DE102014012418B4 - Apparatus and method for drying - Google Patents

Abstract

A device is proposed for drying a moist air stream, comprising at least one inlet valve (16) and one outlet valve (18) and at least one space for an adsorptive desiccant (26), the device (14) via an inlet opening (17) with a container (10) is designed to be connectable to a medium (12) and wherein the device (14) has a hygroscopically impregnated device (24). The device formed as a hygroscopically impregnated disc (24) in this case has a carrier, which is impregnated with a hygroscopic material.

Description

The invention relates to a device and a method for drying a moist air stream.

State of the art

Hygroscopic substances such as hydraulic oils, chemicals and fuels are usually stored in tanks which are in equilibrium with and in contact with the surrounding air. The airborne moisture in the form of atmospheric moisture can contaminate the fabric and cause lasting damage when it enters this tank.

For example, hydraulic oil may contaminate the air due to contamination with atmospheric moisture. This results in a deterioration of the lubricity and wear protection by decomposition of additives result. In addition, it can destroy seals due to hydrolysis and promote the corrosion of metal parts. Furthermore, atmospheric moisture, for example, in contact with isocyanates leads to their crystallization. This can lead to the destruction of a polyurethane plant. In the field of fuels, for example, biofuels and algae are formed in biological fuels and thus lead to a considerable loss of quality of the fuel.

The air flowing into containers for such substances must therefore be dry, so that no moisture can penetrate into the container.

In order to prevent the entry of humidity in the above systems, such devices are already known. Ventilation dryers or dehumidifiers are mounted on the ventilation openings of the tank. The air flowing through these devices is dried by adsorption.

In this case, a drying agent, such as silica gel, is used, with which a container is filled. The air flowing through the container is dried by means of the adsorbing effects of the desiccant. The further air flowing through is cleaned by a filter element.

The DE 10031004 B4 describes a device that supplies a system with adsorptively dried air. The desiccant also contained with a container is protected by means of inlet and outlet valves from the desiccant being unnecessarily in contact with and being charged with the humid ambient air. In this case, valves are arranged so that air can flow through the desiccant in and out of the system.

In the DE 10 2009 049 546 A1 a device for drying a media stream is described. The device has at least two desiccant and inlet and outlet valves. A first desiccant for high and a second desiccant for low humidities is used successively to achieve a better drying performance. In addition, inlet valves are used to prevent unnecessary contact of the desiccants with the environment. The outlet valve controls the exhaust air in front of the desiccants into the environment and thus has the effect of a bypass.

The WO 2007/133403 discloses a "Filter medium and breather filter structure". Thermoplastic bicomponent conjugate fibers may be combined with other media, fibers, and other filter components to form a thermally bonded filter medium. This filter medium can be used in filter units such as breather caps. These filter units are placed in the flow of mobile fluid, such as air, gas or liquid, and can trap particulate matter and / or hazy portions of the mobile stream.

The US 2008/0193704 discloses a protective function of an adsorbent film for organic EL devices used in displays and light sources wherein the adsorbent film is configured to receive water from the environment and also to absorb gases formed in or through the device so that the life of the displays and bulbs can be increased. The adsorbent film for this purpose has a first moisture adsorbing layer on which a chemically adsorbing desiccant and a second moisture adsorbing layer comprising a physically adsorbing desiccant.

In the US 5,575,832 A describes a device that dries moist incoming air through the use of a regenerable, hygroscopic-impregnated filter. The ambient air flowing through an inlet is passed through a filter material, so that dirt particles are deposited. Furthermore, a hygroscopic substance absorbs the humidity. The cyclically outgoing exhaust air regenerates the substance again.

For drying so devices are used, the at least one drying agent, eg. As silica gel or molecular sieve, to dry moist volume flows. Due to the particular structure of the housing, the moist air flow is passed through the bed and the water is removed from this.

A disadvantage of the known devices is that due to the limited capacity of the drying agent (silica gel about 40% and molecular sieve about 25%) the useful life is low without a regeneration of the drying agent.

