Design and test of a novel isolated compressed oxygen self-rescuer for coal mines

To address the oxygen supply issues of traditional coal mine isolated compressed oxygen self-rescuers which provide a fixed oxygen supply rate of 1.2 L/min, causing oxygen shortage during escape (oxygen demand 2.1 L/min) and oxygen waste during seated waiting (oxygen demand 0.5 L/min), as well as problems like easy failure of mechanical pressure indicators, inconvenience in replacing CO₂ absorbents, and unreliable materials for key components, a novel compressed oxygen self-rescuer meeting the GB 24502—2023 Self-rescuer for Coal Mine standard has been designed. By optimizing the flow channel topology of pressure reducer, the oxygen supply rate can be dynamically adjusted between 0.5 L/min and 2.4 L/min to meet the oxygen demands of both escape and seated waiting modes, significantly enhancing the protection time and oxygen supply stability during seated waiting. A low-power and intrinsically safe digital pressure indicator for mining applications has been developed using a diffused silicon pressure sensor, resolving issues of elastic fatigue, nonlinear drift, and high failure rates associated with mechanical indicators. A modular and replaceable canister has been designed to enable the rapid replacement of CO₂ absorbent within 10 seconds. A mathematical model for determining the required amount of CO₂ absorbent was established based on the chemical reaction kinetics of Ca(OH)₂ absorbing CO₂. Additionally, key components such as the shell, oxygen cylinder, and breathing bag have been carefully selected. Experimental results demonstrate that under the rated protection time of 45 minutes, the self-rescuer achieves a seated protection time of over 135 minutes, with an O₂ volume fraction of at least 46.5%, a peak CO₂ volume fraction of 1.46%, a peak inhalation temperature of 41.1 ℃, and a total breathing resistance of no more than 1.2 kPa. In terms of oxygen supply performance, when the working pressure of oxygen cylinder is between 3 MPa and 20 MPa, the self-rescuer provides a constant oxygen supply of 2.3 L/min at a breathing rate of 35 L/min and 0.7 L/min at 10 L/min. Both automatic and manual supplemental oxygen supplies reach 70 L/min, with oxygen supply fluctuations not exceeding 0.1 L/min. The research findings have been applied in multiple self-rescuer manufacturing enterprises and have passed the safety certification inspection based on GB 24502—2023 Self-rescuer for Coal Mine.