Dynamic heating and thermal destruction conditions of quartz particles in polydisperse plasma flow of RF-ICP torch system

Abstract

Numerical simulation of turbulent mixing process of polydisperse quartz particle (particle size distribution in the range of 0.1-0.4 mm) flow with Ar and Ar-H 2 plasma generated by radio frequency inductively coupled plasma (RF-ICP) torch has been made. An approximate two-stage approach has been proposed to calculate the spatial-temporal distributions of temperature and resulting thermal stress in quartz particles during dynamic heating in polydisperse plasma flow. The influence of working gas compositions, particle size distributions, injection angle and flow rate of carrier gas on the thermal destruction conditions of quartz particles has been determined under different particle feed rates. It is found that all the solid quartz particles (0.1-0.4 mm) could be thermal destructed without overheating in RF-ICP torch system, when the hydrogen volume fraction in working gases is more than 1.5%-2% and particle feed rate is in a certain range. The values of the maximum and minimum feed rates have been determined under different hydrogen volume fractions. An optimal particle injection angle and flow rate of carrier gas is found around 50°-60°and 160-220 slpm, under which the value of maximum equivalent thermal stress in quartz particles is highest.

Influence of vacuoles with gas–liquid inclusions on the thermobaric destruction conditions of natural quartz under dynamic heating in an RF-TICP torch system

“…In addition, the baric stress in the particles during heating in argon-hydrogen plasma was also higher than that in pure argon plasma. This indicates that the thermobaric destruction conditions for quartz particles could be realized more easily in argonhydrogen plasma [12]. Compared with the effect of the hydrogen volume fraction, an increase in the coupled power from 6 to 12 kW led to a relatively small increases in particle maximum temperature (about 50-100 K) with G SiO 2 = 1×10 −3 kg s −1 , and the maximum equivalent thermal and baric stresses increased 1.1-1.2 fold.…”

“…The plasma gas was argon (Ar), while the carrier and sheath gases were argon-hydrogen mixtures with an H 2 volume fraction (j) of 0%-5%. The detailed description of the RF-TICP torch system could be found in previous work [12]. The basic dimensional and working parameters of the RF-TICP torch system are listed in table 1.…”

“…In the present work, an approximate two-stage approach was proposed under a relative small Biot number (Bi0.05-0.5). The detailed description of the two-stage approach as well as its accuracy for predicting the thermalstress state of quartz particles has been validated in previous work [12], here we only make a concise introduction. In the first stage, the distribution of temperature in quartz particles is assumed uniform, the particle velocity U p and average temperature T p could be determined by solving the two-coupled magnetohydrodynamic equations by using a particle-incell method [13][14][15][16].…”

“…The turbulent mixing process between thermal plasma flow and homogeneous particle flow could be obtained by k-ε turbulent model [20,21]. The boundary conditions for solving the magnetohydrodynamic equations have been given in [12]. When the quartz particles are supplied through the annular channel into the reactor chamber, there is a slip velocity between the carrier gas and quartz particles, the injection velocity of quartz particles at the exit of annular channel, U p =U 1 •K p , where the correction coefficient K p was set at 0.8, 0.6, 0.5, and 0.4 for quartz particles of diameter d p =0.1, 0.2, 0.3, and 0.4 mm, respectively [15].…”