Dimensioning a stockpile operation using principal component analysis

Mineral processing plants generally have narrow tolerances for the grades of their input raw materials,so stockpiles are often maintained to reduce material variance and ensure consistency.However,designing stockpiles has often proven difficult when the input material consists of multiple sub-materials that have different levels of variances in their grades.In this paper,we address this issue by applying principal component analysis(PCA)to reduce the dimensions of the input data.The study was conducted in three steps.First,we applied PCA to the input data to transform them into a lower-dimension space while retaining 80% of the original variance.Next,we simulated a stockpile operation with various geometric stockpile configurations using a stockpile simulator in MATLAB.We used the variance reduction ratio as the primary criterion for evaluating the efficiency of the stockpiles.Finally,we used multiple regression to identify the relationships between stockpile efficiency and various design parameters and analyzed the regression results based on the original input variables and principal components.The results showed that PCA is indeed useful in solving a stockpile design problem that involves multiple correlated input-material grades.

A study of self-heating characteristics of a pyrrhotite-rich sulphide ore stockpile

Original surface chemistry of sulphidesis altered upon contact with air, leading to ''oxidation'', which is accompanied by evolution of heat. The current study reports results of an investigation on extent of exothermicity of an experimental nickel-copper sulphide stockpile that was formed at a mining site in Sudbury, Canada. The ore contained pentlandite and chalcopyrite that are accompanied by a large quantity of pyrrhotite. The self-heating characteristics were recorded by temperature sensors placed inside the stockpile. Ambient conditions such as temperature, humidity, and wind velocity were simultaneously recorded. The inner temperature of the stockpile indicated significant fluctuations due to rapid changes, particularly in the outside temperature. The minimum and maximum temperatures recorded in the outside and inside were 5 and 10.5, 44.3 and 32 ℃, respectively. The self-heating capacity of the sulphide ore stockpile observed represents a mild case compared to that experienced by coals. Possible reasons are discussed.

Computer controlled measurement of spontaneous combustion in coal stockpiles of the Western Lignite Corporation, Turkey

The spontaneous combustion event in coal stockpiles is inevitable when appropriate environmental conditions are available. The objective of a computerized measurement system is to measure temperature changes existing in a coal stockpile. In order to achieve this intention, the electrical signal conversion of temperatures sensed by 20 temperature sensors placed in certain points inside the coal stockpile, the transfer of these electrical signals into computer media by using analogue-digital conversion unit after applying necessary filterization and upgrading processes and the record of these information into a database in particular time intervals are provided. Afterwards, the diagrams of these time-temperature data are plotted. With the help of these graphs, the competent company will be able to examine the behavior of coal stockpiles in terms of spontaneous combustion and take necessary precautions against self-combustion beforehand.

A FAST STOCKPILE SIMULATION ENGINE AND ITS APPLICATION IN MINERAL ORE HANDLING

This paper presents structures and principles of a fast stockpile simulation engine that enhances automatic material process by providing accurate digital information of material quality distribution within stockpiles.Compared with traditional measurementbased approaches,our simulation technology reduces operation cost by eliminating frequent physical measuring;improves operation accuracy through all-time whole-area contour simulation(instead of measuring a few positions of material layers now and then);and speeds the process through fast simulation and instant response to quality information query.Based on simplified grain dynamics and cellular automata models,the technology can achieve real-time/super-real-time simulation,which is critical to be adopted by the industry.Application of the technology in analyzing mineral ores handling is also discussed.

Modelling of dust emissions induced by flow over stockpiles and through packed beds

Dust emissions during storage of non-moving bulk materials are studied with a numerical method.The model relies on a contact-model-free Discrete Element Method(DEM)to model the bulk particle-fluid interaction and the dust removal coupled with Computational Fluid Dynamics(CFD)to model the gas and the dust phase in a multiphase framework.Here,two storage scenarios are considered:a flown through packed bed and a flown over stockpile.For the first,the performed simulations reveal that the dust discharge can be correlated with the passing fluid pressure drop.For the second,a parameter study of factors influencing the dust emissions is performed.The parameters discussed are the stockpile size,the gas velocity,the slope angle,the particle diameter and the shape of the stockpile,taking into account conical and truncated conical stockpiles.Dust release correlations are obtained for both scenarios,which reflect very well the obtained numerical results.

Bulk Raw Materials Handling and Blending Techniques of Sinter Plant:A Case Study of Ajaokuta Steel Company Limited,Kogi State,Nigeria

Bulk raw materials handling plant and sintering plant preparatory plants are established to receive,blend,stockpile,prepare and supply specified grades of raw materials for smooth operations of iron making plant(Blast furnace),steel making plant(Basic oxygen converter)and lime Plant(calcinations plant).The study discusses bulk raw materials handling and some general problem of scientific analysis and documentation of basic equipment details,stockyard facilities,bulk materials transport systems and sinter processes,for the general knowledge and operational procedures of these plant for effective and efficient operational processes for optical results.Iron ore concentrate supplied from the mines to some extent fluctuate in their chemical composition as a result of the nature of the deposit with various factors controlling beneficiation processes and addition of metal-bearing materials collected as a waste product from the Rolling Mills,Blast Furnace and Sinter Plant which must be recycled through Iron ore concentrate stockyard.The part of the sinter mixture is melted at a temperature about 1300-1480°C and a sequence of reactions shaping the sinter cake to be loaded into the blast furnace to produce iron from a pig.

