System and Method for Obtaining Clean Coal Tars from Pyrolized Coal and Biomass

Abstract

A system and method for collecting hot coal tar gases emanating from a coal containing pyrolytic kiln are described. The hot coal tar gases, comprising a variety of different hydrocarbons as well as inorganic gases arising from the kiln thermal processing are transferred by diffusion and forced convection to a thermal duct in which the temperature is controlled to be maintained at a temperature below that of the kiln. The gaseous hydrocarbon with the highest condensation temperature is the first to liquefy. Additional useful hydrocarbons liquefy as the temperature of the gas continues to cool from the kiln temperature of ˜5000 C to one approaching the minimum duct temperature, ˜175° C. After a number of desirable hydrocarbons present in the coal tar gas have liquefied, the liquid contents are collected, either separately or as a combination of liquid hydrocarbons. The several remaining inorganic and some hydrocarbons gases with condensation temperatures below the minimum duct temperature are separately collected in gaseous form for further processing and/or safe disposal.

1 . A system for reclaiming hot coal tar gases and hydrocarbon coal gas components in a condensed state comprising: a pyrolytic kiln containing hot coal gases, said kiln having at least one open end, an outer shell and an inner core, further comprising means for temperature regulation of said kiln; a duct with a proximal open end, said one open end of said duct and said distal open end of said kiln fixedly connected by a rotatable flange; heating coils in intimate thermal contact with said duct for regulating temperature of said duct, a master control unit; at least one thermal sensor mounted respectively within said kiln and said duct; at least one drain spout coupled to at least one opening on the underside of said duct; at least one collection chamber in close proximity to said drain spout; a fan positioned within said duct; uncondensed hot coal and biomass gases in said kiln core, wherein said gases are driven into said duct by said fan, said condensed gases in said duct collected by at least one collection chamber; a collection drum for collecting uncondensed gases. 
     
     
         2 . A system as in  claim 1 , wherein said duct has a proximal end, a distal end, a top side and an underside. 
     
     
         3 . A system as in  claim 1  wherein said kiln core is mounted concentrically within said outer shell. 
     
     
         4 . A system as in  claim 1  where in said distal open end of said kiln core and open end of said duct provide means for hot coal gases to enter said duct from said kiln core. 
     
     
         5 . A system as in  claim 1  wherein said duct coils control the temperature of said duct by thermal conduction, convection and radiation between said coils and said duct. 
     
     
         6 . A system as in  claim 1  wherein said fan is positioned near the distal end of said duct. 
     
     
         7 . A system as in  claim 1  where in said collection chamber is attached to the underside of said duct. 
     
     
         8 . A system as in  claim 1 , wherein said duct has a length as measured along its outer perimeter along said underside of said duct, said length in the range 1-500 feet. 
     
     
         9 . A system as in  claim 1  wherein said duct has an interior cross sectional area of arbitrary geometry in the range of 1 to 100 square feet. 
     
     
         10 . A system as in  claim 1  wherein said duct is maintained in the temperature range 175-350 C. 
     
     
         11 . A system as in  claim 1  wherein said duct temperature can be a uniform temperature along its entire length. 
     
     
         12 . A system as in  claim 1 , wherein said length dimension of said duct is selected from the group consisting of a linear length and a non-linear length, wherein said duct with said non-linear length dimension has one section lower in height with respect to ground level compared to other lengthwise portions of said non-linear duct. 
     
     
         13 . A system as in  claim 1 , wherein said hot gases flow from said kiln core into said duct. 
     
     
         14 . A system as in  claim 1 , wherein the temperature of said heating coils are determined by said master control unit and at least one thermal sensor. 
     
     
         15 . A system as in  claim 1 , wherein the components of said gases are hydrocarbons with the chemical formula CxHy where x is greater than 9 and y greater than 10. 
     
     
         16 . A system as in  claim 1 , wherein components of said hot hydrocarbon gases in said kiln enter said duct from the distal end of said kiln core at a temperature up to ˜500 C and condense in said duct at a temperature determined by the individual thermodynamic properties of said gas component. 
     
     
         17 . A system as in  claim 1  wherein recoverable hydrocarbon gases condense in said duct in the temperature range ˜175-350 C. 
     
     
         18 . A system as in  claim 1 , wherein at least one opening on underside of said duct further comprises a shutter, said shutter comprising means for controlling the opening and closing of said underside openings. 
     
     
         19 . A system as in  claim 1 , wherein said drain spout is rigidly attached to each of said openings on said underside of said duct. 
     
     
         20 . A system as in  claim 1  wherein said drain spout empties condensed gas components into a collection chamber with said shutter in said open position. 
     
     
         21 . A system as in  claim 1  wherein said fan drives said uncondensed gas components in said duct into said drum. 
     
     
         22 . A method for retrieving condensed fractions of hydrocarbon coal gases emanating from a heated kiln, the steps comprising:
 heating coal and biomass in a pyrolytic oxygen free kiln to a temperature at which coal emits a mixture of gaseous hydrocarbons; capturing said set of gaseous hydrocarbons in a duct, said duct having a top and bottom surface; a flange intimately connecting said duct to one end of said kiln; fastening at least one drain spout near the center of said duct, said drain spout opening controlled by a shutter mounted on said drain spout; positioning a collection chamber under said set of spouts; wrapping heating coils along length of said duct thereby providing a fixed temperatures along length of said duct; controlling said temperature of heating coils and duct by way of a master control unit, positioning at least one thermal sensor in the interior of said duct, said thermal sensor sending temperature information to said computer control system, liquefying individual fractions of gaseous hydrocarbons by cooling at temperatures corresponding to the condensation temperature of said hydrocarbon; positioning a fan mounted within far end of said duct; attaching a collection drum to far end of said duct in close proximity to said fan for sequestering uncondensed gas.   
     
     
         23 . The method of  claim 21  further including collecting said liquefied hydrocarbons from said duct through said drain spouts. 
     
     
         24 . The method of  claim 22  comprising directing said liquefied gases from each said drain spout into an individual collection chamber, further comprising the method of driving uncondensed said gaseous hydrocarbons at the distal end of said duct into said collection drum.