NO146806B - WITH A PLASTIC COVER CLOSABLE, FORM-BLASTED PLASTIC CONTAINER WITH AXIAL LOAD REINFORCEMENT - Google Patents

Description

Procedure for effecting contact between fluids in counter flow.

This invention relates to a method for effecting intimate touch

between fluids, especially between a gas

and-a liquid passing in countercurrent to

each other through a contact zone.

It is well known that in most operations where a gas and a liquid are brought into contact with each other to transfer something

gas (or particles carried by the gas) from

the gas phase to the liquid phase, it is desirable that

the contact area between the two phases is greatest

possible. This is usually achieved by shredding

the liquid and/or to cause the liquid to flow

over a large surface, over which the gas is directed.

In technical operation, columns or towers of various constructions are used for this purpose. These columns and towers are generally arranged in such a way that a liquid stream is introduced at their top and allowed to flow, e.g. by

the help of gravity, inside the tower, while

at the same time, gas is introduced at the tower

bottom and this is allowed to circulate or rise

in countercurrent to the descending fluid.

Different types of are used

such towers or columns. For example, get i

a shower-tower the gas rise upwards through

the room in the tower, which is without mechanical obstacles, while the liquid is supplied

in the form of droplets (e.g. by means of

nozzles or other atomizing devices) that are allowed to fall through the gas.

This device type has the advantages that

the pressure drop is small and the device's construction is simple. But the shower tower has it

disadvantage is that it is relatively large

power consumption to form the droplets which —

together with the relatively small contact surface thus produced and the low degree of turbulence within each formed droplet — results in a low absorption efficiency; especially when it comes to the less soluble gases. Packed towers are therefore generally used, except in cases where clogging due to the existence or formation of a solid phase is a problem. In packed towers, the liquid flow is caused by gravity to flow over the surface of a packing material, while the gas flows, e.g. in counterflow, through the free spaces inside the gasket. In this way, a large contact surface is obtained between the liquid and the gas. Among other types of equipment used for the absorption of gas in a liquid, examples can be mentioned of an aerated tank-absorber in which the gas in the form of small bubbles rises up through a pond of the liquid, as well as bubble plates - or silabsorbers where the gas is driven through a perforated metal plate or through bell-shaped with, slot equipped caps that are immersed in the liquid, and the like.

A packed tower can be advantageous for many applications where gas is to be absorbed, but also has a number of disadvantages which are difficult to overcome. When using the usual types of packing materials, such as crushed stone, coke or specially shaped ceramic bodies, for example Raschig rings, the tower must as a rule have a large volume, but still the passage through it is limited, as free passage of the fluids can only take place through gaps and voids inside the packing. When the free cross-sectional area formed by these spaces and voids is small, the pressure drop, due to friction, through the gasket will be large, and more power consumption is required to circulate the gas; moreover, high speeds are required for a given or desired flow rate of gas. But in such a tower, the gas velocity must as a rule be kept below a certain limit (which limits the size of the passage), because if the gas velocity exceeds this limit, the gas will have a tendency to prevent the liquid from flowing downwards, and may even blow the liquid out completely from the tower. This has been called the flood limit or point. Furthermore, the packing in the towers has a tendency to collapse during its course, whereby the free passage is reduced and the above-mentioned problems are accentuated. In the course of time, the liquid also tends to acquire certain flow channels through the gasket, which also reduces efficiency. In some cases, clogging of the free passage areas can occur, especially if the gases carry with them solid particles, which settle on the packing, and for cleaning it is then necessary to stop the operation of the tower or to connect a duplicate tower.

In French patent no. 1 234 396, a packed ice tower type is proposed where the packing consists of balls of light weight, which can form a "floating" unitary layer, in which the balls are in contact with each other, but still have a certain degree of mutual cohesion freedom of movement. This layer, as a unified unit, has buoyancy and floats or swims in the top area of the tower, where it is stopped from above using a stop plate or a stop grid. The way it works is largely the same as that of a normal seal, especially in that there is a large contact surface between the downward flowing liquid and the rising gas, but the arrangement has certain advantages over the usual systems and is particularly advantageous under certain circumstances. It will, e.g. due to the ball's rotational movement or small linear movement in the layer, no channel formation occurs in the layer; solid particles carried along by the liquid or gas do not settle permanently on the gasket, but are, on the contrary, continuously washed away and removed, so that re-clogging is prevented. But this type of seal also offers considerable resistance to the passage of the liquid and gas, and for certain gas velocities, e.g. above 150 m/min., the flooding point is reached quickly. At this point the liquid no longer flows downwards through the packing, but is held by the gas pressure, as a separate phase, in the upper part of the tower, so that operation stops practically completely.

