WO2009105894A1

WO2009105894A1 - Exhaust gas treatment apparatus and method

Info

Publication number: WO2009105894A1
Application number: PCT/CA2009/000248
Authority: WO
Inventors: Dominic Edward Scappatura
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-02-29
Filing date: 2009-03-02
Publication date: 2009-09-03
Anticipated expiration: 2010-08-29
Also published as: WO2009105894A4; CA2753529A1; US20110000191A1

Abstract

In one aspect, the invention is directed an exhaust gas treatment apparatus that can be used to treat exhaust gas streams from vehicles having gasoline engines or diesel engines, from manufacturing plants, from incineration facilities, from coal fired stations, natural gas turbines or from virtually any exhaust gas stream. In one embodiment, the invention includes a particulate matter remover, a heat exchanger, a first reactor, a second reactor and a reagent protection device for preventing communication of reagent in the second reactor with ambient air.

Description

Title: EXHAUST GAS TREATMENT APPARATUS AND METHOD

FIELD OF THE INVENTION

[0001] The present invention relates to systems and methods for the treatment of exhaust from sources such as gasoline burning, diesel burning, natural gas burning, coal burning and wood burning devices, and plant stacks.

BACKGROUND OF THE INVENTION

[0002] It is generally acknowledged that it would be advantageous to reduce mankind's impact on the environment. To that end, many technologies have been proposed in an effort to reduce emissions from some sources such as gasoline burning, diesel burning, natural gas burning, coal burning and wood burning devices, and plant stacks. However, emissions continue to be a concern from both vehicular sources and plant sources alike. As a result, there is a continuing need to further reduce emissions from such sources.

SUMMARY OF THE INVENTION

[0003] In a first aspect, the invention is directed to an exhaust gas treatment apparatus that can be used to treat exhaust gas streams from vehicles having gasoline engines or diesel engines, from manufacturing plants, from incineration facilities, from coal fired stations, natural gas turbines or from virtually any exhaust gas stream. In one embodiment, the invention includes a particulate matter remover, a heat exchanger, a first reactor, a second reactor and a reagent protection device.

[0004] In a second aspect, the invention is directed to an exhaust gas treatment apparatus for treating an exhaust gas stream, comprising at least one reactor configured to receive the exhaust gas stream, wherein the at least one reactor includes a reagent solution holding section for holding a quantity of reagent solution, wherein the at least one reactor is configured to react the exhaust gas stream with the reagent solution, and a reagent solution protection device downstream from the at least one reactor and being configured for substantially preventing ambient air from being in fluid communication with the reagent solution holding section.

[0005] In a third aspect, the invention is directed to a heat exchanger including a plurality of tubes for transporting a first fluid and a shell for holding the plurality of tubes and for passing a second fluid around the plurality of tubes, wherein each tube has a tube wall that defines a tube interior, wherein the tube has a helical baffle in the tube interior that is configured to urge a fluid flowing therethrough towards the tube wall.

[0006] In a fourth aspect, the invention is directed to a reactor, comprising a reagent solution holding section for holding a quantity of reagent solution, and a reagent holding space adjacent the reagent solution holding section, wherein the reagent holding space is configured for receiving and loosely holding a solid block of reagent, wherein the reagent holding space has a bottom and has a passage at the bottom that is in fluid communication with the reagent solution holding section, so that, during use, solid reagent in the reagent holding space is exposed to reagent solution, thereby drawing solid reagent into solution.

[0007] In a fifth aspect, the invention is directed to a reactor, comprising an exhaust gas treatment apparatus for treating an exhaust gas stream. The apparatus includes a particulate matter remover configured to remove particulate matter from the exhaust gas stream. The apparatus further includes a heat exchanger downstream from the particulate matter remover and configured to condense at least some water vapour in the exhaust gas stream to produce condensate such that at least some gaseous contaminants in the exhaust gas stream dissolve in the condensate. The apparatus further includes a reactor downstream from the heat exchanger. During use, the reactor contains a reagent solution selected to reduce the concentration of at least some contaminants in the exhaust gas stream. The reactor has an exhaust gas stream inlet and an exhaust gas stream outlet. During use, gas pressure in the reactor is higher than ambient air pressure so as to substantially prevent ambient air from communicating with the reagent solution during use. The apparatus further includes a reagent protection device configured to prevent ambient air from communicating with the reagent solution when the gas pressure in the reactor is not higher than ambient air pressure.

[0008] In a sixth aspect, the invention is directed to a method of operating an exhaust gas treatment apparatus, comprising: a. introducing an exhaust gas stream; b. removing particulate matter from the exhaust gas stream; c. cooling the exhaust gas stream to condense out at least some water vapour from the exhaust gas stream to form condensate, wherein the condensate dissolves at least some gaseous contaminants from the exhaust gas stream after step b; d. exposing the exhaust gas stream to a reagent solution and neutralizing at least some contaminants in the exhaust gas stream thereby after step c; e. discharging the exhaust gas stream to atmosphere after step d; f. stopping the exhaust gas stream; and g. preventing exposure of the reagent solution to ambient air after step f.

