Systems for removing odorous emissions from industrial processes

Abstract

A method and apparatus for treating raw exhaust gas (4, 4') containing asphalt vapor and released by equipment (1) of a polymer-bitumen membrane production line is described, wherein an operation involving filler powder (3), such as mixing the filler powder (3) with asphalt (2), is performed, during which the raw exhaust gas (4, 4') is changed from raw exhaust gas (4) substantially free of powder to raw exhaust gas (4') containing the filler powder (3). The method comprises the following steps: firstly conveying the raw exhaust gas (4, 4') together with a solution (9) of a surfactant to a gas scrubbing device (20); contacting the raw exhaust gas (4, 4') with the solution (9) and removing powder from the powder-containing gas (4'), thereby releasing a purified exhaust gas (5) substantially free of the filler powder; conveying the purified exhaust gas (5) to a boiler (40) and burning the asphalt vapor. In a preferred exemplary embodiment, only the powder-containing gas (4') generated during the operation of the device (1) involving the filler powder (3) is conveyed in the gas scrubbing device, while in the remaining steps, the substantially powder-free raw exhaust gas (4) is conveyed directly into the boiler (40) through an automatically selectable direct discharge line (50). In a preferred exemplary embodiment, the gas scrubbing device comprises a tank (25) configured to form a predetermined pressure head of the scrubbing solution (9) inside and having an inlet port for the raw exhaust gas arranged below the liquid pressure head. The method prevents powder from reaching the boiler (40) quickly and thus rendering the burners and heat exchange surfaces ineffective.

Description

Technical Field

[0001] The present invention relates to an improved method and an improved apparatus for treating bitumen vapours emitted by equipment of an apparatus for processing bitumen and fines. A typical example of such an apparatus is a polymer-bitumen membrane production line. Background Art

[0002] As is known, polymer-bitumen membranes are manufactured by hot impregnation of a polymer support skeleton with bitumen. The bitumen is usually provided at a temperature of about 120-130°C so that it is sufficiently fluid for easy transportation and for easy use for impregnation. Due to the temperature and vapor pressure of the bitumen, relatively large amounts of smelly and potentially harmful bitumen vapors are present in the exhaust gases from equipment that stores and processes bitumen. Therefore, these vapors must be removed from the exhaust gases before they are discharged into the atmosphere.

[0003] EP 3018410 A1 discloses an apparatus and method for treating asphalt vapor, wherein a system is provided for: extracting the vapor and mixing the hem with external air; feeding the obtained vapor / air mixture into a boiler as primary air; and adjusting the steam / external air ratio based on the composition of the combustion gas produced by burning the mixture.

[0004] This invention makes it possible to reduce, within the limits set by regulations, the amount of pollutants emitted into the atmosphere together with the combustion gases and, less successfully, to reduce, within acceptable limits, the emitted odoriferous substances (volatile hydrocarbons) contained in said combustion gases and said pollutants. This is an improvement over the previous technology for treating bitumen vapors, which comprised steps of extraction and conveying the vapors through activated carbon filters, scrubbers and other devices. The solution of EP3018410 A1 is particularly suitable for vapors coming from bitumen storage tanks.

[0005] However, it is known that before impregnation, very fine and invisible mineral filler powders are added to the bitumen, for example talc, the maximum value of the grain size distribution curve of which is usually about 0.7 μm. This powder is mainly introduced as a release agent. In fact, the manufactured membranes are wound to form rolls for easier transportation and sale, and such rolls are not prone to loosening when the membrane is used.

[0006] Inevitably, a certain amount of filler powder is sucked from the equipment of the production line and from the vapors sent to the combustion through the gas exhaust pipes. Of particular importance are the equipment known as "melt tanks", which are mixing tanks in which the filler is mixed with the bitumen. Powder suction occurs mainly when the filler is fed into these equipments, until the filler is not completely incorporated into the bitumen by stirring.

[0007] In machines similar to the one described in EP 3018410 A1, powder settles in the burners of the boilers and on the surfaces of the heat exchange equipment used to recover heat from the combustion gases, which gradually reduces the efficiency of said burners and said heat exchange equipment. For this reason, production must be frequently interrupted for cleaning and maintenance of the burners and this equipment, which limits the production rate of the polymer-bitumen membrane production line.

[0008] Furthermore, fillers present in the exhaust gases from the melt tank can reach the chimney and fine dust emissions can occur, which are harmful to health and the environment.

[0009] US 10,080,987 B1 relates to a system for producing HMA type asphalt (hot mix asphalt), in which a so-called "pug mill" is used to mix fine asphalt granules and coarse asphalt granules, and in which a combination of a dryer, a cyclone separator and a

[0010] EP 1 867 784 A1 discloses a method for manufacturing a road surface material based on conglomerate, said conglomerate comprising solid particles embedded in a binding material such as bitumen, wherein the steps of heating at least a portion of said solid particles to a temperature of up to more than 100° C., collecting the vapors thus formed, and separating these vapors into a small fraction of suspended matter and a gaseous fraction, in particular by contacting said vapors with a washing liquid such as water, and possibly the step of allowing said suspended matter to settle, are provided. The method is intended to prevent the emission of vapors containing harmful gaseous substances or fine particles into the atmosphere when manufacturing the road surface material.

[0011] US 4,153,471 relates to an improvement of a previously known process for the circulation of asphalt-aggregate compositions, which comprises the step of exposing the latter directly to hot combustion gases, usually in an elongated drum. From such a process a gaseous mixture containing volatile hydrocarbons and mineral particles is obtained, which is sent to a treatment chamber together with a flame for combustion, in order to achieve the purpose of controlling atmospheric pollution. Summary of the invention

[0012] The object of the present invention is therefore to provide an apparatus for incinerating malodorous gases released by equipment such as polymer-bitumen membrane production lines, said gases containing bitumen vapors and fine powder, which avoids the deposition of powder on the burners and on possible heat exchange surfaces of heat recovery equipment, so as to perform less frequent cleaning / maintenance operations.

[0013] Another object of the present invention is to provide an apparatus which can further reduce the odor of waste generated by a production line, in particular the odor of waste combustion gases.

