Conceptual design of ammonia‐based energy storage system: System design and time‐invariant performance

Chemicals‐based energy storage is promising for integrating intermittent renewables on the utility scale. High round‐trip efficiency, low cost, and considerable flexibility are desirable. To this end, an ammonia‐based energy storage system is proposed. It utilizes a pressurized reversible solid‐oxide fuel cell for power conversion, coupled with external ammonia synthesis and decomposition processes and a steam power cycle. A coupled refrigeration cycle is utilized to recycle nitrogen completely. Pure oxygen, produced as a side‐product in electrochemical water splitting, is used to drive the fuel cell. A first‐principle process model extended by detailed cost calculation is used for process optimization. In this work, the performance of a 100 MW system under time‐invariant operation is studied. The system can achieve a round‐trip efficiency as high as 72%. The lowest levelized cost of delivered energy is obtained at 0.24 $/kWh, which is comparable to that of pumped hydro and compressed air energy storage systems. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1620–1637, 2017     

Evaluating demand response opportunities for power systems resilience using MILP and MINLP Formulations

While peak shaving is commonly used to reduce power costs, chemical process facilities that can reduce power consumption on demand during emergencies (e.g., extreme weather events) bring additional value through improved resilience. For process facilities to effectively negotiate demand response (DR) contracts and make investment decisions regarding flexibility, they need to quantify their additional value to the grid. We present a grid-centric mixed-integer stochastic programming framework to determine the value of DR for improving grid resilience in place of capital investments that can be cost prohibitive for system operators. We formulate problems using both a linear approximation and a nonlinear alternating current power flow model. Our numerical results with both models demonstrate that DR can be used to reduce the capital investment necessary for resilience, increasing the value that chemical process facilities bring through DR. However, the linearized model often underestimates the amount of DR needed in our case studies. Published 2018. This article is a U.S. Government work and is in the public domain in the USA. AIChE J, 65: e16508, 2019     

化工系统消纳可再生能源的电-氢协调储能系统优化设计

针对可再生能源发电间歇性和波动性与化工过程系统氢气需求波动性协调匹配的问题,本文以电-氢储能系统总费用最小为目标,建立了可再生能源发电与化工生产中加氢系统耦合的电-氢协调储能系统优化设计模型,以确定电-氢协调储能系统的最优容量配置和功率调度方案。采用典型案例研究了可再生能源渗透率和电-氢储能系统构成对电-氢储能优化设计和运行特性的影响。研究表明：当化工系统的氢气需求全部由可再生能源发电制氢提供时,在系统中同时采用电池和氢气储罐储能可有效地降低系统的总费用;在该系统中,电池可用于平抑短期内发电侧和负荷侧的波动,氢气储罐可平衡发电侧和负荷侧长期的不匹配;随着可再生能源渗透率的增加,系统的总费用显著增大;为了维持外购氢气流率的稳定,系统中需要增加电解槽和储能系统的容量以解决发电侧和负荷侧的波动和不匹配问题。     

热能在乙烯厂生产中的合理利用

蒸汽动力系统是石化企业的重要组成部分,为整个生产过程提供蒸汽、电力等公用工程。由于生产中产品品种变化及季节不同,必然引起公用工程用量的变化,相应的蒸汽动力系统能否适应所发生的变化,是否具有可调性,将决定企业的产品成本、经济效益和能源利用程度。热能合理利用成为工厂深入挖潜、节能增效的一项重要工作。     

Heat integration and analysis of decarbonised IGCC sites

Integrated gasification combined cycle (IGCC) power generation systems have become of interest due to their high combined heat and power (CHP) generation efficiency and flexibility to include carbon capture and storage (CCS) in order to reduce CO₂ emissions. However, IGCC's biggest challenge is its high cost of energy production. In this study, decarbonised coal IGCC sites integrated with CCS have been investigated for heat integration and economic value analyses. It is envisaged that the high energy production cost of an IGCC site can be offset by maximising site-wide heat recovery and thereby improving the cost of electricity (COE) of CHP generation. Strategies for designing high efficiency CHP networks have been proposed based on thermodynamic heuristics and pinch theory. Additionally, a comprehensive methodology to determine the COE from a process site has been developed. In this work, we have established thermodynamic and economic comparisons between IGCC sites with and without CCS and a trade-off between the degree of decarbonisation and the COE from the heat integrated IGCC sites. The results show that the COE from the heat integrated decarbonised IGCC sites is significantly lower compared to IGCC sites without heat integration making application of CCS in IGCC sites economically competitive.     

