FR2762613A1 - Furnace for thermolysis and energy upgrading of waste materials - Google Patents

Abstract

The furnace for treating waste products with an organic content, consists of a loader (1), and a thermolysis reactor (13) for thermal separation at low pressure and high temperature. There is an air lock (5, 50) on each side of the reactor to ensure that thermolysis takes place in an atmosphere with a very low oxygen content. It has a recuperator (15, 16) at the top of the reactor for the organic gas fraction formed during thermolysis and to feed the gas fraction to a combustion chamber (20) connected to a steam generator (22). A second recuperator (51) at the bottom of the reactor collects the solid carbon products formed during thermolysis and feeds them to a combustion chamber connected to a second steam generator or an outlet system. The gases from the combustion chamber and the steam from the generator are used to dry the waste prior to thermolysis. The waste material is shredded to a controlled size before thermolysis, which takes place in an atmosphere virtually devoid of oxygen at a temperature of 400 - 1000 deg C and a pressure of 5000 - 40000 Pa below atmospheric.

Description

PLANT FOR THERMOLYSIS TREATMENT AND
FOR ENERGY RECOVERY OF WASTE.

Technical area
The invention relates to an installation for the treatment by thermolysis and simultaneously for the energy recovery of waste containing an organic fraction.

Previous techniques
The treatment of waste containing an organic fraction is well known, in particular for the treatment of waste as diverse as automobile grinding residues (RBA), hospital waste also called care activity, used tires, green waste or resulting of biomass, urban and household waste, sludge from sewage treatment plants and sludge from various petroleum products. The treatment of this waste is becoming more and more worrying as a result of the increasingly large quantities to be treated and the increase in the cost of these treatments.

 The thermal dissociation of waste under reduced pressure and at high temperature of material containing an organic function is well known (see in particular document US-A-4,077,868, 4,833,021 and CA-A-1,163,595).

Essentially, a thermal pressure dissociation installation of waste containing an organic fraction, essentially comprises:
- a unit for loading and supplying the waste to be treated;
- and a thermal dissociation reactor under reduced pressure and at
high temperature, for example at a temperature between 400
and 1000 C, especially around 500 "C, under pressure
between 0.1 and 1 atmosphere.

 In document WO-96/1 1742, the Applicant has described an installation of the type in question, in which between the supply means and the reactor, there are two chambers, placed in parallel, each connected to the supply means of the reactor thus allowing loading at atmospheric pressure in one of the two chambers while the other is discharged at reduced pressure into the reactor. This discontinuous / continuous installation well suited to the treatment of large quantities, however has the disadvantage of requiring a significant investment.

 Furthermore, the production of oils by condensation during treatment is practically difficult to manage industrially.

 The invention overcomes these drawbacks. It targets an installation for the thermolysis treatment of waste and for the energy recovery of this waste, which is well suited to the treatment of a wide variety of waste, in small and medium capacities, with a good ratio between investment and operation. It relates more particularly to an installation of the type in question which is reliable and robust, and whose operating conditions scrupulously respect the environment.

 It is aimed at an installation of the type in question in which the energy produced during the treatment is recovered in order to operate in part and autonomously the installation itself and part of the unit capable of producing this waste.

Brief description of the invention
The invention relates to an installation for the thermolysis treatment of waste comprising an organic fraction and having a controlled particle size, and simultaneously for the energy recovery of this waste, of the type essentially comprising:
a unit for loading and supplying the waste to be treated;
a pressurized thermal dissociation thermolysis reactor
reduced at high temperature, characterized:
- in that it includes:
upstream and downstream of the reactor, an airlock intended to maintain a
vacuum in the reactor to ensure thermolysis in a
very low oxygen atmosphere;
means for recovering, at the top of the reactor, the
organic gas fraction formed during thermolysis, and
means for bringing this gaseous fraction to a
combustion feeding a steam generator;
means for recovering solid products from the bottom of the reactor
carbonaceous formed during thermolysis, and to bring these
solid products to a combustion chamber feeding a
steam generator or exhaust system;
- And in that the gases of the combustion chamber and the steam produced by the steam generator, in turn feed the waste production unit and / or a means for previously drying the waste disposed just upstream of the reactor.

 In other words, the invention consists in heating the waste having a controlled particle size under conditions suitable for dissociating this waste, essentially in two phases, respectively a gaseous phase and a solid phase, and this in quasi-absence of oxygen. , but under reduced pressure, or even in a gaseous atmosphere.

 The invention consists in recovering the gaseous phase and the solid phase in order to recover them by producing energy in a combustion chamber intended to heat steam which in turn supplies either the waste production unit and / or aims to dry the waste before it arrives at the reactor.

