KR20180083999A - Filtering media comprising porous network of heat resistant polymer fiber for dust collection of middle-high temperature exhaust gas, and preparation method thereof - Google Patents

Abstract

The present invention relates to a filtering body for collecting dust of exhaust gas at medium and high temperatures, the filtering body comprising: an inorganic fiber support body; a polytetrafluoroethylene (PTFE) layer formed by coating bubbles on the inorganic fiber support body; a porous network comprising heat-resistant polymer fiber attached by performing electrospinning of a heat-resistant solution on the first PTFE layer; and a second PTFE layer formed by coating bubbles on the porous network. According to the present invention, a dust removal efficiency of 99.9% or greater with respect to ultra-fine dust of 2.5 μm can be achieved, and the filtering body having an air permeability of 5 cm^3/cm^2/sec or greater can be provided.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter medium for dust collection of a medium- and high-temperature flue gas including a porous network of heat-resistant polymer fibers,

TECHNICAL FIELD The present invention relates to a filter body for dust collection of a medium-high-temperature flue gas for effectively removing ultrafine dust and a method of manufacturing the same.

Dusts generated by industry differ in physical characteristics such as shape, particle size distribution, apparent density, flow rate, specific surface area, adhesion and cohesiveness, and chemical characteristics such as temperature, humidity and compositional composition for each emission source. This difference in physicochemical properties affects the pore bridge in the pores of the filter during dust collection and the formation of a dust cake attached to the surface of the filter. As a result, Differences in characteristics are shown.

In recent years, researches have been made on the development of materials for high-efficiency and high-temperature filtration materials and optimization of weaving structure. Particularly, researches on the source technology of the filter material applicable to the exhaust gas environment of about 200 ° C to 300 ° C, which can be referred to as the middle and high temperature regions, have been conducted.

For example, Korean Patent Registration No. 10-1433774 discloses a method for producing an inorganic fiber support, a dust of a medium-high temperature flue gas including a polytetrafluoroethylene (PTFE) layer having an average pore size of 30 탆 or less foam-coated on the support, And a collecting filter body. However, the filtration body has a problem that the pore size of the coated foam on the surface is too large and the removal efficiency for PM2.5 dust is so low that it can not be applied to ultrafine dusts in various industrial fields.

The concentration of dust in the combustion gas discharged to industries such as waste incineration plants, coal-fired power plants, and cement kilns is managed by applying emission standards. However, recently, it is necessary to apply the PM2.5 standard for dusts smaller than 2.5 ㎛ in diameter Claims are being raised strongly. In particular, recent interest in the dust and ultrafine dust has been intensively searched through the mass media, and advanced countries such as Japan are demanding the filtration bag removal efficiency based on PM2.5 for combustion gas. Therefore, it is possible to achieve dust removal efficiency of 99.9% for PM2.5 ultra fine dust which can be used anywhere, whether incinerator, coal-fired power plant, or cement kiln, and to maximally delay increase of differential pressure by surface filtering There is a great demand for the development of filtration bags.

Accordingly, the inventors of the present invention have conducted studies on a dust removal system capable of exhibiting a dust removal efficiency of 99.9% or more with respect to ultrafine particulate matter of PM2.5. As a result, it has been found that the heat-resistant polymer fibers are electro- It was confirmed that dust removal efficiency corresponding to PM2.5 can be improved up to 99.9% as a result of reducing the average pore size to 2 탆 by adhering.

An object of the present invention is to provide a filtration body having an air permeability of 5 cm ³ / cm ² / sec or more and a method of manufacturing the same, which achieves a dust removal efficiency of 99.9% or more for ultrafine dusts of 2.5 μm or less.

In order to solve the above problems, the present invention provides an inorganic fiber support; A first polytetrafluoroethylene (PTFE) layer foam coated on the inorganic fiber support; A porous network made of a heat-resistant polymer fiber attached by electrospinning a heat-resistant polymer solution on the first PTFE layer; And a second PTFE layer foam coated on the porous network. The filter medium for dust collection of medium and high temperature flue gas is provided.

In the present invention, the medium- and high-temperature flue gas means a flue gas having a temperature of 200 ° C to 300 ° C, which can be referred to as a mid-high temperature region.

In the present invention, dust means ultrafine dust of 2.5 탆 or less.

In the present invention, the term " inorganic fiber support " refers to a support in the form of an inorganic fiber having heat resistance and chemical resistance suitable for a dust collector for filtration of a combustion exhaust gas.

