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.

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.

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.

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.

Optimization Potentials for the Waste Heat Recovery of a Gas-Steam Combined Cycle Power Plant Based on Absorption Heat Pump

A new waste heat recovery system is presented to recover exhausted steam waste heat from the steam turbine by absorption heat pump(AHP) in a gas-steam combined cycle(GSCC) power plant. The system can decrease energy consumption and further improve the energy utilization. The performance evaluation criteria are calculated, and exergy analysis for key components are implemented in terms of the energy and exergy analysis theory. Besides, the change of these criteria is also revealed before and after modification. The net power output approximately increases by 21738 kW, and equivalent coal consumption decreases by 5.58 g/kWh. A 1.81% and 1.92% increase in the thermal and exergy efficiency is respectively obtained in the new integrated system as the heating load is 401095 kJ at 100% condition. Meanwhile, the appropriate extraction parameters for heating have been also analyzed in the two systems. The proposed scheme can not only save energy consumption but also reduce emission and gain great economic benefit, which is proven to be a huge potential for practical application.

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.

Thermodynamic and Economic Studies of a Combined Cycle for Waste Heat Recovery of Marine Diesel Engine

In the present study,the thermodynamic and economic performance of a combined thermodynamic cycle formed by an ORC and a Kalina cycle,which can simultaneously recover waste heat of exhaust gas and cooling water of marine engine,has been analyzed.Two typical marine engines are selected to be the waste heat source.Six economic indicators are used to analyze the economic performance of this combined thermodynamic cycle system with different marine engine load and under practical comprehensive operating condition of marine engine.The results of the present study show that the combined thermodynamic cycle system with R123 as organic working fluid has the best performance.The system with cis-butene has the worst economic performance.Under practical comprehensive operating conditions of ships,R123 has the shortest Payback Periods,which are 8.51 years and 8.14 years for 8 S70 ME-C10.5 engine and 5G95 ME-C10.5 engine,respectively.Correspondingly,payback Periods of Cyclopentane are 11.95 years and 11.90 years.The above values are much shorter than 25 years which are the lifetime of a marine ship.Under practical comprehensive operating conditions of ships,the combined cycle system can provide output power which is at least equivalent to 25%of engine power.Considering that R123 will be phased out in near future,cyclopentane may be its good successor.Cyclopentane can be used safely by correct handling and installing according to manufacturer's instructions.

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.

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.

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.

回收船舶柴油机余热的双回路有机朗肯循环系统性能分析

为了降低船舶二氧化碳排放,利用双回路有机朗肯循环(DORC)系统对船舶柴油机的排烟和缸套冷却水余热进行回收发电。通过夹点温差法构建热力学模型,高温回路用于回收排烟热量,低温回路用于回收缸套冷却水热量和高温回路冷凝热。分析9对工质组合时DORC系统的冷凝器热力学参数对系统性能的影响,结果表明:随着高温回路的冷凝温度和冷凝热负荷的增高,低温回路蒸发压力和净输出功呈现升高趋势,在高温回路冷凝热负荷为715.2 kW~1 241.2 kW时,系统总净输出功呈现先升高后降低的趋势。当高温回路采用环乙烷,低温回路采用一氯三氟丙烯(反式)为工质时,系统总净输出功可达到410.6 kW。

新型燃煤电厂发电-脱碳-供热一体化的耦合系统

伴随着能源需求的提高,所伴随而来的环境问题也日益加剧,燃烧产生的CO_(2)便是温室气体的直接来源,其中燃煤电厂是主要碳排放源,且在生产过程中产生大量的余热。燃煤电厂脱碳系统和热电联产系统对热源温度要求相近,针对这一特性,可以在控制燃煤电厂的碳排放量的同时,对其过程中产生的余热进行回收利用,提高系统的供热能力。基于燃煤电厂发电系统、固体胺吸收剂脱碳系统以及一次/二次供热系统,创新性地提出了一种发电-脱碳-供热一体化的耦合系统。引入背压式供热汽轮机和背压式脱碳汽轮机取代低压汽轮机,以背压式供热汽轮机和背压式脱碳汽轮机的排汽分别给供热过程和脱碳过程提供热源,在保证脱碳能力的前提下显著降低了耦合系统的发电能力损失。为再进一步提高耦合系统的热力性能,采用吸收式换热技术高效回收脱碳系统释放的低温余热,提高耦合系统的供热能力。计算结果显示,新型发电-脱碳-供热一体化的耦合系统回收了90%以上脱碳系统释放的低温余热,系统的供热能力由785.06 MW提升至1288.94 MW,供热能力升高65%,节能效果显著。

固体氧化物燃料电池和分部加热式S-CO_(2)循环联合发电系统设计与分析

固体氧化物燃料电池(solid oxide fuel cell,SOFC)与余热回收相结合可进一步提高系统能量转换效率。该文设计一种SOFC与分部加热式超临界二氧化碳(partial heating supercritical CO_(2)Brayton cycle,PHSCBC)动力循环集成系统,SOFC系统的出口废气作为高温热源,驱动PHSCBC进行联合发电。建立系统的电化学模型和热力学模型,对系统的能量和(火用)进行综合评价,并通过参数分析,研究汽碳比、燃料流量、压缩机进口温度和压力以及夹点温差对联合发电系统性能的影响。对系统性能进行优化,发现当系统燃料流量为0.54 mol/s、空气流量为6.19 mol/s,可达到净发电功率、发电效率、(火用)效率分别为260.08 kW、61.20%、56.54%,其中提高燃料流量将显著提高系统发电效率。所提出的混合系统具有高效、低成本和清洁的发电和供热性能,是一种具有实际应用前景的先进能量转换技术。

空冷机组空气-烟气余热利用综合分析

在分析空冷机组运行特点的基础上,提出了一种空气-烟气余热联合回收系统,即空冷岛出口的热空气作为锅炉燃烧用风,进入空气预热器被加热,同时在锅炉尾部加装低温省煤器,加热低压凝结水,以节省汽轮机抽汽量.以某典型600MW亚临界直接空冷机组为例,分析了空气-烟气余热联合回收系统的热力学特性和节能效果.结果表明:在典型工况下,空气预热器入口温度可提高约25K,机组供电煤耗降低约1.93g/(kW·h),年节约标准煤约7 000t,节约燃料费700余万元(按机组年运行5 500h,标准煤价格为1 000元/t计算),经济效益显著.

