Construção e avaliação de célula de fluxo para estudo da tensão interfacial dinâmica da interface fluxo líquido - sólido por despolarização da fluorescência
Abstract:Recebido em 8/1/04; aceito em 3/9/04; publicado na web em 17/2/05 DEVELOPMENT OF A FLOW CELL TO STUDY DYNAMIC INTERFACIAL TENSION OF SOLID-LIQUID FLOW BY FLUORESCENCE DEPOLARIZATION. A simple low-cost flow cell was developed, built and optimized in order to observe dynamic interfacial tension of continuous flow systems. Distinct materials can be used in one of the cell walls in order to observe the intermolecular forces between the flowing liquid and the chemical constitution of the walls. The fluorescence dep… Show more
“…Flow Cell. An in-house developed cell (Figure A) was used in order to emphasize the boundary layer where the interaction between the wall and the liquid flow is stronger. 3 (A) Scheme of the flow cell for PLF-FI.…”
Section: Methodsmentioning
confidence: 99%
“…The experimental setup for PLF-FI was described before. , Briefly, a Coherent Inova60 argon laser (Figure B) at multimode, multiline, and 100 mW is reflected by two mirrors (M) through a biconvex borosilicate lens (L1) of 400-mm focal length that focus the laser into the sample (FI) on a 0.02-mm 2 diameter spot. To monitor the laser intensity fluctuations in real time, 10% of the laser beam was diverted by a beam splitter (BS) onto a BPW-21 RS-Electronics photodiode (PD1) with 7.5-mm 2 active area, operating as a current-to-voltage converter with seven optional sensibility ranges.…”
Pipelines for heavy crude oils have recurrent clogging situations due to paraffin deposition that may lower production rates and be responsible for leakages. This work evaluates the effect of three polymers on crude oil wettability and on paraffin deposition inhibition: polypropylene (PP), high-density polyethylene (HDPE), and a vinyl acetate copolymer with 28% oxygen content (EVA28). Under static conditions, the interfacial tension between the crude oil and the linings was determined by the contact angle being 12% and 17% higher for EVA28 and HDPE, respectively, than for that of PP. As the crude oil inside the pipelines is flowing at high rates, the dynamic interfacial tension was also observed for high flow rates when molecular effects overtake hydrodynamic ones. For this, the perturbation of intermolecular orientation within the flow, caused by the beginning of deposit formation and by the wettability, was determined using depolarization of the fluorescence induced by laser. Under flow, EVA28 and HDPE caused an increase of interaction with the crude oil of 79% and 43%, respectively, compared to that of PP. HDPE yielded globular wax deposits. The higher tendency of HDPE than PP to form deposits was attributed to the absence of methyl branches in the first. The EVA28 tendency to form deposits was attributed to the oxygen atoms on the surface as well as to its high polycyclic aromatic hydrocarbon sorption. Thus, under a high flow rate, PP is better suited to inhibit wax deposition than HDPE and EVA28.
“…Flow Cell. An in-house developed cell (Figure A) was used in order to emphasize the boundary layer where the interaction between the wall and the liquid flow is stronger. 3 (A) Scheme of the flow cell for PLF-FI.…”
Section: Methodsmentioning
confidence: 99%
“…The experimental setup for PLF-FI was described before. , Briefly, a Coherent Inova60 argon laser (Figure B) at multimode, multiline, and 100 mW is reflected by two mirrors (M) through a biconvex borosilicate lens (L1) of 400-mm focal length that focus the laser into the sample (FI) on a 0.02-mm 2 diameter spot. To monitor the laser intensity fluctuations in real time, 10% of the laser beam was diverted by a beam splitter (BS) onto a BPW-21 RS-Electronics photodiode (PD1) with 7.5-mm 2 active area, operating as a current-to-voltage converter with seven optional sensibility ranges.…”
Pipelines for heavy crude oils have recurrent clogging situations due to paraffin deposition that may lower production rates and be responsible for leakages. This work evaluates the effect of three polymers on crude oil wettability and on paraffin deposition inhibition: polypropylene (PP), high-density polyethylene (HDPE), and a vinyl acetate copolymer with 28% oxygen content (EVA28). Under static conditions, the interfacial tension between the crude oil and the linings was determined by the contact angle being 12% and 17% higher for EVA28 and HDPE, respectively, than for that of PP. As the crude oil inside the pipelines is flowing at high rates, the dynamic interfacial tension was also observed for high flow rates when molecular effects overtake hydrodynamic ones. For this, the perturbation of intermolecular orientation within the flow, caused by the beginning of deposit formation and by the wettability, was determined using depolarization of the fluorescence induced by laser. Under flow, EVA28 and HDPE caused an increase of interaction with the crude oil of 79% and 43%, respectively, compared to that of PP. HDPE yielded globular wax deposits. The higher tendency of HDPE than PP to form deposits was attributed to the absence of methyl branches in the first. The EVA28 tendency to form deposits was attributed to the oxygen atoms on the surface as well as to its high polycyclic aromatic hydrocarbon sorption. Thus, under a high flow rate, PP is better suited to inhibit wax deposition than HDPE and EVA28.
“…The experimental setup for PLF-FI has been described before. , Briefly, a Coherent Inova60 argon laser (Figure , bottom) in multimode, multiline, and 100 mW is reflected by two mirrors (M1 and M2) through a biconvex borosilicate lens (L1) of 400 mm focal length that focuses the laser to a 0.02 mm 2 diameter spot on the sample (FI). To monitor the laser intensity fluctuations in real time, 10% of the laser beam was diverted by a beam splitter (BS) onto a BPW-21 RS-Electronics photodiode (PD1) with a 7.5 mm 2 active area, operating as a current to voltage converter with seven optional sensitivity ranges.…”
High-density polyethylene (HDPE) and polypropylene (PP) were studied to identify tailor-made materials for walls of pipelines and ducts for crude paraffinic oil that inhibit paraffin depositions. The interfacial interaction was investigated from 50 to 70 degrees C and as a function of the n-C(36)H(74) paraffin concentration added to the paraffinic crude oil. The static and the dynamic interfacial tensions were observed, respectively, by traditional contact angle measurements and by fluorescence depolarization of the natural fluorescent probes of the crude oil, flowing at a high rate. The static interaction showed a low dependence on the n-paraffin content for both surfaces. For PP, it decreased slightly as the n-paraffin concentration increased, evidencing an increase in the liquid-liquid interaction. The dynamic interfacial tension with PP clearly decreased as temperature and n-paraffin concentration increased, the latter effect being attributed to the PP methyl groups hindering the interaction between the n-paraffin and the PP main chain. For the flow on HDPE, the interaction proved to be highly dependent on the n-paraffin concentration and temperature. It increased as n-paraffin was added and temperature decreased. The former effect is attributed to the alignment of the n-paraffin chains within the high rate flowing liquid and the similar molecular geometry of the n-paraffin and the linear polymer surface (almost without branches), which increases the number of sites available for interaction. PP proved to be more suitable for transportation of crude oil rich in paraffins with more than 36 carbon atoms, while HDPE was more suitable for those with smaller paraffinic chains.
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