Coating processes – Particles – flakes – or granules coated or encapsulated
Reexamination Certificate
1999-08-18
2002-05-07
Beck, Shrive P. (Department: 1762)
Coating processes
Particles, flakes, or granules coated or encapsulated
C427S424000, C118S303000, C118S668000, C222S057000
Reexamination Certificate
active
06383562
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention concerns a method and a plant for the preparation of feedstuff pellets by spraying relevant additives in liquid form on a continuous thin layer of the feedstuff pellets. It is generally desirable that in feedstuff pellets there should exist a certain addition of qualified materials such as enzymes, flavouring and vitamins, and it has previously been known to add such materials in solid particle form to the basic material, which is prepared for feeding purposes by pellet pressing. Various recipes can be used, all depending on how the pellets are to be used, and by such mixing in the basic material a precise dosing can be achieved, e.g. based on weighing.
However, most of the relevant additives have proved to be vulnerable to the actual pellet formation process, in that considerable heat is developed when these are pressed, whereby the materials are rendered more or less ineffective or, where some are concerned, are completely ruined. Because of this, an alternative principle of dosing has been employed, i.e. treating the finished and thereafter cooled pellets with the relevant materials in a dissolved or suspended liquid form. Various techniques have been put forward for this purpose, though with inherent disadvantages with regard to capacity, uniformity or dosing precision, and also an undesired crumbling and formation of dust.
It is sufficient here to mention just one of the suggested principles, i.e. the providing of a cascade of the pellet material distributed in a thin layer out over an inclined chute, whereby the quickly down-sliding layer can pass a spraying station from which the layer of pellets can be dosed with the additives through a suitable nozzle arrangement. It is precisiely when this layer is thin and when it is subsequently conveyed for collection, e.g. on a conveyor leading sideways away from the chute, that a certain mixing of the material will occur, whereby it is possible for the product sprayed on the thin layer to spread in a predominantly even manner in the finally collected pellet mass.
There are, however, certain distinct problems connected with this known technique, i.e. partly with regard to the dosing precision of the sprayed-on additives, in that this dosing should, of course, be carefully adapted to suit the current amount of material, i.e. layer thickness and flow-rate of the thin layer of pellets, and partly—of a more practical nature—with regard to the construction height of the plant necessary for establishing a cascade of the thin layer with such a high speed that it is at all possible to operate with a capacity which is of interest in commercial practice.
Both of these problems are quite significant in practice. Consequently, it can clearly be ascertained that the construction height necessary for producing a flow-rate of usable degree will exceed a normal storey height, i.e. the installation of the plant will demand special site conditions. The creation of the thin-layer formation of the pellets could be effected with lower height requirements by feeding the material to a quickly-moving, horizontal conveyor, but for various reasons this solution is not attractive.
Also the second of the above-mentioned problems, i.e. the dosing precision of the additives, is of decisive significance. A plant which should be able to operate with pellet materials of several different kinds will not necessarily deliver these materials in a completely even cascade at uniform speeds and layer thicknesses. Therefore, it can be extremely difficult to determine a correct dosing for the spraying of the pellets. It should be borne in mind that in practice it is current to operate with quite a high capacity, typically 10-100 tons per hour, and with a relatively small addition of liquid, e.g. merely 50 ml-10 litres per ton of material. It is not desirable to operate with additives in specially thin solutions, since the pellets should not be moistened more than is strictly necessary, and for precisely this reason the additives must be held at a minimum, also because in some cases the additives are extremely expensive.
To this can be added that quite strict demands are made on the uniformity of the application both in general and to a particular degree in connection with feedstuff mixtures intended for smaller creatures such as poultry. No useful purpose is served in effecting a dosing of, for example, 200 ml per ton, if the distribution is not good enough to ensure that, at each feeding with a relatively modest amount of feedstuff, the animals will at least receive a more or less representative part of the additives.
It is for this reason so important out of regard for capacity that the dosing of the additives is effected on a quickly-transported flat flow of the material, so that the sparsely dosed additives can be applied to as many of the material particles as at all possible.
It is easy to prescribe that a relevant dosing will be, e.g. 400 ml per ton, but in practice great difficulties have arisen in controlling the current dosing in order to achieve such a desired result while at the same time achieving uniform distribution, and from both the consumer and the producersr's side it has been accepted that appreciable variations can arise with regard to both under- and overdosing to the detriment of the one and the other party respectively, and without any ideal consequences for the animals to be fed.
SUMMARY OF THE INVENTION
With the present invention, the primary intention is to improve the dosing precision of the sprayed-on additives, and in such a way that a distribution of “the dosing per ton” can be effected with appreciably increased precision and good distribution to the advantage of both consumer and manufacturer. While deviations of 10-20% have traditionally had to be accepted, with the invention it will be possible to operate with deviations of only approx. 2%.
One of the uncertainties involved in the use of the down-flow of a thin layer of material on a chute will be that, due to the frictional influences which occur, the different kinds of materials can develop different speeds in their passage through the spraying station, which also applies for one and the same material type, depending on its specific gravity and degree of comminution. Even though these differences in speed are not overwhelmingly great, they can still give rise to appreciable inaccuracies in the effective liquid dosing. A controlled graduation of the spraying capacity could be arranged depending on a measurement of the down-flow speed in or close to the spraying station, but for various reasons this is difficult to realize in practice.
With the present invention it has been found desirable to retain the principle concerning the spraying of a quickly-moving thin layer of material, the reason being that this provides the possibility of good distribution of the expensive elements in the material, but it has also been found desirable to depart from the establishing of a conventional down-flow of the material, in that use is made instead of an ejection arrangement such as a bucket wheel which can eject the flat flow at a controlled desirable speed, so that the flow of material can be fed to the spraying station without having to pass along any longer, friction-generating acceleration section.
There are hereby achieved two substantial advantages, i.e. partly that the speed of the material in the spraying station will be well-controlled regardless of the kind and nature of the material, and partly—purely practical—that the relevant plant can be built with a substantially reduced construction height conventional plants based on gravitational acceleration of the material must necessarily be of a construction height which exceeds normal storey height, otherwise the fall-speed generated will be too low, and for the practical application of the invention it is extremely advantageous that a plant according to the invention can be dimensioned in such a manner that even with the quite great capacity it can still be installed in premises with norm
Beck Shrive P.
Calcagni Jennifer A.
Nixon & Peabody LLP
Safran David S.
Sprout-Matador A/S
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