DE1134095B - Method and device for storing low-boiling gases, in particular oxygen - Google Patents

Description

Method and device for storing low-boiling gases, in particular Oxygen The invention relates to a method and a device for storage low-boiling gases, in particular oxygen, with that in an air separation plant accumulating liquid oxygen content is stored in a pressure tank and the compressed gaseous oxygen content in off-peak times as an excess amount in the The liquid phase of the pressure tank is introduced and removed from it as required.

The problem arises when operating large-scale systems for generating oxygen on, with simultaneous generation of a part as liquid oxygen the excess to supply or store gaseous oxygen for beneficial use.

In practice, only gaseous oxygen is generated Storage to accommodate the production surplus that occurs during off-peak times uneconomical and too expensive. When generating the entire amount of oxygen in liquid Form is the memory problem, viewed from the cost side, less significant, on the other hand, there is the constant expenditure of additional energy for the preparation of the liquid oxygen too high.

The previously known methods, an air separation plant in Keeping off-peak times in operation is based on the fact that a certain production share can also be continuously generated and recycled as liquid oxygen. Through this it makes sense to build the systems as combined gaseous-liquid systems with the ability to drive through in off-peak times and a certain amount of Continuous production of liquid oxygen, with .jedoch then occurring in gaseous form Oxygen must be blown off.

The disadvantages of this known manipulation must therefore be losses of gaseous oxygen and considerable additional costs for additional equipment and machines are accepted.

According to German Patent 935 196 it is known to be gaseous Oxygen in a supply of supercooled, liquid oxygen in pressure storage tanks is stored, to cool and bring to condensation. The plant runs in this Fall during off-peak times with full machine capacity, but it only produces liquid oxygen, which is many times more expensive than production gaseous oxygen. According to the known method, the generated liquid oxygen mostly evaporated again in the heat exchange with the incoming air and in off-peak times condensed in liquid oxygen under pressure build-up. The measure, liquid oxygen to generate it, then to evaporate it with the release of cold and the gas again To condense in the sump of the storage container, however, cannot claim to be profitable to raise.

On the other hand, the view today is unanimously that in Large-scale air separation plants that are supposed to work economically, the greater part Des. Oxygen has to be produced in gaseous form by the separator.

The process according to German patent 683 486 utilizes the Coldness of the nitrogen that is produced at the same time as the oxygen in the air separation process for subcooling the stored, liquid oxygen. This measure alone would but not enough to keep up with the total generated during off-peak times and to supercool stored liquid oxygen for a long time. As it is nowadays It is no longer common to have all of the oxygen and nitrogen produced as a liquid to win, the known method has the problem of the method according to the invention, namely the economic exploitation of the cheap electric ones during off-peak times Little energy for storing gaseous oxygen in liquid oxygen to do. Naturally, the machines belonging to the system are in off-peak times less busy. By applying the subject matter of the invention, however, they become but busy, not for generation. of oxygen but for the conversion of electrical energy into cold, which is stored in the pressure tanks will.

The object on which the invention is based is linked to known fact that with combined ventilation separation plants - d. H. those that, in addition to the possibility of producing gaseous oxygen, also use are equipped with a small portion for liquid oxygen production - excess accumulating, gaseous oxygen in a supply of supercooled liquid oxygen, which is stored in pressure storage tanks, can cool down and cause condensation. The method according to the invention is particularly geared towards using existing ones Equipment for the liquefaction of gaseous oxygen in low-load operation to a large extent to be exploited, with the fact that one gaseous during the introduction Oxygen counteracts the build-up of pressure in the pressure tanks, making things considerably easier in the operation of large oxygen systems as well as energy savings through both Equalization of consumption peaks during normal and full load times as well as through Maintenance of continued generation in off-peak times.

