CN114308051A - Preparation method and application of low-temperature SCR honeycomb type denitration catalyst - Google Patents
Preparation method and application of low-temperature SCR honeycomb type denitration catalyst Download PDFInfo
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Abstract
The invention discloses a preparation method and application of a low-temperature SCR honeycomb type denitration catalyst, wherein the preparation method comprises the following steps: mixing materials, namely adding a carrier, a metal oxide precursor, a release agent, a structural assistant, a binder, a pH regulator and a preservative into a mud mixer for kneading to obtain mud materials; pre-extruding and ageing, namely, obtaining mud sections by the mud materials through a pre-extruder, and then boxing and ageing; and (3) forming, namely sending the aged mud segments into an extruder to obtain honeycomb type fixed length wet blanks, and performing primary sectional drying, secondary drying and sectional calcining on the honeycomb type fixed length wet blanks to obtain the low-temperature SCR honeycomb type denitration catalyst. The low-temperature SCR honeycomb denitration catalyst prepared by the preparation method has good denitration effect and mechanical strength under the low-temperature condition, is wide in raw material source and low in price, and is suitable for industrial production.
Description
Technical Field
The invention relates to the technical field of environmental protection and catalysis, in particular to a preparation method and application of a low-temperature SCR honeycomb denitration catalyst.
Background
At present, coal is used as fossil energy which is wide in domestic reserves and easy to extract, and cannot be completely replaced by natural gas, nuclear energy and new energy for a long time in the future, but a large amount of pollutants generated by coal combustion far exceed the limit of the self-purification capacity of the environment, and cause serious harm to human society and natural ecology; the nitrogen oxide (NOx) is one of the most main atmospheric pollutants, is not only an important precursor for initiating nitric acid type acid rain, photochemical smog, haze and the like, but also causes serious damage to a human respiratory system; along with the increasing requirements of people on environmental protection quality, NO of coal-fired power plant is controlledxThe discharge of (2) is particularly important;
at present, the coal-fired power plants worldwide mostly adopt a Selective Catalytic Reduction (SCR) technology to treat fixed source flue gas; the core of the SCR technology is a catalyst, and the powder catalyst cannot be directly applied to fixed source flue gas denitration, so the forming of the catalyst is particularly suitable for the denitration of fixed source flue gasFor the most part, drying is usually carried out during the forming process to reduce the moisture in the catalyst, and calcination is used to decompose the organic substances to remove impurities, which are particularly important for the mechanical strength of the catalyst and the loading of the catalyst; the most mature denitration catalyst for commercial application is V2O5-WO3(MoO3)/TiO2The temperature window of the catalyst is more between 300 and 420 ℃; for example, application No. 201410038635.0 discloses a method for preparing a honeycomb denitration catalyst, which comprises titanium dioxide, vanadium pentoxide, tungsten trioxide and an auxiliary agent; the preparation method of the catalyst comprises the steps of mixing the raw material components, mixing, stacking and ageing after mixing, filtering the obtained pug, stacking and ageing again, extruding and forming to obtain a wet blank after ageing, and cutting the section of the wet blank to obtain a regular end face fixed-length wet blank and end waste; drying, calcining and forming the regular end face fixed-length wet blank; the end waste is mixed with the filter material for recycling, so that the cost is reduced; however, the use of general commercial catalysts leads to excessively high molding temperature and the direct precision cutting of the two end faces of the wet blank, which does not ensure the mechanical strength of the molded honeycomb, so that the cost is not reduced or increased. For some industrial boilers such as glass kilns and cement kilns, because the exhaust gas temperature is low, the dust content of the exhaust gas is high, and meanwhile, the smoke contains a large amount of catalyst poisons, the catalyst is easy to block and poison; therefore, there is a strong need for a novel catalyst having excellent denitration activity at low temperature to alleviate the problem of removal of nitrogen oxides in different industrial environments; the application number 201910417113.4 discloses a denitration and VOC removal catalyst, a preparation method and a regeneration method, wherein the denitration and VOC removal catalyst is prepared by taking attapulgite as a carrier and taking a molybdenum compound, a palladium simple substance product, a lanthanum compound and a cerium compound as active components; however, since the denitration and VOC-removal catalyst adopts a coating method to load active components on the honeycomb catalyst, the actual active substances of the catalyst are few, the specific surface area is small, the roasting time sequentially spans 5 temperature intervals, the difference of each temperature interval is 50 ℃, and the prepared honeycomb catalyst needs to be frequently replaced due to the service life problem in the actual industrial application.
