Waste minimization centrifuges

Solids control for the drilling fluid system An effective way to reduce the volume of drilling fluid waste is the use of solids control. The efficient use of solids control equipment (for example hydrocyclones and centrifuges) in combination with chemical flocculants minimizes the need for makeup water to dilute the fluid system. An enhanced solids control system designed to compliment a specific drilling operation is a very effective waste minimization technique. 

FIGURE 22.10 Frank M. Tiller et al., Minimizing Total Cost Involving Use of Polyelectrolytes with Waste-water Centrifugation, Advances in Filtration and Separation Technology, vol. 16, American Filtration ... 

Alternatively, the liquid removed in the centrifuge may be the waste material. The section on filter waste minimization and disposal (3.9.2) lists the relevant safety precautions. 

Waste material snch as tank bottoms from crude oil storage tanks constitute a large percentage of refinery solid waste and pose a particularly difficult disposal problem due to the presence of heavy metals. Tank bottoms are comprised of heavy hydrocarbons, solids, water, rust, and scale. Minimization of tank bottoms is carried ont most cost-effectively through careful separation of the oil and water remaining in the tank bottom. Filters and centrifuges can also be used to recover the oil for recycling. 

Many nitrated products are explosives, including DNT, TNT, and nitroglycerine (NG). To minimize the potential for ran away reactions and explosions, the compositions of the feed acids and reaction conditions arc currently better controlled diati formerly. In some processes, 99% or more of the feed UNO reacts. Dispersions (or mixtures) of such a waste acid and the nitration product are relatively safe to handle. Also, centrifugal separators are used in many modem processes to rapidly separate the hydrocarbon and used acid phases. Rapid separation greatly reduces the amounts of nitrated materials in the plant at any given time and reduces undesired reactions of the nitrated products. 

In the first step the (R,S)-nitrile is rapidly and quantitatively hydrolyzed to the (R,S)-amide. The amidase containing biomass is then added so that the (R)-amide is specifically hydrolyzed to the (R)-acid, and the product, the (S)-amide, remains. A completely new isolation process was developed ultra-filtration, electrodialysis, ion-exchange chromatography, reverse osmosis, crystallization, centrifugation, and drying. The product has been produced at a 15 m3 scale and has an ee value of >98%. The isolated yield calculated from the nitrile was >35%. The (R)-acid can be recycled by reacting it with thionyl chloride and ammonia to produce the (R,S)-amide. This results in minimal waste and higher yields. 

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