CN115350697B - Thin-wall honeycomb SCR denitration catalyst and preparation method thereof - Google Patents
Thin-wall honeycomb SCR denitration catalyst and preparation method thereof Download PDFInfo
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- CN115350697B CN115350697B CN202211147855.8A CN202211147855A CN115350697B CN 115350697 B CN115350697 B CN 115350697B CN 202211147855 A CN202211147855 A CN 202211147855A CN 115350697 B CN115350697 B CN 115350697B
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- 239000003054 catalyst Substances 0.000 title claims abstract description 56
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
- 239000000463 material Substances 0.000 claims abstract description 70
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims abstract description 42
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 claims abstract description 26
- 239000004698 Polyethylene Substances 0.000 claims abstract description 22
- -1 polyethylene Polymers 0.000 claims abstract description 22
- 229920000573 polyethylene Polymers 0.000 claims abstract description 22
- 239000003365 glass fiber Substances 0.000 claims abstract description 20
- 239000004408 titanium dioxide Substances 0.000 claims abstract description 18
- 229920002134 Carboxymethyl cellulose Polymers 0.000 claims abstract description 15
- 239000001768 carboxy methyl cellulose Substances 0.000 claims abstract description 15
- 235000010948 carboxy methyl cellulose Nutrition 0.000 claims abstract description 15
- 239000008112 carboxymethyl-cellulose Substances 0.000 claims abstract description 15
- 239000000835 fiber Substances 0.000 claims abstract description 15
- 235000014655 lactic acid Nutrition 0.000 claims abstract description 13
- 239000004310 lactic acid Substances 0.000 claims abstract description 13
- 239000002994 raw material Substances 0.000 claims abstract description 10
- 238000002156 mixing Methods 0.000 claims description 31
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 28
- 239000011449 brick Substances 0.000 claims description 24
- 238000001914 filtration Methods 0.000 claims description 24
- 239000007787 solid Substances 0.000 claims description 21
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 19
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 19
- 238000001035 drying Methods 0.000 claims description 19
- 238000000034 method Methods 0.000 claims description 19
- 238000001354 calcination Methods 0.000 claims description 18
- 239000000203 mixture Substances 0.000 claims description 18
- 238000003756 stirring Methods 0.000 claims description 18
- 238000005520 cutting process Methods 0.000 claims description 17
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- 239000011259 mixed solution Substances 0.000 claims description 16
- 238000001816 cooling Methods 0.000 claims description 11
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- 238000006467 substitution reaction Methods 0.000 claims description 2
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- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 description 3
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- 125000004430 oxygen atom Chemical group O* 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/02—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the alkali- or alkaline earth metals or beryllium
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/8621—Removing nitrogen compounds
- B01D53/8625—Nitrogen oxides
- B01D53/8628—Processes characterised by a specific catalyst
-
- B01J35/56—
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/04—Mixing
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/08—Heat treatment
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2258/00—Sources of waste gases
- B01D2258/02—Other waste gases
- B01D2258/0283—Flue gases
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
Abstract
The invention belongs to the technical field of SCR denitration catalysts, and in particular relates to a thin-wall honeycomb SCR denitration catalyst and a preparation method thereof, wherein the thin-wall honeycomb SCR denitration catalyst is prepared from dry materials and wet materials, and the dry materials are prepared from the following raw materials in percentage by mass: 90-94% of titanium dioxide, 0.5-1% of carboxymethyl cellulose, 2-3% of polyethylene wax, 1% of lactic acid, 6% of glass fiber and 1-3% of RP-chop fiber; the wet material comprises the following components in parts by weight based on 100 parts by weight of the total mass of the dry material and the wet material: the invention is suitable for completing the integral molding of the thin-wall honeycomb SCR denitration catalyst with the wall thickness of less than 0.3mm, and the prepared thin-wall honeycomb SCR denitration catalyst can greatly reduce the pressure drop of a system, reduce the operation and maintenance cost of the system, improve the yield and the production efficiency of the thin-wall porous catalyst, strengthen the mechanical structure of the catalyst and strengthen the mechanical property of a product after being applied to a heavy-duty gas turbine.
Description
Technical Field
The invention belongs to the technical field of SCR denitration catalysts, and particularly relates to a thin-wall honeycomb SCR denitration catalyst and a preparation method thereof.
Background
With the annual rise of the national environmental protection standard, the NOx emission standard in the heavy-duty gas engine field is also brought out. The thin-wall technology is a 'neck clamping' technology which is necessary to face in the field of denitration of the combustion engine, and the problems of low unit denitration efficiency, high pressure loss, overlarge occupied space of a reactor and the like when the combustion engine is subjected to denitration are caused by the excessively thick wall thickness, so that the production of the thin-wall honeycomb SCR denitration catalyst product is very necessary.
