Process and plant for incinerating waste with preheating of the latter

Abstract

The invention relates to a process for incinerating domestic or industrial waste, in a reactor. The combustion is carried out under pressure and with a supply of pure oxygen in the reactor. In the absence of nitrogen, the vapors resulting from the steam expansion turbine are withdrawn in order to preheat the waste before entry thereof into the reactor, then the remaining gases are condensed with a view to the recovery thereof. A plant carrying out the process mainly includes an incineration line, a vapor circuit, a fuel supply line, a nitrogen circuit and an oxygen circuit.

1 . A process for incinerating household or industrial waste in a reactor, characterized in that , said process comprising the steps of:
 combusting waste under pressure and with addition of pure oxygen to the reactor, and in the absence of nitrogen;   tapping off steam from an expansion turbine to preheat the waste before the waste enters the reactor; and   condensing remaining gases in order to recuperate the remaining gases.   
   
   
       2 . The method as claimed in  claim 1 , wherein the oxygen needed for combustion is produced by separating the nitrogen and oxygen from the air, the nitrogen thus produced being used to cool the gases resulting from the combustion of the waste, and the oxygen being injected into the reactor at at least one point. 
   
   
       3 . A plant for incinerating household or industrial waste, said plant comprising:
 a reactor with at least one burner fed by a fuel feed line;   a feed hopper having a shutter at an inlet and outlet thereof and comprising means for preheating the waste using steam tapped from an expansion turbine;   an intermediate hopper to collect the waste preheated in the feed hopper, introducing the preheated waste into the top of the reactor; and   a reactor equipped with three burners, the three burners being comprised of a main burner, an auxiliary burner and a catalytic burner positioned near the combustion gases outlet, each of the three burners being fed with fuel by the fuel line and with pure oxygen by an oxygen production circuit.   
   
   
       4 . The plant as claimed in the preceding claim, characterized in that the  claim 3 , wherein said means for reheating the waste comprises a screw thread in the form of a box with a gas inlet downstream to the screw and a gas outlet upstream to the screw, the gas outlet being at the other end between the screw thread and the inlet shutter. 
   
   
       5 . The plant as claimed in  claim 3 , further comprising:
 a steam circuit attached to the walls of the reactor.   
   
   
       6 . The plant as claimed in  claim 5 , wherein the steam recovery circuit comprises at least one condenser. 
   
   
       7 . The plant as claimed in  claim 3 , further comprising:
 an air separator operating using membrane filters to separate the oxygen and the nitrogen.   
   
   
       8 . The plant as claimed in  claim 3 , further comprising:
 an air separator being comprised of a bank of air compressors and a turbocompressor, separating gaseous nitrogen from liquefied oxygen.   
   
   
       9 . The plant as claimed in  claim 8 , wherein oxygen production circuit comprises, after the air separator and the turbocompressor, an expansion vessel, a liquid oxygen storage tank, an exchanger, wherein the oxygen is gasified to be fed to each of the three burners. 
   
   
       10 . The plant as claimed in  claim 8 , further comprising:
 after the air separator and the turbocompressor, an expansion vessel, a nitrogen tank, three heat exchangers, and a tube-type heat exchanger and a nitrogen recuperation turbine.   
   
   
       11 . The plant as claimed in  claim 5 , wherein the expansion turbine is associated with an electric generator. 
   
   
       12 . The plant as claimed in  claim 3 , wherein the hopper is pressurized to facilitate the expulsion of waste to the combustion reactor. 
   
   
       13 . The plant as claimed in  claim 12 , wherein pressurizing of the intermediate hopper is performed by introducing a gaseous mass under high pressure into said hopper via at least one appropriate orifice. 
   
   
       14 . The plant as claimed in  claim 13 , wherein an orifice via which the gaseous mass is introduced into the intermediate hopper is associated with a remote-controlled valve in order to prevent any leakage of gaseous mass from the intermediate hopper to the hopper while said intermediate hopper is being filled. 
   
   
       15 . The plant as claimed in  claim 12 , wherein the gaseous mass is high-pressure dry steam. 
   
   
       16 . The plant as claimed in  claim 4 , wherein gases leaving the screw thread of the screw are sent to a first condenser is to condense the, condensing water vapor contained in the combustion gases, having passed through a compressor. 
   
   
       17 . The plant as claimed in  claim 15 , wherein water condensate leaving the condenser is bled off to a heat exchanger, the water condensate being vaporized to the form of high-pressure dry steam. 
   
   
       18 . The plant as claimed in  claim 17 , wherein the heat exchanger of comprises a tube bundle in thermal contact with the reactor to recuperate some of the heat given off thereby, this heat being used to vaporize the water. 
   
   
       19 . The plant as claimed in  claim 18 , further comprising:
 a compressor positioned upstream of the exchanger to pressurize the water and to create at this point a back pressure which prevents the reflux of steam toward the condenser.   
   
   
       20 . The plant as claimed in  claim 3 , wherein, after cooling using nitrogen, the combustion gases are conveyed and condensed then introduced into the turbine, and wherein, after expansion, the gases become separated from the condensed water.