As the inorganic fiber support used in the present invention, commercially available glass fibers are preferable.

In the present invention, the inorganic fiber support preferably has a thickness of 400 to 1000 mu m.

In the present invention, " polytetrafluoroethylene (PTFE) " means a fluorine-based resin containing a fluorine compound represented by the following general formula (1) in which all hydrogen of polyethylene is substituted with fluorine. PTFE is known under the trade name Teflon and is chemically resistant to almost all chemicals and has a smooth surface.

[Chemical Formula 1]

_{- (CF 2 CF 2) n} -

In the above formula (1), n is an integer between 100 and 10,000.

The first PTFE layer may be formed by foam coating a coating liquid containing a PTFE resin, which is a heat-resistant water-soluble resin, on the inorganic fiber support.

The first PTFE layer may have pores having an average pore size of 30 탆 or less, and preferably 10 탆 to 30 탆.

The thickness of the first PTFE layer may be 5 to 100 占 퐉, preferably 50 to 100 占 퐉.

Preferably, the first PTFE layer may be formed by foam coating with a coating liquid containing PTFE, a foam stabilizer, a foaming agent and a thickener.

The foam stabilizer means a substance acting as a preservative of the resin foam.

The foaming agent refers to a material that produces bubbles in the resin coating liquid.

The thickener means a substance that acts to keep the resin foam adhered to the fiber. In the present invention, the thickener may be an acrylic thickener, but is not limited thereto.

As described above, since the thickness of the PTFE layer is at most 100 탆, the laminated membrane filter having only a membrane layer of 5 탆 or less is used as a laminated membrane filter (Laminated Membrane Filter ), Which is superior in chemical resistance and heat resistance.

However, since the pore size of the filter body is 10 μm or more and approximately 10 μm to 30 μm, it is not effective enough to remove ultrafine dust of 2.5 μm or less.

Accordingly, the present inventors have attempted to reduce the filter differential pressure and improve the filter performance by forming a porous network of heat-resistant polymer fibers on the foam coated PTFE layer on the surface of the inorganic fiber support.

The filter performance index indicating the relationship between the filter dust removal performance and the filter differential pressure can be expressed by Equation 1 below.

[Formula 1]

P = - ln (1- E ) / P

( P : filter performance index, E : dust collection efficiency, P: filter differential pressure)

Referring to Equation 1, when the pore size of the perforated plate filter is reduced to 10 μm or less in order to remove ultrafine dusts of 2.5 μm or less, the filter differential pressure increases and the filter performance index deteriorates.

Fig. 4 shows a result of simple simulation of the dust removal efficiency by applying the filter theory to the pore sizes shown in Figs. 3 (a) and 3 (b). It can be seen that as the pore size decreases, that is, the fiber diameter d _f becomes thinner, and the dust removal efficiency increases.

However, the inventors of the present invention have found that it is difficult to further reduce the pore size by controlling the bubble size of the PTFE foam. Therefore, the polymer fibers capable of withstanding a high temperature of 270 캜 are produced and attached to many pores (holes) As a result, the performance of dust removal is improved. However, a high performance filter material which does not significantly increase the differential pressure of the filtration body due to the addition of only a few heat-resistant fibers has been developed.

Accordingly, the present inventors have developed a porous network composed of a heat-resistant polymer fiber by spinning a solution containing a heat-resistant polymer on a PTFE layer primarily coated with a foam on a support, thereby improving the filter performance while minimizing an increase in the filter differential pressure, It is confirmed that the removal rate of the ultrafine dust can be 99.9% or more, and the present invention has been completed.

The filtration body of the present invention is characterized in that a heat-resistant polymer solution is electrospun on a foam-coated first PTFE layer to form a porous network made of heat-resistant polymer fibers.

By using the electrospinning method for forming the porous network, the present invention can simplify the process and reduce the process cost as compared with the melt-blow method.

The diameter of the heat-resistant polymer fibers is preferably 0.1 to 2 탆.

In the present invention, the heat-resistant polymer fiber may be a polymer material having heat resistance at 200 to 300 캜, and preferably a meta-aramide having heat resistance at 270 캜.

The solvent of the heat resistant polymer solution is preferably N, N-dimethylacetamide (DMAc), dimethylformamide (DMF), N-methylpyrrolidone (NMP) or DMSO (dimethylsulfoxide (DMSO)).