The present invention provides a method that can be used for many different operations, where it is desired to achieve intimate contact between a liquid and a gas, e.g. where the purpose of the operation is to remove a certain part of the gas by absorbing this part 1 a liquid, or where it is desired to separate out fine particles, solid or liquid, ira a gas in which they are suspended, or where the purpose of the operation is to transfer the goods from one fluid to the other, e.g. by cooling a gas using water, or the like. The invention is particularly useful when it comes to absorption problems which include e.g. leading large volumes of gas in countercurrent to a liquid, and where the purpose is to absorb components of the gas in the liquid. When contact between the gas and the liquid is established using the method according to the invention, a surprisingly high degree of absorption of the gas in the liquid is achieved, and exceptionally high speeds of one or the other of the fluids can be used.

In accordance with the present invention, a liquid is caused to flow downward through a contact zone, which is practically unobstructed, in countercurrent to a gas flowing upward through the same zone, and at the same time a plurality of lightweight elements are caused to move freely and arbitrarily throughout the zone.

The contact zone consists of a chamber of known construction and suitable size, which is equipped with devices for introducing the liquid and circulating the gas. The liquid is preferably introduced at the upper end of the chamber, through suitable introduction devices, which can conveniently consist of a nozzle or a similar device, which simultaneously divides the liquid into a shower of the desired degree of fineness. The gas is preferably introduced at the bottom part of the chamber and rises upwards in countercurrent to the liquid and is finally taken out of the chamber through an outlet, which for this purpose is arranged in the top part of the chamber. A number of lightweight elements of suitable size and shape and of different specific weights are placed inside the chamber, e.g. hollow plastic balls; these are used in such quantity and under such conditions that during the operation of the apparatus they are kept in continuous, random movement inside the chamber.

The invention shall be explained in more detail in connection with the attached drawings.

Fig. 1 schematically shows a vertical section through the contact chamber, where the lightweight elements rest on the bottom of the chamber and

fig. 2 shows a corresponding section, where the lightweight elements are in motion during operation. Fig. 3 shows a modification of the holding grid in fig. 1 and 2. Figs. 4, 5, 6 and 7 illustrate graphically certain experimental results from operation according to the present invention, as well as comparisons with results from previously known methods.

That in fig. The apparatus shown in 1 and 2 comprises a tower 1 of a known type, through which fluids can be directed in countercurrent to each other. The tower has a suitable height and its horizontal cross-section can be rectangular, circular or have any other suitable geometric shape. Part of the tower forms a contact space 2, which is delimited at the top by a grid or a perforated plate 4 and at the bottom by a similar grid or plate 5. The grids can consist of any suitable material, and preferably have openings of such a size that they offer the least possible resistance to gas and liquid flow. The task of the lower grid is primarily to serve as support for the lightweight elements 6 when the device is not in operation, while the upper grid mainly serves to keep the lightweight elements inside the chamber and prevent them from escaping when the device is in operation . The top grid can be looped if the chamber is given sufficient height to prevent the lightweight elements from escaping during the operation of the appliance. As a rule, the gratings will extend horizontally across the tower, but in some cases it may be advantageous to give the uppermost grating 4 the convex upwardly sloping shape shown in fig. 3.

The gasket 6, which consists of light spherical or spheroidal elements is in fig. 1 shown in a static state, i.e. when the apparatus is not in operation, resting in the form of a few stacked layers on the grid 5. It can be seen that only a relatively small part of the chamber's volume is taken up by the gasket. In fig. 2, the same gasket 6 is shown in the state it is in when the apparatus is in operation, namely arbitrarily distributed throughout the entire chamber volume.

The gas is supplied at the lower part of the device through the pipe 8 and flows into the device section 9 below the grid 5. The liquid is supplied to the device's upper section 3, above the grid 4, through the line 12 and the distribution device 13. The gas is drawn away from the upper part of the device through a fog trap 11 and the outflow pipe 14. The liquid is taken out at the bottom of the device, e.g. through pipe 15.

The movement of the individual elements inside the chamber takes place under the influence of various forces, including mainly gravity, the pressure exerted by the rising gas and the shocks exerted by the downward flowing liquid on the individual elements. It is a necessary feature of the present invention that the combined effect of these (and other) active forces keeps the light spherical elements in individual arbitrary movement, so that the elements wander freely over relatively long stretches, e.g. of an order of magnitude that is several times their diameter.

A particular result of such movement is

the fact that the elements are moved arbitrarily through practically the entire inner space of the chamber, and in any case do not form loose accumulations or any liquid unit layer as in the previous method where the lightweight elements lie in close contact with each other and are kept "floating" by buoyancy » in the upper area of the chamber.

The lightweight elements can have different shapes and sizes and consist of different materials. They can conveniently be made of hollow plastic balls, e.g. hollow balls having a thin wall of polyethylene; or of spheres or spheroidal bodies, possibly hollow, which are made of foamed polystyrene or other suitable material of low specific gravity. In what follows, these lightweight elements are often simply called "balls", but this expression should not be considered limiting as far as the shape of the elements is concerned. The balls can have a diameter of up to 10 cm, but will usually be smaller; the optimal size is best chosen empirically and in relation to the overall size of the chamber in which they are to be used. The balls generally have a low specific gravity, so that they do not settle on the bottom of the chamber, but on the contrary, respond easily to the action of the various forces acting inside the chamber. The specific weight of the spheres means the apparent specific weight of each individual sphere, i.e. the sphere's weight divided by the volume bounded by the sphere's outer surface. To be useful in this invention, the specific gravity of the individual spheres must be greater than that of the gas and less than that of the liquid. In practice, values of between approx. 0.01 and approx. 0.9 for the specific gravity of the balls.

It has proven advantageous if balls of different specific weights are used in one and the same operation, as the effect of such a mixture of "heavier" and "lighter" balls results in a more pronounced and more easily controllable arbitrary movement of the balls. In such cases, it is preferable to use highly varying and arbitrarily varying specific weights. A simple method for achieving such an arbitrary distribution of specific weights within a desired area consists, for example, of in using hollow plastic balls, e.g. polyethylene balls, of which a certain number have tiny holes through their wall. The liquid used during operation (or another suitable liquid) will penetrate in different quantities through the small holes, into the interior of the balls, whereby in this simple way an arbitrary distribution of specific weights is obtained within the desired range of these.

In order for the method of the invention to work correctly, it is necessary that the ball elements are kept in arbitrary movement, and that the operation is regulated if necessary so that this type of movement is achieved. The inventors have found that the factors that primarily affect the movement of spherical elements of a given size and specific weight are (a) the amount of elements in relation to the volume of the chamber, and (b) the flow rate of both the gas and the liquid. For elements of a given size or specific weight, there will therefore be a critical limit with respect to the number of such balls that can be used in a chamber of a given volume. It is appropriate to define this critical limit by specifying how much of the chamber volume is filled by the balls when these are in a static state, i.e. when the balls are piled up on the bottom of the chamber. To put the same thing in other words, one can define the critical limit by specifying the relative height of the static layer of the balls, i.e. the height of the layer of balls, when these are stacked evenly on top of each other at the bottom of the chamber — in relation to the overall height of the chamber; or one can — in yet another way — define the critical limit by specifying the relative height of the "free table", i.e. specifying the size of the space between the upper limit of the stacked spheres and the upper grid.

