| 1. |
- Josefsson, Peter, et al.
(författare)
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Controlled seasoning of scots pine chips using an albino strain of ophiostoma
- 2006
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Ingår i: Journal of Industrial and Engineering Chemistry. - : American Chemical Society (ACS). - 1226-086X .- 1876-794X .- 0888-5885 .- 1520-5045. ; 45:7, s. 2374-2380
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Tidskriftsartikel (refereegranskat)abstract
- Traditional seasoning of wood chips normally results in significant yield losses and brightness reduction due to the uncontrolled action of microorganisms. Techniques for reduction of the amount of wood extractives with minimal yield and brightness loss are therefore of interest for the pulp and paper industry. To study a biotechnological approach for reduction of wood extractives, wood chips from sapwood of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) were treated with a commercial albino strain of the sap stain fungus Ophiostoma piliferum. During 2 weeks of controlled seasoning, the content of wood extractives decreased by approximately 40% for Scots pine and 25% for Norway spruce, where the triglyceride contents were degraded to a greater degree. Thermomechanical pulps were produced from untreated and pretreated pine chips. The properties of these pulps and corresponding laboratory sheets were investigated. The pretreated pulps showed less shortened fibers, lower amounts of triglycerides, and enhanced strength properties. The mechanisms behind these effects are discussed. Furthermore, the ability of the albino Ophiostoma piliferum to displace mould growth from wood chips was investigated in a series of experiments. It was concluded that the fungus should preferably be inoculated on fresh chips in order to repress mould growth.
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| 2. |
- Tyrode, Eric, et al.
(författare)
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Emulsion Catastrophic Inversion from Abnormal to Normal Morphology. 4. Following the Emulsion Viscosity during Three Inversion Protocols and Extending the Critical Dispersed-Phase Concept
- 2005
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 44:1, s. 67-74
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Tidskriftsartikel (refereegranskat)abstract
- Three protocols are tested to invert an abnormal emulsion into a normal one: a dynamic process with continuous addn. of an internal phase, continuous stirring of a given emulsion with no addn. of an internal phase, and the combination of the previous ones, i.e., a standstill dynamic process in which the addn. of an internal phase is interrupted at some time and then followed by continued stirring. In situ follow-up of both cond. and viscosity data in a rheomixer vessel provides complementary information to corroborate the crit. dispersed-phase concept as a condition for the inversion to take place in all cases. Some applications are discussed. [on SciFinder (R)]
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| 3. |
- Alander, E. M., et al.
(författare)
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Mechanisms of crystal agglomeration of paracetamol in acetone-water mixtures
- 2005
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 44:15, s. 5788-5794
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Tidskriftsartikel (refereegranskat)abstract
- The mechanisms governing the influence of the solvent composition on the agglomeration in a crystallization process have been investigated. Narrowly sieved paracetamol crystals were suspended in supersaturated acetone-water solutions, and were allowed to grow at isothermal conditions, after which the agglomeration was recorded. In all experiments the same sieve size fraction was used as well as the same magma density. In each experiment the supersaturation was kept constant. Experiments were performed in different solvent compositions at different supersaturation, crystal growth rate, solution viscosity, and agitation rate. For a statistically sufficient number of particles from each experiment, the number of crystals in each product particle was determined by image analysis and multivariate data evaluation. From the resulting number distributions of crystals per product particle, parameters defining the degree of agglomeration were extracted. The experimental results clearly establish that there is an influence of the solvent composition on the degree of agglomeration, which cannot be explained by differences in crystal growth rate, or differences in solution viscosity. The degree of agglomeration is found to decrease with increasing solvent polarity. It is, suggested that the mechanism by which the solvent influence relates to the crystal-solvent interaction and the physicochemical. adhesion forces between crystals in the solution.
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| 4. |
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| 5. |
- Beretta, A., et al.
(författare)
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Experimental and modeling analysis of methane partial oxidation : transient and steady-state behavior of rh-coated honeycomb monoliths
- 2009
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 48:8, s. 3825-3836
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Tidskriftsartikel (refereegranskat)abstract
- The present study consists of an experimental and theoretical study of the performance of Rh-coated honeycomb monoliths for methane partial oxidation. The thermal behavior of Rh-coated honeycomb monoliths was studied under representative operating conditions, at steady state and during light-off. Model analysis (based on a dynamic heterogeneous reactor model that incorporates a kinetic scheme of the process independently developed, and well-assessed correlations for heat and mass transfer) provided a key for interpreting the observed effects. The comprehension of how transport phenomena and surface kinetics affect the reactor behavior leads to the conclusion that the feasibility of small-scale production of syngas via CH(4) catalytic partial oxidation relies on thermal management of the short contact time reactor and not the obtainment of high syngas yields (which is not a challenging task). Severe operating conditions (and high surface temperatures) can deplete the catalyst activity and cause unstable reactor operation. Guidelines for optimal reactor design are proposed.
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| 6. |
- Bialik, Marta Anna, 1978, et al.
(författare)
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Boiling Point Rise Calculations in Sodium Salt Solutions
- 2008
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 47:4, s. 1283-1287
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Tidskriftsartikel (refereegranskat)abstract
- The boiling point rise (elevation) of aqueous industrial solutions is often regarded as an important propertywith respect to chemical process design. This work shows an application of the Pitzer method for calculatingthe activity coefficients to the estimation of the boiling point rise of single-component and multicomponentelectrolyte solutions. Good agreement between experimental and predicted values of the boiling point elevationsof solutions of several salts (NaOH, Na2CO3, Na2SO4, NaCl, Na2S2O3, Na2S, mixed NaOH-Na2CO3, andmixed Na2CO3-Na2SO4) was obtained. A method for using the boiling point rise data to obtain ionic interactionparameters for the Pitzer method is also shown.
