Thesis (Ph.D.)--University of Tulsa, 1990. / Bibliography: leaves 86-91.

Thesis (Ph. D.)--University of Washington, 1991. / Vita. Includes bibliographical references (leaves [162]-168).

Thesis (M.Eng. (Chemical Engineering)) -- University of Pretoria, 2007. / Includes bibliographical references (leaves 69-73)

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (leaves 82-87).

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (p. [119]-126).

Thesis (Ph. D.)--The University of Wisconsin--Madison, 1972. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Thesis (Ph.D.)--McMaster University, 2005. / Includes bibliographical references (leaves 180-190). Also available online.

As the emission legislation becomes more stringent, higher demands are put on the aftertreatment system in trucks. For dealing with nitrous oxides, AdBlue® (urea–water solution) is injected into the exhausts which evaporates and reduces nitrous oxides to nitrogen. At low exhaust temperatures, it is more difficult to evaporate the injected AdBlue® as the exhausts contain less energy. The injected solution may instead form a wall film. In this wall film, side reactions can occur which leads to the formation of deposits. This thesis aims at understanding how and when wall films and deposits are formed. To achieve this, a test rig that allowed visual and infrared observations of the process and variation of governing properties was designed and built. The results show that thicker plates can sustain higher dosages than thinner plates since the temperature drop and film area are smaller for the thicker plate. It was also observed that at plate temperatures >340 °C, the water in the impacting spray evaporated, leaving a urea dust in the gas phase. It is also clear that deposits form faster at higher gas temperatures (> 350 °C) compared to at lower temperatures (200–250 °C). The deposits form at the edge of the wall film in a region with a temperature higher than in the middle of the wall film. At lower temperatures, a wall film that spreads out over a very large area is formed and after a longer time period, deposits form at obstacles and at the wall film edge. Experiments for 2 h at lower temperatures left approximately the same amount of deposits as experiments for 30 min at higher temperatures. / När lagkraven blir strängare sätts högre krav på efterbehandlingssystemet i lastbilar. För att få bort nitrösa gaser injiceras AdBlue® (urea–vattenlösning) in i avgaserna vilken förångas och reducerar de nitrösa gaserna till ofarligt kväve. Vid låga avgastemperaturer är det svårare att förånga den injicerade AdBlue®–lösningen då avgaserna innehåller mindre energi. Den injicerade lösningen kan istället bilda en väggfilm. I denna väggfilm kan sidoreaktioner ske vilket leder till bildning av utfällningar. Detta examensarbete syftar till att öka förståelsen för hur och när väggfilmer och utfällningar bildas. För att uppnå detta designades och byggdes en testrigg i vilken visuella och infraröda observationer kan göras och influerande parametrar varieras. Resultaten visar att tjockare plåtar kan utstå högre doseringar jämfört med tunnare plåtar, eftersom lägre temperaturminskning och film area uppmätts för den tjockare plåten. Det sågs också att vid plåttemperaturer >340 °C så förångades vattnet i AdBlue®-lösningen först och efterlämnade ett ureadamm i gasfasen. Det konstaterades också att utfällningar bildas snabbare vid högre gastemperaturer (> 350 °C) jämfört med vid lägre temperaturer (200–250 °C). Utfällningarna bildas vid kanten av väggfilmen i en region som har en temperatur som är högre än den i mitten av väggfilmen. Vid lägre temperaturer bildas en väggfilm som sprider ut sig över en stor area och med tiden bildas utfällningar vid hinder och vid filmkanten. Experiment under 2 h vid låg gastemperatur gav jämförbara mängder utfällningar som experiment under 30 min vid högre temperatur.

