EAGER: Work Integration through Work Exchange Network Synthesis

在过去十年中，自然资源加速枯竭、温室气体(GHG)排放、气候变化的后果和经济全球化等因素使各行业在审查其做法时更加注重可持续性。其结果是改善了运营，节约了能源，减少了浪费，提高了生产率。但是，根据能源部工业技术计划(ITP)，制造业的能源损失仍然很高(约占总能源消耗的57%)，燃烧排放总量已达到约12.6亿吨二氧化碳(二氧化碳当量)。化学加工工业(CPI)约占美国总能源消耗的20%。这项研究项目旨在改善化工厂的节能。智力优点：热和功是化工厂中两种常见的能量形式。利用热交换网络(HEN)的热集成是CPI中用于热能回收的一种技术。虽然过程功比过程热更昂贵，但有效地利用和再利用过程功还没有得到认真的研究。这里的研究目标是开发类似母鸡的工作交换网络(Wens)。从热力学的角度来看，以温度为状态变量的热流与热能效率直接相关，而以压力为状态变量的工作流可以用来评价机械能效率。工作集成的关键机制是由于压力差异而耦合的流程流之间的工作交换。本研究是对工作集成在过程系统工程中应用的研究。所提出的等温、非等温和绝热条件下功交换的热力学分析将用于功交换区域，以实现热力学上可行和经济上合理的机械能回收。由于WEN是以混合模式运行的，因此WEN合成方法将不同于以连续模式运行的热质交换网络的方法。方法的新颖性还将通过夹点识别、能量成本目标设置和最优工艺流匹配的方法来展示。广泛的影响：在各种化学制造系统中，工艺流需要加压，这需要进行工作压缩，而其他过程可以通过扩展产生功。氨合成、反渗透和冷冻提纯都是众所周知的例子。另一个例子是气体加工业，高压天然气需要用液态二氧化碳冷却，然后膨胀到较低的压力，与液态氮气交换热量，然后在涡轮机中进一步减压，达到其储存压力。如果利用高压气流中的可用机械能对压力较低的气流进行加压，机械能回收可以大大降低运行成本。这不仅具有经济意义，而且还具有环境影响，因为能源效率的提高有助于减少二氧化碳排放。

Over the past decade, accelerated natural resource depletion, greenhouse gas (GHG) emissions, the consequences of climate change, and economic globalization, among other factors, had industries reviewing their practices with a greater focus on sustainability. The results have been improvements in their operations evidenced by energy savings, waste reduction, and gains in productivity. But, according to the DOE Industrial Technology Program (ITP), the energy loss in the manufacturing sectors is still high (approximately 57% of the total energy consumed), and total combustion emissions have reached approximately 1,260 million metric tons of CO2e (carbon dioxide equivalents). The chemical process industries (CPI) account for approximately 20% of the total energy consumed in the U.S. This research project is aimed at improving energy conservation in chemical plants.Intellectual Merit:Heat and work are two common forms of energy in chemical plants. Heat integration, using heat exchanger networks (HENs), is a technique used for thermal energy recovery in the CPI. While process work is more expensive than process heat, using and reusing process work effectively has not been seriously studied. The research goal here is to develop work exchange networks (WENs) that are similar to HENs. From a thermodynamics point of view, heat flow, with temperature as the state variable, is directly related to thermal energy efficiency, while work flow, with pressure as the state variable, can be used to evaluate mechanical energy efficiency. The key mechanism of work integration is work exchange among coupled process streams due to pressure differences. This study is an investigation of using work integration in process systems engineering. The proposed thermodynamic analysis on work exchange under isothermal, non-isothermal, and adiabatic conditions will be used in the work exchange regions for thermodynamically feasible and economically justifiable mechanical energy recovery. Since a WEN is operated in a hybrid mode, the WEN synthesis methodology will be different from those for heat and mass exchanger networks, which are operated in a continuous mode. The methodological novelty will be also demonstrated by the approaches for pinch point identification, energy-cost target setting, and optimal process stream matching.Broader Impacts :In a variety of chemical manufacturing systems, process streams need to be pressurized, which requires work for compression, while other processes can produce work through expansion. Ammonia synthesis, reverse osmosis, and freezing purification are among well-known examples. Another example is the gas processing industry, where high-pressure natural gas needs to be cooled with liquid CO2 and then expanded to a lower pressure to exchange heat with liquid N2, and it is then further depressurized in a turbine to reach its storage pressure. If the available mechanical energy in the high-pressure streams is utilized to pressurize the lower pressure streams, the mechanical energy recovery can greatly reduce operating cost. This is of not only economic significance but also has environmental implications, as energy efficiency improvement could help reduce CO2 emission.