Title of Invention

A METHOD OF PRODUCING IMPROVE GRADE COARSE CONCENTRATES FROM LOW GRADE CHROMITE ORE .

Abstract

A method of producing improve grade coarse chromite concentrates from low grade chromite ore, comprising the steps of crushing a plant feed of chrome ore beneficiation plant analyzing 30-33% Cr2C3 to below 3mm in closed circuit; feeding the crushed below 3mm feed to screw classifier to separate into two fractions of -3+0.5 and -0.5mm; feeding the -3+0.5mm fraction to a first stage jig and collecting the heavier fraction and treating the first stage jig heavier fraction in a second stage jig and collecting the heavier fraction as a coarse concentrate of improve grade of more than 46% Cr2O3.

Full Text

The present invention relates to a method of producing grade coarse chromite concentrates from low grade chromite ore. Chromite resources from mines like Sukinda in the State of Orissa (mined about 4.5 million tonnes per annum) are mostly enriched with ferruginuous type ore. These are different in many respects with other leading world chromite resources particularly in terms of higher near density iron minerals matrix are friability due to varied degree of weathering. During mining operation for marketable grade ores, low grade ores are generated from the mines which are treated in conventional gravity cipcuit at the chrome ore benefication (COB) plant for producing different marketable grade concentrates of below 500 micron size to meet the requirement of different customers. For meeting customer requirement of coarse concentrates (in terms of size) the benefication plant is to be geared up for the same. Though the volume requirement of coarse concentrates is small but strategically, apart from high realisation, their production in COB plant is important. The COB plant, primarily consists of crushing and grinding circuit to reduce the run of mine ore from 300mm to below 0.5mm. The classification circuit consisting of hydrocyclones to classify — 0.5 mm fraction into coarse t—0.5+0.1 mm), fine (—0.1 + 0.038 mm) and slime (-0.038mm) fractions. The benefication circuit consisting of 4 stage spirals in coarse circuit and 3 stage spirals and tables in fine circuit to produce marketable grade concentrates. Three feed samples of different grade (~25, ~ 30, and 35% Cr 0 were characterised for its amenability to produce 2 3 coarse concentrates. The characterisation studies indicated that the coasest particle size at which significant ( ~ 60%) liberation of chromite is below at size below 3 mm. It also indicated that it is possible to produce by gravity methods coarse (-3+0.5 mm) concentrates analysing 42 — 44, 47 - 52 and 50 - 51% Cr 0 with a yield of 30 - 32, 33 - 40 and 2 3 46-47% from samples with feed grade ~ 30, ~ 33 and ~ 37% Cr 0 respectively. 2 3 Based on the above, further benefication studies were carried out for developing a process for method of producing marketable grade coarse chromite concentrates from low grade chromiate ore. The classification test results indicated that by screw classification of below 3 mm crushed 30—33% grade feed sample it is possible to get -3 +0.5mm fraction between 28 and 32% analyzing 25-36% Cr 0 with about 10% of misplaced article 2 3 of below 0.5 mm size. The Jigging test results of -3+0.S mm fractions of -3 mm crushed indicated that it is passible to produce coarse concentrates with ~ 43, ~ 47, ~ 50% Cr O from .— 30, 2 3 ~ 33, and ~ 37% Cr 0 feed grade samples respectively. 2 3 Hence, it is observed that the feed grade with less than 30%. Cr 0 cannot yield marketable grade concentrates. The tailings 2 3 produced by jigging are to be ground to below 0.5 mm for enhancing liberation and needs further treatment, to recover chromite values along with the rest below 0.5 mm fraction. Based on the jig tests with different grade samples the concentrate grade—yield relationship equation was developed which is as follows: Yield ■ 2.6.315* Cr 0 +182.738 2 3 2 where the R value was 0.77 and is valid for 33-54% Cr 0 2 3 feed grade samples. Thus, incorporation of additional circuit comprising 2 stage classification and 2 stage Jigging and multi gravity separation may be required to produce marketable grade coarse Cr 0 ). Techno economic studies indicate that substantial 2 3 returns can be achieved on a moderate investment for additional circuits consisting of classifiers and jigs. Figure 1 of the accompanying drawings show the flow sheet for the method of producing marketable grade coarse chromite concentrates from low grade chromite ore. The plant feed of chrome ore beneficiation plant analysing 30-33% Cr 0 is crushed to below 3 mm in closed circuit. 2 3 This crushed feed of - 3mm is fed to a screw classifier to separate into two fractions a coarser fraction of -3+0.5 and a finer fraction of -0.5 mm size. The -3+0.5 mm fraction is fed to first stage jigs and the heavier fraction is collected. The first stage heavier fraction is treated in second stage jigs and the heavier fraction is collected as a coarse concentrate. The coarse concentrate from second stage jig« i« of marketable grade of more than 46% Cr 0 . 2 3 This is the final product obtained by the method of the present invention. The lighter fractions of first and second stage jig% are combined together to form total tailings. The total tailings generated can be crushed to below 0.5 mm and sent for treating in the chrome are beneficiation plant to produce regular marketable chromite concentrates. WE CLAIM 1. A method of producing improve grade coarse chromite concentrates from low grade chromite ore, comprising the steps of : (a) crushing a plant feed of chrome ore beneficiation plant analyzing 30-33% Cr2O3 to below 3mm in closed circuit; (b) feeding the crushed below 3mm feed to screw classifier to separate into two fractions of -3(+0.5 and -0.5)mm; (c) feeding the -3+0.5mm fraction to a first stage jig and collecting the heavier fraction and (d) treating the first stage jig heavier fraction in a second stage jig and collecting the heavier fraction as a coarse concentrate of improve grade of more than 46% Cr2O3. 2. The method as claimed in claim 1 wherein after step (d), combining the lighter fractions of said first and second stage jigs together to form total tailings which can be crushed to below 0.5mm for treatment in existing chrome ore beneficiation plant for producing regular improve grade chromite concentrates. Dated this 30th day of August 2002. A method of producing improve grade coarse chromite concentrates from low grade chromite ore, comprising the steps of crushing a plant feed of chrome ore beneficiation plant analyzing 30-33% Cr2C3 to below 3mm in closed circuit; feeding the crushed below 3mm feed to screw classifier to separate into two fractions of -3+0.5 and -0.5mm; feeding the -3+0.5mm fraction to a first stage jig and collecting the heavier fraction and treating the first stage jig heavier fraction in a second stage jig and collecting the heavier fraction as a coarse concentrate of improve grade of more than 46% Cr2O3.

Documents:

511-cal-2002-granted-abstract.pdf

511-cal-2002-granted-assignment.pdf

511-cal-2002-granted-claims.pdf

511-cal-2002-granted-correspondence.pdf

511-cal-2002-granted-description (complete).pdf

511-cal-2002-granted-drawings.pdf

511-cal-2002-granted-examination report.pdf

511-cal-2002-granted-form 1.pdf

511-cal-2002-granted-form 13.pdf

511-cal-2002-granted-form 18.pdf

511-cal-2002-granted-form 2.pdf

511-cal-2002-granted-form 3.pdf

511-cal-2002-granted-form 4.pdf

511-cal-2002-granted-form 5.pdf

511-cal-2002-granted-pa.pdf

511-cal-2002-granted-reply to examination report.pdf

511-cal-2002-granted-specification.pdf