 In practice, thermolysis, also referred to as pyrolysis>), is carried out at a temperature between 400 and 10,000 C, in particular in the vicinity of 500 "C, with a pressure in the reactor of 5,000 to 40,000, preferably 10,000 Pascals below atmospheric pressure The residence time of the waste in this reactor is of the order of several tens of minutes, for example of the order of thirty minutes.

 As already said, advantageously, depending on the nature of the waste to be treated, it is ground to have a particle size and a controlled physical consistency, even homogeneous.

 Likewise, advantageously, the waste can undergo a preliminary drying intended to lower the water content of this waste. This heating carried out in an appropriate enclosure can, depending on the nature of the waste to be treated, be carried out in two ways, namely direct or indirect. In direct drying, the mass of waste is heated by a circulation of hot air or recycled steam from the generator characteristic of the invention, or hot air recycled from the combustion chamber. This pre-drying method is particularly suitable for waste with a low volatile solid fraction (dust), such as RBA. When treating sewage sludge, it is preferable to carry out an indirect heating, that is to say to heat the enclosure from the outside, while ensuring a certain mixing intended to break the product to increase the contact surface with air.

 Still depending on the nature of the waste to be treated, it may be useful to carry out prior grinding to bring it to a controlled particle size, preferably homogeneous.

In an advantageous embodiment, on the waste route, between the feed member and the reactor, there is a means of adding an agent for neutralizing the aggressive components, such as for example halogens, sulfur, which avoids the subsequent presence of harmful compounds (SO2
HCl HF) in atmospheric releases. This neutralizing agent, such as for example calcium carbonate, is incorporated into the crushed waste during its conveyance between the supply member and the thermolysis reactor.

This grinding of the waste allows a better distribution of the neutralizing agent and consequently, a better efficiency of this neutralization.

The thermolysis reactor preceded by the airlock characteristic of the invention, operates in the absence of oxygen at a temperature, as already said, between 400 and 10000C, preferably around 500 "C, and the pressure of the reactor is maintained from 5000 to 40,000, preferably 10,000
Pascals below atmospheric pressure. It follows that the waste to be treated which generally advances in thin layers, then decompose under the action of heat into two by-products, respectively a gas for substantially two thirds, and a solid carbonaceous residue for substantially one third . The duration of residence and flow in the reactor is several tens of minutes, in particular thirty minutes. The reactor is heated by any suitable means, such as in particular electricity.

 According to the invention, the two by-products of thermolysis, respectively the gas and the carbonaceous solid residue, are recovered, the first at the top of the reactor and the second at the bottom of the latter.

 According to another characteristic of the invention, the installation comprises at least one airlock arranged upstream and downstream of the reactor. This airlock can be constituted in any known manner, for example by a helical compression screw, by pumps, by guillotine valves or the like.

 According to another characteristic of the invention, the thermolysis gases, recovered from the top of the reactor, are conveyed under the effect of a suction to a combustion chamber which in turn feeds a steam generator. It is important that during the transfer from the reactor to the combustion chamber, the thermolysis gas fraction is kept at high temperature. At the same time, the carbonaceous solid products recovered at the bottom of the reactor are conveyed to another combustion chamber to be burned, this second chamber also in turn supplying another steam generator, or failing this, an evacuation system for final recovery, or even landfill.

 In a simplified embodiment, the combustion gases and carbonaceous solid residues produced by the reactor are conveyed to the same combustion chamber which supplies a single steam generator.

In a variant, the combustion chamber has two hearths, respectively a first hearth for carbonaceous solid products, a second for gases.

 This separate combustion of the two gaseous and solid by-products, respectively, makes it possible to optimize the quality of the combustion and consequently the yields. The hot combustion gases are then globalized to be used in energy form for the production of steam or hot water.

 Thus, it has been determined that the treatment of 200 kilos per hour of hospital waste makes it possible to produce approximately 600 kilos of steam at 8 bars per hour.

 After being recovered, the combustion gases are released into the atmosphere through a traditional chimney under conditions preventing the formation of a plume.

 On the other hand, the carbonaceous solid products, after having been recovered in the combustion chamber, lead to ultimate residues, such as ash of quantities much lower than those of bottom ash from traditional incineration.

Brief description of the figures
Figure 1 illustrates the diagram of an installation according to the invention.

 Figures 2 and 3 show this same installation in summary perspective view, respectively top view and three quarters view (Figure 2), side view and three quarters view (Figure 3).

