MODULE FOR USE ON-BOARD A VEHICLE, FOR DECOMPOSING AN AMMONIA PRECURSOR USING A CATALYST

Abstract

A module for use on-board a vehicle. The module includes a heater and at least a first and a second storage compartment. The first compartment at least partially surrounds the heater, and the second compartment at least partially surrounds the first compartment. The first compartment is configured to perform a first function in a first temperature range, and the second compartment is configured to perform a second function in a second temperature range, the second temperature range being lower than the first temperature range. The first compartment is in fluid communication with the second compartment. One function of the first and second function is receiving an ammonia precursor, and decomposing the ammonia precursor using a catalyst to generate an ammonia solution.

Claims

1-20. (canceled)

21. A module for use on-board a vehicle, the module comprising: a heater; and at least a first storage compartment and a second storage compartment; wherein the first compartment at least partially surrounds the heater, and the second compartment at least partially surrounds the first compartment; the first compartment being configured to perform a first function in a first temperature range, and the second compartment being configured to perform a second function in a second temperature range, the second temperature range being lower than the first temperature range; wherein the first compartment is in fluid communication with the second compartment; wherein one function of the first or second function is decomposing an ammonia precursor using a catalyst to generate an ammonia solution.

22. The module of claim 21, wherein an other function of the first and second function is holding the ammonia precursor solution before it enters the compartment performing the one function and/or holding the generated ammonia solution leaving the compartment performing the one function.

23. The module of claim 21, wherein the heater extends in the first compartment.

24. The module of claim 21, wherein the first compartment includes an outer circumferential wall, and wherein the second compartment surrounds the outer circumferential wall of the first compartment.

25. The module of claim 21, wherein the generated ammonia solution comprises ammonia, carbon dioxide, and water; wherein the one function is the second function; and wherein the first function is a separating function, or separating the generated ammonia solution into a first ammonia rich fraction and a carbon dioxide rich fraction; the first ammonia rich fraction containing a smaller weight percentage of carbon dioxide than the solution and the carbon dioxide rich fraction containing a smaller weight percentage of ammonia than the solution.

26. The module of claim 21, wherein the one function is the first function, and the second function is a buffer function.

27. The module of claim 25, further comprising an output buffer compartment surrounding at least partially the second compartment, the output buffer compartment being in fluid communication with the first compartment and being configured to hold the ammonia rich fraction leaving the first compartment.

28. The module of claim 25, further comprising an input buffer compartment surrounding at least partially the second compartment, the input buffer compartment being in fluid communication with the second compartment and being configured to hold the ammonia precursor solution before entering the second compartment.

29. The module of claim 21, further comprising a valve block configured to connect at least the first and second compartment.

30. The module of claim 29, further comprising a control module configured to control the valve block and the heater such that the one function of the first and second function comprises receiving a fresh ammonia precursor solution whilst outputting a generated ammonia solution, at repetitive moments in time; and such that the other function comprises receiving the ammonia precursor solution before it enters the one compartment and/or receiving the generated ammonia solution leaving the one compartment.

31. The module of claim 25, wherein the control module is configured to control the valve block and the heater such that the ammonia solution in the first compartment is heated at a first temperature; and the ammonia precursor solution in the second compartment is heated at a second temperature lower than the first temperature.

32. The module of claim 27, wherein the valve block is configured to connect the output buffer compartment with the first compartment.

33. The module of claim 28, wherein the valve block is configured to connect the input buffer compartment with the second compartment.

34. The module of claim 32, wherein the control module is configured to control the valve block such that after a separating and decomposing, an ammonia rich fraction is transferred from the first compartment to the output buffer compartment, an ammonia solution is transferred from the second compartment to the first compartment, and an ammonia precursor solution is transferred to the second compartment.

35. The module of claim 33, wherein the control module is further configured to control the valve block such that after a separating and decomposing, an ammonia precursor solution is transferred to the input buffer compartment, and an ammonia precursor solution is transferred from the input buffer compartment to the second compartment.

36. The module of claim 21, further comprising a pump configured to pump fluid between the first compartment and the second compartment.

37. The module of claim 21, wherein each compartment includes a cylindrical inner and outer wall, and/or wherein the first and second compartments are concentric around the heater.