Even if a regeneration takes place, the use of the hygroscopic substance without a drying agent is only conditionally suitable for drying humid air streams. The binding forces and the absolute water absorption capacity are thus limited, since a continuous loading of the hygroscopic substances takes place. This results in a short period of use and the lack of regeneration by the exhaust air flow, since it can flow moist into the system.

The object of the invention is therefore to provide an apparatus and a method that allow a longer useful life of the drying agent used and a higher drying performance.

Disclosure of the invention

A device and method for drying a moist air stream by a combination of adsorptive desiccants and hygroscopic substances is disclosed.

For this purpose, the adsorptive drying agent is combined with a hygroscopically impregnated device, in particular designed as a disk. This results in better drying performance than when using hygroscopic substances without desiccant. The dry exhaust air stream is used to regenerate the desiccants used.

The drying agent is for example silica gel or molecular sieve and the hygroscopically impregnated device is made of hygroscopic substances, or a mixture thereof, optionally provided with a binder, on a carrier material. In this case, the hygroscopic substance is arranged on the disc in the flow direction before the drying agent, so that the moist air flow must first flow through the impregnated disc and then impinges on the drying agent and flows through it.

Desiccants are generally substances that extract water or other solvents. The water can be either chemically bound, for example when using sulfuric acid, calcium chloride or phosphorus pentoxide, or the drying can be carried out by adsorption, such as in molecular sieves or bentonite. Desiccants are used in the industry to dry materials during production to protect end products from unwanted soaking, or as a chemical against physical release or condensation. This serves the longevity of a product, as it also corrosion and undesirable surface changes of a material can be avoided.

Often, chemical compounds having a particularly internal structure are used as drying agents. Such means are for. As silica gel or zeolites. In organic chemical laboratories, anhydrous sodium sulfate or magnesium sulfate is often used as the drying agent. These include water molecules due to their chemical and structural nature, and subsequently change their spatial molecular structure through intermolecular forces. Water molecules can no longer escape from the structure and remain bound.

Other commonly used drying agents are: alumina (regenerable) calcium, calcium hydride, calcium sulfate (regenerable), potassium carbonate (regenerable), potassium hydride, copper sulfate, lithium aluminum hydride or sodium hydroxide.

For example, by the action of heat, some of these desiccants can be regenerated, the bound water is thus expelled, and the desiccant is reusable.

The usable in the device according to the invention silica gel, silica gel or silica gel is an amorphous silica of gel-like, rubbery to solid consistency and is colorless. It has a large inner surface. It is highly hygroscopic (water-attracting) and is suitable as a gelling agent, filter, adsorbent and desiccant. One counts it to the xerogels.

The molecular sieve (or also short molecular sieve) which can likewise be used in the device according to the invention is the functional name for natural and synthetic zeolites or other substances which have a strong adsorption capacity for gases, vapors and solutes with specific molecular sizes. By a suitable choice of the molecular sieve, it is possible to separate molecules of different sizes. In addition to zeolites, there are also carbon molecular sieves.

The molecular sieves have a large internal surface area (600-700 m ² / g) and have uniform pore diameters which are on the order of the diameters of molecules. Depending on the pore size, the adsorption capacity of the material varies.

The ratio between the desiccant and the hygroscopic substance of the hygroscopically impregnated disc in the device according to the invention is determined according to the plant and environmental conditions, but is always designed in favor of the desiccant. For example, under standard conditions, a 15 to 25 mm thick, impregnated disk is used together with 500 to 800 g desiccant.

In order to obtain a good and uniform loading of the hygroscopic substance of the disk impregnated therewith and thus a good air drying, the apparatus in one embodiment of the invention has uniformly distributed inlet openings. In this case, an antechamber is arranged, in which the incoming air flow can be distributed, thereby impinge on the inlet openings uniformly on the impregnated disc and enter into this.

The device according to the invention has the advantage that in this way a good, uniform loading of the hygroscopic substances of the disc is achieved.

Due to the hygroscopic properties of the desiccant and the impregnated disc, these components must be protected from unnecessary loading with atmospheric moisture. In many systems, the air exchange is replete in recurrent and regular intervals. Between these phases, the substances used must not be in contact with the ambient air, otherwise they will be laden with humidity and lose their drying performance. For this reason, intake and exhaust valves are arranged according to the invention. The device has at least in inlet and at least one outlet valve. The valves ensure that there is no exchange between the interior of the device and the environment, as long as no active air exchange of the entire system is needed.

