Dispersion Modeling Analysis

Dispersion Modeling Analysis

Industry:
Pulp & Paper

Service Area:
Air Quality Modeling

Client's Challenge

The client planned to make modifications to their Lime Kilns that included installing natural gas burners.  The modification required a construction permit under the Clean Air Act (CAA) Prevention of Deterioration (PSD) permit program.  The modification to the Lime Kilns resulted in a significant increase in nitrogen dioxide (NO2) emissions.  Under the PSD program any criteria pollutant emissions that results in a significant increase (as defined by the program) requires an air dispersion modeling analysis to demonstrate that the increase in emissions will not exceed the National Ambient Air Quality Standards (NAAQS).  At the time of the project the NO2 NAAQS had just been updated to a more stringent 1-hour standard.

ALL4's Solution

ALL4 worked with the client and the Maine Department of Environmental Quality (MDEP) to develop an air quality modeling protocol that outlined all of the procedures that went into the NAAQS air quality modeling demonstration.  ALL4 completed a preliminary NO2 air quality modeling analysis and determined that a non-default option would have to be used in order to demonstrate compliance with the new 1-hour NO2 NAAQS.  The non-default option, which included accounting for NO to NO2 conversion [known as the Ozone Limiting Method (OLM)] in the atmosphere required MDEP and U.S. EPA Region I approval for use.  ALL4 outlined the approach to MDEP and U.S. EPA Region I and got approval for the non-default option as a part of the air quality modeling protocol.

The Results

ALL4 was able to help the client get the construction permit in order to allow them to install the natural gas burners on their Lime Kilns.  While conducting the final NO2 NAAQS air quality modeling analysis it was determined that additional changes to the model and physical changes to emission units at the facility would have take place in order to demonstration compliance with the new 1-hour NO2 NAAQS.  ALL4 identified the need to increase the height of low paper machine stacks in combination with further refining the OLM method by providing justification of in-stack ratios of NO to NO2 for certain processes (i.e., paper machine dryer combustion units).  These changes enable the client to demonstrate compliance with the 1-hour NO2NAAQS as part of the PSD permit.

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