DE1719577A1 - Drying cartridge - Google Patents

Description

Kali-Chemie Hanover, January 9, 1967

Aktiengesellschaft MH / No.

Patent application

Drying cartridge

Keeping the refrigerants used as working fluids in the Chillers are used, in particular the chlorofluorocarbons, is of crucial importance for the continuous operation of the chillers. The moisture can in the coolant circuit cause serious malfunctions, either through clogging of the expansion valve, or through hydrolysis of the refrigerant under Formation of corrosive acids.

Can be used as a desiccant for installation in the refrigerant circuit In addition to calcium sulfate and active aluminum oxide, mainly silica gels are used. The desiccants come in as solid and as possible granular form for use, but a certain amount of abrasion and dust can never be completely avoided when the desiccant is in the cooling unit the flowing cold liquid and the mechanical vibrations are exposed. Part of this abrasion gets into the coolant and impairs its effectiveness. He can also J5U blockages in valves and other restrictions

The desiccants are therefore usually combined with the help of suitable binders to form larger shaped bodies, which are installed as a whole in a suitable flow-through vessel in the refrigerant circuit. Even with silica gel and also with most of them today

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Used silica gel beads, dust and abrasion cannot be completely avoided despite their great hardness, so that one has to do this goes over to bind silica gel of small grain size with a suitable binder to form moldings. You get up In this way, by using small silica gel grains of approx. 1 mm, drying cartridges are quite compact and have relatively small dimensions, which can also be installed in a relatively simple manner; they also have the advantage that no fine dust and abrasion occur more.

The binding agent for the production of such a drying cartridge must have good binding strength for the drying agent meet the following conditions:

1.) The water absorption capacity of the desiccant may be reduced by the Binders are not reduced so that a high level of operational reliability of the refrigeration system is guaranteed,

2.) The binding agent must be resistant to swelling or dissolution by the refrigerant.

3.) The permeability for the liquid refrigerant must be given, i.e. the flow resistance should remain as low as possible.

It has now been found that these requirements are met when an ethoxylin resin is used as a binder. For every 100 g of desiccant, only approx. 0.3 - 5 g of binder are required to achieve an excellent Maintain bond strength, good permeability and drying capacity. In addition, the ethoxylin resin is not from the Attacked refrigerants. Since it is resistant to a wide variety of organic liquids, such cartridges can also can be used for other drying purposes.

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Various binders have already been proposed for the production of moldings from desiccants, but they have not produced "satisfactory results. For example, large proportions by weight of thermoplastics such as polyvinyl chloride and polyethylene are required in order to achieve a reasonably satisfactory strength. Other polymers, too," such as polyvinyl acetates and Polyvinylather, proved to be just as unsuitable as a larger number of phenol and urea coating resins. Only with polyvinyl butyral strength and Λ permeability were tested achieved slightly better results, but the polyvinyl butyral swells in the chlorofluorocarbon materials. in all aforementioned binders also is the Desiccant capacity reduced.

In addition, the German patent specification 820 133 describes a desiccant for refrigeration machines, which consists of calcium sulfate or lime or other alkaline earth oxides and cellulose acetate or other cellulose derivatives as binders and which can be brought into any desired shape, such as bars, wafers or balls. That the mechanical strength of such desiccant form. body is not sufficient, resulting from the fact that in the to the DP 820 133 related patent of addition - DP 846 844 - for ER- (heightening the fracture resistance is proposed that the drying agent in a housing-like casing to accommodate Moreover, has cellulose acetate disadvantage in. to carbonize the activation of the desiccant by heating. As a result, the pores of the desiccant will be blocked, which thus loses its effectiveness · If this disadvantage is to be avoided, it is necessary to saturate the desiccant prior to use up to 40 # with water, which then through a longer drying

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process at elevated temperature after completion of the molding must be removed again. In addition, a higher pressure of approx. 80 atm is required to produce the molded body. The disadvantages just mentioned also apply to polyamides such. B. nylon.

