Two-stage high-temperature preheated steam gasifier

Abstract

A gasifier combines two reactors using externally generated preheated high temperature steam injection into the first reactor, where the heating demand for gasification is supplied by the sensible energy from the steam. The gasifier can produce a medium and higher LCV syngas. The first reactor is a fixed bed gasification section where the coarse feedstock is gasified, and the second reactor is an entrained-bed gasification section where the liquid and fine feedstock is gasified. Solid coarse feedstock is devolatilized in the first fixed bed reactor of the gasifier with high-temperature steam, and subsequently, in the second reactor subjected to a higher temperature sufficient to crack and destroy tars and oils. Activated carbon may be formed as co-product. The gasifier may be used with various solid and liquid feedstocks. The gasifier is capable of gasifying such different feedstocks simultaneously.

1 - 9 . (canceled) 
     
     
         10 . A two-staged gasifier ( 21 ) for producing synthesis gas and, optionally, activated carbon, from a coarse carbonaceous feedstock, which gasifier comprises:
 a first reactor ( 3 ) provided with an inlet ( 2 ) for a coarse carbonaceous feedstock ( 1 ), a first inlet ( 7 ) for steam; and   a second reactor ( 4 ) provided with a second inlet ( 9 ) for steam, optionally together with air or oxygen;   and an outlet ( 12 ) for synthesis gas;   
       wherein the first and second reactors are separated by a narrowed portion ( 20 ) having a reduced cross-section for restricting passage from the first reactor to the second reactor of solid carbonaceous unreacted substance, wherein the first reactor is capable of being operated at a temperature of at least 600° C., and the second reactor is capable of being operated at a higher temperature, characterized in that the second reactor ( 4 ) is the lower reactor, and the first reactor ( 3 ) is the upper reactor and is a fixed bed reactor, a grate ( 8 ) is provided at the bottom end of the first reactor, inlet ( 7 ) is located adjacent to the bottom of the first rector, so as to enable preheated steam having a temperature of at least 700° C. to be fed into the first reactor from below grate ( 8 ) via inlet ( 7 ), said second reactor is provided with an inlet ( 19 ) for a fine solid carbonaceous feedstock and/or a liquid carbonaceous feedstock, inlet ( 9 ) is located adjacent to the bottom of the second rector so as to enable preheated steam having a temperature of at least 700° C., optionally together with preheated air or oxygen of same temperature, to be fed to the second reactor from below via inlet ( 9 ), and in that a second narrowed portion ( 18 ) having a reduced cross-section is provided at the bottom end of the second reactor ( 4 ). 
     
     
         11 . The two-stage gasifier of  claim 10 , wherein one or more, and preferably all of the inlets ( 7 ,  9 ,  19 ) enter into the gasifier tangentially in corresponding portions ( 20 ,  18 ,  16 ) of the gasifier having inner, circular cross-sections. 
     
     
         12 . The two-stage gasifier of  claim 10 , wherein the inlet ( 19 ) comprises at least two inlets ( 19   a,    19   b ) separated at a maximum distance from each other along the circumference of the circular cross-section. 
     
     
         13 . A process of gasifying a coarse carbonaceous feedstock using a two-stage gasifier, such as the gasifier ( 21 ) specified in  claim 10 , having two reactors ( 3 , 4 ), a first ( 3 ) and a second ( 4 ), respectively, separated by a narrowed portion ( 20 ), in order to produce synthesis gas, optionally together with activated carbon, comprising the steps of:
 (a) feeding a coarse carbonaceous feedstock to the first stage reactor ( 3 ) of the gasifier;   (b) subjecting the coarse carbonaceous feedstock to steam in the first stage reactor at an operational temperature of at least 600° C. of the reactor, to effect gasification of the carbonaceous feedstock,   characterized in the second reactor ( 4 ) is the lower reactor, ant the first reactor ( 3 ) is the upper reactor and is a fixed bed reactor, that no oxygen is fed to the first stage reactor ( 3 ), but only preheated steam having a temperature of at least 700° C., and in a further step (c), wherein any solid and/or liquid carbonaceous materials obtained from step (b) are subjected to preheated steam, optionally together with air or oxygen, in the second stage reactor operating at a temperature of at least 700° C. to obtain any combination of the following products: activated carbon; CO; CO 2 , and heat of combustion.   
     
     
         14 . The process of  claim 13 , comprising a further step (d) of simultaneous feeding of a fine solid carbonaceous, or liquid carbonaceous feedstock, into the second stage reactor of the gasifier. 
     
     
         15 . The process of  claim 13 , wherein in step (c) the steam entering the second stage reactor is preheated to a temperature of 700-1600° C., and preferably 800-1200° C. 
     
     
         16 . The process of  claims 13 , wherein oxygen is used instead of air. 
     
     
         17 . The process of  claim 13 , wherein no air or oxygen is supplied to the gasifier. 
     
     
         18 . The process of  claim 14 , wherein in step (c) the steam entering the second stage reactor is preheated to a temperature of 700-1600° C., and preferably 800-1200° C. 
     
     
         19 . The process of  claims 14 , wherein oxygen is used instead of air. 
     
     
         20 . The process of  claim 14 , wherein no air or oxygen is supplied to the gasifier. 
     
     
         21 . The two-stage gasifier of  claim 11 , wherein the inlet ( 19 ) comprises at least two inlets ( 19   a,    19   b ) separated at a maximum distance from each other along the circumference of the circular cross-section.