JMP Engineering (Corporate)

Black Liquor Recovery Boiler Optimization


  • Increase BLS Throughput
  • Increase Thermal Efficiency
  • Improve Reduction and Green Liquor Quality
  • Reduce Pollutants
  • Stabilize the Process
  • Increase Run-Time Between Water Washes
  • Coordinate Production Rate Changes

Process Summary

The Recovery Optimization System developed by AAI utilizes the latest concepts in control strategy for Recovery Boiler Processes using the tools available in modern computer based control systems and instrumentation typical of a Recovery Boiler. By incorporating functionality which has traditionally been under manual control, and moving to a Liquor BTU based control strategy, the system improves Recovery Boiler throughput and efficiency, reduces carryover, reduces emissions, and stabilizes downstream processes.

A key component of the control strategy is BTU based liquor firing. As opposed to liquor volume or liquor solids flow to the boiler, BTU based firing uses the heat release of the liquor as the most representative value of long-term production rate. The advantage of this method is that heat release can be stabilized relative to production rates. This allows a stable and constant oxidation process to occur on the smelt bed. Once stability is achieved, carryover and emissions are reduced and the boiler can be pushed closer to maximum production rates.

Variations in heat release rate are controlled based on the amount of air being consumed in the furnace. The air consumed by burning liquor is continuously calculated and used to adjust liquor flow such that proper heat is maintained. Consumed air control provides the advantages of uniform burning, better oxygen control, and overall furnace stability. This optimization module functions with either oscillating liquor guns or stationary firing.


AAI furnishes guarantees of performance with installations of Recovery Boiler Optimization System based on a survey of existing Recovery Process operation. Guarantees typically involve measurable system and process parameters such as percentage of time on full automatic, BLS throughput, or percent Excess Oxygen. AAI is confident that installation of a Recovery Boiler Optimization System will result tangible benefit for the end user and is willing to back installations with a firm warranty.

Typical areas of process improvement include:

  • Excess oxygen will be maintained less than or equal to 1.5%, ±.15%
  • Throughput will be maintained greater than a defined tDS/day
  • Automatic control will be provided by the system 95% of the time


AAI believes that competitive advantage can be gained by pulp and paper manufacturers through the proper application and use of today’s computer and control equipment. This is proven everyday by AAI engineers that leverage their technical systems knowledge with process experience to provide clients with significant dollar savings through higher process throughputs and efficiencies. The AAI Recovery Boiler Optimization System is a specific example of this.

The Recovery Boiler Optimization System has been installed and is running at more than 18 locations across North America.