In the prior art, the main catalysts of the SCR technology are concentrated on a V-based catalyst, the optimal active temperature range of the V-based catalyst is 320-420 ℃, the V-based catalyst is difficult to effectively play a role in a low-temperature range of 150-180 ℃, and the V is high in price and high in toxicity.
In view of the above, it is urgently needed to develop a new SCR denitration catalyst, which has better denitration effect and mechanical strength under low temperature conditions, is wide in raw material source and low in cost, and is suitable for industrial production.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a preparation method and application of a low-temperature SCR honeycomb denitration catalyst.
In order to achieve the purpose, the invention adopts the following technical scheme:
the preparation method of the low-temperature SCR honeycomb denitration catalyst provided by the first aspect of the invention comprises the following steps:
s1, mixing materials, namely adding a carrier, a metal oxide precursor, a release agent, a structural assistant, a binder, a pH regulator and a preservative into a pug mixer, and kneading to obtain pug;
s2, pre-extruding and ageing, namely, obtaining mud sections by the mud materials through a pre-extruder, and then boxing and ageing;
and S3, forming, namely feeding the aged mud segment into an extruder to obtain a honeycomb type fixed length wet blank, and performing primary segmented drying, secondary drying and segmented calcining on the honeycomb type fixed length wet blank to obtain the low-temperature SCR honeycomb type denitration catalyst.
Preferably, in step S1, the mass ratio of the carrier, the metal oxide precursor, the release agent, the structural assistant, the binder, the pH adjuster, and the preservative is 100: 10-20: 2-5: 5-8: 1-5: 2-5: 0 to 2.
Preferably, in step S1, the carrier is titanium dioxide or molecular sieve;
the metal oxide precursor is selected from one or more nitrates of Mn, Ce, Cu, Sn, Cr, Fe and Co;
the release agent adopts stearic acid and magnesium stearate;
the structural auxiliary agent adopts glass fiber and paper pulp;
the binder adopts sodium carboxymethyl cellulose (CMC) and polyethylene oxide (PEO);
the pH regulator adopts ammonia water and monoethanolamine;
the preservative is lactic acid.
Preferably, the metal oxide precursor adopts nitrates of Mn, Ce and Cu, and the molar ratio of the nitrates of Mn, Ce and Cu is 1-2: 1-1.5: 0.5 to 1.
Preferably, the step S1 specifically includes the following steps:
s11, preparing an active solution, adding excessive deionized water to dissolve the metal oxide precursor to obtain a precursor solution, and adding a pH regulator to regulate the pH to 6-8 to obtain the active solution;
and S12, adding the carrier, the release agent, the preservative and half of the active solution into a mixer for first stirring, uniformly mixing, adding the other half of the active solution for second stirring, uniformly mixing, adding the structural assistant for third stirring, uniformly mixing again, adding the binder for fourth stirring, uniformly mixing, and stirring for the fifth time until the water content is reduced to 20-28 wt% to obtain the pug.
Preferably, in the step S12,
during the first stirring, the stirring time is 15-30 min, and the stirring speed is 20-30 r/min;
during the second stirring, the stirring time is 35-60 min, the stirring temperature is 75-90 ℃, and the stirring speed is 20-30 r/min;
during the third stirring, the stirring time is 35-60 min, and the stirring speed is 20-30 r/min;
during the fourth stirring, the stirring time is 30-60 min, and the stirring speed is 50-60 r/min;
and in the fifth stirring, firstly stirring for 5-30 min at a stirring speed of 20-30 r/min under the condition that the temperature is less than 60 ℃, and then opening a steam valve to stir at a stirring speed of 20-30 r/min until the water content is reduced to 20-28 wt%.
Preferably, in the step S2, the staling time is not more than 14 days.
Preferably, the staling time is 2-4 days.
Preferably, in the step S3, the one-stage drying includes box-packing drying and box-unpacking drying;
in the drying process of the box, the temperature is increased from 30 ℃ to 60 ℃ at the temperature increase rate of 5-10 ℃/day;
in the box removing and drying process, the temperature is increased from 40 ℃ to 65 ℃ at a temperature increase rate of 5-10 ℃/day.
Preferably, in the step S3, in the secondary drying process, the temperature is increased from 40 ℃ to 65 ℃ at a temperature rate of 5-10 ℃/12h, and the drying time is 2-4 days.
