Design and application of device to add powdered gelling agent to pipeline system for fire prevention in coal mines

•We design a device that stably adds the gelling agent to pipeline system.•We determine its optimal working condition based on field conditions.•Our device can significantly aid in fire prevention and control in mines.

In China, 47.3% of state-owned coal mines are endangered by coal seam spontaneous combustion that threat to the safety of mining. A new technique using foam-gel was developed to control coal spontaneous combustion. In this study, an adding device was designed to facilitate the addition of a powdered gelling agent to pipeline system to form foam-gel. The experimental system was constructed and experiments were carried out to test the performance of the adding device in laboratory. The experimental results showed that the optimum parameters of the inlet pressure and air flow were in the range of 1.6–1.8 MPa and 40–44 m3/h respectively, and the negative pressure ranged from −0.16 MPa to −0.22 MPa accordingly. The average adding rate of powdered gelling agent was 2.06 kg/min and 2.31 kg/min, respectively in lab scale experiment and field application. The adding device was tested at a coal working area and successfully controlled the coal spontaneous combustion occurred in the process of equipment removing. The results of the application promised that the adding device is structurally simple, compact, and easy to operate, and also the foam-gel has a remarkable effect for fire prevention.