DK149325B - PROCEDURE FOR UNIQUE, CLOSED SURFACE COATING OF SINGLE CORN OF AFFECTABLE MATERIALS AND APPARATUS FOR EXERCISING THE PROCEDURE - Google Patents

Description

in 149325

Surface coating of grained materials is a technical task. This coating generally takes place in rotating containers. This has the disadvantage that there is considerable grinding of the grains to be coated. If sufficient intermediate drying is not performed, adhesions may lead to the formation of agglomerates and to the aggregation of the pulp.

Vertebral coating is also known. This has the considerable disadvantage that a uniform fluidized bed with uniform volume concentration is only difficult to maintain. The function of such vertebral layers therefore often leads to operational disturbances.

Another disadvantage lies in the difficulty of carefully dosing the amount of substance to be injected to achieve a uniform distribution of the material to be coated.

Also, the amount of air introduced for the required rapid initial drying of the injected solids is too negligible so that baking 20 of the grains to be coated cannot be avoided. This results in undesirable granules of the grains to be coated and thus no uniform coated material is obtained.

Such vertebral layers are also not divided into zones of different function, such as in a core zone and an edge 25 zone. Furthermore, there is a uniform pressure distribution throughout the vertebral cross section.

These disadvantages of surface coating of grained materials are avoided by the method of the present invention and the apparatus for its practice.

According to the state of the art, the "vortex layer" is used for granulation. German patent publication DE-OS 17 92 752 relates to a process for the continuous production of agglomerates. The material to be agglomerated must fall into a fluidized bed through wet fog vapors.

The apparatus consists of a cylindrical tube closed at the lower end by a lock.

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Neither this second task nor this geometrically different apparatus has made the method or apparatus according to the invention obvious.

German Patent Specification No. 23 41 504 relates to a process for vertebrate spray granulation. Air is blown over a sieve bottom and the granulate formed with an infused fluid is knocked apart by high speed impact arms. This apparatus also uses a cylindrical vortex chamber with uniform pressure. Also, this prior art 10 has led away from the teachings of the invention, since according to this particular, no uniform pressure space is used, but zones with different flow pressures.

German publication specification DE-OS 23 61 998 discloses a method and apparatus for continuous preparation of granules in fluidized layers. The granulation must take place in sub-processes in the compartmental elements in the form of separated cells during the stirring and atomization of the liquid media. This prior art goes a whole different way, as the sub-processes in separate spaces take place one after the other. This proposal does not allow a coating without agglomeration of the granules.

German publication specification DE-OS 27 26 164 relates to a coating apparatus for the production of coating layers on particles. This apparatus consists of a vertical, hollow, cylindrical container in which is placed a hollow cone stub which narrows upwardly. Outside of this cone stub is the storage zone for the material to be coated. The gaseous flow rising through the cone stub absorbs the fine droplets of the coating material. By means of guide members, the entering air is divided into beams and rises upwards. An aerosol flow at substantially the same velocity is provided over the entire cross-section of the chamber. The particles outside the cone stub are entrained by the gaseous flow. The lower part of the cone is referred to as the central zone, ie. as a coating zone. In this zone, the material to be treated comes into contact with the finely sprayed spray. Further up in the hollow cone stub, the liquid state 3 of the coating material deposited on the pellets or particles by solidification or evaporation processes goes into solid state. Agglomeration must be prevented by faster flow of the particles. This should prevent a separation of the particles in the vertical direction. This area of the cone stump is referred to as "drying zone". An expansion and thus a braking and a further drying must occur over the cone stump. The particles must, again, by gravity, fall back into the coating zone. The recirculation should be continued until a desired coating is obtained.

This apparatus and its mode of operation differ considerably from the method of the invention and the apparatus for its practice. The apparatus according to the invention does not use any inner, upwardly narrowed cone stub in a vertical cylindrical container, but, as explained below, by an upwardly extending upper part and a lower short funnel-shaped base. The material to be coated is not outside the zone in which the air flows. Not a "entrapment effect" is used, but a swirl effect. This has the advantage that with less air a core zone with high volume concentration is set for the coating. Furthermore, the coating is carried out in the substantially larger core zone and not in the small cone stub zone.

GB Publication No. 134,426 describes a method for distributing liquid particles on powdered or granulated solid particles. In a cylindrical porous bottom mixing vessel, a secondary air flow produces a particle swirl layer. A higher velocity carrier air flow passes through the fluidized bed, the center of which is located axially below the syringe member. This sprays the particles extracted from the fluidized bed. Thereafter, the carrier air expands into an applied, funnel-shaped top so that the particles fall.

