Reduction of boron emission in wastewater

Technology of boron emission reduction in wastewater originating from Wet Method Flue Gas Desulphurisation Plants

Technology of boron emission reduction in wastewater originating from Wet Method Flue Gas Desulphurisation Plant (Wet Method FGD Plants) developed by RAFAKO S.A. is an innovative solution currently implemented within the project "Innovative technology for changing of the working regime power-generating units class 200 MWe – Program Units 200+" funded by the NCBiR. This method is based on the use of boron-selective sorbent (ion exchange resin) for the treatment of highly saline wastewater. It allows the concentration of boron in wastewater to be lowered to less than 1 ppm (1 mg/l).

The technology is carried out in three key processes: sorption, desorption and regeneration of the deposit. During sorption, there is a selective bonding between boron ions and the structure of the sorbent by creating complex boron connections with specific chelating groups. The desorption process, on the other hand, consists in the controlled release of boron ions associated with sorbent using hydrochloric acid. The regeneration phase, on the other hand, consists in re-preparing the sorbent bed for the sorption process with a solution of sodium hydroxide. An additional unit developed within the framework of this technology consists in treatment of boron solution resulting from the desorption process by precipitating solid, sparingly soluble calcium peroxenic boron salts.

Furthermore, in the light of the parameters of IMOS waste water treated in the classical mechanical-chemical treatment plant and in view of the vulnerability of ion exchange resin to mechanical contaminants, in particular suspensions and colloidal fragmentation impurities as well as the presence in wastewater, after the processes of their chemical treatment, of high-molecular organic compounds and polar compounds, the use of a protective sand and carbon filter is indispensable. It was therefore decided to supplement the boron emission reduction technology with a preliminary unit of wastewater filtration on the aforesaid filters prior to final ion exchange unit.