Pump reservoir, rectification system and process for low-temperature rectification

Abstract

The invention provides a cryogenic pump reservoir (100), for a cryogenic liquid to be fed to a pump (208), with an interior reservoir space (103) extending between a reservoir bottom (101) and a reservoir top (102) and comprising a liquid feeding region (104), which is positioned at a first distance from the reservoir bottom (101) in the direction of the reservoir top (102), and a liquid removing region (105), which is positioned at a second distance from the reservoir bottom (101) in the direction of the reservoir top (102), the second distance being greater than the first distance. It is provided that in the liquid feeding region (104) there is formed a liquid feeding opening (106), that the interior reservoir space (103) is at least partially divided in the liquid feeding region (104) by means of a dividing wall (106), which is arranged in such a way that one of its surfaces (107) is aligned in the direction of the liquid feeding opening (106. A corresponding rectification system (200) and a process for low-temperature rectification are likewise the subject of the present invention.

Claims

1. A cryogenic pump reservoir (100), for a cryogenic liquid to be fed to a pump (208), the pump reservoir (100) comprising an interior reservoir space (103) extending between a reservoir bottom (101) and a reservoir top (102); a liquid feeding region (104), which is positioned at a first distance from the reservoir bottom (101) in the direction of the reservoir top (102); and a liquid removing region (105), which is positioned at a second distance from the reservoir bottom (101) in the direction of the reservoir top (102), the second distance being greater than the first distance, characterized in that in the liquid feeding region (104) there is provided a liquid feeding opening (106), and the interior reservoir space (103) is at least partially divided in the liquid feeding region (104) by a dividing wall (107) having at least one surface, wherein the dividing wall is arranged such that the at least one of its surfaces (108) is aligned in the direction of the liquid feeding opening (106).

2. The cryogenic pump reservoir (100) according to claim 1, in which the reservoir bottom (101) is tapered in a direction away from the interior reservoir space (103), and has a solids outlet (109).

3. The cryogenic pump reservoir (100) according to claim 1 or 2, in which a liquid feeding line is attached to the liquid feeding opening (106) and the liquid feeding line has a line axis in its end region, wherein the dividing wall (107) is arranged in such a way that its surface (108) that is aligned in the direction of the liquid feeding opening (106) and is arranged at an angle of 80 to 100 to the line axis.

4. The cryogenic pump reservoir (100) according to one of the preceding claims, in which the interior reservoir space (103) has in the liquid feeding region (104) a cross section that is divided into two parts by the dividing wall (107), whereby the area of the two parts differs by no more than 20%.

5. The cryogenic pump reservoir (100) according to one of the preceding claims, in which the interior reservoir space (103) between the liquid feeding region (104) and the liquid removing region (105) comprises a gas collecting region (110) that has gas collecting trays (111), and wherein the gas collecting trays (111) comprise gas collecting structures (112) aligned in the direction of the reservoir bottom (101), and wherein attached to one or each of the gas collecting trays (111) are provided gas lines (113) that extend towards of the reservoir top (102).

6. The cryogenic pump reservoir (100) according to claim 5, in which the gas collecting structures (112) are formed as well structures having an opening in the direction of the reservoir bottom (101).

7. The cryogenic pump reservoir (100) according to claim 5, in which the gas collecting structures (112) take the form of a number of grooves in the gas collecting trays (111).

8. The cryogenic pump reservoir (100) according to one of claims 5 to 7, in which at least two gas collecting trays (111) are provided in the gas collecting region (110), and each gas collecting tray (111) partially covers a cross section of the interior reservoir space (103), and the at least two gas collecting trays are arranged offset in relation to one another.

9. The cryogenic pump reservoir (100) according to one of the preceding claims, in which a liquid removing opening (114) is provided in the liquid removing region (105), the liquid removing opening (114) having a vortex breaker (115) which is led out from the interior reservoir space (103).

10. Rectification system (200) comprising: a rectification column (201) having a column top (202), a cooling device (203) and a condensate separator (206) having a liquid removing opening (207), wherein the column top (202) is connected by means of a first line (203) to the cooling device (204); and the cooling device (204) is connected by means of a second line (205) to the condensate separator (206); the system further comprising a cryogenic pump reservoir (100) according to one of the preceding claims, wherein the liquid feeding opening (106) of the pump reservoir (100) is fluidically coupled to the liquid removing opening (207).

11. Rectification system (200) according to claim 10, also comprising a pump (208), which is configured to return the cryogenic liquid from the liquid removing region (105) of the pump reservoir (100) to the column top (202) of the rectification column (201).

12. Rectification system (200) according to claim 10 or 11, in which the pump reservoir (100) has a gas outlet (116), which is connected to a gas inlet (209) of the condensate separator (206).

13. Process for low-temperature rectification, wherein the method comprises using a pump reservoir (100) according to one of claims 1 to 9 or using a rectification system (200) according to one of claims 10 to 12.

