EP2057381B1 - Method for the cyclical pistonless compression of the gas phase of deep-frozen liquefied gases - Google Patents

Abstract

Disclosed is a method for the cyclical pistonless compression of the gas phase of deep-frozen liquefied gases. In said method, deep-frozen liquefied gases are placed in a dosing receptacle, and a metered amount is fed to an evaporator, whereupon the evaporated amount of gas is drawn off or fed into a pipeline system. The dosing receptacle is then once again filled with liquid gas, and the pressure prevailing in the evaporator last used is utilized for pressing the liquid gas out of the dosing receptacle into another evaporator. Different evaporators are cyclically fed from the dosing receptacle while the pressure in the dosing receptacle and, if necessary, in the evaporator that is to be filled is released before a metered amount of the liquefied gas is introduced once again.

Description

The invention relates to a method for cyclic pistonless compression of the gas phase cryogenic liquefied gases. Such a method is for example from the document US-17-2,035,396 known.

For the transport of gases, these are often liquefied, since the volume of liquid gases has a fraction of the gas volume, without having to work at high pressure. Pressure tanks are complex in their construction and are only of limited use for road transport.

Substantial energy is used to liquefy gases, with the energy of overheating and evaporation removed from the product. There is a temperature gradient between the liquefied product and the environment. Refrigerated liquefied gases are stored in so-called cryo-tanks. Cryo-tanks, which may be stationary, are used as latches for the use of gases in the gaseous state. The gases are removed from such a cryo-tank and converted into the gaseous state, with high-performance high-pressure pumps generally being used for this purpose. The liquid is forced by means of such high pressure pumps in the evaporator, wherein the ambient heat or external energy is used for evaporation in the evaporator. In other methods, the liquid gases are immediately evaporated and subsequently compressed by gas compressors to the desired pressure. If gas cylinders with a pressure of, for example, 200 bar or 300 bar are to be filled with such systems, it is usually necessary to use about 40 KWh of power for 1000 Nm ³ / h for the compression. If not the liquid but that already vaporized gas is to be compressed in the sequence, the same amount requires a power of about 400 KWh.

The invention now aims to significantly reduce the costs incurred in such known methods for the evaporation and filling under pressure power, and has the aim to dispense with the use of pumps and compressors, which in addition to an improvement in the power balance and reduced maintenance leads.

To solve this problem, the inventive method of the type mentioned is essentially that cryogenic liquefied gas is placed in a dosing and a metered amount is fed to an evaporator, whereupon the vaporized gas is filled or fed into a pipeline network, whereupon the dosing again is filled with liquid gas and the pressure in the last used evaporator is used to squeeze the liquid gas from the dosing into another evaporator, each cyclically different from each other evaporators are fed from the dosing and the pressure in the dosing and, if necessary, in each case to be filled evaporator is degraded before a renewed introduction of a metered amount of the liquefied gas. The fact that cryogenic liquefied gases are spent in a dosing, can be used without the aid of the pump directly with the initially in a cryogenic tank usually initially existing vapor pressure of about 5 bar or the geodetic pressure to this transport of the cryogenic liquefied gas in the Dosing to accomplish. The fact that the amount is metered in the sequence, which, as it corresponds to a preferred development of the method according to the invention can be done in a simple manner, for example by weighing the metered dose spent in the dosing, it is ensured that in the episode during evaporation a whole certain amount and with known volume a defined the pressure applied to the heat supplied is built up. The fact that now the vaporized gas is filled directly under the resulting pressure during evaporation or fed against dynamic line resistance in a network, a pressure equalization between the evaporator and the consumer or the bottles or tanks to be filled is produced, naturally a residual pressure in the evaporator remains as soon as the corresponding filling valves are closed. In order to be able to continue working cyclically in the sequence, the dosing must be filled again with a metered amount of liquid gas, in which case as long as the original existing in the cryotank vapor pressure or the geodetic pressure is sufficient, as long as the pressure in the dosing under each of these is required for filling printing.

After repeated loading of the dosing but here is a pressure equalization to the evaporator and when starting the system it is sufficient after a renewed loading of the dosing the remaining vapor pressure in the evaporator just used for expressing the metered amount of liquefied gas in another on atmospheric or to allow lower pressure than the pressure in evaporators currently in use evaporator. It is thus loaded with the remaining pressure of the currently used evaporator another evaporator and in the evaporation carried out there again built the vapor pressure, which is provided in the sequence for filling the tank of the bottles or the feed into the pipeline network.

