Modern pulp mills tend to apply cleaner and environment friendly
processes generally by recycling and reusing various streams into the
evaporation system and the reduction of discharges. This kind of closure
leads to a build-up of non-process elements (NPEs) mainly in the
chemical recovery system. Chemicals which accumulate in the mill
cycles originate either from the wood raw material, process water
and make-up chemicals. Natural purging places, generally referred as
kidneys, are associated to the removal of these elements as green liquor
dregs, grits or lime mud. The purpose of this study is to evaluate
the routes of NPEs in a modern eucalyptus kraft pulp mill. An extensive
sampling campaign was carried out at the studied mill. Samples
were taken from all the main process streams to achieve an overall
picture of the inputs, outputs, and enrichment in the mill. Complete
mass balances were accordingly constructed for the entire mill. The
results of this study can be utilized in the non-process element management
at the mill and they serve as a good basic material for the
further mill specific simulations.

Authors’ references:
1. Silvicultural Projects Department - LATU - Av. Italia 6201, C.P. 11500 Montevideo, Uruguay,
2. Oy Metsä-Botnia Ab, Finland
3. UPM Fray Bentos mill – Ruta Puente Puerto Km 307 Fray Bentos, Uruguay
Corresponding author: Javier Doldán – E-mail: jdoldan@latu.org.uy

O PAPEL vol. 72, num. 7, pp. 47 - 52 JUL 2011