The inventors have found that the apparently packed volume of the spheres in a static state (which in the following is called the packing volume) must in no case exceed 50 percent of the volume of the contact zone, and in many cases should be considerably less, depending to a large extent by the specific gravity of the balls. (By the expression "apparent packed volume of the spheres" is meant the volume of the spheres plus the volume of the spaces between them). In other words, this means that the relative height of the static layer of balls must not be more than 50 per cent of the height of the contact chamber and in many cases must be less, particularly depending on the specific weight of the balls; or — put another way — the relative height of the freeboard must be 50 per cent or more of the height of the contact chamber. In practice, there will still be a certain minimum height for freeboard (expressed in absolute values) and if this is exceeded it will be difficult or impossible to achieve the desired arbitrary movement of the balls. The inventors have found that this minimum height of the freeboard is between approx. 150 mm and 1 m, depending on the specific weight of the balls, and the flow rates of the gas and liquid. If the critical amount of packing is exceeded, it is difficult or impossible to keep the balls in arbitrary motion, because as soon as the balls are lifted upwards by the gas stream, they will tend to rise as a united body into the upper part of the chamber, where they soon arrive for installation against the grid that delimits the chamber above. The inventors call this phenomenon "sticking", because the balls are, so to speak, "glued" to the chamber's upper limit grid. If this phenomenon occurs, a liquid layer of the previously mentioned known type is formed, in which the individual spheres can still rotate completely freely, but linear movement is greatly hindered due to the surrounding mass of spheres. If this happens, the pressure drop through the ball mass increases and this so much that for such gas and liquid velocities as are deemed to be used in the method according to the invention, the flooding point is reached quickly, and it is no longer possible to work according to the method of the invention.

It is easily understood that maintenance of the desired type of movement in the individual balls is strongly dependent on the fluid's velocities, especially on the gas flow's velocity. If the gas velocity is very small, it may not be able to exert a sufficient lifting effect to lift the balls up from the bottom of the chamber at all, especially if the specific weight of the balls is relatively large and/or the speed of liquid flow, but in the opposite direction, is relatively large. If, on the other hand, the gas velocity is high, there is a possibility that some or all of the balls will "stick", even if they are present in a quantity that is well above the critical value for the volume of the packing. For example, if you are working with balls of approx. 75 mm diameter, consisting of polystyrene foam (specific gravity approx. 0.023) and a liquid supply of approx. 150 liters per minute, the inventors have found that with a packing volume of 8.3 per cent, the balls had little or no movement at gas velocities up to approx. 115 m/min, and at a gas speed close to 420 m/min. was pronounced in the tendency to "stickiness". (In this experiment the gas was air and the liquid was water). If the packing volume was increased to 16.7 per cent, the sticking point was reached at gas velocities of just over 360 m/min. With polyethylene balls of approx. 38 mm diameter and specific gravity between 0.155 and 0.655, a liquid supply of approx. 150 l/min and a volume packing of 8.3 percent, the balls began to move at gas velocities of approx. 165 m/min, but no sticking point was reached at speeds up to 450 m/min (the latter speed being the maximum obtainable under the test conditions used). With polyethylene balls of this size and specific gravity, no sticking occurred even at lower liquid flow rates (eg 75.81 l/m and 37.9 l/m) and gas velocities up to 540 m/min; with in an experiment where the liquid's flow velocity was equal to zero, sticking of the balls began at gas velocities of approx. 870 m/min.

It should be clear that if and when sticking occurs (when using balls of a given specific weight and a given volume packing) a simple precaution is to reduce the gas velocity slightly or to temporarily increase the liquid supply, or both. Another way of controlling sticking consists in using a convex grid, of the one in fig. 3 showed art. When sticking occurs against a grid that has this shape, the spherical elements will tend to rise up towards the highest middle part of the grid and remain stuck there. If this happens, it is a simple matter to cover the part of the grid with a cover 16, while the rest of the grid, i.e. its largest part, along the circumference, can freely flow through gas. The balls stuck to the middle part of the grid will then begin to fall back towards the bottom under the action of gravity, and are drawn back into the arbitrary turbulent movement inside the chamber. The cover 16 can then be removed again.

