Fluid dedusting system and method

Abstract

A system for dedusting a working fluid, which working fluid has a plurality of suspended particles (40), the system comprising a first duct (100) for passing the working fluid from a first inlet (101 ) to a first outlet (102), a second duct (2) for passing a service fluid from a second inlet (201 ) to a second outlet (202). The said first duct consists of a tubular element (10), which tubular element (10) has an auger element (11 ) inside it in such a way that the said auger element (11 ) defines, together with the internal walls of the tubular element (10), a flow channel that extends helically along the longitudinal axis (A) of the said tubular element (10) and configured for the passage of the working fluid, the said second duct (2) surrounding the external walls of the said tubular element (10). Further, the working fluid has a higher temperature than the service fluid.

Description

[0001] Fluid Dedusting System and Method

[0002] The present invention relates to a system for dedusting a working fluid, which working fluid has a plurality of suspended particles.

[0003] In particular, the system comprises a first passageway for the working fluid, from a first inlet to a first outlet, and a second passageway for a service fluid from a second inlet to a second outlet.

[0004] The invention relates in general to the field of fluid treatment so as to eliminate or limit the presence of unwanted particles contained in the fluids.

[0005] Systems capable of allowing fluid treatments by means of a thermophoresis process are known in the art.

[0006] Some of these systems are characterised by the implementation of a cold wall in contact with the hot gas to be purified, on which the particles contained in the gas are deposited under the effect of the thermophoretic force undergone by such particles, due to the existence of a temperature gradient between the hot gas and the cold wall.

[0007] In this case the deposition yield of the particles on the cold walls decreases progressively, due to the constant cooling of the gas to be purified, in contact with the cold wall.

[0008] Other systems include a first and a second module, placed opposite each other, between which the fluid to be treated circulates. The first module is intended to be brought to a temperature higher than that of the second module in order to generate a temperature gradient that determines the thermophoresis force capable of projecting the unwanted particles, contained in the fluid to be treated, towards the second module.

[0009] The solutions known in the art, however, are not particularly efficient, especially in the case of particles with nanometric dimensions. This limit is due to several factors, including the difficulty of capturing such small particles by traditional filtration, centrifugal or electrostatic separation methods. The nanometric particles, in fact, have low inertiaand high mobility, which makes them difficult to intercept and retain in conventional dedusting systems.

[0010] This problem is particularly felt in the industrial field, for example in pyrolysis plants, where a fraction of the products subjected to thermal decomposition are converted into particulates. This particulate, characterised by very small dimensions, can easily disperse in the process flow and adhere to the inner surfaces of the ducts, forming deposits that, over time, can reduce the efficiency of the system. The progressive accumulation of nanoparticles in ducts and reactors can lead to partial or total obstruction of the flow channels, compromising the correct functioning of the systems and increasing the need for extraordinary maintenance interventions.

[0011] Furthermore, the chemical and physical nature of the particulate generated by the pyrolysis may vary based on the composition of the treated feedstock, making the dedusting process even more complex. In some cases, the removal of the particulate is not sufficient, since the recovery of the nanoparticles that compose it is also necessary. This is particularly relevant for the recovery of valuable materials, such as carbon nanoparticles, precious metals or metal oxides, which could be reused in other industrial processes.

[0012] The complexity of the problem increases further when the fluid to be dedusted is under high pressure conditions, as is the case in many advanced industrial plants. Under such conditions, traditional separation techniques may be ineffective or impractical, as particle removal must occur without altering system pressure or compromising process continuity. The management of pressurised flows containing nanometric particulates requires innovative technological solutions, capable of guaranteeing both a high separation efficiency and the possibility of recovering and reusing the particles without negatively affecting the overall performance of the plant.

[0013] There is therefore a need which is not satisfied by the state-of-the-art to realise a fluid dedusting system which is able to clean the fluid fromparticulates, especially particles with nanometric dimensions, in order to remove such particulates in a continuous and reliable manner.

[0014] The present invention achieves the above objects by providing a system as described above, in which the first duct consists of a tubular element, which tubular element has an auger element inside it in such a way that the auger element defines, together with the internal walls of the tubular element, a flow channel that extends helically along the longitudinal axis of the tubular element and configured for the passage of the working fluid.

[0015] Further, the second duct surrounds the outer walls of the tubular element.

[0016] Finally, the working fluid has a higher temperature than the service fluid.