[0014] These and other objects can be achieved by a method and an apparatus as defined in the following independent claims: The method and the apparatus are defined by independent claims 1 and 7, respectively, as being for treating unpurified exhaust gas, the unpurified exhaust gas containing bitumen vapor and being released by at least one device of an apparatus, such as a polymer-bitumen membrane production line, the apparatus being configured to perform a step of treating filler powder, wherein the filler powder is supplied to the apparatus and / or the apparatus performs an operation of mixing the filler powder with bitumen, such as for the manufacture of polymer-bitumen membranes, and in the step of treating the filler, the unpurified exhaust gas is transformed from a normal unpurified exhaust gas substantially free of powder to a powder-containing unpurified exhaust gas also containing a certain amount of the powder filler. Specific embodiments of the invention are defined by the dependent claims.

[0015] The filler powder generally consists of particles having a diameter of less than 630 μm, which diameter may be a true diameter or an equivalent diameter. In particular, the maximum value of the grain size distribution curve of the filler powder is generally about 0.7 μm.

[0016] In a first aspect of the present invention, the method comprises the following steps:

[0017] - Pre-arrange gas scrubbing plant gas;

[0018] - Pre-arranged boilers;

[0019] - firstly conveying the raw exhaust gas to the gas scrubbing device;

[0020] wherein the gas scrubbing device is configured to receive a scrubbing solution containing a surfactant and to contact the raw exhaust gas with the scrubbing solution;

[0021] - contacting the raw exhaust gas with the scrubbing solution and removing the amount of filler powder from the powder-containing raw exhaust gas such that the gas scrubbing device releases a cleaned exhaust gas substantially free of the filler powder;

[0022] - Secondly, the purified exhaust gas is conveyed to a boiler and the asphalt vapor is combusted, thereby obtaining combustion gas.

[0023] In a second aspect of the present invention, the apparatus comprises:

[0024] - Gas scrubbing plant;

[0025] -boiler;

[0026] - a first exhaust gas conduit between said at least one device and said gas scrubbing installation;

[0027] - a second exhaust gas conduit between the gas scrubbing device and the boiler;

[0028] wherein the gas scrubbing device is configured to receive a scrubbing solution containing a surfactant and to contact the raw exhaust gas with the scrubbing solution,

[0029] causing said powder to be removed from said gas and releasing a purified exhaust gas substantially free of said filler powder;

[0030] - A suction device arranged to convey the unpurified exhaust gas through the first exhaust gas duct and to convey the purified exhaust gas through the second exhaust gas duct.

[0031] In this way, only very small amounts of filler reach the burners of the boiler and possible heat exchange surfaces of the boiler, which can reduce the frequency of maintenance and / or cleaning operations in order to maintain the effectiveness of the burners and the heat exchange surfaces over time and in particular protect them from wear.

[0032] It has also been observed that, surprisingly, most of the unburned malodorous compounds present in the vapor are retained by this filtration system along with the filler, said malodorous compounds being believed to travel through the burner without being burned, and this improves the odor removal performance over the cited prior art and further reduces malodorous emissions.

[0033] The surfactant present in the scrubbing solution serves to improve the wettability of the particles forming the powder by increasing their affinity for water, so as to retain these particles in the mass of the scrubbing solution and prevent them from leaving the scrubbing solution in a secondary transport step / through the secondary exhaust gas conduit together with the purified exhaust gas.

[0034] The surfactant can be selected according to the properties of the powder present in the unpurified exhaust gas. In particular, in the case of polymer-asphalt membrane production equipment, the powder is a filler added to the asphalt to make the membrane and is generally essentially composed of calcium carbonate CaCO3. In this case, preferably, the surfactant is a non-ionic surfactant. For example, the non-ionic surfactant may include an aliphatic glycol, such as propylene glycol. As an alternative, the surfactant may be hexadecyltrimethylammonium chloride, also known as cetrimonium chloride or CTAC. Preferably, the concentration of the surfactant is between 0.1% and 1.0% by weight, even more preferably between 0.2% and 0.4% by weight.

[0035] Preferably, the gas scrubbing device comprises a tank having an inlet nozzle for the raw exhaust gas and an outlet nozzle for the purified exhaust gas, wherein the inlet nozzle and the outlet nozzle are connected to the first exhaust gas pipeline and the second exhaust gas pipeline, respectively, and the tank is configured to form a liquid pressure head at a height above the bottom of the tank, the height being higher than the height of the inlet nozzle, so that in the step of filling the tank with the scrubbing solution, the inlet port is immersed in the scrubbing solution, and so that in the step of introducing the raw exhaust gas into the tank through the inlet nozzle, the raw exhaust gas is subjected to a step of bubbling through the scrubbing solution contained in the tank, which removes the powder from the powder-containing raw exhaust gas.

[0036] Alternatively or additionally, the gas scrubbing device comprises a scrubbing tower comprising:

[0037] - a first inlet nozzle for the raw exhaust gas and a first outlet nozzle for the cleaned exhaust gas, the first inlet nozzle and the first outlet nozzle being arranged at opposite end portions of the scrubber tower;

[0038] - a second inlet nozzle and a second outlet nozzle for the washing solution, the second inlet nozzle and the second outlet nozzle being arranged at opposite end portions of the washing tower;

[0039] wherein the first inlet nozzle and the first outlet nozzle are connected to the first exhaust gas pipeline and the second exhaust gas pipeline respectively,

[0040] wherein the second inlet nozzle is arranged at one of the end portions selected from:

[0041] - said end portion at which said first outlet mouth is arranged,

[0042] - said end portion at which said first inlet mouth is arranged.

[0043] In this way, by performing the following steps:

[0044] - a step of conveying said washing solution through said washing tower between said second inlet nozzle and said second outlet nozzle;

[0045] - said first conveying step, said step comprising the step of conveying said raw exhaust gas through said scrubber between said first inlet nozzle and said first outlet nozzle;

[0046] The steps of countercurrent or isocurrent contact with the scrubbing solution and countercurrent or isocurrent contact with the raw exhaust gas are respectively performed, and the powder is removed from the raw exhaust gas containing the powder.

[0047] Preferably, the method provides a step of conveying the normal unpurified exhaust gas directly into the boiler, wherein when the at least one device performs the step of treating the charge, the step of directly conveying is interrupted and the steps of first conveying and second conveying are performed.

[0048] For this purpose, in an exemplary embodiment according to the second aspect of the invention, the apparatus further comprises:

[0049] - a direct exhaust gas conduit between said at least one device and said boiler;

[0050] a valve group connected to the first exhaust gas duct and to the direct exhaust gas duct so as to selectively deviate the normal unpurified exhaust gas from the first exhaust gas duct to the direct exhaust gas duct and to deviate the powder-laden unpurified exhaust gas from the direct exhaust gas duct to the first exhaust gas duct.

