Inorganic Solidified Foam Generation Device And Experiment Research For Preventing And Controlling Combustion Of Coal

Coal spontaneous combustion is one of the major natural disasters in coal mining. Plugging leaks and controlling wind to prevent coal/oxygen-compounded reactions is the most effective approach for preventing the spontaneous combustion of coal. Inorganic solidified foam is a novel material for preventing coal spontaneous combustion, it is based on fly ash and cement as the base material, adding some admixtures, and through physical and mechanical foaming method, finally formed a compressive capacity of lightweight solid materials. It has characteristics of plugging the wind with good effect, wide coverage, relatively low cost, easy accumulation, enclothe even, so it has broad application prospects in coal mine. Inorganic solidified foam generation device plays a key role in preparing of inorganic solidified foam materials, its main parts are the composite slurry mixing device, aqueous foam generator, foam slurry mixer. This paper carried out the inorganic solidified foam preparation system design optimization and experimental research, research results are as follows:Composite slurry is prepared by a certain proportion of fly ash, cement, admixtures and a percentage of the water in mixing device.The characteristics of composite slurry is high density and difficult to mix uniformity, we designed a high density composite slurry mixing device. Its main principle is to use the screw with a spiral motion, make the composite slurry in the stirred tank produces strong convection and shear mixing effect, enhances the degree of turbulence in the composite slurry, the composite slurry in a relatively short time to achieve rapid mixing. An experimental study is carried out on the mixing uniformity. We proposed to use density standard deviation as a composite slurry evenness index, the influence law of the mixing uniformity on the high density composite slurry mixing device with fill level, mixing time and water cement ratio was obtained. By the analysis, the optimum matching relation of the parameters of the composite slurry mixing device was obtained. When the range of water cement ratio is from 0.4 to 0.6, the range of mixing time is from 6 to 8 min, fill level is 0.55, the mixing uniformity is best.Based on the pore type foaming principle, invented the pore type foam generator, used in the preparation of aqueous foam. Gas-liquid through porous media produce aqueous foam, porosity is gradually increasing from down to up. It mainly consists of the foam chamber, foam tube, compressed air inlet pipe, foaming agent diluent inlet pipe, aqueous foam outlet pipe and the discharge pipe. The foam generator has simple structure, low cost, easy processing and production. The aqueous foam experimental system was established. We determined the evaluation indexes and test methods of the prepared aqueous foam. Operating parameters is studied in the different compressed air flow and foaming agent diluent flow affect the performance of the aqueous foam, obtained the relationship between foaming agent diluent flow and aqueous foam evaluation index curve under different compressed air flow conditions. Provide the basis for the preparation of aqueous foam.We invented a hollow spiral mixer for mixing aqueous foam and composite slurry. Design principle is aqueous foam by means of the various aqueous foam hollow spiral pipe exports with the composite slurry in the mixing chamber mixed by level, and can effectively reduce the bubble broken rate of and increase aqueous foam and composite slurry mixing uniformity. Numerical simulation method is used to optimize the structure of the mixer. We selected the spiral blade pitch p, the hollow spiral pipe diameter D, aqueous foam outlet diameter d as simulation factor, and the three factors three levels orthogonal experiment were done about the structure of mixer. The optimum parameters of the novel mixer are the hollow spiral pipe diameter of 30 mm, the spiral blade pitch of 100 mm, aqueous foam outlet diameter of 14 mm. For the optimal structure of the mixer, we analysed the flow field, pressure drop, turbulent kinetic energy, mixing effect of mixer.The inorganic solidified foam experimental system was established. In order to get the best preparation conditions, an orthogonal test involving rotational speed of mixer, composite slurry flow rate, aqueous foam flow rate, and water/cement ratio was conducted to select the most effective combinational measurement, we used homogeneity and the broken rate of aqueous foam as inorganic solidified foam performance evaluation index. In this experiment, the digital image processing and analysis technique were used to quantitative characterization of inorganic solidified foam bubble holes uniformity, inorganic solidified foam preparation experiment was carried out. The optimum parameters of preparation of inorganic solidified foam combination scheme is rotational speed of mixer of 150 r/min, composite slurry flow rate of 2 m3/h, aqueous foam flow rate of 14 m3/h, water/cement ratio of 0.5.We studied the fire extinguishing performance of inorganic solidified foam. Inorganic solidified foam adhesive curing performance test showed that inorganic solidified foam has good bonding ability of loose coal. Plugging wind performance simulation tests showed that the effect of inorganic solidified foam plugging wind is remarkable.The inhibitor performance experiments showed that inorganic solidified foam with good inhibitory effect of coal spontaneous combustion index gases. Inorganic solidified foam extinguish the coal fire experiments showed that Inorganic solidified foam can cover in the coal pile surface, along the coal fracture seepage gradually into the pile, the structure shape unchanged, with excellent fire performance.