NL1005990C2 - Structured packing for dust and / or heat exchange between a liquid and a gas, as well as a container provided with such a packing. - Google Patents

Description

IA

Structured gasket for dust and / or heat exchange between a liquid and a gas, as well as a holder provided with such a gasket

The present invention relates to a structured packing 5 for dust and / or heat exchange between a liquid and a gas, the structured packing comprising a plurality of mutually parallel corrugated plates, the waves of the plates delimiting channels, and adjacent corrugated plates with their channel direction are arranged crosswise, and the waves of each plate have a wave height H and a wave width B.

Such structured packing is known from the article "distillation columns containing structured packing" by J.A. Fair et al. In Chemical Engineering Progress, Vol. 86, No. 1 January 1990, New York and may further be considered generally known per se. In the case of sinusoidal corrugated plates, a value for the wave width is generally taken around the number π, while for the wave height a number around the value 1 is taken. The unit of π and the value 1 is generally in cm. In such a structured packing, adjacent corrugated sheets (also called corrugated sheets) are always arranged crosswise with respect to each other, such that the flow channels bounded by the corrugated sheets intersect, whereby so-called interfaces at intersections of the open sides of two intersecting channels. are being formed. Flowing, differently directed gas flows come into contact with each other at these interfaces. The pressure drop over a gasket as a result of flow resistances experienced by gas flows flowing therethrough depends to a large extent on the flow resistance encountered by the gas flows at the contact surface with the corrugated plates on the one hand and, on the other hand, on the resistance due to the interfaces occurring at the interfaces. flow effects, also known as interface effects, such as turbulences. The view is that if the H / B ratio is too large, the gas phase does not mix well or less well. For this reason, in practice, a ratio of wave height to wave width is used, which is less than 0.3 to 0.5, i.e. "J <0.3 to 0.5, the aforementioned article". distillation columns containing structured packing mentions 1, values ranging from 0.25 to 0.5. In order to keep the pressure drop over such a structured packing relatively limited, in practice the vertical 1005990

1 B

the corrugated plnlcn mcl lum channel direction mceslal sloped at an angle of about 30 ° relative to the vertical, which angle will in practice not exceed 45 °. This is because with grole (re) 1005990 2 angles of the duct direction relative to the vertical the flow resistance over the gasket becomes too great.

The present invention aims to provide an improved structured packing of the type indicated at the outset.

According to the invention, this object is achieved in that the ratio wave height H to wave width B satisfies the equation ξ è 0.75 · As the ratio § increases, the influence of flow-resistance-causing effects decreases at the so-called interfaces-10 because the mean distance of the gas to this interface is increased with a larger ratio However, this decrease in flow resistance due to so-called interface effects is accompanied by an increase in flow resistance at the contact surface between the corrugated sheets and the gas flows, since 15 with an increase in the ratio § per channel increases the contact area between the plate and the gas flow. Surprisingly, however, it has been found that the increase in flow resistances at the contact surfaces does not outweigh the benefits achieved by the reduction in interfaces (which, incidentally, is also associated with a decrease in the total of interfaces in a gasket) and that other expected disadvantages hardly occur or do not outweigh the benefits achieved. The surprising, advantageous effect appears to already occur at ratios 5 z 0.75. begins to manifest itself clearly in relationships i 1, and in particular occurs at ratio j i 2. It will be clear that, depending on the type of wave profile, the ratio | in practice, an upper limit will also be set, but if the values are too large, the flow area will assume too much of a slit shape with the associated adverse turbulence effects and / or flow resistance effects. Furthermore, in particular with non-rectangular, for instance cylindrical containers, there will be a minimum number of plates in order to realize a sufficient degree of filling of the container.

Particularly with corrugated metal sheets, according to the invention it will be advantageous according to the invention for cost reasons if they have a triangular, trapezoidal or rectangular corrugated profile. Namely, such profiles, in particular triangle-shaped corrugated profiles, can be formed relatively easily by folding out metal sheet or suitable plastic sheet. For flow engineering reasons, however, according to the invention, in practice, preference will often be given to a corrugated plate with an approximately sinusoidal, preferably pure sinusoidal, wave profile.

