In this work, the effect of vapor load and initial feed concentrations on column efficiency and liquid hold-up in a two-and three-phase packed distillation column at total reflux was investigated. Results for the two investigated mixtures (n-heptane, n-hexane, water) and (ethyl acetate, 1-butanol, water) reveal that column efficiency remains almost constant for the former mixture but changes significantly for the latter. Specific liquid hold-up and water to organic-phase volumetric ratio within the column affect the column efficiency due to variations in initial feed concentrations. Influence of vapor load on separation efficiency and specific liquid hold-up is also studied.

Intrinsic rates for the Fischer‐Tropsch synthesis reaction over a promoted iron catalyst fabricated at the Research Institute of the Petroleum Industry (RIPI) have been obtained in the temperature range of 290°C to 310°C, pressure range of 1500 to 2300 kPa, molar hydrogen to carbon monoxide ratio of 0.76 to 1.82, and a space velocity of 3300 h−1 under conditions of constant catalyst activity. To this end, the initial reaction rates have been measured at constant temperature (±1°C) in the absence of diffusion limitations, and power‐law equations have been fitted in terms of the hydrogen and carbon monoxide partial pressures for the reaction rates.

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In the present paper a method has been developed for the determination of (226)Ra in water by the detection, using a solid-state nuclear track detector (SSNTD), of alpha particles from (226)Ra in equilibrium with (222)Rn in micro-precipitates collected on a filter. The micro-precipitates were prepared from environmental water samples by collection of radium with lead as Pb/RaSO(4). Several factors affect the (226)Ra precipitation on the filter and its recovery, in particular the filter pore size. Therefore in this experiment Whatman #42 and Millipore filters with different pore sizes were used. Using a 0.45 microm Millipore filter, the recovery efficiency was increased up to 96%, and the alpha self-absorption and scattering decreased remarkably. For efficient detection of alphas from (226)Ra/(222)Rn in equilibrium, three types of SSNTD were used-polycarbonate (PC) electrochemically etched (ECE), CR-39 and LR-115 chemically etched (CE). By preparing a standard micro-precipitate on a filter with known (226)Ra/(222)Rn characteristics, the calibration response of each detector and its minimum detection limit (MDL) were determined.

One-dimensional model to describe miscible displacement in fractured porous media, was formulated by Jamshidnezhad et al. (1). The basic equations for the fracture (medium 1) and the matrix (medium 2