An account is given of the use in a refinery of an organic corrosion inhibitor. Conventional ammonia injection to a pH of 8 or more in the receiver waters had provided inadequate protection to the usual sites of aggressive corrosion attack in the crude and synthetic crude fractionators, admiralty metal exchanger bundles and depropanizer overhead lines. A change from sweet to sour crude sources aggravated the situation.
Corrosion was strikingly reduced by proportioned injection of 20 ppm of inhibitor on crude input, as evidenced by coupon and inspection studies, and by daily receiver water iron content. The dosage later was reduced to 6-8 ppm based on overhead products plus reflux; the best point of injection was found to be the overhead reflux line. Normal flow of inhibitor apparently is downward. pH must still be maintained at 6.5 to 7.5 by ammonia injection. There have been no discoverable adverse effects on any refinery product at this dosage. While savings of ammonia have been about balanced by the cost of inhibitor, down-time for the pipestill due to restrictions from metallic sulfide accumulation has been cut to 25-35 percent of its former extent. Organic inhibitor has extended the life of the tower several years beyond that expected with ammonia protection alone.5.8.2
