WO2005028115A1

WO2005028115A1 - Improved acceleration nozzle for gas-solids suspension

Info

Publication number: WO2005028115A1
Application number: PCT/FI2003/000685
Authority: WO
Inventors: Jouko Niemi; Jarkko Tamminen
Original assignee: Micropulva Ltd Oy
Priority date: 2003-09-19
Filing date: 2003-09-19
Publication date: 2005-03-31
Also published as: EP1667797A1; AU2003262609A1; EP1667797B1; ATE510626T1

Abstract

The invention relates to an improved acceleration nozzle for gas-solids and a counterjet pulverizer as well as a pulverizing and a classification part for such an acceleration nozzle. The acceleration nozzle is therefore known that in the outlet end of a conventional acceleration nozzle (1) a tubular head (2) is arranged, the flow channel (3) of which is either throughout of the same size or at least as to its end portion tapering the flow direction and in the wall of the head from the direction of the flow channel (3) middle axis (A) several diagonally outwards reaching gas outlet channels (4) are made.

Description

IMPROVED ACCELERATION NOZZLE FOR GAS-SOLIDS SUSPENSION

This present invention relates to an improved acceleration nozzle for gas-solids suspension and a counterjet pulverizer as well as a pulverizing and a classification part.

Usually, in order to accelerate the gas-solids suspension a tubular nozzle is used, the inside diameter of which is either throughout of the same size, or if higher speeds are aimed at, on the output side slightly tapering and on the inlet side slightly expanding.

For instance, in order to reach sufficient speed in order to grind particles of solids, the content of solids of the gas-solids suspension must be relatively low. Therefore, quite a great lot of gas gets into the pulverizing chamber, which partly disturbs the actual pulverizing. In principle the pulverizing procedure needs no working gas. A part of working gas can be removed, after the particles in the nozzle have reached their optimum speed. So it would be desirable to find a means for steering the excess gas out before the pulverizing zone.

This target is reached by means of the acceleration nozzle according to this invention, which is known in that in the outlet end of the conventional acceleration nozzle a tubular head is arranged, the flow channel of which is throughout of the same size or at least to its end portion tapering in the flow direction and that in the wall of the head, from the direction of the flow channel middle axis, several diagonally outwards reaching gas outlet channels are made. Due to this solution, as to their mass greater, typically close to the middle axis of the nozzle moving coarse particles of solids, which have to be ground, have no time to turn to the gas outlet channels, but continue their motion forward according to the law of consistency loosing only a little of kinetic energy developed in the nozzle. In a case, where the head is to its end portion tapering the gas outlet channels are at the beginning of the said head, where the speed of gas-solids suspension is high. Then the amount of particles and the kinetic energy grow further per unit area due to the tapering of the head, when again a part of the quantity of gas used for initial acceleration of the of gas-solids suspension gets out from nozzle over said gas outlet channels. Also the smallest particles of suspension, which need no additional pulverizing, leave over these said gas outlet channels. The gas outlet channels in question are advantageously placed at regular intervals side by side in circular order forming at least one circular ring. If one wants to keep the cross- section of separate gas outlets small said channels can be arranged in several circle rings. The best effect is reached, when suspension gets into the gas outlet channel without causing turbulence in the beginning of gas outlet channels. This is reached if the gas outlet channel forms with the middle axis of the flow channel an angle of 45°.

According to the invention the gas outlet channels can as to their cross-section be, for instance, rectangular or circular and throughout of the same size or as to their end portion tapering or as to their form conical and circular and in some cases they can have the form of longitudinal slits reaching to the outlet of the head.

