Method for separating crusts and substrates

Abstract

 A method for separating crusts and substrates comprises the steps of: classifying mixed ores composed of crusts and substrates, as a first classification step, by at least one first classifier (1), into plurality of groups of classified ores; crushing each of the groups of the classified ores into plurlaity of groups of crushed ores by crushers (2a,2b,2c) equipped with heaters, each, while the classified ores are kept heated; and classifying each of the groups of the crushed ores as a second classification step, by at least one second classifier (3a,3b,3c), thereby to separate the crusts and the substrates. The heating of the classified ores can be separately carried out by an independent heating apparatus before the crushing of the classified ores. The temperature of the heating is at 500 to 1,300°C. 800 to 1,000°C is more preferable.

Description

[0001] The present invention relates to a method for separating crusts, especially cobalt-rich ferromanganese crusts and substrates, and more particularly to the terms and conditions on separation of the crusts and the substrates.

[0002] Crusts are bedded sedimentary resources of sea bottom deposited on the surface of substrates, and valuable metal such as Co, Ni and Mn can be obtained by smelting those crusts. Actually, however, these substrates often mix with crusts when the crusts are mined. Mixing quantity of substrates affects greatly the cost of smelting. For this reason, it is required to separate mixed ores which have been mined into crusts and substrates at a stage before the process of smelting.

[0003] As prior art methods of concentrating ores from gangues, (a) gravity separation, (b) floatation and (c) magnetic separation are known. Any of those, however, cannot be efficiently applied to concentrating crusts, more or less, due to the reasons mentioned below.

[0004] The gravity separation is a method of separating and concentrating the ores by making use of difference of sedimentation rates in sea water, fresh water and other various liquid agents, due to specific gravity difference of ores and gangues. This method, however, is not generally applicable because the specific gravity difference between ores and gangues often is small enough to fail in guaranteeing an accurate and constant concentration. Secondly, the floatation is a method wherein crusts are absorbed and separated by making use of difference of surface chemical properties which crusts and substrates respectively have. On land, most of copper ore deposits exist in the form of sulfide, and cobalt is recovered as a by-product of the main production of copper by making use of concentration through the floatation. Since valuable metals contained in crusts, however, exist in the form of oxides, it is known that application of the floatation to oxides is difficult, compared to application of the same to sulfide. Therefore, the floatation is hard to apply to concentrating crusts. Thirdly, the magnetic separation is a method wherein ores magnetized by powerful magnetic field are absorbed in the magnetic force and separated. But, the difference of the magnetic property between oxides of Co, Ni or the like and other metal compounds or non-metal compounds is so small that the application of this separation method is not satisfactory for concentrating crusts.

[0005] The inventors proposed a method, in a Japanese Patent Application Laid Open No. 12381/88, as a related art, wherein crushing and classifying crusts and substrates are repeated to separate crusts and substrates. This method makes use of difference of brittleness of crusts and substrates, and of weak adhesiveness between crusts and substrates. The mixed ores are crushed into grains and the grains are selected out by a screen and classified into groups of different grain size. This method is comparatively simple, but the efficiency of the separation in this method is limited.

[0006] The object of the present invention is to provide a method for separating crusts and substrates in high efficiency.

[0007] To attain the object, in accordance with the present invention, a method is provided for separating crusts and substrates comprising the steps of classifying mixed ores composed of crusts and substrates, as a first classification step, by at least one first classifier, into plurality of groups of classified ores; crushing each of the groups of the classified ores into plurality of groups of crushed ores by crushers equipped with heaters, each, while the classified ores are kept heated; and classifying each of the groups of the crushed ores as a second classification step, by at least one second classifier, thereby to separate the crusts and the substrates.

[0008] Furthermore, a method is provided for separating crusts and substrates comprising the steps of classifying mixed ores composed of crusts and substrates, as a first classification step, by at least one first classifier, into plurality of groups of classified ores; heating each of the groups of the classified ores by a heating apparatus; subsequently crushing each of the groups of the classified and heated ores, into plurality of grpuos of crushed ores; and classifying each of the groups of the crushed ores, by at least one second classifier, thereby to separate the crusts and the substrates.

[0009] The above object and other objects and advantages of the present invention will become apparent from the detailed description to follow, in conjunction with the appended drawings.

Fig. 1 is a graphic representation showing a relation of compressive strength to heating temperature of crusts of the present invention;

Fig. 2 is an explanatory representation illustrating a principle of the method of the present invention;

Fig. 3 is an explanatory flow diagram of an embodiment of the present invention;

Fig. 4 is a schematic view illustrating an embodiment of a crusher equipped with a heater used in the present invention; and

Fig. 5 is an explanatory flow diagram of another embodiment of the present invention.

