FI67758C - FARING EQUIPMENT FOR ORDERING TORKNING AV PRODUCTS WITH A STEEL GASSTROEM OCH IN TORKVAETSKA - Google Patents

Description

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• C (45) Γ'1 ::; "·; '': y 1C Γ? ICC5 (51) Kv.ik. * / Int.ci. 'F 26 B 21/02 SUOMI_FINLAND (21) Patent application - Patentansöknlng 793735 (22) Application date - Ansöknlngsdag 28 11 70 '' (23) Starting date - Giltighetsdag 28.11 79 (41) Has become public - Blivit offentlig Q5 80

Patent, and National Board of Registration Date of publication | -,. ’. * ftc;

Patent * och registerstyrelsen '' Ansökan utlagd oeh utl.skriften publicerad ^ (32) (33) (31) Privilege requested - Begärd priority 28.11.78 27.06.79 Hungary-Hungary (HU) EE-2605, EE-2605 (71) Energiagazdälkodäsi Intdzet, 33, Bem-rkp., Budapest II, Hungary-Hungary (HU) (72) Läszlö Szucs, Budapest, Andräs Horväth, Budapest,

Emod Sigmond, Budapest, György Waermer, Budapest, Hungary-Hungary (HU) (7 * 0 Oy Kolster Ab (5 * 0 Method and apparatus for drying products with a closed gas stream and drying liquid1 - Förfarande och anordning för torkning av product-ter med en sluten gasström The present invention relates to a method and apparatus for drying products by means of a closed gas stream and a drying liquid which lowers the moisture content of the gas stream.

A method for drying products is well known, in which the substance to be dried is brought into direct contact with a gas, most often air, which is not saturated with water, whereby the substance becomes drier and the gas becomes increasingly saturated with moisture. Currently used drying equipment, especially for large quantities of products, usually dries using low relative humidity air, which is released into the environment after drying. This open gas flow drying involves significant consumption of thermal energy and is also unsatisfactory because in some cases the products to be dried are sensitive to heat. It can also be harmful due to air pollution.

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It was the thermal sensitivity of certain specialty products (drugs, gelatins, nutrients, etc.) that necessitated drying at low temperatures (e.g., ambient or lower). The low relative humidity of the low temperature gas, which is a prerequisite for drying such products, can be achieved by reducing the absolute humidity of the gas. Therefore, for example, U.S. Patent No. 3,257,737 has proposed that the drying gas be contacted with solid adsorbents that absorb moisture from the gas. AT Patent No. 317,857 and GB Patent No. 1,152,440 also suggest the use of drying (hygroscopic) liquids (e.g., aqueous solutions of lithium chloride or ethylene glycol) to separate moisture from the gas. Regeneration of the drying gas in this way also makes it possible to use a closed gas stream. The proposed solutions, which use a drying liquid, cause the liquid to come into contact with the gas stream in sprayed or dispersed form, and the particles entrained in the gas stream remain in the drip separator.

An example of other known arrangements is FI Patent Application No. 485/72 (corresponding to DE Application Publication No. 21 14 935). In this condensing arrangement, the reduction of the water content of the drying air is performed by contacting it with cool water. However, cool water cannot be considered as a drying liquid for water moisture. U.S. Patent No. 2,695,460 describes a device of the same type as U.S. Patent No. 2,686,372. The only difference between the devices of these publications is in the condensation chamber. Other examples include U.S. Patent Nos. 2,249,625, 2,017,027 and NO Patent No. 92,992.

Such a system is theoretically more advantageous in terms of energy use than one that operates with warm air, essentially because it avoids heat losses due to the release of air into the environment. However, until now, a closed gas circulation system has only been used for specific drying problems, and where possible, taking into account the characteristics of the product to be dried, the open warm air method was applied. The reason for this is that traditional types of dryers with a closed gas circuit require large investments, recycling a large amount of gas consumes a lot of energy, and the drying liquid used for regeneration is expensive, which increases operating costs.

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The main object of the invention is a dryer with a closed gas circulation, which is more cost-effective than previously known dryers with a closed gas circulation system and which is competitive with known open air dryers even in the case of a large number of products to be dried.

The invention is based on the following basic ideas: 1. Contact between the gas stream and the drying liquid should not be effected by spraying or dispersing the liquid, but by using a gas-liquid contact device placed in the gas stream to omit the separation of the drying space from the contact space.

2. In a closed air circulation system, the amount of air used for a given purpose is a multiple of the amount of air used in an open system. For this reason, the gas contact device using the drying liquid and the product to be dried must be placed close to each other and in such a way that the direction and speed of the air flow change as little as possible during the cycle.

3. Drying must be carried out in a high-temperature gas stream as permitted by the nature of the product. To achieve this, it is convenient to heat the recyclable gas stream with a drying liquid.

4. When the drying liquid is regenerated, the heat of vaporization of the vapor separated from the liquid must be recovered in the liquid to be regenerated, also taking into account the heating required during regeneration.

5. The device in which the drying liquid is in contact with the gas is designed in such a way that it can be arranged in a modular manner and the countercurrent principle known per se can be applied in the drying of continuously moving products.

Therefore, the invention relates to a method of drying products, in which the product to be dried is brought into a drying space, the substantially closed drying gas stream is continuously circulated so that the drying gas stream sweeps over the product to be dried and contacts at least one drying liquid for removing moisture from the drying liquid, wherein the at least one drying liquid layer is arranged substantially perpendicular to the flow direction of the drying gas stream. The method according to the invention is characterized in that the dry liquid layer or layers are arranged in the drying space or substantially close to the drying space.

The use of a liquid layer according to the invention has an advantage in many respects. First, it obviates the need for a spray separator applied in known systems, whereby the liquid droplets contaminate the gas stream substantially less and less drying liquid is lost. Second, the mass transfer coefficient between the liquid and the gas is more advantageous than with the liquid particles, which makes it possible to use a compact structure as well as a smaller pressure drop in the gas flow. Thirdly, there is no need for a contact space separated from the drying space, so that the liquid surface can be quite close to the product to be dried. A further advantage is that the provision of a liquid layer is not as sensitive a procedure as spraying in a manner known from the prior art, since the risk of clogging is much lower, as is the need for maintenance. This latter factor is particularly significant because dust and other contaminants are often carried with the gas stream, in addition to moisture, into the drying liquid and the holes of the spray nozzles become clogged. Other embodiments of the method according to the invention are set out in subclaims 2 to 18, which are generally described below.

The method according to the invention can advantageously be applied in such a way that the drying liquid layer is substantially horizontal and bubbles of gas are passed through said horizontal liquid layer. In this way, bulk material can be dried, which passes, for example, by a belt conveyor which is passed below or above the horizontal liquid layer.

In another, very preferred embodiment of the method, at least one layer of drying liquid is made by allowing the drying liquid to flow over the liquid film control elements, and said contact is effected by allowing a drying gas stream to pass between said liquid film control elements. The liquid film control elements can form a curtain-like wall, which can, for example, limit the drying space.

Another object of the invention is to dry the product by performing the following steps: the product to be dried is brought into a drying space, the drying gas stream is continuously recirculated to bypass the product to be dried, the drying gas stream is contacted with a drying liquid to remove moisture from the gas and the drying liquid is regenerated by recirculating at least a portion remove moisture from it. Essential to this method is the placement of a heat exchanger between the drying liquid and the product to be dried, so that the drying gas stream transfers heat between the drying liquid and the product to be dried.

It is expedient to raise the temperature of the drying liquid during regeneration to such an extent that when the drying liquid comes into contact with the drying gas stream, the temperature of the gas rises to a predetermined height, preferably above 40 ° C to raise the product temperature to the desired height. This method makes it possible to reduce the amount and velocity of the recycled gas, because as the temperature increases, the amount of moisture that can be removed from one kilogram of air increases, and the heat of vaporization of steam evaporated from the drying liquid during regeneration can be efficiently recovered. An additional advantage is that the cooling used in previous gas-liquid contacts is eliminated, which simplifies the structure of the gas-liquid contact device.

According to a particular embodiment of this method, said regeneration is carried out by evaporating the drying solution, and the steam evaporated from the drying solution is at least partially condensed by the solution to be regenerated. This makes economics very regenerative, during which the heat required by the regenerate can be greatly reduced by using multi-power boiling or multi-stage expansion evaporation. Compared to previous solutions in which the heat of vaporization of vaporized steam is used to heat the air for pre-drying the product, there is an advantage that condensing the steam with a liquid requires a smaller and more economical device than air-operated.

It is practical to boil the drying solution to be regenerated with steam which evaporates from the solution during regeneration. The energy requirement can be reduced by concentrating the drying solution by multi-power heating and by using the incoming solution to be evaporated to condense at least part of the steam that has evaporated during the first or last boiling stage of the regeneration.

Regeneration can be performed by heating the drying solution to be regenerated without boiling it, whereby steam evaporates from the solution. In this case, it is particularly advantageous to regenerate the drying solution with a multistage expansion evaporator.

According to a very preferred embodiment of the method of the invention, the drying solution must be cooled before regeneration due to the cooling of the drying solution during the drying step, so that the drying solution to be regenerated is at a predetermined temperature. The cooling proposed here is essential for controlling the circulation of the drying solution and is intended to supplement the cooling that takes place in the drying solution as it encounters the drying gas flow. The degree of cooling must be adjusted according to the seasons, for example. Cooling is preferably performed during regeneration.

According to another preferred embodiment of the method, the continuous recirculation of the drying gas stream is performed by directing the drying gas stream to a passage section between the product to be dried and the drying liquid, so that at said passage section the ratio of maximum and minimum drying gas flow rates is less than 5: 1 and below the drying gas flow direction. These dimensions require relatively low ventilation power, which is an important factor when considering the economy of the entire drying phase. Ventilation efficiency can be further reduced if a drying gas stream is passed between the product to be dried and the drying liquid without any significant change in speed and direction.

It is expedient to use air as the drying gas and calcium chloride as the drying solution. Calcium chloride solution is particularly preferred due to its low cost. In addition to removing water moisture, the method according to the invention is also suitable for drying substances which contain other types of moisture, using a suitable drying liquid. For example, it is possible to apply this method to drying substances with alcoholic moisture using a closed air stream and gasoline as the drying liquid.

According to another embodiment of the method, the drying gas stream comprises at least two parallel partial gas streams, the product to be dried passes through said partial gas streams and each of said partial gas streams is connected to a drying liquid of a specified concentration and temperature. In this way, the drying program of the product to be dried can be varied within wide limits. According to a very expedient embodiment of the method, for example, each of said partial gas streams is contacted with a drying liquid having a concentration higher than the concentration of the drying liquid associated with the previous partial gas stream with respect to the direction of movement of the product to be dried. This results in countercurrent flow between the product to be dried and the drying liquid.

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The method of the invention can also be implemented by making at least two separate groups of drying liquid films of different concentrations by placing said drying liquid film groups in parallel in the path of said partial gas streams so that each of said gas streams comes into contact with its own, at least one drying liquid film group. In a preferred embodiment, each said film of liquid has its own liquid circulation, wherein the liquid cycle of the last group relative to the direction of movement of the product to be dried is fed with drying liquid from the regenerator, the cycle of each previous group is fed from the next group cycle and the first group cycle is fed to said regenerator. In this way, a countercurrent is created between the drying liquid and the product to be dried.

The product to be dried can also be transported across the partial gas streams and the temperature of the product can be changed as described by adjusting the temperature of the drying liquid separately in each well group of the drying liquid. In this way, the drying temperature mode can be easily programmed for each stage of drying, even in continuous drying.

The invention also relates to an apparatus for drying products comprising at least one drying space for the product to be dried, at least one contact device having means for contacting at least one drying liquid stream with a drying gas stream to remove moisture from the gas, a gas control device for controlling the drying gas flow along a substantially closed path through a drying space in which the drying liquid layer or layers are arranged substantially perpendicular to the flow direction of the drying gas stream;

The device according to the invention is characterized in that the contact device or devices are arranged in or substantially close to the drying space.

