Field of the invention

The invention relates to a device according to the preamble of claim 1. The invention also relates to a method according to the preamble of claim 10.

In the context of the invention, relative terms such as 'above', 'below', 'horizontal', 'vertical', 'upward' and 'downward' are always understood to mean 'in a situation of use above', 'in a situation of use below' and so on. The term 'mist' is used in its broadest sense within the scope of the invention and refers to 'distribution of liquid droplets, such as water droplets, in a gas'. The term 'droplet separator' or 'demister' means 'a device for separating liquid droplets from a mist'.

Background of the invention

It is known to remove a contaminant from gas comprising (i) mixing the gas with a reactant which reacts with the contaminant, and (ii) removing a compound or compounds thus fonned by suitable means.

For example, it is known to remove nitrogen oxide (NO) and nitrogen dioxide (NO ₂ ) from flue gas, comprising (i) mixing the flue gas with ozone (O ₃ ) which reacts with the NO and NO ₂ , and (ii) removing dinitrogen pentaoxide (N ₂ 0 ₅ ) thus formed by means of a wet scrubber in which the gas is contacted with water, by spraying, in the form of a mist, or by forcing the gas through a layer of water, and wherein the N ₂ 0 ₅ dissolves in the water. The aqueous nitric acid solution (HNO ₃ ) thus formed and the purified gas are subsequently discharged separately, see, for example, EPI 852172A1 and EP2719440A1. The present invention now provides a device and a method for removing a contaminant from gas by mixing and reacting with a reactant and using a wet scrubber, thereby achieving fester and better cleaning of the gas, among other advantages.

Summary of the invention

The invention provides a device according to claim 1 and a method according to claim 10. By means of such a device and such a method, a contaminated gas can be cleaned quickly and properly.

Brief description of the drawings

The invention is further elucidated below on the basis of a non-limiting exemplary embodiment of a device according to the invention, schematically shown in figure 1.

Further explanation and exemplary embodiments The device according to the invention shown in figure 1 comprises a wet scrubber (100) comprising a housing (101) which is provided with, going from bottom to top, a first outlet (105) for letting out liquid (13), a first inlet (102) for letting in gas (6), a second inlet (104) for letting in liquid (10), and a second outlet (103) for letting out gas (8). In the housing (101) there are, going from bottom to top, a first space (106) connected to the first outlet (105), a second space (107) filled with a packing, a third space (108) connected to the second inlet (104), a first droplet separator (109) and a fourth space (110) connected to the second outlet (103). The device also comprises first supply and discharge means (200) provided with a fourth inlet (201) for letting in gas (1), a fifth inlet (202) for letting in gas (2) and a third outlet (203) for letting out gas (6) connected to the first inlet (102). The device also comprises second supply and discharge means (300) which are provided with a sixth inlet (301) for letting in liquid (13) connected to the first outlet (105) and a fourth outlet (302) for letting out liquid / dust particles (14).

Now, according to the invention, the housing (101) is also provided with a third inlet (111) for letting in liquid (15) located above the second space (107) and below the second inlet (104), and located in the housing (101) are also a fifth space (112) connected to the third inlet (111) and a second droplet separator (113) located between the fifth space (112) and the third space (108). The wet scrubber (100) here also comprises a passage (114) for passing liquid (16) from the third space (108) to the first space (106). With a certain geomeby of the whole and a certain setting of gas and liquid flows, a layer of liquid (17) is formed at the bottom of the third space (108) through which upward flowing gas (7) is forced. The flow resistance of the passage (114) can herein be controlled by means of control means (not shown) provided for this purpose.

The first supply and discharge means (200) here also comprise a first cyclone (204) for separating dust particles (31) from gas (1) connected to the fourth inlet (201), and here also comprise mixing means (205) for mixing gas (4). The second supply means (300) are here also provided with a fifth outlet (303) for letting out liquid (15) connected to the third inlet (111), and here also comprise filter means (304) connected to the first outlet (105) for filtering coarser dust particles (32) from liquid (13), and here also comprise two second cyclones (305,306) for separating finer, heavier resp. lighter, dust particles from liquid, and here also comprise cleaning means (307) for the chemical cleaning of fluid connected to fifth outlet (303).

A method for removing a contaminant from gas (1) by means of such an device comprises letting in gas (6) through the first inlet (102), letting out gas (8) through the second outlet (103), letting in fluid (10) through the second inlet (104), letting out fluid (13) through the first outlet (105), making fluid (11) flow downward through the housing (101), making gas (7) flow upward through the housing (101), separating liquid drops from gas (7) flowing upward through the housing (101) by means of the first drop separator (109), and collecting liquid (12) in the first space (106). The method here also comprises generating a mist in the third space (108).

According to the invention, the method also comprises letting in liquid (15) into the housing (101) through the third inlet (111), and separating liquid droplets from gas (7) flowing upward through the housing (101) by means of the second droplet separator (113). The method here also comprises generating a mist in the fifth space (112), and here also comprises passing liquid (16) from the third space (108) to the first space (106) by means of the passage (114), wherein the flow resistance of the passage (114) is controlled by the control means (not shown), The method here also comprises at least partly cleaning liquid (13) let out through the first outlet (105) and letting in again at least partly cleaned liquid (15) through the third inlet (111).

