Engineered Automation & Power Solutions

Boiler Flame Safety Application Note

Application Overview

Engineered Software Products designed and commissioned a programmable logic controller (PLC) Flame Safety System and Emergency Shutdown Protection System for a Black Liquor Recovery Boiler and a Multi-Fuel Power Boiler.


Alabama Pine Pulp Mill

The two year project included the commissioning all the PLC controls and interface to a Foxboro I/A distributed control system (DCS) for a $700M new pulp mill project. The Alabama Pine Pulp mill, in Claiborne, Alabama, included two boilers: a bark burning Babcock-Canada Power Boiler capable of generating 150,000 lb/hr of steam and a Babcock & Wilcox Recovery Boiler. The Recovery Boiler was rated for burning 68% solid black liquor at 5.5M lb/day to provide 800,000 lb/hr of steam at 1250 psig.

Application Highlights

  • Factory mutual approval was received for the PLC hardware architecture, I/O requirements, and logic design for each boiler.
  • The Flame Safety System and Emergency Shutdown Protection System for each boiler used GE Fanuc Redundant PLC Processors for online CPU backup. In the event of CPU failure, the redundant system provides a bumpless transfer of control data to the backup PLC.
  • The system design is a hybrid PLC and DCS architecture. The PLC communicates to the DCS over a fiber-optic local area network (LAN) spanning 1,000 feet.
  • The First-Out Fault Logic not only captured the first device to cause a boiler trip, but also the sequence of each related successive device on a CPU scan basis. The fault information is then displayed to the operator via the DCS display.
  • Square root and proportional integral-derivative (PID) algorithms programmed in the PLC enabled back-up protection to the DCS for all critical loops.
  • A distributed I/O system was implemented, in addition to the conventional rack I/O, as a hot standby for critical loop control.
  • The DCS was designed to capture all of the PLCs distributed I/O diagnostic data and display it for the operator. The I/O diagnostic data is essential information for the operators in the event of I/O or device failures.

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