Air Condensation Plant

Abstract

Air condensation plant for condensing steam by direct air cooling includes mutually transversely disposed elongated cooling elements traversible by steam along the length thereof, means for directing a flow of air to a respective side of said cooling elements, adjustable means for covering the side respectively of the cooling elements for controlling the cooling thereof and for preventing freezing, the cooling elements having an upper part through which a preponderant quantity of the steam to be condensated flows, the adjustable covering means being located in front of the upper part of the cooling elements.

Description

The invention relates to air condensation plant for condensing steam, especially exhaust steam turbines by direct air cooling.

Air condensation plants of this general type have been used with respect to the cooling surfaces and the quantity of cooling air for specific operating relationships, for example for measuring total output of the steam turbine for mean cooling air temperature. At higher air temperatures, a specific reduction in efficiency must be taken into consideration because the condensate temperature and therewith exhaust steam pressure increase to predetermined amount. In contrast thereto difficulties arise if the condensation plant is to operate at very low air temperatures and also at very low loading of the steam turbine, and with quantities of steam that are reduced with respect to the normal rating therefor. Special measures must be consequently in order to prevent supercooling or undercooling of the condensate, especially to avoid danger of freezing, because damage can otherwise occur to the condensation plant.

Many efforts have been made heretofore for avoiding danger of freezing. At first it was suggested that the quantity of cooling air be reduced by suitably changing the rotary speed or the position of the blades of the fans or blowers. These measures by themselves, however, are not adequate in all cases because the cooling surfaces for a greater temperature difference than correspond to that for which they are rated continue to be effective, and a great undercooling of the condensate always occurs in spite of reduce heat transfer value on the air side, so that one must take into consideration formation of ice. It would furthermore be of no help in this case if one were to stop one or all of the fans or blowers and thereby attain a marked reduction in the cooling action.

Attempts have therefore been made heretofore to locate the inlet and discharge sides of the cooling elements and the fan or blower in a chamber which is in communication with the outer air through adjusting flaps. When there is danger of freezing, part of the previously warmed cooling air is thereby returned to the fan or blower at the inlet side so that the mean cooling air inlet temperature is always increased to such an extent that no ice formation can occur. Though danger of freezing can be effectively avoided in this manner, one must however take into consideration the coincident marked disadvantages which, in addition to the significant construction costs, are primarily based upon the fact that full fan or blower output for cooling is always necessary.

Consideration has also been given heretofore to branch off part of the cooling air that is being advanced through suitably mounted flaps with a fan or blower that is being driven at a constant speed before the cooling elements are traversed by the flow of cooling air, and to conduct part of the cooling air to the surrounding atmosphere. But this measure also has a disadvantage in that energy for advancing the cooling air is unnecessarily consumed, and the condensation plant is thereby operated uneconomically.

In a heretofore known air condensation plant an attempt has been made to solve this problem by operating part of the cooling elements or all of them in the so-called dephlegmator circuit or system. In this dephlegmator system, the steam flows in the direction opposite to the condensate in the dephlegmator part so that the condensate generally cools off to a temperature not much below the steam temperature. Even if freezing can also be effectively prevented thereby, nevertheless, such a condensation plant is again beset by a disadvantage in that the cooling action is considerably lower then for conventional condensation during which the steam and the condensate both flow in the same direction. Such a condensation plant consequently requires a relatively greater cooling surface and must be accordingly larger, extensive and costlier.

It has been heretofore also suggested that a part of the cooling elements be shut down or rendered inactive at reduced turbine output and lower air temperatures by cutting off the supply of steam to these cooling elements. However, the relatively large steam slide valves that are required and that are subjected to vacuum again call for a high technical outlay, are costly and can cause operational difficulties.

Another heretofore offered suggestion for reducing freezing has been to provide additional tubes shorter than the cooling tubes at a lower part of the cooling tubes of each cooling element at the inlet of the cooling air thereto, i.e., at the location at which there is the greatest danger of freezing, those additional relatively shorter tubes being subjected in the interior thereof to steam which has been conducted through a throttling member. This throttling member, however, reduces the condensation pressure and the condensation temperature therewith, so that the danger of freezing becomes even greater and the problem at hand remains unsolved. Also, the simple addition of flaps for covering a part of the cooling elements has not heretofore permitted the elimination of danger of freezing.

With the foregoing and other objects in view we provide air condensation plant for condensing steam by direct air cooling which comprises mutually transversely disposed elongated cooling elements traversible by steam along the length thereof, means for directing a flow of air to a respective side of said cooling elements, adjustable means for covering the side, respectively, of the cooling elements for controlling the cooling thereof and for preventing freezing, the cooling elements having an upper part through which a preponderant quantity of the steam to be condensated flows, the adjustable covering means being located in front of the upper part of the cooling elements.

