| Spontaneous combustion of coal is one of the main disasters faced in the process of coal mining,once it occurs,it will not only burn and freeze a large amount of coal resources,but also cause serious accidents such as gas explosions,which is seriously harmful.Aiming at the shortcomings of conventional plugging wind fire extinguishing materials in terms of plugging performance,mechanical properties and safety and environmental protection,this thesis takes waste incineration bottom ash and slag as precursors,introduces organic polymer compounds according to its consolidation shortcomings for targeted modification,develops a geopolymer plugging wind fire extinguishing material,and analyzes the performance and formation mechanism of its plugging wind,the main research work and conclusions are as follows:According to the composition characteristics of waste incineration bottom ash,the effects of compressive strength and initial setting time of the ratio of waste incineration bottom ash and granulated blast furnace slag were studied.On this basis,the optimal ratio of waste incineration bottom ash-slag-based cementitious material was selected through orthogonal tests: 70 wt% granulated blast furnace slag,18 wt% alkali initiator content,1.6 alkali initiator modulus and 0.4 water-cement ratio.The physical and chemical properties of waste incineration bottom ash-slag-based cementitious materials and conventional mining cementitious materials were compared and analyzed under the optimal ratio conditions,and the results showed that the waste incineration bottom ash-slag-based plugging materials could be initially set in 10 minutes,and the compressive strength was 4.86 times that of conventional mining cementitious materials in 7 days,and the impermeability performance was increased by more than70.16% compared with mining cement-based materials.Aiming at the problems of shrinkage and cracking at high temperature after consolidation of waste incineration bottom ash-slag-based cementitious materials,based on their structural characteristics,sodium alginate was introduced to modify them,and the effects of sodium alginate addition on the compressive strength and initial setting time of modified plugging and fireproof materials were discussed,and the optimal sodium alginate addition amount was 1 wt‰.The changes of physical and chemical properties of the plugging materials before and after sodium alginate modification were compared,and the results showed that the waste incineration bottom ash-slag-based material had micro-expansion characteristics after the addition of sodium alginate,and its expansion rate reached up to 12‰.Compared with before modification,the compressive strength of the modified material at 7 days increased by18.37% and the fluidity increased by 14.77%,and the modified material showed better anti-cracking performance under the action of 400°C high temperature.At the same time,the test analyzed the physical parameters of the material under different water-solid ratio conditions,and the results showed that the modified sodium alginate material could achieve 35 min initial coagulation under the water-solid ratio of 0.4 to0.6,while maintaining high compressive strength and expansion rate,and the cost index was not significantly higher than that of P· O42.5 cement is smaller than conventional mining cement-based plugging materials.The microstructure,morphology,phase,pore size distribution and pore structure of waste incineration-slag-based fire-proof materials before and after sodium alginate modification were tested by Fourier transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS),X-ray diffractometer(XRD),synchronous thermal analyzer(TG-DSC),mercury pressure meter(MIP)and high-resolution 3D X-ray microscopy imaging system.The modification mechanism of sodium alginate modified by waste incineration bottom ash-slag-based sodium alginate modification of fire-proof material was analyzed.The results show that the structure of silicon oxygen and aluminum oxygen is dissolved under the action of alkali excitation of waste incineration bottom ash and slag,and polycondensation and rearrangement form the waste incineration bottom ash-slag base polymer.At the same time,free calcium ions and sodium alginate formed a gel in the formed geopolymer colloidal structure and interspersed in the geopolymer colloidal structure,thereby forming a geopolymer-calcium alginate gel structure.The air plugging test was carried out by self-made leakage plugging device,and the plugging effect of the waste incineration bottom ash-slag-based sodium alginate modified fire-blocking and extinguishing material was tested,and compared with the conventional mining cement-based plugging material,the results showed that the geopolymer-calcium alginate gel material modified by sodium alginate had better plugging and fire prevention performance.Under the same experimental conditions,the plugging effect of waste incineration bottom ash-slag-based fire-proof materials modified by sodium alginate was significantly improved compared with that of modified pre-modified materials and conventional mining cement-based materials.The above studies show that the developed waste incineration bottom ash-slag-based sodium alginate modified plugging and fire extinguishing material has excellent compressive resistance and good anti-cracking performance,which can reduce the further deformation and cracking affected by mine pressure and temperature in the filling and plugging area to produce new air leakage channels.Good impermeability and expansion performance is conducive to improving the effect of plugging leakage and fire extinguishing,and the controllable initial setting time increases the applicability of the material in the mine.It provides a new technical way for solid waste to be plugged and prevented from spontaneous combustion of coal in the leakage area such as the coal column in the coal mine underground isolation column. |
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