Patent Publication Number: US-2010126069-A1

Title: Gasifier feed system

Description:
Conventional gasifiers operate by having fuel introduced at one end of the gasification retort and gas and residues removed from the other end. This frequently results in powdered char residues being ejected with the gas, causing increased gas dean-up requirements. 
     The present invention provides a solution to this problem by removing the gas from the retort at the fuel inlet end via the fuel feed system which is preferably a combined ram and scroll feed providing a supply of fuel under anaerobic conditions. 
     A preferred version of the invention incorporates a chamber between a ram feeder and a scroll feeder to receive the fuel from one or more ram feeders before delivery to the scroll feeder to assist in the fuel breakdown process. More than one ram can be incorporated to increase or vary the fuel supply and even out its flow. Within the housing a of the inlet system, a cooled gas exit facility is provided to extract the produced gases from the retort. Oils and tars not broken down in the first pass of fuel, owing to a short dwell time within the retort can also be introduced via the inlet system or alternatively from the char outlet for further gasification. Introduced fuels need to be cooled within the feed system to prevent premature gasification by proximity to the hot gases emitted and the high temperature within the retort. 
    
    
     
       By way of example only, a specific embodiment of the present invention will now be described with reference to the accompanying drawings in which: 
         FIG. 1  is a longitudinal section of a gasifier retort with combined fuel feed and gas outlet mechanism with intermediate chamber and single ram. 
         FIG. 2  is a sectional view at A-A of the mechanism with intermediate chamber and single ram feed. 
         FIG. 3  is a sectional view at A-A of the mechanism with intermediate chamber and double ram feed. 
     
    
    
     Dried fuel of a suitable size for gasifying in a rotating retort ( 15 ) is delivered into a feed hopper ( 1 ) whence it is gravity fed into a ram tube ( 12 ) whilst a feeder ram ( 2 ) is retracted by a hydraulic ram ( 10 ) along guides ( 3 ). The feeder ram ( 2 ) is returned to press the fuel charge against a closed guillotine valve  11 . The guillotine valve then opens and the fuel pellet is pushed by the feeder ram towards the scroll ( 4 ) driven by a power unit ( 5 ). The fuel is ejected from the scroll drive at the tube end ( 9 ) into the gasifier. 
     In the preferred embodiment of the invention, an intermediate chamber ( 13 ) is provided between the ram feeder and the scroll. More than one feed ram can be connected to the intermediate chamber or scroll feeder, and this gives the advantage of a possible variation of fuel supply and a smoothing of flow of fuel to the scroll. The scroll is mounted around a hollow central core ( 6 ) through which oils and tars removed from the gas product in a cleaning process are introduced into the retort with the fuel. 
     Because of the high temperature in the gasifier retort and of the gases emitted, in order to avoid premature gasification, the scroll is housed within a static tube ( 16 ) cooled by water introduced and removed via inlets/outlets ( 8 ). and sealed against the rotary retort by seals ( 17 ). 
     The cooling jacket is extended around the scroll to its end ( 9 ) where the fuel is dropped into the gasifier retort. Also housed within tube ( 16 ) is the gas outlet via tube ( 7 ) connecting to the interior of the gasifier retort ( 15 ) and extracting the gas via pipe ( 14 ). Char is removed from the retort by a scroll ( 10 ) and a rotary valve to prevent egress of gas and ingress of air. 
     Whilst the invention has been described in terms of a specific embodiment thereof, it will be apparent that various changes and modifications can be made by one skilled in the art without departing from the spirit and scope thereof.