JPH0443685B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a filter cartridge having a sorption layer for use in gas purification. The present invention is especially useful when removing all detectable vapors and odors from the air is of paramount importance.
Very suitable for compressed air purification.

The technique of purifying fluids by filtration using cartridges is not new. British Patent No. 1236396 (R.
E. Knight et al) shows a device for the purification of gaseous media, but the example shown in that patent has a sorption layer that does not use the maximum volume space available. Moreover, the dust or particle filters located after the sorption layer are very small in size and therefore involve considerable pressure losses. British Patent No. 1265089 (Nutter and Sitter) shows a filter cartridge using a pleated layer of filter paper impregnated with activated carbon.
It has two major drawbacks. One of them is
The other drawback is that the maximum space is not utilized, and the other drawback is that only a small portion of the total weight of the filter paper is sorbent, so the weight of sorbent (which is directly proportional to the weight of contaminant removed) is ) is extremely rare. Furthermore, British Patent No. 4015959 (GA
Grote uses a good sorption layer design, but employs a final step for the capture of poor dust particles, which is a woven mesh element. Moreover, the main oil separation takes place in the same chamber as the woven mesh, and this is done in a very basic manner, i.e. using a pan scrubber, so that the liquid oil is transported to the sorption layer. There is a real danger.

The primary object of the present invention is to provide a purification cartridge consisting of a sorption layer and filter media that provides higher efficiency, lower pressure drop and longer life than conventional ones.

Another object of the present invention is to provide a device with a cartridge under operating pressure or compressed to be used, for example, in cases where almost complete removal of vapors and odors is of great importance. An object of the present invention is to provide a filter cartridge for purifying compressed air during expansion of the air from a state to atmospheric pressure. Examples of air expansion through a cartridge to atmospheric pressure occur in connection with a control valve outlet and an air drive motor.

According to the invention, an elongated rigid support tube extends between a pair of end closure members; an inlet located within one of the closure members, the inlet being housed within the support tube or within an inner tube disposed within the support tube; and extending closely over substantially the entire length between the positions of said pair of end closure members and extending throughout the entire volume. a single sorption layer of oil-absorbing activated carbon consisting of a cylindrical densely packed activated carbon made of porous material and arranged to block gas flow from the sorption layer prior to ejection from the cartridge. A filter cartridge is provided having a tubular filter media. The wall of the inner tube, or part of the support tube, is cylindrical without free passages and supports at least a major part of the sorption layer along its length, and the wall extends from the inlet. The filter media is gas impermeable so that flow occurs longitudinally through the length of the cylindrical sorption layer with respect to its central axis, and the filter media restricts the flow of gas after it has been exhausted from the sorption layer over the wall. the filter media is disposed in series with the sorption layer to capture particulate matter entrained from the sorption layer and to exhaust the gas stream directly from the cartridge; A tubular element through which gas flow flows radially outward from the sorption layer. In one embodiment, the capacity of the sorption layer is advantageously defined by a container in the form of a vertical cylinder having the maximum amount of sorbent material filled into it, as allowed by the capacity limitations of the container. be. The inlet of the gas is then a porous region covering substantially the entire top of the bed, and the outlet is a porous cylindrical or other conventional region at the bottom of the container. Alternatively, the sorption layer may be a self-retaining cylinder. The filter medium is, for example, a pleated filter element or a fibrous tubular element of molded or assembled construction. Alternatively, sintered metal or plastic tubular elements can be used. Where highly efficient purification is required, pleated activated carbon paper is preferably provided downstream of the sorption layer.

In another example of the invention, the sorption layer is a self-contained tubular body contained such that the gas inlet region substantially covers the entire inner surface of the sorption layer and the gas outlet region covers the entire outer curved surface of the sorption layer. It has a vertical cylindrical shape. Alternatively, the sorption layer consists of particles packed between an internal rigid porous tube and a cylindrical filter medium. For particularly efficient removal of vapors and odors from the air, it is advantageous to form the tubular sorption layer with activated carbon particles and the filter medium with filter paper impregnated with finely divided activated carbon, so that The fine particles may constitute an extension of the sorption layer, or the filter medium may be surrounded by another filter medium that does not contain activated carbon.