Further in accordance with the invention the cooling elements are disposed either perpendicularly or inclined with respect to one another. Moreover, the adjustable covering means are in the form of flaps, jalousies, roller blinds or the like.

In view of the construction of the invention in the instant application, dephlegmator operation of the condensation plant is dispensed with, and steam and condensate can flow in the same direction as is conventional for normal condensation plants.

Adjustable flaps that had been heretofore mounted at the cooling elements were generally located in the lower part or region of the cooling elements. In these heretofore known plants however icing occurred and, in fact, frost damage occurred in the cooling tubes at the level of the upper edge of the flaps because the local cooling action through a greater air velocity was even stronger than before due to the heat transfer value improved thereby. No change occurs therein if the flaps are mounted at the cooling air discharge or outlet side of the cooling element. Since the lower half of the cooling tubes is then further subjected to the blast of the cooling air, danger of freezing is still present at least to the same extent to the condensate further condensed at the top of the cooling tubes. If the quantity of cooling air were itself to be reduced, the cooling action in the upper half of the cooling elements would, in fact, be diminished and the condensate would then flow downwardly into the cooling tubes of the lower half of the cooling elements which are subjected to the blast of the cooling air and might freeze there. Only when, in accordance with the invention of the instant application, adjustable covering means are mounted in the upper part of the cooling elements on the air inlet side thereof, which covering means more or less greatly cover the cooling surfaces when there is danger of freezing, can a supercooling or undercooling of the condensate in the still active cooling surfaces of the cooling elements be markedly prevented, if necessary in connection with additional reduction of the cooling air flow. Since only steam flows upwardly in the upper part of the cooling elements and the cooling tubes located there are not subjected to the blast of cooling air which is advanced by the fan or blower, the cooling effect zone shifts downwardly so that one does not even have to be concerned any longer with danger of freezing.

In accordance with the invention, when there is a progressive increase in the covered surface, the flow of cooling air can be additionally reduced arbitrarily or automatically by adjusting of the covering means. The adjustable covering means are formed in a relatively simple manner by flaps. It is possible however to employ in place thereof, jalousies or rolling blinds as long as care is taken that no flutter phenomena occur in the air current.

In accordance with another feature of the invention, we employ pivotable flaps which are pivotable about an axis extending along the upper inner edge of the cooling element. When two cooling elements are disposed so that they are symmetrically inclined with respect to one another, in accordance with the invention, the pivot axes for the flaps of both cooling elements are located in the angle defined by the mutually inclined cooling elements, and accordingly the flaps are freely suspended in vertical position in the rest or neutral position thereof. The flaps are additionally provided, in accordance with another feature of the invention, with elongating or widening portions in order to increase the covering surface. Such elongating or widening portions are slidably secured to the pivotable flaps.

In many cases it is desirable, for example, under extreme conditions, i.e., very low cooling air temperature, low quantities of steam and strong wind action, to apply additional measures against the danger of freezing, also at the outer side of the cooling elements.

Consequently, in accordance with still another feature of the invention, we dispose adjustable covering means additionally on the air outlet side of the cooling elements at a lower part of the cooling elements.

Advantageously further in accordance with the invention, the spacing between the cooling tubes in the cooling elements is increased to such an extent that the cooling air is able to flow upward and over a greater section of the cooling elements parallel to the cooling tubes. If desired, the quantity of cooling air advanced by the fan or blower can thereby be reduced still further.

With the aid of a central control device, control damages for continuous or stepwise reduction of the quantity of cooling air can be given simultaneously with the adjustment of the covering means on the air inlet side at the upper part of the cooling elements and, if desired, also with the adjustment of the covering means at the air discharge side at the lower part of the cooling elements.

Moreover, it is also possible, in accordance with the invention, to permit the operations to be carried out automatically by providing, for example, a control device for automatically adjusting the covering means in dependence upon the tendency of the condensation operating values to vary. Thus, for example, the condensate temperature and possibly also the temperature of the outer air and of the cooling air upstream and downstream of the passage therefor through the cooling elements are converted to control signals. From these temperature values, a remote control or a switch-over to automatic operation can then take place, as desired.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in air condensation plant, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with accompanying drawing, in which:

FIGS. 1 and 2 are greatly simplified and partly schematic, vertical sectional views of two different embodiments of the air condensation plants of our invention.

Corresponding or similar parts in both of the figures are identified by the same reference numerals.

Referring now to the drawing and first, particularly to FIG. 1 thereof, there is shown therein, in section, an air condensation plant according to the invention in which steam that is to be condensed is passed through a line 1 from which it is distributed to symmetrically arrayed and downwardly inclined cooling elements 2 and 3. The cooling elements are provided, respectively, with cooling tubes of which only the longitudinal center lines 4 and 4' thereof are shown in FIG. 1. The condensate that is formed accumulates in lower lines 5 and 5'. A fan or blower 6 is located below the steam line 1 and cooling element 2, 3 assembly and is driven by an electric motor 7. The entire air condensation plant is mounted on a platform 8.

