METHOD AND DEVICE FOR THE PURIFICATION OF EXHAUST GASES

Abstract: The exhaust gas purification device (101) comprises a tight-closed vessel (102) provided with an inlet port (106) and an outlet port (108), both ports being connected to respective intake and exhaust manifolds. A rotary drum (109) is housed in the vessel (102). The rotary drum is mounted idle in the vessel (102). Alternatively, the drum (109) may be provided with motor means. The drum (109) consists of a central hub (110) and a number of vanes (111) projecting radially from the hub (110) and extending vertically. The vessel (102) is filled with a mass of water at a level at least sufficient to cover completely the inlet port (106). Removable filtering layers (113) are provided between a side wall (104) and a cover (105).

Description: Method and device for the purification of exhaust gases DESCRIPTION The present invention relates to the purification of exhaust gases. It is suitable in particular, but not exclusively, to clean gases from processes of combustion of heavy hydrocarbons, fossil and vegetable fuels, both in fixed plants and in automotives, as well as gases from non- combustion chemical processes such as photographic processes and laundry processes . The need of reducing as much as possible the presence of pollutants in exhaust gases, before their release in the air, is well known. Well known are also numerous methods and devices for the more or less effective purification of gases . Devices and processes are known that make use of a mass of water to be passed through by the gases to be treated. While the gases passes through the water, many pollutants are retained by the water. Devices of this kind are disclosed, for example, in EP-A- 0282682, GB-A-641399, GB-A-664317, FR-A-2369416 , FR-A-1411, US-A-3340859, US-A-3768981 , US-A-1892853 , FR-A-1004132 , GB- A-2135208. The more intimate is the mixing of water and gases, the more effective is the cleaning action. However, the more intimate is the mixing, the more difficult is the separation of water from gases before releasing them from the purification device. For this reason the devices disclosed in the above mentioned documents are not very satisfactory: unless they are fed with low pressure gases (i.e. with small amounts of gases), they tend to expell a great quantity of water together with the gases. For sufficient high pressure of the incoming gases, water can even be totally expelled. Water separation means provided by some of the devices can not be sufficient to separate such a huge quantity of water. Object of this invention is to provide a device and a method for the purification of gases by means of a water mass, wherein the risk of expulsion of water together with the purified gases is substantially reduced, without affecting the capability of treating relatively large amount of high pressure gases. Therefore, in a first aspect, this invention relates to amethod for the purification of exhaust gases, causing gases to pass through a water mass, characterised by circulating the water mass in a purification vessel under turbolent motion. Circulation of the water mass under turbolent motion not only facilitates the mixing between water and gases to be cleaned; it has also be found that under such conditions the water mass tends to remain in the purification vessel rather than to be expelled with the gases. Generally, this method may be advantageously used for the treatment of gases of any type. It has proved to be particularly effective for gases from the combustion of heavy hydrocarbons (such as diesel oil, naphtha, fuel oil), fossil and vegetable fuels (coal, wood) . In fact, gases from the combustion of these substances contain a high quantity of heavy pollutants, which are very effectively held back by water. It has also proved effective in the treatment of gases from non-combustion chemical processes such as photographic and laundry processes. Circulation of the water under turbulent motion conditions may be obtained either by means of pumps, turbines or the like, or by directly exploiting the pressure of exhaust gases. In the latter case, pumping means may be provided in an intake manifold connected to the inlet port, to increase the pressure of the gases. In a second aspect, the invention relates to a device for the purification of combustion exhaust gases, comprising a purification vessel, an inlet port of the vessel, an outlet port of the vessel, - a water mass in the purification vessel, to be passed through by the exhaust gases while going from the inlet port to the outlet port, characterised in that the water mass in the purification vessel is circulating under turbulent motion. Such a device allows to implement the method of the invention. According to a first embodiment, the device preferably comprises in the purification vessel : - an inlet chamber where the inlet port is provided, an outlet chamber where the outlet port is provided, a forward course from the inlet chamber to the outlet chamber, a return course from the outlet chamber to the inlet chamber, both the forward and the return courses being obstructed by the water mass circulating therein. Circulation of the water mass can thus occur through the forward course and the