NO137263B - NOZZLE DEVICE FOR REDUCING THE SIZE OF SHOCK-DIVIDIBLE SOLID. - Google Patents

Description

The present invention relates to a nozzle apparatus for reducing

tion of the size of shock-divisible solid matter contained in a fast-flowing medium, comprising a converging and a diverging nozzle section for accelerating the matter. The device is particularly e-

net for processing ores.

The purpose of the invention is to arrive at a nozzle construction which causes not only the working medium, but also the solid substance to reach supersonic speed.

This is achieved by the converging nozzle section being connected to the diverging nozzle section via a channel section which has a length which is sufficient for the mixture of medium and solid to reach the speed of sound. leaves the channel part, whereby the mixture can be accelerated. to supersonic speed in the divergent part.

Other purposes, features and advantages of the invention will

appear from the description and requirements with reference to the drawings,

where:

Figure 1 is a schematic view of the nozzle apparatus according to the present invention,

Figure 2 is a drawing on a larger scale of the pipe channel

which connects the charging container with the receiving container,

Figure 3 is a cross section of. the volute-shaped receiving container,

Figure 4 is a schematic diagram of a two-part apparatus

where the outflow from each system is directed into a common receiving container,

Figure 5 is a drawing on an enlarged scale showing

the details of the common receiving container for the two-part system,

Figure 6 is a schematic diagram of a two-part system using the method and apparatus according to the applicant's patent.

gere OS patent no. 3 257 080..

In the drawings, the letter A denotes a first zone which is connected through a pipe channel or a pipeline B with a second zone C. Flow through the pipe channel B is controlled by a quick-opening valve D. A converging nozzle E connects the outlet of the first zone A with the pipe channel B, while the other end of the pipe channel has a connection with the second zone C through a diverging nozzle F.

Zone A must absorb the solid whose size is to be reduced. A compressible working medium such as steam is introduced

in the zone A through an inlet line G which communicates with the pipe channel B between the valve D and the converging nozzle E. During the introduction of the working medium, the valve D is in the closed position. Introduction of working medium into zone A is continued until a predetermined pressure is reached, whereby potential energy is stored in the zone, the predetermined pressure varying in accordance with the desired size reduction to be achieved for the particular substance being treated.

The term "compressible working medium" as used herein shall include not only water vapor, but any gas or vapor capable of doing useful work during expansion. The terms "solid substance" and "solid particles" are used here interchangeably and refer to the material or substance being treated.

The quick-opening valve D is acted upon so that it suddenly initiates flow from zone A to the second zone C. As soon as the valve opens, a rapid flow into the pipe channel takes place of the mixed flow of the working medium and the particles of the solid substance that are trapped in the working medium, as the solid particles, as explained later, are exposed to shock conditions when they leave the nozzle E.. The pipe channel B is of a length that ensures sufficient time for maximum transfer of kinetic energy from the working medium to the solid particles, so that the particles are accelerated to a high speed at the moment they flow into the diverging nozzle F. During flow through the pipe channel, the solid particles are exposed to additional shock conditions. In the region of the diverging nozzle, the mixed flow of medium and solid particles is accelerated to supersonic flow, which exposes the particles to further shock conditions. The combined flow of medium and solid is then led into the second zone C.

The outflow area from the second zone C is sufficiently large so that no return pressure conditions or effects occur in this zone, which would be the opposite of efficient use of the kinetic energy in the mixture flow when it flows out in this zone.

From zone C, the mixture flow is led through a diverging shaft H which communicates with a centrifugal separator I. This passage is carried out divergently in order to decelerate the flow into the centrifugal separator. The working medium is preferably extracted from the separator I from its upper end, although the medium or part of it can be extracted from the lower end at a low speed. The solid material is sucked off from the lower end of the separator.

