Güney Afrika Cumhuriyeti'nde west Driefontein ve Kloof işletmelerinde Ocak ikliminin incelenmesi
The Search about the mining climate at West Driefontein and Kloof gold mines in South Africa
- Tez No: 19369
- Danışmanlar: DOÇ.DR. GÜNDÜZ ÖKTEN
- Tez Türü: Yüksek Lisans
- Konular: Maden Mühendisliği ve Madencilik, Mining Engineering and Mining
- Anahtar Kelimeler: Altın, Güney Afrika Cumhuriyeti, Maden yatakları, Ocak iklimi, Gold, Republic of South Africa, Ore deposits, Mining climate
- Yıl: 1991
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: Belirtilmemiş.
Özet
ÖZET Güney Afrika'daki çoğu altın madeni gibi Kloof ve West Driefontein altın madenlerinde de ortalama çalışma derinliği 3500 metre civarındadır ve bu. derinlikteki ortalama bakir kayaç sıcaklığı ise 60-65*0. arasında değişmek tedir. Bunun yanında yeraltına gönderilen havanın, otokompresyon dolayısıyla ve ayrıca galeri ve tünellerde; yol alırken kayaçlarla ve makinalarla olan ısı alışverişi nedeni ile sıcaklığı önemli ölçüde artabilmektedir» Bu sıcaklık artışı ile birlikte relatif nem oranının artışı ve bu nemin buharlaşması ile daha da kötüleşen çevre koşulları, yeraltı personelinin çalışma koşullarını, emniyetini ve konforunu ters yönde etkilemektedir» Tüm bu -faktörler, hava yolunun neminin giderilmesi, yeraltına sevkedilen hava miktarının arttırılması ile düzeltilme yoluna gidilse de, artan derinlikle tüm bu metodlar ya çok pahalı hale gelmekte yada başarısızlığa uğramaktadırlar» Bu ise havanın ve servis suyunun ya yeraltına* sevk edilmeden önce yeryüzünde yada yeraltında hava giriş kuyusu dibindeki uygun bir veya. birkaç alanda ve çalışma alanları yakınında soğutulmasını gerektirir.
Özet (Çeviri)
SUMMARY THE SEARCH ABOUT THE MINING CLIMATE AT yEST DRIEFONTEIN AND- KLOOF GOLD MINES IN SOUTH AFRICA Mining has progressed from shallow operations to deep levels extending down to 45ÖÖ metres or more below surface in South Africa. Underground ventilation practice is intimately bound up with m in i rig conditions, Two mining methods are used arı West Driefontein and Kloof. Firstly the longwall method, a system whereby and series of faces are advanced in line in one general direction, with its following development in tunnels. The South African gold mines are typical representatives for longwall mining applied to very hard rock, The gold reef is excavated by conventional drilling and blasting. Short holes are drilled along the face or panel in a side-slushing pattern. Secondly the scattered mining method where the conglomerate horizons are pr ©“”developed and mined in a more dispersed manner. Scattered mining can be selective to control the grade value., and also large numbers of stope faces are provided that can be worked at the same time, The supply arid control of air throughout a mine is one of the major functions of a ventilation department, The efficient of a ventilation system is dependent to a degree on the control and distribution of the ventilating air through the effective use of air control appliances. The dilution of dust and gases and the removal of heat are same of the primary reasons for ventilating mines and poor B±r- control can create bt\ unhealthy and unsafe envi ronment climate on the one hand while increasing the fan power requirements ori the other. Development ends or headings bvg ventilated by means of elect irical fans, usually of the axial flow type and rigid ventilation piping. Piping is normally made of galvanized iron 1 mm, or 1,2 mm, thick, Pipe diameters bv& usually 4 06 mm,, 576 mm. and 76® mm. XII“or special applications, >:i.zes are used. such as in shaft: sinking larger The system used in development ventilation Br& mainly the forcing system and the exhaust overlap system, The forcinq system is the most popular as only one ventilation.duct: is necessary and because it permits the air to he delivered onto the face, By regulation a minimum amount of air of 0.15 m3/s per square metre of face must be blown in. In the forcinq system the air is discharged at a distance of less than 15 m, from the face. In the exhaust overlap system the exhaust column in carried to a point about 30 m. from the face. ft smaller diameter1 forcing column picks up air about 30 m, from the intake of the exhaust: column and conveys it to the face. In order to avoid recirculation of the air quantity blown to the face must be not more than one third of the air quantity exhausted, and the length of the overlap must be at least 10 m. The advantage of the exhaust: overlap system is that the blasting' fumes are removed rapidly from the development end., making earlier re-entry possible. This system is generally