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| 2. |
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| 3. |
- Wik, Torsten, 1968, et al.
(author)
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Modelling the Dynamics of a Trickling Filter for Waste Water Treatment
- 1994
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In: Preprints of the 5th Nordic Process Control Workshop, Lyngby, Denmark.
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Conference paper (other academic/artistic)abstract
- This study concems the dynamics of the nitrifying efficiency of a trickling filter for waste water treatment. In a novel approach, based on minimum plant area usage, a filter will be placed after the secondary sedimentation tanks with recirculation to the activated sludge process stage. The objective of the trickling filter model is to describethe growth of the nitrifying bacteria Nitrosomonas and Nitrobacter in the bio-film. A steady state mass-balance model for the substrates in the film based on Monod kinetics has been formulated. The dynamics of the filter, or the “memory”, is described by a division of the film infour volume fractions, Nitrosomonas, Nitrobacter, inert (non-active) material and water. These fractions are calculated at different depths of the film as well as for various layers of the filter StrUCtUTe. Data from a pilot plant at Rya treatment plant in Gothenburg, Sweden, haveprovided the necessary feedback for calculating model parameters, verifying assumptions etc. A shooting and matching routine in the NAG Fortran library is used for the solution of the model equations. Simulations performed so far have indicated that it can take days and even weeks for changes in the bacteria populations to take place. Thismeans that the working point for the proposed full scale filter at the plant should track the past history of the filter.
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| 4. |
- Skoglundh, Magnus, 1965, et al.
(author)
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Combinations of platinum and palladium on alumina supports as oxidation catalysts
- 1991
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In: Applied Catalysis. - 0166-9834 .- 1873-3867. ; 77:1, s. 9-20
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Journal article (peer-reviewed)abstract
- The effects of the total content of Pd+Pt, the mol-% ratio of Pd to Pt, hydrothermal treatment of the catalyst wash-coat, and the oxygen concentration on the light-off temperature, T50, for the complete oxidation of xylene isomers, propene, and carbon monoxide were studied. The alumina wash-coats were thermally treated at 500°C for 2 h in air or after the thermal treatment, hydrothermslly treated at 814°C for 2 h in 100-% steam. The catalysts were impregnated with 5, 10, and 20 micromol of Pd+Pt per gram of catalyst. The mol-% ratio of Pd to Pt was varied in the range from 0:100 to 100:O. The light-off temperatures had a minimum at a Pd:Pt mol-% ratio of 80:20, and decreased with increasing total metals concentration, increasing oxygen concentration and hydrothermal treatment of the alumina wash-coat.
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| 7. |
- Diehl, Stefan, et al.
(author)
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Analytical and numerical description of the settling process in the activated sludge operation
- 1990
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In: Instrumentation, control, and automation of water and wastewater treatment and transport systems : proceedings of the 5th IAWPRC Workshop held in Yokohama and Kyoto, Japan, 26 July-3 August 1990. - 0080407765 ; , s. 471-478
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Conference paper (peer-reviewed)abstract
- The secondary clarifier or settler is crucial for the whole activated sludge operation. Consequently, it is important to obtain a reliable analytical model as well as a useful numerical method, which can be used in the automatic control of the settling process. Discontinuities (shocks) appear physically, and an analytical description as well as a stable numerical algorithm must be able to handle these discontinuities. A model based on the Kynch theory of sedimentation is used, where the settling flux is a function only of the local concentration and is assumed to have one inflexion point. For such non-convex flux functions, the settling process is qualitatively the same, independent of further assumptions on the shapes of the settling functions. Using the theory of nonlinear conservation laws, the main results obtained are: how to calculate transient and asymptotic behavior; how to control the concentration profile of the settler, in particular the depth of the sludge blanket, for a given load; and, a numerical algorithm which automatically preserves shocks and gives the physically correct solution according to the analytical treatment. The algorithm can be applied on any flux function (with more than one inflexion point).