[0017] A system is therefore created that allows the dedusting of the working fluid by utilising an inertial combination of a cyclonic type, thanks to the peculiar shape of the first duct, and thermophoresis, thanks to the temperature gradient between the working fluid and the service fluid.

[0018] Therefore, the system that is the subject of the present invention utilises the combination of two mechanisms to carry out the collection of the suspended particles of the working fluid, namely the effect of the cyclonic collision of the suspended particles that induces a radial migration towards the cooler wall of the first duct, and the thermophoretic forces applied to the suspended particles thanks to the thermal gradient between the working fluid and the service fluid, which causes the deposition of the particles at the wall of the first duct cooled by the flow of the service fluid.

[0019] Furthermore, as will be apparent from the following description and illustration of some embodiments, the system covered by the present invention has the further advantage of recovering the heat of the working fluid in a regenerative manner.

[0020] The system covered by the present invention in fact makes it possible to obtain a high efficiency heat exchanger, in which the abatement of dust from a hot gas and the recovery of heat take placesimultaneously through the combination of the cyclonic effect and the thermophoretic effect for the deposition of the particles and the subsequent extraction.

[0021] As anticipated, the working fluid along the path identified by the first duct, preferably, has a temperature always higher than the temperature of the service fluid along the path identified by the second duct, so as to establish a temperature gradient that enables the thermophoretic effect on the particulate to be achieved.

[0022] For this reason, the second duct must surround the outer walls of the tubular element constituting the first duct, so as to cool the walls of the tubular element for particle deposition.

[0023] It is obviously possible to provide specific shapes of the second duct in order to optimise the realisation of the temperature gradient.

[0024] In fact, according to a preferred embodiment, the second duct consists of a helical flow channel for the passage of the service fluid, which helical flow channel extends coaxially around the tubular element, in the direction of the longitudinal axis of the tubular element.

[0025] This peculiar configuration of the second duct improves the efficiency of the heat exchange between the working fluid and the service fluid.

[0026] The helical arrangement allows, in fact, a more uniform and prolonged contact between the walls of the two ducts, reducing the formation of inefficient heat exchange zones and favouring a homogeneous distribution of cooling along the entire length of the tubular duct. This design helps increase heat transfer by conduction and convection, making the process more efficient than a simple coaxial cylindrical configuration.

[0027] Advantageously, the system covered by the present invention provides for a flow in the opposite direction of the service fluid with respect to the working fluid, so as to improve the countercurrent heat exchange.

[0028] Therefore, according to a possible implementation variant, the first inlet is positioned at the second outlet, while the second inlet is positioned at the first outlet.As described above, one of the main purposes of the system that is the subject of the present invention is the collection of the nanoparticles obtained from the dedusting process of the working fluid.

[0029] This collection, in the system covered by the present invention, is facilitated by the deposition of the particles on the outer walls of the first duct.

[0030] Once the particles are deposited, it is possible to provide different methods for collecting them, such as for example the extraction of the auger element and / or the tubular element.

[0031] Advantageously, the auger element must not be provided as a single piece with the tubular element, in order to ensure its extraction.

[0032] In this case, preferably, the auger element is provided radially in contact with the inner walls of the tubular element.

[0033] As will be evident from the illustration of some exemplary embodiments, the auger element comprises a shaft mounted coaxial to the tubular element and a plurality of discs positioned parallel to each other and inclined at a given angle with respect to the longitudinal axis of the shaft.

[0034] According to the illustrated variant, the outer edges of the discs are in contact with the outer walls of the tubular element.

[0035] Alternatively, or in combination, according to a preferred embodiment, the auger element is rotatably mounted with respect to the tubular element around the longitudinal axis thereof.

[0036] This variant enables optimisation of the collection of the particles, as it allows the particles to be extracted continuously, without providing for any disassembly of the components of the system, but simply utilising the auger effect of the rotation of the auger element that pushes the deposited particles towards the outside of the tubular element.

[0037] According to a further embodiment, there is a device for collecting the particles deriving from the working fluid, so as to recover and utilise said particles according to operational needs.

[0038] Preferably, the collection device comprises means for compacting said particles.During operation of the system covered by the present invention, significant amounts of particulate matter are accumulated.

[0039] As anticipated, the particulate matter extracted from the hot working fluid to be dedusted is very fine, nanometric in size, so it presents a high risk of fire.

[0040] The compacting of the particulate through the compacting means limits the risk of flammability of the particulate itself.

