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in 2004 for a potential pulp mill in Tasmania using “accepted
modern technology” (AMT) [3].
Emission point Pollutant Units Annual/monthly average
Recovery boiler PM mg NDm–3 50 @3% O2
TRS mg H2S NDm–3 7@ 3% O2
PCDD/PCDF pg I-TEQ NDm–3 100@ 3% O2
Lime kiln PM mg NDm–3 40@ 3% O2
TRS mg H2S NDm–3 16@ 3% O2
PCDD/PCDF pg I-TEQ NDm–3 100@ 3% O2
All sources NOx kg NO2 adt–1 1.3
All sources SO2 kg S adt–1 0.4
PM = Particulate matter (or dust).
TRS = Total reduced sulfur.
NOx = Nitrogen oxides.
SO2 = Sulfur dioxide.
PCDD/PCDF = Polychlorinated dioxins and furans.
NDm3 = normal cubic meter of dry gas.
pg I-TEQ = pg International Toxicity Equivalents.
Environmental Aspects of Pulp Production
Detailed data on the typical emissions and the impact of different measures
Using BAT, for example, wet scrubbing only or with an electrostatic precipitator,
are available in the European Commission report [2].
10.4
Emissions to the Aquatic Environment
Washing following the pulping and bleaching process requires water, the demand
For which has decreased significantly during the past few decades. This is the
Result of more effective washing procedures with improved equipment, and a
Higher degree of countercurrent water flow. The process, which is typically
described as “loop closure”, became possible with the elimination of chlorine and
Hypochlorite from the bleaching sequences, both of which required a low treatment
Temperature and therefore cold dilution water. ECF bleaching allows a
Rather constant high temperature range to be maintained from brownstock washing
To the dryer machine. The positive side effect is a lower demand for energy to
Heat the process water, while the downside is a higher tendency for scaling, for
Example with barium sulfate and calcium oxalate.
Cleaning of the effluent begins with the sedimentation of suspended solids,
which describes mostly the recovery of fiber losses; this step is labeled as “primary
effluent treatment”.
As mentioned previously, wood handling and debarking should be made without
Generating a higher volume of effluent. If de-icing or log washing is required,
The effluent must be made nontoxic by a biological treatment. An example of this
Is woodyard effluent (rain water), which must be collected and treated biologically
(unlike other rain water).
The pulping liquor should be recovered very effectively. Screening and brownstock
Washing should be conducted in a closed loop mode. Spills and leakages
Should be avoided by an optimized process control, but if they do occur enough
Temporary storage volume and evaporation capacity must be made available to
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Emissions to the Atmosphere | | | Deal with these problems. Brownstock washing following an oxygen delignification |