Thermodynamic Assess Of The MID-Low-Temperature Waste Heat Recovery Using Organic Rankine Cycle (ORC)

The waste heat resources is widely exist in the China metallurgical enterprise. The technology recovering high temperature waste heat resources has been development maturely and high temperature waste heat has been recovered efficiently, however, about48%of mid-low-temperature waste heat resource has not been recovered efficiently. Orangic rankine cycle compared with the traditional rankine cycle can adopt low boiling point organic medium can recovery waste heat from mid-low-temperature resource. The organic rankine cycle could simplify system equipment, Improve power efficiency. This paper has studied the ORC in recovering200℃flue gas waste heat.In this paper, setup the mathematical model of evaporator, expansion engine condenser pump internal heat exchanger in ORC. Modeling the ORC system without IHE,ORC system with IHE,ORC system with over heating. Using MATLAB and NIST Refprop, select7kind of organic medium from117kind of organic medium with the highest system evaporation temperature, confirm the optimal evaporation pressure and the optimal condensing temperature in the optimal working point. Multi-objective optimization of the system efficiency evaporation temperature expansion ratio volume flow rate of expander entrance in ORC system. The system has the highest thermal efficiency18.84%using R113as working medium at evaporation pressure of1.84MPa and condensate temperature of300K. Considering environmental performance parameters:Global Warming Potential (GWP) Ozone Depletion Potential (ODP) and toxicity etc. HEXANE ISOHEXANE R123are environmental organic medium.The ORC with overheating and the ORC added IHE effect the performance of the system. Add IHE can improve the thermal efficiency of the system, and with the increase of the recuperated effectiveness, the thermal efficiency of the system will increase.But the recuperated effectiveness was restricted buy the coverage of IHE, can’t approach the theoretical limit.The ORC added superheater obtain higher output power, however, the thermal efficiency of the system will not rise. Study the evaporation pressure, condensing temperature effect the performance of the system. The higher evaporation pressure is, the higher heat efficiency, evaporation temperature, expansion ratio, volume flow rate is. Reduce the condensing temperature, compared with the ascension of evaporation pressure, can improve the thermal efficiency of the system more effectively. The evaporation temperature, the expansion ratio, volume flow rate will improve with the reduction of condensing temperature. Established the preheating section, evaporator section, overheating section of evaporator in MATLAB-SIMULINK. And established expander model, condenser model and pump model. Use HEXANE as working fluid, and obtain the system response curve nearby optimal working point in the optimal operation area.