In the upper region of the cooling elements 2 and 3, as viewed in FIG. 1, flaps 9 and 10 are mounted in the angle defined by the inclined cooling elements 2 and 3. The flap 9 is shown in so-called neutral or rest position, while the flap 10 covers the upper region of the cooling element 3. Thus, the cooling element 2, in the illustrated position of the flap 9 of FIG. 1, is subjected fully and without change to the cooling flow from the flower 6. As shown in FIG. 1 by the arrows 11, the cooling air flows in direction onto the entire length of the cooling element 2 and engages the cooling tubes 4 along the entire length thereof.

The flap 10 is shown in the position which characterizes the operation when there is danger of freezing. A suitably reduced quantity of cooling air then flows in direction of the arrows 12 through only the lower part of the cooling element 3 so that condensation occurs only in the lower part of the cooling tubes 4. In the upper part of the cooling tubes 41, which are protected by the flap 10 from the traversal therethrough of air current from the blower 6, stream flows downwardly. The flaps 9 and 10 are pivotable in direction of the arrows 13 and 14; generally both flaps 9 and 10 being simultaneously pivotable. Only in the event of unusual operating circumstances, for example, if one of the cooling elements 2 and 3 is exposed to powerful solar irradiation while the other of the cooling elements is being simultaneously subjected to a cold wind, can an asymmetrical flap adjustment be made.

In the embodiment of FIG. 2, the air cover flaps are of multipartite construction. The flap 15, which is shown in neutral or rest position in FIG. 2, is formed of a pivotable portion 15a and a portion 15b slideably mounted thereon so as to serve as an elongation member. The slideable portion 15b, as shown, is slid alongside almost the entire length of the pivotable portion 15a in the rest position of the flap 15. On the right-hand side of FIG. 2, there is shown a flap 17 in a position wherein it is fully pivoted against the cooling element 3, the flap 17 being formed of a pivotable flap portion 17a and a slideable elongation portion 17b mounted thereon and slid into its outermost extending position in the figure.

Furthermore, pivotable flaps 16 and 18 are mounted at the outside of the cooling elements 2 and 3 in the lower region, respectively thereof, in order thereby to counter or offset extreme conditions of freezing danger. The flap 16 for the cooling element 2 is shown in normal or neutral position while, in accordance with the illustrated position of the pivotable flap 17 which is extended alongside the cooling element 3 is also pivoted into a position alongside and against the same. An operative means for quite extreme conditions is thus represented by the layout of the flaps 17 and 18 alongside the cooling element 3.

The spacing a between the cooling tubes 4 of the embodiment of FIG. 2 is enlarged to such an extent with respect to the corresponding spacing between the cooling tubes 4 of the embodiment of FIG. 1, so that the cooling air from the blower 6, as represented by the arrows 12, is able to flow in the cooling element 3 along a considerable distance parallel to the tubes 4', the flow path of the cooling air being defined or predetermined by the flaps 17 and 18.

As is furthermore apparent from FIG. 2, automatic adjustment of the pivotable flaps 15 to 18 is possible in connection with a reduction in the blower output. Accordingly, a suitable regulating device 20 is provided, which receives measurement signals over signal lines 21 and 22 from suitable condensate temperature measuring sensors located in the condensate collecting lines or manifolds 5 and 5'. In addition, a suitable temperature measurement signal controlled by the outside temperature, is fed to the regulating device 20 over a signal line 24 from a measuring location 23. Moreover temperature measurements of supplied and discharged cooling air can be obtained at suitable locations.

Conventional command transmitters 25, 26 and 27 are connected to the control device 20 for transmitting adjusting commands that are represented by the lines of action 28 and 29 for suitably adjusting the pivotable flaps 15 and 17. Although not illustrated, it is assumed that suitable telechron or adjustment motors, for example, are located at the respective pivots of the flaps and are properly energizable in accordance with the signals transmitted thereto for adjusting the flaps. Moreover, an action line 30 is shown through which the pole-reversible or adjustable speed drive motor 7 of the blower 6 is influenced or adjustably controlled. For extreme operating conditions, the flaps 16 and 18 are adjustable over the represented action lines 31 and 32.

When a control system is provided which, with the adjustment of the covering devices or flaps on the sides of the cooling elements toward which the air flow is directed, gives off control commands to reduce the quantity of cooling air, this control system can be constructed so that after the executed closing of the covering devices or flaps on the sides toward which the air flow is directed and after the quantity of cooling air has been diminished, at the required or demanded further reduction in the quantity of cooling air, it causes an adjustment of the covering devices on the sides of the cooling elements from which the air flow is discharged in the closing sense depending upon the reduction in the air throughput quantity. Thus, for example, a command to adjust the covering devices or flaps at the air flow discharge side of the cooling elements is given as the last stage for constant or step-wise reduction in the air-blowing output.

