Study on time memory effect of coal gas emission in electrostatic field

Abstract

According to the characteristics of time memory effect of initial velocity of gas bearing coal under the action of electric field, the experimental system of gas emission measurement is established to study the memory effect of different metamorphic degree and damage type of coal under electrostatic field. The experimental results show that the electrostatic field can increase the gas emission capacity of coal. With the increase of voltage, the initial gas emission speed increases first and then decreases, and reaches the maximum value under a certain characteristic voltage and the characteristic voltage of structural coal is larger than that of primary structural coal. Under the continuous load of 8 kV, the initial gas emission speed fluctuates up and down with the power on time, and the power is removed. After the field, the initial velocity of gas emission does not fall back to the state without power on, and the value of gas emission velocity is higher than the initial state, which has a certain time memory effect. The initial velocity of gas emission increases between 5% and 9% for anthracite coal after the electric field effect compared with that without electric field, and there is no obvious difference between the change of primary structural coal and structural coal;however, it is poor in the memory effect, the initial velocity of gas emission of coal with primary structure changes in 5%-8%, while that of structural coal changes in 13%-18%. The reason of time memory effect is that on the one hand, the coal surface is still in electrostatic state after the electrostatic field, and the electric traction force on the coal surface is stronger than that without power on, which causes the increase of gas adsorption and then acts on the gas emission; on the other hand, under the electric field, the coal will generate induced polarization charge to form the excitation electric field, which will continue to affect the gas emission after the loss of electric field to promote the desorption of coal gas.

Keywords

• coal gas
• static field
• memory effect
• initial release velocity
• characteristic voltage