Patent ID: 8002994

Claim:
A method of treating lime mud slurry being generated in a causticizing process at a pulp mill comprising the steps of: (a) feeding a lime mud slurry generated in the pulp mill causticizing process to a disc filter; (b) thickening the lime mud slurry on filter discs of the disc filter; (c) removing the thickened lime mud from the filter discs; and (d) leading the thickened lime mud removed from the filter discs to a lime kiln, wherein the process includes treating the lime mud slurry in at least two filter treatment stages in one and the same disc filter by the steps comprising: (i) providing the disc filter with first and second sets of filter discs associated with first and second filter treatment stages, respectively, such that the first set has a lesser number of filter discs as compared to the number of filter discs in the second set; (ii) feeding the lime mud slurry entering the filter onto only the first set of filter discs of the first filter treatment stage so as to obtain a first thickened lime mud therefrom, (iii) removing the first thickened lime mud from the first set of filter discs of the first filter treatment stage, (iv) re-slurrying the first thickened lime mud which is removed from the first set of filter discs of the first filter treatment stage in liquid to obtain a re-slurried lime mud therefrom, (v) feeding the re-slurried lime mud onto second set of filter discs of the second filter treatment stage to obtain a second thickened lime mud therefrom, and (vi) removing the second thickened lime mud from the second set of filter discs of the second filter treatment stage and leading the removed second thickened lime mud to the lime kiln.