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| 7. |
- Bialik, Marta Anna, 1978, et al.
(författare)
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Solubility and Solid-Phase Composition in Na2CO3-Na2SO4 Solutions at Boiling Temperature: A Modeling Approach
- 2008
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 47:9, s. 3233-3238
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Tidskriftsartikel (refereegranskat)abstract
- Scaling caused by Na2CO3-Na2SO4 double salts constitutes a severe problem in black liquor evaporators.The ability to predict the solubility and solid-phase composition of these species would be conclusive inminimizing the adverse effects of scaling. Experimental solubility data for (sodium sulfate) dicarbonate, acarbonate-rich double salt identified in Na2CO3-Na2SO4 precipitates, were generated and used for fitting anempirical solubility model. A thermodynamically based approach for predicting the solubility and solidphasecomposition, previously used for burkeite precipitates, was applied to solid solutions of dicarbonate.
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| 8. |
- Cho, Paul In-Young, 1970, et al.
(författare)
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Carbon Formation on Nickel and Iron Oxide-Containing Oxygen Carriers for Chemical-Looping Combustion
- 2005
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 44:4, s. 668-676
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Tidskriftsartikel (refereegranskat)abstract
- For combustion with CO2 capture, chemical-looping combustion with inherent separation of CO2 is a promising technology. Two interconnected fluidized beds are used as reactors. In the fuel reactor, a gaseous fuel is oxidized by an oxygen carrier, e.g., metal oxide particles, producing carbon dioxide and water. The reduced oxygen carrier is then transported to the air reactor, where it is oxidized with air back to its original form before it is returned to the fuel reactor. Carbon deposition on oxygen-carrier particles was investigated to assess whether it could have adverse effects on the process. The oxygen-carrier particles used were based on oxides of nickel and iron and produced by freeze granulation. They were sintered at 1300 degreesC for 4 h and sieved to a size range of 125-180 mum. The study of carbon deposition was performed in a laboratory fluidized-bed reactor, simulating a chemical-looping combustion system by exposing the sample to alternating reducing and oxidizing conditions. The particles with nickel oxide were tested at 750, 850, and 950 degreesC, and the particles with iron oxide at 950 degreesC. On the oxygen carrier with nickel oxide, only minor amounts of carbon formed during most of the reduction. However, when more than 80% of the oxygen available was consumed, significant carbon formation started. The formation of carbon was also clearly correlated to low conversion of the fuel. No carbon was formed on the oxygen carrier based on iron oxide. The interpretation for the actual application of this process is that carbon formation should not be a problem, because the process should be run under conditions of high conversions of the fuel.
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| 9. |
- Cho, Paul In-Young, 1970, et al.
(författare)
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Defluidization conditions for fluidized-bed of iron, nickel, and manganese oxide containing oxygen-carriers for chemical-looping combustion
- 2006
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 45:3, s. 968-977
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Tidskriftsartikel (refereegranskat)abstract
- For combustion with CO2 capture, chemical-looping combustion with inherent separation Of CO2 is a promising technology. Chemical-looping combustion uses oxygen carriers that are composed of metal oxide to transfer oxygen from the combustion air to the fuel. The defluidization of oxygen-carrier particles was investigated to improve the understanding of when particle agglomeration may occur. The study was made in a laboratory fluidized-bed reactor at 950 degrees C, simulating a chemical-looping combustion system by exposing the sample to reducing and oxidizing conditions in an alternating manner. The oxygen-carrier particles used were based on oxides of iron, nickel, and manganese and produced by freeze granulation. For iron oxide particles, there was no defluidization of the bed when the content of available oxygen in the particle was high. The defluidization occurred during the oxidation period after long reduction periods, in which a significant reduction of the magnetite to wustite occurred. This is an important observation, because the reduction to wustite is not expected in chemical-looping combustion with high fuel conversion. Thus, laboratory experiments with iron oxide performed with long reduction times may give an unduly exaggerated impression of the risks of agglomeration. For nickel oxide, the defluidization was dependent on the sintering temperature with no defluidization in experiments conducted with particles sintered at 1300 and 1400 degrees C. The nickel oxide particles that were sintered at 1500 degrees C only defluidized once in a total of 49 cycles, whereas the particles that were sintered at 1600 degrees C defluidized already in the first cycle. For the nickel oxide particles, it was not possible to see any effect of the length of the reducing period on the defluidization. There was no defluidization of the manganese oxide particles. The defluidization of the bed leads to agglomeration for the iron oxide particles, but not for the particles of nickel oxide, where the bed was still loosely packed. Carbon was formed on the particles based on nickel oxide and manganese oxide.
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| 10. |
- Dahlström, Christina, 1977-, et al.
