Circulation method

Engineer s method. The drilling fluid is weighted up to kill density while the formation fluid is being circulated out of the hole. Sometimes this technique is known as the one circulation method. 

The alternative method of returning oil from the evaporator to the compressor is to keep it moving, by ensuring a minimum continuous fluid velocity in all parts of the circuit. This is termed the dry expansion circuit. This dynamic circulation method is the decisive... 

In the circulation method, the same solution is continuously passed through the sample, also with continuous monitoring of the concentration, until equilibrium is reached (see Figure 5.15d) (Kurbanbekov et al., 1969 Ash et al., 1973). Although this method requires a less conventional set-up than the immersion or open-flow methods, it presents the following advantages ... 

In 1910 Haber 7 found that in presence of metallic osmium 1 volume of nitrogen unites with 3 volumes of hydrogen at 550° C. and 200 atmospheres, the yield being 8 per cent, of the mixed gases. On the manufacturing scale, osmium can be replaced by the less costly uranium, and a continuous circulation method is employed, with a temperature about 500° C.8 Any carbon monoxide present in the hydrogen should be removed.9... 

A variant, proposed by Nunn and Everett ), and briefly called the null-method keeps the initial composition X2(i) constant by adding 2 to the system when this component adsorbs. The amount added is Just the surface excess. The advantage is that the original amount n2(i) need not be known. This variant may also be combined with the circulation method. 

Circulation method Closed system Single and multi- Lower amount of sample... 

Circulation method Another static method is based on a closed fluid circuit that includes the chromatographic column. A known amount minj of solute or a mixture of several solutes is injected into this circuit and pumped around until equilibrium is established. Samples are taken and analyzed to determine the resulting equilibrium concentration ceq. The mass balance for the equilibrium loading accounts for the hold-up of the complete plant ... 

In studying the kinetics of benzene oxidation to maleic anhydride and in order to eliminate diffusion hindrance, Ioffe and Lyubarskii (151) used the flow-circulating method. The rate of this reaction was found to be proportional to benzene concentration to the power of 0.78, and that of high conversion to the power of 0.71. The rate of maleic anhydride oxidation followed a first order equation. Kinetic equations were derived from experimental results ... 

Belousov et al. (115, 153) studied the kinetics of propene oxidation to acrolein on a cuprous-copper catalyst, using the flow-circulating method. The reaction products were shown to exert a considerable effect on the reaction rate, and this permitted the derivation of a more precise kinetic equation for this reaction. Over the temperature range of 305-365° the rates of propene oxidation to acrolein (wact) and carbon dioxide (wc0i) are fairly well described by equations... 

The kinetic equations derived by using the flow and flow-circulating method show good agreement. 

Temkin et al. (159) studied the kinetics of ethylene oxidation over a stationary silver surface. It was shown by means of the flow-circulating method that the rate of ethylene oxide and carbon dioxide formation was proportional to ethylene concentration in the gas phase, and that there was inhibition with reaction products. 

An alternate method that is quite similar to the circulation method and is described in the literature (Myerson 1977 Myerson and Kirwan 1977) is shown in Figure 2.37. In this method, solution is pumped past a crystal that is suspended from a rod in a chamber. The flow rate can be directly measured by a rotameter, which is not possible in the circulation apparatus. As previously mentioned, the mass or change in dimension of the crystal can be measured at the beginning and end of the experiment or can be directly observed by using a microscope. This method is more difficult to use for several reasons. First, pumping of the solution tends to increase the chance of nucleation as does the presence of the various tubing and connections. Second, the lines must be kept at the desired temperature or material will crystallize in the lines. 

In addition, Korshunov and Drobot [1971KOR/DRO] have attempted to measure the Cl2(g)/02(g) ratio in equilibrium with ThCl4(cr) and ThOCl2(cr) by a circulation method. Their results supposedly for the equilibrium constant of the reaction ... 

Kim S-J, Park J-Y, Lee Y-J, Lee J-Y, Yang J-W (2005). Apphcation of a new electrolyte circulation method for the ex situ electrokinetic bioremediation of a laboratory-prepared pentadecane contaminated kaolinite. Journal of Hazardous Materials 118(1-3) 171-176. 

