A key step in the production of clean energy from biomass gasification is the cleaning of the product gas to remove impurities, such as tars, H2S, HCl, particulates, and alkali compounds. Some gas cleaning systems employ activated carbon (AC), with Brunauer-Ernmett-Teller (BET) surface areas in the range of 800-1300 m(2)/g. Because the operational conditions for the production of AC are similar to those applied in the gasification chamber of a dual fluidized bed gasifier, the possibility to produce AC within the dual fluidized bed gasification (DFBG) process was investigated in the present work. Wood pellets were gasified with steam in a fluidized bed reactor at 800 and 840 degrees C. Part of the unconverted char from this process was further activated with steam in a fixed bed reactor at 850 degrees C. The results obtained indicate that if >= 44% of the char that results from the devolatilization of the wood pellets is gasified (the extent of char conversion), the unconverted char acquires a BET surface area >900 m(2)/g, which makes it suitable for use in gas cleaning processes. Achieving this extent of char conversion in the gasification chamber of industrial dual fluidized gasification plants would remove the need and cost for a second reactor for further activation of the unconverted char. The cost of the produced activated carbon (AC) has been estimated as being 15-fold lower than that of commercially available AC. This suggests that the production of AC as part of the dual fluidized bed gasification process would be cost-effective.

A surprisingly simple and rapid methodology for large-area, lightweight, and thin laminate coatings with remarkable moisture barrier properties is introduced. Commercially available paperboards are coated with thin layers of nanocellulose. The nanocellulose coating induces a surface smoothening effect on the coated sheets as characterized by environmental scanning electron microscopy and white light interferometry. A moisture-protective layer of renewable alkyd resins is deposited on the nanocellulose precoated sheets using a water-borne dispersion coating process or lithographic printing. Through an auto-oxidation process, the applied alkyd resins are transformed into moisture sealant layers. The moisture barrier properties are characterized in detail by water vapor permeability measurements at different levels of relative humidity. The water vapor barrier properties of the nanocellulose precoated substrates were significantly improved by thin layers of renewable alkyd resins. The effect of the alkyd resin properties, coating technologies, and base paper substrates on the final barrier performance of the sheets were studied. It was found that the nanocellulose coating had a notable effect on the homogeneity and barrier performance of the alkyd resin layers and in particular those alkyd resin layers that were applied by printing. The concept is environmentally friendly, energy-efficient, and economic and is ready for scaling-up via continuous roll-to-roll processes. Large-scale renewable coatings applicable for sustainable packaging solutions are foreseen.

This work investigates for the first time how mercury intrusion porosimetry (MIP), NMR-based cryoporometry, and DSC-based thermoporosimetry compare in revealing the porous characteristics of ground calcium carbonate structures compacted over a range of pressures. The comparison is made using the same source samples throughout. MIP, a much-used method in the characterization of porous structures, has the drawback that the high pressure needed to intrude the mercury may either distort the skeletal porous structure of the sample, especially when compressible materials such as cellulose or binders/latex are present, or lead to a reduction in the measured number of large pores due to the shielding by smaller pores. These effects have previously been addressed using bulk modulus corrections and by modeling the structure permeability to account for the potential shielding. Cryoporometry gives detailed information about the pore size distribution of an imbibition saturated structure. Thermoporosimetry is a relatively new candidate in this field, and it yields both pore size distribution and pore volume. Currently it is somewhat limited in the pore size range detectable, but it is relevant to pigmented coatings. Its potential is identified for capturing the pores involved in the progress of imbibition before saturation is reached.

