EP1804947A1

EP1804947A1 - Method and device for evaporating a cryogenic liquid

Info

Publication number: EP1804947A1
Application number: EP05789320A
Authority: EP
Inventors: Robert Eichelmann; Anton Moll; Jan Segatz
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 2004-10-29
Filing date: 2005-09-27
Publication date: 2007-07-11
Also published as: WO2006048082A1

Abstract

The invention relates to a method and a device for evaporating a cryogenic liquid. Said cryogenic liquid is applied, together with water, to a packing (2a, 2b, 2c, 2d, 2e, 2f), and evaporates by direct heat exchange with the water.

Description

description

Method and device for vaporizing a krvogene liquid

The invention relates to a method and apparatus for vaporizing a cryogenic liquid

In cryogenic air separation plants it is sometimes necessary to evaporate larger quantities of cryogenic liquid. The cryogenic liquid to be evaporated can occur, for example, in connection with the emptying of a rectification column. Even with minor breakdowns, in which a short-term cryogenic product is produced with insufficient purity, which is not to be merged with the "pure" product, such can be incurred to be disposed of liquid quantities.

So far, the cryogenic liquid to be evaporated is usually disposed of by means of a steam or Luftejektors. Here, the cryogenic liquid in a

Injected steam or air stream and evaporated in direct heat exchange with the steam or air. Air ejectors are limited to their ^■ evaporation capacity terms. For larger throughputs steam ejectors are therefore used, but have the disadvantage that strong noise and fog or ice emissions are caused. Besides, not at all

Plant locations sufficient steam for operating the steam ejectors available.

Object of the present invention is therefore to show an alternative way of vaporizing cryogenic liquids.

This object is achieved by a method of the type mentioned, in which the cryogenic liquid and water are applied to a package and the cryogenic liquid is evaporated in direct heat exchange with the water.

The device according to the invention is characterized in that a container with a packing, with a supply for the cryogenic liquid, with a distributor for distributing the cryogenic liquid on the package and with a supply for Water and a manifold for distributing the water is provided on the pack.

In the context of the invention it has been shown that it is in principle possible to evaporate even larger amounts of a cryogenic liquid in direct heat exchange with water. The necessary for a sufficient heat transfer to the cryogenic liquid contact surface is provided by the provision of a packing, as used for example in rectification columns.

With packs one differentiates between disorderly and orderly

Packs. Unordered packages, also referred to as packing, are understood to mean elements which can be shaped in the most diverse ways and which are filled into a container through which the streams to be brought into contact with one another are guided.

Ordered packs have, as the name implies, an ordered, regular structure. As a rule, an ordered packing consists of a plurality of mutually parallel plates or plates, which are often provided with a corrugation or embossing.

Both pack types are suitable for evaporating cryogenic liquids according to the invention, but in particular, ordered packings have proven to be useful. Packages are preferably used which have a plurality of mutually parallel, corrugated sheets, which are arranged so that the caused by the corrugation channels of adjacent sheets intersect, so that forms a cross-channel structure.

The cryogenic liquid and water are applied to the packing and undergo direct heat exchange. In this case, the cryogenic liquid is evaporated and there is a laden with water in the form of aerosols vapor stream, which is withdrawn from the pack and disposed of or otherwise used. A great advantage of the invention is that this evaporation takes place without appreciable noise emissions. Preferably, the water and the cryogenic liquid to be evaporated are passed through the packing in cocurrent. Advantageously, the cryogenic liquid and the water are supplied above the package via suitable lines and distributed by distributors evenly on the package in order to fully exploit the large surface area of the package can.

The distribution of the water and the cryogenic liquid is preferably carried out by means of Rohrverteilem. It has been found that it is particularly favorable when the feed of the cryogenic liquid is carried out above the water feed, that is, when the distributor for the cryogenic liquid is arranged above the distributor for the water. Namely, the cryogenic liquid distributor is not wetted by the water sprayed through the water distributor and, on the other hand, has a sufficient distance from the package so that the risk of water splashing from the package to the distributor openings may occur freeze, minimized.