[0041] According to a further embodiment of the system that is the subject of the present invention, the first and second ducts are inserted into an outer tube, there being a layer of low thermal conductivity material interposed between the inner walls of the outer tube and the outer walls of the second duct.

[0042] The coating of the first and second ducts with low heat transmission material makes it possible to obtain a particularly efficient heat exchanger, which makes it possible to reuse the heat generated by the system itself.

[0043] According to a possible embodiment, the service fluid may consist of water.

[0044] In combination with this feature, the working fluid can be constituted by a gas, so as to obtain a gas / water interface that would make it possible to achieve a cooling of the gas at particularly low temperatures.

[0045] The gas preferably consists of hydrogen.

[0046] The presence of water has particularly advantageous aspects in the case of use of the system covered by the present invention in industrial plants.

[0047] In fact, it could be envisaged to use water or a mixture of water and steam to bring the temperature of the working fluid, i.e. the gas, to room temperature, so as to obtain a high energy recovery.

[0048] Thus, as described, the working fluid may consist of a gas or a liquid, or of a mixture of gas and liquid, such as for example water and steam.Furthermore, it is possible to envisage that the system that is the subject of the present invention comprises at least two cooling stages or stations, with different service fluids.

[0049] A first stage with a service fluid at a high initial temperature, such as for example a service fluid consisting of a gas at a temperature higher than 700°C, and a second stage with a service fluid at a lower temperature than the first stage, such as for example a service fluid consisting of water, or water / steam mixture at a temperature lower than 700°C, could therefore be provided.

[0050] Given the advantageous aspects described above, the present invention also relates to a method of dedusting fluids.

[0051] In particular, the method that is the object of the present invention provides for the use of the system for dedusting a working fluid described above.

[0052] The method that is the object of the present invention provides the following steps:

[0053] a) passage of the working fluid inside the first duct,

[0054] b) passage of the service fluid inside the second duct,

[0055] c) transfer of heat from the working fluid to the service fluid, d) deposition of suspended particles of the working fluid on the inner walls of the tubular element,

[0056] e) collection of the deposited particles.

[0057] The method that is the object of the present invention, therefore, utilises the combination of the cyclonic inertial effect and the effect of thermophoresis to deposit and collect the particles, even the particles of nanometric size dispersed in the working fluid.

[0058] According to one embodiment, the step of collecting the deposited particles occurs through the rotation of the auger element.

[0059] In addition, the method subject-matter of the present invention provides that the step of collecting the particles provides for the compaction of the particles themselves.

[0060] It should further be noted that a particularly relevant aspect of the system and method that is the subject of the present invention resides inthe use of the same within industrial plants, such as for example in pyrolysis plants.

[0061] In fact, the features described above allow several advantages to be obtained in combination with pyrolysis plants.

[0062] First of all, an efficient dedusting of the working fluid is obtained, which enables optimisation of the subsequent utilisation of the same.

[0063] In addition, continuity of operation of the plant is ensured, as the collected particulate deriving from the pyrolysis does not accumulate at the various connecting pipes of the pyrolysis plant.

[0064] Finally, it is possible to use the particles deriving from pyrolysis that are dispersed in the working fluid and that are not collected during the pyrolysis process, so that they can be utilised, such as for example in the pyrolysis plants of products based on Carbon or Silicon.

[0065] For this reason, advantageously, it is possible to envisage a system comprising a pyrolyser connected to the dedusting system described.

[0066] Like the pyrolysers known in the art, a combustion chamber is provided that has an outlet nozzle from which the working fluid exits that can be dedusted through the system that is the subject of the present invention.

[0067] The system can also provide for the presence of a gas turbine. The goal is to create an integrated system that connects the pyrolyser to a gas turbine, using the working fluid as fuel to generate electricity.

[0068] The pyrolyser, which serves for the thermal decomposition of organic matter, can therefore be directly powered by the electrical energy produced by the gas turbine.

[0069] The process involves the working fluid, produced within the pyrolyser or at another stage of the industrial process, being used to power the gas turbine. The turbine, by burning the working fluid output from the system covered by the present invention, produces electrical energy which is then used for the operation of the pyrolyser itself. In this way, the plant becomes almost self-sufficient from an energy point ofview, reducing operating costs and increasing the overall efficiency of the plant.

