat of marine diesel engines used in small and medium-sized fishing vessels,which can then be used to heat water up to 55°C–85°C for membrane desalination devices to produce fresh water.A new exhaust-gas heat exchanger of fins and tube,with a reinforced heat transfer tube section,unequal spacing fins,a mixing zone between the fin groups and four routes tube bundle,was designed.Numerical simulations were also used to provide reference information for structural design.Experiments were carried out for exhaust gas waste heat recovery from a marine diesel engine in an engine test bench utilizing the heat exchanger.The experimental results show that the difference between heat absorption by water and heat reduction of exhaust gas is less than 6.5%.After the water flow rate was adjusted,the exhaust gas waste heat recovery efficiency was higher than 70%,and the exhaust-gas heat exchanger’s outlet water temperature was 55°C–85°C at different engine loads.This means that the heat recovery from the exhaust gas of a marine diesel engine meets the requirement to drive a membrane desalination device to produce fresh water for fishers working in small and medium-sized fishing vessels.

Heat Transfer and Energy Utilization of Waste Heat Recovery Device with Different Internal Component

Steel industry is high energy-consuming industry, and its waste?heat recovery is critically?important for energy utilization. In this study, pipeline bundle is used to enhance heat transfer in?waste?heat recovery device,?and?associated gas-solid heat transfer and energy utilization performance with different pipeline arrangement, pipe diameter and shape of internal component are further analyzed. The temperatures of gas and particle in device with pipeline bundle periodically fluctuate in horizontal direction, and those in staggered system distribute more uniformly than those in paralleled system. Compared with paralleled device, exergy and waste heat utilization efficiency of staggered device have been improved, and they are both higher than?those without pipeline. As pipe diameter increases, exergy and waste heat utilization efficiency first increases and then decreases, and they reach the maxima with optimal pipe diameter.?As the width of internal component keeps constant, influence of its shape on heat transfer is very little.

Technical Measures and Selections for Reducing Flue Gas Heat Loss of Large Coal-Fired Boilers

The main technologies for reducing flue gas heat loss of pulverized coal-fired boilers are introduced, and the suitability of these technologies for boiler operation and the principles for selection of these technologies are explored. The main conclusions are： 1） the non-equilibrium control over flue gas flow rates at the inlet of the air heater and the reversal rotation of the air heater rotator should be popularized as regular technologies in large boilers; 2） increasing the area of the air heater to reduce the flue gas heat loss in pulverized coal-fired boilers should be the top option and increasing the area of the economizer be the next choice; 3） low- pressure economizer technology could save energy under special conditions and should be compared with the technology of increasing economizer area in terms of technical economics when the latter is feasible; 4） the hot primary air heater is only suitable to the pnlvefizing system with a large amount of cold air mixed.

Transforming Waste Heat into“Renewable Heat”

Introduction:The current worldwide electric power&heat&cool production has a negative impact on the environment by emissions and enormous leaks of low-potential waste heat.Transformation of unused industrial low power heat into“renewable heat”useful to enhance the efficiency of the system is essential and actual innovation in the field of worldwide environmental protection.By introducing and defining the terminology of low-potential,“renewable”,“green heat”has created a new,parallel category of research in the energy sector.Traditional co-generation systems produce heat for space heating and hot water and generate electricity.Moving to tri-generation allows growing demand for air conditioning for homes,offices and commercial spaces such as server rooms and switchboards to be met simultaneously or on a seasonal basis.Tri-generation,or combined cooling,heat and power,is the process by which some of the heat produced by a co-generation plant is used to generate chilled water for air conditioning or refrigeration.Usually an absorption chiller is linked to the plant to provide this functionality.The technical solution is related to the new efficient manner and system of simultaneous generation of heat/cold from multiple heat sources,which has not yet been known,but in practice required.New system also enables advantageous utilization of solar power in supporting of the cooling output.The innovative system can be operated also within the existing central heating distribution systems.

Machine learning-based multi-objective optimization and thermal assessment of supercritical CO_(2) Rankine cycles for gas turbine waste heat recovery

Technologies for utilizing waste heat for power generation have attracted significant attention in recent years due to their potential to enhance energy efficiency and reduce greenhouse gas emissions.This research focuses on the comparative and optimization analysis of three supercritical carbon dioxide(sCO_(2))Rankine cycles(simple,cascade,and split)for gas turbine waste heat recuperation.The study begins with parametric analysis,investigating the significant effects of key variables,including turbine inlet temperature,condenser inlet temperature,and pinch point temperature,on the thermal performance of advanced sCO_(2) power cycles.To identify the most efficient cycle configuration,a multi-objective optimization approach is employed.This approach combines a Genetic Algorithm with machine learning regression models(Random Forest,XGBoost,Artificial Neural Network,Ridge Regression,and K-Nearest Neighbors)to predict cycle performance using a dataset extracted from cycle simulations.The decision-making process for determining the optimal cycle configuration is facilitated by the TOPSIS(technique for order of preference by similarity to the ideal solution)method.The study's major findings reveal that the split cycle outperforms the simple and cascade configurations in terms of power generation across various operating conditions.The optimized split cycle not only demonstrates superior power output but also exhibits enhanced net power output,heat recovery,system and exergy efficiency of 7.99 MW,76.17%,26.86%and 57.96%,respectively,making it a promising choice for waste heat recovery applications.This research has the potential to contribute to the advancement and widespread adoption of waste heat recovery in energy technologies boosting system efficiency and economic feasibility.It provides a new perspective for future research,contributing to the improvement of energy generation infrastructure.

