<p>Carbon dioxide (CO₂, R-744) has been identified as a promising alternative to conventional working fluids in a number of applications due to its favourable environmental and thermophysical properties. Previous work on residential CO₂ heat pumps has been dealing with systems for either space heating or hot water heating, and it was therefore considered interesting to carry out a theoretical and experimental study of residential CO₂ heat pump systems for combined space heating and hot water heating – so-called integrated CO₂ heat pump systems. The scope of this thesis is limited to brine-to-water and water-to-water heat pumps connected to low-temperature hydronic space heating systems..</p>

<p>The main objective of this thesis is to contribute to the understanding of sea ice processes in the Northern Sea Route, mainly with use of remote sensing data from Synthetic Aperture Radar (SAR). Multivariate data analysis is the main tool used in this work. SAR signatures of different sea ice types and open water in winter were studied, and separation of water and sea ice types using different multivariate regression algorithms was done. Polynya areas along the coasts were investigated. Structure characteristics of different sea ice types and open water were investigated. The summer sea ice in the Laptev Sea was also studied. The Laptev Sea as well as other parts of the Northern Sea Route are expected to become important areas for future oil and gas exploration and exploitation.</p><p>Results from a statistical analysis of 105 SAR images and corresponding meteorological data are presented, covering parts of the Pechora and Kara Sea in the Russian Arctic. Wind, temperature and other variables for the SAR sample areas were collected, and a manual sea ice classification of the SAR samples was performed. All variables were input to different multivariate regression techniques. First, ice was separated from water. Next, young ice was separated from rough first year ice. The study indicated that the mean and standard deviation of the backscattering coefficients together with temperature values were the most important information to separate the classes. </p><p>SAR image data has been used to investigate specific polynya events in detail, addressing widths, refreezing and duration. A polynya index derived from ice concentration data from Special Sensor Microwave Imager (SSM/I) was used in the description of polynya variability during a decade (1990-1999) in response to atmospheric forcing. The observed polynya widths were compared to the results from a simple one-dimensional polynya model. The best agreement was found for the Vize and Ushakova Island and the Novaya Zemlya coast due to low variability of polynya widths. Less agreement was found at the Yamal and Taymyr due to high polynya variability not captured by the model.</p><p>Sample areas of open water, young ice and first year ice were investigated by the angle measure technique (AMT) and classified by multivariate regression. The separation of ice and water was relatively sucessfull, opposed to the separation of young ice and first year ice. The individual samples were best separated on one pixel scale, corresponding to backscattering differences between neighboring pixels. The AMT produce mean angle information that to some extent can be related to ice type.</p><p>Finally, a demonstration and validation study of the capabilities of SAR imagery to provide accurate ice information to support ice navigation was carried out. The experiment was set up in August-September 1997. RADARSAT and ERS-2 SAR images combined with SSM/I data and in situ observations from icebreakers were used. These data were used to analyze ice concentration, ice types, ice drift and other ice features present in this period. The capability of RADARSAT ScanSAR and ERS SAR images to determine these ice parameters during late summer conditions in the Laptev Sea area is discussed.</p>

The main objective of this thesis is to contribute to the understanding of sea ice processes in the Northern Sea Route, mainly with use of remote sensing data from Synthetic Aperture Radar (SAR). Multivariate data analysis is the main tool used in this work. SAR signatures of different sea ice types and open water in winter were studied, and separation of water and sea ice types using different multivariate regression algorithms was done. Polynya areas along the coasts were investigated. Structure characteristics of different sea ice types and open water were investigated. The summer sea ice in the Laptev Sea was also studied. The Laptev Sea as well as other parts of the Northern Sea Route are expected to become important areas for future oil and gas exploration and exploitation. Results from a statistical analysis of 105 SAR images and corresponding meteorological data are presented, covering parts of the Pechora and Kara Sea in the Russian Arctic. Wind, temperature and other variables for the SAR sample areas were collected, and a manual sea ice classification of the SAR samples was performed. All variables were input to different multivariate regression techniques. First, ice was separated from water. Next, young ice was separated from rough first year ice. The study indicated that the mean and standard deviation of the backscattering coefficients together with temperature values were the most important information to separate the classes. SAR image data has been used to investigate specific polynya events in detail, addressing widths, refreezing and duration. A polynya index derived from ice concentration data from Special Sensor Microwave Imager (SSM/I) was used in the description of polynya variability during a decade (1990-1999) in response to atmospheric forcing. The observed polynya widths were compared to the results from a simple one-dimensional polynya model. The best agreement was found for the Vize and Ushakova Island and the Novaya Zemlya coast due to low variability of polynya widths. Less agreement was found at the Yamal and Taymyr due to high polynya variability not captured by the model. Sample areas of open water, young ice and first year ice were investigated by the angle measure technique (AMT) and classified by multivariate regression. The separation of ice and water was relatively sucessfull, opposed to the separation of young ice and first year ice. The individual samples were best separated on one pixel scale, corresponding to backscattering differences between neighboring pixels. The AMT produce mean angle information that to some extent can be related to ice type. Finally, a demonstration and validation study of the capabilities of SAR imagery to provide accurate ice information to support ice navigation was carried out. The experiment was set up in August-September 1997. RADARSAT and ERS-2 SAR images combined with SSM/I data and in situ observations from icebreakers were used. These data were used to analyze ice concentration, ice types, ice drift and other ice features present in this period. The capability of RADARSAT ScanSAR and ERS SAR images to determine these ice parameters during late summer conditions in the Laptev Sea area is discussed.

Carbon dioxide (CO2, R-744) has been identified as a promising alternative to conventional working fluids in a number of applications due to its favourable environmental and thermophysical properties. Previous work on residential CO2 heat pumps has been dealing with systems for either space heating or hot water heating, and it was therefore considered interesting to carry out a theoretical and experimental study of residential CO2 heat pump systems for combined space heating and hot water heating – so-called integrated CO2 heat pump systems. The scope of this thesis is limited to brine-to-water and water-to-water heat pumps connected to low-temperature hydronic space heating systems..

<p>Separation of azeotropic mixtures is a topic of great practical and industrial interest. Most liquid mixtures of organic components form nonideal systems. The presence of some specific groups, particularly polar groups (oxygen, nitrogen, chlorine and fluorine), often results in the formation of azeotropes. Azeotropic mixtures may often be effectively separated by distillation by adding a liquid material (entrainer) to the system.</p><p>For the development of separation processes for azeotropic mixtures, there is a need for insight into the fundamental phenomena of nonideal and azeotropic phase equilibria. This thesis includes a detailed survey on azeotropic phase equilibriumdiagrams of ernarymixtures. Diagram analysis is shown to be an efficient tool for prediction of feasible separations. As a simplifying concept it is proposed that all feasible structures of ternary azeotropic phase equilibrium diagrams can be qualitatively represented by a few elementary cells of which only four have so far been reported to exist. This greatly reduces the complexity of azeotropic istillation analysis and is a key to a simple evaluation of the possibilities and limitations of azeotropic mixtures separation.</p><p>Insights gained from continuous azeotropic distillation is extended to the operation of batch distillation with focus on the dynamics and control of multivessel and extractive batch distillation as processes for separating azeotropic mixtures. Practical implications of this renewed insight for the fine- and specialty chemical industries are given in the concluding pages of the thesis.</p>

Separation of azeotropic mixtures is a topic of great practical and industrial interest. Most liquid mixtures of organic components form nonideal systems. The presence of some specific groups, particularly polar groups (oxygen, nitrogen, chlorine and fluorine), often results in the formation of azeotropes. Azeotropic mixtures may often be effectively separated by distillation by adding a liquid material (entrainer) to the system. For the development of separation processes for azeotropic mixtures, there is a need for insight into the fundamental phenomena of nonideal and azeotropic phase equilibria. This thesis includes a detailed survey on azeotropic phase equilibriumdiagrams of ernarymixtures. Diagram analysis is shown to be an efficient tool for prediction of feasible separations. As a simplifying concept it is proposed that all feasible structures of ternary azeotropic phase equilibrium diagrams can be qualitatively represented by a few elementary cells of which only four have so far been reported to exist. This greatly reduces the complexity of azeotropic istillation analysis and is a key to a simple evaluation of the possibilities and limitations of azeotropic mixtures separation. Insights gained from continuous azeotropic distillation is extended to the operation of batch distillation with focus on the dynamics and control of multivessel and extractive batch distillation as processes for separating azeotropic mixtures. Practical implications of this renewed insight for the fine- and specialty chemical industries are given in the concluding pages of the thesis.

<p>The objective of this work was to explore fundamental aspects of utilizing (DZ) and (ZD) bleaching stages in the prebleaching of oxygen delignified Scandinavian softwood kraft pulp, and compare paper properties of fully bleached pulps with a DEoD₁ED₂ bleached EDF reference pulp. According to the literature, the use of chlorine dioxide and ozone in combination in (DZ) and (ZD) bleaching stages seems advantageous from both environmental and economical points of view. A significant reduction in the formation of chloro-organic compounds and efficient delignification relative to chemical consumption is obtained. </p>

The objective of this work was to explore fundamental aspects of utilizing (DZ) and (ZD) bleaching stages in the prebleaching of oxygen delignified Scandinavian softwood kraft pulp, and compare paper properties of fully bleached pulps with a DEoD1ED2 bleached EDF reference pulp. According to the literature, the use of chlorine dioxide and ozone in combination in (DZ) and (ZD) bleaching stages seems advantageous from both environmental and economical points of view. A significant reduction in the formation of chloro-organic compounds and efficient delignification relative to chemical consumption is obtained.

