Study On Preparation Of Fly Ash Thickened Colloid And Fire-extinguishing Properties

The spontaneous combustion of coal in the goaf has caused huge economic losses and casualties to the safe mining of the coal mine.The currently used grouting fire extinguishing technology has problems such as easy separation of solid and liquid,serious water loss,and poor coverage and accumulation.It has limited effect on coal spontaneous combustion control in goaf,thickened colloid technology can solve the above problems,and prevent coal spontaneous combustion has a good effect.The stable suspension of solid particles in the thickened colloid is the key to ensure its fire extinguishing effect.It can not only prevent the settlement of the pipeline during transportation,but also enhance the effect of covering and cooling the fire extinguishing materials.Combined with the actual situation on site and the environmental protection of materials,this paper proposes a fly ash thickened colloid technology that can stabilize suspended fly ash,has good moisture retention,and is easy to prepare and transport.The research results are as follows:The physical and chemical parameters of thickened colloidal materials were studied,the ratio of thickening agent was determined,and the influencing factors of suspension stability were studied,and the suspension mechanism of fly ash thickened colloid was clarified.The ratio experiment shows that the optimal ratio of polymer X and H in the thickener is 2:3,and the optimal concentration is 3‰;the effect of fly ash amount,PH value and temperature on the suspension stability of thickened colloid is studied as a result,it was found that the fly ash thickened colloid can stabilize the fly ash particles with a mass fraction of less than 100%when the PH value is 5-9,and has good heat resistance.The stable suspension of fly ash particles is not only supported by the spatial network structure formed by the synergistic effect of polymers,but also by the combined effect of Van der Waals gravitation,electric double layer repulsion and space repulsion,so that the thickened colloid exhibits an excellent stable suspension effect.The rheological properties of the thickened colloid of fly ash were studied,the rheological constitutive equation of the thickened colloid was established,the influence of temperature on the viscosity of the thickened colloid was analyzed,and the flow velocity distribution in the long-distance pipeline transportation of the thickened colloid was obtained.Pressure drop and other parameters.Steady-state rheological experiments show that the apparent viscosity of thickened colloids with different amounts of fly ash decreases with increasing shear rate,and the shear stress increases with increasing shear rate,showing obvious shear thinning characteristics;through experiments and fittings,it is found that the fly ash thickened colloid belongs to the yield pseudoplastic fluid,and the rheological constitutive equation of the fly ash thickened colloid is obtained.The effect of temperature on the rheological properties of the thickened colloid of fly ash was studied.It was found that the apparent viscosity of the thickened colloid first increased and decreased with the increase of the experimental temperature,and finally increased;the flow state of the thickened colloid in the pipeline was In laminar flow,the velocity distribution equation of the thickened colloid flowing in the DN100pipeline at a speed of 20m³/h is obtained.The velocity distribution is uniform,and the pressure drop in the pipeline is 1.87×10⁵Pa.The fire-extinguishing properties of thickened fly ash colloids were studied.The static experiment found that the surface of the thickened fly ash colloid with compound colloid concentration greater than 3‰remained wet after 15 days,and it had good water retention and wettability.After the coal lumps were covered with the fly ash thickened colloid,the negative pressure of the vacuum chamber of the plugging test device was measured to be-15.4Pa,and the effect of plugging air was obvious.Through the inhibition experiment,it was found that after the coal sample of Lijiata Mine 311 was treated with the fly ash thickened colloid,the amount of CO and C₂H₄ produced during the oxidation process decreased,and the initial temperature of C₂H₄ delayed relative to the raw coal,and crossed the point temperature is increased by 14°C,and the thickened colloid exhibits good resistance characteristics.Fire extinguishing experiments show that the effect of the fly ash thickened colloid on the concealed fire source is very obvious.After using the thickened colloid to cover the high temperature point,the temperature of the fire source drops to below 50℃at 1400s and to below 25℃at 2100s.Aiming at the characteristics of coal spontaneous combustion tendency in the goaf of Lijiata Coal Mine,the 311 coal mining face was taken as the research object,and a beam tube monitoring system was established on the mining face.Sampling and analysis of the changes,and divided the"three zones"of coal spontaneous combustion in the goaf of 311 face,combined with the existing prevention measures of the coal mine,proposed the use of fly ash thickened colloid to wrap the broken coal body and block the air Application plan for preventing coal spontaneous combustion.This thesis has 75 pictures,7 tables,and 99 references.