CONTAINER FOR STORING A LIQUID, AND USE THEREOF

Abstract

The invention relates to a container for storing a liquid, which tends to decompose into gaseous decomposition components in the case of the conditions prevailing in the container (1) and in the case of which a chemical reaction equilibrium results between gaseous decomposition components and liquid, wherein a floating roof (29) is accommodated in the container (1) and the floating roof (29) comprises floats (33), using which the floating roof (29) floats on the liquid, and wherein the floating roof (29) is guided using a sliding seal (45) in the container (1).

The invention furthermore relates to a device for storing heat, comprising a first container (57) for storing a colder liquid and a second container (59) for storing a hotter liquid and a use of the container and the device for storing heat.

Claims

1-13. (canceled)

14. A container for storing a liquid, which tends to decompose into gaseous decomposition components in the case of the conditions prevailing in the container (1) and in the case of which a chemical reaction in equilibrium results between gaseous decomposition components and liquid, wherein a floating roof (29) is accommodated in the container (1), wherein the floating roof (29) comprises floats (33), using which the floating roof (29) floats on the liquid, and wherein the floating roof (29) is guided using a sliding seal (45) in the container (1), characterized in that the sliding seal (45) is thermally insulated from the liquid stored in the container (1).

15. The container of claim 14, wherein the floating roof (29) is constructed from at least two segments (61), wherein the segments (61) are connected to one another in a movable manner.

16. The container of claim 14, wherein the floating roof (29) has at least one chamber, which contains thermally insulating material.

17. The container of claim 14, wherein feedthroughs (35, 37) are formed in the floating roof (29).

18. The container of claim 17, wherein the feedthroughs (35, 37) are sealed using a movable sealing plate (39).

19. The container of claim 14, wherein the sliding seal (45) has protective units (53) against liquid creeping upward.

20. The container of claim 14, wherein the floating roof (29) is guided on at least one guide in the container.

21. The container of claim 14, wherein the floating roof (29) has units to compensate for thermal expansion.

22. The container of claim 14, wherein the liquid is a molten salt.

23. The container of claim 22, wherein the molten salt is a mixture of nitrite and nitrate salts.

24. A device for storing heat, comprising a first container (57) for storing a colder liquid and a second container (59) for storing a hotter liquid, wherein the containers (57, 59) are connected to one another, so that the colder liquid flows out of the first container (57), after absorbing heat, into the second container (59) and flows out of the second container (59), after emitting heat, into the first container (57), wherein at least the second container (59) is a container according to claim 14.

25. The device of claim 24, wherein a gas compartment (41) is formed in the first container (57) and in the second container (59) above the floating roof (39), and the gas compartments (41) of the first (57) and the second (59) container are connected to one another via a connecting line (67).

26. A solar-thermal power plant comprising the container of claim 14.

27. A solar-thermal power plant comprising the device of claim 25.

Description

[0035] In the figures:

[0036] FIG. 1 shows a container having a floating roof according to the invention,

[0037] FIG. 2 shows a detail of the floating roof,

[0038] FIG. 3 shows a schematic illustration of a solar-thermal power plant in which a container having floating roof is used.

[0039] FIG. 1 shows a container having floating roof designed according to the invention.

[0040] A container 1, as is used, for example, in a solar-thermal power plant as a store for hot heat carrier medium, in particular a molten salt, comprises a container floor 3, a container wall 5, and a ceiling 7.

[0041] Liquid can be introduced into the container via a dip tube 9. Due to the supply of the liquid through the dip tube 9, an unacceptably large amount of turbulence can be prevented from occurring in the liquid during the introduction of the liquid into the container 1. A further reduction of turbulence during the decanting of the liquid into the container 1 can be achieved in that a baffle plate 11 is positioned below the dip tube 9. The liquid flowing in through the dip tube 9 flows onto the baffle plate 11, and is thus deflected and distributed, so that in accordance with the design of the baffle plate 11 or the angle at which the baffle plate 11 is arranged below the dip tube 9, targeted flow widening can be set. A further advantage of the baffle plate 11 is that the inflowing liquid does not strike the container bottom 3 directly and entrain and swirl up solids possibly accumulated there in this way, so that they are distributed in the liquid. The container is designed in the embodiment shown here in this case so that there is always enough liquid in the container 1 that the dip tube 9 is still immersed in the liquid when the container 1 is emptied.

[0042] The removal of the liquid is performed, for example, via a submersible pump 13. The submersible pump 13 is also submersed in the liquid in this case. Liquid can be removed from the container via the submersible pump 13 until the intake connecting piece 15 of the submersible pump 13 is no longer submersed in the liquid. The minimal fill level of the liquid in the container 1 thus results due to the location of the intake connecting piece.

