Cationic surfactants for demulsification of produced water from alkaline-surfactant-polymer flooding

In this research, demulsification of produced water (which is an oil-in-water emulsion) from alkaline–surfactant–polymer flooding, containing sodium alkyl sulfate, was evaluated using five different surfactants from the classes of nonionic, amphoteric, and cationic. It was observed that only single-tail cationic surfactants, namely, dodecyltriemthylammonium chloride (DTAC) and alkyltrimethylammonium bromide (ATAB), with a concentration of 1000 ppm, were capable of attaining transparent separated water phases following 3 h separation at room temperature with relative separation efficiencies, determined using fluorescence spectroscopy, of 89.4 and 59%, respectively. However, the cationic surfactant dimethyldioctadecylammonium chloride (DDOAC) could achieve a relative separation efficiency of only 28.4% after 13 days, in contrast to nonionic and amphoteric surfactants that did not reveal any progress in demulsification. Similarly, given the demulsifier concentration of 1000 ppm, only DTAC and ATAB reduced the negative surface charge of oil droplets in the produced water after 3 h separation, and large droplets were formed owing to their coalescence after the addition of the respective demulsifiers as viewed by optical microscopy. The dominant emulsification mechanism is believed to be electrostatic stabilization. Consequently, the proposed demulsification mechanism is the formation/adsorption of cationic–anionic pairs at the oil–water interface. When comparing the demulsification performances of various demulsifying surfactants, although high interfacial activity (low interfacial tension (IFT)) is an essential feature for a demulsifier to be considered effective, it was concluded that lower equilibrium IFT does not necessarily result in superior separation efficiency, and other parameters such as type, tail branch number (i.e., single-tail or double-tail), and purity of surfactant may have profound effects on both separation efficiency and demulsification speed of the emulsion. From the dynamic IFT data, it was realized that DTAC and ATAB caused faster demulsification than DDOAC. The undesirable demulsification performance of DDOAC might have been due to its double-tail structure, which confined its interfacial adsorption. The operational variables, including salinity, pH, and temperature, in the demulsification process by DTAC were optimized with respect to the changes of IFT, and the optimum values were found to be 2 wt %, 7.0, and 35 °C, respectively

Funcionamiento hidrológico de un humedal ribereño, el Masegar, en el conjunto de los humedales de La Mancha Húmeda de la cuenca alta del rió Cigüela

Fifteen years ago &#194;&#171;La Mancha H&#250;meda&#194;&#187; was deelared Biosphere Reserve by UNESCO, at the request of the Spanish Government. According to a recent deelaration by UNESCO in 1995, such title could be lost if the degradation processes of the wetlands of &#194;&#171;La Mancha H&#250;meda&#194;&#187; continue. &#194;&#171;La Mancha H&#250;meda&#194;&#187; was formed by a hundred of small lakes or wetlands that in area totalled about 200-300 km² and they were distributed over an area of about 25.000 km². These are different types of wetlands (saltwater and freshwater, permanent and ephimeral, riparian and closed basins, etc.). It is estimated that the actual surface of all the wetlands is about 20-30% of that occupied 20 or 30 years ago. The most famous degradation case is that of the &#194;&#171;Tablas de Daimiel National Park&#194;&#187; that has shrinked fram an area of about 15-20km² to less than 1 km²<p> This article presents the general situation of the riverine wetlands of the Cig&#252;ela river and the results of the hydrological functioning of a wetland of modest dimensions, less than 1 km², El Masegar. It is a riparian wetland located in the Cig&#252;ela River basin which has been severely affected by man actions. El Masegar can be considered as an artificial wetland. From an ecological point of view, this wetland seems to have been functioning in a proper way until 1988, when the so called &#194;&#171;Plan de Regeneraci&#243;n H&#237;drica del Parque Nacional de las Tablas de Daimiel&#194;&#187; began. This Plan has not regenerated the Natural Park but has degradated or destroyed the riparian wetlands that existed along the Cig&#252;ela River valley which is about ISO km long. The surface of these wetlands all together was larger than that of Tablas de Daimiel National Park. The study shows that it could be feasible to restore or maintain most of the riparian wetlands of the &#194;&#171;La Mancha H&#250;meda&#194;&#187; without a great economic investment and without social conflicts with the farmers.<br><br>En 1981, a petici&#243;n del Gobierno espa&#241;ol, la UNESCO declar&#243; Reserva de la Biosfera &#194;&#171;La Mancha H&#250;meda&#194;&#187;. En 1995 la UNESCO ha indicado que este t&#237;tulo puede ser retirado si contin&#250;a la degradaci&#243;n del conjunto de humedales que integran esa Reserva de la Biosfera. La &#194;&#171;Mancha H&#250;meda&#194;&#187; estaba formada por un centenar de peque&#241;as lagunas o humedales que totalizaban una superficie de unos 200-300 km² y se repart&#237;an en un &#225;rea de unos 20.000-25.000 km². Las lagunas tienen unas caracter&#237;sticas muy diversas (salinas y dulces, permanentes y ef&#237;meras, ribere&#241;as y endorreicas, etc.). Se estima que la superficie actual conjunta de esas lagunas apenas alcanzan el 20-30% de la que ocupaban hace 20 &#243; 30 a&#241;os. El caso de degradaci&#243;n m&#225;s conocido es el del Parque Nacional de las Tablas de Daimiel, que ha pasado de ocupar una extensi&#243;n de 15-20 km² a menos de 1 km².<p> En este trabajo se analiza la situaci&#243;n general de los humedales del r&#237;o Cig&#252;ela y se presentan los resultados del an&#225;lisis del funcionamiento de un humedal de modestas dimensiones, algo menor de 1 km², El Masegar. Se trata de un humedal ribere&#241;o ubicado en la cuenca del r&#237;o Cig&#252;ela que puede considerarse como un humedal artificial, creado por el hombre. Desde el punto de vista ecol&#243;gico, este humedal parece haber funcionado muy bien hasta que en 1988 comenz&#243; el denominado &#194;&#171;Plan de Regeneraci&#243;n H&#237;drica del Parque Nacional de las Tablas de Daimiel&#194;&#187;. Este plan no s&#243;lo no ha regenerado ese Parque, sino que ha degradado o destruido los humedales ribere&#241;os existentes a lo largo de unos 150 km del valle del r&#237;o Cig&#252;ela. La superficie conjunta de esos humedales era ampliamente superior a la superficie del PNTD. El estudio realizado indica que es posible restaurar o conservar gran parte de los humedales del r&#237;o Cig&#252;ela, sin un gasto econ&#243;mico excesivo y sin conflictos sociales con los agricultores

FLOW INSTABILITY IN LOW-PRESSURE TURBINE BLADE PASSAGES

ABSTRACT The unsteady interaction among shocks, spontaneous condensation and boundary layers were measured in a cascade of tip section turbine blades with steam conditions similar to those that would be experienced by the blade under actual field conditions. Test conditions covered the Mach number range of 1.0 to 1.4, based upon isentropic exit conditions. Inlet temperature conditions were such as to provide fully dry runs, runs with shock and condensation being approximately coincident, and runs with the condensation occurring upstream of the shock. Unsteady pressure data were provided by six miniature pressure transducers embedded in the suction surface of one of the blades in the region of the impingement of the trailing edge shock from the adjacent blade. Spatial integration of the individual transducer signals provided fluctuating forces over the region measured. Unsteady forces were generally low but the nature and level of the fluctuating forces were different near a Mach number of 1.0, where several distinct spikes were present, and responses for some frequencies reached nearly one percent of the steady forces