[0009] In a seventh aspect, the invention is directed to an exhaust gas treatment apparatus for treating an exhaust gas stream. The apparatus includes a particulate matter remover configured to remove particulate matter from the exhaust gas stream. The apparatus further includes a heat exchanger downstream from the particulate matter remover and configured to condense at least some water vapour in the exhaust gas stream to produce condensate such that at least some gaseous contaminants in the exhaust gas stream dissolve in the condensate. The apparatus further includes an upstream reactor that is downstream from the heat exchanger. The upstream reactor contains an upstream reagent solution selected to reduce the concentration of at least one contaminant selected from the group consisting of: chlorides, fluorides, nitrates, nitrites and sulfates. The apparatus further includes a downstream reactor downstream from the upstream reactor. The downstream reactor contains a downstream reagent solution selected to reduce the concentration of at least one contaminant selected from the group consisting of NOx and CO2, wherein the downstream reactor has an exhaust gas stream inlet and an exhaust gas stream outlet. During use, gas pressure in the downstream reactor is higher than ambient air pressure so as to substantially prevent ambient air from communicating with the downstream reagent solution during use. The apparatus further includes a reagent protection device configured to prevent ambient air from communicating with the downstream reagent solution when the gas pressure in the downstream reactor is not higher than ambient air pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention will now be described by way of example only with reference to the attached drawings, in which:

[0011] Figure 1 is a plan view of an exhaust gas stream treatment apparatus in accordance with an embodiment of the present invention;

[0012] Figure 2 is a magnified sectional view of particulate matter remover that is part of the apparatus shown in Figure 1 ; [0013] Figure 3 is a further magnified perspective view of an air deflector that is shown in Figure 2;

[0014] Figure 4 is perspective view of mesh packing element shown in Figure 2;

[0015] Figure 5 is a further magnified sectional elevation view of an injector shown in Figure 2; [0016] Figure 6 is a magnified sectional elevation view of a heat exchanger shown in Figure 1 ;

[0017] Figure 7 is another magnified sectional view of the heat exchanger shown in Figure 1 ; [0018] Figure 8 is an magnified elevation view of components that support the heat exchanger shown in Figure 1 ;

[0019] Figure 9 is a magnified sectional elevation view of first and second reactors shown in Figure 1 ;

[0020] Figure 10 is a perspective view of solid block of first reagent shown in Figure 9;

[0021] Figure 11 is a perspective view of solid block of second reagent shown in Figure 9;

[0022] Figure 12 is a magnified elevation view of a damper shown in

Figure 1 ; [0023] Figure 13 is a magnified sectional view of the damper shown in Figure 1 ;

[0024] Figure 14 is another magnified sectional view of the damper shown in Figure 1 ;

[0025] Figure 15 is a sectional plan view of an optional cooling room for use as part of the apparatus shown in Figure 1 ;

[0026] Figure 16 is a magnified elevation view of a bank of catalysts shown in Figure 15;

[0027] Figure 17 is an elevation view of a turbine that is optionally provided as part of the apparatus shown in Figure 1 ; [0028] Figure 18 is a perspective view of an optional feature on the reactors shown in Figure 8; and

[0029] Figure 19 is a sectional elevation view of one of the reactors shown in Figure 8. DETAILED DESCRIPTION OF THE INVENTION

[0030] Reference is made to Figure 1 , which shows an exhaust gas treatment apparatus 200 in accordance with an embodiment of the present invention. The exhaust gas treatment apparatus 200 includes a particulate matter remover 1 , a heat exchanger 2, a first, or upstream, reactor 3, a second, or downstream, reactor 4 and a reagent isolation device 23. The exhaust gas treatment apparatus 200 has an inlet 202 for receiving an exhaust gas stream 204 (which may be referred to simply as the gas stream 204) from a source (not shown) such as a gasoline burning, diesel burning, natural gas burning, coal burning or wood burning device, or a plant stack. The exhaust gas treatment apparatus 200 treats the exhaust gas stream 204 to reduce the level of numerous contaminants that may be contained in the exhaust gas stream 204, such as NOx, SOx, CO, CO2, particulate matter, soot and other harmful and/or undesirable contaminants, and discharges the cleaned exhaust gas stream from an outlet 206.

[0031] Reference is made to Figure 2, which shows the particulate matter remover 1 in more detail. The particulate matter remover 1 removes particulate matter shown at 208, from the exhaust gas stream 204. The particulate matter remover 1 includes a housing 26. Within the housing there is, in series, a first catalytic converter element 33a, a mesh packing section 210, and a second catalytic converter element 33b. The first catalytic converter element 33a pre-treats the exhaust gas stream 204 to reduce the level of hydrocarbons, NOx and CO (by conversion to CO2) in the gas stream 204. [0032] The mesh packing section 210 includes a helical flow conduit

212, which may be defined by any suitable means, such as, for example, an auger 31. One or more mesh packing members 30 may be positioned in the helical flow conduit 212. In the exemplary embodiment shown in Figure 2, two packing members 30 are provided in series. A mixture 213 of water 222 and a water soluble oil 214 is provided in the packing members 30. The mixture 213 may be, for example, Super Filter Coat spray by Research Products Corporation in Madison, Wisconsin, USA. The mixture 213 is sprayed onto the mesh packing elements 30 from an injector 29. Oil 214 from the mixture 213 is caught by and dwells in the mesh packing elements 30 for some period of time. When the gas stream 204 encounters the mesh packing elements 30, the oil 214 entraps particulate matter 208 that may be entrained in the gas stream 204 and retains the particulate matter 208.

[0033] Beneath the helical flow conduit 212 there is a particulate separation chamber 216 having an upper chamber portion 218 and a lower chamber portion 37 and having a separator member 38 therebetween. The separator member 38 has apertures 220 therethrough permitting fluid communication between the upper and lower chamber portions 218 and 37. The apertures 220 may be of any suitable size or diameter (for circular holes), such as, for example, 1/8 inch. The separator member 38 may be made by any suitable means, such as, from a perforated plate or from a mesh screen material. A perforated plate is preferable. [0034] In use, some of the oil 214 that is present in the mesh packing members 30 leaves them and, along with some of the gas stream 204 enters into the particulate separation chamber 216. At least some of the oil 214 and the particulate matter 208 entrapped therein pass through the apertures 220 and into the lower chamber portion 37, which itself is a particulate collection chamber. The gas stream 204 can pass relatively easily from the lower chamber portion 37 back up into the upper chamber portion 218, however, any oil 214 and particulate matter 208 are inhibited from returning to the upper chamber portion 218 due at least in part to gravity and lack of flow velocity in the gas stream 204 leaving the lower chamber portion 237 thereby inhibiting entrainment of the oil 214 and particulate matter 208.