Preferably, in the step S3, the staged calcination includes large oven calcination and mesh belt kiln calcination;
in the calcining process of the large oven, the heating rate is 5-10 ℃/12h, the calcining temperature is 80-150 ℃, and the calcining time is 6-10 days;
in the calcining process of the mesh belt kiln, the temperature is increased from 20 ℃ to 550 ℃ within 24-33 h, and then the mixture is cooled to room temperature.
According to a second aspect of the invention, the denitration efficiency of the low-temperature SCR honeycomb denitration catalyst obtained by the preparation method of the low-temperature SCR honeycomb denitration catalyst according to the first aspect of the invention reaches over 86% at 170 ℃.
The invention has the beneficial effects that:
1. according to the preparation method of the low-temperature SCR honeycomb denitration catalyst, nitrates are used as active components, titanium dioxide or a molecular sieve is used as a carrier, and a release agent, a structural assistant, a binder, a pH regulator and a preservative are added to prepare the low-temperature SCR honeycomb denitration catalyst, so that the prepared low-temperature SCR honeycomb denitration catalyst has good denitration effect and mechanical strength under a low-temperature condition, is wide in raw material source and low in price, and is suitable for industrial production;
2. the preparation method of the low-temperature SCR honeycomb denitration catalyst adopts a sectional drying and sectional calcining mechanism, solves the problems that the catalyst is easy to ignite, crack and burn out and the like when dried by taking nitrates as metal oxide precursors, and ensures the quality of the catalyst.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
fig. 1 is a process flow diagram of a preparation method of the low-temperature SCR honeycomb-type denitration catalyst of the present invention;
fig. 2 is a schematic diagram showing the weight change of the low-temperature SCR honeycomb denitration catalyst during the dry calcination stage of the present invention.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way.
As shown in fig. 1, the preparation method of the low-temperature SCR honeycomb-type denitration catalyst provided by the present invention includes the following steps:
s1, mixing materials, namely adding a carrier, a metal oxide precursor, a release agent, a structural assistant, a binder, a pH regulator and a preservative into a pug mixer, and kneading to obtain pug;
wherein the mass ratio of the carrier, the metal oxide precursor, the release agent, the structural assistant, the binder, the pH regulator and the preservative is 100: 10-20: 2-5: 5-8: 1-5: 2-5: 0 to 2; the carrier is titanium dioxide or molecular sieve, etc.; the metal oxide precursor is selected from one or more nitrates of Mn, Ce, Cu, Sn, Cr, Fe and Co, wherein the specific composition and proportion of the metal oxide precursor are determined according to various factors such as the temperature, flow, atmosphere and concentration of flue gas to be denitrated, nitrates corresponding to Mn, Ce and Cu are preferentially adopted, and the molar ratio is 1-2: 1-1.5: 0.5 to 1; the release agent adopts stearic acid and magnesium stearate, which is beneficial to kneading and extrusion molding of pug; the structural auxiliary agent adopts glass fiber and paper pulp, so that the plasticity of the pug can be improved, and the forming effect can be improved; the binder adopts sodium carboxymethylcellulose CMC and polyethylene oxide PEO, which can improve the mechanical strength of the formed product; the pH regulator adopts ammonia water and monoethanolamine; the preservative is lactic acid.
The concrete operation is as follows when mixing materials:
s11, preparing an active solution, namely weighing the carrier, the metal oxide precursor, the release agent, the structural auxiliary agent, the binder, the pH regulator and the preservative according to the mass ratio; then preparing a metal oxide precursor according to a certain molar ratio and combining the mass ratio; adding excessive deionized water to dissolve a metal oxide precursor to obtain a precursor solution, and adding a pH regulator (ammonia water and monoethanolamine) to regulate the pH to 6-8 to obtain an active solution;
s12, adding a carrier, a release agent, a preservative and a half of active solution into a mixer for primary stirring, stirring for 15-30 min at a stirring speed of 20-30 r/min, uniformly mixing, adding the other half of active solution for secondary stirring, stirring for 15-30 min at a stirring speed of 20-30 r/min at a temperature of 75-90 ℃, uniformly mixing, adding a structural auxiliary agent for tertiary stirring, stirring for 35-60 min at a stirring speed of 20-30 r/min, uniformly mixing again, adding a binder for tertiary stirring, stirring for 30-60 min at a stirring speed of 50-60 r/min, uniformly mixing, stirring for fifth time at a stirring speed of 20-30 r/min at a temperature of less than 60 ℃, opening a steam valve after stirring for 5-30 min, operating at a stirring speed of 50-60 r/min to control water content, and obtaining pug when the water content is reduced to 20-28 wt%.
