SE505033C2 - Scrubber system for gas cleaning or cooling - Google Patents

Abstract

Polluted gas is cleaned and/or hot gas is cooled, in a method in which the gas is contacted with a finely-divided liquid so as to scrub particles or absorb gaseous pollutants from the gas, or cool the gas. The liquid is applied in a number of umbrella-like shells (hollow-cone sprays) or linear curtains (flat-set sprays) in two or more planes perpendicular to the main flow direction of the gas. Pref. the velocity component of the liquid in a plane perpendicular to the gas flow direction is more than velocity component parallel to that direction. The liquid sprays are arranged so as to alternately spread and concentrate the gas along planes perpendicular to the gas flow direction, with the distance between adjacent rows of jets being insufficient to allow redistribution of the gas flow. Pref. the jets at a given position are arranged to act on a plane where the gas has been concentrated by the action of the jets immediately upstream. Pref. no substantial interaction takes place between droplets arising from adjacent rows of jets.

Description

505 033 10 15 20 25 30 The process is also very teachable where gas cooling must take place in combination with separation of particles or gaseous pollutants in a polluted gas because the good contact between the liquid and the gas promotes not only heat transfer but also gas purification.

TECHNICAL BACKGROUND Cooling of gas in order to adapt its temperature or to extract or recover heat from this gas is an important and common process in modern industrial society.

A large number of methods have been developed and there are a number of methods to choose from when building a gas cooling system.

Heat transfer usually takes place either by means of heat exchangers, recuperative or regenerative, or by direct contact between the hot and the cold medium. This invention relates to transmission with direct contact between a gas and a liquid, so other methods will not be affected.

A method that is advantageous in many contexts is that a hot gas is passed through a rain of undisturbed liquid or past surfaces that are flooded by a liquid.

With these methods, the possibility is prepared partly for the absorption of heat from the gas, partly for the capture of particles in the liquid as well as that gas components in a polluted gas are dissolved in the liquid. The liquid can then also contain the sleeve which transfers the dissolved gas components to a solid form, so that these can be more easily separated from the liquid.

The liquid is recirculated in the cooling device, but a portion is taken out, usually continuously, in order for the absorbed heat to be utilized in another supply. The liquid can also later be treated for the separation of current pollutants, in gaseous form or solid form, possibly for recycling of the substances and the treated liquid can be returned to the gas cooling plant for new use.

A rough division of these gas cooling systems is in open towers, where the gas only meets a distributed liquid, and in filling body scrubbers or filling body columns, where the gas flows through a tower which is filled with e.g. saddle-shaped or slcmvfjeather-shaped small details, which are covered with liquid so that a liquid fi lrn flows downwards over substantially the entire total surface. As filler body scrubbers are not within the scope of the present invention, they will not be treated here.

Examples of open spaces for cooling a gas for the purpose of extracting heat are shown in b1.a. US-3,532,595, in which both vertical tomes and devices with horizontal gas flow are shown and liquid is supplied at a number of levels or positions. US-4, 644,399 discloses a simpler plot where liquid is introduced only at one level but distributed after capture at fl your levels.

US-2,523,441 discloses a combination of an open space with a filler body section.

In a cooling vacuum for heat recovery fi- from a hot polluted gas, liquid is usually supplied at 4-6 levels. At each level there are fl your nozzles that distribute small drops within an area that usually has the shape of a conical shell, hollow art type, or within an entire cone, full art type. The peak angle of this cone is 90 to 1200.

At each level there are nozzles with a distance of 0.5 to 1 m, in a regular grid.

The distance between the levels is 1 to 2 m. At least some levels are located far above the bottom of the plot. The intention is that these will give drops which in the form of a well-distributed rain fall through the tower below a considerable part of its height.

The efficiency of heat transfer is largely dependent on the relative motion between droplets and gas. It is therefore usually preferred that the hot gas moves upwards towards the falling droplets, countercurrent, but for various reasons there is also a cooling gap where the gas moves downwards in the same direction as the falling droplets, cocurrent.

If you want to increase the efficiency of the friend transfer with this method, you have the choice between increasing the height of the empty space or increasing the fl flow of coolant. However you decide, the consequence will be that the pumping work will increase for a given gas volume flow.