14. Process according to claim 13, comprising providing a supply of the cryogenic liquid having a temperature of 90 to 110 C.; and operating the pump reservoir (100) at a pressure level of 19 to 25 bar (abs.).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1 shows a rectification system according to one embodiment of the invention in a schematic representation.

[0034] FIG. 2 shows a pump reservoir according to one embodiment of the invention in a schematic representation.

[0035] FIG. 3 shows parts of a rectification system according to one embodiment of the invention in a schematic representation.

[0036] FIGS. 4a-4c show details of a pump reservoir according to one embodiment of the invention.

[0037] In the figures, corresponding elements bear identical reference signs and, for the sake of clarity, are not explained more than once.

DETAILED DESCRIPTION OF THE INVENTION

[0038] FIG. 1 schematically illustrates a rectification system according to a particularly preferred embodiment of the present invention and is denoted overall by 200.

[0039] The rectification system 200 comprises a rectification column 201, which is illustrated in a greatly simplified form. As explained, this serves the purpose of separating methane or a methane-containing gas mixture from an input mixture. For this purpose, the rectification column 201 has a top condenser of a type that is known in principle, which is denoted here overall by 210.

[0040] In the top condenser 210, a column top, denoted here by 202, of the rectification column 201 is connected by means of a line 203, which has also been referred to above as the first line, to a suitable cooling device 204. The cooling device 204 may in particular comprise one or more heat exchangers, which are operated with a suitable coolant, for example expanded methane. The rectification column 201 may have a bottom evaporator 220, which however may be formed in a known way and is therefore not explained in detail for the sake of clarity.

[0041] In or downstream of the cooling device 204 there forms from a top gas rectification column 201 passed through the first line 203 a two-phase mixture, which is fed to a condensate separator 206 by way of a line 205, which has also been referred to above as the second line. In the condensate separator 206, a condensate is separated and can be drawn off out of the condensate separator by way of a liquid removing opening 207.

[0042] The aim of the condensate separation is in particular to provide a liquid reflux, which can be returned by means of a pump 208 to the column top 202 of the rectification column 201. As explained above, it may happen here however that a corresponding condensate outgases and/or that solids are deposited. To avoid this, a pump reservoir 100 is used, shown here in a greatly simplified form and denoted overall by 100. A pump reservoir 100 that can be used according to one embodiment of the invention is explained in greater detail with reference to FIG. 2.

[0043] At least part of the condensate from the condensate separator 206 is in this case fed to the pump reservoir 100 by way of a liquid feeding opening 106, which is likewise illustrated more specifically in FIG. 2. In particular, one or more further liquid or gaseous streams may be removed from the condensate separator 206 by way of corresponding lines, in a way not illustrated here in detail. A fraction of the condensate that has evaporated in the pump reservoir 100 can be returned by way of a gas outlet 116 into the condensate separator 206 by way of a gas inlet 209. Depositing solids can be drawn off out of the pump reservoir 100 by way of a solids outlet 109. In this way it can be ensured that the pump is only fed a cryogenic liquid, without gaseous and solid fractions. This takes place by way of a liquid removing opening 114.

[0044] As already mentioned, a corresponding pump reservoir according to one embodiment of the invention is schematically illustrated in greater detail in FIG. 2 and is denoted overall by 100.

[0045] The pump reservoir 100 comprises an interior reservoir space 103, extending between a reservoir bottom 101 and a reservoir top 102. As illustrated by a dashed line, in particular the reservoir bottom 101 may be releasably attached by way of a suitable flange releasably to a shell that defines the interior reservoir space and is not separately denoted here. The interior reservoir space comprises a liquid feeding region 104, which is positioned at a first distance from the reservoir bottom 101 in the direction of the reservoir top 102, and a liquid removing region 105, which is positioned at a second distance from the reservoir bottom in the direction of the reservoir top. The second distance is in this case greater than the first distance, i.e. the liquid removing region 105 lies above the liquid feeding region 104 during the operation of the pump reservoir 100. Arranged in the liquid feeding region 104 is the liquid feeding opening 106, which has already been mentioned with reference to FIG. 1.

[0046] In the liquid feeding region 104, the interior reservoir space 103 is at least partially divided by means of a dividing wall 107, which is arranged in such a way that one of its surfaces, denoted here by 108, is aligned in the direction of the liquid feeding opening 106. Furthermore, in the example presented, the reservoir bottom 101 tapers in a direction away from the interior reservoir space 103 and has a solids outlet 109, which has likewise already been mentioned and shown in FIG. 1.