In a preferred embodiment of the present invention, the heat-resistant polymer solution may be prepared by dissolving meta-aramid in N, N-dimethylacetamide (DMAc) or dimethylformamide (DMF). The present inventors have found that a porous network can be easily formed on a support by electing a meta-aramid instead of PTFE which is insoluble in a solvent and dissolving it in N, N-dimethylacetamide (DMAc) or dimethylformamide (DMF) Respectively.

The filter body of the present invention comprises a second PTFE layer foam coated on said porous network.

The present invention can fix a porous network of heat resistant polymeric fibers by foaming a second PTFE layer that is thinner on the surface of the foam coated PTFE layer on which the porous network is formed.

The second PFTE layer may be formed in the same manner as the first PTFE layer.

Preferably, the thickness of the second PTFE layer may be 1 to 50 占 퐉, more preferably 10 to 50 占 퐉.

As a result, the filter body of the present invention can be a filter body having a total of four layers including an inorganic fiber support layer.

The filter material of the present invention may have an average pore size of 2 탆 or less, preferably 0.5 탆 to 2 탆. The filter material of the present invention can also collect ultrafine dusts of 2.5 μm or less by including pores having a size within the above range.

The filter material of the present invention has excellent heat resistance as compared with the conventional filter material and is resistant to heat shrinkage and has a standard dust removal efficiency (after aging) of 99.9% or more based on the number density of dusts having a particle diameter of 2.5 탆 or less, Denitrification efficiency and air permeability may be 5 cm ³ / cm ² / sec or more.

A second aspect of the present invention provides a method for producing a foamed polyurethane foam, comprising the steps of: foam coating a coating liquid containing a PTFE resin on an inorganic fiber support to form a first foamed polytetrafluoroethylene (PTFE) layer on an inorganic fiber support; A second step of electrospinning a heat-resistant polymer solution on the first PTFE layer to form a porous network of heat-resistant polymer fibers; And a third step of foaming-coating a coating solution containing PTFE resin on the porous network to form a foam-coated second PTFE layer. The present invention also provides a method of manufacturing a filter medium for dust collection of medium- and high-temperature flue gas.

In the first step, the coating liquid containing the PTFE resin may be first treated with a foam generator to form a foam liquid, and then the foam liquid may be coated on the surface of the inorganic fiber support to form a foamed PTFE layer.

Preferably, the coating liquid containing the PTFE resin may be a coating liquid containing PTFE, a foam stabilizer, a foaming agent and a thickener.

The first step may be a step of drying the support on which the foam liquid is applied to form a dried foamed PTFE layer.

At this time, the foam generator can generate bubbles by supplying air at a rate of 3 L / min to the dispersion quantitatively while rotating at a speed of 200 to 250 rpm.

The first step may be a step of drying the support coated with the foam liquid in two steps by primary drying and secondary drying to form a porous layer in which a stable foamed PTFE layer is formed.

In one embodiment of the present invention, the drying of the foam-coated support may be performed by primary drying at 80 ° C to 120 ° C and secondary drying at 180 ° C to 220 ° C. The dried support may then be pressed to increase the strength of the microporous PTFE layer and to smooth the surface.

That is, the first step may further include a step of squeezing the dried support.

The pressing process may preferably be performed at a pressure of 200 psi to 700 psi.

The first step may further include a step of forming a surface layer having excellent surface strength by heat-treating the support subjected to the pressing treatment and curing the surface layer.

The heat treatment may preferably be a step of curing by treatment at 340 to 400 캜. The heat treated support may then be cooled to obtain a support having a primarily foam coated PTFE layer formed thereon.

The thickness of the first PTFE layer is preferably 5 to 100 mu m.

By forming the first PTFE layer foam-coated on the surface of the inorganic fiber support as described above, a double-layered filter body can be obtained.

The second step may include a step of electrospinning a heat-resistant polymer solution on the first PTFE layer to form a porous network made of heat-resistant polymer fibers.

In the second step, the voltage used for electrospinning is 5 to 30 kV, the scanning speed may not be limited, more preferably, the voltage used for electrospinning is 20 kV, and the spinning speed is 1 mL / h But is not limited thereto.

The third step may be to fix the porous network of the heat-resistant polymer fibers by foaming-coating a second thin PTFE layer on the surface of the foam-coated PTFE layer on which the porous network is formed.

The thickness of the second PTFE layer is preferably 1 to 50 mu m.

According to the production method of the present invention, a filter body having a total of four layers structure including an inorganic fiber support layer can be produced.

