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PHOENICS Demonstration;

Incineration unit (1997)

The Problem:

The purpose of a secondary combustion chamber in an incineration unit is to prevent the release of certain chemicals emitted by the incinerator from entering the atmosphere. One method of doing so is to raise the gases to such a temperature in the presence of oxygen, as will destroy the chemicals by pyrolysis and/or oxidation.

Computational details:

The combustor's overall dimensions are approximately 2000mm x 950mm x2500mm. There is a primary gas inlet and a secondary air inlet. For the purposes of the demonstration, a single-phase process is assumed and combustion is represented by the "mixed is burned" principle.

The geometry is created using PHOENICS-2.2 and uses a Cartesian 3D grid. The case was run on a 133MHz Pentium PC .

The results:

The plots show the fluid residence time, composition as represented by the family of species, temperature and velocity within the incinerator and at the outlet.

  1. Iso-surfaces of residence-time

  2. Contours of residence times at centre plane

  3. Contours of CO mass concentration at centre plane

  4. Contours of CO2 mass concentration at centre plane

  5. Contours of H2O mass concentration at centre plane

  6. Contours of O2 mass concentration at centre plane

  7. Contours of N2 mass concentration at centre plane

  8. Contours of fluid temperature at centre plane

  9. Velocity vectors at centre plane

  10. Velocity vectors at inlet plane

  11. Temperature vectors at centre plane

No account of heat loss through the incinerator walls is taken. the combustion model employs constants for some material properties, such as specific heat capacity.

For a real fluid, these will vary with both species concentration and with temperature. The variation of specific heat is omitted for the purpose of a demonstration, but this could be simply intrduced.