Electric furnace waste heat recovery method and apparatus
AssigneeJoetsu Denro Kogyo Co., Ltd.
InventorsKoichi Horibe, Minoru Watanabe, Tokuji Machida
Life of this patent
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Abstract
Useful heat is recovered from electric furnaces using two heat recovery systems. Primary heat recovery is effected using liquid water or other cooling liquid and is performed in such a manner that the temperature of the liquid does not exceed its boiling point at atmospheric pressure. Secondary heat recovery is effected by indirect heat exchange between the exhaust gas of the furnace and a gaseous cooling medium and is performed in such a manner that the gaseous medium is heated to a temperature above the boiling point of the cooling liquid. A part or the entirety of the cooling liquid is then heated by the gaseous medium.
Claims8
In an electric furnace that discharges a high temperature exhaust gas laden with dust, said furnace comprising electrode means having first cooling means associated therewith, a cover having conduit means for discharging the exhaust gas from the furnace and having second cooling means associated with said conduit means, means for circulating a first liquid coolant through said first and second cooling means for cooling said electrode means and said conduit means whereby to discharge said first coolant in a heated liquid state under atmospheric pressure;
- a first heat exchanger having internal tube means connected to said conduit means for receiving exhaust gas therefrom, said internal tube means being constructed so as to repel adhesion of dust present in said exhaust gas and so as to be easily cleanable if dust is deposited thereon, said first heat exchanger including means to circulate a second gaseous coolant in indirect heat exchange relationship with said internal tube means whereby to discharge from said first heat exchanger a stream of second gaseous coolant heated to a temperature higher than the boiling point of said first coolant;
- and a second heat exchanger connected to receive and to effect heat exchange between said first coolant and said second coolant whereby said first coolant is heated to a higher temperature.
A process for recovering waste heat from an electric furnace that discharges a high-temperature exhaust gas having high dust loading, which comprises the steps of:
- in a primary heat recovery stage, flowing a relatively cool, heat-exchange liquid in indirect heat-exchange relationship with the high-temperature exhaust gas discharged from said furnace so that said heat-exchange liquid removes heat from the exhaust gas whereby to partially cool the exhaust gas and to effect primary heat recovery therefrom, and thereby heating said heat-exchange liquid to a temperature lower than the boiling point thereof under atmospheric pressure, and then discharging said heated heat-exchange liquid from said primary heat recovery stage into an atmospheric pressure zone;
- in a secondary heat recovery stage, flowing the partially cooled exhaust gas through tube means constructed to repel adhesion of dust and to permit easy removal of any dust deposited thereon and simultaneously passing a relatively cool heat-exchange gas along the opposite side of said tube means in indirect heat-exchange relationship with the exhaust gas so that said heat-exchange gas removes heat from the exhaust gas and is heated to a temperature higher than the boiling point of said heat-exchange liquid, and discharging said heated heat-exchange gas from said secondary heat recovery stage;
- and in a final heat recovery stage, flowing said heat-exchange liquid from said atmospheric pressure zone in heat-exchange relationship with said heat-exchange gas that was discharged from said secondary heat recovery stage, whereby to raise the temperature of said heat-exchange liquid.
Dependencies are inferred from the claim text.