Other preferred embodiments of the device according to the invention are set out in subclaims 20 to 31, which are generally described below.

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In one embodiment of the device according to the invention, a contact device comprises a vessel for providing a substantially horizontal layer of drying liquid, the wall of said vessel having pulverized hoods for pulping drying gas through said liquid layer, said vessel being connected to said liquid recirculation and causing the drying liquid to flow; the drying space is located above or below said container. The drying section preferably comprises a device for conveying the product to be dried through said drying section, said device having openings through which the flow of drying gas can pass but through which the product to be dried cannot fall. The conveying device is preferably an endless belt conveyor, and said air recirculation takes place by fans arranged in parallel along said belt conveyor.

According to another embodiment of the device, the contact device comprises liquid film control elements arranged so that a flow of drying air flows between said liquid film control elements. The reliability is improved and the structure simpler if the contact device further comprises a container for incoming drying liquid, for discharging at least one overflow barrier film from said container, a liquid distributor having at least one distributor surface connected to said at least one overflow seal and directed downwards, as well as a liquid outlet, such that said membrane guide elements are between said liquid distribution surface and said liquid outlet so as to lead liquid films from said surface to said outlet. This embodiment is not particularly sensitive to the contamination that may enter the drying liquid from the drying air stream. It is practical to arrange the liquid film guide elements, preferably strips or fibers, in at least one vertical plane. In thin fibers and in the drying gas stream, excellent heat and mass transfer is created between the membranes of the drying liquid. The strips or fibers can be made of a metal that can withstand the drying liquid or a plastic that can withstand the highest possible temperature of the drying liquid.

A possible embodiment of the drying device according to the invention can be applied to wood products. This embodiment comprises a base, a jacket vault and a partition with openings for the drying gas flow and located between said base and said openings for the drying gas flow and located between said base and said partition, so that said drying space is located between said base and said partition. and said bulkhead, said gas recirculation is provided by fans disposed between said bulkhead and the jacket vault and said contacting device is located in said drying space such that said at least one vertical plane formed by said liquid film guide element is substantially at right angles to said drying gas flow between the base and said bulkhead. In such an arrangement, the liquid film guide element is located at the interface of the drying space or with the cross-section at a substantially right angle to the direction of the gas flow. Thanks to this arrangement, the pressure drop of the gas flow is small, so that little energy is used for ventilation.

In a highly preferred embodiment of the invention, the contact device comprises at least two liquid film modules arranged in parallel, each liquid film module having its own liquid film control elements and a liquid circulating device for circulating liquid to form liquid films. the fluid passage being connected to said fluid recirculation device. Thus, the device includes a single regenerator and yet each liquid film module receives a drying liquid with a different activity.

According to another embodiment, the ratio of the two flow cross-sections of the gas line between any said drying space and said contact device is 0.2-5, and said contact device is positioned in said drying space so that a drying gas flow between the product to be dried and said contact device is less than 30 degrees. It is highly preferred if said flow cross-sectional ratio is 0.2-2, and said change of direction is substantially 0 degrees and the distance between said drying space and said contact device is less than the hydraulic diameter of the gas line between them.

According to a very preferred embodiment of the device, the desiccant of the drying liquid comprises a multi-power evaporator or a multi-stage expansion evaporator. The latter is more expedient because its operation is simpler. Thanks to this embodiment, the regeneration is very economical also in terms of energy consumption.

Another object of the present invention is an industrial product made according to this method.

Further details of the invention will be explained with reference to the accompanying drawings, which show by way of example embodiments of the device according to the invention and in which Fig. 1 is a schematic representation of a first embodiment of a dryer, Fig. 2 is a sectional view of a second embodiment of the dryer according to line BB of Fig. 4; along the line AA in Fig. 4, Fig. 4 is a top view of the second embodiment shown in Figs. 2 and 3, Fig. 5 is a sectional perspective view of a third embodiment of the dryer, Fig. 6 is a top view of the third embodiment cut along the line CC in Fig. 5, Fig. 7 is a second view of Figs. wiring diagram of the drying liquid regenerator of the embodiment, Figs. 8 and 9 are wiring diagrams of two other drying liquid regenerators applicable to the drying apparatus of the present invention, and Fig. 10 is a wiring diagram for a multistage expansion evaporator, which can be used as a regenerator of the drying liquid of the drying device according to the invention.

In all the drawings, the same reference numerals are used for the same or like parts.

Figure 1 schematically shows the jacket 42 of the drying device. The device circulates the gas stream, such as air stream, which dries product 50, e.g., bulk materials, as shown in the figure, circulates in a closed circuit in the direction of the arrow 64. The circulation is effected by a fan 66 driven by an electric motor 46 located on a suspended ceiling 54, shown schematically, without its brackets. The suspended ceiling 54 has openings 47 through which the air flow can pass.

The product 50 is in the drying state under the suspended ceiling 54. After the air stream 117758 has flowed through the product 50 and has become wet, the air stream enters the contact device 43, where the air stream comes into contact with the liquid films 41 formed by the drying liquid. The pump 141 presses the drying liquid into the regenerator 150. The active and hot drying liquid enters the contact device 43 from the overhead line 44, enters the cup-shaped collector 55, from there over the overflow barrier 56 to the liquid distribution surface 57, which is downwards. From the liquid distribution surface, it enters downwardly directed liquid film guide elements 58, for example fibers, which said elements guide it to a liquid discharge channel 62, from which it exits via a pipeline 45.

The drying liquid, which has been diluted and cooled after contact with the air stream, enters the regenerator 150 via line 45. Regenerator 150, exemplified in the drawing, comprises a multi-stage evaporator 151, a liquid circulating pump 141, a pump 142 to remove distillate from the multi-stage evaporator 151 through line 149, and a heat exchanger 143 to which cooling water is supplied to the cooling ends of the heat exchanger 143. The active liquid leaving the regenerator 150 heats as it passes through the condenser 145 and then returns to the contact device 43. The condenser 145 receives heating steam from the pipe end 146 and the pump 147 transports the condensate out through the pipe end 148. The elements of the regenerator 150 as well as the post-regeneration heating are known per se, so that it is not necessary to explain them in detail.

