"Port Townsend Paper Corporation created an Odor Survey Team during the summer of 1993. The purpose of the team was to determine the mill emission sources causing odors offensive to community residents."

"
Local newspapers published information on the
project and a hot line was set up to take odor reports and complaints.

The team met with the callers to fill out an informational survey and ask them to take an odor sample test.

Five emission odors captured in Tedlar bags were compared to the perceived odors
experienced by the caller.

The compiled information will allow the mill to concentrate future efforts on the emission sources that have the greatest impact in the community.


Port Townsend Paper Corporation is a kraft mill and like other kraft mills is characterized
by malodorous organic sulfide gases. Over the years, numerous complaints have been
directed toward the mill concerning the mill odor.

In 1992 the Washington Department of Ecology held a series of public meetings and concluded that most townspeople are concerned with the odors caused by local pulp and paper mills. It was evident that few people knew what was causing the aroma or its impact on the community.

A survey team was organized to:

1. Identify odors
2. Identify odor sources
3. Register complaints and concerns
The identified odor sources could then be examined more closely and possible remedies
could be determined.

The P.T.P.C. project was modeled after the ITT Rayonier P.A. survey concluded in 1992.
Emission Sources Eight major odor emission sources were found. These odors were observed and investigated by the Odor Survey Team It was found that four of the eight odors were similar to each other so all four were grouped into one category.

This distinct odor was synonymous with the M&D digester. The M&D digester Esco valve vents are the largest and most pungent of the four sources with similar odors.

The remaining four distinct mill odor sources are: the power boiler, the recovery furnace,
the lime kiln, and the aeration stabilization basin (ASB). The emission sources from
which samples were taken for the survey are described in the following paragraphs.
M&D Digester.

The M&D digester is a continuous digester used to produce pulp. The digester is
operated under pressure while a rotating Esco valve is used to feed the sawdust into the
digester. As the valve rotates, some vapors from inside the digester are forced out
through the valve and escape to the atmosphere.

Included in this odor category is the brown stock washer vent, smelt dissolving tank vent
and the digester fill vent. Each of these sources smell similar to a very dilute sample
from the M&D digester vents.


Power Boiler

The power boiler uses hog fuel (bark and wood scraps not used in the pulping process) as
its primary fuel source to produce heat and steam for the mill. It also bums oil and
primary treatment sludge as supplementary fuel.

The combustion products from the firing chamber are directed through a wet scrubber to
remove the particulate and ash from the air. The extremely hot air passing through this
wet scrubber produces a large visible steam plume coming from the stack.

Recovery Furnace

95% of the pulping chemicals used to make kraft paper are recyc1ed within the recovery
furnace. Most of the sulfur containing compounds which enter the furnace are fully
oxidized and recovered for reuse in the process.

A trace of S02 is produced by this combustion process but the concentration of 10 to 50 ppm is well below the limit of 200 ppm set by the Washington Department of Ecology.

The new electrostatic precipitator, completed in May, 1993, charges and removes fine particulate matter from the recovery furnace emissions at over 98% efficiency. Total Reduced Sulfur (TRS) gases exiting the furnace are generally below 10 ppm

Lime Kiln

The lime kiln serves two functions for the mill. Its main purpose is to convert calcium
carbonate precipitate (obtained from the white liquor c1arifier) into calcium oxide using
high temperatures (2200° to 2400°F).

The calcium oxide is then used to produce white liquor. The lime kiln also serves as an incinerator for odor gases that the mill collects from other processes. Odor gas compounds are broken down and oxidized to form compounds that can be scrubbed form the exhaust using a Venturi scrubber system.

Aeration Stabilization Basin (ASB)

The ASB is a series of treatment channels that clean the water used in the pulp and paper
making process. This secondary or biological treatment is nothing more than a
duplication of nature's own purification process, except that it is carried out under
contained and controlled conditions at accelerated rates.

Under aerobic conditions, micro-organisms (mostly bacteria and fungi) consume oxygen to convert wastes into the ultimate end products of carbon dioxide and water.

The anaerobic bacteria take over and continue biological action producing methane and hydrogen sulfide.

Pulp and paper mill wastes are essentially non-toxic following this biological treatment.

There are two components for the peculiar ASB odor. For one, sulfur gases produced
from biological action is highly noticeable in low concentrations. Secondly, foul vapors
condensed in the mill get dissolved in the mill effluent. This condensate is transported to
the ASB where the mechanical aeration devices free the dissolved odor gases into the
atmosphere."

Source
"Port Townsend Paper Corporation Odor Survey Report
http://www.docstoc.com/docs/155832734/Port-Townsend-Paper-Corporation-Odor-Survey-Report

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