FIELD OF INVENTION; The present invention relates to a Physical separation process scheme of valuable minerals from residual process slurry and particularly relates to separation of important base metals in their sulfide forms from Mineral Beneficiation Process Tailings.
BACKGROUND OF THE INVENTION;
Rampura Agucha Mine, a captive mine of Hindustan Zinc Limited (HZL), India is one of the major Lead-Zinc deposits in the world. The mineral beneficiation process at Rampura Agucha Mines leads to the present generation of 3.2 million tpa of process Tailing containing some amount of unrealized base metals. Apart from the above mentioned stream, the existing Tailing Dam also contains significant volume of Tailings.
At present, Fresh Tailings contain 1.3-1.4% Zn on an average most of the time, while the distribution spread can exist between 1.2-1.8% Zn (Depending on the Ore Feed Grade to the Plant and Plant operating conditions).
Tailing Dam contains operational tailings since inception of Rampura Agucha Mine operation and thus has wide spread of variation from 1.3-3% of Zn content.
General Mineralogy of Fresh Tailings is-98% of the gangue minerals are in liberated form and liberated Sphalerite grains constitute 0.5%. In the Sphalerite spectrum 23% are in liberated form whose average size is 20-40 microns but are predominantly around 25 microns and 77% are in locked form whose average size is around 20-30 microns as complex locks, of which bimineral locking with gangue accounts for 60-65% and bimineral locking with pyrite accounts for 20%. In the galena spectrum 0% are in liberated form and 100% are in unliberated form whose size is around 20 microns, but intergrowths persist upto 5 microns as fine grained intergrowths and wherein locking with gangue accounts for 85% and with Sphalerite accounts for 10%. The iron content is accounted predominantly by pyrite and to a lesser extent by pyrrhotite.
Previously several works have been reported in Published journals or symposiums or Patents to propose several new developments to treat low grade Pb-Zn Ores, mineralogically Complex Ores. A few Patents and Publications also proposed different Processes and Equipment to recover Copper , Elemental Sulfur, Oxidized Lead -Silver from different process residues including mineral Beneficiation Tailings. But apart from a Single Publication on marmatite flotation from Zn Tailings at Broken Hill Mines, Australia, no significant research has been reported to recover base metal values from a Tailing stream characteristically similar to Rampura Agucha Tailings.
The present invention is aimed to propose a simple and controlled process scheme developed by extensive Research activities to recover Base Metal values from Rampura Agucha Mine's Tailings or a Mineral Beneficiation Process Tailing having similar characteristics.
BRIEF SUMMARY OF THE INVENTION;
The Bulk Flotation process is developed by HZL through it's Research & Development efforts, to produce a Bulk Zn concentrate from Tailings and thus to recover lost metal values in Tailings. The process is basically a flotation process without incorporation of further grinding of Tailings and Bulk concentrate.
In a single aspect, the Process hereby claimed consists of the following steps:
1. Conditioning of Mineral Beneficiation Process Tailings as the First Step with pH
modifier (Lime), collector (SIPX) and Activator (CuSO4).
2. Single Stage Rougher Flotation followed by Single Stage Scavenging with the aid
of Frother (MIBC) and control of Air Flow and Cell Levels.
3. Single Stage Cleaning of Rougher concentrate thus produced with control of pH
and Cell level.
4. Recycling of Scavenger concentrate and Cleaner Tailing to Roughing stage to aid
in up gradation of Bulk Concentrate quality.
Concentrate thus produced contains 9-12 % Zn, 20-30% Fe, 1-3% Pb and 50-70 ppm Ag. The Bulk Concentrate thus produced is amenable to different Acid Leaching processes without taking aid of Roasting. Heap Bioleaching, Direct Leaching, Microwave assisted Leaching Test Programs have always resulted in more than 90% Zn dissolution. Thus HZL Bulk Flotation Process is capable of scavenging residual Metal values from a Zn-Pb Sulfide Ore Beneficiation Process Tailings in to a Bulk Concentrate, which can be successfully treated by a suitable Hydrometallurgical Leaching-Purification Process to extract valuable Base Metals.
