METHOD FOR ACTIVATING/DEACTIVATING A BIOLOGICAL CATALYST USED IN A CONVERSION SYSTEM ON BOARD A VEHICLE

Abstract

It is proposed a method for activating/deactivating a biological catalyst used in a conversion system on board a vehicle, the vehicle comprising a source of energy adapted to activate the biological catalyst for converting a compound into reaction product. The method comprises the steps of: detecting (SI) an event indicative of a filling/refilling of the conversion system with biological catalyst; determining (S2) an amount of energy available at the source of energy; starting at least one conversion operation comprising the steps of: (i) verifying (S3) whether the amount of energy available is greater than or equal to an amount of energy needed for activating the biological catalyst so as to achieve a predetermined level of conversion of said compound; (ii) if said verifying (i) is positive, activating (S4) the biological catalyst; terminating (S7) said at least one conversion operation.

Claims

1. A method for activating/deactivating a biological catalyst used in a conversion system on board a vehicle, the vehicle comprising a source of energy adapted to activate the biological catalyst for converting a compound into reaction product, the conversion system being configured to supply reaction product to a consuming unit on board the vehicle, wherein the method comprises: detecting (SI) an event indicative of a filling/refilling of the conversion system with biological catalyst; determining (S2) an amount of energy available at the source of energy; starting at least one conversion operation comprising: (i) verifying (S3) whether the amount of energy available is greater than or equal to an amount of energy needed for activating the biological catalyst so as to achieve a predetermined level of conversion of said compound; (ii) if said verifying (i) is positive, activating (S4) the biological catalyst. terminating (S7) said at least one conversion operation.

2. The method as claimed in claim 1, wherein the step of terminating said at least one conversion operation comprises: (iii) verifying (S6) whether the amount of energy available is lower than the amount of energy needed for activating the biological catalyst so as to achieve the predetermined level of conversion of said compound; (iv) if said verifying (iii) is positive, deactivating the biological catalyst.

3. The method as claimed in claim 1, wherein the step of terminating said at least one conversion operation comprises: (v) determining a current quantity of reaction product available in the conversion system; (vi) verifying whether the current quantity of reaction product available is greater than or equal to a predetermined target quantity of reaction product; (vii) if said verifying (vi) is positive, deactivating the biological catalyst.

4. The method as claimed in claim 1, wherein the step of terminating said at least one conversion operation comprises: starting a timer for a predetermined amount of time; upon expiry of said timer, deactivating the biological catalyst.

5. The method as claimed in claim 1, wherein the step of terminating said at least one conversion operation comprises: determining at least one parameter characteristic of the reaction product; detecting an event indicative of end-of-conversion based on said at least one parameter; deactivating the biological catalyst.

6. The method as claimed in claim 1, the conversion system comprising a reactor, inside which the conversion of the compound into reaction product takes place, and a container for the storage of reaction product, wherein the method further comprises: after said terminating said at least one conversion operation, conveying reaction product from the reactor towards the container; replenishing the reactor with biological catalyst and/or compound.

7. The method as claimed in claim 1, further comprising: measuring at least one operating parameter of the conversion system; and wherein the amount of energy needed for activating the biological catalyst is determined as a function of the measured operating parameter(s).

8. A vehicle system comprising: a conversion system using a biological catalyst and being configured to supply reaction product to a consuming unit; a source of energy adapted to activate the biological catalyst for converting a compound into reaction product; an electronic controller configured to: detect an event indicative of the filling/refilling of the conversion system with biological catalyst; determine an amount of energy available at the source of energy; start at least one conversion operation and activate the biological catalyst, when the amount of energy available is greater than or equal to an amount of energy needed for activating the biological catalyst so as to achieve a predetermined level of conversion of said compound; terminate said at least one conversion operation.

9. The vehicle system of claim 8, wherein the electronic controller is further configured to verify whether the amount of energy available is lower than the amount of energy needed for activating the biological catalyst so as to achieve the predetermined level of conversion of said compound.

