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CN109967004B - Fluidized bed reactor capable of enhancing heat transfer - Google Patents

Fluidized bed reactor capable of enhancing heat transfer Download PDF

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Publication number
CN109967004B
CN109967004B CN201910185987.1A CN201910185987A CN109967004B CN 109967004 B CN109967004 B CN 109967004B CN 201910185987 A CN201910185987 A CN 201910185987A CN 109967004 B CN109967004 B CN 109967004B
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fluidized bed
distribution plate
bed reactor
heat transfer
lyophobic
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CN109967004A (en
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叶涵辰
王涵青
郭晓云
林王旻
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J8/00Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
    • B01J8/18Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
    • B01J8/24Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)

Abstract

The invention discloses a fluidized bed reactor for enhancing heat transfer, which is characterized in that condensate is sprayed into a fluidized bed to absorb excessive heat generated in the reaction process. In order to avoid the influence of accumulation of liquid on the production stability, the fluidized bed reactor uses a gas distribution plate for resisting liquid deposition and performs special treatment on the wall of the fluidized bed. The surface of the distribution plate and the surface of the wall of the fluidized bed are ultra-lyophobic solid surface layers, condensate entering the reactor is scattered on the surface of the distribution plate and the surface of the wall of the reactor in the form of liquid drops, the specific surface area of the liquid phase is increased, the evaporation rate and the heat transfer rate of the liquid drops are improved, and the problems of blockage of an air inlet hole of the distribution plate and agglomeration of solid particles caused by liquid accumulation in the prior art are solved.

