Renewable hydrogen production concepts from bioethanol reforming with carbon capture

This paper is assessing the hydrogen production from bioethanol at industrial scale (100000 Nm³/h hydrogen equivalent to 300 MW thermal) with carbon capture. Three carbon capture designs were investigated, one based on pre-combustion capture using chemical gas–liquid absorption and two based on chemical looping (one based on syngas and one using direct bioethanol looping). The carbon capture options were compared with the similar designs without carbon capture. The designs were simulated to produce mass and energy balances for quantification of key performance indicators. A particular accent is put on assessment of reforming technologies (steam and oxygen-blown autothermal reforming) and chemical looping units, process integration issues of carbon capture step within the plant, modelling and simulation of whole plant, thermal and power integration of various plant sub-systems by pinch analysis. The results for chemical looping designs (either syngas-based or direct bioethanol) show promising energy efficiency coupled with total carbon capture rate.     

玉门炼化总厂节能潜力及节能途径分析

玉门炼化总厂拥有常减压、催化裂化、柴油加氢改质、酮苯脱蜡(脱油)、催化重整等多套装置,总加工能力达300×104t/a。由于装置加工流程长,产品加工深度大等问题,虽然实施了一些节能措施,但创新性和高技术含量的节能新技术应用较少,2008年全厂综合能耗仍高达85.33kg标油/t原料,与国内先进企业相比差距较大。为此,提出改造催化装置余热锅炉、提高加热炉热效率、开展热联合、综合优化动力系统、充分利用低温余热等节能改造方案。其中,催化装置余热锅炉采用模块化新型结构,以消除露点腐蚀,减少烟气阻力,强化传热能力,消除炉体振动,确保能量回收为主要改造目的;提高加热炉热效率主要从优选加热炉燃烧器,完善烟气热能回收、完善加热炉吹灰、降低散热损失以及调整工艺流程等方面入手。同时,应实现装置间的能量集成优化,采取热电联产工艺,减少低温热能耗损失。预计上述节能改造实施后,全厂综合能耗可降低11~21kg标油/t原料。     

Evaluation of hydrogen production with iron-based chemical looping fed by different biomass

In this study, the iron-based chemical looping process driven by various biomasses for hydrogen production purposes is studied and evaluated thermodynamically through energy and exergy approaches. The overall system consists of some key units (combustor, reducers and oxidizer) a torrefier, a drying chamber, an air separation unit, a heat exchanger, and auxiliary units as well. The biomasses considered are first dried and torrified in the drying chamber and sent to reactors to produce hydrogen. The exergy and energy efficiencies of the iron based chemical looping facility are investigated comparatively for performance evaluation. The maximum exergy destruction and entropy production rates are calculated for the torrefaction process as 123.15 MW and 4926 kW/K respectively. Under the steady–state conditions, a total of 8 kg/s hydrogen is produced via chemical looping process. The highest energy efficiency is obtained in the looping of rice husk with 86% while the highest exergy efficiency is obtained in the looping using sugarcane bagasse with 91%, respectively.     

余热回收吸收式制冷集中空调方案研究

为回收大型炼油装置丰富的低温余热用于生活区的夏季集中空调,本文对余热资源状况和生活区集中空调建筑物供冷负荷分别进行了综合标定和统计计算,在分析比较的基础上确定采用余热热水型溴化锂吸收式制冷冷水机组和半集中式风机盘管全水型空调系统,并利用现有双管制热水集中供暖管网和泵站输送空调冷水,可以显著地节约投资。技术经济分析表明,该方案在技术上可行,节能效果和经济效益十分显著,而且可以大大改善厂区的热污染和居民的生活条件。     

Comparative study of cogeneration systems in a chemical industry

With the large penetration of the natural gas into the Brazilian energy structure, industries such as paper mills and chemical plants are analyzing the feasibility of implementing cogeneration schemes appropriate to this fuel. The analysis of the energy demand patterns of a chemical company from the photographic sector revealed the possibility of using combined cycles or diesel engine cogeneration schemes keeping the existing compression refrigeration units and steam or gas cycle cogeneration systems with absorption refrigeration units. In terms of economic attractiveness, an analysis based on the method of the internal rate of return was performed. The results indicated that the schemes composed by reciprocating engines and combined cycle with compression chillers, as well as the gas cycle scheme with absorption chiller, present return periods of up to 3 years, showing that the investment in cogeneration could be of interest for this plant.     

