Solvent Recovery Column Start-up and Shutdown Procedure

Purpose. Describes the sequence, checks and limits for starting up and shutting down the solvent recovery distillation column so that the unit is brought on line without loss of containment, overpressure or off-specification product.

1.Scope

This procedure applies to the solvent recovery column, its reboiler, condenser, reflux drum, feed and product pumps and the vacuum system. It must be used by the panel operator and the outside operator together, with the shift supervisor authorising each stage. It must be read with the safe operating limits sheet and the alarm response manual for the unit.

2.Pre-start-up checks

Before any start-up the outside operator must walk the unit and confirm that all maintenance permits are closed, all isolations are removed and recorded, blinds are removed to the blind list, all instruments are in service and the relief valves and rupture discs are as listed on the safety critical equipment register. The panel operator must confirm the control system is in the correct mode and that no trips are bypassed. The pre-start-up checklist must be signed by both operators and the supervisor.

• All permits closed and isolations de-isolated
• Blind list reconciled and blinds removed
• Relief devices in service and not isolated
• Level, pressure and temperature transmitters in service
• Emergency shutdown system tested and healthy
• Cooling water and steam available at the required pressure

3.Inerting and leak test

The column must be purged with nitrogen until the oxygen reading at the vent is below the limit on the safe operating limits sheet. The unit must then be pressure tested with nitrogen at the test pressure and held for 30 minutes with no measurable drop. Any leak found must be repaired under permit before proceeding.

4.Establishing feed and heat

Feed must be introduced at the minimum rate until the base level is within the normal band. Steam to the reboiler must be increased in the steps on the ramp table, holding at each step until the column temperature profile is stable. Reflux must be established as soon as the reflux drum level is within range. The outside operator must check for leaks at flanges and pump seals during each step and report to the panel.

5.Bringing product to specification

Product must be routed to the off-specification tank until the laboratory confirms the overhead sample meets specification. The panel operator must then switch product to the finished tank and record the time. Rates may only be increased to the normal rate after the profile has been stable for one hour.

6.Normal shutdown

Feed must be reduced to minimum before steam is reduced. Steam must be removed in steps and the column allowed to cool with reflux until the base temperature is below the limit. The column must then be drained to the slop tank, purged with nitrogen and left under a nitrogen blanket. Every step must be recorded in the shift log.

7.Emergency shutdown

If a high pressure, high temperature or loss of cooling alarm cannot be corrected within the time on the alarm response manual, the panel operator must activate the emergency shutdown. The abnormal situation procedure must then be followed. An emergency shutdown must be recorded as a process safety event.