S2, pre-extruding and ageing, namely, obtaining mud sections by the mud materials through a pre-extruder, then boxing and ageing for at most 14 days, and in a further preferred scheme, ageing time is 48-96 hours;
the pre-squeezing and staling operation is as follows: putting the mud into a pre-extruder to obtain uniform cuboid brick-shaped mud sections, and then boxing and sealing the mud sections in a ageing room at 25 +/-1 ℃ for not more than 14 days, wherein the ageing time is 48-96 hours in a further preferred scheme;
s3, forming, namely feeding the aged mud segment into an extruder to obtain a honeycomb type fixed length wet blank, and performing primary segmented drying, secondary drying and segmented calcining on the honeycomb type fixed length wet blank to obtain the low-temperature SCR honeycomb type denitration catalyst.
The first-stage sectional drying comprises box packing drying and box removing drying; in the drying process of the box, the temperature is increased from 30 ℃ to 60 ℃ at the temperature increase rate of 5-10 ℃/day; in the box removing and drying process, the temperature is increased from 40 ℃ to 65 ℃ at the temperature increase rate of 5-10 ℃/day. In the secondary drying process, the temperature is increased from 50 ℃ to 65 ℃ at the temperature increase rate of 5-10 ℃/12h, and the drying time is 2-4 days. As shown in fig. 2, in the processes of box-packing drying, box-removing drying and secondary drying, the honeycomb type fixed-length wet embryo gradually volatilizes with the rise of temperature, so that the self weight is gradually reduced, and the fixed-length embryo body with lower water content is obtained.
The step calcination comprises large oven calcination and mesh belt kiln calcination; in the calcining process of the large oven, the heating rate is 5-10 ℃/12h, the calcining temperature is 80-150 ℃, and the calcining time is 6-10 days; and in the mesh belt kiln calcining process, the temperature is increased from 20 ℃ to 550 ℃, and the calcining time is 24-33 h. As shown in figure 2, during the large oven calcination and mesh belt kiln calcination, the water content of the fixed-length blank is gradually reduced and the nitrate-type substance is slowly decomposed during the temperature rise to gradually form metal oxide (reaction equation is M)x(NO3)y→MxO+NO2) And finally obtaining the low-temperature SCR honeycomb denitration catalyst.
The molding stage specifically operates as follows: sending the aged mud segment into a spiral continuous extruder for extrusion molding and cutting to obtain a honeycomb type fixed-length wet blank, and then putting the honeycomb type fixed-length wet blank into a drying chamber to perform primary segmented drying (namely box packing drying and box removing drying) to obtain a fixed-length blank body; as shown in fig. 2, in the box-packing drying process, the temperature of the drying chamber is slowly increased from 30 ℃ to 60 ℃ at the heating rate of 5-10 ℃/day, the water vapor in the drying chamber is reduced from 80 wt% to 20 wt%, and in the box-removing drying process, the temperature in the drying chamber is increased from 40 ℃ to 65 ℃ at the heating rate of 5-10 ℃/day; then sending the fixed-length blank into a tunnel kiln, and heating from 40 ℃ to 65 ℃ at a heating rate of 5-10 ℃/12h for secondary drying for 2-4 days; performing segmented calcination on the fixed-length blank after secondary drying, performing large-oven calcination, heating to 80-150 ℃ at a heating rate of 5-10 ℃/12h in a large oven, calcining for 6-10 days, performing mesh belt kiln calcination, calcining for 24-33 h at 20-550 ℃ in a mesh belt kiln, cooling to room temperature, cutting by a sawing bed, and performing module boxing to obtain a finished low-temperature SCR honeycomb denitration catalyst;
the obtained low-temperature SCR honeycomb denitration catalyst has the water vapor content of 10% (volume ratio) and SO2The concentration is 35mg/Nm3The space velocity is 3500h-1And the denitration efficiency reaches over 86 percent under the condition that the temperature is 170 ℃.
The preparation method of the low-temperature SCR honeycomb denitration catalyst according to the present invention is further described below with reference to specific examples.
