Abstract Pressure screening, nowadays the most widely used method for cleaning pulp, has been traditionally investigated as a debris removal process. The aim of this thesis, however, was to study it with a view to the fractionation of pulps, examining systematically and extensively the effects of screening parameters on fractionation under actual working conditions in order to provide an insight into its possibilities and limitations as a fractionation method. The experimental work was performed with a full-scale two-stage pressure screen connected to an industrial TMP process. Fractionation of the pulp was analysed in terms of consistency, freeness, optical fibre length distribution, coarseness index and Bauer-McNett fractions. Two sampling systems were used during the screening experiments, manual and semiautomatic. The latter was assessed to be more reliable, as reflected in lower stochastic variation and the absence of a systematic bias in the mass balance errors over the screen. The poorer reliability of the manual sampling system was offset by the large number of screening tests, however. The results of the screening experiments showed that with a given design of the screen plate, the separation of each fraction was dependent almost exclusively on the mass and volumetric reject rates. The mass flow of fines, defined as the Bauer-McNett P200 fraction, was dependent mostly on the volumetric reject rate, while the mass flow of fibrous fractions (R200, R50, R30, R16) depended mostly on the mass reject rate. The mass reject rate obtained in pressure screening was a result of the choice of operating parameters, but fractionation efficiency could not be affected by using different combinations of these parameters (feed consistency, rotor tip speed and slot velocity) if the mass and volumetric reject rates were kept constant. The slot width together with the contouring of the screen plate affected the fractionation efficiency as compared with the situation at constant mass and volumetric reject rate. Increased fractionation was obtained by reducing the slot width and contouring. The pulp passage ratio, which combines the mass and volumetric reject rates into one parameter, was found to be a expedient way of expressing the fractionation of pulp, as it was possible to present fractionation uniformly as a function of this ratio. The change in freeness was found to correlate quite well with that in Bauer-McNett fractions, and it was a good indicator of fractionation efficiency in screening. Apart from fractionation according to length (or Bauer-McNett fractions), the slotted pressure screen was also found to classify the fibres according to their coarseness. The coarseness difference was partially dependent on the fibre length, but additionally the coarseness in the accept pulp for any given fibre length class was always lower than that in the reject pulp. The difference obtained seemed to depend on the passage ratio of the pulp. This thesis provides new information for the modelling of pulp quality and the design of fractionation experiments, fractionation processes and screen room control strategies.

Объектом исследования является прибор DIY Vector Network Analyzer UVNA-63. Целью работы является разработка программного обеспечения для DIY Vector Network Analyzer UVNA-63. В данной работе описана разработка программного обеспечения в программе Matlab. Описана работа разработанных функций измерения. Описана работы разработанного графического интерфейса. Доработка методики лабораторных работ. Актуальность работы обоснована отсутствием программного обеспечения для проведения измерений на векторном анализаторе цепей, который имеется в распоряжении кафедры и может быть задействован в учебном процессе. Разработанное ПО позволит проводить измерения, производить калибровку аппарата, сохранять полученные данные в различных форматах, отображать полученные данные на графике и устанавливать маркеры на графике. Область применения является учебная сфера. С помощью разработанного программного обеспечение возможно выполнять лабораторные работы и измерять исследуемые устройства. / The object of research is the device DIY Vector Network Analyzer UVNA-63. The purpose of the work is to develop software for DIY Vector Network Analyzer UVNA-63. This paper describes software development in Matlab. The operation of the developed measurement functions is described. The work of the developed graphical interface is described. Refinement of the laboratory work methodology. The relevance of the work is justified by the lack of software for carrying out measurements on a vector network analyzer, which is at the disposal of the department and can be used in the educational process. The developed software will make it possible to carry out measurements, calibrate the apparatus, save the obtained data in various formats, display the obtained data on a graph and set markers on the graph. The scope is the educational area. With the help of the developed software, it is possible to carry out laboratory work and measure the investigated devices.