(författare)
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New Insights into Coating Uniformity and Base Sheet Structures
- 2009
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 48:23, s. 10472-10478
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Tidskriftsartikel (refereegranskat)abstract
- Base sheet structures, such as surface roughness and mass density distribution (formation), have been known to affect coating uniformity. However, the literature is not necessarily consistent in determining which structure controls coating uniformity. This study employed scanning electron microscopy (SEM) and image analysis, combined with autocorrelation and frequency analyses, to investigate the fundamental mechanisms of coating and to resolve some of the controversies in the literature regarding the base sheet effects. The results showed that coating thickness variation resembles a process of random deposition with leveling. At small length scales (in the size of fiber width), leveling causes a very strong dependence of coating thickness variations on the surface profile of the base sheet, whereas at larger length scales, coating thickness variation diminishes in its intensity by the same leveling effect, but still retains a significant correlation with base sheet structure, particularly formation. Frequency analyses clearly showed that the discrepancies in the results for the base sheet effects in the literature are due to the length scales used in the experiments, that is, the sampling area and the resolution of the measurements.
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| 11. |
- Danielsson, Sverker, et al.
(författare)
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Kinetic study of Hexenuronic and Methylglucuronic acid reactions in pulp and in dissolved xylan during kraft pulping of hardwood
- 2006
-
Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 45:7, s. 2174-2178
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Tidskriftsartikel (refereegranskat)abstract
- During kraft pulping, the side group in the xylan backbone, 4-O-methyl-D-glucuronic acid, is partly converted to hexenuronic acid. Simultaneously, degradation reactions of these side groups take place. The rates of these reactions were studied during the kraft pulping of hardwood and were shown to be strongly affected by the location of the x Ian; dissolved xylan had markedly higher methylglucuronic acid and hexenuronic acid contents than pulp xylan did. The degree of substitution of methyl-lucuronic acid in dissolved xylan was found to be higher at reduced cooking temperatures; no such change was seen for pulp xylan. A kinetic model was developed that included the energies of activation for formation (129 U/mol) and degradation (143 U/mol) of hexenuronic acid and dearadation (141 kJ/mol) of methylglucuronic acid and bulk delignification (118 kJ/mol, in accordance with earlier studies). Decreased cooking temperatures thus increase the number of acidic charged groups in the pulp and in dissolved xylan.
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| 12. |
- Eriksson, Malin, et al.
(författare)
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Surface modification of wood fibers using the polyelectrocyte multilayer technique : Effects on fiber joint and paper strength properties
- 2006
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 45, s. 5279-5286
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Tidskriftsartikel (refereegranskat)abstract
- Polyallylamine hydrochloride (PAH) and poly(acrylic acid) (PAA) were used to modify wood fibers by means of the polyelectrolyte multilayer (PEM) technique. Hand sheets and fiber crosses were prepared from the PEM-treated fibers. The sheet strength and fiber-fiber joint strength were evaluated, and the contact zone of the fiber-fiber joint was characterized using a recently developed staining technique. The nonjoined surface area of the paper sheets was estimated by determining nitrogen adsorption via BET analysis, and the results were compared with those of the light scattering measurements frequently used to determine the degree of "bonding" in paper. Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy was used to analyze chemical effects. It was shown that the PEM treatment of fibers increased the strength properties of the sheets through an increase in the number of fiber-fiber joints, increasing the degree of contact in a fiber-fiber joint and creating covalent bonding in the fiber-fiber joint.
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| 13. |
- Ge, Xinlei, et al.
(författare)
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Estimation of Freezing Point Depression, Boiling Point Elevation, and Vaporization Enthalpies of Electrolyte Solutions
- 2009
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 48:4, s. 2229-2235
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Tidskriftsartikel (refereegranskat)abstract
- A novel approach is presented in this work for predicting the values of freezing point depression and boiling point elevation for electrolyte solutions at different concentrations on the basis of the Pitzer theories. This method treats the enthalpy change of the solution between the normal freezing point or boiling point and the real ones to be linear temperature dependence. Compared with the literature values, this method performs very well; also, the temperature-dependent parameters of some salts are incorporated to investigate temperature effects of this method. Furthermore, a method based on the Clausius-Clapeyron equation is derived for estimation of the enthalpy of vaporization of very high concentration solutions at different temperatures, and the predicted results are highly positive.
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| 14. |
- Gómez-Barea, Alberto, et al.
(författare)
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Reduction of Physical Effects during Reactivity Tests in Fluidized Bed
- 2006
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 45:21, s. 7344-7350
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Tidskriftsartikel (refereegranskat)abstract
- The role of transport effects in experiments on the gasification reactivity of biomass char, conducted in a26-mm-diameter bench-scale fluidized bed (FB) reactor, is analyzed. Gasification rates of char were measuredat various particle sizes, CO2 partial pressures, temperatures, and initial char batches. A dedicated methodologyenables evaluation of the transport effects from gas measurements. The separate contributions of fluid-dynamics,external film, and porous diffusional resistances in a typical FB char gasification test are addressed. An optimaladjustment of the operating conditions of the FB is proposed to reduce mass-transport effects as much aspossible. When transport effects cannot be completely eliminated, this work shows how to treat the data toobtain an average reactivity that is useful for reactor simulations.
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| 15. |
- Ji, Xiaoyan, et al.