BRIEF DESCRIPTION OF THE DRAWINGS;
Figure 1 is a brief description of the Process Block Diagram. Figure 2 is a Schematic Flow sheet of the Pilot Facility to carry out the advanced stages of Test work.
DETAILED DESCRIPTION OF THE INVENTION;
As described in Figure 1, Mineral Beneficiation Process Tailings stream 1 for a Pb-Zn Sulfide ore is conditioned in the first process stage A with the addition of reagents. The reagents used are pH modifier (Lime), collector (SIPX) and activator (CuSC^). The conditioned slurry 2 is floated in Rougher Stage B to recover maximum Base Metals locked in the Tailings. The reagents used are Frother (MIBC), Collector (SIPX). The Rougher Tailings stream 4 is Scavenged in Single Scavenger Stage C to float residual base metals. The reagents used are Collector (SIPX) and activator (CuSO4). The Final Tailing stream 5 is neutralized with Lime and disposed off. Rougher concentrate stream 3 is cleaned in Flotation stage D to produce final Bulk Concentrate stream 8. The reagent used is pH modifier (Lime).The Cleaner Tailings 7 and Scavenger Concentrate 6 are
collected together in a Sump (Stage E) and recycled back (Stream 9) to Stage B. The purpose of this recycling is to increase quality of Bulk Concentrate. Through out the Flotation stages Cell Levels, Cell Air Flows and Reagent Addition Rates are to be monitored to control the Froth generation rate, bubble size and quality of froth.
The Bulk Concentrate thus produced primarily consists of Sulfides of Zinc, Lead, Iron etc. and is amenable for different Acid Leaching Processes (Minimum 90% dissolution of Zn content).
The present invention can be applied to any Mineral Beneficiation Process Tailings consisting of Sulfide minerals of Zinc (Sphalerite), Lead (Galena), Silver, Iron (Pyrite and Pyrrhotite). It is also believed that the Process claimed in this invention can be applied to Copper, Nickel and other Base Metal Tailings , occurring in their Sulfide forms, with suitable adjustments and modifications. This scheme can also be suitable in treating non-sulphide mineral containing (partially or fully) similar process residues through use of suitable modifiers or alternative flotation reagents.
The present invention is also advantageous in terms of process simplicity and can be implemented in operating plants with out affecting the configuration of existing processes. Due to the simplicity of the Process, as it primarily involves different permutation-combinations of Flotation Techniques , it can be cost beneficial to the Processes that wish to increase Metal recoveries with low investments. The quality of the Bulk Concentrate can be optimized with the Metal recovery values of the Process and Process demands from Metallurgical refineries and hydrometallurgical facilities.
The different stages of development work to obtain the process claimed hereby are given below:
SECTION 1 (Raw Material Characteristic)
The generated Process Tailings and representative samples from Tailing Dam have been the materials subjected to Test work and Engineering , leading to the present invention. The average particle size distribution of Fresh Tailing at Rampura Agucha Mines is-

(Table Removed)
\The particle size distribution of Old Tailings samples are-

(Table Removed)
There are considerable differences in Fresh and Old Tailings particle size distribution due to the fact that grinding performance at RA Mines has been improving since inception. There will be expected variation in different zones and depths of Tailing Darn as well as.
General Mineralogy of Fresh Tailings is-98% of the gangue minerals are in liberated form and liberated Sphalerite grains constitute 0.5%. In the Sphalerite spectrum 23% are in liberated form whose average size is 20-40 microns but are predominantly around 25 microns and 77% are in locked form whose average size is around 20-30 microns as complex locks, of which bimineral locking with gangue accounts for 60-65% and bimineral locking with pyrite accounts for 20%. In the galena spectrum 0% are in liberated form and 100% are in unliberated form whose size is around 20 microns, but intergrowths persist upto 5 microns as fine grained intergrowths and wherein locking with gangue accounts for 85% and with Sphalerite accounts for 10%. The iron content is accounted predominantly by pyrite and to a lesser extent by pyrrhotite. The composition range of fresh Tailing is Zn (1.3-1.5%), Pb(0.6-0.8%), Fe (8-9%) while for Old Tailing, higher values are expected.