The embodiment of Figure 1 is particularly advantageous when drying products that prevent high temperatures, such as bricks, because in this arrangement the temperature of the drying liquid returning from the contact device 43 and "cooled" there is still high enough to remove moisture during the expansion process.

The use of the multi-stage expansion evaporator 151 in the device according to the invention is particularly advantageous in that it is superior in terms of control, operation and reliability than other multi-power evaporators having the same energy efficiency. Here, evaporation does not take place along the heat transfer surfaces, so that it is less sensitive to scaling and corrosion, and its structure does not become complicated even when its energy efficiency is improved. Of course, an evaporator of a different structure, known per se, can also be used for regeneration.

Similarly, it is very advantageous to use the contact device shown in Figure 1 for the device according to the invention. This structure is not sensitive to contamination entering the liquid from the air stream, and it ensures that the coefficient of heat and mass transfer of the contact between the liquid and the air stream is good.

In the device according to the invention, the drying space can be made and the product 50 to be dried can be placed in many ways (hanging, fluidized bed, geyser, chamber, tunnel or whatever). The product can be moved during the drying process and the drying gas can just as well flow upstream, transversely or downstream of the product.

Figures 2, 3 and 4 show an embodiment of the device according to the invention in which there is a substantially horizontal liquid layer 1 and in which likewise in the horizontal direction the product 2 moves above the liquid layer. The product 2, for example soybeans, enters the conveyor through the opening 3, which in the drawing is a belt conveyor. The belt 4 has air openings 5 which allow air to pass through but do not allow the product 2 to fall. The belt 4 is supported by two wheels 6 which are made so that they can tension and pull the belt, whereby they can be toothed or rubberized for this purpose. The second wheel 6 is driven by an electric motor 8 via a gear 7. The loaded belt 4 of the belt conveyor moves the product 2 through the opening 3 through the drying space 25 in the dryer casing 9, then through the gate 10 to the collector 11, from where the dried product is transferred to storage or use by belt conveyor or hoist. which are not shown in the figure. The empty part of the belt conveyor runs below the jacket 9.

The case 9 below, under the conveyor belt the loaded part is air collecting space 12, and below this overhead, but the conveyor belt the loaded part of a liquid reservoir 13. The liquid reservoir 13 flows desiccant liquid arrow 14 in a direction opposite to the direction of product 2 with respect to a moving direction of the arrow 15 direction. Above the loaded part of the belt conveyor, at the top of the jacket 9, there is an overhead air collection space 16. Four fans 17A, 17B, 17C and 13 67758 17C, respectively driven by electric motors 23A, 23B, 23C and 23D, draw air from the overhead air collection space 22A, 22B, 22B, period and weighing the pressure in the pipes 18A, 18B, 18C and 18D, and the openings 19A, 19B, 19C and 19D to the lower air-collecting space 12. for From here, through the air bubbles in the liquid container 13 in the wall kuplimiskupujen, one of which is shown enlarged in Figure 2, the desiccant liquid layer of the arrow 21 direction, then, starting from the liquid layer 1 through the openings 5 of the belt to the layer formed by the product to be dried 2, and after passing through it, the air returns to the upper air collection layer so that the air circulation is closed. In this embodiment, the liquid container 13 provided with bubble hoods 20 operates a contact device 43 which provides contact between the air stream and the drying liquid.

The four fans 17A, 17B, 17C and 17D provide four closed circulating airflows. The first partial air flow passes through the suction duct 22D and encounters the incoming wet product 2. The second passes through the suction duct 22C, the third through the suction duct 22B and the fourth through the suction duct 22A, and the latter removes the last part of the product 2 from the moisture to be dried. The drying liquid enters the vessel 13 via the pipe connection 26 and leaves through the pipe connection 27. The incoming hot and active liquid is bubbled by the last partial air stream, and the exiting, diluted and cooled liquid is bubbled by the first partial air stream.

The use of a plurality of fans 17A, 17B, 17C and 17D is advantageous not only in view of the flow conditions, but also in order to achieve countercurrent drying of the product 2 with respect to the flow direction of the drying liquid. It is obvious that if only one fan circulated a single air stream, no counter-current drying would occur, despite the fact that the product 2 and the drying liquid 1 would move in opposite directions. The countercurrent effect would be most effective if there were an infinite number of parallel airflows. In this sense, it is expedient to use as many partial air streams as possible in the drying according to the invention.

It can be seen in Figures 2-4 that the drying space 25 and the contact device 43 are placed immediately above each other as if they formed the two "floors" of the jacket 9.

In an embodiment different from the embodiment shown in Figures 2-4 of the same type of arrangement, the liquid container 13 is located above the loaded part of the belt conveyor. This is advantageous when the product 2 has such small particles that could fall into the liquid container 13 through the openings 5 of the belt 4 and could contaminate the liquid to be dried to a detrimental extent. In such an embodiment, the air flow through the openings 19A, 19B, 19C and 19D would first pass through the product 2 and then through the liquid layer 1. Another advantage of this embodiment is that the particles of the product 2 which have fallen through the openings 5 of the price 4 can be collected at the bottom of the jacket 9 and transferred therefrom as a dried product periodically or continuously. It is also preferred that the liquid droplets possibly carried by the air stream from the liquid layer 1 do not reach the product 2, but can, after passing through the fans 17A, 17B, 17C and 17C, be collected in cups or ducts formed by pipes 18A, 18B. 18C and 18d to the bottom from where they can be fed back into the fluid circuit.

In the embodiments shown in Figures 2-4, for example the product 2 can be removed from the liquid layer by means of a tank separator known per se, preferably connected to the drying liquid circuit after the connection 27, for example so that the liquid entering the separation tank can only escape from holes are halfway to the full liquid surface of the tank. It is natural that the tank should be cleaned thoroughly, the liquid should be peeled off and the precipitates removed.