[0035] A drain 35 is provided for the lower chamber portion 37 so as to permit the draining of collected oil 214 and particulate matter 208 on a suitable periodic basis. Additionally, a flange joint 36 may be provided at the interface between the upper and lower chamber portions 218 and 37 to provide access to the mesh packing members 30, to facilitate cleaning of the separator member 38 and the upper and lower chamber portions 218 and 37 generally if necessary.

[0036] A set of one or more gas deflectors 34 may be provided in the particulate separation chamber 216 so as to deflect a portion of the gas stream 204 therein upwards. It has been found that deflecting upwards some of the downwards-traveling gas stream 204 improves the performance of the mesh packing section 210 at removing particulate matter 208. The gas deflectors 34 may be configured as strips that extends downwards at a selected angle, and that have end portions 224 that are curled generally upwards so that exhaust gas 204 that is traveling downwards along the gas deflectors 34 is redirected upwards. This reduces the speed of the gas stream 204 in the particulate separating chamber 216, thereby facilitating separation of the oil 214 and particulate matter 208 from the gas stream 204. The end portions of the gas deflectors 34 may be provided with apertures 65 therethrough to permit oil 214 and particulate matter 208 to fall through thereby inhibiting the buildup of collected matter thereon.

[0037] The gas stream 204 entering the exhaust gas treatment apparatus 200 (Figure 1 ) may be at an elevated temperature and may not be saturated in terms of its water vapour content. As a result, some, and possibly all, of the water 222 that is injected into the gas stream 204 may vaporize.

[0038] The injector 29 may receive the mixture 213 of the oil 214 and water 222 from any suitable source, such as from a reservoir 7. The concentration of water 222 in the mixture 213 may be less than 10% by weight in order to reduce the likelihood of the mixture 213 freezing in cold weather. The concentration of water 222 in the mixture 213 may be higher than 10% (by weight) in warm climates. The presence of the water 222 controls the viscosity of the mixture 213 to facilitate pumping the mixture and spraying of the mixture 213 by the injector 29. A pump 27 may be provided for the delivery of the mixture 213 to the injector 29. A controller 8 may be provided to determine when to activate the injector 29 and pump 27 via electrical lines 39. [0039] Downstream from the mesh packing section 210 is the second catalytic converter element 33b. The second catalytic converter element 33b further removes contaminants from the gas stream 204, and removes hydrocarbons that are present in the gas stream 204 as a result of the injection of the oil 214.

[0040] The particulate matter remover 1 may substantially be made from a suitable stainless steel, aside from the catalytic converter elements 33a and 33b.

[0041] When the gas stream 204 leaves the particulate matter remover 1 , the levels of some gaseous contaminants, such as CO, will have been reduced, and the level of particulate matter has been reduced. CO will have largely been converted to CO2.

[0042] Downstream from the particulate matter remover 1 is a heat exchanger 2. The heat exchanger 2 cools the gas stream 204 enough to condense out some of the water vapour 224. The condensing of the water vapour 224 causes other contaminants to drop out from the gas stream 204. For example, nitrates may become trapped in the condensed water as nitric acid.

[0043] A condensate, shown at 226, collects at the bottom of the heat exchanger 2. The condensate 226 may be drained from the heat exchanger 2 through a heat exchanger drain conduit 228. A manual valve 15a may be provided in the drain conduit 228 for providing manual closure of the drain conduit 228 in the event that, for whatever reason, the heat exchanger 2 requires removal but still contains some condensate. Additionally, an automatic valve 16a may be provided to automatically control the draining of condensate 226. The condensate 226, which contains water and such dissolved contaminants as NOx, SOx and CO2, may be acidic, and may be used for purposes described further below in relation to the second reactor 4. [0044] Condensing out water vapour 224 may also assist in removing at least a portion of any remaining particulate matter 208 that is entrained in the gas stream 204.

[0045] The heat exchanger 2 may have any suitable configuration. For example, the heat exchanger 2 may be generally of a shell-and-tube configuration, having an upstream header 230, a shell and tube section 232, and a downstream header 49.

[0046] One or more baffles 44 may be provided in the upstream header 230 to disperse the gas stream 204 entering therein, thereby urging the gas stream to be more evenly distributed amongst the tubes, shown at 45, in the shell and tube section 232.

[0047] The shell and tube section 232 includes a shell portion 236 and the tubes 45. Coolant 47 is circulated through the shell portion 236 to cool the gas stream 204 passing through the tubes 45. The coolant 47 may be any suitable coolant, such as a liquid coolant.

[0048] The coolant 47 may be transported into and out of the shell portion 236 by a system of coolant transport conduits 42. A pump 12 is provided to drive the circulation of the coolant 47. A compressor 10 is provided to cool the coolant 47. A radiator 11 may also be provided to cool the coolant 47 where the coolant does not require the compressor 10, in order to use less energy when it is possible.

[0049] A controller 13 may be provided to control the operation of the compressor 10 and pump 12 via electrical lines 41. A temperature sensor 14 may be provided for reading the temperature of the gas stream 204 as it leaves the heat exchanger 2, and connected to the controller 13 to provide the temperature information thereto. The controller 13 could be any suitable type of controller, such as a microprocessor based controller, or such as a simple temperature control switch.

[0050] Each tube 45 may optionally be provided with an internal helical baffle 46 along its length. The helical baffle 46 provides a helical flow path to the gas stream 204 passing through the tube 45. The helical flow path causes the gas stream 204 to be urged towards the tube wall shown at 240 as a result of centrifugal force. By urging the gas stream 204 against the tube wall 240, more effective heat transfer can take place between the gas stream 240 and the coolant 47 in the shell portion 236 the gas stream 204 is more effectively cooled when passing through the tube 45. Additionally, the helical baffle 46 increases the friction on the gas stream 204 passing through the tube 45 and thus slows the gas stream 204 down, thereby increasing the amount of time the gas resides in the tube 45 to be cooled. [0051] In the downstream header 49, some of the condensate 226 that forms in the gas stream 204 drops out of the gas stream 204 and collects. A baffle 43 is provided in the floor of the downstream header 49 to hold a portion of the condensate 226 and guide it towards the drain conduit 228, and to inhibit the condensate 226 from leaving the heat exchanger 2 through the gas stream outlet conduit, shown at 242.