<p>Hydrodesulfurization is an important part of the hydrotreating process. More stringent regulations on the quality of fuels bring new requirements to the catalytic processes. The removal of sulfur has become a key issue in the oil refining and this work aims to address several aspects of the process.</p><p>Kinetic studies of the hydrodesulfurization reaction over conventional (molybdenum-based) and new (Pt/Y-zeolite) catalysts are reported. The hydrodesulfurization of both the real oil (light gas oil from Statoil Mongstad refinery) and model compounds (thiophene and dibenzothiophene) over a NiMo/γ-Al₂O₃ catalyst were studied. In a high-pressure study of the light gas oil, substituted alkyl-DBTs were found to be the most difficult to desulfurize and the order of reactivity was found to be DBT > 4-MDBT > 4,6-DMDBT. Steric hindrance together with electronic effects were identified as possible reasons for this behavior. The difference in reactivities of the individual compounds was found to decrease with the increasing reaction temperature. A gas chromatograph equipped with the atomic emission detector (GC-AED) was used for the analysis of the individual components of the oil.</p><p>The initial deactivation and the steady-state kinetics were studied during the HDS of thiophene at atmospheric pressure. Unpromoted Mo/γ-Al₂O₃, CoMo/γ-Al₂O₃, NiMo/γ-Al₂O₃, and phosphorus modified NiMo/γ-Al₂O₃ were used for the deactivation study, while NiMo/γ-Al₂O₃,CoMo/γ-Al₂O₃, and Pt/Y-zeolite (with three different pretreatments) were used for the steadystate study. Several experiments related to the deactivation of Mo/γ-Al₂O₃ and NiMo/γ-Al₂O₃catalysts prepared with the chelating agent (NTA) were also performed and NTA was found to have no significant effect on the activity of the catalysts.</p><p>In the deactivation study, a fast initial decrease in the activity was observed on all the catalysts. However, nickel promoted catalysts were found to be more resistant to deactivation than unpromoted ones. The presence of phosphorus slightly increased the activity of the catalyst towards the thiophene HDS, but had no effect on the deactivation behavior. Several methods to regenerate the catalyst were investigated. During the resulfiding experiments, a difference between Mo/γ-Al₂O₃ and NiMo/γ-Al₂O₃ was observed. Deactivation of the Mo catalyst was more severe with increasing temperature, while for the NiMo catalyst the opposite behavior was observed. Carbon deposition on catalysts followed the similar trend: More carbon was observed on the Mo catalyst at higher temperatures, while the opposite is true for NiMo. The restoration of the activity of NiMo was complete, while the reactivation of the Mo catalyst was only partial. The results from the reactivation experiments with pure H₂ and inert gas (helium) suggest that several mechanisms of the restoration of activity exist: Resulfiding of the desulfided active sites, hydrogenation and removal of the deposited carbonaceous species, and the desorption of the reactants and products from the active sites of the catalyst. Based on the observed results, the higher hydrogenation activity of nickel is assumed to be the reason for the behavior. Hydrogenation causes the faster removal of the deposited carbonaceous species and this leads to the conclusion that the desulfiding of the active sites and the adsorption of the reaction species is significantly less pronounced on the NiMo/γ-Al₂O₃catalyst.</p><p>Characterization studies show differences between standard and NTA-based catalysts. The higher amount of carbon on the NTA catalysts is attributed to the presence of the carboncontaining precursor - NTA. The changes in the surface area and the pore volume were observed only during the sulfiding process. In the case of standard catalysts the surface area and the pore volume decreased, while for the NTA-based catalysts the opposite is true. No change in the surface area and the pore volume with the increasing time on stream indicates that the deactivation is not due to structural changes of the catalyst. The amount of sulfur was found to be constant during the time on stream for all the catalysts.</p><p>In the steady-state study of the HDS of thiophene, CoMo and NiMo catalysts were found to be equally active. The activity of the Pt/Y-zeolite catalyst was found to be comparable to conventional catalysts when based on the amount of active material, but a fast deactivation was observed. The product selectivities during the HDS of thiophene were found to be the same for all standard catalysts, but slightly different for the Pt/Y-zeolite catalyst. This was attributed to a higher hydrogenation activity of the Pt/Y-zeolite catalyst. </p><p>The inhibition effect of other sulfur compounds and aromatics on the high-pressure hydrodesulfurization of dibenzothiophene (DBT), the so-called “matrix effect” was studied. Thiophene and DMDS have the same inhibiting effect on the total conversion of DBT, but differences exist in the effect on the selectivities of the products at low concentrations. The results indicate that the inhibiting effect of H₂S on the direct desulfurization route is stronger than the effect of thiophene on the hydrogenation pathway. In the study of aromatics, both toluene and naphthalene affect the total conversion of DBT. Naphthalene was found to be a much stronger inhibitor and inhibits mainly the direct desulfurization pathway, while the hydrogenation route is more affected by the presence of toluene.</p>