The manufacturing method of the present invention is characterized in that an unwinder 1, a PTFE foam feed nozzle 2, a knife 3 for controlling the foam coating thickness, a heater 4 for dry hardening, a polymer fiber electrospinning device 5, (6) and a winder (7).

Fig. 7 schematically shows an example of the above manufacturing apparatus. In the filter body of the present invention, the glass fiber is fed by the unwinder 1 using the above production apparatus, the PTFE foam is fed onto the conveyed glass fiber through the PTFE foam feed nozzle 2, A knife 3 for adjusting the coating thickness and a heater 4 for drying and curing were sequentially applied to form a first PTFE layer on the glass fiber and then a heat resistant polymer network layer was formed using the polymer fiber electrospinning device 5 And then applying the PTFE foam feed nozzle 2, the knife 3 for controlling the foam coating thickness and the heater 4 for dry hardening in sequence.

The present invention can provide a filter having an air permeability of 5 cm ³ / cm ² / sec or more, achieving a dust removal efficiency of 99.9% or more for ultrafine dust of 2.5 μm or less.

The filter body of the present invention is very useful for a dust removal system for an ultrafine dust generation production facility discharged from an incinerator, a coal-fired power plant, a cement kiln, and the like.

1 is an example of a filtration and dust collecting apparatus.
2 is a schematic view of a filtration bag mounted in a filtration and dust collecting apparatus.
3 shows the relationship between pore size and fiber diameter.
Figure 4 shows the effect of pore size on the trapping performance.
Fig. 5 shows (a) a PTFE foam-coated filtration body, and (b) a PTFE foam-coated filtration body with heat resistant polymer fibers attached thereto.
Fig. 6 is a schematic view of an apparatus for carrying out the production method of the filter body of the present invention. Fig.

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the following examples are provided to further understand the present invention, and the present invention is not limited by the examples.

Example 1: Preparation of filtrate

The foam-coated filter body (GL-TEX-790, Chang-Myung Industry, Korea) was prepared.

FIG. 5A is a photograph of a surface of the filter body manufactured by Chang Myeong Industry, which is enlarged at 800 times magnification. In Figure 5a, it can be seen that the pores of various sizes are layered, and the pore size measurement (PMI measurement) shows that the average pore size is about 20 μm.

A meta-aramid solution was prepared by dissolving 20 g of meta-aramid in 100 ml of N, N-dimethylacetamide (DMAc) on the surface of a foam coating filtrate (GL-TEX-790, Changryong Industry Co., Ltd., Korea). The voltage used for electrospinning was 20 kV and the scanning speed was maintained at 1 mL / h. Then, the PTFE foam is coated to a thickness of about 50 μm or less, followed by primary drying at 80 ° C. to 120 ° C. and secondary drying at 180 ° C. to 220 ° C., followed by compression bonding at a pressure of 200 psi to 700 psi . Then, the mixture was heat-treated at 340 to 400 ° C and cured to produce a filter body having a four-layer structure.

Experimental Example 1: Dust collection performance test

In order to confirm the dust collecting performance of the filter body of Example 1, the weight dust collecting performance was evaluated based on the weight dust collecting performance (%) (Kanazawa Univ.), And the results are shown in Table 1 below.

Experimental Example 2: Scavenging efficiency test

In order to confirm the dust removal efficiency of the filter body of Example 1, the dust removal efficiency was evaluated using a dust collection performance evaluation device of Korea Institute of Industrial Technology, and the results are shown in Table 1 below.

Experimental Example 3: Air permeability test

The air permeability is a performance related to the pore size as a differential pressure characteristic of the filter body, and increases the driving energy by increasing the ID-Fan differential pressure of the dust removing system.

In order to confirm the air permeability of the filter body of Example 1, the air permeability was evaluated by KOTERI and the results are shown in Table 1 below.

Experimental Example 4: Shrinkage Test

In order to confirm the shrinkage ratio of the filter body of Example 1, the shrinkage ratio was evaluated by the Korean Institute of Industrial Technology and the results are shown in Table 1 below.

Experimental Example 5: Wear resistance test

In order to confirm the wear resistance of the filter body of Example 1, the wear resistance was evaluated by the Korea Institute of Industrial Technology, and the results are shown in Table 1 below.