When designing structured packings of the type mentioned at the outset, just as with structured packings according to the invention, an important quantity is the so-called specific surface area, which as a unit has m2 / m3. This specific area is actually the contact area of the plates per cubic meter of gasket. In practice, many values used for this so-called specific surface are: about 125 nf1, about 200 m * 1, about 25 m 1 and about 500 m 1. Assuming that a specific surface area is required, desired or prescribed, according to the invention B and H will advantageously form a solution of the numerically soluble equation: * 5 A = - Γ * sin2 a + (-) 2 da

p Bjo \ | πH

For a specific surface area, this relationship shows a relationship between B and H, which can be represented as a curve in a two-dimensional graph.

In order to be able to realize an optimal liquid irrigation of the structured packing, it is advantageous according to the invention if the corrugated plates are arranged substantially vertically.

According to an advantageous embodiment of the invention, one or more of the corrugated plates with their channel direction are arranged at an angle of approximately 45 ° to the vertical. Preferably, one or more of the corrugated plates with their channel direction are arranged at an angle of about 55 ° to 65 ° from the vertical, such as at an angle of about 60 ° from the vertical. Such channel direction angles are in fact not feasible with structured packings consisting of corrugated plates according to the prior art, since the flow resistance of the pack then takes on too great a value. At relatively larger H / B ratios according to the invention, however, it surprisingly appears possible to increase the angle of the channel direction relative to the vertical, even up to about 70 °. The advantage of a greater angle of the channel direction relative to the vertical is that this achieves a better mass transfer between the gas flowing upwards via the structured packing and the liquid flowing downwards along the structured packing. It should be noted that according to the invention very advantageous effects with regard to the prior art are also realized with channel directions of less than ^ 5 * with respect to the vertical, such as with 10 to 45 ° with respect to the vertical. At such smaller angles, the pressure drop across the packing according to the invention is lower than with conventional packing.

10 When the structured gasket is built into a container in such a way that the corrugated sheets define channels extending between opposite walls or wall parts thereof, the flow resistance of the gas in the edge region adjacent to the wall or wall part at the transition from one channel according to the invention, it is advantageous if the corrugated plates are provided with holes at the channel ends adjacent to the wall parts, in particular at larger angles to the other channel, in particular at larger angles of the channels relative to the vertical. Such holes facilitate the transition of the flowing gas from a unidirectional channel to a channel extending in another crosswise direction. Particularly with containers with a larger cross-sectional area, in the case of cylindrical containers thus with a larger diameter, such an edge area will then preferably extend up to 10 to 20 cm from the wall, depending on the so-called specific surface. Larger cylindrical holders are understood to mean holders with a diameter of 1 m and larger. In particularly smaller containers, such an edge region will extend over a distance of about 10% to 20% of the width / depth of the container, in the case of a cylindrical container over a distance of about 10% to 20% of the diameter of that container. According to an advantageous embodiment, the holes will have a diameter of at least 2 mm, preferably up to 20 mm, or an equivalent flow area in the case of non-round holes.

The invention will be explained in more detail below with reference to drawing 35. Herein shows:

Figure 1 schematically shows a triangular wave profile, in which some quantities thereof are further indicated; 100 5990 5

Figure 2 is a perspective and schematic view of a part of a four-layer structured packing according to the invention;

Figure 3 shows a schematic view, partly in section, of a container according to the invention; Figure 4 schematically one wave of a sinusoidal wave profile;

Figure 5 is a graphical representation of an H / B relationship with a sinusoidal wave profile; and

Figure 6 is a very schematic representation of a test set-up.

Figure 1 schematically shows a triangular wave profile with a wave height H and a wave width B. It will be clear that this wave height H and wave width B are identically attributable to the waves of the sinusoidal wave profile shown in Figure 4.

