and is read out onto a chart to give an almost continuous record of concentration. This signal can also be used directly for automatic process control, according to the company. O n e example of how the instrument is used: control of a furfural extractive distillation column at Phillips' Plains butadiene plant near Borger, Tex. In the column, butene-1 and isobutylene are separated from butadiene. The chromatograph measures butene-1 plus iosbutylene and controls steam to the column reboiler to maintain optim u m separation. In this instrument, two columns are used in series. The first, 30 in. long, is backflushed each cycle to prevent build-up of heavy components. The second one is 40 in. long and, since the heavies don't reach it, is not backflushed. They are both packed with tetraethylene glycol dimethyl ether deposited on 80 to 100 mesh fire brick.
I EQUIPMENT
CHROMATOGRAPHS IN A MINUTE. Phillips' high speed c h r o m a t o g r a p h i c analyzer-controller operates on a 100 tray, 12-ft. d i a m e t e r furfural extractive distillation column a t the company's b u t a d i e n e plant. T h e instrument maintains optimum separation of butene-1 a n d isobutylene from butadiene
Gas Chromatography Gets Faster Column design p a r a m e t e r s a n d f a s t - a c t i n g cut analysis time to a minute or less JTHILLIPS PETROLEUM
has
developed
a process gas chromatograph which gives a single-component analysis in 60 seconds or less. This greatly increased speed paves the w a y to more process control uses for gas chromatography, Phillips savs, For volatile materials, particularly the lighter hydrocarbons, chromatography is already a very satisfactory process analytical m e t h o d . O n e of its big drawbacks for direct process control, however, has b e e n the rather long time it takes to complete an a n a l y s i s five to 15 minutes or longer. Its fast chromatograph goes a long w a y toward overcoming this problem, Phillips says. Company engineers speed up the chromatograph by carefully matching instrument variables and b y selecting— or designing where they h a d to—fastacting hardware. F o r example, they 52
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decrease column d i a m e t e r to about V s iii., use either helium or h y d r o g e n as carrier gas (choice depends on t h e stream being a n a l y z e d ) , a n d lower t h e ratio of liquid p h a s e to c o l u m n packing "well below the s t a n d a r d 30 9
