Manner for separating a solid and a liquid phase in a mass

(54) Name

Sweet Separate a solid and a liquid phase in a mass (57) Saniman features: __, _____ y ​​^ onna text .beskxtYcrj a way to separate a liquid-packed material l ^ Than a liquid with which the fine-grained material is saturated. The material can, for example, beet A of alipspAn, metal-containing beet baths or aetalloxlder train metallurgical wet filters. The bone moist mass (1) is packed in a bsbAllare (2) which is then closed and heated from below. The liquid evaporates initially in the lower portions and drives viteka from the above portions towards

Means the surface, from which accumulated liquid (9) can be diverted. '. Ordinary oil drums can be used in containers. After removal, the containers can be charged in metallurgical furnaces or the material can be dumped together with waste without any harmful environmental impact.

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(56) Cited publications: Sweden 340 592 (82 a: 1/01) Germany 276 664, 1 814 471 2 532 689

IN

7907037-1

The present invention relates to a method of separating a fine-grained, tightly packed solid material from a liquid with which the fine-grained material is soaked. The fine-grained material may in some cases consist of metal compounds, essentially without any value, eg certain beet bath residues which are harmless as far as the environment is concerned but where the liquid phase can be highly toxic or for other reasons harmful to the environment. In other cases, the fine-grained material may be more valuable so that it is desirable to dispose of it. This applies to certain types of beet bath residues as well as certain metal oxides in the form of powder from venturi filters in metallurgical plants. Another material which can be advantageously treated according to the invention is obtained in the processing of objects of high-speed steel and other high-alloy products. In such machining15 grinding operations are often used in combination with cutting oils or other liquids or chemicals. In these operations, a very finely divided chip soaked in a liquid phase, such as oil or an oil emulsion, falls. There is currently no practically useful method of handling these chips, although they represent a great value in the form of alloy metals. On the contrary, the disposal of this material is a complicated waste and environmental problem.

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It is often desirable to be able to remelt the metal content of waste materials of the type described above in. metallurgical furnaces. However, with current technology, this is impossible mainly due to the following three reasons;

if the liquid-soaked material is freely unhurried in the oven, liquid flows down into the bottom of the oven and cools and soaks it so that cracks appear in the oven lining,

- if the liquid-soaked material is unharmed in the oven in closed containers, the volatile constituents evaporate, which in unfavorable conditions give combustion puffs and explosions,

- the large amount of liquid gives a strong smoke development_s which poses a danger to the internal and external environment.

A first object of the present invention is therefore to separate a fine-grained, tightly packed solid material from a liquid with which the fine-grained material is saturated so that the solid material can be disposed of in the desired manner. More specifically, in the event that the liquid phase is toxic or otherwise harmful to the environment, while the solid phase is harmless from an environmental point of view but on the other hand has no major economic value, it is intended to be able to dump the solid material together with other waste material. In the case where the solid phase, on the other hand, contains valuable constituents, for example valuable alloying elements, it is an object of the invention to remove the liquid so that the solid material can be recovered, for example by placing the material on metallurgical furnaces. Another object is also to be able to separate the liquid from the liquid-saturated mass in order to be able to reuse the liquid. These and other objects can be achieved by collecting the pulp in a container, heating the pulp collected in the container from below

7907037-1 so that the liquid, starting in the lowest part of the mass, evaporates in an evaporation zone and drives the liquid in the upper parts of the mass upwards through the mass towards the surface, where the liquid accumulates and from which the liquid is diverted from the container. In order not to ignite the liquid, as it is flammable, the heating takes place without air access. During the later stage of the process, the remaining liquid becomes so hot that a certain oil smoke develops when the liquid consists of or contains oil or similar substances. This smoke or gas can be burned with a safety torch or used to heat the container.

The method according to the invention is based on the following principles:

a) a sufficiently large gas pressure shall be created by heating the container from below in the lower parts of the mass in order to press liquid upwards at a certain desired speed. This condition can be expressed

..........(’)

In this case, dv - = Volume current liquid CL b

A = Horizontal section area © C = Permeability = Vertical pressure gradient

b) The grain size, or rather the tight packing, must be such that gas bubbles can essentially not rise upwards and liquid droplets cannot substantially fall downwards in the space between the grains (particles). Stirring in

7907037-1 the liquid must in other words be prevented by the capillary forces in the atomized mass, the lian may in this case assume that a gas bubble which strives upwards is exposed to two forces in the critical moment when it is to be deflated, namely the upward buoyancy force and the restraining surface tension force. Conversely, a drop of liquid that is being laced and falling down is also affected. Accordingly, if the channels in the mass are smaller than the radii of the critical gas bubbles and the droplets, respectively, the agitation of the liquid is inhibited.

