Plant and method for the recovery of exhausted refractory material

Abstract

Plants and methods recover spent refractory material and comprise at least one receiving area for said refractory material, at least one material sieving area, at least one magnetic separation area, and at least one sorting area. Said receiving area communicates with a first sieving area divides said refractory material in at least two fractions based on sizes of said refractory material. A second sieving area divides a fine fraction into at least two sub-fractions.

Claims

1. A method for recovering spent refractory material in one or more steel plants and reusing finished product of recovered spent refractory material, the method comprising the following steps: a) receiving refractory material coming from demolition of refractory material linings in containers used in steel making, treatment and manufacturing processes, wherein the refractory material includes basic refractory parts comprising at least one of magnesic material and dolomite material, b) sieving and separating the refractory material, and c) collecting the refractory material, wherein step b) comprises the following sub-steps: b1) first sieving of the refractory material into at least two fractions on the basis of a first specific threshold size value, so as to identify a fine fraction and a coarse fraction, b2) magnetically separating the fine fraction, and b3) magnetically separating the coarse fraction into at least one of a magnetic metal part, a nonmagnetic metal part, and a refractory part, and wherein said coarse fraction is fragmented into small granules, b4) second sieving of the fine fraction into three different sub-fractions on the basis of two second specific threshold size values, b5) identifying two sub-fractions with greater size, and b6) nonmagentically separating the two sub-fractions with greater size such that nonmagnetic metal parts are separated with respect to fine parts, b7) producing basic granulate materials as a finished product by a grinding operation of the small granules in combination with said fine parts, wherein the basic granulate materials consist of raw material usable in a melting process in an electric furnace; and b8) partially replacing lime necessary for the melting process in the electric furnace by disposing slag conditioner into the electric furnace, wherein slag conditioner comprises the raw material of the basic granulate materials.

2. The method according to claim 1, wherein the fine parts and/or the coarse fraction are separated on the basis of at least one of chemical properties of the coarse fraction and physical properties of the coarse fraction.

3. The method according to claim 1, wherein an initial step, before step a), comprises sorting spent refractory material according to origin of said material.

Description

(1) These and other characteristics and advantages of the present invention will be more clear from the following description of some embodiments shown in the annexed drawings wherein:

(2) FIG. 1 is a schematic functional block diagram of the plant and method of the present invention according to a possible embodiment;

(3) FIG. 2 is a schematic diagram of the plant and method of the present invention according to a further embodiment.

(4) It is specified that figures annexed to the present patent application are shown in order to better define characteristics and advantages of the plant and method of the present invention.

(5) Therefore such embodiments have to be intended by way of explanation and not as a limitation of the inventive concept of the present invention, that is to provide a plant and method for the recovery of refractory materials that allow the recovery of materials to be optimized, while limiting as much as possible waste products.

(6) With particular reference to FIG. 1, the plant for the recovery of spent refractory material in steel plants, comprises at least one receiving area for the refractory material, at least one material sieving area 2, at least one magnetic separation area 3 and at least one sorting area 4.

(7) Particularly the receiving area 11 communicates with a first sieving area 2 comprising first sieving means intended to divide the refractory material in at least two fractions, of which a coarse fraction and a fine fraction, based on material size.

(8) There being further provided a second sieving area 21 comprising second sieving means intended to divide the fine fraction into at least two additional sub-fractions on the basis of size.

(9) The first and second sieving means can be made according to any methods known in prior art.

(10) For example they can be composed of vibrating screens having grids of specific dimensions intended to filter the material with larger size.

(11) Assuming the pieces of refractory material to be as cubes, according to a preferred embodiment, such grids allow the material to be sorted such that the coarse fraction is composed of pieces with side larger than 50 mm and the fine fraction is composed of pieces with side smaller than 50 mm.

(12) With particular reference to FIG. 1, it is specified that the functional path of coarse fraction is shown in the right side of the figure, while the one of the fine fraction is shown in the left side.

