Ash leaching and crystallization solutions
For mills with high levels of chloride and potassium in the liquor cycle, the Valmet ash treatment systems offer lower corrosion and increased production.
Chloride and potassium enter the liquor cycle with the raw material and cause corrosion in the digester, the evaporators and the recovery boiler. The recovery boiler is especially sensitive to elevated levels of chloride and potassium. Common problems are plugging and increased consumption of sootblowing steam as well as reduced efficiency in the ESP (electrostatic precipitator).
If you frequently need to stop the boiler for water washing and have elevated levels of chloride and/or potassium in the black liquor, a Valmet ash treatment system gives you increased uptime and production.
Valmet has extensive references of ash treatment systems and offers three solutions that remove unwanted chemicals from the electrostatic precipitator ash. Every mill is different, and to find the optimal solution (cost/benefit) a careful analysis is always required.
AshLeach is a well-proven, uniquely simple and effective system that removes chlorides and potassium from ESP ash. AshLeach does not require steam and runs independently of the other chemical recovery systems.
Valmet AshLeach has been providing outstanding value for pulp producers ever since the start of the first unit in 2002. Currently, there are systems up and running all around the globe at mills that produce pulp from eucalyptus, acacia, pine and other wood species. Thanks to the simplicity of the process, an AshLeach plant is very easy to maintain and operate. AshLeach stands for high availability and good long-term performance.
AshLeach Duo is a two-step ash leaching solution that is very effective when treating ash with a high carbonate content. The AshLeach Duo provides better performance than the single stage AshLeach with almost the same simplicity of operation.
In Ash Crystallization, the ash is completely dissolved in water and the solution is evaporated. The resulting crystals of sodium sulfate or carbonate are removed and returned to the liquor cycle. This technology is more complex, but provides the best chloride/potassium removal combined with a high sodium recovery.
Valmet has built and started up the largest ash crystallization system in the world. This plant has a design capacity of 920 tons of ESP ash per day. The startup was smooth and according to plan and the plant went into continuous operation in April 2017.
For more information on the Valmet ash treatment systems, please contact your local Valmet representative.