Study On The Treatment Methods Of Goaf Cavity Fire At Open Pit Mine

Goaf cavity fire is the biggest threat to mining of open pit mine.it not only burns and freezes a lot of coal resources,but also is easy to cause the collapse of large-scale production equipment and affect the economic benefits.Meanwhile,it causes great damage to the ecological environment.Therefore,it is necessary to study and control the goaf cavity fire.Goaf cavity fire has three-dimensional characteristics and the internal space is huge.It is difficult to carry out a full range of fire extinguishing with the traditional technology such as water injection and grouting etc.The foam has strong applicability to open-pit mine fire cavity which has good accumulation,but the foaming performance of the existing open pit foam preparation equipment is weak.It is difficult to meet the needs of the field application.In this paper,using the method of theoretical analysis,experimental research and field combination,conducts the study of the goaf cavity fire control methods based on filling the large flow foam.The main achievements and conclusions are as follows:A new type of large flow foam preparation device was designed.The causes and influencing factors of net foaming were analyzed from the mechanism of bubble formation and mechanical properties of the foam.The device is mainly composed of spiral nozzle group,composite concave and high-pressure centrifugal fan.Spiral nozzle group can be very good foam liquid atomization and spray evenly into the composite concave network online,composite to foam adsorption and film formation,fan for foam preparation and power source.The foaming performance of the large flow foam preparation device was tested.Using the autonomous constructed foaming performance experiment system,using control variables,grouping experiments,to study the influence of gas flow and liquid flow on the performance of the device.Experimental results showed that foaming capacity increases first and then decreases with the increasing of the air flow from 1000 m3/h to 3000m3/h,trends and global production device foam multiple quantity change tendency is similar,the biggest foaming capacity appeared in 2100 ~ 2300m3/h of air flow,for a specific size foam preparation device,the best effect when the production speed is certain.In the range of 6 ~ 16m3/h,the foaming capacity increased gradually with the increase of the amount of liquid flow,while the foaming ratio increased first and then decreased with the increase of liquid flow.The liquid flow quantity is small,the foam is not continuous fragments,the device volume utilization rate is low,the liquid flow quantity is too large,a large surplus of foam bubbles within the foam liquid and no foam,foaming ratio decreased,considering the optimum liquid quantity of the device is 10 ~ 12m3 /h.The accumulation characteristics of foam were studied.The visualization of independent construction goaf cavity model,the bubble in the pile law of goaf cavity in the study showed that the foam has good accumulation ability in limited space,the accumulation process can be divided into three stages: the first stage,the foam along the cavity model bottom plate diffusion flow,the bubble in the late stage a uniform flow state;the second stage,the accumulation of foam overall height is increased,the left wall foam height increasing fast,the first arrival of the third stage model of the roof;foam from both sides,gradually the entire space filled the void model.The industrial practice of extinguishing open pit mine goaf cavity fire was carried out.In view of the coal Pingshuo Anjialing open pit mine goaf cavity fire causes and characteristics,determine the fire control plan of “early fire extinguishing cooling,late goaf full filling”,put forward to high flow perfusion foam as the main body,aided by grouting and injection of high water material comprehensive fire extinguishing method,using the first treatment the fire inside the low fire grouting measures,then the fire area to completely extinguish the fire in the foam,after the fire,the ultra high water material will be completely cavity filling,to prevent the fire again,achieved good results.