Project Synopsis

Provide air pollution control systems process modeling assistance in order to improve and optimize waste incineration facility performance.

Project Summary


The client operates a hazardous waste incineration facility.  The incineration process has an air pollution control system (APC) to remove contaminants from the combustion gases generated during the incineration process.  The APC consists of three (3) wet scrubbing steps – saturator, condenser, and high energy (venturi) scrubber, followed by a baghouse filtration system.  Draft for the combustion and APC processes is provided by an induced draft fan.  Solids in the combustion gas accumulate and plug the process side of the plate-and-frame heat exchangers utilized in the condensing step.  Plugged heat exchangers lead to poor heat transfer and higher condenser outlet temperatures, which in turn lead to reduced system capacity.

Process Engineering Associates, LLC (PROCESS) was contracted by the client to assist the client’s process engineer in modeling the overall APC process utilizing PROCESS‘ (and the client’s) licensed commercial computer process simulation software, Chemstations’ CHEMCAD.  This APC process model would then be used by the client to determine the best and most economical solids removal process for restoring system capacity.

PROCESS performed the following tasks in support of this project:

  • Worked with the client’s process engineer, in PROCESS‘ Oak Ridge, Tennessee office, to finalize the APC model.  This involved revising the client’s original model to incorporate some of PROCESS‘ modeling knowledge to improve the functionality and accuracy of the APC model.  These revisions included:
    • Utilizing dividers, component separators, and feedback controllers to accurately mimic real world operations and departures from saturation, solids capture efficiency (via solids bypassing), and gas exit temperatures.
    • Utilizing a series of feed forward controllers to maintain the APC system water balance in a counter-current (gas versus water) system.
    • Utilizing feed forward controllers to predict and maintain appropriate scrubber liquor blowdown for each individual scrubber step – saturator, condenser, and high energy scrubber – within the overall process mass and energy balance.
    • Utilizing a Gibbs reactor unit operation in ChemCAD to model the gas Reheater burner.  The Reheater is used to maintain the gas temperature, post scrubbers, above its dew point so as not to blind the baghouse with a water and dust blockage.
  • Once the APC model was revised and shown to match current conditions, the project team (PROCESS and the client’s engineers)  performed the following tasks:
    • Sensitivity analysis to determine the effect of saturator outlet gas temperature on condenser outlet gas temperature.
    • Sensitivity analysis to determine the effect of condenser outlet gas temperature on final stack flow and thereby overall system capacity.
    • Sensitivity analysis on the combustion gas solids input to the condenser column liquor recirculation loop to determine the variability of solids input into a proposed clarifier.
  • Provided the final simulation for the client’s internal use as well as an Excel spreadsheet summarizing the results from the various sensitivity analyses.

Industry Type

  • Hazardous Waste Disposal

Utilized Skills

  • Advanced process simulation
  • Thermal oxidation and offgas treatment unit operations

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