Boiler Control Optimization

Industry

Pulp and Paper

Business Issue

A Pulp and Paper company needed to optimize the performance of their boiler system to achieve savings in energy, fuel, and operation.

Project Summary

To improve the control strategy of #2 & #4 boilers controlled by an RS3 system. The main goal was to implement O2 trim control that would optimize the excess air used for efficient combustion in the two boilers.

Fuel consumption is minimized when it is burned with just the right amount of air at all load demands. Too much air in the combustion process causes fuel to be burned needlessly for the sole purpose of heating this excess air. Fuel in the form of heat is wasted up the flue stack. Conversely, too much fuel, in addition to being dangerous, causes unburned fuel to be wasted up the flue.

Cost effective combustion trim control optimizes the air to fuel ratio in the combustion process, resulting in efficient fuel burning. The goal of boiler optimization is to keep the total losses at a minimum. This is accomplished by minimizing excess air and the stack temperatures.

Scope Responsibility

Cornerstone Controls was responsible for the following areas:

  • Executing a control performance audit on combustion control loops to assess the health of equipment.
  • Designing and implementing a control strategy that includes control of oxygen concentration in the combustion gases to ensure that optimum excess air is present.
  • Reviewing and improving boiler control strategy on the RS3 system.
  • Dynamic performance tests at loads.
  • Optimum tuning of main O2 trim loops as well as master and drum level control loops.
  • Once the O2 trim controllers were configured, the oxygen loops were tuned. The tuning was performed so that the loop response meets the responses of the combustion loops. The oxygen loops were tuned following a robust response.  

Results

  • Project produced savings in economic boiler performance.
  • Stable operation and control of O2 in automatic mode.
  • The variability reduction in O2 was between 50% and 60% for #4 boiler.
  • More stable and robust boiler operation.
  • Achieved 2% savings in fuel usage.