Chemical enhanced oil recovery (EOR) represents a series of potential solutions for extracting more oil from resources with already known locations and magnitudes. Unfortunately, many of the chemical additives in use today are not environmentally friendly. In the study a "greener" alternative for increasing viscosity of the injection water is investigated, namely cellulose nanofibrils (CNF). The nanofibrils are combined in systems with anionic sulfonate surfactants, SDBS and AOT, in order to decrease interfacial tension (IFT) between oil and water. In combination, the increase of water viscosity and decrease of IFT should result in higher ultimate oil recovery than if only conventional water flooding was applied. Interactions between cellulose nanofibrils and the surfactants have been investigated through adsorption studies, rheology, and IFT measurements. An observed synergy effect between CNF and surfactants upon viscosity of injection water, as well as with substantial decrease in IFT, leads the authors to the conclusion that an EOR system consisting of CNF and sulfonate surfactants has good potential for future applications.

Highly stabilized mesoporous core-shell-structured oxygen carriers (OCs) were fabricated by a repetitive coating process of alumina supports using the mesopore-forming surfactant assembly method. The wet coating strategy, along with the sol-gel process, was used for the synthesis of mesoporous material-shelled OCs with various shell compositions (i.e., zirconia, titania). The cyclic performance of the synthesized OCs during chemical looping combustion (CLC) was investigated in a thermogravimetric analyzer (TGA). The mesoporous-shelled OCs demonstrated significantly better performance compared to the OCs without mesoporous shells. The synthesized OCs with a mesoporous zirconia/titania shell reveal a unique oxygen capacity of 100% based on active metal oxide for supported NiO and Fe2O3. Also, the synthesized OCs showed no activity loss after 10 cycles. This was attributed to the exceptional core-shell coating strategy, in which the thermally stable mesoporous Zr/Ti layers prevent the sintering and over-reaction of the active metal oxide crystals with the alumina support. 

The use of certain bed materials has been found to increase the steam gasification rate of biomass char. The present work investigates how this phenomenon is influenced by different parameters (e.g., temperature, fuel type, and fuel moisture content), using a laboratory-scale bubbling fluidized bed gasifier. Silica sand, fresh olivine, and activated olivine were employed as bed materials, and three biomass fuels (wood chips, wood pellets, and forest residue pellets) were considered. Switching the bed material from silica sand to activated olivine resulted in a significant increase in the char gasification rate for all three fuels, with further increases noted as the fuel particle size was decreased. The observed effect was strongest (up to 4-fold) during the initial conversion phase (char gasification degrees < 20%) when the temperature was relatively low (≤ 800 °C). The moisture content of the wood chips (0-40%) had no significant effect on the char gasification rate.

Carbon dioxide (CO2) capture is a process that can significantly reduce the amount of CO2 in the atmosphere. In this study, several solid sorbents were examined for their CO2 capturing performance over 30 carbonation-calcination cycles. The sorbents included natural calcined Cadomin limestone (denoted as CD), hydrated calcined Cadomin pellets (denoted as CP), core/shell sorbets with CD and CP as cores, and mesostructured silica (denoted as CD@Si and CP@Si, respectively) and titania (denoted as CD@Ti and CP@Ti) as shells. The core/shell sorbents were prepared with a protective porous shell using the mesoporous silica and titania layers. The surface morphology and porosity of all sorbents were qualified using scanning electron microscopy and were quantified using nitrogen physisorption. X-ray diffraction was also used to identify the crystal phase composition of the sorbents before and after calcination. The CP@Ti pellets showed the best performance in the retention of CO2 uptake over 30 cycles with an activity loss of 50.9%. This is attributed to the formation of a protective layer of thermally stable mesoporous titania using a sol-gel method, which prevented the aggregation of CaO crystals and sorbent sintering. Although the modified core/shell sorbents exhibited an improvement in maintaining the stability of the cyclic operation compared to natural limestone, further study is needed to understand the core/shell sintering phenomenon at high temperatures using other novel materials.