38. An ammonia precursor storage tank comprising a module according to claim 21, wherein the module is integrated in the tank or in or on a wall of the tank, wherein the module is configured to allow ammonia precursor solution stored in the tank to be transferred to one compartment of the first and second compartment, optionally via the other compartment of the first and second compartment.

39. An SCR system for a vehicle comprising a module according to claim 21.

40. A fuel cell system comprising a module according to claim 21.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0025] The accompanying drawings are used to illustrate presently preferred non-limiting exemplary embodiments of devices of the present invention. The above and other advantages of the features and objects of the invention will become more apparent and the invention will be better understood from the following detailed description when read in conjunction with the accompanying drawings, in which:

[0026] FIGS. 1A, 1B, 1C and 1D illustrate schematic perspective views of four exemplary embodiments of a module of the invention;

[0027] FIGS. 2A, 2B, and 2C illustrate schematic cross sections of three exemplary embodiments of a tank with integrated module according to the invention;

[0028] FIG. 3 is a schematic cross section of an exemplary embodiment of a module of the invention with four compartments;

[0029] FIG. 4 is a schematic cross section of an exemplary embodiment of a module of the invention with three compartments;

[0030] FIG. 5 is a schematic cross section of an exemplary embodiment of a module of the invention with an enlarged output buffer;

[0031] FIG. 6 is a schematic cross section of an exemplary embodiment of a tank with a module of the invention and an additional storage capacity;

[0032] FIG. 7 is a schematic cross section of an exemplary embodiment of a module of the invention with additional enzyme storage.

DESCRIPTION OF EMBODIMENTS

[0033] FIG. 1A illustrates an exemplary embodiment of a module 100 for use on-board a vehicle, for decomposing an ammonia precursor AP using a catalyst. The module 100 comprises a heater 50, a first storage compartment 10 and a second storage compartment 20. The first compartment 10 is arranged around the heater 50, and the second compartment 20 is arranged around the first compartment 10, such that, when said heater 50 is operated the first and second compartments are at decreasing temperatures T1, T2 with T2<T1. The first compartment 10 is configured for receiving an ammonia precursor solution AP, and for decomposing the ammonia precursor solution AP using the catalyst and heat from heater 50 to generate an ammonia solution A1. The second compartment 20 is in fluid communication with the first compartment 10 and is configured for holding the generated ammonia solution A1 leaving the first compartment 10. The second compartment 20 functions as an output buffer compartment. When ammonia solution is needed, e.g. for feeding a fuel cell or an SCR system, it can be transferred from the output buffer compartment 20 to the fuel cell or SCR system, see arrow A2.

[0034] FIG. 1B illustrates another exemplary embodiment of a module 100 for use on-board a vehicle, for decomposing an ammonia precursor AP using a catalyst. The module 100 comprises a heater 50, a first storage compartment 30 and a second storage compartment 10. The first compartment 30 is arranged around the heater 50, and the second compartment 10 is arranged around the first compartment 30, such that, when said heater 50 is operated the first and second compartments are at decreasing temperatures T3, T1 with T1<T3. The second compartment 10 is configured for receiving an ammonia precursor solution AP, and for decomposing the ammonia precursor solution AP using the catalyst and heat from heater 50 to generate an ammonia solution A. The generated ammonia solution comprises ammonia, carbon dioxide and water. The first compartment 30 is configured for separating the generated ammonia solution A into a first ammonia rich fraction and a carbon dioxide rich fraction; said first ammonia rich fraction AR containing a smaller weight percentage of carbon dioxide than said solution and said carbon dioxide rich fraction containing a smaller weight percentage of ammonia than said solution. When said fraction AR is needed, e.g. for feeding a fuel cell or an SCR system, it can be transferred from the first compartment 30 to the fuel cell or SCR system. In the illustrated embodiment the first compartment has a single outlet. However, a skilled person understands that two outlets are also an option. The number of outlets typically depends on the separation process which is implemented. If one single outlet is used, e.g. CO2 may be first eliminated (as gas) and next the remaining NH3 solution may be transferred through the same outlet.

