ASSESSMENT OF THE COMPLEXITY OF OCCURRENCE AND GEOLOGICAL VARIABILITY OF THE QUALITY OF HIGH-GRADE ORES DURING THE DEVELOPMENT OF THE C-2 DEPOSIT

The work is devoted to a very topical issue - predicting quality indicators in underground mining of ore deposits. In this work, the conditions and ways of improving the quality of ores during mining were studied on the example of deposits of rich ores in the northern flanks of the Talnakh and Oktyabrsky deposits of Talnakh. The studies were carried out in specific conditions at the mining enterprises of the Polar Division of the Public Joint Stock Company Mining and Metallurgical Company Norilsk Nickel. The northern deposits of the Talnakhskoye deposit represent the main prospect for replenishing the retired production capacities for the extraction of high-grade ores. The significant heterogeneity of the distribution of the metal content in industrial reserves of rich copper-nickel ores is the primary cause of high fluctuations in the quality of ore flow, which requires the use of the most advanced mining technologies to control the quality of ores during extraction. The process of forming the required quality level of mined ores at the mines of the Polar Division of PJSC MMC Norilsk Nickel is of paramount importance. However, during the development of deposits of «rich» ores in the ore stream «mine - processing plant», significant fluctuations in the quality of the ore mass are formed, which lead to losses of metals in the process of concentration and during metallurgical redistribution, thereby reducing the economic efficiency of the entire mining and metallurgical complex, as determines the relevance of the work.

The division defect of a Bacillus subtilis minD noc double mutant can be suppressed by Spx-dependent and Spx-independent mechanisms

During growth, bacteria increase in size and divide. Division is initiated by the formation of the Z-ring, a ring-like cytoskeletal structure formed by treadmilling protofilaments of the tubulin homolog FtsZ. FtsZ localization is thought to be controlled by the Min and Noc systems, and here, we explore why cell division fails at high temperature when the Min and Noc systems are simultaneously mutated. Microfluidic analysis of a minD noc double mutant indicated that FtsZ formed proto-Z-rings at periodic inter-chromosome locations but that the rings failed to mature and become functional. Extragenic suppressor analysis indicated that a variety of mutations restored high temperature growth to the minD noc double mutant, and while many were likely pleiotropic, others implicated the proteolysis of the transcription factor Spx. Further analysis indicated that a Spx-dependent pathway activated the expression of ZapA, a protein that primarily compensates for the absence of Noc. Additionally, an Spx-independent pathway increased the activity of the divisome to reduce the length of the cytokinetic period. Finally, we provide evidence of an as-yet-unidentified protein that is activated by Spx and governs the frequency of polar division and minicell formation. IMPORTANCE Bacteria must properly position the location of the cell division machinery in order to grow, divide, and ensure each daughter cell receives one copy of the chromosome. In B. subtilis , cell division site selection depends on the Min and Noc systems, and while neither is individually essential, cells fail to grow at high temperature when both are mutated. Here, we show that cell division fails in the absence of Min and Noc, not due to a defect in FtsZ localization, but rather a failure in the maturation of the cell division machinery. Suppressor mutations that restored growth were selected and while some activated the expression of ZapA via the Spx stress response pathway, others appeared to directly enhance divisome activity.

The division defect of a Bacillus subtilis minD noc double mutant can be suppressed by Spx-dependent and Spx-independent mechanisms

During growth, bacteria increase in size and divide. Division is initiated by the formation of the Z-ring, an intense ring-like cytoskeletal structure formed by treadmilling protofilaments of the tubulin homolog FtsZ. FtsZ localization is thought to be controlled by the Min and Noc systems, and here, we explore why cell division fails at high temperature when the Min and Noc systems are simultaneously mutated. Microfluidic analysis of a minD noc double mutant indicated that FtsZ formed proto-Z-rings at periodic inter-chromosome locations but that the rings failed to mature and become functional. Extragenic suppressor analysis indicated that a variety of mutations restored high temperature growth to the minD noc double mutant, and while many were likely pleiotropic, others implicated the proteolysis of the transcription factor Spx. Further analysis indicated that a Spx-dependent pathway activated the expression of ZapA, a protein that primarily compensates for the absence of Noc. Additionally, an Spx-independent pathway increased the activity of the divisome to reduce the length of the cytokinetic period. Finally, we provide evidence of an as-yet-unidentified protein that is activated by Spx and governs the frequency of polar division and minicell formation.

Destress blasting in deep mines of NorNickel’s Polar Division

Talnakh and Oktyabrsky ore fields are estimated as rockburst-hazardous starting from the depth of 700 m downward according to safety rules. This means that mining is only permitted within certain protected zones. At the present times, such protected zones are generated in underground mines by means of the large-diameter destressing drilling. Despite proved efficiency, the high cost and large amount of the destressing drilling are the grave faults of this approach. Aiming to save drilling cost, it is proposed to make rock mass rockburst-unhazardous using destress blasting. This article gives a brief description of the destress blasting mechanism. This method has been effectively used in relaxation of pillars from stresses before extraction of the reserves from the pillars both in Russia and abroad. In Oktyabrsky Mine stress relaxation of pillars was implemented by slotting, and the drilling and blasting data were available. This study proposes to destress rock masses by means of directional destress fracturing in horizontal plane through blasting of decked charges of special design. The initial parameters for destress blasting using holes with diameters of 76 and 130 mm are determined. The charge design aimed to ensure a zone of fractures in the horizontal plane, at minimized vertical fracturing is described. This information can be used in planning of full-scale tests to refine parameters and application ranges of the method. For the full-scale tests, it is suggested to undertake destress blasting at different blast patterns on different test sites, and to compare the results with the current destressing method (destressing drilling). Efficiency can be proved using geomechanical and geophysical methods. The authors appreciate participation of V. P. Marysyuk and T. P. Darbinyan from NorNickel’s Polar Division in this study.

