An Approach to Beneficiation of Apatite Ore of Purulia

West Bengal Mineral Development and Trading Corporation operates the apatite mine in Purulia District of West Bengal. The produce three grades of samples, i.e. (i) High grade above 30% P2O5 (ii) Average grade of about 20% P2O5 and (iii)Low grade of 12% P2O5. The average is directly marketed as fertiliser for application in tea garden etc. The medium or average grade sample is mined from areas around the main ore body and contains substantial amount of ferruginous material besides other gangue minerals. The low grade ore is dumped separately and occasionally blended with high grade of ore to prepare the average grade for direct marketing. Thus every bit of apatite from the mines is used except for the top soil. But with reduc-ed demand, the manufacturer is faced with a selling problem and reduced production. Value addition by way of making high grade product is one option to pursue with. The typical problem is of iron removal as presence of high iron hinders value addition in terms of phosphate during down stream operation. Studies on the average grade sample indicated that using suitable processing steps the phos-phate content could be increased to +38% P205 with very low content of iron & silica. The present paper deals approach adopted in beneficiating the average grade apatite ore of Purulia. Key Words: apatite, Purulia, iron, magnetic separation, flotation

Salvaging the values from the rejects of a by-product recovery plant

Two samples of table tailings (-147 pm and -74 pm in size) from refrac¬tory linings of the precious metal recovery (PMR) plant of Indian Copper Complex (ICC), Ghatshila were received to study the possbility to re¬cover residual values of precious metals from them. Analyses, as reported by ICC, were 0.021% Au and 0.39% Ag for the -147 pm sample and 0.023% Au and 0.47%Ag for the -74 pm sample. Multi-Gravity Separator (MGS) studies, with varying design and operating variables, showed three fold upgradation - assay of Au improved from 0.023% to 0.076% and assay of Ag improved from 0.47% to 1.53%. The -74 pm sample yielded better results with MGS than the -147 pm sample

Gravity separation at variable 'g' for management of mineral wastes and pollution

The treatment of mineral wastes in the form of slimes and its utilisation, for management of pollution and conservation of mineral wealth, have become very important now-a-days. Multi Gravity Separator (MGS) is the latest inclusion to various gravity separation machines developed far the treatment offines and ultrafines. In this paper, results of recent studies carried out at NML with MGS using slimes of chromite ore, iron ore, phosphatic soil etc. are discussed to evaluate the effectiveness of the equipment for the treatment of slimes. In most of the cases, three to four fold upgradations have been achieved even at very fine sizes

Modified hydrocycloning for effective elimination of stubborn slimes

The present paper deals with the skillful exploitation of the extremely high shear fields inside a hydrocyclone to effectively eliminate a sticky slime from a phosphate ore before beneficiating the coarser fraction using con¬ventional mineral processing techniques. Earlier studies on samples of the same ore at NML and abroad established that it was necessary to pass the ore through a series of three stages of desliming, each consisting of a step of rigorous attrition scrubbing followed by hydrocycloning, for effective elimination of the slime. With the new approach,by innovative modifica¬tions on the standard hydrocyclone design, it was possible to eliminate all the stages of attrition scrubbing while minimising the stages of hydrocycloning. It could be established that the modified technique not only yielded concentrate of grade comparable to that obtained by employ¬ing the earlier more complex flowsheet, it also improved the P205 recovery

Analysis of the washability characteristics of low-volatile Indian coking coal with crushing at different top sizes - a case study

The effect of comminution on liberation characteristics has been studied for a low volatile coking coal of Indian origin through washability studies. Two parameters, namely "Index of Washability" (IW) and "Near Gravity Material Index" (NGMI), are used to describe the ease of washability. The ROM Coal is crushed to four different top sizes namely, 75 mm, 25 mm, 13 mm and 6mm. On the basis of calculated IW it is observed that relative ease of washabiltiy increases with decrease in top size. The value of IW at -6 mm crushing size is 41.4 which confirm the ease of washing of this coal at this feed size. From the calculated NGMI values the critical specific gravities have bee n estimated. Critical specific gravity suggests that the separation at this specific gravity range is most difficult task using gravity methods. NGMI analysis reveals that the critical specific gravities for crushing to -75 mm, -25 mm, -13 mm and -6mm are 1.65, 1.68, 1.53 and 1.58 respectively

