Electrically accelerated water coalescing

Hydrocarbons, on the other hand, are nonpolar molecules. They are not particularly affected by electricity. We can take advantage of this difference between polar water and nonpolar hydrocarbons to accelerate water settling. 

An electric precipitator contains sets of electric plates. A high-voltage (20,000-V) electric current is applied across these plates, or electrodes. The droplets of water are electrically attracted to these plates, or grids. The water droplets coalesce into larger heavier droplets on the plates. They fall rapidly to the bottom of the electric precipitator vessel. 

If you see the amps on your precipitator creeping up or spiking up, something is beginning to short-circuit the electric grids or insulators. Most commonly, corrosion products are falling off the walls of the precipitator vessel. In my experience, this is the most common cause of precipitator failure. 

On my sulfuric acid production unit in Texas City, we had an electrostatic precipitator to remove a liquid sulfuric acid mist from a flowing gas stream. It worked in the same way as a precipitator in liquid-liquid service. However, the electrodes or grids were not parallel plates. As illustrated in Fig. 33.4, the grids were lead tubes and lead-coated wires. The gas flowed through about 400 8-in diameter lead tubes, arranged in parallel. It was rather like a singlepass, shell-and-tube heat exchanger (see Chap. 22). 

This electric sulfuric acid-mist precipitator worked fine, until one of the lead coated wires inside the tubes broke. Then the entire precipitator would arc. This means the amps would jump up and down, as the single broken wire flapped around inside the tube. I do not know why, but the wires failed only on weekends. Then your fearless author would crawl inside the precipitator, and cut out the broken wire and plug the tube with a wooden plug. I ve saved a piece of the lead wire. It s a memento of what I do best. 

These precipitators may increase the settling rate of water by a factor of 5. For example, settling droplets of sulfuric acid out of alkylate (a light hydrocarbon) by gravity alone might take an hour. A good electric precipitator can do a better job in just 10 min. Precipitators do not really consume much electricity. It is true that the electricity is applied 

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