Emerson Process Management helps process industries better manage plants through intelligent control systems and software, measurement instruments, valves and industry expertise. So when a Malaysian LNG plant sought to address its inefficient acid gas removal process, the plant’s operator turned to Transwater – the Emerson Process Management local business partner in Malaysia – for the solution.
Normally, this process is achieved by feeding the natural gas containing hydrogen sulfide into the bottom of an absorption tower. The gases come in contact with a lean solvent such as a Sulfinol solution, which is fed from the top of the tower. After the amine contacts the gas stream and absorbs the acid gases, it leaves the absorption tower through a level control valve before going to the flash tank.
“This is a severe application because a great portion of the physically absorbed gases separate from the amine solution via out-gassing when pressure differential occurs across the valve,” said Ryan McIntosh, Senior Sales Engineer for Fisher Australia of Emerson Process Management. “The turbulent two-phase flow system resulted in severe vibration and erosion due to the high velocity impingement of the liquid phase on the valve and trim.”
After engineers at Transwater and Emerson Process Management had evaluated the application and studied the root cause of the valve failure, an improvement valve solution was recommended with a Fisher 203 mm x 152 mm EWT body with Whisper Trim III to replace two existing problematic competitor’s valves.
Whisper Trim III, which has specifically designed drilled-hole passages, was selected to control the rapid fluid expansion experienced in this type of service. Potential vibration was further controlled by a valve body designed to limit high velocity flow at the valve outlet.
“The carefully selected trim material combination provides necessary corrosion resistance and protection in the presence of corrosive entrained gases,” explained Mr McIntosh. “These specific trim and valve body technologies together allow the valve to control the level in the amine contactor, without the system vibration and valve erosion damage typically generated by a standard valve.”
To further enhance valve reliability and extend its service life, Emerson also installed the Fisher FIELDVUEâ„¢ DVC6200 digital valve controller, which uses high-performance, linkage-less, non-contact valve travel feedback technology. The performance diagnostics capabilities of the DVC6200 were also included to enable condition and performance monitoring of the entire valve assembly to improve asset management decision making.
The newly installed Fisher EWT globe valves with Whisper Trim III successfully solved the vibration and valve damage problem that the LNG plant was previously experiencing in the acid gas removal unit. As a result, frequent valve maintenance and plant operation disruptions were eliminated due to the enhanced performance.
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