Utilisation of waste heat from exhaust gases of drying process

Nowadays a lot of low-grade heat is wasted from the industry through the off- and flue-gasses with different compositions. These gases provide the sensitive heat with utilisation potential and latent heat with the components for condensation. In this paper, process integration methodology has been applied to the partly condensed streams. A hot composite curve that represents the gas mixture cooling according to equation of state for real gases was drawn to account the gas-liquid equilibrium. According to the pinch analysis methodology, the pinch point was specified and optimal minimal temperature difference was determined. The location of the point where gas and liquid phases can be split for better recuperation of heat energy within heat exchangers is estimated using the developed methodology. The industrial case study of tobacco drying process off-gasses is analysed for heat recovery. The mathematical model was developed by using MathCad software to minimise the total annualised cost using compact plate heat exchangers for waste heat utilisation. The obtained payback period for the required investments is less than six months. The presented method was validated by comparison with industrial test data.

Waste heat recovery and denitrification of flue gases from gas-fired boilers

A waste heat recovery and denitrification system was developed for improving energy conservation and emissions control especially for control of PM2.5 particles and haze. The system uses enhanced heat and mass transfer techniques in a packed heat exchange tower with self-rotation and zero-pressure spraying, low temperature NO oxidation by ozone, and neutralization with an alkali solution. Operating data in a test project gave NOx in the exhaust flue gas of less than 30 mg/Nm3 with an ozone addition rate of 8 kg/h and spray water p H of 7.5–8, an average heat recovery of 3 MW, and an average heat supply of 7.2 MW.

An Experimental Study on Latent Heat Recovery of Exhaust Wet Flue Gas

The experiment was conducted to investigate the heat transfer performance of wet flue gas in a vertical tube. The factors influencing the convective condensation of wet flue gas were experimentally investigated. The measured results indicate that the convective heat transfer of bulk flow and condensation heat transfer of vapor have significant contribution to the total heat transfer and the dominant transport mechanism is dependent upon the vapor fraction in mixture.

金属丝网强化余热回收烟气换热器的试验与数值研究

为探究金属丝网强化元件在余热回收烟气换热器中的应用可行性及其性能表现,对嵌有金属丝网的通道的流动与换热性能开展试验与数值研究。对嵌入不同孔隙率金属丝网的通道进行了试验研究,基于FLUENT软件进行了模拟计算和流场分析,并分析了丝网高度对流动和传热性能的影响。结果表明,相比于传统平直翅片,嵌入金属丝网后通道综合性能指标最大提高58%。综合性能随孔隙率的提高先增后减,0.945为最佳孔隙率。同时,使用高度与流道高度一致的金属丝网,可以获得最佳综合性能。在相同压力损失下,金属丝网通过均匀流体温度、破坏边界层可以比平直翅片通过增加传热面积获得更好的综合性能,证明了金属丝网作为烟气换热器强化元件的可行性。

汽车尾气温差发电系统瞬态回收性能分析

为了预测温差发电(thermoelectric generator, TEG)系统的动态特性,基于COMSOL Multiphy-sics建立了用于求解温差发电系统温度场分布的瞬态计算流体力学(computational fluid dynamics, CFD)模型和用于研究温差发电模块瞬态响应特性的分析模型,提出了混合瞬态CFD-分析模型,并经过瞬态试验验证.结果表明:由于热惯性的影响,TEG系统的转化效率会出现一个瞬时的较高值;相较于尾气温度和质量流量的瞬态波动,热电半导体的热端温度和冷端温度会存在时滞;在美国环保局的高速公路燃油经济性测试(highway fuel economy test, HWFET)模式循环工况下,瞬态模型求解得到整个温差发电系统的平均输出功率、平均转化效率分别为35.63 W和3.40%,瞬态模型的输出电压平均误差为6.41%;该模型能够以较高的精度及较短的计算时间预测温差发电系统在瞬态热源激励下的瞬态响应特性.