The main raw material of the SCR denitration catalyst is anatase titanium dioxide, and because the existing production technology is difficult to achieve integral extrusion molding with the wall thickness of 0.3mm, the existing production technology can only be used for solving the problem, and then the SCR denitration catalyst is prepared by coating titanium dioxide after other materials such as cordierite are used for preparing honeycomb products. Thus, the process is prolonged, the production rate is low, the cost is high, and the high density of the cordierite carrier can cause overload of the SCR system, thereby increasing the installation and maintenance cost. Meanwhile, due to the technology of coating layers, the uneven thickness of coating slurry can cause the wall thickness to be too high and difficult to control, and the wall thickness of the currently better cordierite coated catalyst is about 0.5mm and less than 0.3 mm.
In the existing honeycomb SCR denitration catalyst production formula system, macromolecular organic matters such as PEO are basically contained, and the PEO mainly plays a role in providing plasticity, wherein the PEO is polyethylene oxide, so that the SCR catalyst pug can flow, extrude and shape smoothly. PEO can meet the production of conventional hole-type honeycomb denitration catalysts, but when the wall thickness reaches 0.3mm or less, too viscous PEO can cause uneven water dispersion, so that the conditions of forming plug Kong Laliao and the like occur. This is because PEO has a relatively large molecular weight and is a turbid solution with a relatively high viscosity after dissolution in water, and it is difficult to uniformly disperse the PEO during mixing.
Disclosure of Invention
The invention aims to solve the technical problem of providing a thin-wall honeycomb SCR denitration catalyst, which is suitable for completing the integral forming of the thin-wall honeycomb SCR denitration catalyst with the wall thickness of less than 0.3mm, and the manufactured thin-wall honeycomb SCR denitration catalyst can greatly reduce the pressure drop of a system after being applied to a heavy-duty gas turbine, reduce the operation and maintenance cost of the system, improve the manufacturing rate and the production efficiency of a thin-wall porous catalyst, strengthen the mechanical structure of the catalyst and strengthen the mechanical performance of a product. The invention also provides a scientific and reasonable preparation method.
The thin-wall honeycomb SCR denitration catalyst is prepared from dry materials and wet materials, wherein the dry materials are prepared from the following raw materials in percentage by mass:
84% -91.5% of titanium dioxide, 0.5% -1% of carboxymethyl cellulose, 2% -3% of polyethylene wax, 1% -2% of lactic acid, 4% -7% of glass fiber and 1% -3% of RP-chop fiber;
the wet material comprises the following components in parts by weight based on 100 parts by weight of the total mass of the dry material and the wet material: 20-26 parts of water and 3 parts of ammonia water.
The titanium dioxide is anatase titanium dioxide, the BET range is 80-150 m/g, the grain size is 16+ -4 nm, the peak height is 150+ -10 mm, the grain size D50 is less than or equal to 1.5 mu m, and SO 4 2- The content range is 0.7% -2.1%.
The molecular weight of the carboxymethyl cellulose ranges from 10 ten thousand to 30 ten thousand, preferably 20 ten thousand; the viscosity range is 100-1000 cP, preferably 300-500; the substitution degree is in the range of 0.6 to 0.9.
The molecular weight of the polyethylene wax ranges from 2000 to 5000, preferably from 3000 to 3500;
the diameter of the glass fiber is 6-9 mu m, the length is 3-9 mm, and the preferable length is 6mm; the diameter of the RP-chop fiber is 12-18 mu m, and the length is 3-9 mm, preferably 6mm.
The ammonia water is industrial ammonia water, NH 3 The content is more than or equal to 20 percent.
The preparation method of the thin-wall honeycomb SCR denitration catalyst provided by the invention comprises the following steps:
s1, proportioning: dissolving the carboxymethyl cellulose and the polyethylene wax in the formula amount by using water at 80-100 ℃ to prepare a mixed solution, and carrying out heat tracing on the mixed solution for later use, wherein the heat tracing temperature is 80-85 ℃;
s2, first mixing: mixing and stirring titanium dioxide with the formula amount of 70%, glass fiber with the formula amount of 70% and RP-chop fiber with the formula amount, adding the mixed solution to obtain a dry-wet mixture, keeping the dry-wet mixture at 80-85 ℃, adding water with the formula amount of 70% and ammonia water with the formula amount of 70% into the dry-wet mixture, and stirring;
s3, second mixing: after the electric power of the motor reaches a peak value, sequentially adding 30% of titanium white powder, 30% of glass fiber, 30% of ammonia water, 30% of lactic acid and 30% of water under stirring to obtain pug, stirring until the moisture content of the pug is 22% -26%, the pH value is 7-9 and the plasticity is 0.05-0.1 kgf/mm 2 Cooling and discharging the pug;
wherein, the moisture detection uses an infrared moisture meter, the pH value detection uses a pH meter, the plasticity detection uses an MTS tester, and the detection is performed by a direct method in the plasticity detection in an MTS test system.