Example 1
In this example, the carrier was titanium dioxide, and the metal oxide precursor was Mn (NO)3)2·2H2O、Ce(NO3)3·6H2O and Cu (NO)3)2·9H2O is mixed according to the molar ratio of 1:1:0.5, the release agent adopts stearic acid and magnesium stearate, the structural auxiliary agent adopts glass fiber and paper pulp, the binder adopts sodium carboxymethylcellulose (CMC) and polyethylene oxide (PEO), the pH regulator adopts ammonia water and monoethanolamine, and the preservative adopts lactic acid;
the preparation process comprises the following steps:
s1, mixing materials, namely adding a carrier, a metal oxide precursor, a release agent, a structural assistant, a binder, a pH regulator and a preservative into a pug mixer, and kneading to obtain pug;
the preparation method comprises the following steps of (1) mixing a carrier, a metal oxide precursor, a release agent, a structural assistant, a binder, a pH regulator and a preservative according to a mass ratio of 100: 10: 2: 5: 1: 2: 0.5, mixing, and weighing each component according to the molar ratio of each component in the metal oxide precursor;
s11, adding Mn (NO) into the mixture3)2·2H2O、Ce(NO3)3·6H2O and Cu (NO)3)2·9H2Adding excessive deionized water into O (metal oxide precursor) to dissolve to obtain precursor solution, and adding ammonia water and monoethanolamine to adjust the pH to 7 to obtain active solution;
s12, adding titanium dioxide, stearic acid, magnesium stearate, lactic acid and a half of active solution into a mixer, stirring for the first time at a stirring speed of 30r/min, stirring for 30min, adding the other half of active solution, stirring for the second time at a stirring speed of 30r/min, opening a steam valve to adjust the temperature to 85 ℃, stirring for 60min, adding glass fiber and paper pulp, stirring for the third time at a stirring speed of 30r/min, stirring for 60min, adding CMC (sodium carboxymethylcellulose) and PEO (polyethylene oxide), stirring for the fourth time at a stirring speed of 50r/min, stirring for 60min, cooling to below 60 ℃, stirring for the fifth time at a stirring speed of 20r/min, stirring for 15min, opening a steam valve, operating at a stirring speed of 30r/min to control water content, taking the mixture out of the pot until the water content is reduced to 25 wt% to obtain pug;
s2, pre-squeezing and aging, putting the pug into a pre-squeezing machine to obtain uniform cuboid brick-shaped pug sections, and then boxing and sealing the pug sections in an aging room at 25 +/-1 ℃ for aging for 3 days.
S3, forming, namely, sending the aged mud segment into a spiral continuous extruder for extrusion forming and cutting to obtain a honeycomb type fixed length wet blank with 30 holes, and then putting the honeycomb type fixed length wet blank into a drying chamber for primary sectional drying (namely box packing drying and box removing drying) to obtain a fixed length blank body; wherein the temperature of the drying chamber is slowly increased in the drying process of the pack box, the temperature is increased from 30 ℃ to 60 ℃ at the temperature increase rate of 5 ℃/day, the water vapor in the drying chamber is reduced from 80 wt% to 20 wt%, and the temperature in the drying chamber is increased from 40 ℃ to 65 ℃ at the temperature increase rate of 10 ℃/day in the drying process of the pack box; then sending the fixed-length blank into a tunnel kiln, raising the temperature to 50 ℃ at the heating rate of 10 ℃/12h for secondary drying, wherein the drying time is 3 days; performing sectional calcination on the fixed-length blank after secondary drying, performing large oven calcination, heating to 80 ℃ in a large oven at the heating rate of 8 ℃/12h for 10 days, performing mesh belt kiln calcination, heating the temperature in a mesh belt kiln to 550 ℃ from 20 ℃ within 24h, cooling to room temperature, cutting by a sawing bed, and boxing a module to obtain a finished product of the low-temperature SCR honeycomb denitration catalyst;
the mechanical strength of the low-temperature SCR honeycomb denitration catalyst prepared in the embodiment is 2.5 MPa; at a water vapor content of 10% (volume ratio), SO2The concentration is 35mg/Nm3The space velocity is 3500h-1And the denitration efficiency reaches 86% under the condition that the temperature is 170 ℃.