When the low load period is over, the liquid oxygen tanks become through pressure relief in practically any quantity instantaneously and controllably in gaseous form Oxygen free, which, if necessary, using heat exchangers Part of its coldness for ongoing oxygen production in an energy-saving way can deliver. After the pressure has been reduced completely, a normal portion remains back to oxygen liquid, which is filled into transport tanks in a known manner and can be put to conventional use.

In particular, the invention relates to a method of storage low-boiling gases, in particular oxygen, with that in an air separation plant accumulating liquid oxygen content is stored in a pressure tank and the compressed gaseous oxygen content in off-peak times as an excess amount in the The liquid phase of the pressure tank is introduced and removed from it as required.

Building on this, the invention is characterized in that during of the off-peak times a part of the sucked in and compressed in a turbo compressor The outlet air is branched off from the air to be separated and, after pre-cooling, in a Expansion turbine is expanded with further cooling, whereupon the obtained Amount of cold air in the circuit either through a in or around the liquid phase of the Cooling surface register attached to pressure tanks or in heat exchangers in the Countercurrent to the compressed, gaseous oxygen component flowing into the pressure tank out and in both cases then in further heat exchangers in countercurrent to the partial flow of the compressed output air is heated during its pre-cooling, to then get back to the inlet of the turbo compressor.

According to a further concept of the invention, the expansion turbine the expansion turbine upstream of the rectification column for air separation in the usual way used and between this expansion turbine and the rectification column the Cold air used to cool the pressure tank is branched off. The rectification column Exiting nitrogen can according to the invention - optionally additionally - likewise as a coolant for the cooling surface register or for charging the heat exchangers to cool the compressed, gaseous oxygen component flowing into the pressure tank to be used.

Finally, the cooling surface registers can be used during full load times or normal operation of the system with the help of an additional high-pressure cold generator be supplied with the amount of cold air required for cooling. In doing so, then this amount of cold air from the additional high-pressure cold generator during off-peak times Used to feed heat exchangers, which are used to cool the pressure tank serving compressed, gaseous oxygen component flowing in.

In the device according to the invention, several pressure tank units can be used connected in parallel and housed in a protective container filled with thermal insulation material be. The cooling surface register can then also preferably be outside the pressure tank units attached and connected in parallel. The current of the supplied for condensation Gaseous oxygen can be directed so that the liquid oxygen after Principle of a mammoth pump through the cooling surface register.

Another feature of the invention is that the pressure tanks are vertical can be arranged and then a lower feed for tangential introduction of the gaseous oxygen to be condensed in the sump of the liquid phase. In the center of the vertical pressure tanks are then advantageously plate-shaped Deflection plates arranged.

The method according to the invention and the associated device are as well as for the storage of oxygen also for the storage of others, particularly low-boiling gases, such as nitrogen or noble gases, are suitable.

Several embodiments of the devices for performing the invention Procedure are shown in the drawing. The individual modes of operation are explained in more detail with reference to FIGS. 1 to 9.

A simple embodiment example of a known method for the storage of low-boiling gases, on which the invention builds up will be explained with reference to FIG I to introduce.,: The liquid oxygen produced in the separating device 10 with an insulation 11 is supplied to the pressure tank 2 during normal operation via conduit 6 and kept ready there. In this way, during the low-load period, excess gaseous oxygen can be introduced into the liquid phase of the pressure tanks 2 for condensation via the line 7 using the oxygen compressor 3 instead of the discharge line 8 leading to the consumer when the valve 9 is open, with the valve 12 open via the pressure line 4 . For this purpose the oxygen coming from the compressor 3 pressure line 4 is introduced into the bottom of the pressure tank. 2 Internals in the pressure tanks and a system for fine distribution of the oxygen to be condensed, for example a gas spray pipe or pipe network 5, ensure the best possible mixing of the gas in the liquid. Depending on requirements, by reducing the pressure during full load times with the valve 14 open, gaseous oxygen can again be withdrawn from the pressure tank 2 via the upper discharge line 13 and supplied to the consumer via the discharge line 8.

