EP0072020A1 - Open condenser - Google Patents

Abstract

1. Method for the low-noise introduction of large quantities of steam into a flowing liquid in order to heat the latter, wherein the steam is conducted through heat exchange elements of a heat exchanger wherein the liquid at least at the outlet end of the heat exchange element or elements is conducted substantially axially parallel to said element or elements, characterised in that the steam and the liquid are subjected to such temperature and flow conditions that the issuing steam extends into the liquid parallel to the flow and in the form of coherent stable columns of steam extending downstream from the heat exchange elements.

Description

The invention is directed to a method and a device for the silent introduction of large amounts of steam into a flowing liquid.

According to DE-OS 2 439 562, the heating of water with water vapor is known, the water vapor being passed into an open tube or tube bundle, expanded and condensed therein, and the condensate into the one to be heated, surrounding the tube or tube bundle Water emerges, the pipe length and the pipe diameter are dimensioned such that the entire water vapor is completely relaxed and condensed at the end of the pipe or tube bundle at the latest.

It is also known to inject steam through many small bores to reduce noise by avoiding large steam bubbles, to set the liquid speed high (up to 2o m / sec), to generate high dispersion-promoting turbulence, to set the steam speed high (near the speed of sound) and the steam as far as possible to shoot deep into the liquid.

At least during the heating processes, where the liquid temperatures are still low, and because of the high flow rate, such steam heaters still cause a lot of noise. With such a steam heater (NW 65, water circulation 25 m ³ / h, steam feed 400 kg / h, water outlet temperature 60 ° C) the noise level is 98 dB (A).

Another disadvantage of known steam heaters is the poor controllability. The permissible ratio of maximum to minimum steam feed is a maximum of 7: 1. With smaller amounts of steam, liquid can enter the steam chamber in an uncontrolled manner and lead to condensation shocks.

In the case of special steam heaters with a larger control range, the feed points must be closed gradually as the steam load decreases; electrically and pneumatically operated sliding sleeves are known. Such devices are very prone to failure.

The object of the invention are methods and devices for the low-noise introduction of large amounts of steam in liquids, which are characterized in that safe and stable working is achieved within large control ranges.

In procedural terms, the object is achieved in that the steam is first led to a heat exchanger, at the end of which it still enters the liquid in vapor form, flow conditions being maintained such that the form of a Steam column, which connects to the heat exchange element, extends axially parallel to the flowing liquid into the flowing liquid.

The device is characterized in that, under the operating conditions, the heat exchange surface is not sufficient to fully condense the steam, and the openings of the heat exchange element or elements are designed with respect to the flow in such a way that the emerging steam propagates in the form of the heat exchange elements connected columns into the liquid parallel to the flow.

Further advantageous developments are described in the subclaims.

The decisive advantage of the invention is that a stable and low-noise driving style results within a wide control range. When starting up, where there is a high temperature difference between the steam and the liquid, it can happen that enough heat is extracted from the steam inside the heat exchanger that it condenses there and escapes from the heat exchange elements, which then noiselessly falls below the amount of liquid to be warmed up mixes. The smaller the temperature difference between steam and liquid, the further the front, where the steam condenses in the heat exchange element, will move to the outlet side of the heat exchange element until steam finally enters the liquid. The method aims at the operating conditions, one "Steam column", which comes out of a heat exchange element, extends into the liquid as a stable structure. With changing operating conditions, the length of the steam column and thus the direct condensation surface follows these changes in a simple manner. The openings at the end of the heat exchange elements must be designed and arranged in such a way that the steam column, which protrudes from the heat exchange elements into the liquid, is not sheared off and divided by the flowing liquid, but rather is practically an extended heat exchange element without a partition. The system is stable across the board. Such an operation is new and very advantageous. In the literature it is always advisable to use "open heat exchangers" in such a way that the heat transfer medium condenses completely within the pipes. The device according to the invention is characterized by a smaller "apparatus" heat exchange surface.

In the open capacitor according to the invention, both direct current operation and counter current operation are possible. The disadvantage of counter-current operation compared to direct-current operation, that cooling has to be carried out with relatively warmer liquid due to the added condensate, is offset by the advantage of the larger average temperature difference in counter-current. Whether the advantages or disadvantages predominate can be calculated.

The device according to the invention has an excellent control characteristic. The heater adapts itself automatically to the respective amount of steam, from 0 to the design maximum. The control ratio is theoretically infinite. The control takes place purely hydraulically and without moving parts. There is practically no upper limit since the number of heat exchange elements can be increased as desired. The steam speed therefore does not need to be increased above an optimum.

In the case of straight tubes, a particularly high packing density can be achieved, which results in a large ratio of steam exit areas to the cross-sectional area of the flowing liquid. In relation to the cross-section of the apparatus, high values are set for the direct condensation surface between steam and liquid and thus for the condensation performance.