Upon fluidization of the particles in the cylindrical mixing vessel, lighter particles within the wide grain distribution used, as described in the Examples, are extracted uncontrolled. Density differences in the vertebral layer lead to blowing and flow phenomena, resulting in an inhomogeneous, pulsating eruption distribution over the layer cross section.

5 SE Patent Specification 364,449 describes the general implementation of chemical operations in fluidized layers. The apparatus used has a funnel-shaped base, but to this end cylindrical parts and no upwardly extended upper part are joined.

10 In the cylindrical top, the air introduced from below with high velocity causes disturbing weight turbulence. These cause impact of the injected substances to the wall. This known apparatus therefore needs to reduce said disadvantages tangential auxiliary currents which introduce additional air along the wall. There is no explanation for the mutual dependence between product parameters and air supply setting parameters and the syringe means. Due to this mismatch of parameters, a large amount of cyclone dust and return goods are produced. As the treatment is prolonged, the formation of worn material and de-agglomerated particles is inevitable.

* These disadvantages also apply where this known technique happens to use starting material of 25 uniform grain size.

The process according to the invention for uniform, closed coating of single grains of sprayable material with the nearly uniform grain size of smooth, rough or chopped surface in hot air vortex fountain using an inorganic and / or organic coating material from suspension or solution is characterized by: a predetermined amount of the material to be coated in a steep, upwardly funnel-extending container with a shorter, flatter, funnel-shaped base, at the pressure of a downstream and upwardly directed hot air stream at a core flow rate, forming a core zone in diameter and height limited vortex fountain in the direction of the center axis, and that by means of one or more nozzles arranged at the lower end of the container injection is made in a predetermined amount per minute. time, into the core volume with high volume concentration, of a in the same direction as the hot air from below and upwardly directed suspension or solution at an initial spray angle between 30 ° and 60 ° which suspension is completely and uniformly absorbed by the surface of the material during concomitant drying upon rising of the treated material into the core zone, which material subsequently passes laterally to the rim zone with diminished flow pressure and further along the container wall into the funnel-shaped bottom and back to the vortex fountain, whereby these process steps are repeated during simultaneous drying until the predetermined coating amount is applied, after which drying of the coated material is carried out until a predetermined final moisture.

This novel coating method, contrary to the prior art, uses mandatory grain of 20 at the nearly uniform grain size, and the grains can have both smooth, rough and split surface, and the coating process consists of a combination of mutually matched process parameters of a number of process steps. which runs in a steady state of equilibrium and which can be repeated until the desired coating thickness is obtained, as well as it is also possible to homogeneously connect several successive layers of different chemical composition. The uniformity of the coatings applied by the process of the invention can be detected optically by color addition.

The method according to the invention further has a number of additional advantages. Thus, the complete consumption of the introduced coating material in the high volume core zone zone means that the exhaust air is practically free of solids content. Furthermore, the coating takes place in a very short time, which gives great production capacity. Furthermore, it is especially advantageous in coating biological materials, such as seed grain, that no heating of the material being coated takes place.

The process according to the invention also largely avoids, due to the short path lengths and the only minor mechanical stresses, mutual friction between the grains, and the amount of worn material is limited to a minimum.

The apparatus according to the invention for practicing the present method according to the invention is characterized in that it consists of a container with circular or multilayered cross sections for an upwardly extending upper part and a bottom mounted, funnel-shaped base and with an opening above it, the upper and lower ends carry a sieve end, and the transverse sectional change of the container from the lower sieve end to the upper edge of the lower funnel takes place at an angle of 20 ° to 50 ° with respect to the vertical axis and from the lower edge of the upper to the upper sieve end. is in the ratio of 1: 1.5 - 4.5, and whose upper and lower sieve ends consist of 20 interchangeable screens with the greatest possible free cross-section and a mesh width smaller than the smallest cross-section of the material to be coated, over which the upper screen termination is preferably provided with a suction cap for extracting the exiting hot air, and wherein for injecting the suspension and / or the solution of the coating material in co-flow with the hot air at the lower end of the container is arranged one or more nozzles.

This particular apparatus design has the additional advantage that the apparatus can be operated with very little air-foot use in the vortex and with little energy consumption, and it is very reliable and uniformly functioning.

