DE102011110932A1 - Filter material useful in filter of gas pressure control device for purifying gases, which is useful for liquid e.g. propane, butane or butene, comprises sintered thermoplastic polymer in form of solid and self-supporting filter material - Google Patents

Abstract

Filter material (1) comprises a sintered thermoplastic polymer in the form of a solid and self-supporting filter material containing calcium silicate hydrate. An independent claim is also included for filtering gases comprising sintering calcium silicate hydrate and a thermoplastic polymer to form a solid, self-supporting filter material and introducing the filter material into the gas stream.

Description

The present invention relates to a filter material for gas filters, in particular for filters of pressure regulators for LPG.

Gas pressure regulators serve the gas supply of a gas consumption device with a regulated consumption pressure. The gas, z. As liquefied gas such as propane and butane in particular, is taken from a portable gas cylinder or a stationary gas container. Gas cylinders can start to rust inside, which loosens during transport and can thereby clog the nozzle of the gas pressure regulator. Likewise, impurities may be contained in the gas itself, which adversely affect the gas pressure regulators and the nozzles of the consumer equipment. This can also happen in gas pressure regulators, which are arranged away from a gas container and connected by a pipe with this. Impurities can also come from the pipeline.

For LPG, the simultaneous presence of particulates and contamination of the gas by oil is particularly problematic. As a result, closing the gas pressure regulator can be prevented.

It is therefore state of the art to free the gas flow through filters of impurities. These filters may be arranged in front of the pressure regulator or, preferably, integrated in this. As a filter are usually fabric, nonwovens and the like from pulp, plastic or micro glass fibers, for retaining particles and for adsorbing or absorbing other impurities u. a. Activated carbon, ion exchanger, silica gel used in the gas. Previous filter materials have the problem that particles of the filter material can enter the gas stream. The separation of impurities such as oil succeed only unsatisfactory.

There is thus a need for a filter material which can both retain particles and separate other contaminants from the gas.

Out EP 1 897 436 A2 is a mineral granules known which has a high binding capacity for liquids and therefore can be used as animal litter, bed of construction or oil and chemical binder. The granules are based on powdery and / or granular calcium silicate hydrate and are formed with at least one binder with the addition of water to the granules and dried. The binders used are calcium oxide, calcium hydroxide, magnesium oxide, magnesium hydroxide, bentonite and / or starch.

Surprisingly, it has now been found that by sintering a mixture of these granules and a thermoplastic polymer granules, a very effective filter material for gases can be obtained.

The invention therefore achieves the above object by a filter material comprising calcium silicate hydrate and a thermoplastic polymer which are sintered into a solid, self-supporting filter material. The object is also achieved by using this filter material in a gas pressure regulator and by a method of filtering gases with the filter material.

The sintering of filter materials to form dimensionally stable filter blocks is known per se. For example, describes DE 198 44 167 a special polyethylene as a binder for the production of activated carbon filters, the polyethylene having a high viscosity, so that a relatively stable connection of the activated carbon particles is made possible without a substantial coating thereof by the polyethylene. In the EP 1 488 840 A1 describes a combination filter of a fiber filter material and a sintered polymer granules. However, these materials do not allow satisfactory filtering for pressure regulators of liquefied gases.

With the in EP 1 897 436 A2 On the other hand, granules which are commercially available and, in one embodiment, commercially available under the name Penta99 can achieve very good cleaning successes after sintering into a solid self-supporting filter block. Since this granulate is largely obtained from production residues of pore and foam concrete production, it is inexpensive and resource-saving.

As calcium silicate hydrate is preferably after EP 1 897 436 A2 prepared granules used. According to the invention, however, other calcium silicate hydrates are also suitable.

Particularly preferred are granules with a grain size of 0.1 to 2 mm, a BET specific surface area of about 20 to 30 g / cm ³ and a bulk density of about 545 kg / m ³ . Coarser particles can be adjusted to the desired grain size by grinding and particles that are too fine can be granulated.

It is preferred if the calcium silicate hydrate from 1 to 10 wt .-% clay, preferably bentonite, are mixed. The calcium silicate hydrate can be derived, in particular, from foam and aerated concrete production, or obtained by hydration of cement.

If in the following of calcium silicate hydrate is mentioned, so are both the preferred according to EP 1 897 436 A2 meant granulate produced by a binder as well as other calcium silicate hydrates with suitable particle sizes.

Suitable polymers are those thermoplastic polymers which are inert to the gas to be filtered and have a sufficiently high viscosity to form a porous mass during sintering. Preference is given to polyolefins such as polyethylene or polypropylene, in particular polyethylene. Polytetrafluoroethylene is also useful.

The sintering takes place in a conventional manner. First, the granules of the calcium silicate hydrate and the thermoplastic polymer are mixed. The mixture is filled into a mold, heated to the softening temperature of the polymer, optionally under pressure, and after cooling, the solid self-supporting filter material block is removed from the mold. Temperature, pressure and time on heating are adjusted to the size of the filter block and the polymer and also chosen so that the filter material has the desired porosity.

