Decarboxylation of tetra- and pentacarbon compounds in light hydrocarbon distillation towers
Thread Content
There is an existing distillation tower production unit; the pressure in the tower is 0.32 MPa. The feed contains 0.5% C3 compounds, about 5% C4 compounds, about 10% C5 compounds, with the remainder being heavier fractions of C6 and above. Cooling by normal-temperature circulating water. During operation, it was observed that as more material was fed in, the pressure at the top of the tower became uncontrollable; a balance line connected the reflux tank to the vapor line at the top of the tower. The possible reasons for this issue could be as follows: (1) The nitrogen in the system has not been completely removed, resulting in pressure buildup in the reflux tank and preventing the material from flowing into the condenser. (2) The C3 compound fails to condense, and continuous feeding leads to an accumulation of C3 compounds, causing a sudden rise in pressure. (3) The area of the condenser is insufficient, so that the vaporized material (mainly C4 and C5 compounds) does not condense in time, leading to an increase in pressure. I hope fellow users can help analyze the reasons, or suggest additional possibilities and solutions
Is it possible that the operating pressure is too low? If the butane content is high, the operating pressure needs to be increased
There is too much C3 in the tower; it’s unlikely to be condensed by increasing pressure further. At present, to maintain production, it is necessary to release a small amount of C3 from the top of the tower, either intermittently or continuously.
It’s unlikely that the condenser area is insufficient； During the initial stage of operation, the residual nitrogen in the tower tends to accumulate at the top of the tower, affecting its pressure ； There is a significant amount of 0.5% carbon triolefin; as a non-condensable gas, it also affects the stability of the tower pressure ； The presence of both nitrogen and carbon terpenes can easily cause gas blockages in the condensation lines; as a result, the material at the top of the tower can only flow along the hot path (the top equilibrium line), making it difficult to control the system pressure. It is recommended to follow the same approach as mentioned above: intermittently or continuously release small amounts of nitrogen and carbon terpenes from the top of the tower until pressure is balanced.