Thermodynamic performance of SNG and power coproduction from MSW with recovery of chemical unreacted gas.

A cogeneration system for simultaneously producing synthetic natural gas (SNG) and electric power from municipal solid waste (MSW) is developed. This process provides a disposal method for MSW that is environmentally sustainable and uses as an alternative energy sources. Rather than converting all of the synthesis gas into end products, in the proposed system the unconverted gas is recovered for power generation in a combined-cycle unit. The overall efficiency of the proposed system is 36.33%. The energy efficiency of this system is approximately 8.7% higher than that of a standalone SNG production system, and 15.02% higher than that of an MSW incineration system. A sensitivity analysis shows that by increasing the H/CO ratio (α), SNG production and SNG conversion efficiency can be increased, but the overall efficiency does not increase. Increasing the recycling ratio of the unconverted gas (Ru) benefits for the SNG yield up to a value before Ru/(Ru+1)=0.7, and the overall system efficiency reaches its maximum value at Ru/(Ru+1)=0.9. Therefore, partial recycling of the unreacted gas is more efficient up to a point, and higher recycling ratios are less efficient.