RU2181778C1 - Method for processing slag of carbonaceous ferrochrome - Google Patents

Abstract

FIELD: metallurgy, namely slag processing methods. SUBSTANCE: method comprises steps of crushing slag; separating crushed slag by screening according to particle size no less than (3-5) mm; then subjecting undersize product to pneumatic classifying with separating metallic concentrate and subjecting oversize product of screening and slag product from settling chamber of classifier to magnetic separation. Oversize product of screening is subjected to magnetic separation in magnetic field with intensity (80-95)kA/m and frequency (5.0-9.9)Hz. Slag product from settling chamber of classifier is subjected to separation in magnetic field with intensity (96-150)kA/m and frequency (10-15)Hz in order to provide metal content in it no more than 2%. EFFECT: enhanced degree of metal extraction, improved quality of slag product used as abrasive and refractory materials. 3 cl,4 tbl

Description

 The invention relates to metallurgy, and in particular to methods for processing slag, and can be used in the processing of slag from the production of carbon ferrochrome.

 As a prototype, a method for processing slag of high-carbon ferrochrome (a.s. USSR 1527305) was selected, in which slag larger than 3-8 mm is subjected to pneumatic separation, and slag smaller than 3-8 mm after dedusting in a countercurrent classifier is subjected to sequential separation in weak and strong magnetic fields.

 The disadvantage of this method is the low metal recovery and low quality of slag products.

 The technical problem solved by the invention is to increase the extraction of metal from slag and improve the quality of slag products.

 This problem is solved in that in a method comprising crushing slag, separating crushed slag by screening by particle size at a boundary of 3-5 mm, pneumatic classification and magnetic separation of separation products, the sublattice product is subjected to pneumatic classification with the release of metal concentrate and sedimentation of the slag product in sedimentation the classifier chamber, and the oversize screening product and the slag product from the settling chamber of the classifier are individually subjected to magnetic separation tion with ensuring the metal content in the sieve slag product of not more than 2%. The oversize screening product is separated in a magnetic field with a strength of 80-95 kA / m and a frequency of 5.0-9.9 Hz, and the slag product from the settling chamber of the classifier in a magnetic field with a strength of 96-150 kA / m and a frequency of 10-15 Hz .

 As a result of the processing of metallurgical slag, several commercial products are obtained - metal concentrate and slag products used as abrasive and refractory materials.

 The results of studies of the properties of various fractions of carbon ferrochrome slag after primary crushing of the initial slag up to 70 mm at the crushing and screening complex of the Aktobe ferroalloy plant are presented in Table 1.

An analysis of the results shows that the abrasive ability and refractoriness of the selected slag fractions larger than 5 mm after primary crushing to -70 mm remain almost constant. Fractions smaller than 3 mm have significantly lower abrasion and refractoriness. On average, the abrasive ability of the slag grains of the proposed method is 1.4 times higher than in the prototype, and the fire resistance of the forsterite spinel product obtained by the present method is 250 ^o higher.

 As a result of the use of lump fractions of slag in the proposed method, the content of dust-like slag fractions entering the pneumatic classifier is significantly reduced (Table 2), which contributes to an increase in the output of the abrasive product and to improve the operation of the air purification system after the classifier.

 The use in the proposed method of crushing lump slag in a closed cycle with screening at the border of 3-5 mm allows to increase the exit slit of the crusher and, as a result, reduce the overgrinding of slag products and increase the output of the abrasive class. In addition, the crushing of slag in a closed cycle allows you to more fully reveal the metal kings contained in the slag, without over-grinding and more fully remove them during subsequent magnetic separation.

