Process control of chemicals in fibre furnishes

Durgueil, Eric Jacques (1994-12)

Dissertation (D. Phil.) -- University of Stellenbosch, 1994.

Thesis

ENGLISH SUMMARY: In a competitive and environmentally concerned business atmosphere, the role of wet end chemistry has become extremely important to a paper mill's profitability and long term viability. In the past decade, understanding of the papermaking chemistry has improved and sensors for measurement of the various variables on-line have been developed. Some of these variables are reviewed as well as the instruments which have been evaluated or developed for on-line measurement during this investigation. Process control loops to maintain control over the wet end chemistry during stock preparation are presented as well as an overall strategy to combine all the control variables. The primary thrust behind the control of the chemicals added is to minimise process variability and improve product uniformity as illustrated in this investigation. A reduction in chemical cost and paper losses coupled with improved customer satisfaction are some of the benefits obtained. More work is still required to fully master the multiple interactions and changing statesof wet end chemistry and this will be attained with the improvement of existing or development of new on-line sensors.

AFRIKAANSE OPSOMMING: In In industrie waar streng kompetisie geld en besorgdheid oor die omgewing van groot belang is,speel die toediening van chemiese hulpmiddels by die natkant van In papiermasjien In baie belangrike rol ten opsigte van die winsgewendheid en ·Iewerisvatbaarheid van In papierfabriek. In die afgelope dekade het die begrip ten opsigte van papierchemie toegeneem en sensors vir die meet van veranderlikes in die produksielyn is ontwikkel. Sommige van hierdie veranderlikes word beoordeel sowel as die instrumente wat ge-evalueer of ontwikkel is vir metings in die produksielyn in die loop vanhierdie ondersoek. Prosesuitlegte om beheer oor die chemiese toediening.s gedurende die voorbereiding van die pulpmengsels uit te oefen, word aangebied. In Oorhoofse strategie om al die proses-veranderlikes te kombineer, word terselfdertyd voorgestel. Die minimiseiing van prosesveranderlikheid en die verbetering van die uniformiteit gedurende produksie, is van die groot dryfvere agter die beheer wat uitgeoeferi moet word oor die byvoeging van chemikaliee. Laer chemikaliee-kostes, 'n· vermindering in papierverliese en gepaardgaande tevredenheid van klante is van die voordele wat verkry word. Verdere navorsing isnodig om die komplekse interaksies en veranderlikes van die chemie betrokke by die natkant van In papiermasjien ten volle te bemeester. Oit kan bereik word deur die verbetering van bestaande sensors of die ontwikkeling van nuwe in-Iyn sensors.

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