Solubility of ESP Dust and Optimization of the Recovery of Sodium Sulphate Crystals, 2003 Fall Technical Conference

Any closed-cycle technology must use a process for removal of problematic non-process elements, such as chloride and potassium. Chloride and potassium are minor components which can accumulate in Kraft pulping chemical recovery cycles. Previous studies indicated that Cl- and K+ have adverse effects on thermal properties of fireside deposits in the Kraft recovery boiler. There is an enrichment of Cl- and K+ in recovery boiler electrostatic precipitator dust(ESP) and so it is a good place from which to remove them. The common denominator of all the techniques for Cl- and K+ removal in the recovery cycle, is the dilution of the ashes, firstly on water, with the preferential crystallization of sodium sulfate, in relation to the other salts presents on the ESP. The objective of this work is to evaluate the solubility of the electrostatic precipitator dust on mixtures such as H2O / H2SO4 or H2O / Spent acid (H2SO4 + Na2SO4). The main purpose of this is to obtain sodium sulfate crystals with largest purity and size, minimizing the losses of this salt, which will be re-used in the paper manufacture process.