Vortex mill for controlled milling of particulate solids

Details Vortex mill for controlled milling of particulate solids Vortex mill for controlled milling of particulate solids

2002-02-20

2004-09-14

Rosenbaum, Mark (Department: 3725)

Solid material comminution or disintegration

Processes

By utilizing kinetic energy of projected or suspended material

C241S039000, C241S097000, C241S080000

Reexamination Certificate

active

06789756

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to the milling of solids by use of vortex mills, generally, and more specifically, to the controlled milling of solids thereby.
BACKGROUND OF THE INVENTION
It is known in the art to provide a means for the comminution of particulate solids. Many different milling devices are known. These include, for example, grinding mills, ball mills, rod mills, impact mills, jet mills and vortex mills. With the exception of the jet and vortex mill, in order to obtain particle comminution, most mills rely on an interaction between the particulate solid and another surface, such as the balls in a ball mill, or a baffle or impact surface in an impact mill. Jet and vortex mills do not rely, for their effectiveness, on interaction with other surfaces for particle disintegration. In addition, mills generally provide a milled product having a broad range of particle sizes, including significant proportions of oversized and undersized particles. Specifically, most mills are relatively difficult to control in so far as accurately predetermining a desired final particle size or, more particularly, a specific range of particle sizes. Furthermore, avoidance of excessive proportions of either oversize or under-size particles is often problematic.
In the art a distinction is made between jet pulverizing systems or jet mills and whirl or vortex chamber mills. Generally, in jet mills, particulate solids to be milled are introduced into a chamber where the working fluid is accelerated to high speed using venturi nozzles. Moving at a high speed, particles collide with a target such as a deflecting surface or with other moving particles in the chamber. Specifically, in jet mills particles are milled as a consequence of a collision effect. Operating speeds of particles in jet mills are generally not less than 150-300 m/s. Such jet mills are described for example in U.S. Pat. No. 5,133,504. In other jet mills, introduced coarse particles collide with intersecting high speed fluid jets, to achieve a higher collision speed, as described for example in U.S. Pat. No. 4,546,926. However, in all such jet mills, the problem of producing a range of particle sizes and of controlling the extent of comminution is not fully solved, in so far as the elimination or reduction of production of undesirable, excessive, undersized particles is concerned. Furthermore, such production of undersized particles represents an increase in energy consumption.
Use has been made of whirl or vortex chambers in conjunction with jet mills for the classification or sorting of the ground material emerging from jet milling. In such combined systems the relatively coarse particles are recirculated from the whirling classifier back into the jet mill. Such systems are described, for example, in U.S. Pat. No. 4,219,164, U.S. Pat. No. 4,189,102 and U.S. Pat. No. 4,664,319. In such systems, however, vortex chambers do not effect the milling operation, but rather particle size classification.
Another development of this technology is referred to, for example, in U.S. Pat. No. 4,502,641, which constitutes a combination of jet milling with a vortex chamber. Material to be milled is introduced through a venturi nozzle into a vortex chamber at a speed of about 300 m/s. There is created, in the vortex chamber, a fluid vortex rotating at a substantially lower speed. In the course of the milling process, particles injected into the chamber rotate in the relatively slow fluid vortex and become targets for further high speed particles injected through the venturi nozzle. Collision between particles moving in the vortex and particles introduced through the venturi nozzle, results in impact comminution as in the case of jet-mills mentioned heretofore.
There are further known in the art, vortex chambers which perform so-called resonance whirl or vortex milling. This milling process differs significantly from jet milling. For example, the particle speed in whirl chambers is considerably lower than that in jet mills and the high-speed injection of feed particles into jet mills is unnecessary in vortex mills. Fluid speed through the nozzles of a vortex chamber is generally in the range 50-130 m/s, and particle rotational speed in the vortex chamber no more than 50 m/s. At such low speeds, jet mills become ineffective. Referring to WO 94/08719, WO 98/52694 and SU 1,457,995, there are described whirl or vortex chamber milling devices, fitted with tangential fluid injection nozzles, which carry out “resonance vortex grinding”. The working chamber includes a generally cylindrical body with one or more openings for the introduction of particulate solids. During the milling process, particles reaching the required particle size range are continuously discharged via an axial discharge duct. Further, there may be provided sound generators in the inlet fluid nozzles for interacting with the incoming fluid flow and thereby enhancing the grinding operation as described in WO 94/08719. Additionally, the chamber may be provided with a rotatable internal side-wall adapted for rotation in the direction opposite to the direction of rotation of the vortex as described in SU 1,457,995.
U.S. Pat. No. 5,855,326 to Beliavsky, the present inventor, entitled “Process And Device For Controlled Comminution Of Materials In A Whirl Chamber,” describes a process for the controlled comminution of particulate solid material. The process includes the tangential injection of a working fluid into a working chamber, and the introduction thereinto of particulate solid material. A vortex is created in the chamber and the particulate material undergoes comminution. Control of the milling and the particle size is achieved by accelerating or retarding discharge of the particles from the chamber and by the interaction of particles with mechanical elements provided in the chamber. Particles are caused to move in a random manner in all directions within the vortex and to be retained within the vortex by such mechanical elements. There is further described a cylindrical whirl chamber having an inlet into the chamber for working fluid, means for introducing particulate solid material, a discharge nozzle, and one or more mechanical elements for control of the comminution process.
It is desirable to improve and increase the amount of control in respect of the milling process, particularly with regard to the extent of comminution, to the rate of comminution, to energy conservation and to predetermined particle size.
NOTES
In the description of the present invention, terms such as “top”, “bottom”, “upper”, “lower”, “height” and “side” are utilized for convenience of description and are not necessarily intended to indicate an orientation in space.
SUMMARY OF THE INVENTION
The present invention aims to provide an improved controlled comminution of solids relative to known art.
There is thus provided in accordance with a preferred embodiment of the present invention an improved vortex mill for milling a substantially particulate solid material. The mill includes one or more working chambers having a side-wall defining a generally cylindrical, inward facing surface and a first and a second end wall arranged transversely to the side-wall. The end surfaces are formed contiguously with and transversely to the inward-facing surface, thereby to define therewith each of one or more working chambers.
The mill also includes one or more working fluid inlets for introducing a generally tangential flow of working fluid into the one or more working chamber thereby to create a vortex flow therein. One or more discharge ports are formed in one or more of the end walls, for permitting discharge of working fluid and milled material from the one or more working chambers. One or more working fluid inlets together with one or more discharge ports facilitate the vortex flow within the one or more working chambers For introducing a substantially particulate solid material into the one or more working chambers so as to be taken up in a vortex flow of the working fluid, there are one or

Affiliated with

Also associated with

Rating

Vortex mill for controlled milling of particulate solids does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Vortex mill for controlled milling of particulate solids, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vortex mill for controlled milling of particulate solids will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3271385