 Separation of slag in a particle size range of more than 5 mm in a magnetic field with a strength of 80-95 kA / m and a frequency of 5-9.9 Hz allows one to obtain a magnetic product richer in metal content, and after crushing the slag to a particle size of 3-5 mm or more the opening of metal inclusions, the magnetic separation modes change (tension 96-150 kA / m and frequency 10-15 Hz) in order to more fully recover the metal to obtain slag products with a minimum residual content, which is very important, for example, for the product used in productiongneupornyh products. In the prototype, no metal is extracted from the slag products after the classifier, which significantly reduces the total metal extraction from the slag and limits the possibility of using the slag product for the production of refractory products, since the metal content in such a product should be no more than 2%. Only in this case, the carbon ferrochrome slag meets the requirements of the forsterite spinel product (along with the requirements for refractoriness, fractional composition, etc.).

 The method is as follows.

 After primary crushing of slag from the production of carbon ferrochrome (usually up to a particle size of 70 mm), a -5 mm fraction is sieved to remove industrial waste (sand, quartzite screenings, refractory battle, garbage from cleaning the production area, etc.), after which lump slag is crushed in a closed cycle with test screening at the border of 3-5 mm, the sublattice product of test screening is classified with the release of metal concentrate, and the slag is subjected to separation. Slag separation is carried out in two stages.

 At the first stage, slag separation in the size range of more than 5 mm is carried out in a magnetic field with a strength of 80-95 kA / m and a frequency of 5-9.9 Hz. Such separation modes make it possible to extract the purest metal inclusions from slag and obtain a sufficiently high metal content in the magnetic product.

 In the second stage of slag separation in the particle size range of less than 3 mm, the intensity and frequency of the magnetic field are increased in order to reduce the residual metal content in the forsterite-spinel product by no more than 2% with a maximum yield of this product.

 To justify the optimal magnetic separation modes for slag larger than 5 mm, experiments were carried out using a PBS-90/25 laboratory separator (drum diameter 900 mm, drum length 250 mm), the operating modes and design features of which made it possible to change the magnetic field strength and frequency. Evaluation of the results was carried out according to the yield and quality of the magnetic product. The results of the experiments are given in table.3.

 The analysis shows that for large slag fractions, when the magnetic field is less than 80 kA / m, regardless of the frequency of the magnetic field, the yield of the magnetic product decreases sharply, and when the magnetic field is more than 95 kA / m, also regardless of the frequency of the magnetic field, there is a sharp deterioration in quality magnetic product. When the magnetic field frequency is less than 5 Hz, the quality of the magnetic product sharply decreases, and with an increase in the frequency of the magnetic field more than 9.9 Hz, the yield of the magnetic product sharply decreases.

 To justify the modes of magnetic separation of slag in the particle size range less than 5 mm obtained after pneumatic classification, experiments were conducted on a laboratory separator PBS-90/25 at various intensities and frequencies of the magnetic field. The quality of the forsterite spinel (slag) product and its yield were evaluated. The results of the experiments are given in table.4.

 The analysis shows that when the magnetic field is less than 96 kA / m and the frequency of the magnetic field is increased more than 15 Hz, the metal content in the forsterite-spinel product exceeds the permissible limit of 2%. With an increase in the magnetic field strength of more than 150 kA / m and a decrease in the frequency of the magnetic field of less than 10 Hz, the output of the forsterite spinel product sharply decreases.

Claims (3)

 1. A method of processing carbon ferrochrome slag, including crushing slag, separating crushed slag by screening at the 3-5 mm boundary, pneumatic classification and magnetic separation of separation products, characterized in that the sublattice slag product is subjected to pneumatic classification with the release of metal concentrate and the deposition of slag product in the precipitating chamber of the classifier, and the over-screening product of screening and the under-screening slag product, each separately, are subjected to magnetic separation with especheniem metal content in slag undersize product not more than 2%.  2. The method according to p. 1, characterized in that the separation of the oversize screening product is carried out in a magnetic field with a strength of 80-95 kA / m and a frequency of 5.0-9.9 Hz.  3. The method according to p. 1, characterized in that the separation of the slag product from the sedimentation chamber of the classifier is carried out in a magnetic field with a strength of 96-150 kA / m and a frequency of 10-15 Hz.

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