EP1528342B1 - Process for drying material and apparatus for carrying out the process - Google Patents

Description

Field of the invention

The invention is based on a process for drying of good, in particular of solid insulation of an electrical device, according to the preamble of claim 1. The invention also relates to an apparatus for performing the method.

• Beladen des Autoklaven mit Gut,
• Evakuieren des beladenen Autoklaven,
• Aufheizen des beladenen Autoklaven mit kondensierendem Solventdampf und gegebenenfalls zusätzlich mit der Autoklavheizung, um den überwiegenden Teil des Wasser sowie des gegebenenfalls vorhandenen Isolieröls und der Verunreinigungen aus dem Gut zu entfernen,
• Durchführen von Zwischendrucksenkungen im Autoklaven, um während des Aufheizens ausgewaschenes Isolieröl abzudestillieren und um in besonders schneller und schonender Weise die vorgenannten Substanzen zu entfernen,
• Anlegen von Feinvakuum bei eingeschalteter Autoklavheizung an den Autoklaven, um noch vorhanden Restsubstanzen aus den Feststoffisolationen zu entfernen, und
• Belüften und Entladen des Autoklaven.

In the method, the heat of condensation of a solvent vapor generated in an evaporator is used for rapid and gentle heating of the material. The drying material generally comprises the solid insulation of an electrical device, such as a power transformer. The device or at least its active part containing the solid-state isolations are arranged in a vacuum container, for example an autoclave, held under reduced pressure. When heating from the solid insulating water leaking water is supplied in the form of a solvent and steam containing mixed steam together with unavoidable leakage of a condensation and separation device in which the condensed water separated from the solvent and the leakage air is sucked with a vacuum pump. Optionally present insulating oil and / or impurities are removed by distillation from the solvent. In carrying out this so-called vapor phase method, the following process steps occur:

• Loading the autoclave with good,
• Evacuating the loaded autoclave,
• Heating the loaded autoclave with condensing solvent vapor and possibly also with the autoclave heater, in order to remove most of the water and the optionally existing insulating oil and impurities from the estate,
• Carrying out intermediate pressure reductions in the autoclave in order to distil off washed-out insulating oil during the heating and to remove the abovementioned substances in a particularly rapid and gentle manner,
• Apply fine vacuum with the autoclave heating switched on to the autoclave to remove residual substances from the solid insulation, and
• Aerating and unloading the autoclave.

State of the art

The method of the type mentioned is DE 30 14 831 A removable. A described in this prior art, working by the Vapor phase method drying device for isolierölgetränkte insulations has a the insulators to be dried receiving evacuated autoclave in which a cascade evaporator is arranged. This cascade evaporator is oriented substantially vertically and includes a limited by a plate and a partition flow channel. On the plate heating coils and baffles are arranged. The cascade evaporator is fed by means of a pump solvent, which was heated in a preheater located outside the autoclave. The preheated solvent trickles with the cooperation of the baffles along the plate from top to bottom. Here, the solvent evaporates on the heating coils. The forming solvent vapor flows vertically upward due to the chimney effect in the flow channel and is conducted via a steam inlet into the usable space of the autoclave containing the insulations.

Another drying process was applied in the USA by the companies "General Electric" and "Westinghouse" from about 1960. The solvent was heated in an off-autoclave solvent heater and introduced into the autoclave under vacuum, thereby evaporating as described in the book "A Guide to Transformer Maintenance" by SDMeyers, JJ Kelly, PHParish, p. 496 (Transformer Maintenance Institute, Division SDMyers, Inc. Akron Ohio, 1981). In this case, the solvent is heated substantially above the drying temperature, since the solvent evaporation heat is removed and thereby cools. An accurate temperature control of the solvent vapor is difficult, since various factors such as pressure and temperature in the autoclave affect the evaporation rate and thus also the solvent temperature.

The aforementioned dry process is also described in US 2002/0184784 A1. In this prior art heating fluid is left in the liquid phase leaving outside a dry matter containing vacuum vessel heated. Subsequently, the heated heating fluid is evaporated on or in a vacuum vessel.

The company publication P.K.Gmeiner "Modern vapor drying processes and plants", February 1992, Micafil Vakuumtechnik AG, Zurich MTV / E 0293000/22 described by the vapor phase method working Solventdampftrocknungsanlagen with separate, located outside or inside an autoclave solvent evaporators. All the devices used to carry out the described method, require an autoclave heater and additionally regulate an evaporator with a complex temperature control for controlling the solvent vapor with high accuracy.

The drying of transformers in their own housing instead of in a vacuum-tight container designed as an autoclave has been applied since about 1975. The solvent is evaporated in a lying outside the transformer solvent evaporator and placed over large and long flexible lines in the evacuated transformer housing, as described in the publication G.Oesch, H. Schatzl, "The solvent vapor drying of power transformers" August 1976, Micafil AG, 8048 Zurich / Switzerland (order number MNV 46/1 d).

