EP0191069A1

EP0191069A1 - Method for inhibiting the wear of surfaces of equipment for the treatment of mixtures in water or in humid air

Info

Publication number: EP0191069A1
Application number: EP19850904083
Authority: EP
Inventors: Hassan G. Djawadi; Klaus Janssen; Reiner Labusch; Friedrich Balck
Original assignee: Preussag AG; Preussag AG Metall
Current assignee: Preussag AG; Preussag AG Metall
Priority date: 1984-08-08
Filing date: 1985-07-26
Publication date: 1986-08-20
Also published as: WO1986001277A1; DE3429187A1; AU4678585A; JPS61501719A

Abstract

Les surfaces de parois (7) exposées à l'usure sont refroidies par un agent réfrigérant de façon qu'une couche de glace (15) se renouvellant continûment et de façon réglable quant à son extension et à son épaisseur, se sépare du mélange coulant sur ces surfaces. Les surfaces à refroidir des appareils et machines font partie d'un échangeur de chaleur, à travers lesquelles l'agent réfrigérant est conduit de façon réglable.The wall surfaces (7) exposed to wear are cooled by a cooling agent so that a layer of ice (15) which is continuously renewed and adjustable in terms of its extension and thickness, separates from the flowable mixture on these surfaces. The cooling surfaces of appliances and machines are part of a heat exchanger, through which the refrigerant is adjustable.

Description

Prevention of wear on the surfaces of devices for processing batches in water or moist air.

The invention relates to a method for preventing wear on surfaces of machines and devices for processing batches in water or moisture-containing oil and a device for carrying out such a method.

There are numerous tools and machines in technology that treat aqueous batches or batches in moist air, be it process, be it direct or regulate. For example, it is a known method to send aqueous mixtures of solids, that is to say, for example, suspensions of sand, gravel, ore concentrates or the like, through lines, nozzles or screens or through machines, such as mixers, hydrocyclones and the like, in order to allow certain processes to take place . Because of the speed imparted to them by the flowing water, these solids often hit the walls of the tools and machines, which are mostly made of iron or steel, with considerable force. Depending on the type and nature of these solids, wear or wear occurs on these walls, which can be so considerable that in a relatively short time. Time the proper functioning of the implement or the machine is impaired or even lost. It is therefore necessary, for example, to replace such devices or machines or parts thereof at more or less regular intervals. On the other hand, it is known to protect surfaces that are subject to wear by applying additional layers or to provide them with interchangeable so-called wear layers. However, this means additional investment and thus additional cost and restriction of the use and application of such devices and machines. On the other hand, in some facilities, for example where the particular shape and dimension or dimensioning of the surface fulfills a certain desired function, it is impossible to carry out additional installations because this interferes with this function or the flow pattern is impaired. This is the case, for example, in nozzles such as, for. B. find use in hydrocyclones or in orifices such as B. Orifice plates. Such devices and devices lose their desired effect as wear begins and progresses.

The object of the present invention is therefore to propose a method of the type mentioned at the outset, with which wear phenomena on the surfaces of walls of work areas and machines are avoided without the need to introduce foreign additional substances or materials.

This object is achieved by the method and the device described in the claims.

According to the invention, it is also possible at the same time to control the formation of the ice layer in such a way that process control takes place in certain sections or parts of the device or machine that are important for carrying out a method, for example by particularly strengthening the ice layer in passage openings such as nozzles or is weakened, as a result of which changes in flow velocity and pressure or throughput occur.

It is advantageous here if the cooling of the parts of the devices and machines in question is combined with heating devices so that rapid temperature changes can be carried out, which in turn result in rapid changes in the thickness of the ice layer.

Surprisingly, it has been found that due to the relatively good thermal conductivity in the wall materials of the devices and machines and the relatively poor thermal conductivity in the ice layer, even cooling forms a layer of uniform thickness by itself, so that the flow conditions result from the structure of such an anti-wear protective layer of ice cannot be adversely affected.

The temperatures that are required will of course depend on the circumstances, i.e. H. Devices, machines and their operating conditions, but it has been shown that temperatures of up to -20 ° C are sufficient and that in most cases temperatures between -10 and -15 ° C on the device walls are sufficient.

Any coolant per se, for example brine or frigen, is suitable as the coolant.

The device for carrying out the method now consists in that the equipment and machine parts to be protected against wear are designed as part of a heat exchanger.

