Patent Application
20050253000
The invention relates to a method and an apparatus for the disintegration and tribochemical activation in particular of inorganic materials.
Disintegrators are known for a number of applications. In cement production, for instance, on the industrial scale, chunks of limestone and various additives are first comminuted, then heated to temperatures of 1400° C. to 1600° C., sintered, and then ground to the desired grain sizes. The disadvantage of this method is that a large amount of energy is needed for activating the starting materials.
Known from DE 195 48 645 is attaining an elevated potential energy content and thus increased chemical reactability using tribochemically treated crystals. For instance, mechanical activation of cement facilitates a substantial increase in the strength of the hydrated mineral bonding agent. The reasons for this are the primary particle size and the lattice distortions of these particles.
A plurality of processing methods are available for tribometric processing of starting materials such as e.g. grinding by stressing between two surfaces, or using collisions between freely mobile particles and solid surfaces or collisions among the particles themselves. So-called disintegrators are used for inserting high potential energy into the smallest of particles on a scale of a few 1 μm and for thus causing lattice distortions. The construction principle is characterized by two pin rings or ring gears. In one variant, as described in DE-AS 12 36 915, the particles are comminuted in collisions with pins or teeth. At least three collisions with pins at intervals of no more than 50 ms at a relative speed of at least 15 m/s are required for adequate activation. In this arrangement it is disadvantageous that the wear on the pins is very high, especially when using very hard starting materials.
In another variant, e.g. in accordance with DE 30 34 849 A1, the starting material is primarily comminuted using particle collisions in vortices, the vortices being generated by specially shaped blade rings driven in opposite directions. At the same time wear is substantially reduced on the edges of the blade rings or ring gears that are impacted.
The activation that can be attained with known disintegrators or mills is not adequate for developing novel inorganic bonding agents. Particularly when there are small, light-weight particles such as occur after brief milling, it is not possible to cause these particles to collide at a high relative speed of for instance greater than 100 m/s by embedding these particles in a stream of air or in an air vortex.
The object of the invention is to provide a method and an apparatus for disintegration in which dynamic treatment of the particles occurs with substantially increased energies and rates of effectiveness compared to the prior art. This object of the invention is attained using a disintegrator of the generic type indicated in the foregoing in which the starting materials in the form of a granulate are subjected to impact pressure waves from a broad frequency spectrum and a pulse duration of less than 10 μs. Further comminution of the particles, destroying the crystal lattice structure, occurs due to the effect of the impact pressure waves striking the particles in quick succession at supersonic speed. As a result of this comminution, a conglomerate of mixed crystals occurs that have an increased capacity for crystal formation when water is added later. The impact pressure waves are generated by shaped bodies with aerodynamically shaped profiles and surfaces that are accelerated to the so-called transonic range. With these, impact pressure fronts are generated that pulverize the granulate introduced into the disintegrator to the desired particle size. The shaped bodies move on disks just below supersonic speed. Because of the effect of high mechanical energy, in addition to being comminuted, the particles are activated and thus undergo a change in chemical properties.
In the case of organic substances, pretreatment is required for the purpose of reducing elasticity.
If the relative speed of the air flowing against the shaped bodies, including the particles suspended in the air, is now just below sound velocity, the flow speed can in part reach supersonic speed relative to the shaped body. The speed range below sound velocity at which the air flowing around the formed bodies in part has supersonic speed is called the transonic speed range in the literature (Sigloch: Technische Fluidmechanik, VDI Publishing, 1996).
Appropriate protective gases can be employed instead of air for avoiding chemical reactions.
Depending on the shape of the aerodynamically shaped body, the transonic speed range commences at 0.75 . . . 0.85 Mach and terminates when the shaped body attains sound velocity with regard to the air flowing against it.
If the speed of the air flowing against it relative to the shaped body is in the transonic speed range, supersonic speed relative to the aerodynamic profile of the shaped body occurs in a zone. This zone of air flowing supersonically relative to the shaped body is limited by a forward front, a rear front, and the profile of the shaped body. A transition from supersonic speed to normal speed takes place on the rear front. This transition is accompanied by an impact pressure front, i.e. the air pressure rises to a multiple of normal pressure and then returns to normal pressure after a brief low pressure phase. The special characteristic of this impact pressure front is that the change in pressure is theoretically limited to a few molecule lengths, but in practice it is on the magnitude of 100 μm due to heating and vortices, and in any case is very short with respect to the geometry of the shaped bodies.
These effects are adequately known in the development of support surface profiles for supersonic aircraft and are undesired. The impact pressure front severely stresses the exterior skin of the wings. In addition, the compression of the air into an impact pressure front requires increased propulsion energy for the aircraft. There is therefore an attempt to moderate the effects of the transonic speed range and to overcome this range rapidly (“break the sound barrier”) by specially designing the support surface profiles.