A particular advantage of the method according to the invention is that the pressure drop along the working height of the chamber for different gas velocities is far less than the pressure drop for corresponding velocities in a packed tower of the type previously used. The consequence is that gas and liquid velocities of a very different order of magnitude can be used than was previously possible. Gas velocities of up to 450 m/min and liquid flows of up to 265 l/m per hour can be used at the same time. 0.09 m<2> cross-section without flooding occurring, Dg with a total pressure drop of between 5 and 25 cm water column, the absolute size of the pressure drop depends on such factors as the height of the contact chamber, the specific weight and size of the balls and the packing volume. Diagrams showing the pressure drop for different gas velocities and a given liquid flow are shown in fig. 4. The inventors have thus found that if one works with hollow polyethylene balls (38 mm diameter and specific weight between 0.155 and 0.655) and a volume packing of 8.3 percent, gas velocities of up to to 465 m/min before flooding occurs, and for a liquid supply of the order of magnitude 38-76 l/min, gas velocities of up to 640 m/min can be used before flooding takes place. It is noted that gas velocities in excess of 480-540 m/min are sufficient to hold liquid up in an open pipe (see "The Meteorological Glossary", from the Meteorological Office of the Air Ministry, published by the Chemical Publishing Co., 1940, p . 156). From the comparisons set out below, it appears that the gas and liquid flow rates that can be used in accordance with the present invention are far greater than the highest flow rates that can be used in normal packed towers, where flooding occurs for gas velocities of the order of magnitude 30-120 m/min combined with liquid supplies of no more than 141 l/min. It is also seen that the gas and liquid flow rates which can be used according to the present invention far exceed

those that can be used in the previously known floating layer technique. Because of these larger

speeds, not only is the material throughput (or the tower's capacity) significantly increased, but also the absorption efficiency is markedly improved, and with it also the recovery of the gas component parts that the operation's purpose is to recover.

A useful application of the method can e.g. occur by the absorption of carbon dioxide in alkaline liquid. In this operation, the purpose was to carbonate the working liquid from an initial pH of 11.0-12.5 to a final pH of 9.0-9.2 by means of a flue gas containing oa. 16 volume percent carbon dioxide. The liquid consisted mainly of a sodium hydroxide-sodium carbonate solution and some dissolved solid material (wood). No attempt is made here to extract the carbon dioxide completely from the flue gas; rather, an excess of flue gas (which can be tolerated by the tower size and the power requirement) is normally used so that a carbon dioxide partial pressure is maintained as a driving force, whereby the tower's capacity is increased.

The apparatus used was of the type described above, and had a chamber whose cross-section was 0.09 m and the height was approx. 3 m. The contact zone in the chamber was delimited by an upper and a lower grid, with approx. 1.5 m mutual distance. Polyethylene balls with a diameter of 38 mm and a specific gravity between 0.16 and 0.65 were placed on the bottom grid; the number of balls (ie the volume of the package) was varied from one trial to the next. Carbon dioxide-containing gas was introduced at the bottom of the chamber and allowed to flow upwards through the bottom grid, through the contact zone and the top grid, to an outlet line to the atmosphere. The liquid was introduced in the form of a shower at the top of the chamber and was allowed to pass downwards through the top grate, and through the contact zone in countercurrent to the rising gas, and was collected (with material dissolved therein) in the bottom part of the chamber and pumped on to further be -action. Measurements were made of the gas and liquid flow, of the concentration of C02 in the input and output liquid, in order to determine the partial pressure of carbon dioxide (the driving force), the absorbed amount of gas and the extraction efficiency.

(where M is absorbed gas, calculated at 0.45 mol/hour. V is the packing volume calculated at 28.3 liters, and AP is the average partial pressure of the solution gas calculated at d atm.) and this coefficient is taken as a measure of the absorption efficiency; the coefficient's

Studies carried out by several researchers (see "Absorption and Extraction" by Sherwood & Pigford, 2nd ed., 1952, McGraw-Hill Book Company, p. 364) on the absorption of carbon dioxide in sodium carbonate solution in packed columns show that this absorption constitutes a liquid film-controlled system, i.e. a system in which increased liquid supply will cause the adsorption efficiency to be greater, while variations in the gas supply will have little or no influence on the absorption efficiency.

However, in such an operation, high gas velocities are still advantageous to maintain a high partial pressure (driving force), which increases the tower's capacity. The absorption coefficient can in this case be stated as Kga = CZx, where Z denotes the liquid supply in kg/hour/m<2>, and C and X are constants which are characteristic of the packing, and which are determined experimentally road. The absorption coefficient is also influenced by other work factors or

-conditions, e.g. of the temperature (the coefficient increases with temperature), the concentration of carbonate and the percentage amount of bicarbonate (the coefficient decreases with increasing value of both these factors). The results of the experiments are given in Table I.

