Methods for optimal usage and improved valuation of corrosive petroleum feedstocks and fractions (Law521)

Abstract

The invention is a method to improve the prediction of the corrosivity of organic acids in petroleum crudes, feedstocks and distillation fractions by providing a more accurate, repeatable, and rapid means of determining the TAN from the IR spectrum of the material. The method can be easily practiced in refinery, terminal, and assay laboratories. It can be used in conjunction with models and hardware to optimize the usage and improve the valuation of corrosive feed stocks. The invention can be implemented on-line for blending optimization. It comprises the steps of irradiating a heated petroleum sample with IR radiation to produce its IR absorption spectrum, and predicting the TAN from the spectrum using a linear, multivariate regression model. The IR TAN value is then used as input to blending, valuation, and corrosion models.

1 . A method to determine the organic acid content of petroleum streams comprising: 
 (a) irradiating a sample of said petroleum stream with IR radiation;    (b) determining the absorption spectrum; and    (c) correlating said absorption spectrum with the organic acid content of said petroleum stream using linear multivariant regression analysis.    
     
     
         2 . The method of  claim 1  wherein said organic acid content is in units of ASTM TAN.  
     
     
         3 . The method of  claim 1  further comprising the step of heating a sample of said petroleum stream having boiling points below 1050° F., at a temperature between 25° C. and 125° C. before said irradiating step.  
     
     
         4 . The method of  claim 3  wherein said temperature is between 40° C. and 100° C.  
     
     
         5 . The method of  claim 4  wherein said temperature is between 55° C. and 75° C.  
     
     
         6 . The method of  claim 1  wherein the optical absorbance for every spectral frequency is between 0 and 2.0 absorbance units.  
     
     
         7 . The method of  claim 5  wherein the optical absorbance for every spectral frequency is between 0 and 1.75 absorbance units.  
     
     
         8 . The method of  claim 3  wherein said sample has boiling points below 1050° F.  
     
     
         9 . The method of  claim 3  wherein said sample is a known mixture having boiling points above and below 1050° F.  
     
     
         10 . The method of  claim 1  wherein said IR radiation is in the spectral ranges 1000 and 4800 cm −1 .  
     
     
         11 . The method of  claim 9  wherein said IR radiation is in the spectral ranges 1000-1350 cm −1 , 1550-2200 cm −1 , 2400-2770 cm −1 , and 3420-4800 cm −1 .  
     
     
         12 . The method of  claim 1  further comprising the step of orthogonalizing the absorption spectrum so as to eliminate environmental and instrumental contributions.  
     
     
         13 . The method of  claim 1  further comprising the step of using said orthogonalized spectra of a set of samples, the calibration samples, which are representative of the variability of petroleum feed and process streams, to develop a prediction regression model to predict the TAN of said streams to an accuracy that renders the invention useful to the application.  
     
     
         14 . The method of  claim 13  wherein said number of samples is at least 8 times the number of regression factors in the model, and more preferably 10 times the number of regression factors.  
     
     
         15 . The method of  claim 13  wherein said samples include both whole crudes and pipestill distillation factions.  
     
     
         16 . The method of  claim 13  wherein said average prediction error for a sample set of whole crude and pipestill and laboratory distillation fractions are less than 0.25 and more preferably less than 0.15 TAN units.  
     
     
         17 . The method of  claim 1  utilizing a sufficient number of calibration samples to achieve a predetermined accuracy.  
     
     
         18 . The method of  claim 17  wherein said number of calibration samples exceed 100.  
     
     
         19 . The method of  claim 17  wherein said number of calibration samples exceed 400.  
     
     
         20 . A method to optimize blending of two or more petroleum feedstreams having different levels of TAN wherein the feedstream blend is processed into process streams comprising: 
 (a) blending said feedstreams in certain proportions to form a feedstream blend;    (b) measuring the TAN level of said feedstream blend and/or said processed streams using the method of claim  1 ;    (c) comparing the TAN level of said feedstream blend and/or process streams to a predetermined TAN level; and    (d) adjusting the proportions of said feedstreams in the blending step so that the TAN level of the feedstream blend and/or process streams is equal to or less than said predetermined level.    
     
     
         21 . In a method for determining the value of a crude oil, the improvement which comprises determining the TAN level of the crude oil by the method of  claim 1 , valuing the crude oil according to said TAN level.  
     
     
         22 . A method to optimize the addition of acid neutralizing agents to a petroleum feedstream that is processed into process streams comprising: 
 (a) determining the optical absorbance spectrum of the feedstream and/or processed streams;    (b) predicting the organic acid content and/or corrosion rate of the feedstream and/or processed streams from its spectrum;    (c) adding the neutralizing agent in batch or intermittent or continuously mixed flow;    (d) measuring the optical spectrum of the treated feedstream and/or processed streams;    (e) predicting the remaining acid content and/or the corrosion rate of the treated feedstream and/or processed streams without removing the neutralized products or unreacted neutralizing agent; and    (f) controlling the amount or blend of neutralizing agents, and/or the temperature, pressure, mixing, or flow conditions in the neutralizing process to achieve the target acid level and/or corrosion rate in the treated feedstream and/or processed streams.