Since the most tearing part of the acceleration nozzle is its head, it is according to a most advisable embodiment of the invention detachably fixed to the outlet head of the acceleration nozzle. Then the tapering of the flow channel of the head and at the same time the beginnings of the gas outlet channels are advantageously in the central area of the head. In the end portion of the head the flow channel tapers advantageously so that the decrease of its cross-section corresponds at least the to total cross-section of the inlets of the gas outlet channels and is about 20° of the cross-section of the beginning of the of the head flow channel. The length of the tapering head from the inlet hole of the gas inlet channels to the outlet of the head must be chosen mainly on the basis of consistency and properties of the material to get ground. If the pulverizing material is very light and fine the length of the tapering portion must be very short, while the material to be ground is of more coarse and heavier quality, the tapering part can be relatively long.

Acceleration nozzles of above presented types can be advantageously installed in the pulverizing chamber of the counterjet pulverizer so that two such acceleration nozzles are installed on the opposite sides of the pulverizing chamber as reaching and directed to a common spot in the central part of the pulverizing chamber. The middle axis of the acceleration nozzles intersect advantageously in an angle a little smaller than 180°. In such a counter-jet pulverizer coarse particles of solids accelerated to high speed fly straightforward to the point of collision of both jets of gas-solids, where they hit flying particles of gas-solids and carry out pulverizing. A part of working gas gets out from the accelerating nozzles throughout said gas outlet channels so that they do not cause opposite disturbing gas flows in the pulverizing zone itself Due to the outlet gas channel the heads of nozzles can be taken quite close to each other without notable growth of back pressure. Due to these gas outlet channels less air comes to the collision area, which also has effect on that the exit of particles from the collision area slows causing the particles a pulverizing an impact more effect and longer pulverizing duration.

According to a recommended embodiment between the outlets of both acceleration nozzles a thick spacer plate is arranged, in which there is a passing opening almost as big as the outer periphery of the acceleration nozzle at the intersection of the middle axis of these acceleration nozzles. Then in the said passing opening a marked off pulverizing zone is formed since the sides of the spacer plate steer effectively the gas flows from the gas outlet channels out of the pulverizing zone in question. The best outcome is reached, if the spacer plate has such a form that each lateral face forms a right angle with the middle axis of the accelerating nozzle directed on it.

The pulverizing chamber of the counterjet pulverizer is advisedly cylindrical as to its cross-section, in the one or both ends end of which there is the outlet of ground gas- solids suspension and the nozzles reach through the cylinder mantle.

According to another embodiment a cylindrical partition wall is placed concentrically in the cylindrical pulverizing chamber of the counterjet pulverizer, through which wall the heads of the acceleration nozzles extend so much that the gas outlets end outside the cylindrical partition wall. Then one can be assured that all the amount of gas that leaves through the gas outlet channels takes with it fines that needs no pulverizing, whereby before pulverizing it gets separated from the flow of solids to get ground, whereby pulverizing takes places in a space, where there are no outside gas flows. The composition of gas and fines is advantageously led fully separated off the pulverizing chamber and taken for safekeeping, whereas material ground inside the partition wall is led as separate flow off the pulverizing chamber. Therefore the cylindrical partition wall, is closed from its other end. So then the preliminary classification of the material-gas flow takes place. According to an advisable embodiment the portion of removing gas through the gas out let channels can be controlled regulating the pressure of the space outside the partition wall of the pulverizing chamber. This property can be utilized also in case that the equipment is used mainly as classifier, whereby so much attention is not paid to the pulverizing procedure, or it is totally given up.

In the following the invention is disclosed with reference to the enclosed drawing, where

Fig. 1 shows by way of example a detailed side view an embodiment of the head of the acceleration nozzle according to the invention, partly cut.

Fig. 2 shows the first example of the pulverizing chamber of the counterjet pulverizer according to the invention viewed in the direction of the pulverizing chamber middle axis and cut along the middle axis of the accelerating nozzles.

Fig. 3 shows the alternative embodiment of the pulverizing part of the counterjet pulverizer and the pulverizing chamber seen from the side and cut along the middle axis of the acceleration nozzles.

