| In order to meet the requirement of national economic development,the open-cast coal minings have been employed to exploit a near surface deposits or one that has a low stripping ratio for many years,and are facing major challenges of both quantity and quality such as the decreasing resources,especially the decreasing of the high quality resources despite of favour mining conditions.Furthermore,the pressures of resource recovery,cost relating to after-mine-closure,and the environmental protection are increasing.Other regional trade,industry integration and the development of economic globalization rises the price of production materials.These contribute to the escalation of production costs,and reduce product competitiveness in the market greatly.In the above discussed conditions,the Vietnamese open cast coal industry must continue to improve and innovate technical equipments.It carries on investment according to the depth of mining to inhance production capacity and improve production and management efficiency.According to the theoretical and practical researching results of continuous and semi-continuous process,we put forward a new mining technology which conforms to the geological,technical,economic and safety conditions of Vietnam open-cast coal mining.Based on the study of the characteristics,topography and geological conditions,coal seam structure of the open-cast coal mining in Vietnam,a new depth bottom of open cast coal mining in Vietnam is proposed on the foundation of the depth,length,width,annual production capacity,transportation form and classification of open pit coal minings.In order to improve the reliability of mining technology selection,the economic mathematical model is established,in which the minimum cost is determined by constructing the objective function through the parameters of mining system and the economic.It is noted that the technical index,and the economic and technical indexes of the single bucket transportation will affect the comprehensive benefit of mining production.Through the objective function,the reasonable mining system parameters such as the length of the excavator face and the optimum rock blasting size of the excavator are determined.According to the excavator bucket capacity and the mining system parameters,the reasonable truck load,the number and position of the concentrated benches are carried out.By considering the constraints of equipment selection,such as geological structure(fault,fold...),the structure of the coal seam and the terrain changes(the ups and downsof the terrain will cause great difficulties in the design of the mine road),production,service timelife,transportation distance,mining depth…put forward the objective function of equipment selection and calculate the minimum cost of production.The energy consumption and cost of the mining process mainly depends on the above inferred parameters and the transportation equipment.The reasonable energy consumption and the mining cost are proposed for the purpose of transporting energy consumption unit and the lowest transportation cost unit.Through the selection of reasonable mining technology,Cam Pha mining area,in Quang Ninh province of Viet Nam,is selected as an example,the calculation shows that the method is in line with the actual production-it proved the effectiveness of the method.From this,it can be applies to other mining areas which have similar conditions and situations like Cam Pha.It has shown that the depth bottom of Cam Pha open pit minings are deeper and deeper,the usage of continuous process lead to the increasing in mining costs.Therefore the semi-continuous process of the large-angle belt conveyor is in accordance with the condition of Cam Pha open-pit mining.On the other hand,the economic benefits of semi-continuous process of large-angle belt conveyor are significant,the amount of 846 million yuan can be save per year while the environmental pollution problem has been greatly improved. |
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