Presentation of the invention

The present invention is based on the object of reducing the energy consumption and the throughput time of the method of the type mentioned above and at the same time to provide devices which are particularly suitable for carrying out this method.

In the method according to the invention, the solvent introduced into the vacuum container and heated is injected into a flow channel designed in the manner of a venturi nozzle. In this case, a predominantly solvent vapor containing and guided by a bottleneck of the flow channel jet is formed, which mixes intensively due to suction with an existing already in the vacuum tank content of solvent vapor. Depending on the proportion and / or amount of mixed steam mixed in, as well as on the quantity of the injected hot solvent, the temperature of the solvent vapor passing out of the flow channel can be controlled very precisely. At the same time, optimal circulation and turbulence of the solvent vapor in the vacuum container are ensured by the flow excited by the jet. As a result, the amount of energy required for heating the drying material and the heating time are greatly reduced. The reduction of the heating time is mainly due to the fact that a large circulating amount of solvent vapor and thus a high solvent vapor velocity is maintained even at the end of the heating phase in the vacuum container by strong during the entire heating phase virtually constant injection of heated solvent in the flow channel. Despite the low energy consumption and the short throughput time, the process does not require any elaborate additional components in addition to the components required in conventional processes.

A particularly short cycle time is achieved when the heated solvent is injected into a solvent vapor stream passed through the venturi. As a result of the action of the injected solvent, the velocity and turbulence of the solvent vapor stream passing in the venturi are substantially increased. This results in a high speed and good turbulence of the circulating in the vacuum tank solvent vapor and, accordingly, the drying time is greatly reduced. The increased solvent vapor velocity is also maintained towards the end of the heating phase due to the effect of jetting, which ensures a shorter heating time in the upper temperature range and an even smaller temperature difference across the drying object, thereby significantly improving the quality of the drying.

Advantageously, the aforesaid solvent vapor stream guided in the venturi nozzle is produced in an evaporator arranged in the vacuum container, since then by the Jetwirkung of the injected solvent of the solvent vapor generated by the evaporator is rapidly sucked away from the evaporator, which leads to smaller pressure drop in this evaporator and thus to increased efficiency.

The solvent vapor stream can also be generated in an evaporator arranged outside the vacuum container and guided through the wall into the interior of the vacuum container. As a result of the Jetwirkung then the solvent vapor is better sucked from a guided into the vacuum tank solvent vapor line, which leads to smaller pressure drop between the external evaporator and vacuum tank and thus also to increased efficiency.

Advantageously, the heated solvent is injected into the flow channel at the constriction of the Venturi nozzle. At the bottleneck, the solvent injected into the flow channel has a particularly high velocity. This high speed causes a large negative pressure and thus a strong jet effect, i. a particularly strong suction of a mixed vapor stream of solvent and water vapor formed in the vacuum container during the heating of the material to be dried in the injected solvent.

By changing the inflow and / or outflow cross section of the flow channel, the mixing ratio of injected hot solvent to the mixed vapor already flowing in the vacuum container can also be changed. It can thus be controlled with great speed and good accuracy, the temperature of the emerging from the flow channel Solventdampfstroms.

The method according to the invention is characterized by a particularly high level of efficiency when cold solvent is injected into the mixed steam stream carried in the interior of the vacuum vessel. By injecting cold solvent, for example into a condensation chamber arranged in the vacuum container, part of the solvent vapor present in the mixed steam is sucked in by jet action and condensed. As a result, the proportion of water vapor in the condensation chamber increases and, consequently, less solvent vapor must be present in a condenser outside the vacuum container than condensate are deposited, whereby the energy consumption of the process is further reduced. If the cold solvent is injected into the mixed steam flow in the direction of flow, the mixed steam is strongly sucked in because of the blasting effect and, as a result of intensive mixing, a high degree of heat recuperation is achieved by heating the injected cold solvent.

A further reduction in the energy requirement of the method according to the invention is achieved in that the mixed steam flow is conducted out of the vacuum tank and condensed outside the tank into two or more stages, and heating air is heated with the heat of condensation emitted in a first of the stages when condensing mixed steam is condensed.

In a device which is suitable for carrying out the method according to the invention in a simple and economical manner, which in addition to the vacuum container also has a solvent steam generator and a device for condensing the mixed steam flow, the solvent steam generator contains a flow channel arranged in the interior of the vacuum vessel and designed in the manner of a venturi nozzle and a flow channel the flow channel guided device for injecting heated solvent in the flow channel. By a particularly good mode of action, this device is characterized when the injection device opens at the bottleneck of the venturi into the flow channel. Particularly expedient embodiments of the injection device include a solvent distribution channel which opens into the flow channel with injection openings and / or at least one injection nozzle held in the interior of the flow channel.

Heating energy can be saved and thus the efficiency of the method can be further improved if the heating device provided for heating the vacuum container is designed as a flow heater for the solvent.