Preferred Embodiment 1

[0010] With specific reference to the drawings, a preferred embodiment of the present invention will now be described. Fig. 1 graphically shows a relation of compressive strength of crusts to heating temperature. In this representation, heating time is used for a parameter. As clearly seen therefrom, the heating temperature is overwhelmingly a ruling factor, in comparison with the heating time. Furthermore, it is also seen that at a temperature of 500°C or more, the strength remarkably goes down, and at 800°C or more, it is further reduced, but with lower reducing rate. However, even if the temperature is raised to more than 1,000°C, the strength does not go down so much. Furthermore, when the temperature becomes more than 1,300°C, there is the possibility that heating equipment is in danger of losing heating resistance in the heating process. Consequently, the heating temperature ranges preferably 500° to 1,300°C. 800° to 1,000°C is more preferable.

[0011] The compressive strength of substrates at high temperature is by far stronger than that of crusts shown in this graphic representation. Therefore, most of the substrates are not crushed so much during the heating and crushing process, and they remain as coarse grains or lumps. Consequently, if the classification is carried out after the heating and crushing process, separation of crusts and substrates can be easily attained.

[0012] Referring specifically to Fig. 2, a principle of the present invention will now be explained, based on the aforementioned knowledge. Fig. 2 schematically illustrates the principle forming a basis of the present invention. When mixed ores (C) composed of crusts (A) and substrates (B) are heated, the crusts become so brittle that they can be crushed more easily than the substrates. Due to this reason, if the mixed ores are crushed while kept heated or after having been heated, and subsequently classified, then, the mixed ores are separated into fine grains rich in crusts and coarse grains rich in substrates. In this crushing process, a part of the substrates is crushed into grains almost equal to the fine grain size of the crushed crusts. The ratio, however, of fine grain size substrates included in the fine grains of the crushed crusts are by far smaller than in the case of the mixed ores being crushed at room temperature.

[0013] Now, an embodiment of the present invention, based on the aforementioned principle will be given with specific reference to Fig. 3 of the drawing. Fig. 3 illustrates a flow diagram of an embodiment of the present invention. The present invention is preferably applicable to cobalt-rich ferromanganese. Referential numeral 1 denotes a first multistage classifier for classifying mixed ores composed of crusts and substrates in the first classification step, crushers 2a, 2b and 2c equipped with heaters, each, crushing the mixed ores which are kept heated to form crushed ores, and 3a,3b and 3c second classifiers classifying the crushed ores. Mixed ores composed of crusts and substrates stored in storage yard 4 are supplied into transfer hopper 5 and the mixed ores are transferred from hopper 5 to charging hopper 7 through conveyor 6. Then, the mixed ores are introduced into the first classifier by means of hopper 7. The first classifier classifies the mixed ores into several groups of the mixed ores, by making use of grain size difference through screening, namely into three classes consisting of coarse grain ores, intermediate grain ores and fine grain ores in this embodiment. The first classifier of multistage can be alternated by plurality of single stage classifiers. Following the first classification step, the three different grain ores, each, are put into each of crushers 2a to 2c corresponding to the three different grain ores in size, and are crushed while kept heated. The coarse grain ores are put into crusher 2a, the intermediate grain ores into crusher 2b and the fine grain ores into crusher 2c. In this crushing process, crusts included in the crushed ores become easier to be crushed than substrates as mentioned. Owing to these features of the crusts and substrates, among the ores thus crushed, the fine grains thereof are rich in crusts, while the coarse gains are rich in substrates. It is preferable that the heating temperature and the heating time are controlled, corresponding to kinds and grain sizes of the mixed ores.

[0014] The ores crushed by each of crushers 2a to 2c are further transferred to second classifiers 3a to 3c. Coarse grains of the mixed ores crushed by crusher 2a are transferred to second classifier 3a. Similarly, intermediate grains and fine grains of the mixed ores, each, are tranferred to crushers 2b and 2c. In the second classifiers, the ores are classified through screening into fine grains rich in crusts and coarse grains rich in substrates. The fine grains are put into pulverizer 8 to be pulverized into particles, and then, the particles are transferred to the following step. In the meantime, in the case that a plenty of crusts are still included in the coarse grains, another concentrating method is applied to those crusts.

[0015] As crushers 2a to 2c, an apparatus composed of a rotary kiln with crushing balls or rods therein can be used. Fig. 4 illustrates an embodiment of the crushers equipped with heaters, each. Crushers 2a to 2c, each, comprise cylindrical body 21 having crushing balls 25 of steel in the cylindrical body, a plurality of supporting rollers 22, burner 23 for heating the mixed ores inside the cylindrical body and driving unit 24 for driving a part of the supporting rollers.

