| 1. |
- Nordberg, Åke, et al.
(författare)
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Selective desorption of carbon dioxide from sewage sludge for in-situ methane enrichment : Enrichment experiments in pilot scale
- 2012
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 37, s. 196-204
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Tidskriftsartikel (refereegranskat)abstract
- The application of in-situ methane enrichment for upgrading the biogas from anaerobic digestion to vehicle fuel or natural gas quality, has been studied in pilot scale and by computer simulation of the desorption step. Pilot plant experiments have been performed using a 19 m(3) and 15 m(3) continuously stirred tank reactor operating with municipal sewage sludge at mesophilic conditions connected respectively to a 90 dm(3) and 140 dm(3) external bubble column for selective desorption of CO2. The results show that the CH4 yield is unchanged during the experiments, and accordingly there is no evidence that the oxygen in the air used in the desorption of CO2 has a negative impact on the CH4 producing activity. The sludge recirculation system must be designed to avoid leakage of air into the digester, in order to maintain a low N-2 concentration in the biogas. At best, a biogas with a volume fraction of 87% CH4 and (p N-2 = 2% was obtained. The CH4 loss however amounted to 8%, which is unsatisfactory. The experimental results are compared with previous data in the literature and explanations are deducted for the difference in the performance. Computer simulations reveal that the sludge flow rate recirculated through the desorption column should be as low as possible to minimize the loss of CH4. An increased air flow rate through the desorption column and an increased desorption column volume will promote the desorption of CO2 and improve the ratio of CO2 to CH4 desorption.
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| 2. |
- Ahuja, Dipali, et al.
(författare)
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Investigation of solid-liquid phase diagrams of the sulfamethazine-salicylic acid co-crystal
- 2019
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Ingår i: CrystEngComm. - : ROYAL SOC CHEMISTRY. - 1466-8033. ; 21:18, s. 2863-2874
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Tidskriftsartikel (refereegranskat)abstract
- The influence of temperature and solvent on the solid-liquid phase diagram of the 1 : 1 sulfamethazinesalicylic acid co-crystal has been investigated. Ternary phase diagrams of this co-crystal system have been constructed in three solvents: methanol, acetonitrile and a 7 : 3 (v/v) dimethylsulfoxide-methanol mixture, at three temperatures. The system exhibits congruent dissolution in acetonitrile and the co-crystal solubility has been determined by a gravimetric technique. The Gibbs energy of co-crystal formation from the respective solid components has been estimated from solubility data, together with the corresponding enthalpic and entropic component terms. The Gibbs energy of formation ranges from -5.7 to -7.7 kJ mol -1, with the stability increasing with temperature. In methanol and the DMSO-methanol mixture, the co-crystal dissolves incongruently. It is shown that the solubility ratio of the pure components cannot be used to predict with confidence whether the co-crystal will dissolve congruently or incongruently. The size of the region where the co-crystal is the only stable solid phase is inversely related to the pure component solubility ratio of salicylic acid and sulfamethazine.
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| 3. |
- Ahuja, Dipali, et al.
(författare)
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Solution and calorimetric thermodynamic study of a new 1:1 sulfamethazine-3-methylsalicylic acid co-crystal
- 2020
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Ingår i: CrystEngComm. - : Royal Society of Chemistry (RSC). - 1466-8033. ; 22:20, s. 3463-3473
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Tidskriftsartikel (refereegranskat)abstract
- A new 1:1 co-crystal of sulfamethazine (API, SMT) and 3-methylsalicylic acid (coformer, 3mSA) has been synthesized and its crystal structure solved by single crystal X-ray diffraction (XRD). The co-crystal has been thoroughly characterized by powder XRD, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The pure co-crystal could be synthesized by solvent drop grinding, cooling crystallization and slurry conversion co-crystallization. Ternary phase diagrams have been constructed in methanol and acetonitrile at 30 degrees C. The co-crystal exhibits incongruent dissolution in both solvents. The thermodynamics of co-crystal formation have been estimated from solubility data and calorimetric data, respectively, showing that formation of the SMT-3mSA co-crystal from its solid components is spontaneous and entropy-driven. The co-crystal formation is associated with a 5% increase in molecular volume. A relationship between the size of the region where the co-crystal is the most stable solid phase and the relative solubility of the co-crystal components has been uncovered. The co-crystal region becomes smaller as the solubility ratio increases.
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| 4. |
- Ahuja, D., et al.
(författare)
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Study of three solvates of sulfamethazine
- 2017
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Ingår i: CrystEngComm. - Cambridge, England : Royal Society of Chemistry (RSC). - 1466-8033. ; 19:43, s. 6481-6488
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Tidskriftsartikel (refereegranskat)abstract
- Three novel solvates of sulfamethazine (SMT), an anti-microbial and anti-infective sulfonamide drug with the solvents-dimethylacetamide, dimethylformamide and dimethyl sulfoxide have been identified and characterized by analytical techniques including differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction and Raman spectroscopy. All three are 1:1 solvates. Crystal structure analysis revealed N-H-O type intermolecular hydrogen bonding interactions between SMT and the solvent imparting stability to the solvate structure. Thermal analysis measurements for the stoichiometry of the solvates were in good agreement with the single crystal data. The solubility of the solvates in their respective solvents at 25 °C has been determined.
