Technical Field

[0001 ] The present invention relates to an exhaust after-treatment system and method of reducing pollutants in an exhaust gas resulting from the combustion of a fuel in a combustion engine. In particular, but not exclusively, the present invention involves injecting and igniting hydrogen and oxygen into the exhaust gas from a diesel combustion engine so as to increase the temperature of the exhaust gas to convert at least some of the pollutants in the exhaust gas to non-pollutants.

Background of Invention

[0002] Combustion engines, especially diesel compression engines, produce pollutants, such as nitrogen oxides (NO _x ) and particulate matter (PM), a combination of soot and ash, from the combustion of fuel which may be emitted to atmosphere in the exhaust gas if they are not treated. The PM is typically carbonaceous particulates in the form of soot and ash, which are both extremely harmful to human health. Other pollutants, such as the NO _x, can react to form smog and acid rain. Hence,

environmental regulations have increasingly sought to reduce the emission limits permissible for these pollutants to be emitted to atmosphere.

[0003] Existing methods of reducing the pollutants being produced by combustion engines, especially diesel combustion engines, and then being emitted to atmosphere include before-treatment methods, such as exhaust gas recirculation to lower the combustion temperature of the diesel, and after-treatment methods. After-treatment methods include diesel particulate filters (DPFs) to remove the soot and ash, and chemical conversion methods, such as selective catalytic reduction (SCR), to remove the NO _x. These DPFs, however, regularly become clogged and ineffective. Further, in a typical SCR system, the NO _x present in the exhaust gas is mixed with ammonia and converted to the non-pollutants: nitrogen and water. Here, the ammonia acts as a reductant for a selective catalytic reduction and is typically obtained from urea which is injected into the exhaust gas in the SCR system. The typical SCR system, however, is expensive and thus not generally fitted to diesel engines for automobiles. It is also sensitive to contamination resulting from both normal operation of the SCR system and abnormal events.

[0004] Another existing after-treatment method to reduce pollutants in the exhaust gas, such as NO _x , produced by a diesel engine involves selective non-catalytic reduction (SNCR). In this method, urea or ammonia is again injected in the exhaust gas, but the reduction of the NO _x gases to nitrogen and water occurs without the need for a catalyst due to high temperatures (e.g. over 1000°C) being present in the exhaust gas. The temperature window for the effective reduction of the NO _x gases, however, is relatively narrow so this method may operate ineffectively at times, and a diesel vehicle using this method to minimise pollutants being emitted may fail to always meet the emission limits set by environment regulations.

[0005] The above discussion of background art is included to explain the context of the present invention. It is not to be taken as an admission that any of the documents or other material referred to was published, known or part of the common general knowledge at the priority date of any one of the claims of this specification.

Summary of Invention

[0006] According to one aspect of the present invention, there is provided an exhaust after-treatment system for reducing pollutants in an exhaust gas resulting from combustion of a fuel in a combustion engine, the system including: a tank storing a gaseous fuel; an incinerator located in an exhaust passage carrying the exhaust gas between the combustion engine and an output of the exhaust passage; an injector configured to be controlled to inject a designated volume of the gaseous fuel from the tank into the incinerator; an ignition device configured to be controlled to ignite the designated volume of gaseous fuel in the incinerator; and a controller configured to: instruct the injector to inject the designated volume of gaseous fuel into the incinerator and then to instruct the ignition device to ignite the designated volume of gaseous fuel in the incinerator so as to increase temperature in the incinerator above a designated temperature to convert at least some of the pollutants in the exhaust gas to non-pollutants. [0007] Typically, the fuel is diesel and the combustion engine is a compression ignition engine. For example, the combustion engine is a diesel compression engine or a spark-type ignition engine equipped with Gas Particulate Filter (GPF) and SCR equipment. As mentioned, the combustion of diesel at high pressures and high temperatures in a typical diesel compression engine produces pollutants such as NO _x and particulate matter (PM) such as soot and ash. These pollutants are removed by the exhaust after-treatment system by being destroyed and converted at high temperature to non-pollutants, such as nitrogen, water, and carbon dioxide. It will be appreciated by those persons skilled in the art that other pollutants are present in the exhaust gas such as hydrocarbons and carbon monoxide are also removed by being destroyed and converted at high temperature to non-pollutants.