DESCRIPTION OF THE INVENTION TECHNICAL PROBLEM The open cooling tomes have a significant disadvantage that they are very space-consuming. This also leads to them being expensive to build.

A second disadvantage that follows from the first is that the inch usually has to be made very high. This means that the liquid which, in the form of a rain of drops, must fall down through the tower, must first be pumped up to a considerable height. The operating cost is most significantly affected by this pumping work.

OBJECT OF THE INVENTION Gas cooling with wet washes, e.g. conditioning tower, has been an established technology for decades in the process industries and at incineration plants. Telmiken is well-proven and must be considered both efficient and reliable. The most obvious disadvantages of the above section are that the equipment becomes very space-consuming and thus expensive, and that it is energy-intensive, primarily due to the big porn pair work.

It is therefore a principal object of the present invention to provide an improved method which enables the use of substantially less refrigeration equipment while maintaining the reliability and efficiency of known methods.

Another object of the present invention is to provide a method and a device which also provides a less energy-intensive gas cooling.

SUMMARY OF THE INVENTION The present invention relates to a method of cooling hot gas, wherein the hot gas is conducted in contact with a distributed liquid for transferring heat from the hot gas to the distributed liquid. The distributed liquid is supplied, in the form of substantially umbrella-shaped shells or substantially rectilinear curtains, in substantially regular grid patterns, in two or more planes substantially perpendicular to the main direction of flow of the hot gas. A substantial portion of the non-distributed liquid is supplied so that its velocity component in a plane perpendicular to the main orifice direction of the gas d is greater than its velocity component parallel to or opposite the gas huvud main orifice direction.

The solution to the technical problem posed according to the present invention is achieved by supplying the distributed liquid so that the gas is alternately concentrated and dispersed by the impulse action which the liquid, in directions perpendicular to the main flow direction of the hot gas, exerts on the gas. The perpendicular distance between adjacent planes, in which distributed liquid is supplied, is adjusted so that no significant equalization of the gas flow takes place between the planes. The liquid supply in the adjacent plane is arranged so that, in, in the flow direction of the gas, located downstream of the gas, the flowing hot gas is concentrated by the impulse action of supplied liquid in the plane closest to the upstream.

GENERAL DESCRIPTION OF THE INVENTION In the following description, the word tower is used as a synonym for the word lcyltorn and the word liquid as a synonym for coolant. By the word gas is meant both incoming hot gas and the gas which in the contact portion is during ongoing cooling.

In the process according to the invention, the gas is supplied with a distributed liquid from regularly arranged inlet means. These are hereinafter referred to as nozzles, and can be of a number of designs. The most common forms should be devices which, in the case of a substantially cylindrical body, supply distributed liquid within a hollow cone, rather as an umbrella-shaped shell, or an elongate device which, along a substantially straight line, supply distributed liquid as a curtain generated by an imaginary movement of this line.

The nozzles are arranged so that the distributed liquid upon its introduction gives the gas a lateral movement, i.e. across the main flow direction of the gas, and thus gives a concentration effect. The nozzles mainly supply liquid with a direction perpendicular to the direction of the gas head's fate through the scrubber. The nozzles may be directed in the same direction in an entire plane and in the opposite direction in the next plane, but preferably all planes are provided with radiating, umbrella-forming nozzles or with linear nozzles which distribute liquid in at least two opposite directions.

With nozzles arranged in a grid, supplying liquid in directions substantially perpendicular to the main flow direction of the gas fl, a displacement of the gas and a concentration is effected so that substantially the entire flow passes through the plane through areas not close to any nozzle. With adapted distances between the nozzles, this area is approximately the center of gravity of the surface delimited by the connecting lines between adjacent nozzles.

According to the invention, further nozzles are to be placed in the middle of these centers of gravity in a plane downstream of the first, seen in the direction of the flowing gas. Furthermore, the plane must be laid so close that the gas flow does not have time to be substantially equalized before the gas comes into contact with the distributed liquid from the nozzles in this downstream plane.

