Energy and Exergy Analyses of Fluidized-Bed Municipal Solid Waste Air Gasification

With the aim of optimizing gasification systems, air gasification using simulated municipal solid waste is experimentally investigated in a fluidized-bed reactor. Process parameters considered include equivalence ratio (ER) and temperature. On the basis of the experimental results, energy and exergy analyses are performed to assess the thermodynamic quality. Results reveal that the energy and exergy contents of the produced gas increase first with rising temperature and then decline when the temperature exceeds 650 degrees C. With regard to the ER, a similar tendency is observed with a peak value at an ER of 0.4. The energy content of the produced gas is much higher than its exergy content as a result of the remarkable difference between physical energy and exergy contents of sensible heat. The maximum chemical energy efficiency, total energy efficiency, chemical exergy efficiency, and total exergy efficiency of the, products at the gasifier exit are attained at an ER of 0.4 and a temperature of 650 degrees C, with values of 49.73, 64.05, 47.14, and 51.33%, respectively. The total exergy efficiency is suggested as an effective parameter to evaluate the properties of gasification-based thermal systems, because it expresses the availability of the products from the "first-step" gasifier for subsequent conversion.