But it is also possible to install the two distributors at the same height. This variant is the most advantageous in terms of space requirements. However, in this arrangement, the water manifold and the cryogenic liquid manifolds should be thermally insulated from each other to avoid cold spots, which could also lead to icing. ^'

The experiments carried out with the invention have shown that fears that the outlet openings of the cryogenic liquid distributor could freeze and influence the flow of cryogenic liquid are unfounded. It is assumed that a gas cushion of evaporated cryogenic liquid is formed above the water distributor, which, together with the downward flow of water, ensures that no water flows into this area during the further evaporation in the packing. An icing of the pack or the water distributor is also not observed.

A particularly efficient evaporation of the cryogenic liquid is achieved if the water and the cryogenic liquid are distributed as homogeneously as possible over the entire surface of the package. Preferably, therefore, several layers of an ordered package are provided one above the other. The individual layers are included preferably in each case rotated against each other by 90 °, in order to prevent Maldistributionen within the pack or to keep low. Preferably, 2 to 8 packing layers, more preferably 3 to 5 packing layers are provided.

In a DC flow of water and cryogenic liquid and a

Supplying the streams from above, the uppermost portions of the packing first come in contact with the cryogenic liquid and the water. In these upper areas there is a strong increase in volume due to the evaporation of the cryogenic liquid. In contrast, in the parts of the pack lying further down, the cryogenic liquid has already evaporated and only the heating of the resulting gas takes place.

It is therefore advantageous if the pack consists of several different, stacked packing layers.

It is further advantageous to use a packing of a material with good thermal conductivity, for example to use a copper packing, in order to achieve a higher heat transfer to the cryogenic liquid and to achieve a faster evaporation.

Furthermore, it is advantageous to use packings of a thicker material in the upper region in order to achieve a higher thermal conductivity. It has been found that the smaller free cross-sectional area associated with the larger material thickness is not a problem in practice since the gas volume resulting from the evaporation increases from top to bottom and the gas volume flow is therefore not so high in the upper region.

For this reason, it is also possible to pack in the upper area with a larger packing density, i. a larger surface per volume to use than below.

Preference is given to using water at a temperature between 20 and 60 ^° C., more preferably at a temperature between 30 and 45 ^° C., as the heat carrier. The ratio of the liquid flows of water to cryogenic liquid is preferably between 3 and 6 l / Nm ³ , that is, for the evaporation of 1 Nm ^{3 of} cryogenic liquid, preferably 3 to 6 liters of water are used.

With the method according to the invention arbitrarily large streams of cryogenic liquid can be evaporated. The preferred field of use is the evaporation of 1000 Nm ³ / h to 50,000 Nm ³ / h of cryogenic liquid.

It has been found that for the evaporation of 1 Nm ^{3 of} cryogenic liquid per hour, a packing volume between 0.05 m ³ and 0.5 m ^{3 is} sufficient. Among other things, the required packing volume also depends on the specific surface area of the packing, that is to say on its surface, relative to its volume. Preference is given to using packings having a specific surface area or packing density of between 300 m ² / m ³ and 750 m ² / m ³ , more preferably between 500 m ² / m ³ and 700 m ² / m ³ .

The invention is particularly useful for vaporizing cryogenic liquids resulting from the operation of cryogenic air separation plants, preferably for the vaporization of liquid nitrogen, liquid oxygen, liquid argon, or a mixture thereof.

The invention and further details of the invention are explained in more detail below with reference to the embodiment shown in the drawings. Hereby show:

1 shows a section through a device according to the invention for the evaporation of a cryogenic liquid,

Figure 2 shows a section through the device according to the invention perpendicular to the illustration of Figure 1 and

Figure 3 is a plan view of the manifold for the cryogenic liquid.

The device shown in the figures is suitable for the evaporation of cryogenic liquid, wherein in the following the structure of the device according to the invention and their operation will be explained by way of example with reference to the evaporation of liquid nitrogen from a cryogenic air separation plant.

The device according to the invention has, as can be seen in FIGS. 1 and 2, a container 1. Six layers 2a, 2b, 2c, 2d, 2e, 2f of an ordered packing are arranged one above the other in the container 1. The packing layers 2a, 2b, 2c, 2d, 2e, 2f are supported by a grid 3.

The individual packing layers 2a, 2b, 2c, 2d, 2e, 2f each consist of a multiplicity of packing sheets arranged parallel to one another, each of which is provided with a corrugation extending obliquely to the sheet metal edges, the corrugations of adjacent sheets intersecting one another. Adjacent packing layers are each positioned so that their sheets are arranged rotated by 90 ° to each other.

