In a Hydrocarbon Processing article, Adapting instrumentation to the needs of refineries, Emerson’s Douglas Carlson and Dan Cychosz describe the challenging applications within these refineries and role of instrumentation in meeting these challenges.
Douglas and Dan open highlighting the hazardous conditions that make up the refining process:
- Flammable and explosive—The very nature of hydrocarbons
- Hot—Converting oil into higher-value products takes heat
- Corrosive—High total acid number (TAN) crude oils, hydrogen sulfide (H2S), alkylation acids, etc.
- Viscous—Crude oil can contain residual content with very high boiling points.
One of the key measurement technologies used by refiners is differential pressure (DP). It:
Given the high heat in many applications as the crude oil is distilled into its hydrocarbon components, instruments cannot be directly in contact with the process fluids. Impulse lines can be used with these incompressible fluids but can have issues with high viscosity fluids and cold weather conditions. DP meters with two fill fluids, such as the Rosemount 3051S Thermal Range Expander, can be used in these applications.
…can be used for simple pressure measurements, along with DP, but it is also the most common way of measuring flow and is a frequent choice for level.
The high-temperature fluid is used in the part exposed to the process. It bears the brunt of the heat and stays warm enough to avoid thickening. It sends the pressure value via an intermediate diaphragm to a second fluid designed for lower-temperature operation. This second and less-viscous fluid spans the remaining distance to the transmitter, and is unaffected by lower temperatures, even below freezing.
This extended temperature range, based on fill fluid – maximum 770°F (410°C) to minimum -157°F (-105°C) can be used in pressure, level and flow measurement applications. Measuring the DP across a flow path obstruction, such as an orifice plate:
…can provide data from which the volumetric flow can be calculated. Adding a temperature and static pressure reading and known density characteristics can help convert a volume reading to mass flow.
In the early parts of the refinery process, such as distillation, impurities in the crude can cause clogging by the obstruction creating the differential pressure to be measured. A wedge primary element with remote seals:
…creates a reliable DP flow reading while being resistant to wear or plugging and reducing pressure loss. When mounted in a horizontal pipe run, the wedge cuts in from the side to keep an unobstructed flow path on the top and bottom, so there are no places for particulates or entrained gases to accumulate and impact measurement reliability.
Read the article for other technologies ideal for use in challenging refining applications including Rosemount 3051S Electronic Remote Sensor (ERS) System, conditioning orifice plates, and combining these technologies to solve specific challenges.
Join us at the October 1-5 Emerson Exchange conference where you catch Douglas’ presentation, Hot Process DP-Level Solved with Cool Thermal Range Expander! and Dan’s presentation, Reducing Project Risk for PBF Energy – Toledo Refining Center Hydrocracking Unit SIS Upgrade. You can also connect and interact with other refining industry and pressure, level and flow experts in the Refining, Pressure, Level, and Flow groups in the Emerson Exchange 365 community.