The first mixing and the second mixing are carried out in a mixing machine, and mud is directly discharged without ageing and enters a rotary cone hopper for discharging to a first conveying step.
S4, first conveying: delivering the pug to a filtering system for filtering, wherein the working environment temperature is 60-80 ℃ and the humidity is more than 80%;
s5, filtering: filtering the pug through a first extruder and a filter screen;
s6, pre-extrusion: pre-extruding the materials into solid bricks;
s7, second conveying: feeding the solid bricks into a screw on a second extruder, wherein the working environment temperature is 60-80 ℃ and the humidity is more than 80%;
s8, exhausting: the brick blocks are extruded and cut into sheet materials, and the sheet materials enter a vacuum chamber for exhausting;
the purpose of exhaust is to exhaust air, so that air inclusion is prevented from affecting the subsequent drying process and causing cracking;
s9, extruding: after exhausting, extruding the sheet material by a main screw of a second extruder, and obtaining a strip-shaped blank through a die at an outlet, wherein the pressure of the main screw of the second extruder is 2.5-9.5 MPa, the temperature is 70-85 ℃, the strip-shaped blank is provided with honeycomb holes, the cross section is 150mm, and the wall thickness of the blank is less than 0.3mm;
s10, shaping: setting the strip-shaped blank at room temperature to obtain a solidified blank;
s11, cutting: cutting the solidified blank to obtain a wet unit;
s12, coating: sealing the films at two ends of the wet unit, and placing the wet unit in a kiln;
s13, drying: hot air drying is started in a kiln until the moisture content is lower than 1%, a dry blank is obtained, the drying temperature is 75-85 ℃, and the drying period is 8-12 days;
s14, calcining: calcining the dry blank to obtain the thin-wall honeycomb SCR denitration catalyst, wherein the calcining process comprises the following steps of: heating to 600-620 ℃ from room temperature for 6-8 hours; preserving heat for 2-4 hours at 600-620 ℃; cooling to room temperature from 600-620 ℃ for 6-8 hours;
wherein, steps S5, S6, S8 and S9 all have heat tracing, and the temperature of the heat tracing is 80-85 ℃.
It should be noted that: relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily representing a sequential relationship.
The invention adopts polyethylene wax low molecular weight additive to replace PEO, and simultaneously, in order to ensure that the solid polyethylene wax can be better dispersed in a water system, the heat tracing state is maintained in the mixing and extrusion processes. The polyethylene wax has good lubricating property, can improve the porosity, and is provided with a room temperature incubator after the extrusion end, so that the viscosity of pug changes when the pug is transited from 80 ℃ to 25 ℃ after the extrusion, the polyethylene wax is cooled and thickened, and better shaping of a catalyst wet unit is maintained.
The polyethylene wax functions on the principle that it has the ability to attract nonionic substances through the adjacent valences of the water molecules, which is based on the structural regularity of the ether groups-C-O-C-. Adjacent valences are formed by etherification of the monomer and may be neutralized by the accumulation of water. In the honeycomb catalyst forming process, oxygen atoms of ether groups in the polyethylene wax and H in Me-OH surface groups of raw material particles + There is an association between them which will result in the particles of the starting material being slightly remote from each other due to the charge of the same polarity which repels each other, giving good dispersion of the starting material. The polyether molecular structure is a coiled linear polymer chain and can adsorb a hydration film. Because of the existence of the hydration film, the carrier particles can smoothly generate relative displacement during extrusion, and after the external force is eliminated, the curled polymers can fix the carrier particles again, so that the pug has plasticity.
Compared with the prior art, the invention has the beneficial effects that:
the invention is suitable for integrally forming the thin-wall honeycomb SCR denitration catalyst with the wall thickness of less than 0.3mm; the manufactured thin-wall honeycomb SCR denitration catalyst can greatly reduce the pressure drop of a system and reduce the operation and maintenance cost of the system after being applied to a heavy-duty gas turbine; meanwhile, the preparation rate and the production efficiency of the thin-wall porous catalyst are improved, the mechanical structure of the catalyst is enhanced, and the mechanical performance of the product is enhanced.
