The sparging of the gas bubbles is {HEAD ~ the main mechanism} for mixing, {TAIL ~ catalyst suspension}, and dispersion 
for
The sparging of the gas bubbles is { HEAD ~ the main mechanism } for mixing , { TAIL ~ catalyst suspension } , and dispersion
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH