Heated selective catalytic reduction device

Abstract

Selective catalytic reduction (SCR) device (100) for a diesel engine, said SCR device (100) comprising a preheating module (140) adapted to heat a urea solution flowing from a urea inlet line (101) of the SCR device (100) to an injection module (160), the SCR device (100) further comprising said injection module (160), which is adapted to inject the heated urea solution at a urea outlet line (102) of the SCR device (100). (Shorthand figure: Figure 4)

Description

Title of the invention: Heated selective catalytic reduction device. Technical field of the invention

[0001] The present description relates to internal combustion engines and, specifically, to selective catalytic reduction devices for diesel engines. State of the art

[0002] Diesel engines, particularly those used in heavy-duty applications, require exhaust gas treatment to meet existing emission regulations. These regulations aim to control the emission of nitrogen oxides (NOx) from the exhaust of diesel engines. A common approach to NOx removal uses Selective Catalytic Reduction (SCR) systems. These systems use ammonia as a reducing agent to convert NOx into nitrogen and water.

[0003] Various SCR systems are known in the prior art, and the corresponding processes generally involve the decomposition of a liquid urea solution into urea vapor gas, which is then converted into ammonia gas.

[0004] Figure 1 shows how ammonia is generally generated according to prior art SCR systems. In a first step S1, hydraulic energy is supplied from an external source to convert the liquid urea solution into fine droplets of an aqueous urea solution. After this atomization of the aqueous solution, in a second step S2, heat is supplied internally to transform this atomization into urea vapor. For example, the heat from the exhaust gases of the diesel engine is used to convert the fine droplets of the aqueous solution into urea vapor. In a third step S3, the urea vapor is transformed into ammonia, for example, using the remaining available thermal energy. Finally, in a fourth step S4, the NOx are converted into nitrogen and water, this conversion process generating heat which is then removed from the system.

[0005] During the second and third stages S2 and S3, the heat supplied by the external source accelerates the evaporation process, resulting in the decomposition of urea into ammonia in a shorter time. This conversion process requires a significant amount of thermal energy. This is a common problem encountered when starting diesel engines, which produce a small mass of exhaust gas at low temperatures. In particular, during start-up When cold, the exhaust gas temperature is generally 150°C or lower. The starting temperature therefore hinders this conversion process, limiting the ability of known SCR systems to effectively reduce NOx emissions. However, the efficiency of SCR systems and catalytic converters depends directly on their ability to reach and maintain a minimum operating temperature, preferably around 200°C.

[0006] To solve this problem, as mentioned, prior art systems use the thermal energy of the exhaust gases themselves to facilitate the vaporization of the urea and the subsequent conversion to ammonia. For example, Figure 2 of US Patent Application No. 2007 / 0119153 A1 illustrates the corresponding prior art and depicts an SCR system 20 that includes an aqueous urea supply 31, connected to a pressurized delivery pump 22 via the outlet 32 ​​of this delivery pump 22. The SCR system 20 includes a heater 23 upstream of a controlled injection nozzle, comprising a glow plug 34 that increases the temperature of the urea passing through the heater, thereby improving engine aftertreatment.

[0007] A conduit 31 then connects the heating station 23 to a control valve 33 before the injection nozzle, the whole process of heating, or preheating, the aqueous urea to a temperature approximately above 130 degrees Celsius. The injection nozzle then breaks down the urea stream into small droplets, which increases the specific surface area of ​​the urea to improve heat exchange with the exhaust gases after the control valve 33, in order to produce ammonia.

[0008] However, this system has several limitations because the solution is dispersed over the surfaces of the exhaust system, leading to the problematic accumulation of urea crystal deposits. In cold conditions or during frequent start-stop cycles, these crystals can clog the exhaust system, potentially causing engine failure.

[0009] Another disadvantage of the SCR 20 system is that its operation involves heating a considerable volume of urea, without allowing for optimization of heat transfer. These problems are exacerbated in cold climates or during engine start-up, as the exhaust gas temperature is significantly lower, delaying the activation of the SCR system and reducing its NOx conversion efficiency. The possibility of urea melting in solid form, i.e., urea ice, at ambient temperatures below -11.5 °C is also a problem encountered.

[0010] Therefore, in addition to reducing greenhouse gases through existing devices, and consequently limiting carbon dioxide emissions during the heating of these devices, there is a need to optimize energy distribution thermal management within SCR systems and providing a more efficient solution to accelerate the heating process of such an SCR system, thus overcoming the aforementioned drawbacks of the prior art. There is also a need to facilitate the conversion of NOx at low temperatures and generate savings through more efficient urea dosing, avoiding overdosing. Object of the invention

[0011] In order to address this or these drawbacks, a selective catalytic reduction (SCR) device for a diesel engine is proposed under one of the present terms, said SCR device comprising a preheating module adapted to heat a urea solution circulating from a urea inlet line of the SCR device to an injection module, the SCR device further comprising said injection module, the injection module being adapted to meter and inject in the form of droplets the heated urea solution at the level of a urea outlet line of the SCR device.

[0012] In the present, an SCR system or device is defined as any system or device designed to reduce nitrogen oxide levels emitted by diesel engines by injecting a reducing agent, typically urea, into the exhaust gas stream.

