Papermills manufacturing recycled board usually face severe calcium carbonate scaling problems. We present a mass flow balance simulation of this papermaking process (PS2000, G2-based), coupled with a chemical reaction engine (IPhreeqc). The simulation allows predicting the pH and calcite saturation index throughout the process. Developed chemistry modules can simulate anaerobic microbial activity in the process waters, together with local contact with the atmosphere. Also, chemistry models of the integrated wastewater treatment (with anaerobic and aerobic treatment steps) are developed. The coupled simulation accurately describes the scaling tendency of process waters. This makes it possible to study curative solutions to the scaling problems in recycled board mills. The effect of a biocide treatment is simulated and discussed. This is predicted to largely reduce scaling in the wastewater treatment and limit the amount of generated sludge.
Existing industrial Kraft mills can be the basis for
the deployment
of lignin valorization into added-value products. Lignin can be recovered
by its precipitation from black liquors. However, it is of tremendous
importance to better determine the impact of lignin extraction on
the overall chemical and energy balances of the mill. Therefore, we
have sampled the black liquors from an industrial Kraft mill (treating
softwood), which is a typical European mill. Lignin has been precipitated
by CO2 at a pilot scale in order to quantify the consumption
of chemical commodities. Black liquors and lignin cakes were comprehensively
characterized in order to evaluate the mineral and organic balances.
The experimental results were implemented in a global simulation of
the industrial Kraft mill in order to assess the impact of lignin
recovery from the black liquor on the chemical and energy balances.
The additional consumptions of chemicals are 258–266 kg of
H2SO4 and 163–195 kg of NaOH/t of produced
lignin. The pulp mill capacity can be increased by 1.5 t of pulp/t
of lignin to overcome the steam loss (i.e., 6.7–7.1 t of steam/t
of lignin).
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