Where is the safety valve installed?
Thread Content
Today, while observing the process in the butadiene recovery tower, I noticed that the safety valves were installed at the top of the lower tower, which is quite strange; I thought they were all installed at the top of the upper tower. I asked a few people, and none of them knew; can someone tell me why it’s necessary to do this?
No way, no one knows? What about the designers?
To help everyone understand better, here’s a brief overview of the process; those who are not familiar with the concept of upper and lower towers
The excess dibutylene resulting from the production of styrene-butadiene rubber, nitrile rubber, and ABS resin, which contains residues such as acrylonitrile and styrene (with a dibutylene content of over 85%), is sent to the bottom of the upper section of the dibutylene recovery tower via NaOH washing for conventional distillation. Dibutylene with a concentration of 93% is obtained at the top of the tower, while the remaining material is discharged from the bottom of the tower. To prevent dibutylene from forming self-polymers, the TBc inhibitor is continuously added through the reflux line.
Having too many distillation trays and a tower height of over 100 meters is not practical; therefore, two towers are used, connected to each other by pumps and gas pipelines, allowing them to operate in series – we refer to these as the upper tower and the lower tower. The column where light components are extracted from the top is called the upper column, while the column where heavy components are extracted from the bottom is called the lower column.
The vapor at the top of the lower column is pumped to the bottom of the upper column. The Reconstituted components is obtained from the bottom of the lower tower, while butadiene is obtained from the top of the upper tower. The safety valve is installed at the bottom of the tower. I’m not sure if I understand correctly Installing a safety valve at the bottom of the tower takes into account emergency situations in the gas phase transport within the tower, thereby preventing overpressure. Is there no safety valve on the tower? Let me guess – maybe these two towers were originally connected, forming one system, and a single safety valve would have been sufficient, allowing for a more timely reaction in case of problems?
The gas from the lower tower enters the upper tower through pipes due to pressure differences, while the liquid phase from the upper tower is pumped into the lower tower. The safety valve that should have been installed at the top of the upper tower is actually located at the top of the lower tower; it’s hard to understand why. Could it be that the gas needs to be released from the middle part of the tower?
There is no reboiler in the upper column; if overpressure occurs, it starts from the top of the lower column and then moves on to the upper column
The reboilers are all installed in the lower column, while the safety valves of the other columns are located at the top of those columns; this can’t be the reason, right?
According to design principles, safety pressure relief devices should be installed on the top of all pressure vessels; this is standard practice
Logically, the upper and lower towers should be considered as one tower, so installing one safety valve would be sufficient. The original poster could ask their design institute why they designed it this way