Assessment of destressing drilling efficiency using numerical methods: A case-study of Oktyabrsky deposit

Mineral mining in rockburst-hazardous conditions should involve various precautions in compliance with federal regulations and standards. One of the main methods to prevent rock bursts is destressing drilling. In this method, a yielding zone is artificially created. The strength and deformation characteristics in this zone differ from the same characteristics of enclosing rock mass, and redistribution of stresses takes place as a result. Efficiency of destressing drilling is estimated in terms of ore body S-2 in Komsomolsky Mine. The efficiency criterion is selected to be the safety factor of rock mass with and without destressing drilling. Low efficiency of destressing drilling means that this method is readily replaceable by the other techniques of lesser labor input, for example, by reduction in the rate of mining, or by seasoning of underground excavations for some time required for redistribution of stresses to take place. Based on the theoretical research and the conclusions drawn at NorNickel’s Polar Division, the full-scale tests are scheduled for the implementation in order to gradually abandon destessing drilling in rockburst-hazardous Talnakh and Oktyabrsky ore fields. The authors appreciate participation of V. P. Marysyuk from NorNickel’s Polar Division in this study.

Geomechanical characteristic of ventilation shaft VS-3 in Oktyabrsky mine during extraction of mineral reserves from protective pillar

The strain analysis procedure is discussed in terms of a vertical mine shaft under the impact of extraction of ore reserves from protective pillar in Oktyabrsky mine of NorNickel’s Polar Division. The procedure is used in predictive strain analysis in depth of the shaft in case of different scenarios of protective pillar mining in ventilation shaft No. 3. The calculations show impossibility of preservation of shaft VS-3. Based on the prediction, it was decided on the early analysis of ventilation alternatives in the mine without involvement of shaft VS-3. The implemented research saved significant assets from spending on the shaft maintenance in the period of extraction of ore reserves from the protective pillar. Moreover, the time allowance until disability of shaft VS-3 enables scheduled planning and construction of access gateways to ensure the required ventilation mode in the mine. The authors appreciate participation of D. A. Kotikov, S. Yu. Shilenko, V. V. Balandin, M. P. Sergunin, A. V. Kulov, V. N. Andreev and A. K. Ustinov in the study.

Potential copper plant Vanyukov furnace gas desulphurization capacity

To enable maximum disposal of Vanyukov furnace flue gas, the authors of this paper examined the spare capacity of the Elemental Sulphur Site at the Copper Plant of Nornickel’s Polar Division. Thus, the paper considers an optimized three-stage flue gas treatment process (which also includes a thermal reduction stage) and the possibility to skip the stage of preliminary condensation of sulphur from reduced gas. To estimate how it will affect the overall recovery of sulphur (desulphurization factor), a series of calculations was carried out to compare the Elemental Sulphur Site’s performance during two different treatment processes: a complete process that includes preliminary condensation of sulphur from thermally reduced gas; and a short process, i.e. without preliminary condensation of sulphur. In both cases, the concentration of sulphur dioxide in the Vanyukov furnace gas was [SO2] = 28 vol %. The results of the calculations were verified through experiments conducted on a pilot unit owned by Gipronikel Institute with the gas flow reaching ~1.2 nm3/h, and they confirm the possibility of implementing the three-stage treatment process using the available plant space and reaching the capacity of 40,000 nm3/h and the sulphur recovery of ~89 %. The obtained data on the specific consumption rates of natural gas, oxygen and boiler water can be used for a feasibility study to justify the adoption of the short treatment process at the Elemental Sulphur Site of the Copper Plant of Nornickel’s Polar Division.

Pilot cooling tests conducted for high-copper converter matte ingots at Polar Division of PJSC MMC Norilsk Nickel

This paper describes the test methods that were applied to three ingots of high-copper converter matte with the weight ratio of Cu:Ni ~ 2.3 at Polar Division of PJSC MMC Norilsk Nickel to determine their cooling rate. The obtained results are also discussed. A test heat was done in the converter of the Nadezhdinski Metallurgical Plant, during which the following compositions were closely monitored: that of middlings; that of the finished matte that was discharged at 1,255–1,260 оС and poured in molds at 1,200 and 1,140 оС; and that of metallized matte that was intentionally overheated to 1,285–1,290 оС and poured at 1,200 оС. The cooling time was 82 and 93 hours (for capped ingots). The temperature was monitored with the help of six chromel-alumel thermocouples located at the level of 1,350, 850 and 350 mm from the bottom; three of them in the centre and the other three on a side. The ingots were crushed at the Nickel Plant, and a ~300 kg representative sample with the size of 3 mm was taken from each ingot for flotation tests. Spot samples were taken from the temperature monitoring areas for structural characterization. Based on experimental data, functional dependencies were derived with R2 0.99 that describe the obtained cooling curves. It is shown that due to the use of insulation cap in the structure defining temperature range of 1,150–750 оС, the cooling rate of the ingot top can be considerably decreased (approximately by three times). It is equal to 28–29 оС/h. In the vertically central part of all test ingots — i. e. ~850 mm from the bottom both in the centre and on a side, the cooling rates vary in the range of ~9–10.5 оС/h; in lower monitoring points — i. e. 350 mm from the bottom, they are equal to 24–33 оС/h. The cooling rate of the overheated matte at the top drops to 67 versus 87 оС/h for the uncapped ingot, whereas in the centre and at the bottom it almost remains the same.