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Home » Mine Ventilation in the 21st Century – Development Towards Adaptive Ventilation Systems

Mine Ventilation in the 21st Century – Development Towards Adaptive Ventilation Systems

Mine ventilation and climatization became increasingly important over the last decade. Main challenges and drivers have been the development of mining activities towards greater depths, more complex deposits with a larger areal extent, the further introduction and implementation of diesel-powered vehicles as well as stricter occupational exposure limits and rising energy costs. To meet these requirements and to keep the operation viable, new holistic ventilation concepts, methods and tools need to be developed for providing and guaranteeing sufficient fresh air for safe and efficient operations in underground mines at all times and all locations. Current approaches focus mainly on the development and implementation of ventilation on demand concepts (VOD) and systems. However, the smart and intelligent, safe “Mine of the Future” demands the further development of advanced and adaptive ventilation systems. In this paper, a holistic concept for an advanced and adaptive ventilation system will be introduced and its key components and elements described. Furthermore, the implications on the higher education in the field of mine ventilation and climatization discussed and an exemplary teaching concept presented.

Author: Dr.-Ing. Elisabeth Clausen, Institut für Bergbau, Technische Universität (TU) Clausthal, Clausthal-Zellerfeld

1  Introduction

Mine ventilation can be described as the “lifeblood of a mine, the intake airways being arteries that carry oxygen to the working areas and the return veins that conduct pollutants away to be expelled to the outside atmosphere” (1). Therefore, an effective and efficient ventilation system with the tasks to provide fresh air in sufficient quality and quantity in all operating areas, to dilute and remove occurring contaminants as well as to create a pleasant mine climate is necessary for guaranteeing safe working conditions in underground mining operations. This becomes even more important as ventilation makes up a major fraction of a mine`s total energy consumption – 40 to 50 % in most cases (2, 3). In addition, high energy consumption, which results in the emission of greenhouse gases, as well as the use of certain refrigerants, has direct impacts on the environment (4). As mining companies are major energy users, they are required to reduce their energy intensity and carbon emissions (3). Beside these factors, mine ventilation and climatization systems have been affected over the last years by several additional developments. The main challenges and drivers are (5, 6):

  • mining in harsh conditions, i. e. extreme heat or cold;
  • increase in depth of mining operations;
  • increase in complexity of deposit structures with a more extensive network of excavations, increased size of developments, multiple headings and working areas;
  • increase in grade of mechanization with the usage of trackless machines and its mobility in addition with larger and more powerful diesel equipment and increase in number and size of light vehicles; and
  • reduction in maximum allowable personal exposure levels (7).

To meet these requirements and to keep the operation viable, new holistic ventilation concepts, methods and tools need to be developed to prevent reductions in mine development rates, hold-up of proposed mining projects or even mine closures. In addition, current trends and technological developments, which are based on the successful integration and implementation of sensor systems, modern information and communication systems (ICT) as well as artificial intelligence (AI) offer new opportunities and chances.

One possibility hereby is the improvement of ventilation and air conditioning systems in terms of efficiency and sustainability. Current approaches focus e. g. on the improvement of the main fan performance by using new materials and designs, management and control of leakages, short-circuits and blockages or the development and implementation of ventilation on demand (VOD) systems (3, 8, 9). By utilizing recent advances in sensing and understanding of the environment and to further enhance the integration of and interaction between production, transport and logistics, maintenance and ventilation systems a holistic adaptive ventilation concept will be proposed. In general, the system proposed is not only reactive based on sensor input as most of the VOD approaches are, but additionally utilizes and integrates predictive modeling, simulation and optimization. The general concept for an adaptive ventilation system will be presented and current developments be highlighted in the following section. The implications of these developments on mining engineering education in the field of mine ventilation and climatization will be discussed and an exemplary teaching concept be demonstrated.

2  Adaptive mine ventilation systems

The main tasks of underground mine ventilation systems are to provide airflow in sufficient quantity and quality, to dilute and remove harmful contaminants to safe concentrations and to provide comfortable working conditions. The basic requirements and definition of safe mining conditions varies from country to country depending on their mining history, the pollutants of greatest concern, the perceived dangers associated with those hazards and the political and social structure of the country (1). However, the basis for an efficient and effective ventilation system is to identify and quantify the hazards associated with underground mining operations, like gas, dust, heat and humidity, radiation, explosion and fire, and to develop suitable and (energy-)efficient control strategies (Figure 1).

