The Waste Heat Recovery (WHR) System consists of a steam generation unit and a power generation unit. The steam generation unit is a set of boilers placed in the path of the waste gases. The heat in the gases, sometimes supplemented by additional heat in the co- generation process, is used for generating steam. The steam can be used for other process requirements within the industrial plant, or used for driving a turbine that is connected to the generator. The generated power can either be used for running plant equipment or fed back to the power grid.

The recovered waste heat represents “green energy” since it is a direct savings in the use of fossil fuels with the consequent reduction of carbon dioxide emissions. Furthermore, cooling of the process gases is done without wasting scarce water or diluting with ambient air that would increase the energy consumption of the fans.

Several challenges exist, such as sticky and abrasive dust in the gas, or corrosive vapors such as SO2. The boiler must be custom-designed carefully to handle the specific characteristics of the off-gases. In special cases, like when there is a low gas temperature, an Organic Rankine cycle can be chosen instead of the steam cycle. The recovered waste heat represents “green energy” since it is a direct savings in the use of fossil fuels with the consequent reduction of carbon dioxide emissions. Furthermore, cooling of the process gases is done without wasting scarce water or diluting with ambient air that would increase the energy consumption of the fans.