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| 8. |
- Galbe, Mats, et al.
(author)
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Simulation of ethanol production processes based on enzymatic hydrolysis of woody biomass
- 1994
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In: Computers & Chemical Engineering. - : Elsevier BV. - 1873-4375 .- 0098-1354. ; 18:Suppl. 1, s. 687-691
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Journal article (peer-reviewed)abstract
- The process simulator ASPEN PLUS was used for simulation of an ethanol production process based on enzymatic hydrolysis of lignocellulosic materials. Various process configurations were studied to increase the overall yield of ethanol and to reduce the energy consumption in the process. An increased utilization of the pentosan fraction was achieved by a complex recycling of streams in the process. This increased the total overall yield from 56% to 70%. Internal recycling of an ethamol containing stream increased the ethanol concentration in the distillation feed from 2.6 to 7.1 wt% which decreased the energy consumption in the distillation from 8 to 2 MW. The recycling will however result in increased concentrations of byproducts and inhibitors which requires future investigation of how these new conditions will affect the performance in the hydrolysis and fermentation steps.
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| 9. |
- Hvitt Strömvall, Ann-Margret, 1963, et al.
(author)
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Ambient monoterpenes from stone groundwood pulp production
- 1990
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In: Holzforschung. ; 44, s. 449-452
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Journal article (peer-reviewed)abstract
- Composition and ambient concentrations in air were studied for monoterpenes from stone groundwood production at a Swedish plant using exclusively pulp wood from Norway spruce. Field samples were taken on Tenax adsorption cartridges and analyzed by thermal desorption combined with temperature programmed capillary gas chromatography. The major monoterpenes emitted from the process were alpha-pinene(54-59 %) and beta-pinene(24-28 %). Limonene, 3-carene, beta-phellandrene, camphene and myrcene (1-10 % each) followed in decreasing relative proportions. Total ambient monoterpene concentrations above 500 microgram/m3 were assessed at ground level downwind from the emissions. Photo-oxidants formed in the monoterpene plumes are discussed with respect to forest damage and health hazards.
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| 10. |
- Hvitt Strömvall, Ann-Margret, 1963, et al.
(author)
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Photooxidant-forming monoterpenes in air plumes from kraft pulp industries
- 1993
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In: Environmental Pollution. ; 79, s. 219-223
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Journal article (peer-reviewed)abstract
- Monoterpenes emitted to air from two Swedish kraft (sulphate) pulp-mills were determined by sampling on the Tenax adsorbent followed by laboratory analysis using thermal desorption combined with high-resolution gas chromatography. The composition of the terpenes was found to be similar in the emissions from various parts of the process as well as in the mill plume. The bicyclic terpenes alpha-pinene and 3-carene, originating principally from wood of Scots pine (Pinus sylvestris), predominated among the thirteen assessed hydrocarbon monoterpenes. Terpinolene was the most prominent among the particularly reactive terpenes with a lifetime in ozone-rich air of only a few minutes. The rapid formation of photooxidants by chemical reactions of the terpenes with other components of the mill plume is discussed. It is concluded that a variety of phytotoxic photooxidants are formed which may contribute significantly to forest decline within 50 km of mills located along coasts.
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| 11. |
- Hvitt Strömvall, Ann-Margret, 1963, et al.
(author)
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Terpenes emitted to air from TMP and sulphite pulp mills
- 1992
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In: Holzforschung. ; 46, s. 99-102
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Journal article (peer-reviewed)abstract
- Terpenes were studied at two Swedish pulp mills processing wood from Norway spruce (Picea abies). Field samples were adsorbed from air on Tenax cartridges and analyzed in the laboratory by thermal desorption and gas chromatography.The emissions from a large thermomechanical pulp (TMP) plant consisted mainly of chemically unchanged hydrocarbon monoterpenes from the wood. The major monoterpenes were alpha-pinene (>50 %) and beta-pinene (20-30 %).The proportions of ten additional components were determined in the process emissions, which may be recovered to turpentine.The process emissions from a sulphite pulp mill consisted predominantly of the alkylbenzene para-cymene, formed from monoterpenes by acid reactions in the digestors. The contribution of the emissions to photo-oxidant formation in the surrounding region may be significant for both types of mills.