The nozzle apparatus comprises a charging container 10 which forms zone A. A feed valve 11 and a feed funnel 12

is located at the upper end of the container. The feed valve can be actuated by any suitable valve control means and the control means can be actuated pneumatically or in some other way. The cross-sectional area of the lower end of the container 10 is reduced, as generally indicated at 13, and has an eccentric outlet 14 which is connected to the largest opening of the diverging nozzle E. The smallest end of this nozzle is connected to the pipe channel B.

The material to be treated is delivered to the feed hopper 12 after undergoing a preliminary treatment to form a suitable charge. When the valve 11 is opened, the material flows into the container 10 which forms zone A. The size of the container 10 is subject to large variations and is dependent on the scope of the operation.

After the desired amount of solid or material has been introduced into the charging zone A, the working medium, which is hereafter referred to as steam, is introduced from a supply line 15 through a control valve 16 and into the inlet line G. A pair of inlet ports 16a and 16b are connected to the inlet line G and extends through the pipe channel B preferably in a diametrically opposed relationship with the intention of introducing the working medium into the pipe channel B. The use of opposing inlet ports is desirable. The inlet ports 16a and 16b communicate with the pipe channel B between the quick-opening valve D and the converging nozzle E, so that the working medium is introduced through the pipe channel B and flows through the pipe channel in the direction of the container 10, as the valve D is in the closed position at this time. By introducing the working medium in this way, the line B is swept almost clean of solid particles and the working medium is introduced into the lower end of the container 10, so that a splash or a fluidized layer is formed in the container 10. The introduction of working medium into the lower end of the container also causes transfer of all relatively fine material to the upper part of the layer. With reverse classification, accumulation of fine material in the outflow zone is avoided.

When using the invention in practice, the solid/medium ratio can be varied within wide limits. With saturated steam at 160 kg/cm 2, e.g. the ratio lies anywhere up to approx. 200 to 1. The solid/medium ratio is determined by the extent to which the container 10 is filled with material to be processed and by the amount of working medium introduced. The pressure in the medium introduced into the container 10 is also subject to variations over a large range, usually between 17 and 700 kg/cm 2. The selected pressure depends on the material being processed and the desired degree of splitting.

The valve D is shown as a rotary valve type whose spindle 17 is connected to a suitable control member 18. The valve is a full-port valve, i.e. when the valve is in its open position the port or opening through it is at least as large as the diameter of the pipe channel B. As previously mentioned, the valve is quick-opening, so that after the material has come up to pressure in the first zone A, the valve opens almost instantaneously, so that the pressure is suddenly released. causes the mixed flow of medium and solid to move into and through the pipe channel.

Valve D should be located a sufficient distance downstream from zone A to allow the valve to open fully before any of the solid particles reach the valve body. Use of the nozzle apparatus according to the invention has shown that if an arrangement is not used to protect the valve, the force of the solid material flowing at high speed through the pipe channel B will

and against the closing element in the valve, grind down and destroy the valve very quickly. In the present case, the rapid opening of the valve as well as the location of the valve sufficiently downstream from the container 10 ensures that the valve is fully open before solid particles in significant numbers pass through it. This advantage is strengthened by the fact that the working medium is introduced through the pipe channel B in a direction opposite to the direction of the outflow of material from the container 10, as the introduction of the working medium at this point sweeps the pipe channel almost free of solid matter. Therefore, when the valve is then opened and the flow picks up, the material must be moved from the container 10 to the valve, so that the valve is given sufficient time.

to reach the fully open position before the solid particles reach the valve. In actual use, it has been found that satisfactory results are achieved when the valve is opened in less than 20 milliseconds.

During the opening of the valve D, the mixture flow from the container 10 which forms the first zone flows through the converging nozzle and into the pipe channel B. During the passage of the mixture flow through the converging nozzle E, the nozzle E accelerates the working medium to a high speed, which means that the converts a part of the working medium's enthalpy into kinetic energy. The occupied solid is only slightly accelerated while the medium reaches its maximum speed at the outlet of this nozzle. The high velocity of the medium in relation to the solid causes local zones of supersonic flow to occur on the irregular surfaces of the solid. As these local zones of supersonic flow are highly irregular shock waves of considerable strength occur in these thin zones, as the supersonic zones are associated the shocks are also associated with the solid, so that the solid is subjected to this shock condition as it flows through the nozzle.

As an example of relative velocities at the outlet of the nozzle E into the pipe channel B, it can be mentioned that the medium velocity is in the order of 335 - 365 m/sec., while the velocity of the solid substance is less than 9 m/sec. Since the medium velocity in relation to the velocity of the solid is higher than 335 m/sec. corresponding to a Mach number of 0.6 - 0.7, the shock waves described above occur on the surface of the solid particles. As mentioned, as the shocks occur on the irregular solid surfaces, the shocks are associated with the solid surfaces and are propagated through the solid substance, causing breakage or splitting along non-contiguous planes.

The converging nozzle E can be varied considerably in terms of its shape including its size and length. In practical use, it has been shown that the surface ratio between its large and small end can be varied from 3 to 1 to 8 to 1, preferably 4 to 1. It must be constructed so that a smooth and even inlet to the nozzle is achieved and a well-rounded converging part that merges into pipe channel B. The nozzle should preferably be designed as an eccentric nozzle as shown in fig. 2, so that its lower part of the nozzle wall lies in the same plane as the lower wall part in the container outlet 14 and the lower wall part in channel .B, so that an even undisturbed flow of the mixed flow of medium and solid particles from the lower

end of the container 10 through the nozzle E and into the pipe channel.

During the course of the mixed flow through pipe channel B, the solid is exposed to further shock conditions by the working medium continuing to move at a faster rate than the occupied solid and forming local zones with supersonic flow. During the entire movement of the mixed flow through the pipe channel, the velocity of the solid increases while the velocity of the medium decreases. In a pipe channel of optimal length, the entire flow has the same velocity at the end of the channel. As the mixture flow enters the diverging nozzle F, the medium is accelerated, further in the diverging nozzle and the solid st<p>ff is accelerated at the expense of most of the supplied kinetic energy which is obtained by adiabatic expansion of the medium in the diverging nozzle. From the nozzle F, the flow is fed into the second zone C, which is made up of a volute-shaped recording container or chamber 19. The second zone is referred to hereafter as a shock chamber. and may have a shock or impact plate 20 as shown with dashed lines. in fig. 1, arranged in the chamber.in the path of the mixture stream flowing into the container.

The diverging nozzle F is generally conical and its size, shape and length can be varied considerably. E.g. the ratio of its outlet surface to its inlet surface can be anywhere from 2 to 1 to 10 to 1, its length is such that half, the divergence angle is preferably not greater than. 15°. The inlet end or throat part has the same diameter as the pipe channel B, and as the entire flow is accelerated to approximately sonic speed, the well-known throttling effect occurs in the throat part of the divergent nozzle. When the mixture flow leaves the pipe channel, the mixture flow therefore assumes supersonic flow, so that shock conditions are formed in the nozzle F. The solids are exposed to such shock conditions and further size reduction takes place.

From the nozzle F, the mixture flow runs through the extended inlet 21 which directs the majority of the medium and the fine-grained material in a direction approximately perpendicular to the main axis of the nozzle. The entire mixture stream flows out into the volute-shaped chamber 19 which constitutes zone C. As mentioned, the stop plate 20 can be used in zone C, and its front side is arranged in a plane normal to the axis of the pipe channel B. It is placed at a sufficient distance from the nozzle F so that it does not interfere with the free expansion and flow of the mixture stream. but . is sufficiently close to ensure that ohi. central part of the fast stream will bump against it. In addition to the other shock conditions to which the particles are exposed, the particles are thus exposed to impact forces which cause further size reduction. It is assumed that when the material flows through the pipe channel B, a radial sorting of the material takes place with the largest particles concentrated at or near the center or axis of the pipe channel, while the smaller particles flow along the walls of the pipe channel. When using an impact plate that is placed with the front side so that the larger particles that are ejected from the pipe channel at high speed will hit the plate, the particles are exposed to large impact forces. This causes further breaking up or splitting due to the elastic return movement of the particles and mutual collision between the particles.

