DE19732108C1 - Method of reducing wear on inner walls of particulates conveyance flow pipes - Google Patents

Abstract

The method involves placing, between the inner face of the pipe bore and the particulate-laden fluid conveying stream, radially extending flow channels in the wall of the pipe. The channels are used to feed a fluid sleeve surrounding the particulate laden flow. The fluid sleeve has a pressure which is at least as great as the fluid laden fluid stream internal pressure. The particulate laden fluid stream and the concentric fluid sleeve are fed into the pipe at the same position in front of the entry into the guide pipe. There can be several concentric fluid sleeves defined in the flow.

Description

The invention relates to jet pipes for accelerating and promoting fine-grained particles suspended in a fluid. Serve in particular jet pipes of this type, the fine-grained particles by means of a high-pressure jet, which is formed by a propellant gas, before accelerating in a Jet mill to be crushed by impact.

From the German interpretation DE 21 65 340 B2 is one method and one Impact jet grinding device for fine-grained and powdery solids known, the jet pipes for the acceleration of fine-grained solids in a high-pressure jet before impact crushing. There is the pointed out particularly advantageous acceleration of particles in jet pipes.

The characteristic of this type of particle acceleration for the purpose of grinding is that the particles are suspended in a fluid stream and this suspension stream is under high pressure. If the suspension flow for relaxation by a Nozzle, fluid and particles are particularly advantageous, accelerates in an energy-saving manner.

A disadvantage of these nozzles is that they can handle high Velocity through the moving particles on contact with the Inner tube wall cause high wear of the jet tubes.

In the prior art mentioned, beam pipes are therefore used which consist of a cylindrical sleeve in which interchangeable inserts are arranged. Alternatively, it is proposed that the jet pipes be rectangular Form acceleration channels, the opposite walls of which abrasion-resistant, elastic material.  

From DE 94 20 791 U1 it is known to reduce wear on the Inner walls of jet pipes to accelerate and promote in one Fluid suspended particles, the inner walls wear-reducing agents assign and flow channels with nozzles in the jet pipe wall Provide a fluid flow into the interior of the pipe.

This creates a jet pipe in which an interchangeable Wear part is used, causing wear of the jet pipe itself is prevented.

The inserts and protective coverings from the stated state of the Technology have the major disadvantage that they wear out over time and must be exchanged for new ones. This means additional Cost and time expenditure for the purchase and installation of the new Inserts or protective covers.

The use of abrasion-resistant, elastic walls, as in DE 21 65 340 B2 proposed, is inexpensive only possible with a rectangular channel cross section. The materials commonly used are subject to a certain amount Wear and must, although at longer intervals, against new ones be replaced.

Furthermore, due to the large pipe length of such jet pipes, they are high Energy losses due to wall friction can be expected.

The invention is therefore based on the object of a generic Specify the method by which energy losses due to wall friction are reduced and wear on the inner wall of jet pipes is avoided.

This object is achieved according to the characterizing part of claim 1 solved that between the inside of the jet pipe and the particle-laden Fluid flow via flow channels running radially in the jet pipe wall at least one particle-free, concentric, along the conveying direction of the Jet pipe extending jacket fluid flow is introduced, the pressure  at least the local highest internal wall pressure of the particle-laden Fluid flow is set accordingly or larger.

The jacket fluid flow represents a boundary layer that the particle-laden Keep the fluid jet away from the inner wall of the jet pipe.

In the measures according to the invention, the local suspension pressure is always which changes over the length of the jet pipe. He has to be in everyone Case be less than or equal to the supplied, particle-free fluid flow. In the The most favorable fluidic design is the particle-free one Sheath fluid flow automatically through the high-speed suspension flow sucked in.  

The energy content of the supplied jacket fluid stream can lead to an additional one Acceleration of the particles can be used. An improvement in the effectiveness of Particle acceleration in jet pipes according to DE 21 65 340 B2 is therefore also in expected from an energetic point of view.

The essential structural embodiments are described below with the aid of Described drawings.

Fig. 1 shows the cross section of a jet pipe according to the invention in which the concentric jacket fluid flow is introduced into the jet pipe before the entry of the particle-laden fluid flow.