(13) However these are merely functional diagrams, since both coarse fraction and fine fraction are preferably treated by the same equipment, as regards shared treatments.

(14) Therefore the receiving area 11 communicates with the first sieving area 2 that communicates with at least one material magnetic separation area 3.

(15) There are provided first transfer means intended to convey the coarse fraction in the sorting area 4 as well as second transport means intended to convey the fine fraction to the second sieving area 21.

(16) On the basis of the characteristics of the plant outlined in FIG. 1, the refractory material is treated according to the following method steps: a) receiving the refractory material, area 1, b) sieving and separating the refractory material, areas 2, 21 and 3 c) collecting the refractory material, area 4

(17) The sieving and separating step provides the following sub-steps: b1) first sieving, denoted by 2, of the material into at least two fractions on the basis of a first specific threshold size value, such to identify a fine fraction and a coarse fraction, b2) magnetic separation of the fine fraction, denoted by 3 b3) magnetic separation of the coarse fraction denoted by 3, b4) second sieving of the fine fraction into at least two sub-fractions on the basis of a second specific threshold size value, denoted by 21.

(18) Particularly the fine fraction provides pieces with side smaller than 50 mm and upon the second sieving operation it is further divided into three sub-fractions by using two threshold values, 5 mm and 15 mm.

(19) In this case therefore it will be possible to provide two grids, providing holes with side of 5 mm and side of 15 mm, such to form a fraction A of material with sides having a size from 0 to 5 mm, a fraction B with sides having a size of 5 to 15 mm and a fraction C with sides having a size from 15 to 50 mm.

(20) As it is shown in FIG. 1, fractions B and C with larger size are identified and a nonmagnetic separation 31 is carried out, intended to separate nonmagnetic metal parts with respect to fine parts.

(21) As it will be shown below the fine parts are used for the production of granulate products, while fraction A is stored inside suitable collection areas 6.

(22) Since refractory material exhibits irregular shapes, it is possible to find fractions with one of the dimensions greater than 50 mm.

(23) In this case it is possible to separate such pieces and to crush them such to perform the cycle described above with reference to fine fraction.

(24) As an alternative or in combination it is possible to provide such pieces to be inserted into the cycle of the coarse fraction.

(25) The coarse fraction, after magnetic separation, denoted by 3, is divided into at least one magnetic metal part, at least one nonmagnetic metal part and at least one refractory part, before being collected and stored.

(26) According to a possible embodiment, the refractory part is at least partially divided into small granules, such to use such granules in combination with fine parts for producing basic or aluminous granulate materials.

(27) Moreover, such as described in details in FIG. 2, fine parts and/or the refractory part can be separated on the basis of their chemical-physical characteristics.

(28) With a particular reference to FIG. 1, it is possible to provide a step 10, before receiving the material 1, and related to sorting the spent refractory material on the basis of the origin of said material.

(29) FIG. 2 shows in more details and according to a possible embodiment the method and the plant described up to now and subject matter of the present invention.

(30) On the basis of what shown in FIG. 2, refractory materials are received and taken at the receiving area denoted by 11.

(31) As mentioned above, said materials are divided according to their origin. The discharge operation can be carried out from a motor vehicle, by a dumper or from the demolition area by being conveyed with excavator or wheel loader 7.

(32) Before the first sieving area 2 it is possible to provide to remove metal parts and agglomerates having metric and decimetric size with the help of an excavator or a loader. Such removal can be obtained manually by visually checking the material.

(33) Then the sieving action is carried out, denoted by 2, which is performed at the beginning of the treatment with a twofold aim of separating the fine fraction and of obtaining a coarse fraction, with a size greater than 50 mm, free from fine material in order to facilitate the following sorting step.

(34) Advantageously materials are filtered by batches that correspond to a specific origin.

(35) The screening (or sieving) is carried out by using the automatic plant arranged in the relevant position.

(36) Materials fed with a wheel loader 7 in the hopper 22 are conveyed to a primary sieve 23 from where fine fraction results, preferably with size smaller than 50 mm, intended to be sorted.

