Site-wide low-grade heat recovery with a new cogeneration targeting method

One of the key performance indicators for designing site utility systems is cogeneration potential for the site. A new method has been developed to estimate cogeneration potential of site utility systems by a combination of bottom-up and top-down procedures, which allows systematic optimization of steam levels in the design of site utility configurations. A case study is used to illustrate the usefulness of the new cogeneration targeting method and benefits of optimizing steam levels for reducing the overall energy consumptions for the site. Techno-economic analysis has been carried out to improve heat recovery of low-grade waste heat in process industries, by addressing a wide range of low-grade heat recovery technologies, including heat pumping, organic Rankine cycles, energy recovery from exhaust gases, absorption refrigeration and boiler feed water heating. Simulation models have been built for the evaluation of site-wide impact associated with the introduction of each design option in industrial energy systems in the context of process integration. Integration of heat upgrading technologies within the total site has been demonstrated with a case study for the retrofit scenario.     

A power plant for integrated waste energy recovery from liquid air energy storage and liquefied natural gas

Liquefied natural gas(LNG)is regarded as one of the cleanest fossil fuel and has experienced significant developments in recent years.The liquefaction process of natural gas is energy-intensive,while the regasification of LNG gives out a huge amount of waste energy since plenty of high grade cold energy(-160℃)from LNG is released to sea water directly in most cases,and also sometimes LNG is burned for regasification.On the other hand,liquid air energy storage(LAES)is an emerging energy storage tech-nology for applications such as peak load shifting of power grids,which generates 30％-40％of compres-sion heat(～200℃).Such heat could lead to energy waste if not recovered and used.The recovery of the compression heat is technically feasible but requires additional capital investment,which may not always be economically attractive.Therefore,we propose a power plant for recovering the waste cryo-genic energy from LNG regasification and compression heat from the LAES.The challenge for such a power plant is the wide working temperature range between the low-temperature exergy source(-160℃)and heat source(～200℃).Nitrogen and argon are proposed as the working fluids to address the challenge.Thermodynamic analyses are carried out and the results show that the power plant could achieve a thermal efficiency of 27％and 19％and an exergy efficiency of 40％and 28％for nitrogen and argon,respectively.Here,with the nitrogen as working fluid undergoes a complete Brayton Cycle,while the argon based power plant goes through a combined Brayton and Rankine Cycle.Besides,the economic analysis shows that the payback period of this proposed system is only 2.2 years,utilizing the excess heat from a 5 MW/40MWh LAES system.The findings suggest that the waste energy based power plant could be co-located with the LNG terminal and LAES plant,providing additional power output and reducing energy waste.     

煤制天然气过程全局能量集成优化

我国正在大力发展煤制天然气项目实现清洁能源供给。然而现有煤制天然气示范项目存在能耗大、CO₂排放高、生产成本缺少竞争力的问题。本文从煤制天然气能量系统出发,通过全局能量集成实现煤制天然气项目的节能减排与经济效益的提高。根据煤化工示范项目特点,提出了煤制天然气过程全厂能量系统集成优化策略：建立了煤制天然气各单元过程模型,对全流程的物流和能流展开了详细的模拟计算;利用夹点技术对全厂内各单元过程的能量系统展开了用能分析;利用全局温焓曲线对全厂能量系统进行了分析,揭示出全厂能量利用效率低是由于高品位热量降质利用和低品位余热未得到合理利用引起的。通过装置间热回收集成和增设有机朗肯余热回收装置可有效地提高热回收率。通过全厂能量系统优化集成,燃料煤消耗由现有过程1.26t/kNm³（0℃、101325Pa标准状态）天然气下降到1.07t/kNm³天然气。由于公用工程系统消耗的减少,全厂能量利用效率由原来的57.2%提高到59.6%,同时CO₂排放可以由原来5.02t/kNm³天然气下降到4.66t/kNm³天然气。相比于现有过程,改进过程的总投资仅增加了2%左右,而单位生产成本由1.65CNY/Nm³下降到了1.59CNY/Nm³,对于年产20亿立方米煤制天然气厂每年可节约生产成本1.2亿元。     