[0035] FIG. 1C illustrates an exemplary embodiment of a module 100 for use on-board a vehicle, for decomposing an ammonia precursor AP using a catalyst. The module 100 comprises a heater 50, a first storage compartment 10 and a second storage compartment 40. The first compartment 10 is arranged around the heater 50, and the second compartment 40 is arranged around the first compartment 10, such that, when said heater 50 is operated the first and second compartments are at decreasing temperatures T1, T2 with T2<T1. The second compartment 40 is configured for holding ammonia precursor solution AP1 and is in fluid communication with the first compartment 10, see arrow AP2. The second compartment 40 functions as an input buffer compartment. The first compartment 10 is configured for receiving an ammonia precursor solution AP2, and for decomposing the ammonia precursor solution AP2 using the catalyst and heat from heater 50 to generate an ammonia solution A. When ammonia solution A is needed, e.g. for feeding a fuel cell or an SCR system, it can be transferred from the first compartment 10 to the fuel cell or SCR system.

[0036] FIG. 1D illustrates an exemplary embodiment of a module 100 for use on-board a vehicle, for decomposing an ammonia precursor AP using a catalyst. The module 100 comprises a heater 50, a first storage compartment 10 and a second storage compartment with two sub-compartments 20, 40. The first compartment 10 is arranged around the heater 50, and the second sub-compartments 20, 40 are arranged around the first compartment 10, such that, when said heater 50 is operated the first and second compartments are at decreasing temperatures T1, T2/T2 with T2,T2<T1. The second sub-compartment 40 is configured for holding ammonia precursor solution AP1 and is in fluid communication with the first compartment 10, see arrow AP2. The second sub-compartment 40 functions as an input buffer compartment. The first compartment 10 is configured for receiving the ammonia precursor solution AP2 from the input buffer compartment 40, and for decomposing the ammonia precursor solution AP2 using the catalyst and heat from heater 50 to generate an ammonia solution A1. The second sub-compartment 20 is in fluid communication with the first compartment 10 and is configured for holding the generated ammonia solution A1 leaving the first compartment 10. The second sub-compartment 20 functions as an output buffer compartment. When ammonia solution is needed, e.g. for feeding a fuel cell or an SCR system, it can be transferred from the output buffer compartment 20 to the fuel cell or SCR system, see arrow A2.

[0037] Although not shown in FIGS. 1A-1D, the skilled person understands that the module 100 may further comprise a valve block configured for connecting the first and second compartment, and a control module configured for controlling the valve block and the heater. Preferably the controlling is such that compartment 10 receives a fresh ammonia precursor solution whilst outputting a generated ammonia solution, at repetitive moments in time, and such that compartment 20, 20, 30 receives the ammonia precursor solution before it enters compartment 10 or that compartment 40, 40 receives the generated ammonia solution leaving compartment 10.

[0038] FIGS. 2A, 2B and 2C illustrate that the module 100 may be integrated in a tank 200 (FIG. 2A) or in or on a wall of the tank 200. This may be a bottom wall, a top wall or a side wall of the tank 200. The module 100 is configured for allowing ammonia precursor solution stored in tank 200 to be transferred either directly to compartment 10 (embodiment of FIGS. 1A and 1B) or to an input buffer compartment 40, 40 (embodiment of FIGS. 1C and 1D).

[0039] FIG. 3 illustrates an exemplary embodiment of a module 100 of the invention with four compartments 30, 10, 20, 40 surrounding the heater 50. The compartments 30, 10, 20, 40 correspond with four circular, concentric chambers 3, 2, 4, and 1. The module 100 is intended for being mounted in or adjacent a tank (not shown in FIG. 3) filled with an ammonia precursor solution, typically an Adblue fluid matching the ISO 22241 standard specification and containing 32.50.7 weight % urea.

[0040] The outer compartment 40 is delimited by a cylindrical outer wall 41 and a cylindrical inner wall 42. The cylindrical outer wall 41 has a diameter which is larger than the diameter of the cylindrical inner wall 42. The outer compartment 40 corresponds with chamber 1 which consists in an input buffer receiving ammonia precursor solution from the tank.