Xylan dissolved during kraft cooking and later redeposited on fibre surfaces has been shown to give higher pulp yield and better strength properties. This is economically interesting from an industrial point of view. Many studies have been done to investigate xylan behaviour during kraft cooking, to discover the xylan-cellulose attachment mechanism, to find the optimal xylan retention or adsorption process, and to discover relations between xylan structure and strength enhancement. Most of them have concentrated on hardwood xylan. However, softwoods are the major raw materials for the pulp industries in the northern hemisphere. Earlier studies have shown that the xylan characteristics, rather than simply the amount of xylan, influence the strength-enhancing effect of xylan. To obtain optimal utilization of spruce xylan as a strength enhancer, it is essential to know what the beneficial xylan characteristics are and how cooking conditions affect the characteristics. In this study, kraft cooking of spruce chips was performed under varied cooking conditions and the xylan in the black liquor was precipitated and characterized. It was found that dissolved spruce xylan had a much higher amount of bound lignin compared to previous studies on xylan dissolved from hardwoods. Increased cooking temperature increased the dissolution rate of xylan. The lower alkali charge and higher ionic strength of the cooking liquor resulted in a lower amount of dissolved xylan. Apart from the effect of the amount, cooking conditions also affected substitution of dissolved xylan. Higher temperature and higher ionic strength led to a lower amount of MeGlcA, while the MeGlcA amount of dissolved xylan was preserved during lower alkali cooking. By distinguishing how different cooking conditions affect the characteristics of the xylan dissolved in the black liquor, xylans with different structures were designed to study their effects on pulp strength, that is, the addition of black liquors with certain known xylan characteristics in the kraft cooking process. It was found that the best effect of xylan on tensile strength occurred when the xylan penetrated some distance into the subsurface of the fibre wall. Both low molecular weight and high degree of substitution lowered the tendency of xylan to aggregate, which enabled the dissolved xylan to penetrate some distance into the exposed fibre surface. Upon beating, this xylan was exposed, thus facilitating improvement of fibre-fibre joint formation, which led to increased tensile strength. / <p>QC 20130326</p>

In this study photocatalytic oxidation was investigated as a potential treatment method of VOC emissions from industrial plants. This was done by designing an experimental setup and a photocatalytic reactor for screening of photocatalysts (TiO2). The performance of commercial TiO2 and synthesized TiO2 (pure and Ni-doped) for degrading acetaldehyde when exposed to UV-C light was evaluated at fix reaction conditions. Also, procedure of coating TiO2 on aluminum and stainless steel as well as their stability performance was investigated in the study. For comparison of photocatalysts aluminum was chosen as support material since it showed highest stability at reaction conditions.  The results show that photocatalysts with a high anatase content and high specific surface area present enhanced photocatalytic performance. Commercial TiO2 show significantly higher photocatalytic performance than synthesized TiO2. This may be influenced by higher coating stability presented for commercial TiO2. For synthesized TiO2 non-doped samples present significantly higher performance than Ni-doped TiO2. However, because of coating instabilities it is difficult to determine if this was observed difference in performance was only caused by photocatalytic performance. / I detta arbete undersöktes fotokatalytisk oxidation som potentiell gasreningsteknik för industriella utsläpp av flyktiga organiska kolväten. En experimentell uppsättning konstruerades tillsammans med en fotokatalytisk reaktor designad för att jämföra olika fotokatalysatorers (TiO2) prestanda. Prestandan för både kommersiella fotokatalysatorer samt fotokatalysatorer syntetiserade i arbetet (TiO2 samt Ni-dopad TiO2) jämfördes för att bryta ned acetaldehyd under konstanta reaktionsförhållanden samt bestrålning av UV-C. Aluminum och rostfritt stål undersöktes som supportmaterial för TiO2. För undersökning av olika fotokatalytorers prestanda användes aluminum på grund av en högre stabilitet vid undersökta reaktionsförhållanden. Resultaten från jämförelsen av olika fotokatalysatorer visar att en hög andel anatas form av TiO2 samt en hög specifik ytarea ger en förbättrad fotokatalytisk prestanda. Kommersiell TiO2 visade signifikant högre fotokatalytisk effekt än syntetiserad TiO2. Detta kan bero på en högre stabilitet av TiO2-beläggning på aluminum för kommersiell TiO2 gentemot syntetiserad och inte nödvändigtvis bero av enbart fotokatalytisk aktivitet. För syntetiserad TiO2 visar dopning med Ni signifikant lägre aktivitet än för icke dopad TiO2. På grund av instabilitet i beläggningen av TiO2 på supportmaterialet kan en påverkan av detta inte uteslutas.