16:30
Session 3A: Waste Heat Recovery (1)
Chair: Hua Tian
16:30
20 mins
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Techno-economic analysis of waste heat recovery from ORC with fluctuating industrial sources
Roberto Pili, Alessandro Romagnoli, Hartmut Spliethoff, Christoph Wieland
Abstract: A significant portion of the consumed energy by the industrial sector is rejected as waste heat in the medium temperature range. Organic Rankine Cycles (ORC) are a valuable technology to recover the available waste heat at medium temperatures, and produce electricity or combined heat and power (CHP). A trade-off has to be found between the reduced environmental impact of an industrial site and investment costs for waste heat recovery (WHR). Very challenging for the WHR are the large fluctuations in temperature and/or mass flow rate. In the present work, the economic feasibility of industrial WHR with ORC is analyzed for different applications, with and without heat storage: hot air from clinker cooling (fluctuating heat source temperature), exhaust gas from rolling mill reheating furnace (fluctuating heat source mass flow rate) and a case of exhaust gas from electric arc furnace (both fluctuating heat source temperature and mass flow rate). The different configurations are developed and simulated by combining MATLAB® and EBSILON®Professional. A latent heat buffer with LiNO3 appeared to be the best option for WHR from cement clinker cooling. In case of rolling mill reheating furnace, a design for the minimum mass flow rate and bypass of any exceeding fluctuation appeared the most economic solution, whereas the best environmental performance was achieved for lower bypass of the heat source. In case of electric arc furnace, the best economic solution appeared to be without storage, even though the latent buffer could guarantee the highest CO2-savings. The described design and analysis method should help investors, designers and decision makers take better choices to increase the efficiency and improve the economy of industrial sites with ORC technology.
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16:50
20 mins
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Performance evaluation of an ORC unit integrated to a waste heat recovery system in a steel mill
Miguel Ramirez, Maider Epelde, Mercedes Gomez de Arteche, Andrea Panizza, Alfred Hammerschmid, Marco Baresi, Nicola Monti
Abstract: Waste heat revalorization creates interesting opportunities to energy intensive industries. In the present project a large scale ORC pilot plant along with a waste heat recovery unit (WHRU) in a steel mill has been designed, commissioned and operated. The plant is part of the European Commission funded PITAGORAS project and it has been built by ORI MARTIN in Brescia (Italy). Waste heat is recovered from the fumes of the Electric Arc Furnace (EAF) to produce saturated steam which is then delivered to a district heating (DH) network during heating season and to the ORC for electricity generation during summer. The main challenge was the integration of these systems in a single plant since the heat source is highly unstable and both the DH ad ORC require a steady heat load for their safe operation. A steam accumulator of 150m3 volume was implemented between the WHRU and the ORC/DH systems to maintain a steady discharge pressure, to reduce the fast transients and to extend the supply over longer periods. The ORC has a nominal power output of 1,8MW and the preliminary results of the first weeks of operation of the ORC unit resulted in a net efficiency of 21.7%. Currently the plant is undergoing monitoring campaign which will provide additional data to further evaluate and optimize the system.
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17:10
20 mins
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Techno-Economic Analysis of ORC in Gas Compression Stations Taking Into Account Actual Operating Conditions
Michele Bianchi, Lisa Branchini, Andrea De Pascale, Francesco Melino, Valentina Orlandini, Antonio Peretto, Daniele Archetti, Francesco Campana, Tommaso Ferrari, Nicola Rossetti
Abstract: Gas compressor stations represent a huge potential for exhaust heat recovery, currently under-exploited. Typical installations consist of multiple gas turbine units in mechanical drive arrangement, operated, most of the time, at part-load conditions and with limited conversion efficiency. In this context, this paper investigates the energetic-economic potential of ORC application in typical gas compression facilities, as innovative contribution with respect to literature. The ORC is designed to convert the gas turbines wasted heat into useful power. Additional power output can be used either inside the compression facility, reducing the amount of consumed natural gas and, consequently, the environmental impact, or delivered to the electrical grid. Taking into account real operation of gas turbines in a natural gas compression station, located in North America, additional generated energy and CO2 avoided, thanks to ORC operation, are quantified. Two ORC arrangements, namely with and without intermediate heat transfer fluid, are proposed and the design performance are identified. Influence of topper cycle part load operations on bottomer section are quantified through an off-design thermodynamic evaluation. The goal of the performed analysis is to obtain a detailed scenario of the integrated system operation on yearly basis. Results, for a reference 50 MW compression station, show that the direct heat exchange configuration guarantees up to 66 GWh/year of additional electrical energy, saving up to 36*103 tons/year of CO2, while ORC investment costs can be recovered within 7 years of operation. The performed comprehensive investigation assesses the ORC as a techno-economic profitable technology to recover wasted heat in natural gas compression facilities.
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