Figure 2 shows by way of example in a very schematic manner a structured packing according to the invention, consisting of, for example, four layers of corrugated plates (also called corrugated plates), each with a triangular corrugated profile. Regarding corrugated sheet 2, it will be appreciated that each corrugated sheet 2 defines a plurality of channels extending transversely of the wave direction G. These channels 6 open at the bottom or channels 7 open at the top thus have a channel direction K extending transversely to the wave direction G. It will be clear that the corrugated sheets 3 in this example according to Figure 2 are identical except for their orientation. to the corrugated plates 2. However, as will be apparent to an average skilled person, as far as the essence of the invention is concerned it is by no means necessary that the corrugated plates 2 and 3 are identical except for their orientation, nor that the corrugated plates in the layers 2 are mutually identical. Nor is it important for the essence of the invention that G and K are perpendicular to each other.

As will further be apparent from Figure 2, when crossing upwardly open channels 7 and downwardly open channels 6, these channels form imaginary interfaces 4 bounding there. Furthermore, it will be clear that when gas flows through the channels of adjacent plates, 4 interface effects will occur at these interfaces that adversely affect the flow resistance of the packing as a whole. Furthermore, gas flowing through the packing will experience further flow resistance upon contact with the corrugated plates.

1005990 6

According to the invention it has been found that when a value of 0.75 is taken for the ratio of wave height H to wave width B, an improvement in the flow resistance across the packing as a whole occurs. Particularly from ratios H / B i. 1 this becomes so manifest that great advantages are achieved, which advantages can increase even further when the ratio H / B becomes 2.

The embodiment according to figure 3 shows a container according to the invention which is provided with a gasket 1 according to the invention.

In such a container, liquid is spread on the top side via a spraying device 10 at the top. This liquid flows down the faces of the corrugated plates in such a way that a liquid film is formed on the surfaces of the plates. A gas is supplied to the underside of the packing, which flows upwardly, in countercurrent with the liquid (film), through the packing. During the countercurrent flow, exchange between the liquid and the gas can take place. It should be noted that the flow of the packing with gas and liquid can optionally also take place in co-flow or a cross flow. Advantages also occur with packings according to the invention in the case of co-current and cross-flow flow.

The corrugated sheets of packing 1 are here arranged vertically with a channel direction K with respect to the vertical substantially greater than 50 ° (However, angles smaller than 50 'are also usable and offer great advantages according to the invention.). A lower gasket 11 is arranged under the top gasket 1. In the upper gasket 1, the channel direction runs at an angle of about 60 ° from the vertical. In the lower packing 11, the channel direction extends at an angle of about 5 ° to the vertical, which angle may also be less than 45 ° to 30 from the vertical under conditions, such as, for example, 30 °. By making the angle of the channel direction relative to the vertical smaller at the lower gasket 11, so-called "flooding" problems are prevented. Flooding is understood to mean that a droplet hangs on the underside of the gasket, which is easily taken along by the upward flowing gas. Steeping of the channels of the lower gasket section prevents this from sticking to drops. It should be noted that this steeper placement of the channels in the lower packing section to prevent flooding can also be used separately from a relatively larger H / B ratio and also from relatively large angles of the channel direction of the upper packing 1. However, when, as advantageously possible according to the invention, relatively large angles for the channel direction relative to the vertical are used, in particular in a range from 50 ° to about 70 °, so-called flooding occurs. problem at the bottom of the gasket reinforced for.

Figure 3 further illustrates what is meant by an edge region adjacent to the wall or the wall part of the container. This edge area is indicated there with R and the size of R will generally be about 10 to 20 cm for containers with a diameter of 1 m and larger, while for container with a smaller diameter this R will be about 10¾ to 20¾ of the diameter will amount to. In this so-called edge region, the corrugated plates are provided with holes 5. which facilitate the transition of the gas from a channel running in one direction at an angle to a crossing channel in the other direction, which is sloping in the other direction, so as to facilitate the flow resistance of the lower gasket. Particularly when according to the invention relatively large angles for the channel direction relative to the vertical are used, it will be advantageous to provide the edge areas of the gasket with such holes.

In the following, it will be explained with reference to Figures 4 and 5 how, based on a specific surface area, Ap values for B and H can be determined in the case of a corrugated sheet with a sinusoidal profile.

A sinusoidally folded plate can be described parametrically as: ff 1 / = - (1 cos a) X Q.

with a = 2n _, so that x = - B (-n B 2 π v '30) The length of a small piece of this plate (see figure k) can be described as: ds = yjdy2 + dx2 (2) 100 599 0 8

Starting from equation (1), dy and dx can now be written as:

Η B

dy - - sin α da and dx = —da (3) 2 2 π

Entering formula (3) in formula (2) then results in: ds = - sin2a + (-) 2 da (^)

2 \ | nH

5 The integral of formula (4) s = - Γ sin2a + (-) 2 da = 2H Γ 2 sin2a + (-) 2 da (5)

2 Jo \] nH Jo nH

then gives the total length of the plate, which can be used for the determination of the specific surface area Ap according to the following formula (6): 10 A = -S ’2 = -ίί Γ2 sin2a + (-) 2 da (6)

p BHz B Jo \ | itH

The equation of formula (6) is numerically soluble for B as a function of H or vice versa, if a value is taken for Ap. Figure 5 shows the relationship between B and H when 250 m is taken for "Ap". This curve is denoted by F. In figure 5 the line H = 0.75 B is further drawn. When the intersection of this line If we look at the curve F, it can be seen that this intersection point is slightly above the point closest to the origin of the curve F. The origin is understood to mean the point H = 0 and B = 0.

Referring to formula (6) and figure 5, it can further be noted that starting from figure 5, corresponding curves for other values of A p can be realized in a simple manner. Namely, the curve for Ap = 500 m'1 is easily obtained by dividing all values for B and H by 2 in Figure 5. If for Ap 100 is taken 100 m * 1, then all values for B and H from figure 5®et 2.5 must be multiplied. Likewise, the curves for further values of A p can be determined, as will be clear to an average skilled person.

100599ο 9

With a test set-up as shown very schematically in figure 6, a number of experiments have been carried out, in which packings according to the invention have been compared with packings from the prior art.

5

EXPERIMENT T

In a first experiment, six packing units, numbered 21 and 22, were placed one above the other in a cylindrical container with a diameter of 19.2 cm. Each packing unit 21, 22 consists of a number of vertically arranged, mutually parallel corrugated plates. As shown schematically in Figure 6, the corrugated plates 21 and 22 of adjacent packing units are mutually perpendicular to one another. With the packing units, the channel direction of each plate always makes an angle of ^ 5 ° with the vertical. The wave profiles 15 are herein substantially triangular in shape, with a wave height H and a wave width B, as schematically indicated in Figure 1. For the rest, two test setups were used, of which the specific, structural key figures are shown in the following table: 20

TABLE I

I "11" "__Setup I__Setup II_ _H / B __ (M9__1JL3_ _H in mm__about 10.8__about 20.3_ 25 _B in mm__about 22__about 18_ number of plates per 17 9 packing unit__ tL in mm (height 195 175 packing unit) __ A" m2 / m ^ 250 250

As can be seen from table I, the so-called specific surface area per gasket is set at Ap = 250 m'1, and in arrangement I is designed at an H / B ratio of 0.9, and in arrangement II it is designed at an H / B 35 ratio. of 1.13. for which the H and B can therefore be read from the graph in figure 5. Air has been passed through both arrangements I and II with a so-called superficial gas velocity Ug of 1, 2, 3 and 5 m / s successively. This air is led from the bottom upwards through the packings according to figure 6 fitted in a cylinder in 1005990 10. The pressure drop across the column per setup and per superficial gas velocity is then measured. Superficial gas velocity Ug (in m / s) is understood to mean the average flow velocity of the air relative to the cross-sectional area of the cylinder, which cross-sectional area is therefore 289.53 cm2. The air drawn in from the environment had a temperature of 20 ° C and an atmospheric pressure. The measurement results of this are shown in Table II below.