10. The vehicle system of claim 8, wherein the source of energy is either a fuel cell or a vehicle battery.

11. The vehicle system of claim 8, wherein the electronic controller is further configured such that said terminate said at least one conversion operation comprises: determining a current quantity of reaction product available in the conversion system; verifying whether the current quantity of reaction product available is greater than or equal to a predetermined target quantity of reaction product; if said verifying (vi) is positive, deactivating the biological catalyst.

12. The vehicle system of claim 8, wherein the electronic controller is further configured such that said terminate said at least one conversion operation comprises: starting a timer for a predetermined amount of time; upon expiry of said timer, deactivating the biological catalyst.

13. The vehicle system of claim 8, wherein the electronic controller is further configured such that said terminate said at least one conversion operation comprises: determining at least one parameter characteristic of the reaction product; detecting an event indicative of end-of-conversion based on said at least one parameter; deactivating the biological catalyst.

14. The vehicle system of claim 8, wherein the electronic controller is further configured such that the conversion system comprising a reactor, inside which the conversion of the compound into reaction product takes place, and a container for the storage of reaction product, wherein the method further comprises: after said terminating said at least one conversion operation, conveying reaction product from the reactor towards the container; replenishing the reactor with biological catalyst and/or compound.

15. The vehicle system of claim 8, wherein the electronic controller is further configured to: measure at least one operating parameter of the conversion system; and wherein the amount of energy needed for activating the biological catalyst is determined as a function of the measured operating parameter(s).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0077] 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:

[0078] FIG. 1 is a diagram illustrating an exemplary embodiment of an ammonia generating system using a biological catalyst and to which the method of the present invention may be applied;

[0079] FIG. 2 illustrates an exemplary embodiment of a flow chart of instructions depicting logical operational steps for activating and deactivating the biological catalyst of FIG. 1 in a continuous mode; and

[0080] FIG. 3 illustrates an exemplary embodiment of a flow chart of instructions depicting logical operational steps for activating and deactivating the biological catalyst of FIG. 1 in a batch mode.

[0081] FIG. 4 is a graph illustrating the activity of the enzyme urease in function of the temperature.

DETAILED DESCRIPTION

[0082] FIG. 1 illustrates an exemplary embodiment of an ammonia generating system. The ammonia generating system comprises a tank 10, a retaining unit 20, and a receiving part 30 for receiving the retaining unit 20. The tank 10 is adapted for storing an ammonia precursor solution (i.e. compound), such as a urea solution.

[0083] In embodiments of the invention the tank 10 may be filled with the commercially available liquid ammonia precursor, known as AdBlue and matching the ISO 22241 standard specifications. Such a fluid contains 32.50.7 weight % urea.

[0084] The retaining unit 20 stores a catalyst, typically a biological catalyst, and for instance an enzyme such as urease. The receiving part 30 with the inserted retaining unit 20 constitutes a decomposition area where the conversion of the ammonia precursor into reaction product takes place. A cap (not shown) may be closing the decomposition area prior to operation.

[0085] The receiving part 30 comprises a heater 70. The heater 70 is configured for heating the enzyme and the ammonia precursor solution in the retaining unit 20, when the retaining unit 20 is arranged in the receiving part 30. In the illustrated example, the receiving part 30 is provided with thermal conditioning means 80 for heating and/or cooling the retaining unit 20. The heater 70 heats up the decomposition area at the appropriate temperature for the reaction to occur, i.e. for the decomposing of the ammonia precursor solution into ammonia solution. In other words, the reaction is powered by the heater 70 (i.e. energy supply). Thus, when the heater 70 heats up (i.e. supplies energy to) the decomposition area at the appropriate temperature for the reaction to occur, the enzyme activity increases (i.e. enzyme activation); when the heater stops to heat (i.e. stops to supply energy to) the decomposition area, the enzyme activity decreases (i.e. enzyme deactivation). The heater 70 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. The thermal conditioning elements 80 may contribute to the heating during the decomposition of the ammonia precursor solution. The thermal conditioning elements 80 may also condition the catalysts, typically enzymes, e.g. by cooling the catalyst around 4 C. In that way longer conservation times can be reached, and the decomposition reaction may be interrupted or slowed down while the vehicle is stopped. These thermal conditioning elements 80 can be e.g. Peltier effect devices, isolating elements, phase change materials, or combinations of thereof.