Alternative measures of the method and apparatus according to the invention, respectively, are defined in the subclaims.

These measures relate to the lower and upper limit of the grain diameter at a uniform grain size for the material as well as the grain area of the material to be treated, preferably not exceeding an area of plus / minus 20 percent of the average grain size; where the material should exhibit about the same density.

Further, these alternative measures 5 relate to the high volume concentration expressed by the ratio of the volume of the material to be coated in the core zone to the volume of the core zone, the design of the vortex core zone as a bottom and upward expanding funnel with a certain cross-sectional ratio of the lower cross section and the upper cross-section as well as the flow rate setting at the lower end of the container to determine the core zone height.

Furthermore, said alternative measures relate to the formation of a fine spray mist with spray droplets many times smaller than the average grain size of the material to be coated and the droplet size of the spray mist to be controlled when selecting the nozzle. and by adjusting the spray pressure to 20 depending on the viscosity of the suspension or solution, and setting the outlet pressure such that the rate of spread of the spray drops is greater than the passage rate of the material to be coated.

The said alternative measures also concern that the angle of exit and the rate of spread of the spray drops at the nozzle outlet are limited to an upper value so that, upon complete adsorption of the coating agent, no lateral exit from the core zone and the height of the spray mist in the upper part of the container is regulated by the spray pressure and the air velocity of the incoming hot air, and is limited so that no free spray droplets are penetrated, and further relates to the purification, drying and return of the exhaust air.

Furthermore, the said measures concern examples of the materials to be coated.

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A particular embodiment of the process according to the invention consists in that the predetermined amount of the material is periodically filled in a container and from below with co-flow hot air with a subset of the suspension or solution is introduced into the core zone and coated uniformly and simultaneously subjected to Initial drying, after which a further subset of the suspension or solution is introduced into the container, initial drying is repeated, until this process is repeated until the predetermined coating amount is applied in a homogeneous distribution on the material grains, then drying until the predetermined moisture content is achieved. .

Other alternative measures relate to the apparatus for carrying out the method according to the invention and relate to the presence of a flow aperture which, at the lower sieve end, consists in the provision of an air shaft which conducts the hot air and whose cross-section exhibits defined dimensions and can be changed by means of a 20 aperture, and relates laterally to insertion of one or more nozzle strains.

Further features of the apparatus for carrying out the method of the invention relate to the coating of the inner wall of the container for corrosion protection, for increasing the sliding ability of the material to be coated, and for noise cancellation, which surface coating preferably consists of tear-off smooth surface.

The method according to the invention and the apparatus for its practice are described in more detail in the following example with reference to the drawing.

Example In a container 1, from above 5 kg of a material with spherical grains having a density of 0.9-1.1 kg / liter is filled from above and located within a grain spectrum of 3.0 to 4.75 mm.

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A hot air flow from below and upwardly through the container 1 with a temperature between 40 ° and 100 ° C is controlled, after closing the upper sieve end 4, with an air flap 9 in the air shaft 8 so that in the funnel-shaped lower part 3 of the container 1 begin with dormant grains, and rise in the centrally directed core zone 13 to a vortex fountain relative to the container axis 6, thereby constructing the air inlet together with cross section and shape of the air shaft 8, the cross section of the lower sieve end 5, taking into account its freedom the passage surface and the cross-section and shape of the lower funnel 3 of the container, that the flow of air with the invertebrate material produces a beam-bundled core zone 13 of rotating and 15 swirling ascending grains. From the shape and height of the core zone as a slender funnel with an average diameter of 150 mm and a height of 0.7 to 0.8 meters and with the volume of the introduced amount of grain, there is a calculated average volume concentration in the area of the core zone. of grain in the core zone of approx. 20 to 25 percent. The flow rate and flow pressure decrease with increasing height of the core zone due to the cross-sectional expansion of the flow and pressure loss due to the flow resistance of the particles, and the opposite gravity of the grains decreases their velocity until equilibrium for the flow velocity and sink rate of the grains. turning zone over the core zone 13 'slides outwardly into the region of diminished flow pressure and flow rate at the circumference of the container wall and falls along it. Back into the bottom part 3 of the container 1 where, as a result of their own weight and the slope of the lower funnel 3, greater than the grain angle of the resting grain filling, from all sides uniformly and continuously slides back and forth in the core flow 13 of the vortex fountain 6. The penetrating air flow becomes absolute pressure within the range of blowing performance of from 500 to 2000 Pa water column, and the airspeed in the shaft joins assumed free passages in the range of 6 to 15 meters / second, regulated such that the core zone 13 with overlying turning zone of the vortex fountain 6 does not exceed 3/4 to 4/5 of the container height.