Above the uppermost packing layer 2a is a pipe distributor 4 for the even distribution of water over the packing layer 2a. The pipe distributor 4 has a water supply 5, branch off from the plurality of L-shaped Verteilarme 6, the horizontal legs are arranged parallel to each other and provided with outlet openings 7. The embodiment shown in Figures 1 and 2 has four Verteilarme 6, each with four outlet openings 7, so that there are a total of 16 evenly distributed over the cross section of the container 1 Wasserasutrittspunkte.

Above the distribution arms 6 of the water distributor 4 there is another distributor 8 for the liquid nitrogen to be evaporated. 3 shows a plan view of the manifold 8. The manifold 8, which is also designed as a manifold, has a central, vertical supply line 9, which opens into a main channel 10. From the main channel 10 branch off three Verteilarme 11, each having outlet openings 12.

Below the grate 3 is a gas exhaust pipe 13. The gas exhaust pipe 13 projects horizontally into the free space below the grating 3 and is provided on its underside with an opening 14. By this geometric shape prevents the trickling down from the top liquid enters the gas exhaust pipe 13. At the bottom of the container 1 finally an outlet opening 15 is provided for water.

The cryogenic liquid nitrogen to be evaporated is supplied via the line 9 to the manifold 8 and distributed uniformly over the cross section of the container 1. As a heat carrier 8 hot water at a temperature of 35 to 40 ° C is supplied via the water manifold 4 below the nitrogen spreader.

The liquid nitrogen and water impinge on the uppermost packing layer 2a and undergo direct heat exchange. In this case, the liquid nitrogen evaporates. The nitrogen gas is entrained with the water over the individual packing layers 2a, 2b, 2c, 2d, 2e, 2f down and heated thereby.

The resulting nitrogen gas is withdrawn via the gas exhaust pipe 13 from the container 1, and blown off to the environment or fed to another use.

Experiments with the device according to the invention have shown that the packing ensures optimum heat transfer from the water to the nitrogen, or generally to the cryogenic fluid. Already with only four stacked packing layers shows that the escaping water and the gas formed by the evaporation of the cryogenic fluid have almost the same temperature, that is, that a maximum heat exchange is achieved.

Claims

claims

A process for vaporizing a cryogenic liquid, characterized in that the cryogenic liquid and water are applied to a package (2a, 2b, 2c, 2d, 2e, 2f) and the cryogenic liquid is vaporized in direct heat exchange with the water.

2. The method according to claim 1, characterized in that the cryogenic liquid and the water are passed in cocurrent through the package (2a, 2b, 2c, 2d, 2e, 2f).

3. The method according to any one of claims 1 or 2, characterized in that the cryogenic liquid is applied to an ordered packing (2a, 2b, 2c, 2d, 2e, 2f).

4. The method according to any one of claims 1 to 3, characterized in that the water before the heat exchange with the cryogenic liquid has a temperature between 20 and 60 ⁰ C, preferably between 30 and 45 ⁰ C.

5. The method according to any one of claims 1 to 4, characterized in that the ratio of the flows of water to cryogenic liquid between 3 and 6

Liters / h of water per Nm ³ / h of cryogenic liquid.

6. The method according to any one of claims 1 to 5, characterized in that liquid nitrogen, liquid oxygen, liquid argon or a mixture thereof is evaporated.

7. The method according to any one of claims 1 to 6, characterized in that a stream of 1000 to 50,000 Nm ³ / h of cryogenic liquid is evaporated.

8. Device for evaporating a cryogenic liquid, characterized in that a container (1) with a packing (2a, 2b, 2c, 2d, 2e, 2f), with a feed (9) for the cryogenic liquid, with a distributor ( 8) for distributing the cryogenic liquid to the package (2a, 2b, 2c, 2d, 2e, 2f) as well as with a supply (5) for water and a distributor (4) for distributing the water onto the package (2a, 2b, 2c, 2d, 2e, 2f).

9. Device according to claim 8, characterized in that the distributor (8) for the cryogenic liquid is arranged above the distributor (4) for the water.

10. Device according to one of claims 8 or 9, characterized in that in the container (1) different pack types are provided.

11. Device according to one of claims 8 to 10, characterized in that in the container (1) at least one ordered packing (2a, 2b, 2c, 2d, 2e, 2f) is provided.