[0047] As illustrated in the form of a dotted liquid flow, liquid fed in by way of the liquid feeding opening 106 is backed up at the surface 108 of the dividing wall 107 that is aligned in the direction of the liquid feeding opening 106. Part of the liquid flows under the dividing wall 108 back in the direction of the reservoir bottom 101, and from there into the interior reservoir space 103. Another part flows directly in the direction of the reservoir top into the interior reservoir space 103. In this way, as mentioned, dead volumes in the reservoir bottom 101 can be avoided. As mentioned, the avoidance of corresponding dead volumes or dead zones is advantageous in particular because a precipitation of carbon dioxide caused by evaporating methane can be reduced in this way. Nevertheless, carbon dioxide precipitating in a solid state collects in the reservoir bottom 101, which is in particular conically formed, and can be drawn off out of it by way of the solids outlet 109. It goes without saying here that the reservoir bottom is at least partially not divided by means of the dividing wall 107.

[0048] As likewise mentioned, attached to the liquid feeding opening 106 is a liquid feeding line with a line axis, which is illustrated here in a dash-dotted manner. As likewise already mentioned, the term line axis should be understood here in the geometrical sense, not in the mechanical sense. The line axis runs in particular through the center point of the cross section of the line, which is typically of a circular form. The dividing wall 107 is in this case aligned in particular perpendicularly to line axis of the liquid feeding line, or the part thereof that opens out into the pump reservoir, i.e. the surface 108 of the dividing wall 107 that is oriented in the direction of the liquid feeding opening 106 is arranged in particular at an angle of 80 to 100, in particular perpendicularly, to the line axis. In other words, the surface 108 of the dividing wall 107 faces the liquid feeding opening 106. As likewise mentioned, the dividing wall 107 is in particular arranged centrally in the interior reservoir space, in the liquid feeding region, i.e. the interior reservoir space, which has a specific cross section in the liquid region, for example a circular cross section, is divided into two halves, the area content of which is preferably identical, but in particular differs by no more than 20%.

[0049] Between the liquid feeding region 104 and the liquid removing region 105 there is formed in the pump reservoir 100 or its interior reservoir space 103 a gas collecting region 110, which serves in particular for allowing liquid to be removed without gas from the liquid removing region. For this purpose, the interior reservoir space 103 has in the gas collecting region 110 gas collecting trays 111. These gas collecting trays are respectively provided with gas collecting structures 112, which are aligned in the direction of the reservoir bottom 101. The gas collecting trays 111 also respectively bear gas lines 113, which run in the direction of the reservoir top. In the example shown, the gas collecting structures 112 that are attached to the gas collecting trays 111 take the form of noses, whereby the gas collecting trays together with these gas collecting structures are formed in the manner of wells that open in the direction of the reservoir bottom 101.

[0050] Gas bubbles rising up in the liquid in the interior reservoir space 103 collect in these wells and can in each case be carried away upward by way of the gas lines 113. As also further explained below, the arrangement of the gas collecting trays 111 with the gas collecting structures 112 and the gas lines 113 is in this case in particular such that corresponding gas bubbles can be passed through the liquid removing region 105 without it being possible for them to be drawn off by way of the liquid removing opening 114 and thereby damage the pump 218.

[0051] The mentioned liquid removing opening 114, which may in particular have a vortex breaker 115 in its mouth, opens out in the liquid removing region 105.

[0052] As illustrated by various liquid levels L1-L5, the liquid may be at different heights in the interior liquid space. These depend on a corresponding filling level in the condensate separator 206. The minimum filling level is denoted by L1, the maximum by L5. The gas lines of the gas collecting trays in this case open out above the liquid removing region 105, which lies below the minimum liquid level L1, and below or above corresponding liquid levels. Gas can be removed from a gas space above the liquid levels L1-L5 by way of the mentioned gas outlet 116.

[0053] In FIG. 3, the matter just mentioned of different liquid levels is illustrated once again. FIG. 3 shows here a partial view of FIG. 1; the explanations given there apply correspondingly.

[0054] FIGS. 4A-4C illustrate the column internals already shown in FIG. 2 once again in the form of cross-sectional views through the liquid feeding region 104 (FIG. 4A) and the gas collecting region 110 (FIGS. 4B and 4C).

[0055] As can be seen from FIG. 4A, a cross section of the interior reservoir space 103 in the liquid feeding region 104 is substantially circular. The interior reservoir space is in this case divided into two halves by the dividing wall and the dividing wall 107 is arranged in such a way that its surface 108 that is oriented in the direction of the liquid feeding opening 106 is arranged at an angle perpendicularly to the line axis of the liquid feeding opening 106. Even though a circular cross section of the interior reservoir space 103 is shown in the example presented, it goes without saying that this cross section can also deviate from a circular cross section to the extent claimed. Of course, the same also applies correspondingly to the orientation of the dividing wall 107.

[0056] In the cross-sectional representations of FIGS. 4B and 4C, cross sections through the gas collecting region 110 are respectively illustrated above a gas collecting tray 111 in each case. As can be seen, the gas collecting trays 111 in this case cover the cross section of the reservoir by over half in each case, and the gas collecting trays 111 are arranged at different positions offset in relation to one another. In this way it is ensured that, over the entire cross section of the pump reservoir 111, gas bubbles rising up can be collected and taken past the liquid removing region 105 by way of the corresponding gas lines 113.