[0070] In addition, if the pyrolyser is used for the production of hydrogen as a working fluid, the use of hydrogen as a fuel not only contributes to reducing the emission of CO2, but also optimises the process, considering that hydrogen is a source of energy that, when used in a gas turbine, generates heat and energy without producing pollutants. This integrated energy recovery system represents an advantageous strategy to promote energy efficiency and environmental sustainability in pyrolysis plants, paving the way for a low-carbon industrial future.

[0071] Ultimately, this closed cycle, which utilises the synergy between the pyrolyser and the gas turbine, not only optimises the use of the energy produced, but also favours the recovery and use of a renewable and clean resource, such as hydrogen, to support innovative and sustainable industrial processes.

[0072] These and other features and advantages of the present invention will become clearer from the following disclosure of some exemplary embodiments illustrated in the accompanying drawings, wherein:

[0073] figures 1a and 1b illustrate two schematic diagrams of a section of a possible embodiment of the system that is the subject of the present invention;

[0074] figure 1c illustrates a detail of a section of a schematic diagram of a possible embodiment of the system that is the subject of the present invention;

[0075] figure 2 illustrates a flowchart of a possible embodiment of the method that is the subject of the present invention;

[0076] figure 3a illustrates a diagram of the temperature trend of the working fluid and of the service fluid;

[0077] figure 3b illustrates a diagram of the temperature trend of two different zones of the system covered by the present invention.

[0078] It should be noted that the figures attached to this patent application illustrate only some possible embodiments of the dedustingsystem that is the subject of the present invention, in order to better understand the advantages and characteristics described.

[0079] These embodiments are therefore to be understood as purely illustrative and not limiting to the inventive concept of the present invention, namely to provide a dedusting system capable of dedusting the working fluid by utilising an inertial combination of a cyclonic type and thermophoresis.

[0080] With particular reference to figures 1a and 1b, a section of an embodiment of the dedusting system that is the subject of the present invention is illustrated.

[0081] This system comprises a first duct made up of a tubular element 10 and an auger element 11.

[0082] The auger element 11 has a shaft 12 coaxial to the longitudinal axis A of the tubular element 10 and a plurality of discs 13 arranged parallel to each other along the shaft 12.

[0083] The peripheral edges of the discs 13 are in contact with the inner walls of the tubular element 10 in such a way that the lower and upper walls of each disc 13 define, together with the walls of the shaft 12 and the inner walls of the tubular element 10, a flow channel 100 of the working fluid, in which a section is illustrated in figures 1a and 1b.

[0084] The working fluid flow channel 100 extends helically and coaxially with the tubular element 10, along the axis A of the tubular element 10.

[0085] In particular, in figure 1b the arrow B indicates the inlet direction of the working fluid through the inlet 101 of the first flow channel, while the arrow C indicates the outlet direction of the working fluid through the outlet 102 of the flow channel 100.

[0086] The system also comprises a second duct consisting of a helical flow channel 2 of the service fluid, which extends coaxially with the tubular element 10, along the axis A, and which surrounds the tubular element 10.

[0087] According to the illustrated embodiment, the outer walls 20 of the second duct 2 are partially in contact with the outer walls of the tubular element 10.Furthermore, with particular reference to Figure 1b, the arrow D indicates the direction of entry of the service fluid through the inlet 201 of the second flow channel 2, while the arrow E indicates the direction of exit of the service fluid through the outlet 202 of the second flow channel 2.

[0088] The system is configured in such a way that the working fluid and the service fluid have directions of flow opposite to each other with respect to the longitudinal axis of the tubular element 10.

[0089] In addition, the first duct and the second duct arranged coaxially with each other, are inserted inside a further tubular element 3, while a layer of insulating material 30 is present between the outer surface 20 of the second duct and the inner wall of the further tubular element 3.

[0090] It follows that both the first and second ducts are isolated from the external environment.

[0091] The auger element 11 is mounted inside the tubular element 10 in a rotatable manner with respect to the latter and around the axis A.

[0092] As will be described later, the rotation of the auger element 11 serves to collect the suspended particles within the working fluid.

[0093] As described, the working fluid flowing inside the first duct has a higher temperature than the service fluid flowing inside the second duct, so that a heat exchange takes place between the two fluids.

[0094] In particular, the system that is the subject of the present invention provides two paths, one identified by the flow of the working fluid with the suspended particles inside the first duct and one identified by the flow of the service fluid inside the second duct, configured to improve the convective heat transfer between the working fluid and the service fluid.

[0095] Advantageously, the material constituting the auger element 11 and the tubular element 10 is chosen so as to withstand the maximum temperature reached by the working fluid.