[0016] Cylindrical body 21 has a structure inserting heat insulating material 211 between inner cylinder 212 and outer cylinder 213 so as to prevent the heat insulating material from being damaged by an impact produced by dropping of crushing ball 25. Cylindrical body 21 has riding rings 26 fixed on its outer periphery and is supported by each of supporting rollers 22 through the riding rings. In the cylindrical body, mixed ores introduced thereinto by means of hopper 27 are heated by combustion gas produced by burner 23, and, at the same time, are crushed by self-dropping work of the mixed ores and collision of the mixed ores and crushing balls 25 to form crushed ores. After the completion of the crushing, the crushed ores are discharged through exit hopper 28. It should be noted that when the mixed ores are sufficiently large and heating temperature is sufficiently high, crushing balls 25 are not necessarily required.

[0017] As shown in Fig. 3, if classification of the mixed ores is carried out independently by each of the second classifiers, the classification process can be simplified in view of their constitution. The classification can be effectively performed by a multi-­step method as follows: when crusts and substrates included in the mixed ores which have been discharged out of second classifiers 3a and 3b processing coarse grains and intermediate grains are not satisfactorily separated, the mixed ores of undersize classified by second classifiers 3a and 3b can be again classified correspondingly in second classifiers 3b and 3c which process intermediate grains and fine grains to increase efficiency of concentrating. For the multi-­step method, it is preferable that classifiers 3a,3b and 3c, each, have three different mesh size screenings corresponding to large, intermediate and small mesh in descending order, and the classifiers are set at three different levels in the same order.

[0018] Furthermore, in this embodiment, a method is adopted, wherein heating mixed ores and crushing the same are simultaneously performed by a single apparatus of a crusher equipped with a heater. The heating and crushing process, however, can be independently performed by a heating apparatus such as a high temperature drying furnace and by a crushing device. In other words, the mixed ores are heated by the heating apparatus, followed by the process of crushing the same, whereby the efficiency of the separation can be increased by means of controlling the heat temperature and the heating time, depending on kinds of the mixed ores.

[0019] In this embodiment, mixed ores of crusts and substrates are firstly classified by first classifier 1, and crushers 2a to 2c are set corresponding to levels of grain sizes. This is because impact required for crushing and heating time for elevating temperature upto a predetermined level are different, depending on grain sizes, and efficient heating and crushing can be procured. Besides that, the reason for providing three sets of second classifiers 3a to 3c is that the size distribution of grains of mixed ores crushed by crushers 2a to 2c is different, depending on their sizes and therefore, for example, in the case of taking size distribution of crust grains crushed by crusher 2a, most of crust grain sizes are larger than those crushed by crushers 2b and 2c. Resultantly, if only one of the second classifiers is provided for three of the crushers, the efficiency of the separation of crusts and substrates is degraded and the yield goes down because of a single mesh screen.

[0020] Depending on kinds of mixed ores, heating temperature or heating time, even if the unit number of the second classifier is at least one but less than the number of groups the first classifier classifies, the efficiency of the separation of crusts and substrates and the yield do not always go down.

Preferred Embodiment 2

[0021] In the preferred embodiment 1 shown in Fig. 3, three crushers 2a, 2b and 2c are set, meeting the number of groups classified by first classifier 1. But, depending on kinds of the mixed ores, heating temperature and heating time, a method of the present invention can be carried out without using the first classifier.

[0022] Now, referring specifically to Fig. 5 of the drawing, another embodiment of the present invention will be described.

[0023] Mixed ores stored in storage yard 4 are supplied to crusher 2 equipped with a heater. The mixed ores crushed by crusher 2 are transferred to second classifier 3. In the second classifier, the ores are classified through screening into fine grains rich in crusts and coarse grains rich in substrates.

[0024] Furthermore, in this embodiment, as a crusher, the crusher with a heater is used. But, in stead, the mixed ores are firstly heated by a heating apparatus (not shown), and subsequently crushed by a crusher which is not equipped with a heater.

[0025] The method of the present invention as explained in the foregoing can be effectively incorporated into a crushing step of chloridation-roasting leach process and roasting sulfuration leach process, whereby an integrated process of smelting crusts with high efficiency can be obtained.

[0026] The present invention has advantages in that:

(a) crusts and substrates can be very much efficiently separated and efficiency in smelting the crusts can be increased. This is because in the method, ores composed crusts and substrates are crushed during or after heating, followed by the process of crushing the ores by making use of a feature of crusts. The crusts, if once heated, become very much easy to be crushed in comparison with substrates; and

(b) an integrated process of smelting crusts with high efficiency can be easily obtained by incorporating the steps of the separation method of the present invention in the prior art processes of the chloridation-roasting-leach process and the roasting-­sulfuration-leach process.

