Review the design concept of venting several Propylene Oxide (PO) vent streams to the existing flare stack to eliminate the possibility of backflow of caustic to the PO sources, as well as specify a safety relief device, evaluate existing thermal relief valves on the PO system, and update a SIL-2 reverse flow protection design on the PO feed line to the main reactor at a chemical manufacturing facility.
There are three main Propylene Oxide (PO) storage facilities on-site at the client’s chemical production facility. These include a storage tank, a day tank, and the PO railcar unloading station. The client uses PO in one of its production units as a raw material and transfers the PO throughout the unit. During such transfers, a mixture of PO/N2 is currently vented from these three sources to a caustic venturi scrubber system.
Due to the possibility of a back flow event of caustic (from the venturi scrubber) back to the PO sources, the client contracted Process Engineering Associates, LLC (PROCESS) to review the design concept of venting the three PO vent streams to the existing flare stack. This new concept removes the need for the venturi scrubber in the unit, thereby eliminating the possibility of backflow of caustic to the PO sources. Backflow of caustic to the PO sources could cause a catastrophic event.
In addition to those efforts, PROCESS was tasked to specify a safety relief device on a nitrogen let down skid as well as evaluate existing thermal relief valves on the PO feed line to the main unit reactor. Finally, PROCESS was tasked with updating a SIL-2 (Safety Integrity Level 2) reverse flow protection design on the PO feed line to the main reactor.
This above work scope resulted in the following project deliverables:
- Project report detailing the hydraulics evaluated and the recommended PO vent line sizes required to accommodate the new vent path
- An updated SIL-2 system to prevent backflow from the reactor to the day tank, based on a nitrogen wedge and double block valve setup
- A report documenting the review and validation of a new flare seal pot as part of the new PO vent design and routing
- Safety relief device technical evaluation with supporting calculations for the nitrogen let down safety relief device.
- Proper handling of highly-hazardous chemicals
- Process pressure relief systems design
- Hydraulics evaluation
- SIL systems design and specification.