[0086] In this exemplary embodiment the receiving part 30 is integrated in a filler pipe 15 of the tank 10. The filler pipe 15 is a pipe used for filling the tank 10. As illustrated in FIG. 1, the receiving part 30 is integrated into a head of the tank filler pipe 15. To fill the tank 10, the retaining unit 20 is first removed and the ammonia precursor is refilled through a filling orifice. At the end of a filling operation, the retaining unit 20 (optionally a new one with fresh catalyst) is put in place in the receiving part 30.

[0087] A fluid transfer device 51 allows the transfer of ammonia precursor solution to the decomposition area in the retaining unit 20, via a first pipe section 31. The generated effluents containing the ammonia are collected in buffer reservoir 40, from which they are sent to an ammonia consuming device (not shown), optionally using a fluid transfer device. The generated effluents are conveyed from the retaining unit 20 towards the buffer reservoir 40, via a second pipe section 32. A fluid transfer device can be for example a pump, a valve, a combination of both, gravity, gravity in combination with a valve or a valve in combination with whatever system known in the state of the art to transfer liquid. It is noted that if fluid transfer device 51 is a pump, it can pressurize both the retaining unit 20 and the buffer reservoir 40 so that the effluents can be sent directly to the ammonia consuming device.

[0088] An electronic controller or an electronic control unit (ECU) (not shown) is configured for controlling operation of the fluid transfer device(s) and the heater 70. In the example of FIG. 1, the fluid transfer device(s) and the heater 70 are powered by the vehicle battery.

[0089] The ECU includes a series of computer-executable instructions, as described below in relation to FIGS. 2 and 3. These instructions may reside, for example, in a RAM of the ECU. Alternatively, the instructions may be contained on a data storage device with a computer readable medium (for example, USB key or CD-ROM).

[0090] FIG. 2 illustrates an exemplary embodiment of a flow chart of instructions depicting logical operational steps for activating and deactivating the biological catalyst of FIG. 1 in a continuous mode.

[0091] At step S1, the ECU detects the insertion of a new retaining unit 20 with fresh catalyst in the receiving part 30.

[0092] At step S2, the ECU obtains a measurement of the amount of electrical energy stored in the vehicle battery.

[0093] At step S3, the ECU performs a test which consists in determining whether the measured amount of electrical energy stored in the vehicle battery (at step S2) is higher than or equal to a predetermined threshold level. For example, this threshold level can be set such that it corresponds to 60 W-h, for a battery of 60 A-h at 12 Volts (this corresponds to a capacity of 720 W-h). So, in this example, the threshold level would correspond to 8.3% of the capacity or possible electrical energy content of the battery.

[0094] If the answer to test S3 is yes, the ECU executes step S4. At step S4, a biochemical conversion is performed. More precisely, at step S4 the ECU turns on the fluid transfer device 51 and the heater 70 (i.e. supply of energy), to convey ammonia precursor solution inside the retaining unit 20 and to activate the enzyme, respectively. Advantageously, a check valve 60 is provided in the first pipe section 31 to prevent the ammonia precursor solution in the retaining unit 20 to return inside the tank 10. In such continuous mode, the ammonia precursor solution is fed continuously to the retaining unit 20 (by the fluid transfer device 51) and the reaction product is continuously removed from the retaining unit 20 (by the fluid transfer device 51 or by another fluid transfer device) and transported to the buffer reservoir 40. Advantageously, the decomposition occurs at an ammonia precursor flow rate and residence time suitable to achieve complete or partial conversion for instance, 80%, preferentially 95%, more preferentially 99% or ideally 100% of the ammonia precursor solution is converted into ammonia solution (i.e. reaction product). The residence time is the period of time a fluid is spending inside the retaining unit 20 at a given flow rate.

