Process Modeling

We put our knowledge of combustion, turbulence and chemistry to work for industrial and government clients.

Examples of Process Modeling at REI include:

  • Mass and energy balance calculations for fossil fuel combustion system using REI’s SteamGen Expert process model
  • Heat transfer, flue gas recycle, and mercury behavior in an oxy-combustion retrofit
  • Analyzing an existing industrial process, for example, Combustion and Process Simulation in a Rotary Kiln that was used to guide installation of corrosion-resistant refractory and resulted in a significant reduction in kiln shut downs
  • Optimization and design of new or existing processes using REI’s Computational Workbench or Configured Fireside Simulation (CFS) tools
  • Developing new mathematical descriptions of Mercury Chemistry in power plants or Fuel Chemistry for soot formation
  • Investigation of a novel CO2 capture and sequestration technology involving mineral weathering
  • Gasification of refuse derived fuel
  • Economic impact of air pollution control technologies
  • Mineral matter transformations in fly ash
  • Developing Advanced Computing schemes to make faster, more accurate process models

For more information regarding REI’s modeling services:
Contact us

With EPRI support, REI has developed an integrated process model, MerSimTM, for predicting mercury behavior based on fundamental mechanisms that allow for meaningful extrapolation to new situations, not merely interpolation.  MerSim is a useful tool which may be used to investigate possible compliance strategies for mercury emissions control. It is a user-friendly, module-based model which uses inputs typically known by the utility. MerSim has been developed and validated using 144 data sets from 28 full-scale power plants.  It includes homogeneous and heterogeneous oxidation kinetics, adsorption on fly ash, oxidation across SCRs, and removal and re-emission across wet FGD scrubbers. It can represent impacts of halogen addition and activated carbon injection.  Detailed SO3 calculations are also performed in MerSim to account for interference with mercury removal.


MerSim includes the following modules:

  • Boiler
  • Air Preheater (APH)
  • Selective Catalytic Reduction (SCR)
  • Hot-side Electrostatic Precipitator (HESP)
  • Cold-side Electrostatic Precipitator (CESP)
  • Fabric Filter (FF)
  • Spray Dryer Absorber with Fabric Filter (SDA-FF)
  • Ductwork
  • Wet Flue Gas Desulfurization (wFGD)

MerSim can be used to evaluate compliance strategies:Hg3

  • Analysis of specific coal sources to determine if the plant can maintain compliance if fuels are changed
  • Assessment of current and future compliance status to determine if existing equipment can be tuned to improve mercury reduction
  • Evaluation of pollution control device impacts on plant mercury emissions to determine how planned Air Pollution Control Devices (APCD) changes will impact current emissions
  • Investigation of mercury-specific control technologies



SteamGen Expert (SGE) is a Windows-based program that performs the mass and energy balance calculations for fossil fueled combustion systems. It has a graphic user interface (GUI) allowing a user to set up a flow sheet that contains multiple modules connected by inlet and outlet streams. The current version of SteamGen Expert has ten categories of modules, namely, Furnace, Reactor, Heat Exchanger, Air Preheater, Air Pollution Control, Fuel Prep, Flow, Process, Pump, and Other. A stream can contain solid, liquid, and/or gas phases. The thermodynamic properties of commonly used gaseous, liquid and solid species are built in the program. After the input streams and the operating parameters of the modules in the system are specified, SGE will calculate the pressures, temperatures, and compositions of the outlet streams of all modules on the flow sheet. Energy balance will also be performed for each module in the system. If the heat input to a module is specified, the temperature of the outlet streams will be calculated. If the temperature of the outlet streams of a module is given, the heat input to the module will be calculated.