基于递归式多目标协同进化遗传算法的电厂负荷分配研究

提出以多目标优化方法来完成电厂负荷调度分配。综合考虑了经济性、快速性和稳定性的要求,建立多目标优化的数学模型,采用递归式多目标协同进化遗传算法求解负荷分配问题。与传统多目标算法相比,该方法减少了各个目标之间可能产生的偏移,并且进化过程简单,具有较强的灵活性和实用性。     

电厂和碳捕集装置同步集成与调度优化研究

由于全球碳排放量持续增加所引发的环境问题日益严重,发展低碳技术迫在眉睫。在化石燃料发电厂的尾端加入碳捕集装置能够有效减少燃煤电厂的碳足迹,达成减排指标。然而,碳捕集装置的高设备成本以及运行所附带的效率惩罚和经济惩罚阻碍了其与电厂装置的集成与部署。为了在满足碳减排量的同时有效提高电厂和碳捕集装置的总体效益,建立了一个基于数学规划的系统优化设计与调度方法,将发电厂与一个增加烟气旁路和溶剂储罐的碳捕集装置进行集成,并在电厂蒸汽动力循环部分引入分级透平,旨在考虑电价波动的情况下,充分利用碳捕集装置的操作灵活性与蒸汽透平分级做功的优势,对集成系统进行调度优化。最后,通过算例验证了模型的可靠性与有效性,分析归纳了电厂与碳捕集装置协同调度的主要特性与规律。     

基于全寿命周期成本的压缩空气储能系统储气装置经济性分析

综合考虑压缩空气储能系统经济性对于储能系统的设计和大规模应用具有重要意义。本文基于全寿命周期成本模型分析的方法,建立了不同类型的储气装置成本模型。通过计算储气装置的理论金属消耗量、储气装置的数量,同时在考虑制造难易程度的基础上来确定不同类型储气装置的最佳参数。通过对不同类型的储气装置进行全寿命周期成本分析和比较,可作为设计压缩空气储能系统及其经济性分析的参考。储气装置的全寿命周期成本（LCC）包括早期和后期成本。早期成本主要由原材料和设备成本构成,后期成本主要是运行维护成本。根据分析结果,储气管道的投资成本最低,且没有压力限制。地面储气装置的设备成本一般在2USD/kW·h左右。在确保安全的前提下,降低地面储气装置的LCC有利于压缩空气储能系统的推广实施和工程应用,大规模、有效地提高可再生能源的利用率,降低可再生能源的间歇性对电网运行的影响。     

The multi-period optimisation of an amine-based CO2 capture process integrated with a super-critical coal-fired power station for flexible operation

In this work, we present a model of a super-critical coal-fired power plant integrated with an amine-based CO₂ capture process. We use this model to solve a multi-period dynamic optimisation problem aimed at decoupling the operation of the power plant from the efficiency penalty imposed by the CO₂ capture plant, thus providing the power plant sufficient flexibility to exploit price variation within an electricity market. We evaluate four distinct scenarios: load following, solvent storage, exhaust gas by-pass and time-varying solvent regeneration. The objective is to maximise the decarbonised power plant's short run marginal cost profitability. It is found that while the solvent storage option provides a marginal improvement of 4% in comparison to the load following scenario, the exhaust gas bypass scenario results in a profit reduction of 17% whereas the time-varying solvent regeneration option increases the profitability of the power plant by 16% in comparison to the reference scenario.     

Economic optimization of distributed embedded battery units for large-scale heating,ventilation, and air conditioning applications

Energy costs of space heating and cooling systems can be significantly decreased using energy storage to shift the load from periods of high prices to periods of low prices. In this work, an economically optimal method of controlling large systems with distributed embedded batteries units is proposed. The control system with load shifting outperforms the conventional trade-off curve between cost and occupant comfort. Remarks are also made about the economic viability of these systems moving forward.     

液化石油气储运设施的优化设计

通过新增一套液化石油气裂解原料储运设施工艺系统的优化设计，提高了上海石化2#乙烯装置实际生产能力，并减少了裂解原料单耗和乙烯装置能耗。优化设计方案使本项目采用最少的基建投资和操作费用取得最大经济效益。     

Optimization of the heat plant of district energy systems

This paper presents a scheme to achieve structural and operational optimization for the heat plant in a district energy system. A district energy system consists of energy suppliers and consumers, district heating pipelines and heat storage facilities in a region. Production and consumption of energy and transport of energy as well as storage of heat are taken into account in the model. The problem is formulated as a mixed integer linear programming (MILP) problem where the objective is to minimize the overall cost of the district energy system. Evaluation of the energy production cost is based on the daily operation for every season at the plant located at Suseo in Seoul, Korea. From the results of numerical simulations we can see that the district energy system is well approximated by the proposed model, and that the energy efficiency is improved by the application of the optimal operation conditions provided by the proposed model.     