Experiments 1-11 show the C02 absorption capacity of an absorption tower having a cross section of 0.09 m<2> (1 square root) and which is packed with 38 mm polyethylene balls of specific gravity from 0.16 to 0.66. Experiments 1-8 were carried out according to the method of the present invention, and experiments 9, 10 and 11 were carried out with the fluidized bed technique described in French patent no. 1 234 396 (A.W. Kielbuck). Also listed is a trial 12, which used a conventional, coke-packed tower, which was available at the facility (1.1 m<2> (12.6 square root) cross-section and 10.1 m (37 ft) linear packing ) was applied.

Data regarding linear gas velocity of 120 m/min and a liquid supply of approx.

60 l/min is indicated in fig. 5 a, b, c and d.

It can be seen from Fig. 5a that at 8-50 per cent apparently packed volume the pressure drop increases continuously from 5 to 25 cm water column; and the relationship is characteristic of the arbitrary movement of the balls used according to the invention. If the apparent packed volume is increased from 50 to 60 per cent, the balls rise to the top grid in the zone and a sharp pressure drop occurs to 73.5 cm water column. At 60-80 per cent, and a larger, apparently packed volume, a new characteristic relationship is established with "floating layers". (In experiment 3, where there is only approx. 7.5 mm of free space above the apparently packed volume, the large pressure drop produced resulted in a reduction of the gas flow speed from 120 linear m/min to 60 linear rn/min, on due to the limited performance of the fan For this reason the point for trial 11 (in Table 1) is shown in Fig. 5a 1 in the form of a curve, because with a linear speed of 120 m/min the pressure drop would be much greater.

Fig. 5 b shows the C02 absorption calculated in kg/hour/m<2> and fig. 5c shows the C02 uptake for

water column pressure measurement, on the same scale. These curves also clearly show the discontinuity between the effect achieved where the balls are moved arbitrarily — according to the invention — and the effect achieved when the balls here have limited freedom of movement (flotation technology). A comparison of trials 3 and 10, where the apparent packed volume is 8.3 percent resp. 80 per cent, shows pressure drop values of 8.75 resp. 0.81 in the above scale

(0.45 kg/hour/0.09 m<2>/water column). A more than ten times greater absorption of C02 per unit pressure drop when working according to the invention than when working with fluid layer technology.

Fig. 5d illustrates the relationship of the absorption coefficient to the packed volume, and also shows the markedly better absorption that is obtained when the balls move arbitrarily.

Experiment 12 provides data for a tower packed with coke. It is clearly seen that the C02 uptake per unit pressure drop in this tower, although it is of the same order of magnitude

which you get with low density packing

and with limited movement of balls, the uptake is considerably less than when working with arbitrarily moved balls, according to the invention.

In the construction and operation of a conventional packed tower, an optimal gas velocity is usually chosen by weighing up the construction and operating costs in relation to each other. If, for example, a greater gas velocity is chosen, the bore diameter (for a given performance) may be smaller, but the costs of pumping the gas against the tower pressure will be greater. But as a rule, the speeds used, in continuous operation, will depend on the flooding speed, and not be more than 40-50 per cent of the flooding speed, due to re-clogging of the packing (see Sherwood & Pigford, cited above, page 245) .

Table II gives the flow rates for varied liquid feeds in a typical tower, which is filled with 2.5 cm. Raschig rings, for a gas containing 16 per cent CO., calculated on a dry basis, and which is absorbed at 57°C. Table H's data is shown by curve A in fig. 6 and in the same figure, for comparison, the curve B indicates the overflow point area when working according to the present invention (using polyethylene balls with a specific gravity of 0.16-0.66 and a packing volume of 8.3 per cent. ). Curve B shows that the flooding point at gas velocities up to 510 m/min is not changed by the liquid passage in the entire examined area. The value 510 m/min will vary somewhat depending on the physical properties of the two fluids. It can be seen that the entire speed range which lies above the curve A and below the curve B and which cannot be used in normal packed towers, can be used with advantage in the method of the present invention. It is e.g. tests have been carried out using polyethylene balls (38 mm diameter and specific weight 0.16-0.66), packing volume of 16.7 percent, liquid supply 141 l/min and gas velocities of 345 m/min, with a total pressure drop of approx. 24.5 cm water column. When polystyrene balls (38 mm diameter, specific gravity 0.023) were used and the same fluid velocities were used, the pressure drop was 12.4 cm of water column.