A sorbent is defined as a solid substance that undergoes a phenomenon called sorption, and the sorbed gas or vapor is referred to herein as the sorbate. Sorption is a molecular attraction between the sorbent and the sorbate, where the molecules of the sorbate are attracted to the surface of the sorbent and are retained to some extent.

If the sorbate molecules are held to the surface by physical forces similar to the phenomenon that occurs in condensation, the process is called adsorption. If strong interactions, such as electron transfer, occur between the sorbate and the sorbent surface, the phenomenon is called chemisorption. If the sorbate enters the sorbent body and reacts chemically with it, changing its respective chemical properties, the process is called absorption.

Since sorption is primarily an interfacial phenomenon, porous solids with very large surface areas are potentially the most effective sorbents.

Typical sorbents are:

(a) Activated carbon This is the most versatile sorbent, its large number of pores giving rise to an internal surface area of 600 to 1200 m ² /g, depending on the conditions.

(b) Molecular sieves Many molecular sieves are synthetic crystalline zeolites that have a high affinity for polar molecules.

(c) Activated alumina This is porous aluminum oxide.

(d) Hopcalite This is a porous granular mixture of manganese and copper oxides, used primarily as an oxidizing agent. Catalyzes the oxidation of carbon monoxide to carbon dioxide at room temperature.

(e) Soda lime Commonly used for carbon dioxide sorption.

(f) Silica gel This is partially dehydrated colloidal silica. It has a microporous structure with a large internal surface area and exhibits an affinity for polar molecules such as water vapor. Therefore, it is primarily used as a desiccant and in some forms exhibits a color change from blue to white, indicating the presence of water vapor.

Embodiments of the present invention will be described below with reference to the drawings. Note that the same reference numerals are used for similar parts in each drawing.

In FIG. 1, the lower end is connected to the end cap 9.
A sorbent material 7 is filled in a metal or plastic tube 4 whose upper end is closed by a perforated disk 2 made of perforated or expanded stainless steel.
The layer of porous filter medium 3 consists of disk 2 and sorbent material 7
It is sandwiched between. The disc 2 can also be made of other suitable metal or plastic, woven or molded. The filter media may be, for example, open-pore polyurethane foam, fibers, or sintered materials. In each case the disc 2 may be removed.

A porous supporting outer tube 6 made of porous metal or plastic is provided between the outer peripheries of the end caps 1 and 9, and these caps are joined to the tubes 4 and 6 by resin. The cap 1 is formed to engage the periphery of the perforated disc 2 and hold it in that position, and is resin bonded to the cap 1. A gap is formed between tubes 4 and 6 to accommodate a pleated filter element 5 extending between the end caps, the peaks of the pleats being in contact with tubes 4 and 6. The efficiency of the filter element 5 is preferably 99.999%, but for example DOP
Aerosol efficiency is better than 99.95%. Preferably, the pleated element 5 has an efficiency of greater than 95.5% when tested to British Standard 3928 (British Standard Specifying the Sodium Flame Test for Air Filters). The corrugated elements 5 may contain a medium impregnating the activated carbon.

The body of the tube 4 is fluid-impermeable, but its end is formed as a perforated ring 8.

When the filter is used, the compressed air to be purified enters through the inlet of the end cap 1 as indicated by arrow A and is distributed by the disk 2 to the top of the sorption layer 7. The air then passes through the lower end of the pleated filter element 5 through the perforated ring 8 and through the depth of the bed with a residence time sufficient to remove molecular-sized contaminants. The air then rises over the inner surface of element 5, passes through element 5 leaving particles carried away from the sorption layer adjoining the inner surface, and finally exits through perforated tube 6 as shown by arrow B. Go out. The pore size of the porous ring 8 must be small enough to prevent particulate sorbent from entering the voids between the tube 4 and the folds of the element 5. The perforated ring 8 can be replaced by a perforated disc similar to the disc 2, the space below which communicates with the pleated filter element 5.