Downstream of this second plane a third plane, a fourth plane and so on are arranged in the same way. based on needs. The gas is thus imparted in a zig-zag-like motion through the contact portion.

The distances between the planes must be adapted to the construction of the nozzles so that the liquid supplied in a plane does not substantially interact with opposing liquid from adjacent nozzles in the adjacent planes. However, the distance should be chosen so small that complete drip a in areas as far as possible is avoided.

As a measure of interaction, the part of the droplets from a nozzle that meets a greater concentration or droplet fl fate density fi- than the adjacent nozzle in an adjacent plane can be stated. When this occurs, the droplet density density seen as a distribution in the room across the droplet density must have dropped to at least 10% of the maximum value at the current distance fi from the nozzle.

However, as the efficiency depends on the intensity of the contact between gas and liquid, the distance between the plane and the droplet distribution of the dysomas should preferably be adjusted so that a small interaction takes place. Thus, a small proportion of the droplets from a nozzle should come into contact with a small proportion from said adjacent nozzle. According to the invention, at least 0.01%, preferably at least 0.1% of the maximum droplet density density should be present where a hypothetical boundary line between the fates is drawn at the same density for both flows.

If only two planes with nozzles are used, the cone angle of the "umbrella" can be chosen as arbitrary for the first plane, while for the second plane it is adapted so that the umbrellas from the two planes nominally touch each other.

If several planes with nozzles are necessary, it is advantageous that the liquid is supplied mainly in the plane, i.e. with the cone angle l80 °. Then a simple symmetry is obtained. This angle should be most advantageous even when only two planes are used.

The distribution of nozzles in a plane is advantageously in the form of a regular grid.

If all planes are to be equipped equally, the square structure is the most advantageous. However, it should not entail any significant disadvantages to have a grid with equilateral triangles, even if the plan must then be different in pairs. Even rhombic gratings and, as mentioned, completely rectilinear parallel nozzles can be ringed without major inconvenience. In order to achieve the advantages of the invention, the number of grid points in each plane should be relatively large, at least 16, preferably at least 25. If linear nozzles are used, these should be at least 5 in each plane.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail in connection with the accompanying drawings, where fi g 1 shows a vertical section through a cooling blank with a previously known design. 2 g 2 shows a vertical section through a cooling inch designed according to the present invention fi g 3 shows a proposed distribution of nozzles in a cooling empty with a circular cross-section fi g 4 shows an alternative distribution of nozzles in a cooling empty with a circular cross-section fi g 5 shows the distribution of liquid droplets around some nozzles more detailed fi g 6 shows the drip fl density density distribution as a function of a spatial coordinate for dysoma Fig. 5. fi g 7 shows a proposed distribution of dysoria a cooling inch with a square cross section fi g 8 shows in simplified form the gas disturbance through a cooling empty performed according to the invention.

DESCRIPTION OF THE PROPOSED EMBODIMENT I fi Figure 1 shows, in schematic form, a previously known cooling empty 1a, with an inlet 2 for hot gas, an outlet 3 for cooled gas and an intermediate contact portion 4. At the bottom of the cooling empty 1a is collected in the bottom part 5 coolant 6. The coolant 6 is conveyed with a pump 7 up to manifolds 8, with nozzles 9a arranged in the upper part of the contact portion 4. The level difference between the plane (81-84) with nozzles 9a is approximately 2 m. The nozzles 9a, 505 035 10 15 20 Which are shown greatly simplified, are of the hollow type, i.e. they disperse distributed coolant within a conical shell with a top angle of 120 °. The coolant then falls down as a rain of fine droplets through the contact portion and collects in the bottom part 5. Above the manifolds 8 and the nozzles 9a there is a drip separator 10. Through a line 18 new coolant can be supplied and through another line 19 hot liquid can be used. abducted.

Figure 2 shows, also in schematic form, a blank 1 made according to the present invention. This tower 1 differs from that shown in Figure 1, with its substantially reduced height d. Furthermore, the contact portion 4 is provided with nozzles 9 which disperse distributed liquid substantially horizontally, i.e. as a hollow cone nozzle with a top angle of 180 °.