Hydrodesulfurization is an important part of the hydrotreating process. More stringent regulations on the quality of fuels bring new requirements to the catalytic processes. The removal of sulfur has become a key issue in the oil refining and this work aims to address several aspects of the process. Kinetic studies of the hydrodesulfurization reaction over conventional (molybdenum-based) and new (Pt/Y-zeolite) catalysts are reported. The hydrodesulfurization of both the real oil (light gas oil from Statoil Mongstad refinery) and model compounds (thiophene and dibenzothiophene) over a NiMo/γ-Al2O3 catalyst were studied. In a high-pressure study of the light gas oil, substituted alkyl-DBTs were found to be the most difficult to desulfurize and the order of reactivity was found to be DBT &gt; 4-MDBT &gt; 4,6-DMDBT. Steric hindrance together with electronic effects were identified as possible reasons for this behavior. The difference in reactivities of the individual compounds was found to decrease with the increasing reaction temperature. A gas chromatograph equipped with the atomic emission detector (GC-AED) was used for the analysis of the individual components of the oil. The initial deactivation and the steady-state kinetics were studied during the HDS of thiophene at atmospheric pressure. Unpromoted Mo/γ-Al2O3, CoMo/γ-Al2O3, NiMo/γ-Al2O3, and phosphorus modified NiMo/γ-Al2O3 were used for the deactivation study, while NiMo/γ-Al2O3,CoMo/γ-Al2O3, and Pt/Y-zeolite (with three different pretreatments) were used for the steadystate study. Several experiments related to the deactivation of Mo/γ-Al2O3 and NiMo/γ-Al2O3 catalysts prepared with the chelating agent (NTA) were also performed and NTA was found to have no significant effect on the activity of the catalysts. In the deactivation study, a fast initial decrease in the activity was observed on all the catalysts. However, nickel promoted catalysts were found to be more resistant to deactivation than unpromoted ones. The presence of phosphorus slightly increased the activity of the catalyst towards the thiophene HDS, but had no effect on the deactivation behavior. Several methods to regenerate the catalyst were investigated. During the resulfiding experiments, a difference between Mo/γ-Al2O3 and NiMo/γ-Al2O3 was observed. Deactivation of the Mo catalyst was more severe with increasing temperature, while for the NiMo catalyst the opposite behavior was observed. Carbon deposition on catalysts followed the similar trend: More carbon was observed on the Mo catalyst at higher temperatures, while the opposite is true for NiMo. The restoration of the activity of NiMo was complete, while the reactivation of the Mo catalyst was only partial. The results from the reactivation experiments with pure H2 and inert gas (helium) suggest that several mechanisms of the restoration of activity exist: Resulfiding of the desulfided active sites, hydrogenation and removal of the deposited carbonaceous species, and the desorption of the reactants and products from the active sites of the catalyst. Based on the observed results, the higher hydrogenation activity of nickel is assumed to be the reason for the behavior. Hydrogenation causes the faster removal of the deposited carbonaceous species and this leads to the conclusion that the desulfiding of the active sites and the adsorption of the reaction species is significantly less pronounced on the NiMo/γ-Al2O3 catalyst. Characterization studies show differences between standard and NTA-based catalysts. The higher amount of carbon on the NTA catalysts is attributed to the presence of the carboncontaining precursor - NTA. The changes in the surface area and the pore volume were observed only during the sulfiding process. In the case of standard catalysts the surface area and the pore volume decreased, while for the NTA-based catalysts the opposite is true. No change in the surface area and the pore volume with the increasing time on stream indicates that the deactivation is not due to structural changes of the catalyst. The amount of sulfur was found to be constant during the time on stream for all the catalysts. In the steady-state study of the HDS of thiophene, CoMo and NiMo catalysts were found to be equally active. The activity of the Pt/Y-zeolite catalyst was found to be comparable to conventional catalysts when based on the amount of active material, but a fast deactivation was observed. The product selectivities during the HDS of thiophene were found to be the same for all standard catalysts, but slightly different for the Pt/Y-zeolite catalyst. This was attributed to a higher hydrogenation activity of the Pt/Y-zeolite catalyst. The inhibition effect of other sulfur compounds and aromatics on the high-pressure hydrodesulfurization of dibenzothiophene (DBT), the so-called “matrix effect” was studied. Thiophene and DMDS have the same inhibiting effect on the total conversion of DBT, but differences exist in the effect on the selectivities of the products at low concentrations. The results indicate that the inhibiting effect of H2S on the direct desulfurization route is stronger than the effect of thiophene on the hydrogenation pathway. In the study of aromatics, both toluene and naphthalene affect the total conversion of DBT. Naphthalene was found to be a much stronger inhibitor and inhibits mainly the direct desulfurization pathway, while the hydrogenation route is more affected by the presence of toluene.