DE3626359C2 - Evaporator and method for evaporating a fluid - Google Patents

Description

The invention relates to an evaporator in a liquid pipes to run an evaporation immerse the fluid and one in the liquid bath the steam injector for direct heating of the liquid bath.

Evaporator, whose heat exchange surfaces are in a steam heated liquid bath are preferably used for ver vaporize low-boiling, liquefied gases, such as B. stick substance, oxygen, LNG, natural gas products, etc. used. Each depending on the type and amount of the fluid to be evaporated The heat content of the liquid bath alone is not enough to reduce the To ensure evaporation and to prevent it from getting on excessive heat build-up on the heat exchange surfaces. Around It is therefore necessary in many to meet these boundary conditions Cases required to heat the liquid bath and the If necessary, circulate the liquid. The heating comes with Advantage by blowing steam into the liquid bath before taken, here at the same time by the rising steam blow a circulation of the liquid takes place.  

However, due to the steam injection Problems can arise at the cold phase interfaces Steam strikes come when steam condenses suddenly. The forces released by the steam strikes lead to a strong mechanical load. Such evaporators are therefore very sensitive to changes in the Load behavior, d. H. Changes in the amount of steam. It comes especially in the low load range Steam strikes due to backflow of cold liquid in the steam system.

The evaporators are preferred for applications used, where a rapid change of the Load range (often from 0 to 100% load in a few Seconds). It gets through in the apparatus rapid temperature changes to mechanical stresses (so-called thermal shock stress).

The present invention is based on the object to develop an evaporator of the type mentioned at the beginning, which has a low susceptibility to failure in the entire load range having. In particular, steam shocks at the Feed of steam over the entire occurring Avoided load area and mastered a high one mechanical stability achieved and a high Heat transfer value can be achieved.

This object is achieved in that the Pipes are wound helically, the Pipe outside diameter between 15 and 50 mm, the distance neighboring pipes at least 5 mm and the ratio Winding height / outside diameter between 1.0 and Is 3.0.  

It has been shown that the performance of such Evaporator strongly depends on the geometry selected. Around at the same time the highest possible stability towards mechanical influences and good heat transfer from the liquid bath to the fluid to be evaporated must achieve the dimensioning of the pipes and the Pipe spacing is in the specified range. Although the Requirements regarding stability, heat transfer and Apparently contradicting load behavior, has shown in practice that the Evaporator according to the invention optimally all requirements can be met.

In a preferred development of the invention The tubes are wrapped around a core tube and evaporator the free cross section of the core tube is between the 0.5 and 2 times the free cross-section of the winding.

The use of a core tube increases the stability of the jacket-side liquid flow and reduces the Risk of erosion. In addition, you can define better Set operating states.

In a further preferred embodiment of the The subject of the invention is the steam injector through a or more provided with vapor bubble outlet openings Tubes formed, which are arranged in the region of the winding axis are.

The steam outlet openings are at one vertically aligned winding axis in the lower area of the Winding core or below. The escaping steam condenses within the core tube area, making it too an upward flow of liquid comes. This creates a natural circulation flow, whereby the tubes from a downward facing Liquid flow can be coated.  

In a further advantageous embodiment of the subject matter of the invention, the diameter of the vapor bubble outlet openings is 4 to 8 mm, preferably 6 mm.

In a preferred development of the subject matter of the invention there is a maximum heating surface load for the pipes 50,000 W / m² set.

The heating surface load is provided by a sufficient heating area, d. H. Number of tubes, depending on the Purpose of the evaporator, below this limit posed.

The invention also relates to a method for evaporation a fluid carried in pipes through a liquid bath by heat exchange with this liquid bath, with the steam for direct heating of the liquid bath in the same ge is directed, which is characterized in that at least two steam supply systems are provided and the steam up to a specified maximum quantity only by a stes steam supply system and one of the specified Maximum quantity exceeding quantity exclusively or additionally Lich through one or more other steam supply systems to be led.  

The method according to the invention makes it very broad Load range covered. If the steam supply system for large amounts of steam is designed, then this results Problem that with low steam loads, (e.g. in the area between 1/10 and 1/100 of the maximum load or still below) liquid into the steam supply system penetrates and there are steam strikes. For this The reason according to the invention is at least two such Systems provided, one of the systems for the Steam feed from 0 to an intermediate value is, while the second or the remaining systems of the Intermediate value up to the maximum value the steam feed take over. It is conceivable that the first System continues to deliver steam, i.e. H. the amount of steam of the individual systems add, or that in the Intermediate value exceeding demand the first system switched off and at the same time the other system or systems be regulated to the appropriate value.

In a preferred development of the invention The procedure is through the first Maximum supply quantity supplied to the steam supply system between 2 and 4 t / h, preferably about 3 t / h.

The invention and further details of the invention are shown schematically using Exemplary embodiments explained in more detail.

Here show:  

Figure 1 is a schematic representation of an evaporation process according to the invention.

Fig. 2 shows an embodiment of an evaporator according to the invention;

Fig. 3 shows another embodiment of an evaporator according to the invention;

Fig. 4 shows a detail A from FIG. 3.

Fig. 1 shows a flow diagram of a method for vaporizing a low-boiling liquid. The low-boiling liquid, for example nitrogen, oxygen, argon, ammonia, LNG or a natural gas product, such as methane, propane, butane or a flare gas, is stored in a container 1 in liquid form. The liquefied gas is removed from the container 1 by means of a pipeline 2 and fed to pipes 3 of an evaporator. The evaporator has a container 4 filled with a liquid 6 . The tubes 3 are wound helically around a core tube 5 and are completely immersed in the liquid bath 6 .

