Pyrolysis furnace for dismantling photovoltaic modules and associated pyrolysis process

Abstract

The invention relates to a pyrolysis furnace (1) for recycling photovoltaic modules (100), comprising: at least one pyrolysis chamber (2) for housing the photovoltaic modules (100), a post-combustion chamber (3) fluidly connected to the pyrolysis chamber (2), first heating means (41) for the pyrolysis chamber (2) and second heating means (42, 43) for the post-combustion chamber (3), a neutral gas distribution system (6) configured to inject said neutral gas into the pyrolysis chamber (2), a temperature sensor (31) disposed in the post-combustion chamber (3) for measuring a temperature at the core of said chamber, referred to as the core temperature (Tc), and a controller (C) configured to control the injection of neutral gas by the distribution system (6) as a function of the core temperature (Tc). The invention also relates to a pyrolysis process with an optimized post-combustion charge.Figure to be published with the abbreviation: Figure 2.

Description

Title of the invention: Pyrolysis oven for dismantling photovoltaic modules and associated pyrolysis process. FIELD OF THE INVENTION

[0001] The present invention relates to the field of photovoltaic module recycling. It relates in particular to a batch pyrolysis oven, particularly suitable for the thermal dismantling of photovoltaic modules for the purpose of recycling the materials from which they are made. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0002] Given the exponential increase in photovoltaic panels produced and installed, their recycling becomes essential to recover and valorize the precious materials that compose them (metals, glass, silicon...).

[0003] In a recycling process, the metal frame 110 (“frame”) of the end-of-life photovoltaic panels 200 and the junction box 150 are first separated from the photovoltaic module 100, which is a sandwich of functional layers, generally including a stack of glass 120, polymer layers 131, 132, 133 and photovoltaic cells 140 with semiconductor and metal contacts ([Fig. 1]). The polymer layers may include, in particular, ethylene vinyl acetate (EVA), polyethylene terephthalate (PET), polyvinyl fluoride (PVF) or polyvinylidene fluoride (PVDF).

[0004] It is then known to dismantle the photovoltaic module 100 either by a mechanical process or by thermal treatment based on a pyrolysis and / or combustion process. Tunnel furnaces (continuous processing, combustion process) or batch furnaces (batch processing, pyrolysis or combustion process) can be used. The polymer layers 131, 132, 133, included in the sandwich of functional layers (photovoltaic module), are formed of organic compounds, which can be decomposed by pyrolysis or burned by combustion, thereby inducing the separation of the layers into mineral materials of the sandwich.

[0005] The gases generated by the pyrolysis or combustion of polymers generally pass through a post-combustion chamber whose role is to treat these gases at high temperatures (typically greater than or equal to 850°C, in accordance with current legislation) to ensure their total combustion, thus allowing the release of a gaseous effluent compatible with release into the atmosphere.

[0006] Because it must be maintained at a high temperature and have sufficient volume to ensure a residence time of the gases to be treated greater than 2s (according to the legislation on waste incineration), a post-combustion chamber is a strong contributor to energy costs in a pyrolysis furnace. SUBJECT OF THE INVENTION

[0007] The present invention provides a pyrolysis furnace particularly suited for the thermal dismantling of photovoltaic modules and allowing for optimization of the afterburner chamber load, in order to minimize energy costs. The invention also relates to an associated pyrolysis process. BRIEF DESCRIPTION OF THE INVENTION

[0008] The invention relates to a pyrolysis oven for recycling photovoltaic modules, configured for batch processing and comprising:

[0009] - at least one pyrolysis chamber intended to house a batch of modules photovoltaic panels, and insulated from the outside by a sealed door,

[0010] - an afterburner chamber fluidically connected on one side to the enclosure of pyrolysis, and on the other hand, to a gas evacuation,

[0011] - of first heating means for the pyrolysis chamber and of second heating methods for the afterburner chamber,

[0012] - a neutral gas distribution system, configured to inject said neutral gas within the pyrolysis chamber,

[0013] - a temperature sensor, disposed in the afterburner chamber, for to measure a temperature at the core of said chamber, called the core temperature,

[0014] - a controller configured to control the injection of neutral gas by the system of distribution as a function of core temperature.

