Studies into the application of controlled recirculation ventilation in Canadian underground mines

Increasing energy costs and the need to conserve energy compounded with low mineral prices have prompted some Canadian mines especially potash producers, to examine their operations and identify potential saving methods. Re-using or recirculating a fraction of ventilating air may enable these mines to reduce winter heating costs.;The economic payback periods for systems proposed for Rocanville Division and CCP are 2 and 3 years respectively. Recirculation percentages of 30%, 64.4% and 23% are feasible for CCP, Rocanville Division and the H-W mine. The recirculation percentages for the proposed systems were determined using Air Quality Index criteria.;Dust deposition studies conducted at CCP in return airways indicate that 65% of dust by weight is deposited within a distance of 550 metres from the face. In terms of dust and other contaminant conditions in the return airways, it can be concluded that there is potential for use of recirculation in the face area.;Guidelines for recirculation systems in gassy and dusty mines are developed. The main features for these recirculation system design guidelines are safety, economic gain, and system performance.;Gas and dust concentrations were monitored in the intake and exhaust airways to assess the potential for recirculating exhaust air. The results indicate that the mine pollutant concentrations in potash mines are low and stable. Trial recirculation experiments returning 20-47% exhaust air into the fresh air airway did not cause signficiant increases in mixed intake pollutant levels. Two types of recirculation systems--namely variable and fixed quantity--are developed. Detailed designs of recirculation systems for Central Canada Potash of Noranda Minerals Inc. and Rocanville Division, Potash Corporation of Saskatchewan are discussed and recommendations made for the selection and positioning of on-line monitoring, control and telemetry systems. A controlled recirculation system conceptual design for the H-W mine is given.;The author's contribution to ventilation is in the use of controlled recirculation to reduce winter heating costs and increase underground airflow, also the guidelines developed for recirculation in gassy and dusty mines.;The overall conclusion is that controlled recirculation is a practical method of reducing winter heating cost and/or increasing mine airflows. The financial potential and technology to implement a working system exist.