[0008] In an embodiment, the gaseous fuel includes hydrogen and oxygen, and the hydrogen and oxygen is ignited in the incinerator to increase the temperature in the incinerator above a normal temperature of the exhaust gas (e.g. above around 400°C). Alternatively, the gaseous fuel could be just hydrogen. For example, the combustion of hydrogen and oxygen raises the temperature in the incinerator to above 1000 °C.

[0009] As mentioned, existing after-treatment methods include diesel particulate filters (DPFs). In an embodiment where existing DPF devices are used, the incinerator may be provided by the DPF. For example, the incinerator of the exhaust after-treatment system may be incorporated into an existing passive DPF device by providing a new hydrogen-oxygen gas delivery tube that enters the exhaust after- treatment system just before the existing passive DPF device, utilizing the existing passive DPF as the incineration chamber. This arrangement converts or utilizes existing components and reduces the overall cost of the exhaust after-treatment system. In another example, the incinerator may be incorporated into an existing active DPF device by converting the existing diesel fuel delivery tube that feeds into the active DPF to a hydrogen-oxygen gas delivery tube that enters the exhaust system in the same location as the former diesel fuel delivery. This example utilizes the existing active DPF as the incinerator, but now uses Flydrogen-oxygen gas instead of diesel fuel; thus also converting or utilizing existing components and reducing the overall cost of the new system.

[0010] In another embodiment, for vehicles without any DPF device, the incinerator of the exhaust after-treatment system is installed just before the muffler of the vehicles.

[0011 ] In a further embodiment, the hydrogen and oxygen are stored in the tank in a substantially stoichiometric ratio. However, other ratios are envisaged depending on, for example, the desired temperature of the incinerator.

[0012] In an embodiment, the system further includes one or more sensors configured to sense the pollutants in the exhaust gas in the exhaust passage.

Specifically, the sensors are located before the incinerator to sense pollutants in the exhaust gas produced by the engine. In the embodiment, the controller is further configured to receive data from the one or more sensors indicative of a level of the pollutants in the exhaust gas. Further, the controller is configured to instruct the injector to inject the designated volume of gaseous fuel into the incinerator and to instruct the ignition device to ignite the designated volume of gaseous fuel in the incinerator when the level of the pollutants in the exhaust gas exceeds a threshold level. For example, the threshold level of the pollutants sensed in the exhaust gas is the minimum emission limits permissible for these pollutants to be emitted to atmosphere that are prescribed by various regulations.

[0013] In another embodiment, the controller instructs the injector to inject the designated volume of gaseous fuel into the incinerator and then to instruct the ignition device to ignite the designated volume of gaseous fuel in the incinerator at regular intervals so that the incinerator is regularly incinerating the pollutants. It will be appreciated by those persons skilled in the art that the flow of the gaseous fuel, such as hydrogen and oxygen, into the incinerator may vary based on characteristics of the engine, such as engine speed, and engine load, etc.

[0014] It will also be appreciated by those persons skilled in the art that the designated volume of gaseous fuel and the size of the tank (or delivery system) will be based on the type and capacity of the combustion engine. For example, the tank/delivery system may have a storage capacity of 1 L or a delivery system may have any delivery rate required by the applicaiton. It will also be appreciated that the designated temperature of the incinerator to convert pollutants to non-pollutants is based on several variables, such as the level of the pollutants in the exhaust gas which is a result of the quality of the diesel fuel as well as the level of sulphur content and contaminants in the diesel fuel, etc. Further, the designated temperature can be selected based on the level of the pollutants in the exhaust gas sensed by the sensors.

[0015] In an embodiment, the system further includes an electrolyser for generating the hydrogen and oxygen. In an example, the combustion engine is a diesel combustion engine on a truck and the electrolyser is located on the truck. In the embodiment, the system includes a gaseous fuel passage located between the electrolyser and the tank for carrying the hydrogen and oxygen to the tank.

[0016] In another embodiment, the tank includes a first valve located between the tank and the electrolyser and a second valve located between the tank and the combustion engine, whereby during operation of the combustion engine the first and second valve are configured to be controlled by the controller to open so that the hydrogen and oxygen generated by the electrolyser is carried to the combustion engine for combustion. That is, the hydrogen and oxygen generated by the electrolyser is used as a before-treatment method of reducing pollutants by being injected into the fuel-air mixture for combustion in the engine so as to reduce the pollutants produced in the exhaust gas.

