Steel mill thermal energy recovery for calcination

Abstract

The invention relates to a steelmaking thermal energy recovery system. The steelmaking thermal energy recovery system comprises a steelmaking waste flue gas, a calcinable material, and a kiln. The steelmaking waste flue gas provides at least a portion of the thermal energy to the kiln for calcination of the calcinable material.

We claim:  
     
         1 . A steelmaking thermal energy recovery system comprising: 
 a steelmaking waste flue gas;    a calcinable material; and    a kiln wherein the steelmaking waste flue gas provides at least a portion of the thermal energy to the kiln for calcination of the calcinable material.    
     
     
         2 . The steelmaking thermal energy recovery system of  claim 1 , further comprising an air control system for dilution of the waste flue gas to maintain gas temperatures.  
     
     
         3 . The steelmaking thermal energy recovery system of  claim 2 , wherein the waste gas temperature is maintained from about 1650 to about 2010° F.  
     
     
         4 . The steelmaking thermal energy recovery system of  claim 1 , wherein the steelmaking waste flue gas is a hot rolling mill tunnel furnace flue gas.  
     
     
         5 . The steelmaking thermal energy recovery system of  claim 1 , wherein the calcinable material comprises limestone.  
     
     
         6 . The steelmaking thermal energy recovery system of  claim 1 , wherein the calcinable material comprises dolomitic limestone.  
     
     
         7 . The steelmaking thermal energy recovery system of  claim 1 , wherein the kiln is a rotary kiln, a vertical kiln, a rotary hearth kiln, a fluidized bed kiln, or a regenerative lime kiln.  
     
     
         8 . The steelmaking thermal energy recovery system of  claim 1 , wherein the kiln does not have a lime cooling zone.  
     
     
         9 . The steelmaking thermal energy recovery system of  claim 1 , wherein the kiln is adjustable to produce varying degrees of calcination from between about 20% to about 100% calcinated.  
     
     
         10 . The steelmaking thermal energy recovery system of  claim 1 , wherein the steelmaking thermal energy recovery system comprises the captive production of at least a partially calcined material to a steelmaking facility.  
     
     
         11 . The steelmaking thermal energy recovery system of  claim 10 , wherein the captive production comprises storing and transporting the at least partially calcined material at elevated temperatures.  
     
     
         12 . The steelmaking thermal energy recovery system of  claim 11 , wherein the elevated temperatures comprise about 200° F. to about 2,000° F.  
     
     
         13 . The steelmaking thermal energy recovery system of  claim 1 , wherein the captive production comprises adding the at least partially calcined material to a steel melting furnace.  
     
     
         14 . A means of providing the thermal energy requirement for calcination operations located adjacent to steel making operations by re-using waste off gases from the steelmaking operation.  
     
     
         15 . A method of calcinating limestone comprising: 
 providing a kiln;    supplying limestone as feedstock for calcination;    further providing a steel manufacturing operation's hot waste gases as a heat source; and    heating the limestone within the kiln to the calcination temperature.    
     
     
         16 . The method of  claim 15 , wherein the steel manufacturing operation is a hot strip mill tunnel furnace.  
     
     
         17 . The method of  claim 15 , further comprising calcinating from about 20% to about 100% complete calcination.  
     
     
         18 . The method of  claim 15 , wherein the step of supplying limestone further comprises supplying limestone as dolomitic limestonestone.  
     
     
         19 . The method of  claim 15 , further wherein the step of supplying limestone further comprises supplying a low-grade lime.  
     
     
         20 . The method of  claim 15 , wherein the step of supplying limestone further comprises supplying a partially calcined limestone material from a conventional calcining operation.  
     
     
         21 . The method of  claim 15 , wherein the waste steelmaking operation gases comprise about 20% to about 100% of the total thermal energy required for the calcination.  
     
     
         22 . A method of steelmaking comprising: 
 making a first heat of steel in a melting operation;    converting the heat to slabs;    heating the slabs;    capturing hot off gases from the heating of slabs; and    supplying the hot off gases to a calcination process.    
     
     
         23 . The method of  claim 22 , further comprising the step of supplying limestone as feedstock to the calcination process.  
     
     
         24 . The method of  claim 23 , wherein the limestone feedstock for calcination comprises calcium and dolomitic limestone.  
     
     
         25 . The method of  claim 23 , further comprising the step of at least partially calcinating the limestone with the hot off gases.  
     
     
         26 . The method of  claim 23 , further comprising packaging the calcinated product at an elevated temperature of about 200° to 2,000° F.  
     
     
         27 . The method of  claim 23 , further comprising the step of supplying the calcinated product back to the melting operation to form slag in a second heat of steel.  
     
     
         28 . The method of  claim 27 , wherein the limestone added back to the melting operation comprises an elevated temperature of about 200 to 2,000° F.  
     
     
         29 . A captive calcination facility comprising: 
 a raw material wherein the raw material comprises at least some calcinable material;    a waste flue gas from a steel making continuous process;    a kiln wherein the steelmaking waste flue gas provides at least a portion of the thermal energy to the kiln to calcinate the calcinable material; and    a steel melting operation wherein at least a portion of the calcinated material from the kiln is added to the steel to form slag.