According to the invention, the method can be improved by counteracting the pressure build-up in the pressure tanks during the period in which gaseous oxygen is introduced. This is done by utilizing usable cold during the low load period to cool the pressure tanks 2 , which is shown in the flow diagram of FIG. Since the air turbo compressor 15 connected upstream of the separating apparatus 10 can only be operated with partial load during the off-peak period for oxygen generation, it is possible to use valve 17 and line 18 to transfer the proportion of the air volume sucked in via line 16 to a pair of switchable heat exchangers 19 up to full load (Regenerators) to be supplied, to be cooled therein and to be fed via line 20 to an additional expansion turbine 21 , where it is expanded to produce cooling. This amount of cold air flows through line 22 through a cooling surface register 23 which is attached in or around the liquid phase in pressure tank 2. The condensation capacity of pressure tank 2 is increased by this type of dissipation of the condensation heat of the gaseous oxygen supplied Via line 24 and heat exchanger 19 and line 25 in the circuit back to turbo compressor 15. In this air circuit, for example, the following temperatures prevail: behind turbo compressor 15 about + 20 ° C corresponding to the temperature of the cooling water used, behind heat exchanger 19 and in front of the Expansion turbine 21 about -150 ° C, behind the expansion turbine 21 about -180 ° C, behind the cooling surface register 23 about -153 ° C and after passing the heat exchanger 19 about + 17 ° C.

If it initially seems correct to place the heat exchange surfaces in the pressure tanks 2 to increase the condensation capacity - this is intended to cool the liquid at any time - it should be pointed out that the precooling of the gaseous oxygen to be introduced into this pressure tank 2 is also advantageous can be what is shown in the flow diagram of FIG. Instead of the cooling surface register 23 in the pressure tanks 2, the gaseous oxygen to be liquefied is then cooled behind the oxygen compressor 3 and behind the valve 12 within the line 4 in a switchable pair of heat exchangers 26 (regenerators) by the cold air flow in these heat exchangers 26 becoming cold releases the gaseous oxygen.

The improvements described above can be simplified even further according to the invention in an even closer analogy to the devices present in an air separation plant. With the omission of additional heat exchangers (regenerator pairs) 19 and an additional expansion turbine 21 as in FIG. 2, the cooling air to be fed to the pressure tanks 2 is now taken off at points 27 and 28 according to FIG.

FIG. 4 shows the guidance of the air flow which, after the regenerators 30 which are usually present, is passed into the expansion turbine 29, which is also present. Behind these two existing devices, a partial air flow is now taken at 28 and fed to the cooling surface register 23 in or around the liquid phase of the pressure tanks 2 via the lines 31 and 22 . After it has given off part of its cold there, this air flow is fed back into the system via the line 24 upstream of the regenerators 30. Part of the air precooled in the regenerators 30 can also be branched off at 27 in front of the expansion turbine 29 and added to the cold air flow in line 22. In any case, the turbo compressor 15 belonging to the air separation system and the other cold-generating and cold-exchanging parts of the air separation system are operated at full power.

It should be pointed out that, in a modification of this method, the nitrogen leaving the head of the separating apparatus 10 can also be supplied in whole or in part to the cooling surface registers 23 in or around the liquid phase of the pressure tanks 2 via line 32 before entering the regenerators 30, which can also be seen from FIG. With this variation, too, the air turbo compressors belonging to the system as well as the cold generating and exchanging parts of the air separation system are operated at full power. The case for the excess oxygen generation amount of air is to pass after leaving the expansion turbine 29 without the air separation apparatus 10, fed to the regenerators 30 and adjusted so that the refrigeration balance of these regenerators is balanced.

