Patent Application
20070114308
The invention relates to an air vortex mill for mill-drying a flowable product with a gas-air flow-through mill chamber with several grinding stages arranged in the mill chamber, formed by a rotor comprising a multitude of grinding plates and a stator housing, as well as a device for transporting the product into the mill chamber.
Utilization of an air vortex mill for not only grinding but also and predominantly for drying of wet products is known from U.S. Pat. No. 5,984,212. It is, however, a problem if the products to be dried involve viscous, sticky, oily products, which, if one doses the product laterally into the mill chamber, deposit themselves upon the rotating grinding plates, produce baked-on deposits at the outer walls—in the worst case block the mill and cause it to shut down—and which do not become dry in the short dwelling time.
In the past, one availed oneself of the remedy by first mixing these products outside of the rotor and/or prior to introduction into the rotor, in a continuously or intermittently operating mixing system with already dried product or with other products, so that said entire mixture resulted in a crumbly mass, which could be transported via proportioning screw, and which was then conducted to the rotor for mill-drying.
Such work involving the mixing drum constitutes additional equipment expense, added thermal burden for the retro-mixed product, an additional burden perhaps also for the mill-drying process, need for additional space including further drawbacks.
An attempt to laterally pipe in similar products failed a number of times—the machine either clogged up with too large a nozzle cross-section aperture, or with sufficiently small nozzle cross-section and proper supply pressure, the nozzle became clogged, in particular due to the high temperature of the hot air which flows past the nozzle and the relatively small nozzle cross-section.
In some products, impurities cannot be avoided or cannot be removed through filtration, in particular when viscous products are involved, so that the nozzles can also be come clogged by foreign bodies in the suspension. Utilization or pre-mixing of compressed air with the nozzle and possible cooling of the nozzles did not produce the desired result.
From DE 38 11 910 A1 it is known to press wet product in foil-like thin fashion through a slit extending approximately parallel to the rotor axis, directly into the area between stator housing and grinding plates. This solution did not find acceptance on the market.
The object of the present invention is based on eliminating the problems of the initially described kind in an air vortex mill.
According to the invention, said object is solved by the characterizing features of the patent claims.
With feeding the product according to the invention, the initially named difficulties no longer occur. During operation, the product exits from the multiplicity of the relatively small exit apertures distributed over the circumference of the grinding chamber. The gas serving for drying the product directly passes the orifices and efficiently carries the product along.
Numerous additional advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments.
The invention may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention.
In FIGS. 1 to 9, the mill is respectively identified with 1, its cylindrical housing with 2, its grinding chamber formed by housing 2 with 3, the rotor located in the grinding chamber 3 with 4, the drive motor for rotor 4 with 5, and a ring-shaped product supply line with 6. On the shaft 7 of rotor 4 are located in known fashion (compare U.S. Pat. No. 4,747,550) grinding discs 8, which support grinding plates 9, arranged vertically on the pheriphery. Not shown are impingement surfaces supported by the cylindrical housing wall 2, facing the grinding plates 9. The rotor axis, essentially extending vertically, is identified with 10, the outlet of the mill with 14.
On its under-side, rotor 4 is equipped with a ventilator disc and/or a blower wheel 11. It assures adequate supply of preferably hot carrier gas, for example air, which is supplied to the mill during operation via the connection stub 12 (arrow 13). The product supply lines 6 represented in FIGS. 1 to 7 are located in the lower region of the grinding chamber 3. They are respectively fitted with a connection stub 15, leading to the exterior, by means of which the delivery of the product takes place (arrow 16). In the interior of the grinding chamber the supply lines 6 present boreholes forming outlet apertures 18, through which the supplied product enters into the grinding chamber 3. The outlet apertures 18 are essentially uniformly distributed over the circumference of the grinding chamber 3. Depending upon the supplied product, the diameters of the boreholes measure from one to several millimeters. They are appropriately designed in such fashion that the product is essentially sprayed vertically in upward direction. With the aid of the ventilator 11, arranged approximately at the level of the outlet apertures 18, and an annular disc 19 located underneath, the hot air entering through stub 12 is radially conducted to the outside in such manner that it efficiently carries along the injected or sprayed-in product (arrows 20 in
In all exemplary embodiments, the supply lines 6 are respectively designed as annular lines, which envelope the lower region of the grinding chamber 3. The objective of the essentially uniform product supply would also be attained by a supply line 6 which is designed as ring segment, which envelopes, only partially, preferably predominantly, the lower region of the grinding chamber 3. The supply line 6 may comprise several segments, which can be dismantled in simple fashion and cleaned externally. In addition, it may be appropriate to provide a device that can be operated from the outside, with the aid of which it is possible to change the cross-section of the outlet apertures 18.
In the embodiment according to
Products of more viscous consistency can be conducted in known fashion by means of a screw 25 (variations b and c). A component of variation (c) is a prior positioned mixer 26, in which the crude product can be mixed together with already dried product and other materials, such as carrier materials, added substances or similar.
In the exemplary embodiment according to
The annular line 6 of the exemplary embodiment according to
In the system depicted in
In the event that it should be necessary to cool the small pipes 41 which penetrate the housing wall 2, these may be designed with—a dual wall, and a cooling agent may flow through the thereby produced surrounding space. As depicted in
During operation of the depicted exemplary embodiments, the product to be dried exits from the multiplicity of outlet apertures 18 into the grinding chamber 3. The hot air, supplied via connection stub 12 and steered with the aid of annular disc 19 and blower wheel 11 in the direction of the outlet apertures 18, carries along the product and transports it into the grinding slot between the grinding plates 9 and the not represented impingement surfaces. There, effective vortex and drying action takes place, and, depending upon product, further comminution as well. The final product leaves the mill at 14 and is conducted—as represented for example in
The following are some examples:
When compared with state of the art methods, significant improvement is achieved in the evaporation efficiency and grinding output, amounting in some products to more than 50%.
In addition, there is the benefit that the invention also permits thorough cleaning and subsequent drying of the grinding chamber 3. For that purpose, cleaning liquid is sprayed into the grinding chamber 3 via the supply line 6. The cleaning phase is then followed by drying via hot air, which, in this case, is appropriately likewise supplied to the grinding chamber 3 via supply line 6.
The invention has been described with reference to the preferred embodiments. Modifications and alterations may occur to others upon reading and understanding the preceding detailed+description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2005 055 563.2 | Nov 2005 | DE | national |