SECTION 2 (Initial Test Work)
Raw Material used: Fresh Tailing from RA Mine's beneficiation plant. Feed analysis was Zn: 2.5 %, Pb:0.9%, Fe: 11.7%, Ag: 26 ppm
Equipment Used: 2.5 L OK Batch Froth Flotation cell
The summary of the Test results are given below:
Bulk Concentrate quality -Zn: 10-15%, Pb : 2-3 %, Fe: 25-30 %, Ag: 60-65 ppm Metal Recoveries- Zn: 50-65 %, Pb: 30-45%, Fe: 45-60 %, Ag: 30-40 %
SECTION 3 (Variation Test Work)
Raw Material used: Fresh Tailing from RA Mine's beneficiation plant. Feed analysis was Zn: 1.3 %, Pb:0.6%, Fe: 9%, Ag: 26 ppm
Equipment Used: 1.5 L OK Batch Froth Flotation cell The summary of the Test results are given below: Roughing Test Results
Bulk Concentrate quality -Zn : 3-4%, Pb : 0.8-1 %, Fe: 12-13 % Metal Recoveries- Zn: 45-55 %, Pb: 15-30%, Fe: 18-36 %
Cleaning Test Results
Bulk Concentrate quality- Zn: 9-10%, Pb: 0.8-1% , Fe: 19-20%
Mass pull i.e. Bulk Concentrate: Tailing (ratio between bulk concentrate and tailing as feed) =10-15%
SECTION 4 (Old Tailing Test Work)
Raw Material used: Representative Tailing samples from various depths from RA Mine's Tailing Dam. Feed analysis was Zn: 1.3-3 %, Pb: 0.5-0.8%, Fe: 8-12%
Equipment Used: 1.5 L OK Batch Froth Flotation cell
pH was regulated between 6 to 8.
Air flow rate was kept between 7-10 LPM.
MIBC addition: 0.5-1 ml
CuSO4 addition: 3-4.8 ml
SIPX addition: 0.7-1 ml
The summary of the Test results are given below: Roughing Test Results
Bulk Concentrate quality -Zn : 4-7%, Pb: 0.8-1.3 %, Fe: 13-22 % Metal Recoveries- Zn: 55-75 %, Pb: 25-35%, Fe: 25-40 %
Cleaning Test Results
Bulk Concentrate quality- Zn: 9-11%, Pb: 1-1.4%, Fe: 20-22% Mass pull i.e. Bulk Concentrate: Tailing = 15-20% SECTION 5 (Pilot Test Program)
Based on the above Test results, a Pilot Plant facility was Engineered and set up to treat Live Tailings facility. The Set-up Scheme is described in Figure 2 and detailed below:
Pilot Plant treatment capacity: 40-50 tph of Live Tailings
Pilot Plant description: It consists of a Rougher + Conditioner Tank (16-18 m3 capacity with a rotor-stator assembly, Residence Time-7-10 mins), a Scavenger (8 m3 mechanical flotation tank with rotor stator) cell (Residence Time-5 mins) and a Cleaner (8 m3 mechanical flotation tank with rotor stator) cell (Residence Time-10-12 mins). Scavenger concentrate and Cleaner Tails can be pumped back to roughing.
A joint purpose cell for Conditioning and Roughing. Capacity 16-18 m3 , shape-Cylindrical Tank with peripheral launder. Cell level control can be controlled by
Local Automation Panel.
