AU2008259650A1

AU2008259650A1 - Process and plant for incinerating waste with preheating of the latter

Info

Publication number: AU2008259650A1
Application number: AU2008259650A
Authority: AU
Inventors: Hasan Sigergok
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-05-18
Filing date: 2008-05-16
Publication date: 2008-12-11
Anticipated expiration: 2028-05-16
Also published as: CO6251345A2; CN101688667B; ES2769590T3; MY157924A; IL201784A0; WO2008149025A3; AP2009005071A0; JP5395062B2; NZ581947A; CN101688667A; EP2167877A2; WO2008149025A2; AP2560A; ZA200908745B; US20100199897A1; BRPI0810284A2; FR2916258A1; AU2008259650B2; FR2916258B1; EP2167877B1

Description

WO 2008/149025 PCT/FR2008/050849 PROCESS AND PA4NT FOR INCINERATING WASTE WITH PRSmEATING OF THE LATTER The invention relates to a method for incinerating 5 household or industrial waste in a reactor with preheating of the waste by a steam circuit the steam for which comes from the bLeam expansion turbine (TRV). The object of the invention is to obtain within the 10 incinerator complete combustion without any unburnt matter, without any troublesome residue, without releasing gas into the atmosphere, in order to protect the environment from any pollution. 15 Another object of the invention is to recuperate the thermal energy released, to convert it into electrical energy, and to reuse soine of this energy within the plant itself. The amount of electrical energy recuperatod is approaching 75%, excluding the energy 20 reinjected into the plant, These objects are achieved by the invention which consists in a process for incinerating household or industrial waste in a combustion reactor, charactexized 25 in that: - Lhe combustion is carried cut under pressure and with the addition of pure oxygen to the reactor, and in the absence of nitrogen, - the steam from the expansion turbine is tapped off 30 to preheat the waste before it enters the reactor, - then thy remaining gases are cundensabed in order to recuperate them. Furthermore, the method is characterized in that the 35 oxygen needed for combustion is produced by separating the nitrogen and oxygen from the air, the nitrogon thus produced being used in particular to cool the gases resulting from the combustion of the waste, and the NO 20081149025 - 2 - PCT/FR2008/050849 oxygen being injected into the reactor at at least one point. The method as defined allows better destruction of 5 dioxins, unburnt matter, compound of nitrates, carbonates and phosphates which give rise to oxides A plant according to the invention, in order to implement the process, is characterized in that it 10 comprises: - a feed hopper (TA) having at its inlet and at its outlet a shutter and comprising means; - a feed screw capable of preheating the waste using steam tapped from the expansion turbine (TRV); 15 - an intermediate hopper able to collect the waste reheated in the feed hopper and introduce it into the top of the reactor, and - a reactor equipped with three burners, these being a main burner (BP), an auxiliary burner (BA) and a 20 catalytic burner (BC) positioned near the combustion gases outlet, each of these three burners being fed with fuel by the fuel line (3) and with pure oxygen by an oxygen production circuit (5) , the core of the reactor uumprises a 25 cathode wall based on metals of the tungsten or tantalum type, chosen for their refractory nature. As a preference, the oxygen is produced by separating air into nitrogen and oxygen. 30 The invention will be better undersLood with the aid of the description which follows, given with reference to the following attached figures: 35 - figure 1: an overview of a waste incineration plant According to the invention, - figure 2; a diagram ot the water vaporization circuit of the plant, WO 2008/149025 - 3 - PCT/FR2008/050849 - figure 3: a detailed diagram of the feed hopper and of the feed screw according to the invention. 5 Reference is made first of all to figure 1 which shows a plant in its entirety, this plant essentially comprising: - an incineration line 1, 10 - a steam circuit 2, - a fuel feed line 3, - a nitrogen circuit 4, - an oxygen circuit. 15 Incineration line (1). Trucks containing the wastc that is to be destroyed are unloaded under gravity into a feed hopper (TA) the outlet of which is equipped with a shutter (OFI). 20 A feed screw (VA) receives the waste from the feed hopper (TA) and conveys it and tips it into An intermediate hopper (TI) via an inlet situated at the top of said hopper (TI) and equipped with a shutter 25 (0F2). The feed screw (VA) also allows the waste to be preheated as will be explained later on. The intermediate hopper (TI) has a central bottom outlet $0 equipped with a shutter (OF3) and via which it loads the waste under gravity into an inlet chute opening onto an opening shutter (OF4) of a combustion reactor (RC) and at the top thereof. 35 For preference, the hopper (TI) is pressurized at a temperature close to 900*C to accelerate the reforming of and removal of halides from the POPs in order to facilitate the expulsion of waste to the combustion reactor. Advantageously, the pressurizing will be WO 2008/149025 - 4 - PCT/FR2008/050849 performed by introducing a mass of steam at high pressure and hiyh temperature in excess of 10000C into the hopper (TI) via at least one appropriate orifice. This gaseous mass at high pressure will have the 5 advantage of fluidizing the mass of waste procent in the hopper TI and as a result of making it easier to cause it to flow to the nombustion reactor (RC) . In order to prevent any leak of gaseous mass from the intermediate hopper to the hopper TA while said 10 intermediate hopper is being filled, the orifice via which the gaseous mass is introduced will be associated with a remote-contrnlled valve. This valve will be in the position of closing off the orifice when the hopper loading hatch is in the open position and will be in 15 the position in which the orifice is open when the loading hatch of the intermediate hopper is in the closed position. It will be possible to use several hoppers each in turn 20 communicating with the feed hopper and each in turn communicating with the reactor RC. This arrangement will allow one intermediate hopper to be filled from the feed hopper when the other or one of the other hopper(s) is in the process of unloading into the 25 reactor (RC), It will be possible to incorporate, after the feed hopper, a tank that will allow the waste to be mixed with an additive based on sodium hydrnxide or on 30 potassium hydroxide in order, at temperatures close to 20'C, to neutralizc acid in a firsL phase and the halides bound up in the inorganic molecules. Halides present in the POPs (persistent organic 35 pollutants) will be eliminated or fixed using alkali metal hydroxides in th( intermediate hopper at temperatures close to 1000 9