The sorption material can be granular or powdery, but also fibrous, especially in the case of activated carbon.
A self-supporting block of activated carbon, typically cylindrical or tubular, can be used. These are composed of granules held together by a binder that has minimal effect on the activity and internal surface area of the activated carbon. Alternatively, a sintered block of activated carbon can be used. When these sorbents in the form of blocks are used, the disk 2 and the filter medium 3
may be excluded.

Figure 2 shows a modification of the filter of Figure 1, in which, instead of the pleated filter elements, a fibrillar tubular element 10 constructed as described in (for example British Patent No. 1603519) is used. There is. Between the microfiber element and the tube 4, in order to ensure direct communication between the porous ring 8 and the entire inner surface of the microfiber element,
An air gap 11 is provided.

FIG. 3 shows an example of an adaptation of the filter of FIG. 1 where a deeper sorption layer and a significantly shorter pleated filter are required. For this purpose, an adapter 12 is connected to the lower end of the tube 4.
The adapter 12 is located at the upper end of the pleated filter element 5 which extends downwardly between the perforated ring or tube 8 and the plastic transparent support tube 13 and seals therein. The dye-impregnated fibers 14 are also interposed between the perforated tube 8 and the pleated elements. The bottom of the device is covered and sealed by an end cap 9. The support tube 13 is preferably made of plastic and is provided with holes for the air outlet. Alternatively, when support tube 13 is impermeable, support tube 13 can terminate short of end cap 9 to form a circumferential air gap. The dye, pleated elements 5 and transparent tube 13 provide an indicator of whether oil contaminants have been removed from the air before entering the sorption layer. In this case, the pleated elements 5 initially remain white, but if the oil reaches the perforated tube 8 and becomes colored as it passes through the dye-impregnated fibers, this colored oil leaves the pleated filter elements. Make it dirty. When this occurs, a step is taken to replace the sorbent cartridge.

FIG. 4 shows a modification of the filter of FIG. 3 in which the pleated filter elements 5 are replaced by fine fiber filter tubes 10. FIG. This element is based on British Patent No.
1014882 (Domnick Hunter), it simply consists of fine fiber paper housed inside a porous support tube 6 directly supporting the lower end of the sorption layer. The colored indicator of FIG. 3 can be incorporated into this filter in the same way as the filter of FIGS. 1 and 2. Figures 5 and 6 are
It shows how a sorption layer in a housing consisting of a ball screwed into a body 17 with an inlet and an outlet, as indicated by arrows A and B, can be used for high volume applications. In this case, the bowl 19 and the purification system consisting of the sorption layer 7 and the pleated filter element 5 are constructed as a unit that can be disposed of at the end of its useful life. The ball provides a non-porous support tube for the pleated element and also provides a lower end cap. The purified air rises outside the pleated filter,
It flows to the expanded upper end of the ball as shown by arrow C. After flowing over the end of the end cap 1 and around the socket 20 for the inlet of the end cap 1,
The purified air exits from outlet B. There is a gasket 15 between the end cap 1 and the socket 20.
is provided. The air to be purified is supplied to the sorption layer through the socket 20. A gasket 18 is attached between the top of the ball 19 and the body 17.

Due to the air-impermeable walls of the balls 19, the air must travel through the depth of the sorption layer 7, thus providing the highest efficiency in the removal of sorbates. The granular sorbent is packed in such a way as to avoid free passage through the sorption layer, and its particle size is selected to obtain optimal performance. It should be noted that the sorption layer can be composed of one or more layers of different sorbents. For example, when purifying gas using a hopcalite catalyst to oxidize carbon monoxide to carbon dioxide, great care must be taken to remove other sorbates that would impair the catalytic action on carbon monoxide. Must be. In particular, moisture should be removed from the gas by other sorbents such as anhydrous calcium chloride located upstream of the hopcalite. It is also advisable to provide another small desiccant layer directly below the hopcalite for protection during storage and installation.