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| 5. |
- Aisling, Lynch, et al.
(författare)
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Crystal Growth of Single Salicylamide Crystals
- 2019
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 19:12, s. 7230-7239
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Tidskriftsartikel (refereegranskat)abstract
- Growth of single salicylamide crystals was investigated in a nonstirred growth cuvette and on a rotating disk. In the growth cuvette the crystal growth rates were measured for both primary nucleated crystals and seed crystals manually inserted into the cuvette. In the rotating disk experiments multiple seed crystals were attached to a disk that was rotated in a supersaturated solution. The crystal growth rates in the length and width direction were precisely measured in situ for each individual crystal, and growth rates were also extracted for a specific crystal facet, that is, (200). In all cases, the growth rate was considerably faster in the rotating disk experiments, shown to be governed by surface integration. Solvent was found to impact the growth rates of the crystal facets in part by creating different surface features. The influence of the supersaturation on the crystal growth rate depended on the solvent; in general, an increasing trend was observed. At relatively low supersaturations, it was discovered that the growth process will focus on repairing morphological defects. Within the range of experimental conditions, the growth kinetics were strongly affected by the temperature as was further indicated by the relatively high activation energy values obtained. The crystal seed quality was found to have a substantial impact on the growth rate, with rougher crystals leading to quicker growth. A wide growth rate dispersion was obtained for both crystal growth methods, found to be reduced by using seed crystals with high quality, lower supersaturations, and also within certain solvents.
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| 6. |
- Alander, Eva M., et al.
(författare)
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Agglomeration and adhesion free energy of paracetamol crystals in organic solvents
- 2007
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Ingår i: AIChE Journal. - : Wiley. - 0001-1541 .- 1547-5905. ; 53:10, s. 2590-2605
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Tidskriftsartikel (refereegranskat)abstract
- The agglomeration of paracetamol during crystallization in different pure solvents has been investigated. Narrowly sieved crystals were suspended as seeds and allowed to grow and agglomerate at constant supersaturation and temperature. Particles from each experiment were examined by image analysis and multivariate data evaluation, for the number of crystals per particle. From the resulting number distribution, parameters defining the degree of agglomeration were extracted. The degree of agglomeration among the product particles is fairly low in water, methanol, and ethanol, while it is substantial in acetone particularly, but also in acetonitrile and methyl ethyl ketone. Surfaces of large, well-grown paracetamol crystals have been characterized by contact angle measurements. The surface free energy components of different crystal faces have been estimated using Lifshitz-van der Waals acid-base theory. The data are used for estimation of the solid-liquid interfacial free energy of each face in the solvents of the agglomeration experiments and the corresponding crystal-crystal adhesion free energy of pairs of faces. The degree of agglomeration in different solvents does correlate to the free energies of adhesion. This supports the hypothesis that the influence of the solvent on the crystal agglomeration relates to physico-chemical adhesion forces between crystal faces in the solution.
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| 7. |
- Alander, E. M., et al.
(författare)
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Characterization of paracetamol agglomerates by image analysis and strength measurement
- 2003
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Ingår i: Powder Technology. - : Elsevier BV. - 0032-5910 .- 1873-328X. ; 130:1-3, s. 298-306
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Tidskriftsartikel (refereegranskat)abstract
- Paracetamol is crystallized in different solvents and techniques are developed and used to characterize the product. The product particles from three different solvent compositions: ethylene glycol, acetone and an acetone-water mixture (30-70 wt.%) have been examined. Product properties visually observed are quantified by image analysis and evaluation of measured image descriptors with Principal Component Analysis (PCA). The agglomerate strength has been determined by crushing single agglomerates. Depending on the solvent, the content of single crystals and agglomerates differ. Agglomerates differ by the number and size of crystals grown together, as well as by the strength.
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| 8. |
- 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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| 9. |
- Albero Caro, Jesus, et al.
(författare)
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Semibatch reaction crystallization of salicylic acid
- 2014
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Ingår i: Chemical engineering research & design. - : Elsevier BV. - 0263-8762 .- 1744-3563. ; 92:3, s. 522-533
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Tidskriftsartikel (refereegranskat)abstract
- Reaction crystallization of salicylic acid has been investigated by experiments and modeling. In the experimental work, dilute hydrochloric acid has been added to an agitated aqueous solution of sodium salicylate in 1 L scale, and product crystals have been characterized by image analysis. The results show that the product crystal number mean size at first increases with increasing agitation rate but then gradually decreases again at further increase in stirring rate. At lower stirring rate, larger crystals are obtained when the feeding point is located close to the agitator instead of being located out in the bulk solution. The mean crystal size increases with decreasing feeding rate and with decreasing reactant concentrations. There is a decrease in mean size with increasing feed pipe diameter. These trends in the experimental results show great similarity with previous results on benzoic acid. The experimental results have been examined by a population balance model accounting for meso and micro mixing, and crystal nucleation and growth rate dispersion. It is found that the crystallization kinetic parameter estimation is quite complex, and the objective function hyper surface contains many different minima. Hence, parameter estimation has to rely on a combination of mathematical optimization strategies and a scientific understanding of the physical meaning of the parameters and their relation to current theories. As opposed to our previous work on benzoic acid, it has not been possible to find a set of kinetic parameters that provides for a good description of all experimental data.
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| 10. |
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