The case for Let-down modules (pre-built skid units) in Ebullated Bed Hydrocracking.

Presented By

Michael Lemeshev - MOGAS

Conference: Galveston 2019

A stepwise (three-tiered) approach is required to reduce pressure in a safe and mechanically feasible manner. Each stage reduces the reaction pressure by flowing the products through a specialized control valve. These valves have an extremely short life cycle, especially when compared to the time frame between regularly scheduled hydrocracking unit shutdowns. There is a need for redundancy in this circuit. If a specialty control valve lasts for six months, there must be a way for the unit not to have to shut down to switch to and utilize a spare control valve.

Let-down modules allow for this exact operation. However, there is much to be considered from a safety and operability standpoint. Consider a setup that allows switching, while the unit is up and running, between a standby control valve and an operational one. With pressures across the control valves that can be more than 1000psi and temperatures at over 900o F, these valves are very shock sensitive. It makes sense not to shock them thermally. Additionally, the flow contains hydrogen, which if in a high enough concentration and leaked, it can be an asphyxiant.

Typically, EPC’s are not equipped, from an experiential standpoint, to fully attend to all these issues/aspects. It pays huge dividends to have an experienced manufacturer, like MOGAS, provide a literal plug-and-play module that is capable and safe.

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