The liquefied gas is fed to the tubes 3 at the lower end. On its way up through the pipe windings, the liquefied gas evaporates by exchanging heat with the water bath 6 . The vaporized gas is withdrawn from the upper end of the tube windings by means of a line 7 .

To heat the liquid 6 , steam is introduced via a steam introduction system 11 in the lower region of the liquid bath. The steam is supplied inside the core tube 5 near its lower end. In addition to heating the liquid, the introduction of steam causes the liquid to circulate naturally, as indicated by arrows 12 . The rising vapor bubbles cause warm liquid to rise inside the core tube, while at the same time colder liquid flows down the tube.

Excess condensate is removed through a line 8 from the upper edge of the container 4 and pumped into a liquid container 9 . Steam is removed from the head of the container 9 via a line 10 and fed to the steam supply system 11 . The liquid used is preferably water.

Fig. 2 shows an evaporator according to the invention in longitudinal section. The same reference numerals as in FIG. 1 are used for analog components. The evaporator has a nozzle 14 for the supply of the fluid to be evaporated, which is connected via a tube guided downward through the core tube to a tube cup into which the tubes 3 wound around the core tube 5 are inserted. The upper ends of the tubes 3 are combined in a tube cup 15 , through which the evaporated fluid is removed. Another nozzle 16 at the upper end of the evaporator is used to supply steam. The connecting piece 16 is connected to a tube 13 leading downward within the core tube 5 , which ends shortly before the lower end of the core tube 5 and the end face of which is closed. At its lower end, the tube 13 has steam outlet openings 17 distributed over its circumference, through which steam bubbles emerge into the liquid 6 .

The tube 13 has, for example, a nominal width of 50 mm, 100 openings 17 are provided, each of which has a diameter of 6 mm. The outer diameter of the outermost winding is approximately 1000 mm, the distance from the lowest to the upper winding is, for example, 1500 mm, ie the ratio of the winding height to the winding diameter is 1.50. The free cross-section of the tube winding is approx. 0.21 m², that of the core tube approx. 0.49 m², ie the free cross-section of the core tube is 1.7 times as large as that of the winding.

The evaporator also has a nozzle 19 for supplying liquid and an overflow 18 for excess condensate.

FIG. 3 shows a further embodiment of an evaporator according to the invention, in which, in contrast to the evaporator according to FIG. 2, two steam supply systems 20 , 21 are provided, both of which open into the liquid 6 below the lower edge of the core tube 5 . The first steam supply system has a connecting piece 20 which is connected to a pipe 22 leading downward through the core pipe 5 . The tube, which has a diameter of 80 mm, has steam outlet openings 17 with a diameter of 6 mm each at its lower end. A second steam supply system has a pipe 23 leading downward from a connecting piece 21 through the core pipe. The tube 23 , the diameter of which is 150 mm, likewise has steam outlet openings 17, each with a diameter of 6 mm, at its lower end.

If the steam requirement is between 0 and 3 t / h, the steam is supplied exclusively through the thinner tube 22 . If a larger amount of steam is required, the steam supply to the nozzle 20 is suddenly interrupted and the steam is instead supplied to the nozzle 21 . A quantity of steam which is between the minimum value of 3 t / h and a predetermined maximum value is accordingly supplied via the nozzle 21 . Instead, it is also possible to use two steam supply systems of the same type, each of which can supply, for example, between 0 and 3 t steam / h. If there is a demand between 0 and 3 t / h, the steam is only supplied via one of the systems; if there is a higher demand, the first system remains at the maximum value, while for the second system between 0 and 3 t / h of steam depending on the demand be fed. In an analogous manner, more than two such systems can also be operated.

FIG. 4 shows a section A from FIG. 3. As an example, six tubes 3 of a winding are drawn out, the outer diameter d of which is between 15 and 50 mm. The distance between adjacent pipes ( 1 ₁ in the horizontal, 1 ₂ in the vertical direction) is at least 5 mm and is preferably in the range between 10 and 25 mm for 1 ₁ and between 5 and 20 mm for 1 ₂.

Claims (7)

1. Evaporator with in a liquid bath Roh Ren to guide a fluid to be evaporated and with a plunging into the liquid bath steam injector for direct heating of the liquid bath, characterized in that the tubes ( 3 ) are wound helically, the tube outer diameter between 15 and 50 mm, the distance between adjacent tubes ( 3 ) is at least 5 mm and the ratio of the winding height / winding outer diameter is between 1.0 and 3.0. 2. Evaporator according to claim 1, characterized in that the tubes ( 3 ) are wound around a core tube ( 5 ) and the free cross section of the core tube ( 5 ) is between 0.5 and 2 times the free cross section of the winding. 3. Vaporizer according to claim 1 or 2, characterized in that the steam injector is formed by one or more with steam outlet openings ( 17 ) provided with tubes ( 13 ; 22 , 23 ) which are arranged in the region of the winding axis. 4. Evaporator according to one of claims 1 to 3, characterized in that the diameter of the Dampfblasenaus outlet openings ( 17 ) is between 4 and 8 mm. 5. Evaporator according to one of claims 1 to 4, characterized in that a heating surface load for the tubes ( 3 ) is set to a maximum of 50,000 W / m². 6. Method of evaporating a pipe through a river fluid carried by heat exchange with this Liquid bath where steam is used to directly heat the Liquid bath is passed into the same, thereby ge indicates that at least two steam supply systems are provided, and the steam up to a predetermined Maximum amount only through a first steam addition system and at a the specified maximum amount exceeding the quantity exclusively or additionally supplied by one or more other steam supply systems leads. 7. The method according to claim 6, characterized in that the supplied by the first steam supply system The maximum quantity is between 2 and 4 t / h.