Plastic and nonmetallic article shaping or treating: processes – Formation of solid particulate material directly from molten... – By extrusion spraying or gravity fall through orifice
Patent
1995-05-25
1996-09-24
Theisen, Mary Lynn
Plastic and nonmetallic article shaping or treating: processes
Formation of solid particulate material directly from molten...
By extrusion spraying or gravity fall through orifice
264 5, 264 8, 425 6, 425 8, B29B 910
Patent
active
055588212
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention concerns a method and an apparatus for purifying the exhaust air of installations for consolidating molten substances that are delivered onto cooling surfaces, in particular onto a cooling belt, and solidify there.
Methods and apparatuses of this kind are known (EP 0 012 192 BI). In devices of this kind used in practice, in order to extract the vapors released by the molten substance, for example sulfur vapors, the entire device is covered by an extraction hood which ensures that the resulting exhaust air can be removed and purified in a defined manner. This is generally done by means of downstream filters, which are relatively complex. A disadvantage of the known purification methods is that the quantities of dust removed with the exhaust air, which can be considerable, are lost for purposes of product generation.
The underlying object of the invention is to implement a method and an apparatus of the aforesaid kind in such a way that less product dust occurs from the outset.
SUMMARY OF THE INVENTION
This object is achieved by the method according to the invention by the fact that the pressure difference between the vapor pressure of the molten substance after delivery onto the cooling surfaces and the saturation pressure in the space through which the solidifying molten substance passes, as well as the flow velocity of the vapors given off by the molten substance, are kept as small as possible.
With this configuration the precipitated quantity (proportional to the difference in vapor pressure) that occurs as dust can be kept small from the outset. If the vapor flow velocity, on which the separated quantity also depends proportionally, also remains low, it then becomes possible to prevent most dust production, so that complex downstream purification devices for the exhaust air can largely be dispensed with. In a development of the method according to the invention, the saturation pressure is matched, in a simple manner, to the vapor pressure ratio of the molten substance as it cools by heating the space through which the molten substance passes. This feature makes it possible, especially in the case of materials such as sulfur which crystallize readily, to match the respective active pressure of the product as closely as possible to the saturation pressure, which depends on temperature. The quantity of product crystallizing out thus becomes smaller, less dust occurs, and purification can be less complex.
The method according to the invention can be performed in a particularly simple manner, with an apparatus that possesses a delivery device for the molten substance and a cooling belt circulating beneath it, on which the molten substance is guided to a removal point and is thereby solidified, if the delivery device and the cooling belt are covered by a hood provided with heating devices, the heating devices of which can be controlled such that the temperature beneath the hood can be modified in the direction in which the belt travels. The hood can be placed as close as possible to the cooling belt so that the space available for the vapors remains as small as possible and the flow velocity of the vapors that would otherwise rise upward is minimized. Lastly, it is also advantageous to provide sealing means at the entry and exit point between cooling belt and hood so as to keep leakage as low as possible and eliminate dust production in this manner as well. In a particularly simple embodiment, the hood .can consist of a double-walled panel, running parallel to the cooling belt, with controllable heating elements set in it.
BRIEF DESCRIPTION OF THE DRAWING
The invention is shown in the drawing with reference to an exemplary embodiments, and will be explained below.
The single drawing schematically shows an apparatus for producing granulated material from a molten substance, which operates with a cooling belt. Associated with the schematically depicted device is a diagram showing the change in vapor pressure of the molten substance delivered onto the cooling belt
REFERENCES:
patent: 3473740 (1969-10-01), Davis
patent: 5286181 (1994-02-01), Schwager
patent: 5295799 (1994-03-01), Prewitt
patent: 5332378 (1994-07-01), Harreither
Santrade Ltd.
Theisen Mary Lynn
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