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| 12. |
- Ramnäs, Olle Jerker, 1941, et al.
(author)
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Characterization of sixty alkenes in a cat-cracked gasoline naphtha by gas chromatography
- 1994
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In: Chromatographia. ; 38, s. 222-226
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Journal article (peer-reviewed)abstract
- The alkene-rich petrol fraction from refinery fluid catalytic cracking (FCC) has been characterized by GC and GC-MS. Quantitative proportions and retention data of 52 acyclic and 11 cyclic C5–C7 alkenes are given. Relative retentions are reported for methylsilicone and aluminium oxide stationary phases as methylene units (MU). Applications of mass spectra, single-ion GC-MS monitoring and retention data for identifications are demonstrated.
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| 15. |
- Berntsson, Thore, 1947
(author)
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Industriell värmepumpsteknik
- 1992
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Reports (other academic/artistic)abstract
- Med industriell värmepump menas i denna rapport alla tillämpningar av värmepumptekniken, som använder industriellt sekundärvärme som värmekälla och levererar det producerade värmet till industrins processer eller byggnader och/eller till ett fjärrvärmenät. Jämfört med motsvarande för byggnadsuppvärmning har industriella värmepumpar i många fall följande fördelar:· Höga COP (Coefficient of Performance) beroende på små temperaturlyft och/eller hög temperaturnivå.· Lång årlig drifttid.· Relativt liten investeringskostnad, beroende på stora enheter och små avstånd mellan värmekälla och värmesänka.· Produktionen av spillvärme och behovet av värme uppträder samtidigt i tiden. Trots detta är alltså antalet värmepumpinstallationer i industrin litet jämfört med sådana för byggnadsuppvärmning. Det nämns ofta att huvudorsaken till detta är industrins krav på korta pay-off-tider. Detta är dock inte hela sanningen. Även i situationer där man kan påvisa korta pay-off-tider har värmepumpar hittills installerats endast i liten utsträckning. Andra viktiga orsaker är:· Brist på experiment- och demonstrationsanläggningar i olika typer av industrier.· Osäkerheten hos användarna om driftsäkerheten.· Brist på bra hårdvara för vissa typer av tillämpningar.· Brist på kunskapskombinationen processteknik/värmepumpteknik i industrier och konsultföretag.· Bristande kunskap om processintegration av värmepumpar. Med "industriell" värmepump menas i denna rapport alla tillämpningar av värmepumptekniken, som använder industriellt sekundärvärme som värmekälla och levererar det producerade värmet till industrins processer eller byggnader och/eller till ett fjärrvärmenät.
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| 16. |
- Berntsson, Thore, 1947
(author)
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Processintegration i industrin
- 1992
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In: Artikel till Värmeforsks årsredovisning. ; Febr 1992:2
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Journal article (other academic/artistic)
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| 17. |
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| 19. |
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| 20. |
- Pettersson, Gösta, et al.
(author)
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Model studies of the regulation of the Calvin photosynthesis cycle by cytosolic metabolites
- 1990
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In: Biomedica Biochimica Acta. - 0232-766X. ; 49:8-9, s. 723-732
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Journal article (peer-reviewed)abstract
- A kinetic model for photosynthetic carbohydrate formation in the chloroplast of C3 plants is presented which includes consideration of the interaction of the phosphate translocator of the chloroplast envelope with external reactants such as 3-phosphoglycerate, dihydroxyacetone phosphate, and glyceraldehyde 3-phosphate in addition to inorganic (ortho)phosphate. The model is shown to account satisfactorily for experimentally observed effects of such reactants on the rates of carbon dioxide fixation and starch production in isolated chloroplast. The predictions of the model with regard to the regulation of stromal processes of photosynthetic carbohydrate formation by cytosolic concentration variables have been examined. The results indicate that the cytosolic concentrations of metabolites that interact with the phosphate translocator represent important regulatory signals. Increasing levels of exported photosynthetic (phosphoglycerates and triose phosphates) in the cytosol do not suppress the rate of photosynthetic carbon dioxide fixation, but redirects reaction flux such that starch production within the chloroplast is favoured at the expense of a decreased rate of photosynthate export to the cytosol.
