Estimation of mining time-span to improve the solution time in long-term production planning

Long-term production planning in open-pit mines is a precedence-constraint knapsack problem. A spatial representation of the mining region (called the block-model) is the primary input of mine planning models. One should note that as the number of blocks and periods to be planned increases, the number of decision variables increases. This paper presents a fast yet straightforward algorithm to reduce binary variables in open-pit mine production planning models. The algorithm considers mining capacity, processing capacity, and pit deepening rate to estimate the time span within which a block is mineable. This paper applies the algorithm in 12 different cases. The number of blocks varies from 1000 to 240000, and the mining periods range from 6 to 30 years. According to the results, this algorithm is helpful for problem size reduction

Micromechanical Properties of Injection-Molded Starch–Wood Particle Composites

The micromechanical properties of injection molded starch–wood particle composites were investigated as a function of particle content and humidity conditions. The composite materials were characterized by scanning electron microscopy and X-ray diffraction methods. The microhardness of the composites was shown to increase notably with the concentration of the wood particles. In addition,creep behavior under the indenter and temperature dependence were evaluated in terms of the independent contribution of the starch matrix and the wood microparticles to the hardness value. The influence of drying time on the density and weight uptake of the injection-molded composites was highlighted. The results revealed the role of the mechanism of water evaporation, showing that the dependence of water uptake and temperature was greater for the starch–wood composites than for the pure starch sample. Experiments performed during the drying process at 70°C indicated that the wood in the starch composites did not prevent water loss from the samples.Peer reviewe

Wybór strategii określania warunku opłacalności wydobycia w kopalniach odkrywkowych w warunkach niepewności cen w oparciu o wielokryterialny system rankingowy z uwzględnieniem czynników ryzyka

Cut-off Grade Strategy (COGS) is a concept that directly influences the financial, technical, economic, environmental, and legal issues in relation to exploitation of a mineral resource. A decision making system is proposed to select the best technically feasible COGS under price uncertainty. In the proposed system both the conventional discounted cash flow and modern simulation based real option valuations are used to evaluate the alternative strategies. Then the conventional expected value criterion and a multiple criteria ranking system were used to rank the strategies based on the two valuation methods. In the multiple criteria ranking system besides the expected value other stochastic orders expressing abilities of strategies in producing extra profits, minimizing losses and achieving the predefined goals of the exploitation strategy are considered. Finally, the best strategy is selected based on the overall average rank of strategies through all ranking systems. The proposed system was examined using the data of Sungun Copper Mine. To assess the merits of the alternatives better, ranking process was done at both high (prevailing economic condition) and low price conditions. Ranking results revealed that at different price conditions and valuation methods, different results would be obtained. It is concluded that these differences are due to the different behavior of the embedded option to close the mine early, which is more likely to be exercised under low price condition rather than high price condition. The proposed system would enhance the quality of decision making process by providing a more informative and certain platform for project evaluation.Strategia doboru granicy opłacalności (COGS) jest koncepcją mająca bezpośredni wpływ na kwestie finansowe, techniczne, ekonomiczne, środowiskowe oraz prawne związane z eksploatacją surowców naturalnych. Zaproponowano system decyzyjny umożliwiający wybór najkorzystniejszej fizycznie wykonalnej strategii doboru opłacalności wydobycia w warunkach niepewności cen. W proponowanym systemie do analizy alternatywnych strategii wykorzystuje się konwencjonalne metody oparte o analizy przepływu strumienia gotówki oraz nowoczesne techniki symulacji rzeczywistych opcji. Następnie zastosowano tradycyjny system oparty o kryterium wartości oczekiwanej oraz system rankingu wielokryterialnego do określenia rankingu strategii, w oparciu o dwie metody oceny. W systemie wielokryterialnym obok wartości oczekiwanej uwzględnia się inne dane stochastyczne określające zdolność poszczególnych strategii do generowania dodatkowych zysków, do ograniczania strat i osiągania wcześniej zdefiniowanych celów. W etapie końcowym dokonuje się wyboru optymalnej strategii w oparciu o całkowity ranking strategii uwzględnionych w systemie. Proponowane podejście testowano w oparciu o dane uzyskane z kopalni miedzi Sungun. Aby ocenić zalety najlepszej alternatywy, ranking przeprowadzono przyjmując warunki wysokich i niskich cen. Wyniki rankingu wykazały, że w warunkach różnych cen i przy zastosowaniu różnych metod oceny, uzyskane rezultaty będą się różnić. Należy wnioskować, że różnice te spowodowane są różnicami w podejściu do wbudowanej opcji wczesnego zamknięcia kopalni, która ma większą szansę na realizację w warunkach niskich cen, a nie wysokich. Proponowany system podniesie jakość procesu decyzyjnego poprzez dostarczenie platformy dodatkowych informacji dla oceny przedsięwzięcia

An environmental oriented model for optimum cut off grades in open pit mining projects to minimize acid mine drainage

