Gasifier

Abstract

An apparatus and process for converting carbonaceous or other material with calorific value, wood, plastic, sewage, etc into high quality gas preferably to fuel a reciprocating gas engine for the generation of electricity. Wet fuel is delivered via conveyer 13 to fuel hopper 14. From the hopper the fuel is fed into the dryer 15 by a screw feeder The dried fuel then is checked for size via a trommel 16 where the correctly sized fuel passes through and the oversized fuel goes onto the reject conveyer 22 where it is delivered for shredding. The correct sized dry fuel is transported via a conveyer 17. The fuel is then fed via a feed system, to avoid the ingress of air, into the gasifier 19. The gas is cooled and cleaned in the gas quench unit 20. The gas is then compressed and stored. The char is quenched in a water trough then fed by a screw conveyer to a dryer 29 then stored in a hopper 30. Oils and tars that are carried over with the gas are removed by an extraction unit 27 and stored in storage vessel 28. From storage the oils are used as a fuel along with the char via burners 1 to fuel the char reburner 2. The combustion air used in the char reburner is taken from the dryer. This air is dried in 25 by the forced draft fan 26 then sent to the combusters 1. Any slag that is produced in the char reburner is ejected as a vitrified slag into a trough 32 where it is removed for further processing. The hot gases from the char re-burner are treated by Nox suppression system 3. The temperature is then controlled at 4 before heating the gasifier 5. Having heated the gasifier the hot gases are guided via ducts 6 to a further stage of temperature control 7. From there they heat the dryer before being guided via duct 9 to a bag filter 10 that collects any dust allowing the clean exhaust to pass to the chimney 12 via an induced draft fan 11.

1 . An apparatus and process for the treatment of material with a significant usable convertible calorific value comprising an externally heated rotary, approximately horizontal, un-pressurised internal cylindrical vessel within a static outer vessel with a feed mechanism for ingress of suitably sized fuel designed to ensure anaerobic conditions within the said inner vessel.  
   
   
       2 . An apparatus as claimed in  claim 1 , wherein the longitudinal axes of the vessels are inclined at an angle in excess of 1% to the horizontal.  
   
   
       3 . An apparatus as claimed in  claim 2  in which the heating of the volume between the inner and outer vessels is achieved by hot gases produced in the process.  
   
   
       4 . An apparatus as claimed in  claim 3 , in which the fuel material is indirectly heated to approximately 850° C. in an oxygen free atmosphere.  
   
   
       5 . An apparatus as claimed in  claim 4  in which the heating medium is supplied by the product of the process.  
   
   
       6 . An apparatus as claimed in any one of  claims 3  to  5  in which the internal rotary vessel is provided with internal longitudinal substantially parallel vanes.  
   
   
       7 . An apparatus as claimed in  claim 6  in which the said vanes are of a profile to restrict the fall of the material whilst providing an increased heated surface area.  
   
   
       8 . An apparatus as claimed in  claim 7  in which the vanes are substantially L shaped in cross section.  
   
   
       9 . An apparatus as claimed in  claim 8  in which the vanes are attached by means of bolts and interlocking mortises to allow for expansion and contraction whilst holding the vanes firmly in place.  
   
   
       10 . An apparatus as claimed in any one of  claims 1  to  9  in which the outer vessel is insulated with a heat retentive material.  
   
   
       11 . An apparatus as claimed in any one of the previous claims including a gas quench system.  
   
   
       12 . An apparatus as claimed in any one of the previous claims including a secondary gasifier.  
   
   
       13 . An apparatus and process as claimed in  claim 12  in which the secondary gasifier comprises two substantially concentric dynamic spirals induced by tangential introduction of fuel into a refractory lined vessel.  
   
   
       14 . An apparatus as claimed in  claim 13  in which the secondary gasifier is fuelled by char, oils and/or tar  
   
   
       15 . An apparatus as claimed in  claim 14  in which the secondary gasifier is fuelled principally by the product of the primary gasifier.  
   
   
       16 . An apparatus as claimed in any of  claims 12  to  14   7  in which the exhaust gas from the secondary gasifier is ducted to heat the primary gasifier which in turn provides a fuel source for the secondary gasifier.  
   
   
       17 . An apparatus as claimed in  claim 16  in which residual ash is ejected at the base of the secondary gasifier allowing cleaned gases to be extracted by the cyclonic flow.  
   
   
       18 . An apparatus as claimed in any of  claims 13  to  17  in which steam is injected into the secondary gasifier with the fuel.  
   
   
       19 . An apparatus as claimed in any of  claims 13  to  18  in which contaminated liquors are injected into the secondary gasifier for cleaning and purification.  
   
   
       20 . An apparatus and process for the gasification of waste residues or any other fuel of significant calorific value constructed or adapted to operate substantially as described herein with reference to and as illustrated in the drawing.