The effectiveness of the present method is clearly shown in Table III, which indicates a comparison between this method and that with 2.5 cm Raschig rings. It is seen that in order to achieve the same results, expressed as total gas absorption, under the same deposition conditions, the conventional packed tower must have a cross-section that is 5.5 times larger and a packing height that is 12 times larger (and a packing volume that is 65 times larger) than in an absorber according to the present invention. This clearly shows the effectiveness of the invention.

In another attempt, the invention's

method used for the absorption of sulfur dioxide 1 sodium hydroxide, for the production of sodium bisulphite liquid which was to be used in the production of cellulose. In this example, multiple zone operation was used in some of the experiments, where the fluids passed through two or more series-arranged contact zones; such an arrangement has proven to be beneficial, e.g. in terms of absorption capacity and pressure drop, the latter of which is less than when using a single layer and the same total amount of packing. The results of some experiments of this nature are shown in a table

IV.

In yet another example of use of the invention, where sulfur dioxide was absorbed in a slurry of magnesium hydroxide, liquid supplies of over approx. 295 l/m, and gas speeds of over 300 m/min.

In a further exemplary embodiment, the contact chamber of the invention was used to effect cooling and dehumidification of warm moist air, by directing it in countercurrent to cooling water. The studies of these heat and mass transfers were carried out in a tower with a 0.09 m<2> cross-section, which was mostly of the type described above, but which consisted of three zones arranged vertically in sequence, each 1, 2 m high, and where each zone had a 12.7 cm high packing (in static condition) of polyethylene balls of 38 mm diameter and specific gravity 0.16—

0.66. The flows, 1 temperature and humidity of the incoming air, as well as the temperature of the incoming and outgoing water were measured. The results of these tests are collected in Table V, which shows a transition quantity that is significantly greater than those stated in the literature for ordinary towers. The results of these tests are summarized in Table V, which shows a transmission amount which is considerably greater than that which the literature indicates for ordinary towers. The results of these experiments are further illustrated graphically in fig. 7.

It is clear that the method according to the invention can be used for

many and different operations where it

applies to providing contact between a liquid

and another fluid, e.g. by absorption,

scrubbing, cleaning, heat exchange and

similar, where it is necessary to have intimate contact between the fluids, and where contact between the fluids is achieved by

these are fed in countercurrent to each other through a contact zone.

Claims (5)

1. Method for bringing about mutual contact between a gas and a liquid, whereby the gas flows upwards through a contact zone containing fluidized lightweight elements and finely divided liquid flows in a countercurrent downwards through this contact zone, characterized in that the lightweight elements are kept in arbitrary movement throughout the zone by the pressure of the upward-flowing gas and by impact from the downward-flowing liquid particles. 2. Method as stated in claim 1, characterized in that the number of elements in motion in the entire mentioned zone is so large that the total volume of said elements, when these is not in motion, does not make up more than 50 per cent of the volume of the zone in question. 3. Method as stated in claims 1-2, characterized in that the lightweight elements used are practically spherical and have a diameter of less than 10 cm and a specific weight that is less than the specific weight of the liquid, but greater than the specific weight of the gas, preferably between 0.01 and 0.9, possibly arbitrarily varying between these values. 4. Method as stated in claims 1-3, characterized in that the upward gas flows with a linear speed of between 100 and 550 m/minute and that the speed of the downward-flowing liquid is between 10 and 40 liters per minute per dm<2> cross-section, preferably a gas velocity of between 150 and 200 m/min. and a liquid rate of between 4 and 30 liters per minute per dm<2 >cross section. 5. Method as indicated in claims 1-4, characterized in that the liquid and the gas are passed through a number of contact zones which are arranged in series. Publications cited: French Patent No. 1,234,396. Swedish Patent No. 21,049.