Environmental concerns on mining activities started near the end of the 20th century and is still underway. Due to mining activities, the adverse environmental impact has been significant throughout the history of mankind, whereas the minerals produced by mining activities have been providing the basis for human civilization. The legacy of past mining practices is large quantities of acid generating waste materials and tailings that caused abounding acid mine drainage problems. Modern mining environmental management tends to focus on concerns over the impact of waste disposal on surface primarily in the form of tailings and waste materials structures. Sustainable development principles are being increasingly applied by mining companies in developed and developing countries. Operating costs per unit of operation is recognized to be one the most important sustainable mining practice indicator and cut off grade is considered to be a well-founded representative for this indicator. In this paper, a developed model for optimum cut off grades is presented that not only relies on economical aspects but also minimizes adverse environmental impact in the form of acid mine drainage elimination or mitigation against the approach of postponing the restoration/reclamation activities at the end of the project’s life

Determination of Ultimate Pit Limits in Open Mines Using Real Option Approach

Planning and design procedure of an open pit mining project just can be started after ultimate pit determination. In the carried out study in this paper it was shown that the most important factor in ultimate pit determination and in consequence in the whole planning and design procedure of an open pit mine is the metal price. Metal price fluctuations in recent years were exaggerated and imposed a high degree of uncertainty to the mine planning procedure while none of the existent algorithms of the pit limit determination consider the metal price uncertainty. Real Option Approach (ROA) is an efficient method of decision making in the condition of uncertainty. This approach usually used for evaluation of defined natural resources projects up to now. This study considering the metal price uncertainty used real option approach to prepare a methodology for determining the Ultimate Pit Limits (UPL). The study was carried out on a non-ferrous metallic cylindrical ore deposit but the achieved methodology can be adjusted for all kinds of the deposits. The achieved methodology was comprehensively described through the examples in a way that can be used by the mine planners

Using silver nano particles for sampling of toxic mercury vapors from industrial air sample

Introduction: Mercury is one of the toxic metals that damages the nervous system and kidneys. Therefore, monitoring of mercury vapors in the environments is essential. .Material and Method: A new adsorbent was made from silver nanoparticles on a bed of quartz. The nano-adsorbent was capable for sampling of the trace amounts of mercury vapor from air. In this study, the required mercury vapor was generate by hydride generation atomic absorption spectrometry and the necessary analysis was performed by cold vapor atomic absorption spectrometry. . Results: Mercury vapors in the Stationary phase, were concentrated as much as 2300 times (Atomic absorption detection limit was 1.15 microgram per liter of air). Thus by this stationary phase, the trace amounts of mercury vapors can be detected up to 0.5 nano gram per liter of air. The detected value of the presented method is 200 times lower than the occupational safety and health administration (OSHA) standards for mercury vapors. Heater accessory at the temperature of 245 °C was used for thermal desorption of mercury from nano silver adsorbent. Optimal time of desorption was obtained 150 seconds and the Repeatability of the method was 58 times. The mercury vapors absorbed on nano silver adsorbent could be maintained at 80 days at the room temperature (25 °C). .Conclusion: The presented adsorbent is very useful for sampling of the trace amounts of mercury vapors from air. Moreover, it can be regenerated easily is suitable or sampling at 25 to 70 °C. Due to oxidation of silver and reduction in uptake of nanoparticles, oven temperature of 245 °C is used for the recovery of metallic silver. Low amount of adsorbent, high absorbency, high repeatability for sampling, low cost and high accuracy are of the advantages of the presented method

A Stochastic Simulation Framework for Truck and Shovel Selection and Sizing in Open Pit Mines

Material handling in open pit mining accounts for about 50% of production costs. The selection and deployment of efficient, safe, and economic loading and haulage systems is thus critical to the production process. The problems of truck and shovel selection and sizing include determination of the optimal number and capacities of haulage and loading units, as well as their allocation and operational strategies. Critical survey and analysis of the literature has shown that deterministic, stochastic, and experimental approaches to these problems result in considerably different outputs. This paper presents a comprehensive simulation framework for the problem of truck and shovel selection and sizing based on the random processes underlying the network-continuous-discrete event nature of the mining operation. The framework builds on previous research in this field and attempts to address limitations of available methodologies in the form of a comprehensive algorithm. To test the validity of the framework a large open pit mine was evaluated. The stochastic processes governing the uncertainties underlying the material loading and haulage input variables were defined and built into the stochastic model. Discrete event simulation was used to simulate the stochastic model. The proposed model resulted in several modifications to the case study

Incorporating environmental issues into optimum cut-off grades modeling at porphyry copper deposits

Cut-off grade is defined as the grade which discriminates between ore and waste within a given orebody. Determination of a complete optimum cut-off grade policy is a very important function during mine life. Using the modified optimum cut-off grade model presented in this paper not only the net present value of a porphyry copper mining project is maximized, but also the adverse environmental impacts of the project are minimized simultaneously. This methodology is more effective in long-range planning. For showing the effectiveness of the model, two scenarios are considered in a hypothetical deposit and the results show that incorporating the modified optimum cut-off grade policy, the net present value will be increased by 3.6% in comparison with the Base Case.Acid-generating rocks Cut-off grade policy Mine design and planning Porphyry coppers