AN APPARATUS FOR COLLECTING A VOLATILE CONDENSATE AND FOR SEPARATING NON-CONDENSIBLE GAS THEREFROM

Abstract: In systems or units for collecting volatile liquids, e.g. refrigerants from scrapped refrigeration systems, the liquid may be successively filled into a closed collector tank (12), inasfar as the vapour of the liquid as collected in the upper space of the tank will just be condensated down into the liquid as this rises in the tank. However, there will be separated also an amount of non-condensible gas, e.g. atmospheric air, that will cause a steadily increasing pressure in the tank, so that it is necessary to regularly effect a venting of the tank, that is a gas blow-off, by suitably controlling an upper blow-off valve (20) on the tank. All according to the temperature such a blow-off, however, may be connected with a more or less pronounced and undesirable blow-off of the condensible gas, and according to the invention this latter blow-off is minimized by the blow-off valve (20) being controlled from a differential pressostat (P), which is influenced partly by the actual pressure in the collector tank and partly by the vapour pressure of from a confined volume (26) of the liquid in its pure state. Thereby the pressure contribution from the condensible gas in the tank, no matter the temperature, is compensated for, and thereby a more favorable controlling of the blow-off for minimizing the undesired part of the blow-off product will be achieved.

Description: An apparatus for collecting a volatile condensate and for separating non-condensible gas therefrom. The present invention relates to an apparatus for condensing a volatile liquid, e.g. a refrigerant, and collecting the condensate in a collector tank, compris¬ ing a condenser unit having its outlet connected to the collector tank, and a gas exhaust valve, which is mounted at the top of the collector tank and is control¬ lable, responding to the pressure in the collector tank, for intermittently discharging of non-condensible gas as separated from the condensate. In systems for purifying and reclaiming of volatile liquids, in particular by emptying or renewal of old . refrigeration systems, it is relevant to collect the volatile liquid, e.g. R-12, R-22 or R-134A, upon the liquid being brought from its gaseous phase into its liquid phase in a condenser, such that the collected liquid may be reused. In principle the condensate may be filled into the collector tank without the latter having to be vented, because the vapour or gas of the conden¬ sate in the upper tank space will maintain its gas pres¬ sure also when this space is narrowed by the progressive charging of liquid condensate into the tank; as the condensate rises in the tank the gas will diffuse or condense down into the liquid, such that the gas pres¬ sure above the liquid will remain constant when the tem¬ perature is constant. Normally, however, there will occur a certain separation of non-condensible gas, main¬ ly of atmospheric air, and as the tank is filled this gas will give rise to an increased pressure in the tank, concurrently with a further pressure build-up due to the separation of non-condensible gas from the currently introduced condensate. This increased pressure gives rise to some prob- lems, e.g. an increase of the condensation pressure, whereby more energy is needed for the condensation of the volatile liquid, and if the collector tank is to be utilized just reasonably effectively, i.e. to be widely filled for collecting reasonably large portions of the condensate, ready for delivery, then it is in practice imperative to carry out, from time to time, a blowing off of the non-condensible gas from the tank, and it is well known that this can be done based on the use of a pressure switch controlled blow-off valve at the top of the tank. Hereby a blowing off can be initiated auto¬ matically, when the pressure in the tank has risen to a predetermined maximum, and it can be interrupted when the pressure has decreased suitably, optionally con¬ trolled just by the hysteresis of the pressure switch. However, the blowing off itself gives rise to prob¬ lems, viz. in that along with the letting out of the non-condensible gases, in the following named air, a certain amount of condensible gas will inevitably be expelled, and as well known it is already from an en¬ vironmental point of view very unlucky if this could involve a release of considerable amounts of refrigerant gas, mainly originating from the refrigerants R-12 and R-22, which have a decomposing effect on the ozone layer around the planet. Such a co-outflow of the condensible gas is particularly noticeable when the temperature is relatively high, because the concentration or the pres¬ sure contribution of the condensible gas will then be relatively high in the collector tank. This circumstance is made even worse by the fact that during the opening time of the blow-off valve the pressure in the collector tank will be reduced such that the condensate will eva¬ porate further, whereby towards the end of the blow-off period there will occur a further increased content of the condensible gas in the blow-off product. A possible solution to this problem