Entropy production and chemical reactions in nonequilibrium plasma

In this work, methods based upon nonequilibrium thermodynamics are elucidated to predict stationary states of chemical reactions in nonequilibrium plasma, and limits for energy conversion efficiency. CO₂ splitting is used as an example reaction. Expectations from the theoretical framework are compared to experimental results, and reasonable agreement is obtained. The key conclusion is that the probability of observing either reactants or products increases with the amount of energy dissipated by that side of the reaction as heat through collisions with hot electrons. The side of the reaction that dissipates more energy as heat has a higher probability of occurrence. Furthermore, endergonic chemical reactions in nonequilibrium plasma, such as CO₂ splitting at low temperature, require an intrinsic energy dissipation to satisfy the second law of thermodynamics—a sufficient and necessary waste. This intrinsic dissipation limits the maximum theoretical energy conversion efficiency.     

Centralised utility system planning for a Total Site Heat Integration network

Total Site Heat Integration (TSHI) is a technique of exchanging heat among multiple processes via a centralised utility system. An analysis of the integrated multiple processes, also known as the Total Site (TS) system sensitivity, is needed to characterise the effects of a plant maintenance shutdown, to determine the operational changes needed for the utility production and to plan mitigation actions. This paper presents an improved Total Site Sensitivity Table (TSST) to be used as a systematic tool for this purpose. The TSST can be used to consider various ‘what if’ scenarios. This tool can be used to determine the optimum size of a utility generation system, to design the backup generators and piping needed in the system and to assess the external utilities that might need to be bought and stored. The methodology is demonstrated by using an Illustrated Case Study consisting of three processes. During the TS normal operation, the Total Site Problem Table Algorithm (TS-PTA) shows that the system requires 1065 kW of High Pressure Steam and 645.5 kW of Medium Pressure Steam as the heating utility, while for the cooling utility, 553.5 kW of Low Pressure Steam and 3085 kW of cooling water are required. The results of the modified TSST proposed that a boiler and a cooling tower with the system design requiring a maximum capacity of 2.172 MW of steam and 4.1865 MW of cooling water are needed to ensure an operational flexibility between the three integrated processes.     

High pyroelectric response over a broad temperature range in NBT-BZT: SiO2 composites for energy harvesting

Pyroelectric energy harvesting is considered a highly promising technology for converting low-grade waste heat into electricity, but the practical applications of pyroelectric generators is limited by the their poor energy densities and instability. In this work, we construct SiO₂ networks with low heat capacities in NBT-BZT ceramics. These networks improve the heat transfer (dT/dt) and broaden the pyroelectric temperature region of the composites by reducing heat absorption capacity, thereby leading to high pyroelectric energy density and stability. The temperature range of the NBT-BZT composite with 0.1 wt% SiO₂ for pyroelectric coefficient higher than 20 × 10^?4 C m^?2 K^?1 is increased to 20 °C, This increase results in the high thermostability of energy harvesting. In addition, the NBT-BZT: 0.1 wt% SiO₂ composites show an optimized pyroelectric energy density of 110 u J cm^-3, nearly three times that of the pure NBT-BZT ceramics. This work is beneficial for the application of high-performance pyroelectric materials for devices used in energy harvesting.     

余热发电技术在云南建水铁合金厂上的应用

铁合金属冶炼耗能已超过全国工业能耗的2%,推广余热回收发电技术有利于降低企业能耗,提高能源利用效率。结合云南建水铁合金余热发电工程应用实例,总结了铁合金领域的余热发电技术特点。提出了铁合金领域采用先进的余热回收技术和低压蒸汽余热发电技术,节能、环保效益明显,该工程的余热发电机组发电量9.6×107 kW·h/a,供电量8.832×107kW·h/a,节约标煤3.56×104 t/a,减排二氧化碳8.68×104 t/a,取得了可观的节能效益、经济效益、环境效益和社会效益。     

废热溴化锂吸收式动力、冷量、热量梯阶转换系统发生特性

以废热溴化锂吸收式动力、冷量、热量梯阶转换系统为研究对象,对系统进行理论分析和热力学计算。此系统将废热中的一部分能量进行动力转化,余下一部分能量转化为热量和冷量,实现能量的梯阶转换,从而对废热进行更加合理的利用。通过理论分析和对热力学计算结果的对比分析,得到发生压力与发生温度对系统能量转化的影响。     