A control or regulating device which satisfies these requirements, can contain a series circuit or sequential connection which, when the air-blowing power is reduced, first ensures that the upper covering devices at the sides of the cooling elements to which the air flow is directed, are increasingly closed. As the next stage, after the executed full closing of these covering devices, an even further reduction of the air flow throughput is then produced. Finally, after attaining adjustment of the air blower output at its lowest value, the outer covering devices are closed.

One may naturally also propose to assign the adjustment of the outer covering devices or flaps to a separate regulating device wherein, for example, the flap adjustment is made dependent upon the quantity of air throughput. Use may also be made, thereby, of an automatic adjustment wherein suitable flaps are placed in neutral or rest position thereof by weight or spring loading in closed condition and are fully opened only by the cooling air flow. If the quantity of cooling air should then drop below a specific minimum value, automatic closing of the covering devices or flaps is effected by spring force or weight-loading.

Claims

We claim:

1. Air condensation plant for condensing steam by direct air cooling which comprises mutually transversely disposed elongated cooling elements traversible by steam along the length thereof, means for directing a flow of air to a respective side of said cooling elements, adjustable means for covering said side, respectively, of said cooling elements for controlling the cooling thereof and for preventing freezing, said cooling elements having an upper part through which a preponderant quantity of the steam to be condensed flows, said adjustable covering means compromising flaps and being located in front of said upper part of said cooling elements.

2. Air condensation plant according to claim 1, wherein said cooling elements extend at an inclination toward one another.

3. Air condensation plant according to claim 1, wherein said cover means are adjustable so as to progressively increase the area of the side of the respective cooling elements that is covered thereby, said air flow directing means being adjustable for reducing the flow of cooling air to the respective side of said cooling element.

4. Air condensation plant according to claim 1, wherein said adjustable flaps are pivotable about an axis extending along the upper inner edge of said cooling elements.

5. Air condensation plant according to claim 1, including a symmetrical assembly of two of said cooling elements leaning toward one another at an inclined angle, the adjustable flaps of both said cooling elements being pivotbale about axes located in the angle defined by said cooling elements, said flaps, in neutral position thereof, being suspended substantially vertically.

6. Air condensation plant according to claim 1, wherein said flaps are provided with parts movable for enlarging the covering area of said flaps.

7. Air condensation plant according to claim 6, wherein said flaps are respectively formed of pivotable flap parts and flap parts that are slidably mounted on said pivotable flap parts.

8. Air condensation plant according to claim 1, wherein said cooling elements have a lower portion of the respective side thereof to which the flow of air is directed by said directing means, said adjustable covering means being located at said lower portion.

9. Air condensation plant according to claim 8, wherein said cooling elements each comprise a plurality of cooling tubes spaced from one another so as to form a flow path for the cooling air substantially parallel to said cooling tubes.

10. Air condensation plant according to claim 1, wherein said cooling elements, respectively, have an inlet side for the air flow directed by said directing means, and a discharge side for the air flow passing through said cooling elements, and including control means for issuing control commands for reducing the air flow from said flow directing means simultaneously with the adjustment of said covering means.

11. Air condensation plant according to claim 1, including adjustable covering means located at said discharge side of said cooling elements, said control means being adapted to issue control commands for reducing the air flow from said flow directing means simultaneously with the adjustment of said covering means at said discharge side of said cooling elements.

12. AIr condensation plant according to claim 10, including a control device for automatically adjusting said covering means in dependence upon the variability of a condensation operating value.

13. Air condensation plant according to claim 12, wherein said condensation operating value is the condensate temperature, said adjustment being effective in accordance with said condensate temperature with respect to the temperature of the outer air and the temperatures of the cooling air flow at said inlet and outlet sides of said cooling elements.

14. Air condensation plant according to claim 11, wherein said control device, in response to said covering means being fully closed at said inlet side of said cooling elements, and said cooling air being reduced, is adapted, upon a required further reduction of the cooling air flow, to adjust said covering means at said outlet side of said cooling elements in closing sense in dependence upon the reduction in the cooling air throughput.

15. Air condensation plant according to claim 11, wherein said air flow directing means is adjustable for reducing the output thereof to a minimum, said control device being thereby actuable for simultaneously closing said covering means at said discharge side of said cooling elements.

16. Air condensation plant according to claim 11, wherein said control device is connected in a series circuit for closing said covering means at said inlet side at an initially slight reduction of the air flow output of said air flow directing means, for further reducing the air flow after said covering means is completely closed, and for closing said covering means at said discharge side after air flow is reduced to a minimum.