Non-Carbonate Scale Removal
During the chemical processes carried out in the cellulose, pulp and paper industries, ‘green liquor’ (a dissolved smelt mainly consisting of sodium carbonate and sodium sulfide) is causticised by being reacted with calcium oxide in order to obtain ‘white liquor’. This is a crucial stage of the kraft process, which involves the breaking down of wood into wood pulp.
In this pulp mill in Chile, two lines of green liquor (Line A and Line B) were pumped from the dissolver tank to the clarifier tank, and both displayed encrustations of scale up to 2” thick, which caused flow rate to decrease considerably over time, thereby decreasing the efficiency of the plant’s entire operation.
In a trial installation, two HydroFLOW units were mounted on Line B only, and the amount of scale present in the two pipelines was compared after one year. As can be seen from the images below, Line A continued to display significant scale, whereas Line B displayed a reduction in scale thickness of between 75 and 100% (with complete eradication of scale seen in many parts of the pipeline). Flow rate increased in Line B in accordance with this and the valves and pumps surrounding Line B were found to function normally and to also be protected from scaling by the HydroFLOW units mounted on the pipeline.