Fig. 1. Adaptive mine ventilation system. // Bild 1. Adaptives wettertechnisches System. Source/Quelle: TUC

Factors that contribute to the occurrence of hazards are natural factors, like depth below surface, geology, gas content of strata as well as physical and geochemical properties of the rock and design factors, like mining method, mining layout and type, size and location of equipment. Beside ancillary control methods like dust suppression or the installation of refrigeration systems, the airflow will be mainly controlled by using main fans, booster fans and auxiliary ventilation, airlocks or additional regulators (1). In connection with the further implementation of information and communication as well as sensor technologies in underground mining operations, current approaches for the efficient control of ventilation systems mainly focus on the development of ventilation on demand (VOD) control systems, like ABB SmartVentilation (10) or Howden Simsmart (11). An overview and more detailed information on VOD and examples for its successful implementation will be given in the papers of Dicks/Clausen, pp. 334 to 341, and Engler/Kegenhoff/Papesch, pp. 342 to 355 in this journal.

However, to further enhance the interaction between mining processes and the ventilation system, new holistic concepts in terms of adaptive mine ventilation systems need to be developed. Today’s systems for ventilation on demand utilize input data from sensors to react to the occurred and measured situation. However, more advanced systems can be coupled with dynamic simulations and machine learning to provide predictive models for real-time optimization. A mining or ventilation system itself can be understood as a cyber-physical system (CPS), which is seen as “the next generation of embedded ICT systems that are interconnected and collaborating […], providing citizens and businesses with a wide range of innovative applications and services” (12). The physical component comprises all objects, sensors and actuators in the system. The system itself includes a holistic systems engineering approach considering the context management and relationships between the different objects and entities in the system. All information is available within the cyber system, allowing for process modeling, (real-time) simulation, optimization based on self-learning models and the communication within the network (13). For being able to adapt to changing environments and conditions and to cope with uncertain and emerging situations, the system does not only control the operation, but also need to be adaptive in the sense of being self-aware, context-aware, and goal-aware (14).

The basis for the development of adaptive ventilation systems is beside suitable ICT structures a detailed understanding of the system itself, the status and location of relevant objects and the knowledge about its behavior as well as relationships and more importantly the understanding of the (overall) effects of changes in the system. To meet current requirements a detailed understanding of the overall ventilation system through thorough ventilation network analysis and calculation, supported by appropriate mine ventilation software, as well as of the (secondary) face ventilation by studying fluid behaviors using computational fluid dynamics and its integration in the sense of integrated hierarchical approaches are required.

2.1  Mine ventilation software

Nowadays mine ventilation software is widely used for ventilation network analysis and calculation. Common and commercial software packages, like VNETPC and MINE FIRE by Mine Ventilation Associates (MVA) (15), ICAMPS MineVent by Ohio Automation (16), VUMA by Bluhm Burton Engineering (17) and VENTSIM Visual by Chasm Consulting (18) as well as the MULTIFLUX Software (non-commercial) by the University of Reno (19), are designed to model and simulate compressible ventilation models, airflows, pressures, thermodynamic properties and some of them additionally contaminants, automated natural ventilation pressure, transient flow processes, financials and fire. The calculations are based on the iterative Hardy-Cross-Method, which allows the calculation of airflows in a model by progressively adjusting the airflow values until the estimation error is within acceptable limits. The software solutions are mainly used for planning purposes (20). New developments also allow the integration of live sensor data (see Stewart/Aminossadati/Kizil, pp. 356 to 363 in this journal), which offers new opportunities in the field of dynamic simulation and predictive analytics.

2.2  Computational fluid dynamics (CFD)

For analyzing fluid dynamics related to the face ventilation by considering the properties (i. a. pressure, temperature, velocity, density) of the gases involved, the mathematical models required cannot be solved analytically. Therefore, computational fluid dynamics (CFD) is used for analysis. In CFD the Navier-Stokes-equations, which describe the relationship between velocity, pressure, temperature and density of a fluid, are solved numerically. Additional simplifications are made and constraints put on by boundary conditions. The flow domain itself is divided into a pattern of regular or irregular smaller volume elements (discretization), namely a mesh or grid. The fluid flow equations are then solved iteratively for each of these volumes elements. CFD simulations can incorporate multiple phase flow and dispersion as well as particle transport. For multiple continuous fluids simultaneously existing in a medium the Euler-Euler model is used, which utilizes the concept of phase fractions per volume (21, 22). CFD simulations can be performed for a steady state, e. g. a constant velocity field, or time dependent (transient). A good example for transient simulations is the dispersion and transport of gases.

Advantages of CFD simulations are, that the properties can be measured at each point in the flow domain, a larger variation of parameters for optimization is possible as well as being efficient related to time and costs compared to full-scale models. However, such a model does strongly rely on the quality of the input data as well as a thorough validation of the initial model.

Typical applications for mine ventilation processes are modeling of the behavior of gases in difficult geological conditions (23), modeling of the behavior of blast fumes connected with after blast re-entry times (24), investigations of the effect of recirculation or modeling of the behavior of dynamic gas sources like LHDs (22, 25).