The arrangement of the valves in the device takes place in such a way that the inlet flow (supply air) and the outlet air flow (exhaust air) flow through the entire device.

The drying agent used in the device has adsorptive properties and absorbs the humidity due to the polar surface attractive forces. The binding forces can be resolved by increasing the temperature or changing the partial pressure of water vapor. A desiccant such as silica gel can be at least partially regenerated under normal conditions. The desiccant is generally capable of reversibly adsorbing water. The drying agent is present, for example, in the form of beads. A bead shape of the individual particles allows optimal passage of the moist process air without the formation of channels. A uniform Karngrößenverteilung at high bulk density contributes to this. In addition, abrasion is very small in a bead form of the individual particles.

The used carrier material of the impregnated disc can be, for example but not limited to, an open-pore foam which is punched out in particular in the form of a disc. The size of the pores is selected according to the requirements of the plant, since then determines the resulting pressure build-up in the operating process. A hygroscopic mixture of suitable substances is applied to the substrate of the disc or the disc immersed therein and ends with the drying of the discs in the oven. In this way, when used in dry, crystalline form, the hygroscopic mixture is applied to the pores of the support material. As a result, an enlarged surface is created in order to bind the water particles of the incoming air through the contact with the substance.

Hygroscopic substances or a mixture of hygroscopic substances such as, for example, magnesium sulfate, lithium chloride or calcium chloride are used to impregnate the pane. These substances are then mixed or individually blended with hygroscopic binders such as polyvinylpyrrolidone to prevent early liquefaction upon ingestion.

Magnesium sulfate is a colorless, odorless, highly hygroscopic solid with a bitter taste. There are several hydrates, the most important being the magnesium sulfate heptahydrate MgSO ₄ .7H ₂ O.

Calcium chloride is a chloride of the alkaline earth metal calcium with the molecular formula CaCl ₂ . Calcium chloride forms colorless crystals in pure form and is strongly hygroscopic in the anhydrous state. It easily absorbs water from the environment, forming a hydrate complex. Anhydrous calcium chloride is due to its hygroscopy an important desiccant in the laboratory, for example in the desiccator, and in the technical chemistry of gases and liquids.

Lithium chloride LiCl, the lithium salt of hydrochloric acid, forms colorless, highly hygroscopic crystals. In addition to the anhydrous lithium chloride, various hydrates still exist. Lithium chloride solutions are highly hygroscopic. They reduce the water vapor pressure by approx. 90%. Out In aqueous solutions, anhydrous lithium chloride crystallizes only at temperatures above 98 ° C. At lower temperatures you get one of the hydrate forms. The solubility in water is about 450 g LiCl / kg solution.

Furthermore, a hygroscopic binder can be used, for example polyvinylpyrrolidone. Polyvinylpyrrolidone (PVP), also polyvidone or povidone, is a polymer of the compound vinylpyrrolidone. PVP is a hygroscopic, amorphous powder with a white to light yellow color.

A mixture of said hygroscopic substances such as magnesium sulfate, lithium chloride or calcium dichloride with the hygroscopic binder polyvinylpyrrolidone has been found to be suitable for the impregnation of the above-described disk of the already described support material. However, this does not exclude the mixture of other suitable ingredients or the use of another suitable carrier material.

The moist supply air flow from the environment passes through the inlet valve into the antechamber, distributes itself and flows uniformly through the inlet openings into the impregnated, hygroscopically impregnated pane or through it. Thereafter, the supply air flow through the drying agent and then into the system, so for example a tank.

By using the impregnated pane, the moist supply air flow can be dried from, for example, 80% relative humidity to 40% relative humidity. The remaining water content in the supply air is dried as it flows through the desiccant.

The amount of salt mixtures and the drying agent can be varied depending on the conditions of the system and the performance adjustable.