[0013] In the present text, it is understood that the injection module includes a urea injector. This injector is configured to supply a controllable or controlled quantity of urea solution to the diesel engine, and more specifically to meter this quantity of urea into the diesel engine's exhaust system.

[0014] In the present context, a urea outlet line is, for example, a urea outlet channel, or simply an outlet orifice for urea. For example, a urea outlet line is adapted to inject urea into the exhaust line of a diesel engine to which the SCR device is connected.

[0015] The urea injector includes a nozzle for metering the supply of urea solution to the diesel engine. In this context, a nozzle can be understood as a device designed to control the direction or characteristics of a fluid flow as it exits a closed chamber or conduit. This arrangement allows for the precise atomization of the liquid urea solution into fine droplets and ensures homogeneous mixing with the exhaust gases.

[0016] The object of this article optimizes the selective catalytic reduction process for diesel engines by improving the efficiency of introducing urea into the exhaust gas stream through preheating before injection. This addresses several critical limitations of existing systems. First, by efficiently preheating the urea solution before injection, the device avoids the need for high temperatures at engine start-up, thus enabling faster and more appropriate vaporization of the urea. This It also prevents the accumulation of urea crystal deposits that could clog the exhaust system. Secondly, this approach ensures that thermal energy is used directly to convert urea into ammonia rather than simply heating the exhaust walls, thus increasing the availability and efficiency of thermal energy. Furthermore, the system's rapid response allows for efficient operation even under frequent start-up conditions or in cold environments, overcoming the latency issues and inefficiencies of traditional SCR systems. It also enables NOx emissions to be reduced to extremely low levels to ensure regulatory compliance. Overall, this provides a device that leads to reduced urea consumption, lower CO2 emissions, and savings in materials used.

[0017] According to one embodiment, the injection of the heated urea solution is implemented by a spraying module comprising the injection module, the spraying module connecting the preheating module to the urea outlet line.

[0018] Alternatively, the injection of the heated urea solution is implemented by a spraying module comprising the injection module, the spraying module connecting the preheating module and / or the injection module to the urea outlet line.

[0019] This allows for efficient and homogeneous distribution of the heated urea in the exhaust gas stream of a diesel engine, thanks to the configuration of the spray module, which is designed to connect the preheating module to the outlet line. This arrangement ensures optimal atomization of the urea solution, facilitating a more complete catalytic reaction and thus reducing the likelihood of the formation of deposits detrimental to the efficiency of the catalytic reduction system.

[0020] According to one embodiment, the SCR device comprises a main body which integrates the preheating module and the injection module inside said main body, the main body comprising at least one coolant inlet from outside the main body to inside the main body, the main body further comprising at least one coolant outlet from outside the main body to outside the main body.

[0021] This allows for maintaining an optimal temperature of the internal components, particularly the preheating module and the injection module, thanks to an integrated cooling fluid circulation system within the main body of the SCR device. The inlet and outlet of the cooling fluid facilitate effective heat control, which preserves the functionality and longevity of the modules.

[0022] According to one possible embodiment, the inlet and / or outlet of the cooling fluid can or rather can be connected to the spray module or to a cooling jacket, in particular a cooling jacket for the spray module.

[0023] According to one embodiment, the main body of the SCR device comprises at least one cooling jacket, the at least one cooling jacket being arranged to surround the injection module, the at least one cooling jacket being further adapted to allow the circulation of the cooling fluid between the at least one cooling fluid inlet and the at least one cooling fluid outlet.

[0024] This allows for efficient temperature management around the injection module by using a cooling jacket that encloses it. The jacket's configuration ensures adequate circulation of the cooling fluid, thus facilitating the absorption and dissipation of excess heat. This thermal management promotes stable and prolonged performance of the injection module, while reducing the risk of thermal degradation of nearby heat-sensitive components.

[0025] According to one possible embodiment, the SCR device includes a cooling fluid control valve. This provides a means of temperature control, in particular so that the use of this valve can control the system cooling as desired. In particular, this also ensures thermal protection of the spray module.

[0026] According to one embodiment, the preheating module includes at least one thermal concentrator, the at least one thermal concentrator being positioned along a flow of circulation of the urea solution between the preheating module and the injection module.

[0027] This maximizes thermal efficiency by concentrating heat directly along the path of the urea solution between the preheating module and the injection module. This also enables heat exchange by forced convection. Furthermore, by strategically positioning at least one thermal concentrator, the SCR device optimizes the temperature of the urea solution to promote faster and more complete vaporization. This precise temperature control facilitates improved ammonia conversion, which is essential for the effective reduction of NOx emissions under various operating conditions.

[0028] The use of thermal concentrators also helps to reduce heat loss by convection to the ambient air, allowing the system to maintain superior thermal efficiency while reaching its optimal operating temperature more quickly. This configuration ensures a reduction in pollutant emissions that complies with strict emission standards, while maintaining consistent performance of the SCR device. Thus, the device offers greater control. Precise and efficient temperature control, crucial for the environmental and operational performance of the diesel engine.