[0041] The ammonia precursor solution in chamber 1 is carried to chamber 2 which corresponds with the second compartment 10. The second compartment 10 has a cylindrical outer wall 11 and a cylindrical inner wall 12. The cylindrical outer wall 11 has a diameter which is larger than the diameter of the cylindrical inner wall 12. Chamber 2 is used as a conversion unit for the ammonia precursor solution, using a catalyst, e.g. a biological catalyst such as an enzyme, to produce effluents comprising ammonia. In the example of an enzyme, the enzyme may be immobilized in granular form and may be introduced in chamber 2 through a cap (not illustrated), e.g. on the top or the bottom of the module.

[0042] The effluents from chamber 2 are carried into chamber 3 which corresponds with the first compartment 30. The first compartment has a cylindrical outer wall 31. The heater 50 is arranged centrally in the first compartment 30. Chamber 3 works as a separation unit. Separation may comprise transforming the effluents (produced in chamber 2) in an aqua ammonia solution with a low concentration of carbonates.

[0043] The aqua ammonia solution with low concentration of carbonates is carried in chamber 4 which corresponds with a third compartment 20. The third compartment 20 has a cylindrical outer wall 21 and a cylindrical inner wall 22. The cylindrical outer wall 21 corresponds with the inner wall 42 of the outer compartment 40. The cylindrical inner wall 22 corresponds with the outer wall 11 of the second compartment 10. Chamber 4 is a buffer to store the effluents after the separation step.

[0044] The heater 50 may be a tubular heater inserted along the axis of the chambers.

[0045] In the illustrated embodiment a pump 60 and a flow distribution multivalve 70 are located on the top of the module. The pump 60, heater 50 and flow distribution multivalve 70 are connected to an engine control unit (ECU, not indicated on the drawing).

[0046] As an advantage, the module of FIG. 3 presents an optimized heat transfer, with minimal heat losses. The chambers 1, 2, 3, and 4 (i.e. the compartments 10, 20, 30, 40) and the heater 50 are designed so that the fluid temperature T1 in chamber 2 corresponds to the required temperature for catalyst activity and the fluid temperature in chamber 3 corresponds with a suitable temperature T3 (T3>T1) for the separation process. In a preferred embodiment where enzymes are used as the catalyst, heater 50 and compartments 10, 20, 30, 40 are designed for causing a temperature T1 suitable for enzymatic activity, e.g. within a 40 C.-60 C. temperature range. Temperature T3 in chamber 3 may be e.g. between 70 C. and 95 C.

[0047] Chambers 1 and 4 at the periphery of the module 100 act as a thermal buffer, when the device is activated, thus limiting the power needed for heating chambers 3 and 2. For a supplemental thermal insulation, the outer periphery 41 of the module 100 may be moulded as a double wall, such that an air gap is formed creating an additional insulation layer. Also, PCM materials may be used to further maintain the temperature at the operating conditions, at the end of a heating phase.

[0048] The module 100 further comprises a check valve 80 which prevents chamber 1 from emptying when the liquid level in the tank is lower than the liquid level in chamber 1.

[0049] The design of FIG. 3, when the module is placed in the tank, also provides intrinsic safety as regards the risks associated with ammonia solutions. If a leak occurs in chamber 2, 3 or 4, the content of these chambers 2, 3 or 4 is to be diluted with the ammonia precursor solution inside the tank, thus avoiding any waste outside the vehicle. The outlet of the venting pathways of the module 100 is located also inside the tank, meaning that the ammonia gas atmosphere which is potentially generated in chamber 3 during the separation process is trapped in the ammonia precursor solution, and not rejected in the environment of the vehicle.

[0050] The compartments 10, 20, 30, 40 of module 100 may be moulded in plastic material, e.g. PA, PA66, PPA, POM. The connection between the module 100 and the tank may be a mason jar-type or a cam-lock type connection. As explained with reference to FIGS. 2A-2C, the module 100 may be suitably mounted on or in the top of the tank, entirely inside the tank, on or in the bottom of the tank.

[0051] Module Operation

[0052] The initiating phase, i.e. the first use of the module 100, goes through the following steps:

[0053] AThe ammonia precursor solution is pumped from the tank through inlet 1a in chamber 1. Port 1b of the distribution multivalve 70 is connected to port 2a, port 2b is connected to port 3a, port 3b is connected to pump inlet 6a, and pump outlet 6b is connected to valve outlet 7a. Pump 60 is operated in order to fill subsequently chambers 2 and 3. Venting is provided through outlet 7a. The heater 50 is powered in order to get the required temperatures in chambers 3 and 2. Filling chamber 3 with ammonia precursor solution enhances the thermal transfer from heater 50 to chamber 2.

[0054] BWhen the enzymatic conversion is completed in chamber 2, the ammonia precursor solution in chamber 3 is evacuated. The multivalve 70 provides fluid connection between port 3a and pump inlet 6a, between pump outlet 6b and valve outlet 7a. Port 7b is connected to port 3b. Thus, the ammonia precursor solution in chamber 3 is sent back to the tank, and venting is provided via a pathway between ports 7a and 3b.

[0055] CThe generated ammonia solution in chamber 2 is transferred to chamber 3. To achieve that, port 2a is in fluid communication with the pump inlet 6a, and pump outlet 6b is connected to port 3a. Chamber 2 is vented through the connection of inlet 7a to port 2b. Venting of chamber 3 occurs by connecting port 3b to valve outlet 7b.

[0056] DChamber 2 is filled again with ammonia precursor solution. For that, port 1a is connected to pump inlet 6a, pump outlet 6b to port 2a, and chamber 2 is vented through port 2b connected to valve inlet 7a. When powering the heater 50, the separation process takes place in chamber 3, whilst ammonia precursor conversion occurs in the chamber 2.

[0057] EWhen separation is achieved in chamber 3 and enzymatic conversion is completed in chamber 2, the effluents in chamber 3 are transferred to chamber 4: port 3a is connected to pump inlet 6a, pump outlet 6b is connected to port 4a; chamber 3 is vented by connecting port 3b to port 7a and chamber 4 is vented through the connection between port 4b and valve outlet 7b.

[0058] When required by the De-NOx function of the selective catalytic reduction (SCR) system, the reductant solution in chamber 4 is transported to the exhaust line, by connecting port 4a to pump inlet 6a and pump outlet 6b to valve outlet 7c. Chamber 4 is vented by connecting valve inlet 7a to port 4b.

[0059] After the initiating phase, the module works as follows: converted ammonia precursor solution in chamber 2 is transferred to chamber 3 according to step C. Chamber 2 is re-filled with ammonia precursor solution according to step D. Chamber 1 is also filled with ammonia precursor solution by connecting port 1b to pump inlet 6a and pump outlet 6b to port 1d. Ammonia precursor solution is sucked through inlet 1a and chamber 1 is vented by connecting port 1c to valve outlet 7b. This provides a pre-heating of the ammonia precursor solution in chamber 1 during the conversion step occurring in chamber 2 and the separation step occurring in chamber 3, when heater 50 is operated. When the decomposition reaction and the separation process are completed, the content of chamber 3 is transferred to chamber 4, the content of chamber 2 is transferred to chamber 3, and chamber 2 is filled with the content of chamber 1. Chamber 1 is re-filled with ammonia precursor solution from the tank.

[0060] The module 100 further comprises a control module 150 configured for controlling the valve block 70, the pump 60, and the heater 50 such that the above described mode of operation is performed. More in particular the control module 150 is configured for controlling the valve block 70, the pump 60 and the heater 50 such that the ammonia solution in said first compartment 30 is heated at a first temperature, and the ammonia precursor solution in the second compartment 10 is heated at a second temperature lower than said first temperature. The control module 150 is configured for controlling said valve block 70 such that after a separating and decomposing step, an ammonia rich fraction is transferred from the first compartment 30 to the output buffer compartment 20, an ammonia solution is transferred from the second compartment 10 to the first compartment 30, an ammonia precursor solution is transferred to the input buffer compartment 40 (from a tank), and an ammonia precursor solution is transferred from said input buffer compartment 40 to said second compartment 10.

[0061] In the mode of operation explained above, the module 100 works in a batch mode. In another embodiment the module may work with a continuous flow. The module 100 can be part of an SCR system. Alternatively or in addition, the module 100 can also be used to feed a fuel cell.