[0017] In an embodiment, the system further includes a flash back arrestor associated with the tank configured to dampen an explosion resulting from the designated volume of gaseous fuel in the incinerator being ignited by at least partially venting the explosion to atmosphere. In the embodiment, the tank includes a flash back arrestor valve located between the tank and the flash back arrestor whereby the flash back arrestor valve is configured to be controlled by the controller to open when the designated volume of gaseous fuel in the incinerator is ignited. That is, the flash back arrestor has an opening with the flash back arrestor valve at one end and a further opening that is at least partially open at the other end so that when an explosion event occurs (however remote) it is vented to atmosphere via the further opening. In the embodiment, the flash back arrestor has a relief valve adjacent the further opening so that if any possible back pressure explosion event occurs it is vented to atmosphere via the further opening.

[0018] In an embodiment, the injector includes an injector valve located between the tank and the incinerator and configured to be controlled by the controller to open when the designated volume of gaseous fuel is injected into the incinerator and when the designated volume of gaseous fuel is ignited. In the embodiment, the injector valve is a metering valve that provides the designated volume of gaseous fuel into the incinerator.

[0019] With reference to an embodiment described above, the second valve between the engine and the tank is further configured to be controlled by the controller to close when the injector valve is open and the designated volume of gaseous fuel is injected into the incinerator. In yet another embodiment, the first and second valves are both configured to be controlled by the controller to close when the injector valve is open and the designated volume of gaseous fuel is injected into the incinerator.

[0020] According to another aspect of the present invention, there is provided an exhaust after-treatment method of reducing pollutants in an exhaust gas resulting from combustion of fuel in a combustion engine, the method including: storing a gaseous fuel in a tank; injecting a designated volume of the gaseous fuel from the tank into an incinerator located in an exhaust passage carrying the exhaust gas between the combustion engine and an output of the exhaust passage; and igniting the designated volume of gaseous fuel in the incinerator so as to increase

temperature in the incinerator above a designated temperature to convert at least some of the pollutants in the exhaust gas to non-pollutants.

Brief Description of Drawings

[0021 ] Embodiments of the invention will now be described with reference to the accompanying drawings. It is to be understood that the embodiments are given by way of illustration only and the invention is not limited by this illustration. In the drawings:

[0022] Figure 1 is a representation of an exhaust after-treatment system

according to an embodiment of the present invention;

[0023] Figure 2 is a representation of an exhaust after-treatment system

according to another embodiment of the present invention;

[0024] Figure 3 is a representation of a tank of an exhaust after-treatment system according to an embodiment of the present invention; and

[0025] Figure 4 is a flow chart of a an exhaust after-treatment method according to an embodiment of the present invention.

Detailed Description

[0026] An exhaust after-treatment system 10 for reducing pollutants in an exhaust gas resulting from combustion of a fuel in a combustion engine 12 is shown in Figure 1 and in more detail in Figure 2. The fuel in relation to the embodiments shown in Figures 1 and 2 is diesel and the combustion engine is a diesel compression engine. Thus, as mentioned above, the combustion of diesel at typically high pressures and high temperatures in a diesel compression engine produces pollutants, such as nitrous oxides (NO _x ), particulate matter (PM), soot, ash, and other pollutants that operation of the system 10 reduces from being emitted to atmosphere. For example, the engine 12 is a diesel engine for a car, truck, locomotive, marine vessel, or a power generation unit.

[0027] Figure 1 and 2 show components of the system 10 that are required for reducing the volume of pollutants that would be emitted to atmosphere. Specifically, the engine 12 is connected to an exhaust passage 14 for carrying the exhaust gas from the engine 12 to an output of the exhaust passage 14, typically via a muffler (not shown). It will be appreciated by those persons skilled in the art that also located on the exhaust passage 14 before the output are other components that are not shown, such as filters, etc. [0028] The system 10 shown in Figures 1 and 2 includes a tank 16 for storing a gaseous fuel, in the form of hydrogen and oxygen, and an incinerator 18 located in the exhaust passage 14 between the engine 12 and the output of the exhaust passage 14. The system 10 further includes a controller 20 configured to control the components of the system 10 to reduce the volume of pollutants being emitted to atmosphere. The controller 20 includes a memory (not shown) that contains software code stored thereon to be implemented by a processor (not shown) of the controller 20 to control the components of the system 10.

[0029] The system 10 includes an injector 22 located adjacent the tank 26 which is configured to be controlled by the controller 20 to inject a designated volume of the gaseous fuel from the tank into the incinerator 18. The system 10 also includes an ignition device 24 located in the incinerator which is configured to be controlled by the controller 20 to ignite the designated volume of gaseous fuel in the incinerator 18.

