Proposal and Assessment of an Engine-Based Distributed Steam and Power Cogeneration System Integrated with an Absorption-Compression Heat Pump

Abstract

Internal combustion engine-based poly-generation systems have been widely used for energy savings and emissions reductions. To maximize their thermodynamic and environmental performance potentials, the efficient recovery of flue gas and jacket water heat is essential. In a conventional internal combustion engine-based steam and power cogeneration system, the low-temperature (less than 170°C) heat from flue gas and jacket water is usually directly discharged to the environment, which dramatically reduces the thermal and economic performance. In this work, a high-temperature heat pump is employed to recover this part of low-temperature heat for steam generation. The sensible heat of the flue gas and jacket water is cascade utilized in a steam generator and a heat pump. Simulation results show that the process steam yield of the proposed system is almost doubled (increased by 703 kg/h) compared to that of an engine-based cogeneration system without a heat pump. The proposed system can reduce natural gas consumption, CO2 and NOx emissions by approximately 199,069 m3, 372.64 tons and 3.02 tons per year, respectively, with a primary energy ratio and exergy efficiency of 72.52% and 46.28%, respectively. Moreover, the proposed system has a lower payback period with a value of 5.11 years, and the determining factors that affect the payback period are natural gas and electricity prices. The total net present value of the proposed system within its lifespan is 2,441,581 USD, and an extra profit of 785,748 USD can be obtained compared to the reference system. This is a promising approach for replacing gas boilers for process steam production in industrial sectors.