In the case of the embodiment shown in Figures 3 and 4, the diluted drying liquid, in this embodiment the drying solution, enters a liquid condenser comprising a liquid circulation pump 28, a steam condenser 29 cooled by an incoming dilute solution, a distillate 31 for removing distillate from a pump 30, and a pump 36 The pump 28 pumps the diluted solution through the condenser 29 as a coolant, from there the solution enters the evaporator 31 via the conduit 32. The evaporator 31 heats with the steam coming through the pipe connection 31 and the condensate of the heating steam exits through the pipe connection 34. The vapor evaporated from the solution enters the condenser 29 from the evaporator 31 via line 35, where it condenses and the pump 3Q removes the distillate. The system of the pump 30 is such that it can also remove non-condensable gases with the distillate. From the evaporator 31, a pump 36 is pumped via line 24 67758 15 to a condensed, active solution tube to connection 26 through which liquid returns to tank 13. This drying liquid regenerator is also shown in the circuit diagram of Figure 7 for clarity.

For the sake of clarity, Figures 2-4 show the simplest possible evaporator which, during regeneration, uses only the incoming solution as a coolant to condense the vapor vaporized from the solution. However, according to the invention, it is more practical to use a multi-stage evaporator, such as that shown in Figures 1 or 10, instead of a multi-power evaporator with a higher energy efficiency, for example those shown in Figures 8 or 9.

Instead of a belt conveyor, it is of course possible to use another conveyor as well, and the product 2 can also be passed through the drying space obliquely and not only horizontally. The cross-section of the liquid tank 13 is much larger than the cross-section of the pipe connections 26 and 27, and it is therefore practical to allow the drying liquid to flow into and out of the liquid tank 13 in addition to one inlet and outlet pipe connection. through.

Figures 5 and 6 show another embodiment in which the product 50 moves horizontally and a contact device placed next to the product 50 provides a vertical liquid film 41 of drying liquid.

The product 50, sawn wood in the drawing, is placed trailers 51, which wheels support the shaft 52 in the bearings and moving slowly surface direction of the arrow 53 direction. Above the product 50, the intermediate space 54 closes the drying space 40.

The entire drying device is closed from above by a jacket vault 65, to which the false ceiling 54 is connected by means of brackets 65A. The jacket vault 65 is closed on two sides by walls 37 and 38, respectively, with gates 39 for the product 50. Air circulates in the direction of the arrows 64 under the action of fans 66 and 66 'driven by electric motors 46 and 46' located in the partition 69. From the fans 66 and 66 ', an air flow continues between the mantle vault 65 and the suspended ceiling 54, then through the opening 47 in the suspended ceiling 54 to the drying space through the second opening 47A between the base 49 and the suspended ceiling 54 back to the fans 16 67758 66 and 66'. Since the embodiment shown has two fans 66 and 66 ', two parallel partial air streams are generated.

The contact device 43 of this embodiment shown in Figs. 5 and 6 comprises three liquid film modules 48A, 48B and 48C placed immediately in parallel. Each module has a separate fluid circuit and all modules have a common fluid sub-passage 62 through which they communicate with a regenerator, which is not shown here by means of pipe connections 67 and 68. Regeneraatto from the Rista-active hot desiccant liquid comes into the putkiliitok-67, then is diluted by circulation in nestekalvomodu-gels 48A, 48B and 48C as it passes along the channel 62 in the direction of arrow 63, then it comes through the pipe connection 68 to the regenerator.

The regenerator may be as shown in Figure 1 or 4, but the multi-power evaporators shown in Figures 8 and 9 may also be used, as may the multi-stage expansion evaporator shown in Figure 10.

The liquid film modules 48A, 48B and 48C are similar in structure, which is why we will only explain the liquid film module 48V. An upper basin 55A is located below the bulkhead 54 and is limited by an overflow barrier 56A. A downwardly directed fluid distribution surface 57A is connected to the overflow barrier 56A. From the liquid distribution surface 57A proceeds downwards the liquid film guide elements 58A, which may be, for example, the fibers shown in the drawing. A liquid film is formed around each element 58A, and all elements 58A of the liquid film module 48A together form a group of liquid films, characterized in that all elements of the group carry with them a drying liquid of the same concentration. The elements 58A extend into the collecting channel 62 below. The suction pipe 59A leaves the bottom of the channel 62, thus leading to a liquid circulation pump 60A for drying liquid. The pump 60A circulates the liquid through the pipe 61A to the upper basin 55A, from there through the overflow barrier 56A to the liquid distribution surface 57A and then through the elements 53A to the lower collecting channel 62.

The upper basin 55A is separate from the adjacent basin of the liquid film module 48A, but the common lower channel 62 allows the fluid circuits in the tubes 61A, 61B and 61C to pass fluid through it to each other. Sections of lower channel 62 which belong to liquid film modules 48A, 48B and 48C are respectively separated from each 17 67758 each other in the openings of the separating elements, so that the liquid is always flowing in the direction of arrow 63, without a backward interference. On leaving the receiver in the direction of the arrow 63 the first liquid film module 48C within the first fluid circulation of hot and active liquid from the regenerator. This is diluted by the air flow from the drying space 40, so that the liquid entering the second liquid circuit belonging to the liquid film module 48B formed by the overflow of the first liquid circuit is somewhat diluted. The overflow of the last, third in the drawing, liquid circuit returns as a diluted and cooled drying liquid to the regenerator, said liquid containing all the moisture removed by the air stream from the product 50.

The two fans 66 and 66 'provide two parallel partial airflows. The velocity of each partial air flow should be such that the air flow does not interfere with the liquid films passing along the control elements 58A, 58B and 58C, i.e. the air flow does not remove liquid particles from the film as it passes. 1-5 m / sec. is the appropriate speed. shown in Figures 5 and 6, the shape of which is similar to that shown in Figures 2-4, to carry out the drying-vastavir method of operation, as the product 50 moving slowly in the direction of arrow 53 as it passes through the drying compartment 40 meets air streams which have been contacted with more and more active desiccant liquid. A prerequisite for said countercurrent drying here is at least two partial air streams. It is expedient for each liquid membrane module 48A, 48B and 48C to have its own partial air flow, i.e. the number of fans is the same as for the liquid membrane modules.

