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CN-121988234-A - Method for regulating and controlling residence time of particles with different particle sizes in multi-bin fluidized bed reactor and inhibiting back mixing of particles among bins

CN121988234ACN 121988234 ACN121988234 ACN 121988234ACN-121988234-A

Abstract

The invention relates to a method for regulating and controlling the residence time of particles with different particle sizes in a multi-bin fluidized bed reactor and inhibiting the back mixing of particles among bins, which can realize the regulation and control of the residence time of the particles with different particle sizes in a fluidized bed. The multi-bin fluidized bed reactor comprises an air inlet (1), an air chamber (2), a distribution plate (3), a fluidization bin (4), a feed inlet (5), an expansion section (6), an air outlet (7), a discharge outlet (8), an inner member inlet (9), an inner member outlet (10), n lifting-out inner members (11) and a lifting-out inner member gas inlet (12). The fluidized bed air inlet (1) is connected with the air chamber (2), the air outlet (7) is positioned at the top of the fluidized bed, the feed inlet (5) is connected with the upper part of the leftmost fluidization bin, and the discharge outlet (8) is connected with the middle part of the rightmost fluidization bin. The invention can regulate and control the residence time of particles with different particle sizes in the fluidized bed, and can also almost completely inhibit the back mixing of particles between adjacent bins.

Inventors

  • ZHU QINGSHAN
  • LU SHUAI

Assignees

  • 中国科学院过程工程研究所

Dates

Publication Date
20260508
Application Date
20260121

Claims (5)

  1. 1. A method of regulating residence time of particles of different size fractions and inhibiting back mixing of particles between bins in a multi-bin fluidized bed reactor, the multi-bin fluidized bed reactor comprising n number of eutectoid internals disposed in a fluidized bed; The bottom ends of the n lifting and separating inner members form an included angle alpha with the distribution plate, and gas inlets of the n lifting and separating inner members are communicated with the gas inlets of the lifting and separating inner members through pipelines penetrating through the air chambers; The inside of any one of the cyclone internal components is of a cavity structure, the lower part is provided with an internal component inlet, the upper part is provided with an internal component outlet, the internal component inlet is arranged on one side of a fluidized bed feed inlet, and the internal component outlet is arranged on one side of a fluidized bed discharge outlet; The ratio of the residence time of the particles with different particle sizes in the fluidized bed is controlled by controlling the process of the lift-out entrainment of the particles with different particle sizes in the lift-out inner member (11) and the difficulty of entering the fluidization bin (4) from the lift-out inner member (11); The aeration entrainment degree of the particles with different particle sizes in the aeration inner member (11) is enhanced by changing the air speed of the inner member air inlet (12); reducing the lift-out entrainment of coarse particles in the lift-out inner member (11) by reducing the conical angle alpha at the bottom of the lift-out inner member; increasing the difficulty of different particle size particles entering the fluidization bin (4) from the cyclone inner member (11) by increasing the distance between the inner member outlet (10) and the distribution plate (3); Increasing the number of different size fraction particle lift-off entrainment by increasing the number of lift-off internals (11); The lifting-separating inner member (11) simultaneously plays a role in eliminating particle back mixing between adjacent fluidization bins (4), increases the along-way resistance of particle back mixing between adjacent bins by increasing the gas speed of the inner member gas inlet (12), and simultaneously regulates and controls the probability and frequency of particle back mixing by regulating and controlling the distance between the inner member outlet (10) and the distribution plate (3); The number n of the inner components (11) is determined by the ratio of the particle sizes of the particles with different particle sizes and the gas speed of the gas inlet (12) of the inner components; The cross-sectional area of the inner member is between the minimum cross-sectional area A min and the cross-sectional area of the fluidization chamber, preferably the minimum cross-sectional area; The minimum cross-sectional area A min is calculated using the following formula: ; wherein the minimum cross-sectional area A min ,m 2 ; the feeding mass flow rate Q, kg/s of the fluidized bed; Particle density ρ, kg/m 3 ; Raising the inlet gas velocity u, m/s of the inner member; the terminal velocity u t , m/s of the particles; the initial fluidization velocity u mf , m/s of the particles; k is a regulation parameter related to the orifice shape of the inner member, 0.2< k <5, m is a regulation parameter related to the orifice shape of the inner member and the particle characteristics, 1< m <5; the orifice size of the winnowing inner member inlet (9) and the orifice size of the winnowing inner member outlet (10) are equal, and the equivalent diameter is 30-50 times of the diameter of the coarsest particles; The inner component (11) is supplied with air through an inner component air inlet (12) and then uniformly enters the inner component air outlet pipeline (11) through the distribution plate (3), and the air inlet speed is between the air speed of the fluidization bin (4) and the terminal speed of the coarsest particles; The gas speed of the inner member gas inlet (12) is regulated and controlled according to the regulation and control requirement of the residence time of the multi-particle size particles, the gas speed of the inner member gas inlet (12) is gradually close to the terminal speed of the coarse particles as the power relation between the time required by the complete reaction of the coarse and fine particles and the particle size ratio of the coarse and fine particles increases, and when the gas speed of the inner member gas inlet (12) is set at the terminal speed of a certain particle size, the average residence time ratio of the particle size and the fine particles reaches the maximum value; The distance between the inner member inlet (9) and the distribution plate (3) is smaller than the distance between the fluidized bed discharge hole (8) and the distribution plate (3), and the distance is gradually reduced as the power relation between the time required for complete reaction of the particles and the ratio of the particle size of the particles increases; the distance between the inner member outlet (10) and the distribution plate (3) is between the distance between the discharge hole (8) and the distribution plate (3) and the distance between the feed inlet (5) and the distribution plate (3), and the distance is gradually increased along with the increase of the power of the ratio of the time required by the complete reaction of the fine particles to the particle size of the coarse and fine particles; The conical angle alpha of the bottom of the lifting inner member (11) is between 75 degrees and 90 degrees, and the angle is gradually reduced as the power relation between the time required for the complete reaction of the particles and the diameter of the particles increases; The projection length of the conical section at the bottom of the lifting inner member (11) on the distribution plate is smaller than 1/4 of the length of a single fluidization bin, and the height of the conical section is obtained according to the projection length and the conical angle of the conical section on the distribution plate; The height of the lifting inner member (11) is equal to that of the fluidization bin (4), the distance from the bottom of the expansion section (6) to the distribution plate (3) is equal, the lifting inner member is a baffle between adjacent fluidization bins (4), and particle back mixing between the adjacent bins can be completely eliminated.
  2. 2. The method of claim 1, wherein the distribution plate separates the fluidized bed, the upper portion of the distribution plate is a fluidization chamber, the lower portion of the distribution plate is a plenum, the air inlet is connected to the plenum, the air outlet is connected to the top of the fluidization chamber, the fluidized bed feed inlet is connected to the leftmost fluidization chamber, and the fluidized bed discharge outlet is connected to the rightmost fluidization chamber.
  3. 3. The method according to claim 1, wherein the area of the fluid bed feed inlet is equal to the area of the fluid bed discharge outlet and is equal to 1-5 times the cross-sectional area of the internals inlet or internals outlet.
  4. 4. The method according to claim 1, wherein the number n of the inner members is in the range 1≤n≤10.
  5. 5. The method according to claim 1, wherein the inner component is of an upper column lower cone structure, in particular a square column bin body at the upper part, a square or rectangular cross section, four vertical walls and a square cone funnel at the lower part; Or alternatively The inner component is of a cylindrical structure, the whole of the inner component is a square cylindrical bin body, the cross section of the inner component is square or rectangular, four walls of the inner component are vertical, and the inner component is integrally formed.

Description

Method for regulating and controlling residence time of particles with different particle sizes in multi-bin fluidized bed reactor and inhibiting back mixing of particles among bins Technical Field The invention relates to the fields of chemical industry, metallurgy and energy, in particular to a method for regulating and controlling the residence time of particles with different particle sizes in a multi-bin fluidized bed reactor and inhibiting the back mixing of particles among bins. Background Fluidization is widely used in gas-solid non-catalytic reactions for treating particles in chemical, metallurgical, energy, food and pharmaceutical industries. However, in practice, the material treated by the fluidized bed generally exhibits a multi-grade character, and the time required for the completion of the different grade particles is generally proportional to the diameter of the particles, and can be calculated from the "unreacted core model". According to this model, the reaction process can be divided into three main steps, namely, firstly, the gas diffuses to the surface of the particles through the gas film layer outside the surface of the particles (out-diffusion control step), then, the gas reaches the interface of the unreacted portion of the particles through the reacted portion inside the particles (in-diffusion control step), and finally, the gas reacts with the particles at the interface of the unreacted portion of the particles (chemical reaction control step). From the unreacted nucleation model, the reaction rate of the particles is mainly controlled by the three speed control steps of external diffusion, internal diffusion and chemical reaction. In the three speed control steps described above, the time required for the complete reaction of the particles is related to the particle size of the particles as follows: and (3) controlling out diffusion: And (3) inner diffusion control: Chemical reaction control: Where τ is the time required for the particle to react completely, ρ B is the particle density, R S is the particle radius, v is the stoichiometric number, M B is the molar mass of the particle, C Ab is the reactant gas concentration, D eff is the effective diffusion coefficient of the gas in the product layer inside the particle, k s is the reaction rate constant, and k G is the gas film layer mass transfer coefficient (approximately inversely proportional to the reynolds number or R s0.5). Therefore, if the reaction conversion rate of the particles is to be improved, it is necessary to control the residence time of the particles in the fluidized bed according to the time required for the particles to completely react. The fluidized bed is designed by adopting the average residence time of particles, and meanwhile, the residence time of the particles with different particle diameters in the fluidized bed is almost the same, so that the problems of inconsistent conversion rate of the particles with different particle diameters, incomplete coarse particle reaction, excessive fine particle reaction and the like are caused, and the conversion rate of gas-solid reaction in the fluidized bed is greatly reduced. Therefore, it is necessary to control the residence time of different size fraction particles in the fluidized bed to match the time required for their reaction. European patent US6224819B1 discloses a fluidized bed system, wherein three particle discharge ports are formed in the fluidized bed through optimal design of the fluidized bed, coarse particles are discharged from the lower discharge port of the fluidized bed, fine particles are discharged from the upper discharge port of the fluidized bed, ultrafine particles are discharged from a top recovery pipeline, and the residence time of particles with different particle sizes in the fluidized bed is regulated and controlled. However, the particle residence time regulation can only meet the requirement of one control mechanism, and the limitation is large. Therefore, there is a need to develop a method for controlling the residence time of different size fraction particles in a multi-bin fluidized bed reactor that can control the residence time of different size fraction particles to meet different control mechanism requirements without affecting the fluidization state of the particles in the main bin of the fluidized bed. Disclosure of Invention In view of the problems existing in the prior art, the invention aims to provide a method for regulating and controlling the residence time of particles with different particle sizes in a multi-bin fluidized bed reactor and inhibiting back mixing of particles among bins, which can regulate and control the residence time of the particles with different particle sizes in the fluidized bed to meet the requirements of different control mechanisms. In order to achieve the above object, the present invention provides a method for controlling residence time of particles of different size fractions a