A Computer Oriented Algorithm to Determine the Raw-Mixture Composition for Sintering

Sintering is an agglomeration process of fine part-icles and widely used as a standard method for preparation of blast furnace-feed. In iron-ore sintering, iron ore fines viz. iron ore crushed to ---10 mm size, classifier fines, cyclone underflow, blue-dust etc. together with other iron-bearing waste materials viz. mill-scale, flue dust etc. are mixed with fluxing materials like limestone, dolomite etc. and sintered in a continuously operated sinter strand or a bench-scale sinter pot. The sintering of fine particles results from incipient fusion of materi-als due to heat liberated by combustion of coke-breeze incorporated in the raw mixture and also exothermic heat liberated through complex chemical reactions taking place during the process of sintering. Water added during mixing helps to maintain a proper permeability and return fines act as a supporting structure for the mixture

Enumerative geometry of Calabi-Yau 4-folds

Gromov-Witten theory is used to define an enumerative geometry of curves in Calabi-Yau 4-folds. The main technique is to find exact solutions to moving multiple cover integrals. The resulting invariants are analogous to the BPS counts of Gopakumar and Vafa for Calabi-Yau 3-folds. We conjecture the 4-fold invariants to be integers and expect a sheaf theoretic explanation. Several local Calabi-Yau 4-folds are solved exactly. Compact cases, including the sextic Calabi-Yau in CP5, are also studied. A complete solution of the Gromov-Witten theory of the sextic is conjecturally obtained by the holomorphic anomaly equation.Comment: 44 page

Use of blue dust in sintering

Sintering studies were undertaken through a full factorial design of experi¬ment to estimate the quantitative effect of blue dust along with other process variables. Responses from the experiments were then correlated with the process variables through a regression equation. The coefficients of the equation indicated that the coke breeze exerted maximum influence on the strength. It was possible to incorporate blue dust to the extent of 40% with respect to total iron ore fraction without impairing the properties of sinter

A Beneficiation Scheme for Reduction of Alumina in Iron Ores from Barsua

In order to improve blast furnace productivity by reducing the alumina of iron ore fines from the present level of 3.3-3.9% to the desired level of 2.5%, a detailed characterisation followed by beneficiation studies compris-ing crushing, dry screening, washing, gravity separation of fines and slimes, on the seven individual 'type' and a 'composite' iron ore samples from Barsua Iron Mines were carried out at NML, Jamshedpur to find the amenability of beneficiation and develop a flow-sheet. Based on the find-ings from the studies, two conceptual flowsheets were designed.The first one consisted of crushing the composite sample (62.26% Fe, 2.01% Si02 and 4.22% A1203) to 25 mm followed by wet processing comprising scrubbing & wet screening at 8 mm and classification of -8mm fraction into sand (+100#) and slime (-100#). The -8+1 mm fraction of the sand would be subjected to jigging and -1mm+100 # fraction to tabling. The cyclone underflow obtained by treating the slime would be subjected to tabling as well. The yield of the combined concentrate of fines would be 28% and analyse 64.09% Fe, 1.9% Si02 and 2.95% A1203. The +8 mm lumps, 45% by weight would analyse 63.69% Fe, 1.52% Si02 and 3.8% A1203. Based on mainly grade and physical characteristics of individual type samples, the Second Flowsheet consists of separate proportioning, blending and treatment of two group of ores viz., Direct Ore (Friable, Mineable Transi-tional and Blue Dust) and Beneficiable Ore (Soft Lamina-ted , Lateritic , Hard Laminated and Massive). The flow-sheet consists of dry processing of Direct Ore (29% by weight with 63.55% Fe, 1.69% Si02 and 2.45% A1203) and wet processing of Beneficiable Ore (71% by weight with 61.39% Fe, 2.22% Si02 and 5.09% A1203). The Dry Circuit would consist of crushing the Direct to -25 mm and screening at 8 mm. The lumps and fines would weigh 8% and 21% and analyse 62.62% Fe, 1.79% Si02 and 2.92% A1203 and 63.9% Fe, 1.65% SiO2 and 2.27% Al2O3 respectively. The Benefic-iable will go through the wet circuit as described for the first flowsheet. The washed lump would be 36.43% by weight and analyse 63.4% Fe, 1.38% Si02 and 4.05% Al2O3. The combined lumps from Dry Circuit and Wet Circuit would be 44.43% by weight and analyse 63.25% Fe, 1.45% Si02 and 3.85% A1203.The combined fines from Dry Circuit and Wet Circuit (without concentrates from slime) would weigh 35.62% and analyse 64.1% Fe, 1.59% Si02 and 2.56% A1203. The yield will improve by an additional amount of 5-6% with slight increase in Al2O3 (2.85%) if table con-centrates from cyclone underflow and overflow are recovered. Although quality or quantity of lumps remain almost same in both the cases, there is substantial improvement in grade and yield of fines in the second flowsheet

Physical method of upgradation for low grade wolframite pre-concentrate from Degana, Rajasthan