[0043] The liquid sucked in by the submersible pump 13 flows out of the container 1 through a flow pipe 17. The drive of the submersible pump 13 is performed using a pump shaft 19, which is guided through the cover 7 of the container 1. For protection against entering liquid, the pump shaft 19 is guided in a pipe 21. Since in particular in the case of long submersible pumps, i.e., in the case of great height of the container 1 and correspondingly long flow pipe 17 and pump shaft 19, the flow pipe 17 and the pump shaft 19 are segmented, flow pipe 17 and pump shaft 19 are preferably guided in an envelope pipe 21. The envelope pipe 21 prevents uncontrolled gas exchange between the lower side and the upper side of the floating roof. It is preferable for the envelope pipe to be sealed against the gas phase above the floating roof, while it is open at the lower end. This prevents gas loaded with a high concentration of nitrogen oxides from penetrating into the gas compartment above the floating roof. The envelope pipe preferably has a sufficiently large diameter that the dip tube can be pulled through the envelope pipe, for example, for maintenance purposes.

[0044] In the embodiment shown here, a distributor 25 is located below the submersible pump 13. It can be embodied in the form of a perforated floor, for example. The distributor is located in this case at the position of the lowest liquid level in the container 1. The distributor 25 is used to dampen turbulence which can arise due to the inflow of the liquid, so that the liquid remains calm above the distributor 25 and no waves arise on the surface, due to which the floating roof 29 can begin to move. If, as shown here, a distributor 25 is provided, the possibility exists of, for example, guiding the dip tube 9 through a feedthrough 27 in the distributor 25 and fixing it on the distributor 25. In addition, the envelope pipe 21 of the submersible pump 13 can also be fixed on the distributor 25. The fixing of dip tube 9 and submersible pump 13 prevents them from beginning to oscillate and thus being able to cause damage to installations or to the container 1.

[0045] According to the invention, a floating roof 29 is accommodated in the container 1. The floating roof 29 floats in this case on the surface 31 of the liquid in the container. For this purpose, floats 33 are formed on the floating roof 29, which float on the liquid and support the floating roof 29. In the embodiment shown here, the entire floating roof 29 is not in contact with the surface 31 of the liquid, but rather only the floats 33. However, it is alternatively also possible to form the entire floating roof 29 in the form of floats, so that the entire floating roof 29 floats on the surface 31 of the liquid. In particular in the case of use as a hot tank of a solar-thermal power plant, it is preferable if the floating roof is embodied as thermally insulating. For this purpose it is possible, for example, to design the floating roof 29 as a hollow body and to fill it with an insulation material. Alternatively, the possibility also exists of manufacturing the floating roof 29 entirely from the insulation material. In particular steel-plate-clad ceramics having gas inclusion, for example, foamed ceramic or foamed glass, which are temperature-stable and pressure-stable and enable very thin cladding plates to be used, are suitable as insulation materials. Alternatively, it is also possible, for example, to use typical inorganic fibre mats for thermal insulation, but then occurring external pressures must be absorbed by an envelope which is embodied as sufficiently stable.

[0046] Feedthroughs for installations are formed in the floating roof in the embodiment shown here. The dip tube 9 is guided through a first feedthrough 35 and the submersible pump 13 is guided through a second feedthrough 37. In this case, the second feedthrough 37 is made sufficiently large that the pump head of the submersible pump 13 can be inserted through the feedthrough into the container.

[0047] In order that no gas can escape from the liquid through the floating roof 29, the feedthroughs 35, 37 are preferably provided with a movable sealing plate 39. The movable sealing plate 39 is designed in this case so that it can both rise and fall vertically with the floating roof 29 and a horizontal movement is additionally possible, to prevent excessively large force action on the installations, by which damage can be induced, in the event of pipes of the installations which do not extend completely vertically, for example, dip tube 9 and envelope pipe 23.

[0048] To prevent tilting of the floating roof 29 when the floating roof 29 rises and falls, a guide 40 is preferably provided, along which the floating roof 29 is guided. For example, a guide rod can be attached on the container wall 5 as the guide 40 and the floating roof 29 encloses the guide rod so that the floating roof 29 is moved along the guide rod. Alternatively, it is also possible to provide guide rods in the container interior, which are guided through corresponding feedthroughs in the floating roof 29. In addition, the installations, for example, the dip tube 9 or the envelope pipe 23 of the submersible pump 13, can also be used as the guide.

[0049] A gas compartment 41 is above the floating roof 29, between floating roof 29 and cover 7 of the container. To prevent the gas in the gas compartment from being compressed when the floating roof 29 rises, a gas outlet 43 is provided in the cover.

[0050] If the container 1 is part of a two-tank system, for example, as is used in solar-thermal power plants, in which the colder liquid is stored in a first container and the warmer liquid is stored in a second container, so that in each case one container is emptied and the other is filled accordingly, it is preferable if the containers are connected to one another via the gas outlet 43 in the cover, so that in each case the gas can flow out of the container which is emptied into the container which is filled. In the case of thermal insulation of the floating roof 29, it is possible in this case that the gas phases in the first container and in the second container have essentially equal temperature and therefore, at equal pressure, also equal specific volume.

[0051] FIG. 2 shows a detail of the floating roof 29.

[0052] The floating roof 29 is guided using a sliding seal 45 on the container wall. The compartment below the floating roof 29 is sealed off in relation to the gas compartment 41 using the sliding seal 45, so that no decomposition gas arising from the liquid can escape into the gas compartment 41. Furthermore, this also prevents gaseous and liquid contaminants in particular from being able to reach the liquid from the gas compartment 41.