In the simplest case, the heat exchanger can be a jacket or a second wall, that part of the device and the machine '':; ^■ }: ι 11. ! : surrounds, whose inner surface is to be protected against wear. As soon as this jacket or the resulting cavity is supplied with the coolant, the temperature of this wall part of the device or the machine drops to such an extent that the process water, which flows through the device or the machine in the form of a suspension or a mixture, is noticeable the inner surface, which is to be protected against wear, forms an ice layer. The ice layer can be regulated accordingly by the temperature of the coolant and it only needs to have a small thickness, which in the rarest cases rises beyond a few millimeters. Wear of this ice layer is insignificant because it builds up again and again.

Instead of the jacket or the second wall, which forms a space for the flow of the coolant, a pipe coil or the like can also be placed on the wall part of the device to be protected in the machine. Lay the line that is in good thermal contact with the outer surface of the part of the machine that is to be protected. The material from which the device or the machine is made should be as good a heat conductor as possible, which also applies to the coil or similar guide means, i. H . made of a metal, such as steel or brass or copper. These substances have a high thermal conductivity, whereas the ice layer has a very low thermal conductivity.

This practically universally applicable method is an ideal solution for protecting surfaces against wear in devices in which water or moist air is used as transport or Equipment is used.

The process can be adapted to a wide variety of devices and machines. It is easy to use and economical compared to the conventional investments that would otherwise be required.

In the above, it is stated that the method is useful for a variety of devices and machines.

In order not to excessively extend the present application, but to describe it in a manner that is understandable to the person skilled in the art, the method according to the invention on a machine is now to be described as representative of all other machines in question here, which are used in technology, in particular in the field of classification of granules in suspended form has found widespread use, namely using the example of a hydrocyclone.

Hydrocyclones have been known for many years and are used to separate solids from aqueous suspensions, the suspension being fed under pressure to the so-called entry cylinder of the cyclone via a tangentially arranged inlet opening. The suspension then merges into a cone adjoining the entry cylinder, in which the suspension assumes spiral movements at a considerable speed and moves downwards. As a result of the centrifugal forces that occur, the solids in the suspension are thrown out of the stream, hit the inner surface of the cone, and finally exit the so-called underflow nozzle at the lower end of the cone, while part of the liquid and possibly lighter and / or finer particles and Solid particles rise up the center line of the cone and emerge from an overflow opening.

In the case of such a working device as the hydrocyclone, there is, of course, heavy wear on this conical inner wall, which ultimately leads to destruction, but which also impairs the proper operation of the hydrocyclion.

The method according to the invention, transferred to such a hydrocyclone, now consists in cooling that part of the hydrocyclion which is subject to wear, by forming a heat exchanger or by being in or having a good heat-conducting connection or being surrounded by it . In the case of a hydrocyclone, the heat exchanger is thus arranged such that it surrounds the cone or at least part of the cone and the underflow nozzle, so that when a coolant with a sufficiently low temperature or flow rate is passed through, an ice layer on the inner surface of the cone and, if desired, is formed on the underflow nozzle which is subject to wear.

This layer of ice, the thickness of which can be between fractions of a millimeter and a few millimeters, protects the inner surface of the cone against direct contact with the solids which are suspended in the water, so that damage to the metallic surface of the cone Hydrocycling cannot occur because the solids now come into contact with the ice layer. Wear of this layer of ice is insignificant, as it repeatedly forms from the water in which the solids are suspended. Brine or a refrigerant such as Frigen can be used as the coolant. In the course of the formation of the hydrocyclion according to the invention, it is advantageous if the heat exchanger which surrounds the cone and the discharge end or the underflow nozzle is divided into several sections which can be supplied individually with coolant or with brine, so that the Heat dissipation or cold supply to different parts of the cone and the discharge end can be locally increased or decreased.

If cooling is particularly strong in the area of the underflow nozzle or the discharge opening, the cross section of which is important for the separation process with regard to the grain fractions to be separated, a particularly thick layer of ice can form. The separation process can be changed by controlling the thickness of the ice layer in the region of the discharge opening in this way. It can therefore at certain times or for certain substances or suspensions during the operation of the. Cross section of the underflow nozzle can be narrowed or expanded at the end of the cone.

It has been found to be particularly advantageous that the ice layer on the inner wall of the cone, as well as in the area of the discharge opening and the subsequent line, does not run suddenly or step-wise due to the temperature profile in the wall and water, but rather in the direction of flow of the water slowly and steadily increasing.

Ice formation begins within that part of the cone which comes into contact with the coolant or refrigerant, and a relatively thin layer of ice forms, which slowly increases in thickness in the direction of flow of the suspension. So there are favorable flow conditions. The hydrodynamic vacuum generated by the flow, like other conditions resulting from the flow process, have no measurable effect on the formation of the ice layer. It is only necessary to ensure that both the water inside the cyclone and the refrigerant flow over the wall of the cone correctly and evenly in the areas in question.