10

TABLE II

Setup II

Ug in m / s Δρ in Pa / m Δρ in Pa / m 15 _1 ^ 0__91__67_ _2 ^ 0__285__211_ _3j0__561__4i6_ 5,0 1385 1107 20 From the experimental measurement data in table II it appears that the packing according to the invention (in arrangement II) has a pressure drop which is generally about 25% lower than the pressure drop in setup I.

EXPERIMENT II

With the same setups I and II as used in experiment I.

experiment II was carried out. The difference here is that in experiment II a water film was also applied to the gaskets by spraying water at the top of the arrangement of figure 6. The amount of water W is expressed in kg / s / m2, that is to say in kilograms of water per second spread over a cross-sectional area of the cylindrical container, which in this case, as indicated above, is approximately 289.5 cm2. In experiment II, it was determined for three quantities of water W per arrangement at which superficial gas velocity Ug a pressure drop per meter of packing of 800 Pa / m 35 occurs. The results found here are shown in Table III.

1005990 11

TABLE III

_____Setup I__Setup II_ W in kg / s / m2 Ug in m / s Ug in m / s 5 _2j8__2M__2 ^ 98_ _5_155__2J7__2 / 76_ 8.33 1.9 * »2.60

Table III shows that in arrangement II 23% higher gas velocities are permissible before a pressure drop of 800 Pa / m is reached. This means that with a packing according to the invention at a certain pressure drop, in the example 800 Pa / m, an approximately 23% higher throughput capacity is achievable.

1005990

Claims (13)

12 1. Structured packing for dust and / or heat exchange between a liquid and a gas, the structured packing 5 comprising a plurality of mutually parallel corrugated plates, the waves of the plates delimiting channels, and adjacent plates with respect to their channel direction are arranged crosswise, and the waves of each plate have a wave height H and a wave width B, characterized in that the ratio wave height H to wave-10 width B satisfies the equation: § 2: 0.75 Structured packing according to claim 1, characterized in that the ratio of wave height H to wave width B satisfies the equation J 2 1, Structured packing according to claim 1 or claim 2, 15, characterized in that the ratio of wave height H to wave width B satisfies the equation | 2 2. Structured packing according to one or more of the preceding claims 1-3, characterized in that one or more of the corrugated sheets have a triangular corrugated profile. Structured packing according to one or more of the preceding claims, characterized in that one or more of the corrugated plates have a sinusoidal wave profile. Structured packing according to one or more of the preceding claims, in which the corrugated plates have a sinusoidal wave profile, characterized in that for a determined desired specific surface area Ap, B and H form a solution of the numerically soluble equation: Λ = - Γ 2 sin2a + (-) 2 da p B Jo \ J nH Structured packing according to one or more of the preceding claims, characterized in that the corrugated plates are arranged substantially vertically. Structured packing according to claim 7, characterized in that one or more of the corrugated plates with their channel direction are arranged at an angle of about a 70 ° with respect to the vertical. 100599η 13 Structured gasket according to claim 7 or claim 8, characterized in that one or more of the corrugated plates with their channel direction are arranged at an angle of approximately 55 * 65 ° to the vertical, such as at an angle of approximately 60 ° relative to the vertical. A container, in particular an exchange container, provided with a structured gasket according to any one of the preceding claims, wherein the corrugated sheets define channels extending between opposite walls or wall parts of the container, characterized. 10 that the corrugated plates are provided with holes at the channel ends adjacent to the wall parts. A container according to claim 10, characterized in. that the holes are arranged in an edge region adjacent to the wall or the wall part, which extends to 10 to 20 cm from the wall. A container according to claim 10 or claim 11, characterized in that the holes are arranged in an edge region adjacent to the wall or the wall part, which extends over a distance of about 10% to 20 # of the diameter of the container. Holder according to one or more of claims 10-12, characterized in that. that the holes have a diameter of at least 2 mm to preferably a maximum of 20 mm or an equivalent flow-through area. 100 5990