Alkylation
Flow measurement
The alkylation units are a sensitive but key process in many refineries. It’s a conversion process unit used to convert isobutene and low-molecular-weight alkenes into alkylate, which is a very high-octane component of the end-product gasoline or petrol. Sulfuric acid is used as a catalyst to produce alkylates out of hydrocarbons. ‘Fresh’ (high concentration) acid enters the process and is mixed with the hydrocarbons in a series of reactors and settlers.
Measurement of the sulfuric acid concentration in the alkylation process is very important to ensure a high product quality. If the concentration is higher than required, acid consumption costs are too high. If the concentration is lower than required, the efficiency of the process is reduced.
A coriolis flowmeter is a great solution for getting the most accurate and reliable measurement of both mass flow rate and in-situ process density for this application.
The analog output signal from the flowmeter is connected to an IS PR 9116B universal converter. The output from the 9116B (located in the safe area), is connected to the control system. In addition, the 9116B adds a relay alarm contact for sensor breakage detection.
Application:
> Need more information? Please contact us.
What is an alkylation unit and what flow measurements are critical in the process?
An alkylation (alky) unit combines light olefins (butylene) with isobutane in the presence of a strong acid catalyst (HF or H2SO4) to produce alkylate — a high-octane, clean-burning gasoline blending component. Critical flow measurements include the olefin feed rate, isobutane recycle flow, acid circulation rate, and product rundown flow. Accurate flow measurement maintains the correct isobutane-to-olefin ratio, which directly affects product octane and catalyst consumption. PR Electronics signal conditioners ensure these measurements reach the DCS with full accuracy and intrinsic safety protection.
Why does alkylation unit instrumentation require particularly robust signal conditioning?
Alkylation units using HF (hydrofluoric acid) or H2SO4 (sulfuric acid) catalysts present extreme corrosion and safety hazards. Instrumentation must operate reliably in this harsh chemical environment, and safety loops for acid leak detection and emergency shutdown require SIL-rated signal conditioning. The PR 9106B provides SIL 2/3 certified signal isolation, while the PR 9116A Universal Converter handles diverse input types from the various flow, temperature, and pressure instruments monitoring the alkylation reaction, acid settler, and product fractionation sections.
