Crude oil dehydrator/desalter control system

A system for controlling the content of an impurity in a crude oil stream comprising:

• means for adding a demulsifier to a stream of produced wet crude oil,
• means receiving the produced wet crude oil stream with demulsifier for separating produced water and gas from the crude oil to provide a separated crude oil stream,
• first mixing means receiving water and the separated crude oil for mixing the water with the separated crude oil to provide a crude oil/water stream,
• first means for sensing a pressure drop across the first mixing means and providing a first pressure drop signal representative thereof,
• first dehydrator means for removing substantial amounts of water from the crude oil/water stream to provide a crude oil stream,
• second mixing means receiving wash water and the crude oil stream from the first dehydrator means for mixing the wash water and the crude oil to provide a crude oil/wash water stream,
• second dehydrator means receiving the crude oil/wash water stream for removing substantial amounts of the water to provide a dehydrated crude oil stream,
• means for monitoring the content of the impurity in the dehydrated crude oil stream and providing an impurity content signal representative thereof, and
• means for controlling the adding of the demulsifier to the produced wet crude oil stream and for controlling at least one of the mixing means in accordance with the impurity content signal from the monitor means and the first pressure drop signal from the first sensing means.