In contrast, the disadvantages described do not occur when using ethoxylin resin as a binder. Ethoxylin resins have that great advantage 'that no volume contraction occurs during hardening, so that the moldings produced using ethoxylin resins harden completely free of tension and therefore also do not tear. After curing, the moldings completely fill the mold, they are dimensionally stable and have a high degree of strength. The drying cartridges made with ethoxylin resins have the following advantages:

1.) Even the addition of very small amounts of the binder result in moldings of high strength. Only 0.3 to 5 g of ethoxylin resin are required for 100 g of desiccant. A support the molded body by a housing-like envelope, for. B. by a wire mesh, as described in German Patent 846 844 is not required.

2.) Because of the high binding force of the binder, it is also possible to use Desiccants, such as those obtained during manufacture, can be used without being reduced to fine grain sizes beforehand would have to be ground. In particular, pearl-shaped Desiccant with a grain size of more than 1.5 mm is used will. The molded bodies produced in this way have a flow resistance that is not significantly greater than that of the pure desiccant.

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3.) The binding agent increases the water absorption capacity of the Desiccant not reduced "

4.) The drying cartridge is against refrigerants, especially against Fluorocarbon resistant.

5.) In the production of the moldings, the use of Solvents are dispensed with. The hardening can therefore take place in one operation, and it is particularly necessary no vacuum can be applied, which simplifies production is increased and cheaper.

6.) For reactivation, those saturated with water vapor can Cartridges can be heated to temperatures of up to 160 ° C without charring of the binding agent.

As the drying agent the usual adsorptive desiccant such as silica gel, alumina, _{aluminosilicates}} Kagnesiumoxid silica gels or molecular sieves in bead form and / or can be used grained.

The production of the moldings according to the invention is explained using the following example: (

example

100 g of a commercially available pearl-shaped silica gel with a diameter of 2 to 6 mm are intimately mixed with 4 g of a commercially available ethoxylin resin (e.g. AraldiiS, manufacturer Ciba) and poured into a metal mold. Then the shape!

held,

the shaped body for two hours at 100 ° to 120 ° G without pressure

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The moldings produced in this way have good water absorption capacity good permeability and mechanical strength. They are also affected by chlorofluorocarbons not dissolved.

The water absorption capacity of the molded body was determined by wetting tested with air of various relative humidity at a temperature of 25 ° C and with that of the pure Desiccant compared. The capacity of the desiccant was only insignificantly reduced.

Water vapor adsorption at 25 ⁰ C in equilibrium:

pure desiccant

r.F. Moldings 10 r.F. 5.1 wt. 20th r.F. 9.5 " 60 r.F. 31.4 " 80 34.6 "

5.6 wt.

9.9 "33.1 ^M 36.6"

To measure the flow resistance of the drying cartridge, it is placed in a cylinder, its lower base is provided with a gas inlet pipe and the top with is closed with a pierced stopper. An Eohr is passed through the stopper, which is attached to a flow meter connected. So that there is no air space between the drying cartridge and the cylinder wall, the drying cartridge provided with a seal. There is a gas from below, ζ. Β. Air or nitrogen, introduced into the cylinder and a certain Flow rate adjusted. The gas inlet pipe is connected to a pressure gauge on which the

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Pressure generated by the molded body can be read.

To measure the flow resistance of the desiccant alone, it is placed in a wire basket that has the same volume as the shaped body, introduced into the cylinder.

The following values were measured:

1) Desiccant cartridge according to registration

at flow rate HO l / h 2.5 mm WS "■. η 100 l / h 1.6 mm WS

2) desiccant alone

100 g silica gel beads 0 2 - 6 mm at a flow rate of HO l / h 2.5 mm water «■« ■ 100 l / h 1.3 mm WS

To test the durability, the drying cartridge was placed in monofluorotrichloromethane at 20 ° C. for 6 weeks. There were no signs of swelling; their properties were not changed.

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Claims (3)

Claims 1.) Drying cartridge made of a solid adsorptive desiccant and an organic synthetic resin as a binder, characterized in that that an ethoxylin resin is used as a binder. 2.) drying cartridge according to claim 1, characterized in that on 100 grams of desiccant 0.3 to 5 grams of ethoxylin resin can be used. 3.) drying cartridge according to claim 1, characterized in that as adsorptive desiccant silica gel, molecular sieves and / or active aluminum oxide in pearl form and / or in granular form can be used. 1098U / 0709