Patent ID: 6652829
Filing Date: 2003-11-25
Classification: C01B,C01G,C01P,F27B

Abstract:
A method for continuously calcinating product to form mixed metal oxide pigments comprising:(i) providing a continuously operated indirectly heated rotary furnace having a heating cavity; (ii) introducing raw ungranulated batch pigment precursor feedstock including from about 0.5% to about 25% by weight flux mineralizer and product to be calcined into said heating cavity of said furnace while said heating cavity is maintained at a temperature of from about 1600Â° F. to about 2300Â° F., said flux mineralizer providing at least in part a controlled atmosphere during heating, the controlled atmosphere comprising an atmosphere that is depleted of oxygen and is halogen rich and comprises less than 25% by volume ambient air; (iii) maintaining the controlled atmosphere by at least partially sealing the heating cavity to promote the calcination of at least a portion of said product in said heating cavity during the heating of said feedstock thereby forming mixed metal oxide pigments; and (iv) discharging and recovering the mixed metal oxide pigments; wherein said product to be calcined comprises a mixture of oxides of zirconium, vanadium and silicon, and said flux mineralizer comprises a mixture of K2ZrF6 and K2SO4, and said method renders a blue pigment.