return course . Advantageously, the vessel comprises a lower water tank, wherein the forward course and the return course are obtained by means of baffles, and wherein the inlet chamber and the outlet chamber are obtained above the tank and are open downwards towards the same tank, at a height lower than the minimum level foreseen for the water in the tank. This structure results to be extremely compact, and therefore of easy installation. Preferably, the forward course follows a labyrinth-like path, obtained by means of baffles located in the tank. The overall dimensions being the same, this device extends the forward course and facilitates the onset of a turbulent motion in the water mass. According to a second embodiment, the devices preferably comprises a rotating drum in the vessel, the drum being provided with a plurality of vanes. Circulation of the water mass in the vessel can thus occur following the motion of the vanes of the drum. The drum may be mounted idle in the vessel, to rotate under the thrust of the incoming exhaust gases. Alternatively, in case the thrust of the incoming gases is not sufficient to rotate the drum, the drum may be provided with motor means . Preferably, the vessel have a substantially cylindrical shape, with vertical axis coincident with the axis of the drum, and with the inlet port arranged so that the flow of incoming gases is substantially tangential with respect to the vessel and the drum. This disposition facilitates significantly the circulation of the water. In both embodiments, preferably, to prevent backflowing due to counter-pressures in gas exhaust ducts, the inlet port and/or the outlet port are protected by a nonreturn valve, for instance a clack valve. Preferably, there are provided means to prevent droplets sprayed by water turbulent motion from entering gas ducts. For instance, such means may comprise a mechanical net- filter on the inlet port and/or the outlet port. Always to hold back water and to prevent it from entering the gas exhaust ducts, the device preferably comprises a filtering layer between the lower tank and the outlet chamber, and possibly also a water separator in an exhaust manifold connected to the outlet port. To facilitate maintenance, the filtering layer may be housed in an extractable drawer, tightly-mounted in the vessel. Further characteristics and advantages of the invention will appear more clearly from the following description, wherein reference is made to the attached drawings, wherein: Figure 1 is a perspective view, in transparency and partly sectioned, of a device according to a first embodiment of the invention; - Figure 2 is a diagram showing in plan the forward course and the return course of the device of Figure 1 ; - Figure 3 is a perspective, partly sectioned, of a device according to a second embodiment of the invention; - Figure 4 is a section view of the device of Figure 3. According to the first embodiment of the invention shown in the figures 1 and 2, 1 indicates a purification device as a whole, which device comprises a tight-closed purification vessel 2. Vessel 2 has an essentially parallelepiped shape, but it can have any other suitable form. In vessel 2 a tank 3 is included which occupies all the lower part of vessel 2. Tank 3 is open upwards and is intended to be filled with water when running. Above tank 3, in vessel 2, three chambers are defined, adjoining one another, all of them open downwards towards tank 3: an inlet chamber 4, an outlet chamber 5 and an auxiliary chamber 6. Chambers 4, 5, 6 are separated from one another by vertical baffles 7 and 8; baffle 7 separates the outlet chamber 5 from the inlet 4 and auxiliary 6 chambers, baffle 8 separates the inlet chamber from the auxiliary chamber. Baffles 7 and 8 are sealed with respect to one another and the vessel inner walls, but interrupted in the lower part at a height lower than the minimum level foreseen for the water in tank 3. In this way, chambers 4, 5, 6 are in communication with one another only through the water present in tank 3. On inlet chamber 4, an inlet port 9a is open, connected to an intake manifold 9. The inlet port 9a is provided with a nonreturn valve 10 of the clack type, and a mechanical net- filter 11. On outlet chamber 5, an outlet port is open, which in the case shown consists of four mouths 13, distributed across the upper face of chamber 5 and connected to the same exhaust manifold 12. Each of mouths 13 is provided with a nonreturn valve 14 of the clack type and a mechanical net- filter 15. Besides, exhaust manifold 12 is also provided with a water separator 16. Valves 10, 14, filters 11, 15 and the separator 16 are components known in themselves, and therefore they will not be described in detail . On the auxiliary chamber 6, an opening 17 is provided for water filling up, provided with a closing stopper 18. In tank 4, baffles 19 are so arranged as to define a labyrinth-like forward course and a return course between the inlet chamber 4 and the outlet chamber 5. In vessel 2, between the outlet chamber 5 and tank 3, one or several filtering layers 20 are optionally provided, mounted each on respective extractable tight -mounted drawers 21. The device 1 works as follows. Tank 3 must be filled with a