Cryogenic grinding of cloves

Studies on cryogenic grinding of clove were conducted to observe influence of parameters, viz., grinding temperature, rotor speed, sieve size and feed rate on sieve choking characteristics, particle size distribution, volume mean diameter, specific energy consumption and volatile oil content. It was observed that the clove could be successfully ground at temperatures below -50C without any deposition over the sieve surface. An increase in temperature in the cryogenic range (-110 to -50C) had no significant effect on volatile oil content, whereas temperatures in the range of 55 to 85C significantly reduced the volatile oil content from 11.0 to 9.3 mL/100 g. Thus, cryogenic grinding resulted in 29.5% more volatile oil in comparison to that of ambient grinding. When grinding temperature was increased from -110 to -50C, there were increases in particle size for the same cumulative volume fraction. The volume mean diameter of clove powder increased quadratically from 119 to 153 micrometer with increases in temperature from -110 to -50C at constant feed rate of 1.5 kg/h, rotor speed of 69 m/s and sieve opening size of 0.5 mm. It increased quadratically from 119 to 140 micrometer with increase in feed rate from 1.5 to 6 kg/h with the grinding temperature constant at -110C. The specific energy consumption during grinding increased quadratically from 62 to 81 kJ/kg with increases in grinding temperature from -110 to -50C at a typical feed rate of 1.5 kg/h, rotor speed of 69 m/s and sieve size of 0.5 mm. The specific energy consumption increased quadratically from 62 to 85 kJ/kg with the increase in feed rate from 1.5 to 6 kg/h with constant grinding temperature of -110C, rotor speed of 69 m/s and sieve opening size of 0.5 mm.