[0051] As described, some equipment of the production line or even individual equipment involved in the polymer-bitumen membrane production cycle releases powder-containing gases during some filter processing operations, typically during the step of feeding filler into the equipment and during the early steps of mixing the feed with bitumen.

[0052] Preferably, at a given moment, the steps of first and secondly conveying the powder-containing unpurified exhaust gas are performed only from a group of equipment currently involved in such a step of treating the filler, while the step of directly conveying the normal unpurified exhaust gas is performed from the remaining equipment of the multiple equipment that is not involved in any filter treatment operation.

[0053] For this purpose, in an exemplary embodiment according to the second aspect of the present invention, the first exhaust gas pipeline and the direct exhaust gas pipeline have a corresponding connecting branch to each of the plurality of devices, and the valve group mentioned above is arranged on each of these connecting branches to selectively open / close each connecting branch between the corresponding device and the first exhaust gas pipeline or the direct exhaust gas pipeline. Each valve group may include two two-way valves, one two-way valve is arranged along the connecting branch to the first exhaust gas pipeline, and the other two-way valve is arranged along the connecting branch to the direct exhaust gas pipeline, or each valve group may include a diverting three-way valve, wherein an outlet nozzle is arranged at the root of the connecting branch to the direct exhaust gas pipeline, and the other outlet nozzle is arranged at the root of the connecting branch to the first exhaust gas pipeline.

[0054] In this case, the operation of the valve group for diverting the flow of the raw exhaust gas from a predetermined device from the direct exhaust gas pipeline to the first exhaust gas pipeline or vice versa is automatically performed when the step of treating the filler starts or ends in this device, respectively.

[0055] For this purpose, preferably, the apparatus comprises a control unit configured to:

[0056] - receiving a filling process in progress signal indicating that a filling process step is being performed in said apparatus, and

[0057] - transmitting a raw exhaust gas redirection signal to said valve group to redirect said raw exhaust gas from said direct raw gas conduit to said first raw gas conduit depending on whether said apparatus is performing / not performing said step of treating said charge.

[0058] The filler processing in progress signal may be generated in a manner known to the skilled person, for example, the filler processing in progress signal may be a signal from a system of limit switch devices detecting the open or closed state of a filler inlet valve of each device in which the step of processing the filler can be performed, such a system cooperating for example with a timer switch which switches after a predetermined time has elapsed since such inlet valve was opened and / or closed. As an alternative, such a filler processing in progress signal may be automatically generated when an opening command is sent to the inlet valve or when an actuation command is sent to a different member to feed the filler into the device, or the signal may even be triggered by a powder presence detector arranged to detect the presence of powder above the bitumen present in the device.

[0059] Preferably, the method provides for the step of mixing the raw exhaust gas or the purified or normal raw exhaust gas with external air extracted preferably at a temperature set between 5° C. and 40° C., such that a mixture external air / raw exhaust gas is obtained. For this purpose, the apparatus comprises means for mixing external air with raw, purified or normal raw exhaust gas, preferably located on a branch arranged for feeding primary air to the boiler, the direct exhaust gas duct and the second exhaust gas duct merging into the branch.

[0060] Advantageously, the step of secondarily conveying the purified exhaust gases and / or the step of directly conveying are performed in such a way that the purified exhaust gases are kept inside the boiler for a residence time of at least 2 seconds. For this purpose, the size of the combustion chamber of the boiler and the characteristics of the suction means, which are typically fans, are selected in a consistent manner to provide a predetermined gas flow rate through the combustion chamber to provide a residence time longer than this minimum value.

[0061] Preferably, the step of secondary conveying and / or the step of direct conveying is performed in such a way that the mixture is fed into the boiler as primary air. For this purpose, the second exhaust gas duct and / or the direct exhaust gas duct is pneumatically connected to a primary air feed member of the boiler.

[0062] Preferably, the method provides the following steps:

[0063] - measuring the oxygen and / or carbon monoxide content in the combustion gases downstream of the boiler;

[0064] - comparing the oxygen and / or carbon monoxide content with a corresponding predetermined lower limit value for oxygen content and an upper limit value for carbon monoxide content;

[0065] And the step of mixing with external air provides the step of adjusting the proportion of external air in the mixture in such a way as to maintain the oxygen and / or carbon monoxide content in the combustion gases above and below the predetermined limits, respectively.

[0066] For this purpose, the apparatus also comprises:

[0067] - means for measuring the oxygen and / or carbon monoxide content in the combustion gas, the means being configured to emit corresponding combustion gas oxygen and / or carbon monoxide concentration signals;

[0068] - a logic unit, the logic unit being configured to:

[0069] - receiving the concentration signal and / or the concentration signals;

[0070] - comparing the oxygen and / or carbon monoxide concentration signal and / or the oxygen and / or carbon monoxide concentration signal with a predetermined lower limit value and a predetermined upper limit value of the oxygen and / or carbon monoxide content, respectively;

[0071] - generating a regulating signal and transmitting said regulating signal to the means for mixing external air in order to adjust the proportion of external air in said mixture in order to keep the content of oxygen and / or carbon monoxide above and below said predetermined limit values, respectively.

[0072] The exhaust gas treatment method described above for reducing odorous emissions relates to exhaust gases containing asphalt vapor and filler powder, however, the method can also be generally used to treat industrial exhaust gases in which there is a problem of reducing odor and at the same time powdered solids are present in the exhaust gas flow, as is the case with exhaust gas manifolds in some distillation equipment, filtering equipment in which filters are provided which require pre-prepared diatomaceous earth prefabricated plates, etc.

[0073] A method for producing a polymer-bitumen membrane also falls within the scope of the present invention, the method comprising the steps of mixing a filler powder with bitumen, thereby obtaining a polymer-bitumen membrane, and obtaining an unpurified exhaust gas containing bitumen vapor and a residue of the filler powder, and the method also includes a method for treating the unpurified exhaust gas in which at least one of the characteristics described above is provided.

