JMP Engineering (Corporate)

Advanced Control for the Pulp Stock Preparation Process


  • Establish repeatable and accurate dilution and consistency control
  • Coordinate production rate changes
  • Stabilize the process
  • Provide consistent operation from shift to shift

Process Summary

The key to the stock preparation area is repeatable and accurate dilution and consistency control. AAI has developed an Advanced Consistency Technique (ACTâ„¢) for the stock preparation area that provides the capability of raising these controls from an “art form” to a science.

Benefits expected to be gained are significantly improved dilution control, reduced variation in consistency and improved overall process stability at various loads, which will all translate to increased product throughput. Additionally, the user interface to the stock preparation process, for both operations and maintenance, will be improved through the use of AAI’s graphics and techniques. This will promote the automation of many functions which normally require manual intervention.

Advanced Stock Preparation Control

The key controls in a stock preparation system are dilution and consistency control. Consistency control of paper stock slurries are considered among the most important and difficult control solutions in the mill. Process efficiency and the ease of equipment operation depend largely on the value and uniformity of consistency of the pulp and stock supply. In AAI’s opinion, the use of P&ID controllers in this application has provided marginal success.

From AAI’s vantage point, assuming the basic control engineering is accomplished, the measure of the success of a stock preparation project will be the enhancement of the current control philosophy. The AAI approach is a hybrid system that combines the strength of Robust Regulatory control, which can operate as a stand alone system, and the AAI Advanced Consistency Technique (ACTâ„¢).

This technology produces a platform to implement rule based control solutions for dilution and consistency control. This is not a ‘black box’ solution but a tool that the mill can use and continue to refine as time progresses.


AAI furnishes guarantees of performance with installations of Stock Prep System based on a survey of existing process operation. Guarantees typically involve measurable system and process parameters such as percentage of time on full automatic, process throughput, or reduction in process variation. AAI is confident that installation of a Stock Prep Advanced Control System will result tangible benefit for the end user and is willing to back installations with a firm warranty. However, for the benefit of the client as well as AAI, it is important that a set of precisely measurable parameters make up the boundaries for determining process performance before and after system installation.


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