Drawings
FIG. 1, a schematic diagram of the apparatus of the present invention;
FIG. 2, a process flow diagram of the present invention;
in the figure, 1, a storage tank; 2. a mixer; 3. rotating the cone bucket; 4. a first conveyor; 5. a first extruder; 6. a filter screen; 7, a pre-extruder; 8. a second conveyor; 9. a second extruder; 10. a vacuum chamber; 11. a strip-shaped blank; 12. a room temperature incubator; 13. a cutting device; 14. coating equipment; 15. and (5) a chamber kiln.
Detailed Description
The technical scheme of the invention will be clearly and completely described below with reference to the accompanying drawings and examples.
In actual operation, the temperature control allows a fluctuating temperature difference of 2 ℃; all the raw materials used in the examples and comparative examples, except for the specific descriptions, were of commercial grade.
Example 1
The thin-wall honeycomb SCR denitration catalyst is prepared from dry materials and wet materials, wherein the dry materials are prepared from the following raw materials in percentage by mass:
87.8% of titanium dioxide, 0.7% of carboxymethyl cellulose, 2% of polyethylene wax, 1.5% of lactic acid, 6% of glass fiber and 2% of RP-chop fiber;
the wet material comprises the following components in parts by weight based on 100 parts by weight of the total mass of the dry material and the wet material: 25 parts of water and 3 parts of ammonia water.
As shown in FIG. 1, the preparation method of the thin-wall honeycomb SCR denitration catalyst provided by the invention comprises the following steps:
s1, proportioning: dissolving carboxymethyl cellulose and polyethylene wax with water at 80 ℃ to prepare a mixed solution, wherein the mixed solution needs to be heated to 85 ℃ for standby, and the process is carried out in a storage tank 1;
s2, first mixing: mixing and stirring titanium dioxide with the formula amount of 70%, glass fiber with the formula amount of 70% and RP-chop fiber with the formula amount, adding the mixed solution to obtain a dry-wet mixture, keeping the dry-wet mixture at 80 ℃, adding water with the formula amount of 70% and ammonia water with the formula amount of 70% into the dry-wet mixture, and stirring;
s3, second mixing: after the electric power of the motor reaches the peak value, adding titanium dioxide with the formula amount of 30%, glass fiber with the formula amount of 30%, ammonia water with the formula amount of 30%, lactic acid with the formula amount of 30% and water with the formula amount of 30% in sequence under stirring to obtain pug, cooling and discharging the pug, wherein the moisture content of the discharged pug is 24.02%, the pH value is 8.1, and the plasticity is 0.08kgf/mm 2 ，；
The first mixing and the second mixing are carried out in a mixing machine 2, and mud materials are discharged and enter a rotary cone hopper 3 for discharging to a first conveying step;
s4, first conveying: the pug is conveyed to a filtering system through a first conveyor 4 for filtering, and the working environment temperature is 74 ℃ and the humidity is 82%;
s5, filtering: filtering the pug through a first extruder 5 and a filter screen 6;
s6, pre-extrusion: pre-extruding the materials into solid bricks, wherein the pre-extrusion is completed through a pre-extruder 7, and the pre-extruder extrudes pug into solid bricks with the solid length of about 25 cm;
s7, second conveying: feeding the solid bricks into a screw on a second extruder 9 through a second conveyor 8, wherein the working environment temperature is 72 ℃ and the humidity is 83%;
s8, exhausting: the bricks are extruded and chopped into sheet materials, and the sheet materials enter a vacuum chamber 10 for exhausting;
s9, extruding: after the exhaust, the flaky material is extruded by a main screw of a second extruder 9, a strip-shaped blank 11 is obtained through an outlet die, the pressure of the main screw of the second extruder 9 is 6.9MPa, the temperature is 82 ℃, the strip-shaped blank 11 is provided with honeycomb holes, the cross section is 150mm, and the wall thickness of the blank is 0.21mm;
s10, shaping: the strip-shaped blank is placed in a room temperature incubator 12 for internal setting to obtain a solidified blank;
s11, cutting: cutting the solidified blank by a cutting device 13 to obtain a wet unit;
s12, coating: the wet unit is sealed by film sticking at two ends of the film coating equipment 14 and is placed in a chamber kiln 15;
s13, drying: hot air drying is started in a kiln 15 until the moisture content is lower than 1%, a dry blank is obtained, the drying temperature is 75 ℃, and the drying period is 12 days;
s14, calcining: calcining the dry blank to obtain the thin-wall honeycomb SCR denitration catalyst, wherein the calcining process comprises the following steps of: heating from room temperature to 615 ℃ for 8 hours; preserving heat for 2h at 615 ℃; cooling to room temperature from 615 ℃ for 8h.
