This invention relates to explosion proof exhaust systems and in particular to an explosion poof exhaust system which includes a flame arrester integrated with an emission control device.
Many pieces of equipment (e.g., internal combustion operated industrial machinery) have to be operated in areas where gases and flammable substances are present. The heat generated by the engines and the exhaust fumes of these pieces of equipment may cause the gases and/or flammable material present in the area to ignite and/or explode. It is therefore necessary to reduce the external surface temperature of the pieces of equipment and to prevent sparks/flames from being emitted out of the exhaust. It is further necessary and/or desirable to reduce the pollutants emitted by the pieces of equipment for, among others, not adding to the gases and flammable substances already present.
Presently available systems, as shown in Prior Art
Known prior art systems are relatively complex and the need to perform frequent cleaning and maintenance imposes severe restrictions on their use.
Systems embodying the invention include an exhaust system mounted via explosion proof flanges to the engine cylinder head. The exhaust system includes a flame-arrester-oxidizing device comprising a duct having an input end and an output end and a passageway between the input and output ends for passing the exhaust gases. An oxidizing and filtering device comprising metal foils coated by a noble metal (e.g., platinum, or the like) is firmly and securely affixed across the passageway. In addition, an insulator layer is mounted over the external wall of the duct. A jacket is mounted over the insulator through which a coolant (water or the like) can pass to cool the external surface of the system, in contact with the atmosphere, to a temperature (e.g., 90 degrees centigrade) below a prescribed level. At the same time, the insulator layer insures that the coolant does not lower the temperature within the duct's passageway to a value which would prevent oxidation. By maintaining the temperature within the duct at an elevated temperature, the exhaust fumes and pollutants from the engine, passing through and along the metal foils, are oxidized resulting in mostly water vapour and gases being emitted at the exhaust output of the device. Thus, the flame arrester oxidizing device of the invention functions as a remover of pollutants and is generally self cleaning. This eliminates the need for frequent cleaning and maintenance present in the prior art.
In one embodiment the engine exhaust is fed to a first heat exchanger for cooling the very hot exhaust fumes prior to their passing through the flame-arrester-oxidizing device. The exhaust output from the flame-arrester-oxidizing device is then passed through to an additional flame arrester. The output of the additional flame arrestor is then passed through a dry secondary cooler which includes spark arresting properties.
In the accompanying drawings, which are not drawn to scale, like reference characters denote like components; and
Selected components of the intake/exhaust assembly shown in
The intake portion of the system shown in
In addition to protecting the air intake system against unexpected flames, flame arrester 15 also has an air shut off valve built into it. This valve is used to cut off the air supply to the engine, causing the engine to shutdown, upon receipt of certain signals from the engine control system. The functioning of the control system is described below.
The engine control system (see
For example, the exhaust air and the radiator coolant have respective maximum temperature limits. When their maximum temperature is exceeded, the system transmits a signal activating (shutting off) the air intake valve. Engine oil pressure has a minimum acceptable limit. Upon detecting lower than acceptable pressure, the control system activates the air shut off valve. Similarly, internal combustion engines have maximum acceptable speeds. Exceeding these speeds can cause great damage to the engine and adversely affect safety. Engine operating speed is constantly monitored by the system and any overspeed condition triggers the actuation of the air shut off valve.
Selected components of the cooling assembly shown in
The primary heat exchanger 2 functions to lower the temperature of the gases exiting the engine. For example, heat exchanger 2 can lower the temperature of the exhaust gases from 400 degrees Centigrade to 200 degrees Centigrade. The output of heat exchanger 2 is then passed to, and through, flame arresting and oxidizing device 3. As described below, flame arresting device 3 also functions to oxidize the pollutants in the exhaust fumes. Thus, heat exchanger 2 functions to lower the temperature of the fumes to ensure that the flame arrestor 3 can effectively function as a flame arrester. At the same time, heat exchanger 2 does not lower the temperature of the gases/fumes to device 3 below the level which would inhibit device 3 from functioning as an oxidizer. As is shown in
The flame arrester 3 includes a structure providing a passageway for the “hot” exhaust fumes to pass from heat exchanger 2 to succeeding portions of the exhaust system with many pollutants vaporized. The passageway may be of any suitable shape for allowing the passage of the exhaust gases and fumes. For ease of description the structure is referred to herein as a duct, but it should be evident that it may be also be referred to as a pipe, tube, channel or any like structure. As shown in
Attached to, and located across, the inner surface 299b of the duct wall/shell 299 are corrugated metal (e.g., corrugated sheet metal) foils forming a mesh 301 (as shown in
The metal foils (sheets) 351 of the flame arrestor 3 are coated with a noble metal (e.g., platinum or palladium, or any like metal which is suitable to sustain oxidation), by a selected procedure, to oxidize the fumes and gases passing through the interior portion of the flame arrester 3 as shown in
The interior portion (i.e., the space or opening formed by and or between the inner surfaces of the walls/shell of the duct) of the flame arrestor 3 (see
One embodiment of a foil structure suitable to form a flame arrester/oxidizer in accordance with the invention is shown in
The size of the cells, i.e., their spacing, as illustrated in
Thus, as shown in
In
The combination of primary heat exchanger 2, flame arrester 3 and additional heat exchanger 4 functions as an explosion proofing device to contain the explosions and high temperatures of the exhaust system of the engine. Also, the flange 1 is attached to the cylinder head 13 via a special method and attaching means to obtain a very compact closed joint. The integrity of this joint is critical. Repeated cycles of higher and lower temperature exhaust cycles caused by varying engine loads inherent in most work environments can cause the sealing material to crack. This action can initially diminish and eventually render worthless the sealing effectiveness. Loss of sealing would release high temperature exhaust gases in hazardous areas negating the benefits of explosion proof solutions and creating unsafe work environment. Sealing methods used by prior art in this area are inadequate for long term durability of engines. The combination of a special coupling design and the choice of sealant in systems embodying the invention ensures against sealing degradation resulting in safe operations and long term durability. The sealant used in the invention is an acrylic based adhesive particularly suitable for high temperature applications. It retains its shape and sealing capacity over a wide range of temperatures, is resistant to oils, fuels, lubricants and chemicals. Additionally, it can withstand high pressures without degradation in sealing effectiveness.