A simple control of the temperature and mixing ratio of the solvent vapor emerging from the flow channel can be achieved in that a directional plate delimiting the flow channel is designed to be adjustable while changing the inflow and / or outflow cross section of the flow channel.

A large amount of heating energy is saved by arranging in the vacuum container a condensation chamber of the condensation device which receives at least one injection nozzle for cold solvent and through which the mixed gas flows. Advantageously, this condensation chamber is designed as a flow channel for the mixed gas and has on the inflow side acting as an inflow channel of a venturi sheet and / or a drain plate and / or downstream a baffle.

The required heating energy is additionally reduced by the fact that the condensation device has an air-cooled condenser arranged outside the vacuum container for generating heating air.

In a further preferred embodiment of the drying device according to the invention, the vacuum container is designed as a housing of a transformer and arranged in a preferably heatable with air Wärmeisolierhaus.

Description of the drawing

Fig.1

eine Trocknungsvorrichtung nach der Erfindung, enthaltend einen geschnitten dargestellten, Feststoffisolationen eines Transformators als Trocknungsgut aufnehmenden Vakuumbehälter, einen Solventdampferzeuger zum Aufheizen, Zuführen und Verteilen von Solvent und zum Erzeugen von Solventdampf und einen Vorrichtung zum Kondensieren von Solventdampf,

Fig.2

eine erste Ausführungsform des in der Trocknungsvorrichtung nach Fig.1 enthaltenen Solventdampferzeugers,

Fig.3

eine zweite Ausführungsform des in der Trocknungsvorrichtung nach Fig.1 enthaltenen Solventdampferzeugers,

Fig.4

eine erste Ausführungsform der in der Trocknungsvorrichtung nach Fig.1 enthaltenen Kondensationsvorrichtung,

Fig.5

eine zweite Ausführungsform der in der Trocknungsvorrichtung nach Fig.1 enthaltenen Kondensationsvorrichtung,

Fig.6

eine abgewandelte Ausführungsform der Trocknungsvorrichtung nach Fig.1, bei der der Vakuumbehälter vom Gehäuse eines Transformators gebildet ist,

Fig.7

eine Ausführungsform des in der Trocknungsvorrichtung nach Fig.6 enthaltenen Solventdampferzeugers,

Fig.8

eine erste Ausführungsform der in der Trocknungsvorrichtung nach Fig.6 enthaltenen Kondensationsvorrichtung,

Fig.9

eine zweite Ausführungsform der in der Trocknungsvorrichtung nach Fig.6 enthaltenen Kondensationsvorrichtung,

Fig.10

eine abgewandelte Ausführungsform der Trocknungsvorrichtung nach Fig.1, bei der im Vakuumbehälter zusätzlich ein weiterer Solventverdampfer angeordnet ist, und

Fig.11

eine abgewandelte Ausführungsform der Trocknungsvorrichtung nach Fig.1, bei der dem Vakuumbehälter Solventverdampf zuführbar ist, der ausserhalb des Vakuumbehälters erzeugt werden kann.

Preferred embodiments of the invention will be described with reference to the accompanying drawings. Hereby shows:

Fig.1

a drying device according to the invention, comprising a cut-off solid insulation of a transformer as a vacuum-receiving vacuum vessel, a solvent steam generator for heating, supplying and distributing solvent and for generating solvent vapor and a device for condensing solvent vapor,

Fig.2

a first embodiment of the solvent steam generator contained in the drying apparatus according to Figure 1,

Figure 3

a second embodiment of the solvent steam generator contained in the drying apparatus according to Figure 1,

Figure 4

a first embodiment of the condensation device contained in the drying apparatus according to Figure 1,

Figure 5

a second embodiment of the condensation device contained in the drying apparatus according to Figure 1,

Figure 6

a modified embodiment of the drying device according to Figure 1, wherein the vacuum container is formed by the housing of a transformer,

Figure 7

an embodiment of the solvent steam generator contained in the drying device according to Figure 6,

Figure 8

a first embodiment of the condensation device contained in the drying device according to Figure 6,

Figure 9

a second embodiment of the condensation device contained in the drying device according to Figure 6,

Figure 10

a modified embodiment of the drying apparatus according to Figure 1, wherein in the vacuum container in addition a further solvent evaporator is arranged, and

Figure 11

a modified embodiment of the drying apparatus according to Figure 1, in which the vacuum vessel solvent evaporation can be supplied, which can be generated outside the vacuum vessel.