Example 2
In this example, the carrier was titanium dioxide, and the metal oxide precursor was Mn (NO)3)2·2H2O、Ce(NO3)3·6H2O and Cu (NO)3)2·9H2The O is prepared according to the molar ratio of 2:1:1, the release agent adopts stearic acid and magnesium stearate, the structural auxiliary agent adopts glass fiber and paper pulp, the binder adopts sodium carboxymethylcellulose (CMC) and polyethylene oxide (PEO), the pH regulator adopts ammonia water and monoethanolamine, and the preservative adopts lactic acid;
the preparation process comprises the following steps:
s1, mixing materials, namely adding a carrier, a metal oxide precursor, a release agent, a structural assistant, a binder, a pH regulator and a preservative into a pug mixer, and kneading to obtain pug;
the preparation method comprises the following steps of (1) mixing a carrier, a metal oxide precursor, a release agent, a structural assistant, a binder, a pH regulator and a preservative according to a mass ratio of 100: 20: 5: 8: 5: 5: 2, proportioning, and weighing each component according to the molar ratio of each component in the metal oxide precursor;
s11, adding Mn (NO) into the mixture3)2·2H2O、Ce(NO3)3·6H2O and Cu (NO)3)2·9H2Adding excessive deionized water into O (metal oxide precursor) to dissolve to obtain precursor solution, adding ammonia water and monoethanolamine to regulate pH to 8 to obtain active solution；
S12, adding titanium dioxide, stearic acid, magnesium stearate, lactic acid and a half of active solution into a mixer, stirring for the first time at a stirring speed of 20r/min, stirring for 15min, adding the other half of active solution, stirring for the second time at a stirring speed of 30r/min, opening a steam valve to adjust the temperature to 90 ℃, stirring for 35min, stirring for uniform mixing, adding glass fiber and paper pulp, stirring for the third time at a stirring speed of 30r/min, stirring for 35min, adding sodium carboxymethylcellulose (CMC) and polyethylene oxide (PEO), stirring for the fourth time at a stirring speed of 60r/min, stirring for 60min, cooling to a temperature below 60 ℃, stirring for the fifth time at a stirring speed of 30r/min, opening a steam valve after stirring for 5min, operating at a stirring speed of 20r/min to control water content, taking the mixture out of the pot until the water content is reduced to 25 wt% to obtain pug;
s2, pre-extruding and ageing, putting the pug into a pre-extruder to obtain uniform cuboid brick-shaped pug sections, and then boxing and sealing the pug sections in an ageing room at 25 +/-1 ℃ for ageing for 4 days.
S3, forming, namely, sending the aged mud segment into a spiral continuous extruder for extrusion forming and cutting to obtain a honeycomb type fixed length wet blank with 30 holes, and then putting the honeycomb type fixed length wet blank into a drying chamber for primary sectional drying (namely box packing drying and box removing drying) to obtain a fixed length blank body; wherein the temperature of the drying chamber is slowly increased in the drying process of the pack box, the temperature is increased from 30 ℃ to 60 ℃ at the temperature increase rate of 10 ℃/day, the water vapor in the drying chamber is reduced from 80 wt% to 20 wt%, and the temperature in the drying chamber is increased from 40 ℃ to 65 ℃ at the temperature increase rate of 5 ℃/day in the drying process of the pack box; then sending the fixed-length blank into a tunnel kiln, raising the temperature to 65 ℃ at the heating rate of 5 ℃/12h for secondary drying, wherein the drying time is 4 days; performing segmented calcination on the fixed-length blank after secondary drying, performing large-oven calcination, heating to 150 ℃ in a large oven at a heating rate of 10 ℃/12h for 6 days, performing mesh belt kiln calcination, heating the mesh belt kiln from 20 ℃ to 500 ℃ within 33h, cooling to room temperature, cutting by a sawing bed, and boxing a module to obtain a finished product of the low-temperature SCR honeycomb denitration catalyst;
in this exampleThe mechanical strength of the prepared low-temperature SCR honeycomb denitration catalyst is 2.2 MPa; at a water vapor content of 10% (volume ratio), SO2The concentration is 35mg/Nm3The space velocity is 3500h-1And the denitration efficiency reaches 89% under the condition that the temperature is 170 ℃.
