KR100225150B1 - Method for deagglomerating and re-exposing catalyst in a fluid bed reactor - Google Patents

Abstract

Fluidized bed catalysts that lost their activity or fluidity through agglomeration, contamination of the catalyst surface, or physical or chemical changes may be powdered and / or reexposed. The flowing catalyst is contacted with a high velocity gas sufficient to cause multiple collisions between the catalyst particles to atomize the particles and / or to wear the surface of the particles to re-expose the catalyst.

Description

Catalytic Separation and Re-Exposure Method of Fluidized Bed Reactors

1 is a schematic cross-sectional view of a fluidized bed reactor showing an embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

1 fluidized bed reactor 2 fluidized bed catalyst bed

3, 5, 8: line 4: gas distribution grid

6: cyclone 7: dipleg

9: nozzle

The present invention relates to a method for improving the performance of a fluidized bed catalyst which has lost activity or fluidity due to contaminants or other physical or chemical changes on the catalyst surface. More specifically, the present invention relates to a method of exposing a fresh catalyst by abrasion of the catalyst surface in use to remove a thin layer of catalyst surface. In addition, the present invention relates to a method for powder separation of catalyst particles.

In a fluidized bed catalytic reactor, the microsolid particles of the catalyst are in contact with a typical vapor reaction medium. The catalyst particles appear to be suspended and suspended in the gas stream by rising flow of the process gas and appear to be suspended liquids, hereinafter referred to as fluidized beds.

One of the best known applications of fluid bed reactor technology is oil catalytic cracking for the production of gizoline and other light hydrocarbons. Other uses include coking of residues; Coke vaporization; Catalytic oxidation of benzene or butane to maleic anhydride; Ammoxidation of propylene to acrylonitrile; And hydrogen chloride oxidation to chlorine. The present invention focuses on catalysts used in fluidized bed reactors. Through use and the passage of time, some fluidized bed catalysts may become entangled by contaminants or by-products generated by the reaction, or because the surface of the catalyst becomes less catalytic through physical or chemical transitions. , Loses activity. In addition, because contaminants or physical or chemical changes occur on the surface of the catalyst, some catalysts become tacky and the small fluidized bed particles aggregate into larger particles. The agglomerated particles lead to a reduction of the catalyst surface area, thereby affecting the performance of the entire fluidized bed catalyst. In addition, the agglomerated particles interfere with the natural circulation and flow of the catalyst bed.

A typical solution to this problem is to replace all or part of the catalyst in the fluidized bed reactor. This is very costly in view of the cost of the catalyst as well as the loss of production caused by shutting down the fluidized bed reactor for catalyst exchange.

It is an object of the present invention to provide a method which can prolong the catalyst life by solving the above problems caused by agglomeration, contamination of the catalyst surface or physical or chemical changes.

As a result of this research, a method of deagglomerating a fluidized bed catalyst and re-exposing the surface of a fluidized bed catalyst whose activity or fluidity has been lost due to contamination or physical or chemical change of the catalyst surface has been found. This method is intended to be carried out in a working fluidized bed reactor, but may optionally be carried out continuously or discontinuously outside the reactor.

In a preferred embodiment, the method allows the fluidized bed reactor to have at least one injection nozzle for supplying gas from a source external to the reactor. The injection nozzle is positioned in the reactor so that the injection nozzle is immersed in the catalyst bed so that the gas discharged from the injection nozzle can immediately contact the catalyst. The gas exits from the exposure at an escape rate sufficient to contact the fluidized fluidized bed catalyst particles and cause multiple collisions between the catalyst particles. The surface of the catalyst is abraded by the impact of multiple collisions of catalyst particles, removing contaminants or less catalytic material on the catalyst surface and exposing fresh catalyst.

Fluidized bed reactors are reaction vessels in which a gas-solid or liquid-solid contact process takes place. In the reactor, the fine solid particle layer (ie fluid bed catalyst) is suspended and separated by the use of a process gas or liquid stream. Fluidized bed reactors exist in all shapes and sizes. Typically, the reactor has a grid that allows the process feed to pass while supporting the catalyst bed near the bottom of the reactor. The remainder of this description focuses on the practice of the present invention in gas-solid contacting processes. However, the method described here can be equally applied to the liquid-solid contact process.

In a gas-solid contact process, the process generating gas exits the top of the reactor. The product gas typically carries the catalyst particles with it, so that the product gas is passed through a separator to remove catalyst particles recovered in the catalyst through a dipleg. The separator is a solid recovery device such as a cyclone and a filter.