The exhaust air flowing out of the system is discharged into the environment through the device via the outlet valve. The dry exhaust air flows opposite to the supply air flow through the desiccant and the hygroscopic disk, which are thereby regenerated.

The method according to the invention has the advantage that to prolong the useful life of the device, the drying agent used and the hygroscopically impregnated disc are regenerated by the dry exhaust air. Due to the binding forces of the hygroscopic substances, a very large proportion of the bound water can be removed with each exhaust air stream. Because the binding forces of the hygroscopic substances to water are less than the binding forces of the desiccant, the substance can be regenerated more easily after being loaded with water than the desiccant.

Further advantages and advantageous embodiments of the invention are the following description of the figures, the drawings and the claims removed.

An exemplary embodiment of the solution according to the invention will be explained in more detail below with reference to the attached schematic drawings. It shows:

1 shows schematically a system with a container with its contents and a device arranged thereon for drying in flowing supply air,

2 schematically shows the plant with the device for drying after 1 with exhaust air,

3 Fig. 3 illustrates the apparatus for drying in a suspended arrangement with incoming humid air in the adsorption or air drying phase,

4 indicates the air flow in the device for drying 3 in the hanging position during the regeneration of the device,

5 shows the device for drying with incoming moist air in another embodiment with an inner tube and

6 indicates the device for drying 5 during the exhaust phase of the process in training with the inner tube.

In 1 is a plant for air drying 100 shown. There is a container 10 with a particular liquid medium 12 almost half filled in this embodiment. The fluid level drops, creating a vacuum that starts the process.

On the container 10 is a device for drying 14 arranged. This has at least one inlet valve 16 and at least one exhaust valve 18 on. The medium 12 in the plant 100 decreases, it creates a negative pressure. The air is drawn in from the environment, this is, so to speak, an "inhalation" of the supply air. The air 20 represented by arrows, flows through the at the bottom 22 the device for drying 14 arranged inlet valve 16 in an anteroom 19 one. After that, the air flows through 20 a hygroscopic impregnated disc 24 ,

The used carrier material of the disc 24 may be an open-cell foam, in the form of the disc 24 is punched out. The size of the pores will vary depending on the requirement of the plant 100 selected, since then determines the resulting pressure build-up in the operating process. The application of the hygroscopic mixture to the substrate of the disc 24 ends with the drying of the disc 24 in the drying cabinet. In this way, when used in dry, crystalline form, the hygroscopic mixture is applied to the pores of the support material. As a result, an enlarged surface is created in order to bind the water particles of the incoming air through the contact with the substance.

The impregnating agent can be prepared from salt hydrates or mixtures thereof. In this case, for example, magnesium sulfate heptahydrate and / or calcium chloride dihydrate can be dissolved in a certain composition in distilled water and used alone or mixed in this mixture or in particular with a binder, for example polyvinylpyrrolidone, wherein the disc 24 made of foam is immersed therein or wetted with the salt hydrate mixture. Subsequently, the disc 24 dried in an oven at about 98 ° C. But it can also other suitable substances for impregnation of the disc 24 are used insofar as they have sufficient hygroscopic properties and can be applied well to the substrate.

By using the impregnated disc 24 For example, the moist supply air flow can be dried from 80% relative humidity to 40% relative humidity.

After passing through the air through the air 24 the pre-dried air flows into a room with desiccant 26 , The remaining water content in the supply air is thereby flowing through the desiccant 26 dried. The airflow is then in the container 10 with the medium 12 directed. For this purpose, the air flow flows through an opening 17 , This is done via a connection piece 28 that the device for drying 14 with the container 10 combines.

2 shows the plant 100 with the device for drying 14 to 1 at exhaust air. The air 20 flows in the direction of the arrows. The medium 12 in the plant 100 rises, it creates an overpressure in the container 10 , The air 20 is expressed in the environment, there is an "exhalation" of the exhaust air.

This is the air flow 20 in the opposite direction as in 1 represented by the device for drying 14 pushed out. The exhaust air flows through the device 14 , The dry air regenerates the desiccant in the area 26 at least in large part. The hygroscopically impregnated disc 24 is also regenerated, but this almost completely. The moist air is released into the environment.