One 8 m3 mechanical flotation cell with rotor stator for Scavenging. Cell level
control-Manual
One 8 m3 mechanical flotation cell with rotor stator for Cleaning of Rougher
concentrate. Cell level control-Manual
Sump for collection of Scavenger concentrate and cleaner tails.
Horizontal Pump to recycle the above sump material to Rougher Cell.
Air for the flotation is fed from Plant Blower
Reagents are added from Tanks situated on cell platforms
Tailing feed is taken dynamically from the delivery line of Plant Tailing Thickener u/f Pump. Feed rate can be adjusted by opening/closing of Butterfly valve situated on the feed line.
The reagent additions were kept as MIBC Frother : 5-7 ml/min, CuSC>4 Activator: 1000-1500ml/min, SIPX collector: 200-300 ml/min. No pH regulation was applied as live Tailings usually have pH range of 6-7.
The summary of the results are given below:
Feed - Zn: 1-1.5%, Pb: 0.5-0.7 %, Fe : 9-12%
Bulk Concentrate quality -Zn : 6-20%, Pb : 0.9-2 %, Fe: 14-25 %
Metal Recoveries- Zn: 35-60 %, Pb: 25-33%, Fe: 21-45 %
SECTION 6 (Bulk Concentrate Features)
The average particle size distribution for Bulk Concentrate is-
(Table Removed)
A Mineralogical analysis of Bulk Concentrate was carried out and the summary is-82 % of the minerals are in liberated form, of which liberated sphalerite grains constitute 4% . In the sphalerite spectrum 19 % are in liberated form and 81 % are in unliberated form of which bimineral locking with gangue accounts for 78 % .1.63.% grains of galena are liberated and in the galena spectrum 25 % are in liberated and 75 % are in unliberated form wherein locking with gangue accounts. The gangue minerals are represented by Mica ,Quartz, feldspar and Graphite. The Graphite grains are totally liberated and > 74 microns with little interlocking with sulfide minerals . There are very few oxides in the form of Goethite (Iron Oxide ) and no carbonates nor arsenides . Mercury is a trace element which occurs in atomic substitution with Pb and Zn and will be in traces only . Arsenopyrite ( Fe As 82 )was not seen . Iron sulfides are predominantly in the form of Pyrite and minor Pyrrhotitie .
SECTION 7 (Amenability of Concentrate for Metal Extraction)
The Bulk Concentrate thus produced is amenable for Base Metal extraction by a suitable hydrometallurgical process other than conventional Roast-Leach process. Different Test works were carried out with different Technologies to ascertain extraction efficiency of Zn from Bulk Concentrate. The summary is given below:
(Table Removed)

WE CLAIM!:
1. A process for the recovery of valuable Base Metals from Mineral Beneficiation
Process Tailings comprising Sulfide minerals of the Base Metals. The process
consists of:
Subjecting Tailing slurry to a Conditioning step with suitable reagent dosages
followed by a Roughing Flotation step and then a Scavenging Flotation step. The
Rougher Bulk concentrate thus produced is treated in a Cleaning Flotation stage
to generate the final Bulk Concentrate.
Cleaner Tailing and Scavenger Concentrate are recycled together to Roughing
stage to upgrade Bulk Concentrate quality.
Adjustment of rougher, scavenger and cleaner streams configurations makes it
possible to balance concentrate quality and economic recovery for specific raw
material constitution and operating parameters.
2. A process as claimed in Claim 1, which is believed to be capable of successful
application in treating tailings of different Mineral Beneficiation Processes
treating sulfide ores of base metals. Necessary adjustments and modifications are
to be incorporated depending on the Raw Material characteristics and Project
economics.
3. A process as claimed in Claim 1, which can be applied to generate a Low Grade
Bulk Concentrate containing valuable base metals. This concentrate can be further
treated via a suitable Hydrometallurgical Process apart from conventional Roast-
Leach process to extract metals. The achievable concentrate quality and Process
Economics will be the key determining factors for Technology selection.