CN114345245A - 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 chemical industry, and particularly relates to a fixed bed chemical chain reaction device and an integral oxygen carrier preparation method. The apparatus, comprising: the heat-insulating ceramic material comprises a shell, a heat-insulating material, a ceramic heat accumulator and a plurality of integral oxygen carriers; the heat-insulating material is fixed inside the shell; the ceramic heat accumulator is fixed in the heat insulation material; a plurality of straight-through holes with the same size are formed in the ceramic heat accumulator along the length direction of the fixed bed chemical-looping reaction device, and one or more integral oxygen carriers are filled in each straight-through hole. The condition that the temperature fluctuation inside the reactor is overlarge due to heat absorption and release in the chemical chain oxidation-reduction cycle process is effectively relieved, the problems that the reaction performance is reduced due to heat absorption and temperature reduction of the partial oxidation reaction of the gas phase fuel and the partial sintering inactivation and service life of the oxygen carrier are reduced due to excessive heat release and temperature rise of the oxygen carrier regeneration reaction are effectively solved, meanwhile, radial heat mass transfer is strengthened, and the product selectivity is improved.
Description
Technical Field
The invention belongs to the technical field of energy 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 an extremely important position in chemical production. With the increasing demand for raw materials in the fields of materials and chemical industry, the syngas capacity will continue to increase. The existing industrial synthesis gas preparation mainly depends on natural gas steam reforming and coal gasification, and both methods consume a large amount of energy and water resources, and gradually lose competitiveness under the constraints of future environmental protection and double carbon targets.
Chemical chain partial oxidation has recently received much attention from the industry as an emerging technology for efficiently producing synthesis gas. The principle is that transition metal oxide is used as an oxygen carrier, the selective oxidation characteristic of lattice oxygen in the oxygen carrier is utilized, carbon-containing fuel is partially oxidized by the lattice oxygen in the oxygen carrier at a certain temperature to generate synthesis gas, and then oxidizing atmosphere is used for supplementing the lattice oxygen lacking in the oxygen carrier and enabling the oxygen carrier to obtain heat, so that the oxidation regeneration of the oxygen carrier is completed. The oxygen carrier plays roles of supplying oxygen, heat and catalysis in the process. The carbonaceous fuel can be continuously converted to syngas by the continuous cycling 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 are abraded due to violent collision, so that the service life of the oxygen carrier is obviously shortened, 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 oxygen carrier is mainly used for selectively oxidizing the gas-phase reactant. The fixed bed chemical-looping reaction device can effectively avoid the problems of difficult adjustment and oxygen carrier abrasion during the chemical-looping reaction of treating the gas-phase carbon-containing fuel. However, the fixed bed chemical-looping 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-looping reaction device filled with an integral oxygen carrier has great development potential in treating chemical-looping partial oxidation reaction of gas-phase carbon-containing fuel, and compared with a fixed bed reaction device taking particles as fillers, the fixed bed chemical-looping reaction device has the advantage that the bed pressure drop is remarkably reduced.
There are few examples of the use of fixed bed chemical looping reactors loaded with monolithic oxygen carriers for the chemical looping partial oxidation of carbonaceous fuels. However, the prior fixed bed chemical-looping 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 effects in the chemical chain reaction process are 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 has simple pore-forming mode, generally adopts an extrusion forming method, is difficult to optimize the channel structure, and particularly has no radial mass transfer channel, so that the conversion rate and the selectivity of the chemical chain partial oxidation reaction are low; 3. the existing integral oxygen carrier is usually prepared by coating active components on a carrier, and the oxygen carrying capacity is low because of containing more inert components, and the effective reaction time of the oxygen carrier is obviously shortened.
Disclosure of Invention
The invention provides a fixed bed chemical-looping reaction device and an integral oxygen carrier preparation method, aiming at the problems that the reactor is low in heat storage capacity, the integral oxygen carrier pore-forming mode is simple, the optimization of a pore structure is difficult, and particularly, a radial mass transfer channel is not provided, so that the conversion rate and selectivity of a chemical-looping partial oxidation reaction are low, the oxygen carrier oxygen carrying capacity is low, the effective reaction time is short, and the like.
