Burners with high turndown ratio

Abstract

Various burner configurations for combustion of a particulate fuel such as sawdust, and many types of varying moisture content biomass fuels such as poultry litter. The burners exhibit a high turndown ratio. the burners include a housing defining an upright combustion chamber lined with refractory material and generally circular cross section, a main combustion region within an upper extent the combustion chamber, an initial combustion zone at a lower end of the combustion chamber of reduced-size cross-section compared to the combustion chamber and a transition region increasing in cross-section from the initial combustion zone to the main combustion region. A principal fuel (e.g., sawdust) is supplied with combustion air to the initial combustion region, and an auxiliary ignition fuel supplies heat to the initial combustion region for igniting the principal fuel. Multiple sets of tuyeres are provided for controllably introducing combustion air tangentially regions of the combustion chamber for contributing to cyclonic combustion flow in such a manner as to increase diameter of combustion upwardly within the combustion chamber. A counterflow arrangement, e.g., counterflow tuyere, disrupts cyclonic flow near a ceiling of the combustion chamber, through which a choke or exit provide escape from the combustion chamber of exhaust gases resulting from combustion. In operation, the principal fuel is ignited in the initial combustion region, and burns with cyclonic flow extending upwardly through the transition region with increasingly greater combustion diameter into the combustion chamber. A smoke or combustible gas combustor may be combined into the burner, so that that burner provides its high temperature air for preheat purposes to the combustor, which includes a venturi at which further combustion air is introduced for complete combustion in a gas combustion chamber of the combustor.

Dependencies are inferred from the claim text.