Ways to carry out the invention

In all figures, like reference numerals designate like-acting parts. The drying devices shown in the figures are used for drying of goods, in particular the solid insulation of one or more electrical devices and the removal of possibly existing in the insulation insulating oil. The 1 contains a vacuum-tight container 1 which is loaded with an electrical device containing solid insulation, for example a transformer, or, as shown, only with its active part 1.1 containing the solid-state insulation. The vacuum container 1 can be heated by means of heating pipes 2. The heating energy is transmitted in a heat generator 3 to a flowing in the tubes 2 heat transfer medium for heating the vacuum container 1. The heating tubes 2 are surrounded by a double jacket and together with the jacket form a solvent heater 4 of a solvent steam generator. In the solvent heater, cold solvent is heated. The solvent is generally a light oil having a significantly higher boiling point than water and a substantially lower boiling point than an insulating oil optionally present in the solid insulation. The heated solvent is fed via a not shown in Figure 1 Solventverbindungsleitung in a lying within the vacuum container 1, optionally tubular, Solventverteilkanal 5 of the solvent steam generator. The solvent distribution channel 5 can be advantageously designed as an exposed tube with injection openings and or injectors. As a result, a cost-effective device is achieved. The solvent distribution channel 5 has injection openings or injection nozzles for the solvent. In the region of the injection openings, the narrowest cross section of a flow channel 5.2 designed in the manner of a Venturi nozzle is formed, which is formed by a suitably curved straightening plate 6, an outer wall of the solvent distribution channel 5 and the wall of the vacuum container 1. The straightening plate 6 can be changed by turning and / or moving in its position. As a result, the inflow cross section located upstream of the nozzle throat of the Venturi nozzle and the outflow cross section of the flow channel 5.2 located downstream of the nozzle throat can be increased or reduced. The vacuum container 1 has at the bottom in its bottom an outlet opening for condensed solvent, which opens into a drain container 7, as well as any insulating oil which may have been washed out of the solid insulation by the solvent. In the drain tank 7 a executed as a switch level indicator 7.1 is arranged. The drain tank 7 is connected via shut-off valve 20.1 with a feed pump 8. The outlet of the feed pump 8 is connected via shut-off valve 20.3 with the Solventerhitzer 4 or alternatively via shut-off valve 20.6 with a Solventvorratstank 9 or via shut-off valve 20.7 with an oil tank 19 for receiving the optionally existing insulating oil, which was removed during drying of the material to be dried 1.1 by the solvent from the solid insulation and was subsequently separated by distillation from the solvent.

Opposite the flow channel 5.2, a condensation device is arranged in the vacuum container 1 with a condensation chamber 10 for heat recuperation, a baffle 10.1, baffles 10.2 and injectors 11. The condensation chamber 10 is open down to the interior of the vacuum container 1 and has at its upper end a through Wall of the container 1 guided outlet opening 10.3, which leads via a mixing steam line 15 and a Dampfabsperrventil 20 to a mixed steam condenser 16. The mixed steam condenser 16 has two outlets, one of which is connected to a vacuum system 18 and the other via a shut-off valve 21 to a separation tank 17. The separation tank 17 has two outputs, one of which acts on a drainage valve serving water 22 and the other is connected to the input of a Solventförderpumpe 8.1, whose output either via a check valve 20.5 to the injection nozzles 11, or via shut-off valves 20.4 and 20.6 leads to the solvent reservoir tank 9.

The structure of two embodiments of the proposed in the drying apparatus of Figure 1 Solventdampferzeugers can be seen from Figures 2 and 3. In the embodiment according to FIG. 2, the solvent heater 4 of the solvent steam generator has vertically aligned heating pipes 2. Obviously, the cold solvent is guided by means of a feed line 4.2 at the lower end in the solvent heater 4 and heated there. At the upper end of the Solventerhitzers 4 heated solvent over which the above-mentioned and now marked with the reference numeral 4.1 Solvent connection line through the wall of the vacuum vessel 1 in the arranged inside the container Solventverteilkanal 5 is performed. By virtue of the injection openings already mentioned above and now designated by the reference numeral 5.1, the heated solvent can emerge as an intensive solvent flow 5.3 from the solvent distribution channel 5 into the flow channel 5.2 and there with a solvent and steam containing mixed steam from the container interior to a steam containing predominantly solvent vapor 5.4 unite. The flow channel 5.2 can over the extend entire length and / or width of a wall of the container and possibly also consist of several short sections. If the solvent distribution channel is designed as an exposed tube with injection openings or injection nozzles, then the mixed vapor emerging from the distribution tube, expanding and partially evaporating solvent, the mixing steam in the flow channel sucked in on both sides of the manifold.

In the embodiment of the solvent steam generator according to Figure 3, in contrast to the embodiment of Figure 2, the heating pipes 2 of the Solventerhitzers 4 predominantly oriented horizontally and the flow channel 5.2 limiting straightening plate 6 is rotatable. The rotation of the straightening plate 6 can be achieved by a mechanical adjusting device 6.2, which acts via a lever mechanism on the rotatably mounted at a point 6.1 straightening plate 6. Here, the straightening plate between two positions 5.5 resp. 5.6 are rotated in which the flow channel 5.2 with almost unchanged cross-section of the nozzle throat maximum inflow for the sucked from the vacuum tank 1 aforementioned mixed steam and minimum Abströmquerschnitt for mixed steam containing solvent flow has 5.4 (5.5 position) or minimum inflow cross section for the incoming mixed steam and maximum Outflow cross section for the mixed steam containing solvent flow 5.4 (position 5.6). Depending on the position of the straightening plate 6 and thus dimensioning of the flow channel 5.2, the proportion of mixed steam in the flow channel 5.2 as well as the temperature of the solvent vapor flow 5.4 emerging from the flow channel 5.2 can be adjusted.

