EAGER: Work Integration through Work Exchange Network Synthesis

在过去十年中，自然资源加速枯竭、温室气体排放、气候变化的后果和经济全球化等因素促使各行业审查其做法，更加注重可持续性。其结果是改善了他们的业务，节省了能源，减少了废物，提高了生产力。但是，根据美国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%），总燃烧排放量已达到约12.6亿公吨CO2e（二氧化碳当量）。化学过程工业（CPI）约占美国总能源消耗的20%。本研究项目旨在提高化学工厂的节能水平。智力成果：热能和功是化学工厂中两种常见的能源形式。 使用热交换器网络（HENS）的热集成是用于CPI中的热能回收的技术。虽然过程功比过程热更昂贵，但有效地使用和再利用过程功尚未得到认真研究。这里的研究目标是开发类似于HEN的工作交换网络（WEN）。 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功流则可以用来评价机械能效率。 功集成的关键机制是耦合过程流之间由于压差引起的功交换。本研究是一项在过程系统工程中使用工作整合的研究。在等温、非等温和绝热条件下对功交换的拟议热力学分析将用于功交换区域，以实现在物理上可行且在经济上合理的机械能回收。由于WEN以混合模式操作，因此WEN合成方法将不同于以连续模式操作的热质交换器网络的合成方法。方法的新奇也将证明的方法识别的夹点，能源成本的目标设定，和最佳的工艺流程matching.Broader影响：在各种化学制造系统，工艺流程需要加压，这需要工作的压缩，而其他过程可以通过膨胀产生的工作。氨合成、反渗透和冷冻纯化是众所周知的例子。另一个例子是气体加工工业，其中高压天然气需要用液态CO2冷却，然后膨胀到较低压力以与液态N2交换热量，然后在涡轮机中进一步减压以达到其存储压力。如果利用高压流中的可用机械能来加压低压流，则机械能回收可大大降低操作成本。这不仅具有经济意义，而且具有环境影响，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.