The materials used to manufacture the cone and those of the heat exchanger are not of crucial importance because the thermal conductivities of the metals are significantly higher than those of the ice, so that the ice acts as an insulating material on the inside of the cone.

In order to produce an ice layer which is completely sufficient to solve the problem and which only needs to be a few millimeters thick, it is not necessary to generate temperatures which are substantially lower than -20 ° C. Temperatures between -10 and -15 ° C are already sufficient. The required value depends on the water temperature, the flow rate and the desired ice thickness.

For the purpose of faster and more sensitive regulation of the ice layer and to avoid the complete freezing of the content of the hydrocyclion, at least in the area of the cone if there is no inflow and discharge, it is advantageous in the inventive sense to additionally create heating devices with which the wall temperature ¬ temperatures of the cone can be brought quickly to temperatures in the region of the O-point, for example, in the absence of additional suspension suspension. To increase the effectiveness of the process, the suspension can also be precooled to low degrees.

The invention will now be explained in more detail using a hydrocyclone, for example.

In the drawing:

Fig. 1 shows a schematic cross section through a

Hydrocyclone according to the invention, Fig. 2 shows a cross section through part of the cone of

1 with a form of

3 shows a section similar to that of FIG. 2 with a different heat exchanger shape, and FIG. 4 shows a section similar to that of FIGS. 2 and 3 with a further embodiment of a heat exchanger.

Since a hydrocyclone is a perfectly symmetrical structure, only the left half is shown in FIG. 1, in which the entire hydrocyclone is shown. The right half corresponds to the left half with the exception of the inflow and the overflow, which are only available in each case.

2 to 4, only part of the symmetrical cone with discharge opening is also shown, but different forms of the heat exchanger. The following can be said in detail. 1 consists of the inlet 1, which opens tangentially into the entry cylinder 2. The entry cylinder 2 is closed off at the top by a plate into which a so-called vortex finder 3 opens and one Establishes connection between the entry cylinder and the head piece 4. A vent valve 5 is contained in the head piece 4 and a pipeline 6 which opens into it and functions as an overflow.

At the lower end of the entry cylinder 2 is the cone, which is the most essential piece of the hydrocyclic. The cone 7 merges into an underflow nozzle with discharge line 8, which can be controlled in cross-section in known hydrocyclones.

The suspension of water and solids to be separated in the hydrocyclone is fed tangentially into the feed cylinder via inlet 1 under high pressure. The actual separation then takes place in the cone 7 ^' , "where the denser material is thrown against the inner wall of the cone 7 due to the centrifugal force, which can be quite significant.

The lighter parts rise in the middle with the excess water, flow through the vortex finder 3 and into the head piece 4 and finally through the upper course 6.

The area in which wear can mainly occur in the exemplary embodiment shown is covered in FIG. 1 by the clamp 9. In this area, on the outside of the cone 7 and the discharge line 8, a heat exchanger 10 is arranged, which is represented here by a jacket 11 which, at a certain, substantially uniform distance, the lower end of the cone and discharge line 7 or 8 surrounds and is provided with inlet and drain pipe connections.

This jacket or heat exchanger 10 can of course also a considerably larger part of the outer surface of the cone 7 cover . This will essentially depend on the operational requirements and other practical considerations. So if in Fig. 1 the heat exchanger only covers about half of the cone 7 and part of the discharge line 8, it can instead extend up to the connecting flange 14 with the cylinder 2 Eϊntragzy.

In Fig. 1, this heat exchanger is a jacket that surrounds the cone and the discharge line. It can of course also be designed in a different way, for example as shown in FIG. 2. Here again the reference 7 denotes the cone and the reference 8 the discharge line. The heat exchanger 10 here is a tube I T ', which is wound spirally around the desired part of the cone 7 and the discharge line 8 and has an inlet 12 and an outlet 13. It is only essential for such a configuration that the contact with the wall of the cone 7 in the area is designed to be as large as possible and with good heat conductivity. Instead of a round tube, for example made of copper, the heat exchanger can also be formed by a rectangular tube which, with one of its surfaces, lies closely against the surface of the cone 7 and the discharge opening 8. Otherwise, all measures can be taken which serve to improve the heat transfer from the exchanger tube to the cone wall and vice versa.

In FIG. 2, the reference number 15 now denotes the layer of ice which forms and which, according to the invention, protects against wear.