Secondary pyrolysis in fluidized bed fast pyrolysis of biomass is the focus of this work. A novel computational fluid dynamics (CFD) model coupled with a comprehensive chemistry scheme (134 species and 4169 reactions, in CHEMKIN format) has been developed to investigate this complex phenomenon. Previous results from a transient three-dimensional model of primary pyrolysis were used for the source terms of primary products in this model. A parametric study of reaction atmospheres (H2O, N2, H2, CO2, CO) has been performed. For the N2 and H2O atmosphere, results of the model compared favorably to experimentally obtained yields after the temperature was adjusted to a value higher than that used in experiments. One notable deviation versus experiments is pyrolytic water yield and yield of higher hydrocarbons. The model suggests a not overly strong impact of the reaction atmosphere. However, both chemical and physical effects were observed. Most notably, effects could be seen on the yield of various compounds, temperature profile throughout the reactor system, residence time, radical concentration, and turbulent intensity. At the investigated temperature (873 K), turbulent intensity appeared to have the strongest influence on liquid yield. With the aid of acceleration techniques, most importantly dimension reduction, chemistry agglomeration, and in-situ tabulation, a converged solution could be obtained within a reasonable time (∼30 h). As such, a new potentially useful method has been suggested for numerical analysis of fast pyrolysis.

The aim of this study was to develop a model that predicts the gas solubility and the sorption and desorption kinetics in polymer granulates over large temperature and pressure intervals. Besides the part predicting the solubility and diffusivity, the model involves the simultaneous solution of the diffusion equation and the heat equation in three dimensions using a finite element method (FEM). When the temperature- and pressure-dependent solubility of a specific polymer/gas combination is not known, an improved version of the non-equilibrium lattice fluid model (NELF) is used to predict the solubility. The improvement of the NELF model includes the use of Hansen's solubility parameters, and it uses pressure-volume-temperature (PVT) data from two new empirical models, which accurately estimate polymer densities over a wide range of temperatures and pressures. The new solubility model predicted the solubility-pressure data of N2 in poly(ethyl methacrylate) and N 2 and CH4 in polycarbonate (PC) at pressures below 4.5 MPa, without using any adjustable interaction parameters. The model was used to predict the solubility of N2 in poly(ether-ether-ketone) (PEEK) and PC at a very high pressure (67 MPa). Experimental N2 solubility data were obtained with a specially built reactor yielding high pressure and temperature. For PEEK, it was possible to predict the very high pressure solubility using a gas-polymer interaction parameter obtained from data taken at low pressures. In addition, a new free-volume-based diffusivity model requiring no adjustable interaction parameters was developed, and it successfully predicted the desorption kinetics of N2 from PEEK and PC.

Different alternatives to the conventional recovery of spent pulping liquors in the kraft pulping process have been studied by equilibrium calculations. These calculations were performed using FactSage. Three different black liquor gasification systems with addition of TiO2 for direct causticization were studied: (i) MTCI conditions (600 °C and 0.3 MPa), (ii) Chemrec atmospheric booster conditions (950 °C and 0.1 MPa), and (iii) Chemrec pressurized system conditions (950 °C and 3 MPa). The studies of the influence of the molar ratio TiO2/Na2O showed that a TiO2/ Na2O molar ratio of 0.5 is needed to capture all of the sodium in the condensed phase as sodium titanates (i.e., achieve complete direct causticization). Furthermore, at these conditions all of the sulfur is released to the gas phase. Different forms of sodium titanates are formed depending on the TiO2/Na2O molar ratio, and conceptually all of them could be used to produce NaOH in the consecutive leaching step.

Superhydrophobic surfaces have been fabricated in a continuous spray process, where an alkyl ketene dimer (AKD) wax is dissolved in supercritical carbon dioxide (scCO₂) and sprayed onto the substrate. The mass of extracted AKD from scCO₂ has been investigated as well as the pressure, temperature, and flow of CO₂ at the steady-state spray conditions. Several different substrates such as glass, aluminum, paper, poly(ethylene terephthalate) (PET), and polytetrafluoroethylene (PTFE) have been successfully coated, and the superhydrophobic properties have been evaluated by measurement of water contact angle, water drop friction, scanning electron microscopy (SEM), and surface topography. The most efficient spray process, considering surface properties and mass of extracted AKD, is obtained at the lowest temperature investigated, 67 °C, and the highest pressure evaluated in this study, 25 MPa. We also show that the influence of preexpansion conditions (p, T) on the surface temperature at the selected spray distance (3 cm) is negligible by measurement with an infrared camera during spraying.

