Kaarlo Nieminen

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Hot water extraction of wood at elevated temperatures may be a suitable method to produce hemicellulose-lean pulps and to recover xylan-derived products from the water extract. In this study, water extractions of birch wood were conducted at temperatures between 180 and 240 °C in a batch reactor. Xylan was extensively removed, whereas cellulose was partly(More)
We have developed mathematical models for evaluating the atmospheric dispersion of selected chemical warfare agents (CWA), including the evaporation and settling of contaminant liquid droplets. The models and numerical results presented may be utilised for designing protection and control measures against the conceivable use of CWA's. The model AERCLOUD(More)
The amount of residual lignin in birch wood after a hot water extraction in a batch reactor was investigated as a function of extraction temperature and time. A kinetic model fitting the experimental data was then developed to explain delignification of wood during a hot water treatment. Results showed that delignification kinetics involves simultaneous(More)
The fatigue behavior of the wood fiber cell wall under mechanical treatment in refining was simulated dynamically using a finite element method. The effect of the amplitude and frequency of impacts on the mechanical breakdown of the fiber wall structure was examined. The proposed model of the fiber cell wall was constructed from elementary microfibrils in(More)
The present study reports on a revised kinetic model for alkaline degradation of cellulose accounting for primary peeling/stopping reactions as well as for alkaline hydrolysis followed by secondary peeling. Oxalic acid pretreated cotton linters was utilised as the model substrate for the prehydrolysis-soda anthraquinone process. The main emphasis was(More)
The effect of the bar leading edge form profile on the shortening of softwood fibres is examined. The leading edge form profile is described numerically as the radius of fitted curvature having the shape of a circle, or as an angular form profile having certain side dimensions. The results indicate that when the leading edge form profile has a radius(More)
Hemicellulose lean pulps are a raw material source for numerous high value products. We have previously presented the IONCELL-P(ulp) process, a hemicellulose extraction method, based on a binary mixture of ionic liquid and water. The IONCELL-P process does not suffer from yield losses or polymer degradation and retains the Cellulose I crystalline form. In(More)
A mathematical model is presented, in which the yield loss (YL) and the decline in polymerization of carbohydrates is comprehended. The model is applicable to the treatment of cellulose and hemicelluloses in alkaline media, and it features the actions of peeling, stopping, and alkaline hydrolysis of the polymer chains. The peeling reaction is further(More)
The accessibility and reactivity of cellulose are key parameters in its conversion into various products. Several indirect measures, such as water retention value (WRV), fiber saturation point (FSP) and specific surface area (SSA), are often used to characterize cellulosic samples for their reactivity. In this paper, we report on using oxidation with(More)