4.1 Usually organic chlorides do not occur naturally in crude oil. When present, they result from contamination in some manner, such as disposal of waste solvent or as use for dewaxing a pipeline or other equipment.
4.1.1 While an uncontaminated crude oil will contain zero ppm of organic chloride, a very small amount is capable of being handled in a refinery.
4.1.2 A rule of thumb used by refiners is <1 ppm organic chlorides in the whole crude, and 5 ppm in the light naphtha, when the naphtha fraction is 20 % of the original sample.
4.1.2.1 For refiners to ensure < 1 ppm organic chloride in the crude oil, the amount measured in the naphtha fraction must be < 1/f (where f is the naphtha fraction calculated with Eq 3).
4.1.3 Any organic halide present in the crude oil almost always distills into the naphtha fraction. Some varieties can break down during fractionation but most survive this process and are destroyed during further refining usually during hydro-treating (desulfurization of the naphtha).
4.2 Sometimes other halides have been used for dewaxing crude oil; in such cases, any organic halides will cause the same problems as the organic chlorides.
4.3 Organic chloride species are potentially damaging to refinery processes. Hydrochloric acid can be produced in hydrotreating 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.
1.1 These test methods cover the determination of organic chloride (above 1 μg/g organically-bound chlorine) in crude oils, using either distillation and sodium biphenyl reduction or distillation and microcoulometry.
1.2 These test methods involve 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 5 regarding potential interferences.
1.3 Test Method A covers the determination of organic chloride in the washed naphtha fraction of crude oil by sodium biphenyl reduction followed by potentiometric titration.
1.4 Test Method B covers the determination of organic chloride in the washed naphtha fraction of crude oil by oxidative combustion followed by microcoulometric titration.
1.5 The values stated in......
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