[0029] According to one embodiment, the thermal concentrator comprises at least one urea solution circulation channel and at least one heating element, the at least one heating element being disposed around the at least one urea solution circulation channel and / or being disposed in the at least one urea solution circulation channel.

[0030] In this context, a heating element is any component capable of converting energy, for example, electrical energy, into heat. One advantage of having a dedicated heating element is the ability to maintain operational efficiency even in cold conditions where the thermal energy of the exhaust gases is insufficient. By keeping the urea solution in liquid form until it reaches the injector, the high metering accuracy of the injector, designed for precise liquid metering, is also maintained. This then allows, by means of an associated sprayer, the injection of urea in very fine droplets, leading to a more efficient reduction of nitrogen oxides in the exhaust and compliance with stringent emission standards.For example, this injection in the form of droplets is achievable by a pressure release, when the boiling point of urea at ambient pressure, typically 100 to 104 °C, is reached in the SCR device.

[0031] This allows for a highly controlled and efficient heat distribution along the heat exchange path of the urea solution, particularly by forced convection, thanks to the strategic placement of heating elements around and within the circulation channels. The presence of multiple heating elements ensures uniform and adjustable heating, thus optimizing urea vaporization and promoting a homogeneous and efficient catalytic reaction. This device also allows for flexible adaptation to variations in thermal requirements, depending on the operating conditions of the diesel engine. Furthermore, temperature measurement combined with urea injection using an associated sprayer makes it possible to determine the actual density of the aqueous solution, and therefore to ensure more precise mass dosing of the urea.

[0032] According to one embodiment, the thermal concentrator has a heat exchange surface with the flow of the urea solution circulating between the preheating module and the injection module, said heat exchange surface being greater than or equal to 30 square centimeters and less than or equal to 60 square centimeters.

[0033] This optimizes heat exchange by ensuring sufficient contact surface area between the thermal concentrator and the urea solution to guarantee a Adequate and constant temperature is maintained during the preparation of the solution for the catalytic reaction. By defining a precise heat exchange surface area between 30 and 60 cm², the device effectively balances the rise and retention of heat required for urea vaporization, thus improving the efficiency of ammonia conversion and meeting stringent NOx reduction standards.

[0034] According to one embodiment, the thermal concentrator is adapted to provide a thermal power density to the flow of the urea solution circulating between the preheating module and the injection module, said thermal power density being greater than or equal to 10 watts per square centimeter and less than or equal to 20 watts per square centimeter.

[0035] This enables forced convection through circulation of the urea solution, which optimizes thermal efficiency by providing a suitable power density that maximizes heat transfer without compromising the components through excessive overheating. By establishing a thermal power density between 10 and 20 watts per square centimeter, the SCR device optimally utilizes energy to heat the urea solution, thus ensuring an efficient catalytic reaction for NOx conversion under varying conditions. This specific range helps maintain a balance between thermal performance and energy management.

[0036] According to different embodiments, the thermal concentrator:

[0037] - has a hollow cylindrical shape,

[0038] - a principal axis of said hollow cylindrical shape is substantially parallel to the flow rate of the urea solution,

[0039] - at least one circulation channel comprises an internal helical groove,

[0040] - at least one circulation channel comprises an external helical groove,

[0041] - the internal helical groove is formed in an internal surface of the concentrator thermal,

[0042] - the external helical groove is formed in an external surface of the concentrator thermal, and / or

[0043] - at least one radial groove connects one end of the internal helical groove to one end of the external helical groove at the level of a base of the hollow cylindrical shape.

[0044] This allows for precise control of heat transfer and heat exchange between the thermal concentrator and the urea solution, thus optimizing the efficiency of the catalytic reduction of NOx. The hollow cylindrical design with internal and external helical grooves facilitates uniform distribution of the urea solution, maximizing surface-liquid contact.

[0045] According to one embodiment, the preheating module further comprises at least one pair of concentric O-rings.

[0046] This allows for effective thermal and mechanical insulation to be maintained between the thermal concentrator and the other components of the preheating module. Brief description of the figures

[0047] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analysis of the accompanying drawings, on which:

[0048] [Fig.1], the [Fig.1], which has been previously described, illustrates a process for generating ammonia according to the state of the art,

[0049] [Fig.2], the [Fig.2], which has been previously described, illustrates an SCR device according to the state of the art,

[0050] [Fig. 3], the [Fig. 3], illustrates a three-dimensional view of an SCR device according to a method of implementation,

[0051] [Fig.4], the [Fig.4], illustrates a cross-sectional view of the SCR device according to this mode of realization,

[0052] [Fig. 5], the [Fig. 5], illustrates a three-dimensional view of a thermal concentrator according to one embodiment,

[0053] [Fig.6], the [Fig.6], illustrates another three-dimensional view of the concentrator thermal according to a particular embodiment,

[0054] [Fig.7], the [Fig.7], illustrates a side view of the thermal concentrator in operation according to a particular embodiment,

[0055] [Fig.8], the [Fig.8], illustrates a cross-sectional view of the thermal concentrator in operation according to a particular embodiment, and

[0056] [Fig.9], the [Fig.9], illustrates a schematic diagram of the circulation of a fluid in the thermal concentrator according to one embodiment.