The fine-grained material and the boundary layer flowing out of the pipe channel at high speed seek towards the inner inclined plate in the nozzle F and towards the curved surface in the inlet 21, so that a part of the working medium and fine material is led outwards from the axial direction when the mixed flow enters the container 19. The heavier solid particles collide with the surface 20 and collide with each other.

From fig. 3, which is a cross-section of the volute-shaped container 19, it will be clear that the mixture flow enters the container parallel to the axis of generation of the volute. The medium and the solid will flow in all directions as soon as it enters the volute chamber and some of the particles will collide with the inner wall of the chamber so that they are exposed to further impact. The volute shape of the container gives the medium and finely divided particles a rotational movement, so that the medium and the solid particles are directed towards the outlet end 19a in the chamber in one-dimensional flow.

The container 19 serves as a device for converting a three-dimensional flow of the mixture stream into a one-dimensional flow in the longitudinal direction of the shaft H. It is clear that when the solid substance has flowed through the system and into the second zone there is a size reduction or splitting of it solid matter effectively carried out.

From the volute-shaped container 19, which forms the impact or receiving section C, the working medium and split material flow downwards through the shaft H and into the centrifugal separator. outlet pipe 25.

During operation, the ore or other material is introduced as

to be treated, through the feed funnel 12 through the feed valve 11 and into the container 10 which forms the charging zone A. After zone A is charged with solids, the valve 11 is closed and the inlet valve 16 for the working medium is opened to admit the working medium through the line G into the pipe channel B and then into the lower end of the container 10. If desired, part of the working medium can be introduced through an auxiliary line 15a which communicates with the upper end of the container 10, flow through the line being controlled by a valve 15b. The introduction of working medium continues until pressure

ket in the container has reached the desired operating pressure, after which the valves 16 and 15b are closed. It is preferred that the introduction of steam takes place as quickly as possible to minimize condensation.

The quick-opening valve D in the pipe channel B is opened either at the same time as the valves 16 and 15a are closed or immediately after to establish a connection between the lower end of zone A and the pipe channel B. At the beginning of the opening of the valve D, the solid particles are at the lower end of the container 10 approximately at rest while the working medium immediately flows through the nozzle and into the pipe channel, during which the medium flows around these particles at high speed. The relative velocity between the working medium and the solid particles leads to a transonic condition which can be defined as a condition where local zones are supersonic and sonic and subsonic flow simultaneously take place in the flow. The supersonic zone occurs on the surface of the solid particles hit by the medium flow. As is known, shock waves always occur in such supersonic zones, due to the fact that the flow consists of expansion waves that propagate downstream and compression waves that propagate

is done against the direction of flow. The compression waves catch up with each other and create shock waves, so that the solid substance is exposed to shocks that occur in the supersonic zones associated with solid surfaces. When valve D is therefore opened, the conditions are such that the solid particles in the flow are exposed to shock waves.

When shock is transmitted through a solid and arrives

to a discontinuity such as a crystal face, a fracture plane or a free surface, a new shock wave is reflected while the incident shock is transmitted forward through the material. The magnitude of the reflected and transmitted shocks depends on the discontinuity the character of the teat; under favorable conditions, an incident shock can be reflected in such a way that tension occurs which causes

fracture between the common surfaces of crystals.. This does not produce

only an external splitting, but because the forces that divide the solid into single crystals or grains are mainly tensile forces, the tendency to break up the grains themselves is very small and the tendency to incomplete division at the crystal boundaries is small. The process therefore produces a clean and well-defined splitting of the material grains. Such a well-defined split. is advantageous when reducing the size or crumbling of many substances.

It is believed that the effectiveness of the splitting system shown here is most likely due to the fact that typical materials such as ores or minerals are significantly weaker under tension than under pressure. When they are affected as described above, solid particles split up more easily or are reduced in size more easily than when the reduction is attempted by means of conventional crushing or grinding.

At the inlet to pipe channel B, the speed of the working medium accelerates rapidly, while the solid material just begins to accelerate. As previously explained, this relative speed between the working medium and the solid leads to a transonic flow, where local zones of supersonic, sonic and subsonic flow simultaneously take place. Supersonic zones occur on the surface of the solid particles and create shock waves which are associated with the particles, and which propagate through the solid and cause splitting in areas of discontinuity.

By using a pipe channel of sufficient length and approximately the same cross-sectional area over the entire length, energy is transferred from the working medium to the solid substance and the mixed flow of medium and solid substance at high speed. It is desirable to accelerate the mixture flow to a high velocity, so that when it flows into the diverging nozzle F, shock conditions occur in the nozzle F. Moreover, if an impact plate 23 is placed in the receiving zone C, the high shock velocity will increase the size reduction . The mixing flow leaves pipe channel B at the sonic velocity of the particular flow type. The flow in the nozzle F therefore becomes supersonic and shock waves are created which expose the particles to further forces which reduce their size. During the movement of the flow through the nozzle, the medium expands and flows at supersonic speed into zone C. If an impact plate 23 is used in zone C, the larger particles in the mixing flow which are concentrated in or near the flow axis will be thrown with great force and speed towards the plate. This impact action not only breaks up or splits the particles, but also produces elastic return motion which leads to mutual collision between the particles as they are thrown back from the impact surface. This increases the collisions between the larger particles and causes further size reduction. The volute-shaped chamber 19 which constitutes zone C gives the medium and the split material a rotational movement and directs it towards the outlet 19a.

From zone C, the medium and the particles are guided downwards into the centrifugal separator I by means of the shaft H. Inside the separator, the particles are separated and discharged through the outlet line 24, while the working medium escapes through the upper outlet 25.

Although it is assumed that the size reduction and splitting of the solid substance is primarily due to the substance being exposed to shock conditions throughout entire systems, a certain additional effect can be achieved by means of thermal shock. When steam is used as a working medium, heat is led into the material and as the process progresses, some of this heat can be used for expansion of the surface layer of the particles, which can cause initial splitting or breakage. The sudden expansion of the medium as it flows into zone C can also be considered a factor, because additional energy is released which can affect the solid. In any case, practice has shown that a system as described here effectively provides size reduction and splitting of solids.

In fig. 4 and 5 show an embodiment of the invention where two separate systems of the construction described above work in mutually opposite directions.

In fig. 4 is the first system indicated by Roman numerals

I and comprises the same elements as described above, namely the charging zone A, the converging nozzle E, the channel B, the quick-opening valve D and the diverging nozzle F. The second system is designated by Roman numeral II and comprises the same elements A, B, D , E and F. The two-part system utilizes a common receiving zone or impact chamber designated by the letter C.

The respective pipe channels B in systems I and II communicate through the nozzle F with the common second zone C. Zone C consists of a volute-shaped container 19b of the same construction as the chamber 19, except that it has a connection for the two resisting

end nozzles F on opposite sides of the volute.

In the container 19a, two deflector plates 26 and 27 (fig. 5) are arranged which are placed at a distance from each other and which are also placed at a distance from the end of the nozzle F. Each plate is provided with a central opening 28 which can be reinforced with an annular insert 29 of hardened material fitted in the opening. The deflector plates 26 and 27 are aligned with the openings 28 axially in line with the axis of their respective nozzles D leading into zone C'. The distance between the deflector plates is such that they do not cause an adverse back pressure effect which may interfere with the free flow of the mixture stream as it enters zone C. The plates are, however, sufficiently close to the end of the nozzles to ensure that the middle part of each stream passes through the openings 28 and collides with the oppositely directed current. The distance between the plates is not critical, but they should be sufficiently spaced to allow free flow of material from between the plates after impact has taken place.