When designing the open capacitor, a wide variety of requirements can be met depending on the material and geometry. The heat exchange elements can be cylindrical or box-shaped. A forced redirection of the liquid flow can be carried out within the bundle. In principle, it is also possible to send the liquid through the heat exchange elements and to guide the steam around the elements; guidance of the steam can also be achieved by the exchange elements charged with liquid; in this case the steam columns emerge from the "jacket area" and are surrounded by corresponding "liquid columns" from the heat exchange elements. In order to achieve high performance, the steam must be introduced into a flowing liquid. A pump and corresponding guide elements around the heat exchange elements (often identical to the housing) are normally required. However, a convection flow can also be sufficient. Since the state in which the steam column emerges vertically upwards or downwards is the most stable, a vertical arrangement of the heat exchange elements is preferred. In the case of very long heat exchange elements, support against one another may be necessary in order to prevent the individual elements from hitting or sagging. A screen mesh can also perform this task.

In order to achieve a low-eddy flow at the ends of the heat exchange elements, it is advisable to chamfer the ends. An inner chamfer or outer chamfer is particularly useful for thick-walled pipes.

The largest control range and the greatest steam output can be achieved with vertical installation and steam guidance from top to bottom.

The device can be produced inexpensively from standard pipeline parts; they are also available in stainless steel quality. The tube sheets can be made from standard flanges on NC machines. If necessary, the apparatus can also be inserted into a corresponding piping system without its own housing.

• Fig. 1 einseitig offener Rohrbündelkondensator;
• Fig. 2 einseitig offener Flachkammerkondensator;
• Fig. 3 Dampfanwärmer im Gegenstrombetrieb;
• Fig. 4 Dampfanwärmer im Gleichstrombetrieb;
• Fig. 5 eckiger Flachkammerkondensator;
• Fig. 6 Schnitt durch den oberen Teil des Einsatzes eines Kondensators nach Fig. 5;
• Fig. 7 offener Rohrbündelkondensator in einem Behälter.

The invention is illustrated in the drawing and further described below. Show it:

• Fig. 1 open tube bundle condenser;
• 2 flat chamber capacitor open on one side;
• Fig. 3 steam heater in counterflow operation;
• Fig. 4 steam heater in DC operation;
• Fig. 5 angular flat chamber capacitor;
• 6 shows a section through the upper part of the use of a capacitor according to FIG. 5;
• Fig. 7 open tube condenser in a container.

The open tube bundle condenser, as is shown schematically in FIG. 1, essentially consists of a plug-in tube bundle 1 which projects into a housing 2. The upper part of the device is very similar to a "classic" heat exchanger. In the space around the pipes 3, the liquid enters or exits through the connector 4 attached to the side of the housing. The main difference occurs in the lower area of the apparatus. The tubes 3 do not end in a tube sheet 5 as above but open out freely. Steam is fed through the nozzle 7. If the liquid enters at 4 and exits the nozzle 6, there is direct current operation, it enters at 6 and exits at 4, counter-current operation. Irrespective of whether the operation is carried out in cocurrent or countercurrent operation, very stable steam columns 8 can protrude from the tubes 3 into the liquid at low temperature differences between liquid and steam.

Vertical tube bundles 1 are preferred. A particularly compact "steam column" is obtained when steam is introduced from top to bottom; in the opposite case, the steam column is drawn out longer.

The tubes 3 can run out bluntly; In order to generate as little eddy as possible, it can be advantageous to chamfer the pipes inside or outside.

FIG. 2 shows a tube bundle 1 with a different design. Instead of straight cylindrical tubes as in FIG. 1, flat chambers are present here. In the case of a longer inner tube bundle, it may make sense to use support fabrics to improve the mechanical stability or baffles to divert the flow around the tubes; they are not drawn here. At the end of the tube bundle, however, the flow around the tubes should run largely parallel and with little swirl to the tubes. Since the pressure differences inside and outside the flat chamber are very small, the wall thickness can be very small.

Typical applications are shown in Figures 3 and 4. The same features have the same reference numerals in both figures. In Fig. 3 the steam heater 20 is operated in countercurrent, in Fig. 4 in cocurrent for heating an agitator tank 21. The water 22 in the heating jacket 23 of the agitator tank 21 is circulated through pipes 24 through the centrifugal pump 25 and thereby conveyed by the heater 20. The cas opens to increase the temperature kadentemperature control 26, the valve 27, and steam 28 flows into the heater 20. A pressure control 29 keeps the pressure in the system constant by discharging excess condensate (possibly also cooling water) via valve 30. If the product temperature in the agitator tank 21 is to be lowered, the temperature control 26 closes the steam valve 27 and opens the cooling water valve 31.

