The increased challenges refiners face with frequent crude changes, processing of new opportunity crudes, and limited mechanical systems have resulted in difficult operations that require alternative treatment methods. In terms of chemical treatment, one potential option to alleviate difficult desalter operations is the use of acidification aids. This paper will cover the key drivers for desalter acidification, the benefits from this approach and the downstream effects (e.g., corrosion, fouling) from the application of this type of technology. Also discussed will be the different type of chemistries, reactions, the fate of acids in the desalting operation, and their potential impacts on downstream operations. Field experience and observations from acidification programs will be presented and discussed.
Enhancing desalter oil water separation (reduce oil under carry and water carryover)
Extracting amine/amine salt contamination from crude oil3
Contaminant removal (e.g., oil soluble metals; acid soluble particulates, calcium carbonate (CaCO3), iron sulfide (FeXSy))
Cost effectiveness
Ease of control
Low volatility
Does not impact wastewater
Does not impact downstream processing units
Does not generate solids
Processing lower quality crude oils such as those containing high levels of solids, asphaltenes, oil soluble metals and inorganic metal contaminants provides for higher profit margins as long as the refiner can meet finished product specifications, while minimizing the impact on the crude unit?s overhead system, downstream units, and the wastewater treatment plant. An important aspect of any acidification program is to determine if there will be any processing difficulties during crude unit operations focusing on the desalting aspect of the crude feedstock. Injection of an organic acid or transitioning from one acid to another acid must be transparent. This means no desalter operational issues should be encountered when using an acid injection program. Ultimately, good or improved desalting performance should always be the expectation of any acidification program. An effective acidification program can minimize crude unit upsets and lost production. Operational challenges such as high conductivity, crude oil-water emulsions, oil undercarry, corrosivity, fouling tendencies, as well as catalyst poisoning do present themselves if not effectively managed when processing difficult crude oils as blend components in a refinery?s feedstock. Desalter acidification has been shown to be an effective means of resolving difficult emulsions in desalters while enhancing the effectiveness of the applied desalting demulsifiers.1,2 Some of the reasons that refiners may turn to using acidification additives are:Acidification additives typically are either mineral acids (e.g., sulfuric acid) or simple organic acids (e.g., acetic acid, glycolic acid, citric acid). There are both positive and negative impacts associated with most of the acids used as adjunct chemistries to acidify desalter wash water. The acid program selected should meet the following criteria:
Emulsions can be stabilized by surface-active polar asphaltene and resin fractions within the crude oil. Rigid interfacial films form at the oil water interface and interfere with the coalescence of brine droplets.