When a color change indication is required, the ball 19 is made of a transparent plastic material and the dye-containing layer is located as in FIG. 3, ie between the porous ring 8 and the pleated element 5.

The present invention can be advantageously used to completely remove oil from compressed air, particularly in applications such as purified breathing air and air equipment. In both of these cases, the sorbent material is activated carbon. To protect the sorbent from liquid oil, Military Standard 282 (DOP) (UK Ministry of Defense standard for performance testing of filter units, protective clothing, gas masks and related products) is used.
A high efficiency oil removal filter using a borosilicate glass microfiber structure with an efficiency of greater than 99.999% when tested in accordance with the present invention may be used immediately upstream.
The arrangement can be such that two pressure housings are used in close proximity to each other, i.e. the upstream one contains the ultra-high efficiency (UHE) filter element and the downstream one contains the sorption layer. . Alternatively, a single housing with upper and lower chambers having two separate pressures can be used. The lower chamber then houses a UHE filter element, by means of which the recovered oil aerosol is discharged by conventional equipment. The air is then directed by an internal porting device within the housing to the cartridge containing the absorbent within the upper chamber. In both cases, the first,
Replaceable cartridges (with or without color indicating means), as shown in FIGS. 2, 3, and 4, or cartridges with integrated filter balls, as shown in FIGS. 5 and 6, can be used.

Although the amount of oil across the UHE filter can be varied according to conditions, it has been found that typically an amount of 0.1 mg/m ³ of oil in aerosol form is not unusual. This is because an oil vapor layer is always present. The combined result is an unpleasant oily odor of hydrocarbon vapors and a fine aerosol, eg less than 1 micron in diameter. A sorption layer of activated carbon particles is ideal for removing contaminants, leaving less than 0.001 mg/m ³ of oil contaminants in the exit air, resulting in odor-free conditions. Air that has undergone this process is perfectly applicable for absorption or air installations, and is particularly suitable when the air flow rate is less than 5% of the maximum flow rate. The activated carbon layer has an oil vapor removal efficiency of over 99.9% and a particle removal efficiency of over 99.999% when tested to British Standard 4400 (British Standard Specifying Methods for Sodium Chloride Particle Testing for Ventilator Filters). have. The weight of the sorption layer used is proportional to the lifetime of the sorbent, and activated carbon can hold up to 50% of its own weight of adsorbed vapor.

When pleated filter media or elements 5 are used for the final filtration, a combination of activated carbon-impregnated paper and downstream conventional filter paper (for particle retention) is advantageous. It has been found that the fine activated carbon particles used in such filter papers are generally much more active than the larger particles. Therefore, it is desirable to use this medium in the final step of the purification to remove small amounts of vapor that have crossed the sorption layer. This type of impregnated paper is manufactured by "CHDexter" in the United States.
of Windsor Locks”.

In the case of cartridge filters employing a sorbent layer of granular activated carbon with pleated activated carbon paper as the filter media, as shown in Figures 1, 3 and 5, the test results show that the overall efficiency as described above is showed that it was more than 99.9% when removing hydrocarbon vapors. Such test results also showed that the granular layer removed most of the vapor, while the activated carbon paper removed the remainder. However, for some applications such filter cartridges are unsuitable because the operating pressure drop is too great when the required contact time between air and carbon particles is maintained. Experiments have shown that to obtain maximum absorption efficiency by the activated carbon layer, the gas velocity should not exceed 300 feet (91.50 m)/min and the gas should have a minimum contact time of 0.1 seconds. was calculated and proven. The contact time is
It is a function of the depth of the layer and the speed through which the air passes. In order to meet these conditions, it has been found advantageous to pack the carbon grains in the form of relatively thick-walled tubes.