Fig. 4 shows the second embodiment of the pulverizing and the classification part of the counterjet pulverizer, the pulverizing chamber seen from the side and cut along the axis of the acceleration nozzles. As shown in figure 1 acceleration nozzle 1 according to the invention is formed of a conventional nozzle 1, in the outlet end of which a tubular head 2 is arranged, the flow channel of which is at least as to its end portion tapering the flow direction and that in the wall of head 2, at the beginning of the tapering, several gas outlets 4 are made reaching diagonally from middle axis A of flow channel 3 to the outside. Gas outlets 4 are advantageously placed at regular intervals side by side in circular order so that the excess gas gets off nozzle 1, 2 evenly almost from the same place in the nozzle lengthwise direction. Advantageously each gas outlet channel 4 forms an angle of about of 45° with middle axis A of the flow channel. Gas outlet channel 4 can as to its cross-section be circular or rectangular, and it can as to its cross-section be either throughout of the same size or as to its end portion extending as per figure 1.

The tubular head 2 of acceleration nozzle 1 is advantageously detachably fixed to the outlet end of conventional acceleration nozzle 1 so that when worn out it is easily replaced. Then gas outlet channels 4 are advantageously positioned in the centre of this head 2. Fixing of head to in the end of acceleration nozzle lis suitably done by means of a special fixing bushing 9.

The pulverizing chamber 5 of the counter jet pulverizer shown in figure 2 is as to its cross-section cylindrical, whereby two acceleration nozzles 1 with their heads 2 reach from opposite sides mainly in direction of the radius through the cylindrical mantle surface of the cylindrical pulverizing chamber 5 so that that they are directed to common point B in the centre of pulverizing chamber 5, where middle axis A of acceleration nozzles 1,2 cross each other in an angle of .180°. Gas outlet openings 4 end in pulverizing chamber 5 close to its mantle surface, so that the excess gas and possible fines gets out along the mantle surfaces of pulverizing chamber 5 to outlets 8 in its both ends without disturbing pulverizing that takes place in its central part.

According to an advisable embodiment of the invention in pulverizing chamber 5 a thick spacer plate 6 is installed between the outlet ends of both acceleration nozzles 1,2 and at a distance from both of them so that pulverizing chamber 5 is partly divided into two sections. In spacer plate 6 in front of both acceleration nozzles 1,2 a passing opening 7 is made, mainly as big as the outer circle of acceleration nozzles 1,2, which opening forms a pulverizing zone protected against disturbing gas flows. A notable amount of the gas from the outlet acceleration nozzle 1,2 leaves through the gap between head 2 of both acceleration nozzles and spacer plate 6, the width advantageously adjustable according to the material to be pulverized in changing the distance between heads 2 of acceleration nozzles 1. Due to this, the spacer plate has a form that each lateral face forms a right angle with middle axis A of acceleration nozzle 1,2 directed against it. As per the embodiment in figure 2 this spacer plate 6 extends from the mantle wall of pulverizing chamber 5 from the side, which is farthest from the outlets of acceleration nozzles 1.

On the other hand, in the counterjet pulverizer there is according to figure 3, only one outlet 8 of ground gas-solids suspension 8 so the other end of cylindrical pulverizing chamber 5 is closed with a thick metal platelO. In this embodiment spacer plate 6 according to this invention extends from the closing metal platelO. Since outlet 8 of pulverizing chamber 5 is only in one chamber end the acceleration nozzles 1 are slightly tilted towards outlet 8, whereby also the thickness of spacer plate 6 expands correspondingly towards outlet 8. The ground gas-solids suspension leaves in direction C.

In cylindrical pulverizing part 5 of the counterjet pulverizer according to figure 4 a cylindrical partition wall 6a is arranged concentrically, the other end of which is closed. Heads 2 of acceleration nozzles 1 protrude into pulverizing part 7a, formed inside this partition wall 6a, so much, that outlets 4 get outside this partition wall 6a so that the gas- fines suspension removed from acceleration nozzles 1,2 through gas out lets 4 gets into the space outside partition wall 6a of pulverizing part 5, from where it has to be removed as a separate flow D, whereas the gas suspension of ground material is removed from pulverizing part 7a in direction of arrow C for further processing. Accordingly, in this pulverizing chamber preliminary classification takes place at the same time. By control of the pressure outside partition wall 6a in pulverizing chamber 5 it is possible at the same time to adjust from acceleration nozzles 1,2 the portion of removing gas-fines of the total amount of gas-solids suspension fed through acceleration nozzles 1,2.