C.

WO 2008/149025 - 5 - PCT/FR2008/050849 The combustion of waste produces fly ash and gases. The fly ash drops to Lhe bottom of the reactor (RC) and then into a bottom ash hopper (TC) situated under the reactor (RC) . This bottom ash hopper conveys the fly 5 ash to an ash cooling recuperqtor (RCE) via a shutter (0F5). The recuperator RCE mixes the fly ash with water and initiates reactions beLween the oxides and the water to form soluble hydroxides. Next, the insoluble fly ash is tipped into a truck which takes it away 10 (ic). All the fly ash, except for the .air pollution control residue (APCR) will be processed using water at temperatures of between 200 and 400*C, at the outlet 15 from the reactor. No additional energy is needed to obtain these temperatures because the dilution of alkali metal oxides is exothermal. A processing circuit enablt5 soluble waste to be 20 separated from insoluble waste, the insoluble waste being sent for sedimentation and some of the soluble content will crystallize and be able to be reused. The soluble part will be reintroduced into the feed hopper following the separation of tho salts of the halides, 25 and of the sulfates of potassium and of sodium. The combustion reactor (RC) is equipped with refractory bricks for good thermal insulation and a cathode wall based on tungsten or tantalum at the heart of the 30 reactor ensures that the waste is burnt at very high temperatures ranging between 1500-30000c, and is so using three burners (BP, BA, BC) fed with fuel and with oxygen and respectively: 35 - a main burner (BP) positioned at the base of the combustion reactor (RC), - an auxiliary burner (BA) positioned in the middle part of the combuaLiun reactor (RC), WO 2008/149025 - 6 - PCT/FR2008/050849 - a catalytic burner (BC) positioned at the upper part of the reactor and near the outlet of the gases, combustion gases 5 completing and optimizing the combustion. 5 The primary and auxiliary burners operate with an exce.5 of uxyyen at a rate of reaction 10 to 20 times higher than the habitual speed of combustion reactions. 10 The reactor (RC) is designed to operate at constant high pressure and constant high temperature, and its inlets and outloto therefore consist of hatches that constitute heat shields and provide sealing. 15 The combustion reactor will preferably be a thermal oxidation reactor (TOR). The hoppers also operate under pressure and consist of air look with their inlet and outlet shutters. 20 Safety valves CE1 and CE2 are also provided in the reactor and in the intermediate hopper. The shutters OFI to OF5 can be actuated by motors 25 external to the elements to which they are fitted. The motors will be of any known type. Without implying any limitation, they could consist of remote-controlled electric, hydraulic or pneumatic cylinder actuators. 30 The combustion gases are capped from the outlet (la) at the top o± the reactor (RC) and senL through a pipe (SGC) to a particulate filter (PF) and then into heat exchangers ECT1, ECT2 toward an expansion turbine (TRGC). 35 The expansion turbine (TRCC) is advantageously associated with an electric energy generator (GE3) and so some of the heat energy of the combustion gases is thus converted into electricity.

