A furnace draft study begins by building a dynamic model of the existing plant using our proprietary software, ProTRAX. ProTRAX is a modular, dynamic simulation system based on first principles of mass, energy, and momentum conservation. All ProTRAX models built by TRAX with this software meet or exceed the ISA Standard for accuracy of Fossil-Fuel Power Plant Simulators (ISA-S77.20).
The furnace draft dynamic model is comprised of a process model and a control system model. TRAX builds the model using design and plant operating data. Individual components such as furnaces, superheaters, precipitators, air heaters, fans, scrubbers, dampers, and ducts are dropped onto a page and connected to one another to represent the plant configuration. The resulting schematics closely resemble piping and instrumentation diagrams (P&IDs), with individual pieces of equipment, equipment numbers, and line numbers.
A complete set of SAMA modules, which can be used to simulate controls, are part of the ProTRAX software. Control parameters (such as proportional or integral gains, high and low limits, etc.) are all built into the model.
TRAX then verifies the accuracy of the model at multiple steady-state conditions, as well as through a dynamic event. Once the existing configuration plant model is validated, the model is modified to reflect the proposed equipment and controls changes that will occur at the plant.
Next, transient testing begins and the model is subjected to many different scenarios, such as fan trips, MFTs, mis operation, or catastrophic equipment failure. Through these transient events, pressures, flows, and temperatures are monitored throughout the system. The transients allow investigation of plant dynamics caused by actuator stroke time, control system gains, or plant runbacks. The analysis done during the dynamic events can provide information that cannot be obtained with normal steady-state analysis, such as utilization of a vent stack, flow reversals, and optimum control system tuning. A full review of proposed controls changes performed as part of a furnace draft study can also confirm control compliance with industry guidelines such as the NFPA 85 code.
Once transient tests are complete, the results are analyzed to identify excessive pressure, flow, temperature, electrical current excursions, or other undesirable behaviors. TRAX Energy Solutions will develop and test process or control logic changes to prevent or remediate the excessive conditions. An example is shown in the figure below, which illustrates furnace pressure during an MFT event using the existing control logic, and the same event after implementing the TRAX control system recommendations. Process and control modifications can be tested individually, or in combination, to determine what works best.
.png)