(37) The fine fraction is subjected to iron removal by means of overband magnetic separator 24 and then conveyed to the sieve 25 where preferably the following grain size fractions are obtained: 0/5 mm-mm and 15/50 mm.

(38) 5/15 and 15/50 mm fractions, intended for being subjected to nonmagnetic separation, are stored in box B13 and B14.

(39) The 0/5 mm fraction is conveyed to storage silos A1-A and A1-B for Dolomite or Magnesic material respectively.

(40) The nonmagnetic separation, denoted by 31, provides the 5/15 mm and 15/50 mm fractions resulting from the sieving process described above, to be mechanically treated such to separate the nonmagnetic metal parts present therein that have not been previously sorted by the magnetic separation.

(41) Nonmagnetic separation is carried out alternatively on 5/15 mm and 15/50 mm fractions on an automatic and independent treatment line.

(42) Materials to be treated are introduced in the hopper 32 from where they are conveyed to the inductive separator 33. The metal fraction is discharged from the belt 34 into a bin 35, the inert fraction is stored in box B15.

(43) 5/15 mm and 15/50 mm fractions are intended for production of 5/50 mm basic granulates. These are transferred by the wheel loader 7 in boxes B11 and B12, for Dolomite and Magnesic materials respectively.

(44) In order to limit dust generation during the treatments on fine fraction, it is possible to provide a dust collecting plant, denoted by numeral 9 in FIG. 2.

(45) The coarse fraction deriving from screening or sieving process 2 is composed of refractory materials of different qualities used in the several refractory constructions, generally bricks or parts thereof.

(46) Such materials are subjected to a sorting operation, denoted by 3, such to separate: 1. Magnetic metal parts 2. Nonmagnetic metal parts 3. Aluminous refractories 4. Spinel refractories 5. Slag agglomerates 6. Non suitable foreign parts, if any 7. Basic refractories

(47) Materials having a grain size greater than 50 mm are loaded in the bin 35 by the wheel loader 7 by batch corresponding to their origin. The magnetic sorting operation, if carried out in line with grinding operation, denoted by 8, is performed based on magnesic or dolomite material.

(48) Separation of magnetic metal parts is carried out by the overband separator 36.

(49) Magnesic or dolomite basic refractory parts correspond to the part remaining after the sorting process.

(50) All the other fractions are sorted by the operators on the sorting belt 37.

(51) Positively sorted fractions are collected in metal bins that then are discharged in corresponding storage boxes.

(52) Basic fractions are collected in box B10 or directly sent to grinding, denoted by 8.

(53) Grinding operation acts for producing basic granulates of 0/5 mm and 5/50 mm with the basic fraction larger than 50 mm being sorted. It is carried out on the basis of magnesic or dolomite material.

(54) The production of such granulates is carried out in a suitable jaw crusher 81 recirculating on vibrating screen with 3 grids.

(55) The 0/5 mm fraction is conveyed to storage silos.

(56) 5/15 mm and 15/50 mm fractions are conveyed together to boxes B11 or B12 depending on the quality of the produced material.

(57) The feeding to grinding operation is carried out in line with sorting operation in hopper 82.

(58) According to the embodiment shown in FIG. 2 it is possible to provide to package dolomite or magnesic basic granulates, corresponding to fraction A of FIG. 1.

(59) Such products are packed in bags on pallet such to be used in the electric furnace as slag conditioner.

(60) Packaging is carried out by the automatic plant P1 being charged under silos A1-A and A1-B.

(61) As described above, finished products are stored in suitable boxes, for bulk material and in warehouse area in bags waiting for being shipped and being reused.

(62) The products obtained can be summarized as: dolomite granulate 5/50 mm/bulk magnesic granulate 5/50 mm/bulk dolomite granulate 0/5 mm/big bag magnesic granulate 0/5 mm/big bag nonmagnetic steel/bulk magnetic steel/bulk aluminous materials/bulk aluminous materials: spinel/bulk slag/bulk waste/bulk