Horizontal gasifier and the thermochemical conversion of combustible carbonaceous material in a counter-current proces

Abstract

A horizontal gasifier features a closed body (3) with thermal insulation containing a helical feed screw (4) for the feedstock (2), a vertical feed inlet (1) for the feedstock (2) located at one end of the body (3), an inlet (7) for the oxidizing gas (6), and an ash collector (5) at the other end of the body (3), and an outlet (9) for volatile products (8). The gasifier is characterized by a gasification zone (21) in the final section of the body (3), with the shaft (4b) of the helical feeder (4) being completely hollow along its length and equipped with inlet openings (18) for introducing a supplementary portion of oxidizing gas (6) located in a segment extending beyond the body (3) on the side where the feed inlet (1) is located, and outlet openings (20) for this portion of oxidizing gas located in the gasification zone (21).

1 . A horizontal gasifier with a closed body ( 3 ) equipped with thermal insulation, wherein a helical feed screw ( 4 ) for feedstock ( 2 ) is located, equipped with a vertical feed inlet ( 1 ) for feedstock ( 2 ) positioned at one end of the body ( 3 ), an inlet ( 7 ) for oxidizing gas ( 6 ), and an ash collector ( 5 ) located at the other end of the body ( 3 ), an outlet ( 9 ) for volatile products ( 8 ), and at least two flow meters and at least two temperature sensors, characterized in that the final zone of the body ( 3 ) forms a gasification zone ( 21 ), and the shaft ( 4   b ) of the helical feeder ( 4 ) is completely hollow along its length and equipped with inlet openings ( 18 ) for introducing a supplementary portion of oxidizing gas ( 6 ) located in a segment extending beyond the body ( 3 ) on the side where the feed inlet ( 1 ) is located and outlet openings ( 20 ) for this portion of oxidizing gas located in the gasification zone ( 21 ), and the outlet ( 9 ) for volatile products ( 8 ) is located between the feed inlet ( 1 ) and the oxidizing gas inlet ( 7 ), and the inlets ( 7 ) and ( 18 ) for oxidizing gas ( 6 ) are equipped with independent mass flow meters ( 6   a ) and ( 6   b ) connected to at least two temperature sensors ( 23 ) located in the body ( 3 ). 
     
     
         2 . The gasifier according to  claim 1 , characterized in that the body ( 3 ) in the gasification zone ( 21 ) is equipped with an internal layer of thermal insulation ( 22 ). 
     
     
         3 . The gasifier according to  claim 1 , characterized in that the segment of the hollow shaft ( 4   b ) of the feeder ( 4 ) with inlet openings ( 18 ) is in a sealed distribution box ( 16 ), to which a supplementary portion of oxidizing gas ( 6 ) is supplied through a flow meter ( 6   a ). 
     
     
         4 . The gasifier according to  claim 1 , characterized in that the hollow shaft ( 4   b ) of the helical feeder ( 4 ) has thermal insulation ( 14 ) in the gasification zone ( 21 ). 
     
     
         5 . The gasifier according to  claim 1 , characterized in that the outer diameter of the feeder's helices ( 4   a ) is at least 2 cm smaller than the smallest linear gap in the body ( 3 ) along its entire length. 
     
     
         6 . The gasifier according to  claim 1 , characterized in that the outlet ( 8 ) for volatile products is equipped with a shield ( 9   a ). 
     
     
         7 . The gasifier according to  claim 1 , characterized in that the feed inlet ( 1 ) is equipped with a sealed flap or gate ( 1   a ). 
     
     
         8 . The gasifier according to  claim 1 , characterized in that the body ( 3 ) has any closed cross-section. 
     
     
         9 . The gasifier according to  claim 1 , characterized in that the body ( 3 ) is made of metal with a melting temperature higher than 1200° C. 
     
     
         10 . A method for the thermochemical conversion of carbonaceous combustible material ( 2 ) in a horizontal gasifier, in a counter-current process, comprising feeding the carbonaceous material ( 2 ) into the body ( 3 ) of the gasifier through a vertical feed inlet ( 1 ) and moving it using a horizontal helical feeder ( 4 ) towards the end of the body ( 3 ), where a gasification zone ( 21 ) is located, while simultaneously supplying oxidizing gas ( 6 ) in a counter-current arrangement, and collecting solid product ( 11 ) at the end of the body opposite the feed inlet ( 1 ) for the feedstock ( 2 ), characterized in that a part of the oxidizing gas ( 6 ) is supplied through an inlet opening ( 7 ) located at the end of the body ( 3 ) near the gasification zone ( 21 ), and a supplementary portion of the oxidizing gas ( 6 ) is supplied from the side of the body ( 3 ) through a flow meter ( 6   a ) located at the vertical feed inlet ( 1 ) via a sealed conduit ( 4   b ) with at least one inlet opening ( 18 ) at one end of the conduit ( 4   b ) and outlet openings ( 20 ) at the end located in the gasification zone ( 21 ), and the resulting volatile products ( 8 ) are discharged through an outlet nozzle ( 9 ) located in the upper cover ( 3   a ) of the central part of the body ( 3 ). 
     
     
         11 . The method according to  claim 10 , characterized in that for a given feed rate of a specific feedstock, expressed in kg/h, the total consumption of oxidizing gas ( 6 ) expressed in kg/h of free oxygen (O2) is regulated through feedback based on the calorific or heat values of all gaseous and vapor components as products ( 8 ) of the pyro-gasification of the carbonaceous material ( 2 ) exiting through the outlet nozzle ( 9 ), with the mass flow rate of the oxidizing gas ( 6 ) controlled automatically by flow meters ( 6   a ) and ( 6   b ) based on readings from temperature sensors ( 23 ) submerged in at least two locations in the body ( 3 ). 
     
     
         12 . The method according to  claim 10 , characterized in that atmospheric air or air enriched with oxygen (O2) up to a maximum of 90% by volume is used as the oxidizing gas ( 6 ). 
     
     
         13 . The method according to  claim 10 , characterized in that the supplementary portion of the oxidizing gas ( 6 ) supplied from the feed inlet ( 1 ) side constitutes from 20% to 30%. 
     
     
         14 . The method according to  claim 10 , characterized in that the oxidizing gas ( 6 ) is dosed through two separate mass flow meters: one ( 6   b ) at the inlet ( 7 ) in the gasification zone ( 21 ) and the other ( 6   a ) at the inlet to the distributor ( 16 ) supplying the oxidizer to the inlet openings ( 18 ) on the hollow shaft of the feeder ( 4 ). 
     
     
         15 . The method according to  claim 10 , characterized in that the oxidizing gas ( 6 ) supplied through the inlet ( 7 ) is preheated by waste or process heat. 
     
     
         16 . The method according to  claim 10 , characterized in that the space between the feeder elements ( 4 ) and the inner walls of the body ( 3 ) is filled with feedstock ( 2 ) or solid products of the gradual conversion of this feedstock along the entire length of the feeder from the location of the feed inlet ( 1 ) to the beginning of the product collector ( 5 ). 
     
     
         17 . The method according to  claim 10 , characterized in that the carbonaceous combustible material ( 2 ) subjected to pyro-gasification is a solid, dry, or moist body with a particle size not exceeding the smallest linear gap between the helix ( 4   a ) of the feeder and the nearest inner walls of the body ( 3 ) or a mixture of such a body with oily substances in proportions still allowing the free flow of oxidizing gas ( 6 ) through such feedstock pushed by the helix in a gas-tight body filled with feedstock to a sealed product collector ( 5 ).