In order to achieve the purpose, the technical scheme of the invention is as follows:
in a first aspect, the present invention provides a fixed bed chemical looping reaction apparatus, comprising: the heat-insulating ceramic material comprises a shell, a heat-insulating material, a ceramic heat accumulator and a plurality of integral oxygen carriers;
the heat-insulating material is fixed inside the shell; the ceramic heat accumulator is fixed in the heat insulation material; a plurality of straight-through holes with the same size are formed in the ceramic heat accumulator along the length direction of the fixed bed chemical-looping reaction device, and one or more integral oxygen carriers are filled in each straight-through hole.
Furthermore, the integral oxygen carrier is molded in a 3D printing mode, an interconnected pore structure is arranged in the integral oxygen carrier, and adjacent axial channels are connected through radial channels.
Furthermore, gaps among the heat insulation material, the shell and the ceramic heat accumulator are sealed by bentonite.
Furthermore, the two ends of the shell are respectively connected with an end socket in a sealing manner, and the end sockets are provided with interfaces for connecting pipelines.
Furthermore, a partition plate is arranged in the end socket to form two reaction channels which are not communicated with each other.
In a second aspect, the invention provides a preparation method of an integral oxygen carrier, which comprises the following steps:
s1, structural modeling, namely modeling the three-dimensional structure of the integral oxygen carrier by using three-dimensional modeling software, and designing and optimizing the pore structure of the integral oxygen carrier through simulation;
s2, preparing slurry, namely screening the transition metal oxide powder to the particle size of 45-75 microns, and mixing the transition metal oxide powder with uniform thickness with deionized water, a binder, a plasticizer and a dispersant to prepare the stably 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 on a carbon crystal glass flat plate into the integral oxygen carrier primary blank by using a direct-writing 3D printer;
s4, drying and curing, 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 cure the integral oxygen carrier primary blank and separate the integral oxygen carrier primary blank from the carbon crystal glass plate;
and S5, sintering and forming, namely performing high-temperature heat treatment on the primary blank of the integral oxygen carrier dried and solidified in the step S4 to obtain a finished product of the integral oxygen carrier.
Further, in the step S2, the mass fractions of the components of the slurry are 30-60 wt% of transition metal oxide powder, 10-20 wt% of deionized water, 20-40 wt% of a binder, 5-15 wt% of a plasticizer and 2-5 wt% of a dispersant;
the binder is one or more of polyvinyl alcohol, polyethylene glycol, polyacrylamide, methylcellulose, ethyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinylpyrrolidone, polyacrylic acid and polyacrylic resin;
the plasticizer is one or a combination of more than one of dimethyl phthalate, dibutyl phthalate, dioctyl phthalate, epoxy butyl oleate, epoxy octyl oleate, epoxy decyl oleate, tributyl citrate and acetyl tributyl citrate;
the dispersant is one or more of ethylenediamine tetramethylene phosphate, hydroxyl ethylidene diphosphoric acid and amino trimethylene phosphate.
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 step S4 are as follows: drying at constant temperature of 40-60 ℃ for 2-6 h to separate the integral oxygen carrier primary blank from the carbon crystal glass plate; and drying the integral oxygen carrier primary blank at the temperature of 110-150 ℃ for 12-20 h.
Further, the high temperature heat treatment conditions in step S5 are: and heating the dried and solidified integral oxygen carrier primary blank to 800-1200 ℃ at a heating rate of 1-10 ℃/min in the air atmosphere, keeping the temperature for 2-8 h, 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-looping reaction device can effectively relieve the condition of overlarge temperature fluctuation inside the reactor caused by heat absorption and release in the chemical-looping oxidation-reduction process, thereby effectively solving the problems of reaction performance reduction caused by heat absorption and temperature reduction of partial oxidation reaction of gas-phase fuel and partial sintering inactivation and service life reduction of the oxygen carrier caused by excessive heat release and temperature rise of regeneration reaction of the oxygen carrier.
2. The integral oxygen carrier primary blank printed by the slurry can completely remove auxiliary components such as a binder, a plasticizer, a dispersant and the like in the sintering process, the prepared integral oxygen carrier is finally and completely sintered by active oxygen carrier powder, and an inert carrier is not needed, so that the integral oxygen carrier prepared by 3D printing provided by the invention has higher proportion of active components and oxygen carrying amount and longer effective reaction time compared with other integral oxygen carriers.