芳烃联合装置模拟与优化(Ⅴ)——二甲苯精馏单元的模拟与优化

二甲苯精馏单元是PX联合装置的重要组成部分,其作用是通过精馏的方法,将来自连续重整、歧化及烷基转移和异构化单元的C8+A原料分离成符合吸附分离单元要求的C8芳烃、歧化及烷基转移单元所需的C9+A。采用Aspen Plus流程模拟软件,对芳烃联合装置中二甲苯精馏单元包括二甲苯塔、邻二甲苯塔、重芳烃塔等塔设备及换热流程进行模拟,通过模型对过程的关键参数如回流比、塔底热负荷、塔压、塔顶采出量等进行综合分析,在各塔产品控制指标(PX纯度和OX纯度)达标前提下,选择最优的操作参数,降低装置能耗,提升装置经济效益。通过对中国石化四套PX装置中的二甲苯精馏单元进行模拟优化,合计实现装置节能效益881万元,并指导装置产品方案的切换,在降低装置能耗和提升装置经济效益的同时,也提高了中国石化芳烃装置二甲苯精馏单元的精细化操作水平。     

Step-by-step process integration method for the improvements and optimization of sodium tripolyphosphate process plant

Improvement and optimization of a complex chemical plant motivated by energy savings is presented in this paper. The reference object of the research is the sodium tripolyphosphate plant in “IHP-Prahovo”, the biggest factory for producing chemical products in Serbia and Montenegro. The research is done by using a step-by-step process integration approach, which combines several computer-based simulation/optimization methodologies. The evaluation of obtained results indicates considerable possibilities for plant efficiency improvement.     

Performance characteristics of a Diesel engine power plant

Performance of an actual Diesel engine power plant with a rated output of 120 MW is analyzed based on the first and second laws of thermodynamics. The plant consists of seven identical Diesel engines and various subsystems including turbochargers, fuel heating units and heat exchangers performing various useful tasks. The engine runs on heavy fuel oil, and the pollutant emissions from the engine are greatly reduced by effective treatment systems. The characteristics and performance parameters of the internal combustion engines of the plant are evaluated. The mass, energy and exergy balances are verified for each flow stream in the power plant. The work and heat interactions, the exergy losses and the efficiencies of various components based on both energy and exergy concepts are evaluated. The thermal and the exergy efficiencies of the plant are determined to be 47% and 44%, respectively. The engine irreversibilities are due mostly to the irreversible combustion process and account for 32% of the total exergy input and 57% of the total irreversibilities in the plant. Most of the remaining irreversibilities in the plant occur in the desulphurization, intercooler, compressor and lubrication oil cooler units. The results should provide a realistic and meaningful ground for the performance evaluation of Diesel engine power units, and it may be used in the design and analysis of such systems.     

我国炼油企业能量利用策略研究

炼油企业能量利用策略是指炼油企业在生产过程中如何合理地分配能量的策略。近年来,我国炼油加工能力快速增长,装置规模不断扩大,2008年原油加工量达3.42×108t,开工负荷率77.3%,生产汽煤柴成品油2.08×108t,千万吨级炼厂增加到11家。同时炼油技术水平不断提高,油品清洁化进程加快。但与国际先进水平相比,我国炼油企业普遍能耗较高,在能量利用方面存在观念落后、政策体制不够完善、主要生产装置能量利用率较低、装置间热联合程度较低等问题。要提高我国炼油企业能量利用效率,必须健全法规制度,加强主要装置和装置之间的能量利用策略,强化工艺过程之内、工艺与热力系统之间、工艺与储运系统之间及厂际之间的综合优化,大力推行炼化一体化和装置规模大型化,提高装置间热联合效率,应用热电联产技术,延长装置安全运行周期。     

Hierarchically structured exergetic and exergoeconomic analysis and evaluation of energy conversion processes