The mass ratio of calcium silicate hydrate to polymer is typically from 2: 1 to 0.5: 1, preferably about 1: 1.

The shape of the filter block can be almost arbitrary. Cylindrical shapes have proven useful, but also star-shaped geometries or plates are advantageous, depending on the installation situation.

It is possible to produce the filter according to the invention as a combination filter by providing one or more layers of one or more further filter material (s). The layers are preferably firmly connected by sintering, so that no bypass for the gas to be filtered is possible. If more than one further layer is present, the further layers may be the same or different. As a further layer z. As membranes, fabrics and especially fiber materials, micro-glass fiber materials are particularly preferred.

The fiber materials are preferably bound with a binder. Suitable binders are polyolefins, polyvinyl fluoride (PVDF), epoxy resin, silicates and many more. Preference is given to PVDF and epoxy resins.

Particularly preferred is a filter with an upstream layer of fiber material, in particular micro-glass fiber material and a layer of polymer and calcium silicate hydrate sintered on it.

In a further preferred embodiment, a three-layered filter material is provided comprising a first layer of sintered polymer granules, a second layer of fiber material, and a third layer of sintered polymer granules, wherein calcium silicate hydrate is incorporated in one or both layers of polymer granules.

Likewise, a filter of the filter material according to the invention combined with other filters, for. B. connected in series. For this purpose, the same materials as previously mentioned for the second layer into consideration.

The filter material according to the invention can be produced in virtually any layer thicknesses. For use in gas pressure regulators, for example, cylindrical shapes with layer thicknesses of 1 to 50 mm, in particular from 3 to 40 mm are suitable. In the case of combined filter materials, the layer thickness of a first, preferably fiber filter layer of 1 to 20 mm, preferably from 3 to 5 mm and the thickness of the filter layer of the filter material according to the invention preferably from 10 to 30 mm, preferably from 15 to 20 mm. It should be emphasized that the layer thickness is not limited in principle, layer thicknesses of 500 mm are quite possible for the erfindungnsmäßige Filtwermaterial.

The filter material is ideal for filtering gases such as air, LPG and compressed gases. In particular, it can be used instead of previously used materials as a filter in gas pressure regulators. It is advantageous that the self-supporting and self-supporting filter material requires no support layers and no particles of the filter material can get into the gas stream.

If desired, a filter change indication may be provided in the filter material. For example, a colorant applied to the inflow side, which dissolves in the contaminant (eg oil or water) and is introduced by this into the filter material, is suitable. The depletion of the filter material is then signaled by the color becoming visible on the other side of the filter.

The inventive method comprises introducing the filter material according to the invention into a gas stream. In a first embodiment, the filter material is introduced into a filter which is integrated in a gas pressure regulator. In a further embodiment, the filter material is introduced into a filter in a gas line. The gas may be LPG or compressed gas. The method is also suitable for exhaust gas or exhaust air purification.

The arrangement of the filter material in a filter housing takes place in a conventional manner. The filter material is typically provided with end caps, over which it is sealed to the housing. In an advantageous variant, the sealing can be effected by a corresponding shaping of the sintered material, so that end caps can be dispensed with.

A particularly preferred application of the filters according to the invention is the filtration of exhaust air. Here, almost 100% separation of the oil aerosols can be achieved, which hitherto was not possible with reasonable effort. Filters for the exhaust air filtration typically have much larger dimensions than those for compressed gas control devices. Usual outer diameter of 50 to 100 mm, preferably about 70 mm and lengths of 300 to 1000 mm, preferably about 500 mm. It is preferred to provide these filters with an inner support layer of sintered polyethylene.

The invention will be explained with reference to the following figures and examples, but without being limited to the specifically described embodiments. Unless otherwise stated or necessarily different from the context, percentages are based on weight, in case of doubt on the total weight of the mixture.

The invention also relates to all combinations of preferred embodiments, as far as these are not mutually exclusive. The words "about" or "approximately" in connection with a numerical value mean that at least 10% higher or lower values or 5% higher or lower values and in any case 1% higher or lower values are included.

In 1 is a filter material according to the invention 1 partially cut and shown in perspective view. The inner upstream layer 2 is formed by a micro-glass fiber material. At this layer 2 is a layer 3 of calcium silicate hydrate and polymer sintered. The filter material is, for. B. by means of adhesive, with end caps 4 provided by a seal in a filter housing.

2 shows a cross section through the filter material along the line AA in 1 .

example 1

The filter efficiency of filter materials according to the invention and known filters was determined in a test stand. For this purpose, a DEHS aerosol was generated with a particle generator ATM 266. The filter material was mounted in a housing on the test bench and connected to a particle counter. The particle counter had a sampling flow of 300 l / h, which was drawn directly over the filter. To determine the distribution of the aerodynamic quantities was an Aerodynamic Particle Sizer APS 3321, TSI. Inc. used. The geometric particle size was calculated from the aerodynamic size by dividing it by the root of the aerosol density.

Filter 1 was a sintered filter according to the invention of polyethylene and penta99 in a weight ratio of 1: 1.

Filter 2 corresponded to filter 1, in addition, a use was used.

