CN114345245B - Fixed bed chemical chain reaction device and integral oxygen carrier preparation method - Google Patents
Fixed bed chemical chain reaction device and integral oxygen carrier preparation method Download PDFInfo
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Abstract
The invention belongs to the technical field of energy and chemical industry, and particularly relates to a fixed bed chemical chain reaction device and an integral oxygen carrier preparation method. The device comprises: the device comprises a shell, a heat insulation material, a ceramic heat accumulator and a plurality of integral oxygen carriers; the heat insulation material is fixed in the shell; the ceramic heat accumulator is fixed in the heat insulating material; the ceramic heat accumulator is internally provided with a plurality of through holes with the same size along the length direction of the fixed bed chemical chain reaction device, and each through hole is filled with one or a plurality of integral oxygen carriers. The method effectively relieves the condition of overlarge temperature fluctuation in the reactor caused by heat absorption in the chemical chain oxidation-reduction cycle process, further effectively solves the problem of reduced reaction performance caused by heat absorption and temperature reduction in the gas-phase fuel partial oxidation reaction, and the problems of local sintering deactivation and reduced service life of the oxygen carrier caused by excessive heat release and temperature rise in the oxygen carrier regeneration reaction, and simultaneously strengthens radial heat mass transfer and improves the selectivity of products.
Description
Technical Field
The invention belongs to the technical field of energy and chemical industry, and particularly relates to a fixed bed chemical chain reaction device and an integral oxygen carrier preparation method.
Background
Synthesis gas (co+h) 2 ) Is an important chemical raw material, can convert the synthesis gas into various chemicals through different reaction paths, and has extremely important position in chemical production. With the increasing demand of materials and chemical industry for raw materials, the production capacity of the synthesis gas is continuously improved. The existing industrial synthesis gas preparation mainly depends on natural gas steam reforming and coal gasification, and the two methods consume a large amount of energy and water resources, so that the competitiveness of the synthesis gas is gradually lost under the constraints of environmental protection and 'double carbon' targets in the future.
Chemical chain partial oxidation technology has received widespread attention in recent years as an emerging technology for efficiently producing synthesis gas. The principle is that transition metal oxide is used as oxygen carrier, and the selective oxidation characteristic of lattice oxygen in the oxygen carrier is utilized to oxidize the lattice oxygen in the oxygen carrier to form synthetic gas at certain temperature, and then the oxygen carrier is supplemented with oxygen in oxidizing atmosphere to obtain heat and complete the oxidation regeneration of the oxygen carrier. The oxygen carrier plays roles of oxygen supply, heat supply and catalysis in the process. The conversion of carbonaceous fuel to synthesis gas is continuously maintained by the continuous circulation of the oxygen carrier in the reducing and oxidizing environment.
The existing carbon-containing fuel chemical chain partial oxidation reaction device is a double-circulation fluidized bed reactor, the device is difficult to adjust in actual operation, and oxygen carrier particles can be worn due to severe collision, so that the service life of the oxygen carrier is obviously reduced, and the operation cost is greatly improved. In addition, the reaction performance between the solid phase reactant and the oxygen carrier in the fluidized bed reactor is poor, and the selective oxidation of the gas phase reactant by the oxygen carrier is mainly relied on. The fixed bed chemical chain reaction device can effectively avoid the problems of difficult regulation and oxygen carrier abrasion during the chemical chain reaction of treating the gas phase carbon-containing fuel. However, the fixed bed chemical chain reaction device using the particle oxygen carrier as the filler has the problems of high bed pressure drop, low heat and mass transfer efficiency, large power consumption, poor reaction performance and the like. In recent years, a fixed bed chemical chain reaction device filled with an integral oxygen carrier has great development potential in the process of chemical chain partial oxidation reaction of gas-phase carbon-containing fuel, and compared with a fixed bed reaction device filled with particles, the fixed bed chemical chain reaction device has the advantage that the pressure drop of a bed layer is remarkably reduced.
There are few examples of fixed bed chemical chain reaction units packed with monolithic oxygen carriers for use in carbon-containing fuel chemical chain partial oxidation processes. However, the existing fixed bed chemical chain reaction device and the integral oxygen carrier have the following problems: 1. the heat storage capacity of the reactor is low, and the heat absorption and release effect in the chemical chain reaction process is obvious, so that the temperature fluctuation in the reactor is large, and the service life and the reaction performance of the oxygen carrier are further influenced; 2. the existing integral oxygen carrier pore-forming mode is simple, an extrusion molding method is generally adopted, the pore channel structure is difficult to optimize, and particularly, a radial mass transfer channel is not provided, so that the conversion rate and the selectivity of the chemical chain partial oxidation reaction are low; 3. the existing integral oxygen carrier is prepared by coating active components on a carrier, and has low oxygen carrying capacity due to the fact that the carrier contains more inert components, so that the effective reaction time of the oxygen carrier is obviously shortened.
Disclosure of Invention
Aiming at the problems that the reactor has low heat storage capacity, the integral oxygen carrier pore-forming mode is simple, the pore channel structure is difficult to optimize, and particularly, a radial mass transfer channel is not provided, so that the conversion rate and the selectivity of the partial oxidation reaction of a chemical chain are low, the oxygen carrier has low oxygen carrying capacity, the effective reaction time is short and the like, the invention provides a fixed bed chemical chain reaction device and an integral oxygen carrier preparation method.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
in a first aspect, the present invention provides a fixed bed chemical chain reaction apparatus comprising: the device comprises a shell, a heat insulation material, a ceramic heat accumulator and a plurality of integral oxygen carriers;
the heat insulation material is fixed in the shell; the ceramic heat accumulator is fixed in the heat insulating material; the ceramic heat accumulator is internally provided with a plurality of through holes with the same size along the length direction of the fixed bed chemical chain reaction device, and each through hole is filled with one or a plurality of integral oxygen carriers.
Furthermore, the integral oxygen carrier is formed in a 3D printing mode, an interconnection pore canal structure is arranged in the integral oxygen carrier, and adjacent axial channels are connected through radial channels.
Further, the gaps among the heat insulation material, the shell and the ceramic heat accumulator are sealed by bentonite.
Further, two ends of the shell are respectively connected with a sealing head in a sealing mode, and the sealing heads are provided with connectors for connecting pipelines.
Further, a partition plate is arranged in the seal head to form two reaction channels which are not communicated with each other.
In a second aspect, the present invention provides a method for preparing an integral oxygen carrier, comprising the steps of:
s1, modeling a structure, namely modeling a three-dimensional structure of the integral oxygen carrier by using three-dimensional modeling software, and performing design optimization on a pore channel structure of the integral oxygen carrier by simulation;
s2, preparing slurry, namely screening transition metal oxide powder to a particle size of 45-75 mu m, and mixing the transition metal oxide powder with uniform thickness with deionized water, a binder, a plasticizer and a dispersing agent to prepare stable and dispersed slurry;
s3, printing a primary blank, converting the integral oxygen carrier three-dimensional structure model designed in the step S1 into a source code which can be identified by a 3D printer, and printing the slurry prepared in the step S2 into the integral oxygen carrier primary blank on a carbon crystal glass plate by using a direct-writing 3D printer;
s4, drying and solidifying, namely taking out the carbon crystal glass plate and the printed integral oxygen carrier primary blank in the step S3 together, and drying under a certain condition to solidify the integral oxygen carrier primary blank and separate the integral oxygen carrier primary blank from the carbon crystal glass plate;
s5, sintering and forming, and carrying out high-temperature heat treatment on the integral oxygen carrier primary blank after drying and curing in the step S4 to obtain an integral oxygen carrier finished product.
Further, in the step S2, the mass fraction of each component of the slurry is 30-60wt% of transition metal oxide powder, 10-20wt% of deionized water, 20-40wt% of a binder, 5-15wt% of a plasticizer and 2-5wt% of a dispersing agent;
the binder is one or more of polyvinyl alcohol, polyethylene glycol, polyacrylamide, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinylpyrrolidone, polyacrylic acid and polyacrylic resin;
the plasticizer is one or more of dimethyl phthalate, dibutyl phthalate, dioctyl phthalate, epoxy butyl oleate, epoxy octyl oleate, epoxy decyl oleate, tributyl citrate and acetyl tributyl citrate;
the dispersing agent is one or the combination of more than one of ethylenediamine tetramethylene phosphoric acid, hydroxyethylidene diphosphate and aminotrimethylene phosphoric acid.
Further, the printing parameters of the direct-write printer in step S3 are: the air pressure of the charging barrel is 0.2-0.6 MPa, the air flow pulse time is 0.05-0.2 s, the diameter of the spray head is 0.2-1.0 mm, and the moving speed of the spray head is 50-150 mm/s.
Further, the drying conditions in the step S4 are as follows: firstly, drying for 2-6 hours at a constant temperature of 40-60 ℃ to separate an integral oxygen carrier primary blank from a carbon crystal glass plate; and drying the integral oxygen carrier primary blank for 12-20 hours at the temperature of 110-150 ℃.
Further, the high-temperature heat treatment conditions in the step S5 are as follows: heating the dried and solidified integral oxygen carrier primary blank to 800-1200 ℃ at a heating rate of 1-10 ℃ per minute under the air atmosphere, keeping the temperature for 2-8 hours, and naturally cooling to room temperature.
Compared with the prior art, the invention has the following beneficial effects:
1. the combination of the ceramic heat accumulator and the integral oxygen carrier in the fixed bed chemical chain reaction device can effectively relieve the situation of overlarge temperature fluctuation in the reactor caused by heat absorption in the chemical chain oxidation-reduction cycle process, thereby effectively solving the problem of reduced reaction performance caused by heat absorption and temperature reduction in the gas phase fuel partial oxidation reaction, and the problem of local sintering deactivation and reduced service life of the oxygen carrier caused by excessive heat release and temperature rise in the oxygen carrier regeneration reaction.
2. Auxiliary components such as a binder, a plasticizer, a dispersing agent and the like can be completely removed from the integral oxygen carrier primary blank printed by the slurry in the sintering process, and the prepared integral oxygen carrier is finally completely sintered by active oxygen carrier powder without using an inert carrier, so that the integral oxygen carrier prepared by 3D printing has higher proportion of active components and oxygen carrying amount compared with other integral oxygen carriers, and the effective reaction time is longer.
3. The integral oxygen carrier is prepared by a 3D printing method, the pore canal structure of the integral oxygen carrier can be optimally designed according to experimental and simulation results, the radial heat and mass transfer capacity of the integral oxygen carrier shaft is improved, and the conversion rate and the selectivity of the chemical chain partial oxidation reaction are further improved; particularly for carbonaceous organic matters with larger molecular weight, the reaction of the carbonaceous organic matters and an oxygen carrier is easy to be controlled by diffusion, and the change of a pore channel structure can have a remarkable influence on the selectivity of a product. In addition, the optimized pore structure has obvious effect on the distribution of the temperature field in the control integral oxygen carrier, and can effectively avoid hot spots.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:
FIG. 1 is a schematic diagram of a single atmosphere structure of a fixed bed chemical chain reaction device of the present invention;
FIG. 2 is a schematic diagram of the single atmosphere parallel operation of the fixed bed chemical chain reaction device of the present invention;
FIG. 3 is a schematic diagram of a double atmosphere structure of a fixed bed chemical chain reaction device of the present invention;
FIG. 4 is a schematic diagram showing the operation of a double-atmosphere structure of a fixed bed chemical chain reaction device of the present invention;
FIG. 5 is a schematic diagram of a biomass pyrolysis coupling fixed bed chemical chain conversion process;
FIG. 6 is a schematic structural view of a 3D printed monolithic oxygen carrier;
1-end socket; 2-a housing; 3-a thermal insulation material; 4-ceramic heat accumulator; 5-monolithic oxygen carrier; 6-through holes;
wherein the 1-end socket comprises an 11-interface; 12-separator.
Detailed Description
The invention will be described in detail below with reference to the drawings in connection with embodiments. It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
The following detailed description is exemplary and is intended to provide further details of the invention. Unless defined otherwise, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the invention.
Example 1:
as shown in fig. 2, two identical single-atmosphere fixed bed chemical chain reaction devices are operated in parallel through a pipeline and a pneumatic butterfly valve for chemical chain partial oxidation reaction of natural gas. Wherein, one fixed bed chemical chain reaction device 1 carries out partial oxidation reaction of natural gas, and the other fixed bed chemical chain reaction device carries out oxidation regeneration reaction of the oxygen carrier. The continuous operation of the chemical chain process is realized by continuously switching the valve to ensure that the two fixed bed chemical chain reaction devices respectively perform reactions at different stages and realize oxidation-reduction circulation.
As shown in fig. 1, each fixed bed chemical chain reaction device comprises a steel shell 2, a heat insulation material 3, a ceramic heat accumulator 4 and seven integral oxygen carriers 5; the ceramic heat accumulator 4 is internally provided with seven parallel through holes 6 with the same size along the length direction of the fixed bed chemical chain reaction device, one of the seven through holes 6 takes one as a circle center, the other six through holes are annularly arranged, the integral oxygen carrier 5 is filled in the through holes 6, each through hole 6 is internally filled with an integral oxygen carrier 5, and two ends of the shell 2 are respectively provided with a sealing head 1.
The steel housing 2 provides sufficient structural strength and tightness to ensure that the reaction can run smoothly; the heat insulating material 3 is fixed in the shell 2 and is made of quartz sand, clay and dolomite and used for maintaining the temperature in the fixed bed chemical chain reaction device; the ceramic heat accumulator 4 is fixed in the space surrounded by the heat-insulating material 3. In addition, the gaps among the heat insulating material 3, the shell 2 and the ceramic heat accumulator 4 are sealed by using bentonite as a binder, so that reactant air flow is avoided.
The ceramic heat accumulator 4 is formed MgO and Al 2 O 3 One or more of cordierite and mullite are preferably Al with good heat conduction and large heat storage capacity 2 O 3 Ceramic material of Al 2 O 3 The ceramic material is formed in one step in an extrusion forming mode and is arranged in the fixed bed chemical chain reaction device. The ceramic heat accumulator 4 can be used as a heat accumulation pool in the chemical chain oxidation-reduction reaction process, can absorb heat when the oxygen carrier is oxidized, and can release heat when the oxygen carrier is reduced, so that the temperature fluctuation in the fixed bed chemical chain reaction device is reduced to a certain extent, and the reaction performance is improved. The size of the through hole on the ceramic heat accumulator can be calculated according to the specific heat capacity and the heat conductivity coefficient of the ceramic heat accumulator and the heat released and absorbed in the oxidation-reduction cycle process of chemical chain reaction, and the relative volume and the layout of the ceramic heat accumulator and the integral oxygen carrier are determined according to the heat quantity and the heat exchange efficiency of specific reaction.
The material of the monolithic oxygen carrier 5 is one or a combination of more than one of single transition metal oxide, transition metal composite oxide and supported transition metal oxide with oxygen supply, heat carrying and catalytic capability, preferably a transition metal composite oxide, such as perovskite, spinel and the like, with unique catalytic effect and selective oxidation capability.
The monolithic oxygen carrier 5 is prepared by 3D printing, in this example, a transition metal composite oxide is used, the composition of which is NiFe 2 O 4 Spinel composite metal oxide. Wherein Ni and Fe have synergistic effect, so NiFe 2 O 4 The integral oxygen carrier has higher conversion rate and selectivity to the partial oxidation reaction of the chemical chain of the natural gas; at the same time, niFe 2 O 4 The spinel composite oxide has high stability, and active components are not easy to be sintered and deactivated, so NiFe 2 O 4 The monolithic oxygen carrier can still maintain high reactivity after multiple oxidation-reduction cycles.
NiFe 2 O 4 The integral oxygen carrier 5 has rich interconnected pore canal structure, honeycomb porous structure in axial direction, radial open pores between adjacent axial pore canal to improve radial heat and mass transfer capabilityThe reaction performance is improved, and the specific structure is shown in figure 6. The structure remarkably reduces the bed pressure drop of the fixed bed chemical chain reaction device 1 and reduces the power consumption. Meanwhile, the internal porous structure strengthens the contact between the reactant and the oxygen carrier, reduces the self-cracking proportion of the natural gas in the reactor, and remarkably improves CO and H in the chemical chain partial oxidation reaction of the natural gas 2 Is selected from the group consisting of (1). In addition, the integral oxygen carrier 5 can be flexibly installed and detached in the ceramic heat accumulator 4.
The cross section of each through hole 6 is one of a circle, a triangle, a regular hexagon or other regular shapes, preferably a circle, so that the structural strength of the ceramic heat accumulator and the integral oxygen carrier is higher; the outer contour and the size of the integral oxygen carrier 5 can be determined according to the cross-sectional shape and the size of the through hole, and the outer contour and the shape of the through hole of the integral oxygen carrier are kept consistent, and the size is slightly smaller than the size of the through hole so as to ensure that the integral oxygen carrier can be smoothly installed and detached.
In addition, the embodiment also provides 3D printing of NiFe 2 O 4 The method of the integral oxygen carrier comprises the following specific steps:
s11, initially modeling the three-dimensional structure of the integrated oxygen carrier, and simulating the main components of natural gas and NiFe by using simulation software 2 O 4 And analyzing the distribution of the flow field and the temperature field in the pore canal of the integral oxygen carrier according to the reaction of the integral oxygen carrier, optimizing the pore canal structure according to the simulation result, avoiding the occurrence of flow stagnation areas and local hot spots, and finally obtaining a reasonable three-dimensional pore canal structure.
S12, niFe to be synthesized 2 O 4 Sieving the powder to a particle size of 45-75 mu m (200-325 mesh), and uniformly sizing NiFe 2 O 4 The powder, deionized water, a binder, a plasticizer and a dispersing agent are mixed and stirred for 12 hours to prepare stable dispersed slurry, wherein the mass fraction of each component of the slurry is 30-60wt% of transition metal oxide powder, 10-20wt% of deionized water, 20-40wt% of the binder, 5-15wt% of the plasticizer and 2-5wt% of the dispersing agent.
Wherein NiFe 2 O 4 The mass percentages of the powder, the deionized water, the binder, the plasticizer and the dispersing agent are 55wt respectivelyPercent, 8wt%, 20wt%, 12wt% and 5wt%.
The deionized water and the binder are used for regulating and controlling the rheological property of the slurry, the plasticizer is used for improving the strength of the integral oxygen carrier blank after printing and forming, and the dispersing agent is used for improving the dispersion stability of the transition metal oxide powder in the slurry. The binder is one or more of polyvinyl alcohol, polyethylene glycol, polyacrylamide, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinylpyrrolidone, polyacrylic acid and polyacrylic resin; the plasticizer is one or more of dimethyl phthalate, dibutyl phthalate, dioctyl phthalate, epoxy butyl oleate, epoxy octyl oleate, epoxy decyl oleate, tributyl citrate and acetyl tributyl citrate; the dispersing agent is one or more of ethylenediamine tetramethylene phosphoric acid, hydroxyethylidene diphosphate and aminotrimethylene phosphoric acid
In this embodiment, the binder comprises the following components in mass ratio of 1:1, wherein the plasticizer component is dibutyl phthalate and the dispersant component is ethylenediamine tetramethylene phosphate.
S13, using three-dimensional model slicing software to design the NiFe in the step S11 2 O 4 Converting the integral oxygen carrier three-dimensional structure model into a source code which can be identified by a 3D printer, and printing the slurry prepared in the step S12 on a carbon crystal glass plate to form NiFe by using a direct-writing 3D printer 2 O 4 An integral oxygen carrier primary blank.
The direct-writing 3D printer uses compressed air to drive feeding, and the working parameters are as follows: the air pressure of the charging barrel is 0.2-0.6 MPa, the air flow pulse time is 0.05-0.2 s, the diameter of the spray head is 0.2-1.0 mm, and the moving speed of the spray head is 50-150 mm/s. Specifically, the air pressure of the charging barrel is 0.45MPa, the air flow pulse time is 0.1s, the diameter of the spray head is 0.5mm, and the moving speed of the spray head is 80mm/s. For slurries with different viscosities, the discharge amount and the moving speed of the spray head are matched by adjusting the pressure of the charging barrel.
S14, the carbon crystal glass plate in the step S13 and the printed NiFe 2 O 4 Integral oxygen carrier primary blank togetherTaking out, and drying at constant temperature of 50deg.C for 4 hr to obtain NiFe 2 O 4 Separating the integral oxygen carrier from the carbon crystal glass plate; then NiFe is added 2 O 4 The integral oxygen carrier primary blank is dried for 12 hours at the temperature of 120 ℃ to be dried and solidified and has certain strength.
S15, drying and solidifying the NiFe in the step S14 2 O 4 Heating the integral oxygen carrier primary blank to 1000 ℃ at a heating rate of 2 ℃ per minute under the air atmosphere, and keeping the temperature for 6 hours to enable the integral oxygen carrier primary blank to be sintered and formed and fully oxidized, and then taking out the integral oxygen carrier primary blank after natural cooling to obtain NiFe 2 O 4 And (5) an integral oxygen carrier finished product.
In successful preparation of NiFe 2 O 4 After the integral oxygen carrier, the natural gas chemical chain partial oxidation process is subjected to aging treatment in order to ensure that the product distribution does not generate obvious difference in each cycle of the natural gas chemical chain partial oxidation process. I.e. ready-to-prepare NiFe 2 O 4 Use of H in a tube furnace at 800 ℃ for monolithic oxygen carriers 2 Reducing, oxidizing with air at the same temperature, repeating the operation for 5 times to obtain NiFe 2 O 4 The oxidation-reduction reaction performance of the monolithic oxygen carrier tends to be stable.
Example 2:
as shown in fig. 4, a double-atmosphere fixed bed chemical chain reaction device is operated by a pipeline and a pneumatic butterfly valve and is used for the chemical chain partial oxidation reaction of carbon-based fuel, taking biomass pyrolysis volatile as an example.
As shown in fig. 5, in the biomass pyrolysis coupling fixed bed chemical chain conversion process, volatile matters generated by biomass pyrolysis are directly conveyed to a fixed bed chemical chain reaction device through a high-temperature pipeline to perform partial oxidation reaction, and are converted into synthesis gas.
A single double-atmosphere fixed bed chemical chain reaction device is divided into two reaction areas which are not communicated with each other. Wherein, one reaction area carries out partial oxidation reaction of biomass pyrolysis volatile matters, and the other reaction area carries out regeneration of oxygen carriers. The continuous operation of the chemical chain process is realized by continuously switching the valves to ensure that the two reaction areas respectively carry out reactions in different stages.
As shown in fig. 3, the fixed bed chemical chain reaction device comprises a steel shell 2, a sealing head 1, a heat insulation material 3, a ceramic heat accumulator 4 and six integral oxygen carriers 5; six parallel through holes 6 with the same size are formed in the ceramic heat accumulator 4 along the length direction of the fixed bed chemical chain reaction device, the integral oxygen carriers 5 are filled in the through holes 6, and each through hole 6 is filled with one integral oxygen carrier 5.
The outside of the seal head 1 is provided with two interfaces 11, the inside is provided with a baffle 12, the inside is divided into two reaction channels, and the three integral oxygen carriers at the upper part and the three integral oxygen carriers at the lower part respectively form two reaction channels which are not communicated with each other.
The steel housing 2 provides sufficient structural strength and tightness to ensure that the reaction can run smoothly; a thermal insulation material 3, which is made of aluminum silicate and composite silicate and is used for maintaining the temperature inside the fixed bed chemical chain reaction device, is fixed inside the shell 2; the ceramic heat accumulator 4 is fixed in the space surrounded by the heat-insulating material 3. In addition, the gaps among the heat insulating material 3, the shell 2 and the ceramic heat accumulator 4 are sealed by using bentonite as a binder, so that reactant air flow is avoided.
The ceramic heat accumulator 4 uses cordierite and Al 2 O 3 The ceramic material is formed in one step in an extrusion forming mode, is integrated and is arranged in the fixed bed chemical chain reaction device. The ceramic heat accumulator 4 can be used as a heat accumulation pool in the chemical chain oxidation-reduction reaction process, and can absorb heat when the oxygen carrier is oxidized and release heat when the oxygen carrier is reduced; meanwhile, heat can be mutually transferred between the partial oxidation reaction side and the oxygen carrier oxidation regeneration side. The buffering action of the ceramic heat accumulator 4 can reduce the temperature fluctuation in the fixed bed chemical chain reaction device to a certain extent.
The monolithic oxygen carrier 5 is prepared by 3D printing, preferably by using a transition metal composite oxide composed of NiO-Fe 2 O 3 -CeO 2 A composite metal oxide. Wherein, ni has catalytic cracking effect on tar in biomass pyrolysis volatile matters, and the conversion rate of reactants is obviously improved; fe has selective oxidation to reactantIs such that CO and H in the product 2 The proportion is obviously improved; ceO (CeO) 2 Has obvious elimination effect on carbon deposition generated in the reaction process, and can further improve the conversion rate and selectivity in the reaction process.
NiO-Fe 2 O 3 -CeO 2 The monolithic oxygen carrier 5 is axially honeycomb porous structure with radial openings between adjacent axial cells to enhance radial heat and mass transfer capability, the specific structure is shown in fig. 6. The structure obviously reduces the bed pressure drop of the fixed bed chemical chain reaction device and reduces the power consumption. Meanwhile, the partial oxidation reaction between the tar macromolecules and the oxygen carrier in the biomass volatile matters is controlled by diffusion, so that the structure is very beneficial to improving the conversion rate of the tar macromolecules.
In addition, the embodiment also provides 3D printing of NiO-Fe 2 O 3 -CeO 2 The method of the integral oxygen carrier comprises the following specific steps:
s21, initially modeling the three-dimensional structure of the integrated oxygen carrier, and simulating main components of biomass pyrolysis volatile components and NiO-Fe by using simulation software 2 O 3 -CeO 2 And analyzing the distribution of the flow field and the temperature field in the pore canal of the integral oxygen carrier according to the reaction of the integral oxygen carrier, optimizing the pore canal structure according to the simulation result, avoiding the occurrence of flow stagnation areas and local hot spots, and finally obtaining a reasonable three-dimensional pore canal structure.
S22, synthesizing NiO-Fe by a high-temperature solid phase method 2 O 3 -CeO 2 Sieving the composite oxide powder to a particle size of 96 μm (160) mesh or less, and separating NiO-Fe with uniform thickness 2 O 3 -CeO 2 The powder is mixed with deionized water, a binder, a plasticizer and a dispersing agent and stirred for 24 hours to prepare stable dispersed slurry. Wherein NiO-Fe 2 O 3 -CeO 2 The mass percentages of the powder, deionized water, binder, plasticizer and dispersant are 45wt%, 10wt%, 25wt%, 12wt% and 8wt%, respectively. The binder comprises the following components in percentage by mass: 1, wherein the components of the plasticizer are polyvinyl alcohol and polyacrylamide are 1:1 and dioctyl phthalate, and the dispersing agent is amino trimethyl orthophosphoric acid.
S23, using three-dimensional model slicing software to slice NiO-Fe designed in the step S21 2 O 3 -CeO 2 Converting the integral oxygen carrier three-dimensional structure model into a source code which can be identified by a 3D printer, and printing the slurry prepared in the step S22 into NiO-Fe on a carbon crystal glass plate by using a direct-writing 3D printer 2 O 3 -CeO 2 An integral oxygen carrier primary blank. The direct-writing 3D printer uses compressed air to drive feeding, and the working parameters are as follows: the air pressure of the charging barrel is 0.55MPa, the air flow pulse time is 0.05s, the diameter of the spray head is 0.3mm, and the moving speed of the spray head is 100mm/s.
S24, the carbon crystal glass plate in the step S23 and the printed NiO-Fe 2 O 3 -CeO 2 Taking out the integral oxygen carrier primary blank together, and drying at constant temperature of 40 ℃ for 6 hours to enable NiO-Fe 2 O 3 -CeO 2 Separating the integral oxygen carrier from the carbon crystal glass plate; then NiO-Fe 2 O 3 -CeO 2 The integral oxygen carrier primary blank is dried for 12 hours at the temperature of 150 ℃ so that the integral oxygen carrier primary blank is dried and solidified and has certain strength.
S25, drying and solidifying the NiO-Fe in the step S24 2 O 3 -CeO 2 Heating the integral oxygen carrier primary blank to 1200 ℃ at a temperature rising rate of 5 ℃ per minute under the air atmosphere, keeping the temperature for 2 hours, sintering and forming the integral oxygen carrier primary blank and fully oxidizing the integral oxygen carrier primary blank, and taking out the integral oxygen carrier primary blank after natural cooling to obtain NiO-Fe 2 O 3 -CeO 2 And (5) an integral oxygen carrier finished product.
In the successful preparation of NiO-Fe 2 O 3 -CeO 2 After the integral oxygen carrier, the natural gas chemical chain partial oxidation process is subjected to aging treatment in order to ensure that the product distribution does not generate obvious difference in each cycle of the natural gas chemical chain partial oxidation process. I.e. prepared NiO-Fe 2 O 3 -CeO 2 Use of H in a tube furnace at 850 ℃ for monolithic oxygen carriers 2 Reducing, oxidizing with air at the same temperature, repeating the operation for 5 times to obtain NiO-Fe 2 O 3 -CeO 2 The oxidation-reduction reaction performance of the monolithic oxygen carrier tends to be stable.
Example 3:
in this embodiment, the method for preparing the monolithic oxygen carrier by using the supported transition metal oxide, a transition metal oxide encapsulated by a molecular sieve and adopting a 3D printing mode comprises the following specific steps:
s31, dispersing a commercial SBA-15 molecular sieve in absolute ethyl alcohol by using a surfactant, and mixing the molecular sieve with La (NO 3 ) 3 ·6H 2 O、Ni(NO 3 ) 2 ·6H 2 O and Fe (NO) 3 ) 3 ·9H 2 The O aqueous solution was thoroughly mixed. The well mixed solution was dried at 80 ℃ to obtain a powder precursor, which was then milled to a suitable particle size. Calcining the ground powder precursor at 800 ℃ by introducing air to finally obtain LaFe 0.5 Ni 0.5 O 3 SBA-15 powder.
S32, constructing a three-dimensional pore structure of the integral oxygen carrier by using three-dimensional modeling software to obtain LaFe 0.5 Ni 0.5 O 3 Configuration of SBA-15 monolithic oxygen carrier.
S33, synthesizing LaFe 0.5 Ni 0.5 O 3 SBA-15 powder was sieved to a particle size of 53 μm (270) mesh or less, and LaFe having a uniform particle size was obtained 0.5 Ni 0.5 O 3 SBA-15 powder, deionized water, a binder, a plasticizer and a dispersing agent are mixed and stirred for 12 hours to prepare stable dispersed slurry. Wherein LaFe 0.5 Ni 0.5 O 3 The mass percentages of SBA-15 powder, deionized water, binder, plasticizer and dispersant are 60wt%, 20wt%, 8wt%, 10wt% and 2wt%, respectively. The binder comprises the following components in percentage by mass: 1, wherein the components of the plasticizer are ethyl cellulose and carboxymethyl cellulose, and the components of the plasticizer are 1:1, and the dispersing agent is hydroxyethylidene diphosphate.
S34, using three-dimensional model slicing software to design the LaFe in the step S32 0.5 Ni 0.5 O 3 The SBA-15 integral oxygen carrier three-dimensional structure model is converted into a source code which can be identified by a 3D printer, and the slurry prepared in the step S33 is printed on a carbon crystal glass plate by using a direct writing 3D printer to form LaFe 0.5 Ni 0.5 O 3 SBA-15 monolithic oxygen carrier preform. The direct-writing 3D printer uses compressed air to drive feeding, and the working parameters are as follows: the air pressure of the charging barrel is 0.2MPa, the air flow pulse time is 0.1s, the diameter of the spray head is 0.6mm, and the moving speed of the spray head is 50mm/s.
S35, the carbon crystal glass plate in the step S34 and the printed LaFe 0.5 Ni 0.5 O 3 Taking out the integral oxygen carrier blank of SBA-15, and drying at 60 deg.C for 2 hr to obtain LaFe 0.5 Ni 0.5 O 3 Separating the SBA-15 integral oxygen carrier from the carbon crystal glass plate; then LaFe is added 0.5 Ni 0.5 O 3 The SBA-15 integral oxygen carrier primary blank is dried for 20 hours at the temperature of 110 ℃ so as to be dried and solidified and have certain strength.
S36, drying and solidifying the LaFe in the step S35 0.5 Ni 0.5 O 3 Heating the SBA-15 integral oxygen carrier primary blank to 800 ℃ at a heating rate of 1 ℃ per min under the air atmosphere, keeping the temperature for 8 hours to enable the oxygen carrier primary blank to be sintered and formed and fully oxidized, and then taking out after natural cooling to obtain LaFe 0.5 Ni 0.5 O 3 SBA-15 monolithic oxygen carrier product.
Preferably, the drying conditions are: firstly, drying for 2-6 hours at a constant temperature of 40-60 ℃ to separate an integral oxygen carrier primary blank from a carbon crystal glass plate; and drying the integral oxygen carrier primary blank for 12-20 hours at the temperature of 110-150 ℃ to enable the integral oxygen carrier primary blank to be dried and solidified and have certain strength.
Preferably, the high temperature heat treatment conditions are: heating the dried and solidified integral oxygen carrier primary blank to 800-1200 ℃ at a heating rate of 1-10 ℃ per minute under an air atmosphere, and keeping the temperature for 2-8 hours to enable the oxygen carrier to be sintered and formed and fully oxidized, and then taking out after natural cooling.
It will be appreciated by those skilled in the art that the present invention can be carried out in other embodiments without departing from the spirit or essential characteristics thereof. Accordingly, the above disclosed embodiments are illustrative in all respects, and not exclusive. All changes that come within the scope of the invention or equivalents thereto are intended to be embraced therein.
Finally, it should be noted that: the above embodiments are only for illustrating the technical aspects of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the above embodiments, it should be understood by those of ordinary skill in the art that: modifications and equivalents may be made to the specific embodiments of the invention without departing from the spirit and scope of the invention, which is intended to be covered by the claims.
Claims (8)
1. A fixed bed chemical looping reaction apparatus, comprising: the device comprises a shell (2), a heat insulation material (3), a ceramic heat accumulator (4) and a plurality of integral oxygen carriers (5);
the heat insulation material (3) is fixed in the shell (2); the ceramic heat accumulator (4) is fixed in the heat insulating material (3); a plurality of through holes (6) with the same size are formed in the ceramic heat accumulator (4) along the length direction of the fixed bed chemical chain reaction device, and one or more integral oxygen carriers (5) are filled in each through hole (6);
the integral oxygen carrier (5) is formed in a 3D printing mode, an interconnection pore canal structure is arranged in the integral oxygen carrier, and adjacent axial channels are connected through radial channels;
the fixed bed chemical chain reaction device is used for carrying out partial oxidation reaction;
the preparation method of the integral oxygen carrier comprises the following steps:
s1, modeling a structure, namely modeling a three-dimensional structure of the integral oxygen carrier by using three-dimensional modeling software, and performing design optimization on a pore channel structure of the integral oxygen carrier by simulation;
s2, preparing slurry, namely screening the transition metal oxide powder to a particle size of 45-75 mu m, and mixing the transition metal oxide powder with deionized water, a binder, a plasticizer and a dispersing agent to prepare slurry;
s3, printing a primary blank, converting the integral oxygen carrier three-dimensional structure model designed in the step S1 into a 3D printer source code, and printing the slurry prepared in the step S2 into an integral oxygen carrier primary blank on a carbon crystal glass plate by using a direct-writing 3D printer;
s4, drying and solidifying, namely taking out the carbon crystal glass plate and the printed integral oxygen carrier primary blank in the step S3 together, and drying to solidify the integral oxygen carrier primary blank and separate the integral oxygen carrier primary blank from the carbon crystal glass plate;
s5, sintering and forming, and carrying out high-temperature heat treatment on the integral oxygen carrier primary blank after drying and curing in the step S4 to obtain the integral oxygen carrier.
2. The fixed bed chemical chain reaction device according to claim 1, wherein the gap between the thermal insulation material (3), the shell (2) and the ceramic heat accumulator (4) is sealed by bentonite.
3. A fixed bed chemical chain reaction device according to claim 1, characterized in that the two ends of the housing (2) are respectively connected with a sealing head in a sealing way, and the sealing heads are provided with connectors (11) for connecting pipelines.
4. A fixed bed chemical looping reaction apparatus according to claim 3, wherein a partition (12) is provided in said closure head to form two mutually non-communicating reaction channels.
5. The fixed bed chemical chain reaction device according to claim 1, wherein the mass fraction of each component of the slurry in the step S2 is 30-60wt% of transition metal oxide powder, 10-20wt% of deionized water, 20-40wt% of a binder, 5-15wt% of a plasticizer and 2-5wt% of a dispersing agent;
the binder is one or more of polyvinyl alcohol, polyethylene glycol, polyacrylamide, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinylpyrrolidone, polyacrylic acid and polyacrylic resin;
the plasticizer is one or more of dimethyl phthalate, dibutyl phthalate, dioctyl phthalate, epoxy butyl oleate, epoxy octyl oleate, epoxy decyl oleate, tributyl citrate and acetyl tributyl citrate;
the dispersing agent is one or more of ethylenediamine tetramethylene phosphoric acid, hydroxyethylidene diphosphate and aminotrimethylene phosphoric acid.
6. The fixed bed chemical chain reaction apparatus according to claim 1, wherein the printing parameters of the direct-writing 3D printer in step S3 are: the air pressure of the charging barrel is 0.2-0.6 MPa, the air flow pulse time is 0.05-0.2 s, the diameter of the spray head is 0.2-1.0 mm, and the moving speed of the spray head is 50-150 mm/s.
7. The fixed bed chemical looping reaction apparatus according to claim 1, wherein the drying conditions in step S4 are: firstly, drying for 2-6 hours at a constant temperature of 40-60 ℃ to separate an integral oxygen carrier primary blank from a carbon crystal glass plate; and drying the integral oxygen carrier primary blank for 12-20 hours at the temperature of 110-150 ℃.
8. The fixed bed chemical looping reaction apparatus according to claim 1, wherein the high temperature heat treatment conditions in step S5 are: heating the dried and solidified integral oxygen carrier primary blank to 800-1200 ℃ at a heating rate of 1-10 ℃ per minute under the air atmosphere, keeping the temperature for 2-8 hours, and naturally cooling to room temperature.
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