3. The integral oxygen carrier is prepared by a 3D printing method, and the pore structure of the integral oxygen carrier can be optimally designed through experimental and simulation results, so that the axial radial heat and mass transfer capacity of the integral oxygen carrier is improved, and the conversion rate and selectivity of a chemical chain partial oxidation reaction are further improved; particularly for carbon-containing organic matters with larger molecular weight, the reaction of the carbon-containing organic matters with the oxygen carrier is easy to be controlled by diffusion, and the change of the pore channel structure can obviously influence the selectivity of the product. In addition, the optimized pore structure has an obvious effect on the distribution of the temperature field in the integral oxygen carrier, and hot spots can be effectively avoided.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.
In the drawings:
FIG. 1 is a schematic diagram of a single atmosphere structure of a fixed bed chemical-looping reaction apparatus according to the present invention;
FIG. 2 is a schematic view of the single-atmosphere parallel operation of the fixed bed chemical-looping reaction apparatus of the present invention;
FIG. 3 is a schematic diagram of a dual atmosphere structure of a fixed bed chemical-looping reaction apparatus according to the present invention;
FIG. 4 is a schematic diagram of the operation of the double-atmosphere structure of the fixed bed chemical-looping reaction apparatus according to the present invention;
FIG. 5 is a schematic diagram of a biomass pyrolysis coupled fixed bed chemical chain conversion process;
FIG. 6 is a schematic structural diagram of a 3D printing integral oxygen carrier;
1-sealing head; 2-a housing; 3-heat insulation material; 4-a ceramic thermal accumulator; 5-integral oxygen carrier; 6-straight through hole;
wherein the 1-end socket comprises an 11-interface; 12-a separator.
Detailed Description
The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
The following detailed description is exemplary in nature and is intended to provide further details of the invention. Unless otherwise defined, 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 exemplary embodiments according to the invention.
Example 1:
as shown in fig. 2, two identical single atmosphere fixed bed chemical chain reaction devices work in parallel through a pipeline and a pneumatic butterfly valve and are used for the chemical chain partial oxidation reaction of natural gas. Wherein, one fixed bed chemical chain reaction device 1 carries out the natural gas partial oxidation reaction, and the other fixed bed chemical chain reaction device carries out the oxidation regeneration reaction of the oxygen carrier. The two fixed bed chemical chain reaction devices are ensured to respectively carry out reactions in different stages by continuously switching the valves, so that the oxidation-reduction cycle is realized, and the continuous operation of the chemical chain process is realized.
As shown in fig. 1, each fixed bed chemical-looping reaction device comprises a steel shell 2, a thermal insulation material 3, a ceramic heat accumulator 4 and seven integral oxygen carriers 5; seven parallel straight-through holes 6 with the same size are formed in the ceramic heat accumulator 4 along the length direction of the fixed bed chemical-looping reaction device, one of the seven straight-through holes 6 is used as the center of a circle, the other six straight-through holes are arranged in an annular mode, the integral oxygen carriers 5 are filled in the straight-through holes 6, the integral oxygen carriers 5 are filled in each straight-through hole 6, and the two ends of the shell 2 are respectively provided with an end socket 1.
The steel shell 2 provides sufficient structural strength and sealing to ensure smooth operation of the reaction; the heat insulation material 3 is fixed inside the shell 2, is made of quartz sand, clay and dolomite and is used for maintaining the temperature inside the fixed bed chemical chain reaction device; the ceramic heat accumulator 4 is fixed in the space enclosed by the heat insulation material 3. In addition, the gaps between the heat insulating material 3 and the shell 2 and between the heat insulating material and the ceramic heat accumulator 4 are sealed by bentonite serving as a bonding agent, so that reactant gas flow is prevented from passing through the gaps.
The ceramic heat accumulator 4 is formed MgO or Al2O3One or more of cordierite and mullite, preferably Al having good thermal conductivity and large heat storage capacity2O3Ceramic material, using Al2O3The ceramic material is formed at one time by extrusion forming and is arranged in the fixed bed chemical-looping reaction device. The ceramic heat accumulator 4 can be used as a heat accumulation pool in the chemical chain oxidation-reduction reaction process, the oxygen carrier can absorb heat when being oxidized, and the oxygen carrier can release heat when being 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 of the specific reaction and the heat exchange efficiency.
