Debottleneck the solvent recovery column through management of change

What is going on

The solvent recovery column is limited to about 85 percent of nameplate feed rate because the reboiler reaches its steam duty limit before the column floods. Customers are being turned away and used solvent is stockpiling in T-310. MOC-26-034 proposes a feed preheater using low pressure steam and a bypass tie-in on the feed line, which will require a hot work permit for the tie-in. The change affects the column heat balance, the relief case, the safe operating limits and the emergency shutdown logic. The reflux pump trip and the six minute limit excursion on 2 September are still under investigation. Ingrid Solberg wants the performance analysis and the complete management of change request, with the hazard assessment and the pre-implementation actions, before the permit for the tie-in can be issued.

Your brief

Analyse the column performance data to confirm the bottleneck, evaluate the preheater and bypass option against alternatives, complete the management of change request with a hazard assessment and an assessment of the effect on safety case control measures and safe operating limits, and define the pre-implementation actions and the pre-start-up safety review.

Work through it

You do not need to do it all. Doing a few of these will show you what the work is like. Your ticks and notes stay on this device.

• Read the management of change policy, the management of change request template, the column start-up and shutdown procedure and the safety critical equipment register entries for the column, and review MOC-26-034 and PW-26-0788 in the registers.
• Extract the column operating data from the shift log and the control system trends and analyse feed rate, reboiler steam, reflux ratio, differential pressure and product purity to confirm where the bottleneck sits.
• Calculate the energy and mass transfer effect of preheating the feed and estimate the achievable feed rate, stating the assumptions and the heat balance.
• Evaluate at least two alternatives to the preheater, such as reboiler modification or feed composition control, on capacity, cost, safety and environmental effect.
• Complete the hazard assessment in the change request covering overpressure and relief, tube leak and materials compatibility, alarm and trip settings, the emergency shutdown logic, operability and the environmental licence limits on emissions.
• Identify every safety case control measure and safe operating limit affected and state whether the change requires a safety case revision or regulator notification.
• Define the pre-implementation actions including drawing updates, procedure changes, training, relief study and the pre-start-up safety review, and update MOC-26-034 in the management of change register with the classification and actions.
• Prepare a summary for the Technical Services Manager with the analysis, the recommendation and the conditions under which the hot work permit for the tie-in can be issued.

What someone in this role would produce

• Column performance analysis with bottleneck confirmed
• Heat balance and capacity estimate with assumptions
• Alternatives evaluation
• Completed management of change request with hazard assessment
• Pre-implementation action list and register update