WO 2008/149025 - 7 - FCT/FR2008/050849 The water vapor is condensed and the gaseous oxides are removed (1b) to (CGC) . Some of the water from CV2 is reintroduced into the compressor (7), having passed 5 through an osmotic filter. Steam circuit (2) Advantageously, some of the condensed water can be 10 recuperated and vaporized into the form of high pressure and high-temperature dry steam to form the high-pressure gaseous mass introduced into the intermediate hopper. Thus, upon leaving the condenser (CV1) the water will be bled to a heat exchanger 6 15 where it is vaporized into the form of high-pressure dry steam. Advantageously, the heat exchanger may consist of a tube bundle in thermal contact with the reactor (RC) to recuperate some of the heat given off by the latter, thereby uLabilizing the temperature 20 inside the reactor, this heat being used to vaporize the water and most of the steam being directed to an expansion turbine (TRV), another proportion of it being injected into a pipe (TI). 25 The steam leaving the TRV is introduced into a preheating device (SP) incorporated into an endless feed screw (VA) provided between the feed hopper (TA) and the intermediate hopper (TI) . This feed screw (TA) comprises a longitudinal shaft (2d) on which a scnrew 30 thread (2c) is mounted. A drive member of any known type will be coupled to the shaft of LIe Ss.w. The preheating device (SP) is preferably, but nonlimitingly, that of figure 3 which consists of a 35 screw thread (2c) 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 between the screw thread and the inlet shutter (OUk1) . The upstream and downstream inlets are each formed of a blind axial WO 2008/149025 - 8 - PCT/FR2008/050849 drilling made in the shaft (2d) at a corresponding end and of a radial drilling made in said shaft and opening, at one end, into the blind axial drilling and into the box form that the screw thread (2c) exhibits. 5 The steam is injected axially into the start of the screw thread and heats up the waste as it travels along the screw thread, then leaves the thread to be sent to a first condenser (CV1), having passed through a compressor 7. 10 As a preference, a compressor 7 may be positioned upstream of the excohanger 6 to pressurize the water and create at this point a back pressure that prevents the reflux of steam to the condenser (CV1). 15 It may be pointed out that the circulation of steam through the screw is countercurrent with respect to the progress of the waste carried by this screw The condonsero (CV1, CV2, CGC) are of the conventional 20 type with tube-type heat exchangers through which a refrigerant from an evaporator-type refrigeration device (EFF) passes. The tapped-off combustion gases arc gaaea which are 25 oxidized and stabilized without dioxin and without unburnt iLaLter in the duct SGC. Some of their heat energy is converted into electrical energy in a generator associated with the turbine (TRGC) and most of the energy is used to heat up the nitrogen. 30 Following cooling using nitrogen, Lhe; combustion gases are conveyed to ECTI and ECT2. These gases are condensed and then introduced into the turbine TRGC which converts the energy of the combustion gases back 35 into electrical energy. Following expansion, the gases are separated from the steam, because the latter condenses.

Claims

1. A process for incinerating household or industrial waste in a reactor (RC), characterized in that: 5 - the combustion is carried out under pressure and with the addition of pure oxygen to the reactor, and in the aboonce of nitrogen, - the steam from the expansion turbine is tapped off to preheat the waste before it enters the reactor, 10 - then the remaining gases are condensed in order to recuperate them.

2. The method as claimed in the preceding claim, characterized in LIat the oxygen needed tor combustion 15 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. 20

3. A plant for incinerating household or industrial waste, of the type comprising a reactor (RC) with at least one burner fed by a fuel feed line (3), characterized in that it comprises: 25 - a feed hopper (TA) having at its inlet and at its outlet a shutter iid comprising means capable of preheating the waste using steam tapped from the expansion turbine (TRV) - an intermediate hopper (TI) able to collect the 30 waste preheated in the feed hopper and introduce it into the top of the reactor, - a reactor equipped with three burners, these being a main burner (BP), an auxiliary burner (BA) and a catalytic burner (BC) positioned near the 35 combustion gases outlet, each of these three burners being fed with fuel by the fuel line (3) and with pure oxygen by an oxygen production circuit (5) . WO 2008/149025 - 14 - PCT/FR200/050849

4. The plant as claimed in the preceding claim, characterized in that the feed hopper means capable of reheating the waste consists of a screw thread (2c) in tfhe form of a box with a gas inlet downstream to the 5 screw and a gas outlet upstream to the snrew, the gas outlet being at the other end between the screw thread and the inlet shutter (OFl).

5. The plant as claimed in one of claims 3 and 4, 10 characterized in that it comprises a steam circuit (2) attached to the walls of the reactor.

6. The plant as claimed in the preceding claim, characterized in that the Steam recovery circuit 15 comprises at least one condenser (CVI).

7. The plant as claimed in one of claims 3 to 6, characterized in that it comprises an air separator operating using membrane filters to separuage the oxygen 20 and the nitrogen.

8. The plant as claimed in one of claims 3 to 6, characterized in that it comprises an air separator formed of a bank of air compressors (BCA) and of a 25 turbocompressor TCA able to separate gaseous nitrogen from liquefied oxygen.

9. The plant as claimed in claim 8, characterized in that the oxygen production circuit (5) comprises, after 30 the air separator and the turbocompressor, an expansion vessel (BDA), a liquid oxygen storage tank (ROL), an exchanger (CFF2) in which the oxygen is gasified to be fed tv each of the three burners (BP, BA, BC). 35

10. The plant as claimed in claim 8, characterized in that it comprises, after ths air separator and the turbocompressor, an expansion vessel (BDA), a nitrogen tank (RAG) , three heat exchanger (CFF2, ECTI, ECT2) WO 2008/149025 - 15 - PCT/FR2008/050849 then a tube-type heat exchanger and a nitrogen recuperation turbine (iRA) .

11. The plant as claimed in one of claims 5 and 6, 5 characterized in that the expand on turbine (TRV) is associated with an electric generator.

12. The plant as claimed in any one of claims 3 to 11, characterized in that the hopper (TI) is pressurized to 10 facilitate the expulsion of waste to the combustion reactor.

13. The plant as claimed in claim 12, characterized in that the pressurizing of the intermediate hopper (TI) 15 is performed by introducing a gaseous mass under high pressure into said hopper (TI) via at least one appropriate orifice.

14. The plant as claimed ila cletim 13, characterized in 20 that the orifice via which the gaseous mass is introduced into the intermediate hopper (TI) is associated with a remote-controlled valve in order to prevent any leakage of gaseous mass from the intermediate hopper to tho hopper (TA) while said 25 intermediate hopper is being filled.

15. The plant as claimed in claim 12 or claim 13, characterized in that the gaseous mass is high-pressure dry steam. 30

16. The plant as claimed in claim 4, characterized in that the gases leaving the screw thread of the screw are sent to a first condenser (CV1) the purpose of which is to condense the water vapor contained in the 35 combustion gases, having passed through a compressor

17. The plant as clained in claims 15 and 16 considered together, characterized in that some of the WO 2008/149025 - 16 - PCT/FR2008/050849 water condensate leaving the condenser (CV2) is bled off to a beat exchanger (/) where it is vaporized to the form of high-pressure dry steam. 5

18. The plant as claimed in claim 17, characterized in that the heat exchanger consists of a tube bundle in thermal Contact with Lhe reactor (RC) to recuperate some of the heat given off thereby, this heat being used to vaporize the water. 10

19. The plant as claimed in claim 18, characterized in that a compressor (7) is positioned upstream of the exchanger to pressurize the water and to create at this point a back pressure which prevents the reflux of 15 steam toward the condenser (CV1).

20. The plant as claimed in any one of claims 3 to 19, characterized in that after cooling using nitrogen, the combustion gases are conveyed to ECT1 and kCT2; these 20 combustion gases are condensed then introduced into the turbine TRGC; after expansion, the gases become separated from the condensed water.