W

The power of gravity · C ^_etching - $_gas) · G

Surface tension force F ^. = * 2 ^ r

At the critical minimum bubble or droplet radius, F ^ = The critical minimum bubble or droplet radius, r ^ ri ^&gt; which determines the desired, lowest tat packing degree, is thus:

^rkrxt = ...........

The following applies r =: radius of the bubble surface tension liquid - gas $ = density g = acceleration of gravity

The degree of tightness should therefore be such that the minimum width of the channels between the particles does not exceed twice the critical line

e) The gas pressure in the bottom of the vessel shall be higher than the hydrostatic pressure of the liquid but lower than the hydrostatic pressure of the whole overlying mass.

Otherwise gas seeks up through the mass from underlying portions. This gives the expression:

^Patm ⁺ $ liquid * $ * + h ^) &lt; ^Pgas ^Patm ⁺ fmassa ·

S '^hrs2 ⁺ 'liquid' ^g * ^hrs1 whereby h ^ = the height of the liquid which accumulates on the surface of the mass h ^ = the height of the liquid-soaked mass. ···. · .. (3)

By combining condition (3) with equation (1), the maximum separation rate can be calculated.

According to a development form of the invention, there is also provided a method of separating the liquid from the solid material by a substantially continuous process. A purpose of this form of development is also to achieve a further improved heat economy and preferably also a higher degree of purity of the products through a substantially continuous countercurrent process.

An object of yet another embodiment of the invention is to further increase the "maximum" separation rate.

According to the development of the invention, this is done by increasing the gas pressure gradient in the vertical direction in the mass by amplifying the difference between the gas pressure Pg_as the lower part of the mass and the pressure on the solid phase in the upper surface of the mass in addition to what is achieved by the heating.

This can be achieved by applying an external pressure P y to the solid phase from above, for example by pressing a screen cloth which is permeable to the liquid but not to the solid phase against the solid phase. Another way is vacuum suction on the top of the container, ie vacuum suction from the container space over the surface of the pulp. Both of these options can also be combined. Equation (3) can thus be extended according to (4):

^Pvacuum ⁺ ^ liquid 'β * (^hrsin ⁺ &lt; ^Pgas &lt; ^Py ^{+ P}vacuum ⁺ $ mass * ^ 2 ⁺ ^ liquid * .......

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Through either or both of these measures, the pressure difference between the gas pressure increases

P gas in the displacement zone in the lower part of the mass ooh the pressure of the solid gas on the surface of the mass. At the same time, the steam formation temperature is affected in a favorable direction.

The invention will now be further explained by the description of some preferred embodiments with reference to the accompanying drawing figures, which schematically describe the principles of the embodiments.

Fig. 1 shows a container containing a liquid-containing mass, from which the liquid phase is being separated from the solid phase.

'

Pig. 2 shows a battery of containers whose liquid contents are being separated.

Pig. 3 illustrates a development of the invention for continuous liquid separation.

Pig. 4 illustrates a further development of the invention and shows a container containing a liquid-containing mass, in which the liquid phase is being separated from the solid phase, and

Pig. 5 shows the pressure conditions in the container at that in Fig. 4 illustrated the embodiment of the invention, respectively in the embodiment according to Figs. 1.

Referring first to Pig. 1 denotes a jelly-like mass of metal-containing particles soaked in a liquid generally with the number 1. When the metal-containing particles consist of metal oxides obtained from wet filters from metallurgical furnaces or of metal compounds from beet baths, the particles normally have

7907037-1 "microscopic" size, ie from any ym up to about 100 / um. As the particles consist of grinding chips, the majority of the chips have sizes ranging from very small, comparatively round particles from sizes about 0 5 / um to slightly larger, usually elongated particles with sizes about 150 x 20yum. This mixture of fine particles and liquid gives a mass 1 with characteristic gelatinous consistency. The pulp is collected in a container 2, which according to the embodiment consists of an ordinary oil plate barrel which is normally used as a transport container for the waste product in question. The container 2 is hermetically sealed with a lid 3. For heating the contents of the container 2, a burner 4 is arranged below the container. Other heating methods are of course also conceivable, such as, for example, heating with an oil burner, which has been used successfully in experiments performed. Electric heating is also conceivable in principle. The number 5 denotes a line for diverting combustible gas. An overflow drain has been designated 6. Shut-off valves in the gas line 5 and in the overflow drain 6, respectively, have been designated 7 and ö. Liquid which subsequently collects on the surface of the pulp has been designated 9.