[0057] Unless otherwise indicated, common or similar elements in several figures bear the same reference signs and have identical or similar characteristics, so that these common elements are generally not described again for the sake of simplicity. Description of the implementation methods

[0058] Figures 1 and 2 have been described in the context of the state of the art.

[0059] Figure 3 represents a three-dimensional view of an SCR device according to a mode of the realization of the invention.

[0060] The present papers describe embodiments of SCR devices in the non-limiting context of use with a diesel engine to optimize NOx emission reduction by injecting a liquid, such as preheated urea, into an exhaust line. However, the possibility of using other fluids and other applications, for example in the case of a fuel cell, is not excluded. fuel, the use of water vapor for dispersion in the form of fine droplets.

[0061] The three-dimensional view of [Fig.3] illustrates an SCR 100 device comprising a plurality of modules, including a connection module 120, a preheating module 140, also called a "heating module", an injection module 160 and an optional spraying module 170.

[0062] As shown, the preheating module 140 includes a urea inlet line 101 through which urea can be supplied to the SCR device 100. The urea inlet line 101 is, for example, connected to an external pump (not shown), which supplies the SCR device 100 with a pressurized liquid, for example, a liquid urea solution. The pump itself is connected to an external reservoir (not shown) capable of supplying sufficient urea to allow the SCR device 100 to operate.

[0063] As shown, between the preheating module 140 and the injection module 160, there may be one or more orifices 165, these orifices being made on a surface of the main body of the SCR device 100, thus creating an interface separating the preheating module 140 and the injection module 160. For example, a plurality of orifices 165 in the form of a band of holes makes it possible to form a thermal barrier which thermally insulates at least partially the two modules, so as to maximize the transfer of thermal energy to the aqueous urea solution circulating in the SCR device 100, in particular from the preheating module 140 to the injection module 160. The SCR device 100 is thus thermally insulated from the cold mass of the system's exhaust.

[0064] For example, when starting a diesel engine to which the SCR device is connected, a plurality of orifices 165 provides cold thermal insulation which reduces the heating of the exhaust and the injection module 160, and hot thermal insulation which thermally protects the preheating module 140 from the injection module 160 when the latter is in operation.

[0065] The injection module 160, or the spray module 170 if present, includes a urea outlet line 102 for expelling the urea, and then dispersing and / or spraying it into fine droplets at the level of the exhaust gas stream of an internal combustion engine, in particular a diesel engine (not shown) to which the SCR device 100 is connected.

[0066] According to one possible embodiment, the injection module 160 includes the spray module 170. In this case, the spray module 170 is located downstream of the injection module 160 and connects the injection module 160 to the urea outlet line 102.

[0067] According to one possible embodiment, the SCR 100 device consists of a main body, for example a stainless steel frame, which includes the preheating module 140, the injection module 160. The main body may also include the spraying module 170 if the latter is present in the SCR 100 device.

[0068] According to one possible embodiment, the connection module 120 is located above the urea inlet line 101 and allows the main body of the SCR device 100 to be connected to an internal combustion engine (not shown). This engine is, for example, located above and / or to the sides of the main body. The connection module 120 includes suitable attachment means for this purpose, the use of welds being a possible alternative. The connection module 120 allows the main body of the SCR device 100 to be mechanically, electronically, and / or thermally connected to a diesel engine (not shown), as well as to a control device. For example, the connection module provides an electrical connection to the heating elements.

[0069] The preheating module 140 is intended to preheat the flow of urea solution passing through it. The injection module 160 is intended to inject the urea into the exhaust gas flow, while the spraying module 170 can optionally distribute the urea to the exhaust outlet or directly to the exhaust gas.

[0070] The main body of the SCR device 100 may also include the fluid inlet connector 101 from the external pump, connecting the latter to the preheating module 140.

[0071] According to one possible embodiment, the main body of the SCR device 100 is connected to or comprises a coolant inlet, denoted 103, and a coolant outlet 104, the inlet and outlet functionalities of 103 and 104 being reversible. This allows the coolant to circulate within the main body of the SCR device 100, for example, in a cooling jacket as described below. The coolant inlet 103 and outlet 104, which is preferably a coolant, are, for example, thermally connected to the injection module 160. The coolant is, for example, diesel engine coolant when the SCR device 100 is connected to it, or alternatively, a circulating aqueous urea solution.

[0072] According to one possible embodiment, when present, the spray module 170 is located in the lower part of the SCR device 100 and includes or is connected to the urea outlet line 102, for example by means of a vaporizer, a sprayer or a sprayer.

[0073] According to one possible embodiment, when present, the spray module 170 is configured to allow precise dosing of urea and / or uniform distribution thereof.

[0074] For example, in terms of overall results, the SCR device described above makes it possible to obtain a high urea mass flow rate, in particular exceeding 1.5 kilograms per hour, with the temperature raised to approximately 140-150°C, considering a 32.5% aqueous urea solution. In this example, during startup, low thermal inertia and an electrical power of up to 600 watts provide a heating time of one or more minutes, with high thermal responsiveness, and therefore high energy efficiency with a limited risk of overheating.

[0075] Figure 4 represents a detailed cross-sectional view of an SCR device according to one embodiment of the invention.

[0076] According to various possible embodiments, the connection module 120 itself includes a cover 126, for example a hood, covering and able to protect the top of the SCR device 100. A fixing element 122 for the cover of the SCR device 100, for example one or more fixing nuts, may also be provided in or on the connection module 120.

[0077] The presence of this connection module 120 and / or the hood defined by the cover 126 reduces heat convection and can also be used as a support for electrical connections. By blocking convection from the top of the SCR device 100, heat exchange with the outside is reduced, thus increasing overall efficiency.

[0078] According to one possible embodiment, the connection module 120 comprises various elements for measuring and / or controlling measurable physical quantities within the SCR 100 device. These measuring elements may include, but are not limited to, thermistors adapted to provide temperature measurements, electronic interconnection elements, a printed circuit board, or a processor configured to control the temperature at various points within the SCR 100 device, or the urea flow rate. As an alternative to thermistors, other types of temperature sensors may be used, for example, an infrared sensor.

[0079] According to one possible embodiment, the connection module 120 includes one or more thermal insulation sheets, for example comprising an insulating plastic material or an insulating synthetic resin, preferably heat-resistant, in order to prevent heat conduction from or to the main body of the SCR 100 device.

[0080] According to one possible embodiment, the injection module 160 includes an injector 168 equipped with an injection nozzle. This injection nozzle allows the injection A reducing agent, such as a long-lasting solution, is introduced into the exhaust gas stream of an internal combustion engine to implement selective catalytic reduction. The nozzle of injector 168 can also be adapted to atomize the reducing agent using compressed air or a propellant gas.

[0081] According to one possible embodiment, the preheating module 140 includes at least one thermal concentrator 150. The at least one thermal concentrator 150 minimizes heat losses by convection to the outside, thus improving the thermal efficiency of the system.

[0082] According to one possible embodiment, the preheating module 140 further includes a supply channel 147 which is connected to the injection module 160. The supply channel 147 allows the urea supplied by the pump to be directed to the injector 168, by passing the urea through at least one thermal concentrator 150.

[0083] According to various possible variants, at least one thermal concentrator 150 is arranged around, along and / or near the supply channel 147, or includes it.

[0084] By way of non-limitation, at least one thermal concentrator 150 has the function of concentrating heat on the urea solution flow which flows from the urea inlet line 101 to the injection module 160. It is understood that this does not exclude the possibility of providing several thermal concentrators, for example arranged in series along the urea solution flow, or of having complementary functions, for example those of being a heat exchanger or a thermal regulator, these functions possibly being controlled by corresponding electronics.

[0085] The at least one thermal concentrator 150 can take various and varied forms.

[0086] According to one possible embodiment, a heating body 143 is arranged around the thermal concentrator 150, allowing the internal elements of the preheating module 140 and / or the thermal concentrator 150 to be accommodated.

[0087] According to one possible embodiment, a cover enclosing the contents of the preheating module 140, the heating element 143, and / or the thermal concentrator 150, for example on the sides of the main body of the SCR device 100, is present. This cover is, for example, formed by a protective and / or insulating cap. This cover may be made of a polymer, in particular polyphenylene sulfide. The cover, as well as the cap if present, provides physical protection for the components inside the SCR device 100, while also providing thermal and electrical insulation.

[0088] According to one possible embodiment, the preheating module 140 further includes one or more thermal insulation seals to prevent heat loss as well as leaks of fluids or gases.

[0089] For example, with regard to this or these thermal insulation seals, the preheating module 140 includes at least one internal O-ring 144 located at and around a first distance from the thermal concentrator 150. In addition, the preheating module 140 may also include at least one external O-ring 146 located at and around a second distance from the thermal concentrator 150, the second distance being greater than the first distance. In particular, if the thermal concentrator 150 has a substantially circular shape, as is the case, for example, for a coil or a cylindrical radiator, the first distance is an internal diameter of this substantially circular shape and the second distance is an external diameter of this substantially circular shape.

[0090] In the aforementioned example, the thermal insulation seal(s) isolate the hydraulics comprising and / or surrounding the preheating module 140, preventing leaks. This also allows the fluid or liquids circulating in the system to be in contact with the walls, the thermal concentrator, and the heating element 141. Surprisingly, it has been observed that the central part of the heating element 141 contributes to heating the aqueous urea solution that is directed to the injection module 160.

[0091] According to one possible embodiment, a weld may be added or made to connect one or more of the thermal insulation seals, for example, two concentric O-rings. Furthermore, for O-rings, a weld may be added between their inner and outer diameters.

[0092] According to one possible embodiment, the thermal insulation seal(s) 144 and 146 are O-rings made of an elastomer, for example a fluoroelastomer, with the advantage of being resistant to high temperatures while maintaining excellent sealing. Advantageously, moreover, the use of thermal insulation seals makes it easy to disassemble and extract the thermal concentrator 150 from the SCR device 100.

[0093] According to an alternative embodiment, the thermal insulation seal(s) 144 and 146 can be replaced by welds if it is desirable for the thermal concentrator 150 to be permanently integrated into the SCR device 100, particularly within its main body. This ensures that the device is sealed against the pressurized aqueous urea solution. Furthermore, the use of welds or other equivalent types of permanent fastening also provides more available volume for other components within the main body of the SCR device, while reducing design costs.

[0094] According to one possible embodiment, the thermal concentrator 150 comprises several circuits adapted to circulate the urea initially supplied to the SCR device 100. As illustrated. For example, the thermal concentrator 150 comprises an external circulation circuit 145 and an internal circulation circuit 147, the latter acting as a supply channel for the injector 168 located below.

[0095] According to one possible embodiment, the main body of the SCR 100 device is positioned to surround the urea line, in particular the feed channel 147 and / or the injector 168. In this embodiment, "surround" means "enclose" (or "partially enclose" if the overmolded housing has an opening) without the two elements necessarily being in direct contact with each other. The housing of the main body provides a robust and durable structure that protects the urea injector and its components and provides an effective means of guiding the liquids.

[0096] According to one possible embodiment, the injection module 160 includes a connection 162, this connection 162 allowing one or more heating elements, and for example the thermal concentrator 150, to be mechanically connected to the main body of the SCR device 100.

[0097] According to one possible embodiment, the preheating module 140 and / or the injection module 160 includes a communication channel 164, this communication channel allowing the external circulation circuit 145 and the internal circulation circuit 147 to be connected, for example to allow the passage of heat and / or the passage of urea.

[0098] According to one possible embodiment, the main body of the SCR 100 device, the injection module 160 and / or the spraying module 170 comprise one or more cooling jackets 166, this or these cooling jackets 166 surrounding the lower part of the main body of the SCR 100 device.

[0099] Advantageously, the presence of the thermal concentrator 150 and, when present, of a cooling jacket 166, allows the SCR device 100, in operation, to maintain an optimal temperature around the injector 168 and the aforementioned components by circulating a cooling fluid inside this cooling jacket. This also allows for the removal of excess heat, i.e., the thermal energy that cannot be used to heat the urea solution passing through the thermal concentrator 150. To this end, the thermal concentrator 150 includes at least one heating element 151.

[0100] According to one possible embodiment, the cooling fluid is a coolant, for example mineral or organic, which is supplied by the cooling fluid inlet 103 located in the lower part of the injection module 160, and which can be discharged via the cooling fluid outlet 104, also located in the lower part of the injection module 160.

[0101] According to one possible embodiment, the injection module 160 comprises a plurality of electronic elements configured to control the operation of the injector 168 and / or the spray module 170 located in the lower part of the SCR device 100. For example, these electronic elements may be integrated into the injection module 160 in combination with means for protecting these electronic elements against heat exposure. Alternatively, these electronic elements may be located away from the heat sources present in the injection module 160.

[0102] According to one possible embodiment, the spray module 170 includes an interface 182 allowing a user to control the parameters of the injector 168 or the urea spray at the level of a urea outlet line 102. The spray module 170 may also include various fastening elements, such as a flange sealed by one or more gaskets, or a plurality of bolts, although welds may also be used.

[0103] Figures 5 and 6 represent, respectively, a top three-dimensional view and a bottom three-dimensional view of a thermal concentrator according to an embodiment of the invention.

[0104] According to one possible embodiment, the thermal concentrator 150 is designed to be included or connected to the preheating module 140 and allows for efficient management of the heat concentration on the flow of the urea solution which circulates through it, and linking with the injection module 160 located downstream.

[0105] Preferably, the heat exchange surface made possible by the thermal concentrator 150 for the fluid passing through it is between 30 and 60 square centimeters (cm2), for example 32 cm2 or 45 cm2.

[0106] According to one possible embodiment, the thermal concentrator 150 allows the urea solution to be heated more rapidly, for example with a maximum fluid velocity of 70 millimeters per second, thus achieving a homogeneous temperature distribution throughout the thermal concentrator 150, with a maximum variation of 13 °C. It is also possible to ensure that the maximum achievable temperature does not exceed 150 °C, thereby preventing potential overheating and guaranteeing the durability and reliability of the device.

[0107] All embodiments of the thermal concentrator 150 described herein provide a suitable compromise between pressure drop, heat exchange surface area, and forced convection heat transfer coefficient for a urea solution. It is also possible to adapt the electrical power required for injection, preferably between 80 and 900 watts, for example 860 watts.

[0108] According to one possible embodiment, the thermal concentrator 150 comprises a plurality of heating elements and / or cavities 151 adapted to be able to to house such heating elements, for example heating cartridges or electric resistors. If several heating elements are present, they can be electrically powered with several wires or with a single structure.

[0109] For example, eight cavities 151a, 151b, 151c, 151d, 151e, 151If, 151g, 151h are hollowed out vertically in a direction parallel to the main axis of the cylindrical structure of the thermal concentrator 150, and are distributed symmetrically around a ninth central cavity 152 passing through the middle of the upper base of the thermal concentrator 150. According to this arrangement, the eight cavities 151a-151h are diametrically opposed in pairs with respect to the central cavity 152. The central cavity 152 may extend or coincide with the internal circulation circuit 147.