Filter 3 was a combination sintered filter according to the invention with an inner layer of micro glass fibers bonded with PVDF and an outer layer of polyethylene and penta99 in a weight ratio of 1: 1.

Filter 4 was a commercially available filter from Truma, as used for liquefied gases.

The results are summarized in Table 1.

Example 2

For a sintered combination filter with an inner layer of epoxy resin-bonded micro glass fibers and an outer layer of polyethylene and penta99 in a weight ratio of 1: 1, the filter effect was determined analogously to Example 1, wherein at a mass flow of 300 l / h and 30 l / h was measured. The results summarize Table 2 together. Table 2 particle size Mass flow 300 l / h Mass flow 30 l / h aerodynamic [μm] geometric [μm] Separate degrees [%] Spread [%] Separate degrees [%] Spread [%] 0.542 0.57 99.92 0.07 99.99 0.01 0.583 0.61 99.94 0.01 100.00 0.00 0.626 0.66 99.96 0.02 99.99 0.00 0.673 0.71 99.99 0.01 99.99 0.01 0.723 0.76 99.99 0.01 100.00 0.00 0.777 0.81 99.99 0.01 99.99 0.02 0.835 0.88 100.00 0.01 100.00 0.00 0,898 0.94 100.00 0.01 100.00 0.00 0.965 1.01 100.00 0.00 99.99 0.02 1,037 1.09 100.00 0.00 100.00 0.00 1,114 1.17 100.00 0.01 100.00 0.00 1,197 1.25 99.99 0.02 100.00 0.00 1,286 1.35 100.00 0.00 100.00 0.00 1,382 1.45 100.00 0.00 100.00 0.00 1,486 1.56 100.00 0.00 100.00 0.00 1,596 1.67 100.00 0.00 100.00 0.00 1,715 1.80 100.00 0.00 100.00 0.00 1,843 1.93 100.00 0.00 100.00 0.00 1,981 2.08 100.00 0.00 100.00 0.00 2,129 2.23 100.00 0.00 100.00 0.00 2,288 2.40 100.00 0.00 100.00 0.00 2,458 2.58 100.00 0.00 100.00 0.00 2,642 2.77 100.00 0.00 100.00 0.00 2,839 2.98 100.00 0.00 100.00 0.00 3,051 3.20 100.00 0.00 100.00 0.00 3,278 3.44 100.00 0.00 100.00 0.00 3,523 3.69 100.00 0.00 100.00 0.00 3,786 3.97 100.00 0.00 100.00 0.00 4,068 4.26 100.00 0.00 100.00 0.00 4.371 4.58 100.00 0.00 100.00 0.00 4.698 4.92 100.00 0.00 100.00 0.00 5,048 5.29 100.00 0.00 100.00 0.00 5,425 5.69 100.00 0.00 100.00 0.00

It can be seen that all filter variants according to the invention bring about a markedly better separation of the aerosol particles, especially in the case of the fine particles, in comparison to the commercial filter according to the prior art. The Verunreingung of gases can thus be significantly reduced. On the other hand, no improvement was achieved by using the tub.

LIST OF REFERENCE NUMBERS

1

filter

2

Micro glass fiber layer

3

Layer of calcium silicate and polymer

4

endcap

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1897436 A2 [0006, 0010, 0011, 0014]
• DE 19844167 [0009]
• EP 1488840 A1 [0009]

Claims (12)

A filter material comprising a thermoplastic polymer sintered into a solid, self-supporting filter material, characterized in that calcium silicate hydrate is contained. Filter material according to claim 1, characterized in that the calcium silicate hydrate is a flour-shaped urd / or granular calcium silicate hydrate which is formed into a granulate with at least one binder selected from calcium oxide, calcium hydroxide, magnesium oxide, magnesium hydroxide, bentonite, starch and mixtures thereof. Filter material according to claim 1 or 2, characterized in that 1 to 10 wt .-% clay, preferably bentonite, based on the total weight of the calcium silicate hydrate are included. Filter material according to at least one of claims 1 to 3, characterized in that the calcium silicate hydrate has a particle size in the range of 0.1 to 2 mm. Use of a filter material according to one of claims 1 to 4 in a filter of a gas pressure regulating device. Use according to claim 5, characterized in that it is a gas pressure regulating device for liquid gas, in particular for propane, butane, propane, butene or mixtures thereof. A process for the filtration of gases, characterized in that calcium silicate hydrate and a thermoplastic polymer are sintered to a solid, self-supporting filter material and the filter material is introduced into the gas stream. A method according to claim 7, characterized in that the filter material is introduced into a gas pressure regulator, a gas line or an exhaust pipe. A method according to claim 7 or 8, characterized in that are used as calcium silicate hydrate waste from the foam and aerated concrete production. A method according to claim 9, characterized in that the calcium silicate hydrate is adjusted by grinding and / or granulation to a particle size of 0.1 to 2 mm. Process according to at least one of Claims 7 to 10, characterized in that 1 to 10% by weight of bentonite, based on the weight of the calcium silicate hydrate, are added. A filter for purifying gases comprising a filter material according to any one of claims 1 to 4.

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