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Fractionating Column

The vapors from the top of the Soaker entered the Fractionating Column through an 18" transfer pipeline. The different components in the vapor have different boiling points, depending on their molecular weight. These components are separated in the column, which was about 8' diameter, 100' tall with 36 trays. The light molecules, such as butane and propane flow out of the top, while the heavy oils are pumped out from the bottom of the column. Quite a lot of coke was deposited in the lower sections of the column, especially on the bottom dish. There was a large alloy steel strainer inside the column to prevent coke pieces entering the pump suction. The strainer was conical, about 36" diameter at the base and 24" diameter at the top, and 48" high. It had slotted holes and covered the 10" outlet pipe at the center of the bottom dish completely. On inspection, we found that 60-70% of this strainer was plugged with coke.

The column had a 4" thick insulation layer, so that heat loss by radiation was minimized. As a result, the column remained hot for a few days after it was ready for entry. Workers had to come out every 30 minutes to cool off and drink water. When working inside columns, they would enter through one of the six column man-ways, and work their way up through the trays, by opening the tray man-ways. Coming down frequently, meant that the actual work done in each trip was quite small. The work inside the column needed 13 days for execution.

Piping Arrangement

Figure 37.3 Piping Arrangement

286 Chapter 37

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