Filter material structure and method for synergistically removing dioxin by using pressed powder layer

Abstract

The invention discloses a filter material structure and a method for synergistically removing dioxin by using a pressed powder layer, which can enable a filter material to have a dust adsorption function and synergistically treat dioxin during sludge incineration. The filter material structure comprises base cloth, a fiber layer, a membrane layer and a pulp layer; the base cloth is a polyphenylene sulfide and polyimide blended needled felt, and the surface density of the base cloth is 500-520g / m < 2 >; the surface layer of the base cloth is mixed with polyimide or polyphenylene sulfide fibers which are not more than 1d; carrying out surface consolidation treatment on the dust facing surface of the fiber layer by utilizing a spunlace process, and presetting a primary micropore structure with pore size distribution on a surface component of the fiber layer; in the dust-containing flue gas filtering process, the primary microporous structure is used as a screening template to intercept initial dust particles in a specific particle size range in flue gas, and a compact layer with a specific secondary microporous aperture is induced and generated on the surface of a filter material by utilizing a bridging effect; the aperture of the secondary micropores of the pressed powder layer is configured to be matched with the average free path of dioxin molecules in smoke or the particle size of dioxin carrier particles.

Description

Technical Field

[0001] This invention belongs to the field of sludge incineration technology, and specifically refers to a filter media structure and a method for synergistic removal of dioxins using a powder cake layer. Background Technology

[0002] Dioxins (PCDD / Fs) are a class of highly toxic tricyclic aromatic organic compounds. These substances are neither artificially produced nor have any practical use; rather, they are byproducts of combustion and various industrial processes. Major sources of dioxins in the environment include: evaporation from the use of chlorophenols for wood preservation and schistosomiasis control; emissions from incineration industries; the use of defoliants; pesticide preparation; paper bleaching; and emissions from vehicle exhaust.

[0003] In urban sludge incineration or sludge-to-waste incineration, although the total emissions of dioxins in the flue gas are relatively low, their toxicity is high and monitoring standards are stringent (common limits ≤0.10 ng TEQ / Nm³). 3 The existing treatment method involves simultaneously spraying high specific surface area activated carbon (PAC) at the rear end of PTFE filter bags / cartridges to adsorb dioxins. However, when this method is applied to sludge incineration, the following drawbacks still exist: (1) Poor cost-effectiveness: In sludge incineration, the concentration of dioxins is low, but the cost and operating expenses of the PAC system are comparable to those of high-load waste incineration.

[0004] (2) Limited layout: The space behind the furnace is relatively compact, making it difficult to add powder injection and storage equipment.

[0005] (3) Complex operation and maintenance: Activated carbon powder is flammable, and the powder management and safety requirements are high.

[0006] Therefore, there is an urgent need for a low-cost treatment solution that does not rely on an external PAC system but can ensure that dioxin emissions meet standards. Summary of the Invention

[0007] The main objective of this invention is to provide a filter media structure and a method for synergistic removal of dioxins using a powder cake layer, thereby solving the problems existing in the prior art. This allows the filter media itself to have dust adsorption function, and to synergistically treat dioxins during sludge incineration.

[0008] To achieve the above objectives, one solution of the present invention is: A filter media structure includes a base fabric, a fiber layer, a membrane layer, and a slurry layer; the base fabric is a blended needle-punched felt of polyphenylene sulfide and polyimide, with an areal density of 500~520 g / m³. 2The base fabric surface layer is mixed with polyimide or polyphenylene sulfide fibers of no more than 1 d to form an ultra-fine denier fiber layer; the dust-facing surface of the fiber layer is surface-consolidated using a hydroentangling process, and a native microporous structure with a preset pore size distribution is constructed on the surface of the fiber layer by adjusting the jet pressure, nozzle density, and hydroentangling energy distribution of the hydroentangling machine; during the filtration of dusty flue gas, the native microporous structure acts as a screening template to intercept initial dust particles within a specific particle size range in the flue gas, and induces the formation of a powder cake layer with a specific secondary micropore size on the filter material surface using the bridging effect; the secondary micropore size of the powder cake layer is constructed to match the mean free path of dioxin molecules or the particle size of dioxin carrier particles in the flue gas.

[0009] By controlling the jet pressure of the hydroentangling machine, a dense two-dimensional planar entanglement is formed on the surface of the fiber layer, and the average pore size of the original microporous structure on the filter material surface is controlled within the range of 10~15 micrometers.

[0010] The powder cake layer formed by the induced primary microporous structure has a secondary micropore with an average pore diameter that is 1 / 5 to 1 / 10 smaller than the average pore diameter of the primary micropore.

[0011] The base fabric has a film layer attached to its surface. The film layer is a polytetrafluoroethylene film with 0.3μm micropores, and is formed by grinding wheel embossing to create a height difference of 40~60μm.

[0012] In the post-processing stage of fiber felt, its surface is coated with 0.5~1wt% water-based silicone-acrylic / acrylic emulsion at a rate of 0.3~0.5g / m. 2 To form a slurry layer.

