Process Monitoring and Control

The wealth of detail given by GC about the composition of streams leaving reactors and purification units such as distillation columns can, in principle, be used for manual, semiautomatic or fully automatic process

Figure 4 Illustration of how the equilibrium, A p B # C, is displaced in a GCC reactor.
Figure 5 Illustration of how a primary product, ROH, is preserved from secondary reactions with oxygen in a GCR.

control. Automatic GC has been applied to determine gasoline components and a linear algorithm has been developed relating Reid vapour pressures, boiling points and ASTM distillation curves to component indices with good correlations and repeatability. The method has been developed further to enable the RON of a gasoline to be determined automatically by GC analysis with a standard deviation of only 0.09 for RON values in the range 90 to 100. The method has not yet been taken to the point of closing a control loop so that a reactor or a distillation column is controlled by GC, although this closure is feasible.

GC suffers as the control element because of the time needed for analysis. The response time of the plant must be longer than the time for analysis, which is usually tens of minutes, and there is a clear need to develop faster GC based on short narrow-bore open-tubular columns and variants. It is relevant that a method called the 'optical octane dipstick' is now being used in many refineries. This uses a nondisper-sive near-infrared analyser (NIR) to determine the absorbence at five wavelengths. Apparently a very good measure of RON is obtained from an algorithm linking these absorbencies to ASTM/RONs determined in a standard Petter engine. Clearly this spec-troscopic method is faster than GC but can only be used for a narrow range of RONs and composition. The more detailed compositional description by GC analysis could outweigh its present relative slowness. The NIR control units already in use pave the way forward by posing a challenge to the analyst to speed up chromatographic methods. If the challenge can be met, then the closing of control loops for catalytic reactors based on GC will follow.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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