3 provides the device for drying 14 in a suspended arrangement with incoming moist air in the adsorption or air drying phase. The inlet valve 16 and the exhaust valve 18 are especially important to the hygroscopically impregnated disc 24 to protect against unnecessary loading during downtime. Between the inlet valve 16 and the impregnated disc 24 is an entrance hall 19 educated. This anteroom 19 has inlet openings 21 on, through which the air flow is well distributed us thus on the impregnated disk 24 meets.

As a drying agent in the range 26 For example, silica gel can be used. The drying agent is in particular spherical or pearl-shaped.

In an upper area of the device for drying 14 can be an oil separator 30 be arranged. This oil separator 30 does not have to have any hygroscopic properties and can be designed as a disk to absorb oil vapor to protect the desiccant. The oil separator element 30 may also be formed in another embodiment and is not limited to a training as a disc.

The airflow 20 flows through an outlet opening 17 over the connection piece 28 in a container. The connection piece 28 is in this illustration at the top of the device for drying 14 arranged because it is a hanging execution.

The moist air flows through the hygroscopically impregnated disk in advance 24 and is dried to a certain residual moisture. The residual moisture flows through the desiccant in the range 26 and the air is dried there to a minimum value.

In the device 14 can be a filter element 32 be arranged integrated.

In 4 to 3 is the airflow 20 in the device for drying 14 shown in a hanging arrangement with supply air during the regeneration or exhaust phase. At the same time the opening opens 17 that over the connector 28 connected to a container, in case of overpressure in the container. The moist air flows through the inlet opening 17 , the desiccant in the range 26 and the hygroscopically impregnated disc 24 and flows through the vestibule 19 over the opened outlet valve 18 out. The dry air regenerates the desiccant in the room 26 and especially the hygroscopically impregnated disc 24 , The humid air is carried into the environment.

In 5 is the airflow 20 in the device for drying 14 shown in a standing training during the adsorption phase. The inlet valve opens 16 at low pressure in the container, otherwise it acts as a protection against the surrounding air. The moist air flows through the hygroscopically impregnated disk 24 and is dried to a certain residual moisture. The residual moisture flows through the desiccant in the area 26 and the air is dried there to a minimum value.

In the filter element 32 The air is freed from any remaining particles. Through an inner tube 34 the air flows through the opening 17 in the container. The inner tube 34 serves the diversion of the air flow 20 to a connector 28 to the next container. Especially in the upright position comes this inner tube 34 used because the valves 16 . 18 on the bottom 22 the device for drying 14 are arranged to be protected from the weather, especially rain.

The connection piece 28 is for mounting on the system 100 suitably trained.

In 6 to 5 is the airflow 20 in the device for drying 14 in standing training with supply air during the regeneration or exhaust phase shown. At the same time the opening opens 17 and the exhaust valve 18 at overpressure in the container. The humid air flows through the connection piece 28 , the inner tube 34 , the filter 32 , the desiccant in the range 26 and the hygroscopically impregnated disc 24 and flows through the vestibule 19 via the outlet valve 18 out. The dry air regenerates the desiccant in the room 26 to a large extent and especially the hygroscopically impregnated disk 24 almost complete. The humid air is carried into the environment.

All in the description, the following claims and the drawings illustrated features may be essential to the invention both individually and in any combination.

LIST OF REFERENCE NUMBERS

10

container

12

medium

14

Device for drying

16

intake valve

17

opening

18

outlet valve

19

anteroom

20

airflow

21

inlets

22

bottom

24

hygroscopic impregnated disc

26

Room with desiccant

28

connector

30

oil separating

32

filter element

34

inner tube

100

Plant for air drying

Claims (20)