The construction of two embodiments of the condensation device contained in the drying apparatus according to FIG. 1 can be seen in FIGS. 4 and 5. In the embodiment according to FIG. 4, cold solvent 14 is guided via a solvent line 14.3 connected to the shut-off valve 20.5 to the injection nozzles 11 and injected in the opposite direction to a mixed steam stream 13 which passes from below into the condensation space 10 and contains solvent and water vapor. This leads to an advantageous intensive turbulence of the injected cold solvent 14 with the mixed vapor stream 13 sucked into the condensation chamber 10. In this way, the condensation of solvent vapor 14.1 from the Mixed steam flow 13 at the injected cold solvent 14 optimized. The injected solvent 14 and the condensed solvent vapor 14.1 flow to the drainage vessel 7 and are pumped off with the feed pump 8 while remaining mixed steam 14.2 is removed from the mixed steam flow 13 via the mixing steam line 15 from the condensation space 10 and fed to a mixed steam condenser 16.

In the embodiment according to FIG. 5, cold solvent 14 is injected via the injection nozzles 11, 11.1 in the same direction as the mixed steam flow 13 in the latter. As a result of this and by means of a straightening plate 12 attached to the inlet of the condensation space 10 and delimiting the inflow side of a nozzle, a strong flow is caused, which sucks the mixed steam as stream 13 from the interior of the vacuum container 1 into the condensation space 10. As a result of the same flow direction of cold solvent 14 and mixed steam 13, the condensation section is slightly extended. At least one baffle 10.2 is mounted in front of the outlet opening 10.3, so that any solvent drops are deposited.

The operation of the device is as follows:
With the vacuum system 18, the vacuum container 1, the mixed steam condenser 16 and the separation tank 17 are evacuated. At the same time, the solvent supply tank 9 draws solvent via the shut-off valves 20.6 and 20.3 and the solvent heater 4 into the vacuum container 1 until the filling level indicator 7.1 is flooded. In the heating phase that follows, the solvent present in the vacuum tank 1 is circulated by the feed pump 8 and heated in the solvent heater 4 to a temperature slightly above a predetermined drying temperature. The heated solvent is heated to normal or possibly higher pressure. Upon discharge of the solvent from the injection openings 5.1 of the Solventverteilkanals 5, the pressure in the solvent 5.3 drops sharply and evaporates a portion of the heated solvent with simultaneous cooling by the amount of its heat of vaporization. The resulting solvent vapor 5.4 condenses on the active part and heats it with simultaneous evaporation of the water contained in the solid insulation, resulting in the formation of the solvent and steam containing mixed steam in the vacuum vessel 1. in the Vacuum container 1 resulting and optionally insulating solvent-containing solvent condensate is fed back to the Solventverteilkanal 5 with the feed pump 8 via the solvent heater 4 for evaporation. The solvent 5.3 is advantageously injected at the nozzle throat via the injection openings 5.1 in the flow channel 5.2. This results in a particularly high flow velocity and a correspondingly high negative pressure. This leads to a jet effect, through which the mixed steam present in the vacuum tank 1 is sucked into the flow channel 5.2. The sucked mixed steam mixes with the injected solvent 5.3 and the solvent vapor 5.4 formed during injection. This produces the advantageous effect, on the one hand, of achieving fast and accurate temperature control of the solvent vapor 5.4 entering the vacuum vessel 1, and, on the other hand, circulating the mixed vapor at increased speed turbulently in the vacuum vessel 1 by sucking in the mixed vapor into the flow channel 5.2, thereby heating up of the electrical Trocknungsguts 1.1 is significantly accelerated.

If the insulation of the electrical material to be dried 1.1 contain insulating oil, this is washed out by the condensing solvent and mixes with the solvent to a solvent / oil mixture. The oil content is not evaporated in the solvent steam generator. Therefore, with continuous removal of mixed steam from the vacuum tank 1 and condensation of the extracted mixed steam in the mixing steam condenser 16, the oil content in the vacuum tank 1 steadily increases until practically only pure oil is present. This oil is brought with the feed pump 8 via shut-off valve 20.7 in the oil tank 19. Thereafter, solvent is again drawn into the vacuum container 1 via the solvent heater 4 and evaporated in the manner previously mentioned.

The injection nozzles 11, 11.1, the stored in the separation vessel 17 cold solvent with the feed pump 8.1 via shut-off valve 20.5 is supplied and injected into the condensation chamber 10. On the large surface of the injected cold solvent 14, the solvent vapor component of mixed steam 13 sucked into the condensation space 10 condenses to form the condensed solvent 14.1. As a result, water vapor can advantageously accumulate in the condensation chamber 10. It will be less Solvent vapor led to the mixed steam condenser 16. This saves energy, which is required on the one hand for heating the solvent and on the other hand for cooling the mixed steam condenser 16. The injected solvent and the condensed solvent vapor flow via the drain tank 7 to the feed pump 8 and are fed via shut-off valve 20.3 to the solvent heater 4.

The solvent vapor-enriched in the condensation chamber 10 solvent vapor is controlled by the Dampfabsperrventil 20 fed to the mixed steam condenser 16 and condensed. Resulting air leakage is pumped off with the vacuum system 18. The solvent and water-containing condensate is then separated by sedimentation in the separation vessel 17 and the solvent with the pump 8.1 via shut-off valve 20.5 again fed to the injection nozzles 11, 11.1.

Once the material to be dried 1.1 is heated to a temperature sufficient to dry the solid insulation respectively. to wash out any existing insulating oil, the feed pump 8 is turned off and the Dampfabsperrventil 20 fully open. By means of condensation of solvent and steam in the mixed steam condenser 16, the pressure in the vacuum tank 1 is lowered and at the same time the resulting in the separation tank 17 Solvent condensate with the feed pump 8.1 via the valves 20.4, 20.6 fed to the Solventvorratstank 9.

After lowering the pressure in the vacuum container 1 to such a low level that no condensation of water and only minimal condensation of solvent in the mixed steam condenser 16 is obtained, the shut-off valve 21 is closed and the pressure in the vacuum container 1 with the vacuum pump 18 for a certain period of time to low Vacuum values lowered. Remaining residual water as well as possibly existing impurities are removed by condensation. After completion of this so-called fine vacuum phase of the vacuum vessel 1 is vented and then the dried material 1.1 is removed from the vacuum tank 1.

In the embodiment of the drying device according to FIG. 6, the vacuum container 1 is designed as a housing of a transformer, which contains the material to be dried, in this case too, the active part containing the solid insulation 1.1 of the transformer absorbs. The transformer housing 1 is arranged in a thermal insulation house 1.5, which can be heated by the heat generator 3. The heat generator 3 is designed as an air heater. The heating energy is supplied through the tubes 2. Air heated by the tubes 2 is conveyed as a heat carrier with the aid of a hot air fan 3.1 via a housing feedthrough 3.3 into the heat insulating house 1.5. About a housing bushing 3.2 air is brought from the Wärmeisoliergehäuse 1.5 back to the air heater and reheated. Also in this embodiment of the drying device, the heating tubes 2 are surrounded by a double jacket and are heated by the heat generator 3, both the transformer housing 1 and the solvent. In contrast to the embodiment of Figure 1, the transformer housing 1, however, with Abdeckflanschen 1.3 vacuum-tight openings 1.2, through which openings otherwise the power connections of the active part 1.1 are performed. In one of these openings 1.2, the flow channel 5.2, which is supplied with hot solvent by the solvent heater 4 via the solvent connection line 4.1, is arranged. Instead of a Solventverteilkanals 5 with injection openings 5.1, in this embodiment, the solvent steam generator now arranged at the Düsenengstelle the Venturi nozzle and aligned in the direction of the nozzle axis injection nozzle 5.7, which is fed via line 4.1 with hot solvent. Further solvent steam generators, each with a flow channel and with one or optionally also with a plurality of injection nozzles 5.7, can be provided at other openings 1.2 of the transformer housing 1. As can be seen from Figure 7, the flow channel 5.2 is formed substantially axially symmetrical and is limited by a fixed and largely curved around the axis Venturiblech 6.3 and by the adjustable running straightening 6. Downstream is on the straightening plate 6 additionally a baffle 6.4 arranged. Through the sheet metal 6.4, non-evaporated solvent passing from the channel 5.2 is guided to the wall of the transformer housing 1 and can be quickly removed from the housing 1 and supplied to the solvent heater 4 via a drain opening 1.4 (FIG.

In a further opening 1.2 transformer housing 1, the condensation chamber 10 is arranged. Two embodiments of this condensation chamber can be seen from Figures 8 and 9, wherein the embodiment of Figure 8 is largely the Embodiment corresponds to Figure 5 and the Fig.9 largely that of FIG. In the embodiment of Figure 8, however, an air-cooled condenser 23 is still shown, which is connected to the outlet opening 10.3 of the condensation chamber 10 via the line 15 and the mixing steam condenser 16 is preceded by forming an additional condensation stage for the enriched steam containing mixed steam 14.2. Air heated in the air-cooled condenser 23 is conveyed by a fan 23.1 via an inlet opening 23.2 into the heat insulating housing 1.4 for heating purposes. In the condenser 23 with the release of heat of condensation for heating the air separated solvent is fed via an outlet opening 23.3 the drain tank 7. Remaining mixing steam and leakage air are supplied via an outlet opening 23.4 the water-cooled mixed steam condenser 16 and treated according to the drying apparatus according to Fig.1.

