Abstract: Remarkable suppression of the formation of pollutants: NO.sub.x, CO and UHC, in the flameless combustion of gaseous fuel with excess air is achieved by passing the fuel and air through a porous surface combustor directly into an adiabatic zone, and by controlling the amount of excess air to be greater than about 50% but not greater than about 150% in excess of the stoichiometric requirement. The furnace with the adiabatic zone for the suppression of pollutants will preferably have a refractory body as part of the adiabatic zone.

Abstract: A dryer for paper and similar fibrous web materials including a dryer roll having an outer cylindrically-shaped wall, a radiant heat source within the dryer roll adapted to heat the wall substantially uniformly about the entire periphery thereof, and nip-forming means forming a pressure nip with the dryer roll.

Abstract: A segmented radiant burner assembly for installation in the combustion chambers of firetube boilers and the like. The individual segments can be assembled together for on-site installation within the boiler. The segments include support structures comprising mounting flanges which are secured together in series to form the burner assembly. Gas and thermal sealing between the active material of the burner and the inactive support structure is provided by a sealing system which includes a dense fiber composition material and adhesive agent of ceramic composition. The mixture of unburned reactants is directed through a valving and manifold system into separate plena within the burner segments. The flow rates of reactants to the different burner segments is selectively controlled in a sequence which achieves a broad firing rate range.

Abstract: The burner system is adapted for retrofit into the combustion chambers of firetube boilers. The burner is comprised of a hollow shell molded from a porous ceramic fiber matrix. Fuel and air reactants flow outwardly through the fiber matrix shell and are combusted along a shallow reaction zone on the outer surface. Heat is transferred primarily by radiation to the walls of the combustion chamber at temperatures which result in relatively low NO.sub.x emissions and high combustion efficiencies as compared to boiler systems with conventional burners.

Abstract: A process and system of operation for combusting nitrogen-containing fuels with resulting low NO.sub.x emissions. A fuel-rich mixture of the fuel is combusted in a catalytic bed which is carried by a support structure. Active or passive means are provided for limiting transfer of heat from the bed into the support structure for minimizing formation of NO.sub.x during combustion. The active means for limiting the heat transfer includes, in different embodiments, electrical resistance back heating, induction back heating, exhaust gas back heating, and combustion fired back heating. The passive means for limiting the heat transfer includes, in different embodiments, a body of heat insulating material between the bed and support structure, or the insulating effect of the outer cells of the bed within a recess in the support structure.

Abstract: A process and system for combusting a nitrogen-containing fuel to produce low NO.sub.x levels in the exhaust emissions. A stream of the fuel mixed with air is combusted in two or more fuel-rich zones having catalytic beds. The stoichiometry of the mixture in each zone is controlled for the particular catalytic material employed so that a minimum of NO.sub.x precursors is formed upon combustion in the zones. Additional air is injected into the flow to maintain the predetermined stoichiometry in the downstream zones. The beds of the fuel-rich zones can be comprised of different catalytic materials having different theoretical air proportion at which the NO.sub.x precursors are at a minimum. The beds of the fuel-rich zones can also be comprised of the same catalyst material having different minima at which NO.sub.x precursors are formed at different theoretical air proportions.

Abstract: A process and system of apparatus for stoichiometrically combusting fuel and air reactants. A stream of the reactants is directed through an upstream zone for combustion about cylinders comprised of a catalytic material. A plurality of heat sink conduits are spaced about the cylinders for absorbing radiant energy from the cylinders, and a coolant medium is directed through the conduits for extracting thermal energy at a controlled rate. Products from the upstream zone are directed through a combustor in a downstream zone for adiabatic combustion, and products from the combustor are directed in heat exchange relationship with a coolant medium which extracts residual energy from the stream.