[0052] A baffle 48 is provided in the downstream header 49. The baffle 48 directs the gas stream 204 upwards away from the gas stream outlet conduit 242 so that the gas stream 204 gains further cooling from the walls of the downstream header 49, which are in contact with the coolant 47. After the further cooling takes place, the gas stream 204 and much of the condensate 226 entrained therein leaves the heat exchanger 2 through the gas stream outlet conduit 242. The baffle 48 may also serve to inhibit the gas stream 204 from leaving the heat exchanger 2 before having a chance to drop out entrained condensate 226. [0053] The gas stream 204 leaving the heat exchanger 2 includes some entrained water droplets with dissolved contaminants such as NOx, SOx and CO2 from having been cooled in the heat exchanger 2.

[0054] The heat exchanger 2 may be made from a suitable stainless steel. [0055] A tray 64 and associated drain 68 may be provided under the heat exchanger 2 to collect condensate that may form thereon from the extemal environment, for embodiments wherein the heat exchanger 2 is mounted in an area of a vehicle such as the trunk.

[0056] Referring to Figure 1 , downstream from the heat exchanger 2, and upstream from the second reactor 4 is the first, or upstream, reactor 3, which may reduce the levels of one or more of such contaminants as chlorides, fluorides, nitrates, nitrites, sulfates and particulate matter. The first reactor 3 is shown in more detail in Figure 9. The first reactor 3 has a reagent solution holding section 244 and a separation area 246. An inlet conduit 248 transports the gas stream 204 with entrained contaminants into the reagent solution holding section 244. The inlet conduit 248 may have a flared end 53 to assist in dispersing the gas stream 204 into a first reagent solution 250 held in the reagent solution holding section 244.

[0057] The first reagent solution 250 may be, for example, an aqueous solution of soda ash (ie. Sodium Carbonate) or some other suitable solution. The soda ash may be fed into the solution in any suitable way. For example, a solid block of soda ash, shown at 51a, may be provided in the reagent solution holding section 244. Additionally or alternatively, a generally C-shaped solid block, shown at 51 b (see Figure 10), may be provided around the outside of the reagent solution holding section 244. An opening 252 at the bottom of the wall 254 that defines the reagent solution holding section 244 exposes the C-shaped solid block 51 b to the solution, thereby keeping the solution fed with solid reagent.

[0058] The C-shaped solid block 51 b is loosely held in a reagent holding space 256, which may be a hollow cylindrical space 256 that surrounds the reagent solution holding section 244, and that is defined by the wall 254 and an outer wall 258.

[0059] As the bottommost portion of the C-shaped solid block 51b is consumed, it preferably slides downward to present more solid reagent at the opening 252 for feeding into solution. [0060] The C-shaped solid block 51b has a longitudinal channel 260

(Figure 10). The channel 260 permits the solid block 51b to clear components 19a and 66 (Figure 9) that are mounted to the wall 254.

[0061] A flange joint 20a may be provided to permit the first reactor 3 to be opened, for any maintenance purposes, and for replacement of the solid blocks 51a and 51 b as necessary.

[0062] A drain conduit 66a is provided so that some first reagent solution 250 is continuously drained off. New reagent is introduced, as described above, via the solid blocks 51a and 51 b. This permits the first reagent solution 250 to be maintained in a state where it can react as needed with the incoming gas stream 204. A water intake port shown at 19a is provided for replenishing the first reactor 3 with water as necessary. For example, water may need to be fed periodically into the first reactor 3 to make up for water lost from drainage through drain line 66a. Water may additionally be fed to the water intake port 19a during the addition of one or both blocks of soda ash 51a and 51 b. During operation, however, a significant amount of water may come in the form of entrained droplets in the gas stream 204 itself.

[0063] The flow of first reagent solution 250 through drain conduit 66a may be controlled by an automatic valve 16b, which may be controlled by any suitable means. The drain conduit 66a extends down to an effluent collection tank 5, where effluent is held. Periodically the effluent collection tank 5 may be drained or otherwise emptied. The draining or emptying may be done manually or by automatic means. For example, a quick disconnect coupling (not shown) may be provided on the tank 5, that can periodically receive a hose (not shown) for draining the tank 5. The effluent that may be formed in the effluent collection tank 5 may itself have some use. For example, the effluent may be treated to separate out its water content, during which some chemicals may be separated off. For example, it is contemplated that chemicals that are useful as a fertilizer may be separated off. [0064] The first reactor 3 may further include a manual drain valve

22a for manually draining the first reactor 3 of any liquid prior to opening the flange joint 20a.

[0065] As the gas stream 204 reacts with the first reagent solution 250 bubbles 261 form. When the gas stream 204 leaves the first reagent solution 250, it brings with it bubbles 261. The gas stream 204 and bubbles 261 pass upwards through the separation section 246, where the gas encounters a plurality of apertured members 262 which break the bubbles

261 thereby separating the liquid from the gas stream 204. [0066] The apertured members 262 have apertures 264 and may be, for example, apertured plates, or screens. Some of the apertured members

262 may have the same size apertures 264. A first apertured member, shown at 262a may have apertures 264 that are about 3/32 inch. The first apertured member 262a is oriented generally horizontally. In the embodiment shown in Figure 9, above the first apertured member 262a are ten other apertured members 262. The apertures 264 on the second, third and fourth members, identified as 262b may be about 1/8 inch. The apertures 264 on the fifth, sixth and seventh members, identified as 262c, may be about 3/16 inch. The apertures 264 on the eighth, ninth and tenth members, identified as 262d may be about 3/8 inch. The apertures 264 on the eleventh member, identified as 262e may be about 3/32 inch. At least some of the apertured members 262 may be arranged in a series wherein at least some alternate between horizontal and angled orientations. The non parallel arrangement inhibits the gas stream 204 from flowing in a purely linear path up through the separation section 246, and increases the degree of contact that takes place between the apertured members 262 and the gas stream 204 and bubbles 261.