In contrast to the embodiment of Figure 1, the finished assembled transformer is introduced into the Wärmeisoliergehäuse 1 and instead of housing bushings for the power connections of the active part 1.1 for carrying the line 4.1 and the injector 5.7 and to close the Condensation chamber 10 required connection flanges 1.3 mounted. With the help of flexible lines 4.1 and 15 and a condensate drain connected to the drain 1.4, the interior of the transformer housing 1 is connected to the other components of the drying device. To facilitate this assembly work, the components can be conveniently mounted on sliding or mobile frame. The drying process can now - as described in the embodiment of the drying apparatus of Figure 1 - be performed. In contrast to the method as described in connection with the embodiment according to FIG. 1, however, air heated in the condenser 23 during the condensation of mixed steam is now conducted into the heat insulating house 1.5. Thus, the heat of condensation of the solvent deposited in the condenser to improve the efficiency of the drying process is utilized in a particularly advantageous manner.

In the embodiment of the drying device according to the invention shown in FIG. 10, a solvent steam generator 24, generally designed as a cascade evaporator, is arranged in the vacuum container 1. Solvent and heat are supplied to this steam generator from the outside through the wall of the vacuum container 1. The amount of solvent supplied is controlled by means of a Solventabsperrventils 20.9. The heat is formed in a heat generator 24.2 arranged outside the vacuum container. Solvent vapor 29 formed in the evaporator 24 flows through a solvent vapor outlet 24.1 into the flow channel 5.2. Reference numeral 25 denotes a solvent heater located outside the vacuum container 1, in which the solvent is preheated and the preheated solvent is metered into the solvent distribution channel 5 located in the flow channel 5.2 via a solvent shut-off valve 20.8. The injection nozzles 5.7 of the Solventverteilkanals 5 are arranged in the region of the bottleneck of the venturi.

The preheated solvent 5.3 injected in the direction of the solvent vapor stream 29 sucks the solvent vapor out of the evaporator 24 as a result of the action of action and thus increases its flow velocity. At the same time, the speed of the mixing steam flow 30 already carried in the flow channel 5.2 is also increased. The steam flow 5.4 emerging from the flow channel 5.2 therefore has a high flow velocity and good turbulence. This results in a higher flow velocity and better turbulence of the circulating in the vacuum vessel solvent vapor stream than in conventional methods. As a result, the drying times are reduced with low energy consumption. As a result of the Jetwirkung remains the desired high solvent vapor velocity in the autoclave even at the end of the heating phase. This leads to a shorter heating time in the upper temperature range and accordingly ensures a small temperature difference over the drying material 1.1 and thus also an improved drying quality.

In the embodiment according to the invention of the drying device according to FIG. 11, in contrast to the embodiment according to FIG. 10, the solvent vapor stream 29 is produced in an external solvent evaporator 26, for example a large evaporator or a downdraft evaporator, arranged outside the vacuum vessel 1 and via an inlet connection 27 and a Deflection plate 28 containing steam line led to the flow channel 5.2. As a result of the action of the heated solvent injected in the direction of the steam flow 29, the solvent vapor from the steam line and the mixed steam from the autoclave 1 are sucked off analogously to the embodiment according to FIG. 10, thus advantageously increasing the flow velocity and the turbulence of the steam flow 5.4.

LIST OF REFERENCE NUMBERS

1

Vacuum container, transformer housing

1.1

Drying material (electrical device, active part of the device)

1.2

housing openings

1.3

covering flange

1.4

condensate drain

1.5

Wärmeisolierhaus

2

heating pipes

3

Heat generator, air heater

3.1

Hot air fan

3.2, 3.3

Enclosure openings

4

Solventerhitzer

4.1

Solvent connecting line

4.2

Solventzuführleitung

5

Solventverteilkanal

5.1

Injection port

5.2

flow channel

5.3

heated solvent

5.4

solvent vapor

5.5

Location of a straightening plate 6 for maximum entry area of 5.2

5.6

Location of a straightening plate 6 for minimum entry area of 5.2

5.7

injection

6

directional sheet

6.1

Fulcrum of the straightening plate

6.2

Adjustment device for the straightening plate

6.3

venturi sheet

6.4

baffle

7

drain tank

7.1

level indicator

8, 8.1

feed pumps

9

Solvent supply tank

10

Condensation room of heat recuperation

10.1

baffle

10.2

baffle

10.3

outlet opening

10.4

drain sheet

11

injectors

12

directional sheet

13

Mixed vapor stream

14

cold solvent

14.1

Condensed solvent

14.2

Solvent vapor with enriched water vapor

14.3

Solvent line

15

Mixing steam line

16

Mixing steam condenser

17

separation vessel

18

vacuum system

19

oil tank

20

steam regulator

20.1-20.7

Solvent-Ölabsperrventile

20.8, 20.9

Solventabsperrventile

21

Solvent-vacuum shut

22

Water drain valve

23

air-cooled condenser

23.1

fan

23.2

inlet opening

23.3

Outlet opening (solvent condensate)