[0074] Also falling within the scope of the present invention is a device for producing a polymer-bitumen membrane, the device being configured to carry out the steps of mixing a filler powder with bitumen, thereby obtaining a polymer-bitumen membrane, and obtaining an unpurified exhaust gas containing asphalt vapor and a residue of the filler powder, and the device also comprising an apparatus for treating the unpurified exhaust gas comprising at least one of the features described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] The present invention will now be illustrated by way of an illustrative but non-limiting description of exemplary embodiments of the invention, with reference to the accompanying drawings, in which:

[0076] - Figure 1 A process flow chart showing an apparatus for treating asphalt vapor containing fine powder according to the present invention;

[0077] - Figure 2 shows a process flow diagram of an apparatus for treating such vapors according to an exemplary embodiment of the invention, wherein the gas scrubbing device comprises a tank containing a scrubbing solution, and the raw exhaust gas to be scrubbed is fed below the pressure head of this scrubbing solution;

[0078] - Figure 3 A process flow diagram of an apparatus for treating such vapors according to an exemplary embodiment of the present invention is shown, wherein the gas scrubbing device comprises a scrubbing tower arranged to form a countercurrent flow of raw exhaust gas to be cleaned and a countercurrent flow of a scrubbing solution;

[0079] - Figure 4 A process flow diagram of an apparatus for treating such vapors according to an exemplary embodiment of the present invention is shown, wherein a direct exhaust gas conduit to the oven and a valve group for selectively diverting the raw exhaust gas from the gas scrubbing device to the direct conduit and vice versa are also provided;

[0080] - Figure 5 A process flow diagram of an apparatus for processing such vapors according to an exemplary embodiment of the present invention is shown, the apparatus being suitable for a production line comprising a plurality of devices configured to process asphalt and filler powders, wherein a process such as Figure 4 The direct exhaust gas pipeline shown in , and a plurality of connecting branches to the direct exhaust gas pipeline and to the pipeline leading to the gas scrubbing device are provided;

[0081] - Figure 6 Shown with Figure 5 A process flow diagram of an apparatus similar to an apparatus of the type described above, wherein the apparatus is configured to allow each device to automatically switch between a direct exhaust gas conduit and a conduit to a gas scrubbing device;

[0082] - Figure 7 Shown with Figure 5 A process flow diagram of an apparatus similar to that of the apparatus of claim 1, wherein means are provided for mixing outside air with raw exhaust gas fed to a boiler;

[0083] - Figure 8 Schematically shows Figure 8 Modification of the flowchart;

[0084] - Fig. 9 A process flow diagram is shown for a device which also processes the always powder-free exhaust gases in the oven as a separate feed. DETAILED DESCRIPTION

[0085] With reference to the accompanying drawings, a method and apparatus for treating raw exhaust gases released by parts of an apparatus, typically a polymer-bitumen membrane production line, are described. In particular, the described technology can be used to treat exhaust gases from a melt tank of a polymer-bitumen membrane production line, typically during a step of loading and early mixing of a filler powder such as fine talc, in which, for example, the size of most of the particles is about the maximum value of the grain size distribution curve of 0.7 μm.

[0086] Figure 1The melt tank 1 of an apparatus such as a polymer-bitumen film production line is schematically shown, i.e., an apparatus used as a mixer of bitumen 2 and filler powder 3, as well as a temporary storage and supply unit for bitumen 2. The melt tank 1 generally comprises: a tank 90; a mixing member 91 for mixing bitumen 2 and filler powder 3, in this case a mechanical stirrer 91; and a filler powder feeding member 3, in this case, for example a hopper 92 and / or a valve 93 to be opened when the step of loading the filler powder 3 into the tank 90 is performed. The means for feeding the filler powder 3 may also include means (not shown) for conveying the filler powder 3 from a reservoir of the filler powder 3 to the melt tank 1, such as a pneumatic conveyor, a bucket conveyor or any other known conveyor for solid matter, including an electromechanical actuation system. The melt tank 1 is also equipped with a discharge line 19 and a corresponding discharge valve in order to transfer the bitumen-filler mixture to a subsequent operation, usually to a polymer-bitumen film production step.

[0087] The melting tank 1 is maintained under suction by means of exhaust gas lines 10, 30 and suction means 11, as described in more detail below, the main reason for which is to prevent the diffusion of bad smelling vapors into the working area. Due to the suction, the gas stream of unpurified exhaust gas 4, 4' is steadily released by the device 1 during each step of the working cycle in which it is involved.

[0088] As expected, the step of processing the filler powder 3 in the melting tank 1 mainly includes the operations of feeding the filler powder 3 into the tank 90 and mixing the filler powder 3 with the asphalt 2. In other steps of the working cycle involving the melting tank 1, that is, when only the asphalt 2 is present in the tank 90, or once the filler powder 3 has been completely incorporated into the asphalt 2, the unpurified exhaust gas is a normal unpurified exhaust gas 4 that is substantially free of filler powder 3. In contrast, during the step of processing the filler powder 3, including the above-mentioned operations, the unpurified exhaust gas is transformed from the normal unpurified exhaust gas 4 that is substantially free of powder to the unpurified exhaust gas 4' containing powder, that is, the exhaust gas containing a certain amount of the filler powder 3 in addition to the asphalt vapor.

[0089] In addition to a boiler 40 having the features described, for example, in EP 3018410 A1, the method according to the invention also provides for a pre-arranged gas scrubber 20. The gas scrubber 20 and the boiler 40 are arranged in such a way that the raw exhaust gas 4, 4', in particular the raw exhaust gas 4' containing fines, is first conveyed to the gas scrubber 20 and then as a purified, substantially fines-free exhaust gas 5 or directly as normal raw exhaust gas 4 to the boiler 40.

[0090] For this purpose, the apparatus comprises, in addition to the gas scrubber 20 and the boiler 40, a first exhaust gas conduit 10 between the device 1 and the gas scrubber 20 and a second exhaust gas conduit 30 between the gas scrubber 20 and the boiler 40. The apparatus further comprises a suction device 11, which is arranged to convey the raw exhaust gas 4, 4', in particular the raw exhaust gas 4' containing powder and the cleaned exhaust gas 5, respectively, through the first exhaust gas conduit 10 and the second exhaust gas conduit 30. In a preferred exemplary embodiment, the suction device is a fan 11 and is arranged along the first exhaust gas conduit 10, i.e. between the device 1 and the gas scrubber 20.

[0091] The gas scrubbing device 20 is configured to receive a scrubbing solution 9 containing a surfactant and to contact the raw exhaust gas 4, 4′ with the scrubbing solution 9 so as to remove a certain amount of filler powder 3 present in the powder-containing raw exhaust gas 4′ and obtain a purified exhaust gas 5 substantially free of filler powder 3 from the gas scrubbing device 20.

[0092] The cleaned exhaust gas subsequently passes into a boiler 40 , in which combustion of the bitumen vapors contained in the boiler takes place, whereby combustion gas 8 is obtained, for example in the manner described in EP 3 018 410 A1.

