Energy utilities from low temperature industrial waste heat : Analysis of a few cycles

Abstract

Global demand for secondary energy is increasing steadily with time. Most of this global demand is catered to by fossil fuel-based power plants. These fossil fuel-based power plants are responsible for the most of the greenhouse gas emission. Fossil fuel resources are also finite in nature. Extensive production of secondary energy using renewable resources may reduce fossil fuel consumption and corresponding greenhouse gas emission to some extent. Satisfying global demand for secondary energy with minimum environmental impact is very challenging. Though installed capacity of renewable energy is increasing, it is not possible to replace fossil fuel-based power plant by renewable one in near future. As substantial part of industrial energy input through combustion of fuel is rejected as waste heat, this waste heat can also be utilized to produce secondary energy through innovative cycles. This would reduce fossil fuel consumption and corresponding emission of greenhouse gases to some extent. It should be noted that steam-based Rankine cycle is the best possible option for producing power from any heat source available at or above 200°C. Conversion of available waste heat into power is very challenging if temperature of the heat source is below 200°C. In the present study, low grade heat driven cycles (power cycles as well as combined power & refrigeration cycle) are proposed to achieve better thermodynamic performance. The cycles are assumed to be driven by low grade heat of the flue gas with temperature ranging from 150°C to 200°C.