Fluidized bed catalysts are fine solid particles that vary in size, weight, shape and composition depending on the application. Macroscopically, fluid bed catalysts are mostly powdery. Macroscopically, however, such catalysts may also appear as small beads. Fluidized bed catalyst particles typically range in size from 10 to 200 microns.

In some applications, the effectiveness of a fluidized bed catalyst is lost due to the formation of contaminants on the catalyst surface or due to physical or chemical changes. This state may lead to a decrease in catalytic activity or to make the catalyst sticky, resulting in loss of fluidity and / or catalytic activity by agglomeration of the catalyst particles.

In the practice of the present invention, the fluidized bed reactor has one or more injection nozzles therein, and supplies high-speed gas into the catalyst through the injection nozzles. During the practice of the present invention, the catalyst is maintained under fluidized conditions caused by other gases which raise, stir and float the catalyst particles in the process upflow or upflow. The force of the gas stream causes multiple collisions between the flowing catalyst particles, and the impact caused by the collision of the catalyst particles wears off the surface of the catalyst and removes contaminants on the surface, resulting in a fresh catalyst. Will be revealed. In addition, the impact caused by the collision of the catalyst particles powders (ie, pulverizes) the agglomerated catalyst particles. The invention may also be practiced in any vessel equipped with any means (such as nozzles or gas distribution grids or plates with one or more holes) to make contact with the high velocity gas stream and the flowing catalyst particles.

Preferably, the present invention is practiced in a fluidized bed reactor equipped with one or more nozzles. The nozzles used here can be any size or shape and provide a spray pattern. The nozzle may be as simple as an end-opening pipe or may be a short tube whose end is tapered or clamped to accelerate or direct the flow of gas through the tube. Small holes, such as 0.016 inches in diameter (in a gas distribution grid triad of three injection holes of 0.016 inches in diameter) are used. Typical hole sizes range from 0.0625 inches to 0.250 inches in diameter. More typical hole sizes are between 0.125 inches and 0.1875 inches in diameter. Preferred nozzle hole sizes are 9/64 inches and 5/32 inches in diameter. The escape velocity of the gas should be sufficient to have sufficient force to multiply the catalyst particles and wear the catalyst surface. Typically, the harder the catalyst, the greater the escape rate. Escape speeds up to sound speed can also be used. The nozzle holes and the flow rate of the gas are sized with respect to the gas velocity used. Preferred gas velocities range from 200 to 1200 feet per second. More preferred gas velocities are between 600 and 1100 feet per second. Preferably, the gas velocity is such that the gas-catalyst contact zone extends several inches in front of the nozzle into the catalyst bed. The nozzle may be directed to supply a high velocity gas stream that is either cocurrent, countercurrent or crossflow to the fluidization process gas. Preferably, the nozzle is directed to supply a high velocity gas stream that is co-current with the fluidization process gas.

The nozzle or nozzles can be located anywhere in the catalyst bed as long as the injection gas can be in contact with the flowing catalyst particles. For example, the nozzles may be located directly inside the wall of the reactor or at the center of the reactor. In order to maximize the effectiveness of the present invention, the nozzle should be located at the largest catalyst circulation inside the reactor. This is done in order to maximize the amount of charge of the entire catalyst in contact with the gas. For this reason, the injection nozzle is preferably located at or near the deep leg opening (ie the point of incidence at which the catalyst is withdrawn from the separator into the reactor). Care must be taken to ensure that the gas exiting the nozzle does not propagate the catalyst to any internal component of the reactor, because a collision between the catalyst and the reactor component is more than a crushing of the catalyst and if such a collision is repeated, the reactor component will be damaged. Because it becomes.

The high velocity gas may be any gas or vaporized liquid that is inert or beneficial to the process. Typically, this gas is supplied to the nozzle from a source outside the reactor. Where fluidized bed reactors are used for oxidation, air is typically used. However, an inert gas such as nitrogen or a reaction feed gas may be used. In the practice of the invention in a commercial scale reactor in operation, the incremental increase in total gas output can be neglected.

The process for powder separation and / or re-exposure of the catalyst may be carried out intermittently or continuously, depending on the demands of the catalyst and the number of nozzles, the position of the nozzles and the nozzle parameters such as the exit velocity of the gas leaving the nozzle. .

Contaminants or less catalytic material on the catalyst surface that are abraded from the catalyst are typically removed from the reactor together with the reactor effluent and separated from the reaction preparation by suitable separation methods (eg cyclone devices, filters, etc.). . The key to the practice of the present invention is to maximize the re-exposure of the catalyst surface and / or the powder atomization of the catalyst, while on the other hand the minimum amount of wear on the catalyst surface is minimized to minimize the loss of the catalyst. To control the gas velocity and position the nozzles.

1, an embodiment of the present invention is shown. Within the fluidized bed reactor 1 is a bed 2 of fluidized bed catalyst. The process feed gas enters the reactor via line 3 and enters the catalyst bed through gas distribution grid 4. The vapor reaction product comprising suspended transported catalyst particles enters the cyclone 6 where the reaction product and catalyst are separated. The steam reaction product is withdrawn from the reactor via line (5). The catalyst is recovered to the catalyst layer 2 through the deep leg 7. The high velocity gas is fed into the reactor via line 8 and enters the catalyst bed through nozzle 9.

The invention is used in any catalytic fluidized bed process where the catalyst surface is contaminated by reaction by-products or by physical or chemical changes in catalyst composition. In such situations, the catalyst loses activity and / or fluidity. By abrading the catalyst surface, new catalyst is exposed or the catalyst is powdered to restore activity and / or fluidity and extend catalyst life. Representative processes to which the present invention can be applied include oil catalytic cracking for the production of gasoline and other light hydrocarbons, coking, residue of coking, oxidation of benzene or n-butane to maleic anhydride, acrylonitrile of propylene Ammoxidation of furnace and hydrogen chloride to chlorine.

As described herein, the high velocity gas is contacted with a fluidized catalyst in a working reactor. The present invention can also be practiced by placing a plurality of nozzles inside a deep leg. The fluidized bed reactor also includes a regenerator that removes the catalyst that is treated or reactivated and returned to the reactor, and as described above, within the regenerator chamber or within the catalyst transfer line between the reactor and the regenerator chamber. And re-exposure of the catalyst surface and / or powder separation of the catalyst. Finally, the present invention can also be carried out by removing the catalyst from the reaction apparatus, reexposure of the catalyst surface and / or powder separation of the catalyst as described above, and then returning the catalyst to the reaction apparatus.

As described above, according to the present invention, the agglomerated catalyst particles can be powdered and contaminants formed on the surface of the catalyst particles through contamination or physical or chemical changes can be removed, thereby restoring the activity or fluidity of the catalyst. Not only can this be effective, but it also has the effect of extending the life of the catalyst. In addition, in the present invention, since the catalyst is not abraded more than necessary to expose the new catalyst, the amount of abrasion of the catalyst is small, and therefore, there is an advantageous effect in terms of the catalyst price.

The present invention is not limited to the form described above, and many modifications and variations are possible in light of the above teaching. The purpose of this description is to explain the principles and practical applications of the invention to enable those skilled in the art to utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated.

Claims (8)

The method of at least one of the process of at least one of the step of powdering the fluidized bed catalyst particles in the use of acrylonitrile or maleic anhydride in the preparation of acrylonitrile or maleic anhydride, or by re-exposing the surface of the fluidized bed catalyst particles. Silver causes multiple collisions between catalyst particles with an impact sufficient to at least one of the fluidized bed catalyst particles in a fluidized state to pulverize the fluidized bed catalyst particles or to abrad the surface of the catalyst particles to remove the contaminated or changed surface. Contacting a gas having a velocity between about 200 and 1200 feet per second sufficient to The method of claim 1 wherein the gas is air or nitrogen. A method according to claim 1, wherein the method is carried out in a vessel provided with means for contacting the gas stream with a flow catalyst. As a method for at least one of powdering catalyst bed particles that have become contaminated or undergo physical or chemical changes during the production of acrylonitrile or maleic anhydride, or re-exposing the fluid bed catalyst particles, (a) a fluidized bed having at least one injection nozzle configured to supply gas from a source external to the reactor, the nozzle being immersed in the catalyst particles such that the gas discharged from the nozzle is in immediate contact with the catalyst particles; In the reactor, maintaining the catalyst particles in a fluidized state; And (b) about 200 and 1200 feet per second resulting in multiple collisions between catalyst particles with an impact sufficient to at least one of pulverizing the fluidized bed catalyst particles or abrading the surface of the catalyst particles to remove the contaminated or changed surface Passing gas through the nozzle having an escape velocity from the nozzle therebetween. The method of claim 4 wherein the gas is air or nitrogen. 5. The fluidized bed reactor according to claim 4, wherein the fluidized bed reactor has a cyclone for separating the catalyst from the gas effluent stream, the cyclone having a dipleg for returning the catalyst to the reactor, wherein the nozzle Located near the outlet for discharging the catalyst from the reactor. 5. The method of claim 4, wherein the method of reexposing the catalyst surface is carried out while the fluidized bed reactor is producing maleic anhydride or acrylonitrile. 5. The method of claim 4, wherein the diameter of the aperture opening in the nozzle is between 0.125 inches and 0.1875 inches.