Permitting, Startup, and Repermitting of the Wood Waste Cogeneration Boiler at Kimberly-Clark, Everett, Washington, 1998 Environmental Conference Proceedings

Richard C. Abrams

Environmental Manager

Kimberly-Clark Corporation

Scott Paper Company (now Kimberly-Clark) entered into discussions in 1991 with the Snohomish County Public Utility District about joint construction of a new wood waste boiler with cogeneration capacity. The major area of concern was quickly identified to be increased emissions of NOx. However, an advanced boiler design combined with an ammonia injection deNOx system guaranteed such low NOx emission levels that neither a PSD permit nor offset credits were needed. Permits were obtained, the boiler was built, and startup operations commenced in July of 1995. After startup, however, a problem arose. Ammonia injection caused excessive ammonia slip and the generation of a visible ammonium chloride salt plume.

Something had to be done, but this would require cutting back on the ammonia injection rate, thus increasing NOx emissions which would lead to a permit violation. So the mill sought alternative sources of NOx reduction. The most obvious source of NOx credits at the mill was the ammonium base sulfite recovery boiler, unregulated for NOx but with an uncontrolled emission rate three times that from the wood waste boiler. Trials were performed to add ammonia to the recovery boiler. These were highly successful. The air Regulatory Order from the Department of Ecology was renegotiated to “bubble” the site. Currently the wood waste boiler is running at a reduced ammonia addition rate, which still cuts NOx with no plume generation. The additional required NOx reduction is obtained by ammonia injection to the recovery boiler.