[0093] The surfactant present in the washing solution 9 may be selected from well-known surfactants, and its concentration may depend on the type of surfactant selected and the type of washing device 20 used.

[0094] The surfactant present in the scrubbing solution 9 may also be selected depending on the nature of the powder present in the powder-containing raw exhaust gas 4'. In particular, in the case of an apparatus for producing a polymer-bitumen membrane, the powder is a filler added to the bitumen to produce the membrane, the filler typically consisting essentially of calcium carbonate CaCO3. In this case, preferably, the surfactant is a non-ionic surfactant. For example, the non-ionic surfactant may include an aliphatic glycol, in particular propylene glycol. As an alternative, the surfactant may be hexadecyltrimethylammonium chloride, also known as cetrimide or CTAC. Preferably, the concentration of such a surfactant in the scrubbing solution 9 is set between 0.1% and 1.0% by weight, more preferably between 0.2% and 0.4% by weight, based on the amount of the scrubbing solution 9. Preferably, the gas scrubbing device 20 has Figure 2 and 3 One of the forms shown in .

[0095] Specifically, refer to Figure 2, the gas scrubbing device 20 comprises a tank 25 having an inlet nozzle 21 and an outlet nozzle 23 for raw exhaust gas 4, 4', specifically raw exhaust gas 4' containing powder and cleaned exhaust gas 5, respectively, the inlet nozzle and the outlet nozzle being connected to the first exhaust gas pipeline 10 and the second exhaust gas pipeline 30, respectively. The inlet nozzle 21 for the raw exhaust gas 4, 4' is arranged at a predetermined height h from the bottom 29 of the tank 25. For example, as shown in the figure, the inlet nozzle 21 may include an open end of a portion 15 of the first exhaust gas pipeline 10 arranged as a dip tube in the tank 25, but may also include a nozzle (not shown) arranged on the outer shell of the tank 25 at a distance h from the bottom 29.

[0096] The tank 25 is configured to form a liquid pressure head at a height H above the inlet nozzle 21 from the bottom 29, so that the inlet is immersed in the scrubbing solution 9. In more detail, the tank 25 is configured to be filled with the scrubbing solution 9 through the pipe 39 and the liquid inlet nozzle 22 up to a predetermined water level H above the bottom 29, which is higher than the height h of the inlet nozzle 21 above the bottom 29, so that the inlet nozzle 21 of the raw exhaust gas 4, 4 ′ is immersed in the scrubbing solution 9. In this way, by introducing the raw exhaust gas 4, 4 ′ into the tank 25 through the inlet nozzle 21, the raw exhaust gas is bubbled through the scrubbing solution 9 contained in the tank, which allows the removal of filler powder 3 present in the gas in the case of a raw exhaust gas 4 ′ containing powder. A liquid discharge nozzle 24 is also provided, which can be used to periodically change the solution 9 of the gas scrubbing device 20 or to allow a continuous flow, and the gooseneck section is preferably arranged to extend vertically to a height H above the bottom 29 to maintain the liquid pressure head.

[0097] As an alternative to the tank, Figure 3As shown in, or in addition to the tank, the gas scrubbing device 20 still comprises a tank 125, but in the form of a scrubbing tower 125, i.e. an elongated tank, having an inlet mouth 121 and an outlet mouth 123 for the raw exhaust gas 4, 4′, in particular the raw exhaust gas 4′ containing powder, and the cleaned exhaust gas 5, respectively, and connected to the first exhaust gas pipeline 10 and the second exhaust gas pipeline 30, respectively. The scrubbing tower 125 also comprises a second inlet mouth 122 and a second outlet mouth 124 for the scrubbing solution 9, which are arranged at opposite end portions of the scrubbing tower 125. In the exemplary embodiment as depicted, the second inlet mouth 122 is arranged at the end portion 123′ at which the first outlet mouth 123 is arranged in such a way that the step of countercurrently contacting the raw exhaust gas 4, 4′ with the scrubbing solution 9 is performed by conveying the raw exhaust gas 4, 4′ through the scrubbing tower 125 between the first inlet mouth 121 and the first outlet mouth 123 and by conveying the scrubbing solution 9 between the second inlet mouth 122 and the second outlet mouth 124. In an exemplary embodiment not shown, the second inlet nozzle 122 is arranged at the end portion 121′ at which the first inlet nozzle 121 is arranged in such a manner that a step of bringing the raw exhaust gas 4, 4′ into isocurrent contact with the scrubbing solution 9 is performed by conveying the raw exhaust gas 4, 4′ between the first inlet nozzle 121 and the first outlet nozzle 123 through the scrubbing tower 125 and by conveying the scrubbing solution 9 between the second inlet nozzle 122 and the second outlet nozzle 124.

[0098] In the case of a powder-containing raw exhaust gas 4 ′, such a countercurrent or isocurrent contacting step allows the removal of the filler powder 3 present in said powder-containing raw exhaust gas.

[0099] In the preferred embodiment Figure 3 In the exemplary embodiment of the present invention, the washing tower 125 is arranged vertically, even in the exemplary embodiment not shown, a horizontal arrangement of the washing tower 125 is possible, or in any case, arranged at a certain angle relative to the vertical direction. Figure 3 In the exemplary embodiment of the wash tower 125, the wash tower 125 is arranged with the end portion 121' as the lower end portion and therefore also with the first exhaust gas inlet nozzle 121 as the lower nozzle, which is preferred, even in the exemplary embodiment not shown, the arrangement of the wash tower 125 can also have the end portion 121 as the upper end portion and therefore with the first exhaust gas inlet nozzle 121 as the upper nozzle.

[0100] However, the present invention is not limited to the gas scrubbing device 20 in the form described above.

[0101] In an exemplary embodiment, the method provides for conveying only powder-containing unpurified exhaust gas 4′, such as specified, powder-containing unpurified exhaust gas released by the device 1 only during the step of processing filler powder 3, through the gas scrubbing device 20, and provides for conveying normal unpurified exhaust gas 4 that is essentially free of powder, i.e. normal unpurified exhaust gas released in other steps of the manufacturing cycle in which the device 1 is involved, directly to the boiler.

