Gas atomization of molten materials using by-product off-gases

Abstract

Metallurgical processes and systems for gas atomization of molten slag and/or molten metals from a metallurgical furnace are integrated with off-gas handling processes and equipment, such that the off-gases are fed to the gas atomization plant for atomizing the molten slag and/or molten metal. The use of by-product off-gases for atomizing molten slag and/or molten metals provides a number of benefits, including elimination of off-gas handling and treatment equipment, centralization and upgrading of heat via atomization to improve heat recovery, prevention of oxidation of granular products of atomization, and reduction of CO 2 emissions. A process for preparing a granular product comprises: feeding a molten material and a by-product off-gas to a dispersion apparatus; and contacting the gas with the molten material in the dispersion apparatus, whereby the molten material is dispersed and solidified by contact with the gas to form the granular product.

1 . A process for preparing a granular product, comprising:
 (a) providing a molten material;   (b) feeding the molten material to a dispersion apparatus;   (c) feeding a gas to the dispersion apparatus, wherein the gas is a by-product off-gas;   (d) contacting the gas with the molten material in the dispersion apparatus, whereby the molten material is dispersed and solidified by contact with the gas to form said granular product.   
     
     
         2 . The process of  claim 1 , wherein the molten material is molten metal or molten slag produced by a metallurgical process conducted in a metallurgical furnace. 
     
     
         3 . The process of  claim 2 , wherein the molten material is molten metal and wherein the granular product comprises metal granules. 
     
     
         4 . The process of  claim 2 , wherein the molten material is molten slag and wherein the granular product comprises slag granules. 
     
     
         5 . The process of  claim 2 , wherein the dispersion apparatus comprises a gas atomization plant. 
     
     
         6 . The process of  claim 5 , further comprising an induced draft (ID) fan for blowing the by-product off-gas to the dispersion apparatus. 
     
     
         7 . The process of  claim 6 , wherein the metallurgical furnace includes a furnace cooling system, wherein the by-product off-gas comprises air exhausted by the furnace cooling system, and whereby the ID fan extracts the air from the furnace cooling system. 
     
     
         8 . The process of  claim 6 , wherein the by-product off-gas comprises a furnace off-gas from an interior of the metallurgical furnace, and whereby the ID fan extracts the furnace off-gas from the metallurgical furnace. 
     
     
         9 . The process of  claim 6 , wherein the gas atomization plant produces a hot off-gas, and wherein the hot off-gas is used in downstream process equipment for energy transfer. 
     
     
         10 . The process of  claim 9 , wherein the downstream process equipment comprises a drying unit or a pre-heating unit. 
     
     
         11 . The process of  claim 10 , wherein the by-product off-gas supplied to the gas atomization plant is laden with particulates. 
     
     
         12 . The process of  claim 3 , wherein the off-gas supplied to the gas atomization plant is substantially oxygen-free. 
     
     
         13 . The process of  claim 1 , wherein the by-product off-gas is substantially oxygen-free and is enriched in one or more gases selected from the group consisting of N 2 , H 2 O, CO 2 , CO, H 2  and SO 2 . 
     
     
         14 . The process of  claim 12 , wherein the molten material atomized using the by-product off-gas becomes less oxidized than material that would have otherwise been atomized by air. 
     
     
         15 . The process of  claim 1 , wherein the dispersion apparatus comprises a gas atomization plant;
 wherein the gas atomization plant produces a hot off-gas;   wherein the off-gas supplied to the gas atomization plant includes an undesirable component; and   wherein the undesirable component contained in the off-gas supplied to the gas atomization plant is contacted with the molten material during the formation of said granular product, such that a concentration of the undesirable component in the hot off-gas is less than a concentration of the undesirable component in the off-gas supplied to the gas atomization plant.   
     
     
         16 . The process of  claim 15 , wherein the undesirable component is a gas or a particulate solid. 
     
     
         17 . The process of  claim 15 , wherein the undesirable component is CO 2 , a sulphur-containing species such as SO 2 , SO 3 , and H 2 S; a nitrogen oxide selected from NO and NO 2 , a phosphorus-containing gas; a gaseous organic species; fluorides (such as HF and SiF 4 ), and combinations of one or more thereof; and
 wherein at least a portion of the undesirable component is dissolved in the molten material during formation of said granular product.   
     
     
         18 . The process of  claim 17 , wherein the gaseous organic species is selected from furans and dioxins, and combinations thereof; and
 wherein at least a portion of the gaseous organic species is combusted and/or dissolved in the molten material during formation of said granular product.   
     
     
         19 . The process of  claim 15 , wherein the undesirable component is a particulate solid. 
     
     
         20 . The process of  claim 19 , wherein the particulate solid is dust; and wherein the dust becomes incorporated into the granular product during the formation of the granular product. 
     
     
         21 . The process of  claim 15 , wherein the undesirable component is CO 2 ; and wherein a portion of the CO 2  in the off-gas supplied to the gas atomization plant is captured in the granular product. 
     
     
         22 . The process of  claim 21 , wherein the hot off-gas produced by the gas atomization plant is converted to synthetic gas in a downstream reformer. 
     
     
         23 . A system for preparing a granular product, comprising:
 (a) a metallurgical furnace containing a molten material selected from one or more of molten metal and molten slag;   (b) a gas atomization plant located proximate to the metallurgical furnace;   (c) a gas supply system for supplying a by-product off-gas to the gas atomization plant;   (d) a molten material supply system for transporting the molten material from the metallurgical furnace to the gas atomization plant.   
     
     
         24 . The system of  claim 23 , wherein the molten material comprises slag, and wherein the molten material supply system comprises a slag vessel or launder. 
     
     
         25 . The system of  claim 23 , further comprising an ID fan for blowing the by-product off-gas to the gas atomization apparatus. 
     
     
         26 . The system of  claim 25 , wherein the system further comprises an air cooling system for cooling the metallurgical furnace. 
     
     
         27 . The system of  claim 26 , wherein the by-product off-gas comprises air exhausted by the furnace air cooling system, and wherein the system further comprises a conduit for conveying the by-product off-gas from the furnace to the gas atomization plant. 
     
     
         28 . The system of  claim 23 , wherein the by-product off-gas comprises off-gases exhausted from the metallurgical furnace, and wherein the system further comprises a conduit for conveying the by-product off-gas from the metallurgical furnace to the gas atomization plant. 
     
     
         29 . The system of  claim 28 , further comprising a fume and dust capture hood for collecting the off-gases exhausted from the metallurgical furnace, wherein the conduit for conveying the by-product off-gas to the gas atomization plant is adapted to receive the off-gases from the fume and dust capture hood. 
     
     
         30 . The system of  claim 23 , wherein the molten material atomized using the by-product off-gas becomes less oxidized than material that would have otherwise been atomized by air. 
     
     
         31 . A product from off-gas atomization that is less oxidized than the same product atomized through an air atomization plant.