Such a tubular body of activated carbon is shown in FIG. 7 as a rigid self-retaining tube with heat-fused particles. A binder may be added if necessary. In operation, compressed air enters the central part of the granule tube along the length of the tube in the direction of arrow A and passes approximately radially outward through the granule tube wall until it comes into close contact with this granule tube 7. and enters a surrounding pleated activated carbon paper filter element 5. A perforated rigid outer tube 6 supports the pleated elements. The end caps 1, 9 seal the grain tube 7, the corrugated elements 5 and the perforated tube 6. The granular tube sorption layer 7 reduces the gas velocity while maintaining a satisfactory sorption efficiency without excessive pressure losses.

FIG. 6 shows that particles of activated carbon, although coarse, are filled in the annular space between the inner rigid porous tube 21 and the pleated activated carbon filter element 5 to form a sorption layer 7.

In Figure 7, the granular activated carbon layer 7 provides most of the vapor trapping action in the first stage, and the pleated paper provides the second stage with high vapor removal efficiency due to the large surface area of carbon particles as mentioned above. Perform vapor capture. The pleated paper also acts as a dust filter to prevent particles from falling off and falling downward.

Particularly in compressed air systems where oil and water are present, it is necessary to keep the sorption layer dry. For example, liquid contaminants must be removed upstream, especially when cartridges are used to clean the exhaust gas of vacuum pumps, such as oil-injected rotary vane pumps. This can be done by a separate filter at a predetermined distance from the filter cartridge.

The tubular cartridge of Figure 7 is shown in British Patent Application No.
It is advantageous to use it in combination with a compressed air filter silencer as shown in No. 7935745 (Publication No. 2033247). This is because filter silencers remove dust and liquid contaminants while reducing noise, but do not remove oily odors. In this device, a tubular sorption cartridge is sealed to the casing of the filter silencer by means of providing an intervening space that keeps the sorbent material dry.

Coloring instruction means is provided, and the ball 19
When (Fig. 5) is metal or other non-permeable material, the ball is provided with a sight glass by which oily contaminants in the sorption unit are observed which exhibit a color change. . In the case of dye-impregnated fibers, the impregnation is carried out using waxoline, which is manufactured by ICI by using an organic solvent carrier.
This is done using a led. This changes the oil's natural color to a deep red, and the dye is unaffected by water. The sight glass can be a standard sight level indicator commonly used for metal filter balls.

Since the sorption layer has a defined lifetime depending on the size of the layer and the concentration of absorbent, it is sometimes desirable to employ a dual cartridge filter system. In a dual system, two sorption layers are used in parallel, with a valve separating them so that they can be switched without interrupting the air supply. In some cases, the sorbent material is regenerated or reactivated, but this is expensive and time consuming. In yet other embodiments, a dual system having a valve system and timer means is contemplated. The valve system and timer means operate automatically to provide an alert indicating the need to replace a used sorption cartridge with a new one or to manually replace a sorption cartridge.

The material of construction of the filter should be corrosion resistant, for example plastic, aluminum, stainless steel, or corrosion resistant mild steel such as tin steel.

[Brief explanation of drawings]

1 and 3 are views showing one side vertical cross section of different cartridge filters of the present invention, respectively, and FIGS. 2 and 4 show the lower end of a modification of the cartridge filter of FIGS. 1 and 3. 5 is a vertical sectional view of another cartridge filter, FIG. 6 is a horizontal sectional view of the filter of FIG. 5, and FIG. 7 is a right side view of the other two cartridge filters. Half and left half Y
It is a figure showing all the -Y vertical cross sections.

