Page 101 - Advances In Productive, Safe, and Responsible Coal Mining

Mine ventilation networks optimized for safety and productivity 85

6.2 Mine ventilation network design and planning

Whether for coal or metal and nonmetal mines, mine ventilation networks must be
carefully planned and laid out in conjunction with mine design and production plan-
ning. Mine ventilation demands change significantly over the life of the mine. A mine
ventilation system can be expanded over the life of the mine by adding air supply and
exhaust capacity by means of additional shafts, drifts, and fans. Conversely, mined-
out areas should be sealed as soon as they no longer require ventilation. Between
major expansions or consolidations, the ventilation system must be designed to supply
sufficient airflow capacities to all areas of the mine. The ventilation engineer must
work in close cooperation with both long-term and short-term planners to understand
exact ventilation demands at any time during the mining process. This includes know-
ing the individual ventilation demands of all pieces of mining equipment and sizing
the mine openings to match these demands without generating undue airflow resis-
tance. If Eqs. (6.2) or (6.3) are applied to circular cross-section airways, one can easily
see that the resistance is proportional to the 5th power of the inverse diameter. Increas-
ing the airway size by 15% reduces resistance by 50%, and increasing its size by 25%
will cut resistance by 67%.
A mine planning engineer will lay out drift dimensions primarily based on the size
of the equipment that will be used. Increasing airway size beyond this minimum
often conflicts with ground control demands. If airways cannot be increased in cross
section, ventilation engineers should consider adding one or more parallel airways.
Two identical airways in parallel will cut resistance by 75%, while three airways will
cut it by 87%.
When designing air shafts, the diameter is also an important consideration. The
minimum diameter is sometimes determined by hoisting or equipment size require-
ments. The ventilation engineer should weigh carefully whether it is worth increasing
the diameter in order to reduce resistance, thereby saving on ventilation power costs.
This is usually a simple economic consideration, and many ventilation planning pro-
grams offer ways to calculate such power savings.
For planning purposes, mine airway resistances and fan power requirements can be
calculated from initial assumptions of airway geometry and resistance. As the mine is
developed, air quantity and pressure surveys should be conducted every 6 months to
establish an accurate mine ventilation model using a computer network calculation
program. A valid computer model can then be used to project ventilation requirements
for future stages of mine development and to assist the mine planning engineer by
establishing required airway geometries, new air shafts requirements, and future
fan specifications.

6.3 Mine air quality and dust monitoring

US mine regulations are published in the Code of Federal Regulations (CFR) [2]. For
underground coal mines, 30 CFR §75.321 requires that mine air contain a minimum of
19.5% oxygen (O 2 ) and less than 0.5% carbon dioxide (CO 2 ). Similar standards exist