Wherein, steps S5, S6, S8 and S9 all have heat tracing, and the heat tracing temperature is 80 ℃.
Example 2
The thin-wall honeycomb SCR denitration catalyst is prepared from dry materials and wet materials, wherein the dry materials are prepared from the following raw materials in percentage by mass:
87.3% of titanium dioxide, 0.7% of carboxymethyl cellulose, 2.5% of polyethylene wax, 1.5% of lactic acid, 6% of glass fiber and 2% of RP-chop fiber;
the wet material comprises the following components in parts by weight based on 100 parts by weight of the total mass of the dry material and the wet material: 25 parts of water and 3 parts of ammonia water.
As shown in FIG. 1, the preparation method of the thin-wall honeycomb SCR denitration catalyst provided by the invention comprises the following steps:
s1, proportioning: dissolving carboxymethyl cellulose and polyethylene wax with water at 90 ℃ to prepare a mixed solution, wherein the mixed solution needs to be heated to 85 ℃ for standby, and the process is carried out in a storage tank 1;
s2, first mixing: mixing and stirring titanium dioxide with the formula amount of 70%, glass fiber with the formula amount of 70% and RP-chop fiber with the formula amount, adding the mixed solution to obtain a dry-wet mixture, keeping the dry-wet mixture at 85 ℃, adding water with the formula amount of 70% and ammonia water with the formula amount of 70% into the dry-wet mixture, and stirring;
s3, second mixing: after the electric power of the motor reaches the peak value, sequentially adding 30% of titanium white powder, 30% of glass fiber, 30% of ammonia water, 30% of lactic acid and 30% of water under stirring to obtain pug, cooling and discharging the pug, wherein the moisture content of the discharged pug is 23.65%, the pH value is 8.2, and the plasticity is 0.07kgf/mm 2 ，；
The first mixing and the second mixing are carried out in a mixing machine 2, and mud materials are discharged and enter a rotary cone hopper 3 for discharging to a first conveying step;
s4, first conveying: the pug is conveyed to a filtering system for filtering by a first conveyor 4, the working environment temperature is 79 ℃, and the humidity is 86%;
s5, filtering: filtering the pug through a first extruder 5 and a filter screen 6;
s6, pre-extrusion: pre-extruding the materials into solid bricks, wherein the pre-extrusion is completed through a pre-extruder 7, and the pre-extruder extrudes pug into solid bricks with the solid length of about 25 cm;
s7, second conveying: feeding the solid bricks into a screw on a second extruder 9 through a second conveyor 8, wherein the working environment temperature is 77 ℃ and the humidity is 85%;
s8, exhausting: the bricks are extruded and chopped into sheet materials, and the sheet materials enter a vacuum chamber 10 for exhausting;
s9, extruding: after exhausting, extruding the sheet material by a main screw of a second extruder 9, and obtaining a strip-shaped blank 11 through an outlet die, wherein the pressure of the main screw of the second extruder 9 is 5.4MPa, the temperature is 75 ℃, the strip-shaped blank 11 is provided with honeycomb holes, the cross section is 150mm, and the wall thickness of the blank is 0.19mm;
s10, shaping: the strip-shaped blank is placed in a room temperature incubator 12 for internal setting to obtain a solidified blank;
s11, cutting: cutting the solidified blank by a cutting device 13 to obtain a wet unit;
s12, coating: the wet unit is sealed by film sticking at two ends of the film coating equipment 14 and is placed in a chamber kiln 15;
s13, drying: hot air drying is started in the chamber kiln 15 until the moisture content is lower than 1%, a dry blank is obtained, the drying temperature is 80 ℃, and the drying period is 12 days;
s14, calcining: calcining the dry blank to obtain the thin-wall honeycomb SCR denitration catalyst, wherein the calcining process comprises the following steps of: heating from room temperature to 615 ℃ for 8 hours; preserving heat for 2h at 615 ℃; cooling to room temperature from 615 ℃ for 8h.
Wherein, steps S5, S6, S8 and S9 all have heat tracing, and the heat tracing temperature is 85 ℃.
Example 3
The thin-wall honeycomb SCR denitration catalyst is prepared from dry materials and wet materials, wherein the dry materials are prepared from the following raw materials in percentage by mass:
88.4% of titanium dioxide, 0.6% of carboxymethyl cellulose, 3% of polyethylene wax, 1% of lactic acid, 6% of glass fiber and 1% of RP-chop fiber;
the wet material comprises the following components in parts by weight based on 100 parts by weight of the total mass of the dry material and the wet material: 23 parts of water and 3 parts of ammonia water.