2.3  Integrated hierarchical approach

To combine the advantages of both individual modeling and simulation techniques and tools – mine ventilation software and computational fluid dynamics – a hierarchical approach is proposed, which is integrating the results and outcomes in an iterative manner. Individual results from the (optimum) secondary face ventilation obtaining by the usage of CFD will then be integrated in the overall ventilation network for validation and to review the feasibility of the approach and results (21, 22, 23). The main features of the mine ventilation software within the hierarchical approach are the representation of the ventilation system in terms of compressible ventilation network analysis and calculation, the demonstration, modification and analysis of varying ventilation situations, the analysis on plausibility and feasibility of the results from CFD analysis while considering the effect and processes within the entire ventilation network. The main functionalities and features of the CFD analysis within the hierarchical approach are the (multiphase) flow modeling and simulation for specific (spatially limited) areas while considering relevant fluid properties, like pressure, temperature, heat and acceleration for the development and analysis of (optimum) secondary face ventilation strategies.

3  Implications on higher education in Mine ventilation and climatization

“Technological innovation is the key to future sustainability for the mining sector” (26). This transition of mining operations towards Mining 4.0 (27) also incorporates a new or adapted skillset of future graduating mining engineers. „The mining engineer (of the future) needs to become (…) an integrator of diverse skill sets and best practices, and a coordinator of an increasingly interdisciplinary team” (28). Future mining engineers need to have a deep disciplinary knowledge while at the same time being strong in personal and interpersonal skills, leadership, innovation, entrepreneurship and collaboration. These resulting demands for higher education in mining engineering nowadays cannot entirely and sufficiently be addressed by traditional teaching and learning approaches, so that there is a requirement for rethinking and reshaping today`s mining engineering education. During the last five years the education in the field of mine ventilation and climatization has been restructured at Clausthal University of Technology. The innovative and holistic approach InVent – Innovations in Mine Ventilation Education follows the overall objective to educate confident graduates with excellent professionalism, leadership, critical thinking, communication and additional skills important for a successful transition to the world of work. Beside a strong focus on intended learning outcomes, emphasis is put on:

  • the development and integration of innovative, (inter)active and cooperative teaching and learning concepts and methods;
  • fostering self-regulated and self-driven students learning; and
  • consistent and consequent alignment to learning outcomes and acquisition of competences according to the theory of constructive alignment.

A deliberate alignment was made between the development of innovative learning activities suitable for achieving the specific learning objectives and well-designed assessment and (formative and summative) feedback concepts. The concept comprises beside (inter)active and cooperative teaching and learning activities in class additional elements, suitable for the connection and application of theoretical knowledge to (real-case) practical scenarios. This elements facilitates learning through hands-on learning in a ventilation laboratory (Figure 2), learning at authentic learning venues, like the teaching and research mine Rammelsberg as well as through the integration of project-based learning with real-case scenarios e. g. at Sasso San Gottardo, Switzerland (29, 30, 31).

Fig. 2. Ventilation lab at Clausthal University of Technology. // Bild 2. Wetterlabor an der TU Clausthal. Source/Quelle: TUC

Future developments in education will focus on the implementation of interdisciplinary project-based learning and of virtual and augmented reality elements (32).

4  Summary

An effective and efficient mine ventilation system is one of the key issues for guaranteeing safe working conditions in underground mining operations. Over the last decades this become even more important as mines are generally getting deeper and more complex with larger areal extents and increase in mechanization and regulatory constraints. To meet these requirements VOD concepts aiming at the target-oriented face ventilation by controlling primary as well as secondary ventilation systems has gained growing attention over the last years.

However, to further enhance the integration between mining processes and the ventilation system and in combination with the increased use of ICT and sensor technologies, a new holistic concept in terms of an adaptive mine ventilation system was presented. The main differentiation is, that adaptive ventilation systems being able to adapt to changing environments and conditions by not only being reactive based on sensor input, as most of the VOD approaches are, but also by utilizing and integrating dynamic simulation, predictive analytics and (real-time) optimization. The ventilation system itself can then be understood as a cyber-physical system (CPS), which refers by term to the “tight conjoining of and coordination between computational and physical resources” (33). The basis for the development of adaptive ventilation systems is beside suitable ICT structures a detailed understanding of the system itself, the status and location of relevant objects and the knowledge about its behavior and relationships. In addition a detailed understanding of the (overall) effects of changes in the system, which can be i. a. realized using mine ventilation software, computational fluid dynamics and its integration using a hierarchical approach is necessary.

Furthermore, implications of these new development on mining engineering education were highlighted and an innovative learning and teaching approach “InVent” be demonstrated.

References / Quellenverzeichnis

References / Quellenverzeichnis

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(31) Edelbro, C.; Hulthén, E.; Clausen, E.; O’Donoghue, J.; Herrera, K.; Edström, K.; Bhadani, K.; Jonsson, S.; Beaulieu, A.; Kamp, A.; Försth, M.: European Initiative on CDIO in Raw Material Programmes.

Author: Dr.-Ing. Elisabeth Clausen, Institut für Bergbau, Technische Universität (TU) Clausthal, Clausthal-Zellerfeld