[0096] Similarly, the material constituting the second flow channel 2 is also chosen so as to withstand the maximum temperature reached by the service fluid.

[0097] The interaction between the working fluid and the service fluid thus creates a thermal exchange between the fluids in such a way that, withparticular reference to Figure 1b, the working fluid, from the inlet 101 to the outlet 102 of its path, is cooled from a temperature level T_A-high to a temperature level T_A-low, while the service fluid, from the inlet 201 to the outlet 202 of its path, is heated from a temperature level T_B-low to a temperature level T_B-high.

[0098] Preferably, the temperature level T_A-low of the working fluid is higher than the temperature level T_B-high of the service fluid.

[0099] On the basis of the characteristics described, it is possible to illustrate the operation of the dedusting system and method that is the subject of the present invention, with particular reference to figures 1 c and 2.

[0100] A flowchart of a possible embodiment of the dedusting method is illustrated in figure 2.

[0101] This method uses the system described above and provides for flowing the working fluid with the suspended particles to be dedusted into the first duct, step 301 , and, at the same time, for flowing the service fluid into the second duct, step 302.

[0102] The flow of the two fluids causes a transfer of heat from the working fluid to the service fluid, step 303.

[0103] As will be described later, the transfer of heat 303 and the flow of the fluids within the peculiar shape of the first and second ducts causes the deposition of the suspended particles of the working fluid on the inner walls of the tubular element, step 304.

[0104] Once the particles have been deposited, it is possible to provide a step of collecting, step 305, said particles.

[0105] The collection step 305 can take place through the rotation of the auger element 11 , which can therefore serve both to define the first flow channel for the working fluid and to extract the particles no longer suspended in the working fluid.

[0106] The illustrated method utilises the combination of the thermophoresis mechanism, given by the temperature gradient between the two fluids, and the cyclonic inertial mechanism, according to the procedure described below and with particular reference to Figure 1c.Figure 1c illustrates a detail of the system that is the subject of the present invention, in which some portions of the first duct 100, some portions of the second duct 2 are illustrated, and in which the contact between the outer walls 20 of the second duct 2 with the outer walls of the tubular element 10 is visible.

[0107] In particular, while the high temperature working fluid with suspended particles flows in the first duct 100, the suspended particles 40 undergo a cyclonic motion that induces a centrifugal force FC on the particles given by:

[0108] Fc = mp * vA2 / r

[0109] Where mp is the mass of the suspended particle 40, v is the tangential velocity and r is the local radius of curvature. This force pushes the particles radially outward, towards the inner walls of the tubular element 10, opposing the aerodynamic drag force described, for low Reynolds number flows, as:

[0110] Fd = 6 * IT * p * Rp * (v-vg)

[0111] The latter is influenced by fluid viscosity p, particle size Rp and flow dynamics.

[0112] When the centrifugal force exceeds the resisting force, radial displacement of the particles toward the inner wall of the tubular element 10 is facilitated.

[0113] At the same time, the tubular element 10, in particular the inner and outer walls of the tubular element 10, is externally cooled by the second duct 2 and a thermal gradient is established through the flow of the fluids.

[0114] This gradient induces a thermophoretic force acting in the direction of the decreasing temperature,

[0115] FT = -A * p * RpA2 *(VT / T) / kWhere A is the mean free path of the fluid molecules, k is the thermal conductivity of the fluid and VT is the imposed temperature gradient.

[0116] This force further enhances the deposition of particles on the inner wall of the tubular element 10 as illustrated by the particles 41 of Figure 1c.

[0117] Once the particles 41 have accumulated on the inner wall of the tubular element 10, the rotating mechanism of the auger element 11 aids collection and extraction outside the system, leaving the surface free for further particle deposition.

[0118] Figure 3a illustrates a graph in which the trend of the temperature of the working fluid, indicated as 50, and of the service fluid, indicated as 51 , in the first duct 100 and in the second duct 2, respectively, is reported.

[0119] In particular, Figure 4a refers to a specific case study of an example of embodiment of the system that is the subject of the present invention, in which the working fluid is hydrogen gas, while the service fluid is methane gas.

[0120] With reference to the specific embodiment, the material of the first duct 100 is graphite, the material of the second duct 2 is steel and the insulation on the outer side of the system is carbon felt with thermal conductivity respectively equal to 25 W*(m*K)A-1 for graphite, 45 W*(m*K)A-1 for steel and 0.2 W*(m*K)A-1 for carbon felt.