As mentioned, the movement of the material through each pipe channel causes B with high. speed, that the material is sorted or classified radially so that the main part of the larger particles is concentrated in or near the middle part or axis of each pipe channel. As explained, the finely divided substance and part of the medium seek towards the inner surface of the pipe channels and nozzles and are directed radially outwards.

By correctly positioning the ends of the deflector plates 26 and 27 in relation to the pipe channels, the central parts of each stream of medium and solid will pass through the opening 29 in its deflector plate and collide with the other stream. As the flows have a high velocity when they arrive at zone C, it is clear that collisions between the two central parts of the flow will do a large amount of additional work in reducing the size of the particles. The deflector plates also serve to guide the smaller particles that hit the plates in a direction radially outwards from the plate axis.

The arrangement where two particle streams collide at high speed has been found to be particularly satisfactory when a system as shown in fig. 1, but this two-part system arrangement does not necessarily have to include all the specific elements of this system. As long as the system produces a particle stream that radiates into a second or recording zone, this arrangement constitutes a significant advantage.

As an example, fig. 6 shown in schematic diagram

a two-part system using the method and apparatus according to

■ the applicant's former US patent document 3 257 080. System I comprises a first zone AA, a pipe channel BB with a control valve DD and an inlet line GG for the working medium. System II comprises the same elements and in both systems the pipe channels BB are connected by a common second support section CC.

Zone CC comprises the perforated plates 26 and 27 arranged at a distance from each other with central openings 28. The operation and the way the two fast flows are directed towards each other to initiate splitting and size reduction by means of shock circuits is the same as described above with consideration of the use of two-part systems, each of which is constructed in accordance with fig. 1.

It appears that the energy in the fast currents is converted into shock forces to which the particles are exposed, so that the splitting or size reduction that occurs in each system (as shown in Fig. 1 of this application or as shown in the applicant's previous patent document) is supplemented by the shock forces that develop by the strong collision between the two fast currents.

It is clear that in this embodiment of the invention the larger particles which have avoided splitting in each pipe channel and each nozzle system will experience strong mutual collisions. As each stream moves at high speed, extremely large impact forces are developed which cause further splitting or size reduction of these particles, which take place in the impact zone between the plates 26 and 27. The strong impact state between the two streams creates a violent turbulence in the impact zone, which causes mutual collisions between the particles, and this effect further contributes to the size reduction of the particles.

As described above, the systems use a quick-acting, quick-opening valve in the pipe channel that connects the first zone to the second zone. It is important that a sudden opening of the pipe channel takes place, and although the valve is preferred, it is clear that other devices such as a rupture membrane can be used. When a rupture membrane is used, the membrane should be designed to withstand a predetermined pressure equal to the pressure to which the material is exposed in the first zone. When this predetermined pressure is reached, the membrane bursts momentarily, so that the pipe channel opens momentarily and allows flow through as described above.

Claims (2)

1. Nozzle device for reducing the size of shock-divisible solids trapped in a fast-flowing medium, comprising a converging and a diverging nozzle section for accelerating the substance, characterized in that the converging nozzle section (E) is connected to the diverging nozzle section (F) via a channel section (B) which has a length sufficient for the mixture of medium and solid substance to reach the speed of sound as it leaves the channel part (B), whereby the mixture can be accelerated to supersonic speed in the diverging part. 2. Apparatus as stated in claim 1, characterized in that the channel section (B) is elongated and has a substantially constant cross-sectional area over its entire length in order to increase the speed of the mixture flow and provide shock conditions in the elongated channel section (B).