In the liquid film modules 48A, 48B and 48C, the concentration of the circulating drying liquids can be increased in a different order than the state of the modules. The order can be obtained by appropriately combining the individual parts belonging to the separate modules of the channel 62. For example, from the portion of the liquid film module 48C of the channel 62, the drying liquid may enter the portion of the liquid film module 48A instead of the liquid film module 48B through the separating element 162, and from there the portion of the liquid film module 48B. In this way, the device according to the invention can be programmed taking into account the drying instructions of the product 50 passing through the drying space 40.

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In the illustrated embodiment, the contacting device 40 on the left side of the drying chamber 43, forming as it were "nestever-O '. Since the liquid film 41 provided according to the invention is substantially drip-free, the contact device 43 can be placed on the right side of the drying space 40, in addition to being divided into two parts, for example between the two stacks of wood shown in Fig. 5. According to the invention, the only important thing is that the closed air flow passes through the contact device 43 during the recirculation, and that the contact device 43 and the drying space 40 are positioned so that the direction and speed of the air flow change as little as possible between them.

It is clear that in all the mentioned embodiments these conditions are met.

The contact device 43 shown in Fig. 5 is of the same type as shown in Fig. 1, but it can be made in another way. Several contact devices suitable for the device according to the invention are described in U.S. Pat. 3,857,911 and 4,009,229 in Hungarian Pat. 168,451 and British Patent no.

1,363,523. In the device according to the invention, it is very advantageous to use a 40-50% aqueous solution of calcium chloride as the drying liquid. Contamination in the drying liquid can be removed in the tank in the same way as in the embodiments shown in Figures 2-4.

Figures 5 and 6 do not show the regenerator, as it may be the same as in any of Figures 1,4,8,9 and 10. With correctly selected regeneration, it is also possible to ensure that the active solution coming through the pipe connection 67 is hot enough to heat the air flow and thereby the product 50. By means of the liquid film modules 48A, 48B and 48C it is possible to adjust the temperature program for the product 50 passing through the drying space 40.

Figures 7,8,9 and 10 show different regenerator solutions. Given that the regenerator is made by combining different devices known per se, the various regenerators used in the invention are shown in Figures 7, 8, 9 and 10 exclusively as wiring diagrams. For the sake of clarity, each phase in the wiring diagram is marked with a separate diagram symbol, but the invention can also be applied in such a way that, for example, more than one device is placed in the same sheath.

19 67758

Figure 7 shows a wiring diagram of the regenerator shown in Figures 2-4, which is explained in detail in connection with these figures.

Figure 8 represents a regenerator in which steam evaporated from the drying liquid is used to boil the liquid to be regenerated, and steam from the outgoing active liquid heats the incoming diluted liquid- This regenerator is a multi-power evaporator.

Pump 70 pumps dilute liquid to condenser 71, where it acts as condenser for condenser 71, after which it reheats as it cools the liquid evaporating in heat exchangers 72 and 73 and finally enters evaporator 75 via line 74. This evaporator is heated from the outside by heat. According to the illustrated embodiment, steam is taken in through the pipe connection 76, condensed and the condensate is discharged via the pipe 77. Naturally, flue gas, radiant heat, solar energy or something else can be used for heating. From here, the liquid passes through the heat exchanger 73 and the choke 78 to the evaporator 79, where it is again boiled by the steam generated in the evaporator 75. The pump 83 pumps the liquid from here through the heat exchanger 72 to a pipe connection 80 connected to a pipe connection leading to the active liquid dryer body, for example pipe connection 67 in Fig. 6. The steam generated in the evaporator 79 enters the line 84 and the evaporator 79 enters the condenser 81 71, where they both heat the dilute incoming drying liquid. Pump 82 removes condensed distillate and non-condensed gases.

Figure 9 shows a wiring diagram of a regenerator which is also a multi-power evaporator and in which steam evaporated from a dilute solution is used to heat the incoming dilute, regenerable liquid.

The diluted liquid is pumped by the pump 90 to the condenser 91 as a coolant, it heats there, then cools the exiting already condensed liquid in the heat exchanger 92, it heats continuously and enters the evaporator 93. From here the pump 94 passes through the heat exchanger 95 where it heats the active liquid. further to the evaporator 96. Here it evaporates under the action of heat introduced from outside, for example steam coming through the pipe connection 97. The steam condensate escapes via the pipe connection 20 67758 98. The steam generated in evaporator 96 boils the dilute liquid in evaporator 93. The condensed active liquid enters the heat exchanger 95 via the line 99, then the heat exchanger 92 and exits via the pipe connection 100 towards the dryer body, for example the pipe connection 67 in Fig. 6. , where it heats the diluted liquid, and the pump 103 removes the condensed distillate as well as the non-condensed gases.

Figure 10 shows a wiring diagram of another embodiment of a regenerator, in which the heat generated by the condensation of the steam removed from the liquid by expansion evaporation only heats the liquid to be regenerated, but does not cause it to boil. This Rege aerator is a multi-stage expansion evaporator.

The diluted liquid is forced through the condensers 112, 113 and 114 by a pump 111. As it leaves the condenser 114, the liquid passes through the choke 115. The pump 111 and the choke 115 are arranged so that the pressure of the liquid as it passes through the condensers 112, 113 and 114 is higher all the way than the saturation pressure, so that no evaporation occurs at any point. In the condensers 112, 113 and 114, the temperature of the diluted liquid acting as a coolant rises. After the choke 115, steam separates from the liquid in the evaporator 116 without heat transfer. This steam condenses in the condenser 113. The liquid enters the evaporator 117, where it is separated by more steam which condenses in the condenser 112. The remaining condensed, active liquid is conveyed by the pump 118 back to the dryer body, for example to pipe connection 67 in 112, where gas is separated from it. Pump 120 pumps out distillate and non-condensable gases.

