Power Production from Waste Gasification / Thermal Oxidation
IET’s Waste Gasification / Thermal Oxidation (WG/TO) system is an environmentally safe process for the destruction of solid waste. This is achieved as a two-stage process.
The first stage is called the Primary. In this stage, waste is loaded directly into the primary cells without need for preprocessing or sorting of any kind. When the cell is full, the load doors are closed and the process started. A supplemental fuel burner is used to heat the primary cell to a temperature of about 450°F. At this time, the burner can be shut off and the temperature is controlled by opening or closing an air-inlet valve, typically maintaining temperatures between 700 and 1,000°F. The primary operates as a sub-stochiometric process, maintaining oxygen levels in the primary at a point that is too low for open combustion. This environment promotes the conversion of the solids into a gas. This gas is a low-Btu mixture primarily made up of carbon monoxide and volatile organic compounds.
The gas from the primary is vented into a secondary chamber, commonly called the Secondary. Here, the gas passes through a specially designed air ring that brings the oxygen levels back up to a point that makes the gases combustible. This gas is then ignited by the secondary burners. The gas burns to complete combustion, eliminating all of the CO and volatile organic compounds. The resulting temperature is typically in the range of 1,600 to 2,000°F.
The resulting hot air from the secondary can then be vented through a waste heat boiler to produce steam. This steam is then routed through a steam turbine to produce electrical power. From a typical 100 ton per day system, enough gas is produced to generate 4.0 MW of electrical power. Variations in waste composition can influence the total amount of power produced.
As system sizes get larger, the efficiency of boilers and turbines increase and the per-ton power production may increase by 50%.