It may also have a further improvement of the method are achieved according to the invention in that one according to Fig. 5 so using one of the additional refrigeration serving high-pressure section 33 can be switched, that means if no excess low pressure air to the cooling surface registers 23 supplied in normal operation, in the pressure tank 2 this cooling surface register 23 can be cooled by cold, relaxed high-pressure air with the valves 34 and 35 open via the supply lines 36 and 22 and the discharge lines 24 and 37. This allows the relatively warm and pressurized amount of liquid oxygen present in the pressure tanks 2 at the end of the low load period to cool down again during the long normal operating period, so that it can be withdrawn as normal liquid oxygen at the usual low temperatures. During low-load operation, however, as also shown in Fig. 5, after switching to another heat exchanger 38, this high-pressure air circuit with open valves 39 and 40 via the supply line 41 and a discharge line increase the condensation capacity of the pressure tanks 2 by increasing its coldness to the Gaseous oxygen within the line 4, which is then to be liquefied, releases. Since the relatively warm amount of liquid oxygen in the pressure tanks 2 can be cooled down during the normal load period a multiple of the time compared to the low load period, even a relatively small cooling capacity through the high pressure part 33 is extremely effective.

In order to keep the increase in the cost of the pressure tanks 2 for the liquid oxygen due to thicker wall thicknesses within limits, a further inventive concept is such that the necessary tank capacity is divided into several units 43 and housed within a single protective container 44 filled with thermal insulation material, which is shown in Figs.

To reduce the cost of the necessary through the lying under the previous representations in the pressure tank 2 cooling area register 23 Construction Fig. 6 is proposed, finally, according to attach the total area of the cooling surface of the register 23 outside of the tank units 43 and the flow of blown in for condensation via line 4 oxygen so as to steer that the liquid oxygen is guided like a mammoth pump through the cooling surface register 23, which is now outside. On the other hand, there is also the possibility here of all or part of the gaseous oxygen via fine distribution systems, e.g. B. gas spray tubes 5 to feed the liquid phases in the individual tank units 43 via line 4 .

In the event that the method is to be used in its initially described, simplified form - that is, without internals in the pressure tank 2 - it is proposed according to FIGS. 8 and 9 to set up the pressure tank units 43 vertically in order to achieve the longest possible flow path. Furthermore, a tangential introduction 45 of the gaseous oxygen to be condensed should then take place in order to achieve optimal mixing. As a result, the liquid content of the pressure tanks 2 is set in rotation, with non-condensed, gaseous oxygen tending towards the zone of lower pressure, ie the lowest circumferential speed, and thus towards the center. Internals in the form of plate-shaped baffles 46 improve the mixing.

Furthermore, it is proposed to mount the temperature sensor 2 to determine the given operating condition in each tank capacity for the liquefaction of gaseous oxygen in various zones of the pressure tank. Since the intimate mixing of the gas in the liquid and the constant movement of the bath during the introduction of gaseous oxygen will bring the tank contents closer to the state of equilibrium, the respective condensation capacity can then be determined from the measured variables pressure and temperature up to the prescribed, still permissible maximum pressure.

Finally, the special advantages and the technical progress of the method and the device according to the invention should also be shown with regard to the state of the art according to German patents 683 486 and 935 196: On weekends and holidays, the so-called off-peak times, electricity is cheap. According to the invention, the generating plant does not have to be shut down or throttled in spite of the low oxygen requirement; rather, the turbo compressor 15 is operated with an undiminished amount of electricity, whereby the cheap electricity price can be fully exploited. However, since only part of the air compressed by the turbo-compressor is required for the generation of oxygen during the off-peak period, it is possible to feed the other part via line 18, heat exchanger 19 and line 20 to an expansion turbine 21, where the air is relaxed in a cold-conducting manner and fed to the cooling surface registers 23 can be. The cheap energy in off-peak times is therefore mainly used to generate cold and as such is stored in a buffer of liquid oxygen. Despite the low oxygen consumption during off-peak periods, gaseous oxygen can therefore continue to be produced and absorbed and condensed in the storage tanks.

In contrast, according to the German patent specification 935 196, a more expensive one Trodden path. The system also runs at full machine capacity in off-peak times further, but it only produces liquid oxygen.

