System and method for the removal of non-process elements from electrostatic precipitator ashes in a kraft pulp process

A method for removal of non-process elements from electrostatic precipitator ashes in a kraft pulp process with an ash treatment step, the method comprising the following steps:

• a) in a first tank (1) with agitation means (2), adding a strong acid containing sulfur to a slurry or saturated ash solution (4) to lower its pH between 8 and 10;
• b) transferring the slurry or saturated ash solution resulting from the previous step (4′) to a second tank (5) with second agitation means (2′);
• c) in the second tank (5) with the second agitation means (2′), adding CO2 to the slurry or saturated ash solution (4′) via a recirculation loop (6),
• wherein the CO2 added has a purity degree between 99.00 and 100.0% or a purity degree between 1.0 and 98.9%.