Journal
APPLIED SCIENCES-BASEL
Volume 9, Issue 10, Pages -Publisher
MDPI
DOI: 10.3390/app9102169
Keywords
black liquor; solids content; time-domain NMR; low-field NMR; NMR relaxation; online; H-1 spin-spin relaxation rate
Categories
Funding
- Centre for Economic Development, Transport and the Environment (ELY Centre) for South Savo (Finland)
- European Regional Development Fund (ERDF)
- Suur-Savon Energiasaatio sr
- [A73842]
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Black liquor, a valuable by-product of the pulp production process, is used for the recovery of chemicals and serves as an energy source for the pulp mill. Before entering the recovery unit, black liquor runs through several stages of evaporation, wherein the solids content (SC) can be used to control the evaporation effectiveness. In the current study, the time-domain nuclear magnetic resonance (TD-NMR) technique was applied to determine the SC of black liquor. The TD-NMR system was modified for flowing samples, so that the black liquor could be pumped through the system, followed by the measurement of the spin-spin relaxation rate, R-2. A temperature correction was also applied to reduce deviations in the R-2 caused by the sample temperature. The SC was calculated based on a linear model between the R-2 and the SC values determined gravimetrically, where good agreement was shown. The online TD-NMR system was tested at a pulp mill for the SC estimation of weak black liquor over seven days without any fouling, which demonstrated the feasibility of the method in a harsh industrial environment. Therefore, the potential of the TD-NMR technology as a technique for controlling the black liquor evaporation process was demonstrated.
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