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Implosion Prevention and Furnace Draft Exploration

A draft study offers a range of benefits, including assurance that proposed new equipment is sized properly, prediction of system pressures during extreme plant events, and evaluation of existing control logic. Conducting a furnace draft study during an equipment or controls upgrade is an important part of ensuring the safety of a plant in its new configuration.

Discovering system pressure and flow changes after equipment updates and ensuring proper controls response can be key in preventing severe structural damage or implosion. TRAX offers a draft analysis study to help clients learn more about potential operating hazards and controls remediation that can be taken to help mitigate those risks.

What Does a Draft Study Do?

A draft study uses mathematical modeling to closely investigate pressure, flow and temperatures in a power plant or other facility.

When TRAX conducts a study, our clients often want to know about the impacts of a process change and how to lessen or eliminate negative and severe excursions and effects. The dynamic models developed as part of a draft study can be used to verify NFPA 85 compliance, optimize plant operation, and ensure implosion protection. TRAX can even test control logic across the load range, tuning the controls to avoid nuisance trips while retaining the desired functionality.

  • How does resizing fans affect the plant pressure profile?
  • Could a different ducting configuration around updated environmental equipment improve losses?
  • If a plant is retrofitted to gas or a hydrogen blend, will an MFT cause a severe pressure excursion or implosion?
  • How can the controls be optimized to handle carbon capture additions?

TRAX can retune controls for a safer, more effective response

Implosion can be a risk with newly added environmental equipment. The added pressure drop from the new equipment, aging ductwork, inadequate fan trip interlock logic, and insufficient fuel trip kicker logic can lead to severe negative pressure in the furnace, which can cause the ductwork leaving the furnace to implode, resulting in danger to employees, extensive downtime, lost generation and expensive repairs. TRAX can retune controls for a safer, more effective response using the client’s specified design limits as guidance.

Using a Draft Study: Analyzing New Equipment and Improving Effectiveness of Controls

A furnace draft study begins by building a high-fidelity dynamic model of the existing plant and verifying the accuracy of the model at multiple steady-state conditions, as well as through a dynamic event. These existing configuration tests can often reveal valuable information about current plant behavior that may not be captured by the plant historian due to transmitter range limits or infrequent field readings.

See a detailed, step-by-step breakdown of the TRAX study process

Once we have a validated model, TRAX can begin to examine a client's area of interest. Typically, process follows several key steps:

  • New Configuration. Modify the model to reflect the proposed equipment and controls changes that the client wishes to investigate. TRAX also performs a full review of proposed controls changes to confirm compliance with NFPA 85 code.
  • Dynamic Testing. Transient testing begins and the model is subjected to scenarios such as fan trips, MFTs, mis‑operation, or catastrophic equipment failure. Pressures, flows and temperatures are monitored. 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 specialized information, such as the effects when a vent stack is used, flow reversals and optimum control system tuning.
  • Analysis and Reporting. Once the transient tests are complete, the results are analyzed to identify excessive pressure, flow or temperature, as well as other undesirable behaviors. TRAX then develops and tests process or control logic changes in conjunction with the client’s needs to prevent or reduce the excessive conditions. The following figure illustrates furnace pressure during a plant MFT event using the existing control logic, and the same event after implementing TRAX control system recommendations. All findings are presented to the client.

Implosion Prevention and Furnace Draft Exploration

November 2, 2023

TRAX has delivered a carbon capture simulator for a 150 MW coal-fired unit that models the capture of the full flue gas stream.  The system provides both CO2 and SO2 capture, delivering the captured CO2 to a pipeline for industrial use and underground storage.

TRAX Carbon Capture Model Included:

—CO2 and SO2 capture
—Sulfuric acid plant
—CO2 and SO2 amines filtration and purification
—CO2 compression
—CO2 pipeline and cavern

As shown below, TRAX built a modular simulation replicating the plant layout using our software, ProTRAX.  ProTRAX contains a full suite of modules specific to carbon capture functions and can model a wide variety of processes.  TRAX also virtually replicated the user interface that appears in the plant.  

Model Scope

ProTRAX is a modular software that can easily integrate multiple models for larger projects.


TRAX organizes the simulator model to match the layout of the site or process being modeled.


Depending on the Absorber module selected, the module can remove water vapor (H2O), carbon dioxide (CO2), and/or sulfur dioxide (SO2) from an air or gas stream.


Each ProTRAX module is backed by comprehensive documentation, including a general description, module inputs and outputs, and mathematical formulae.


The training value of a simulator occurs in the interactive screens that replicate the site equipment.

Upon initial delivery, the TRAX simulator was used to debug control logic and processes prior to site installation and to provide operations training prior to plant startup.  There was a clear need to begin training operators as early as possible since they had multiple unfamiliar systems to learn.

Thanks to the ProTRAX simulator, our customer gained considerable insight into control functionality and system interactions, resulting in modification to some control logic and correction of simple errors.  TRAX was able to assist with controls tuning, and helped in development of initial plant Operating Procedures.

The latest upgrade brings the model into alignment with the as-built plant condition by updating and tuning the simulator models to match the current plant dynamics. In addition, TRAX has updated the simulator controls and HMI graphics to the as-built state.  Keeping the simulator aligned with the current plant condition is critical to maintaining a positive training value, and is of paramount importance to the customer.