回收余热的热电联产IGCC电站研究

整体煤气化联合循环(integrated gasification combined cycle,IGCC)作为洁净煤发电技术,发展为供热机组后,可实现更为清洁的煤基热电联产技术。另一方面,IGCC目前投资较高,若能实现与集中供热结合,供热收益可大幅度改善IGCC的经济性,而以热定电的形式保证了IGCC的年发电小时数,为IGCC的商业化推广提供了一条有力的途径。进行汽轮机乏汽余热回收与烟气余热回收后,IGCC的总体能源利用效率会进一步提高,经济性也将大幅改善。该文研究结果表明:400 MW级的IGCC热电联产系统的热电比为47.2%,总体能源利用效率为57.6%;进行余热回收后,热电比为55.6%,总体能源利用效率为60.8%;在热力站进行吸收式换热改造后,热电比为62.0%,总体能源利用效率为63.4%。

低温热源喷射式发电制冷复合系统特性分析

提出一种低温热源喷射式发电制冷复合系统。该系统将有机物朗肯循环与喷射式制冷循环相结合,利用透平排气驱动喷射器工作,同时实现发电和制冷的功能。在定义系统评价指标的基础上,选取性能优良的有机物R245fa作为工质,建立系统仿真模型,进行计算分析。计算结果表明,在热源蒸发温度Tg=120℃,制冷蒸发温度Te=7℃,冷凝温度Tc=25℃的标准工况下,系统的热力学第一定律效率可达37%,热力学第一定律折合效率可达15.6%,火用效率可达37.5%。分析同时表明,提高热源蒸发温度Tg,提高制冷蒸发温度Te,降低冷凝温度Tc,有利于提高系统的工作性能;提高透平膨胀比β可以提高系统电冷比R。

地铁余热-地源热泵联合供暖系统研究进展

综述了利用地铁余热-地源热泵联合供暖系统的研究现状。提出了余热供暖以及地铁余热利用的相关方案。通过对地铁余热-地源热泵联合供暖的实验和应用情况进行概述,总结了地铁余热-地源热泵联合供暖的特点,即节能减排等优点和输送距离限制等缺点。阐述了地铁余热-地源热泵联合供暖冬夏季的运行方式,对余热回收方式进行分析,指出了地铁余热-地源热泵发展趋势,并对地铁余热-地源热泵联合供热系统的前景进行展望,以期为今后的研究提供理论参考和实验依据。

燃气-蒸汽联合循环电厂烟气余热回收系统研究

通过分析锅炉烟气余热回收的2个关键问题,提出了基于烟气余热深度回收的集中供热新流程。该流程一方面将吸收式热泵与低温热网回水2种技术结合,实现排烟的深度降温;另一方面采用烟囱与喷淋塔合为一体的紧凑结构,在有效克服烟气带来的露点腐蚀问题的同时,提高余热回收的可行性。以3台FT8-3机组联合循环系统为研究对象,设计了烟气余热回收机组(由水-水板式换热器与吸收式热泵两部分构成)。综合考虑余热回收的投资与运行成本,对不同排烟温度下新系统的关键参数进行了优化,指出实现小端差水-水板式换热是提高系统经济性的关键。

以液化天然气为冷源的超临界CO_2-跨临界CO_2冷电联供系统

为了提高超临界CO2布雷顿循环(SCO2循环)的低温余热回收效率,采用跨临界CO2循环(TCO2循环)作为底循环对再压缩式SCO2循环进行余热回收,并采用液化天然气(LNG)为冷源对工质进行冷凝,建立了以LNG为冷源的再压缩式SCO2-TCO2冷电联供系统,以同时输出电量和制冷量。对系统进行火用分析比较,并研究了关键热力参数对系统净输出功率、制冷量、系统热效率和系统火用效率的影响。结果显示:使用LNG作为冷源,降低了TCO2循环的冷凝温度,提高了低温回收热效率,系统的热效率(动力)在给定的条件下达到54.47%;提高LNG的入口温度,可以减小系统火用损;高温回热器换热效率增加,系统热效率和火用效率均增加;SCO2透平膨胀比增加,系统热效率降低,但火用效率增加;TCO2透平进口压力升高,系统热效率和火用效率均呈现先减小再升高后减小的变化趋势;随着冷凝温度升高,系统热效率降低,但火用效率先减小后增加。

柴油机与斯特林机联合动力循环仿真

提出将柴油机高温尾气作为斯特林发动机外部热源,构建联合动力循环,进而探究柴油机工况参数对斯特林机性能的影响规律。在确定斯特林发动机主要结构参数前提下,采用GT-Power和Simulink软件建立了柴油机与斯特林机的联合热力循环仿真模型。通过改变柴油机工作参数,得到斯特林机指示功率的变化情况。研究结果表明:斯特林机指示功率随着柴油机负荷及涡后温度的增而逐渐增大;在柴油机喷油提前角逐渐减小时,斯特林发动机功率略有上升,但柴油机的功率降低明显。最后,提出了柴油机-斯特林复合发动机模型,并在理论上进行能量利用率的模拟计算,结果显示复合发动机使柴油机的平均有效功率增加约10%。