In accordance with the invention, the effects of the transonic speed range are used for the comminution and activation of mineral granulate. The use of the impact pressure front is very efficient due to two factors. First, the impact pressure front is a very brief pulse with a build-up time of a few μs. Second, the immediate succession of pressure increase and pressure decrease is very effective in terms of mechanically stressing the granulate. In terms of spectrum, the pressure impact can be understood as the sum of pressure waves of very different frequencies. Thus, depending on the steepness of the pressure impact, frequency portions of pressure waves with a few 100 kHz are also included. Therefore portions of a characteristic breaking frequency that is particularly effective in the direction of the desired comminution and activation occur for different particle sizes and consistency.
The inventive structure of the disintegrator thus subjects the granulate, that is, the particles, to several hundred of these impact pressure fronts successively. This is initially attained by using a plurality of shaped bodies that rotate about a common axis. In addition, a counter-rotating group of shaped bodies prevents the relative speed of the shaped bodies from being reduced with respect to the air with the embedded granulate, that is, particles, due to pulling effects. Thus the particles move relatively slowly, relative to sound velocity, through the disintegration space due to alternating pulling of the particles in the one or other direction.
The repetition rate of the impact pressure fronts is in the supersonic range, are inaudible, and can be dampened relatively well to protect operators.
When the forward surfaces of the shaped body are designed suitably, the particles seldom collide with the shaped bodies because in particular smaller particles are pulled around the surface of the shaped bodies. It is not necessary to provide special armoring or protection of the forward surfaces of the shaped bodies. It is only on the outlet side, that is, in the rear area relative to the flow, that higher loads occur at the point of intersection between the impact pressure front and the surface of the shaped body, and these loads can be supported by suitable materials such as high-alloy tool steels. It is useful to design the surface of the shaped body as a so-called sub-critical profile, that is, the flow around it is largely laminar (Sigloch: Technische Fluidmechanik; VDI Publishing, 1996). The shaped body is for instance rounded on the forward front and its off-flow surfaces meet at an acute angle.
The invention is described in greater detail in the following using an exemplary embodiment.
a illustrates the profile of the shaped body, with the flow going around it in the sub-sonic range;
b illustrates the position of the supersonic range relative to a shaped body that is in an air flow in the transonic range;
a illustrates a typically shaped body 1 together with flow lines 9 in the subsonic range. The flow lines 9 initially flow in a laminar manner around the profile of the shaped body 1, whereby, depending on the profile of the shaped body 1, the laminar flow can tear away in the rear area of the shaped body 1 and turbulences 3 can occur.
b illustrates the speeds in the so-called transonic speed range. Relative to the surface of the shaped body 1, a zone forms in which the relative speed of the flowing air in part attains sound velocity. The region is labeled “Ma>1” in
The granulate 7 is added via the filling hopper 31 near the center of the disintegrator to the filling chamber 18. Here the granulate 7 travels into the area of the impact pressure fronts 4 and is pulverized on the way to the exterior areas.
In the design of the inventive disintegrator it should be noted that the disks 15 and 16 rotating at great speed and the shaped bodies 1 affixed thereto pull air along with them, and this air is driven outward by centrifugal forces. While in the disintegration space 29 a continuous change occurs in the rotational speed and thus the speed of the particles 30 is decelerated again and again, the centrifugal force for the two exterior surfaces 38 and 39 of the two disks 15 and 16 remains unchanged. In particular for the disk B 16, through which passes the filling hopper 31, the centrifugally accelerated air can lead to undesired suction of the granulate 7 out of the filling hopper 31 at the external surface 39 of the disk B 16 and granulate 7 can be conveyed directly to the outlet 34, circumventing the effects of the shaped bodies 1. This effect can be corrected when the exterior surface 39 of the disk B 16 is relatively well sealed against the housing 20 by a sealing ring 35. Another solution for this problem is to arrange scoops 19 on the exterior surface 39 of the disk B 16; these then counteract the centrifugal force using an opposing air flow.
After passing through the disintegrator space 29, the particles are removed at the outlet 34, as can be seen in
It has been demonstrated that having the granulate 7 pass through the disintegrator just one time is adequate in terms of the desired comminution and activation. The described apparatus works continuously. As much granulate 7 as can be added to the filling chamber 18 based on the geometry of the filling hopper 31 becomes fully prepared powder made of particles 30 at the outlet 34.
Legend
| Number | Date | Country | Kind |
|---|---|---|---|
| 102 48 612.3 | Oct 2002 | DE | national |
| 102 59 456.2 | Dec 2002 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/DE03/03402 | 10/14/2003 | WO | 7/6/2005 |