Although this has not normally been shown to be necessary, it is per se possible to separate the upper part of the partially dried mass from the bottom and middle portions and transfer the former to a new container for continued liquid evaporation. In this way, a mass can be obtained which is practically free of liquid.

The invention can be illustrated by the following examples.

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Example 1

An oil barrel with 110 liters of a mass consisting of high-speed grinding chips soaked in cutting oil was heated from below with an oil burner. The oil content at the start of the experiment was 32.5 weight5 percent. After 10 hours, the oil content in the bottom part of the vessel had dropped to less than 0.2, ie this part of the container was practically free of oil. The center of the pulp had also been substantially completely oiled, while the outer portions at the level indicated in Fig. 1 had been lowered to 4.2 and 2.3 ¢, respectively. In the uppermost part of the mass, the oil content in the center was 17.0% and in the outer parts 9.5 and 15, respectively. The sampling points have been marked in Fig. 1. At the top was an oil layer which was drained through the overflow drain. line 5 and burned in a safety torch »

A number of containers consisting of ordinary oil drums were oiled in this way. The containers containing the contents of a 30 ton electric arc furnace were then melted in quantities up to 2 tonnes 20 per batch. 1.5 tonnes per batch proved to be a suitable amount corresponding to 5 of the total addition of raw materials. No tendencies to combustion puffs, risks of accelerated feed wear or remarkable smoke development could be detected.

Example 2

In this case, the mass 1 consisted of sludge consisting of secreted metal compounds. These very small particles consisted mainly of iron compounds. The liquid consisted of an aqueous solution. This mass containing about 45% water was heated in an oil barrel according to the invention in the manner illustrated in Fig. 1. The water 9 which subsequently accumulated on the upper surface was drained, after which the substantially dried material could be dumped together with other waste material without causing any harmful effect on the environment.

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Fig. 2 schematically shows a production plant for carrying out the method according to the embodiment of the invention illustrated in Fig. 1. The containers 1 are as shown in the figure arranged on a common fireplace 10. The evaporated liquid is led through a line 11 to a collecting container 12. The gas formed during the liquid evaporation is used, in cases where it is combustible, according to this embodiment for heating in the fireplace 10. and is thereby diverted through a line 13.

Fig. 3 shows a plant for continuous treatment according to the invention. In this embodiment of the method according to the invention, the raw material is assumed to be in the form of a sludge with a very large liquid content, for example a sludge containing beet bath residues. The plant shown in Fig. 3 is therefore provided with a sedimentation basin 21 with filling means 22 for new raw material. The basin 21 has a sloping bottom so that sediment preferably accumulates in the deepest part of the basin. To transport sediment from other parts of the pool bottom, suitable means of transport can be arranged.

In Fig. 3 this has been symbolically illustrated by a straight 23. The sludge in the pool 21 has been designated 24.

The basin 21. transforms in its deepest part into a container in the form of a shaft 25, in which the sedimented, liquid-containing mass gradually accumulates. Under the shaft 25 a heat source 26 is arranged. According to the embodiment this consists of a number of oil burners but can also consist of gas burners, electric heating means, equipment for utilizing waste heat from another process, or of combinations of said heat sources.

A draining device for the liquid phase has been designated 30. According to the embodiment, this consists of a overflow drain. Other draining means are also conceivable, such as, for example, a suction device. Arranged in the bottom part of the shaft container 25 is a discharge channel 27 for materials with a high dry content. Arranged in the discharge channel 27 are transport means, for example a screw conveyor 28, which is driven by a motor 29. The screw conveyor 28 also extends through the lower part of the shaft 25, so that the dry material in the bottom part of the shaft can be discharged through the channel 27. The channel 27 opens into a receiving chamber 31, which is under overpressure. This has been symbolically marked in Fig. 3 by an air pump 32. A container for separated material has been designated 34. In order to increase the separation capacity for liquid in the shaft 25, the equipment can also be supplemented with a filter press 33. For a further increase in capacity, it is also possible to exercise

7907037-1 shaft 25 for a negative pressure. This requires, however, a modified design of the plant, which is not shown in Fig. 3.

