Drying and gas or vapor contact with solids – Apparatus – Rotary or swinging carrier or rack
Reexamination Certificate
1999-03-25
2001-01-09
Ferensic, Denise L. (Department: 3749)
Drying and gas or vapor contact with solids
Apparatus
Rotary or swinging carrier or rack
C034S179000, C034S183000
Reexamination Certificate
active
06170168
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns an annular drying element. Such drying elements, which constitute a heat exchanger, are used in drying plants for indirect heating or cooling of moist, comminuted materials, e.g. biological materials such as fishmeal, comminuted offal from slaughterhouses, mash from breweries and similar materials of animal, vegetable or chemical origin.
The drying plant comprises a stationary housing and a rotatable rotor with a number of annular drying elements disposed at intervals. The rotor has means for supplying the medium for heating or cooling. For heating, steam is often used, and thus the rotor is also provided with means for the removal of a condensate thereof.
2. Description of the Prior Art
Plants of this type are known, e.g. from U.S. Pat. No. 3,923,097 (Atlas, DK) and U.S. Pat. No. 4,982,514 (Atlas, DK), and have been in use for many years. The plants have an opening in the one end for the supply of raw material, and an opening in the opposite end for the removal of the material after it has been treated. The transport through the plant is effected mainly as a consequence of the continuous filling with new raw material and the continuous removal of the treated material, but the transport can be increased or reduced by using vanes, lifting elements or the like, e.g. disposed directly on the drying elements. The transport through the plant is possible because the annular drying elements do not extend completely out to the stationary housing. Rotating driers with stirrers or transport vanes are known, e.g. from U.S. Pat. No. 3,800,865 (Stord Bartz, NO) or U.S. Pat. No. 3,777,810 (The Strong Scott Company, US).
In older constructions, cf. e.g. GB Patent No. 952,099 (A/S Myrens Verksted, NO), use has been made of a rotating drier with drying elements built up of tubes, e.g. annular or helical tube constructions, which can be configured so that the steam condensate is led towards a tapping-off point during the rotation. Furthermore, from U.S. Pat. No. 4,074,751 (Unice Machine Company, US) there are known rotating heat exchangers of tubes arranged for the heating or cooling of a fluid mass, e.g. sugar massecuites.
In the latter two constructions, the product to be heat treated or dried is fed forward in the plant by passing through the openings in the drying elements which arise between the tubes. This can have advantages with regard to the stirring and the transport of the product, but has great disadvantages with regard to the avoidance of the product settling on the drying element. Moreover, drying elements of this kind do not have as large a heating surface as the plate-formed drying elements mentioned earlier.
SUMMARY OF THE INVENTION
The invention also concerns a drying plant. If a drying plant with drying elements as explained above is to be used for the heat treatment, drying or cooling of a relatively fluid product, e.g. a very greasy or oily product, e.g. the boiling of oil- or fat-containing offal from slaughter-houses, the stirring in the product mass can cause increased processing time. Therefore, the need can arise for an increase in the stirring of the product mass.
By configuring the annular drying elements according to the invention, it is achieved that all of the known advantages with plate-formed drying elements are retained, and at the same time the possibility is provided of obtaining a changed product-flow through the plant.
There are many advantages from the point of view of production technique with drying elements of plate-formed elements, and as a rule a greater heat-exchange surface is achieved than with drying elements configured as tube constructions.
Moreover, the drying element of the kind disclosed in the application has advantages in that it can be produced by the welding together of parts which are configured in such a way that the welding can be automated in a simple manner by using automatic welding machines or welding robots, which reduces the production costs.
The openings in the annular plate elements are preferably configured by the insertion of a tube piece in each opening, preferably so that the longitudinal axes of the tube pieces are parallel with the axis of the drying element. Good possibilities are hereby achieved of simplifying the production of the drying elements.
However, the annular drying element according to the invention is preferably configured in such a way that it is built up of two substantially identical plate elements and, preferably has tube pieces inserted as stays between the plate elements at their oppositely-lying openings. There is hereby achieved a great degree of simplification in the production of the drying elements, and at the same time herewith a very strong and rigid construction is achieved which can tolerate a high pressure, which makes it possible to use steam at a high temperature as the heating medium.
The tubular stays are preferably configured with a circular cross-sectional profile. Among other things, this makes it possible to use tubes of standard manufacture which can be cut off in the desired lengths.
The tubular stays are preferably distributed over the surface of the drying element, so that there is minimal deflection or deformation of the drying element when pressurized steam is used as the heating medium.
The length of the tubular stays can be at least the thickness of the element. If the tube length corresponds to the thickness of the element, there is the possibility of being able to use scraping elements in the drying plant which scrape the drying elements clean, which e.g. can be relevant at that end where the product is most moist, or in that zone where the product is the most sticky. However, the tubular stays can also be of a length which is greater than the thickness of the element, and the free ends of the tubes can be configured so that they constitute a carrier or a stirring element for the product to be dried.
For certain constructions, it can be an advantage to configure the drying element by making use of tubular stays with different clearances on the same drying element. The possibility is hereby achieved of variations regarding where there may be larger openings and where there may be smaller openings on the drying element.
Finally, the drying element according to the invention can be configured in circles concentric with an outer edge of the drying element which offers important advantages from the point of view of production technique.
By configuring the plant a number of annular drying elements an increased stirring in the product mass can be achieved without this giving rise to other substantial disadvantages. An increased stirring will result in a quicker treatment of the product mass, e.g. possibility of quicker heat treatment, which increases the capacity of the plant. The mounted axial elements serve as stirrers and, depending on their configuration, also as lifting elements, so that the product mass can be stirred thoroughly if there is a need for it.
How many axial elements are mounted and which form they shall have will depend on the current conditions and the actual product, e.g. the degree to which it is desired to increase the stirring, and to what degree the transport of the product can possibly be desired to be reduced, in that the elements fill out some of the through-going openings in the rotor's drying elements.
Depending on how the stirring is desired to be carried out, the elements can be configured to extend over all of the drying elements. In brief, the number and the length of the axial elements are contributory factors in determining where in the drier an increased stirring is desired, and how great the increased stirring shall be.
It can be an advantage if the elements are configured as a tube with clearance. When using tubes as elements, e.g. tubes with circular cross-sectional profile, in many respects a suitably increased stirring is achieved without any considerable increase in the weight of the rotor. An advantage here is also that use can be made of standard tubes as
Fosbøl Peder
Jørgensen Finn
Antonelli Terry Stout & Kraus LLP
Atlas-Stord Denmark A/S
Ferensic Denise L.
Mattera Michelle A
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