Abstract
The Colombian mining sector is characterized by the production of coal, nickel, emeralds, gold, and construction materials. It is considered by the National Development Plan of Colombia 2018-2022 as an economic agent that boosts development in the region and one that requires the strengthening of its policies and environmental liability. Therefore, this paper aims to show the importance of implementing methodologies based on the logic of nature (exergy) that objectively indicate the environmental impact of an extractive gold activity, such as open-pit gold mining. The extractive activity or process to be studied consists of the following stages: topsoil removal by using machinery and explosives to create craters and to access the mineral present in the subsoil; the physical transformation of the extracted material through crushing, grinding, gravimetric separation, flotation, leaching, adsorption, elution, and electrodeposition, along with smelting and casting to obtain gold and silver ingots. Thus, this paper analyzes the exergy performance of each unit process of the open-pit extractive process. The obtained results are used in a sensitivity analysis, which determines the system efficiency, by assuming the increase of gold in the extracted material in the exploitation stage, by using the same supplies and input of the current process. In other cases, the open-pit mining process is analyzed by changing its technologies in the mining process and assuming that this change reduces the inlet ore to 60%, by discarding 40% of material without gold and by reducing supply consumption by 25%. By improving the system efficiency, the exergy destroyed is reduced and the emissions to the environment diminish. Therefore, this method may be implemented as a basic guideline when it comes to decision-making processes in the planning of the extractive processes by integrating the environmental Q5 component with gold production.
Highlights
Since the industrial revolution, societies have increased their energy demand in an exponential way, rendering the efficient use of energy a fundamental issue, especially due to the economic and environmental problems associated with its misuse [1]
The methodology used is based on the one proposed by Valero [12]. She proposes a methodology which is capable of evaluating the natural capital of the earth from its minerals, as a non-reactive mixture or with a coefficient of reactivity equal to one, where the natural capital of the earth is calculated like the chemical exergy of a solution, combined with a traditional exergy analysis
The results obtained after the exergy analysis will be shown in four sections: the first talks about the balance of exergy in each stage of the process
Summary
Societies have increased their energy demand in an exponential way, rendering the efficient use of energy a fundamental issue, especially due to the economic and environmental problems associated with its misuse [1]. In order to use energy resources more efficiently in any process, first of all, the different flows and energy transformations involved must be clearly determined. According to the First Law of Thermodynamics, energy is rather a conservative magnitude and, as such, it is neither possible to destroy it nor create it, instead it is only possible to transform it from one form into another [2]. The Second Law of Thermodynamics states that energy cannot be created or destroyed, its quality may be degraded [3]. In order to perform a thorough energy analysis, it is necessary to bear in mind the statement of the Second Law of Thermodynamics, from which the concept of exergy springs. Exergy is defined as the maximum work that can be obtained when
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