Claims (1)

[Scope of Claims] 1. An elongated rigid support tube extending between a pair of end closure members; arranged to remove molecular-sized oil contaminants from a gas stream entering an inlet and extending closely along substantially the entire length between the positions of the pair of end closure members, the entire volume being a single sorption layer of oil-absorbing activated carbon consisting of a cylinder of closely packed activated carbon comprising a porous body and arranged to block gas flow from the sorption layer prior to ejection from the cartridge; A filter cartridge comprising a tubular filter medium provided with a tubular filter medium, wherein the wall of said inner tube, or a portion of said support tube, is cylindrical without free passages and has a sorption layer along its length. supporting at least a major portion of the sorption layer, the wall being gas impermeable such that flow occurs from the inlet through the entire length of the sorption layer in a longitudinal direction with respect to the central axis of the sorption layer; in series with the sorption layer to accommodate the gas flow after it has been exhausted over the wall from the sorption layer, to capture particulate matter carried from the sorption layer, and to exhaust the gas flow immediately from the cartridge. a filter cartridge, characterized in that the filter medium is a tubular element through which the gas flow flows radially outwardly from the sorption layer. 2 In use, the sorption layer has a gas velocity of 300 ft/min (12 cm/min) with a contact time of 0.1 seconds with the activated carbon.
2. A filter cartridge according to claim 1, characterized in that it is designed in relation to the system in which it is used to pass at a linear velocity lower than 1 sec). 3. Filter cartridge according to claim 1 or 2, characterized in that the tubular element surrounds at least part of the sorption layer. 4. The capacity of said sorption layer is defined by a container in the form of a vertical cylinder having the maximum amount of activated carbon loaded into it, as allowed by the capacity limitations of the container, said container being approximately at the top of the sorption layer. Claim 1, characterized in that it comprises an all-encompassing gas inlet region and a gas outlet region surrounding the lowest part of the sorption layer and/or covering the bottom of the sorption layer,
3. The filter cartridge according to 2 or 3. 5. The sorption layer is a solid body contained such that the gas inlet region covers substantially the entire top of the sorption layer and the gas outlet region surrounds the bottom of the sorption layer and/or covers the bottom of the sorption layer. 4. A filter cartridge according to claim 1, 2 or 3, characterized in that it is in the form of a self-retaining vertical cylinder. 6. Claim 1 characterized in that the filter media is a tubular pleated filter element having an efficiency of greater than 99.95% when tested according to British Standard 3928 and housed within a porous rigid external support tube. 5. The filter cartridge according to any one of items 5 to 5. 7. According to any one of claims 1 to 6, the sorption layer consists of activated carbon particles and the filter medium is a tubular pleated filter element consisting of filter paper impregnated with fine activated carbon particles. Filter cartridge as described. 8. A filter cartridge according to any one of claims 1 to 5, characterized in that the filter medium is a microfibrous tubular element of molded or assembled construction. 9. A filter cartridge according to claim 4 or 5, characterized in that the filter medium consists of tubular pleated filter elements or fibrillated tubular elements surrounding and extending along the entire length of the sorption layer. 10. A filter car according to claim 4 or 5, characterized in that the filter medium consists of a tubular pleated filter element or a fibrous tubular element surrounding and extending along a relatively short lower portion of the sorption layer. Tritsuji. 11 The sorption layer and the filter medium are contained within a ball formed to be separably mounted on the upper end of a body having an inlet and an outlet, the sorption layer being adapted to receive gas from the inlet. and the filter media is arranged in such a way that the sorption layer and the ball are arranged so as to receive gas passing through the sorption layer on one side and directing gas passing through the filter medium to an outlet along the other side. 11. A filter cartridge according to any one of claims 1 to 10, characterized in that it is a tubular pleated filter element located between. 12 A dye is interposed between the sorption layer and the filter medium, and when passing through the dye, the oil carried by the compressed gas is dyed, thereby changing the color of the filter medium and preventing oil contamination. The filter cartridge according to any one of claims 1 to 11, characterized in that the filter cartridge is configured to detect. 13. The filter cartridge of claim 12, wherein the dye is provided by dye-impregnated fibers interposed between the sorption layer and the filter medium. 14 A high efficiency filter is connected upstream to remove oil or other liquids from the compressed gas stream introduced into the cartridge, thereby keeping the sorption layer dry and removing vapors and odors. A filter cartridge according to any one of claims 1 to 13, wherein the cartridge is dried to a sufficient extent.