三聚氰胺装置与大尿素装置联产改造

河南煤业化工集团中原大化公司的尿素装置与三聚氰胺装置联产后,由于大量甲铵返回,造成系统的能耗和物耗大幅上涨。经过对系统进行分析和计算,制定了改造方案,进而实现了尿素装置高负荷、安全和经济的运行。     

改造系统实现尿素装置高负荷运行

重庆建峰化工股份有限公司三聚氰胺装置投产后由于大量甲铵液返回，造成尿素系统实际负荷增加到115％，尿素系统的分解和回收能力无法满足高负荷运行的要求，造成系统的能耗和物耗大幅上涨。经过对系统进行分析、计算，制定了扩能改造方案，进而实现了尿素装置高负荷、安全、经济的运行。     

LNG接收站BOG多阶压缩再液化工艺优化分析

LNG接收站蒸发气体(BOG)处理量和液化天然气(LNG)外输量的波动对BOG再冷凝工艺提出低能耗、大弹性、易操作的要求。以系统总能耗最小为目标函数,对建立的BOG多阶压缩再液化工艺模型中压缩阶数和阶压比等参数进行了优化,并分析了该工艺模型在工况波动影响系统能耗时的各阶压比的抗干扰性及系统的操作弹性。结果表明:多阶压缩工艺系统阶数越多,系统的总压比、总能耗越小,BOG处理能力也越大;但随着系统阶数的增加,节能效果降低。多阶再液化工艺中二阶系统比现有一阶系统的操作弹性增大12%,且在LNG与BOG质量比≤10时,二阶系统的BOG压缩功耗可节约33%以上。针对一般气源型接收站工况,二阶系统是节能且操作弹性大的BOG处理工艺。     

Air separation with cryogenic energy storage: Optimal scheduling considering electric energy and reserve markets

The concept of cryogenic energy storage (CES) is to store energy in the form of liquid gas and vaporize it when needed to drive a turbine. Although CES on an industrial scale is a relatively new approach, the technology is well known and essentially part of any air separation unit that utilizes cryogenic separation. In this work, the operational benefits of adding CES to an existing air separation plant are assessed. Three new potential opportunities are investigated: (1) increasing the plant's flexibility for load shifting, (2) storing purchased energy and selling it back to the market during higher‐price periods, and (3) creating additional revenue by providing operating reserve capacity. A mixed‐integer linear programming scheduling model is developed and a robust optimization approach is applied to model the uncertainty in reserve demand. The proposed model is applied to an industrial case study, which shows significant potential economic benefits. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1547–1558, 2015     

Optimization of steel production scheduling with complex time-sensitive electricity cost

Energy-intensive industries can take advantage of process flexibility to reduce operating costs by optimal scheduling of production tasks. In this study, we develop an MILP formulation to extend a continuous-time model with energy-awareness to optimize the daily production schedules and the electricity purchase including the load commitment problem. The sources of electricity that are considered are purchase on volatile markets, time-of-use and base load contracts, as well as onsite generation. The possibility to sell electricity back to the grid is also included. The model is applied to the melt shop section of a stainless steel plant. Due to the large-scale nature of the combinatorial problem, we propose a bi-level heuristic algorithm to tackle instances of industrial size. Case studies show that the potential impact of high prices in the day-ahead markets of electricity can be mitigated by jointly optimizing the production schedule and the associated net electricity consumption cost.     

30万t/a合成氨装置(布朗流程)氨回收系统的改造与运行

简述了锦西天然气化工有限公司30万t/a合成氨装置(美国布朗流程)氨回收系统的工艺流程;介绍了氨回收系统存在的问题以及历次技改的情况。针对氨吸收能力差这一主要问题,实施了更换氨吸收塔内件的技术改造。技改效果表明:①氨吸收塔可在弛放气量5 200~10 000 m3/h的高负荷下运行,提高了系统的操作弹性;②出塔气体达到氨含量1 000×10-6的排放要求;③出塔气体无液体夹带;④因增加负荷可创经济效益355万元/a;⑤改善了现场环境。     

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.