23.4

Outlet opening (mixed steam)

24

(internal) solvent evaporator

24.1

Solvent steam outlet

24.2

heat generator

25

Solventerhitzer

26

(external) solvent evaporator

27

access nozzle

28

baffle

29

Solvent vapor stream

30

Mixed vapor stream

Claims (17)

1. A method for drying a product (1.1), preferably solid insulations of an electrical device, by the vapour phase method, whereby the product (1.1), containing at least water, if necessary insulating oil, as well as contaminants, is heated in a vacuum tank (1) in a vacuum by the condensation of solvent vapour (5.4), thereby forming a mixed vapour flow (13) containing at least solvent and water vapour, which flow is then condensed and water and solvent are separated from its condensate, in which method solvent fed into the vacuum tank (1) is heated at a pressure which exceeds the pressure prevailing in the vacuum tank (1), and the heated solvent is introduced into a flow duct (5.2) arranged inside the vacuum tank (1), in which it is evaporated, characterised in that the heated solvent (5.3) is injected into the flow duct (5.2) designed in the manner of a Venturi nozzle, with the formation of a hot solvent vapour flow (5.4).
2. The method according to Claim 1, characterised in that the heated solvent (5.3) is injected into a solvent vapour flow (29) guided through the Venturi nozzle.
3. The method according to Claim 2, characterised in that the solvent vapour flow (29) is generated in an evaporator (24) arranged in the vacuum tank (1).
4. The method according to Claim 2, characterised in that the solvent vapour flow (29) is generated in an evaporator (26) arranged outside the vacuum tank (1) and is guided through the wall into the interior of the vacuum tank (1).
5. The method according to one of Claims 1 to 4, characterised in that the heated solvent (5.3) is injected into the flow duct (5.2) at the narrow point of the Venturi nozzle.
6. The method according to any one of Claims 1 to 5, characterised in that the feed and discharge cross-sections of the Venturi nozzle are modified.
7. The method according to any one of Claims 1 to 6, characterised in that in the vacuum tank (1) cold solvent (14) is injected into the mixed vapour flow (13).
8. The method according to Claim 7, characterised in that the cold solvent (14) is injected in the direction of flow into the mixed vapour flow (13).
9. The method according to Claim 7, characterised in that the cold solvent (14) is injected against the direction of flow into the mixed vapour flow (13).
10. A device for implementing the method according to any one of Claims 1 to 9, containing not only the vacuum tank (1) receiving the drying product (1.1), but also a solvent vapour generator with a flow duct (5.2) arranged inside the vacuum tank (1), and a device for condensing the mixed vapour flow (13), characterised in that the flow duct (5.2) is designed in the manner of a Venturi nozzle, and in that the solvent vapour generator has a device guided into the flow duct (5.2) for injecting heated solvent.
11. The device according to Claim 10, characterised in that the injection device lies downstream from a vapour outlet opening (24.1) of a solvent evaporator (24) arrange din the vacuum chamber (1), or lies downstream from a vapour outlet opening (24.1) of a solvent vapour pipe (27, 28) guided from the outside into the vacuum tank (1), which pipe can be fed with solvent vapour from a solvent evaporator (26) arranged outside the vacuum chamber (1).
12. The device according to Claim 11, characterised in that the flow duct (5.2) is arranged in the region of the vapour outlet opening (24.1).
13. The device according to any one of Claims 10 to 12, characterised in that the injection device contains a solvent distribution duct (5) opening with injection openings (5.1) and/or injection nozzles, at least in the region of the narrow point of the Venturi nozzle, into the flow duct (5.2), and/or at least one injection nozzle (5.7) retained in the region of the narrow point of the Venturi nozzle inside the flow duct (5.2).
14. The device according to Claim 13, characterised in that the solvent distribution duct (5) is designed as a bare pipe.
15. The device according to any one of Claims 10 to 14, characterised in that a guide plate (6) limiting the flow duct (5.2) is designed so that it is adjustable by changing the feed and/or discharge cross-section of the flow duct (5.2).
16. The device according to any one of Claims 10 to 15, characterised in that a condensation space (10) of the condensation device, receiving at least one injection nozzle (11) for cold solvent and the mixed vapour flow (13), is arranged in the vacuum tank (1).
17. The device according to any one of Claims 10 to 16, characterised in that the vacuum tank (1) is designed as a housing of a transformer and is arranged in a heat insulation house (1.5) that can be heated preferably with air.

Images