[0013] The second solution of the present invention is: A method for synergistic removal of dioxins using a powder cake layer includes installing filter media having the aforementioned filter media structure in a flue gas processor of a sludge incineration system, and comprising: Step 1: Add 1-2 wt% of wood or coconut shell powder during the sludge conditioning stage so that ≥8 wt% of microporous carbonaceous material is retained in the incineration fly ash. Step 2: Start the waste incineration system. The flue gas forms a powder cake layer after passing through the filter material, which is used for the physical adsorption of dioxins. Step 3: Perform pulse cleaning according to the preset cycle. After the powder cake layer is completely peeled off, it falls into the ash hopper for collection. Step 4: Repeat steps 2 and 3 to complete the incineration of all waste.

[0014] The sludge incineration system is pre-coated with 3~5g / m³ at startup. 2 Wood-based activated carbon micro powder.

[0015] After adopting the above technical solution, the present invention has the following technical effects: (I) No PAC system is required, which can save 30-50% of equipment investment and operating costs; (II) It can synergistically remove particulate matter and low-concentration dioxins, achieving simultaneous control; (III) It is convenient for mass production in industry, requiring only the adjustment of mature processes such as needle punching, singeing, and coating; (IV) Its adsorption layer is automatically renewed, maintenance is simple, and operating resistance is stable; (V) It avoids the risks of storing, transporting and exploding large doses of activated carbon powder, thus improving safety. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the adsorption-cleaning cycle process in a specific embodiment of the present invention. Detailed Implementation

[0017] To further explain the technical solution of the present invention, the present invention will be described in detail below through specific embodiments.

[0018] This invention discloses a filter material structure, comprising a base fabric, a fiber layer, a membrane layer, and a slurry layer; The base fabric is a blended needle-punched felt made of polyphenylene sulfide (PPS) and polyimide (PI), with a surface density of 500~520 g / m². 2 It can provide the overall temperature resistance of the filter media; The surface layer of the base fabric is mixed with polyimide (PI) or polyphenylene sulfide (PPS) fibers of no more than 1 denier to form an ultra-fine denier fiber layer, which can provide a fine nap and increase dust accumulation points. The surface of the fiber layer is consolidated using a hydroentangling process. By adjusting the jet pressure, nozzle density, and hydroentangling energy distribution of the hydroentangling machine, a native microporous structure with a pre-defined pore size distribution is constructed on the surface of the fiber layer. During the filtration of dusty flue gas, this native microporous structure acts as a screening template, intercepting initial dust particles within a specific size range in the flue gas. It also induces the formation of a powder cake layer with specific secondary micropore sizes on the filter material surface using a bridging effect. The secondary micropore sizes of the powder cake layer are configured to match the mean free path of dioxin molecules or the particle size of dioxin carrier particles in the flue gas, thereby achieving dioxin capture through physical adsorption or capillary coagulation.

[0019] In some embodiments, by controlling the jet pressure of the hydroentanglement machine, a dense two-dimensional planar entanglement is formed on the surface of the fiber layer, thereby controlling the average pore size of the original microporous structure on the filter material surface within the range of 10 to 15 micrometers.

[0020] In some embodiments, the powder cake layer induced by the above-mentioned primary microporous structure has a secondary micropore with an average pore size that is less than 1 / 5 to 1 / 10 of the average pore size of the primary micropore, and the tortuosity of the flow channel formed by the secondary microporous structure is sufficient to prolong the dioxin residence time.

[0021] In some embodiments, a membrane layer is attached to the surface of the base fabric. The membrane layer is a polytetrafluoroethylene (PTFE) membrane with 0.3 μm micropores, and a height difference of 40~60 μm is formed by embossing. The initial resistance when flue gas comes into contact with the filter material can be controlled by the membrane layer on the surface of the base fabric, and the microsteps formed by the embossing on it can serve as "anchor points". In some embodiments, during the post-processing stage of the fiber felt, its surface is coated with 0.5~1wt% of an aqueous silicone / acrylic emulsion at a rate of 0.3~0.5 g / m². 2 This forms a slurry layer; the slurry on the surface can form a peelable, lightly sticky layer on the filter material during its initial operation, improving the efficiency of the first dust collection.

[0022] The above-mentioned filter material structure, through existing mass-producible processes such as fiber denier reduction, hydroentangling reinforcement, hot roller coating, and low-viscosity sizing, can construct a "dust-easily-adhering seed layer" on the surface of the filter material, which promotes the rapid and uniform formation of dust cake layer on the surface of the filter material, so as to facilitate the synergistic treatment of dioxins with subsequent methods.