Example

[0027] Mixed ores of crusts and substrates consisting of 20% of less than 30mm, 60% of 30 to 50mm and 20% of more than 50 but 100mm or less in grain size were classified by first classifier 1 respectively into three groups of fine, intermediate and coarse grains. These three grains were put into each of rotary kilns 2a, 2b, and 2c with crushing balls, correspondingly in descending order of grain size to be crushed into three groups of the crushed grains. In the operation, the temperature of heating each group of the mixed ores was 900°C, and the time of heating them, each, was 5, 3 and 1 minute correspondingly to each of the groups. The crushed grains of the mixed ores, each, were put into second classifiers 3a, 3b and 3c. The size distribution of crusts were remarkably different from that of almost uncrushed substrates after both were discharged from the rotary kilns. Consequently, the crusts and the substrates could be easily separated.

[0028] The crusts discharged below the screening of the second classifiers were transferred to the following step of smelting the crusts. The substrates remaining on the screening were thrown away or sent to another process of concentrating the same.

Claims

1. A method for separating crusts and substrates comprising the steps of:
      classifying mixed ores (C) composed of crusts (A) and substrates (B), as a first classification step, by at least one first classifier (1), into plurality of groups of classified ores; and
      classifying each of the groups of the crushed ores, as a second classification step, by at least one second classifier (3a,3b,3c) thereby to separate the crusts (A) and the substrates (B),
      characterized by crushing each of the groups of the classified ores into plurality of grounds of crushed ores by crushers (2a,2b,2c) equipped with heaters (23), each, whole the classified ores are kept heated.

2. The method of claim 1, characterized in that said keeping the classified ores heated includes keeping the classified ores heated at 500 to 1,300°C.

3. The method of claim 2, characterized in that said keeping the classified ores includes keeping the classified ores heated at 800 to 1,000°C.

4. The method of claim 1, characterized in that said at least one second classifier (3a,3b,3c) includes being equal to or less than the number of the groups of the classified ores in the first classification step.

5. The method of claim 1, characterized in that said the at least one second classifier (3a,3b,3c) includes two or more second classifiers (3a,3b,3c).

6. The method of claim 5, characterized in that two or more second classifiers (3a,3b,3c) include having different mesh size screenings, undersize ores classified by one of the two or more second classifiers (3a,3b,3c) with a larger mesh size screening being supplied into another with a smaller mesh size screening.

7. A method for separating mixed ores of crusts and substrates comprising the steps of:
      classifying mixed ores (C) composed of crusts (A) and substrates (3), as a first classification step, by at least one first classifier (1), into plurality of groups of classified ores; and
      classifying each of the groups of the crushed ores, by at least one second classifier (3a,3b,3c), thereby to separate the crusts (A) and the substrates (B),
      characterized by heating each of the groups of the classified ores by a heating apparatus (23); and
      subsequently crushing each of the groups of the classified and heated ores into plurality of groups of crushed ores.

8. The method of claim 7, characterized in that said heating the classified ores includes heating the classified ores at 500 to 1,300°C.

9. The method to claim 8, characterized in that said heating the classified ores includes heating the classified ores at 800 to 1,000°C.

10. The method of claim 7, characterized in that said at least one second classifier (3a,3b,3c) includes equal to or less than the number of the groups of the classified ores in the first classification step.

11. The method of claim 7, characterized in that said at least one second classifier (3a,3b,3c) includes two or more second classifiers (3a,3b,3c).

12. The method of claim 11, characterized in that said two or more second classifiers (3a,3b,3c) include having different mesh size screenings, undersize ores classified by one of the two or more second classifiers (3a,3b,3c) with a larger mesh size screening being supplied into another with a smaller mesh size screening.

13. A method for separating crusts and substrates comprising the step of:
      classifying the crushed ores, thereby to separate the crusts (A) and the substrates (B),
      characterized by crushing mixed ores (C) composed of crusts (A) and substrates (B) into crushed ores while the mixed ores (C) are kept heated.

14. The method of claim 13, characterized in that said keeping the classified ores heated includes keeping the classified ores heated at 500 to 1,300°C.

15. The method of claim 14, characterized in that said keeping the classified ores includes keeping the classified ores heated at 800 to 1,000°C.

16. The method for separating mixed ores of crusts and substrates comprising the step of:
      classifying the crushed ores, thereby to separate the crusts (A) and the substrates (B),
      characterized by heating mixed ores (C) composed of crusts (A) and substrates (B); and
      subsequently crushing the mixed ores (C) heated into crushed ores.

17. The method of claim 16, characterized in that said heating the classified ores includes heating the classified ores at 500 to 1,300°C.

18. The method of claim 17, characterized in that said heating the classified ores includes heating the classified ores at 800 to 1,000°C.

Drawing