 Figure 4 is a schematic summary representation of a simplified installation according to the invention.

Way of realizing the invention
Referring to Figures 1 to 3, the installation according to the invention comprises a station (1) for receiving the waste (2) to be treated comprising an organic fraction, such as hospital waste, used tires, waste shredding of cars (RBA), green or biomass waste, urban or household waste, sludge from sewage treatment plants, or even petroleum waste.

 This waste is brought into a grinding unit (3) intended to bring it to a controlled particle size, preferably homogeneous. The ground waste is then brought into a hopper (4), then into an airlock (5), and from there into a drying enclosure heated directly or indirectly. The vapors (7) from drying are captured at the top of the enclosure (6) by a pipe (8) to be brought to the combustion chamber. The dried waste (10) is first added to (11) a neutralizing agent such as calcium carbonate, then is then conveyed by a conveyor (12) to the inlet of the reactor (13).

 This thermolysis reactor (13) can be of the type described in document WO-96/11742 of the Applicant, in particular in FIGS. 6, 9 and 10 of this document, or of another equivalent known type. This reactor (13) is preferably heated with electricity. It is important that this reactor (13) heated to a temperature close to 500 ° C., with a vacuum of the order of ten thousand (10,000) Pascals below atmospheric pressure, operates in oxygen deficiency. The residence time of the waste (10) in this reactor is approximately thirty minutes.

 Thermolysis causes the formation of two by-products, respectively an organic gas fraction recovered upwards by the piping (15) and a fraction of carbonaceous solid products recovered downwards (18).

 According to a characteristic of the invention, the installation comprises means (15) for recovering at the top of the reactor (13), in particular by means of piping and a fan (16), the organic gaseous fraction formed during thermolysis to bring it to a combustion chamber (20). This combustion chamber of horizontal cylindrical type has an inlet (21) of propane gas making it possible to make a make-up, to guarantee the maintenance of temperature during the start and stop phases and to ensure a pilot flame. This combustion chamber (20) in turn feeds a steam generator (22), for example of the double circulation boiler type supplied with water (23).

 In an advantageous embodiment, the clean combustion gases from the combustion chamber (20) are brought by a pipe (25) into the dryer (6), in particular to ensure direct drying of the waste to be treated. The steam produced by the generator (22) is brought by a pipe (26) to the same dryer (6) to ensure the indirect drying of the waste to be treated or to be used on the waste production site (1).

 The reference (30) designates a combustion air supply fan and the reference (31) the burner of the combustion chamber (20). In parallel, the tube (8) for extracting the vapors from the dryer (6) is associated with a vacuum cleaner (9) which brings these vapors into the combustion chamber itself (20).

 The fumes from the generator (22) are brought through the pipe (35) in a cyclone (36) from where they are extracted by a fan (37) connected to the external chimney (38) of discharge into the atmosphere.

 In an advantageous variant, the waste reception area (1) (2) is surmounted by a hood (40) associated with a pipe (41) bringing the vacuum air into the combustion chamber (20) to serve combustion air make-up. In this way, thanks to a fan (not shown), the vapors naturally emanating from waste, especially hospital waste, are evacuated then burned, and do not spread in the treatment enclosure.

 According to another characteristic of the invention, the carbonaceous solid residues (16) formed during thermolysis first pass through an airlock (50) similar to (5), then on a conveyor (51) making it possible to extract these tailings at the bottom of the reactor (13). These carbon-based solid residues (18) are rich in carbon, but also in polluting products, such as chlorine, sulfur, and contain inorganic fractions, such as metal, glass, stones, or even multiple residues. These residues which are embedded in the very fine powdery powder resulting from the thermolysis of the organic fraction, are screened in (52) according to their particle size and their nature, and the carbonaceous fraction (53) is brought to a second combustion chamber (60 ) similar to (20), also supplied with propane gas (61), and whose gas outlet (62) similar to (25) can be connected to the dryer (6). This combustion chamber is associated as before with a steam generator (65) supplied with water (66) to supply steam at (67) analogous to (26), to also be connected to the dryer (6). The combustion ashes are removed at (68) to be landfilled.

 The metal parts (71) resulting from this screening (52) are notably stored (72). The inorganic fraction essentially comprising metals, glass, pebbles, ultimate residues, is subject to additional screening to recover recyclable materials and the non-recoverable fraction (75) consisting of solid residues, which are removed (76 ) to be landfilled (77).

 The vapors (26,67) produced by the generators (22,65) are used either to dry in (6) the waste (1) to be treated and / or to supply energy to the unit producing this waste.

 In this way, the installation rejects outside (38) only clean smoke (25) and ultimate residues (77) or ash (68) recoverable, since all the energy produced is transformed into steam for be reinjected into the installation or to be upgraded upstream.

 The gas fractions (8,15) brought into the first combustion chamber (20) are burned at a temperature close to 850 "C for approximately two seconds. The thermal destruction is then complete, which makes it possible to optimize the recovery of the energy content of waste in the form of vapor (26.67).

 The installation according to the invention therefore makes it possible to successfully treat the most varied waste comprising an organic fraction. It also allows and above all an energy recovery from this thermolysis treatment by allowing recovery in two phases, respectively a gas phase (15) and a solid phase (18), and the combustion of these two phases (20,60) allows producing steam (26,67) (or hot water) intended to supply the drying (6) and / or the waste production unit (1). Thus, during operation, the installation is almost energy self-sufficient, which makes it very attractive in terms of investment and operation.

 Figure 4 illustrates another simplified embodiment of the invention. For convenience, the same references have been used as in FIG. 1.

In this installation, the waste to be treated having an acceptable humidity level, there is no dryer (6), especially since the low capacity (200 kg / h) does not justify a heavy investment (dryer + specific combustion chamber).

 In this simplified version, in addition to the absence of the dryer (6), the combustion chamber (20) is unique, but has a double hearth, respectively a first hearth for treating the thermolysis vapors supplied by the pipe (17) and a second hearth for treating carbonaceous residues (53) brought by the conveyor (51). This simplified embodiment is advantageous for the treatment of low-capacity hospital waste, for example between 100 and 300 kg / h.

The installation according to the invention has many advantages compared to those known to date. We can cite:
operational simplicity;
the use of proven equipment,
a modular concept allowing easy and quick installation;
absence of liquid discharge;
excellent safety and good quality of the heat treatment,
since there is no unburnt;
the fact that from waste you only get ashes;
. the possibility of quick starts and stops and
clean, with possibility of standby;
competitive investment costs, processing costs and
low maintenance, no additional costs linked to treatment
for wastewater;
very good energy recovery from waste, since for 200
kilos / hour of hospital waste, we can get up to 600
kilos / hour of steam at 8 bars or equivalent.

 In this way, this installation can be successfully used for the treatment of waste of all kinds, such as domestic, industrial, hospital waste, sludge from treatment plants or others, or even on the site of production of this waste. , but without resorting to heavy installations, which we know to be more and more expensive and difficult to operate under conditions which respect the environment.

Claims (7)

AND CLAIMS  1 / Installation for the thermolysis treatment of waste comprising an organic fraction and having a controlled particle size, and simultaneously for the energy recovery of this waste, of the type essentially comprising:  a loading unit (1) and supply of waste to be treated;  . a thermolysis reactor (13) for thermal dissociation under  reduced pressure at high temperature,  characterized:  - in that it includes:  . upstream (5) and downstream (50) of the reactor (13), an airlock intended for  maintain a vacuum in the reactor to ensure  thermolysis in an atmosphere with very low oxygen content;  means (15) for recovering, at the top of the reactor  (13), the organic gas fraction formed during thermolysis,  and means (16) for bringing this gaseous fraction to a  combustion chamber (20) supplying a generator  steam (22);  . means (51) for recovering at the bottom of the reactor (13) the  carbonaceous solid products (18) formed during thermolysis, and  to bring these solid products to a combustion chamber  (60) supplying a steam generator (65) or an exhaust system  - and in that the gases from the combustion chamber and the steam produced by the steam generator, in turn feed the waste production unit and / or a means for previously drying the waste disposed just upstream of the reactor ( 13).  2 / Installation according to claim I, characterized in that the waste is previously ground to bring it to a controlled particle size, preferably homogeneous.  3 / Installation according to claim 1, characterized in that the waste is subjected beforehand to drying intended to lower their water content.  4 / Installation according to claim 1, characterized in that on the waste path, between the feed member (1) and the reactor (13), there is an addition means (11) of an agent neutralization of aggressive components.  5 / Installation according to one of the preceding claims, characterized in that the thermolysis reactor (13) operates in almost absence of oxygen at a temperature between 400 and 10000C, under a pressure maintained between 5000 and 40000 Pascals below atmospheric pressure.  6 / Installation according to one of the preceding claims, characterized in that the airlocks (5.50) are chosen from the group consisting of helical compression screws, pumps, guillotine valves.  7 / Installation according to claim 1, characterized in that during the transfer from the reactor (13) to the combustion chamber (20), the gaseous fraction of thermolysis is maintained at high temperature.