The material of the integral oxygen carrier 5 is one or the 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, and is preferably transition metal composite oxide, such as perovskite, spinel and other composite oxides with unique catalytic effect and selective oxidation capability.
The integral oxygen carrier 5 is prepared by 3D printing, in this embodiment, a transition metal composite oxide is used, and the composition of the transition metal composite oxide is NiFe2O4Spinel complex metal oxide. Wherein Ni and Fe have synergistic effect, so NiFe2O4The 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, NiFe2O4The spinel composite oxide has high stability, and the active component is not easy to be sintered and deactivated, so that NiFe2O4The monolithic oxygen carrier can still keep higher reactivity after multiple oxidation-reduction cycles.
NiFe2O4The integral oxygen carrier 5 has a rich interconnected pore structure inside, the axial direction is a honeycomb-shaped porous structure, and radial holes are formed between adjacent axial pore channels so as to improve the radial heat and mass transfer capacity and improve the reaction performance, and the specific structure is shown in fig. 6. The structure obviously reduces the bed pressure drop of the fixed bed chemical-looping reaction device 1 and reduces the power consumption. Meanwhile, the contact between reactants and the oxygen carrier is strengthened by the internal porous structure, the self-cracking proportion of natural gas in the reactor is reduced, and the CO and H in the chemical chain partial oxidation reaction of the natural gas are obviously improved2Selectivity of (2). In addition, the monolithic oxygen carrier 5 can be flexibly mounted and dismounted in the ceramic heat accumulator 4.
The cross section of each straight-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 outline and the size of the integral oxygen carrier 5 can be determined according to the cross section shape and the size of the through hole, the outline of the integral oxygen carrier is consistent with the shape of the through hole, and the size of the integral oxygen carrier is slightly smaller than the size of the through hole, so that the integral oxygen carrier can be smoothly installed and disassembled.
In addition, the embodiment also provides 3D printing NiFe2O4The method of the integral oxygen carrier comprises the following specific steps:
s11, initially modeling the three-dimensional structure of the integral oxygen carrier, and simulating the main components of the natural gas and NiFe by using simulation software2O4And (3) the reaction of the integral oxygen carrier, analyzing the distribution of a flow field and a temperature field inside the pore channel of the integral oxygen carrier, optimizing the pore channel structure according to a simulation result, avoiding a flow stagnation area and a local hot spot, and finally obtaining a reasonable three-dimensional pore channel structure.
S12 NiFe to be synthesized2O4Sieving the powder to obtain NiFe powder with particle size of 45-75 μm (200-325 mesh), and homogenizing2O4The powder, deionized water, a binder, a plasticizer and a dispersant are mixed and stirred for 12 hours to prepare a stably dispersed slurry, and the mass fractions of the components of the slurry are 30-60 wt% of transition metal oxide powder, 10-20 wt% of deionized water, 20-40 wt% of the binder, 5-15 wt% of the plasticizer and 2-5 wt% of the dispersant.
Wherein, NiFe2O4The mass percentages of the powder, the deionized water, the binder, the plasticizer and the dispersant are respectively 55 wt%, 8 wt%, 20 wt%, 12 wt% and 5 wt%.
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 printed and molded integral oxygen carrier primary blank, and the dispersant 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, methylcellulose, ethyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinylpyrrolidone, polyacrylic acid and polyacrylic resin; the plasticizer is one or a combination of more than one of dimethyl phthalate, dibutyl phthalate, dioctyl phthalate, epoxy butyl oleate, epoxy octyl oleate, epoxy decyl oleate, tributyl citrate and acetyl tributyl citrate; the dispersant is one or more of ethylene diamine tetra methylene phosphoric acid, hydroxyl ethylene diphosphonic acid and amino trimethylene phosphoric acid
In this embodiment, the binder comprises the following components in a mass ratio of 1: 1, the plasticizer component is dibutyl phthalate, and the dispersant is ethylenediamine tetra-methylene phosphate.
S13, using three-dimensional model slicing software to slice the NiFe designed in the step S112O4Converting 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 into NiFe on a carbon crystal glass flat plate by using a direct-writing 3D printer2O4And (3) 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 80 mm/s. For the slurry with different viscosities, the pressure of the charging barrel is adjusted to ensure that the discharging amount is matched with the moving speed of the spray head.
S14, mixing the carbon crystal glass plate in the step S13 and the printed NiFe2O4Taking out the integral oxygen carrier blank, drying at 50 deg.C for 4 hr to obtain NiFe2O4Separating the integral oxygen carrier from the carbon crystal glass plate; then adding NiFe2O4And drying the integral oxygen carrier primary blank at the temperature of 120 ℃ for 12h to ensure that the integral oxygen carrier primary blank is dried and solidified and has certain strength.
S15, drying the solidified NiFe in the step S142O4Heating the integral oxygen carrier primary blank to 1000 ℃ at the heating rate of 2 ℃/min in the air atmosphere, keeping the temperature for 6 hours to ensure that the integral oxygen carrier primary blank is sintered and molded and is fully oxidized, and then naturally cooling the integral oxygen carrier primary blank and taking the integral oxygen carrier primary blank out to obtain NiFe2O4And (5) forming a finished product of the integral oxygen carrier.
In the successful preparation of NiFe2O4After the integral oxygen carrier, in order to ensure that the product distribution does not generate obvious difference in each cycle process of the natural gas chemical chain partial oxidation process, the integral oxygen carrier is subjected to aging treatment. Ready to be preparedNiFe2O4Monolithic oxygen carriers using H in 800 ℃ tube furnaces2Reducing, oxidizing with air at the same temperature, and repeating the operation for 5 times to obtain NiFe2O4The oxidation-reduction reaction performance of the integral oxygen carrier tends to be stable.
Example 2:
as shown in fig. 4, a dual atmosphere fixed bed chemical looping reaction device works through a pipeline and a pneumatic butterfly valve, and is used for the chemical looping 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-looping conversion process, the volatile matter generated by biomass pyrolysis is directly conveyed to the fixed bed chemical-looping reaction device through the high-temperature pipeline for partial oxidation reaction, and is converted into synthesis gas.
The single double-atmosphere fixed bed chemical chain reaction device is divided into two reaction areas which are not communicated with each other. One reaction area is used for carrying out partial oxidation reaction of biomass pyrolysis volatile matters, and the other reaction area is used for regenerating the oxygen carrier. The continuous operation of the chemical chain process is realized by ensuring that the two reaction areas respectively carry out reactions in different stages by continuously switching the valves.
As shown in fig. 3, the fixed bed chemical-looping reaction device comprises a steel shell 2, a seal head 1, a heat insulating 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-looping reaction device, the integral oxygen carriers 5 are filled in the through holes 6, and one integral oxygen carrier 5 is filled in each through hole 6.
The two interfaces 11 are arranged outside the end socket 1, the partition plate 12 is arranged inside the end socket and divides the interior into two reaction channels, and the three integral oxygen carriers on the upper portion and the three integral oxygen carriers on the lower portion respectively form two reaction channels which are not communicated with each other.
The steel shell 2 provides sufficient structural strength and sealing to ensure smooth operation of the reaction; the heat insulation material 3 is fixed inside the shell 2, is made of aluminum silicate and composite silicate and is used for maintaining the temperature inside the fixed bed chemical chain reaction device; the ceramic heat accumulator 4 is fixed in the space enclosed by the heat insulation material 3. In addition, the gaps between the heat insulating material 3 and the shell 2 and between the heat insulating material and the ceramic heat accumulator 4 are sealed by bentonite serving as a bonding agent, so that reactant gas flow is prevented from passing through the gaps.
Cordierite and Al are used for the ceramic heat storage body 42O3The ceramic material is formed in one step by extrusion forming, is an integral body and is arranged in the fixed bed chemical-looping reaction device. The ceramic heat accumulator 4 can be used as a heat accumulation pool in the chemical chain oxidation-reduction reaction process, the oxygen carrier can absorb heat when being oxidized, and the oxygen carrier can release heat when being reduced; meanwhile, heat can be mutually transferred between the partial oxidation reaction side and the oxygen carrier oxidation regeneration side. The buffer action of the ceramic heat accumulator 4 can reduce the temperature fluctuation in the fixed bed chemical-looping reaction device to a certain extent.
The integral oxygen carrier 5 is prepared by 3D printing, preferably, a transition metal composite oxide is adopted, and the composition of the transition metal composite oxide is NiO-Fe2O3-CeO2A 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; the Fe has the characteristic of selective oxidation to reactants, so that CO and H in the product2The proportion is obviously improved; CeO (CeO)2The method has obvious effect of eliminating carbon deposition generated in the reaction process, and can further improve the conversion rate and selectivity of the reaction process.
NiO-Fe2O3-CeO2The integral oxygen carrier 5 is axially of a honeycomb porous structure, radial holes are formed between adjacent axial pore channels to improve the radial heat and mass transfer capacity, and the specific structure is shown in fig. 6. The structure obviously reduces the bed pressure drop of the fixed bed chemical-looping reaction device and reduces the power consumption. Meanwhile, because the partial oxidation reaction between the tar macromolecules and the oxygen carrier in the biomass volatile is controlled by diffusion, the structure is very favorable for improving the conversion rate of the tar macromolecules.
In addition, the embodiment also provides 3D printing NiO-Fe2O3-CeO2Method of monolithic oxygen carrier, in particularThe method comprises the following steps:
s21, modeling the three-dimensional structure of the integral oxygen carrier preliminarily, and simulating the main components of biomass pyrolysis volatiles and NiO-Fe by using simulation software2O3-CeO2And (3) the reaction of the integral oxygen carrier, analyzing the distribution of a flow field and a temperature field inside the pore channel of the integral oxygen carrier, optimizing the pore channel structure according to a simulation result, avoiding a flow stagnation area and a local hot spot, and finally obtaining a reasonable three-dimensional pore channel structure.
S22 NiO-Fe synthesized by high temperature solid phase method2O3-CeO2The composite oxide powder was sieved to have a particle size of 96 μm (160) mesh or less, and NiO-Fe having a uniform thickness was added2O3-CeO2And mixing and stirring the powder with deionized water, a binder, a plasticizer and a dispersing agent for 24 hours to prepare stably dispersed slurry. Wherein NiO-Fe2O3-CeO2The mass percentages of the powder, the deionized water, the binder, the plasticizer and the dispersant are respectively 45 wt%, 10 wt%, 25 wt%, 12 wt% and 8 wt%. The adhesive comprises the following components in percentage by mass of 1: 1, polyvinyl alcohol and polyacrylamide, and the plasticizer components are 1: 1 dibutyl phthalate and dioctyl phthalate, and the dispersant is amino trimethylene phosphoric acid.
S23, using three-dimensional model slicing software to convert the NiO-Fe designed in the step S212O3-CeO2Converting 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 flat plate by using a direct-writing 3D printer2O3-CeO2And (3) 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 100 mm/s.
S24, mixing the carbon crystal glass flat plate in the step S23 and the printed NiO-Fe2O3-CeO2Taking out the integral oxygen carrier primary blank together, and drying at constant temperature of 40 ℃ for 6h to ensure that NiO-Fe2O3-CeO2Integral oxygen carrier and carbon crystalSeparating the glass plate; then NiO-Fe2O3-CeO2And drying the integral oxygen carrier primary blank at the temperature of 150 ℃ for 12h to ensure that the integral oxygen carrier primary blank is dried and solidified and has certain strength.
S25, drying the solidified NiO-Fe in the step S242O3-CeO2Heating the integral oxygen carrier primary blank to 1200 ℃ at the heating rate of 5 ℃/min in the air atmosphere, keeping the temperature for 2h to ensure that the integral oxygen carrier primary blank is sintered and molded and is fully oxidized, and then naturally cooling the integral oxygen carrier primary blank and taking the integral oxygen carrier primary blank out to obtain NiO-Fe2O3-CeO2And (5) forming a finished product of the integral oxygen carrier.
In the successful preparation of NiO-Fe2O3-CeO2After the integral oxygen carrier, in order to ensure that the product distribution does not generate obvious difference in each cycle process of the natural gas chemical chain partial oxidation process, the integral oxygen carrier is subjected to aging treatment. NiO-Fe to be prepared2O3-CeO2Monolithic oxygen carriers using H in a tube furnace at 850 deg.C2Reducing, oxidizing with air at the same temperature, and repeating the operation for 5 times to obtain NiO-Fe2O3-CeO2The oxidation-reduction reaction performance of the integral oxygen carrier tends to be stable.
Example 3:
in this embodiment, a method for preparing an integral oxygen carrier by using a supported transition metal oxide, a transition metal oxide encapsulated by a molecular sieve, in a 3D printing manner includes the following specific steps:
s31, dispersing the commercial SBA-15 molecular sieve in absolute ethyl alcohol by using a surfactant, and mixing the absolute ethyl alcohol with La (NO) with a certain stoichiometric ratio3)3·6H2O、Ni(NO3)2·6H2O and Fe (NO)3)3·9H2The aqueous O solution was mixed well. And drying the fully mixed solution at 80 ℃ to obtain a powder precursor, and grinding the powder precursor to a proper particle size. Introducing air into the ground powder precursor for calcination at 800 ℃ to finally obtain LaFe0.5Ni0.5O3SBA-15 powder.
S32 construction of tri-layer of integral oxygen carrier by using three-dimensional modeling softwareMaintaining the pore canal structure to obtain LaFe0.5Ni0.5O3Configuration of the/SBA-15 monolithic oxygen carrier.
S33, synthesizing LaFe0.5Ni0.5O3The SBA-15 powder was sieved to a particle size of 53 μm (270) mesh or less and the LaFe powder was homogenized0.5Ni0.5O3The SBA-15 powder, deionized water, a binder, a plasticizer and a dispersant are mixed and stirred for 12 hours to prepare a stably dispersed slurry. Wherein, LaFe0.5Ni0.5O3The mass percentages of the/SBA-15 powder, the deionized water, the binder, the plasticizer and the dispersant are respectively 60 wt%, 20 wt%, 8 wt%, 10 wt% and 2 wt%. The adhesive comprises the following components in percentage by mass of 1: 1, and plasticizer components of 1: 1 tributyl citrate and acetyl tributyl citrate, and the dispersant is hydroxy ethylidene diphosphate.
S34, using three-dimensional model slicing software to slice the LaFe designed in the step S320.5Ni0.5O3Converting the SBA-15 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 S33 into LaFe on a carbon crystal glass flat plate by using a direct-writing 3D printer0.5Ni0.5O3SBA-15 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 0.2MPa, 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 50 mm/s.
S35, mixing the carbon crystal glass plate in the step S34 and the printed LaFe0.5Ni0.5O3The primary blank of the SBA-15 integral oxygen carrier is taken out together and dried for 2 hours at the constant temperature of 60 ℃ to ensure that the LaFe0.5Ni0.5O3The SBA-15 integral oxygen carrier is separated from the carbon crystal glass plate; then adding LaFe0.5Ni0.5O3Drying the SBA-15 integral oxygen carrier primary blank at the temperature of 110 ℃ for 20 hours to ensure that the primary blank is dried and solidified and has certain strength.
S36, drying the solidified LaFe in the step S350.5Ni0.5O3SBA-15 integral oxygen carrier primary blank in airHeating to 800 ℃ at a heating rate of 1 ℃/min in the atmosphere, keeping the temperature for 8 hours to ensure that the mixture is sintered, molded and fully oxidized, and then naturally cooling and taking out to obtain LaFe0.5Ni0.5O3The SBA-15 integral oxygen carrier finished product.
Preferably, the drying conditions are: drying at constant temperature of 40-60 ℃ for 2-6 h to separate the integral oxygen carrier primary blank from the carbon crystal glass plate; and drying the integral oxygen carrier primary blank at the temperature of 110-150 ℃ for 12-20 h to ensure that the integral oxygen carrier primary blank is dried and solidified and has certain strength.
Preferably, the high-temperature heat treatment conditions are as follows: and heating the dried and solidified integral oxygen carrier primary blank to 800-1200 ℃ at a heating rate of 1-10 ℃/min in the air atmosphere, keeping the temperature for 2-8 hours to ensure that the oxygen carrier is sintered and molded and is fully oxidized, and then naturally cooling and taking out.
It will be appreciated by those skilled in the art that the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The embodiments disclosed above are therefore to be considered in all respects as illustrative and not restrictive. All changes which come within the scope of or equivalence to the invention are intended to be embraced therein.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.
Claims (10)
1. A fixed bed chemical looping reaction apparatus, comprising: the heat-insulating ceramic heat-accumulating body comprises a shell (2), a heat-insulating material (3), a ceramic heat-accumulating body (4) and a plurality of integral oxygen carriers (5);
the heat-insulating material (3) is fixed in the shell (2); the ceramic heat accumulator (4) is fixed in the heat insulation 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-looping reaction device (1), and one or more integral oxygen carriers (5) are filled in each through hole (6).
2. A fixed bed chemical looping reaction device according to claim 1, characterized in that said monolithic oxygen carrier (5) is shaped by means of 3D printing and has an interconnected pore structure inside, and adjacent axial channels are connected by means of radial channels.
3. A fixed bed chemical looping reaction device according to claim 1, characterized in that the gaps between said thermal insulating material (3), said shell (2) and said ceramic thermal mass (4) are sealed with bentonite.
4. A fixed bed chemical looping reaction device according to claim 1, characterized in that two ends of said housing (2) are each hermetically connected with a head (7), said heads (7) being provided with a port (11) for connecting a pipeline.
5. A fixed bed chemical looping reaction device according to claim 1, characterized in that said closure head (7) is provided with a partition (12) which forms two reaction channels which are not communicated with each other.
6. The preparation method of the integral oxygen carrier is characterized by comprising the following steps:
s1, structural modeling, namely modeling the three-dimensional structure of the integral oxygen carrier by using three-dimensional modeling software, and designing and optimizing the pore structure of the integral oxygen carrier through simulation;
s2, preparing slurry, namely screening the transition metal oxide powder to the particle size of 45-75 microns, and mixing the transition metal oxide powder with deionized water, a binder, a plasticizer and a dispersing agent to prepare the 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 on a carbon crystal glass flat plate into the integral oxygen carrier primary blank by using a direct-writing 3D printer;
s4, drying and curing, namely taking out the carbon crystal glass plate and the printed integral oxygen carrier primary blank in the step S3 together, and drying to cure the integral oxygen carrier primary blank and separate the integral oxygen carrier primary blank from the carbon crystal glass plate;
and S5, sintering and forming, namely performing high-temperature heat treatment on the primary blank of the integral oxygen carrier dried and solidified in the step S4 to obtain a finished product of the integral oxygen carrier.
7. The preparation method of the monolithic oxygen carrier as claimed in claim 6, wherein the mass fractions of the components of the slurry in the step S2 are 30-60 wt% of the transition metal oxide powder, 10-20 wt% of deionized water, 20-40 wt% of the binder, 5-15 wt% of the plasticizer and 2-5 wt% of the dispersant;
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 the combination of more than one of dimethyl phthalate, dibutyl phthalate, dioctyl phthalate, epoxy butyl oleate, epoxy octyl oleate, epoxy decyl oleate, tributyl citrate and acetyl tributyl citrate;
the dispersant is one or more of ethylenediamine tetramethylene phosphate, hydroxyl ethylidene diphosphate and amino trimethylene phosphate.
8. The preparation method of the integral oxygen carrier as claimed in claim 6, wherein the printing parameters of the direct-write printer in the step S3 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.
9. The method for preparing a monolithic oxygen carrier according to claim 6, wherein the drying conditions in step S4 are as follows: drying at constant temperature of 40-60 ℃ for 2-6 h to separate the integral oxygen carrier primary blank from the carbon crystal glass plate; and drying the integral oxygen carrier primary blank at the temperature of 110-150 ℃ for 12-20 h.
10. The preparation method of the monolithic oxygen carrier according to claim 6, wherein the high temperature heat treatment conditions in the step S5 are as follows: and heating the dried and solidified integral oxygen carrier primary blank to 800-1200 ℃ at a heating rate of 1-10 ℃/min in the air atmosphere, keeping the temperature for 2-8 h, and naturally cooling to room temperature.
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