Contraption ( 14 ) for drying a moist air stream, comprising at least one inlet valve ( 16 ) and an outlet valve ( 18 ) and at least one space for an adsorptive desiccant ( 26 ), the device ( 14 ) at least one opening ( 17 ) and with a container ( 10 ) for a medium ( 12 ) via a connecting piece ( 28 ) is connectable and wherein the opening ( 17 ) between the space for the adsorbent drying agent ( 26 ) and the container ( 10 ), characterized in that the device ( 14 ) one in the flow direction of the moist air flow in front of the space for the adsorbent drying agent ( 26 ) hygroscopically impregnated device ( 24 ) having. Contraption ( 14 ) according to claim 1, characterized in that the hygroscopically impregnated device ( 24 ) as a disk ( 24 ) is formed and comprises a carrier, which is impregnated with a hygroscopic material. Contraption ( 14 ) according to claim 2, characterized in that the carrier is formed of an open-pore material. Contraption ( 14 ) according to claim 3, characterized in that the carrier material is formed from foam. Contraption ( 14 ) according to one of claims 2 to 4, characterized in that the hygroscopic material for impregnating the device ( 24 ) is a salt hydrate or a mixture of salt hydrates. Contraption ( 14 ) according to claim 5, characterized in that the hygroscopic material are mixed individually or in combination with each other with a hygroscopic binder. Contraption ( 14 ) according to claim 6, characterized in that the hygroscopic binder is polyvinylpyrrolidone. Contraption ( 14 ) according to one of the preceding claims, characterized in that the hygroscopically impregnated device ( 24 ) Is formed 15 to 25 mm thick. Contraption ( 14 ) according to one of the preceding claims, characterized in that the device has an anteroom ( 19 ) as well as inlet openings ( 21 ), the distribution of incoming humid air before impacting the hygroscopically impregnated device ( 24 ) serve. Contraption ( 14 ) according to one of the preceding claims, characterized in that an inner tube ( 34 ) within the space for the adsorptive desiccant ( 26 ) is arranged such that the inner tube ( 34 ) via the connector ( 28 ) with the container ( 10 ) is formed connected Contraption ( 14 ) according to one of the preceding claims, characterized in that the device ( 14 ) an oil separation element ( 30 ) having. Method for drying a moist air stream, comprising the following steps: opening an inlet valve ( 16 ) a device for drying ( 14 ) at negative pressure in a container ( 10 ) • inflow of moist air into the device ( 14 ) • flow through a hygroscopically impregnated device ( 24 ), thereby drying the air stream ( 20 ) • passing through a room with adsorptive desiccant ( 26 ), thereby drying the residual moisture • outflow of the dry air stream ( 20 ) through an opening ( 17 ) into a container ( 10 ) A method according to claim 12, characterized in that the moist air in an antechamber ( 19 ), wherein the moist air through inlet openings ( 21 ) and distributed before being applied to the hygroscopically impregnated device ( 24 ). Method according to one of claims 12 or 13, characterized in that the air flow ( 20 ) before flowing out a filter element ( 32 ) flows through to remove particles. Method according to one of claims 12 to 14, characterized in that the outflow of the air stream ( 20 ) through an inner tube ( 34 ) via a connecting piece ( 28 ) into a container ( 10 ) with a medium ( 12 ) he follows. Method according to one of claims 12 to 15, characterized in that the air flow ( 20 ) after flowing through the space with the adsorptive desiccant ( 26 ) an area with an oil separation element ( 36 ) flows through. Method according to one of claims 12 to 16, characterized in that for the regeneration of a device ( 14 ) are carried out according to one of claims 1 to 11, the following method steps: • opening the exhaust valve ( 18 ) at overpressure due to increase in the medium ( 12 ) in the container ( 10 ) • the dry exhaust air flows through the opening ( 17 ) into the device ( 14 ) • passing the dry exhaust air through the device ( 14 ) • Regenerating the adsorptive desiccant in the room ( 26 ) • regeneration of the hygroscopically impregnated device ( 24 ) • Outflow of humidified exhaust air through the outlet valve ( 18 ) in the nearby areas. A method according to claim 17, characterized in that (after opening of the exhaust valve 18 ) the exhaust air through the connector ( 28 ) through the inner tube ( 34 ) flows. Method according to one of the preceding claims 17 or 18, characterized in that the regeneration of the drying agent in the room ( 26 ) as well as the hydroscopically impregnated device ( 24 ) by discharging water to the exhaust air. Use of the device ( 14 ) according to one of claims 1 to 11 in an annex ( 100 ) with at least one container ( 10 ).

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