The PDCA circulation method is firstly put forward by Deming, a American management expert. It is a currently widely rrsed management model in the implementation of safety management process in the industries [Zhang Cui 2002). Its management model is showed in Figure 1. 

MAL1 Malanowski, S. Experimental methods for vapour liquid equilibria. Part 1. Circulation methods. Fluid Phase Equilib. 8 (1982) 197-219. 

The behavior of the solubility curves in the same temperature region but at pressures above the critical was determined by Petit and Weil at Grenoble. Their results, obtained by the circulation method, show the t3rpical horizontal section above the 27 K temperature (see Fig. 4). This peculiar behavior was also noticed by us while making some isobaric measurements on the solid-gas equilibrium above the critical temperature of hydrogen when the flow method was used. From an inspection of Fig. 2, it follows that there is a possibility of the retrograde increase of the concentration of the fluid in the supercritical region. Such an effect, however, cannot easily be detected by adynamic method as applied to our measurements on liquid-solid equilibrium. Consequently, we used the static method in our determinations. 

In 1908, Haber et al. was awarded a patent on ammonia synthesis from its elements by using high pressure circulating method, in which ammonia was condensed and separated continuously and N2-H2 mixture was recycled under high pressures, as shown in Fig. 1.4. 

Circulation Method. A common method for obtaining vapor-liquid equilibrium (Refs. 11, 13, 16, 23, 27, 35) is by circulating the vapor through a system and bringing it into repeated contact with the liquid imtil no further change in the composition of either takes place. A schematic diagram of such a system is shown in Fig. 1-1. The vapor above the liquid in vessel A is removed, passed through... 

Hala jet (8) classify VLE measurement techniques in five major groups distillation methods, circulation methods, static methods, dew-point/bubble-point methods, and flow methods. One could add to this list some rather specialized techniques, but in the main most modern low-pressure VLE work is done on two major types of equipment circulation stills and static equilibrium cells. 

In circulating methods, the aqueous surfactant solution is pumped and sprayed in a shower or is allowed to fall onto the solution surface (fall/recycle principle). An AFNOR norm based on this fall/recycle principle is presently in draft form [25] In a water-jacketed glass tube, a defined volume of aqueous surfactant solution (minimum 1 g of surfactant/ liter) is pumped and dropped freely from a fixed distance onto a bed of the same surfactant solution. The tested foaming solution is recycled continuously at a constant flow rate. This method is useful for assessing the foaming profile of surfactants and for the study of efficacy of foam-control agents like EOPO (ethylene oxide-propylene oxide) block copolymers [26]. 

One of the eagerly desired features is to widen the range in operating temperature. The same EMF output, as the calculated value, can be obtained even at 923 K, which is 50 K lower in operating temperature compared with the result in fig. 52. The sensor can also detect the concentration accurately over a wide range, ifom 30 ppm to 1 %, and was found to exhibit the same characteristics as demonstrated in the sensor with the gas circulation method. 

Isobaric-isothermal methods are often also called dynamic methods. One or more fluid streams are pumped continuoirsly into a thermostated equilibriirm cell. The pressure is kept constant during the experiment by controlling an effluent stream, irsually of the vapor phase. One can distinguish between continuorrs-flow methods and semi-flow methods. In continuous-flow methods, both phases flow throrrgh the eqrrihbrirrm cell. They can be used only for systems where the time needed to attain phase equilibrium is sufficiently short. Therefore, such equipment is usually not applied to polymer solutions. In semi-flow methods, only one phase is flowing while the other stays in the equilibrium phase. They are sometimes called gas-saturation methods or pure-gas circulation methods and can be used to measure gas solubilities in liquids and melts or solubilities of liquid or solid substances in supercritical fluids. 

Circulation method from bottom to top, perpendicular to the electrode ... 

Bobrova II, Bobrov NN, Simonova LG, Parmon VN. Direct catalytic oxidation of methane to formaldehyde new investigation opportunities provided by an improved flow circulation method. Kinet Catal 2007 48 676-92. 

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