[0015] According to other advantageous and non-limiting features of the invention, taken alone or in any technically feasible combination: • a boundary zone between the pyrolysis chamber and the post-combustion chamber is located in a part of the pyrolysis chamber which extends above the photovoltaic modules, called the upper part; • the distribution system is located in a part of the pyrolysis chamber which extends below the photovoltaic modules, known as the lower part; • the distribution system is configured to inject the neutral gas into the pyrolysis chamber with a variable flow rate between 0 and 300 Nm3 / h, preferably between 50 Nm3 / h and 200 Nm3 / h; • the injection of neutral gas is controlled by the core temperature so that the flow rate varies to maintain the core temperature above a minimum temperature and below a maximum temperature; • the minimum temperature is above 850°C, preferably above or equal to 900°C; • the maximum temperature is between 1000°C and 1400°C; • The pyrolysis oven comprises a plurality of pyrolysis chambers, all fluidly connected to the post-combustion chamber.

[0016] The invention also relates to a pyrolysis process for recycling photovoltaic modules, implemented in a pyrolysis furnace as described above, the process comprising the following steps:

[0017] 1) the introduction of a batch of photovoltaic modules into the pyrolysis chamber and the airtight door closure, the photovoltaic modules comprising polymer layers,

[0018] 2) the temperature rise of the afterburner chamber at least up to a regulated temperature, and the temperature rise of the pyrolysis chamber up to a pyrolysis temperature, respectively using the second and first heating means, the second heating means being operated with an initial heating power,

[0019] 3) the generation of pyrolysis gas in the pyrolysis chamber, by decomposition thermal properties of polymer layers,

[0020] 4) the reduction of the heating power of the second heating means, to less than 90% of the initial heating power,

[0021] 5) the injection of neutral gas into the pyrolysis chamber to push the gases of pyrolysis towards the post-combustion chamber, with neutral gas injection being carried out at a modulated flow rate so as to maintain the central temperature of the combustion chamber greater than or equal to a minimum temperature which is itself higher than the regulatory temperature,

[0022] 6) the incineration of pyrolysis gases in the post-combustion chamber.

[0023] According to other advantageous and non-limiting features of the invention, taken alone or in any technically feasible combination: • at step 4), the heating power of the second means of heating corresponds to less than 70%, less than 50%, or even less than 30%, or even less than 20% of the initial heating power; • steps 1) to 6) apply to each of the pyrolysis chambers in a pyrolysis furnace comprising a plurality of pyrolysis chambers, all fluidly connected to the post-combustion chamber; • the sequence of steps 2) to 6) in each pyrolysis chamber is desynchronized from this same sequence in the other pyrolysis chambers, so that the afterburner chamber receives pyrolysis gases from only one pyrolysis chamber at a time. BRIEF DESCRIPTION OF THE FIGURES

[0024] Other features and advantages of the invention will become apparent from the detailed description of the invention which follows with reference to the accompanying figures in which:

[0025] [Fig.1] Fig.1 presents an exploded view of a photovoltaic panel;

[0026] [Fig.2] Fig.2 presents a pyrolysis oven according to the present invention;

[0027] [Fig.3] Fig.3 presents an example of a pyrolysis process not in accordance with the invention;

[0028] [Fig.4] Fig.4 presents an example of a pyrolysis process according to the present invention;

[0029] [Fig.5] Fig.5 presents a particular embodiment of a pyrolysis oven according to the invention.

[0030] The figures are schematic representations which, for the purpose of readability, are not necessarily to scale. DETAILED DESCRIPTION OF THE INVENTION

[0031] The present invention relates to a pyrolysis oven for recycling photovoltaic modules 100.

[0032] For the thermal dismantling of modules 100, with a view to recovering the mineral materials from which they are formed, a pyrolysis process is preferred to a combustion process in which the risk of degradation of the materials to be recycled is high, because the temperature during combustion is not controlled (possible melting of metals).

[0033] Figure 2 schematically presents an oven 1 according to the invention. It is configured to perform batch processing, and not continuous processing like tunnel furnaces. A batch consists of a set of 100 photovoltaic modules, held in one or more supports 500, which will be introduced into furnace 1 to be processed, then removed from said furnace after processing.

[0034] The oven 1 includes at least one pyrolysis chamber 2 intended to house the batch of photovoltaic modules 100. The chamber 2 is isolated from the outside by a sealed door 25. In a particular embodiment which will be described later, the oven 1 may include a plurality of pyrolysis chambers 2, independent of each other, each intended to house a batch of modules 100.