[0067] Baffles 54a and 50a are provided above the separation section

246 to control the gas stream 204 to prevent portions of the gas stream 204 from being preferentially exhausted through the outlet 266, and to inhibit the presence of any dead zones of reduced flow. [0068] Quick release couplings 17 are provided at the inlet, shown at

270, and the outlet 266 of the first reactor 3, to facilitate removal of the reactor 3 from the conduit shown at 272 leading from the heat exchanger 2 (Figure 1 ), and from the transfer conduit 266, for maintenance purposes. A suitable quick disconnect coupling (not shown) may also be provided on the drain conduit 66a for this purpose. The quick release couplings 17 permit the first reactor 3 to be replaced quickly with a fresh first reactor 3, thereby permitting a vehicle to be returned to operation quickly. Whatever cleaning or other maintenance needs to be carried out on the removed first reactor 3 can then be carried out without causing delay in returning the vehicle to operation.

[0069] The first reactor 3 may be made from a suitable polymeric material or a suitable metal such as steel, though the apertured members 262a-k may be made from a suitable polymeric material or a suitable metal, such as a suitable steel.

[0070] The gas stream 204 leaves the first reactor 3 through the outlet 266 and into a transfer conduit 268 that leads to an inlet 274 to the second reactor 4. The second reactor 4 includes a reagent solution holding section 276 and a separation section 278. An inlet conduit 280 that extends downwards into the second reactor 4 ends at an outlet section 58 in the reagent solution holding section 276. The outlet section 58 is apertured, with apertures that are sized to promote the release of gas from the gas stream 204 in the form of suitably sized bubbles 282 into a second reagent solution 57, which may be a solution that is 50% by weight potassium hydroxide (KOH) and 50% water, or some other suitable solution. The outlet section 58 may be, for example, a micro-screen. The outlet section 58 preferably has at least about two times the surface area as the cross- sectional surface area of the inlet conduit 280 to reduce any backpressure that is created at the exhaust source (eg. the engine). The bubbles 282 react with the second reagent solution 57 in an exothermic reaction, which removes some contaminants, such as at least some NOx and CO2 from the gas stream 204. [0071] The effectiveness of the second reactor 4 at removing NOx and CO2 in particular is significantly improved by the presence of the first reactor 3, which removes contaminants, such as chlorides, fluorides, nitrites and sulfates, among others, at least some of which would significantly reduce the effectiveness of the second reactor 4 if they weren't removed or reduced in concentration in the first reactor 3.

[0072] The bubbles 282 rise and grasp the contaminants and the gas stream 204 leaves the second reagent solution 57 and enters the separation section 278 where the gas stream 204 passes through a series of apertured members 284. In the embodiment shown in Figure 9, there may be 11 apertured members 284 in total. The apertured members 284 may be similar to the apertured members 262. The bubbles 282 break down on the apertured members 284 thereby separating the gas stream 204 from the bubbles 282. The lowermost apertured member, shown as 284a, may be positioned about 1/2 inch to 3/4 inch above the highest point of the outlet section 58.

[0073] The apertured members 284 may be arranged so that at least some of them are at an angle relative to another that is immediately above or immediately below, so as to inhibit the gas stream 204 from flowing in a purely linear path up through the separation section 278, which in turn increases the degree of contact that takes place between the apertured members 284 and the gas stream 204 and bubbles 282.

[0074] Baffles 54b and 50b are provided above the separation section

278 to control the gas stream 204 to prevent portions of the gas stream 204 from being preferentially exhausted through the outlet, shown at 287, and to inhibit the presence of any dead zones of reduced flow.

[0075] Quick release couplings 17 are provided at the inlet, shown at

288, and the outlet 287 of the second reactor 4, to facilitate removal of the reactor 4 from the transfer conduit shown at 266 leading from the first reactor 3, and from the outlet conduit 289, for maintenance purposes. A suitable quick disconnect coupling (not shown) may also be provided on the drain conduit 66a for this purpose. The quick release couplings 17 permit the second reactor 4 to be replaced quickly with a fresh second reactor 4, thereby permitting a vehicle to be returned to operation quickly. Whatever cleaning or other maintenance needs to be carried out on the removed second reactor 4 can then be carried out without causing delay in returning the vehicle to operation.

[0076] The potassium hydroxide may be provided in the form of a C- shaped solid block, shown at 56 (see Figure 11 ). The C-shaped solid block 56 may be similar to the C-shaped solid block of soda ash 51 in Figure 10 and may thus have a longitudinal channel 290 that permits the block 56 of potassium hydroxide to clear a water intake port 19b and a drain conduit 66b that are mounted on the second reactor 4.

[0077] An opening 291 at the bottom of the wall 292 that defines the reagent solution holding section 276 exposes the C-shaped solid block 56 to the solution, thereby keeping the solution fed with solid reagent. [0078] The C-shaped solid block 56 is loosely held in a reagent holding space 294, which may be a hollow cylindrical space 294 that surrounds the reagent solution holding section 276, and that is defined by the wall 292 and an outer wall 296.

[0079] As the bottommost portion of the C-shaped solid block 56 is consumed, it preferably slides downward to present more solid reagent at the opening 291 for feeding into solution.

[0080] A flange joint 20b may be provided to permit the second reactor 4 to be opened, for any maintenance purposes, and for replacement of the solid block 56 as necessary. [0081] The drain conduit 66b is provided so that some second reagent solution 257 is continuously drained off. New reagent is introduced, as described above, via the solid block 56. This permits the second reagent solution 57 to be maintained in a state where it can react as needed with the incoming gas stream 204. The water intake port shown at 19b is provided for replenishing the second reactor 4 with water as necessary. For example, water may need to be fed periodically into the first reactor 3 to make up for water lost from drainage through drain line 66a.

