INFLUENCE OF LOW-FREQUENCY VIBRATION ON DESORPTION CHARACTERISTICS OF COAL SAMPLES
(1. School of Energy Engineering，Xi'an University of Science and Technology，Xi'an，Shaanxi 710054，China；
2. School of Science，Xi'an University of Science and Technology，Xi'an，Shaanxi 710054，China)
Abstract：The excited and testing system of gas adsorption and desorption is developed to study the influence of low-frequency vibration on gas desorption characteristics of coal sample. The test results show that the amount and velocity of gas desorption increase，and the velocity of attenuation becomes fast with the decrease in vibration frequency；the attenuation coefficient and desorption intensity of coal sample gradually decrease with time. Using related knowledge about the theory of gas desorption velocity and vibration to analyze the test results. It is shown that low-frequency vibration can lead the porosity of coal to weakening，permeability to decrease and diffusion rate to slow down，all of which are no advantage for the coal gas desorption. With the effects of disturbances，adsorpted accompanying molecules can obtain desorption energy，but the gas desorption capacity is small because of the decrease in diffusion rate and desorption velocity；without the effects of disturbances，the porosity of coal sample doesn¢t change. Although the adsorpted accompanying molecules cannot obtain desorption energy，the desorption velocity and gas desorption capacity are larger than those in the effect of vibration because of the larger diffusion rate and permeability. Therefore，the weakening of the porosity of coal samples and increased molecular mean free path under low-frequency vibration can lead to slow diffusion of molecules. Meanwhile，lots of tiny porosity layers are formed at the vibration face，which increase the adsorption sites inside the coal samples；and then slow down the coal gas desorption.
2010, Vol. 29 