(författare)
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Ion-based SAFT2 to represent aqueous single- and multiple-salt solutions at 298.15 K
- 2006
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 45, s. 7719-7728
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Tidskriftsartikel (refereegranskat)abstract
- SAFT2 with individual-ion parameters, referred to as ion-based SAFT2, is used to represent the properties of aqueous electrolyte solutions. A new set of parameters for 5 cations (Li+, Na+, K+, Ca2+, and Mg2+) and 6 anions (Cl-, Br-, I-, NO3-, SO42-,and HCO3-) is obtained from the fitting of the experimental mean ionic activity coefficients and liquid densities of 24 aqueous single-salt solutions at 298.15 K. The ion parameters are universal and transferable to different salts containing the same ion. Because of the peculiar segment energy of K+, a mixing rule with a binary interaction parameter for the segment energy describing the shortrange interactions between K+ and other cations is needed. The binary interaction parameter is derived from the osmotic coefficients of chloride solutions. The predictions of the osmotic coefficients, vapor pressures, and liquid densities of single- and multiple-salt solutions including seawater (brine) are found to agree with experimental data.
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| 16. |
- Ji, Xiaoyan, et al.
(författare)
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Ion-based statistical associating fluid theory (SAFT2) to represent aqueous single-salt solutions at temperatures and pressures up to 473.15 K and 1000 bar
- 2007
-
Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 46:13, s. 4667-4677
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Tidskriftsartikel (refereegranskat)abstract
- Ion-based SAFT2 is used to represent the properties of aqueous single-salt solutions in the temperature, pressure, and concentration ranges of 298.15-473.15 K, 1.013-1000 bar, and 0-6 mol/kgH2O in ionic strength, respectively. The short-range interaction between cation and anion is needed to capture the effect of pressure on the properties of electrolyte solutions. A new set of parameters at 298.15 K for five cations (Li+, Na+, K+, Ca2+, Mg2+) and seven anions (Cl-, Br-, I-, NO3-, HCO3-, SO42-, CO32-) is obtained from the fitting of the experimental mean ionic activity coefficients and liquid densities of 26 aqueous single-salt solutions. An additional set of ion-specific coefficients used in the temperature-dependent parameter expressions for five cations (Li+, Na+, K+, Ca2+, Mg2+) and five anions (Cl-, Br-, HCO3-, SO42-, CO32-) is obtained from the fitting of the experimental mean ionic activity coefficients and liquid densities of 15 aqueous single-salt solutions at low pressures and temperatures up to 473.15 K. The activity coefficients, osmotic coefficients, water activities, densities, and vapor pressures of single-salt solutions at elevated temperatures and pressures are predicted without any adjustment.
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| 17. |
- Ji, Xiaoyan, et al.
(författare)
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SAFT1-RPM approximation extended to phase equilibria and densities of CO2-H2O and CO2-H2O-NaCl systems
- 2005
-
Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 44, s. 8419-8427
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Tidskriftsartikel (refereegranskat)abstract
- In SAFT1-RPM approximations of CO2-H2O and CO2-H2O-NaCl systems, relevant to oil recovery and CO2 sequestration, CO2 is modeled as a molecule with three association sites, two sites of type O and one site of type C. H2O is modeled as a molecule with four association sites, two sites of type O and two sites of type H. The salt is modeled as a molecule composed of two charged, but nonassociating, spherical segments, of which one represents the cation and one represents the anion. For the CO2-H2O system, only one type of cross-association is assigned, i.e., between the site of type O in CO2 and the site of type H in H2O. Using temperature-dependent parameters, SAFT1-RPM is found to represent the density and equilibrium data for the CO2-H2O system, including the minimum H2O concentration in the CO2-rich phase in the y-P diagram. For the CO2-H2O-NaCl system, an additional binary interaction constant is used, the same for both CO2-Na+ and CO2-Cl- pairs, which is needed to correct the short-range interactions. SAFT1-RPM is also found to represent the equilibrium and density data for the CO2-H2O-NaCl system.
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| 18. |
- Ji, Xiaoyan, et al.
(författare)
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Statistical associating fluid theory coupled with restricted primitive model to represent aqueous strong electrolytes : multiple-salt solutions
- 2005
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 44, s. 7584-7590
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Tidskriftsartikel (refereegranskat)abstract
- Statistical associating fluid theory coupled with the restricted primitive model (SAFT1-RPM), previously proposed for representing single-salt solutions in water, is extended to multiple-salt solutions using a mixing rule for the hydrated diameter. A binary adjustable parameter in this mixing rule, for a pair of salts, is obtained from experimental osmotic coefficients of the corresponding ternary system. The ternary systems considered contain water and all pairs of NaCl, KCl, NaBr, and KBr. LiCl + NaCl and LiCl + KCl pairs are also correlated. The adjustable parameters are used to predict the density of the ternary systems with or without common ions, the solubility of two ternary systems, and the osmotic coefficient of a quaternary NaCl-KCl-LiCl-H2O solution.
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| 19. |
- Ji, Yuanhui, et al.
(författare)
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Thermodynamic analysis on the mineralization of trace organic contaminants with oxidants in advanced oxidation processes
- 2009
-
Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 48:23, s. 10728-10733
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Tidskriftsartikel (refereegranskat)abstract
- There is a growing demand for the efficient treatment of organic polluted wastewaters by advanced oxidation processes (AOPs) which calls for the determination of the mineralization order of ease for the organic contaminants with oxidants. The mineralization abilities of organic contaminants in AOPs are investigated in this work. Photocatalytic experiments for three representative organic contaminants are carried out, and their corresponding reaction rates are determined experimentally. Meanwhile, molar Gibbs free energy changes Delta(r)G(m)degrees for the reactions of 31 organic contaminants (10 chlorinated hydrocarbons, four brominated hydrocarbons, I I aromatic hydrocarbons and their derivatives, three chloroacetic acid, and three chloroacetyl chloride) with oxidants of (OH)-O-center dot, H2O2, O-center dot(-), O-3, and O-2 are calculated, and the mineralization order of ease is determined theoretically on the basis of Delta(r)G(m)degrees. The agreement of the theoretical and experimental mineralization abilities for most of the organic contaminants investigated implies the reliability of the determination of the mineralization ability from the magnitude of Delta(r)G(m)degrees for the mineralization of trace organic contaminants. Results also show that for most of the organic contaminants studied, the mineralization abilities are (OH)-O-center dot > H2O2 > O-center dot(-) > O-3 > O-2, and the mineralization ability of the organic contaminants depends on not only the oxidants but also the structure and properties of the organic contaminants themselves, and the degradation reaction products.
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| 20. |
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| 21. |
- Kronberger, B., et al.
(författare)
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Design and Fluid Dynamic Analysis of a Bench-Scale Combustion System with CO2 Separation-Chemical-Looping Combustion
- 2005
-
Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 44:3, s. 546-556
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Tidskriftsartikel (refereegranskat)abstract
- Chemical-looping combustion (CLC) is a novel combustion technology with inherent separation of the greenhouse gas CO2. The technique involves the combustion of gaseous fuel using a metal oxide for oxygen transfer. The system consists of two reactors, a fuel reactor and an air reactor, and an oxygen carrier in the form of a metal oxide that transports oxygen from the air to the fuel. Direct contact between fuel and combustion air is avoided, and the products from combustion are kept separated from the rest of the flue gases. A dual-fluidized bed reactor system representing a 10-kW CLC prototype was designed. A scaled flow model was built and investigated. Gas velocities and designs were varied, while solids circulation rate and gas leakage between the reactors as well as static pressure balance and residence time distribution of gas and particles were measured. Results show that the solids circulation rates were sufficient and the gas leakage could be decreased to very low values.
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| 22. |
- Lanza, Roberto, 1977-, et al.
(författare)
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Gas Phase Chemistry in Cellulose Fast Pyrolysis
- 2009
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 48:3, s. 1391-1399
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Tidskriftsartikel (refereegranskat)abstract
- We experimentally and theoretically studied cellulose pyrolysis at high temperature and short residence time. We investigated the gas phase chemistry with dedicated experiments and feeding intermediates. Results have been also compared with equilibrium calculations, both single (gas) phase and allowing for solid C formation. Our aim was to understand the cellulose degradation mechanism and particularly the role of gas phase chemistry. We provided evidence of a simplified mechanism, where CO formation is a first, fast step that can be related to levoglucosan ring opening, while H(2) comes from a totally different route, based on hydrocarbon reforming reactions, which also provide further CO. In addition, butadiene was identified as a key intermediate in the decomposition sequence. The different paths and rates of CO formation and H2 formation explain why the ratio of CO to H(2) is not constant, particularly at short residence time. A two-stage process or longer contact time is required, if aiming at syngas production.
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| 23. |
- Norgren, Magnus, et al.
(författare)
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Sulfate and Surfactants as Boosters of Kraft Lignin Precipitation
- 2009
-
Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 48:10, s. 5098-5104
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Tidskriftsartikel (refereegranskat)abstract
- In the spirit of the biorefinery concept, an increasing interest in further utilization of technical lignins outside the pulp mills has arisen. In this context optimization of the precipitation process to increase the yield of the lignin recovered is of great importance. The objectives of this investigation have been to study how specific salts and surfactants affect kraft lignin yield during precipitation and washing. From the results it was seen that additions of sodium sulfate increased the yield of precipitation at elevated temperatures at much lower concentrations than sodium chloride. Earlier studies of the effect of monovalent salts on kraft lignin stability have shown that specific ions either increase or decrease the fort-nation of precipitates during kraft lignin aggregation. Thus, the presented results in this study further strengthen this dependency concerning divalent anions. Regarding the role of surfactants as precipitation enhancers, cationic surfactants gave rise to fast aggregation and relatively high yields. This was found mainly due to attractive electrostatic interactions between the cationic surfactant headgroup and the oppositely charged groups on the kraft lignin macromolecules, introducing an increased degree of hydrophobicity of the lignin and thus a decreased stability. The nonionic surfactants tested affected the system very differently. In some cases the aggregation was fast and the aggregates became relatively large before settling, whereas some surfactants induced the formation of relatively dense precipitates that settled rapidly. Concerning kraft lignin precipitate washing, calcium chloride at concentrations in the millimolar region decreased the lignin losses dramatically.
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| 24. |
- Norgren, Magnus, et al.
(författare)
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Sulfate and Surfactants as Precipitation Boosters in Kraft Lignin Separation
- 2009
-
Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 48:10, s. 5098-5104
-
Tidskriftsartikel (refereegranskat)abstract
- In the spirit of the biorefinery concept, an increasing interest in further utilization of technical lignins outside the pulp mills has arisen. In this context optimization of the precipitation process to increase the yield of the lignin recovered is of great importance. The objectives of this investigation have been to study how specific salts and surfactants affect kraft lignin yield during precipitation and washing. From the results it was seen that additions of sodium sulfate increased the yield of precipitation at elevated temperatures at much lower concentrations than sodium chloride. Earlier studies of the effect of monovalent salts on kraft lignin stability have shown that specific ions either increase or decrease the fort-nation of precipitates during kraft lignin aggregation. Thus, the presented results in this study further strengthen this dependency concerning divalent anions. Regarding the role of surfactants as precipitation enhancers, cationic surfactants gave rise to fast aggregation and relatively high yields. This was found mainly due to attractive electrostatic interactions between the cationic surfactant headgroup and the oppositely charged groups on the kraft lignin macromolecules, introducing an increased degree of hydrophobicity of the lignin and thus a decreased stability. The nonionic surfactants tested affected the system very differently. In some cases the aggregation was fast and the aggregates became relatively large before settling, whereas some surfactants induced the formation of relatively dense precipitates that settled rapidly. Concerning kraft lignin precipitate washing, calcium chloride at concentrations in the millimolar region decreased the lignin losses dramatically.
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| 25. |
- Olsson, Louise, 1974, et al.
(författare)
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Global kinetic model for lean NOx traps
- 2005
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 44:9, s. 3021-3032
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Tidskriftsartikel (refereegranskat)abstract
- Modeling and flow reactor experiments are used to investigate the global kinetics for lean NO x traps (LNTs). Experiments were conducted with a Pt/Rh/BaO/Al 2 O 3 model catalyst, and the inlet feed gas was switched between lean and rich periods. It has previously been observed that NO oxidation to NO 2 is important for NO x storage, and therefore a global mechanism for NO oxidation on Pt/Al 2 O 3 is developed. This is then used in the NO x trap model, after the parameters had been adjusted to match the NO and NO 2 concentrations from experiments on the Pt/Rh/BaO/Al 2 O 3 catalyst. The mass transport of NO and NO 2 inside the particles is described by a shrinking-core model. Further, it is found that two global reaction steps are needed for storage in order to explain the experimental observations: one step for the formation of barium nitrates and the other step for the formation of loosely bound barium nitrites. Reaction steps were added to the model for regeneration of the trap with C 3 H 6 . The model is tuned based on six experiments at three different temperatures and two different NO concentration levels. The model is able to adequately describe NO x storage during the lean period, the NO reduction during the regeneration period, the NO x breakthrough peaks observed initially in the rich period, and the relation between the measured NO and NO 2 concentrations. Experimentally, we have observed that only a fraction of the barium is used for storage in our model catalysts. In the simulations, only 7% of the barium is used for NO x storage. In addition, TEM experiments have shown that our barium particles are large, and therefore a model is evaluated using an inert core in the center of the particle, which resulted in an equally good fit. However, when using catalysts with small particles, which probably is the case in commercial catalysts, a model without an inert core in barium particles seems to be the most realistic one. The model with an inert core is validated with three additional experiments not included in the fitting procedure. In these experiments the oxygen concentration was lowered to 4% during the lean period, compared to 8% O 2 in the experiments used when adjusting the kinetic parameters. The model can simulate the experimental features of these experiments well. © 2005 American Chemical Society.
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| 26. |
- Olsson, Louise, 1974, et al.
(författare)
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Global Kinetic Modelling of a Supplier Barium- and Potassium- Containing Lean NOx Trap
- 2006
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 45:26, s. 8883-8890
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Tidskriftsartikel (refereegranskat)abstract
- Kinetic modeling, in combination with flow reactor experiments, was used in this study to simulate a supplier lean NOx trap (LNT). The LNT catalyst used is a commercial catalyst that contains barium and potassium as storage components. The results presented in this paper are a continuation of a previous study, where a global kinetic model for NOx storage was developed for a model Pt/Rh/BaO/Al2O3 catalyst. In this work, a simplified model is used, where NO oxidation, nitrite, and nitrate formation are lumped together into one reaction, and the model predicts the total NOx. In this model, only one reaction step must be tuned for each storage component: that is, in our case, one reaction for the formation of barium nitrate and one reaction for potassium nitrate. A broad range of experimental conditions was used when developing this model; five temperatures (200, 300, 400, 500, and 600 degrees C) and three different inlet NO concentrations (100, 200, and 300 ppm) were used. Water and CO2 were present in all experiments, because these can affect the storage behavior. The reductant used in the regeneration period was CO. Long lean and rich cycles were used to capture the kinetics of the reactions accurately. The model was able to describe all 15 experiments well and could adequately capture the amount of stored NOx during the lean period and the NOx conversion during the rich period, including the NOx breakthrough peak that occurred at the beginning of the rich period. The model was validated with short lean-rich cycling experiments, where the lean period was 30 s and the rich period was 2 s. The model could predict the outlet NOx concentration well, and the error for the average conversion was only 1%-2% in the validation simulations.
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| 27. |
- Plieva, Fatima, et al.
(författare)
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Macroporous gel particles as novel sorbent materials: Rational design
- 2008
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 47:12, s. 4131-4141
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Tidskriftsartikel (refereegranskat)abstract
- A novel design approach to form macroporous gels is presented. Macroporous gels (MGs), known as cryogels(or gels prepared at subzero temperatures), were prepared inside a protective plastic core (so-called, housing), thus making them resistant to shear forces at stirring. MGs are highly elastic polymeric materials with pore sizes up to 100 mu m and spongelike morphology. Design of MGs inside a protective plastic core (defined as macroporous gel particles, MGPs) allows for expanding the potential applications of such polymeric materials, even to processes in well-stirred bioreactors. MGPs are resistant to attrition caused by continuous stirring, at 400 rpm, while the MGs (prepared under the same conditions) were completely crushed within 1-2 h of stirring. MGPs with a different functionality were prepared and used in the model sorption experiments. Thus, polyacrylamide-based MGPs of different porosities and bearing metal-chelate ligand, iminodiacetate (IDA), were used for capture of Cu(II)-ions at low concentration from water. Because of the large size of interconnected pores in the MGPs, targets of different sizes (low molecular weight targets as Cu(II)-ions and particulate targets as yeast cells) can be captured on the MGPs (bearing specific ligands to the targets) from a complex mixture. The MGPs can be dried, stored in the dried state, and reswollen when required. The open permeable porous structure of MGPs and high stability at stirring together with ease of preparation make the MGPs a very attractive, novel, robust sorbent medium for different biotechnological applications.
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| 28. |
- Regner, Mårten, et al.
(författare)
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Influence of viscosity ratio on the mixing process in a static mixer : Numerical study
- 2008
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 47:9, s. 3030-3036
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 29. |
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| 30. |
- Shulman, Alexander, 1978, et al.
(författare)
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High reactivity and mechanical durability of NiO/NiAl2O 4 and NiO/NiAl2O4/MgAl2O4 oxygen carrier particles used for more than 1000 h in a 10 kW CLC reactor
- 2009
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 48:15, s. 7400-7405
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Tidskriftsartikel (refereegranskat)abstract
- Chemical-looping combustion (CLC) is a promising technology for CO 2 capture in the process of combustion of gaseous fossil fuels. Oxygen carrier materials based on Ni/NiO on NiAl2O4 and on NiAl2O4/MgAl2O4 support have previously shown high initial activity combined with high conversion of methane and low concentration of outgoing CO. The feasibility of the Ni/NiO system for CLC depends largely on the lifetime of the oxygen carrier particles in the reactor due to the high price of the material. Avoiding chemical and physical degradation of oxygen carriers is essential for long-term industrial-scale chemical-looping combustion operations, and the particles' activity and mechanical durability have to remain high during long operation times. In this study, a series of oxygen carrier samples were collected from a 10 kW CLC combustor operated for a total of 1016 h using oxygen carrier materials based on NiO/NiAl2O4 (N-VITO) for 405 h and a mixture of used NiO/NiAl2O4 with fresh NiO/NiAl2O 4/MgAl2O4(N-VITOMg) for 611 h, respectively. These samples were collected after certain time intervals and analyzed in terms of reactivity with methane in a quartz batch reactor. Also, the structural and mechanical properties of these samples were investigated by means of powder XRD, BET surface area measurements, light and scanning electron microscopy, energy dispersive X-ray spectrometry, and crushing strength evaluation. It was shown that both N-VITO and N-VITO/N-VITOMg demonstrate high reactivity and mechanical durability after having been used for more than 1000 h in the CLC 10 kW reactor, which makes them excellent candidates for applications within the area of chemical-looping combustion.
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| 31. |
- Stelte, Wolfgang, et al.
(författare)
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Preparation and characterization of cellulose nanofibers from two commercial hardwood and softwood pulps
- 2009
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 48:24, s. 11211-11219
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work was to study the mechanical fibrillation process for the preparation of cellulose nanofibers from two commercial hard- and softwood cellulose pulps. The process consisted of initial refining and subsequent high-pressure homogenization. The progress in fibrillation was studied using different microscopy techniques, mechanical testing, and fiber density measurements of cellulose films prepared after different processing stages. The mechanical properties of cellulose films showed an increase in strength and stiffness with decreasing fiber size, and this stabilized after a certain number of passes in the homogenizer. Atomic force microscopy studies showed that the obtained cellulose nanofibers had diameters in the 10-25-nm range. The significant difference between the two samples was that the ultimate failure strain for cellulose films made of softwood fibers increased during the process whereas it remained constantly low for hardwood cellulose films. This difference could be due to the presence of shorter fibers and more defects in the films. An important point to note is that excessive processing reduced properties, as seen by the decrease in failure strain of softwood fiber films, and could also decrease other properties such as strength if the number of processing steps were further increased.
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| 32. |
- Svärd, Michael, et al.
(författare)
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Force Fields and Point Charges for Crystal Structure Modeling
- 2009
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 48:6, s. 2899-2912
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Tidskriftsartikel (refereegranskat)abstract
- Molecular simulation is increasingly used by chemical engineers and industrial chemists in process and product development. In particular, the possibility to predict the structure and stability of potential polymorphs of a substance is of tremendous interest to the pharmaceutical and specialty chemicals industry. Molecular mechanics modeling relies on the use of parametrized force fields and methods of assigning point charges to the atoms in the molecules. In commercial molecular simulation software, a wide variety of such combinations are available, and there is a need for critical assessment of the capabilities of the different alternatives. In the present work, the performance of several molecular mechanics force fields combined with different methods for the assignment of atomic point charges have been examined with regard to their ability to calculate absolute crystal lattice energies and their capacity to identify the experimental structure as a minimum on the potential energy hypersurface. Seven small, aromatic monomolecular crystalline compounds are used in the evaluation. It is found that the majority of the examined methods cannot be used to reliably predict absolute lattice energies. The most promising results were obtained with the Pcff force field using integral charges, and the Dreiding force field using Gasteiger charges, both of which performed with an accuracy of the same order of magnitude as the variations in experimental lattice energies. Overall, it has been observed that the best results are achieved if the same force field method is used to relax the crystal structure and calculate the energy, and to optimize and calculate the energy of the gas phase molecule used for the correction for changes in molecular geometry. The Pcff and Compass force fields with integral charges have been found to predict relaxed structures closest to the experimental ones. In addition, five different methods for determining point charges fitted to the electrostatic potential (ESP charges), available in the same software, have been evaluated. For each method, the molecular geometries of 10 small, organic molecules were optimized, and ESP charges calculated and analyzed for linear correlation with a set of reference charges of an accepted standard method, HF/6-31G*. Dmol-3 gives charges that correlate well with the reference charge. The charges from Vamp are not linearly scalable to the HF/6-31G*-level, which is attributed partly to the geometry optimization but mainly to the calculation of the ESP and the subsequent charge fit.
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| 33. |
- Teleki, Alexandra, et al.
(författare)
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Role of Gas-Aerosol Mixing during in Situ Coating of Flame-Made Titania Particles
- 2009
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 48:1, s. 85-92
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Tidskriftsartikel (refereegranskat)abstract
- Rutile TiO(2) particles of 40 nm average diameter were made by flame spray pyrolysis (FSP) and in situ coated with ultrathin (2-4 nm) SiO(2) layers. The spray flame was enclosed by a quartz glass tube while hexarnethyldisiloxane (HMDSO) vapor-laden N(2) was injected in swirling crossflow to and downstream of the flame through a metal torus pipe ring. The as-prepared powders were characterized by transmission electron microscopy (TEM), X-ray diffraction, and nitrogen adsorption. The effect of mixing between HMDSO-laden N2 jets and freshly made titania aerosol on product coating quality was investigated by varying systematically the number and gas flowrate through these jets experimentally and by computational fluid dynamics. The coating quality of titanium dioxide was evaluated further by photocatalysis of isopropanol to acetone under UV light using suspensions of the above particles.
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| 34. |
- Virtanen, Pasi, et al.
(författare)
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Kinetics of cinnamaldehyde hydrogenation by supported ionic liquid catalysts (SILCA)
- 2009
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Ingår i: Industrial & Engineering Chemistry Research. - Washington : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 48:23, s. 10335-10342
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Tidskriftsartikel (refereegranskat)abstract
- The research of ionic liquids and their applications in catalysis are attracting increasing attention in chemistry and chemical engineering. A supported ionic liquid catalyst (SILCA) consists of immobilized catalytic species (e.g., transition-metal particles, metal complexes, or enzymes) residing in an ionic liquid layer immobilized on a porous solid support. The kinetics of cinnamaldehyde hydrogenation over SILCAs that contained palladium nanoparticles in ionic liquid, which, in turn, was immobilized oil active carbon cloth (ACC), was studied and modeled in detail. A mechanistic kinetic model, which describes the differences of the activity and selectivity of the catalysts consisting of different ionic liquids, was developed. The model explained the experimental results well.
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| 35. |
- Wågberg, Lars, et al.
(författare)
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Hyperbranched polymers as a fixing agent for dissolved and colloidal substances on fiber and SIO2 surfaces
- 2007
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 46:7, s. 2212-2219
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Tidskriftsartikel (refereegranskat)abstract
- Hyperbranched polymers (polyesteramides) were used as a cationic fixing agent to remove dissolved and colloidal substances (DCS) from the water phase in a fiber suspension. The relative turbidity, electrophoretic mobility, and average diameter of the colloidal particles were determined as a function of polyelectrolyte concentration. The results indicated that maximum removal of DCS was achieved at about zero electrophoretic mobility of the suspension where the negative surface charges of particles were neutralized by the oppositely charged hyperbranched polymer. The amount of hyperbranched polymers needed to maximize DCS fixation on the fibers was higher than the amount of poly-DADMAC (diallyldimethylammonium chloride) needed to reach the same effect. This was found to be due to the lower molecular weight and lower charge density of hyperbranched polymers. The lower molecular mass allowed penetration of these polymers into pores of fibers that resulted in higher polymer consumption before removal of the dissolved and colloidal substances from the fiber suspensions. A lower charge density further resulted in a higher saturation adsorption of the hyperbranched polymer. Experiments with both DCS and model-latex particles showed that the initial increase in relative turbidity was due to the aggregation of particles before fixation to fibers. The results from quartz crystal microbalance with dissipation (QCM-D) experiments showed that the efficiency of hyperbranched polymer and poly-DADMAC was similar even if they had different structure. Therefore, this study highlights the importance of molecular mass and charge density of the polymers as well as the surface structure of polymer layers which in turn gives implications for development of new structures of fixing agents.
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| 36. |
- Zhang, Weidong, et al.
(författare)
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Algebraic solution to H2 control problems : II. The multivariable decoupling case
- 2006
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 45:21, s. 7163-7176
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Tidskriftsartikel (refereegranskat)abstract
- The control of multivariable systems with time delays is an important problem in linear control systems. The goal of this paper is to develop an algebraic design method for multivariable systems with multiple time delays. In the method, the algebra-based input-output design technique is adopted, because it is easy to understand and use, and it requires no state variables. We focus mainly on decoupled response. First, all stabilizing decoupling controllers are parametrized. Second, the optimal decoupling controller is derived by minimizing the sensitivity function. Finally, the performance and robustness are analyzed and a simple tuning rule is developed for quantitative performance and robustness. The most important feature of the proposed method is that the controller is optimal, analytical, and can provide decoupling response. Typical examples are provided to illustrate the proposed method
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