Method of treating fly ash of a recovery boiler

The present invention relates to a method of treating fly ash containing sodium sulfate from a recovery boiler of a chemical pulp mill. This method comprises at least the following steps: a) ash is dissolved in an aqueous solution and the pH of the solution is adjusted with alkali for precipitating impurities， b) the solution is filtered for removing the impurities containing precipitate， c) sodium sulfate is crystallized from the solution and the crystals are separated from the solution by filtering or by centrifugation， and d) the crystallized sodium sulfate is used as initial material for producing sodium and sulfur containing chemicals or as process chemical.

本发明涉及一种处理源自化学制浆厂回收锅炉的含硫酸钠飞灰的方法。该方法至少包含以下步骤：
a) 将飞灰溶解于水溶液中，以碱调节溶液pH，使杂质析出；
b) 过滤该溶液以移除沉淀出的杂质；
c) 从溶液中结晶析出硫酸钠，并通过过滤或离心方式将晶体与母液分离；
d) 将所得结晶硫酸钠用作制备含钠、硫类化学品的起始原料，或作为工艺用化学品。