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| 21. |
- Pinheiro, H. M., et al.
(author)
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Quinones as external electron acceptors in steroid dehydrogenation with entrapped cells in organic medium
- 1993
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In: Biocatalysis and Biotransformation. - : Informa UK Limited. - 1024-2422. ; 7:2, s. 83-96
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Journal article (peer-reviewed)abstract
- A series of quinone-based compounds were tested for their ability to act as external electron acceptors in the 1-dehydrogenation of-αmethyl-hydrocortisone-21-acetate, with polyurethane-entrapped Arthrobacter simplex cells in buffer-saturated n-decan-1-ol. This organic solvent was needed to solubilize the steroid substrate. In aqueous medium, the conversion with free cells virtually stopped after one hour, probably due to substrate limitation. All the tested quinones acted as external electron acceptors, increasing the bioconversion rate. The process kinetics were complex. However, when keeping the concentration of one of the substrates (steroid or quinone) constant and varying that of the other, Michaelis-Menten kinetics provided a reasonably good model for the initial reaction rates, and apparent kinetic constants were estimated. The most effective of the tested external electron acceptors were 2,6-dimethyl-p-benzoquinone and menadione. Mass transfer limitations seemed to appear after some hours of reaction, with low concentrations of the more efficient quinones, when the biocatalyst microenvironment was quinone- and possibly oxygen-depleted. Monosodium glutamate was included with the cells in the immobilisation foam, as an activity-stabilizing agent. It was observed that some of the quinones apparently formed complexes with this glutamate, thereby influencing the kinetics of the process. The catalytic half-life of the system depended on the quinone concentration and optimal values (60-80 h) were observed at 1 mM levels of 2,6-dimethyl-p-benzoquinone or menadione. Quinone toxicity, direct or through the formation of peroxides in the aerobic reoxidation process, may be at the origin of enzyme deactivation.
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| 22. |
- Wide, Ann, 1962-, et al.
(author)
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Sätt vid kloratframställning : [Method of preparing chlorate]
- 1990
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Patent (pop. science, debate, etc.)abstract
- The invention discloses a method in the electrolytic production of alkali metal chlorate which is recovered by crystallization and separation of the crystals from a solution recycled to the electrolysis process. A given proportion of the crystals formed are separated and removed from the mother liquor after they have been in contact with the mother liquor for a shorter period of time than the remaining crystals, whereby they obtain a sulphate content which is higher than in the crystals that have been in contact with the mother liquor for a longer period of time.
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| 23. |
- Åhlby, Lena, 1961, et al.
(author)
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The Compression/Absorption cycle: A high-temperature application
- 1990
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In: BHRA International Conference on Application and Efficiency of Heat Pump Systems in Environmentally Sensitive Times. ; München, Germany:1-3 October 1990, s. 15-
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Conference paper (other academic/artistic)abstract
- A comparison of the performances of a compression/absorption cycle using the two mixturesNH3/H2O and NH3/H2O-60% LiBr shows an improvement in COP for the ternary working fluid. The improvement, however, is small; for the examples chosen it is about 5%. The advantages of the ternary mixture, such as a lower vapour pressure, a higher heat of vaporization and a reduced specific heat of solution, compared to the binary NH3/H2O, are to a large extent eliminated by the increase of the recirculation flow caused by the addition of saltAnother effect of the increase in solution flow is a change in the location of the optimum operating point for the ternary compared to the binary mixture.
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