The level difference between the planes with nozzles is in this case only 20-60 cm. For the sake of clarity, the drawing at this point is not to scale, and the actual difference in height between the spaces la in fi gur 1 and 1 in fi gur 2 is greater than that which deviates from these in schematic form. The parts of Figure 2 that correspond to Figure 1 have been provided with similar reference numerals.

Figure 3 shows for a practical case the distribution of nozzles 9 over the cross section in a blank with a circular cross section. The diameter of the tom is approximately 12 m and inside this about 100 nozzles 9 have been arranged in each plane in a square lattice pattern with the pitch of about 1 m. The distribution is indicated by the circles 31 which illustrate how the non-distributed liquid 6 is injected at each lattice groove. Figure 3a shows in this way the distribution of the nozzles 9 in the planes 81 and 83 in fi gur 2 and fi gur 3b shows the corresponding distribution of the nozzles in the planes 82 and 84.

To prevent some gas from passing almost rectilinearly through the tower along the walls, nozzle distribution according to Figure 4 can be considered. Here, the entire circumference of the tom is equipped with nozzles 9 which are directed inwards and inject liquid in a substantially semicircular shape and the distribution of nozzles 9 inside the tower has been adapted accordingly. As can be seen, the pattern does not become completely regular and the adjustment of the distribution of the dysomas in the next plane must be done in a way that deviates somewhat from the theoretically desirable.

Figure 5 shows in more detail how the nozzles 9 in two adjacent planes are arranged in relation to each other and in which area a distributed liquid is supplied, through an imaginary vertical section diagonally through the patterns in Figure 3. To facilitate the description, the scale is distorted so that the distances in altitude has increased in relation to the distances in the horizontal plane. 10 15 20 25 30 505 033 From a nozzle 51 in the plane 81 comes a distributed liquid in a desolation 61. From a nozzle 52 in the plane 82 comes an opposite fate 62. The flows 61 and 62 are not limited by indicated flow lines 511, 512 and 521 , 522, but these denote the limit within which the majority of the flows fi nns. The flows partially interfere with each other and the boundary where they are substantially equal is indicated by a line 66. Here, however, the droplet density is significantly less than in the central part.

Figure 6 shows an example of drip fate density distribution for drip fate in i gur 5 in the section along line 65. By drip fate density is meant mass per per unit area. The figure shows the gradual decrease of fl fate with increasing distance from each plane. Line 66 denotes, as approached above the boundary, the areas where the respective drip fate is predominant.

According to the present invention, the distance between planes 81 and 82 must be adapted to the distribution of distributed liquid so that the droplet density densities 61 and 62 at boundary line 66 are both less than 10% of the maximum value present near planes 81, 82. Maximum utilization of the advantage of the invention presupposes between planes 81, 82 does not become too large. The drop-density densities 61, 62 should therefore at boundary line 66 exceed 0.01% of the maximum value, preferably exceed 0.1% of the maximum value.

Figure 7 shows for a practical case the distribution of nozzles 9 over the cross section in a tower with a square cross section. The side of the square is approximately 12.4 m and inside this approximately 100 nozzles 9 have been arranged in each plane in a square grid pattern with the pitch approximately 1.2 m. The distribution is indicated by the circles 71 which illustrate how the non-distributed liquid 6 is injected at each grid point. . Figure 7a shows in this way the distribution of the nozzles 9 in planes 81 and 83 in fi gur 2 and fi gur 7b shows the corresponding distribution of the nozzles in planes 82 and 84. Figure 7 shows that square cross-sections do not have to deviate from the theoretically desirable regular grid.

Figure 8 shows in simplified form how the gas flows through the contact portion 4.

Flow line ema 11 curves in meander shape around the nozzles 9.

The function of the device is as follows. Gas enters the blank 1 through the inlet 2 to the contact portion 4. It flows substantially vertically upwards until it comes close to the first plane 81 with nozzles 9.

Liquid 6 is injected through the nozzles 9 at a speed of 10-15 rn / s substantially horizontally into the gas. The gas is affected by the distributed liquid and is carried by it in a direction which is approximately horizontal until it meets another gas flowing in the opposite direction approximately midway between the nozzles 9 in the same plane 81.