As shown in FIG. 1, the preparation method of the thin-wall honeycomb SCR denitration catalyst provided by the invention comprises the following steps:
s1, proportioning: dissolving carboxymethyl cellulose and polyethylene wax with water at 100deg.C to obtain mixed solution, wherein the mixed solution needs heat tracing temperature of 82 deg.C for use, and the process is carried out in a storage tank 1;
s2, first mixing: mixing and stirring titanium dioxide with the formula amount of 70%, glass fiber with the formula amount of 70% and RP-chop fiber with the formula amount, adding the mixed solution to obtain a dry-wet mixture, keeping the dry-wet mixture at 80 ℃, adding water with the formula amount of 70% and ammonia water with the formula amount of 70% into the dry-wet mixture, and stirring;
s3, second mixing: after the electric power of the motor reaches the peak value, sequentially adding 30% of titanium white powder, 30% of glass fiber, 30% of ammonia water, 30% of lactic acid and 30% of water under stirring to obtain pug, cooling and discharging the pug, wherein the moisture content of the discharged pug is 22.06%, the pH value is 8.0, and the plasticity is 0.08kgf/mm 2 ，；
Both the first mixing and the second mixing are carried out in a mixer 2;
s4, first conveying: the pug is conveyed to a filtering system through a first conveyor 4 for filtering, and the working environment temperature is 65 ℃ and the humidity is 82%;
s5, filtering: filtering the pug through a first extruder 5 and a filter screen 6;
s6, pre-extrusion: pre-extruding the materials into solid bricks, wherein the pre-extrusion is completed through a pre-extruder 7, and the pre-extruder extrudes pug into solid bricks with the solid length of about 25 cm;
s7, second conveying: feeding the solid bricks into a screw on a second extruder 9 through a second conveyor 8, wherein the working environment temperature is 65 ℃ and the humidity is 82%;
s8, exhausting: the bricks are extruded and chopped into sheet materials, and the sheet materials enter a vacuum chamber 10 for exhausting;
s9, extruding: after the exhaust, the flaky material is extruded by a main screw of a second extruder 9, a strip-shaped blank 11 is obtained through an outlet die, the pressure of the main screw of the second extruder 9 is 8.4MPa, the temperature is 78 ℃, the strip-shaped blank 11 is provided with honeycomb holes, the cross section is 150mm, and the wall thickness of the blank is 0.27mm;
s10, shaping: the strip-shaped blank is placed in a room temperature incubator 12 for internal setting to obtain a solidified blank;
s11, cutting: cutting the solidified blank by a cutting device 13 to obtain a wet unit;
s12, coating: the wet unit is sealed by film sticking at two ends of the film coating equipment 14 and is placed in a chamber kiln 15;
s13, drying: hot air drying is started in the chamber kiln 15 until the moisture content is lower than 1%, a dry blank is obtained, the drying temperature is 80 ℃, and the drying period is 8 days;
s14, calcining: calcining the dry blank to obtain the thin-wall honeycomb SCR denitration catalyst, wherein the calcining process comprises the following steps of: heating from room temperature to 615 ℃ for 8 hours; preserving heat for 2h at 615 ℃; cooling to room temperature from 615 ℃ for 8h.
Wherein, steps S5, S6, S8 and S9 all have heat tracing, and the heat tracing temperature is 80 ℃.
Comparative example 1
The thin-wall honeycomb SCR denitration catalyst is prepared from dry materials and wet materials, wherein the dry materials are prepared from the following raw materials in percentage by mass:
85.5% of titanium dioxide, 1% of carboxymethyl cellulose, 3% of polyethylene oxide (PEO), 2% of lactic acid, 6% of glass fiber and 2.5% of RP-chop fiber;
the wet material comprises the following components in parts by weight based on 100 parts by weight of the total mass of the dry material and the wet material: 23 parts of water and 3 parts of ammonia water.