The recessed nozzle contour should be mentioned as a special feature because the introduced jacket fluid flow enveloping the particle-laden central jet should lay. The nozzle extension must be the turbulent mixing of the two Take rays into account. The suspended particles should pass through the Sheath fluid flow receive a pulse directed to the axis of symmetry of the nozzle.

Fig. 2 shows the cross-section of a radiant tube according to the invention wherein a plurality of sheath fluid flows concentrically to one another and distributed over the length inserted into the radiant tube.

This embodiment takes into account the turbulent mixing because it does not is to prevent particles from blocking the jacket fluid flow after a long distance punch through. The inflow offset over the length ensures the repeated one Building new boundary layers.

Fig. 3 shows the cross-section of a radiant tube according to the invention in which the concentric sheath fluid stream is introduced via the lance length continuously in the jet and the jet pipe wall consists of a material having pore structure.

To adjust the local, over the length variable pressure levels can the jet pipe may be surrounded by several separate chambers. The Partition walls of the chamber can optionally be led into the porous nozzle material to avoid flow short circuits.

Fig. 4 shows the cross-section of a radiant tube according to the invention in which the concentric sheath fluid stream is introduced via the lance length continuously in the jet pipe and having the jet pipe wall radially extending flow channels.

In the embodiment variant shown, one is fed Fluid flow under such high pressure, so that the locally highest Internal wall pressure is overcome. The lower for flow sections Require inflow pressures, these z. B. about changes in wall thickness Nozzle reached. Starting from an optimal inner contour of the jet pipe in the flow area, the different wall thicknesses are indicated by a adapted radiant tube outer contour.

Generally, adapting to local pressure levels can not only be done via Changes in wall thickness can be brought about, but also about changes the pore structure, pore size, channel shape, channel cross-section or similar

Basically, the jet pipe according to the invention can be used both for Gas flows can also be used for liquids. It is also possible also a liquid stream as a jacket fluid stream for a gas jet pipe use. This has the advantage that the boundary layer is more stable and not so particles can penetrate quickly. It is also possible that a Liquid is used as the jacket fluid flow, which is in the non-critical, divergent The jet tube part evaporates, i.e. no more than in the emerging suspension separate phase occurs.

Claims (11)

1. A method for reducing wear on the inner walls of jet pipes which serve to accelerate and convey particles suspended in a fluid, wear-reducing agents being assigned to the inner walls and flow channels for introducing a fluid flow into the pipe interior being provided in the jet pipe wall, characterized in that that at least one particle-free, concentric jacket fluid stream running along the conveying direction of the jet pipe is introduced between the inner wall of the jet pipe and the particle-laden fluid stream via flow channels running radially in the jet pipe wall, the pressure of which is adjusted at least to the local highest inner wall pressure of the particle-laden fluid stream. 2. The method according to claim 1, characterized in that the particle-laden Fluid flow and the concentric jacket fluid flow in the same place the inlet into the jet pipe. 3. The method according to claim 1 or 2, characterized in that the concentric jacket fluid flow in front of the narrowest cross section of the jet pipe is introduced. 4. The method according to any one of claims 1 to 3, characterized in that several jacket fluid flows concentric to each other in the jet pipe be introduced. 5. The method according to any one of claims 1 to 4, characterized in that the concentric jacket fluid flow continuously in the nozzle is inserted. 6. The method according to any one of claims 1 to 5, characterized in that the jacket fluid flow is introduced via flow channels, the number in axial direction is changed.   7. The method according to any one of claims 1 to 6, characterized in that the jacket fluid flow is introduced through holes in the jet pipe, whereby for the bores are preferably selected to have different diameters. 8. The method according to any one of claims 1 to 7, characterized in that the Adjustment of the local pressure level of the particle-laden fluid flow is carried out by a material of the jet pipe wall with a pore structure, preferably by choosing a different packing structure of the pore structure in axial direction. 9. The method according to any one of claims 1 to 8, characterized in that the Adjustment of the local pressure level of the particle-laden fluid flow by changing the wall thickness of the jet pipe, preferably by continuous Change in wall thickness. 10. The method according to any one of claims 1 to 9, characterized in that the jacket fluid flow is introduced into the jet pipe at high pressure. 11. The method according to any one of claims 1 to 10, characterized in that the jacket fluid flow from the particle-laden fluid flow is higher Speed is sucked.