[0102] Figure 4 It relates to an exemplary embodiment of an apparatus configured for this purpose, wherein a direct exhaust gas duct 50 between the apparatus 1 and the boiler 40 and a valve group 13, 53 connected to the first exhaust gas duct 10 and the direct exhaust gas duct 50 are also provided to selectively deviate the normal unpurified exhaust gas 4 from the first exhaust gas duct 10 to the direct exhaust gas duct 50 at the end of each step of processing the filler powder 3 and to deviate the unpurified exhaust gas 4' from the direct exhaust gas duct 50 to the first exhaust gas duct 10 at the beginning of each step of processing the filler powder 3 by the apparatus 1. Figure 4 In the exemplary embodiment of the present invention, the direct exhaust gas duct has a suction device 51 for the normal raw exhaust gas, typically a fan 51, which is different from the suction device 11 for the raw exhaust gas containing powder.

[0103] In practice, the polymer-bitumen membrane production line or unit may include a plurality of melt tanks 1, 1'. At a given moment, one or some melt tanks 1' may be performing a step of treating filler powder 3 and thus releasing unpurified exhaust gas 4' containing powder, while other melt tanks 1 are performing a step before the step of treating filler powder 3, specifically a step of loading / storing asphalt 2 between receiving filler powder 3, or a step after the step of treating filler powder 3, specifically a step of mixing asphalt 2 and filler powder 3 at a later stage, or a step of feeding asphalt 2 containing filler powder 3 to an impregnation tank; these latter melt tanks 1 therefore release normal unpurified exhaust gas 4 substantially free of filler powder 3.

[0104] Figure 5An exemplary embodiment of such an apparatus relates to a plurality of melting tanks 1, 1', which are configured to convey only the unpurified exhaust gas 4' containing powder from the device 1' through the gas scrubbing device 20 during the step of treating the filler powder 3. Three devices 1, 1' are shown, of which one device 1' participates in the step of treating the filler powder 3 and releases the unpurified exhaust gas 4' containing powder, while the other two devices 1 do not participate in this treatment step and release normal unpurified exhaust gas 4. In this case, the first exhaust gas pipeline 10 and the direct exhaust gas pipeline 50 have corresponding connecting branches 12, 52 to each device 1, 1', and a valve group 13, 53 is arranged on each of these connecting branches 12, 52, which is configured to selectively open / close each connecting branch 12, 52 between the corresponding device 1, 1' and the first exhaust gas pipeline 10 or the direct exhaust gas pipeline 50, respectively. Even if Figure 5 The valve group includes two two-way valves 13, 53, one of which is arranged along the connecting branch 12 to the first exhaust gas pipeline 10, and the other two-way valve is arranged along the connecting branch 52 to the direct exhaust gas pipeline 50. In an exemplary embodiment not shown, such a valve group may include a diverter three-way valve having an outlet nozzle arranged at the root of the connecting branch 52 to the direct exhaust gas pipeline 50 and having another outlet nozzle arranged at the root of the connecting branch 12 to the first exhaust gas pipeline 10.

[0105] Preferably, the valve block 13 , 53 has a servo-actuated actuator 16 , 56 for automatic operation when the corresponding device 1 , 1 ′ starts or ends a step of processing the filler powder 3 . Figure 6 An exemplary embodiment of an apparatus is provided for this purpose and comprises a plurality of devices or melting tanks 1, 1'. This exemplary embodiment comprises a plurality of devices or melting tanks 1, 1'. Figure 4 1 is also valid in the case of a production line of a single melting tank 1 shown in . In this case, a control unit 60 is provided, which is configured to receive a start / stop signal 61 of a step of processing the filler powder 3 in the device 1 ′ / 1 and is also configured to transmit a signal 64 to the valve group 13, 53, that is, in this case to the actuator 16, 56 to do the following:

[0106] - diverting the normal raw exhaust gas 4 which is being transformed into the powder-containing raw exhaust gas 4' from the direct exhaust gas duct 50 into the first exhaust gas duct 10; and

[0107] - diverting the powder-laden raw exhaust gas 4 ′, which is being transformed into normal raw exhaust gas 4 , from the first exhaust gas duct 10 into the direct exhaust gas duct 50 ,

[0108] The above two items are carried out separately.

[0109] exist Figure 6 In the exemplary embodiment of the embodiment of the invention, the start / stop signal 61 of the step of processing the filler powder 3 is generated by a limit switch device system 66 associated with the inlet valve 93 of the filler powder 3 so as to detect the open / closed state indicating whether the valve 93 of the filler powder 3 is open and / or closed. Preferably, a timer switch device is provided for generating and transmitting the signal 61 for deviating the raw exhaust gas 4, 4' based on the standard mixing time believed to be sufficient mixing of the filler powder 3 and the asphalt 2 therein relative to the moment when the valve 93 is closed. For simplicity, only the signals 61, 64 related to the device 1' are shown, but it should be understood that a similar configuration will be used for the device 1 shown. In an exemplary embodiment not shown, the signal 64 for deviating the normal raw exhaust gas 4 can be automatically generated when an opening command is sent to the inlet valve 93 of the filler, or when an actuation command is sent to a different member (if any) for conveying the filler 3 as specified above. Alternatively, the signal 64 deviating from the normal unpurified exhaust gas 4 can be triggered by a powder presence detector (not shown) arranged above the head of the asphalt 2 in the device 1 and configured to emit an indication of the presence and / or absence of powder in the space above the asphalt 2.

[0110] In an improvement, the method provides for mixing normal unpurified exhaust gas 4 or purified exhaust gas 5 with external air 6 preferably extracted at a temperature set between 5°C and 40°C, so that a mixture 7 of external air and purified exhaust gas 5 or normal unpurified exhaust gas 4 is obtained.

[0111] Figure 7 An exemplary embodiment of an apparatus configured for this purpose is provided in which a mixing member 54 is provided for mixing external air 6 with raw exhaust gas fed to the boiler, which raw exhaust gas may be the purified exhaust gas 5 from the second exhaust gas duct 30 or the normal raw exhaust gas 4 from the direct exhaust gas duct 30. Preferably, as Figure 8 As shown in FIG. 1 , the mixing member 54 is arranged along a feed branch 55 of primary air to the boiler 40 , to which the second exhaust gas duct 30 and the direct exhaust gas duct 50 merge.

[0112] Advantageously, the cleaned exhaust gas 5 and / or the normal raw exhaust gas 4 are delivered in such a way that the raw exhaust gas maintains a residence time of at least two seconds in the combustion chamber of the boiler 40. For this purpose, the size of the combustion chamber and the characteristics of the suction device 11 (usually a fan) are selected cooperatively.