As shown in fig. 1, the preparation method of the thin-walled honeycomb SCR denitration catalyst of the present comparative example includes the following steps:
s1, proportioning: mixing carboxymethyl cellulose and polyethylene oxide powder together, and dissolving the mixture with water at 90 ℃ to prepare a mixed solution after the dry mixing is finished, wherein the process is carried out in a storage tank 1;
s2, mixing: mixing and stirring the titanium dioxide, the glass fiber and the RP-chop fiber according to the formula amount, adding the mixed solution to obtain a dry-wet mixture, adding the water, the ammonia water and the lactic acid according to the formula amount into the dry-wet mixture at the temperature of about 45 ℃, and stirring to obtain pug, wherein the step is carried out in a mixer 2;
s3, discharging: after the electric power of the monitoring machine reaches the peak value, the pug is cooled and discharged, the moisture content of the discharged pug is 27.4 percent, the pH value is 8.0, and the plasticity is 0.09kgf/mm 2 ；
S4, first conveying: the pug is conveyed to a filtering system for filtering through a first conveyor 4, the first conveying working environment is provided with cooling water circulation, the purposes of cooling and controlling the material temperature are achieved, the cooling water temperature is controlled at 20 ℃, and the brick temperature is 28 ℃;
s5, filtering: filtering the pug through a first extruder 5 and a filter screen 6;
s6, pre-extrusion: pre-extruding the materials into solid bricks, wherein the pre-extrusion is completed through a pre-extruder 7, and the pre-extruder extrudes pug into solid bricks with the solid length of about 25 cm;
s7, second conveying: feeding the solid bricks into a screw on a second extruder 9 through a second conveyor 8, wherein cooling water is circulated in a second conveying working environment, the temperature of the cooling water is controlled at 20 ℃, and finally the temperature of the bricks is 26 ℃;
s8, exhausting: the bricks are extruded and chopped into sheet materials, and the sheet materials enter a vacuum chamber 10 for exhausting;
s9, extruding: after exhausting, extruding the sheet material by a main screw of a second extruder 9, and obtaining a strip-shaped blank 11 through an outlet die, wherein the pressure of the main screw of the second extruder 9 is 5.6MPa, the temperature is 34 ℃, the temperature of cooling water is controlled during extrusion, the temperature of the cooling water is set to 15 ℃, the strip-shaped blank 11 is provided with honeycomb holes, the cross section is 150mm, and the wall thickness of the blank is 0.53mm;
s10, shaping: the strip-shaped blank is placed in a room temperature incubator 12 for internal setting to obtain a solidified blank;
s11, cutting: cutting the solidified blank by a cutting device 13 to obtain a wet unit;
s12, coating: the wet unit is sealed by film sticking at two ends of the film coating equipment 14 and is placed in a chamber kiln 15;
s13, drying: hot air drying is started in the chamber kiln 15 until the moisture content is lower than 1%, a dry blank is obtained, the drying temperature is 80 ℃, and the drying period is 12 days;
s14, calcining: calcining the dry blank to obtain the thin-wall honeycomb SCR denitration catalyst, wherein the calcining process comprises the following steps of: heating from room temperature to 615 ℃ for 8 hours; preserving heat for 2h at 615 ℃; cooling to room temperature from 615 ℃ for 8h.
Performance test:
the compression resistance detection method comprises the following steps: for a honeycomb catalyst sample with complete unit structure, a sample with a height of 150mm + -2 mm was cut at the hardened end as a complete sample for the determination of axial compressive strength and radial compressive strength. The sample should be kept structurally intact and crack-free, and the cut surface is flat and smooth and perpendicular to the catalyst pore wall. The length of 4 different positions of the pressed surface of the sample is measured, and the difference between the heights of any two measurement points is not more than 2% of the average height. The two samples are respectively arranged at the central positions of two pressing plates of the pressure testing machine in the axial direction and the radial direction, the pressure testing machine is started, the pressure is continuously and evenly applied at the pressurizing rate of 1125N/s until the samples are completely broken or the pressure testing machine is completely stopped, and the maximum pressure indication value at the moment is recorded.
Shear viscosity was measured using a capillary rheometer using a DA-1.0-16-180-24 die with a bore diameter of 1mm; setting the heating temperature of the charging barrel to be 30 ℃, and setting the water temperature of an external cooling water circulation system to be 30 ℃; setting the test shear rate to be in the range of 20-3000s -1 Selecting 12 shear rate sampling points, using up and down shear rate detection curve during detection, and recording shear rate 1000s -1 Shear viscosity in the state.
Performance tests were performed on the SCR denitration catalysts obtained in examples 1 to 3 and comparative example 1, axial compression resistance and radial compression resistance were performed on the pugs obtained in examples 1 to 3 and comparative example 1, shear viscosity was performed on the pugs obtained in examples 1 to 3 and comparative example 1, and the values of the test results are shown in table 1,
table 1 performance test data for examples 1 to 3 and comparative example 1
As can be seen from Table 1, the mechanical strength and the flow property of examples 1 to 3 are greatly improved compared with those of comparative example 1; with the improvement of the addition amount of the polyethylene wax, the mechanical strength is improved, but the viscosity of the corresponding pug is also improved, and the fluidity is slightly reduced, so that the addition amount of the polyethylene wax is 2-3% and is suitable for thin-wall extrusion in comprehensive consideration, and the addition amount of the polyethylene wax is 2.5% and is the optimal addition amount, so that both the mechanical strength and the fluidity of the product can be achieved.