焦化炉废气余热回收利用的技术研究

讨论了焦化炉废气余热回收利用技术的现状、特点、存在的问题及发展方向,针对这些问题提出了多元化技术路线、提高技术成熟度和加强政策引导等建议。同时,强调行业间的合作和产学研合作的重要性,共同推动焦化炉废气余热回收技术的发展和应用。

一种氧压浸出换热乏汽余热回收装置

概述了一种氧压浸出换热乏汽余热回收装置,介绍了该装置的结构,探讨了该装置的工作原理及工作中的自动化控制,结合某厂的生产实践,进行能耗经济核算,为换热器乏汽及相关领域的余热回收提供有价参考。

氢氧化铝焙烧余热回收利用路径研究及应用

拜耳法工艺生产氧化铝,氢氧化铝焙烧工序能耗在综合能耗中占比在30%以上,其中有约16%能耗是以热量形式随产品及烟气带走。本文对氢氧化铝焙烧过程能耗构成进行热平衡计算分析,并对焙烧余热利用的工艺路线、换热设备等进行对比研究,寻找出高效余热利用方案,并在生产中进行实施,取得了理想的节能效果。

山东某石化集团新建化验楼热管热回收系统能耗分析

实验场所为了排除废气通常要求的换气次数高,所需的排风量、新风量巨大,如果利用排风热回收装置回收排风中的冷热量,并用其对室外新风进行一定的预处理,不仅能提高室内空气品质,还可以达到节能经济和环保的双重目的。通过对山东某石化集团有限公司新建化验楼功能配套项目的通风系统进行设计,并配置热管余热回收系统对该通风系统的排风进行冷、热量回收,经过对热回收系统的能耗分析,得到该系统的热回收设备投资回收期不到两年,充分展现了在该化验楼中配置热回收系统具有显著的节能效益和经济效益。

低温有机朗肯循环的热力学分析

汽车燃油热量仅1/3为有效能量(作为动力),其余2/3为废热,通过冷却水或排气方式排入大气,不仅极大浪费了能源而且污染了环境。以发动机的废热利用作为有机朗肯循环(ORC)的热源分析,通过对ORC系统进行数学建模,改变系统运行工况,来评价不同工质的系统循环性能并指出R245fa和R123是比较适合的循环工质。在热力学分析的基础上,与其他文献中试验数据进行了比较,结果表明本文模型是可靠的,为有机朗肯循环的系统设计指明了方向。

天然气锅炉烟气余热利用节能改造工程实测分析

针对天然气锅炉等热能动力设备排烟温度高,造成能源浪费和环境污染的现状,应用自主研发的高效紧凑防腐型烟气冷凝热能回收利用装置,对一既有锅炉房进行了烟气余热回收利用节能改造和跟踪实测。分析了锅炉耗气量、排烟温度及热效率的变化,结果表明,排烟温度由150～200℃降到50℃以下,仅烟气余热回收装置就使锅炉热效率提高10%以上,且由于该装置提高了锅炉进水温度,从而提高了锅炉本体燃烧效率,使锅炉低热值总效率超过100%,锅炉高热值效率超过95%,锅炉房总节能率达25.6%。

内燃机排气余热回收温差电单偶的模拟分析

选取Bi2Te3和CoSb3两种温差电材料对温差电单偶建立了数学模型,导出温差电单偶的功率和效率计算公式,分析冷热端陶瓷片表面温度、温差电单偶长度以及表面对流传热系数对温差电单偶性能的影响,并对比两种材料在相同条件下的性能.分析结果表明:提高热面温度、降低冷面温度、缩短温差电单偶的长度和提高热表面对流传热系数均可以提高温差电单偶的最大输出功率,但最大转换效率却不能随之持续增大,缩短温差电单偶的长度甚至会使最大转换效率降低.两种材料的温差电单偶相比较,Bi2Te3材料制成的温差电单偶更适用于对600,K以下的低温热量进行回收,而CoSb3材料制成的温差电单偶则更适用于对内燃机排气等700,K以上的中高温热量进行回收.

燃煤锅炉烟气余热深度回收及脱水性能分析

电站锅炉烟气余热深度回收及烟气脱水是提高机组热效率、降低水耗率的重要途径之一。本文以某亚临界330 MW机组为对象,提出了烟气余热深度利用与烟气脱水的系统流程,研究了余热利用系统与回热系统的集成方案,基于等效焓降法计算了各方案的热力性能,并对关键参数进行了敏感性分析。结果表明:利用氟塑料烟气余热换热器(FGC1)和烟气脱水换热器(FGC2)可实现烟气余热的深度回收及水分的脱除,降低了机组的发电煤耗率和水耗率;闭式水互联的串并联集成方案d性能最优,设计工况下可节约发电标准煤耗率3.03 g/(k W?h),回收冷凝水5.7 t/h;随着FGC1出口烟气温度的下降,煤耗率增加,但其换热面积也增加,当烟气温度一定时,方案d所需换热面积最小。