Experimental Study on Rheological Properties of Coal Gangue Slurry Based on Response Surface Methodology

Abstract

To handle the gangue well and control the settlement of the surface, as well as to reduce the risk of water bleeding, settlement and even blockage and pipe breaking of the gangue slurry in the process of conveying, the rheological characteristics of the slurry should be studied. The rheological properties of slurry with different concentrations prepared from gangue samples of the Ningtiaota coal mine were tested, and the correlation between the rheological characteristics of the coal gangue filling slurry and three factors, namely the gangue mass fraction, grain gradation and standing time, were studied by a single factor method and response surface methodology. The results show that the fitting curve of the Herschel–Bulkley model is mostly linear, that is, the shear stress of coal gangue paste increases as a function of the shear rate. Therefore, these two concentrations are too small to form a stable network structure to wrap large particles and can easily cause pipe blockage. The yield shear stress and plastic viscosity show an exponential increase with the increasing mass fraction. The shear stress and apparent viscosity of the pastes with mass fractions of 60% and 65%, respectively, increase significantly after 20, 40 and 60 min of standing. According to the comprehensive test results and the response surface, the optimization method is as follows: mass fraction of 72%; aggregate grading for 4.75~1.18 mm particle size is 30%, for 1.18~0.425 mm particle size is 40%, for 0.425~0.075 mm particle size is 10%, for less than 0.075 mm particle size is 20%; with different standing times, the yield shear stress of slurry ranges from 103.02 to 131.645 Pa; and the plastic viscosity ranges from 0.54 to 0.64 Pa.s. With the increase of the standing time, the slurry settlement is relatively small, and is a more ideal gangue slurry proportion.

Simulation test study on filling flow law of gangue slurry in goaf

“…Sun et al 22 studied the effects of gangue mass fraction, particle gradation and standing time on the rheological properties of gangue filling slurry, and confirmed that the characteristics of coal gangue slurry belong to Bingham fluid. Jin et al 23 , 24 analyzed the particle size distribution of coal gangue-fly ash mixture under different mixing ratios, and studied the effects of gradation and concentration on the rheological parameters of coal gangue-fly ash slurry.…”

“…The main components of the gangue slurry used in the test are gangue powder, fly ash, and water. The injection time is short, and the viscosity timeliness will not occur in a certain period of time 22 , 42 . The main viscosity change of gangue slurry is only related to the injected medium and the seepage channel.…”

Numerical Study of Gangue Slurry Deposition Behavior in Pipelines Considering Viscosity Change

“…Before Figure 3 shows that the plastic viscosity of the gangue slurry becomes more significant with the increase in mass concentration. With the increase in the number of particles, the shear rate increases, and the gangue particles collide, resulting in a shear thickening phenomenon, and the viscosity of the slurry gradually increases [2,9,18]. At the same time, there is a concentration interval in which the viscosity growth rate is significant.…”

“…The fluidity of gangue slurry directly affects its transportation performance [18,19]. If the prepared gangue slurry's viscosity is too high, resistance in pipeline transportation is apparent.…”

“…However, the research at this stage does not consider the influence of the viscosity change of the slurry on the rule of motion of the coal gangue slurry. The more common perception is that the viscosity of gangue slurry is not constant [2,12,18]. The viscosity change will inevitably affect the slurry flow and particle deposition laws.…”