Minerological aspects of lead sintering

A brief overview on lead sinter microstructure is presented. Characteristic micro-structural features of a good and bad sinter are highlighted and these are used in a case study involving use of a low grade and complex concentrate of lead (-40% Pb) in the sintering operation. The plant sinter produced exhibited low strength and its nticrostructural examination revealed non-uniform distribution of porosity along with unsintered galena and low melting lead silicate phase. Part replacement of limestone by lime helped in producing sinter with good physical properties and desirable microstructure. The sinter with modified feed chemistry had more uniform distribution of porosity and presence of primarily a Pb-Fe silicate phase characterised by a (Pb+Fe):Si mole ratio of 3:1. Ca-Pb-Zn-Fe-Al-silicate phase identified as hardysonite and a spine! phase of the type (Fe,Zn)O.(Fe,Al),OJ. Lead nietal/oxide/sulphide occurred in the sinter only rarely. The likely implications of lime addition to the sinter charge mix are discussed Key Words: Lead. Complex and low grade concentrate. Sintering. Process Mineralog

Characterization and its implication on beneficiation of low grade iron ore by gravity separation

Studies were undertaken on low grade iron ore sample from Noamundi iron ore mines. The objective of this study was to examine the possibility of the physical beneficiation of low grade iron ore sample by physical methods for the blast furnace route of iron production. The present investigation relies on petrography and ore mineralogical characterization, ore textures (primary, secondary, metamorphic), liberation characters and its impact on the mineral beneficiation methods to produce quality concentrate. The geological characters, alteration mineralogy, morphometric variation, ore microscopy (using model microscope with transmitted and reflected light) and thereby understanding the genesis has given proper insight into the occurrence of various minerals. In addition to this, representative samples were employed for detailed investigation by using XRD, SEM-EDS and cathodoluminescence (CL) studies for confirmation of major as well as minor ore minerals and associated gangue minerals. Investigations suggest that lateritic iron ore samples obtained from the study area are composed of hematite (two generations), goethite (two generations) and limonitic material (younger generation) in association with major gangue minerals such as clay minerals (kaolinite, illite), bauxitic minerals(gibbsite, boehmite and diaspore), cryptocrystalline silica(japer, chert) and crystalline quartz as well as apatite and collophane. Fair liberation obtained below 74 micron size. It was interesting to find that inspite of the complex mineralogy of iron ore, beneficiation results using gravity separation like multi gravity separator (MGS), particularly in finer size ranges was encouraging. The result of ore-gangue mineralogical studies were found quite useful in evaluating the separation efficacy of gravity separation process. The process mineralogical data corroborated well with beneficiation results

Studies on Medium Grade Ilmenite-Depleted Beach Placer deposit of Chavakkad Ponnani Coast, Kerala

In the present paper, characterization, beneficiation and further value addition studies carried out with samples collected from unexploited Chavakkad ponnani (CP) area of Kerala coast have been reported. Characterization studies involve size and chemical analyses, sink and float studies and optical microscopy. total 21 samples were collected from 18 km. stretch of CP area at almost 1 km. apart. While sink and float studies and optical microscopy were carried on with all individual samples, detail characterization and beneficiation studies were undertaken with composite samples-one prepared from all 21 samples and the second from few selected samples. Pre-concentration followed by high tension separation and magnetic separation yielded product containing more than 95% THM with around 90% recovery. Further value addition studies with generated ilmenite concentrate was found to produce synthetic rutile, through reduction followed by oxidation and leaching, containing more than 94% TiO2

Sociobiological Control of Plasmid copy number

Background:
All known mechanisms and genes responsible for the regulation of plasmid replication lie with the plasmid rather than the chromosome. It is possible therefore that there can be copy-up mutants. Copy-up mutants will have within host selective advantage. This would eventually result into instability of bacteria-plasmid association. In spite of this possibility low copy number plasmids appear to exist stably in host populations. We examined this paradox using a computer simulation model.

Model:
Our multilevel selection model assumes a wild type with tightly regulated replication to ensure low copy number. A mutant with slightly relaxed replication regulation can act as a “cheater” or “selfish” plasmid and can enjoy a greater within-host-fitness. However the host of a cheater plasmid has to pay a greater cost. As a result, in host level competition, host cell with low copy number plasmid has a greater fitness. Furthermore, another mutant that has lost the genes required for conjugation was introduced in the model. The non-conjugal mutant was assumed to undergo conjugal transfer in the presence of another conjugal plasmid in the host cell.

Results:
The simulatons showed that if the cost of carrying a plasmid was low, the copy-up mutant could drive the wild type to extinction or very low frequencies. Consequently, another mutant with a higher copy number could invade the first invader. This process could result into an increasing copy number. However above a certain copy number within-host selection was overcompensated by host level selection leading to a rock-paper-scissor (RPS) like situation. The RPS situation allowed the coexistence of high and low copy number plasmids. The non-conjugal “hypercheaters” could further arrest the copy numbers to a substantially lower level.

Conclusions:
These sociobiological interactions might explain the stability of copy numbers better than molecular mechanisms of replication regulation alone