Description

Fluidized bed reactor capable of enhancing heat transfer
Technical Field
The invention relates to a fluidized bed reactor for enhancing heat transfer, in particular to a gas distribution plate of the fluidized bed reactor.
Technical Field
Fluidized bed reactors are widely used in various industrial processes due to their high mass and heat transfer efficiency. In some production processes, due to the strong exothermic reaction effect, proper reaction operating temperatures cannot be maintained by heat transfer through the walls and entrainment of heat by the fluidizing gas. To achieve this part of the reaction is operated in a fluidized-bed reactor, by spraying a condensate such as an organic solvent into the fluidized bed, the excess heat is absorbed by the latent heat required for the evaporation of the condensate.
In the prior condensation technology, after condensate is introduced into a reactor, liquid drops are easy to cover the surface of a distribution plate and the inner wall surface of a fluidized bed to form a liquid film, and when local uneven spraying exists in the process of spraying the condensate, the phenomenon of liquid accumulation is particularly serious. The liquid film evaporation rate is slower due to the smaller specific surface area of the liquid film. When the liquid film covers the upper surface and the inner wall surface of the distribution plate, the heat transfer resistance is increased, and the heat transfer efficiency of the fluidized bed and the outside is reduced. At the same time, because the existence of the liquid causes the agglomeration of solid particles in the fluidized bed due to the liquid bridge force, the particles are bonded into blocks and block the air inlet holes of the distribution plate, so that the resistance of the distribution plate is increased, and the operation of the fluidized bed is adversely affected.
Therefore, the novel gas distribution plate is developed to solve the problems of accumulation of liquid film on the inner wall surface and blockage of the air inlet holes of the distribution plate, and has important significance for stabilizing industrial production and improving the quality of polyethylene products.
Disclosure of Invention
The object of the present invention is to provide a fluidized bed reactor with enhanced heat transfer, the schematic of which is shown in fig. 1. In order to overcome the defects in the prior art, the invention adopts the technical means that:
a nozzle is arranged on the side wall of the fluidized bed reaction zone and is used as a liquid phase feeding port. And spraying corresponding condensate into the fluidized bed through the nozzle. And when condensate evaporates, heat is absorbed, and the excessive heat in the reactor is carried out. The nozzle may be an oval nozzle, a square nozzle, a solid cone nozzle, a fan nozzle. The number of the nozzles is not less than 1.
The inner wall surface of the fluidized bed reactor and the upper surface of the gas distribution plate are coated with a layer of ultra-lyophobic solid surface so as to realize the acceleration of the liquid accumulation and development rate of condensate.
In the prior art, the liquid film evaporation rate is slower due to the smaller specific surface area of the liquid film. In order to realize the enhancement of the liquid film evaporation rate, the liquid accumulation exists in a form of one liquid drop on the surface by changing the contact mode between the surface of the reactor and the liquid film, so that the specific surface area of the liquid is increased, and the liquid film evaporation rate is increased.
The advancing contact angle of the ultra lyophobic solid surface used in the patent and condensate is more than 140 degrees, and the retreating contact angle is more than 135 degrees.
Furthermore, the surface of the ultra lyophobic solid is of a special structure and is formed by arranging a plurality of structural units on the upper surface of the distribution plate. The structural unit can be in the shape of a cone or a cylinder, and one of the bottom surface of the cone or the bottom surface of the cylinder is connected with the upper surface of the gas distribution plate.
Further, the height of the structural unit is 100 μm to 800. Mu.m, preferably 800. Mu.m; the diameter of the bottom surface of the cone is preferably 10 μm to 90. Mu.m, preferably 90. Mu.m. The diameter expansion ratio of the cone is preferably 0.05-0.2; the spacing between the structural units is preferably 10 μm to 400. Mu.m, preferably 200. Mu.m.
The cones or cylinders are preferably arranged vertically and in a rectangular, square or circular array on the upper surface of the distribution plate.
The invention also aims to provide a preparation method of the ultra-lyophobic solid surface. The preparation method can be one of a phase separation method, a stencil printing method, a shop spinning method, a sol-gel method, a stencil extrusion method, a laser and plasma etching method, a stretching method or a corrosion method. Further, the solvent used to prepare the ultralyophobic solid surface may be a fluorine-containing organic solvent.
The principle of realizing the ultra-lyophobic property of the ultra-lyophobic surface through analysis is shown in figure 1: the condensate spreads in the form of droplets on the ultralyophobic surface. The drop-like pattern on the surface of the ultralyophobic distribution plate has an order of magnitude higher heat transfer efficiency than the film shape of the liquid on the distribution plate. The liquid drop moves towards the gap of the structural unit under the action of gravity, and the liquid phase is rebounded to the surface of the grid under the action of capillary force due to the small gap of the structural unit, so that the contact state between the liquid drop and the wall surface is changed from Wenzal state to Cassie state.
Compared with the prior art, the invention has the following beneficial effects:
The special treated material is adopted as the surface of the distribution plate and the inner wall surface of the reaction gas, the condensate is dispersed on the surface in the form of liquid drops, the wetting state of the liquid drops is in a Cassie mode suspended on the structure instead of a Wenzel mode trapped in the structure, the specific surface area of the liquid phase is greatly increased, the heat transfer rate is improved, the problem of blockage of the air inlet holes of the distribution plate is solved to a certain extent, and the long-period operation of an industrial device is facilitated.
Drawings
FIG. 1 is a schematic view of a fluidized bed reactor with enhanced heat transfer
In fig. 2, (a) is a schematic view of Wenzal in a wet state, and (b) is a schematic view of Cassie in a wet state;
FIG. 3 is a schematic illustration of the surface structure of an ultralyophobic solid on the upper surface of a gas distribution plate;
fig. 4 is a schematic structure of a gas distribution plate (small circles are gas inlet holes).
In the figure, a 1-gas phase feed port; 2-a liquid phase feed inlet; 3-gas phase outlet; 4-the surface of the side wall ultra lyophobic solid; 5-gas distribution plate.
Detailed Description
Specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that these examples are provided to aid in understanding the present invention and are not intended to limit the present invention. Furthermore, it is possible to provide a device for the treatment of a disease. The technical features mentioned in the embodiments of the invention described below can be combined with one another as long as they do not conflict with one another.
As shown in fig. 1, which is a schematic view of the fluidized bed reactor for enhancing heat transfer of the present invention, the fluidized bed reactor has a gas phase feed port 1 and a gas phase outlet port 3; the side wall of the fluidized bed reactor is provided with a liquid phase feed inlet 2; the upper surface of the gas distribution plate 5 of the fluidized bed reactor and the inner surface of the reactor wall are provided with ultra-lyophobic solid surfaces 4.
Example 1
In a liquid deposition resistant gas distribution plate as described in fig. 2, gas inlets are provided in the gas distribution plate, and the opening ratio is 5%. And (3) dripping polyvinyl alcohol on the upper surface of the gas distribution plate by adopting a template extrusion method, and drying to obtain the lyophobic surface. And then obtaining square grids by using a wire cutting machine. As shown in FIG. 3, after special processing, a special structure is formed on the upper surface of the gas distribution plate, namely a plurality of square cones with similar shapes and sizes are closely arranged in an array shape. In this embodiment, the height of each cone is 800 μm, and the diameter of the upper surface circle of the cone-shaped structural unit increases linearly from 20 μm to 90 μm from top to bottom, with a center distance of 200 μm. The top of the square cone adopts a chemical corrosion method to generate nano patterns, and the average diameter of the nano pattern is 3 mu m. Wherein the shape thereof can be pyramid, cylinder or prism; the size of the structural unit can be adjusted at the height of 100-800 mu m, the diameter of the upper surface circle of the conical structural unit can be 10-50 mu m, the diameter expansion ratio of the conical structural unit can be 0.05-0.2, and the spacing between the structural units can be 10-400 mu m.
Through tests, the advancing contact angle theta adv of condensate on the gas distribution plate is=168 degrees plus or minus 2 degrees, the retreating contact angle theta rec is=160 degrees plus or minus 2 degrees, which shows that the structure has good super lyophobic property and achieves the expected effect.
Example 2
Example 2 is the use of a fluidized bed reactor with enhanced heat transfer in a polyethylene production process. After the ultra lyophobic treatment of the inner wall surface of the fluidized bed and the gas distribution plate by the manufacturing method described in example 1, linear low density polyethylene was produced in a condensed state, and its actual performance was tested as follows:
1) Linear low density polyethylene product run data
The reaction raw materials are as follows: ethylene, 1-butene, hydrogen
Volume content of condensate in the circulating gas: 5-6%
2) Continuous 18 months of operation
The flow of the circulating gas and condensate is stable, no obvious fluctuation phenomenon exists, the pressure difference of the gas distribution plate does not increase, and the phenomenon that the gas distribution plate is blocked is shown.
3) Examination after 24 months of continuous operation:
The gas distribution plate has no agglomeration, powder deposition, adhesion and other conditions, the gas distribution plate is clean, the grid structure on the surface of the gas distribution plate is not destroyed, 856 gas distribution plates 1 are arranged Is not blocked as shown in fig. 4.
The results show that the fluidized bed reactor of the present invention was used for production, and no operational problems of production runs and adverse effects of products were detected. The liquid film is dispersed on the surface of the gas distribution plate in the form of liquid drops, and the evaporation rate is high due to the small specific surface area, so that the problem that polymer powder blocks the gas inlet holes of the gas distribution plate is solved, the period of stable production of the fluidized bed is improved, and the fluidized bed can safely and stably run under the condition of ensuring the constant circulation gas quantity.

Claims (4)

1. The fluidized bed reactor for enhancing heat transfer is characterized in that a liquid phase feed port is arranged on the side wall of the fluidized bed reactor; the upper surface of the gas distribution plate of the fluidized bed reactor and the inner surface of the reactor wall are provided with ultra-lyophobic solid surfaces; the ultra-lyophobic solid surface of the gas distribution plate is formed by arranging a plurality of structural units on the upper surface of the distribution plate; the shape of the structural unit is cone or cylinder; the height of the structural unit is 100-800 mu m; the diameter of the bottom surface of the cone is 10-90 mu m, the diameter expansion ratio of the cone is 0.05-0.2, and the spacing between structural units is 10-400 mu m; the advancing contact angle of the ultra-lyophobic solid surface and condensate is more than 140 degrees, and the retreating contact angle is more than 135 degrees; the preparation method of the ultra lyophobic solid surface is one or more of a phase separation method, a stencil printing method, a shop spinning method, a sol-gel method, a stencil extrusion method, a laser and plasma etching method, a stretching method or a corrosion method; the solvent used in the preparation method of the ultra lyophobic solid surface is a fluorine-containing organic solvent.
2. An enhanced heat transfer fluidized bed reactor according to claim 1 wherein said reactor liquid phase feed openings are provided with nozzles, the number of liquid phase feed openings being not less than 1.
3. A fluidized bed reactor for enhancing heat transfer as claimed in claim 1, wherein said nozzle is selected from the group consisting of oval nozzle, square nozzle, solid cone nozzle, fan nozzle.
4. An enhanced heat transfer fluidized bed reactor as set forth in claim 1, wherein said structural units are arranged in a rectangular, square or circular array on the upper surface of the distribution plate.
CN201910185987.1A 2019-03-12 2019-03-12 Fluidized bed reactor capable of enhancing heat transfer Active CN109967004B (en)

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CN107573531A (en) * 2017-07-13 2018-01-12 大连理工大学 A kind of hot pressing processing method of the super-hydrophobic cylindrical-array of large scale of drop pie spring
CN108295610A (en) * 2018-04-10 2018-07-20 北京英华高科技有限公司 A kind of novel type non-filtering air cleaning facility
CN210121469U (en) * 2019-03-12 2020-03-03 叶涵辰 Fluidized bed reactor with enhanced heat transfer

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DE4206490C2 (en) * 1992-03-02 1994-03-10 Fraunhofer Ges Forschung Electrically conductive gas distribution structure for a fuel cell and method for its production
ATE274052T1 (en) * 1995-10-06 2004-09-15 Az Univ Amsterdam SOLID SUPPORT FOR CELL CULTURE, IN PARTICULAR FOR LIVER CELL CULTURE, BIOLOGICAL REACTOR AND BIOLOGICAL REACTOR CONTAINING SUCH SUPPORT AND THE USE THEREOF IN AN ARTIFICIAL LIVER DEVICE
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CN107303478A (en) * 2016-04-25 2017-10-31 中国石油化工股份有限公司 Fluidized-bed reactor, olefinic polymerization device and olefine polymerizing process
CN107573531A (en) * 2017-07-13 2018-01-12 大连理工大学 A kind of hot pressing processing method of the super-hydrophobic cylindrical-array of large scale of drop pie spring
CN108295610A (en) * 2018-04-10 2018-07-20 北京英华高科技有限公司 A kind of novel type non-filtering air cleaning facility
CN210121469U (en) * 2019-03-12 2020-03-03 叶涵辰 Fluidized bed reactor with enhanced heat transfer

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