Mercer Rosenthal, located in Germany, has commissioned a new cooking liquor evaporator (CLE) system aimed at improving energy and water efficiency at its pulp mill.
The targeted upgrade, supplied by Valmet, entered operation in early November 2025.
The project focuses on reducing losses in the cooking area, one of the mill’s most energy-intensive processes. By lowering avoidable steam consumption and improving condensate recovery, the new system strengthens the site’s steam-and-power balance while reducing fresh water demand.
Under the new configuration, a portion of hot black liquor from the digester is routed through a pre-evaporator. Medium-pressure steam supplies the heat, and the resulting vapor is returned to the digester, replacing part of the direct steam previously required. At the same time, hot condensate is recovered and returned to the boiler system at a higher temperature.
Based on project documentation, the CLE system is expected to deliver several measurable benefits:
- Lower steam demand in cooking, estimated at about 7.8 tonnes per hour
- Additional on-site electricity generation, around 0.97 MW by freeing steam for the turbine
- Reduced fresh water intake, roughly 22 m³ per hour (about 2%)
- Lower water-treatment chemical use, linked to reduced make-up water needs
The mill is currently validating performance against pre-upgrade baselines under comparable operating conditions.
The project reflects Mercer’s broader operational approach. Mercer’s strategy prioritizes precision upgrades over capacity expansion.
Mercer is a global producer of sustainably sourced forest products, with a focus on market kraft pulp, solid wood products, and bio-based solutions. Headquartered in Canada, the company operates pulp mills and sawmills in North America and Europe, supplying customers worldwide.
Source: Mercer
