Method and Equipment for Heat Recovery

Abstract

The present invention relates to a method and equipment for recovering heat from exhaust gas removed from an industrial process, such as an electrolysis process for the production of aluminium. Heat is recovered by means of an extraction/suction system, where the exhaust gas contains dust and/or particles. The heat is recovered as the exhaust gas is brought into contact with heat-recovery elements. Flow conditions and the design of the heat recovery elements are such that the deposits of the dust and/or particles on the surfaces stated are kept at a stable, limited level. In preferred embodiments, the heat-recovery elements have a circular or an extended, elliptical cross-section and may be equipped with fins or ribs.

1 - 14 . (canceled) 
   
   
       15 . A method for recovering heat from exhaust gas removed from an industrial process by means of an extraction/suction system, where the exhaust gas contains dust and/or particles, and where the heat is recovered by the exhaust gas being brought into contact with the external surface of one or more heat-recovery elements, wherein
 the elements are designed with respect to parameters of the exhaust gas in such a way that the deposits of the dust and/or particles on the surfaces stated are kept at a stable, limited level.   
   
   
       16 . A method in accordance with  claim 15 , wherein the flow speed of the exhaust gas is higher than 10 m/s and less than 25 m/s. 
   
   
       17 . A method in accordance with  claim 15 , wherein the temperature of the exhaust gas is in the order of 120° C.-600° C. 
   
   
       18 . A method in accordance with  claim 15 , wherein the industrial process is an electrolysis process for production of aluminium. 
   
   
       19 . A method in accordance with  claim 18 , wherein the velocity of the exhaust gas is 12 m/s. 
   
   
       20 . A method in accordance with  claim 18 , wherein the gas is raw from one or more electrolysis cells. 
   
   
       21 . Equipment for recovering heat from an exhaust gas containing dust and/or particles that is removed from an industrial process by means of an extraction/suction system or equivalent, where the equipment comprises at least one hollow element designed to allow a heat-recovery medium to flow through it, the stated hollow element(s) is(are) positioned principally so that the prevailing longitudinal direction of the element(s) is across the prevailing direction of flow of the exhaust gas, wherein
 the hollow element(s) is(are) furthermore designed with respect to parameters of the exhaust gas so that deposits caused by the dust and/or particles are kept at a limited, stable level.   
   
   
       22 . Equipment in accordance with  claim 21 , wherein the hollow element or elements is/are designed to have a principally circular cross-section. 
   
   
       23 . Equipment in accordance with  claim 21 , wherein the hollow element or elements is/are designed to have a principally extended, oval cross-section, where the longitudinal axis of the cross-section is principally coincident with the prevailing direction of flow of the exhaust gas. 
   
   
       24 . Equipment in accordance with  claim 21 , wherein the hollow element or elements is/are equipped with ribs or fins for improved heat recovery. 
   
   
       25 . Equipment in accordance with  claim 21 , wherein the heat-recovery medium is water/steam or air. 
   
   
       26 . Equipment in accordance with  claim 21 , wherein the hollow element or elements is/are made of galvanized carbon steel. 
   
   
       27 . Equipment in accordance with  claim 21 , wherein at least one hollow element is enclosed by walls that form a channel section for coupling to/integration with the extraction/suction system.