[0023] refer to Figure 1 As shown, the present invention also discloses a method for synergistic removal of dioxins using a powder cake layer, wherein a filter media having the above-described filter media structure is installed in a flue gas processor of a sludge incineration system, and includes: Step 1: During the sludge conditioning stage, add 1-2 wt% of fine wood or coconut shell powder to ensure that the incineration fly ash (SiO2, Al2O3, CaO) retains ≥8 wt% microporous carbonaceous matter; if necessary, a small amount (3-5 g / m³) can be pre-coated before starting the machine. 2 Wood-based activated carbon micro powder; Step 2: Start the waste incineration system. After the flue gas passes through the filter media, a powder cake layer is formed for the physical adsorption of dioxins. The operating temperature is generally 150~180℃. Specifically, the powder cake layer is composed of inorganic ash and microporous carbonaceous particles, and its specific surface area can reach 250~450m². 2 / g, pore size main peak <2nm, adapted to the molecular scale of dioxins, can physically adsorb dioxins to reduce concentration; Step 3: Perform pulse cleaning according to the preset cycle (e.g., once every 10 minutes). After the powder cake layer is completely peeled off, it falls into the ash hopper for collection; the surface layer and membrane of the filter material are still intact. Step 4: Repeat steps 2 and 3 to complete the incineration of all waste.

[0024] The technical effects of this invention are demonstrated below through a set of experimental data:

[0025] As can be seen from the above data, the emission levels achieved by using this invention for flue gas treatment can meet or even reach excellent levels, and the cost is low, making it valuable for market promotion.

[0026] Through the above solution, the present invention has the following technical effects: (I) No PAC system is required, which can save 30-50% of equipment investment and operating costs; (II) It can synergistically remove particulate matter and low-concentration dioxins, achieving simultaneous control; (III) It is convenient for mass production in industry, requiring only the adjustment of mature processes such as hydroentangling, singeing, post-treatment, and coating; (IV) Its adsorption layer is automatically renewed, maintenance is simple, and operating resistance is stable; (V) It avoids the risks of storing, transporting and exploding large doses of activated carbon powder, thus improving safety.

[0027] The above embodiments and figures are not intended to limit the product form and style of the present invention. Any appropriate changes or modifications made by those skilled in the art should be considered as not departing from the patent scope of the present invention.

Claims

1. A filter material structure, characterized in that: comprising a base cloth, a fiber layer, a membrane layer and a slurry layer; the surface layer of the base cloth is mixed with polyimide or polyphenylene sulfide fibers not more than 1d to form a superfine fiber layer; the dust-facing surface of the fiber layer is subjected to surface consolidation treatment by using a water jet process, and by adjusting the jet pressure, nozzle density and water jet energy distribution of the water jet machine, a primary micropore structure with a preset pore size distribution is formed on the surface of the fiber layer; during the filtration process of dust-containing flue gas, the primary micropore structure acts as a screening template to intercept initial dust particles in the flue gas within a certain particle size range, and a powder cake layer with a specific secondary micropore pore size is induced on the surface of the filter material by using the bridging effect; the secondary micropore pore size of the powder cake layer is configured to match the average free path of dioxin molecules or the particle size of dioxin carrier particles in the flue gas.

2. The filter material structure of claim 1, characterized in that: by controlling the jet pressure of the water jet machine, the surface of the fiber layer forms a dense two-dimensional planar entanglement, and the average pore size of the primary micropore structure on the surface of the filter material is controlled within the range of 10-15 microns. The base cloth is a blended needled felt of polyphenylene sulfide and polyimide, and the area density is 500-520 g / m 2 ; 3. The filter material structure of claim 1, characterized in that: the powder cake layer induced by the primary micropore structure has an average pore size of the secondary micropores that is less than 1 / 5 to 1 / 10 of the average pore size of the primary micropores.

4. The filter material structure of claim 1, characterized in that: the surface of the base cloth is attached with a membrane layer, which is a 0.3μm microporous polytetrafluoroethylene membrane and is formed with a 40-60μm height difference by a grinding wheel embossing.

5. The filter material structure of claim 1, characterized in that: the filter material with the filter material structure as claimed in any one of claims 1 to 5 is installed in a flue gas treatment device of a sludge incineration system, and comprises: step 1: incorporating 1-2wt% of wood or coconut shell fine powder during the sludge conditioning stage, so that ≥8wt% of microporous carbon is retained in the incineration fly ash; step 2: starting the garbage incineration system, and the flue gas forms a powder cake layer after passing through the filter material, which is used for physical adsorption of dioxin; step 3: performing pulse cleaning according to a preset periodic cycle, and the powder cake layer is completely stripped and falls into the ash bucket for collection; step 4: repeating steps 2 and 3 to complete the incineration of all garbage.

7. The method for removing dioxin by using a powder cake layer of claim 6, characterized in that ​ ​ ​ ​ ​ ​ In the post-processing stage of the fiber felt, the surface is coated with 0.5-1 wt% water-based silicone / acrylic emulsion, 0.3-0.5 g / m 2 to form a pulp layer.

6. A method for synergistically removing dioxins using a layer of pressed powder, characterized by, ​ ​ ​ ​ ​ ​ The sludge incineration system is pre-coated with 3~5g / m 2 of wood-based activated carbon powder at start-up.

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