  • The program performs mass balance for C, H, O, N and S elements as well as ash in typical fossil fuel related applications.
  • There are about 30 available gas species for a user to choose from with built-in chemical and physical properties. Solid and liquid fuels can be specified based on their elemental composition and heating values.
  • Combustion reactions in a furnace can be modeled using the Furnace module.
  • Gas phase equilibrium calculation can be performed using the Equilibirum Reactor module.
  • Physical process such as moisture vaporization can be modeled using the Pulverizer module.
  • Streams can be split or combined using the Slitter and Union modules.
  • Liquid and solid phases in a stream can be separated using the Phase Separator module.
  • Pressure change in a stream and energy addition/removal to a stream can be modeled using the Fan module.
  • Valence based equivalence ratio and particle/droplet loading for each stream, if applicable, can be calculated and displayed. Actual stoichiometric ratio can be obtained using a tool in the program.
  • The program contains a tool to solve the required flow rate for a fuel or oxidizer stream based on the desired oxygen concentration in a product stream.
  • The program performs the conversion between particle burnout and loss on ignition (LOI) for solid fuel combustion and the conversion of NOx emissions between ppm, lb/MMBtu, and other units.
  • A user can choose his or her preferred unit of physical quantity for data input and output.
  • Detailed calculation data can be exported to a Microsoft Excel spreadsheet.
  • The current version has a context-sensitive help system.



Furnace Expert program is a handy tool for an engineer to perform basic mass and energy balances for a variety of combustion systems ranging from a simple combustion test facility to a utility power plant. It can be used to arrange the fuel and oxidizer distributions inside a combustor or gasifier to achieve desired stoichiometries. Since the code has the built-in properties for commonly used species, it can also be used to calculate the properties of a stream such as heat capacity, enthalpy, heating values, sensible heat, density, and molecular weight. For Computational Fluid Dynamics (CFD) modelers, Furnace Expert can be used as a tool to calculate the inlet and outlet boundary conditions or to check the CFD simulation results.


Contact us for more information.

KILNVIEW is a Windows-based, one-dimensional, steady state rotary kiln model with an easy-to-use graphical users interface (GUI) for performing process calculations. KILNVIEW can be configured for mineral processing and waste incineration applications.


  • model direct and indirect firingkilnview1
  • model fuel-rich and fuel-lean conditions in kiln
  • compute required secondary air flow rate to
  • achieve specified kiln off gas composition.
  • complex feed and burner mixtures
  • mid-kiln injection of high BTU waste
  • includes effects of:
    • solid-phase reactions
    • entrainment of fines
    • melting & drying of the feed
    • combustion of organic matter in feed
    • sizing of feed


  • process optimization
  • determine impact on process of operating variables
  • examine impact of variations in feed composition
  • quantify technical risk of capital improvements
  • analysis of process economics
  • development of control algorithms
  • train plant personnel

Configured Models

The functionality of KilnView can be extended to create a configured model tailored to the exact requirements of a customer’s kiln-based process. The configured model can include simple heat and mass balance box models for pre-heaters, pre-calciners, cyclones, scrubbers, baghouses, stacks, secondary reactors as well as economic analysis information. All components within a KilnView configured model communicate in a seamless manner to provide a true a plug and play functionality.


Shown above is a tool for designing and modeling incineration schemes. A rotary kiln and secondary combustion chamber are fixed components in the model, but the engineer is allowed to select and position up to four air pollution control devices. Once the design is complete, the model is executed and the results displayed in the form of pop-up graphs, charts, and data boxes on the screen.


Shown above is a configured model for a process that utilizes recycled flue gas to optimize oxygen usage.

Interactive Modeling Tool for Detailed Chemical Kinetics Computations Using Ideal Reactor Networks

ModLink is an easy-to-use graphical user interface (GUI) for performing detailed chemical kinetics computations using networks of idealized reactors. ModLink allows efficient investigation of process conditions and inputs on the system using a detailed description of the chemistry.


  • Easy to use GUI allows creating reactor networks containing linked Plug Flow Reactor (PFR) and Perfectly-Stirred Reactor (PSR) objects.
  • Nodes placed between reactors control stream input and output with ability to mix separate streams automatically and calculate mixing cup properties.
  • PFR Reactors: can be performed assuming constant pressure, temperature or volume; or variable volume or variable temperature conditions.
  • PSR Reactors: can be performed assuming adiabatic or constant temperature conditions.
  • Thermochemical properties at reactor outlets are easily extracted and imported into plotting packages.



modlink3  modlink4