Heating – Work chamber having heating means – Combustion products heat work by contact
Patent
1997-08-28
2000-03-14
Jeffery, John A.
Heating
Work chamber having heating means
Combustion products heat work by contact
432179, F27D 1700
Patent
active
060364866
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to the recovery of heat from furnaces and, more particularly, the recovery of heat from fuel fired furnaces utilizing cassette regenerators.
2. Description of the Prior Art
Most commercial glass is produced in high temperature air/fuel furnaces where solid raw materials are melted, reacted to form stabilized silicates and degassed of entrained gases to allow downstream forming of a homogeneous product. Energy input to the furnace in the form of natural gas or oil firing and electrical resistance heating (electric boosting) melts the raw materials, provides heat of reaction and raises the molten temperature while decreasing viscosity to allow for proper degassing of the glass. The vast majority of these furnaces use air to support combustion. Different furnace designs have evolved in each segment of the glass industry which are specifically tailored to the particular demands of the end use product. Examples of traditional furnace designs include the regenerative melter, recuperative melter, all-electric melter and direct fired unit melter.
By far, the dominant furnace design for the glass industry is the regenerative melter. A typical regenerative melter includes at least two burners, two regenerators, a flow reversal system and associated controls. Paired sets of burners are located on opposed sides of the furnace or are end port fired where both systems are on the same wall of the furnace. A heat regenerator communicates with each burner. The burners and regenerators are closely coupled by a length of refractory lined duct to suit the space available on site. When the first burner of a pair fires, using combustion air fed to the base of its regenerator, the second burner of the pair acts as an exhaust port drawing off waste gas, thereby heating the regenerator for the second burner. When this heated regenerator is sufficiently charged, the reversal system operates to reverse the firing system. The second burner of the pair fires to heat the furnace and the first burner, in time, acts as an exhaust port, thereby heating the regenerator for the first burner. The combustion air is then directed through the hot regenerator of the second burner to preheat the air prior to combustion. After a period of time, the flow of exhaust gases and combustion air through the regenerators is again reversed to maintain heating of the combustion air.
These regenerators typically take the form of latticed brick work or "checkers" through which the combustion air passes on its way to the burner to preheat the combustion air and through which the exhaust gases from the furnace pass on their way to the stack. The exhaust gases transfer their sensible heat to the regenerator bricks as they pass through. On the reverse cycle, clean combustion air brought in at ambient temperature is passed through the previously heated regenerator of the firing burner and thus picks up sensible heat from the bricks. In this way, the regenerator preheats the air prior to combustion.
In an alternative traditional furnace design, recuperative heat exchangers, rather than regenerators, are used to preheat the combustion air. Recuperative heat exchangers differ from regenerative heat exchangers in that the exhaust gases and combustion air flow through different piping systems and do not mix. The recuperator acts as a simple indirect heat exchanger. Heat from the exhaust gases flowing through one conduit is transferred to combustion air flowing through another conduit.
As an alternative to conventional air/fuel furnaces, oxy-fuel fired furnaces have been developed. In an oxy-fuel fired furnace, oxygen gas instead of air is used to support combustion. Unlike conventional air/fuel furnaces, the oxygen is not preheated prior to being mixed with the fuel such as natural gas or oil. Therefore, no regenerators or recuperators are typically associated with oxy-fuel fired furnaces. Oxy-fuel fired furnaces offer some advantages over typical air/fuel furnaces, such as generally
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Air Products and Chemicals, Inc., Development of an Advanced Glass Melting System--The Thermally Efficient Alternative Melter, Feb. 1992, p. 138.
John Bost, The Use of Waste-Heat Gases from a Glass Furnace to Operate a Turbine, pp. 37-42.
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Argent Ronald D.
Dickinson Gordon
Hoyle Christopher J.
Ward Trevor
Frazier-Simplex, Inc.
Jeffery John A.
Wilson Gregory A.
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