resides in the mounting of a cooler element in connection with a blow-out pipe from the collector tank, such that the exhausted gas will generally be cooled to the condensa¬ tion temperature of the condensible gas, whereby the critical fraction of the gas is condensed and falls back into the tank without getting out to the atmosphere. However, experiments have shown that in practice this solution is unrealistically expensive, if it shall be reasonably effective, since during the relatively brief blow-out periods a particularly intensive heat exchange with the blow-out gases should take place. It should be mentioned that in another connection an interesting solution to a similar kind of problem has been suggested, viz. according to DE-B2-25,15,605, which discloses a refrigeration system having means for sepa¬ ration of such air, which penetrates into the refrig¬ erant during the operation, and which is currently sepa¬ rated in the condenser unit of the system. This unit is provided with a built-in, integrated control device for the blow-off valve, consisting of a bellow mounted in the discharge duct from the condenser, the condensate therefrom flowing further downwardly into an accumula¬ tion container. That container has a lower outlet for the condensate and and upper inlet for the gas to be condensed, and in the container there is mounted a float which will serve to close the outlet when the liquid level is low, while for a high liquid level it will close the downlet of condensate from the upper condenser chamber and therewith also close the upflow of hot gas to the condenser, this providing for security in case of operational interruptions. The said bellow is partly filled with the refrigerant as used in the entire system, whereby the bellow, through a rod, seeks to press a valve head into closing engagement with an upper blow-off opening for gas, while the bellow, rigidly supported at its lower side, is inversely influenced to be compressed by the gas pressure existing in the con¬ denser chamber. Thereby the blow-off valve will be opened when in this chamber there is built up a notice¬ able overpressure originating from the partial pressure of the non-condensible gas, while the bellow will also serve the purpose of compensating out the partial pres¬ sure of the condensible gas, viz. by the inner pressure in the bellow, whereby the said unlucky temperature dependence will be eliminated. The invention is based on the consideration that at least the basic principle of this known proposal can be used with advantage in the connection relevant to the invention, although in that connection there are circum¬ stances speaking against such use. In collector tanks in systems for purifying volatile liquids there will nat¬ urally occur a much heavier separation of impurities, including air, than in the current operation of a re¬ frigeration system, and a result could be that the blow-off valve would adjust itself to a kind of equili¬ brium, in which the release currently corresponds to the actual separation of air from the hot gas delivered to the condenser. Such a more or less permanent opening of the blow-off valve would not be advantageous, because the associated, undesired release of condensible gas would then be rather pronounced. It would be better if the blow-off can be arranged during limited intervals of time, when the concentration of air in the gas filled partial volume of the tank is higher than an average value, as the total of co-blown-out condensible gas would then be relatively smaller. Besides, the discussed known proposal will be problematic to transfer to a system of the type her considered, because the control system should be mounted inside the space from which the blow-out takes place, i.e. with high requirements as to a preadjustment according to the detailed operational conditions of the single system; by a series production of the systems or units in question the detailed opera¬ tional conditions of the single units cannot possibly be known, and this applies to liquid cleaning units still pore than to refrigeration systems, since the cleaning units should be able to handle both more and less pol¬ luted liquids, while for refrigeration systems there will be certain standards for maximum pollution of the refrigerant. According to the invention use is made of a col¬ lector tank as a separate unit, but of course flow con¬ nected with the condenser unit, such that the condensate is introduced into the collector tank e.g. at the bottom thereof or preferably at a pipe mouth located in a rela¬ tively high level in the tank. For controlling the blow-off valve a differential pressostat is used, which is connected partly directly with the interior of the tank and partly with a limited amount of the actual liquid enclosed in a sensor pocket mounted in heat con¬ ducting connection with the tank or the contents there¬ of. With this arrangement the differential pressostat will receive on both connector stubs the vapour pressure of the condensate liquid, and these applied pressures will balance each other out irrespectively of the level of the pressure - and therewith irrespectively of the temperature of the condensed liquid