The butene content in propane at the bottom of the propylene distillation column in the ethylene plant is high
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What could be the reason for the high butene content in propane at the bottom of the propylene distillation column in an ethylene plant? Are there any other reasons besides the high temperature of the sensitive plate and low reflux in the low-pressure depropanization column, as well as the carryover of C4 in C3? Thank you!
The most likely reason is poor separation performance in the depropanization tower; the specific causes need to be analyzed one by one. In addition to high reboiling temperature and low reflux, other issues may include large variations in feed composition, low tray efficiency, and high column load. Is the green oil produced by the hydrogenation of C3 compounds removed effectively? Is there recycled material containing reorganized components?
Both the high-pressure depropanization column and the low-pressure depropanization column need to be analyzed. It has little to do with the propylene column. Are there any blockages in the trays of the propane tower? The separation effect is not good. In the pyrolysis feedstock, has the content of the heavy components increased? The content of naphthenes needs to be checked. At this point, it is necessary to increase the reflux in the high-pressure propane column and the low-pressure propane column, sacrificing energy in exchange for increased mass.
Apart from the propylene column itself, which already takes feed into account, the feed is divided into two streams: one comes from the low-depropanization column and is likely to contain C4, while the other comes from the bottom of the deethanization column (if it is this stream, the pre-cooling demethanization column will also experience reactions). Samples need to be taken from these two sources for analysis