Diseño de un sistema de Ciclo Rankine Orgánico mediante el aprovechamiento de calor residual industrial para la producción de mínimo 10 kW de potencia

Abstract

In the present project, a design proposed was developed for a cogeneration system based on Organic Rankine Cycle (ORC onwards) with heat recovery of industrial waste gases from the TECSOL LTDA activated carbon plant. Initially, to select the appropriate Working Fluid, a Pugh Matrix with 15 possible fluids was used, which, according to the weight of certain thermodynamic characteristics, resulted in 3 refrigerants that fulfilled the work requirements in the proposed system (R601 , R123, R601a). The theoretical thermodynamic states of these three fluids were then calculated at different pressure ratios, giving the best result, after a performance analysis, of R123 with a pressure ratio of 1: 6.25, and with a yield of 10%; Subsequently, the temperature and mass flow interval of the waste exhaust gases in the TECSOL LTDA plant was determined, obtaining as a result that the temperature interval between the waste gases and the working fluid must be 240 ° C because, between the longer this interval, the area required in the evaporator will be smaller and its efficiency will increase. With respect to the mass flow, it was determined that there should be a minimum of 2.43 kg / s of the 8.33 kg / s available at the point before the hydrocyclone for the production of 10 kWe of power. For the design and selection of the ORC elements it was concluded that the evaporator requires a transfer area of ​​6 m2 with a number of 52 copper tubes with two steps and a length of 1.37 m, also presented an efficiency of 53% . The condenser requires a transfer area of ​​126 m2 with a number of 376 copper tubes divided into two steps and a length of 3.19 m and presented an efficiency of 40%. The expansion system was selected by means of a direct comparison method where both technical and economic criteria were evaluated among six possible alternatives (axial turbine, radial turbine, positive displacement expander, pallet expander, Screw Expander and Scroll Expander) resulting in better option a Scroll Expander, with an associated volumetric ratio of 1:8 and that has an efficiency of 70%. Likewise, a 10 kWe PMG synchronous generator with 220 V, 60 Hz at 900 RPM was selected. The pump selected is Grundfos brand model NB 40-315 / 336 axial suction that allows the pressure ratio calculated for the operation of the system of 1: 6.25 and that has an efficiency of 85%. The net efficiency of the cycle was 10%. Finally, a CAD model of the final ORC system was elaborated in order to outline a possible configuration of the equipment and its dimensions and an assembly diagram that shows the approximate maximum dimensions and the basic accessories that should compose the system is attached.