Clean fuel gas made by the gasification of coal

Abstract

A fuel preparation apparatus in which coal or coal and other carbon containing material is converted to an environmentally acceptable fuel gas by the reaction with air and steam at a pressure of from 20 to 90 pounds per square inch absolute suitable for providing fuel to a gas turbine, or a stoker type or other boiler having a coal delivery system, a coal crusher, coal storage bins, lock hoppers, a gasifier vessel of two stages, liquid and solid separator vessels, heat and steam recovery vessels, equipment to control the flow of steam and air to the gasifier so as to maintain fuel quality, and a gas clean up plant that will remove environmentally unacceptable components of the gas such as hydrogen sulphide and other sulphur containing compounds and tars and light oils.

What is claimed is:  
     
         1 . An apparatus for converting a volume of coal to a fuel gas, comprising: 
 a coal feed system;    a gasifier comprised of an upper vessel joined to a lower vessel, wherein the gasifier is connected to the coal feed system; and    a system of ash and liquid removal equipment connected to the gasifier.    
     
     
         2 . The apparatus according to  claim 1 , further including a sulphur removal plant connected to the system of ash and liquid removal equipment  
     
     
         3 . The apparatus according to  claim 1  in which the coal feed system includes in the volume of coal, a mixture comprising a coal fine and tar produced from the gasifier.  
     
     
         4 . The apparatus according to  claim 3  wherein said mixture further comprises a biomass added to the coal fine and the tar in a proportion ranging by weight from one to five parts of the biomass to each one part of the coal fines.  
     
     
         5 . The apparatus according to  claim 1  wherein said upper vessel of the gasifier has a flow area ranging from about 60% to 90% of the flow area of said lower vessel.  
     
     
         6 . The apparatus according to  claim 5  wherein said upper vessel has a refractory material lining.  
     
     
         7 . The apparatus according to  claim 5  wherein said upper vessel includes a water jacket surrounding said upper vessel.  
     
     
         8 . The apparatus according to  claim 1  further including a line accessing the gasifier at a junction between said upper vessel and said lower vessel to allow for a withdrawal of the fuel gas produced in said lower vessel which is approximately 55% to 70%, by volume, of the total fuel gas produced in the gasifier.  
     
     
         9 . The apparatus according to  claim 8  further including a temperature measuring probe inserted into the junction between said upper vessel and said lower vessel.  
     
     
         10 . The apparatus according to  claim 1  further including a steam source and an air source connected through a bottom of the gasifier.  
     
     
         11 . The apparatus according to  claim 10  wherein the steam source produces an amount of steam added to the gasifier in a ratio of 0.4 to 0.6 times the weight of coal added to the gasifier.  
     
     
         12 . The apparatus according to  claim 1 , further including a sulphur clean up plant connected to the system of ash and liquid removal equipment, wherein the sulphur clean up plant has a solvent including a solution, in a volume of water, a mixture of potassium carbonate and potassium bicarbonate, small amounts of sodium salts of anthraquinone disulphonic acid (ADA), sodium vanadate, PDS or lignin extract as a catalyst to separate sulphur from the solvent.  
     
     
         13 . The apparatus according to  claim 1 , further including a coal distributing and stirring mechanism mounted above the volume of coal in the gasifier.  
     
     
         14 . The apparatus according to  claim 1 , wherein the system of ash and liquid removal equipment includes an electrostatic device selected from a group of electrostatic devices consisting of an electrostatic precipitator and a wet electrostatic precipitator.  
     
     
         15 . The apparatus according to  claim 1 , further including a computer control system connected to the apparatus for converting the volume of coal to the fuel gas.  
     
     
         16 . A method for converting a coal to a gas, comprising: 
 gasifying the coal at a first temperature in a first vessel; and    gasifying the coal in a second vessel at a second temperature which is lower than the first temperature by flowing the gas from the first vessel into the second vessel.    
     
     
         17 . The method according to  claim 16 , further including passing the coal through a flow area in the second vessel which is smaller than the flow area of the first vessel.  
     
     
         18 . The method according to  claim 16 , further including operating the second vessel and the first vessel at a pressure ranging from about 20 to 90 pounds per square inch absolute.  
     
     
         19 . The method according to  claim 16 , further including operating the second vessel and the first vessel by adding an air mixture having an oxygen concentration up to as much as 45% of the air mixture.  
     
     
         20 . The method according to  claim 16 , further including varying a height of the second vessel by less than twenty-five percent by adjudging the height according to the reactivity of the coal, performed prior to said steps of gasifying the coal.