Method and installation for variable power gasification of combustible materials

Abstract

The gasification process according to the invention involves an installation comprising a treatment chamber in which the materials to be treated pass successively through a drying/pyrolysis zone of variable dimensions in which a pyrolysis gas extraction takes place, then through a gasification zone of variable dimensions in which a syngas extraction takes place. The pyrolysis gas is injected into the roof of the treatment chamber ( 8 ) with an oxidizing gas, so as to generate an exothermic oxidation reaction provides the energy necessary for the pyrolysis and gasification reactions. The dimensions and/or the position of the drying/pyrolysis and gasification zones are controlled as a function of the amounts of material to be treated introduced into the treatment chamber ( 8 ), their nature and/or energy requirements.

1 . A method for variable power gasification of combustible materials with an installation which comprises a reactor comprising a treatment chamber wherein the materials to be treated successively pass through a drying/pyrolysis zone with variable dimensions in which pyrolysis gas extraction is carried out, and then through a gasification zone with variable dimensions in which synthesis gas extraction is carried out, the pyrolysis gas extracted in the drying/pyrolysis zone being injected into the airspace of the treatment chamber with an oxidizing gas, so as to generate an exothermic oxidation reaction providing the energy required for pyrolysis and gasification reactions, wherein the dimensions and/or the position of the drying/pyrolysis and gasification zones are adjusted according to the amounts of material to be treated, introduced into the treatment chamber, to their nature and/or power output requirements, in that the treatment chamber comprises a single oxidation zone in the airspace of the reactor, and wherein the combustible material substantially circulates horizontally by means of a pusher or the like allowing the combustible material to advance from upstream to downstream from the reactor, this reactor being positioned along a substantially horizontal axis. 
   
   
       2 . The method according to  claim 1 , wherein the treatment chamber comprises between the drying/pyrolysis zone and the gasification zone, a mixed multifunctional zone in which either pyrolysis gas extraction or synthesis gas extraction may be carried out, the type of extraction carried out in this zone being determined according to the amounts of materials introduced into the treatment chamber, to the nature of this material and/or to the power output needs. 
   
   
       3 . The method according to  claim 2 , wherein at least one of the aforesaid zones comprises several controllable successive gas extraction areas, and wherein the variation of the dimensions and/or of the position of said zones is obtained by partial or total deactivation of said areas. 
   
   
       4 . The method according to  claim 3 , wherein the temperature of the gasification gases is controlled by acting on the flow rate of oxidizing gas injected into said chamber. 
   
   
       5 . The method according to  claim 3 , wherein the temperature of the pyrolysis gases is controlled by acting on the flow rate of the pyrolysis gases injected into the treatment chamber. 
   
   
       6 . The method according to  claim 3 , wherein the relative flow rates of the oxidizer injected into the reactor and of extraction of the gasification fuel gas maintains the reactor depressurized. 
   
   
       7 . The method according to  claim 3 , wherein the produced power output is controlled by the supply of combustible material, the displacement rate of the combustible material by means of a piston or the like, the flow rate and quality of the injected oxidizer, the volume of the pyrolysis zone, the recirculation flow rate, the volume of the gasification zone, the flow rate of extraction of the gasification gas. 
   
   
       8 . The method according to  claim 2 , wherein the synthesis gas is subject to a scrubbing treatment with recovery of the substantial heat of said gas. 
   
   
       9 . The method according to  claim 8 , wherein the aforesaid scrubbing is carried out by means of a falling oil film generated in the exchanger tubes in which said gas flows. 
   
   
       10 . An installation for applying the method comprising a fixed bed reactor which comprises a treatment chamber, this reactor and this chamber being connected at one of their ends to a combustible material supply system comprise at their other end a system for extracting ashes and, this chamber comprising three regions corresponding to the three main phases of the treatment, i.e.: a drying/pyrolysis region located in a first portion of the combustible material bed, a gasification region located in the second portion of the bed of the fuel and an oxidation region occupying the airspace located above the bed, wherein the chamber comprises a substantially horizontal sole surmounted by a bed divided into at least three zones, i.e.:
 a first upstream zone with variable dimensions where only a drying/pyrolysis process is carried out, this zone being connected to means for extracting the pyrolysis gas with variable flow rate, these extraction means being connected to a common pyrolysis gas extraction circuit connected to a burner supplied with an oxidizing gas such as air or oxygen and positioned so as to generate an exothermic oxidation reaction in the airspace of the chamber, which provides the energy required for the pyrolysis, gasification and degradation reactions of the tars or other organic molecules contained in the pyrolysis gases,   a last zone with variable dimensions where only a gasification process is carried out which results from a reduction phase produced during the passage of the gas generated by the oxidation reaction through the carbonized bed during the drying/pyrolysis process, this downstream zone being equipped with means for extracting with a variable flow rate the synthesis gas obtained by this gasification process, connected to a common circuit for extracting synthesis gases,   a multifunctional zone with variable dimensions located between the first and the last zone, this multifunctional zone may totally or partly be a drying/pyrolysis zone and/or totally or partly be a gasification zone, and/or totally or partly be a deactivated zone, and is connected to extraction means connected to the common pyrolysis gas extraction circuit via a circuit with adjustable flow rate on the one hand, and to the common synthesis gas extraction circuit via a circuit with adjustable flow rate on the other hand.   
   
   
       11 . The installation according to  claim 10 , wherein the supply system comprises a supply airlock which delivers the material to be treated to the inside of the treatment chamber on a discharge area of a pusher with an alternating movement. 
   
   
       12 . The installation according to  claim 11 , wherein the aforesaid extraction areas each comprise a grid on which the material bed may circulate and under which a hopper is positioned, the lower portion of which is provided with an obturator connected to a sleeve immersed in the water of a tank, at least one synthesis and/or pyrolysis gas extraction circuit opening inside the hopper and controlled by valves. 
   
   
       13 . The installation according to  claim 12 , wherein the aforesaid pyrolysis gas extraction circuit comprises a turbine which delivers into the aforesaid burner. 
   
   
       14 . The installation according to  claim 13 , wherein oxidizer is delivered by a circuit passing through the secondary of a heat exchanger, the primary of which is mounted in the circuit for extracting the synthesis gas. 
   
   
       15 . The installation according to  claim 14 , wherein the treatment chamber comprises a system for extracting ashes comprising a well, the lower end of which is immersed in the water contained in a tank for recovering ashes. 
   
   
       16 . The installation according to  claim 15 , wherein the aforesaid sole is tilted relatively to the horizontal. 
   
   
       17 . The installation according to  claim 16 , comprising a gas scrubbing system comprising i.a. a three-fluid exchanger inside which the gas circulates in vertical tubes inside which oil entering by overflow forms films falling along the inner walls of said tubes before finally reaching an oil reserve, the substantial heat of the gas being transferred to the water by passing through the oil films and the walls of the tubes. 
   
   
       18 . The installation according to  claim 17 , wherein before reaching the exchanger the water circulates in a coil-shaped circuit positioned in the aforesaid reserve.