by Lee Ju Yong, Applications and Customer Service, Emerson
Most of us know that conductivity is an excellent way to detect the interface between a non-conductive liquid, such as a hydrocarbon, and a conductive aqueous solution. Even more impressive, however, is hearing how this vital analysis is saving time and money for real companies. Here’s a great example.
Hanwha Total Petrochemicals is headquartered in Seoul, South Korea, but operates a large petrochemical complex, consisting of 13 separate plants, at Daesan, in Korea’s Chungnam Province. The company manufactures building block chemicals that go into the making of a host of other chemicals needed for various consumer products. It starts with a naphtha cracker, yielding propylene and ethylene, which are the raw materials in the production of many of polymers, like naphtha.
The naphtha is kept in storage tanks before use. During storage, water accumulates and sinks to the bottom of the tank. Because water interferes with the cracking process, it must be periodically removed. Conductivity is ideal for monitoring the drain. The water has a conductivity between 650 and 1000 uS/cm, and the naphtha has essentially no conductivity. As the water drains, the conductivity is high. When the water/naphtha interface is present, the naphtha in the interface, being non-conductive, causes the conductivity to drop. When naphtha alone is present, the conductivity is practically zero. Thus, by stopping the drain at the first sign of a conductivity drop, the operators are ensured that only water has been drained with minimum loss of naphtha.
Prior to Hanwha Total Petrochemical’s decision to use the conductivity analyzer, draining the tank of water was manual, requiring substantial human intervention. One person was positioned at the control valve at the tank outlet to watch the water drain. This person used a visual check to make sure that only water drained out. If naphtha was observed, the person called to the DCS to close the valve in order to minimize the loss of naphtha.
The simple addition of a Rosemount 1066 conductivity analyzer and sensors has significantly reduced the personnel hour demands on the plant’s staff, and even more significantly, has dramatically reduced leakage of costly naphtha from the tank. In addition, naphtha in wastewater increases the load on wastewater treatment and makes it more difficult to comply with environmental regulations – possibly leading to fines.
Conductivity analysis is one of the most used liquid measurements – for good reason. A simple addition of instrumentation can significantly improve the process efficiency, quality, and reliability.
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