[0082] The flow of second reagent solution 57 through drain conduit

66b may be controlled by a third automatic valve 16c, which may be controlled by any suitable means.

[0083] The drain conduit 66b extends to a mixing tank 21.

Additionally, the drain conduit 228 (Figure 1 ) extends from the heat exchanger 2 to the mixing tank 21 , so that drained reagent solution 57 and drained condensate 226 (Figure 6) can mix. Because the condensate 226 (Figure 6) is acidic and the reagent solution 57 is basic, mixing of the two will serve to neutralize both at least to some degree. A mixing tank drain conduit 298 connects the mixing tank 21 to the effluent collection tank 5.

[0084] The effluent that is collected in the effluent collection tank 5 may have a relatively high solids content, and may essentially be in solid form (in the form of particles).

[0085] The second reactor 4 may further include a manual drain valve

22b for manually draining the second reactor 4 of any liquid prior to opening the flange joint 20b.

[0086] The second reactor 4 may be made from a suitable polymeric material or a suitable metal, such as steel, though the apertured members 284a-k may be made from a suitable polymeric material or a suitable metal, such as a suitable steel.

[0087] Referring to Figure 9, a one way intake valve 18 may be provided on the transfer conduit 268 between the first and second reactors 3 and 4. The one way intake valve 18 permits ambient air to enter the transfer conduit 266 in the event that there is a sufficiently high pressure differential between the two reactors 3 and 4. In the event of a sufficiently high pressure differential between the two reactors 3 and 4, such as might occur during sufficiently hard acceleration, braking or cornering, there is an increased risk that reagent solution from one of the reactors 3 or 4 (the one at relatively higher pressure) could spill over into the other of the reactors 3 or 4. By permitting ambient air to enter the transfer conduit 268, any pressure differential is at least reduced thereby reducing the risk of spill.

[0088] During use, gas pressure in the second reactor 4 is higher than ambient air pressure, thereby substantially preventing ambient air from communicating with the second reagent solution 57. If ambient air were permitted to be in fluid communication with the second reagent solution 57 then the reagent would quickly neutralize through reaction with gaseous components of the ambient air. When the exhaust gas treatment apparatus 200 is not in use, however, the gas pressure in the second reactor 4 may possibly not be higher than ambient air pressure. Referring to Figure 1 , a reagent protection device 300 is provided downstream from the second reactor 4, which substantially prevents ambient air from entering the outlet 206 and reacting with the second reagent solution 57 when the apparatus 200 is not operating. [0089] The reagent protection device 300 may be any suitable device, such as, for example, a motor-driven damper 23 (Figure 14). The damper 23 includes a damper blade 61 , a seal 59, mounting brackets for the damper blade 61 , a motor mount 60 and a motor 302. When the exhaust gas treatment apparatus 200 is not in operation, the damper 23 is moved to a closed position wherein it seals against the seal 59 so that ambient air is substantially prevented from being in fluid communication with the second reagent solution 57. When an exhaust gas stream 204 is being generated, (eg. when a vehicle ignition key is inserted into the ignition keyhole on the vehicle dashboard or on the vehicle's steering column in embodiments wherein the apparatus 200 is vehicle mounted) the damper 23 opens automatically (ie. moves to an open position) permitting the gas stream 204 to pass therethrough from the second reactor 4 and out to atmosphere. It will be noted that by linking the damper 23 to the vehicle key, the damper 23 functions as a theft deterrent, since the vehicle's operation would be prevented if the exhaust were sealed off. [0090] The damper 23 could alternatively be any other suitable device for protecting the second reagent solution. For example, the damper 23 could be replaced by some suitable type of valve.

[0091] With reference to Figure 1 , in an exemplary embodiment for vehicular use, selected dimensions for the system 10 are provided as follows: For a vehicular exhaust pipe that is 1 1/4 inch in diameter, the particulate matter remover 1 may employ a 2 inch diameter auger 31 with a 2 inch flight pitch. A 2 inch diameter conduit would lead from the particulate matter remover 1 to the heat exchanger 2. The heat exchanger 2 may have a diameter of 6 inches and a length of about 10 inches. A 2 inch diameter conduit may carry the gas stream 204 from the heat exchanger 2 to the first reactor 3. It will be noted that the backpressure created by this aforementioned selection of dimensions is not so great as to significantly hamper the function of the vehicle's engine, but is not so low that the gas stream 204 passes through the system 10 too quickly without a usefully significant removal of contaminants.

[0092] Reference is made to Figure 15 which shows an optionally provided cooling room 70 that may be used in embodiments wherein the gas stream 204 is coming from a source such as a production plant, an incineration facility or a generating station such as a coal-fired generating station. In such situations, the gas stream 204 may be relatively hot. The cooling room 70 houses a conduit 77 that has a gas inlet 74. The gas stream 204 passes from the inlet 74 to a series of baffles 76. The gas stream 204 may be directed through a generally serpentine flow path by the baffles 76. Suitable deflectors 72 may be provided to assist the flow of the gas stream 204. The conduit 77, baffles 76 and deflectors 72 may be made from any suitable material, such as a temperature resistant steel. The room 70 may include a roof and may be steel-encased.

[0093] At the gas outlet 73 of the cooling room 70 there is positioned a bank 75 of catalysts 78 (Figure 16) which receive the cooled gas stream

204 and remove contaminants therefrom. After the gas stream 204 (Figure

15) leaves the bank 75 of catalysts 78 (Figure 16), the gas stream 204 may pass through a turbine 79 (Figure 17) for the purpose of rotating the turbine 79. The rotational energy in the turbine 79 may be used for any suitable purpose, such as for the generation of electricity by providing a generator (not shown) that is connected to the output shaft 80 of the turbine 79. [0094] Reference is made to Figure 18, which shows an optional feature provided at the top of one or both of the first and second reactors 3 for facilitating the loading of a C-shaped solid block of reagent 51 b or 56 into the reactor 3 or 4. A C-shaped cover plate 81 is provided, and is mounted to cover and seal a C-shaped aperture 304 on an annular shoulder 604 above the hollow cylindrical space 256 or 294 in the reactor 3 or 4 to substantially prevent the influx of ambient air into the reactor 3 or 4. In the hollow cylindrical space 256 or 294, spaced below the C-shaped aperture 304, a pair of overlapping flexible seal members 82a and 82b are provided. When the cover plate 81 is opened, the seal members 82a and 82b seal the reactor 3 or 4 off, inhibiting ambient air from being in fluid communication with the reagent solution 244 or 57. As the C-shaped solid block of reagent 51 b or 56 is lowered down, the seal members 82a and 82b seal against it to inhibit ambient air from entering the reactor 3 or 4. Once the C-shaped solid block 51 b or 56 is in place, the seal members 82a and 82b close and the cover plate 81 may be reinstalled.

[0095] Reference is made to Figure 1. The components shown in

Figure 1 are exemplary components that permit one to carry out a method of operating an exhaust gas treatment apparatus, such as for example, the exhaust gas treatment apparatus 200. In a first step an exhaust gas stream may be introduced. In another step particulate matter may be removed from the exhaust gas stream. The particular matter may be removed by any suitable device (eg. the particulate matter remover 1 ), and may be removed by more than one device (eg. the particulate matter remover 1 and the heat exchanger 2). In another step, the exhaust gas stream may be cooled to condense out at least some water vapour from the exhaust gas stream to form condensate. The condensate dissolves at least some gaseous contaminants from the exhaust gas stream. In another step, the exhaust gas stream is exposed to a reagent solution to reduce the concentration of at least some contaminants in the exhaust gas stream thereby after the aforementioned cooling step. In another step, the exhaust gas stream is discharged to atmosphere after being exposed to the reagent solution. In another step, the exhaust gas stream is stopped. Another step entails preventing exposure of the reagent solution to ambient air so as to protect the reagent solution.

[0096] Several optional steps may be included in the aforementioned method. For example, the reagent solution may be a downstream reagent solution, and wherein the method may further comprise exposing the exhaust gas stream to an upstream reagent solution prior to exposure to the downstream reagent solution. The upstream reagent solution is selected to reduce the concentration in the exhaust gas stream of at least one contaminant selected from the group consisting of: chlorides, fluorides, nitrates, nitrites and sulfates. The downstream reagent solution is selected to reduce the concentration in the exhaust gas stream of at least one contaminant selected from the group consisting of NOx and CO2.

[0097] In the step wherein the exhaust gas stream is exposed to the reagent solution the method may further include causing bubbling of the exhaust gas stream in the reagent solution.

[0098] In the step wherein the exhaust gas stream is cooled, the method may further include capturing at least portion of the condensate, and the method may further include mixing a selected amount of the captured condensate with a selected amount of the reagent solution. The condensate is acidic and the reagent solution is basic.

[0099] In this disclosure, the term 'ambient air pressure' means air pressure of air outside the apparatus 200. The term 'atmosphere' refers to the air outside the apparatus 200.

[00100] While two reactors (ie. reactors 3 and 4) have been disclosed as being part of the apparatus 200, it is optionally possible to have fewer

(eg. reactor 3 only, or reactor 4 only) as part of the apparatus 200. It is also optionally possible to have three or more reactors. For example, it is optionally possible to add one or more reactors at some suitable position, (eg. downstream from the second reactor 4), that remove methanol and formaldehyde from the exhaust gas stream 204. Such reactors may have any suitable structure, and may be similar to the reactors 3 and 4.

[00101] While the above description constitutes a plurality of embodiments of the present invention, it will be appreciated that the present invention is susceptible to further modification and change without departing from the fair meaning of the accompanying claims.

Claims

Claims:

1. An exhaust gas treatment apparatus for treating an exhaust gas stream, comprising: a particulate matter remover configured to remove particulate matter from the exhaust gas stream; a heat exchanger downstream from the particulate matter remover and configured to condense at least some water vapour in the exhaust gas stream to produce condensate such that at least some gaseous contaminants in the exhaust gas stream dissolve in the condensate; a reactor downstream from the heat exchanger, wherein, during use, the reactor contains a reagent solution selected to reduce the concentration of at least some contaminants in the exhaust gas stream, wherein the reactor has an exhaust gas stream inlet and an exhaust gas stream outlet, wherein, during use, gas pressure in the reactor is higher than ambient air pressure so as to substantially prevent ambient air from communicating with the reagent solution during use; and a reagent protection device configured to prevent ambient air from communicating with the reagent solution when the gas pressure in the reactor is not higher than ambient air pressure.

2. An exhaust gas treatment apparatus as claimed in claim 1 , wherein the reactor is a downstream reactor and wherein the reagent solution is a downstream reagent solution, and wherein the exhaust gas treatment apparatus further comprises an upstream reactor that is upstream from the downstream reactor and that is downstream from the heat exchanger, wherein, during use, the upstream reactor contains an upstream reagent solution selected to reduce the concentration in the exhaust gas stream of at least one contaminant selected from the group consisting of: chlorides, fluorides, nitrates, nitrites and sulfates, and wherein the downstream reagent solution is selected to reduce the concentration in the exhaust gas stream of at least one contaminant selected from the group consisting of NOx and CO2.

3. An exhaust gas treatment apparatus as claimed in claim 2, wherein the downstream reagent solution includes KOH.

4. An exhaust gas treatment apparatus as claimed in claim 3, wherein the upstream reagent solution includes Sodium Carbonate.

5. An exhaust gas treatment apparatus as claimed in claim 2, wherein the downstream reactor has an inlet conduit for the exhaust gas stream and wherein the inlet conduit has an outlet section that, during use, is immersed in the downstream reagent solution, wherein the outlet section is apertured to induce the exhaust gas stream to form bubbles in the downstream reagent solution.