[0110] According to one possible embodiment, at least one heating element (not visible) is inserted into these cavities 151a to 15 Ih, to deliver a heating power of between 40 and 80 watts.

[0111] According to one possible embodiment, the at least one heating element is geometrically adapted to the thermal concentrator 150 to ensure the best transfer of thermal power from the at least one heating element to the thermal concentrator 150.

[0112] Preferably, the distribution of cavities and heating elements is implemented so as to maintain a temperature difference not exceeding a predetermined temperature between them, thus ensuring thermal homogeneity reducing the risk of hot spots, which could affect the performance of the thermal concentrator 150.

[0113] According to one possible embodiment, the inner helical groove 156 has a rectangular cross-section, which defines a groove optimally adapted to transfer the fluid from the outer helical circuit to the inner helical circuit of the thermal concentrator 150. This also allows for a homogeneous distribution of the fluid and, consequently, of the heat. The rectangular cross-section of this groove also allows for a stable and controlled flow, ensuring that the temperature is maintained as constant as possible throughout the interior of the thermal concentrator 150.

[0114] According to one possible embodiment, and as illustrated, the thermal concentrator 150 further comprises an external helical groove 154, here formed on the external surface of the thermal concentrator 150, for example on its lateral surface. This rectangular cross-section 154 defines another circulation channel for the fluid, which maximizes the contact area with the cooling fluid located and circulating outside the thermal concentrator 150. This also ensures that the flow is distributed uniformly through the external helical groove, leading to efficient heat dissipation throughout the device's operation.

[0115] According to one possible embodiment, the connection between the external and internal circuits of the thermal concentrator 150 is made by means of at least one radial groove 158 connecting the two grooves at their ends, this radial groove, which can also be called a lateral or transverse groove, being located at the lower base of the thermal concentrator 150.

[0116] According to one possible embodiment, the thermal concentrator 150 is made of a material that is both resistant to corrosion from the continuous passage of heated urea, for example, stainless steel. Advantageously, this material can be stainless steel, to facilitate welding within the SCR 100 device, and offering a compromise between reducing the effects of corrosion related to the passage of urea through the device and thermal conductivity. Although stainless steel has a lower thermal conductivity coefficient than copper, the geometry of the thermal concentrator 150 as described herein facilitates heat exchange. Alternatively, other materials can be used, for example, aluminum or copper alloys, with means of corrosion protection.

[0117] According to one possible embodiment, it is conceivable to adjust the dimensions of the grooves and the throat in order to optimize the circulation speed of the urea in the thermal concentrator 150. In particular, it is possible to adapt this circulation speed so as to increase or even maximize the coefficient of thermal convection within the urea or, more generally, of any fluid to be injected.

[0118] According to one possible embodiment, the heat exchange surface permitted by the thermal concentrator 150 is obtained by adjusting the diameter of the thermal concentrator 150 selected to be cylindrical in shape.

[0119] Without limitation, the dimensions of the thermal concentrator 150, of the internal helical groove 156 if present and / or of the external helical groove 154 if present, is or are chosen to allow as large an exchange surface as possible between the thermal concentrator 150 and the urea circulating in it.

[0120] According to one possible embodiment, the thermal power density supplied by the thermal concentrator 150 is between 10 watts per square centimeter (W / cm²) and 20 W / cm². It is possible to adapt the structure, shape, and dimensions of the thermal concentrator 150 and / or the SCR device 100 on this basis to obtain this range of values, and thus maintain temperatures allowing optimal heat dissipation of the urea when it is supplied to the injector of the SCR device 100.

[0121] According to one possible embodiment, the thermal concentrator 150 includes one or more springs adapted to change, increase or decrease the heat exchange surface, for example by modifying the height of the thermal concentrator 150 or by moving one or more of the heating elements in the cavities 151. These springs are preferably helical with a flat or circular cross-section, and can replace the groove defined by the inner helical groove 156 and / or the groove defined by the outer helical groove 154. This also makes it possible to enhance the overall performance of the thermal concentrator 150, and therefore of the SCR device 100, over time, or depending on the operating conditions, by increasing or decreasing the efficiency of the heat exchange, which modifies the thermal power supplied to the system.

[0122] According to one possible embodiment, this efficiency can be further enhanced when the thermal concentrator 150 includes this or these springs in combination with a thread of the internal helical groove 156 and / or the external helical groove 154. For example, modifying the dimensions of the grooves and grooves (internal and / or external) makes it possible to change the cross-sections of the helical grooves 154 and 156, in order to guarantee a different fluid velocity depending on the situation, and optimizing the convective heat transfer coefficient on the thermal concentrator 150.

[0123] In an example not shown, the thermal concentrator 150 may comprise a sheet metal plate, an inner spring, and an outer spring arranged to form a substantially cylindrical shape around the urea line. By arranging the two springs so as to be concentric with respect to each other, it is then possible to combine these elements to force the liquid to flow between the coils of the springs, which then serve as guides in place of the grooves 154 and 156 described previously. This also allows the urea to flow directly from the preheating module 140 to the injection module 160 without the need for any pipes, reducing the risk of thermal bridging. This also significantly reduces the manufacturing costs of the device.