At a water vapor content of 10% (volume ratio), SO2The concentration is 35mg/Nm3The space velocity is 3500h-1Example 3
In this example, the carrier was titanium dioxide, and the metal oxide precursor was Mn (NO)3)2·2H2O、Ce(NO3)3·6H2O and Cu (NO)3)2·9H2O is proportioned according to the molar ratio of 1:1.5:0.5, the release agent adopts stearic acid and magnesium stearate, the structural auxiliary agent adopts glass fiber and paper pulp, the binder adopts sodium carboxymethylcellulose (CMC) and polyethylene oxide (PEO), the pH regulator adopts ammonia water and monoethanolamine, and the preservative adopts lactic acid;
the preparation process comprises the following steps:
s1, mixing materials, namely adding a carrier, a metal oxide precursor, a release agent, a structural assistant, a binder, a pH regulator and a preservative into a pug mixer, and kneading to obtain pug;
the preparation method comprises the following steps of (1) mixing a carrier, a metal oxide precursor, a release agent, a structural assistant, a binder, a pH regulator and a preservative according to a mass ratio of 100: 15: 3: 7: 3: 4: 1, proportioning, and weighing each component according to the molar ratio of each component in the metal oxide precursor;
s11, adding Mn (NO) into the mixture3)2·2H2O、Ce(NO3)3·6H2O and Cu (NO)3)2·9H2Adding excessive deionized water into O (metal oxide precursor) to dissolve to obtain precursor solution, and adding ammonia water and monoethanolamine to adjust the pH to 7 to obtain active solution;
s12, adding titanium dioxide, stearic acid, magnesium stearate, lactic acid and a half of active solution into a mixer, stirring for the first time at a stirring speed of 30r/min, stirring for 20min, adding the other half of active solution, stirring for the second time at a stirring speed of 30r/min, opening a steam valve to adjust the temperature to 85 ℃, stirring for 50min, adding glass fiber and paper pulp, stirring for the third time at a stirring speed of 30r/min, stirring for 45min, adding sodium carboxymethylcellulose (CMC) and polyethylene oxide (PEO), stirring for the fourth time at a stirring speed of 55r/min, stirring for 50min, cooling to below 60 ℃, stirring for the fifth time at a stirring speed of 30r/min, stirring for 20min, opening a steam valve, controlling the water content at a stirring speed of 20r/min, taking the mixture out of the pot until the water content is reduced to 26 wt% to obtain pug;
s2, pre-extruding and ageing, putting the pug into a pre-extruder to obtain uniform cuboid brick-shaped pug sections, and then boxing and sealing the pug sections in an ageing chamber at 25 +/-1 ℃ for ageing for 7 days.
S3, forming, namely, sending the aged mud segment into a spiral continuous extruder for extrusion forming and cutting to obtain a honeycomb type fixed length wet blank with 30 holes, and then putting the honeycomb type fixed length wet blank into a drying chamber for primary sectional drying (namely box packing drying and box removing drying) to obtain a fixed length blank body; wherein the temperature of the drying chamber is slowly increased in the drying process of the pack box, the temperature is increased from 30 ℃ to 60 ℃ at the temperature increase rate of 8 ℃/day, the water vapor in the drying chamber is reduced from 80 wt% to 20 wt%, and the temperature in the drying chamber is increased from 40 ℃ to 65 ℃ at the temperature increase rate of 7 ℃/day in the drying process of the pack box; then sending the fixed-length blank into a tunnel kiln, raising the temperature to 58 ℃ at the heating rate of 6 ℃/12h for secondary drying, wherein the drying time is 3 days; performing sectional calcination on the fixed-length blank after secondary drying, performing large-oven calcination, heating to 110 ℃ in a large oven at the heating rate of 8 ℃/12h for 8 days, performing mesh belt kiln calcination, heating the temperature in a mesh belt kiln from 20 ℃ to 500 ℃ within 29h, cooling to room temperature, cutting by a sawing bed, and boxing a module to obtain a finished product of the low-temperature SCR honeycomb denitration catalyst;
the mechanical strength of the low-temperature SCR honeycomb denitration catalyst prepared in the embodiment is 2.0 MPa; at a water vapor content of 10% (volume ratio), SO2The concentration is 35mg/Nm3The space velocity is 3500h-1And the denitration efficiency reaches 83 percent under the condition that the temperature is 170 ℃.
With reference to embodiments 1 to 3, according to the preparation method of the low-temperature SCR honeycomb denitration catalyst, nitrates are used as a metal oxide precursor, titanium dioxide or a molecular sieve is used as a carrier, and a release agent, a structural assistant, a binder, a pH regulator and a preservative are added to prepare the low-temperature SCR honeycomb denitration catalyst, so that the prepared low-temperature SCR honeycomb denitration catalyst has a good denitration effect and mechanical strength under a low-temperature condition, is wide in raw material source and low in cost, and is suitable for industrial production; the preparation method of the low-temperature SCR honeycomb denitration catalyst adopts a sectional dry impurity and sectional calcination mechanism, solves the problems that the nitrate-type molded low-temperature catalyst is easy to ignite, crack and burn and the like, and ensures the quality of the catalyst.
Although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (12)
1. A preparation method of a low-temperature SCR honeycomb type denitration catalyst is characterized by comprising the following steps:
s1, mixing materials, namely adding a carrier, a metal oxide precursor, a release agent, a structural assistant, a binder, a pH regulator and a preservative into a pug mixer, and kneading to obtain pug;
s2, pre-extruding and ageing, namely, obtaining mud sections by the mud materials through a pre-extruder, and then boxing and ageing;
and S3, forming, namely feeding the aged mud segment into an extruder to obtain a honeycomb type fixed length wet blank, and performing primary segmented drying, secondary drying and segmented calcining on the honeycomb type fixed length wet blank to obtain the low-temperature SCR honeycomb type denitration catalyst.
