- Energy-efficiency for reduced costs
- Highest dry solids liquors with maximum availability using crystallization technology
- Cleanest reusable condensates using the minimum amount of steam
- Lowest steam and electricity consumption
ANDRITZ evaporation plants are well-proven in installations around the world. There are a variety of configurations and models available – from pre-evaporators to multiple-effect evaporation trains – to accommodate even the most challenging pulp mill or effluent plant evaporation needs
The major advantage to ANDRITZ multiple-effect evaporators is the utilization of proven lamella heating surfaces for high efficiency and reliability.
Black liquor evaporation is an essential part of the chemical recovery process as it significantly concentrates the dry solid matter in black liquor so that the liquor can be effectively combusted in recovery boiler. The water removed from the liquor can be segregated and processed so that it can be reused in the mill – reducing fresh water requirements, effluents, and saving money.
ANDRITZ evaporators and concentrators, with their lamella heating surfaces, are adept at processing the spent cooking liquors or mill effluents using the minimum amount of energy while maximizing product dry solids, plant availability, and condensate quality. The lamella heating surfaces are inherently non-scaling. This allows the use of various heat sources inside the lamella, allowing the mill to select the most energy-efficient process connection.
Black liquor is a complex solution of water, organic, and inorganic components. This composition varies from mill to mill, so the evaporation system must be flexible in design over a wide range of operating parameters. The physical properties of black liquor change significantly when it is concentrated. Concentrated black liquor has high viscosity, which can cause significant problems with fouling if these characteristics are not accounted for in system design.
ANDRITZ systems employ crystallization technology to produce the highest dry solids product with minimum downtime for washing and cleaning of the equipment internals. As an option, systems for treating the liquor to reduce its viscosity, and systems for de-activating the calcium in the black liquor to prevent scaling, can be integrated directly into the evaporation plant.
The stripper is part of the multiple-effect evaporator system. Typically, the heat source for the stripper is from effect #1 and the stripper vapors are condensed in effect #2 to maximize energy efficiency.
The process inside and ANDRITZ evaporator relies on a free flow falling film of liquor over the surface of the lamella. This ensures low vapor velocities and low shear rates inside the evaporator, which eliminates foam generation in difficult applications.
Uniform liquor distribution of the liquor over the lamellas, and the continuous redistribution of the liquor created by the dimpled shape of the lamella surface, ensure a completely wetted heating surface and eliminate local scaling or over-concentration of liquor. The lamella heating surface ensures that water-soluble scaling can be washed away by a simple dilution wash, eliminating the need for time-consuming and costly outages for cleaning.
The design of the ANDRITZ evaporator takes full advantage of the lamella heating surface to optimize liquor distribution and internal circulation flows. This results in excellent coverage and distribution of the liquor over the entire heating surface with minimum pumping power – saving capital and energy costs.
Highly efficient condensate segregation in the evaporator ducts and lamellas, plus the integrated stripping of foul condensate fractions, produce clean and re-usable water. Methanol in the liquor is separated from the condensate and recovered as an auxiliary fuel in an ANDRITZ methanol liquefaction system.
Crystallization technology is used in the integrated system for removal of chlorides and potassium. Energy is conserved by using the secondary vapor from the evaporator for the crystallization process.
The use of fully integrated foul condensate stripping, optimized liquor distribution, and the ability to use various heat sources within a single thermal effect ensure an evaporation system that meets unique customer requirements while providing the best possible availability and energy efficiency.