The output from flame arrestor/heat exchanger 4 and coupler 5 is passed through piping 7 to secondary cooler 8. The secondary cooler 8 is specially constructed to further reduce the temperature of the exhaust fumes and to act as a spark arrestor. The internal construction has a very high efficiency in reducing the exhaust temperature by a double stage cooling device constructed by parallel metal pipes acting as radiators. Furthermore, in the internal side of the pipes an helical metal structure is located to increase the cooling efficiency and to act as a spark arrestor system. Thus, for example, cooler 8 functions to reduce the temperature of particles passing through from the primary heat exchange section. Like the design of the flame arrestor 3, spark arrestor 8 is also designed around the principle of dry cooling. This makes the system compact and provides for far greater cooling than the wet cooling systems found on some machines.
In systems embodying the invention, particles which have not been oxidized by, and in, flame arrestor 3 may pass through and reach particle filter 12. Filter 12 will block particles exceeding specified values from being exhausted to the atmosphere. Note that filter 12 is much more accessible than device 3 and it is much easier to change this filter than to change flame arrestor/oxidizer 3.
An important aspect of the system is to ensure that the exhaust apparatus of the engine is explosion proof and that the temperature of the exhaust fumes is reduced to be less than a specified value for operation in a potentially explosive atmosphere. Also, the exhaust emissions are drastically decreased and the flame arresting device is automatically cleaned.
The cooling system is considered, and referred to as, a “dry” system as the exhaust fumes do not come in direct contact with the cooling liquid. As shown in
The fumes from the engine head exit ports pass first through the primary heat exchanger explosion proof flanged to the cylinder head and then into the spark arresting cooler.
The reduction of the diesel engine pollutants is extremely drastic and can be in the range noted below:
(a) carbon monoxide (CO) reduction is approximately 90%,
(b) total hydrocarbons (HC) are reduced approximately 70%,
(c) nitrogen oxides (NOx) are diminished by approximately 35%,
(d) diesel particulate matter (DPM) is diminished by approximately 40%.
The exhaust system embodying the invention integrates an emission control device into an explosion proof fumes cooling system. Furthermore, the system has a high degree of automatic self cleaning and therefore it does not need extensive routine maintenance. Systems embodying the invention overcome the disadvantage of known flame arrestors which need to be cleaned every 8 to 12 hours and which requires physically removing the flame arresting device, burning off the particulate matter and reattaching the flame arrestor on the machine. Employing prior art structures and processes would take at least one and a half hours and presents the following disadvantages: (1) the necessity to have an on site service person available to perform this task every eight to twelve hours; (2) incurring costs for cleaning apparatus; (3) incurring premium labour charges to carry out this task; and (4) most importantly, there is a forced equipment down time several times a day interrupting operations that require engine power around the clock. The total cost of these activities over the useful life of the equipment generally exceeds the initial cost of the engine. Apparatus embodying the invention eliminate these disadvantages.
The apparatus embodying the invention is also very compact and ergonomically designed and easily fits into the engine compartments. The compactness of this apparatus is very appealing to machinery manufacturers. A mobile piece of equipment driven by an internal combustion engine is always pressed for physical space around the engine. The dry cooling and especially designed heat exchangers associated with this system permit installation of flame proof solutions in applications previously encumbered by space constraints. Systems embodying the invention provide commercially viable solutions and open new markets for explosion proof solutions.
The dramatic reduction in carbon monoxide, hydrocarbons, nitrous oxides and diesel particulate matter vastly expands the indoor areas where diesel powered equipment can be operated. This is expected to result in meaningful increases in operational efficiencies in many applications.
Any change in engine back pressure is minimal and therefore the engine maintains a good performance. The practical advantages of the novel system are evident when compared to presently available explosion proof systems.
The invention is applicable for use with the exhaust from any type of internal combustion engine, including, but not limited to, a diesel engine, a liquid propane engine, a compressed natural gas engine and a gasoline (petrol) engine.
This application claims priority from provisional application Ser. No. 60/880,235 filed Jan. 12, 2007 for Explosion Protection System with Integrated Emission Control Device
Number | Date | Country | |
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60880235 | Jan 2007 | US |