MXPA00002560A - Method for determining the corrosiveness of naphtenic acid in crude oil and refinery streams - Google Patents

Abstract

A method for determining corrosiveness of naphthenic acid in a fluid includes the steps of:providing a fluid containing naphthenic acid;providing iron powder having a surface area of at least about 0.01 m<2>/g;contacting the fluid and the powder for a period of time so as to provide a portion of the iron as dissolved iron dissolved in the fluid;and measuring iron concentration of the fluid containing the dissolved iron, so as to provide a measure of corrosion potential of the naphthenic acid over the period of time.

Description

METHOD FOR DETERMINING THE CORROSIVITY OF NAFETY ACID IN RAW PETROLEUM AND REFINERY CURRENTS BACKGROUND OF THE INVENTION The present invention relates to a method for determining the corrosivity of naphthenic acid contained in crude oils and refinery streams. The corrosivity of several components in crude oil and refinery streams is a real problem, because the excessively corrosive components in such streams can destroy the distillation units in the refinery and other equipment as well. A widely accepted method to represent the corrosivity of a crude oil and / or refinery stream is the total number of acid (TAN), which is determined as the number of milligrams of KOH per gram of material in question. It has been found, however, that the total acid number is not an accurate indicator of the corrosivity of the crude oil and / or refinery stream in question, since the acidity is not necessarily directly correlated with corrosivity. The conventional method for measuring the corrosivity of naphthenic acid is by placing coupons in the corrosive medium for a time given to the tempexatnxa yr ^ xesión xeLev.ant? Sy j? E according to "Standard Practice to Prepare, Clean and Evaluate Coxrosion Test Specimens 'Gl-90 and "Standard Guide for the Corrosion Test in High Temperature Environment or High or Both' X GJ.U-.97_, in Volume Q3__Q2_ ^ Wear and Exosion, Metallic Corrosion, of the Book 1998 Annual Standard of ASTM, Section 3 Methods of Testing Metals and Analytical Procedures "- A natural method - to increase the corrosivity of naphthenic acid is a method for measuring the weight loss described in a standard The paper entitled "Corrosion by Naphthenic Acid in a Facility of Phtefinex to.", by Baaian-iíi ala?, _ et al., presented as the article in the International Annual Conference of NACiL, jion = ton., Tx, 1993 ^ These methods of loss of pe They measure corrosion as a total event, and they do not distinguish between the corrosion processes caused by sulfur and by naphthenic acid, which causes the corrosion of the corrosion. attack by naphthenic acid is soluble, Bab an-Xibal film, corrosion of a coupon. steel in units of mg / cm2, which is the weight of the corrosion products, and the total weight loss jn xaiUpulgadas per year, the cua-L is- The corrosion rate .. From these data they calculated a speed ratio of corrosion to product s. of corrosion. If this ratio is less than 10, they establish that the contribution of the naïve acid is small or non-existent. However, if the ratio exceeds 10, then it is said that naphthenic acid has made a significant contribution to the coxrosion process ^ The method does not work well with crude oils, because during the test the crude oil tends to form a layer of cogue together with a film of ..corrosion on the surface of the coupon. This results in erxoxes when the film of corrosion is measured. Considering the above, it is clear that there remains a need for a simple, reliable and effective method paxa-medix the coxxosivity of acid -naxrén.ica. Contained in a Luido, such as crude oil or refinery streams. It is therefore the primary object of the present invention to provide a medium method from which the naphthenic acid correlation can be easily determined. It is an additional object of the present invention to provide a method wherein the required materials They are easily available. It is still an additional object of the invention to provide a method that can be easily incorporated for measurements made in the field, or n laboratories and the like. Other objects and advantages of JL_a pxesonte invention will appear below.

BRIEF .J2E-SCRJLPCJ: QN.J-IE J_A J ^ yj N LQN According to the present invention, the objects and advantages of the invention have been easily maintained. According to the invention, a method is provided to determine the corrosivity of naphthenic acid in liquid, the method comprising the steps of: providing a fluid containing naphthenic acid to provide iron powder which finishes a surface area of at least about 0.01 m2 / g; contacting the fluid with the powder for a period of time, to provide a portion of the iron as dissolved iron in the fl ower and jedix JThe concentration of iron in the fluid containing the dissolved iron, to provide a measure of the corrosion potential of the acid. nattenic during that period of time. The method can be carried out at a known temperature, preferably in a known temperature range, to provide the measurement of the corrosion potential at vaxia = tempexatuxas. According to the present invention, the use of particulate iron or A powder form having a high surface area advantageously allows a high molar ratio of iron to naphthenic acid to be maintained, so that naphthenic acid is the limiting. Factox of the reaction, and a good measure of corrosivity can be obtained due to this .