Claims (8)
1. The preparation method of the thin-wall honeycomb SCR denitration catalyst is characterized by comprising dry materials and wet materials, wherein the dry materials are prepared from the following raw materials in percentage by mass:
84% -91.5% of titanium dioxide, 0.5% -1% of carboxymethyl cellulose, 2% -3% of polyethylene wax, 1% -2% of lactic acid, 4% -7% of glass fiber and 1% -3% of RP-chop fiber;
the wet material comprises the following components in parts by weight based on 100 parts by weight of the total mass of the dry material and the wet material: 20-26 parts of water and 3 parts of ammonia water;
the molecular weight range of the polyethylene wax is 2000-5000;
the preparation method comprises the following steps:
s1, proportioning: dissolving the carboxymethyl cellulose and the polyethylene wax in the formula amount by using water at the temperature of 80-100 ℃ to prepare a mixed solution;
s2, first mixing: mixing and stirring titanium dioxide with the formula amount of 70%, glass fiber with the formula amount of 70% and RP-chop fiber with the formula amount, adding the mixed solution to obtain a dry-wet mixture, keeping the dry-wet mixture at 80-85 ℃, adding water with the formula amount of 70% and ammonia water with the formula amount of 70% into the dry-wet mixture, and stirring;
s3, second mixing: sequentially adding titanium dioxide with the formula amount of 30%, glass fiber with the formula amount of 30%, ammonia water with the formula amount of 30%, lactic acid with the formula amount of 30% and the formula amount of 30% under stirringWater to obtain pug, stirring until the moisture content of the pug is 22% -26% and the plasticity is 0.05-0.1 kgf/mm 2 The pH value is 7-9, and the pug is cooled and discharged;
s4, first conveying: delivering the pug to a filtering system for filtering;
s5, filtering: filtering the pug through a first extruder and a filter screen;
s6, pre-extrusion: pre-extruding the materials into solid bricks;
s7, second conveying: feeding the solid bricks to a second extruder upper screw;
s8, exhausting: the brick blocks are extruded and cut into sheet materials, and the sheet materials enter a vacuum chamber for exhausting;
s9, extruding: after exhausting, extruding the flaky material by a main screw of a second extruder, and obtaining a strip-shaped blank by a die at an outlet;
s10, shaping: setting the strip-shaped blank at room temperature to obtain a solidified blank;
s11, cutting: cutting the solidified blank to obtain a wet unit;
s12, coating: sealing the films at two ends of the wet unit, and placing the wet unit in a kiln;
s13, drying: hot air drying is started in a kiln until the moisture content is lower than 1%, so as to obtain a dry blank;
s14, calcining: calcining the dry blank to obtain a thin-wall honeycomb SCR denitration catalyst;
wherein, steps S5, S6, S8 and S9 all have heat tracing, and the temperature of the heat tracing is 80-85 ℃.
2. The method for preparing the thin-wall honeycomb SCR denitration catalyst according to claim 1, wherein the titanium dioxide is anatase titanium dioxide and has a BET range of 80-150 m 2 Per g, grain size 16+ -4 nm, peak height 150+ -10 mm, grain size D50 less than or equal to 1.5 μm, SO 4 2- The content range is 0.7% -2.1%.
3. The method for preparing the thin-wall honeycomb SCR denitration catalyst according to claim 1, wherein the molecular weight of the carboxymethyl cellulose is 10 ten thousand to 30 ten thousand, the viscosity is 100 to 1000cP, and the substitution degree is 0.6 to 0.9.
4. The preparation method of the thin-wall honeycomb type SCR denitration catalyst according to claim 1, which is characterized in that the glass fiber has a diameter of 6-9 μm and a length of 3-9 mm; the diameter of the RP-chop fiber is 12-18 mu m, and the length is 3-9 mm.
5. The method for preparing the thin-wall honeycomb SCR denitration catalyst according to claim 1, wherein the main screw pressure of the second extruder is 2.5-9.5 MPa, and the temperature is 70-85 ℃.
6. The method for preparing the thin-walled honeycomb SCR denitration catalyst according to claim 1, wherein the working environment temperature of the steps S4 and S7 is 60-80 ℃, and the humidity is more than 80%.
7. The preparation method of the thin-wall honeycomb type SCR denitration catalyst according to claim 1, wherein the drying temperature is 75-85 ℃, and the drying period is 8-12 days.
8. The method for preparing a thin-walled honeycomb SCR denitration catalyst according to claim 1, wherein the calcining step comprises: heating to 600-620 ℃ from room temperature for 6-8 hours; preserving heat for 2-4 hours at 600-620 ℃; cooling to room temperature from 600-620 ℃ for 6-8 h.
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