The phenomena called cockle are small wrinkles on the paper surface that appear during paper production. This condition poses significant economic and operability problems in the production of magazine paper, as it deteriorates the printabilty of the paper. There are many and varied sources that can lead to cockle, and their detection is often very complicated. In this work a multivariate hierarchical approach is proposed to analyze the cause of cockle. The hierarchy has two levels, the first of which is a three-way decomposition and analysis of the data collected from sections of a paper machine. The second level is a two-way decomposition and analysis between the combined loadings from the three-way decomposition and the measured cockle data. The results show that this approach is capable of identifying the important process sections and process variables, in spite of the large dimensionality of the problem. Data analyzed from two real industrial paper machines, involving several grades of paper, are used to demonstrate the proposed hierarchical approach.

Phenomenological modeling of black liquor evaporators, found in the pulp and paper industry, presents a very challenging task. The physicochemical phenomena that occur do not lend themselves readily to known mechanisms, and in many instances, data to support these hypotheses are difficult to obtain. In this work, a distributed-parameter model (a system of partial differential equations) based on first-principles knowledge about the fluid dynamics and heat-transfer processes is developed for a falling film lamella type evaporator. Primarily, the model describes falling film evaporation on one lamella. The model is solved using orthogonal collocation on finite elements in the presence of scaling and disturbances in the mass feed rate, feed dry solids content, and wall temperature.

This work studies the control of a single falling-film evaporator and a multiple-effect fallingfilm evaporator plant. The specific case studied is the concentration of solids found in the liquor that is part of the production of sulfate (kraft) pulp. The concentrated stream is the feed to the recovery boiler, a unit operation that plays a significant role in the economics of the pulp mill. The disturbance compensation of a single-loop strategy based on proportional-integral feedback controllers is compared against a model-based strategy that uses optimal control theory.

The overall goal of the present study was to identify the high molecular weight species formed during the synthesis and processing of polymeric methylene diphenyl diisocyanate (PMDI) and determine the root cause of the viscosity buildup in these materials. Initial studies focused on the use of MALDI-TOF mass spectrometry to examine the PMDI mixture and MALDI-TOF/TOF CID fragmentation for elucidating the degradation mechanisms of the identified compounds. The low molecular mass portion of the MALDI spectrum was observed to contain the expected PMDI and small quantities of carbodiimides (CDIs). The high molecular mass portion of the spectrum primarily contained 1,3-diazetidine branched carbodiimide dimers, uretonimine branched CDIs, and imino-s-triazine along with low levels of guanidine branched CDIs. The results of this study indicate that the root cause of the observed CDI defects was extensive branch formation through unexpected side reactions catalyzed by iron(III). These reactions lead to a buildup of viscosity which poses a significant challenge during the processing of these materials.