Evaluation of the efficiency and economic benefit of energy conversion processes and technologies requires a scientifically based analysis. The hierarchically structured exergetic analysis provides a detailed characterization of complex technical systems. By defining corresponding evaluation coefficients, the exergetic efficiency can be assessed for units within the whole system.Based on this exergetic analysis, a thermoeconomic evaluation method is developed. A cost function is defined for all units, subsystems and the total plant, so that the cost flow in the system can be calculated. Three dimensionless coefficients, the Pauer factor, the loss coefficient and the cost factor, enable pinpointing cost intensive process units, allocating cost in cases of co-production and gaining insight for future design improvements.The methodology is demonstrated by a biomass gasification plant producing electricity, heat and cold.     

Analysis of solar chemical processes for hydrogen production from water splitting thermochemical cycles

This paper presents a process analysis of ZnO/Zn, Fe₃O₄/FeO and Fe₂O₃/Fe₃O₄ thermochemical cycles as potential high efficiency, large scale and environmentally attractive routes to produce hydrogen by concentrated solar energy. Mass and energy balances allowed estimation of the efficiency of solar thermal energy to hydrogen conversion for current process data, accounting for chemical conversion limitations. Then, the process was optimized by taking into account possible improvements in chemical conversion and heat recoveries. Coupling of the thermochemical process with a solar tower plant providing concentrated solar energy was considered to scale up the system. An economic assessment gave a hydrogen production cost of 7.98$ kg⁻¹ and 14.75$ kg⁻¹ of H₂ for, respectively a 55 MW_th and 11 MW_th solar tower plant operating 40 years.     

System gains from widening the system boundaries: analysis of the material and energy balance during renovation of a coke oven battery

The coke oven plant has a central role in the iron and steel making process in an integrated steel plant. The subject of this research is to study how the production and energy system at the steel industry, with a connected combined heat and power plant, is affected by renovation of the coke oven. The aim is to investigate the interaction between the different processes and how the choice of system boundary affects the operation practice for the steel plant. MILP‐based optimization models have been developed and used for the evaluation. The analysis shows that it is very important to take the interactions between the different production units in the system into consideration when making the analysis. A system optimization with a boundary including the whole system has a greater potential for minimizing the total system cost than one that only includes the processes where the actual changes are made. Conclusions are also drawn regarding the production practice for the specific system. Copyright © 2004 John Wiley & Sons, Ltd.     

宝钢连续退火机组烟气余热的利用

为提高能源利用效率,确保宝钢完成＂十二五＂节能目标,宝山钢铁股份有限公司冷轧厂率先对连续退火机组的烟气余热进行利用。叙述了机组原余热利用系统的工艺流程及其缺点以及机组余热利用控制系统的运行情况,提出,机组余热利用工艺系统的改造方案。     

Managing a reservoir-based hydro-energy plant: building understanding in the buy and sell decisions in a changing environment

This paper describes a modelling process at a Norwegian chemical producer, who owns 20% of a reservoir based hydro-energy plant. While the initial objective was to increase the profitability of the energy plant (in particular by an improved understanding of buying and selling decisions and a reconciliation of the managerial and engineering points of view in the context of a liberalised energy market) the process resulted in the company's decision to refocus on its core-business. The process illustrates how a modelling process can lead to a fundamental reframing of the issue, resulting in major change for the company.     

2PE装置副生蒸汽回收利用技术的研究

本文用能量平衡及能级平衡理论,在上海石化塑料部两套装置间建立蒸汽喷射式热泵供热系统,利用热泵将2PE装置在生产过程中排放的副生蒸汽回收,将其能量品位提高后供其他装置使用,取得了显著的效益。     

Analysis of a feasible polygeneration system for power and methanol production taking natural gas and biomass as materials

