Enrichment of Iron from Bauxite Waste in Chemical Looping Combustion

Abstract

A method of recovering enriched iron fines from bauxite waste includes calcining particles of bauxite waste to form oxygen carrier particles, subjecting the oxygen carrier particles to chemical looping combustion at a temperature of about 950° C.-1,050° C. for energy production and to produce the enriched iron fines as a by-product from the oxygen carrier particles via natural attrition and collecting the enriched iron fines.

What is claimed: 
     
         1 . A method of recovering enriched iron fines from bauxite waste, comprising:
 calcining particles of bauxite waste to form oxygen carrier particles;   subjecting the oxygen carrier particles to chemical looping combustion at a temperature of about 950° C.-1,050° C. by (a) cyclically reducing the oxygen carrier particles in presence of a gaseous reducing agent and absence of a solid reducing agent that generates combustion ash and (b) oxidizing the oxygen carrier particles in presence of an oxidizing agent to produce energy and the enriched iron fines as a by-product from the oxygen carrier particles via natural attrition; and   collecting the enriched iron fines.   
     
     
         2 . The method of  claim 1 , wherein the calcining of the particles of bauxite waste includes heating the particles of bauxite waste to a predetermined temperature for a predetermined period of time needed to form the oxygen carrier particles. 
     
     
         3 . The method of  claim 1 , wherein the gaseous reducing agent is selected from a group of reducing agents consisting of hydrogen, carbon monoxide, gaseous fuels and mixtures thereof. 
     
     
         4 . The method of  claim 1 , wherein the gaseous reducing agent is provided at a concentration of 5-20 vol %. 
     
     
         5 . The method of  claim 1 , wherein the gaseous reducing agent is provided at a concentration of 10-20 vol %. 
     
     
         6 . The method of  claim 1 , wherein the gaseous reducing agent is provided at a concentration of 12-18 vol %. 
     
     
         7 . The method of  claim 1 , wherein the gaseous reducing agent is provided at a concentration of about 15 vol %. 
     
     
         8 . The method of  claim 1 , wherein the gaseous reducing agent is provided at a concentration of greater than 10 vol %. 
     
     
         9 . The method of  claim 1 , wherein the gaseous reducing agent is provided at a concentration of greater than 12 vol %. 
     
     
         10 . The method of  claim 1 , wherein the gaseous reducing agent is provided at a concentration of greater than 15 vol %. 
     
     
         11 . The method of  claim 1 , further including purging the reactor bed with an inert gas between reducing and oxidizing. 
     
     
         12 . The method of  claim 1 , wherein the oxidizing agent is air or oxygen mixed with a type of inert gas at greater than 4 vol %. 
     
     
         13 . The method of  claim 1 , wherein the collecting of the iron enriched fines is done by using a gas-solid separation device, a baghouse, an electrostatic precipitator, a cyclone or a combination thereof. 
     
     
         14 . The method of  claim 1 , wherein (a) the reducing includes subjecting the oxygen carrier particles in a reactor bed to heating, cooling or maintaining temperature in the presence of a reducing agent, and (b) the oxidizing includes subjecting the oxygen carrier particles in the reactor bed to heating in the presence of an oxidizing agent. 
     
     
         15 . The method of  claim 14 , wherein the heating of the oxygen carrier particles during the reducing and the oxidizing cycles is to a temperature of between about 950° C. and about 1050° C. 
     
     
         16 . The method of  claim 1 , further including maintaining an oxygen transport capacity of 3.5-5.0 during processing. 
     
     
         17 . The method of  claim 1 , further including maintaining a superficial velocity of 0.2-0.4 m/s during processing. 
     
     
         18 . The method of  claim 1 , further including using bauxite waste characterized by having about 40-45 wt % Fe 2 O 3  and about 55-60 wt % inert phases, a skeleton density of less than 4,000 kg/m 3  and a mean crush strength greater than 7.5 N. 
     
     
         19 . A method of recovering enriched iron fines from bauxite waste, comprising:
 calcining particles of bauxite waste to form oxygen carrier particles;   subjecting the oxygen carrier particles to chemical looping combustion at a temperature above 1000° C. by (a) cyclically reducing the oxygen carrier particles in presence of a gaseous reducing agent and absence of a solid reducing agent that generates combustion ash and (b) oxidizing the oxygen carrier particles in presence of an oxidizing agent to produce a spent flue gas and the enriched iron fines as a by-product from the oxygen carrier particles via natural attrition;   collecting the enriched iron fines from the spent flue gas; and   using the spent flue gas to generate steam for power generation.   
     
     
         20 . A method of recovering enriched iron fines from bauxite waste, comprising:
 subjecting the oxygen carrier particles made from bauxite waste to chemical looping combustion at a temperature above 1000° C. by (a) cyclically reducing the oxygen carrier particles in presence of a gaseous reducing agent and absence of a solid reducing agent that generates combustion ash and (b) oxidizing the oxygen carrier particles in presence of an oxidizing agent to produce a spent flue gas and the enriched iron fines as a by-product from the oxygen carrier particles via natural attrition;   collecting the enriched iron fines; and   using the spent flue gas, following the collecting of the enriched iron fines, to generate steam for power generation.