[0095] On the other hand, if the answer to test S3 is no, the process return to step S2.

[0096] Optionally, the test at step S3 can further consist in verifying that there is a need to produce reaction product. To this aim, the ECU can perform the following steps: [0097] determining (or measuring) a quantity of reaction product stored in the buffer reservoir 40; [0098] determining whether the quantity of reaction product stored is higher than or equal to a predetermined required quantity.

[0099] For example, this required quantity can be set such that it corresponds to 20 to 60% of the total volume corresponding to the sum of the volume of ammonia precursor and the volume of reaction product, or ideally 30 to 40% of such volume.

[0100] Optionally, the test at step S3 can yet further consist in measuring the level of ammonia precursor solution stored in the tank 10 and verifying whether there is enough quantity of ammonia precursor solution for a conversion operation.

[0101] At step S5, the ECU obtains a measurement of the amount of electrical energy stored in the vehicle battery.

[0102] At step S6, the ECU performs a test which consists in determining whether the measured amount of electrical energy stored in the vehicle battery (at step S5) is higher than or equal to the predetermined threshold level.

[0103] If the answer to test S6 is yes, the process return to step S4 so as to continue the biochemical conversion.

[0104] On the other hand, if the answer to test S6 is no, the ECU turns off (at step S7) the fluid transfer device 51 and the heater 70 (i.e. stop of the energy supply). Thus, at step S7 the ECU deactivates the enzyme and stops the biochemical conversion. Then, the process can return to step S2.

[0105] In a particular embodiment, the thermal conditioning elements 80 can further be used to activate the enzyme to its optimal reaction temperature.

[0106] FIG. 3 illustrates an exemplary embodiment of a flow chart of instructions depicting logical operational steps for activating and deactivating the biological catalyst of FIG. 1 in a batch mode. In this exemplary embodiment, a secondary fluid transfer device (not shown) is placed in the second pipe section 32 between the head of the tank filler pipe and the buffer reservoir 40. For example, the secondary fluid transfer device is a controllable valve. The controllable valve is arranged in the second pipe section 32 and is configured such that when it is closed, the solution present in the retaining unit 20 cannot flow in the second pipe section 32 towards the buffer reservoir 40, and when it is opened, the solution present in the retaining unit 20 is evacuated out of the retaining unit 20 and is guided towards the buffer reservoir 40.

[0107] Steps S10, S20 and S30 of FIG. 3 are similar to the above-described steps S1, S2 and S3 of FIG. 2, respectively, and their descriptions are not repeated hereafter.

[0108] If the answer to test S30 is yes, the ECU executes step S40.

[0109] On the other hand, if the answer to test S30 is no, the process return to step S20.

[0110] At step S40, a biochemical conversion is performed. More precisely, at step S40, the ECU turns on the fluid transfer device 51 and the heater 70, to convey ammonia precursor solution inside the retaining unit 20 and to activate the enzyme, respectively. The fluid transfer device 51 is controlled such that a predetermined quantity of ammonia precursor solution is moved inside the retaining unit 20. The fluid transfer device 51 is turned off once the predetermined quantity of ammonia precursor solution has been moved inside the retaining unit 20. Further, at step S40 the controllable valve is closed.

[0111] At step S50, the ECU monitors the progress of the conversion. More precisely, the ECU performs a test which consists in detecting an event indicative of end-of-conversion. To this aim, the ECU can perform the following steps: [0112] measuring (by means of a physical sensor) the electrical conductivity of the solution in the retaining unit 20; [0113] determining whether the measured electrical conductivity is higher than or equal to a predetermined target electrical conductivity.