[0053] To improve the leak-tightness, it is advantageous if a sealing lip 47 is additionally located above the sliding seal. The sealing lip 47 is guided in this case along the container wall 5 and has an additional sealing action.

[0054] Below the sliding seal 45, ribs 49 are formed on the floats 33. The ribs 49 are spaced apart from one another, so that a gas compartment 51 is formed in each case between the ribs 49. The ribs 49 can be used as an additional seal. Furthermore, in particular the gas compartment 51 acts as additional insulation, so that the temperature in the region of the sliding seal 45 is lower than directly above the liquid. In this way, the sliding seal 45 is protected from excessively high temperatures and possible damage as a result of the high temperatures. In particular, it is also possible in this way to use sealing materials which would be damaged at the high temperatures of the liquid.

[0055] To furthermore prevent liquid creeping upward from the container from coming into contact with the sliding seal 45, it is advantageous to attach a drip edge 53 above the sliding seal 45. Liquid creeping upward drips off on the drip edge 53 and falls back downward into the liquid.

[0056] In contrast to the embodiment shown in FIG. 1 having unfilled floats 33, the floats are filled with a thermally insulating material 55 in the embodiment shown in FIG. 2. This prevents the floats from acting as thermal bridges and dissipating heat from the liquid to the gas compartment 41 above the floating roof 29.

[0057] FIG. 3 shows a solar-thermal power plant in which at least one container 1 having floating roof 29 is used.

[0058] In a solar-thermal power plant having a first container 57 for storing a colder liquid and a second container 59 for storing a hotter liquid, at least the second container 59 is equipped with a floating roof 29. In the embodiment shown here, the floating roof 29 is constructed from multiple segments 61, which are connected to one another so they are movable. The segments 61 are each equipped with floats in this case, so that each segment floats per se on the surface of the liquid. The liquid which is stored in the first container 57 and in the second container 59 is used as a heat carrier medium and is typically a molten salt. Salts which are used for the molten salt are in particular nitrates and nitrites of the alkali metals and alkaline earth metals and also arbitrary mixtures thereof. A typically used salt is a mixture of sodium nitrate and sodium nitrite in the weight ratio of 60:40.

[0059] In operation of the solar-thermal power plant, at times having incident solar radiation, the liquid is removed from the first container 57 and conducted through a solar field 63. The solar field 63 has receivers 65, in which the liquid is heated by incident solar energy. The liquid thus heated is introduced into the second container 59. In this case, the liquid volume decreases in the first container 57, whereby the gas compartment enlarges. At the same time, the liquid volume increases in the second container 59, so that the gas compartment 41 in the second container 59 shrinks. In this case, the gas from the gas compartment of the second container 59 is introduced via a gas pendulum line 67 into the first container 57. Excess gas, which can arise, for example, due to outgassing of gases dissolved in the liquid, which can enter the gas phase, for example, if the first container 57 is not equipped with a floating roof, can be removed via a gas outlet 69.

[0060] To generate power, the hot liquid from the second container 59 is supplied to a first heat exchanger 71 of a steam cycle 73. In the first heat exchanger 71, the water is vaporized and superheated by a heat transfer from the hot liquid to the water cycle. The superheated steam thus generated drives a steam turbine 75, which in turn drives a generator 77 to generate power. The superheated steam is relaxed in this case in the steam turbine 75.

[0061] The steam flowing out of the steam turbine 75 is condensed in a second heat exchanger 79, wherein the heat from the water of the steam cycle 73 is transferred to a cooling cycle 81. The cycle 81 is typically also operated using water, wherein the water of the cooling cycle 81 is cooled down in a cooling tower 83.

[0062] After the condensation, the water of the steam cycle 73 is compressed using a pump back to the pressure which is required to drive the steam turbine 75, before the water again flows into the first heat exchanger 71 for vaporization and super heating.

[0063] For example, parabolic troughs or Fresnel receivers can be used as the receivers 65 in the solar field 63. Alternatively, it is also possible to use a central receiver of a tower power plant instead of the solar field 63, wherein the liquid is then heated in the tower.

TABLE-US-00001 List of reference numerals 1 container 3 container bottom 5 container wall 7 cover 9 dip tube 11 baffle plate 13 submersible pump 15 intake connecting piece 17 flow pipe 19 pump shaft 21 pipe 23 envelope pipe 25 distributor 27 feedthrough 29 floating roof 31 surface of the liquid 33 float 35 first feedthrough 37 second feedthrough 39 movable sealing plate 40 guide 41 gas compartment 43 gas outlet 45 sliding seal 47 sealing lip 49 rib 51 gas compartment 53 drip edge 55 thermally insulating material 57 first container 59 second container 61 segment 63 solar field 65 receiver 67 gas pendulum line 69 gas outlet 71 first heat exchanger 73 steam cycle 75 steam turbine 77 generator 79 second heat exchanger 81 cooling cycle 83 cooling tower