2. The method according to claim 1, wherein in step S1, the carrier, the metal oxide precursor, the release agent, the structural assistant, the binder, the pH adjuster, and the corrosion inhibitor are mixed in a mass ratio of 100: 10-20: 2-5: 5-8: 1-5: 2-5: 0 to 2.
3. The preparation method of the low-temperature SCR honeycomb denitration catalyst according to claim 2, wherein in the step S1, the carrier is titanium dioxide or a molecular sieve;
the metal oxide precursor is selected from one or more nitrates of Mn, Ce, Cu, Sn, Cr, Fe and Co;
the release agent adopts stearic acid and magnesium stearate;
the structural auxiliary agent adopts glass fiber and paper pulp;
the binder adopts sodium carboxymethyl cellulose (CMC) and polyethylene oxide (PEO);
the pH regulator adopts ammonia water and monoethanolamine;
the preservative is lactic acid.
4. The preparation method of the low-temperature SCR honeycomb type denitration catalyst according to claim 3, wherein the metal oxide precursor is nitrate of Mn, Ce and Cu, and the molar ratio of the nitrate of Mn, Ce and Cu is 1-2: 1-1.5: 0.5 to 1.
5. The preparation method of the low-temperature SCR honeycomb-type denitration catalyst according to claim 3, wherein the step S1 specifically comprises the following steps:
s11, preparing an active solution, adding excessive deionized water to dissolve the metal oxide precursor to obtain a precursor solution, and adding a pH regulator to regulate the pH to 6-8 to obtain the active solution;
and S12, adding the carrier, the release agent, the preservative and half of the active solution into a mixer for first stirring, uniformly mixing, adding the other half of the active solution for second stirring, uniformly mixing, adding the structural assistant for third stirring, uniformly mixing again, adding the binder for fourth stirring, uniformly mixing, and stirring for the fifth time until the water content is reduced to 20-28 wt% to obtain the pug.
6. The method according to claim 5, wherein in step S12,
during the first stirring, the stirring time is 15-30 min, and the stirring speed is 20-30 r/min;
during the second stirring, the stirring time is 35-60 min, the stirring temperature is 75-90 ℃, and the stirring speed is 20-30 r/min;
during the third stirring, the stirring time is 35-60 min, and the stirring speed is 20-30 r/min;
during the fourth stirring, the stirring time is 30-60 min, and the stirring speed is 50-60 r/min;
and in the fifth stirring, firstly stirring for 5-30 min at a stirring speed of 20-30 r/min under the condition that the temperature is less than 60 ℃, and then opening a steam valve to stir at a stirring speed of 20-30 r/min until the water content is reduced to 20-28 wt%.
7. The method according to claim 1, wherein in step S2, the aging time is not more than 14 days.
8. The preparation method of the low-temperature SCR honeycomb type denitration catalyst according to claim 7, wherein the aging time is 2 to 4 days.
9. The method of preparing a low-temperature SCR honeycomb denitration catalyst according to claim 1, wherein in step S3, the primary stage drying includes pack drying and debock drying;
in the drying process of the box, the temperature is increased from 30 ℃ to 60 ℃ at the temperature increase rate of 5-10 ℃/day;
in the box removing and drying process, the temperature is increased from 40 ℃ to 65 ℃ at a temperature increase rate of 5-10 ℃/day.
10. The preparation method of the low-temperature SCR honeycomb denitration catalyst according to claim 1, wherein in the step S3, the temperature is increased from 40 ℃ to 65 ℃ at a temperature rate of 5-10 ℃/12h in the secondary drying process, and the drying time is 2-4 days.
11. The method for preparing the low-temperature SCR honeycomb-type denitration catalyst according to claim 1, wherein in the step S3, the staged calcination comprises large oven calcination and mesh belt kiln calcination;
in the calcining process of the large oven, the heating rate is 5-10 ℃/12h, the temperature is 80-150 ℃, and the calcining time is 6-10 days;
in the calcining process of the mesh belt kiln, the temperature is increased from 20 ℃ to 550 ℃ within 24-33 h, and then the mixture is cooled to room temperature.
12. The low-temperature SCR honeycomb denitration catalyst obtained by the preparation method of the low-temperature SCR honeycomb denitration catalyst according to any one of claims 1 to 11 has denitration efficiency of over 86% at 170 ℃.
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