Comparative thermodynamic analysis of an improved ORC process with integrated injection of process fluid. (1st March 2023)

• Record Type: Journal Article
• Authors: Krail, Jürgen; Beckmann, Georg; Schittl, Florian; Piringer, Gerhard
• Is Part Of: Energy. Volume 266(2023)
• Publication Date: 2023-03-01
• Subjects: Waste heat recovery -- Organic Rankine Cycle (ORC) -- Process simulation -- Improved process design -- Process efficiency; A auxiliary units (electric motors for fansand pumps) -- B boiler -- C cycle -- CO condenser -- CC condensate cooler -- CP condensate pump -- EL electric -- EV evaporator -- FA fan -- FP feed pump -- G generator -- I mean values state parameters inlet -- IN inlet stream -- IS isentropic -- HP high pressure stage -- HS heat source -- M mechanic -- NET net value -- LP low pressure (exhaust vapour) -- MI mixing chamber -- MIN minimum -- MO motor -- MP medium pressure stage -- O mean values state parameters outlet -- OUT outlet stream -- PH preheater -- PU pump -- R recuperator -- REF reference conditions -- REL relative -- TO thermo oil -- TOB thermo oil boiler -- TOP thermo oil pump -- TU turbine -- VG vapour generator -- WF working fluid -- WHS waste heat source -- WHR waste heat recovery; Power resources -- Periodicals; Power (Mechanics) -- Periodicals; Energy consumption -- Periodicals; 333.7905
• DOI: 10.1016/j.energy.2022.126352
• Languages: English
• ISSNs: 0360-5442

Abstract

Abstract: In contrast to water-steam Rankine cycles, the ORC process uses organic working fluids. For working fluids of the dry class, a recuperator heat exchanger is frequently installed to increase the cycle efficiency. This paper analyses an improved ORC process with these features: A liquid working fluid stream is injected into the vapour flow between the high-pressure and the medium-pressure stage of the turbine. Furthermore, the recuperator is replaced by a spray condenser. The main objective is to increase efficiency with moderate changes in the process layout. A thermodynamic comparison of the improved process with a state-of-the-art ORC process is carried out by simulations and optimisations. A significant efficiency gain for the improved ORC process is obtained by a combination of the aforementioned features, mainly because of an increase of the mass flow in the economiser of the vapour generator (better heat utilization) and a corresponding mass flow in the medium stage of the turbine (additional power production). As a use case, waste heat utilization from a clinker cooler at a temperature level of 275 °C was simulated. The improved process would lead to a significant increase in the overall net efficiency by up to 14%, compared to a state-of-the-art ORC process.