Evidently, the intention of the drawings is only to enlighten the idea of the invention and not to restrict the invention. For the expert on the branch it is obvious that the details of the object of the invention can be modified within the limits of the enclosed claims.

Claims

1. Improved acceleration nozzle for gas-solids suspension where in a conventional acceleration nozzle a (1), where in the outlet end a tubular head (2) without shoulders on the inside is arranged, the flow channel (3) of which is either throughout of the same size or at least as to its end portion tapering in the flow direction, characterized in that in the wall of the head, from the direction of the flow channel (3) middle axis (A), several diagonally outwards reaching gas outlet channels (4) are made.

2. Acceleration nozzle according to claim 1 characterized in that gas outlet channels (4) are placed at regular intervals side by side in circular order advantageously at the beginning of the tapering in the flow channel.

3. Acceleration nozzle according to claim 2 characterized in that each gas outlet channel (4) forms an angle of about of 45° with middle axis (A) of flow channel (3).

4. Acceleration nozzle according to claim 3 characterized in that gas outlet channels (4) are as to their cross-section, rectangular or circular and throughout of the same size or to their end portion tapering.

5. Acceleration nozzle according to claim 3 characterized in that gas outlet channels (4) are formed of longitudinal slits reaching to the outlet of head (2).

6. Acceleration nozzle according to any above claim characterized in that said tubular head (2) is detachably fixed to the outlet end of the conventional acceleration nozzle 1.

7. Acceleration nozzle according to claim 6 characterized in that gas outlet channels (4) are positioned in the central area of head (2).

8. Acceleration nozzle according to claim 1 characterized in that the flow channel in the end portion of the head (2) is tapering so that the cross-section of it corresponds at least total cross-section area of the inlet openings in gas outlet channels (4) and is at least about 20 % of the cross-section area in the beginning of the head (2) portion.

9. Counterjet pulverizer for an acceleration nozzle according to some of claims 1 - 8, where two such acceleration nozzles (1, 2) are installed reaching to the opposite sides of pulverizing chamber (5) directed to a common point (B) in the centre of chamber (5), characterized in that between the outlet heads of both acceleration nozzles (1, 2) a spacer plate (6) is arranged, in which there is a passing opening (7) almost as big as the outer periphery of acceleration nozzle (1, 2) at the intersection point (B) of axis (A).

10. Acceleration nozzle according to claim 10 characterized in that spacer plate (6) has such a form that each lateral face forms a right angle with the middle axis (A) of the accelerating nozzle (1, 2) directed on it.

11. Acceleration nozzle according to claim 11 characterized in that pulverizing chamber (5) is cylindrical as to its cross-section, in the one or both ends end of which there is outlet of ground gas-solids suspension.

12. Counterjet pulverizer according to claim 9 characterized in that cylindrical pulverizing chamber (5) cylindrical partition wall (6a) is arranged concentrically, through which heads (2) of acceleration nozzles (1) protrude so much so that gas outlet channels (4) in them end up outside cylindrical partition wall (6a).

13. Counterjet pulverizer according to claim 13 characterized in that cylindrical partition wall (6a) is closed from its other end and the gas-solids suspension of ground material gets out of pulverizing space (7a) as a separate flow (C) and the gas-solids suspension removed through gas outlet channels (4) gets out as its own flow (D) in the opposite direction.

14. Counterjet pulverizer according to claim 14 characterized in that in the pressure space outside partition wall (6a) of pulverizing chamber (5) can be controlled through gas outlet channels (4) in order to keep the amount or portion of gas-fines at a level wanted.