[0062] FIG. 4 illustrates another exemplary embodiment of a module 100 designed for a system with no need of further effluents separation after the catalytic conversion of the ammonia precursor solution, e.g. Adblue. The module 100 is similar with this difference that compartment 30 has been omitted. The same reference numerals have been used to indicate the same or similar components. The module 100 has three chambers 1, 2 and 4: chamber 1 as an input buffer, chamber 2 for ammonia precursor conversion, and chamber 4 for storage of the generated ammonia solution coming from chamber 2. A catalyst, e.g. an enzyme, is inserted in chamber 2, partially filling its volume. The ammonia precursor solution is sucked by pump 60, through inlet 1a and multivalve 70, and the enzymatic reaction is thermally activated with heater 50. After full conversion, the effluents are transferred into chamber 4. Chamber 2 is now ready for refilling with urea solution and further conversion. The effluents in chamber 4 may be sent to an exhaust line through the outlet 7c. The functioning of the module is basically the same as the one which is described in FIG. 3, except for the transfers from and to the separation chamber 3. Chamber 1 is used for pre-heating the ammonia precursor solution at a suitable temperature for the catalytic conversion.

[0063] FIG. 5 illustrates an embodiment which is similar to the module 100 of FIG. 3, except that a larger volume is provided for the storage of the separated effluents. The design of the output buffer consists of two chambers 4 and 4 in fluidic communication through the tube 4g. After separation, the effluents are transferred from chamber 3 to chamber 4, by connecting the port 3a to the port 4b via pump 60, and venting chamber 4 through the tube 4g, chamber 4 and tube 4e, with a connection between the port 4a and the valve outlet 7b. When the liquid level in chamber 4 reaches orifice 4c of tube 4g, the solution in chamber 3 is transferred to the chamber 4 by connecting port 3a to port 4a. The venting path of the chamber 4 is achieved through the tube 4g, and the connection of the port 4b to the valve outlet 7b. Tube 4f is used to pump the separated effluents in the chamber 4.

[0064] The design of the module 100 of FIG. 5 allows an easy insertion of the module 100 inside a tank, especially in a tank with a limited height and a limited diameter of the opening in the tank wall for mounting the module; first side 4d is inserted through the opening in the tank wall, and then the rest of module 100 is inserted whilst operating a pivotal movement during assembly.

[0065] FIG. 6 illustrates an exemplary embodiment of a tank 200 in which a module 100 similar to the module of FIG. 3, is arranged. In this embodiment, chamber 4 of the module 100 is in fluidic connection with a storage capacity 250, inserted in the ammonia precursor tank 200 and external to the module 100. The volume of the storage capacity 250 may be e.g. up to 20 to 40% of the volume of the tank 200. The storage capacity 250 may have a variable volume, working as a bladder tank. Depending on the conversion rate of the catalyst, and the efficiency of the separation process, this storage capacity 250 may be integrated in the module. Also, the size of the chambers 2 and 3 may be reduced to allow for such integration. The module 100 works in a similar way as the module 100 of FIG. 5. The separated effluents flow to storage capacity 250 when the liquid level reaches opening 251a of line 251 connecting chamber 4 with storage capacity 250. The storage capacity 250 is vented via line 252 with port 4b connected to valve outlet 7b. Check valve 254 on line 253 is implemented so that chamber 4 can be filled with the solution coming from chamber 3, which constitutes an advantage for heat transfer, as chamber 4 is then not anymore an air gap. When the injection of the ammonia solution is required in the SCR system or when feeding a fuel cell is required, the separated effluents in storage capacity may be sucked by pump 60 in chamber 4 through port 4a. The effluents in the capacity storage 250 are transferred into chamber 4 through the line 253.