Fluorocarbon, organosilicon, and hydrocarbon plasma coatings were used to modify the surface permeable pigment-coated paper, and their impact on UV-varnish absorption was investigated. According to mercury porosimetry results, the plasma coatings had no influence on the porous structure of the paper. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) results showed characteristic surface chemical compositions for each plasma coating. The fluorocarbon plasma coating increased the UV-varnish contact angles significantly, whereas the hydrocarbon plasma coating had no clear influence. When the UV varnish was applied with a flexography unit including nip pressure, the role of surface chemical composition seemed to become minimal. The viscosity of the UV varnish was shown to impact the absorption rate with and without external pressure.

The mixing process in a Lightnin Series 45 static mixer, 40 mm in diameter, has been investigated using computational fluid dynamics and the volume of fluid (VOF) method, a method developed for immiscible fluids but here used for miscible. The mixing process was investigated for two liquids that had viscosities ranging from 0.003 to 51.2 Pa s, and the volumetric flow rate proportion between the liquids was varied between 1/1 and 4/1. The flow rate was 0.1 m/s, and two Reynolds numbers, 1 and 70, were investigated. The mixer performance was evaluated using the rate of striation thinning, and it was found that the greater the difference in viscosity the worse the mixer performance. This effect is due to the difference in elongation rate between the liquids, which exists until equilibrium in shear stress has been reached at the interface between the liquids. For higher Re numbers close to a point when secondary motions start to have significance for the rate of striation thinning, a lower viscosity of the added liquid results in an increase in mixing performance. It was further found that the VOF method can be used to model the mixing of dissimilar liquids in static mixers, but since the thickness of the striations decreases rapidly with the number of mixer elements, the VOF method is most suitable when investigating mixing processes over a small number of mixer elements. © 2008 American Chemical Society.

In this investigation, a modified Poisson-Boltzmann approach has been used to estimate the mean ion concentration distributions of ionic species present in black liquors around charged kraft lignin macromolecules at industrially relevant conditions. The distributions were utilized to predict the double layer repulsion and, further, predict the overall pair interaction potentials between two kraft lignin macromolecules or particles immersed in the black liquor electrolyte. The properties of softwood black liquors were used as input data to the model. The numerical results predicted the pair interaction potentials to remain repulsive up to salt concentrations of about 2.5 M at pOH 1. The critical coagulation concentration of salt was predicted to decrease as the pOH of the black liquor was increased. The predictions at 65 °C and moderate levels of pOH (3.5) and salt concentration (1.9 M) were found to be in good agreement with previous observations reported in the literature.

Calcium oxide (CaO) has been investigated as a high-temperature performance sorption material for carbon capture due to its high carbon dioxide (CO2) capacity, low cost, and environmental benignity. Unfortunately, commercialized application of CaO materials has been hindered by severe capacity loss during cycling operations. In an attempt to overcome these problems, this study investigated the effects of adding zirconia-based ceramic dopants and coating sorbents with highly crystalline zirconium dioxide (ZrO2) layers derived from the hydrolysis of zirconium butoxide to control the growth of ZrO2 crystals. Uncoated natural Cadomin delivered a high CO2 capture capacity of more than 13 mol CO2/kg, while the zirconia-coated sorbents showed excellent cycling stability corresponding to a maximum capacity of retention of 79% after 21 cycles at high temperatures. More importantly, the highly crystalline ZrO2-coated sorbents doped by zirconia-based sorbents exhibited a significantly lower decay capacity compared to the uncoated sorbents, which could be attributed to the formation of a perovskite structure that is resistant at high temperatures and a high-temperature-resistant ceramic layer through the solid-state reaction of the highly mesoporous crystalline ZrO2 layer with CaO. These results shed light on the development of sorbents with special structures and superior chemical and mechanical properties for high-performance calcium looping or regenerative calcium cycle processes. (Graph Presented). 

