ISSUE
This Mitsubishi Paper mill struggled with hard calcium carbonate scale building up in its black liquor evaporators. As scale accumulated on the heated surfaces, the temperature difference (delta T) between the heating steam and the black liquor kept rising. Once delta T exceeds 20 °C, the evaporator is no longer considered operational and has to be shut down for cleaning. Before treatment, that point was reached in roughly a month, which made it difficult to hold the intended four-month operating cycle. At worst, the process had to be stopped for cleaning every month. Chemical injections only pushed the problem downstream to the second effect evaporator, and the acid used for cleaning was corrosive to the equipment.
SOLUTION
Altum's high-power ultrasound solution was installed externally on the inlet pipe, with no need to dismantle equipment or stop production. Instead of letting scale form uncontrollably on the hot surfaces, the ultrasound triggers controlled nucleation. It creates small, uniform crystals while the black liquor is still in the flow, so the particles stay suspended and pass through rather than adhering to the heated tubes as scale.
RESULTS
With ultrasonic treatment, delta T stayed constant instead of climbing past the 20 °C limit, enabling stable, continuous operation for four months. When the evaporator was opened after sonication, the surfaces were visibly cleaner than before. Scaling was prevented to the point that the hydrochloric acid cleaning previously needed during maintenance breaks was no longer necessary, and no chemical injections were required during operating cycle.
Overall, with Altum's solution:
- 90+ days continuous operation
- No additional energy needed
- Zero anti-fouling chemicals (10+ t less chemicals used annually)
- A more stable, predictable and efficient process
For the full story, including the measured temperature data and more on how the technology works, read our in-depth article on the Mitsubishi Paper case.