and its vapour. On one of the connector stubs there will additionally occur the pressure contribution from the separated air in the tank, and the pressostat can be adjusted so as to open the valve by any desired value of this partial pressure. Moreover, the pressostat will be adjustable with respect to its hysteresis, such that the valve can be abruptly closed after a predetermined drop of the said partial pressure in the tank, without being reopened until the partial pressure has again increased to the opening value. The blow-off function will in this manner be con- trollable in a well defined and optimized way for each single system or apparatus unit, and the units may be produced as standard units without beforehand being adjusted to special operational conditions. Moreover, the adjustment can be changed in a simple manner at any time, e.g. for optimizing the unit to changed opera¬ tional conditions such as the purification or more or less polluted liquids, respectively, which for a full optimizing may require a resetting of the pressure range or hysteresis of the pressostat. In the following the invention is explained in more detail with reference to the drawing, in which Fig. 1 is a schematic view for illustration of the invention, while Fig. 2 is a more detailed view of a preferred embo¬ diment of an apparatus according to the invention. In Fig 1 is indicated a purification system 2 for refrigerant supplied from a source 4, e.g. the refrig¬ eration system of a car to be scrapped. In the system 2 the refrigerant will be cleaned for different, sub¬ stances, mainly water, but not for non-condensible gases, and the refrigerant, in gaseous phase, is de¬ livered to a condenser 6, from which the condensate is conveyed further through a conduit 8 to a connector stub 10 at the bottom of a collector tank 12. The bottom stub. 10 is also, through a valve 16, connected with a dis¬ charge conduit 16. At its top the tank 12 has a blow-out pipe 18 pro¬ vided with a valve 20, viz. a solenoid valve controlled by a pressostat P. The latter is a differential presso¬ stat, which, through a switch K, controls the opening and closing of the valve 20 in dependence of a pressure applied to a connector stub Rl being higher or lower than a pressure applied to another connector stub R2. Through a conduit 22 the connector stub Rl is connected directly with the space inside the tank, while the con- nector stub R2, through a conduit 24, is connected with a capsule 26 inside the tank The capsule 26 is filled with a liquid that is widely equivalent or identical with the condensate liquid in its pure condition, e.g. one of the refrig¬ erants R-12, R-22 or R-134A, and it will thus be the vapour pressure from this clean liquid that will be transferred to the input stub R2 of the pressostat. To the stub Rl will be transferred the total pressure in the tank 12, i.e. the vapour or gas pressure both from the condensate in the tank at the same temperature and from the further pressure source constituted by the non-condensible gas and air as separated from the.con¬ densate, mainly atmospheric air. This air is compressed all according to the raising of the liquid level in the tank, so it will provide for a relatively increasing pressure on the input stub Rl. Inside the pressostat P the input stub Rl is con¬ nected to a bellow Bl, which, through a rod 28, exerts a pressure on another bellow B2 connected to the stub R2. The switch K is controlled bγ_ the rod 28, such that the switch will be closed and cause the blow-off valve 20 to open, when the overpressure from the separated air in the tank 12 reaches a certain, presetable value. The pressostat exhibits a certain hysteresis, such that the valve 20 will not be closed until after a noticeable pressure drop in the tank 12 and thereafter will not be reopened until after a following noticeable increase of the pressure in the tank. Therefore, with a suitable adjustment of the pressostat it is possible to achieve quite ideal conditions for the discussed blow-off of the air without any compromising blow-off of condensible gas. A certain associated blow-off of the latter will be inevitable, but with a correctly adjusted system the amounts will be so small that they will be negligible even according to strict criteria. In the embodiment shown in Fig. 2 it is illustrated by way of example that the switch K is a micro switch 30, which is mounted on a carrier plate 32 and has an actuation knob 34 that is depressible for operating the switch by means of a pivot arm 36 hinged at 38 and hav¬ ing a free end portion 40, which is depressible by a side cam 42 on the connector rod 28 between the bellows Bl and B2. By an adjustment of the carrier plate 32 upwardly or downwardly it will then be possible to ad¬ just the level of the differential pressure to which the pressostat responds, and by adjusting the switch 30 horizontally on the carrier plate 32 an adjustment of the hysteresis function of the pressostat, given by. the larger or smaller distance between the switch cam 34 and the pivot axis of the switch arm 36, will be effected, Thus, the pressostat will be adjustable to different optimized manners of reaction. The capsule 26, which in Fig. 1 is shown located inside the tank, is in Fig. 2 shown located in a bore in a tank head block 42 of alu¬ minium or a correspondingly well heat conducting mate¬ rial, whereby this particular temperature/pressure sen¬ sor will be in close contact, in a constructively simple manner, with the operatively significant area of the tank, viz. the upper blow-off area, the temperature of which will be decisive for the blow-off pressure. Alter¬ natively, as shown by dotted lines, the sensor capsule or pocket 26 may be constituted by a capillary tube 48 wound about the upper end of the tank 12 in heat con¬ ducting connection therewith. The capillary tube con¬ nections to the two input stubs of the pressostat should have approximately equal lengths. The supply pipe for letting the condensate into the tank 12, according to Fig. 2, man have its mouthing 50 located at a relatively high level in the tank, whereby the supplied liquid during its introduction and follow¬ ing downfall gets good possibilities for separation of air and other non-condensible gases to be blown off later on. Suitably the tank is filled up to only some 80% of its volume, e.g. as represented by the filling level shown in Fig. 2, with the supply mouthing 50 located slightly thereabove. By a still higher filling level there may tend to be an increased concentration af con¬ densible gas in the blow-off product. It should be mentioned that the aim of mounting, as in Fig. 2, the sensor pocket 26' in indirect contact with with the tank chamber is to achieve that the sensor will not react to sudden, brief temperature variations in the supplied condensate, but rather react to the present average temperature. With the use o .the .capil¬ lary tube 48 wound about the tank a heat insulation should be arranged at the outside. As mentioned, the sensor pocket should contain the same liquid as the condensate in its pure state, this providing for the highest degree of optimizing of the blow-off function. This, however, will not exclude that a slightly deviating liquid be used, if according to experience it will provide for a result with a desired, sufficient degree of optimizing. Besides, with the em¬ bodiment according to Fig. 2 it will be relatively easy to readjust the device to the handling of another liquid, because the sensor pocket and its connection to the pressostat will be easy to replace by a correspond¬ ing set containing the new liquid. The invention, of course, will also comprise a system or unit, in which the blow-off valve 20 is con¬ trolled manually, when the pressostat is alternatively used for a suitable signalling, e.g. by the switch K operating to control the operation of a signal lamp L.

Claims: C L A I M S : 1. An apparatus for condensing volatile liquids and collecting the condensate in a collector tank, including a condenser unit in delivery connection with the col¬ lector tank and a gas blow-off valve, which is mounted at the top of the collector tank and is controllable, depending of the pressure in the collector tank, to effect an intermittent blow-off of non-condensible gas separated from the condensate, characterized by the combination of the condenser unit being mounted se¬ parated from the collector tank, preferably with a de¬ livery conduit for condensate debaμching into the lower end of the collector tank, and of the gas blow-off valve being controlled or controllable by means for measuring or indicating the differential pressure between the actual vapour pressure of the condensed liquid and the total gas pressure in the collector tank, said valve being adapted to be opened or openable when the total pressure exceeds the condensate vapour pressure with a predetermined value, and the required means for measur¬ ing the condensate vapour pressure comprising a measur¬ ing container holding a confined partial volume of the relevant condensate or a liquid widely corresponding thereto, this container being mounted in heat conducting connection with the interior of the collector tank. 2. An apparatus according to claim 1, characterized in that the measuring container is constituted by a capsule or a capillary tube, which is mounted in heat conducting connection with the collector tank or the contents thereof and is pipe connected with an external differential pressure gauge, which is additionally tube connected with the tank chamber itself, the differential pressure gauge constituting a control unit for indicat¬ ing the presence of non-condensible gas and/or for on/- off controlling the blow-off valve between respective upper and lower limits for the differential pressure. 3. An apparatus according to claim 2, characterized in that the measuring container is mounted at the upper end of the collector tank, optionally at the outside thereof or embedded in a head block of a heat conducting material. 4. An apparatus according to claim 2, characterized in that the external differential pressure gauge is adjustable with respect to the said upper and lower limits of the differential pressure.

Inventors: GRAMKOW ASGER, GRAMKOW, ASGER
Applicants: GRAMKOW A S A, A'GRAMKOW A/S
Application year: 1991
Main classification: F25B43
IPC codes: B01D5, F25B43, F25B45