[0066] FIG. 7 illustrates a further variant of a module 100 which is similar to the module of FIG. 3. The module 100 of FIG. 7 provides an improved way of adding an immobilized catalyst, in particular immobilized enzymes, in chamber 2, when the top of the module 100 is not easily accessible due to the integration of the SCR system in a vehicle. In this embodiment, the enzymes are enclosed in a strainer 400 which is introduced in a storage capacity 410. Storage capacity 410 may be conveniently located in the vehicle, so that the strainer 400 is easily inserted and removed. The strainer 400 is connected to flow distribution multivalve 70 through an outlet 420. Chamber 2 is also equipped with a strainer 450. The enzyme is transferred from strainer 400 to strainer 450 by flushing with ammonia precursor solution. The ammonia precursor solution is pumped in chamber 2 from channel 460 to line 430 and flushes the enzyme in line 440 through outlet 420. The enzyme is introduced in strainer 450 through inlet 470. The enzyme transfer from the storage capacity 410 to the strainer 450 can be progressive or by steps, in order to partially refresh the catalyst for urea decomposition in chamber 2, which is an advantage as regards enzyme durability. After the required amount of enzyme is added to the strainer 450, the storage capacity 410 can be drained in order to further limit the contact with ammonia precursor solution and to increase the enzyme storage limit. The storage capacity 410 may be thermally protected, by implementing a thermal conditioning means, such as a heater, a cooler, a device based on the Peltier effect, or PCM materials. The storage capacity 410 could also be located in a thermally protected area in the vehicle. When the immobilized enzyme has to be removed from the strainer 450, because it has lost most of its activity, the content of strainer 450 is flushed to strainer 410 through line 440. After trapping the immobilized enzyme, the remaining fluid returns to chamber 2 through line 430.

[0067] Preferably, the pumping time is chosen to be long enough in order to empty the immobilized enzyme from the strainer 450. The strainer 400 may be a cartridge or retaining unit containing the enzymes, e.g. as disclosed in EP 15 162 678.5 filed on 7 Apr. 2015 in the name of the Applicant, the entire of which is included herein by reference.

[0068] An example of a urea decomposition system is disclosed in patent applications WO 2015032811 and WO 2014095894 in the name of the Applicant, the contents of which are included herein by reference. In those applications the Applicant has proposed two new methods for generating ammonia on board a vehicle (passenger car, truck, etc.) based on a biological catalysis. Biological catalysis comprises all forms of catalysis in which the activating species (i.e. biological catalysts) is a biological entity or a combination of such. Included among these are enzymes, subcellular organelles, whole cells and multicellular organisms. More precisely, according to a first method, a protein component is used to catalyse the hydrolysis (i.e. decomposition) of an ammonia precursor solution (for example, urea) into a mixture comprising at least ammonia, carbon dioxide and water. Such first method is described in more detail in patent application WO 2015032811. According to a second method proposed by the Applicant, a protein component is used to catalyse the hydrolysis (i.e. decomposition) of an ammonia precursor solution (for example, urea) into ammonia gas. For example, the generated ammonia gas can be directed (i.e. transmitted) to a solid absorbing matrix where it is stored thereon by sorption. Such second method is described in more detail in patent application WO 2014095894.

[0069] In embodiments of the invention the heater 50 heats up the decomposition area at the appropriate temperature for the reaction, i.e. for the decomposing of the ammonia precursor into ammonia. In the event that the biological catalyst is urease, a suitable temperature T1 would be from around 40 to 60 C. The heater 50 can be of any type as known in the state of the art. Typically a resistive heater is well suited. However, it is also possible to provide, as a heater, a conduit through which the cooling liquid of the engine is circulated.

[0070] The catalyst can have several shapes. In the case of enzymes, they can be powder, pellets, granules or beads; the enzymes can be immobilized or not on a substrate, and the substrate can be part of the chamber 2.

[0071] Embodiments of the invention may also be used in an ammonia precursor booster system comprising a storage compartment for storing ammonia precursor granules, and a dissolving compartment for storing an ammonia precursor solution, and for dissolving ammonia precursor granules in the ammonia precursor solution, a decomposition unit, and optionally one or more buffers. The dissolving compartment, the decomposition unit and the one or more buffers could be implemented as a module with a plurality of concentric compartments. An example of such a booster system is disclosed in European patent application EP 14177713 filed on 18 Jul. 2014 in the name of the Applicant, the content of which is included herein by reference.

[0072] Also further developed embodiments of the module of the invention may comprise a conversion unit for converting ammonia into hydrogen, and a hydrogen fuel cell.

[0073] Whilst the principles of the invention have been set out above in connection with specific embodiments, it is to be understood that this description is merely made by way of example and not as a limitation of the scope of protection which is determined by the appended claims.