There is also the following difference between the subject matter of the invention and the known method: In order to compensate for fluctuating decreases, according to the invention the compressor 3 provided for gas delivery (via line 8) is used and more compressed gaseous oxygen introduced into the storage tanks 2 under pressure build-up. In contrast can the regenerator or cold accumulator 27 (German patent specification 935196) not utilize economically in the intended manner. With today's systems it concerns fluctuations in off-peak times, mainly on the weekends, and it is not possible to get through the cold of a few days of oxygen deprivation to be held recuperatively in memories. Such memories are in their capacity designed so that they can store the cold for a few minutes (regenerators in air separation plants switch every 3 to 10 minutes). With the continuously operable cooling registers 23 in the pressure tanks 2 according to the invention is a better one Effect can be achieved than with the heat exchanger 27, which can be operated discontinuously the well-known system, which is only a few minutes of cold in an economical design able to save. Allow pressure tanks with cooling registers of economical size cold storage over many hours.

The invention also discloses a solution to both normal as to slow down the pressure build-up in the storage tanks and the storage liquid during off-peak periods to cool down again and again. It is particularly important to note the use of an additional High pressure refrigeration unit 33 reminds. The invention also differs here from German patent specification 935 196.

Claims (10)

PATENT CLAIMS: 1. Process for storing low-boiling gases, in particular oxygen, with the liquid occurring in an air separation plant Oxygen content stored in a pressure tank and the compressed gaseous oxygen content in off-peak times as an excess portion in the liquid phase of the pressure tank is initiated and removed from this as required, characterized in that During the off-peak times, some of the sucked in and in a turbo compressor compressed output air is branched off from the air to be separated and after pre-cooling is expanded in an expansion turbine with further cooling, whereupon the obtained Cold air in the circuit either through one in or around the liquid phase of the pressure tank attached cooling surface register conducted or in heat exchangers in countercurrent to the compressed, gaseous oxygen content flowing into the pressure tank out and in both cases then in further heat exchangers in countercurrent to the partial flow of the compressed output air is heated during its pre-cooling, to then get back to the inlet of the turbo compressor. 2. Procedure according to Claim 1, characterized in that the rectification column is used as the expansion turbine used for air separation in the usual way upstream expansion turbine and between this expansion turbine and the rectification column for cooling the Cold air serving pressure tanks is branched off. 3. The method according to claim 2, characterized characterized in that the nitrogen leaving the rectification column - optionally additionally - as a coolant for the cooling surface register or for charging the Heat exchanger for cooling the compressed, gaseous flowing into the pressure tank Oxygen content is used. 4. The method according to claim 1, characterized in that that the cooling surface register during full load times or normal operation of the System with the help of an additional high-pressure cold generator with the for cooling necessary quantities of cold air are supplied. 5. The method according to claim 4, characterized in that the cold air quantities of the additional high-pressure cold generator are used during the off-peak times to fill heat exchangers which are used to cool the compressed, gaseous oxygen component flowing into the pressure tank. 6. Device for performing the method according to a of the preceding claims, characterized in that several pressure tank units (43) connected in parallel and in a protective container filled with thermal insulation material (44) are housed. 7. Apparatus according to claim 6, characterized in that that the cooling surface register (23) is attached outside of the pressure tank units (43) and these are connected in parallel. B. Method according to claim 7, characterized in that that the flow of the gaseous oxygen supplied for condensation is so directed that the liquid oxygen flows through the cooling surface register according to the principle of a mammoth pump to be led. 9. Device for performing the method according to one of the preceding claims, characterized in that the pressure tanks (2) are arranged vertically and have a lower feed to the tangential introduction (45) of the gaseous oxygen to be condensed into the sump of the liquid phase. 10. Device according to claim 9, characterized in that in the center of the vertical pressure tanks (2) plate-shaped baffles (46) are arranged. Considered publications: German patent specifications No. 683 486, 935196.