My question concerns narrow or "light" naphtha. As a broker and trader, most of the product I see has an IBP (initial boiling point) low range of 40 degrees Celsius. I have a client seeking to purchase product with specs stating 35 degrees. I believe this to be highly unusual, or is this a common specification? Please advise.
Answers
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19/08/2009
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Alan Goelzer, Jacobs Consultancy, alan.goelzer@jacobs.com
For wider boiling naphthas and light naphthas [both petro-naphthas and sales naphthas], values for IBP(D86) and T05(D86) can be variable within the framework of ASTM D86 distillation methods. This is in part due to substantial allowables for "loss" during initial stages of the test protocol and sampling methods and sample containers employed. Thus, the lower IBP(D86) may not be too meaningful versus the higher IBP(D86) specification, particularly depending upon absolute values for T50(D86) and Reid Vapor Pressure.
The intent of the particular client may be to obtain a naphtha or light naphtha with increased concentrations of either pentanes or butanes or both. For a naphtha or light naphtha exhibiting given narrow range of T50(D86) distillation temperatures, a better indicator of increased volume fractions of butanes and pentanes can be inferred by increases in Reid vapor pressure, typically as measured by the mini-method assuming that samples are drawn into pressure cylinder samplers and properly cooled to 0C before drawing aliquot for RVP testing.
RVP contributions of pentanes tend to run in the range of 16-18 psi times volume fraction concentration. RVP contributions of butanes tend to run in the range of 55 to 60 psi times volume fraction concentration.
Note that frequently the allowable RVP of a naphtha or light naphtha may be limited or constrained by the nature of the shipping method or by nature of the shipping and receiving storage tanks.
As additional comment ---The potential value of a wider boiling naphtha or light naphtha to a specific petroleum refinery or petrochemical plant is actually a function of the gas chromatography-based "PIANO by carbon number spectrum" for the naphtha along with its Bromine Number test value [and Maleic Anhydride Value if Bromine Number is greater than perhaps 3-5 g Br2 per 100 g]. Acronym PIANO stands for normal paraffins / isoparaffins / mono-aromatics / cyclo-paraffins or naphthenes / olefins.
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12/08/2009
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Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
It is not highly unusual to have 35 degree C IBP of LN (Light Naphtha). LN may have even lower IBP.
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