In the condenser 114, the diluted, regenerable liquid must be heated by external heat, for example steam, which is taken in via the pipe connection 121 and the steam condensate is discharged through the pipe connection 122.

From the point of view of monitoring the regenerator equipment, it is important to modify the embodiments described above so that only a part of the diluted drying liquid is concentrated and the other part is mixed with the concentrated part. This mixture must be used as an active drying liquid in the dryer body.

To simplify the description of the above embodiment, only two evaporators, i.e. stages, were presented, but of course it is possible and recommended from the point of view of energy efficiency to use several stages.

It can be seen from Figure 10 that if the excess steam generated in the regenerator cannot be used in the dryer body or if the heat losses of the imaging body are small (e.g. in summer), the drying liquid regeneration system must be balanced. Figure 10 shows two suitable solutions that can be used separately, but also together. According to the first solution, the condenser 112 must be provided with an external coolant, for example cooling water, and an additional cooling surface, for example a pipe coil. The latter can be placed in a separate jacket, in which case the steam spaces must be connected by pipelines. For example, the cooling water may enter the heat exchanger through the pipe connection 123 and exit through the pipe connection 124. According to another solution, the diluted liquid entering the condenser 112 is precooled in a heat exchanger 127, which is cooled by a substance, for example water, coming from the pipe connection 125 and leaving through the pipe connection 126.

These two solutions can also be used in the embodiments according to Figures 7, 8 and 9. In this case, the additional cooled condenser of Fig. 10 corresponds to condenser 29 in Fig. 7, condenser 81 in Fig. 8 and condenser 91 in Fig. 9. Heat exchanger 127 in Fig. 10 must be placed between condensers 29, 71 and 91 and pumps 28, 70 and 90 in Figs. 7, 8 and 9, respectively. is placed in the water of said condensers.

Because various modifications may be made to the embodiments set forth herein without departing from the spirit of the invention, it is to be understood that all aspects set forth or illustrated herein are to be construed as illustrative and not restrictive.

Claims (31)