The device briefly described above is intended to operate in the following manner. Through the line 22 raw material in the form of sludge is supplied to the basin 21. The solid material settles and accumulates in the shaft 25, whereby if necessary the razor 23 or similar aids are used. The shaft - the container 25 - is heated from below by means of the heating equipment 26. The liquid in the mass contained in the shaft 25 will then evaporate in the lower part of the shaft. Provided that the criteria set out in the preamble to the description are met, the steam will push up liquid in the upward direction through the shaft. By adapting the heat supply, dry material can be taken out substantially continuously by means of the screw conveyor 28 through the discharge channel 27 all the while new material is supplied to the shaft 25 from above. The upward force of the zone evaporation on the liquid in the mass is thus regulated so that it keeps pace with the supply of new liquid through the continuous supply of new moist mass to the shaft 25 and to the removal of dried material from the bottom part of the shaft. The lower part of the shaft 25 is at the same time under a certain overpressure, which prevents the steam from leaving the shaft through the discharge channel 27. In order to be able to carry out the process completely continuously, it is suitable that the leaching of dry material from the chamber 31 takes place through a pressure lock. It is also possible for the shaft 25 to be provided with several discharge channels, which can be operated alternately, so that discharge can take place without interruption in the discharge.

Fig. 4 and Fig. 5 illustrate a further development of the method according to the invention. The pulp to be disposed of may be of the same kind as those mentioned in connection with Fig. 1 or of another kind as stated in the description introduction. Refering to

Fig. 4 denotes a container, for example an oil barrel, with the number 41, and a lid has been designated 42. The moist mass in the container 41 has been denoted 43. In the illustrated situation, the liquid has been separated from the lower parts of the mass in the container. The lower, drier part, which thus mainly consists of comparatively dry powder, has been designated 44. Between the dry part 44 and the liquid-soaked mass 43 there is an evaporation zone 45 formed by the contents of the container being heated from below by a number of burners 46. The number 47 denotes a line for diverting combustible gas from the container 41. The line 47 is connected to an air pump 48 to produce a negative pressure in „7907037-1 in the container in the space 49 above the mass 43.

In order to increase the pressure on the solid phase in the mass 43, i.e. on the amount of solid particles in the mass, a piston 50 is arranged which can be pressed down against the mass 43 by means of a rod 51, which is sealingly mounted in the lid 42. The pressing of the piston 50 against the mass 43 takes place via a screen cloth 52 which can let liquid through from the mass 43 which is substantially impermeable to the solid particles from the mass 43. The liquid filtered through the screen 52 gradually passes through openings 53 in the piston 50 and accumulates as an increasing amount of separated liquid 54. The amount of liquid 54 is sucked out of the container 41 by replacing the line 47 with a liquid extraction line, after the vacuum pump 48 has been disconnected. Alternatively, draining can take place under "vacuum" through a specially arranged device for liquid extraction. It is also possible to remove the amount of liquid 54 as a final operation after completion of separation of the liquid from the solid phase in the container.

Gradually, the evaporation zone 45 corrodes upwards in the mass 43. Fig. 5 thus illustrates the situation picture when approximately half the amount of the mass in the container has been treated. The pressure conditions in the container are schematically illustrated in the diagram in Fig. 5. The solid line thus illustrates the conditions according to the embodiment of the invention, whereby a pressure difference &amp; p ^ exists between the pressure in the "dry" part 44 of the mass in the container and the gas pressure on the surface of the mass. The dashed line in the diagram in Fig. 5 illustrates corresponding conditions in the case where the pressure in the space 49 in the upper part of the container 41 corresponds to atmospheric pressure and the piston 50 is not pressed against the mass 43. The pressure difference A obtained in this case is significantly lower than the pressure difference A p. The method according to the embodiment can also be combined with continuous supply of new pulp to the upper part of the container and continuous removal of separated liquid and dried material, keeping the evaporation zone level substantially constant in the room.

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