Coal-to-Gas Fuel Conversion Studies

Coal-to-Gas Fuel Conversion Studies

As conventional coal-fired units are phased out in significant numbers, implementing gas-firing has become a way to retain generating resources and meet emissions goals. However, converting to gas will lead to changes in the unit dynamics for both normal and abnormal operation.

By modifying the unit — typically adding natural gas valves and burners and updating the controls at a minimum — airflow through the unit will change. Fan tuning may be required, or entirely new fans may be needed. Tuning the unit for gas valve stroke times will help ensure draft system pressures remain within the expected values during normal operation. In addition, units also need to examine their compliance with NFPA 85 recommendations. Changes made to the controls during the conversion may no longer meet NFPA guidance.

During severe and abnormal operation, a gas-firing unit will also see a different pressure profile than a coal-firing unit. The rapid nature of a gas fuel shutoff will produce more severe pressure excursions to the unit and, in conducting a study, TRAX can recommend unit-specific controls measures that can help minimize these extreme excursions and tune the unit operation.

Coal to Gas Fuel Conversion Studies

Comparison of a master fuel trip when firing with coal and firing with gas. Firing gas produces an almost
immediate fireball collapse, along with a dramatic drop in pressure.

Want more information? Contact Us to get an in-depth look at the TRAX process for conducting a study.

Coal-to-Gas Fuel Conversion Studies

June 29, 2022

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.