water mass sufficient to reach the minimum level. Special additives may be added to water, according to the specific use, for instance in case of use in cold conditions, an antifreeze will be advisable. Gases to be purified are fed to intake manifold 9 wherefrom they reach the inlet chamber 4. In such chamber 4, gases can exhaust only by passing through water. Thanks to the pressure of gases (spontaneous if it is sufficient, otherwise forced by suitable pumping means) , gases enter the underlying water mass, pushing it in the forward course formed in tank 3 by baffles 19. Pushed by the pressure of inlet gases, water is stirred by a whirling and turbulent motion, and is caused to circulate through the forward and the return courses. Passing through water, gases are purified from many pollutants that are present at the inlet, especially heavy substances that are held back by water. In outlet chamber 5, purified gases can come out of the water mass and rise therefore towards mouths 13 to exhaust manifold 12. In rising, purified gases pass through the possible filtering layers 20, unloading during their passing any suspended droplets of water. Further possible suspended water is held back by filters 15 and/or recovered from separator 16, before coming out from device 1. In the same way, filter 11 prevents water droplets from accidentally reflow into the intake manifold 9. Nonreturn valves 10 and 14 prevent possible counter- pressures from causing water or gases from exhaust manifold 13 from reflowing into vessel 2 and therefrom into intake manifold 9. The device 1 proved extremely effective in reducing heavy pollutants, which are effectively held back by water. In particular, a device with about 30 1 water, applied to a 2500 cm turbocharged diesel engine has allowed to reduce pollutants by over 80%, measured according to EC test 72/306. According to the second embodiment of the invention shown in the figures 3 and 4, 101 indicates a purification device as a whole, which device comprises a tight-closed purification vessel 102. Vessel 102 has an essentially cylindrical shape, with a vertical axis A, a circular horizontal base 103 and a side wall 104. The side wall 104 of the vessel 102 is closed on the top by a cover 105; suitable sealing means (not shown) are provided between the side wall 104 and the cover 105 to ensure the tight-closure of the vessel 102. The vessel 102 is provided with an inlet port 106 (divided into two superimposed mouths 107 m the example shown) and an outlet port 108, both ports 106 and 108 are connected to respective intake and exhaust manifolds, not shown. The mouths 107 of inlet port 106 are provided m the side wall 104 of the vessel 102, and are oriented m a direction that is substantially tangential to the side wall 104 of the vessel 102. The outlet port 108 is provided on the top of the cover 105 of the vessel 102; the cover 105 is slightly funnel-shaped, so as to facilitate collection of the outgoing gases into the outlet port 108. In the vessel 102, a rotating drum 109 is housed, having a vertical axis A coincident with the axis of the vessel 102. The drum 109 consists of a central hub 110 and a number of vanes 111, projecting radially from the hub 110 and extended vertically; two reinforcing rims 112 may be provided between the vanes 111, connecting their respective bottom and top external edges. The vessel 102 is filled with a mass of water, at a level at least sufficient to cover completely the inlet port 106. Similarly to the first embodiment shown m figures 1 and 2, the inlet and outlet ports 106 and 108 of the vessel 102 may be provided with non-return valve means. Such means are not shown for the second embodiment m figures 3 and 4. Also similarly to the first embodiment shown m figures 1 and 2, the vessel 102 may comprise means to retain water droplets from going out of the vessel 102. In the embodiment shown m figures 3 and 4, removable filtering layers 113 are shown, provided between the side wall 104 and the cover 105. The device 101 works in a way similar to device 1. It is to be noted as a difference that the particular position and shape of the inlet port 106 causes the incoming gases to induce a rotational motion in the water mass within the vessel 102. This motion determines a circulation of the water mass within the vessel 102, such circulation being under conditions of turbulent motion. The rotating drum 109 is mounted idle in the vessel 102; alternatively, the drum may be provided with motor means. Anyway, the presence of the rotating drum 109 facilitates the circulation of the water mass, being the drum motorized or not . If not motorized, the drum 109 guides the circulation, that is powered by the pressure of the gases. If motorized, the drum 109 may also contribute to actually drive the water mass. This may be useful in case the pressure of gases is not sufficient to induce circulation of the water mass; this may be the case with combustion gases from fixed plants or with exhaust gases from non- combustion processes. The drum 109 shown in the drawings is not motorized and the vanes 111 are shaped accordingly. If the drum is motorized, a different shape may be preferred, according to the power to be transferred to the water mass.

