An extremely interesting special class among heterogeneous reaction systems is that of liquid-liquid electron exchange. Scibona, Danesi, and Orlandini (13) recently pointed out the possible application of this type of system in the processing of aqueous solutions. Thus, for example, aqueous solutions of multivalent metallic ions can be reduced or oxidized by their contact with an immiscible organic phase containing, appropriately, an organic-soluble reductant or oxidant. The result is a change in the valence state of a species in the aqueous phase without introduction of extraneous components, except for the addition or removal of a proton. For this to be effectively achieved the reactants (and their oxidation or reduction products) must be substantially insoluble in the opposite phase.As these authors pointed out, the same result can be accomplished by using solid electron-exchange polymers ( 5 ) but the use of a liquid-liquid system offers the possibility of faster oxidation-reduction rates. Their proposal, in essence, suggests an analogous development in the general area of heterogeneous electron exchange reactions to that which has occurred in the field of ion exchange. In that area liquid ion exchange (9) has assumed an important processing role in recent years, particularly in nuclear technology for recovering uranium and related values from ore-leach liquors (4, 6). Since the technique for conducting liquid ion exchange operations is identical to that employed for general solvent extraction, the same advantages would accrue to liquid electron exchange operations. In particular, the ease of adaptation to continuous, countercurrent contacting would be a noteworthy operational advantage.The study of Scibona, Danesi, and Orlandini (13) was No information was given, however, as to how the reaction rates might be affected by changes in the degree of agitation, the relative volumes of the two phases or the temperature. In this study rates of reduction of tetravalent cerium ions I: Ce (IV) ] by tetrachlorohydroquinone (TCH) in stirred liquid-liquid systems were investigated quite extensively. The aqueous phase was the continuous phase, contained the Ce(1V)' oxidant ions and was in all cases made 1N with respect to sulfuric acid. The immiscible organic dispersed phase (an equivolume mixture of carbon tetrachloride and 2-octanone) served as the solvent for the solid reductant, TCH. Dispersion was accomplished by stirring the two-phase system in a baffled beaker with a flat-blade, turbine impeller rotating at a constant speed. The influence of several variables on the kinetics of reduction of ceric ions [Ce (IV) ] to cerous ions [Ce(III) ] was considered. Among these were the concentrations of Ce( IV) and TCH in their respective phases, the volume of the dispersed organic phase, the rotational speed of the stirrer and the temperature. An interesting deduction of the present work is that the rate of reduction of Ce (IV) by TCH appears to be directly proportional to the interfacial area of the stirred two-phase 9 Throu...
Scale control within produced fluids both topside and downhole in oil/gas production facilities is critical to the effective production of hydrocarbons in a safe, economic and environmentally acceptable manner. This paper will focus on the scale challenges associated with production of produced water that contains significant amounts of barium, sulphate and dissolved iron ions. While this challenge is not unusual in production operations the presence of dissolved oxygen in the topside process just prior to discharge has resulted in a very challenging environment for barium sulphate scale inhibition. This paper will outline the challenge of scale control in the presence of ferrous and ferric ion. The inhibitor selection program undertaken will be outlined as well as the critical factors that had to be taken into account given this application was for offshore Norway where environmental characteristics of production chemicals can restrict the choices of chemical suitable for this application. The development of an application strategy for the selected environmentally acceptable chemical will be outlined along with the monitoring program to ensure not only that the chemical is applied at the correct treatment rate but that it performs as expected from the laboratory performance testing results and can be optimised as brine composition changes with time. Introduction The subject field is located in the Norwegian sector of the North Sea and came on stream in December 1998. The 8 production and 3 injection wells are tied into the wellhead platform and the oil processed at an FPSO. The distance between the well head platform and the ship is 1 km. The water depth is 86 m. The oil is exported by tankers and the produced gas re-injected. Map of the fields location is shown in figure 1. Water injection utilises seawater for reservoir support and is incompatible with the formation water. Over the years scale squeeze treatments have been applied to production wells to control sulphate scale. This is supplemented by application of scale inhibitor on the wellhead platform to prevent further deposition during transport of fluids to the FPSO and during its processing prior to discharge to sea. The field's formation water and a typical produced water chemistry arriving at the FPSO is presented in Table 1. The "extreme PW" outlined in Table 1 refers to the produced water expected when a well with high concentration of formation water is flowing with a well with a high proportion of seawater. The range of process conditions is presented in Table 2.
An operator in the North Sea has successfully employed a kinetic hydrate inhibitor (KHI) for over a decade. This operator produces through two 13 mile flowlines, separated into wet gas and fluids, to a multiphase host facility. At this host facility, the two production streams recombine in a slug catcher upstream of the separation system. The wet gas line operates continuously under conditions of hydrate stability requiring the use of a KHI. As additional wells have been tied into the subsea production stream, conditions have changed necessitating advancement in KHI technology.The new production introduces formation water of considerable salinity into the production stream as well as increasing the temperature of commingled fluids in the slug catcher. As KHI polymers possess inverse solubility profiles with respect to temperature and salinity, gunking was frequently observed in the production slug catcher. The precipitated polymer, in addition to sand and organic solids in the system, caused frequent upsets and deferred production. Accordingly, a KHI polymer with improved solubility profile (cloud point) was targeted for this application. The KHI performance and compatibility with incumbent corrosion inhibitor were confirmed and optimized to a 50% reduction in treatment rate by autoclave experiments under the established qualification protocols. Solubility experiments confirmed the compatibility of the new KHI with the expected temperature and salinity parameters of the full production.This paper provides a detailed history of this 10ϩ year application, recent qualification process, and field application of this new KHI offering.
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