That is, in use, the controller 20 instructs the injector 22 to inject the designated volume of hydrogen and oxygen into the incinerator 18 and then instructs the ignition device 24 to ignite the designated volume of hydrogen and oxygen in the incinerator 18 so as to increase the temperature in the incinerator 18 above a designated temperature above the normal temperature of the exhaust gas (e.g. above 400°C) to convert at least some of the pollutants, especially the soot and the ash, in the exhaust gas in the exhaust passage 14 to non-pollutants.

[0030] The tank 16 contains hydrogen and oxygen stored at a stoichiometric ratio, and when the designated volume of hydrogen and oxygen is ignited in the incinerator 18, the temperature very quickly rises to above 1000°C. At these high temperatures, at least some of the soot, ash, NO _x and other pollutants are destroyed and converted to non-pollutants. For example, the NO _x are converted to non-pollutants such as water and nitrogen by at least the reaction of the NO _x with hydrocarbon radicals present in the exhaust gas at the high temperature.

[0031 ] Figure 2 shows an embodiment of the system 10 in more detail, in which the system 10 includes one or more sensors 26 configured to sense a level of the pollutants, such as soot and ash, in the exhaust gas in the exhaust passage 14. The sensors 26 are located before the incinerator 18, and the controller 20 is configured to receive data from the sensors 26 indicative of the level of pollutants in the exhaust gas in the exhaust passage 14. During operation of the system 10 - that is, during operation of the diesel engine - the controller 20 receives the data from the sensors 26 and when the level of the pollutants in the exhaust gas is sensed as exceeding a threshold level, the controller 20 instructs the injector 22 to inject the designated volume of hydrogen and oxygen into the incinerator 18 and then instructs the ignition device 24 to ignite the designated volume of hydrogen and oxygen in the incinerator 18. As mentioned, the threshold level of the pollutants sensed in the exhaust gas is the minimum emission limits permissible for these pollutants to be emitted to atmosphere that are prescribed by various regulations. The designated volume of hydrogen and oxygen is then burnt in the incinerator 18 causing a rapid rise in temperature in the incinerator 18.

[0032] Figure 2 also shows the system 10 including an electrolyser 28 for generating the hydrogen and oxygen, as well as a gaseous fuel passage located between the electrolyser 28 and the tank 16 for carrying the hydrogen and oxygen to the tank 16 and a gaseous fuel passage between the tank 16 and the engine 12. As mentioned, the hydrogen and oxygen generated by the electrolyser 28 is used as a before-treatment method of reducing pollutants, including NO _x , by being injected into the fuel-air mixture of the engine 12 so as to reduce the pollutants produced in the combustion of diesel by the engine 12. Specifically, the electrolyser 28 is configured to be controlled by the controller 20 to deliver a metered amount of hydrogen and oxygen to the air intake of the engine 12 for the before combustion treatment. This before combustion treatment improves the combustion of diesel by the engine 12 to reduce production of pollutants and improve the fuel efficiency of the engine 12.

Additional benefits of this before combustion treatment include resolving engine knock and reducing the generation of in-cylinder particulate matter.

[0033] The system 10 further includes a flash back arrestor 30 associated with the tank 16 that is configured to dampen the explosion of gasses resulting from the designated volume of hydrogen and oxygen being burnt in the incinerator 18 by at least partially venting the explosion to atmosphere. As seen in more detail in Figure 3, the flash back arrestor 30 has an opening at one end that is at least partially open at the end so that when the explosion occurs it is vented to atmosphere via the opening. Operation of the flash back arrestor 30 will be described below in more detail with respect to Figure 3. The tank 16 can be built with high strength

polycarbonate plastic and then filament wound with Kevlar. As mentioned, the size and volume of the tank 16 depends on the engine 12 characteristics, as well as the pressure requirements for the storage of the hydrogen and oxygen. It will be appreciated by those persons skilled in the art that the hydrogen and oxygen are stored at low pressure in the tank 16.

[0034] The tank 16 is also shown in Figure 3 as having a number of valves that are controlled by the controller 20 to control operation of the system 10. It will be appreciated by those persons skilled in the art that these valves need not be located on the tank 16 and instead could be located at any point along the various passages that connect the tank 16 to other components of the system 10. Notwithstanding, the tank 16 includes a first valve 32 located between the tank 16 and the electrolyser 28, and a second valve 34 located between the tank 16 and the combustion engine 12.