[0035] The furnace 1 also includes a post-combustion chamber 3 fluidically connected, on the one hand, to the pyrolysis chamber 2, at a proximal region 3a of the post-combustion chamber 3, and on the other hand, to a gas vent 9, at a distal region 3b of the post-combustion chamber 3. At least two temperature sensors are provided to measure the temperature: a first sensor 31 disposed in a central region 3c of the post-combustion chamber 3, for A central temperature (Tc) is measured, and a second sensor (32) positioned in the distal region (3b) is used to measure an outlet temperature (Ts). Both the central temperature (Tc) and the outlet temperature (Ts) are expected to be greater than or equal to 850°C to ensure the complete combustion of the pyrolysis gases, which are organic, toxic, and combustible. As mentioned in the introduction, the regulatory temperature of 850°C is defined by waste incineration legislation.

[0036] In general, a temperature sensor is also provided in the pyrolysis chamber 2.

[0037] To enable the heating of the pyrolysis chamber 2 and the post-combustion chamber 3, the oven 1 includes heating means, named first heating means 41 for heating the chamber 2 and second heating means 42,43 for heating the chamber 3.

[0038] These heating means may take the form of burners supplied by a commercial fuel gas distribution circuit G1 and a distribution circuit for an oxygen-containing gas G2 (oxidizer). The commercial fuel gas is, for example, natural gas or liquefied petroleum gas (LPG). The oxygen-containing gas may be air.

[0039] It should be noted that pyrolysis is an anaerobic process during which organic matter (polymer, grease, etc.) is evaporated by the action of heat. Therefore, it is critical in such a process to limit the oxygen content in chamber 2 to prevent the polymers from burning. The oxygen content in pyrolysis chamber 2 during the pyrolysis phase of the polymer layers of modules 100 is preferably less than 5%, or even less than 4%. The pyrolysis temperature in chamber 2 is typically between 300°C and 600°C.

[0040] As mentioned previously, pyrolysis gases generated in enclosure 2 will pass through a boundary zone between enclosure 2 and chamber 3, and enter the proximal region 3a of said chamber 3; they will then pass through the core (central region 3c) of the afterburner chamber 3. The gases resulting from the decomposition of the pyrolysis gases will finally reach the distal region 3b of chamber 3, connected to the vent 9. The vent 9 is also connected to a combustion gas treatment unit (for example, scrubber), after which the fluid can be released into the atmosphere.

[0041] A vacuum is generally created in the furnace 1 by means of a fan placed downstream of the exhaust 9. This suction mainly compensates for the overpressure generated by the combustion of the commercial fuel gas by the first heating means 41 in the pyrolysis chamber 2. Although the pyrolysis gases are substantially carried along by this flow, this fan does not constitute an active system for managing the charge of the post-combustion chamber 3 with pyrolysis gas.

[0042] To optimize this load, the furnace 1 according to the invention includes a neutral gas distribution system 6, configured to inject said neutral gas (for example, nitrogen or argon) into the pyrolysis chamber 2. The injection of the neutral gas is intended to provide a piston effect, enabling the pyrolysis gases (highly flammable) contained in the chamber 2 to be conveyed to the afterburner chamber 3, where they will be incinerated and consequently generate thermal energy. This energy makes it possible to drastically reduce the consumption of commercial fuel gas by the secondary heating means 42, 43. In addition, since pyrolysis gases release a great deal of energy when burning, the central temperature Tc of the afterburning chamber 3 can advantageously be increased, typically between 900°C and 1400°C, or preferably between 950°C and 1200°C, and thus shorten the duration of the overall pyrolysis process.

[0043] In the embodiment illustrated in [Fig. 2], the boundary zone between the pyrolysis chamber 2 and the afterburner chamber 3 is located in the upper part 2a of the chamber 2, which extends above the batch of photovoltaic modules 100. The part of the chamber distant from the boundary zone extends below the batch of photovoltaic modules 100 and corresponds to a so-called lower part 2b. In such a configuration, it is understood that the injection of neutral gas in the lower part 2b of the chamber 2 will generally push the pyrolysis gases towards the upper part 2a, in particular towards the boundary zone and the proximal region 3a of the afterburner chamber 3.

[0044] Advantageously, the distribution system 6 is configured to inject the neutral gas into the pyrolysis chamber 2 with a variable flow rate between 0 and 300 Nm3 / h (norm cubic meters per hour), preferably between 50 Nm3 / h and 200 Nm3 / h. It preferably comprises a plurality of injection nozzles uniformly distributed throughout all or part of the lower part 2b of the pyrolysis chamber 2. It is preferable that the neutral gas has a high temperature (above 300°C, or even above 400°C) at the time of its injection, to limit its impact on the temperature of the chamber 2. The distribution system 6 is therefore advantageously made of stainless steel and equipped with heating means.

[0045] The furnace 1 according to the invention further comprises a controller C configured to control the injection of neutral gas by the distribution system 6 as a function of the central temperature Tc of the post-combustion chamber 3. Advantageously, the injection of neutral gas is controlled by the central temperature Tc so that the injection flow rate by the distribution system 6 varies to maintain the central temperature Tc, as stable as possible, above a minimum temperature Tmin and advantageously below a maximum temperature Tmax.

[0046] The injection of neutral gas is done progressively to avoid sudden variations in pressure in enclosure 2 or in temperature in the post-combustion chamber 3. For this, a proportional opening valve can be implemented and controlled by an electronic regulator comprising a set of PID (Proportional, Integral, Derivative) adjusted to meet the need.

[0047] The minimum temperature Tmin is necessarily higher than the regulatory temperature (currently 850°C). It is preferably greater than or equal to 860°C, 870°C, 900°C, 920°C, 950°C, 970°C, or even 1000°C.

[0048] The maximum temperature Tmax is typically between 1000°C and 1400°C, between 1000°C and 1200°C or between 1200°C and 1400°C.

[0049] The advantages of the oven 1 according to the invention will be better understood with the description of the pyrolysis process, which is also the subject of the present invention.

[0050] A pyrolysis process, which aims at recycling photovoltaic modules 100, typically comprises four main thermal phases, as illustrated in [Fig.3]: - a preliminary preheating phase of chamber 2 up to approximately 300°C; the temperature of the post-combustion chamber 3 being at least equal to the regulatory temperature; - a pyrolysis phase, between 300°C and 500°C, under an oxygen-poor or oxygen-free atmosphere (typically less than 5% by volume of oxygen), during which the polymers are decomposed and pyrolysis gases are generated in enclosure 2 and conveyed to the afterburner chamber 3 to be burned, at a temperature greater than or equal to 850°C (regulatory temperature); - an oxidation phase, between 450°C and 600°C, under an oxidizing atmosphere (air), during which the carbon residues potentially formed during the previous phase are decomposed; - a cooling phase, down to a temperature allowing the removal of mineral materials from the dismantling of the modules.

[0051] When the delivery of pyrolysis gases to the afterburner chamber 3 is not actively controlled, their relatively erratic arrival causes thermal energy spikes: the core temperature Tc of the afterburner chamber 3 therefore varies in a highly random, sawtooth pattern, as seen in [Fig. 3] during part P2 (during which the polymers begin to decompose and form pyrolysis gases) of the pyrolysis phase. These erratic variations also make it difficult to minimize atmospheric emissions, particularly the generation of nitrogen oxides (NOx).

[0052] The pyrolysis process according to the invention proposes the optimization of the pyrolysis gas charge of the post-combustion chamber 3, so as to target a central temperature Tc greater than or equal to the minimum temperature Tmin and as stable as possible, and to significantly reduce the consumption of commercial fuel gas at the level of the second heating means 42,43, during all or part of the pyrolysis phase.

[0053] The pyrolysis process, in an oven 1 as mentioned above, includes a first step 1) corresponding to the introduction of a batch of photovoltaic modules 100 into the pyrolysis chamber 2 and the closing of the sealed door 25.

[0054] The next step 2) comprises raising the temperature Tc of the afterburner chamber 3 to the regulatory temperature (or higher), using the second heating means 42, 43, and raising the temperature Tenclosed of the pyrolysis chamber 2 to the pyrolysis temperature, using the first heating means 4L

[0055] To reach the required temperature, the second heating means 42, 43 are operated with an initial heating power. Note that the temperature rise of the pyrolysis chamber 2 is only initiated after the post-combustion chamber 3 has reached said required temperature.

[0056] Step 2) corresponds to the preliminary phase illustrated in [Fig.4].

