SELECTION OF VENTILATION EQUIPMENT AND FANS FOR UNDERGROUND USE AT THE TEPAKUTAN POTASSIUM DEPOSIT

ABSTRACT

The article analyses the structure and operation of the central ventilation system used in the Tepakutan underground potash mine. The central system, equipped with VOM-20 fans, operates in three modes: normal, reverse, and zero mode, which together ensure stable air distribution and safe working conditions during emergencies. The mine also utilizes VME-6 local ventilation devices and 500 mm diameter flexible ducts to supply air to underground working panels. Air quality is monitored at nine control stations, with air distribution regulated using stationary and temporary barriers. A comparative analysis of VOM-20 and VOD-21M fan models reveals the superior technical performance of the VOD-21M, justifying its implementation in the mine’s ventilation scheme. The study includes airflow temperature and pressure behaviour across shaft sections, highlighting the system’s adaptability to varying thermal depressions and geological conditions.

АННОТАЦИЯ

В статье проанализирована структура и принципы работы центральной вентиляционной системы, используемой на подземном калийном руднике Тюбегатан. Центральная установка с вентиляторами VOM-20 функционирует в трёх режимах: нормальном, реверсивном и нулевом, что обеспечивает стабильное распределение воздуха и безопасность при аварийных ситуациях. Для локальной вентиляции используются установки VME-6 с гибкими воздуховодами диаметром 500 мм. Контроль за качеством воздуха осуществляется с помощью девяти измерительных станций, а регулирование воздушных потоков обеспечивается стационарными и временными перегородками. Сравнительный анализ вентиляторов VOM-20 и VOD-21M показал техническое преимущество последнего, что обосновывает целесообразность его применения в вентиляционной системе шахты. Также рассматриваются температурные и депрессионные изменения воздушного потока по сечениям ствола, подчёркивая адаптивность системы к геотермальным условиям шахты.

Keywords: Tyubegatan mining deposit, sylvinite ore, potassium salts, central ventilation, VOM-20 fan, VOD-21M fan, air distribution, airflow monitoring, underground mining, mine safety, thermal depression.

Ключевые слова: Тюбегатанское месторождение, сильвинитовая руда, калийные соли, центральная вентиляция, вентилятор VOM-20, вентилятор VOD-21M, распределение воздуха, контроль воздушного потока, подземные работы, безопасность шахты, тепловая депрессия.

Introduction. The central ventilation system for underground workings at the Tepakutan mine is located in the main ventilation drift of the shaft-side structure. Its operating principle is based on extracting air from the mine field through inclined shafts No. 2 and 3. During the excavation of underground panels, local ventilation units of the VEM-6 model are used. Two VOM-20 ventilation units are installed and operated on a rotational 15-day working and standby cycle according to safety regulations. Due to the suction-type ventilation system, airflow control is categorized into three modes[1-11]:

Normal (working condition); Reverse; Zero (with the fan off).

Materials and methods. In normal mode, 3500 m³/s of air is drawn into the mine. In reverse mode, 60% of this airflow is directed into the mine field. In zero mode, air movement depends solely on internal mine depressions.

Airflow velocity was measured using Testo 405i digital anemometers (accuracy ±0.1 m/s), and air temperature was monitored using K-type thermocouples (accuracy ±0.5°C). Measurements were conducted every 3 hours for 14 days. Overall measurement error was limited to 2.5% for airflow and 1.8% for temperature.

Nine measuring stations were established, of which five monitor incoming and four monitor outgoing air parameters. The system ensures the provision of 6 m³/min of air per worker underground.

Prefabricated ventilation pipes (diameter: 500 mm) maintain a 20-meter distance from the excavation face. Fixed, movable, and temporary barriers organize proper air distribution. As mining progresses on two levels, vertical boreholes connect layers for airflow. Calculation of the Operation of the VOM-20 Fan in Summer. Rock temperatures at different depths were considered as: +14.5°C (900 m), +19.2°C (770 m), and +23.1°C (550 m). Air temperature changes were computed using the adiabatic lapse rate formula: ΔT=G*h

Depression (ΔP) was evaluated using Bernoulli’s equation, accounting for drift friction and constant air properties. Thermal depressions in contours 1 to 5 peaked at 4.959 Pa and decreased to 0.0232 Pa toward the shaft end.

Depressions between ventilation and panel drifts were positive (contours 34–73), aiding airflow, but turned negative in contours 74–75, hindering movement..

Results and discussion. At the shaft collar (900 m), atmospheric pressure is 710 mmHg. At the deepest point (190 m), it reaches 772 mmHg. Air temperature decreases notably in inclined shafts (branches 1–5): from +38°C to +21°C, with rock temperature at +19.2°C. In working zones (networks 96, 97, 98), air temperature remains below +22.1°C. As summer temperatures do not exceed +26°C, no additional cooling devices are required.     

Table 1.

Comparative Performance of VOM-20 and VOD-21M

To improve mine air quality and temperature control further, hybrid systems incorporating localized cooling devices can be considered. Portable evaporative or compressor-based units near working faces may reduce thermal stress without increasing main system loads.

Figure 1 below shows the VME-6 local ventilation fan and VOM-20 central ventilation fan currently used in the mine.

Figure 1. Local VME-6 and VOM-20 central ventilation fans

Below shows the external appearance and technical characteristics of the proposed VOD-21M fan, shown in Fig 2. In addition to McPherson [1, 8, 11], Wallace et al. (2020) investigated hybrid systems in Canadian potash mines, and Zhang & Yu (2019) explored AI-based airflow optimization in Chinese deep mines. These studies highlight global trends toward smart and energy-efficient ventilation strategies.

Replacing VOM-20 with VOD-21M units would save approximately 8.9% in energy annually. At $0.12/kWh and 6000 operational hours per year, each unit would save ~$3,500 annually. Given a $18,000 unit cost, the payback period is approximately 2.6 years, excluding maintenance savings and downtime reduction.

Figure 2. VOD-21M Ventilator

Conclusion. The comparison results demonstrate that considering the superior technical capabilities of the VOD-21M ventilation fan compared to the VOM-20 ventilation fan, it is recommended to implement the VOD-21M ventilation fan at the Tepakutan mine. When operating a panel positioned along the uplift of a mineral deposit, after completing the upper section of the chamber, it connects to the adjacent chamber through interconnecting passages between the chambers. In this configuration, a closed space of no more than 10 meters is maintained in the chamber. The turning radius of the passages between chambers is 20 meters.

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