By means of a pump, the prepared suspension or solution whose solids content forms the coating on the grains and whose viscosity at a solids content of 20 to 30% is between 0.5 and 1.0 Pa s, is fed to the nozzle stock 10 at a in accordance with the spray image adjustable pressure for the nozzles of 50 to 120 bar, which nozzle stem in the lower funnel 3 of the container 1 holds one or more nozzles 11 which, in co-flow with the lower flowing hot air, must spray the suspension or solution in the core zone below 15 an initial spray angle of 60 ° and in the form of spray droplets with a diameter of less than 0.2 mm. The spray angle narrows as a result of the hot air flow rate with increasing distance from the nozzle orifice and, depending on the choice of nozzle and pump pressure, must be only so large that the spray zone 12, by the discharge of the spray drops of the hot air in the axial direction and by increasing adsorption of the spray droplets at the grain droplets as As a result of the high volume concentration of the grains and their slower rate of propagation relative to the spray drops in the core zone 13 of the vortex fountain 6, both at the perimeter and at the height, the spraying of the container wall 2 and the upper sloping exit 4 is delimited.

As soon as the hot air flow parameters for adjusting the vortex fountain and the hot air flow parameters, selecting and applying the spray nozzles, and selecting the spray pressure for the purity of the spray drops and the restriction of the spray zone according to the stated conditions are met, the adjustment egg is fulfilled. Under the condition that the coating should cause a 10 percent weight gain for the grains with respect to solids and the suspension or solution has a solids content of 20% by weight, 2.5 kg of suspension or solution must be sprayed for coating 5 kg of grain. which the nozzle set provides after adjustment and under the predetermined spray pressure over a defined short time.

5 The coating process is then divided in time into spray and drying phases so that the initial drying phase takes place simultaneously with the spraying phase. Upon completion of spraying and drying phase, a clean drying time follows which, depending on the temperature of the hot air, comprises a defined short period of time and is limited in time by the fact that the exhaust air temperature during this drying time does not increase significantly. As long as the energy of the hot air is used only to evaporate the suspension or solution that moistens the grains, the grain assumes exactly the cooling limit temperature corresponding to the vapor pressure of the liquid and the air state, and the exhaust air temperature remains constant. First, upon complete drying of the surface and diminished dust transition of the liquid from the grain into the vapor phase due to increased diffusion resistance 20 of the drying layer, this layer is heated from the interior of the grain. The target for the rise in material temperature is the rise in exhaust air temperature, after which either the temperature of the supplied hot air can be partially or completely regulated down to the determined material final temperature, or material can be extracted at a certain reached exhaust air temperature and then cooled in a suitable cooling apparatus with a cold air. desired temperature. When sampling during the drying phase, the process determines the end of the drying time, after which the material must not exceed a temperature of e.g. 40 ° C and a residual humidity of 12 to 13 percent. As soon as the drying time required for these values is determined, under the constant parameters of the process, many batches of the same material can be coated according to this temporal program.

As mentioned, the homogeneity of the coating on the surface of the individual grains can be demonstrated by optical comparison by color addition to the coating liquid. The homogeneity and the complete application of the coating amount can be measured from grain to grain by adding a known substance to the coating liquid and chemically detecting it on the individual grains.

This test confirms for materials coated by the process of the invention the homogeneity of the coating. However, this homogeneity does not simply mean coating with a mass of the same chemical composition. The process according to the invention also allows, as mentioned, to connect several successive layers with different chemical composition homogeneously to each other.

The technological embodiment is not limited to particular materials to be coated when they meet the parameters of the process according to the invention. Thus, grained natural products as well as inorganic, technically granular, spreadable materials having a smooth, rough or choppy surface can be coated underneath. obtaining a uniform, closed surface.

In addition to this wide application in the materials to be coated, the method of the invention offers the technical advantage of a uniform coating of high distribution accuracy with a predetermined amount or layer thickness of the substance to be applied.

The process according to the invention makes it possible to use the inorganic and / or organic substances known in the prior art as suspension or solution.

