Pulp Mill DCS Upgrade

Project

Design, document, configure, and provide start-up support for the migration of a pulp mill operating and monitoring control system in order to improve life-cycle supportability.

Architecture
  • Siemens PCS 7 Distributed Control System (DCS), redundant controllers, redundant communication units, Input/Output (I/O) modules, and redundant Human Machine Interface (HMI) servers, workstations, and clients.
  • A control panel housing the dedicated PCS 7 controllers, redundant communication units, redundant power supplies, and I/O modules.
  • Multiple remote panels containing Siemens redundant communication units and I/O modules.
  • PCS 7 Engineering Station (ES) software to develop and manage both the HMI and controller configuration.
  • OSIsoft PI system communicating with the Siemens PCS 7 DCS via a PI-DCS interface.
Implementation

The pulp mill was controlled by a Moore Products Co. MYCRO DCS. The MYCRO system, a 1980s technology, had operator consoles connected to Multi-Loop Controllers (MLCs) via a proprietary network. In addition, an independent computer interface provided a process data connection to OSIsoft PI, the plant historian.

The MYCRO system was obsolete and parts were increasingly harder to obtain. Further, the existing DCS was difficult to maintain, as not many engineers were familiar with its configuration and programming techniques, making process control improvements hard to implement. The customer chose to replace the MYCRO DCS with a Siemens PCS 7 DCS over four phases—each stand alone. Phase 1 of the upgrade contained approximately 550 I/O points, replaced two MLCs associated with the digester and pulping process, and set the foundation for further Siemens PCS 7 work. Phase 2 contained approximately 450 I/O points and replaced the controllers around the bleaching and washer systems. Phase 3 is being configured in the bleaching controller and replaces the controls associated with ClO2 production and chemical preparation. Phase 4 will upgrade the brown stock washer controls and the balance of plant completing the replacement and decommissioning of the MYCRO equipment. Phases 3 and 4 are expected to contain an additional 800 I/O points.

The OSIsoft PI historical data system continues to provide long term process data recording. The system communicates to the DCS via the PCS 7 OS OPC server. Additionally, the PI system supplies setpoints and control parameters to the DCS control loops, which are required for production.

Status

Introduction of PCS 7 in the pulp mill provided an improved operator interface and in turn improved operability. New process techniques are easier to implement and troubleshooting process problems is faster—due to better and faster data presentation and organization.

Currently, the pulping process—chip handling, Kamyr digester and diffuser—is running on PCS 7 and being monitored on eight (8) flat screen monitors. The bleaching process—five (5) washers, chemical addition and bleached storage—is running on a second control panel and being monitored on another set of eight (8) flat screens. Phase 3 of the upgrade—the chemical reactors and chemical preparation portion—is currently in development and scheduled for startup in 2014. Phase 4 engineering is expected to start in 2015 immediately following Phase 3 startup.