[0113] Preferably, the method provides for measuring the oxygen and / or carbon monoxide content in the combustion gases 8 downstream of the boiler 40 and comparing this detected content with a predetermined lower limit value for the O2 content and a predetermined upper limit value for the CO content, and the step of mixing with the external air 6 comprises a step of adjusting the proportion of external air 6 in the mixture 7 in such a way that the oxygen and / or carbon monoxide content in the combustion gases 8 is maintained above and below said predetermined limit values, respectively.

[0114] For this purpose, Figure 7 As still shown in the figure, the apparatus also includes a device 80 for measuring the oxygen and / or carbon monoxide content in the combustion gas 8, the device being configured to emit corresponding O2 and / or CO concentration signals 81 in the combustion gas, and the apparatus also includes a logic unit 60′, the logic unit being configured to receive one and / or more concentration signals 81 so as to compare the latter with a predetermined lower limit value of the O2 content and a predetermined upper limit value of the CO content, respectively, and to generate an adjustment signal 82 for adjusting the proportion of external air 6 in the mixture 7 and transmit the adjustment signal to the mixing member 54 so as to keep the oxygen and / or carbon monoxide content above and below these limits, respectively.

[0115] Fig. 9 An exemplary embodiment of an apparatus is schematically shown, in which a further direct exhaust gas duct 70 is provided, into which a suction branch 76 from a corresponding extraction hood 75 of the vapour without filler powder merges. This duct itself has a suction device 71, typically a fan 71. In addition, the first exhaust gas duct 10, the direct exhaust gas duct 50 and the further direct exhaust gas duct 70 merge into a manifold 99 along which shut-off valves 97, 98 are arranged, the manifold possibly being equipped with corresponding actuators (not shown) for remote control. In its normal position, the valve 97 is closed to separate the first exhaust gas duct 10 through which the raw exhaust gas 4' containing powder flows to the gas scrubbing device 20 from the direct exhaust gas ducts 50 and 70 through which the raw exhaust gas without powder flows directly into the boiler 40. In contrast, the valve 98 is normally open. This configuration of the manifold 99 makes it possible to use each of the fans 11, 51 and 71 as a backup fan for any other of the fans in the event of a suspension of service.

[0116] The foregoing description of the exemplary specific embodiments of the present invention will fully disclose the present invention from the perspective of the concept, so that other embodiments will be able to modify and / or adapt such embodiments in various applications by applying current knowledge without further study and without departing from the present invention, and therefore such adaptations and modifications must be considered equivalent to the specific embodiments. For this reason, without departing from the field of the present invention, the components and materials used to perform the different functions described herein may have different properties. It should be understood that the wording or terminology used herein is for the purpose of description rather than limitation.

Claims

1. A method for treating unpurified exhaust gas (4, 4'), the unpurified exhaust gas containing asphalt vapor released by at least one device (1, 1') configured to perform a step of treating filler powder (3), wherein the filler powder (3) is supplied to the device (1, 1') and / or the device performs an operation of mixing the filler powder (3) with asphalt (2), during which the unpurified exhaust gas (4, 4') is transformed from normal unpurified exhaust gas (4) without powder to powder-containing unpurified exhaust gas (4') also containing a certain amount of the filler powder (3), the method comprising the following steps: - a pre-arranged gas scrubbing device (20) configured to supply a scrubbing solution (9) containing a surfactant; - Pre-arrangement of boiler (40); - firstly conveying the unpurified exhaust gas (4, 4') containing a certain amount of the filler powder to the gas scrubbing device (20); - bringing the raw exhaust gas (4, 4') containing a certain amount of the filler powder into contact with the washing solution (9) containing a surfactant; - removing said amount of said filler powder from said powder-containing raw exhaust gas; - releasing purified exhaust gas (5) free of the filler powder through the gas scrubbing device (20); - Secondly, the purified exhaust gas (5) is transported to the boiler (40) and the purified exhaust gas (5) is burned to obtain combustion gas (8).

2. The method according to claim 1, wherein the apparatus (1, 1') is part of a polymer-bitumen membrane production line.

3. The method according to claim 1, wherein the step of pre-arranging the gas scrubbing device (20) provides the following steps: a pre-arranged tank (25) having an inlet nozzle (21) for the unpurified exhaust gas (4, 4') and an outlet nozzle (23) for the purified exhaust gas (5); - filling the tank (25) with the washing solution (9) up to a predetermined water level (H) above the bottom (29) of the tank (25), the water level (H) being higher than the height (h) of the inlet nozzle (21) above the bottom, so that the inlet nozzle (21) is submerged by the washing solution (9); wherein the step of first conveying the raw exhaust gas (4, 4') comprises the following steps: introducing the raw exhaust gas (4, 4') into the tank (25) through the inlet nozzle (21); and - bubbling the raw exhaust gas (4, 4') through the washing solution (9) contained in the tank (25) so as to carry out a step of contacting the raw exhaust gas (4, 4') containing a certain amount of the filler powder with the washing solution (9).

4. The method according to claim 1, wherein the step of pre-arranging a gas scrubbing device provides a step of pre-arranging a scrubbing tower (125), the scrubbing tower (125) comprising: a first inlet nozzle (121) for the raw exhaust gas (4, 4') and a first outlet nozzle (123) for the cleaned exhaust gas (5), the first inlet nozzle and the first outlet nozzle being arranged at opposite end portions of the scrubbing tower (125); a second inlet nozzle (122) and a second outlet nozzle (124) for the washing solution (9), the second inlet nozzle and the second outlet nozzle being arranged at opposite end portions of the washing tower (125); wherein the second inlet nozzle (122) is arranged in one of the end portions selected from the group consisting of: - said end portion at which said first outlet mouth (123) is arranged, - said end portion at which said first inlet mouth (121) is arranged; - a step of conveying the washing solution (9) through the washing tower (125) between the second inlet nozzle (122) and the second outlet nozzle (124), wherein the step of first conveying the raw exhaust gas (4, 4') comprises the steps of conveying the raw exhaust gas (4, 4') through the scrubbing tower (125) between the first inlet nozzle (121) and the first outlet nozzle (123) so as to provide the scrubbing solution (9) in the form of a countercurrent contact step or an isocurrent contact step, respectively and the step of contacting the raw exhaust gas (4, 4') containing a certain amount of the filler powder with the washing solution (9) to convert the raw exhaust gas (4, 4') into the purified exhaust gas (5).

