Revalidation of a Diesel Hydrotreater Case Study


The Challenge

An international oil and gas company requested ioMosaic perform a relief system revalidation of the DHT at a feed rate of 60,000 bbls/day in a previous assignment. The client desired to increase unit throughput to 78,000 bbls/day or higher and thus ioMosaic evaluated the relief safety at 92,000 bbls/day.

Our Approach

ioMosaic recalculated the relief loads using the higher throughput and determined that valves were rate dependent and would limit throughput for safe operation. The scope comprised of 43 valves, including valves protecting a reactor, a drying tower, heat exchangers and vessels. ioMosaic worked with the client to finalize the mass balance, which was slightly different than the original studies. ioMosaic validated previously identified relief scenarios, updated calculations of relief loads and relief stream properties, provided report documentation, offered recommendations to address potential deficiencies and calculated a new charge limit.

The Benefits

ioMosaic provided the client with a summary report indicating that the throughput of the system was limited by one valve, and indicated other non-rate limiting valves that did not have adequate capacity. This report allowed the client to efficiently focus mitigation options to operate safely at the higher throughput.

Follow-on work from this project included performing a remediation calculation on the pinch-point valveand re-validating the system for a feedstock with a higher naphtha concentration. This second study identified a separate valve that was limiting safe operation for naphtha co-processing. ioMosaic provided a safeguarding graph, which showed the maximum concentration of naphtha that could be processed for a given flowrate. ioMosaic also recalculated the relief loads using the new heat and material balance on six valves. In addition, ioMosaic provided revised calculations to support the client’s mitigation for overpressure protection of a reboiler.

Learn More

Our mission is to help you protect your people, your plant, your stakeholder value and our planet. To learn more about how we can help you manage risk, call us at 1.844.ioMosaic.