With the heating described, noise formation when introducing steam into liquid is practically avoided, since it is possible with these apparatuses to suppress the otherwise usual bubble formation with inevitable cavitation. By cooling the steam in the heat exchange elements, the steam speed is considerably reduced, or at the beginning of a heating process only condensate emerges from the pipe ends anyway. But even if the steam has not yet condensed inside the tube and steam columns 8 extend into the liquid, a stable, stationary state is formed without cavitation impacts. For these reasons, the tubes 3 of the tube bundle 2 should have high heat conduction; Plastic pipes, which have occasionally been proposed for noise reduction, would be less suitable. Straight, equally long pipes have proven their worth best. For example, a heater as shown in Fig. 1 was equipped with 132 stainless steel tubes; the wall thickness of a tube was 1 mm, the diameter 6 mm and the length 800 mm. The housing, also made of stainless steel, had the nominal size 100. With such a heater, a 10 m ³ agitator tank was heated by means of pressurized water heating circuits by introducing 400 kg of water vapor / h. The water circulation rate was approx. 25 m ³ / h, water temperature before steam introduction 25 ° C, the maximum permitted water circulation temperature was 130 ° C, the water pressure at the entrance to the heater 4.2 bar, the steam pressure 5 bar. The noise level during operation was 70 dB (A). It was not measurably increased by the introduction of steam. On the other hand, with a steam jet of a conventional design and roughly comparable output, a noise level of 98 dB (A) is measured at the beginning of the heating process and a noise level of 80 dB (A) is still measured at the end of the heating process. Another advantage of the heater according to the invention is the relatively low pressure drop on the liquid side and the very large steam control ratio. In the heater described above, the pressure loss without steam input was less than 0.1 bar; with conventional warmers it is 0.6 bar. According to the manufacturer, the permissible steam control ratio is 1: 7; in special versions up to 1:60. In the case described above, the steam input varied between 0 and 400 kg / h; the steam control ratio is practically infinite. Via an enlarged valve, steam input of 1200 kg / h was achieved without the noise increasing. The upper limit of performance has not yet been reached.

Another form of the device according to the invention is shown in FIGS. 5 and 6. It deals a flat chamber bundle 40 similar to that in FIG. 2 in a rectangular housing. 41. The steam enters laterally through the flange 42 and the liquid flows through the housing 41 in cocurrent from top 43 to bottom 44, or in countercurrent from 44 to 43.

Details of the heat exchange elements are shown in section in Fig. 6. The steam enters the cage 45 at the flange 42; this has the function of supporting the flat chamber heat exchanger elements 46 and of ensuring the steam distribution. Rings 44 are installed within the flat chambers 46, which are intended to prevent the flat chambers from being pressed together, but to allow steam to pass through. Rings 48 are in turn to ensure a minimum distance between the flat chambers 46 between the flat chambers 46. Knobs 49 on the outside of the flat chambers also have the same function. In addition, these knobs 49 still serve to improve the heat transfer. The flat chambers and the rings are pressed together with the yoke 50.

According to FIG. 7, a tube condenser can also be operated for heating without forced circulation. Cooler liquid is sucked in through the openings 61 at the bottom of the housing 62, into which the heat exchange elements 63 open at the top, by suction of steam via the flange 60. There is a convection flow. Stable steam columns can also form here, due to the heat exchange extend elements 63 upwards into the liquid. In order to avoid the formation of eddies, which could tear bubbles out of the steam columns, steam and liquid flows should always be routed in parallel near the ends of the heat exchange elements. The steam should flow into the liquid as vertically as possible. With a horizontal steam column, the end of the column is due. the lower vapor density bent upwards, at least with large steam outputs and thus long steam columns, steam bubbles are torn out of the columns and can cavitate.

Claims (5)

1) Process for the low-noise introduction of large amounts of steam into a flowing liquid, characterized in that the steam is first passed through a heat exchanger, at the end of which it still enters the liquid in vapor form, flow conditions being maintained such that it is in the form of a steam column, which connects to the heat exchange element, extends axially parallel to the flowing liquid into the flowing liquid. 2) Device for the low-noise introduction of large amounts of steam into a flowing liquid, the steam being passed into a tube bundle open on one side as a heat exchanger, characterized in that the heat exchange surface is not sufficient under the operating conditions to fully condense the steam, and the openings of the or the heat exchange elements (3, 10, 46, 63) are designed with respect to the flow such that the emerging steam extends into the liquid parallel to the flow in the form of continuous columns (8) propagating from the heat exchange elements. 3) Device according to claim 2, characterized in that the flow is vertical. 4) Device according to claims 2 and 3, characterized in that the heat exchange elements are straight tubes (3,63). 5) Device according to claims 2 and 3, characterized in that the heat exchange elements (10,46) are prismatic.

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