For example, nitrogen oxide and nitrogen dioxide can be removed from a flue gas (1) by means of the method and the device, as schematically shown in figure 1 and described above. To this end, the flue gas (1) is let in through the fourth inlet (201) and dust particles (31) are subsequently removed therefrom by means of the first cyclone (204). The remaining gas (3) is combined with ozone (2) let in through the fifth inlet (202). The composite gas (4) then flows (5) through the mixing means (205) and is thereby mixed to a certain desired mixing degree. The mixed gas (6) is then let in through the first inlet (102) into the housing (101) and then flows through a gas distributor (115) into the second space (107) and further upward (7) through the housing (101). Via the second inlet (104), here fresh, water (10) is let in into the third space (108), wherein mist (108) is formed therein also. Through the third inlet

(111), here cleaned and recycled, water (15) is let in into the fifth space (112), wherein mist

(112) is formed therein also. The first drop separator (109) and the second drop separator

(113) separate water droplets from upward flowing gas (7). Water separated by the second droplet separator (113) flows downward (11) through the fifth space (112), the second space (107) and the gas distributor (115) to the first space (106). Water separated by the first droplet separator (109) flows downward through the third space (108) and further (16) through the passage (114) to the first space (106). In the packing, here a number of loosely packed metal rings, the fifth space (112) and the third space (108), upward flowing gas (7) in the housing (101) comes into contact successively with downward flowing water (11), with mist, a layer of water (17) and again with mist, wherein formed dinitrogen pentaoxide is dissolved. The nitric acid solution thus formed flows partly downward (11) through the second space (107) and partly downward (16) through the passage (114), is collected (12) in the first space (106), and then let out (13) through the first outlet (105). The gas which has been completely or partly depleted of nitrogen oxide and nitrogen dioxide is collected in the fourth space (110) and let out (8) through the second outlet (103) and blown off (9) to the environment by means of a gas pump (206). The nitric acid solution (13) let out through the first outlet (105) is, after cleaning by means of the filter means (304), the two second cyclones (305;306) and the cleaning means (307), at least partly recycled and let in through the third inlet (111) back into the housing (101) c.q. the fifth space (112).

It will be clear that within the scope of the invention, in addition to the method and the device, as schematically shown in figure 1 and described above, all kinds of other embodiments are also possible. For instance, the combination of flue gas (1) and ozone (2) can also take place between the fourth inlet (201) and the first cyclone (204). Also, the use of one or more cyclones (204,305,306) and/or mixing means (205) and/or filtering means (304) and/or cleaning means (307), depending on a given application, can be omitted. Instead of loosely packed rings of metal, the packing can for instance also consist of objects of another suitable shape or material. As droplet separators (109,113), in the given example mesh pad demisters, also suitable demisting cyclones can be used. For instance, also cleaned and recycled water can be let in into the third space (108) via the second inlet (104). For instance, also fresh water can be let in via the third inlet (111) into the fifth space (112).

A contaminated gas can be cleaned quickly and properly by means of a device and method according to the invention. By cleaning and recycling used fluid, water and energy are saved. Due to the use of cyclones, the device is more durable and more compact than known devices. Reference numbers used

100 wet scrubber

101 housing (of 100) 102 first inlet (of 101)

103 second outlet (of 101)

104 second inlet (of 101)

105 first outlet (of 101) 106 first space (in 101)

107 second space (in 101, packed)

108 third space (in 101)

109 first droplet separator (in 101 )

110 fourth space (in 101)

111 third inlet (of 101)

112 fifth space (in 101)

113 second droplet separator (in 101)

114 passage (from 108 to 106)

115 gas distributor (in 101)

200 first supply and discharge means (for gas)

201 fourth inlet (of 200)

202 fifth inlet (of 200)

203 third outlet (of 200)

204 first cyclone (of 200)

205 mixing means (of 200)

206 gas pump (of 200)

207 sixth outlet (of 200)

208 seventh inlet (of 200)

300 second supply and discharge means (for liquid)

301 sixth inlet (of 300) 302 fourth outlet (of 300)

303 fifth outlet (of 300)

304 filter means 300)

305 first second cyclone (of 300)

306 second second cyclone (of 300)

307 cleaning means (of 300)

308 fluid pump (of 300)

309 seventh outlet (of 300)

1 gas (inflowing 200 via 201)

2 gas (inflowing 200 via 202)

3 gas (outflowing 204)

4 gas (inflowing 205)

5 gas (flowing through 205)

6 gas (outflowing 200 via 203; inflowing 101 via 102)

7 gas (flowing upward through 101)

8 gas (outflowing 101 via 103; inflowing 200 via 208)

9 gas (outflowing 200 via 207)

10 liquid (inflowing 101 via 104; outflowing 300 via 309)

11 liquid (flowing down through 101)

12 liquid (collected in 106)

13 liquid (outflowing 101 via 105; inflowing 300 via 301)

14 liquid / dust particles (outflowing 300 via 302)

15 liquid (outflowing 300 via 303; inflowing 101 via 111)

16 liquid (flowing through 114)

17 liquid (layer on top of 113)

31 dust particles (separated from 1 by means of 204)

32 dust particles (separated from 13 by means of 304)