In the context of chemical recycling of mixed plastics and paper, multitemperature step pyrolysis has shown good potential for the separation of oxygenated products from hydrocarbons. Here, we report results of an investigation of the first pyrolysis step at low temperature, which involves the dehydrochlorination of polyvinyl chloride (PVC) and the pyrolysis of cellulose, the main component of paper. Calcium oxide (CaO), selected for its chloride adsorption ability and its catalytic activity on biooil deoxygenation, was used for upgrading the downstream products from the pyrolysis. Additionally, we studied the performance of CaO for the simultaneous adsorption of HCl and for reforming cellulose pyrolysates in the temperature range of 300-600 °C with feedstock to CaO ratios of 1:0.2, 1:0.4, and 1:1. It was found that the suitable catalytic temperature for HCl and acetic acid adsorption is lower than 400 °C. This is due to the desorption of HCl from CaCl2 and Ca(OH)Cl in the presence of water and CO2 at 400 °C and higher. A larger amount of CaO resulted in a more efficient reduction of acids and the organic liquids were found to have lower amounts of oxygen. A comparison between the cases of neat and mixed feedstock showed that pyrolysis of mixed feedstock produced more water, H2, CO, and polycyclic aromatic hydrocarbons (PAHs) when compared to the case of neat materials over CaO

A recently published dimensional scaling of infiltration of water-based inkjet fluids was used to revisit published inkjet printability data on mineral-pigment-based, inkjet-receptive coated papers. The dimensional scaling was developed using simple fluids on homogeneous isotropic media and applied on uncoated papers using complex inkjet fluids but so far has not been related to printability. It is shown that the scaling can also work for coated papers using commercial dye- and pigment-based inks with a suggested relation to printability as given by the color gamut area, in which the primary factor is the product of permeability and capillary pressure. A successful scaling suggests that inkjet printability can be predicted from flow and materials parameters, namely, porosity, viscosity, imbibed volume, permeability, and capillary pressure, and would be of general applicability in other areas of inkjet printing. The results further imply the usefulness of the approach in other functional surface modification using waterborne procedures on hard or soft porous materials.

Natural fatty alcohols are one of the major oleochemicals and can be produced by catalytic hydrogenation of fatty acid methyl esters. In the commercial multiphase process, the hydrogen availability to the solid catalyst limits the reaction rate. By adding propane to the reaction mixture, we can utilize the unique properties of supercritical fluids, properties between those of gases and liquids. Using propane, a substantially homogeneous supercritical phase is created, whereby hydrogen has complete access to the solid catalyst. At high substrate concentrations, a rapid fall of the reaction rate was observed, and the benefits of the propane addition were completely lost. This fall depends on a split of the supercritical reaction mixture into two phases (a substrate-rich and a hydrogen-rich phase). If this phase split occurred using small catalyst particles (?32 ?m), the pressure drop over the catalyst bed increased sharply because the formed liquid droplets blocked the void space in the porous catalyst bed. These two phenomena were used to deduce the product and substrate solubility in the reaction mixture. The product showed the most unfavorable solubility which increased with higher pressure. Under our process conditions (150 bar, 280 °C, and 11 mol % hydrogen), a single phase was observed up to 2 mol % (i.e., 15% by mass) product. Besides the minimum pressure in the catalyst bed, substrate transport limitation could be shown to be an important factor in process optimization. Therefore, egg-shell catalysts or fine catalyst particles (100-300 ?m) should preferably be used in the continuous supercritical reactors.