6. An exhaust gas treatment apparatus as claimed in claim 5, wherein the downstream reactor includes a downstream reactor separation section, wherein the downstream reactor separation section includes at least one downstream reactor separation section apertured member configured for breaking bubbles leaving the downstream reagent solution in the exhaust gas stream.

7. An exhaust gas treatment apparatus as claimed in claim 2, wherein the upstream reactor includes an upstream reactor separation section, wherein the upstream reactor separation section includes at least one upstream reactor separation section apertured member configured for breaking bubbles leaving the upstream reagent solution in the exhaust gas stream.

8. An exhaust gas treatment apparatus as claimed in claim 1 , wherein the reactor further includes a reagent holding space configured for loosely holding a solid block of reagent, wherein the reagent holding space has a bottom and a reagent holding space outlet at the bottom, wherein the reagent holding space outlet, during use, is immersed in the reagent solution so as to expose a lower portion of the solid block of reagent to the reagent solution.

9. An exhaust gas treatment apparatus as claimed in claim 1 , wherein the heat exchanger is configured to capture at least a portion of the condensate formed therein, and wherein the exhaust gas treatment apparatus further comprises a mixing tank, wherein a reactor drain conduit connects the reactor to the mixing tank to permit a selected amount of reagent solution to drain from the reactor to the mixing tank during use, wherein a heat exchanger drain conduit connects the heat exchanger to the mixing tank to permit captured condensate to drain from the heat exchanger to the mixing tank, wherein the condensate is acidic and wherein the reagent solution is basic.

10. An exhaust gas treatment apparatus as claimed in claim 9, further comprising an effluent collection tank, wherein a mixing tank drain conduit connects the mixing tank to the effluent collection tank to permit draining of mixed condensate and reagent solution into the effluent collection tank.

11. An exhaust gas treatment apparatus as claimed in claim 1 , wherein the reagent protection device includes a damper that is movable between a closed position wherein the reagent protection device substantially prevents ambient air from communicating with the solution of reagent and an open position wherein the reagent protection device permits the exhaust gas stream to pass through the reactor.

12. A method of operating an exhaust gas treatment apparatus, comprising: a. introducing an exhaust gas stream; b. removing particulate matter from the exhaust gas stream; c. cooling the exhaust gas stream to condense out at least some water vapour from the exhaust gas stream to form condensate, wherein the condensate dissolves at least some gaseous contaminants from the exhaust gas stream after step b; d. exposing the exhaust gas stream to a reagent solution and neutralizing at least some contaminants in the exhaust gas stream thereby after step c; e. discharging the exhaust gas stream to atmosphere after step d; f. stopping the exhaust gas stream; and g. preventing exposure of the reagent solution to ambient air after step f.

13. A method of operating an exhaust gas treatment apparatus as claimed in claim 12, wherein the reagent solution is a downstream reagent solution, and wherein the method further comprises exposing the exhaust gas stream to an upstream reagent solution prior to step d, wherein the upstream reagent solution is selected to reduce the concentration in the exhaust gas stream of at least one contaminant selected from the group consisting of: chlorides, fluorides, nitrates, nitrites and sulfates, and wherein the downstream reagent solution is selected to reduce the concentration in the exhaust gas stream of at least one contaminant selected from the group consisting of NOx and CO2.

14. A method of operating an exhaust gas treatment apparatus as claimed in claim 13, wherein the downstream reagent solution includes KOH.

15. A method of operating an exhaust gas treatment apparatus as claimed in claim 14, wherein the upstream reagent solution includes Sodium Carbonate.

16. A method of operating an exhaust gas treatment apparatus as claimed in claim 13, wherein step d includes causing bubbling of the exhaust gas stream in the downstream reagent solution.

17. A method of operating an exhaust gas treatment apparatus as claimed in claim 12, further comprising: h. capturing at least portion of the condensate formed during step c; and i. mixing a selected amount of the condensate captured in step h with a selected amount of reagent solution used in step d, wherein the condensate is acidic and wherein the reagent solution is basic.

18. An exhaust gas treatment apparatus for treating an exhaust gas stream, comprising: a particulate matter remover configured to remove particulate matter from the exhaust gas stream; a heat exchanger downstream from the particulate matter remover and configured to condense at least some water vapour in the exhaust gas stream to produce condensate such that at least some gaseous contaminants in the exhaust gas stream dissolve in the condensate; an upstream reactor that is downstream from the heat exchanger, wherein the upstream reactor contains an upstream reagent solution selected to reduce the concentration of at least one contaminant selected from the group consisting of: chlorides, fluorides, nitrates, nitrites and sulfates; a downstream reactor downstream from the upstream reactor, wherein the downstream reactor contains a downstream reagent solution selected to reduce the concentration of at least one contaminant selected from the group consisting of NOx and CO2, wherein the downstream reactor has an exhaust gas stream inlet and an exhaust gas stream outlet, wherein, during use, gas pressure in the downstream reactor is higher than ambient air pressure so as to substantially prevent ambient air from communicating with the downstream reagent solution during use; and a reagent protection device configured to prevent ambient air from communicating with the downstream reagent solution when the gas pressure in the downstream reactor is not higher than ambient air pressure.

19. A heat exchanger including a plurality of tubes for transporting a first fluid, and a shell for holding the plurality of tubes and for passing a second fluid around the plurality of tubes, wherein each tube has a tube wall that defines a tube interior, wherein the tube has a helical baffle in the tube interior that is configured to urge a fluid flowing therethrough towards the tube wall.

20. A reactor, comprising: a reagent solution holding section for holding a quantity of reagent solution; and a reagent holding space adjacent the reagent solution holding section, wherein the reagent holding space is configured for receiving and loosely holding a solid block of reagent, wherein the reagent holding space has a bottom and has a passage at the bottom that is in fluid communication with the reagent solution holding section, such that, during use, solid reagent in the reagent holding space is exposed to reagent solution.