移动利用废热技术及合同能源管理模式在硫酸厂的应用

介绍了移动利用废热蒸汽节能技术的开发和应用情况.圣火科技（河南）有限责任公司采用移动利用废热蒸汽节能技术回收硫酸厂放空废热生产蒸汽,用于印染厂生产.该项目通过合同能源管理模式实施,促进了硫酸厂和印染厂的热能利用合作,实现了节能减排.     

Suppressed grain growth and enhanced irradiation resistance of nano-grained waste form under electronic energy loss

The effects of both nuclear energy loss and electronic energy loss need to be taken into consideration in the ceramic-based waste forms under repository environment. However, the irradiation responses of ceramic-based waste forms to each type of energy loss are somewhat different. In this study, the microstructure evolutions of ultrafine nano and micro Gd₂Zr₂O₇-based waste forms were systematically studied under predominant electronic energy loss simulated by multi-energy He⁺ irradiation, and compared to those under predominant nuclear energy loss. The results reveal that the fewer He bubble chains, ribbon-like He bubbles and smaller microcracks were observed in the irradiated nano-grained sample. Additionally, nano-grained sample displayed a lower degree of amorphization and higher atomic order compared to micro-grained samples when subjected to predominant electronic energy loss. Moreover, the irradiation dominated by nuclear energy loss can easily induce the grain growth of nano-grained Gd₂Zr₂O₇-based waste form, but in the present study this phenomenon was not observed under multi-energy He⁺ irradiation. Consequently, under predominant electronic energy loss, the thermodynamic instability and driving force for grain growth due to excess surface energy in the ultrafine nano sample can be suppressed. As a result, the sample demonstrated enhanced irradiation resistance due to the more efficient absorption and elimination of defects at grain boundaries induced by electronic excitation. We elucidated that enhanced irradiation resistance of the waste forms by tailoring the grain size requires the consideration of the effects of electronic energy loss and nuclear energy loss, which can provide guidance for the design and optimization of highly irradiation-resistant nuclear waste forms.     

不同余热情况下有机朗肯循环和卡琳娜循环能量性能对比

有机朗肯循环和卡琳娜循环都是发展前景广阔的低温余热动力利用技术,这两种技术在余热利用方面各有其优势和劣势。在炼厂中,余热资源分布广泛,针对不同余热热源选择合适的动力循环系统对能量的有效利用具有实际意义。热效率和(火用)效率是评价动力循环系统的两个重要指标。通过将余热资源分成3类,即显热热源、复合热源和潜热热源,用Aspen Hysys软件对有机朗肯循环和卡琳娜循环进行流程模拟,考察了余热资源特性对有机朗肯循环和卡琳娜循环能量性能的影响。结果表明当余热为显热热源时,卡琳娜循环系统优于有机朗肯循环;当余热为复合热源且潜热与显热比R=1或当余热为潜热热源时,有机朗肯循环优于卡琳娜循环。     

Improved Energy Efficiency of Power-to-X Processes Using Heat Pumps Towards Mobility Sector Defossilization

Combining Power-to-X (PtX) processes with high temperature heat pumps (HTHP) can significantly increase their energy efficiency. Evaluating the example of oxymethylene ethers (OME) production from H₂ via H₂O electrolysis and captured CO₂ from air shows that by upgrading waste heat streams using HTHP, a process overall energy efficiency of higher than 61 % can be achieved compared to 30 % in conventional integrated processes. Thereby, the waste heat stream from H₂O electrolysis already covers the low temperature heat demand for CO₂ capture via direct air capture, not only for OME but also for various PtX products. Importantly, a significant lever for the energy efficiency enhancement is the consideration of other low temperature heat-demanding sectors. High overall process energy efficiencies and the electrification of the industry are key aspects towards a sustainable mobility sector.     

板翅式换热器在燃油燃气锅炉余热回收中的应用研究

燃油燃气锅炉排放的烟气多为低品味余热,传统余热回收装置体积大,空间布置困难,且成本高,经济性差。为此,本文采用板翅式换热器作为燃油锅炉余热回收装置,对其进行了余热回收实验和经济性评价。实验表明其节能环保功效优于传统的余热回收装置,且成本低、投资回收期短、使用寿命长,具有良好的推广应用价值。     

节能减排的全局过程集成技术的研究与应用进展

对20世纪末至今全局过程集成技术的研究进展做了评述,从全局温焓曲线、顶层分析法、热电联产优化的R—曲线到跨装置热集成原理进行了比较系统地介绍。在此基础上,描述了综合使用这些基本方法的策略和现有的工具软件。最后将国外和国内在炼油和化工中应用全局过程集成技术的情况及经济效益分别做了归纳总结。     

硫酸法钛白粉真空结晶工序余热资源分析与利用

钛白粉生产企业属于高耗能企业,节省能耗是钛白粉生产企业的必由之路。根据国家“十二五”节能规划中的余热余压回收政策,采用吸收式余热回收技术,回收硫酸法钛白粉生产过程中真空结晶工序的余热,使得不能直接利用的低温热能能够提供给水解、包膜等工序的用热需求。以一条12万t/a硫酸法钛白粉生产线为例进行设计,每年可节约标煤1万t以上,起到很好的节能减排效果。     

A target‐oriented solid‐gas thermochemical sorption heat transformer for integrated energy storage and energy upgrade

An innovative target‐oriented solid‐gas thermochemical sorption heat transformer is developed for the integrated energy storage and energy upgrade of low‐grade thermal energy. The operating principle of the proposed energy storage system is based on the reversible solid‐gas chemical reaction whereby thermal energy is stored in form of chemical bonds with thermochemical sorption process. A novel thermochemical sorption cycle is proposed to upgrade the stored thermal energy by using a pressure‐reducing desorption method during energy storage process and a temperature‐lift adsorption technique during energy release process. Theoretical analysis showed that the proposed target‐oriented thermochemical sorption heat transformer is effective for the integrated energy storage and energy upgrade, and the low‐grade thermal energy can be upgraded from 87 to 171^°C using a group of sorption working pair MnCl₂‐CaCl₂‐NH₃. Moreover, it can give the flexibility of deciding the temperature magnitude of energy upgrade by choosing appropriate sorption working pairs. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1334–1347, 2013     

Recent developments in Process Integration

Process Integration supporting process design, integration and optimisation has been around for more than 40 years. Its development has been closely related to developing the Chemical Engineering, implementation of mathematical modelling and the application of information technology. Its development has been accelerating as the methodology has been able to provide answers and support for important issues regarding economic development—energy, water and resources better utilisation and savings. This contribution is targeted towards a short overview of recent achievements and future challenges.     

大型煤化工项目低品位热能利用研究

介绍了有机朗肯循环发电机组的基本原理和螺杆膨胀发电机组的基本结构;简述了利用低压蒸汽冷凝液余热的经济效益和节能减排效益。研究结果表明：采用螺杆膨胀发电机组回收低温余热,不仅可以提高项目能效0．2％,还可减少排放CO225532 t/a,节约标准煤9820 t/a。     

玻璃熔窑纯低温余热发电前景看好

当今社会节能已成为继煤炭、电力、石油和天然气之后的“第五能源”,而现在玻璃行业普遍存在着热量利用率低、烟气余热利用不足的问题。作者认为,目前兴起的玻璃窑炉纯低温余热发电实现节能降耗,提高热效率,前景看好.     

空气源沼气机热泵部分负荷性能

提出了一种沼气机热泵能源综合利用节能系统,并据此构建了系统实验平台,进行了系统性能实验.根据理论分析和实验数据研究了沼气消耗量、余热回收利用、制热系数COP及一次能源利用率PER随沼气机负荷率的变化趋势.结果表明:该节能系统具有较好的部分负荷特性,在仅考虑沼气机排烟余热回收利用的情况下,系统COP最高可达4.18,PER最高可达1.4.因此,空气源沼气机热泵节能系统明显提高了供热能力、降低了能耗,实现了沼气能源的综合有效利用.