Preparation of alkoxides for the synthesis of ceramics

The literature is reviewed to summarize methodologies for synthesizing metal alkoxides applicable as organic precursors to high-purity, well-characterized ceramic powders. Typical examples of preparation techniques, patents, and commercial manufacturing methods are provided, and special precautions noted. Basically, metal alkoxide synthesis is determined by the electronegativity of the metal concerned; synthetic routes may lead directly from the metal or a metal halide, or may be indirect, involving alcoholysis.     

The application of lognormal models of transient operations in the flexible manufacturing environment

Fundamental aspects of models that might be used to design and/or manage operations in the flexible manufacturing environment are presented in this paper and demonstrated in hypothetical, but typical, examples. Applications suggest use to coordinate production and assembly operations so that lots are completed as scheduled with minimal levels of in-process inventory. Specific examples include coordinating the delivery of components required to assemble a product, analyzing the throughput and productivity of a robotic cell, and managing the flow of materials amongst cells. Numerical tests in these contexts indicate that the modeling approach, which approximates transient (as well as steady state) operations, gives results that compare favorably with those derived from a simulation model at a substantial runtime advantage. The approach appears to offer a viable means of conceptualizing transient operations and is supported by empirical justification.     

A FMS physical simulator

An integrated scale model of a flexible production line and an automated storage and retrieval system is described. The scale model is developed for the Department of Industrial and Systems Engineering at the University of Southern California. The model has been used for educational purposes as well as for physical simulation of new scheduling and control algorithms.     

Kinetics of dissolution of synthetic scheelite by an alkaline EDTA leach solution

The dissolution rate of synthetic scheelite in an alkaline EDTA leach solution under atmospheric pressure has been determined by use of a rotating disc method. The effects of disc rotation speed, temperature, reagent concentration and pH of leach solution have been investigated. The dissolution rate was proportional to the square root of the disc rotation speed. The apparent activation energy of dissolution of synthetic scheelite was 22 kJ mol⁻¹ within the experimental temperature region of 24 to 99°C. A first order dependence of dissolution rate on EDTA concentration was observed. It has been shown from the experimental results that the dissolution reaction was controlled by the mass transfer in the aqueous solution.     

An alternate process for the recovery of uranium by ion exchange: A study of the HIMIX process

An alternative approach to the recovery of uranium by ion exchange involves the additional loading of uranium onto a partially loaded resin followed by the elution of uranium from the more highly charged resin. The conditioning of the resin in this manner provides for the possible displacement of impurities from the resin and the production of an eluate suitable for the direct precipitation of yellowcake at a reduced consumption of eluant.This paper presents the results of pilot-plant and bench-scale experiments on the conditioning and elution steps. Variables such as the initial uranium concentration of the conditioning liquor, pH, temperature, and contact time were considered in the conditioning process together with the behaviour of thorium and iron impurities. In the elution work the effects of eluant flowrate, sulphuric acid concentration, elution temperature, and initial uranium loading on eluate uranium concentration and elution time were studied. The extent to which the further adsorption of uranium onto the resin together with thorium and iron displacement can be realized is indicated. In addition it is shown that an eluate suitable for yellowcake production can be obtained at an acid consumption significantly less than in the conventional processes.     

Automotive fuel from bioelectrochemical conversion of lignocellulosic materials

A 2-stage experimental process has been developed to extract n-valeric, 2-methylbutanoic, 3-methylbutanoic, and caproic acids from species of lignocellulosic materials and convert these to liquid, gasoline-range hydrocarbons. The energy consumption in the conversion step is 1.0–1.60 kWh/kg of product. Our process offers an alternative production procedure for automotive fuels.     

Energy analysis applied to food processing

We use first-law and second-law efficiencies on 2 multi-process food processing plants. These efficiencies are 59.6 and 19.4% for a condensed milk plant and 43.0 and 15.5% for the bakery plant. Improvements in both first-law and second-law efficiencies for the bakery can be achieved by reducing the mass of dough moulds and recovery of energy in the bake-oven exhaust to heat the air in the proofing oven. Replacement of the flash-cooling process in the condensed-milk plant by a combination of boiling at 100 °C and cooling via a vapour-compression refrigerator would lead to significant improvements in plant efficiencies.