Methods for measuring 228Ra were reviewed to select a brief and simple screening procedure under NIPDW Regulations for public water supplies. A two-step method was considered to concentrate Ra by evaporation or co-precipitation and to count it with a gas ionization detector, a liquid-scintillation detector, or a Ge detector with multichannel analyzer. Gross beta particle counting appears to be feasible for screening to meet the 0.04 Bq L-1 detection limit. One can utilize the same sample volume as currently collected and measure radiation with commonly available equipment in reasonable time. The required sample volumes were estimated on the basis of known counting efficiencies and background count rates. Gamma-ray spectral analysis is the recommended option, however, because 226Ra and 228Ra can be determined directly and simultaneously. Several aspects of the method were examined to assure that the concentration procedure is nearly quantitative and that the detection limit can be reached with a 3.8-L sample in a 6000-s counting period. The method was tested with Ra tracer solutions and EPA intercomparison samples over the range of 0.04 to 1 Bq L-1. It was found appropriate for 228Ra and 226Ra analyses.

Gas-to-liquids technology has become an intensely investigated field in the petrochemical industries. The obvious reason is the vast reserves of stranded natural gas (currently flared, reinjected or not produced) and the desire to monetise these resources. Conventional wisdom has gravitated to some variation of Fischer- Tropsch technology to produce hydrocarbon liquids from natural gas. We have developed an entirely different approach for this conversion and licensed the technology to Synfuels International of Dallas for commercialisation.The new process has several advantages: it is simple; it should be economical for flows ranging from 10 MMSCFD through 500 MMSCFD; it can be skid-mounted (at lower flow rates) for transportation to site; it appears that the cost of fluids produced would be less than $20 per barrel; it is nearly energy self-sufficient; water can be a by-product; and the nominal product is a light gasoline with about a C7 molecular weight that can be converted into a heavier fraction with extra processing. This paper presents some details of the process and discusses results from a 100 MSCFD pilot unit.

The design and control of binary distillation columns have been the focus of a great deal of industrial and academic research. However, the effect of the feed characteristics on the controllability of the column has remained unclear. This paper first examines how feed tray location affects the inherent controllability of a binary distillation column. It is shown that controllability can be significantly improved by feeding on a nonoptimum tray. The effects of feed thermal condition are also explored. Generic rules are proposed to improve the controllability of the column by changing the thermal condition of the feed.

In continuous processes where products are changed frequently, the time required to transition from one product to the next can significantly impact the overall operating cost by changing the cycle time and inventory profiles. The design of the plant influences the dynamics of this transition and consequently the overall cost. In this paper we present a methodology to incorporate the effect of transition time into the design of a continuous multiproduct process. The design of an exothermic continuous stirred tank reactor is used to demonstrate this algorithm. The resulting design is not necessarily the steady-state economic choice nor the design that makes the transition the fastest but rather an economic compromise of the two objectives.

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