Tungsten is a strategic metal and mostly used in defence. It is also used in cutting tools, industrial, electrical, textile and leather sectors. India's tungsten reserves are very limited and the only workable deposit is restricted to Degana in Rajasthan. Tungsten deposit occurs in association with metamorphic rocks and granite igneous rock throughout the world. At Degana, two types of deposit are being worked at, one being quartz load wherein wolframite is mineralised in quartz vein and the other is finely disseminated tungsten mineralisation in the granite body. The sample under investigation belonged to off-grade tungsten pre-concentrate - I (PC - 1) produced at Degana Plant site, assaying 14.50% WOe 20.20% SiO, and 4.13% S. The objective of this study was to find the upgradation conforming to DMRL specification i.e. final wolframite concentrate with >65.0% WO,, and S and SiO, < 1.0% each. Detailed studies indicated that grinding the feed to 200 mesh followed by sulphide flotation at 4.5 and 8.0 pH and repeated vanning of non-sulphide could produce a wanner concen¬trate assaying 64.8% WO,. 1.0% SiO, and 3.0% S with a distribution of 48.8% WO3 in it. Thorough desliming followed by sulphide flotation and then treating on vanner times could produce a concentrate analysing 68.47% WO j, 0.5% SiO3 and 0.48% S which conforms to the DMRL sped¬fications

Beneficiation of Low Grade Chromite Ores from Sukinda

In order to produce directly marketable chrome ore for export and domestic industries, most of the chromite ore beneficiation plants in Sukinda region treat selected rich ores with rejection of huge quantities of low and sub-grade ore (10-38% Cr2O3). Beneficiation is mostly limited to curshing, grinding, desliming and hydrosizing to prod-uce a concentrate of about 50% Cr203 with a yield of about 25-35%. By this also, a huge amount of sub grade fines of about 35-40% Cr203 has been accumulating in the mines. Currently very little efforts are made to treat these low grade ores or recover values from waste dumps. Recently, a study was undertaken at NML. to explore the possibility of developing a flowsheet to produce chromite concentrate preferably with Cr203 content of about 50% with Si02 about 2% from waste dumps analysing between 20 to 23% Cr203, with a view to using these as additional source of feed stock. Detailed physical characterisation, mineralogical analysis, bench and pilot scale studies were undertaken on these samples. The beneficiation process essentially invo- lved removal of ferruginous slime at stages by washing and hydrocycloning and enrichment of different size classified fractions by. simple gravity separation techniques like spiralling and tabling. It was observed that by adoption of the above operations, it was possible to upgrade these low grade ores to obtain concentrate having Cr203 of desired grade with high recovery

Modification of Hilbert's Space-Filling Curve to Avoid Obstacles: A Robotic Path-Planning Strategy

This paper addresses the problem of exploring a region using the Hilbert's space-filling curve in the presence of obstacles. No prior knowledge of the region being explored is assumed. An online algorithm is proposed which can implement evasive strategies to avoid obstacles comprising a single or two blocked unit squares placed side by side and successfully explore the entire region. The strategies are specified by the change in the waypoint array which robot going to follow. The fractal nature of the Hilbert's space-filling curve has been exploited in proving the validity of the solution

Gravity concentration of fines and ultrafines

Concentration of fines by gravity methods remains one of the challenging problems to the world mineral industry. Considering the increasing losses of mineral values and the search for an economic process, it has been the major concern of the researchers and the practicing engineers to develop an efficient fine gravity separator. The development of some of the recent fine gravity separators with the application of high centrifugal forces has resulted in improvement in the separation efficiency. In the last four de¬cades extensive studies have been carried out at National Metallurgical Laboratory (NML), Jamshedpur to develop gravity based processes for low grade ores, fines and industrial wastes involving the conventional separators to the latest equipment like multi-gravity separator for their economic exploitation. In this paper an attempt has been made to briefly present a review of the gravity concentration processes with a particular reference to the recent advances in the processing of fines. The salient results obtained from the recent studies carried out on beneficiation of lean grade finely disseminated tungsten ore, iron ore slimes and chromite slimes at NML using some fine gravity separators like Bartles-Motley Vanner GEC-duplex concentrator and MGS are discussed

Gopakumar-Vafa invariants via vanishing cycles

In this paper, we propose an ansatz for defining Gopakumar-Vafa invariants of Calabi-Yau threefolds, using perverse sheaves of vanishing cycles. Our proposal is a modification of a recent approach of Kiem-Li, which is itself based on earlier ideas of Hosono-Saito-Takahashi. We conjecture that these invariants are equivalent to other curve-counting theories such as Gromov-Witten theory and Pandharipande-Thomas theory. Our main theorem is that, for local surfaces, our invariants agree with PT invariants for irreducible one-cycles. We also give a counter-example to the Kiem-Li conjectures, where our invariants match the predicted answer. Finally, we give examples where our invariant matches the expected answer in cases where the cycle is non-reduced, non-planar, or non-primitive.Comment: 63 pages, many improvements of the exposition following referee comments, final version to appear in Inventione

Studies on Beach Placers of Kerala Coast

In the present paper, studies carried out on beach placer samples of Kerala coast in general and contribut-ions of NML and its current activities in particular on beach sands of Kerala have been discussed. While earlier beneficiation study at NML was on purification of zircon, present study, under network project, consist of charac-terization of samples from different areas to identify prospective area that will be taken up for development of process technology. Characterisation studies involve size and chemical analyses, sink and float studies, optical microscopy and scanning electron microscopy. Samples from four different areas (Valarpattanam Azhikod (VA), Chava-kkad Ponnani (CP), Neendakara Kayamkulam (NK) and Warkala coast) were studied. It has been found that while heavy mineral concentration at NK and Warkala coast is quite high, the same at CP is rather low in comparison and at VA it's not significant