Claims: CLAIMS 1. A method for the purification of exhaust gases, causing gases to pass through a water mass, characterised by circulating the water mass in a purification vessel under turbolent motion. 2. The method according to claim 1, wherein the circulation of the water flow under turbulent motion is helped by the pressure of exhaust gases. 3. The method according to claim 1, wherein the circulation of the water flow is helped by mechanical devices in the purification vessels. 4. The method according to claim 1, wherein the exhaust gases are fed to the purification vessel by an intake manifold, either provided with pumping means or not. 5. A device for the purification of combustion exhaust gases, comprising a purification vessel, an inlet port of the vessel, an outlet port of the vessel, - a water mass in the purification vessel, to be passed through by the exhaust gases while going from the inlet port to the outlet port, characterised in that the water mass in the purification vessel is circulating under turbulent motion. 6. The device according to claim 5, comprising in the purification vessel: an inlet chamber where the inlet port is provided, an outlet chamber where the outlet port is provided, - a forward course from the inlet chamber to the outlet chamber, a return course from the outlet chamber to the inlet chamber, both the forward and the return courses being obstructed by the water mass circulating therein. 7. The device according to claim 6, wherein the vessel comprises a lower water tank, wherein the forward course and the return course are obtained by means of baffles, and wherein the inlet chamber and the outlet chamber are obtained above the tank and are open downwards towards the same tank, at a height lower than the minimum level foreseen for the water in the tank. 8. The device according to claim 7, wherein the forward course follows a labyrinth-like path. 9. The device according to claim 5, comprising a rotating drum in the vessel, the drum being provided with a plurality of vanes. 10. The device according to claim 9, wherein the drum is mounted idle in the vessel, to rotate under the thrust of the incoming exhaust gases. 11. The device according to claim 9, wherein the drum is provided with motor means. 12. The device according to any of claims 9 to 11, wherein the vessel have a substantially cylindrical shape, with vertical axis coincident with the axis of the drum, and with the inlet port arranged so that the flow of incoming gases is substantially tangential with respect to the vessel and the drum. 13. The device according to any of claims 5 to 12, wherein the inlet port and/or the outlet port are protected by a nonreturn valve . 14. The device according to claim 13, wherein the nonreturn valve is a clack valve. 15. The device according to any of claims 5 to 14, wherein the inlet port and/or the outlet port are protected by a net-filter. 16. The device according to claim 7, comprising a filtering layer between the lower tank and the outlet chamber. 17. The device according to claim 16, wherein the filtering layer is housed in an extractable drawing, tight -mounted in the vessel . 18. The device according to any of claims 5 to 17, comprising a water separator in an exhaust manifold connected to the outlet port.

Inventors: PAGANI ACHILLE, PAGANI, ACHILLE
Applicants: PAGANI ACHILLE, PAGANI, ACHILLE
Application year: 1998
Main classification: F01N3
IPC codes: F01N3