A mathematical model for open pit mine production scheduling with Grade Engineering and stockpiling

This paper presents the development and implementation of an innovative mixed integer programming based mathematical model for an open pit mining operation with Grade Engineering framework.Grade Engineering comprises a range of coarse-separation based pre-processing techniques that separate the desirable(i.e.high-grade)and undesirable(i.e.low-grade or uneconomic)materials and ensure the delivery of only selected quantity of high quality(or high-grade)material to energy,water,and cost-intensive processing plant.The model maximizes the net present value under a range of operational and processing constraints.Given that the proposed model is computationally complex,the authors employ a data preprocessing procedure and then evaluate the performance of the model at several practical instances using computation time,optimality gap,and the net present value as valid measures.In addition,a comparison of the proposed and traditional(without Grade Engineering)models reflects that the proposed model outperforms the traditional formulation.

Effects of China's Corn Stockpiling System Reform on Family Farms' Decision to Join Cooperatives

Reform of the corn stockpiling policy is a key initiative for advancing China's market-based grain stockpiling reform. It is a critical component of China's exploration of a price formation mechanism for agricultural products. Evaluating the effectiveness of such reform is therefore of great relevance. Based on nationwide farm monitoring data of 2014, 2015 and 2016, this paper examines the effects of the corn stockpiling reform on the decision of family farms to join cooperatives. Our finding suggests that after other factors that influence the decision of family farms to join cooperatives are controlled for, the probability of corn farms to join cooperatives in the Northeast and Inner Mongolia, where the corn stockpiling reform was carried out in 2016, is significantly higher compared with the probability of corn farms in non-reform areas that did so. The reason is that after the reform, corn producers must sell their corn to the market instead of to the State, bringing them sales problems, which could be mitigated to some extent by joining cooperatives.Thus, the corn stockpiling reform incentivized the market-based behavior of agricultural producers, giving play to the role of market mechanisms in regulating production and demand.

Revisiting Emergency Food Reserve Policy and Practiceunder Disaster and Extreme Climate Events

All food systems will continue to be affected by disasters and extreme climate events. Triggered by recent food crises around the world and climate change concerns,some governments have been trying to develop more robust and resilient food systems. One of the oldest options for many governments is to stockpile emergency food reserves for the purpose of food security and disaster preparedness. In the aftermath of the world food price crises in2007–2008 and 2011, some governments in Asia have been maintaining emergency food reserves to ensure greater supply and price stability. Disasters and extreme climate events help governments to justify emergency food reserves. This research examined emergency food reserve policies in Indonesia, the Philippines, and Malaysia.Emergency food reserves emerged as a practice where the shared objectives of development, disaster risk reduction,and climate change adaptation have been demonstrated by governments. The findings suggest that most governments maintain the strong view that adequate emergency food reserves can buffer national food price shocks and shocks from disasters and climate change, and soften disruptions in trade due to export bans during times of disasters and climate emergencies.Under global climate change scenarios, food security is at risk and volatile(Porter et al. 2014). The expected increase in climate extremes has generated anticipatory actions from governments, including a new push for EFR policy adoption. Triggered by recent disasters and climate change concerns, some governments have been trying to develop more robust and resilient food systems(Fan and Brzeska 2014; Porter et al. 2014). For many countries in Asia, this means the renewed adoption of EFR. Unfortunately, we argue that this is not well understood in climate change adaptation studies as well as contemporary disaster studies.The Association of Southeast Asian Nations(ASEAN)first initiated a Food Security Reserve Agreement in 1979,with the purpose of meeting emergency requirements(ASEAN 1979). Policymakers have been aware of the susceptibility of the region to natural hazards and the possibility of food shortages. But it took 30 years, until soon after the world food crisis in 2007–2008(Hadley and Fan 2010), for the association plus three additional East Asian nations(China, Japan, South Korea) to establish the ASEAN Plus Three Emergency Rice Reserve(APTERR)in 2009, as a mechanism to address potential food shortages in the region in the light of climate and market uncertainties. The final formal agreement was signed in October 2011 in Jakarta(APTERR 2017).The Association of Southeast Asian Nations also established the ASEAN Food Security Information System(AFSIS) that functions as a central information repository for five commodities—rice, maize, soybeans, sugar, and cassava. AFSIS not only monitors and analyzes production,import, export, inventory stock, price, food security ratio,and self-sufficiency ratio for these commodities but also provides data on losses from both floods and droughts in every member state(Lassa et al. 2016). In theory, AFSIS serves as an early warning mechanism for ASEAN to trigger the activation of APTERR's response mechanism(Saengbangka 2014, personal interview; AFSIS 2017).This article argues that EFR can function as a means of disaster risk reduction, including climate change adaptation, and aims to understand why governments in Asia are readopting emergency food reserves as national policies,with a focus on Indonesia, the Philippines, and Malaysia.We also explore how disasters and climate change strengthen or weaken government narratives in support of emergency food reserves.

A discussion of irrational stockpiling behaviour during crisis

One of the ubiquitous human behaviours observed in natural disasters and humanitarian crisis is irrational stock-piling(also known as hoarding or panic buying).Limited,distorted and exaggerated information during crisis disturbs people’s judgement and results in aberrant actions which can be explained with economics and psychol-ogy theories.The objective of this paper is to examine the perplexing stockpiling phenomena during disasters like COVID-19 pandemic and discuss its immediate and long-term impact on economy,society and local communities.