[0114] If the answer to test S50 is yes, the ECU turns off the heater 70 and opens the controllable valve (step S60). The solution present in the retaining unit 20 is evacuated (for example by gravity) out of the retaining unit 20 and is guided towards the buffer reservoir 40. Then, the ECU executes step S70 (described hereafter).

[0115] In another embodiment, step S60 can be performed at the same time as the refilling of new ammonia precursor in the batch loop as part of step 40. This is particularly advantageous since the fresh ammonia precursor (i.e. newly introduced in the retaining unit) will automatically push the effluents out of the retaining unit.

[0116] In another embodiment, it can be advantageous to take into account the thermal inertia of the system. This means that after the heater is off the solution is not immediately transferred to the buffer, as conversion is still running.

[0117] On the other hand, if the answer to test S50 is no, the test S50 is repeated.

[0118] In the example described above, the control of the conversion time period is based on an electrical conductivity comparison.

[0119] In another example, the control of the conversion time period can be based on a time model or a time table, for instance the time necessary to obtain the required level of conversion can be tabulated depending upon the ageing of the enzymes, the number of conversion operation performed, the age of the enzymes, a temperature history during idle periods, etc. It can further be based on data provided by a chemical/physical sensor during the reaction: for instance, the total conversion time period can be calculated as 3 times the time it took to increase the electrical conductivity by a factor of 10; so if the electrical conductivity has been multiplied by 10 in 15 minutes, the total duration of the conversion can be fixed at 45 minutes.

[0120] At step S70, after complete evacuation of the effluents present in the retaining unit 20, the ECU closes the controllable valve and obtains a measurement of the amount of electrical energy stored in the vehicle battery.

[0121] At step S80, the ECU performs a test which consists in determining whether the measured amount of electrical energy stored in the vehicle battery (at step S70) is higher than or equal to the predetermined threshold level.

[0122] If the answer to test S80 is yes, the process return to step S50, so as to replenish the retaining unit 20 with ammonia precursor solution and start a new conversion operation.

[0123] On the other hand, if the answer to test S5 is no, the process can return to step S10 (or S20).

[0124] FIG. 4 represents the influence of the temperature on the activity of the enzyme urease during the decomposition (i.e. conversion) of ammonia precursor (i.e. compound) into ammonia (i.e. reaction product) described in Danial et al., Braz. Arch. Biol. Technol. v. 58 n. 2: pp. 147-153, March/April 2015.

[0125] In order to study the optimal temperature of the free and immobilized urease, the enzymes were incubated for 30 min into 1.0 mL of 3% (w/v) ammonia precursor at pH 7.5 and temperatures from 30 to 70 C. The optimal temperature was taken as 100% activity and the relative activity at each temperature was calculated as a percentage of the 100% activity. The support material used for urease immobilization was alginate.

[0126] This study shows that the catalytic activity of the urease increases gradually with the temperature (i.e. energy supply). As the temperature rises, the ammonia precursor and the urease have more and more kinetic energy. Thus, the chances of successful collision between the ammonia precursor and the urease are increased. In this way, the rate of the decomposition of the ammonia precursor solution into ammonia solution (i.e. conversion rate) increases progressively with the temperature until reaching a plateau.

[0127] This study highlights that the catalytic activity of the urease is at its greatest (i.e. plateau) at a temperature around 40-50 C. In other words, that means that the interval of temperature 40-50 C. is the optimal temperature interval wherein the urease has its optimal catalytic activity.

[0128] This study highlights that above this optimal temperature interval the urease loses gradually its catalytic activity. Indeed, the structure of the urease begins to denature since at higher temperatures intra- and intermolecular bonds are broken as the urease gains even more kinetic energy. Consequently, the rate of the decomposition of ammonia precursor solution into ammonia solution decreases gradually.

[0129] Then, based on this result, the decomposition rate (i.e. conversion rate) can be controlled by the temperature (i.e. energy supply).

[0130] 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.