A method of drying products, wherein a product (2, 50) to be dried is introduced into a drying chamber (25, 40), a drying gas stream (64) is circulated in a substantially closed path continuously so that the drying gas stream (64) passes the product (2, 50) to be dried and contacted with at least one layer (1, 41) of desiccant liquid to remove moisture from the gas, the desiccant liquid being regenerated by circulating at least a portion thereof through a regenerator (150 ) for removing moisture from the desiccant liquid, wherein at least one layer of desiccant liquid (1, 41) is disposed substantially perpendicular to the flow direction of the drying gas stream (64), characterized in that the layer (s) of desiccant liquid ( (25, 40) or substantially at the drying chamber. 2. A method according to claim 1, characterized in that at least one layer (1) of desiccant liquid is a substantially horizontal liquid layer and that the dry gas stream (64) is allowed to bubble through this layer. 3. A method according to claim 1, characterized in that at least one layer (41) of desiccant liquid is provided by the desiccant liquid flowing on liquid film-conducting elements (58A, 58B, 58C) arranged in a plurality of vertical pipes, and the contact is made to stand by conducting the dry gas stream (64) over or between the liquid film conducting elements (58, 58A, 58B, 58c). Method according to one of claims 1-3, characterized in that the product (2, 50) to be dried is moved during the drying process in, through and from the drying chamber (25, 40), and that between the desiccant liquid (1, 41) circulated through the regenerator (150) and the product (2, 50) to be dried, a continuous heat transfer is achieved by transferring the dry gas stream (64) from the desiccant liquid (1, 41) to the product (2, 50) to be dried. 5. A process according to claim 4, characterized in that the heat transfer occurs by heating the desiccant liquid (1, 41) during the regeneration, such that the drying gas (64) is heated to a predetermined temperature by contact with the desiccant liquid (1, 41) during the gas circulation. 6. A method according to claim 5, characterized in that the predetermined temperature of the drying gas (64) is at least 40 ° C. 29 67758 7. A process according to any one of claims 1-6, characterized in that the desiccant liquid (1, 41) is a desiccant solution, the regeneration being carried out by evaporation of the desiccant solution (1, 41) and evaporating the excess acid. from the desiccant solution is at least partially condensed by the desiccant solution to be regenerated. Process according to claim 7, characterized in that the evaporation is carried out by a multi-stage evaporator and that the evaporator during the first boiling of the desiccant solution (1, 41) is at least partially condensed by the incoming desiccant solution (1, 41) to be regenerated (Fig. 8). . 9. A process according to claim 7, characterized in that the evaporation is carried out by means of a multi-stage evaporator and that the steam evaporated during the last boiling of the desiccant solution (1, 41) is at least partially condensed by the incoming desiccant solution (1, 41) to be regenerated (Figure 9). . 10. A method according to claim 7, characterized in that the evaporation is carried out by a multi-step expansion evaporation. Method according to any of claims 7-10, characterized in that the desiccant solution (1, 41) is cooled after the contact and prior to regeneration, depending on the cooling of the desiccant solution (1, 41) during the contact, so that the incoming desiccant solution (1, 41) to be regenerated reaches a predetermined temperature. Method according to any one of claims 1-11, characterized in that a continuous circulation of the dry gas stream (64) is effected by passing the dry gas stream along a distance in the drying chamber (25, 40) between the product (2, 50) to be dried. and the desiccant liquid (1, 41) say that the ratio between the maximum and minimum velocities of the dry gas stream (64) along this distance is less than 5: 1 and the change in the flow direction of the dry gas stream (64) is less than 30 °. 13. A method according to claim 12, characterized in that the drying gas stream (64) within the drying chamber (25, 40.) is passed between the product (2, 50) to be dried and the desiccant liquid (1, 41) substantially without change in speed and direction. Process according to any of claims 1-13, characterized in that the desiccant solution is an aqueous solution of calcium chloride and that the desiccant gas is air. 30 67758 15. A method according to any one of claims 1 to 14, characterized in that the drying gas stream (64) consists of an ethereal tone two parallel partial gas streams. that the product (2, 50) to be dried is moved transversely to the partial gas streams and that each partial gas stream is separately contacted with a desiccant liquid (1, 41) of specific concentration and temperature. 16. A method according to claim 15, characterized in that each partial gas stream is contacted with a desiccant liquid which is more concentrated than the desiccant liquid (1, 41) which contacts the preceding gas stream in the relative direction of movement of the product (2, 50). ) to be dried. 17. A method according to claim 15 or 16, characterized in that at least two separate liquid film modules (48A, 48B, 48C) with desiccant films of different concentration are used, whereby the liquid film modules with desiccant films are arranged side by side in the path of the partial gas streams. that each partial gas stream (64) is contacted with its own liquid film module or its own liquid film modules provided with desiccant liquid films. 18. A method according to claim 17, characterized in that each liquid film module (eg 48A) with desiccant film is provided with a separate liquid circulation device (60A), the circulating device of the liquid film module (eg 48C) being the last in relation to the direction of movement of the product (50) to be dried measured with the regenerating desiccant liquid (41) coming from the regenerator (150), that the circulation device of each preceding liquid film module (e.g. 48B) is measured with overflow from the circulating device of the subsequent 48 ) and that the overflow from the circulation device of the first liquid film module (48A) is conducted to the regenerator (150). Apparatus for drying products, which apparatus comprises at least one drying chamber (25, 40) for the product (2, 50) to be dried, at least one contact device (43) having means (13, 58) for generating at least one layers (1, 41) of desiccant liquid for contact with a drying gas stream (64) for removing moisture from the gas, gas conducting device (12, 16, 18B, 49, 54, 65) for conducting the drying gas stream (64) in a substantially closed path through the contact device (43) or each contact device and through the drying chamber (25, 40), wherein the desiccant liquid layer (1, 41) or each desiccant-liquid layer is disposed substantially perpendicular to the direction of flow of the gas stream (64), gas circulation means 66, 17A, 17B, 17C, 17D) through which drying gas trominate (64) is circulated along the closed path, a regenerator (150) for removing moisture from the desiccant liquid (1, 41) and a liquid circulation device (36, 141) for circulation of at least part of the drying liquid (1, 41) through the regenerator (150) and through the contact device (s) (43), characterized in that the contact device (43) or devices are in the drying chamber (25, 40) or substantially at the drying chamber. 20. Apparatus according to claim 19, characterized in that the contact device (43) or devices has a receptacle (13) for generating a substantially horizontal layer (1) of desiccant liquid, the vessel (13) having bubbling caps (20) on its wall. for bubbling the dry gas stream (64) through this liquid layer (1) and connected to the liquid circulation device (36) such that the desiccant liquid flows along the vessel (13), the drying chamber (25) being arranged above or below the vessel (13). Apparatus according to claim 20, characterized in that the drying chamber (25) has a device (4) for transporting the product (2) to be dried through the drying chamber (25), the transport device (4) having apertures (5) for passing through the drying gas stream, which, however, does not allow the product (2) to be dried to fall out. 22. Apparatus according to claim 21, characterized in that the conveying device is an endless belt conveyor (4) and that the gas circulating means consist of fans (17A, 17B, 17C, 17C) placed side by side along the belt conveyor (4). 23. Apparatus according to claim 19, characterized in that the contact device (43) or devices has liquid film conducting elements (58) arranged in a plurality of substantially vertical pipes which run substantially vertically in relation to the flow direction of the dry gas stream (64). Apparatus according to claim 23, characterized in that the contact device (43) or devices has a vessel (55) for receiving and storing incoming desiccant liquid, at least one overflow (56) for conducting the liquid in film form out of the vessel (55). and liquid dispensing device having at least one distributing surface (57) coupled to at least one overflow (56) and facing downwards, and liquid outlet means (62) and providing the 32 6 7 7 5 8 film-conducting elements (58) between the liquid distribution surface (57) and the liquid outlet means (62) such that the liquid films (41) are conducted from the distribution surface (57) into the outlet means (62). Apparatus according to claim 23 or 24, characterized in that the apparatus further comprises a bottom floor (49), a roof shell (65) and an intermediate roof (54) provided with openings (47, 47A) for penetration. of the dry gas stream and lying between the bottom floor (49) and the roof shell (65), that the drying chamber (40) lies between the bottom floor (49) and the intermediate roof (54), that the gas circulating means are fans (66, 66 ') placed between the intermediate roof (54) and the roof shell (65), wherein the contact device (s) (43) is arranged in the drying chamber (40) or substantially at the drying chamber such that the substantially vertical webs where the liquid film conducting elements (58, 58A, 58B, 58C) are located themselves, extending between the bottom floor (49) and the intermediate roof (54). Apparatus according to any one of claims 23-25, characterized in that at least one contact device (43) has at least two liquid film modules (48A, 48B, 48C) next to each other, each liquid film module (e.g. 48A) having its own liquid film conductor. elements (e.g., 58A) and their own liquid circulation device (e.g., 60A, 71A), which produces a fluid flow circuit for forming the liquid films on their own liquid film conducting elements, that the liquid film modules (48A, 48B, 48C) are provided with a a common liquid channel (62) which joins the liquid circulation devices with each other, whereby the common liquid channel (62) is coupled to the liquid circulation means (e.g. 36), and the gas circulation means (66, 66 ', 17A, 17B, 17C, 17D) are arranged so that at least two parallel partial gas streams circulate so that each partial gas stream passes at least one separate liquid film module (48A, 48B, 48C). Apparatus according to any one of claims 19-26, characterized in that the respective ratio of two flow cross sections of the gas conducting means (37, 38, 49, 54) in the drying chamber (40) between the product (50) which is to be dried and at least one contact device (43) is between 0.2 and 5, and the contact device (43) or devices are arranged in the drying chamber (40) or substantially at the drying chamber so that it is between the product (50) to be