Another type of heat exchanger is shown in FIG. 3, namely that there is not a uniform heat exchanger as in FIGS. 1 and 2, but individual, individually controllable exchanges are shear, which here have the reference numerals A, B, C and D, each with inflow and outflow. In this way, the temperatures in the wall of the cone 7 or the discharge line 8 can be controlled according to the desired operating conditions. It is therefore possible, for example, to cool section C, which is of particular importance for the separation function of the hydrocyclion, because it contains the discharge opening of the discharge line and thus determines the grain belt which is discharged, than sections A, B and D, namely, so that a change occurs, ie a reduction in the cross-sectional opening at the discharge end of the cone, so as to influence the separation process. In addition, it may well be that the wear in the area of section A is only slight, so that here the ice layer to be produced need only have a small thickness and therefore the coolant supply is less strong or the coolant is at lower temperatures have needs.

Since the thermal conductivity in the wall of the hydrocyclic is particularly good and the heat transfers between liquid, i.e. water, inside the hydrocyclic and the transition between coolant and wall ^'of the cone are also no problems, an ice layer will result which, as shown in Fig 2, extends beyond the directly cooled section of the cone and gradually becomes thinner in order to be completely omitted. So there are favorable transitions and thus flow conditions inside the cone.

FIG. 4 shows a heat exchanger as in FIG. 2, but only for the sake of simplicity. It can just as well be one according to FIG. 1 or act according to FIG. 3. It is crucial in this illustration that additional heating devices are available. In the example according to FIG. 4, these are provided in the form of heating lines for a liquid heating medium or electrical resistance heating lines and are illustrated by the small circles 16. The power supply takes place at 17 and 18. This form of combination of cooling and heating devices is intended to enable a particularly rapid regulation or control of the ice layer, and it is intended to prevent, in the event of failure to supply suspension via line 1 and a fault of the discharge via line 8, a freezing of the content of the hydrocyclic occurs.

The above description of the embodiment shown in the drawing clearly shows the operating method. Thus, if a separation process is to be carried out using the hydrocyclone design according to FIG. 1, a coolant is passed through the heat exchanger 10 with the entry of the suspension into the hydrocyclone or a corresponding time beforehand, so that a part of the water in the suspension is on top of that Heat exchanger 10 detected surface forms an ice layer in the interior of the cone and the discharge line (15 in FIG. 2). This ice formation starts at 0 ° C.

The ice layer then acted because of the inherent poor thermal conductivity as an insulating layer, while the thermal conductivity through the metal of the cone and possibly. Pipeline walls is extraordinarily good. The thermal conductivity for ice is, for example, 22 mW / cm / K and that for brass and copper is 970 mW / cm / K and 3900 mW / cm / K. 3, for example, the ice layer in the area of the discharge opening to the discharge line 8 can be particularly controlled, so that the cross-section and thus the separation process of the hydrocyclization can be influenced.

The formation of the ice layer and the monitoring of the ice layer formed or its thickness change for the purpose of changing the cross-section of nozzles, for example, is carried out using known measuring devices, for example by means of electrical, optical or other probes which are guided through the cyclone wall and whose measuring signals in turn is coupled to the control of the refrigerant line, so that the control takes place automatically.

Claims

Expectations

1. A method for preventing wear on surfaces of machines and equipment for processing batches in water or moisture-containing air, characterized in that the wall parts subject to wear are cooled such that on the surface of the wall part subject to wear from the Be ¬ propellant water forms a controllable layer of ice.

2. The method according to claim 1, characterized in that a coolant, z. B. Brine, frigen or liquid nitrogen is used.

3. The method according to claim 1 and 2, characterized in that the cooling of the wall part subject to wear is combined with a heater for rapid temperature changes.

4. The method according to claim 1 to 3, characterized in that ver¬ by means of a controlled change in the thickness of the ice layer, a controllability for nozzles, orifice plates etc. is additionally achieved to protect against wear.

5. Apparatus for performing the method according to claim 1 to 4, characterized in that at least the part which is subject to wear forms part of a heat exchanger.

6. The device according to claim 5, characterized in that the heat exchanger is a jacket (11) with supply and discharge lines (12, 13) or comprises a spirally wound coil (1 V) or channels which are arranged parallel to the direction of flow and the or that surround the part of the device or machine that is subject to wear.

7. The device according to claim 5 and. 6, characterized in that heating devices are accommodated in the heat exchanger or in addition to the heat exchanger (10).

8. Apparatus according to claim 5 to 7, characterized in that electrical, optical or other probes are arranged in the areas of the ice layer forming on the surfaces of parts of the machines and devices for the purpose of measuring the ice layer thickness and with the cooling line for automatic control are coupled.