Optimized liquid-phase oxidation
Disclosed is an optimized process and apparatus for more efficiently and economically carrying out the liquid-phase oxidation of an oxidizable compound. Such liquid-phase oxidation is carried out in a bubble column reactor that provides for a highly efficient reaction at relatively low temperatures. When the oxidized compound is para-xylene and the product from the oxidation reaction is crude terephthalic acid (CTA), such CTA product can be purified and separated by more economical techniques than could be employed if the CTA were formed by a conventional high-temperature oxidation process.
1. In a bubble column reactor for reacting a predominately liquid-phase stream and a predominately gas-phase stream, the improvement comprising:
a vessel shell defining an elongated reaction zone, wherein said vessel shell is elongated along a central shell axis, wherein said reaction zone presents axially-spaced normally-upper and normally-lower ends;
one or more gas openings for introducing said predominately gas-phase feed into said reaction zone;
one or more liquid openings for introducing said predominately liquid-phase feed into said reaction zone; and
one or more baffles disposed in said reaction zone generally above at least one of said gas openings, wherein said baffle comprises a plurality of laterally-spaced baffle members, wherein said baffles present one or more exposed outer surfaces, wherein less than about 50 percent of the total upwardly-facing surface area of said exposed outer surfaces is formed by substantially planar surfaces inclined less than about 20 degrees from horizontal.
2. The bubble column reactor of claim 1 wherein said baffle has an open area in the range of from about 10 to about 90 percent.
3. The bubble column reactor of claim 1 wherein said baffle has an open area in the range of from about 25 to about 75 percent.
4. The bubble column reactor of claim 1 wherein less than about 35 percent of the total upwardly-facing surface area of said exposed outer surfaces is formed by substantially planar surfaces inclined less than about 20 degrees from horizontal.
5. The bubble column reactor of claim 1 wherein said baffle has an open area in the range of from about 35 to about 65 percent, wherein less than 25 percent of the total upwardly-facing surface area of said exposed outer surfaces is formed by substantially planar surfaces inclined less than about 20 degrees from horizontal.
6. The bubble column reactor of claim 1 wherein each of said baffle members present a substantially cylindrical exposed outer surface.
7. The bubble column reactor of claim 1 wherein each of said baffle members present an inverted V-shaped upwardly-facing exposed outer surface.
8. The bubble column reactor of claim 1 wherein said reactor comprises a plurality of vertically-spaced baffles disposed in said reaction zone.
9. The bubble column reactor of claim 1 wherein said reaction zone has a maximum length (L), a maximum diameter (D), and an L:D ratio of at least about 6:1.
10. The bubble column reactor of claim 9 wherein said L:D ratio is in the range of from 8:1 to 20:1.
11. The bubble column reactor of claim 9 wherein substantially all of the cumulative open area defined by all of said gas openings is located within about 0.25 D of the normally-lower end of said reaction zone.
12. The bubble column reactor of claim 9 wherein at least about 30 percent of the cumulative open area defined by all of said liquid openings is located within about 1.5 D of the gas opening located closest to said normally-lower end.
13. The bubble column reactor of claim 1 wherein at least two of said liquid openings are axially-spaced from one another by at least about 0.5 D.
14. The bubble column reactor of claim 1 wherein said baffles are not configured to significantly heat or cool the contents of said reactor.
15. The bubble column reactor of claim 1 wherein a substantial portion of exposed outer surfaces has a surface finish of 125 micron RMS or less.