Feasibility assessment of refinery waste heat-to-power conversion using an organic Rankine cycle H.C. Jung a , Susan Krumdieck a,⇑ , Tony Vranjes b a Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand b The New Zealand Refining Company Limited (Refining NZ), Whangarei, New Zealand article info Article history: Received 22 December 2012 Accepted 27 September 2013 Keywords: Waste heat Thermal system modelling Organic Rankine cycle (ORC) Feasibility study Low-carbon power Low-temperature power generation Recycled energy abstract Industrial waste heat is a large potential resource for generation of carbon-free electricity. This study investigates the technical and economic feasibility of converting waste heat from a stream of liquid ker- osene which must be cooled down to control the vacuum distillation temperature. The process conditions were determined for a simple 250 kW organic Rankine cycle (ORC) with a heat extraction loop. The pinch point technique was adopted to determine the optimum evaporation and condensation temperatures and assess the influence of the kerosene temperature at the evaporator exit on net power output. The oper- ating conditions and performance of the ORC system were evaluated with eight potential refrigerants and refrigerant mixtures such as R123, R134a, R245fa, isobutane, butane, pentane, an equimolar mixture of butane and pentane, and a mixture of 40% isobutane and 50% butane on a mole basis. A financial model was established for the total plant cost. Results show that isobutane, of the pure fluids, yields the best plant efficiency of 6.8% with approximately half of the kerosene flow available, and the efficiency can be increased up to 7.6% using the butane/pentane mixture. The optimum kerosene temperature at the evaporator outlet is estimated to be 70 °C for all the fluid, except the butane/pentane mixture, which meets the design constraint not to disturb the existing distillation process. A capital cost target of $3000/kW could be achieved with a payback period of 6.8 years and the internal rate of return (IRR) of 21.8%. Therefore, if the detailed engineering, component fabrication and construction can be achieved within the cost target, the installation of a 250 kW ORC waste heat power converter on the kerosene cool- ing line would be technically feasible and economically viable. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Many manufacturing industries discharge large amounts of en- ergy in the form of waste heat and it is more and more significant to recover this waste heat to achieve huge energy savings and reduce environmental impact by improving industrial energy effi- ciency. The industrial waste heat released from many manufactur- ing processes has a relatively high temperature enough to drive a power cycle and produce electricity for on-site use or sale. The oil refining, steel making and glass making industries operate the major process plants consuming large quantities of energy and also producing huge amount of waste heat. As much as 20–50% of the energy used during the manufacturing processes is released to the atmosphere, and in some cases (e.g., industrial furnaces), the energy efficiency can be improved by 10% to as much as 50% by recapturing the waste heat [1]. It was estimated that waste heat recovery in a midsize cement plant contributes to a potential enhancement in energy efficiency up to 20% and a reduction in the CO 2 emissions up to 10,000 ton/year [2]. The important factors affecting the feasibility of waste heat recovery are the flow rate, temperature, pressure, chemical compo- sition, and allowable temperature and pressure drops. The amount of energy available in the waste heat sources is defined as a func- tion of the flow rate, temperature, enthalpy or specific heat of the waste heat stream. The energy transfer rate in heat recovery exchangers is influenced by the parameters of temperature, flow velocity and fluid phase. The chemical make-up of the waste heat stream can limit the type of heat exchanger material and also yield fouling issues. The minimum allowable temperature is normally set by the dew point temperature in exhaust gas streams as the li- quid phase may cause corrosion problem in heat exchangers. Li- quid waste heat streams may also have lower temperature limits set by solubility of dissolved minerals or fats and wax [3]. Industrial waste heat discharged to the environment can be classified into four categories: liquid streams at between 50 and 300 °C, flue gases at between 150 and 800 °C, steam at between 100 and 250 °C, and process gases and vapours at between 80 and 500 °C [4]. According to a report from the US Department of 0196-8904/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.enconman.2013.09.057 ⇑ Corresponding author. Address: Private Bag 4800, Christchurch 8041, New Zealand. Tel.: +64 3 364 2987x7249; fax: +64 3 364 2078. E-mail address: susan.krumdieck@canterbury.ac.nz (S. Krumdieck). Energy Conversion and Management 77 (2014) 396–407 Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman