JPH04354530A - Agglomeration device by countercurrent air flow - Google Patents

Abstract

PURPOSE: To enlarge particle size by granulating a raw material comprising each fine particle. CONSTITUTION: A plant controlling particle size distribution of wet, fine particle supplied from a vertical granulating apparatus and granulation process are disclosed, where the granulation apparatus drived by countercurrent of gases are equipped between vertical granulation plant 2 and fluidized bed dryer 10, this conduct control of the distribution of particle size in the granulation apparatus.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to the enlargement of particle size by agglomerating raw materials consisting of individual fine particles into particles of larger size. In particular, the present invention relates to agglomerating wet or wet particles into larger sized particles, resulting in a more uniform particle size distribution of the raw material.

0002

BACKGROUND OF THE INVENTION A variety of conventional processing techniques can be used to form feedstocks of individual particulates and expand the size of the particles. Such processing includes spray drying, rotary and vertical agglomeration, pressure compaction, melting, and agglomeration from liquid suspended feedstocks; however, the feedstocks produced by all of these processing techniques vary in particle size. The particle size varies and is distributed over a wide range. Since the particle size distribution can vary widely, it is no exception to work with products ranging from 10 to 5.000 microns in diameter. A large particle size distribution causes certain dissatisfaction with product properties. For example, products with a narrower range of particle sizes have reduced quality differences. That is, when mixing or blending with other raw materials, products with uniform or near-uniform particle sizes will be more evenly mixed, and products with large particle sizes will have fewer problems with dust control.

For some raw materials, the presence of powder increases the need for agitation to wet the product and bring it into solution. Also, because of the size variation, the particles wet out unevenly and thus have a negative impact on the solution. Often, when the masses of raw materials are large, they are wetted from the outside and form a product barrier with a high degree of condensation.
This inhibits internal wetting, resulting in the formation of undispersed lumps of material that is essentially viscous and lumpy. Various methods have been proposed to increase the size of raw materials consisting of individual fine particles.

[0004] Although this problem can be solved by stirring the mixture, in some cases sophisticated mixing equipment is required to completely separate all the particles of a composition that varies widely in particle size. may be required. However, it is preferable to solve this problem by creating a bulk powder with a more uniform distribution of particle sizes. Agglomeration creates a product with more uniform particle size, which provides a more even distribution of raw materials and improves their separation, and reduces bulk density (bulk density).
This improves the controllability of density. These factors are related to the overall particle size distribution of the feedstock. Other benefits of uniformly distributed particle sizes include improved flow properties, uniform handling and measurement, and in some cases better bulk transportability. The problem of dust is also eliminated as very fine flocculent powders are no longer present.

Fluidization is a method of holding particles in turbulent suspension by aeration with heated or cooled gas or air. At the right flow rate, the particles behave more like a boiling liquid. Due to flow action,
Close contact between suspended particles and gas. This fluidization method includes drying, heating, cooling, calcining,
Useful for conventional methods such as reaction or agglomeration. There are no moving parts in this fluidization method. With gas or air, the product is continuously flowed through the fluidized bed until it is discharged. Forming large particles from fine powders is often a problem for conventional processing equipment. If necessary, the powder must be made viscous so that the raw material is agglomerated. This often creates problems with raw materials accumulating on the processing equipment.
As a result, clogging may occur. The design of the present invention uses the advantages of fluidized bed agitation, which eliminates the problems associated with other means of selectively enlarging particles.

[0006] US Patent No. 3,700,461 (Dic
Kens et al.) relate to suspended agglomeration with a gas for agglomerating fine particles that are wettable to water, in which the raw material to be agglomerated is fed to an inlet at the base of a chamber that wets this material; The raw material is suspended in a gaseous medium (air) within this chamber. This is basically a co-current fluidization method.

US Pat. No. 3,143,428 (Rei
Mers et al.) relate to dividing the agglomeration process into two distinct but sequential steps. In the first step, a downwardly flowing curtain of powdered raw material encounters a balanced downwardly focused jet stream or a horizontally balanced opposing jet stream. In another agitation stage, the raw material encounters the action of a downwardly or horizontally directed substantially dry stream or opposing jets of air, which jets flow into the powder after it has been wetted. The action moves the moist powders in a turbulent manner, so that a sufficient number of collisions occur between the particles for the formation of agglomerates of these powders. Although agglomeration occurs in the turbulent flow region, in practice the solids and liquids fall together directly into the fluidized bed dryer. The convection time in the "agglomeration zone" of the raw material to be agglomerated is very short and there appears to be little or no control over the particle size distribution of the final product.

US Pat. No. 4,640,839 (Hsu
) relates to agglomerating water-soluble raw materials by introducing the raw materials of individual particles into a flow through a humidification zone. This method attempts to produce an agglomerated product with a grain structure with sharp edges. This prior art method attempts to control the shape, color and density of the product texture or particles to resemble roasted and ground coffee particles. Accordingly, this prior art method and the products made thereby are accomplished by adding humidity to a relatively dry product that enters the agglomeration device. It has been found that the flow and compressed air flow together in a downstream direction in co-current motion parallel to the axis of the agglomeration device and the centrally located supply tube. The flow is diffused through the wall annulus at very low pressure and flows downstream from the orifice at subsonic speed in the vicinity of the incoming particles along and towards the flow axis.

US Pat. No. 4,197,086 (Tay
lor) relates to a method and apparatus for agglomerating solid non-combustible waste. In this apparatus and method, waste consisting of individual particles of solid material is heated and fluidized in a non-combustible granular material. The granular material is a slurry containing the material to be agglomerated, which is introduced into this layer. The combustible material in the slurry is then partially oxidized by the heat generated by the fuel, which is mixed with the material in the slurry to dry and agglomerate the material. be. The '86 process involves combustion in a fluid medium whereby the waste is agglomerated through partial oxidation by the heat generated by the fuel mixed with the waste.

In accordance with the present invention, an improved agglomeration system and particle size distribution for wet particulates can be produced from the system. The present invention can add a degree of process control that is lacking in prior art agglomeration methods.

[0011]

SUMMARY OF THE INVENTION The present invention provides advantageous improvements to agglomeration methods and apparatus that provide improved particle size distribution.

According to the invention, improved results can be obtained by inserting a countercurrent air-driven agglomeration device between the vertical agglomeration device and the fluidized bed dryer. In the vertical agglomeration device, essentially dry solids and fluid are brought into contact and mixed together, and the resulting falling fluid moves downward into the next region of the process. In existing agglomeration technology, the next area is usually a fluidized bed dryer.

Although vertical agglomeration equipment can be operated effectively to produce a product of a particular density or desired average particle size, it provides little or no control over the particle size distribution of the agglomerate. The particle size distribution of the agglomerates is determined overall by a variety of factors. Such factors include, to the exclusion of other factors, the convection time of the particles within the agglomeration equipment, the particle size distribution before blending, and the density at which the feedstock is introduced into the system. It's not a thing.

[0014] The countercurrent agglomeration device of the invention therefore comprises a flotation chamber with an inverted conical cross-section, an air supply opening at the bottom of the flotation chamber and a baffled exhaust means at the top.

Although the invention is not limited by any principle of operation, the invention provides that moist particles entering a conical chamber from a vertical agglomeration device are suspended by rapidly upwardly flowing air or gas. It is believed that Particles with sufficient density fall through the chamber and are ejected from the bottom. Meanwhile, suspended particles move randomly within the turbulent flow of gas within the chamber. As the number of moist particles increases, the probability of collision also increases. Therefore, as the particles interact, separation and agglomeration occur;
This is done until the resulting particles are no longer able to float in the turbulent flow of gas and finally fall and are ejected from the bottom of the conical chamber.

[0016] The present invention also provides an apparatus for processing feedstock consisting of individual microparticles with moisture to obtain larger desired particles. The apparatus according to the invention has means for discharging air or inert gas at high speed into the region of the inverted conical chamber, while the moist raw material containing fine particles is fed into this region from a vertical agglomeration device. The device also includes means for regulating the exhaust air or gas to prevent powder from being delivered and expelled into the exhaust stream and for retaining particulates within the conical chamber for further processing. You can.

The device of the invention operates on the general principle that a rapidly moving vertical stream of air or gas suspends solid particles by balancing entrainment forces and gravity. Particles that fall leaving the vertical agglomeration device vary in size. By using a flow of air or gas and adjusting the flow rate of the gas or air flow, only particles of a particular size and density can be suspended. The flow rate of this gas or air flow is determined by the diameter of the entrainment chamber within the inverted conical region.

The above and other objects, features and advantages of the present invention will become more fully apparent from the following detailed description of the preferred embodiments when taken in conjunction with the accompanying drawings.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus shown in FIG. 1 is an input chute for wet solids coming from a vertical agglomeration device. The moist solids are introduced into the top of the agglomeration chamber having an inverted conical cross-section according to the invention, and an air introduction means or orifice, such as a sparger ring, is attached to the bottom of the conical section. This introduction means interlocks with the outer wall of the conical part to form an annular gap which, when opened, allows the solids leaving the conical agglomeration chamber above to be discharged.

Other suitable devices such as adjustable pressure regulating valves for adjusting the air or gas flow rate may also be provided to monitor and control the flow rate and pressure, if the flow is used as a flow gas. The temperature of the stream supplied to the introduction means may be monitored and controlled. The introduction means comprises a porous ring, collar or series of tubes so as to form an inlet for fluidizing the gaseous raw material. Although it is possible to use any gaseous medium as the fluidizing gas, it has been found to be particularly effective, convenient and inexpensive to introduce air into the chamber to form a fluidized layer therein. ing. Air is introduced into the chamber 3 via the introduction means.
and then through this chamber 3 to the exhaust port 4 in the upper part 15 of this chamber.

The wall structure forms an annular channel 8 that surrounds the gas introduction ring 7 . An annular channel 8 is mounted above the drying means and aligned on the conveyor leading to this drying means. The drying chamber is
The chamber of a dryer well known in the industry, such as a fluidized bed dryer. Such a dryer has suitable conventional equipment connected thereto through which heated air or gas is circulated at a rate that fluidizes the particles falling onto it.

Only when fluidizing air or gas from the sparger ring 7 is present in the chamber 3, the dust generated within the fluidized bed dryer is removed from the fluidized bed dryer via a separate exhaust port. . A conveyor system 11 removes the dried particles from the dryer 10 in preparation for packaging or other processing. For example, raw materials can be easily shifted and separated into acceptable oversized and fine-sized products. Fine products can be reintroduced into the pneumatic conveying system of the inverted conical chamber, and oversized raw materials are passed through the necessary grinding rollers and returned to the shifting device.

In this preferred construction, the agglomeration chamber 3
has a peripheral wall 18 disposed in a substantially vertical position. The walls of the chamber can be made of any suitable non-reactive material that can be used when handling the raw materials being processed within the chamber. chamber 3
has an inverted conical shape, the cross-sectional area of the upper part 15 of the chamber being larger than the cross-sectional area of the lower part 14 of the chamber. By maintaining a larger cross-sectional area in the upper part 15 of the chamber 3 than in the lower part 14, the gas flow rate in the upper part of the chamber 3 is reduced. Due to the relatively large cross-sectional area in the upper part 15 of the chamber 3, this flow rate is reduced. This allows the raw material consisting of individual particles to be suspended within the chamber, creating a "fluidized state" of solid material.

[0024] "Fluidized state" refers to the solid state that occurs when an upward flow of gas or air passes through a mass of raw material consisting of individual particulates, creating a high-velocity turbulent motion. Concerning the floating of objects. Due to this turbulence, the moist particles supplied from the vertical agglomeration device 2 move in a turbulent flow, which causes a large number of collisions between the moist particles, which in turn Agglomeration is carried out according to the theories currently believed to explain the process. The inverted conical chamber 3 used in this device has been found to be suitable for this action.

Near the top of the wall of the inverted conical chamber is an exhaust port 4 . The exhaust port 4 provides means for fluidizing gas to escape from the chamber. To prevent fine particles from being ejected from the chamber, baffle means are provided which cooperate with the exhaust port. As shown, the solids input chute from the vertical solidification device 2 enters the agglomeration chamber 3 near and between the baffle means 5 with counterflow of air. This confinement of the fine particles and input solids by the baffle means prevents them from leaving the agglomeration chamber 3.

In operation of the exemplary apparatus described herein, a feedstock consisting of individual fine particles is introduced from a vertical solidifier into an inverted conical chamber via a solids input chute. By adjusting the flow rate of the fluidizing gas entering from the bottom opening, fine particles are retained and suspended within the fluidizing region, while larger particles from the vertical solidifier fall through chamber 3 and form a conical shape. It is discharged from the lower opening 8 of the area. The amount of gas flowing through the chamber can be adjusted by suitable regulating means. chamber 3
By moving the gaseous medium through the chamber, fluidizing turbulence can be generated within the chamber. Due to the turbulent flow in the chamber 3, the raw material consisting of individual particulates with suspended moisture collides with each other and agglomerates into larger sized particles and clumps. After agglomerating the particles to a sufficient size by successive accretions,
The enlarged particles overcome the buoyancy of the fluidizing gas medium. The agglomerated particles are then discharged through the lower opening of the conical region 8 for further drying, cooling, sieving and other steps.

In the vertical agglomeration device 2, solids and liquids are combined to produce a wet or moist product and are processed to create a specific density or target a predetermined average particle size. Can be done. However, the vertical agglomerator 2 provides little control over the particle size distribution of the agglomerates produced therein.

In the inverse agglomeration chamber 3, the particle size distribution and product density can be controlled independently. Therefore, by increasing the residence time of a certain percentage of wet product exiting the vertical agglomeration device 2, the wet product can collide with other particulates 25 and agglomerate into larger particles 24. In this case, there is little or no effect on the density of the final product.

Although the following examples demonstrate the process of the apparatus described above, it will be understood that the invention is not limited to the particular materials or apparatus described herein.

EXAMPLE The particle equation and design behavior of the bulk device of the present invention was developed based on the following information.

The operation of the inverted conical agglomeration device is based on the principle that a vertical flow of gas (air) can suspend solid particles by balancing entrainment forces and gravity. To the extent that the particles falling from the vertical agglomeration device vary in size, the airflow can be used to suspend only certain particle sizes. Furthermore, the range of particles that can be suspended within a chamber of constant diameter is specific to the air flow rate.

The size of particles suspended by an air stream with a given apparent velocity can be predicted by the following formula: U = (ps-pa) (g) (d) 2/18 (μ) where, U: Apparent flow velocity of air ps: Density of solid pa: Density of air g: Acceleration due to gravity μ: Viscosity of air d : Particle size The apparent velocity of the air stream is controlled by the cross-sectional diameter of the entrainment chamber (the container through which the air passes) and the volume of the air, according to the following formula: U = (Va/3.1416(r)2) where: U: apparent flow velocity of air Va: flow rate of air r: radius of chamber The chamber was designed to suspend a range of particles until they formed. When the particles are large enough, they fall through the entrained air stream and exit the conical area.

The conical chamber has a radius of 5 inches (12.7 cm) at the bottom and a radius of 12 inches (30 cm) at the top.
5 cm) according to the above equation. The height required to create stable flow conditions is six times the radius of the top section, or in this case 72 inches.
82.9 cm).

This apparatus was installed between a vertical agglomeration unit and a fluidized bed dryer in a synthetic detergent pilot plant. The process in the vertical agglomeration unit is 300 lb/hr (136.
2 kg/hour) of synthetic detergent was produced. When the inverted conical agglomeration zone was operated, the flow rate of air from the blower was adjusted to suspend and selectively agglomerate the following particle sizes. Droplet entrainment speed
Particle range 650
ft/min (198.1m/min) 710μm 470ft/min (143.3m/min) 350μm1
70ft/min (51.8m/min) 210μm1
00 ft/min (30.5 m/min) 160 μm For example, when suspending and binding particles less than 350 microns from a vertical agglomerator, an inverted conical agglomeration area of 47
To produce an average airflow of 0 ft/min (143.3 m/min), the airflow volume must be 1476 cubic ft/min (4 m/min).
1.8 m3/min) (1 atm, 25°C).

In another test of the inverted cone agglomerator, the prototype device was placed in-line between a vertical agglomerator and a fluidized bed dryer. Air was used as the fluidizing medium. 2 inches (5 inches) centered in the bottom opening of the chamber.
．． Air entered through a nozzle of 0.08 cm). For this test, three settings were used: (1) maximum capacity (5200 cubic feet/hour (147.2 m3/hour));
, (2) half capacity (2610 cubic feet/hour (73
．． (9 m3/hr)), and (3) the process was operated without air entering the chamber.

In these three tests, samples were collected at the base of the inverted conical chamber and at the outlet of the fluidized bed. These samples were analyzed for density and particle size distribution. The percentage of fine particles that did not combine with larger particles was estimated by visually determining the percentage of colored trace particles that did not combine with the final product.

Below is a summary of the results obtained during these tests. (a) The agglomerates exiting the chamber showed a 50% reduction for -60 mesh particles, while the density was only reduced by 0.5%. (b) When operating an inverted conical agglomeration chamber, the overall particle size distribution was narrower by 20% (standard deviation). (c) By using tracking colored particles, 80% of the fine particles are bound in the vertical agglomeration device and virtually all -60 mesh particles are bound as they exit the inverted conical agglomeration chamber. I found out that there is.

While several embodiments of the invention have been described and illustrated, it will be apparent to those skilled in the art that modifications and variations thereof will come within the scope of the invention. It is therefore intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of the invention.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an apparatus according to an embodiment of the invention.

FIG. 2 is an enlarged schematic cross-sectional view of the device shown in FIG. 1;

FIG. 3: Line 3 of the reverse air agglomeration device of the present invention.
It is a sectional view taken at -3.

[Explanation of symbols]

3. Agglomeration chamber 4 Exhaust port 5 Baffle means 7 Sparger ring 8 Lower opening

Claims (7)

[Claims] 1. A method for producing an agglomerated material sorted by size from a fine raw material containing moisture and consisting of individual fine particles, comprising: (a) a fine raw material containing moisture and consisting of individual fine particles; introducing the raw material in the form of freely falling particles into the upper part of the inverted conical chamber; (b) suspending said raw material consisting of individual particulates in a countercurrent of upwardly directed gas; (c) said A process in which a raw material containing moisture and consisting of individual fine particles undergoes intense random motion within a gas stream, the gas stream generating turbulence in the raw material containing moisture and consisting of individual fine particles at a sufficient velocity. and (d) forming the moistened, enlarged agglomerated particles into an inverted conical chamber while being supported by the gas flow. the moist agglomerated particles being caused to fall downwardly from the air to a means for drying the moist agglomerated particles. 2. The method of claim 1, wherein the gas for said gas flow is air. 3. A method for controlling the particle size distribution of an agglomerated material formed from a raw material consisting of individual fine particles having moisture, comprising: (a) the fine particles having moisture and consisting of individual fine particles; (b) suspending said fine raw material consisting of individual fine particles in a countercurrent flow of gas having a selected flow rate; (c) agglomerating a raw material consisting of suspended individual particles into particles of sufficient particle size to overcome the floating action of the countercurrent gas; and (d) removing the agglomerated particles from the chamber. ; A method including; 4. characterized in that the moist, fine raw material constituted by individual fine particles is introduced into the conical chamber from a vertical agglomeration device having a wide initial broad particle size distribution; 4. The method according to claim 3, wherein: 5. An apparatus for producing an agglomerated material sorted by size from a moist, fine raw material consisting of individual fine particles, the apparatus comprising: an agglomerated material having an upper opening and a lower opening and having a substantially vertical inverted conical shape; an agglomeration chamber in which the cross-sectional area of the lower opening is smaller than the cross-sectional area of the upper opening; the moisture is introduced into the agglomeration chamber through the upper opening and the individual fine particles are formed; means for substantially continuously supplying fine raw materials downward; means for introducing fluidizing gas upward into the chamber in a countercurrent manner near the lower opening; the fluidizing gas is Sufficient flow velocity is used to suspend the fine raw material containing moisture and consisting of individual fine particles, and generate sufficient turbulence to cause the particles to agglomerate each other, and the agglomerated particles are then means for overcoming the floating flow velocity of the fluidizing gas and dropping from the chamber through the lower opening of the chamber for further processing; and means for drying the agglomerated particles falling from the agglomeration chamber. 6. The exhaust means according to claim 5, wherein the exhaust means is a baffled exhaust means, whereby the agglomerated fine particles are not exhausted from the agglomeration chamber by the fluidizing gas being exhausted. equipment. 7. The upper opening is connected to the outlet of the vertical agglomeration device to supply a fine raw material containing moisture and consisting of individual fine particles to the conical agglomeration chamber. equipment.