Evaluation items Assessment Methods Certification Criteria Comparative Example 1 Comparative Example 2 Example 1 Dust collection performance test
(%) Heavy dust collection performance (%)
(Kanazawa Univ.) - Standard dust: PM2.5
- Dust concentration: 3.0 g / m ³
- Filtration rate: 1m / min 99.9 80.0 99.9
Exhaustion efficiency test
(%) Effluent efficiency (%)
(Korea Institute of Industrial Technology, collection performance evaluation device) - Standard dust: PM2.5
- Dust concentration: 3.0 g / m ³
- Exhaustion pressure 4 kg / cm ² 85  85 85 Air permeability
(m ³ / m ² / sec)  Commissioned by KOTERI  - KS K ISO 9237, 125 Pa 2.7 13.5 > 5 Contraction ratio Korea Institute of Industrial Technology - KS K 3841
(Determination of deformation through SEM photo analysis) 300 ° C, 30 minute exposure
(Coating film deformation) 350 ° C, 30 minute exposure
(No strain) 350 ° C, 30 minute exposure (no deformation)
Wear resistance Korea Institute of Industrial Technology  - KS K 0650  Transformed to 100 times friction  Begin to deform with 1000 times of friction Begin to deform with 1000 times of friction

Comparative Example 1: Micro-circle triple filter (glass cloth woven fabric + PTFE laminating)

Comparative Example 2: GL-TEX 790 (pore size 20 탆)

As shown in Table 1, Comparative Example 2 exhibited a dust removal rate of 80% for the PM2.5 standard dust, whereas the filter material of Example 1 exhibited a dust removal rate as high as 99.9%. Comparative Example 1 also showed a dust removal rate as high as 99.9%, whereas Comparative Example 1 had a very low air permeability of 2.7, while the filtrate of Example 1 was as high as 5 or more.

As shown in Table 1, the filter material of Example 1 was not deformed when exposed to 350 ° C. for 30 minutes as in the conventional product, and the wear resistance was also high.

Claims (16)

Inorganic fiber support;
A first polytetrafluoroethylene (PTFE) layer foam coated on the inorganic fiber support;
A porous network made of a heat-resistant polymer fiber attached by electrospinning a heat-resistant polymer solution on the first PTFE layer; And
And a second PTFE layer foam coated on said porous network. The filter medium according to claim 1, wherein the inorganic fiber support is glass fiber. The filter body according to claim 1, wherein the first PTFE layer is formed by foam coating with a coating liquid containing PTFE, a foam stabilizer, a foaming agent and a thickener. The filter element of claim 1, wherein the thickness of the first PTFE layer is between 5 and 100 탆. The filter element according to claim 1, wherein the second PTFE layer has a thickness of 1 to 50 탆. The filter medium according to claim 1, wherein the heat-resistant polymer is a meta-aramid. The heat resistant polymer solution according to claim 1, wherein the solvent of the heat resistant polymer solution is N, N-dimethylacetamide (DMAc) or dimethylformamide (DMF), N-methylpyrrolidone (NMP), or dimethylsulfoxide Lt; / RTI > The filter element according to claim 1, wherein the heat-resistant polymer fibers have a diameter of 0.1 to 2 탆. The filter medium according to claim 1, wherein the filtration body has an average pore size of 0.5 to 2 μm. The filter according to claim 1, wherein the filter body has a dust removal efficiency of 99.9% or more, an exhaustion efficiency of more than 85%, and an air permeability of 5 cm ³ / cm ² / sec or more for ultrafine dust of 2.5 μm or less. . A first step of foam coating a coating solution containing a PTFE resin on an inorganic fiber support to form a first foamed polytetrafluoroethylene (PTFE) layer on an inorganic fiber support;
A second step of electrospinning a heat-resistant polymer solution on the first PTFE layer to form a porous network of heat-resistant polymer fibers; And
And a third step of foaming-coating a coating liquid containing a PTFE resin on the porous network to form a foam-coated second PTFE layer. The method for producing a filter medium for dust collection of medium and high-temperature flue gas according to claim 1, 12. The method according to claim 11, wherein the coating liquid containing the PTFE resin is a coating liquid containing PTFE, a foam stabilizer, a foaming agent, and a thickener. The method of claim 11, wherein the first step further comprises a step of first drying the foam-coated first PTFE layer at 80 ° C to 120 ° C, followed by secondary drying at 180 ° C to 220 ° C. Way. 12. The method of claim 11, wherein the first step further comprises compressing the support having the dried first PTFE layer at a pressure of 200 psi to 700 psi. 12. The method according to claim 11, wherein the heat-resistant polymer is a meta-aramid. The manufacturing method according to claim 11, wherein the voltage used for electrospinning in the second step is 5 to 30 kV.

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