Refrigeration – Cryogenic treatment of gas or gas mixture – Separation of gas mixture
Reexamination Certificate
2003-03-07
2004-06-15
Doerrler, William C. (Department: 3744)
Refrigeration
Cryogenic treatment of gas or gas mixture
Separation of gas mixture
C062S903000, C165S143000, C165S145000
Reexamination Certificate
active
06748763
ABSTRACT:
The invention relates to a bath condenser with a condenser block that has evaporation passages for a liquid and liquefaction passages for a heating medium and at least two circulation sections that are located on top of one another, the evaporation passages each having on the lower end of a circulation section at least one entry opening for the liquid and on the upper end of a circulation section at least one exit opening, and there being means for routing liquid from an exit opening of one circulation section to an entry opening of the underlying circulation section.
In a low-temperature air separation system with a pressure column (commonly referred to as a high pressure column) and a low-pressure column, liquid oxygen from the low-pressure column is evaporated against gaseous nitrogen from the pressure column in indirect heat exchange in a heat exchanger, the nitrogen condensing.
The heat exchanger is implemented essentially in two different basic forms. In a falling-film evaporator, the liquid to be evaporated is delivered at the top to the evaporation passages via a distribution system that at the same time forms a gas seal. The liquid runs down as a liquid film over the heating surface, its being partially evaporated. The resulting gas and the unevaporated residual liquid emerge at the bottom from the falling-film evaporator. The liquid collects in the collecting space located under the condenser, while the gas portion is relayed on.
In a bath condenser, on the other hand, the condenser block is in the liquid bath from which liquid is to be evaporated. The liquid from underneath enters the evaporation passages of the condenser block and is partially evaporated against the heating medium that flows through the liquefaction passages. The density of the medium that is evaporating in the evaporation passages is less than the density of the surrounding liquid bath, resulting in a siphon action, so that liquid from the liquid bath flows into the evaporation passages. The greater the immersion depth of the condenser block in the liquid bath, the higher the average hydrostatic pressure becomes in the evaporation passages and the more poorly the liquid evaporates, since the boiling point of the liquid rises according to the vapor pressure curve.
The efficiency of a bath condenser can therefore be increased by dividing the condenser block into several sections that are located on top of one another, hereinafter called circulation sections. The advantage of one such arrangement is that the immersion depth for several circulation sections is smaller than for a single high condenser block. Thus, the hydrostatic pressure in the evaporation passages becomes less, and the liquid can evaporate more easily.
German patent application 199 39 294 discloses a multistory bath condenser in which there are two condenser blocks parallel to one another and in which between the blocks for each story there are liquid storage tanks for the liquid that is to be evaporated. The evaporation passages are divided vertically into several stories that each form its own circulation section, Thus the immersion depth is kept relatively small.
In the individual circulation sections, liquid flows from underneath into the evaporation passages and emerges again as a liquid-gas mixture on the top end of the circulation section on the side of the condenser block that is opposite the entry side. The emerging liquid is routed around the condenser block via lines and flows back again into the liquid storage tank. The complex piping and large space requirement that arise due to the two parallel condenser blocks and the necessary piping are disadvantageous in this arrangement.
The object of this invention is therefore to develop a compact multistory bath condenser.
This object is achieved by a bath condenser of the initially mentioned type, in which the means for routing the liquid connect only exit openings and entry openings that are located on the same side of the condenser block.
As claimed in the invention, the bath condenser consists of at least two circulation sections that are located on top of one another and that are each supplied with liquid from its own liquid storage tank. The vertical subdivision of the bath condenser can greatly reduce the liquid level in the liquid storage tanks of the respective circulation sections relative to the liquid level in the single continuous condenser block.
The liquid enters the evaporation passages via the entry openings that are located on the bottom end of a circulation section, flows upward, partially evaporates and leaves the passages on the top end of the circulation section via suitable exit openings. The liquid portion in the liquid-gas mixture emerging from the passages flows, on the one hand, back to the entry openings of this circulation section, and, on the other hand, depending on the liquid level in the liquid storage tank of the circulation section, to the entry openings of the underlying circulation section in order to be overturned there in turn via the evaporation passages.
The exit and entry openings between which liquid flows are all located on the same side of the condenser block in the bath condenser as claimed in the invention. Therefore, complex piping is not necessary to repeatedly overturn the liquid within a circulation section or to feed it to an adjacent circulation section.
Preferably at most two sides of the condenser block are provided with entry and/or exit openings. As claimed in the invention, however, the entry and exit openings that are located on different sides of the condenser block are not connected to one another on the liquid side outside of the condenser block, i.e., the liquid that emerges from an exit opening on one side of the condenser block cannot flow into an entry opening that is on the other side of the condenser block. Within the condenser block, however, fundamentally exchange of liquid between the evaporation passages to a small degree is possible, since the corrugated sheets that separate the individual evaporation passages from one anther are often perforated. If there are entry and exit openings on both sides of the condenser block, the condenser block has two parallel groups of evaporation passages between which no liquid is exchanged. The liquid emerging from the exit openings on one side is routed exclusively in the evaporation passages with entry openings that are likewise located on this side.
In an especially preferred embodiment, on the two opposing sides of the condenser block, there are entry and exit openings to the evaporation passages in each case. In this case, it is especially advantageous if the condenser block is built mirror-symmetrically to the center plane between these two sides.
A more compact execution of the bath condenser can be achieved by all entry and exit openings being located on the same side of the heat exchanger. Lines to connect the entry or exit openings to one another are only necessary on the outside of the condenser block. The other three lateral boundaries of the bath condenser are formed by the outside walls of the condenser block. If nothing else arises from this connection, the indications “top”, “bottom” and “laterally” each relate to the alignment of the condenser that is present during operation of the bath condenser and in which the individual circulation sections are located essentially vertically on top of one another.
Preferably the flow connection between the entry or exit openings and the evaporation passages is produced by horizontally or obliquely running channels. The condenser block is built from several corrugated plates that are stacked on top of one another and that are each bordered by flat partitions. In this case, the plates and partitions form the liquefaction and evaporation passages. In the area of the entry or exit openings to the evaporation passages, the corrugated plates are arranged slanted so that fluid that flows into the evaporation passages that run vertically is deflected to the entry or exit openings that are located in a side wall of the conden
Hecht Thomas
Schweigert Karl Heinrich
Sotzek Manfred
Wanner Alfred
Doerrler William C.
Linde AG
Millen White Zelano & Branigan P.C.
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