[0121] Thermo-fluid-dynamic simulations demonstrate the thermal behaviour of the system as shown in figure 3a.

[0122] In the example shown, the first duct 100 carries hydrogen gas with an inlet temperature of 1673 K (FIG 30.0 m) and the second duct 2 carries methane gas with an inlet temperature of 298 K. The thermal efficiency of the system allows the heat exchanger to cool the hydrogen down to 1230 K, heating the methane up to 856 K.

[0123] Finally, Figure 3b also refers to the embodiment described in relation to Figure 3a, but illustrates the temperature trends not with reference to the fluids in circulation, but with reference to two specific areas of the system that is the subject of the present invention.In particular, as illustrated in the left part of Figure 3b, it is possible to identify two end zones of the system that is the subject of the present invention, respectively a "hot zone" 62 and a "cold zone" 63.

[0124] The hot zone 62 corresponds to the inlet zone of the working fluid, as indicated by reference 101 of figure 1b, while the cold zone 63 corresponds to the outlet of the working fluid, as indicated by reference 102 of figure 1 b.

[0125] To the right of figure 3b is a graph indicating the temperature levels, respectively of the hot zone, line 60, and of the cold zone, line 61, as a function of the radial direction from the first to the second duct.

[0126] In fact, part of the system covered by the present invention is illustrated in overprint in figure 3b, in order to illustrate the temperature trends in the different areas of the system itself.

[0127] While the invention is subject to various modifications and alternative constructions, some preferred embodiments have been shown in the drawings and described in detail.

[0128] It should be understood, however, that there is no intention to limit the invention to the specific illustrated embodiment but, on the contrary, the aim is to cover all the modifications, alternative constructions and equivalents falling within the scope of the invention as defined in the claims.

[0129] The use of “for example”, “etc.”, “or” indicates non-exclusive alternatives without limitation, unless otherwise indicated.

[0130] The use of “includes” means “includes, but not limited to” unless otherwise indicated.

Claims

CLAIMS1. A system for dedusting a working fluid, which working fluid has a plurality of suspended particles (40), the system comprisinga first duct (100) for passing the working fluid from a first inlet (101) to a first outlet (102),a second duct (2) for passing a service fluid from a second inlet (201 ) to a second outlet (202),characterised in thatsaid first duct consists of a tubular element (10), which tubular element (10) has inside it an auger element (11 ) in such a way that said auger element (11) defines, together with the inner walls of the tubular element (10), a flow channel that extends helically along the longitudinal axis (A) of said tubular element (10) and configured for the passage of the working fluid,surrounding said second duct (2) the outer walls of said tubular element (10),the working fluid having a higher temperature than the service fluid.

2. System according to claim 1, wherein said second duct (2) consists of a helical flow channel for the passage of the service fluid, which helical flow channel extends coaxially around the tubular element (10) and along the longitudinal axis (A) of said tubular element (10).

3. System according to claim 1 or claim 2, wherein said first inlet (101) is positioned at said second outlet (202), said second inlet (201) being positioned at said first outlet (102).

4. System according to one or more of the preceding claims, wherein said auger element (11 ) is radially in contact with the inner walls of said tubular element (10).

5. System according to one or more of the preceding claims, wherein said auger element (11) is mounted rotatable with respect to said tubular element (10) around the longitudinal axis (A) of said tubular element (10).

6. System according to one or more of the preceding claims, wherein there is a device for collecting the particles (41 ) deriving from theworking fluid, said collection device comprising means for compacting said particles (41).

7. System according to one or more of the preceding claims, wherein said first (100) and second (2) ducts are inserted inside an outer tube (3), there being a layer of low thermal conductivity material (30) interposed between the inner walls of the outer tube (3) and the outer walls of said second duct (2).

8. A method of dedusting a working fluid by using the dedusting system according to one or more of claims 1 to 7,characterised in that it provides the following steps:a) passage of the working fluid inside the first duct (301 ), b) passage of the service fluid inside the second duct (302), c) transfer of heat from the working fluid to the service fluid (303), d) deposition of the suspended particles of the working fluid on the inner walls of the tubular element (304),e) collecting the deposited particles (305).

9. A method according to claim 8, wherein the step of collecting the deposited particles takes place through the rotation of the auger element.

10. Method according to claim 8 or claim 9, wherein the step of collecting the particles comprises compacting the particles.

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