[0057] The following steps 3) to 6) of the process according to the invention are carried out during the phase pyrolysis ([Fig.4]), simultaneously.

[0058] When the pyrolysis temperature is reached in enclosure 2, pyrolysis gases are generated by thermal decomposition of the polymer layers 131,132,133 contained in the photovoltaic modules 100 (step 3).

[0059] The heating power of the second heating means 42, 43 is reduced to less than 90% of the initial heating power (step 4). Preferably, it is reduced to less than 80%, 70%, 60%, 50%, 40%, 30%, or even 20% of the initial heating power. The reduction in the heating power of the second heating means 42, 43 corresponds to a reduction in the commercial fuel gas supply rate. The commercial gas consumption is reduced in the same proportion as the heating power, which is particularly advantageous in terms of energy costs.

[0060] Neutral gas is injected into chamber 2 using the distribution system 6, so as to push the pyrolysis gases towards the afterburner chamber 3 (step 5). This injection is controlled by the controller C. The neutral gas flow rate is modulated to maintain the core temperature Tc of the afterburner chamber 3 above the defined minimum temperature Tmin. The injection A neutral gas supply, controlled by the central temperature Tc, allows for the control of the pyrolysis gas charge in the afterburner chamber 3. This charge replaces the commercial fuel gas, the consumption of which can be significantly reduced during at least part P2 of the pyrolysis phase. Of course, the supply of oxidizer (e.g., air) to the secondary heating means 42, 43 remains necessary to enable combustion.

[0061] The pyrolysis gases are incinerated in the afterburner chamber 3 (step 6). The significant energy they release makes it possible to maintain the core temperature Tc of chamber 3 above 850°C, greater than or equal to 900°C, 950°C, or even 1000°C. Since the pyrolysis gases are continuously and in a controlled manner conveyed from the pyrolysis chamber 2 to the afterburner chamber 3, and their combustion is carried out at a higher temperature, the pyrolysis phase can advantageously be shortened. The reduction in pyrolysis time is another advantage of the present invention, which also results in energy savings.

[0062] Let us recall that after the pyrolysis phase, the other phases (oxidation, cooling) can be implemented in a conventional way.

[0063] According to a particular embodiment of the invention, the pyrolysis furnace 1 comprises a plurality of pyrolysis chambers 2i, 2ii, 2iii, 2iv ([Fig. 5]). Steps 1) to 6) of the described pyrolysis process apply to each of the chambers 2i, 2ii, 2iii, 2iv. However, the pyrolysis phase in each chamber is desynchronized from that in the other chambers. In other words, the afterburner 3 is supplied with pyrolysis gas from only one chamber at a time (chamber 2iii in [Fig. 5]). The chamber(s) that are in the loading or unloading phase (for example, chamber 2i) is / are isolated from the afterburner 3 by a hatch 7i, 7ii, 7iii, 7iv, and connected to a chimney. From the preliminary heating phase to the cooling phase, the chambers 2ii,2iii,2iv have their hatch 7ii,7iii,7iv open to allow direct communication with chamber 3.However, only one pyrolysis phase takes place in chamber 2iii, chambers 2ii and 2iv being respectively in the preliminary and cooling phases.

[0064] This multi-chamber configuration of the pyrolysis furnace 1 further optimizes the energy costs associated with the post-combustion chamber 3, which represent more than 65% of the total heating costs of a conventional pyrolysis furnace. Indeed, the energy cost associated with heating the post-combustion chamber 3 is amortized over several pyrolysis cycles, and the multiple pyrolysis phases (one pyrolysis phase in each chamber 2i, 2ii, 2iii, 2iv) are achieved by optimizing the pyrolysis gas charge according to the process of the invention.

[0065] The present invention optimizes the pyrolysis gas charge delivered to the afterburner chamber 3, thereby significantly reducing the consumption of commercial fuel gas required to maintain the chamber 3 at a high temperature. Furthermore, maintaining a relatively stable and high core temperature Tc of the afterburner chamber 3 (above a defined minimum temperature) throughout the pyrolysis phase reduces the duration of the pyrolysis phase and improves the quality of the atmospheric gas emissions after venting 9 and treatment. All of this results in significant energy savings compared to a conventional pyrolysis process.

