Reference crude rate

An existing refinery that has declared a revised Reference Crude Rate of more than 115 percent of the initial Reference Crude Rate. 

For drugs used for chronic exposure, one number or rate such as the crude rate is not likely to be Informative without reference to time. To be useful as a summary measure of combined safety data from several smdies and which would estimate an overall rate that describes experiences of all participants exposed for varying time periods, there is a need to stratify for time as well as other factors. (O Neill 1987, p 20)... 

In the simplest and most often used form, the screw has a free channel cross-section that diminishes at a steady rate from the feed to the delivery end. The ratio of the channel depths from feed to die region along the screw is usually referred to as the compression ratio, since it gives a crude indication of the relative conveying capacities at feed and discharge. 

To elucidate the possible causes of the decrease in suppression potential, the effects of flow residence time and relative pulsating fuel amount were examined. One possible explanation for the above trend is the reduction in flow residence time as the flow rate was increased. At these conditions some of the larger fuel droplets that persisted in the downstream may not have had enough time to react completely if the residence time became very short. When the residence time was estimated by the reference time scale which is the combustor length divided by inlet velocity (Fig. 21.12), the general trend appears to be consistent with the expectation. The scatter in the plot reflects the crudeness of the estimation larger droplets do not follow the carrier flow very well. 

Some special problems arise at sea. When crude oil is spilled on the ocean, a slick is formed which spreads out from the source with a rate that depends on the oil viscosity. With sufficient energy an O/W emulsion may be formed, which helps disperse oil into the water column and away from sensitive shorelines. Otherwise, the oil may pick up water to form a water-in-oil emulsion, or mousse ( chocolate mousse ). These mousse emulsions can have high water contents and have very high viscosities, with weathering they can become semi-solid and considerably more difficult to handle, very much like the rag-layer emulsions referred to above. The presence of mechanically strong films makes it hard to get demulsifiers into these emulsions, so they are hard to break. See Chapter 9. 

The enhanced fouling rates and metal contamination (from the crude oil) generally makes atmospheric residua unsuitable as a cracker feedstock. However, some crude oils produce a waxy residual of low metal content (often referred to as low sulphur waxy residua, LSWR). Although more expensive than fuel oil, LSWR is considerably cheaper than gas oil and is an attractive feedstock for some gas oil cracker operations. 

Catalyst — A substance added to a reacting system, e.g., chemical reaction, which alters the rate of the reaction without itself being consumed. Most catalysts are used to increase the rate of a reaction. For example, the metal vanadium is often present in trace amounts in crude oils and acts as a catalyst to accelerate the rate of chemical oxidation of certain hydrocarbons as the oil weathers. Catalysts, such as silica and alumina, are also used during the refining of petroleum to increase the rate at which large hydrocarbon molecules are split into smaller ones, a process referred to as catalytic cracking. 

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