Significance and Use
5.1 Organic chlorides do not occur naturally in crude oil. When present, they result from contamination in some manner, such as disposal of chlorinated solvent used in many dewaxing pipeline or other equipment operations.
5.1.1 Uncontaminated crude oil will contain no detectable organic chloride, and most refineries can handle very small amounts without deleterious effects.
5.1.1.1 Most trade contracts specify that no organic chloride is present in the crude oil.
5.1.2 Several pipelines have set specification limits less than 1 μg/g organic chlorides in the whole crude, and less than 5 μg/g in the light naphtha, based on the yield of naphtha being 20 % of the original sample.
5.1.2.1 To ensure less than 1 μg/g organic chloride in the crude oil, the amount measured in the naphtha fraction shall be less than 1/f (where f is the naphtha fraction calculated with Eq 1). For example, a crude oil sample with 1 μg/g of organic chloride but a 10 % yield of naphtha would create a naphtha containing 10 μg/g organic chloride. Further, a crude containing 1 μg/g of organic chloride but a 40 % yield of naphtha would create a naphtha containing 2.5 μg/g organic chloride. Due to the difference in naphtha yields, the impact on refining operations can be significantly different.
5.1.2.2 Since crude oil deposits worldwide exhibit different yields of naphtha, the working range of detection for this method shall cover a broad range, possibly as high as 50 μg/g in a naphtha fraction.
5.1.3 Organic chloride present in the crude oil (for example, methylene chloride, perchloroethylene, etc.) is usually distilled into the naphtha fraction. Some compounds break down during fractionation and produce hydrochloric acid, which has a corrosive effect. Some compounds survive fractionation and are destroyed during hydro-treating (desulfurization of the naphtha).
5.2 Other halides can also be used for dewaxing crude oil; in such cases, any organic halides will have similar impact on the refining operations as the organic chlorides.
5.3 Organic chloride species are potentially damaging to refinery processes. Hydrochloric acid can be produced in hydro- treating or reforming reactors and the acid accumulates in condensing regions of the refinery. Unexpected concentrations of organic chlorides cannot be effectively neutralized and damage can result. Organic chlorides are not known to be naturally present in crude oils and usually result from cleaning operations at producing sites, pipelines, or tanks. It is important for the oil industry to have common methods available for the determination of organic chlorides in crude oil, particularly when transfer of custody is involved.
Scope
1.1 This test method covers the determination of organic chloride (above 1 μg/g organically-bound chlorine) in crude oils, using distillation and combustion ion chromatography.
1.2 This test method involves the distillation of crude oil test specimens to obtain a naphtha fraction prior to chloride determination. The chloride content of the naphtha fraction of the whole crude oil can thereby be obtained. See Section 6 regarding potential interferences.
1.3 The test procedure covers the determination of organic chloride in the washed naphtha fraction of crude oil by combustion ion chromatography. Other halides can be determined but are not included in the precision statement of the test method.
1.4 The values stated in SI units are to be regarded as standard. The preferred concentration units are micrograms of chloride per gram of sample.
1.4.1 Exception—The values given in parentheses are for information only.
1.5 Warning—Mercury has been designated by many regulatory agencies as a hazardous substance that can cause serious medical issues. Mercury, or its vapor, has been demonstrated to be hazardous to health and corrosive to materials. Use caution when handling mercury and mercury-containing products. See the applicable product Safety Data Sheet (SDS) for additional information. The potential exists that selling mercury or mercury-containing products, or both, is prohibited by local or national law. Users must determine legality of sales in their location.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
