Stove controls are an integral part of a blast furnace, managing the stoves which provide the hot blast. Although many three stove and four stove control systems are still functioning, however the underlying control system, often a DCS, is expensive and outdated. Older controls tend to deteriorate due to blast furnace atmosphere, particularly in remote I/O locations. These legacy control systems are difficult to get parts for and maintain. Support costs are very high, and diagnostics and tuning are minimal. Rather than simply upgrading the control system to the “latest” version, why not replace the control system with an open, integrated, proven platform?
IPACT offers a replacement stove control system that is compatible with three and four stove systems in cyclic, parallel, lapped parallel and staggered parallel four stove operation. IPACT has over 200 years of combined experience working with blast furnaces. The IPACT Stove Control System leverages the industry standard, ControlLogix PLCs for the new controls. The Stove Control System provides a completely tunable and flexible implementation. IPACT usually recommends modernization implementation as a four step process:
- Analysis of existing stove control strategy
- Implementation of IPACT Stove Control System based on client parameters after configuration of IPACT Stove Control System
- Commissioning the new stove controls
- Advanced Modeling based analysis of the performance and attributes of stoves
IPACT investigates and analyzes the existing control system. The investigation will determine whether any field I/O needs to be moved and produce (or update) drawings based on the investigation. As part of the analysis, IPACT reviews the mode of operation, the symmetry of the performance, and configuration of the stoves. Consideration is given to implementation of energy saving strategies such as fuel gas injection systems and waste-heat recovery at this stage. The analysis reviews the differing conditions of the stoves, thermal efficiency, heating and heat transfer properties. All this information, as well as information that can be accessed from whatever existing information systems, is used for the configuration and initial optimization of IPACT Stove Control System.
During this phase, IPACT configures the stove control system to the client’s stove control architecture. The configuration often provides enhancements to the legacy control system. For instance, the IPACT Stove Control System can run in manual mode, semi-automatic and fully automatic mode. Generally, IPACT recommends running in a semi-automatic mode (change of stoves is triggered manually) until a sufficient base line and stabilization period has completed. During implementation, using learnings from the analysis phase, IPACT creates a sophisticated simulation model of the stove control system. This allows IPACT to thoroughly test the system prior to commissioning. This simulation takes into account different physical properties and thermal properties of blast furnace processes and stove controls, models movement of flows, temperatures and valve operation. After commissioning, IPACT recommends that the simulation be installed in laboratory or training environments to allow new users to train on the operation of the stove controls.
The commissioning of the stove control system will be relatively painless. IPACT thoroughly tests the application against the simulation and then runs the stove control system in parallel with the existing system. The simulation not only tests the functionality of the process model but also network and server loading. IPACT’s goal for commissioning is to transition the system from the legacy controls to the new stove controls with minimum disruption to operations. IPACT recommends transitioning the system incrementally during regularly scheduled outages at a pace consistent with the budget. A typical transition plan might include:
1) Assemble and wire sub-panels.
2) Break down work into task lists to allow multiple teams to execute simultaneously during planned downtime.
3) The IPACT Stove Control System will run in “shadow mode” with the legacy system controlling all outputs, but the IPACT Stove Control System receiving all inputs for on-site testing and I/O checkout under running conditions.
4) During the next planned downtime, the IPACT Stove Control System would be cutover and controlling the stove system using legacy I/O.
5) During other planned downtime, legacy I/O could be replaced rack-by-rack with A-B I/O as required.
6) Any functions remaining in the legacy system, most likely control loops could be moved when convenient even while IPACT Stove Control System is running. Control functions may need to be replaced on scheduled downtimes, but the control functions can be moved as time and budget allow.
After the commissioning of the stove control system, IPACT recommends a settling in period for the system. This gives the operators time to adjust to any differences in the new system and for the System to stabilize. Further, the new information system will have an opportunity to collect data regarding the performance and physical characteristics of the different stoves operating with the new controls. IPACT, the client’s process engineers and laboratory personnel will use the data collected to develop models for: heat and mass balance, burden and hearth-wear, and a kinetic process model all which will enable closed-loop control of the stoves. These models allow the client to refine the tuning and optimizing the blast furnace, the IPACT Stove Control System, and achieve maximum performance.
- A PLC based solution that is fully documented, including diagnostic SFC’s, and supportable by existing plant personnel.
- A reduction of errant stove cycle changes, reducing required maintenance.
- A reduction of the fluctuations in blast furnace operating parameters providing a more uniform product quality.
- A modern, open information system easily enabling analysis to drive process improvements.
- A tunable stove control model optimizing fuel and cycle times during all operating modes.
- Individualized stove controls tuned and optimized to provide the best performance for each stove.
- A more optimized firing practice during the gas cycle.
- A reduction in energy usage.
- Improved stove performance when the blast furnace is throttled due to reduced downstream demand (e.g., blowing at 50% wind because of a BOF outage).
- Maximized stove life.
- Stove Control System can provide condition based monitoring information to the CMMS, resulting in reduced maintenance and fewer emergency repairs.
- Routine engineering maintenance of I/O scaling, alarm limits, etc. can be done from the HMI and does not require programming in PLC or System Platform.
- Enhanced combustion control model – simple, flexible, adapts to handle common instrumentation issues.
- Combustion control programmed using A-B function blocks for easy understanding.
- An improved ability to correlate stove operation to furnace operation.
- An improved ability to report on stove cycles for utility usage.
The IPACT Stove Control System meets client demands for stove controls that provide reliable operation, minimal maintenance, improved safety and reduced downtime. IPACT is an expert on plant modernizations which not only replace obsolete equipment but provide an opportunity for improved performance, lower maintenance requirements and improved environmental compliance. IPACT is a reliable, highly experienced engineering company and we look forward to working with you!