Since the liquid droplets here have a significantly lower droplet density density than near the nozzle 9, they spread over larger volumes with increasing distance, the gas passes between the liquid droplets upwards towards the next plane 82 in the middle of a nozzle 9 in this second plane.

The gas flow thus concentrated by the impulse of the washing liquid in plane 81 is dissipated there by the impulse of the liquid droplets injected into the gas by this nozzle 9.

The gas also moves there substantially horizontally until it meets gas carried by the liquid droplets fi- from nearby nozzles 9.

The process is then repeated when passing to level 83 and so on. Through the repeated reversal and the alternating acceleration and deceleration, an intense and efficient interaction between gas and liquid is obtained. Liquid entrained by the gas in the form of distributed droplets is separated in the droplet separator 10.

Via the line 19 a part of the liquid can be drained for utilization of heat and via a second line 18 new liquid is supplied as required, preferably by redistributing the extracted part or its cooling in an application not shown.

ALTERNATIVE EMBODIMENTS The process according to the invention is of course not limited to the exemplary embodiment described above, but can be varied in a number of ways within the scope of the following patents.

As mentioned earlier, nozzles of different designs can be used and the nozzles can be arranged in a number of different ways. The regular grids are preferable, but deviations can be accepted without major disadvantage. Triangular or rhombic grids can give very good results. An advantageous alternative is that each arm plane has nozzles arranged in a triangular grid and that every other has nozzles arranged in a hexagonal grid.

Furthermore, of course, the process can be used in processes other than cooling hot gases. The method can advantageously be applied in most contexts where a gas is to be contacted with a non-distributed liquid. An example of this is the separation of particulate or gaseous pollutants from hot gases.

Claims (20)