Co-utilization of natural gas and biomass is a successful way to make efficient use of them for chemical production and power generation, for biomass is rich in carbon while natural gas is rich in hydrogen. The present paper therefore proposes a new polygeneration system taking biomass and natural gas as materials for methanol production and power generation. The new polygeneration system can achieve the optimal ratio of H₂ to CO for methanol production by adjusting input ratio of natural gas to biomass without any energy penalty. Thus, the suggested system can eliminate CO to H₂ shift process and CO₂ remove process, which can avoid material and energy destruction; however, those processes are otherwise necessary in individual biomass to methanol plant. Moreover, the new system eliminates the CO₂ addition process; however, the addition of CO₂ is necessary in individual natural gas to methanol plant, which causes extra energy penalty. This system combined chemical production and power generation together, in order to achieve the cascaded utilization of chemical and physical energy of natural gas and biomass. In a further way, we investigated the key processes, to maximize the utilization of energy and improve system performance.     

Integration of a heat pump into the heat supply system of a cheese production plant

The food processing industry in Ukraine is widely developed and continues to develop. The majority of the enterprises of the food processing industry use the technological process with refrigerating cycles. Basically it uses ammonia refrigeration units. In existing ammonia refrigeration units waste energy from ammonia overheat after compression is not used. This waste energy can be used for heating of other technological streams. It can be achieved by detailed inspection of the technological streams system and further heat integration of the ammonia unit into a heating system of the enterprise. In this study an inspection of a cheese production plant has been conducted and the opportunity to heat integration of an existing ammonia refrigeration unit into technological process is considered. At present energy from ammonia superheating and condensation is not used and is expelled into the atmosphere through the cooling tower. There are two options for use of this heat: first without additional compression of ammonia and second with additional compression of ammonia stream. Both cases are considered.     

Energy recovery in petrochemical complexes through heat integration retrofit analysis

This paper proposes the principles of how to define a boundary for heat integration in petrochemical complexes which are composed of several interconnected processing units. In order to obtain retrofit schemes that offer significant energy saving potential and are easy to implement, heat integration strategies are also developed in this study. Two case studies based on an aniline plant and an aromatic hydrocarbon plant, each one comprising several processing units, are presented to illustrate the application of these principles and strategies. The boundary for heat integration in each plant can be the whole plant or its individual processing units, the choice of which is determined by their energy saving potentials. Based on energy saving potential, each processing unit in the aniline plant was selected as the boundary for heat integration. The boundary for heat integration in the aromatic hydrocarbon plant, by contrast, was the whole plant. Retrofit schemes for the heat exchanger networks of the two plants, developed using pinch analysis, revealed that significant heating utility savings could be realized with a small number of network structure modifications.     

碳化法纳米碳酸钙生产过程的余热利用与节能增效

对碳化法纳米碳酸钙生产过程的能耗及节能措施进行了分析,针对某纳米碳酸钙生产厂的余热资源情况进行了调研,提出了一套余热梯级利用方案,将中高温余热用于溴化锂制冷机组替代部分原电制冷机组,将低温余热用于预热工艺用水、浆液和干燥空气。分析结果表明,该余热利用方案可获得良好的节能增效效果。     

Design of an integrated process for simultaneous chemical looping hydrogen production and electricity generation with CO2 capture

This study was aimed at proposing a novel integrated process for co-production of hydrogen and electricity through integrating biomass gasification, chemical looping combustion, and electrical power generation cycle with CO₂ capture. Syngas obtained from biomass gasification was used as fuel for chemical looping combustion process. Calcium oxide metal oxide was used as oxygen carrier in the chemical looping system. The effluent stream of the chemical looping system was then transferred through a bottoming power generation cycle with carbon capture capability. The products achieved through the proposed process were highly-pure hydrogen and electricity generated by chemical looping and power generation cycle, respectively. Moreover, LNG cold energy was used as heat sink to improve the electrical power generation efficiency of the process. Sensitivity analysis was also carried out to scrutinize the effects of influential parameters, i.e., carbonator temperature, steam/biomass ratio, gasification temperature, gas turbine inlet stream temperature, and liquefied natural gas (LNG) flow rate on the plant performance. Overall, the optimum heat integration was achieved among the sub-systems of the plant while a high energy efficiency and zero CO₂ emission were also accomplished. The findings of the present study could assist future investigations in analyzing the performance of integrated processes and in investigating optimal operating conditions of such systems.