The apparatus for carrying out the method according to the invention, with its geometric dimensioning and its objectives in connection with the setting parameters of the method according to the invention, offers the advantageous option for different materials to be coated, specifically to adjust the amount to be applied, or the layer thickness or the diameter of the coated material.

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Claims (8)

149325 A method for uniformly sealed single grain granular surface coating of sprinkler materials having, on the nearly uniform grain size, smooth, rough or cleft surface in hot air vortex fountain using an inorganic and / or organic coating agent from a suspension or solution, characterized in that a predetermined amount of the material to be coated is contained in a steep, upwardly funnel-extending 10 container with a shorter, flatter, funnel-shaped base, at the pressure of a downward and upwardly directed hot air stream forming at a core zone a diameter and height-limited vortex fountain in the direction of the center axis, and by means of one or more nozzles disposed at the lower end of the container, injection in a predetermined amount per hour, into the high volume core flow stream, of one in the same direction such as the hot air from below and upwardly directed suspension or solution at an initial spray angle between 20 ° and 60 ° which suspension is completely and uniformly absorbed by the surface of the material during concomitant drying upon ascent of the treated material into the core zone, which material then laterally slides into the rim zone with diminished flow pressure and further along the container wall. in the funnel-shaped bottom and back to the vortex fountain, whereby these process steps are repeated during simultaneous drying until the predetermined amount of coating is applied, after which drying of the coated material is done until a predetermined final moisture. Method according to claim 1, characterized in that the material to be coated does not respectively exceed or exceed a grain diameter of 0,5 mm as lower and 15 mm as upper grain boundary at a uniform grain size for the material in a batch. wherein the material preferably has a grain area not exceeding a range of ± 20 percent of the average grain size and exhibits approximately the same density. Process according to claim 1 or 2, characterized in that a core zone is used which exhibits one or more of the following characteristics: (i) its high volume concentration is provided by the ratio of the volume of the material to be coated in the core zone: the volume of the core zone and amounts from 10: 100 to 35: 100, 10 (ii) it produces, generated by means of a hot air introduced from below through a flow mixer, a downward and upwardly extending steep funnel whose cross-sectional relationship between the lower cross section formed by the flow mixer diameter and 15 upper cross sections are 1: 1,2 - 2, and / or (iii) it has a height of from 3/4 to 4/5 of the container height, which height is adjusted by controlling the flow rate at the lower end of the container. . Method according to any one of claims 1-3, characterized in that the suspension or solution is sprayed at such a high pressure at the nozzle outlet that a fine spray mist with spray droplets that is many times smaller than the average grain size is formed. of the material, and that the spray droplet size is controlled by the choice of nozzle and by adjusting the spray pressure depending on the viscosity of the suspension or solution, the outlet pressure being preferably set such that the rate of propagation of the spray droplets is greater than the passage speed of the material to be coated. Process according to any one of claims 1-4, characterized in that the angle of discharge and the rate of spread of the spray droplets 35 in the spray mist at the nozzle outlet is limited to an upper value such that upon complete adsorption of the coating agent at the surface of the material. to be coated, there is no lateral exit from the cross section of the core zone with high volume concentration, and the height of the spray mist of spray droplets in the upper portion of the vessel is regulated by the spray pressure and air velocity of the incoming hot air. complete adsorption of the coating agent onto the surface of the material to be coated is restricted so that no free spray droplets are above the core zone height, whereby the cooled, vapor-laden exhaust air is aspirated, the vapor phase is separated off by condensation, and the air is returned in whole or in part after cleaning and heating. Process according to any one of claims 1-5, characterized in that granular is used as the material to be coated. 15 spices, seed grains or pharmaceuticals. Process according to any one of claims 1-6, characterized in that a container is continuously filled in a continuous process with a predetermined amount of the material to be coated and the hot air is introduced from below in co-flow. with a subset of the suspension or solution, or variously composed suspensions or solutions in the core zone of the material to be coated, and uniformly coated simultaneously with initial drying, after which an additional subset of the suspension is injected or the solution or by another suspension or solution, initial drying is carried out, whereby this process is repeated in further process steps until the predetermined coating amounts are homogeneously distributed on the granules of material, after which the coated material is dried in a further process step until a defined final moisture, and the coated material then in a y-derl During each process step, air is cooled and withdrawn, the exhaust air is discharged, dried and purified and recirculated. Apparatus for uniform, closed coating of single grains of sprayable material according to any one of claims 1-7, characterized in that: