Artificial ground freezing of underground mines in cold regions using thermosyphons with air insulation

Abstract

Current practice of underground artificial ground freezing (AGF) typically involves huge refrigeration systems of large economic and environmental costs. In this study, a novel AGF technique is proposed deploying available cold wind in cold regions. This is achieved by a static heat transfer device called thermosyphon equipped with an air insulation layer. A refrigeration unit can be optionally integrated to meet additional cooling requirements. The introduction of air insulation isolates the thermosyphon from ground zones where freezing is not needed, resulting in: (1) steering the cooling resources (cold wind or refrigeration) towards zones of interest; and (2) minimizing refrigeration load. This design is demonstrated using well-validated mathematical models from our previous work based on two-phase enthalpy method of the ground coupled with a thermal resistance network for the thermosyphon. Two Canadian mines are considered: the Cigar Lake Mine and the Giant Mine. The results show that our proposed design can speed the freezing time by 30% at the Giant Mine and by two months at the Cigar Lake Mine. Further, a cooling load of 2.4 GWh can be saved at the Cigar Lake Mine. Overall, this study provides mining practitioners with sustainable solutions of underground AGF.