Ventilation system optimisation to reduce particulate matter (PM) and gas concentrations in Kazakhstan underground mines: simulation and experimental validations

Collaborative Research Grants Program 2020-2022

BACKGROUND
Kazakhstan's mineral resources are characterized by a large variety of mining deposits. The country is among the world's leading countries in its reserves of chromite, wolfram, lead, zinc, manganese, silver and uranium. It also has significant reserves of bauxite, copper, gold, iron ore, coal, natural gas and petroleum. Kazakhstan is one of the 10 leading countries in the world for a significant number of mineral resources (Richard, 2005). There are approximately 220 registered mining enterprises in the country. The larger domestic companies have been established by local entrepreneurs. Large foreign mining companies, some with local subsidiary companies, active in Kazakhstan include Glencore, Rio Tinto, Iluka Resources, Central Asia Metals Plc, Areva Sa, ArcelorMittal, Yildirim Group, Russian Copper Company and Rusal. There is a national operator of mineral assets in Tau-Ken Samruk, and geological exploration is carried out by the national exploration company,Kazgeology. Both Kazgeology and Tau_Ken Samruk work with foreign companies to explore, develop, and operate assets. A new mining code has been developed based on the Western Australian model, which aims to produce a simplified procedure for granting rights for investors and subsoil exploration. This legislation is effective from last year 2018 and will particularly benefit smaller companies (https://im-mining.com/2017/02/24/kazakhstan-mining-scene/).
Kazakhstan has a large number of operating mines producing blasting fumes, diesel toxic gases and particular matter (PM). Mine ventilation system must provide fresh air for miners to ensure a safe working environment. Old diesel engine equipment is still in use at Kazakhstan mines and it’s also the primary source of miners’ exposure to submicrometer PM including Ultrafine particles (particles with aerodynamics diameter less than 100 nm), gases, and noise. Emission standards are continuously pushing the improvement of new technologies and approaches toward reducing the emissions. Bugarski (2012) stated that one of the approaches that can be implemented to reduce exposure of miners to diesel emissions is to develop strategies to control diesel contaminants. Diluting contaminants by supplying fresh air is one the most prominent strategies. Also underground mine ventilation system optimisation should be elaborated in compliant with Health and Safety requirements. Underground mine ventilation system design in Kazakhstan is based on standards and regulations approved in early nineties of last century, which were adopted yet from Soviet era normative. Those normative utilise calculation methodologies based on requirements for outmoded equipment. Main problem is that old outdated local regulations use overestimated airflow quantity to dilute diesel emissions and dust, and a complicated ventilation network. However, mine safety has to consider the risks associated with the deficit of fresh air for mine gas dilution, and removal from the mine workings. According to Kazakhstan Mining Regulations the quantity of air required for the respiration of personnel is about 0.1 m3/s of air for each person. The mine dust limit is 2 mg/m3. The Threshold Limit Value (TLV) (Stellman) for NOx is 0.0001%, for СО is 0.0016%, for NO2 is 0.0025%, for SO2 is 0.00035%, and for H2S is 0.00066% (Kazakhstan mining regulations, 2004). However, the underground mine ventilation system design in Kazakhstan is based on standards and regulations approved in early nineties of last century, which were adopted from Soviet era normative. The main problem is that old local regulations use the outdated calculation methodologies to diluting diesel contaminants and dust, and a complicated ventilation network design.
The current research proposal is aimed address issues associated with mine ventilation system optimisation to reduce particulate matter and gas concentrations in Kazakhstan underground mines. The optimisation approach will propose a modified mine ventilation design which will be validated by experimental data. Furthermore, the exposure of the mine workers to PM10, PM2.5, PM1, UFPs, particle surface area concentration, black carbon, trace elements and gases including NOx, NO2 SO2, CO and non-methane Volatile Organic Carbons (VOCs) will be assessed.
SCIENTIFIC NOVELTY AND SIGNIFICANCE
This study will provide a comprehensive evaluation of air quality in Kazakhstan’s underground mines including PM mass, number, and surface area concentrations, PM composition, and gas concentration. Additionally, it offers the optimum ventilation design to reduce the exposure of the mine workers to PM and gases produced during mining activities. Measurements will be conducted in Akmola underground mines, Ridder-Sokolniy underground mine and Maleyevskiy underground mine through the establishment of air monitoring stations at different parts of the mines. The measurements will include the concentrations of criteria pollutants and more specifically: PM, NOx, NO2, SO2, CO, and non-methane VOCs. The distribution of pollutants over the mines will also be investigated. Another key direction of this project will be to investigate the PM morphology. This project is highly relevant to Kazakhstan 2050 Strategy where the government of Kazakhstan appreciates the importance of the mining industry to the country and where President Nazarbayev unveiled the 100 steps national plan the key reforms for the mining industry, notably steps 74 and 75:
74. Transparency and predictability of subsoil use shall be maintained via introduction of the CRIRSCO reporting standards
75. Simplified contracting procedures using the best international experience shall be introduced in the mining industry.
In mid-2018 the Kazakhstan Code for the Public Reporting of Exploration Results, Mineral Resources and Mineral Reserves was approved by the CRIRSCO committee and so joins the family of international reporting codes under the CRIRSCO umbrella. International reporting requires to follow the higher standards for air quality and produce environmental monitoring to protect public health. The outcomes of this study will provide critical information to policy makers to help plan for the future mining environment in Kazakhstan and will modify mining ventilation regulation standards. This project is novel both from applied and fundamental research points of view. The novel aspects of this project are discussed below:
WP1. (Measurements)
Real-time monitoring of PM mass size distribution, Organic Carbon (OC) and Elemental Carbon (EC) of PM, Black carbon concentration, trace element concentration, PM morphology, ultrafine particle (UFP) number size distributions, particle surface area concentration and criteria gas concentrations in Akmola mines, Ridder-Sokolniy and Maleyevskiy mines.
Currently at Kazakhstan mines have not been produced any continuous measurements for PM, particularly using real-time size distribution monitors for particle mass and ultrafine particles number concentrations. Such data will be critical to assess the exposure of the workers in the mines. Also, no data exist in the literature related to air quality in mines addressing the PM morphology and PM compositions including black carbon and trace element concentrations in Central Asia including Kazakhstan.
WP2. (Modeling)
Modeling the distribution of criteria gases and PM (DPM) for optimization of ventilation systems used in underground mines operating in Kazakhstan, and the model validation using measurements provided in WP1. No research exists in the literature on optimisation of mine ventilation system based on modern requirements to air quality in Kazakhstan and over Central Asia.

IMPACT OF THE RESULTS ON THE DEVELOPMENT OF SCIENCE AND TECHNOLOGY
The first and key step for the developing and implementing pollution prevention policies by decision makers is to have reliable air quality monitoring data that will be provided by this study. The outcome of this study will provide the information necessary for Mine Health and Safety scientists to estimate health risks and safety action costs due to exposure to ambient air pollutants. Social, energy and environmental scientists and economists will have a better understanding of the impact of socio-economical changes related with Kazakhstan mining industry on mines’ air quality. Exposure to diesel emissions has been also linked to adverse health effects. Therefore, it is of great interest for mining companies to implement adequate diesel emission control strategies. Optimizing diesel emission control strategies would not only improve working conditions, but also offers benefits in terms of cost. This is due to decrease in airflow requirements for modern engines to dilute diesel emissions. Changes in Kazakhstan Mining Code might involve implementation of modern Tier III and Tier IV diesel engines standards to Kazakhstan underground mines and change of diesel mining equipment to electric power equipment. The results of this study will trigger future research on air quality and ventilation system optimizations in underground mines.

EXPECTED SOCIAL AND ECONOMIC EFFECTS
Air pollution control is an expensive process that requires involvement of mining sector to reduce the pollution’s social and economic effects. Kazakhstan 2050 Strategy and Kazakhstan New Mining Code assign environmental quality as one of the goals necessary to improve the current socio-economic issues in Kazakhstan.
Through this long-term strategy, Kazakhstan aims to be among top 30 developed countries with the goal of economic security as well as the well-being of the citizens. To meet this goal, sustained air quality monitoring will be essential. Assessment of the air quality will raise the public awareness and help policy makers and related governmental officials to design comprehensive programs throughout the mining sectors to have the air quality attain recommended USA/European/Australasian standards. This study is among the first steps toward that goal.