Computational Fluid Dynamic (CFD) Model
General Overview

Detroit Stoker Company (DSC) creates computer models of clients' industrial furnaces as part of DSC engineering process design to improve system performance and reduce emissions. A technique known as Computation Fluid Dynamics (CFD) Modeling is used to estimate flue gas properties within a unit and to assist in determining the design and operation of primary and secondary air systems to help characterize proper emission controls and performance improvements. Once constructed, the computer model can be modified to estimate the effects of changes in design and operating conditions.

The model is crated using proprietary simulations code GLACIER CFD with specific proprietary sub-routines, which perform both calculations of gas properties and particle phase solutions.

The model contains innumerable cells that define the geometry of the client's unit. Each cell is described by a set of coefficients, which characterize the flue gas properties. These properties include temperature, density, velocity, and chemical composition. Certain cells are identified as mass or energy sources, other as places where mass or energy leaves the system. These mass and energy balances are repeatedly calculated on all the cells until the coefficients no longer change or converge. The converged data is then review.

This CFD model also includes particle mechanic calculations which are computed by following the mean path of discrete groups of particles or particle clouds. The particle reaction processes include fuel devolatilization, char oxidation, and gas particle interchange. These computations contain actual fuel distribution test data compiled from DSC's fuel spreader test facility in Monroe, Michigan. The way the solid fuel is injected into the furnace, by the spreader, is an important aspect of combustion modeling. The particles are started at the exit plane of the spreader/distributor, thus incorporating the suspension reactions occurring from flight between the spreader and the bed. DSC's fuel spreader test facility is used as validation for fuel particle deposition rates and particle size distribution.

In a typical project, the client's unit is first modeled without design changes or operating changes to determine the baseline temperature, flow behavior, and flue gas conditions. Once these specific behaviors are identified, a model simulating new overfire air injection is performed. The overfire/primary air configurations are adjusted to optimize flow behavior and flue gas conditions. Changes to baseline emission results are compared.

Input data describing the physical unit and its operation must be supplied by the client. This data must be sufficient to establish the boiler dimensions as well as mass and energy inputs and outputs for the evaluation conditions. This includes a set of side and front sectional profiles, burners, existing secondary air nozzle sizes and locations, gas flow paths, refractory lining, tube spacing, and any other factors that influence the system performance.

Operations data must include mass flow rates and temperatures for fuels and combustion air. The fuel heating value and chemical composition are required for the fuel. If specific information is not available, then a best estimate should be developed. Additional process information may be requested, by DSC, if required to properly complete the model.

Actual field data should be provided when available. This data provides a basis for interpretation of model results and also allows the model to be fine-tuned to the client's unit to better represent true operating conditions.

A report describing the final model results will be prepared and provided to the client. The report will include a representation of the model results, brief description of the design or operating parameter modifications and supplemental discussion addressing data interpretation and conclusions. Every effort will be made to supply the client with sufficient documentation to adequately represent the model results.