These include wallboard grade gypsum and water contaminated with bitumen, heavy metals and ash. The gypsum is sold to wall board companies and the water is used in laying concrete bricks stored in specified sites. The nickel and vanadium can later be flaked out and sold to steal manufacturers. Thus, the recycling of byproducts is completed. The level of NOx emissions is kept low by a reburn process.
All fuels produce nitrogen oxides as a result of the combustion process.
Typical coal-fired boilers burn coal in a single combustion zone, injecting large amounts of air so that the fuel burns completely. The high flame temperatures cause concentrations of nitrogen in the air. This then reacts with the oxygen in the sir to form nitrogen oxide pollutants. Reburn technology helps to reduce NOx emissions by staging combustion in the boiler. Both fuel and air supplied to the main combustion zone are reduced.