OPT800 Vapor

ABB AbilityTM Advanced Process Control for high production and energy efficiency of multiple-effect evaporator plants

OPT800 Vapor is an Advanced Process Control (APC) solution for controlling and monitoring of the multiple-effect evaporation plant. Using a multivariable model-based approach, the solution controls the strong liquor production rate and dry solids content to minimize energy consumption and increase evaporation plant capacity.

Black liquor evaporation is a very important part of the recovery process. The evaporation unit provides the link between the fiberline and recovery sections and plays a major role in the operation of pulp mills.

Ensuring the production of strong black liquor with on-target dry solids content and minimum variability is the key to stabilizing the recovery section and optimizing steam utilization. The multi-effect evaporators use low and medium steam pressure to transform weak black liquor with a dry solids content of 15-20% into strong black liquor with a dry solids content of 80-85%.

OPT800 Vapor solves these challenges by providing tighter control of the evaporation process, reducing variability of the black liquor quality while also lowering operating costs and increasing capacity.

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  • Dry solids control to optimize steam economy and provide higher evaporation capacity
  • Production rate controls
  • Real-time adaptive modelling: Automatic adjustments based on process changes
  • Higher-order model support: Captures process dynamics accurately
  • Cost optimizer: Looks for ways to optimize operational costs within process constraints
  • Evaporators performance monitoring
  • KPI Dashboard and control usage reports by day/shift  
  • Performance monitoring, with both on-site and remote access for customers and ABB 
  • Task oriented and user friendly customizable operator displays


  • Increased production rates
  • Removes bottlenecks
  • Reduced strong liquor dry solids variations
  • Decreased energy consumption, giving steam savings

How it works – Stabilizing black liquor quality and lowering costs

OPT800 Vapor effectively uses a multivariable model-based approach to optimize the black liquor dry solids profile across the multi-effect evaporation process.  OPT800 Vapor coordinates the gradual rise of the boiling point of the individual effects (or evaporators) as well as the feed and intermediate liquor flows. By reducing the variability in the black liquor dry solids, the APC solution minimizes overall steam consumption while stabilizing operations. This results in fewer upsets and longer intervals between cleanings.

The included production rate control ensures fast and smooth changes during swings in the production rate by efficiently coordinating the various operating parameters (i.e., flows and boiling point rise) to ensure minimal disturbance to the system. The liquor tank levels are also maintained within desired levels to ensure optimum inventory levels and smooth transitions during disturbances and process upsets. Control performance will not degrade over time with always-on monitoring and analysis of the APC solution.

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