10 15 20 25 30 505 033 11 PATENT REQUIREMENTS A method of cooling hot gas, wherein the hot gas is conducted in contact with a redistributed liquid to transfer heat from the hot gas to this non-distributed liquid and wherein the fi divided liquid is supplied, in the form of substantially umbrella-shaped shells or substantially rectilinear curtains, substantially regular grid patterns, in two or plan your planes substantially perpendicular to the main inlet direction of the hot gas and a substantial part of the fi ndistributed liquid is supplied so that its velocity component in a plane perpendicular to gas fl the main flow direction of the , characterized in that the distributed liquid is supplied so that the gas is alternately concentrated and dispersed by the impulse action which the liquid, in directions perpendicular to the main flow direction of the polluted gas, exerts on the gas, by the perpendicular distance between adjacent planes, in which fi n elated liquid is added, adjusted so that no significant equalization of gas fl fate takes place between the planes and that the liquid supply in the adjacent plane is arranged so that it, in, in the direction of flow of the gas, downstream plane, takes place where the flowing hot gas is concentrated by impulse action from to in the nearest upstream plane. 2. A method according to claim 1, characterized in that the distributed liquid is supplied in the form of droplets so that these, at an obtuse angle, meet other droplets supplied in the same plane and that these oncoming droplets preferably have substantially equal density distribution. 3. A method according to claim 2, characterized in that the perpendicular distance between adjacent planes, in which distributed liquid is fed, is adjusted so that no significant interaction, between droplets fed in different planes, takes place between droplets in opposite directions. 10 15 20 25 30 35 505 035 12 4. A method according to claim 2, characterized in that a substantial part of the distributed liquid is supplied with a direction which is within an angle of 20 ° symmetrically about a plane perpendicular to the main flow direction of the gas. 5. A method according to claim 4, characterized in that the main part of the distributed liquid is supplied with a direction which is within an angle of 20 °, preferably within an angle of 100, symmetrically located around a plane perpendicular to the main flow direction of the gas. Method according to claim 5, characterized in that the perpendicular distance between adjacent planes, in which distributed liquid is supplied, is adapted so that the interaction, between adjacent opposite fl fates of droplets applied in different planes, does not occur between the majority of these drop fl fates in the area. directly between current supply points. 7. A method according to claim 6, characterized in that the perpendicular distance between adjacent planes, in which distributed liquid is supplied is adjusted so that the overlap between adjacent opposite fls of droplets applied in different planes, gives a correspondence of the density distribution in the two droplet fl fates, only at points where the density of the flow of fm distributed liquid in each fl fate, is not more than 10% of the maximum at the current distance from the supply point. Method according to claim 6, characterized in that the perpendicular distance between adjacent planes, into which distributed liquid is supplied is adjusted so that the overlap between adjacent opposite fl fates of droplets supplied in different planes gives a correspondence of the density distribution in the two the drop fl fatalities, only at points where the density of the fl fate of fm distributed liquid in each fl fate, is at least 0.01%, preferably at least 0.1% of the maximum at the current distance from the supply point. Apparatus for carrying out the method according to any one of the preceding claims, comprising an inlet (2) for hot gas, an outlet (3) for cold gas and a contact portion (4) located therebetween, through which the gas is caused to flow and in which inlet means (9) for injecting liquid-distributed liquid, in the form of substantially umbrella-shaped shells or substantially rectilinear curtains, arranged to supply a substantial part of the non-distributed liquid so that its velocity component in a plane perpendicular to the gas flow direction ) is greater than its velocity component parallel to or opposite gas gas the main flow direction fl l of fate fl l), in substantially regular lattice patterns are arranged in two or fl eras, towards the main flow direction (41) of the gas substantially perpendicular, plane (81-84), to supply finely divided liquid so that concentrated and dispersed by the impulse action of the liquid, in directions perpendicular to the main flow direction the increase (41) of the hot gas exerted on the gas, characterized in that the perpendicular distance between adjacent planes (8l, 82), with inlet means (9), is so small that no significant equalization of gas fl fate takes place between the plane and that the inlet means (9), in adjacent planes (81, 82), are arranged so that, in the downstream plane (82) located in the direction of flow of the gas, they are located where the flowing hot gas is concentrated by the impulse action of supplied liquid in the nearest upstream plane (81). Device according to claim 9, characterized in that the inserts (9) are substantially radiating nozzles and that the nozzles (9) in the respective planes (81-84) are arranged in a substantially regular grid pattern. Device according to claim 9, characterized in that the inserts (9) are substantially rectilinear nozzles and that the nozzles (9) in the respective planes (81-84) are arranged in a substantially regular pattern. Device according to claim 10, characterized in that the grid patterns are substantially triangular, square or hexagonal and preferably composed of equilateral urer gurus. Device according to claim 12, characterized in that the lattice patterns are substantially square grid patterns and that the lattice pattern is substantially the same in all planes (81-84). Device according to claim ll, characterized in that the lines are straight and substantially parallel and preferably evenly distributed over the cross section of the contact pair (4). Device according to one of Claims 10 to 14, characterized in that the nozzles (9) are arranged to supply the gas-distributed liquid substantially disc-shaped in the respective plane (81-84). 10 15 20 505 035 14 Device according to claim 10, 12 or 13, characterized in that the lattice patterns in the adjacent plane (81, 82) are offset so that the lattice points in a downstream, seen in the main flow direction of the gas, located plane (82) are substantially center of gravity. - the points of the polygons generated by lines between adjacent lattice points in the nearest upstream plane (81). Device according to claim 11, 14 or 15, characterized in that the lines in the adjacent planes (81, 82) are displaced so that they are located substantially in a plane (82) located downstream, seen in the main direction of flow of the gas. center For an imaginary center line in the middle between adjacent lines in the plane closest to the upstream (81). Device according to claim 16 or 17, characterized in that the perpendicular distance between adjacent planes (81, 82) is substantially less than the distance between adjacent grid points or adjacent lines in each plane. Device according to claim 16, wherein the cross section of the contact portion (4) has a diameter or a longest side exceeding 1 m, preferably exceeding 5 m, characterized in that the lattice patterns are substantially square grid patterns and that the number of lattice points in each plane is at least 16. Device according to claim 17, wherein the cross section of the contact portion (4) has a diameter or a longest side exceeding 1 m, preferably exceeding 5 m, characterized in that the lines are uniformly distributed over the cross section of the contact panel (4) and that the number of lines in each plane is at least 5.