Process and Technology
Wheelabrator Technologies’ energy from waste process is simple and proven over many years of continuous improvement and operational service.
The diagram below illustrates the process:
Weighed refuse lorries enter an enclosed reception area and unload into a concrete receiving pit. There are regular but random checks on the incoming lorries that are extensively inspected for waste that is unacceptable. Assuming the load is suitable overhead cranes transfer the refuse into one of a number of boiler feed hoppers. Inside each boiler an inclined, reciprocating grate system slowly moves the refuse through a combustion process in which temperatures exceed 1,370 degrees Centigrade. Such heat ensures the complete combustion of the refuse. Air for the combustion process is drawn from the enclosed reception area, which maintains a negative pressure and thereby preventing the release of odours or dust.
Highly engineered boilers surrounding the grate systems recover the thermal energy that is released during the combustion process and convert water in the boiler tubes into high-pressure steam. The steam is then used to drive a turbine generator to create electrical energy. Finally, depending upon local needs, the steam can be used for district heating, utilised once again through cooling or routed for industrial uses (sometimes known as Combined Heat and Power). The aim is to reduce any waste of energy or resources to an absolute minimum.
An integrated array of systems controls the emissions from the combustion process. These systems are the subject of constant development and innovation and include a selective non-catalytic reduction system to control ozone–forming nitrogen oxides, and state of the art spray dryer absorbers (also known as dry scrubbers) to control acid gases, heavy metals and organic pollutants. Activated carbon is injected into the flue gases to capture mercury and other trace elements, and fabric filters (often called bag houses) collect particulate matter down to the micro level. Between them these control systems thoroughly clean the emissions to meet the most rigorous standards set by national and local regulators. The whole cleaning process is constantly monitored and recorded by sophisticated computerised systems.
The whole plant is managed and monitored by computerised control systems that are constantly supervised by highly trained operators, ensuring our plants are always compliant with the highest standards.
Increasingly our potential customer partners, particularly in the UK and Europe, are looking to create plants aesthetically pleasing as well as environmentally safe and highly efficient. This has, therefore, become a significant element in the various bids we have made in the UK.