As mentioned, during operation of the engine 12, these first 32 and second 34 valves are controlled by the controller 20 to be open so that the hydrogen and oxygen generated by the electrolyser 28 is carried to the engine for combustion.

[0035] The tank 16 also includes a flash back arrestor valve 36 located between the tank 16 and the flash back arrestor 30, whereby the flash back arrestor valve 36 is configured to be controlled by the controller 20 to open when the designated volume of hydrogen and oxygen is ignited in the incinerator 18 to effect operation of the flash back arrestor 30. That is, the flash back arrestor valve 36 is open so that when the explosion occurs in the incinerator 18 it is vented to atmosphere via the opening 31 in one end of the flash back arrestor 30. It can also be seen in Figure 3 that the flash back arrestor valve 36 is located in the opening 33 in the opposed end of the flash back arrestor 30. The opening 31 in the flash back arrestor 30 is only partially open so as to dampen and extinguish the explosion when it occurs in the incinerator 18.

[0036] Further, in an embodiment, the flash back arrestor valve 36 is further configured to be controlled by the controller 20 to open when the designated volume of hydrogen and oxygen is injected into the incinerator 18, via the injector 22 to receive air from atmosphere via the opening 31 into the tank 16.

[0037] Figure 3 shows the injector 22 in the form of an injector valve 38 located between the tank 16 and the incinerator 18 which is configured to be controlled by the controller 20 to open when the designated volume of hydrogen and oxygen is injected into the incinerator 18 and when the designated volume of hydrogen and oxygen is ignited in the incinerator 18. That is, in normal use of the system 10, the first 32 and second valves 34 are configured by the controller to be open so that hydrogen and oxygen generated by the electrolyser 28 are fed into the engine 12 for improved combustion of diesel by the engine 12. When the controller 20 determines that the sensors 26 have sensed a higher than a threshold level of pollutants in the exhaust gas from the engine 12 in the exhaust passage 14, the controller 20 instructs the second valve 34 to close, and the injector valve 38 and the flash back arrestor valve 36 to open. With the flash back arrestor valve 36 open, the tank 16 receives air from atmosphere and injects the designated volume of hydrogen and oxygen in the tank 16 into the incinerator 18 via the open injector valve 38. When the hydrogen and oxygen is ignited in the incinerator 18, the controller 20 instructs the first valve 32 to electrolyser 28 to also close but leaves open the flash back arrestor valve 36 and the injector valve 38. Thus, if a resultant explosion event occurs from igniting the hydrogen and oxygen in the incinerator 18, it is vented to atmosphere via the tank 16 and the flash back arrestor 30.

[0038] In another embodiment, during a quick acceleration moment of the vehicle with the engine 12, the controller 20 also instructs the second valve 34 to close, and the injector valve 38 and the flash back arrestor valve 36 to open as above. Again, the tank 16 receives air from atmosphere and injects the designated volume of hydrogen and oxygen in the tank 16 into the incinerator 18 via the open injector valve 38 for ignition. It will be appreciated by those persons skilled in the art that in respect of this embodiment, quick acceleration events product more pollutants than normal operation of the engine 12 and thus after-treatment for reducing pollutants is also required. [0039] Referring now to Figure 4, there is shown a flow chart of an exhaust after- treatment method 40 of reducing pollutants in an exhaust gas resulting from

combustion of fuel in a combustion engine. The method 40 includes the steps of: storing 42 a gaseous fuel in a tank; injecting 44 a designated volume of the gaseous fuel from the tank into an incinerator located in an exhaust passage carrying the exhaust gas between the combustion engine and an output of the exhaust passage; and igniting 46 the designated volume of gaseous fuel in the incinerator so as to increase temperature in the incinerator above a designated temperature to convert at least some of the pollutants in the exhaust gas to non-pollutants.

[0040] In addition, it will be appreciated by those persons skilled in the art that further aspects of the method 40 will be apparent from the above description of the system 10. Further, the persons skilled in the art will also appreciate that at least part of the method 40 could be embodied in software (e.g. program code) that is implemented by a processor of the controller 20 that is configured to control the system 10. The software could be supplied in a number of ways, for example on a memory of the controller 20, or on a tangible computer readable medium, such as a disc or a flash memory device.

[0041 ] Those skilled in the art will also appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications.