Proceedings of the
Second International Energy 2030 Conference,
November 4-5, 2008, Abu Dhabi, U.A.E.
Clean Power Generation from Wastes using
High Temperature Air Combustion Technology
Prof. Ashwani K. Gupta
University of Maryland, USA
Abstract
The flameless oxidation of fuels or high temperature combustion is new and innovative means for the
conversion of chemical energy to thermal energy of fuels. In excess enthalpy combustion the thermal
energy released is fed back to the fresh reactants so that the temperatures obtained with excess enthalpy
combustion are much higher than its counterpart with normal temperature air. However, flameless or
colorless oxidation of fuels is obtained by using the fundamental design principles of High Temperature
Air Combustion (HiTAC) technology in which high temperature combustion air at low oxygen
concentration (obtained by heat and gas recirculation) is used in the combustion chamber. High
temperature of the air is obtained by preheating the air with the exhaust gases from a furnace or reactor.
The peak temperature in the flame zone is much reduced with the use of diluted low oxygen concentration
combustion air even though the air is preheated to high temperatures. This low oxygen concentration (or
diluted) air is obtained from the exhaust gases by recirculating part of the combustion products into the
incoming hot combustion air. The combustion air is preheated to temperatures in excess of 1000 oC,
depending on the application, using honeycomb type or ceramic ball type heat exchangers. Honeycomb
type heat exchangers are more effective than the ceramic ball type heat exchangers. Most of the previous
research activities have been focused on gaseous fuels, such as, methane, propane, liquefied petroleum gas
(LPG) and process gases. The HiTAC technology has also been demonstrated to provide significant
benefits with wastes and low grade fuels for applications to various processes, and industrial and power
systems.
Waste generation is one of the main environmental problems faced by almost all countries around the
World. The waste problem is of serious concern in almost all the developed countries, including UAE.
Stable and increased annual solid waste generation imposes new challenges for waste management. In the
traditional solution of landfill one can find either new terrains or overload the existing landfills. One of the
solutions is to decrease the volume of wastes disposed at landfills sites by recycling selected materials
(e.g., glass, metals, paper, etc.) or use some thermal destruction method to destruct the waste. Incineration
is a feasible method since municipal solid wastes are characterized by an average heating value of 5,500
Btu/lb (or 12,793 J/g). Selected wastes can also be used as co-firing fuels in furnaces and boilers. Some of
the methods in thermal destructive option include pyrolysis and gasification of wastes. Gasification is
thermochemical conversion of any solid, liquid or gaseous carbonaceous material by means of free or
bound oxygen at increased temperatures, usually in the range of 700-1800 oC. High temperature air
combustion technology offers clean energy conversion of wastes and low grade fuels to gaseous fuels.
