Hague International

Aqua-chem, Inc.

Paul G LaHaye

John W Bjerklie

Gerald G Gallant, Jr

Kenneth G Hagen

Glenn D Craig

Robert A Penty

David T Feuling

Ivan G Most

An internally recirculating burner designed to operate at a low level of excess air without producing intolerable levels of particulate (smoke) and oxides of nitrogen using ambient or highly preheated atmospheric air as an oxidant. The burner operates with a flame front outside of the burner in the combustion chamber with recirculation of furnace gas being provided by the geometric configuration of the burner and the energy provided by the incoming combustion air. A nozzle means for controlling the combustion air flow is disclosed concentric with the burner center body. The nozzle is comprised of a fixed ceramic nozzle plate having annularly arranged distribution holes and a nozzle plus also preferably of ceramic supported to open and close the annular flow passage between the nozzle and the burner center body as well as the annular flow distribution holes. The air discharged through the nozzle flows along the surface of the center body creating a pressure depression at the point of discharge causing the furnace gas to flow from the furnace chamber to the passage formed by the burner barrel and the outside diameter of the recirculating sleeve. The recirculated gas joins the incoming combustion air and flows parallel to the combustion air through the annular passage formed by the inside diameter of the recirculating sleeve and the outside diameter of the center body. Some mixing of the combustion air and the recirculating gas occurs within the recirculating sleeve. A flame holder forming a portion of the center body central tube at the discharge end of the burner creates eddies and provides for a flame holding zone in which the fuel can be injected and the flame sustained. The flame thus formed extends into the combustion zone to the point at which the combustion reaction is completed.

Recirculating burner

The heat exchange tube has a porous thermal shock resistant outer shell composed of a corrosion resistant ceramic material that may have a finned outer surface or a plain cylindrical outer surface. The outer shell contains an inner tube composed of a dense nonporous ceramic which is capable of containing high pressure gases, but which may not be as thermally shock resistant or corrosion resistant as the outer shell. The inner tube is formed of a dense ceramic material such as a highly dense silicon carbide or silicon nitride having at each end a like density insert. The end inserts provide sealing surfaces to contact other components in the heat exchanger such as identical ceramic tube assemblies to form a gas-type pressure seal. The inner tube can be fabricated by a deposition technique such as a chemical or physical vapor deposition, and alternatively, can be made separately and press fitted into the outer shell or the outer shell can be cast or otherwise formed around the inner tube. As an alternative solution, the dense inner tube and end seals can be integrated into a single component performing the functions of all three components, i.e., the two end seals and the inner tube.

Composite ceramic heat exchange tube

A primary combustion chamber is located above a secondary combustion chamber with a support grate between the two for supporting particulate solid waste fuel to be burned efficiently. Primary air is introduced to the primary combustion chamber with secondary air introduced below the grate into a combustion gas flow to cause complete burning in the secondary combustion chamber. A brick wall screen means of high temperature, corrosion-resistant brick forms the secondary combustion chamber to allow exhaust gaseous product to exit therethrough while screening out ash which can be removed from the combustion area. The gaseous product passed through the screen is then passed to a heat exchanger to utilize part of the heat produced for heating primary and secondary air used in the combustor. The exhaust gas from the heat exchanger can then be put to use in a boiler or other energy producing device.

Solid fuel combustor and method of burning

An energy conserving process furnace has a recuperator to utilize heat derived from exhaust gases in order to reduce fossil fuel consumption of the furnace. Elongated, enhanced surface ceramic heat exchanger tubes are used in the recuperator to recover heat energy from the exhaust gas. A preferred sealing arrangement is used between the metal and ceramic tubes to contain the combustion air. Heat is added by the recuperator to combustion air used in a fluid fuel burner. The ceramic tubes are provided with vibration protective mechanisms to prolong useful life under severe mechanical vibration encountered in some applications. In a method of operating a slot furnace, exhaust gas is exhausted from a side of the furnace through the slot or a passageway having an elongated horizontal cross section. In the preferred arrangement a second passage or air curtain passageway is positioned adjacent the first passageway to permit proper gas flow through a recuperator. The recuperator is designed to recoup heat from exhaust gas in the first passageway and provide such heat as energy to heat combustion air used in the furnace. The second passageway by-passes the recuperator to avoid passing colder room air through the recuperator and to protect the operator from high temperature exhaust gas. The heat exchange ceramic tubes are designed to operate at temperatures of 1300.degree. F. and above without damage and with good sealing properties between elements. The system preferably includes a recirculating burner means which acts to reduce the combustion air requirements and to provide a combustion zone low in oxygen so as to prevent scale formation and oxidation of metals being treated in the furnace area.

Energy conserving process furnace system and components thereof

An energy conserving process furnace has a recuperator to utilize heat derived from exhaust gases in order to reduce fossil fuel consumption of the furnace. Elongated, enhanced surface ceramic heat exchanger tubes are used in the recuperator to recover heat energy from the exhaust gas. A preferred sealing arrangement is used between the metal and ceramic tubes to contain the combustion air. Heat is added by the recuperator to combustion air used in a fluid fuel burner. A recirculating burner has a flame front outside of the burner in the combustion chamber. The recirculating burner means acts to reduce the combustion air requirements and to provide a combustion zone low in oxygen so as to prevent scale formation and oxidation of metals being treated in the furnace area.

Fuel is burned in a primary combustion chamber with less than the air required for stoichiometric combustion so that the combustion gases have a high carbon monoxide (CO) and hydrocarbon content and the temperature of the gases is held below that at which significant nitrogen oxides (NO.sub.2) would be produced. The combustion gases are then passed through a secondary combustion zone in which more air is injected into the gas stream to oxidize the CO and hydrocarbons to carbon dioxide (CO.sub.2). The secondary burner comprises a plurality of foraminous tubes through which secondary air is emitted. Combustion in the secondary zone is maintained at a temperature below that at which nitrogen oxides (NO.sub.x) will be produced in significant quantities.

Reduction of gaseous pollutants in combustion flue gas

An energy conserving process furnace has a recuperator to utilize heat derived from exhaust gases in order to reduce fossil fuel consumption of the furnace. Elongated, enhanced surface ceramic heat exchanger tubes are used in the recuperator to recover heat energy from the exhaust gas. A preferred sealing arrangement is used between the metal and ceramic tubes to contain the combustion air. Heat is added by the recuperator to combustion air used in a fluid fuel burner. The ceramic tubes are provided with vibration protective mechanisms to prolong useful life under severe mechanical vibration encountered in some applications. In a method of operating a slot furnace, exhaust gas is exhausted from a side of the furnace through the slot or a passageway having an elongated horizontal cross section. In the preferred arrangement a second passage or air curtain passageway is positioned adjacent the first passageway to permit proper gas flow through a recuperator. The recuperator is designed to recoup heat from exhaust gas in the first passageway and provide such heat as energy to heat combustion air used in the furnace. The second passageway by-passes the recuperator to avoid passing colder room air through the recuperator and to protect the operator from high temperature exhaust gas. The heat exchange ceramic tubes are designed to operate at temperatures of 1300.degree. F and above without damage and with good sealing properties between elements. The system preferably includes a recirculating burner means which acts to reduce the combustion air requirements and to provide a combustion zone low in oxygen so as to prevent scale formation and oxidation of metals being treated in the furnace area.

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Cape Elizabeth, ME, United States of America

Paul G LaHaye