In order to prevent a total of the dosing and the evaporator achieve the same pressure level by cyclic pressure equalization, a selective pressure reduction must be made in each case, according to the invention this is done so that after the cyclic charging each different evaporator and the use the residual pressure in each case one of the two evaporators, the pressure in the metering vessel and, if necessary, in each case to be filled evaporator is reduced before the renewed introduction of a metered amount of the liquefied gas. In this way, it is always possible to maintain the required pressure difference in the system without the aid of pumps, which allows an alternating or cyclic charging of separate evaporators from a cryogenic tank with a defined vapor pressure.

The required pressure reduction can be made in principle in various ways. According to a preferred embodiment of the method according to the invention is in this case proceeded so that the pressure reduction from the metering vessel or the evaporator is reduced via a throttle in the gas space of the tank, a consumer or the atmosphere. The term throttle here means any device which serves to reduce the pressure. Conventional pressure reducing valves are here due to the temperature conditions, as they occur when working with liquefied gases and the respective expansions, suitable only conditionally, the pressure reduction could of course also be done by forwarding in another consumer and / or against the atmosphere, if as in 2 In case of gas losses can be accepted. In a particularly advantageous manner, however, the procedure is that the pressure reduction in a condenser is made as a throttle. A condenser serves to substantially reduce the volume, since liquid gas is again eliminated from the gas phase and in this way the pressure is drastically reduced. Such a condenser thus meets the criteria of the invention required throttle to return the gas and the liquid in the sequence in the cryo-tank, which indeed has a much lower vapor pressure.

In a particularly simple manner, this procedure can be such that the liquefaction and the pressure reduction in the Throttle by spraying liquefied gas and subsequent mixing condensation is made.

It is possible to completely or partially condense the injected gas by co-condensation in the cryo-tank. In this case, the gas can be pressed from below through the liquid or condensed by blowing liquid into the gas.

As already mentioned, it is essential for the safe operation and in particular for the filling of gas cylinders or tanks, that a metered amount of gases is filled. For this purpose, as already mentioned, preference is given to the amount metered into the dosing tank being determined by weighing, with the filled compressed gas quantity also being measured, in particular weighed, in order to control it.

In order to find quickly reproducible pressure conditions and a smooth operation at the beginning of the filling process, a correspondingly defined initial state must be set at the beginning, for which the procedure according to the invention is advantageously such that the containers, condenser and pipelines are cold-rolled before the start of the first evaporation ,

The invention will be explained in more detail with reference to an embodiment schematically illustrated in the drawing.

In the drawing, A designates a cryo-tank. B denotes a metering container, wherein in the line leading to the cryo-tank, a condenser designated C is switched on as a throttle. D denotes a first evaporator. Parallel to this first evaporator D exists a second evaporator E, wherein alternately from the respective active evaporator a schematically denoted by F. Consumer device, such as a bottle is filled.

With G a scale for the filled into the dosing B amount is indicated schematically. Likewise, there is a scale indicated by H for the measurement of the filled into the bottle F amount.

The valves connected in the respectively marked lines are designated consecutively with 1 to 19 and connected as follows in the individual process steps:

For cold running of the condenser, the product is liquid in the cryo-tank A, wherein the remaining facilities, and in particular the dosing B and the evaporators D and E are in this initial phase at atmospheric pressure. In Cryo-Tank A there is a slight overpressure of mostly about 5 bar. After opening the valves 1 and 2 liquid product flows under the pressure in the cryo-tank in the condenser C until the gas phase is in equilibrium with the liquid phase. An opening of the valves 10 and 11 leads to the venting of gas initially located in the condenser in the atmosphere or in the gas space of the cryo-tank A.

During the subsequent cold run of the metering, valves 1, 3 and 8 are opened. In this case, liquid product flows from the cryo-tank into the dosing tank, the valves being closed when the predetermined dosing weight determined by the balance G is reached. Through the valve 8 is vented in the open position of the dosing against the cryo-tank A.

In a subsequent opening of the valves 4, 6 and a further keeping open the valve 8, the liquid product from the dosing B flows into the first evaporator D. Again, a pressure equalization takes place via the valve 8 against the cryo-tank A, wherein immediately following the emptying the metering the valve 6 and the valve 4 are closed to separate it from the evaporator D.

In the subsequent evaporation in the evaporator D, the product is completely evaporated, after which the valves 14 and 19 are opened after complete evaporation to spend the now gaseous product in the bottle F. On this occasion, a check by weighing by means of the schematically indicated balance H can be made.