5. The method according to claim 1, comprising the steps of: - Directly conveying the normal unpurified exhaust gas (4) to the boiler (40), wherein when the at least one device (1) performs the step of treating the filler powder, the step of directly conveying the normal unpurified exhaust gas (4) to the boiler (40) is interrupted and the step of first conveying the unpurified exhaust gas (4, 4') to the gas scrubbing device (20) and the step of secondly conveying the purified exhaust gas (5) to the boiler (40) are performed.

6. A method according to claim 5, wherein the powder-containing unpurified exhaust gas (4') is released by at least one device (1') among a plurality of devices (1, 1') during a corresponding step of processing the filler powder (3), and the steps of first conveying the unpurified exhaust gas (4, 4') to the gas scrubbing device (20) and secondly conveying the purified exhaust gas (5) to the boiler (40) are selectively performed from at least one device (1') among the plurality of devices, while the step of directly conveying the normal unpurified exhaust gas (4) is performed from the remaining devices (1) among the plurality of devices (1, 1').

7. An apparatus for producing a polymer-bitumen membrane, comprising at least one device (1, 1') of a polymer-bitumen membrane production line, the device being configured to perform a step of mixing a filler powder (3) with bitumen (2), in which the device (1, 1') is supplied with the filler powder (3) and / or the device performs an operation of mixing the filler powder (3) with the bitumen (2), and during the step of mixing the filler powder (3), the unpurified exhaust gas (4, 4') containing bitumen vapor released by the at least one device (1, 1') is transformed from normal unpurified exhaust gas (4) without powder to unpurified exhaust gas (4') containing powder also containing the filler powder (3), - an apparatus for treating raw exhaust gases (4, 4') containing bitumen vapors released by at least one of the devices (1, 1'), comprising: a gas scrubbing device (20), the gas scrubbing device comprising an inlet conduit for receiving a scrubbing solution (9) containing a surfactant, the gas scrubbing device (20) being configured to bring the raw exhaust gas (4, 4') containing a certain amount of the filler powder into contact with the scrubbing solution (9) containing a surfactant; - boiler (40); a first exhaust gas conduit (10) between the at least one device (1) and the gas scrubbing device (20), the first exhaust gas conduit (10) being arranged to convey the raw exhaust gas (4, 4') containing a certain amount of the filler powder to the gas scrubbing device (20); a second exhaust gas conduit (30) between the gas scrubbing device (20) and the boiler (40), the second exhaust gas conduit being arranged to release the cleaned exhaust gas (5) free of the filler powder from the gas scrubbing device (20) directly to the boiler; - a suction device (11) arranged to convey the raw exhaust gas (4, 4') through the first exhaust gas duct (10) and to allow the purified exhaust gas (5) to exit through the second exhaust gas duct (30) to reach the boiler (40).

8. Apparatus according to claim 7, wherein the gas scrubbing device (20) comprises a tank (25) having an inlet nozzle (21) for the unpurified exhaust gas (4, 4') and an outlet nozzle (23) for the purified exhaust gas (5), wherein the inlet nozzle (21) and the outlet nozzle (23) are connected to the first exhaust gas pipeline (10) and the second exhaust gas pipeline (30), respectively, The tank (25) is configured to form a pressure head of the washing solution (9) at a height (H) above the bottom (29) of the tank (25), the height being higher than the height (h) of the inlet nozzle (21), so that the inlet nozzle (21) is immersed in the washing solution (9), The raw exhaust gas (4, 4') is caused to bubble through the scrubbing solution (9) by introducing the raw exhaust gas (4, 4') into the tank (25) through the inlet nozzle (21).

9. The apparatus according to claim 7, wherein the gas scrubbing device (20) comprises a scrubbing tower (125), the scrubbing tower comprising: a first inlet nozzle (121) for the raw exhaust gas (4, 4') and a first outlet nozzle (123) for the cleaned exhaust gas (5), the first inlet nozzle and the first outlet nozzle being arranged at opposite end portions of the scrubbing tower (125); a second inlet nozzle (122) and a second outlet nozzle (124) for the washing solution (9), the second inlet nozzle and the second outlet nozzle being arranged at opposite end portions (121', 123') of the washing tower (125); wherein the first inlet nozzle (121) and the first outlet nozzle (123) are connected to the first exhaust gas pipeline (10) and the second exhaust gas pipeline (30), respectively, wherein the second inlet nozzle (122) is arranged at one of the end portions (121', 123') selected from: - said end portion (123') at which said first outlet mouth (123) is arranged, - said end portion (121') at which said first inlet mouth (121) is arranged; In order to provide a countercurrent flow or an isocurrent flow of the scrubbing solution (9) and the raw exhaust gas (4, 4') converted into the purified exhaust gas (5) in the scrubbing tower (125), respectively.

10. The apparatus of claim 7, further comprising: - a direct exhaust gas conduit (50) between the at least one device (1) and the boiler (40); a valve group (13, 53) connected to the first exhaust gas pipeline (10) and to the direct exhaust gas pipeline (50), and arranged to selectively allow the normal unpurified exhaust gas (4) to The exhaust gas pipeline (10) deviates from the first exhaust gas pipeline to the direct exhaust gas pipeline (50) and the raw exhaust gas (4') containing powder is deviated from the direct exhaust gas pipeline (50) to the first exhaust gas pipeline (10).

11. The apparatus according to claim 10, wherein the first exhaust gas pipeline (10) and the direct exhaust gas pipeline (50) have corresponding connecting branches (12, 52) to each of the plurality of devices (1, 1') of the production line, wherein the valve group (13, 53) is arranged along each of the connecting branches (12, 52) and is configured to selectively open / close the connecting branches (12, 52) in the connecting branches between the corresponding device and the first exhaust gas pipeline (10) or the direct exhaust gas pipeline (50), The device further comprises a control unit configured to - receiving a filler processing ongoing signal (61) indicating that a filler powder processing step is being performed in the apparatus (1, 1'), and - transmitting a raw exhaust gas redirection signal to the valve group to redirect the raw exhaust gas (4, 4') from the direct exhaust gas pipeline (50) to the first exhaust gas pipeline (10) according to whether the device (1, 1') is performing / not performing the filler powder processing step.

12. A method for producing a polymer-bitumen membrane, the method comprising the steps of: A filler powder (3) is mixed with bitumen (2), thereby obtaining a polymer-bitumen film and obtaining an unpurified exhaust gas (4, 4') containing bitumen vapor and residues of the filler powder (3), characterized in that the method comprises a method for treating the unpurified exhaust gas (4, 4') as defined in claims 1 to 6.

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