[0066] Of course, the invention is not limited to the embodiments and examples described, and alternative embodiments can be made without departing from the scope of the invention.

Claims

Demands

1. Pyrolysis furnace (1) for recycling photovoltaic modules (100), configured for batch processing and comprising: - at least one pyrolysis chamber (2) intended to accommodate a batch of photovoltaic modules (100), and isolated from the outside by a sealed door (25), - a post-combustion chamber (3) fluidically connected on one side to the pyrolysis chamber (2), and on the other side to a gas vent (9), - first heating means (41) for the pyrolysis chamber (2) and second heating means (42, 43) for the post-combustion chamber (3), - a neutral gas distribution system (6), configured to inject said neutral gas into the pyrolysis chamber (2), - a temperature sensor (31), disposed in the post-combustion chamber (3), for measuring a temperature at the core of said chamber, called the core temperature (Tc),- a controller (C) configured to control the injection of neutral gas by the distribution system (6) as a function of the central temperature (Tc).

2. Pyrolysis furnace (1) according to the preceding claim, wherein: - a boundary zone between the pyrolysis chamber (2) and the post-combustion chamber (3) is located in a part of the pyrolysis chamber (2) which extends above the photovoltaic modules (100), referred to as the upper part (2a), and - the distribution system (6) is disposed in a part of the pyrolysis chamber (2) which extends below the photovoltaic modules (100), referred to as the lower part (2b).

3. Pyrolysis oven (1) according to any one of the preceding claims, wherein the distribution system (6) is configured to inject the neutral gas into the pyrolysis chamber (2) with a flow rate that can be modulated between 0 and 300 Nm3 / h, preferably between 50 Nm3 / h and 200 Nm3 / h.

4. Pyrolysis furnace (1) according to the preceding claim, wherein the injection of neutral gas is controlled by the core temperature (Tc) such that the flow rate varies to maintain the core temperature (Tc ) above a minimum temperature (Tmin) and below a maximum temperature (Tmax).

5. Pyrolysis oven (1) according to the preceding claim, wherein the minimum temperature (Tmin) is greater than 850°C, preferably greater than or equal to 900°C.

6. Pyrolysis oven (1) according to one of the two preceding claims, wherein the maximum temperature (Tmax) is between 1000°C and 1400°C.

7. Pyrolysis furnace (1) according to any one of the preceding claims, comprising a plurality of pyrolysis chambers (2i,2ii,2iii,2iv), all fluidly connected to the post-combustion chamber (3).

8. A pyrolysis process for recycling photovoltaic modules (100), implemented in a pyrolysis furnace (1) according to any one of the preceding claims, the process comprising the following steps: 1) introducing a batch of photovoltaic modules (100) into the pyrolysis chamber (2) and closing the airtight door (25), the photovoltaic modules (100) comprising polymer layers (131, 132, 133), 2) heating the afterburner chamber (3) at least to a regulatory temperature, and heating the pyrolysis chamber (2) to a pyrolysis temperature, respectively, using the second (42, 43) and first (41) heating means, the second heating means (42, 43) being operated with an initial heating power, 3) generating pyrolysis gas in the pyrolysis chamber (2), by thermal decomposition of polymer layers (131,132,133),4) reducing the heating power of the second heating means (42,43) to less than 90% of the initial heating power, 5) injecting neutral gas into the pyrolysis chamber (2) to push the pyrolysis gases towards the post-combustion chamber (3), the injection of neutral gas being carried out at a modulated flow rate so as to maintain the central temperature (Tc) of the combustion chamber (3) greater than or equal to a minimum temperature (Tmin) itself greater than the regulatory temperature, 6) the incineration of pyrolysis gases in the post-combustion chamber (3).

9. Pyrolysis process according to the preceding claim, wherein in step 4), the heating power of the second heating means (42,43) corresponds to less than 70%, less than 50%, or even less than 30%, or even less than 20% of the initial heating power.

10. A pyrolysis process according to one of the two preceding claims, implemented in a pyrolysis oven according to claim 7, wherein: - steps 1) to 6) are applied to each of the pyrolysis chambers (2i,2ii,2iii,2iv), and - the sequence of steps 2) to 6) in each pyrolysis chamber is desynchronized from this same sequence in the other pyrolysis chambers, so that the afterburner chamber (3) receives pyrolysis gases from only one pyrolysis chamber (2iii) at a time.

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