used when long single ends need to be developed at high speed. In stopes which arm the main production areas in a mine, ventilation air is caused, as far as practicable., to concentrate along the face. Host stopes have a centre gully which is used far the transport of men, material and ore, with strike gullies connecting to the faces. Obviously leakage via the centre gully will robe the working face of much of its air, over 50 percent of the air reaching a s tope will travel that way if not prevented. However the use of brattices and doors in centre gullies, comb i vied with the use of adequate strike walls, is successful in coursing the bulk of the air to the face, In the case of scattered stopes, which form the great majority of stopes on Kloof and West Driefontein gold mines air coursed to the face by means of strike walls made of waste rock, brick walls or cur”t a iri s made of plastic materials. The continuation of mining activities normally involves operating at ever greater* depths, arid one of the serious problems which arises in deep level mining is the high temperature of the environment, The high temperatures in deep level mining such as Kloof and West Driefontein, produce atmospheres which have an adverse effect on the comfort and efficiency of the underground personnel and to some extent: on the safety and health. These adverse effects are aggravated by the increased humidity caused by the evaporation of moisture, relative XIIIhumidities being above 85 percent' in most hot working places, The degree of wetness of mine airways and working areas has a profound influence on heat flow, on the other hand the wet mining has to be practised to settle dust and reduce the pneumoconiosis risk, Productivity decreases with increase in wet-bulb temperature, for a given air velocity, and unless temperatures can be kept below the critical limits, work becomes either impossible or so inefficient as to be uneconomical, ft detailed knowledge of the sources from which heat enters the mine air is essential in the estimation of the air volumes and refrigeration required to provide tolerable environmental conditions underground, The principal sources of heat affecting the ventilating air are auto compression, heat from rock, water, machinery, men, explosives, ligthing, compressed air, oxidation of minerals arid timbers and mine fires. Strictly speaking auto compression is not a source of heat, for it results in an increasing temperature of either Bir or water as a result of the conversion of potential energy into entalphy, and not as a result of a flow of heat from an external source, The rate at which the virgin rock temperatures varies with depth thus depends mainly upon the termal conductivity of the rock, while the actual value of the virgin rock temperature at a particular depth will depend upon the temperature gradient and upon the rock temperature at the surface, Virgin rock temperatures range from approximately 25°C at 1O00 metres below surface to 70 °C or- more on the deep levels in Witwatersrand in which Kloof and West Driefontein take place, As mining depths continually increase, the task of p r o v i d in g s a t i s f a c t o r y e n v i r onnıen i: a 1 c o n d i t i o n s underground becomes progressively more difficult and expensive. Two strategies have been adopted to overcome the environmental problems, The first is to devise methods for the reduction, at the source, of the heat and pollutant loads on the underground environment, and the second is to devise improved methods for conditioning the underground environment. Reducing the heat flow from rock can be achieved by keeping the dry-bulb temperature of the air above or- as close as possible to the temperature of the rock. This means that evaporation of water- into the air must be reduced to a minimum, It is also important to note that the heat can be transfer-red to the air at a higher rate from a wet surface than from a dry one. find also intake airways must be kept as dry as possible, drain covers mre used and that drains do not over-flow, v T UWhere* possible, machinery should he installed on the return sides of the mines and individual working in order to decrease t hie heat pick-up. Another- point worth noting is that the dust, gases arid moisture in the return air have an adverse effect on machinery. Heat from hot pipes can be eliminated by insulating them with material such as polyurethane or fiberglass, Increasing the volume of air means that the heat pick- up per cubic metre of air will be less and conditions will improve. In other words extra air dilutes the heat, This can be achieved by reducing leakage to a minimum, exercising good air control, installing larger fans, developing extra airways in parallel with existing ones and reducing shaft and air- way resistances. Under hot conditions mart carı work harder and have a lower risk of heat stroke if they ^r<s acclimatized to such conditions, The need for- acclimatization of men to work at high wet--bulb temperatures in South African gold mines has been recognized for many years. it is recommended by the Research Laboratories of the Chamber of Mines that mine managers should consider instituting acclimatization practices when the wet-bulb temperatures in working places reach 27,S°C, Obviously, workers employed in areas where t hi e we t --bu lb temperatures are higher than 27, 5<:'C should be acclimatized. As a last resort, when all other efforts to reduce hot conditions in working places have failed, the installation of cooling plants to cool the air may be considered. Cooling plants should be considered as a last resort because of the great expense involved in purchasing and operating them. Mine air can be cooled either on surface before it enters the downcast shaft, or underground at or near the bottom of the downcast shaft, or* in the working places, Surface air- cooling is the cheapest and easiest application of refrigeration because maintenance and supervision av*e easy, and because the heat which :i."s removed from the downcast air carı be rejected to the atmosphere, However it is not practical to cool the air lower- than 3-JC, which means that very little cooling can be done during winter, In other words, the best that can he ' achieved by means of surface refrigeration is to provide slightly better- than winter conditions in -the mine working places throughout the year,Bulk underground cooling, i, e. the cooling of a large volume of air at one or more convenient places near the bot tons of the mine, results in a much better- positional efficiency than surface cooling and because of the warmer conditions the plant can be run at full load throughout the year, Heat rejection is however, much more difficult and expensive because the heat has to be transferred to a limited flow of upcast air which is already hot and humid, ft suitable substance, known as the refrigerant, circulates corrtiniously through vapour compression machines in order to produce chilled service water- in the refrigeration plant. The refrigerant enters the evaporator as a liquid arid is evaporated, the heat required for this being obtained from the substance being cooled, The resultant vapour then enters the compressor, where it is compressed to a higher pressure and then discharged into the condenser, In the condenser the re frige ran t vapour is cooled and condensed to a liquid, the latent heat released being transferred to the circulating condenser water, The liquid refrigerant leaves the condenser w\d passes through an expansion ft water circuit connects the condenser return airway where heat is rejected or given off, The water- passes through the condenser-', where the refrigerant gas gives off heat to the water which is then very hot, flows to the return airway. It is sprayed into return air- iri a cooling tower, the water is much hotter- thari the return air leaving the tower is then much hotter and the water- in the dam is cooler. The water- is then sent back to the condenser to be re--heated and the cycle is repeated. Another water- circuit also connects the evaporator- to the working places which require cooling. T hie water- passes throughi the evaporator, where heat is removed from it to evaporate the refrigerant, The water then leaves the evaporator as chilled water- arid flows to the working place which needs cooling, Here it passes through a cooling coil similar to the radiator in a car. Hot air- is sucked by a fan and blown over- the cooling coil, and heat is transferred from the air to the water, The air leaving the coil is then cooler and can be delivered directly to the working face, The water is sent back to repeated. The positional efficiency of this method is obviously high but the cost is also very high. The insulated pipes arid the air- coolers and fans may cost more than the cooling plant itself, depending on the distance nr\d the pressures involved. YUTIn a deep gold mines with a high virgin rock temperature it may be possible to distribute only 20% to 30% of the required cooling by means of service water while the remainder still has to be achieved by means of direct air cooling, either by means of bulk spray chamber-;: or by means of coil heat exchangers, XVII
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