After closing the valves prevails in the evaporator D, the last formed by evaporation of vapor pressure.

As a result, the valves 1, 3 and 8 are again opened, whereupon cryogenic liquefied gas in turn flows from the cryo-tank A into the dosing tank B and, as described above, a dosage is carried out, the measured values of the balance G being taken into account.

After closing the valves just opened and then opening the valves 4, 5, 6, 14 and 17, the metered amount of cryogenic liquefied gas is pressed with the prevailing pressure in the evaporator D from the dosing into the further evaporator E, whereupon the valves are closed again , Subsequently, the cryogenic liquefied gas evaporates in the evaporator E, after which the valves 15 and 19 are opened after complete evaporation and again a container or the bottle F can be filled. After a check by means of the balance H, the valves are closed again so that now the evaporator and the dosing tank are under a correspondingly higher pressure than at the beginning of the process. As soon as this pressure, and in particular the pressure in the dosing container, exceeds the pressure in the cryo-tank, it is no longer possible without further ado to effect a renewed filling of the dosing container with the aid of the geodetic pressure. It must therefore be here a throttled pressure reduction, assuming is that the dosing after the last described drainage is under the pressure of the evaporator D. The valves 7, 9 and 12 are opened in sequence, whereupon in the heat exchanger of the condenser the gaseous product is cooled as far as possible by liquid product, so that the pressure is reduced accordingly and the throttling in the valve 9, the steam line is reached.

After a previous pressure equalization, the filling of the dosing tank is possible again with the geodetic pressure. However, in order to enable the sedimentation of the metered quantity of cryogenic liquefied gas from the metering container into the evaporator D, this evaporator to be filled must of course again be brought to a pressure level which is lower than the still available pressure level, which consists of the other evaporator is available for squeezing the dosing available. In other words, this means that the next to be filled evaporator, in this case the evaporator D, must be subjected to a corresponding pressure equalization and as well as the dosing B are brought in a suitable manner to the pressure in the gas space of the cryo-tank A or below got to. This is achieved by opening the valves 14 and 17 and depending on the volume by opening the valve 8 with immediate backward expansion in the gas space of the cryo-tank A or by opening the valve 7 and return via the condenser.

After the subsequent charging of the metering container in the manner already described, the pressure remaining in the evaporator E can again be used by opening the valves 4 and 6 and 16 to press the metered quantity of liquefied gas into the evaporator D, whereupon, as already described above, continues to proceed.

In the respective throttling or pressure reduction in the condenser is undercooled by opening the valve 13 Liquid from the top of the condenser into the heat exchanger area of the condenser. By opening the valves 11 and 12, a pressure equalization between the condenser C and the cryo-tank A is reached, whereupon the process by opening the valves 1 and 2 is again set to the initial state, which enables new cycles.

Claims (7)

1. A method for the cyclical pistonless compression of the gas phase of cryogenically liquefied gases, characterised in that cryogenically liquefied gases are placed in a dosing receptacle (B) and a metered amount is fed to an evaporator (D), whereupon the evaporated amount of gas is drawn off or fed into a ductwork (F), whereupon the dosing receptacle (B) is then once again filled with liquid gas, and the pressure prevailing in the evaporator (D, E) last used is utilised for pressing the liquid gas out of the dosing receptacle (B) into another evaporator (E), wherein different evaporators (D, E) are cyclically fed from the dosing receptacle (B) and the pressure in the dosing receptacle (B) and, if necessary, in the evaporator (D, E) that is to be filled, is released before a metered amount of the liquefied gas is introduced once again.
2. The method according to claim 1, characterised in that the pressure is released from the dosing receptacle (B) or the evaporator (D, E) via a throttle (10, 11) into the gas space of the tank (A), a consumer (F) or the atmosphere.
3. The method according to claim 1 or 2, characterised in that the pressure release takes place in a liquefier (C) as a throttle (9).
4. The method according to claim 1, 2 or 3, characterised in that the liquefaction (C) and the pressure release is carried out by spraying in liquefied gas and subsequent mixed condensation, wherein mixed condensation by passing the gas through the liquid phase of the tank (A) is also possible.
5. The method according to any one of claims 1 to 4, characterised in that the amount metered in to the dosing receptacle (B) is preferably determined by weighing (G).
6. The method according to any one of claims 1 to 5, characterised in that the amount of compressed gas drawn off is measured in each case, in particular is weighed.
7. The method according to any one of claims 1 to 6, characterised in that the container (A, B), liquefier (C) and the pipelines are run cold before beginning the first evaporation.

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