[0124] According to other examples, it is also possible to enlarge the thermal concentrator 150 by increasing its diameter if it is cylindrical and / or the number of heating elements. This is particularly advantageous for handling larger thermal loads, especially for applications requiring diesel exhaust fluid flow rates exceeding 1.5 kilograms per hour, for example, for diesel engines in agricultural machinery, while reducing harmful emissions from their exhaust gases.

[0125] Figures 7 and 8 represent, respectively, a cross-sectional view and a profile view of a thermal concentrator in operation according to one embodiment.

[0126] As illustrated, the thermal concentrator 150 is here cylindrical in shape and includes elements described in previous embodiments.

[0127] As shown in the section in the "XZ" plane of the thermal concentrator 150, the thermal concentrator 150 is equipped with multiple heating elements, only the cavities 151a, 151b, 151c, 151d, 151h and 151 being visible, which can house heating cartridges. The external helical groove 154 maximizes the contact surface with the aqueous urea solution to be heated, ensuring efficient heat dissipation. Also shown are an internal O-ring 144 and an external O-ring 146 ensuring the sealing of the assembly.

[0128] The arrows represent the directions of urea flow in the grooves defined respectively by the external helical groove 156 and the internal helical groove 154. The grooves of the two grooves are connected at their ends by the radial groove 158, which can be located at the lower base of the thermal concentrator 150 and / or at the base of the internal helical groove 154.

[0129] In particular, the urea solution circulates in the thermal concentrator 150 via the channels defined by the internal helical groove 154 and the external helical groove 156.

[0130] Fig. 9 illustrates the schematic diagram of the circulation of the urea solution in the thermal concentrator.

[0131] In particular, the thermal concentrator 150 is represented here so as to show separately the direction of circulation of the heated urea solution, which enters through the left side of the top of the external helical groove 156 and exits through the right side of the top of the internal helical groove 154.

[0132] As shown, the urea solution comes into contact with the thermal concentrator 150 at the upper left arrow shown in [Fig.9], then flows down towards the bottom of the thermal concentrator 150 following the different turns formed by the external helical groove 156.

[0133] Upon reaching the base of the thermal concentrator 150, the urea solution then flows through the radial groove 158 and is directed towards the interior of the thermal concentrator 150 via the small horizontal channel formed by it. This channel then curves to become vertical, forming the internal helical groove 154, which creates a counter-current flowing upwards towards the top of the injector. The urea solution can then be reintroduced into or expelled from the thermal concentrator 150 after this heat exchange has taken place.

Claims

Demands

1. Selective catalytic reduction device, SCR, (100) for a diesel engine, said SCR device (100) comprising: - a preheating module (140) adapted to heat a urea solution flowing from a urea inlet line (101) of the SCR device (100) to an injection module (160), - said injection module (160), adapted to meter and inject in droplet form the heated urea solution at a urea outlet line (102) of the SCR device (100).

2. SCR device (100) according to claim 1, wherein the injection of the heated urea solution is carried out by a spray module (170) comprising the injection module (160), the spray module (170) connecting the preheating module (140) to the urea outlet line (102).

3. SCR device (100) according to any one of the preceding claims, wherein the preheating module (140) comprises at least one thermal concentrator (150), the at least one thermal concentrator (150) being positioned along a flow of circulation of the urea solution between the preheating module (140) and the injection module (160).

4. SCR device (100) according to claim 3, wherein the thermal concentrator (150) comprises at least one circulation channel (154, 156) of the urea solution and at least one heating element (151a, 151b, 151c, 151d, 151e, 151f, 151g, 151h), the at least one heating element (151a, 151b, 151c, 151d, 151e, 151f, 151g, 151h) being disposed around the at least one circulation channel (154, 156) of the urea solution and / or being disposed in the at least one circulation channel (154, 156) of the urea solution.

5. SCR device (100) according to claim 3 or 4, wherein the thermal concentrator (150) has a heat exchange surface with the flow of the urea solution circulating between the preheating module (140) and the injection module (160), said heat exchange surface being greater than or equal to 30 square centimeters and less than or equal to 60 square centimeters.

6. SCR device (100) according to any one of claims 3 to 5, wherein the thermal concentrator (150) is adapted to provide a thermal power density to the solution flow of urea circulating between the preheating module (140) and the injection module (160), said thermal power density being greater than or equal to 10 watts per square centimeter and less than or equal to 20 watts per square centimeter.

7. SCR device (100) according to any one of claims 3 to 6, wherein the thermal concentrator (150) has a hollow cylindrical shape, a principal axis of said hollow cylindrical shape being substantially parallel to the circulation flow of the urea solution, the at least one circulation channel (154, 156) comprising an internal helical groove (154) and an external helical groove (156), the internal helical groove (154) being formed in an internal surface of the thermal concentrator (150) and the external helical groove (156) being formed in an external surface of the thermal concentrator (150), at least one radial groove (158) connecting one end of the internal helical groove (154) to another end of the external helical groove (156) at a base of the hollow cylindrical shape.

8. SCR device (100) according to any one of claims 3 to 7, wherein the preheating module (140) further comprises at least one pair of concentric O-rings (144, 146).

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