DES € RXPCl? N JDE.TALLADA The invention is related to a method to determine the. coxxosivity of naphlene acid in nn fluid. Typical fluids that can be advantageously measured according to X. This invention includes crude p_etxols, refinery streams and the like. Current streams typically contain naphthenic acid, which can be corrosive to the critical equipment used in the distillation process. According to the present invention, examples of typical xefineria contaminants that may be tested include, but are not limited to, fluids distilled at atmospheric pressure, vacuum distillate fluids and the like. Other hydrocarbon streams that can be tested using the method of the present invention include a wide variety of crude oils, viscous oils. light oils and similar. The method of the present invention advantageously leads to measuring the corrosivity of the naphthenic acid contained in the fluid. According to the invention, a sample of the fluid to be tested is obtained, for example from a refinery stream or another hydrocarbon stream. or as a fixed or similar sample. According to the invention, J or the coxxient or sample is mixed with a powder or particulate iron (Fe0) which has a high surface area, preferably under an inert atmosphere, and at temperatures or conditions of oxidized oxides. What do you want? are evaluated to determine corrosivity. Under such conditions, a portion of the high surface axle of Jalexxo reacts with the fluid to become dissolved (as Fe + 2) in the organic phase. and a portion _xestánte esXá pxesente as a solid (Fe0). According to the present invention, unreacted solid iron is then removed through homogenization and .filtxax the mixed plexus. The concentration of dissolved iron in the remaining organic phase is then measured using well-known methods. and conventional. The rate of corrosion of the naphthenic acid is then easily determined from the concentration of ice measured in the organic phase, typically as iron naphthenate, for the time during which the dust and current were brought into contact. . This corososivity is preferably determined and provided in terms of units of reaction rate and / or ppm. According to the present invention, the iron powder to be mixed is substantially an iron powder of high surface area, which preferably it has a supexficial area of at least about 0..01, _m2 ./- g, more preferably between about 0.05 and 2 m2 / g ^ and more preferably between about 0.1 and 1 m2 / g. In addition, the powder preferably has an average particle size of less than or equal to about 5.Q.mu.m. Nitrogen powder is preferably -mixed with the stream, or sample to be evaluated in sufficient quantities to provide a molar ratio. of iron to naphthenic acid in the stream of at least about 1: 2, and preferably greater than about 80: 1.

In accordance with the present invention, it has been found that this advantageous stage of the photopoxizes the naphthenic acid which is the limiting factor in the reactions that take place, thereby providing an accurate and reliable measurement of the current corrosivity of naphthenic acid. This is unlike conventional methods that depend on the total number of unreliable acid (TAN), and / or the rate of weight loss of solid carbon steel coupons. The iron powder and the coxygen to be measured in accordance with the present invention are preferably put in contact by metering sufficiently to provide a substantially homogeneous mixture of powder of ixxxx and Jl current. and the contact time is monitored.

Following a desired time, as shown above, the mixture will contain a portion of iron as iron.

(Fe0) solid that did not react, while another portion of iron (Fe + 2) will be dissolved in the organic phase, typically with iron naphthenate. The organic phase containing both, the solid hlexx that did not react and the concentration of dissolved iron that reacted is then treated through conventional homogenization and filtration steps, to separate and remove unreacted solid iron, which can advantageously be recycled for future use. The remaining organic phase or stream is then measured to determine the dissolved iron concentration using conventional methods, such as, for example, the induced coupled plasma (ICP) method. The coxrosivity can vary with the temperature, and it is therefore preferred to carry out the contacting or mixing step at a known temperature, preferably in a range of known temperatures, by which Xa measurement of the coxossivity is correlated to the particular temperature. In this way, a range of corrosivity values can be provided for the temperature range. As discussed above, the contacting or mixing step is preferably carried out under an inert atmosphere such as nitrogen or axon, PD: example ^ This atmosphere is inert with respect to the iron powder, to advantageously avoid oxidation thereof . Of course, other types of inert atmospheres for the herb may be used. As - expuo above, it will be appreciated that the method -of the -present J-nvenr. In proportion to a direct measure of the corrosivity of naphthenic acid as desired. This method can conveniently be used to evaluate such co-xxxivity in inflows or currents that have a total acid number of between about D and 200 mg KOR ^. In addition, the method of the present invention is particularly advantageous for use to treat Worms t J is like a cut of 50 ° GJ-500 ° C of a current drawn from any point of a refinery, it should also be appreciated that the method of The present invention is carried out using a particulate or powdery form, which is readily available and thus contributes to the economic value of the present invention. Finally, the px method allows measurements with a high degree of accuracy and repeatability, which can be obtained from any desired site. The invention can be incoxpopulated in other ways, carried out in other ways without departing from it. of the spirit or essential texts of Xa xaisma. The present embodiment is therefore to be considered as in all aspects i, "clear and not restrictive, the scope of the invention is indicated by the claims, and all XQ changes that come within the meaning and range of equivalence it is proposed that they be included in it.

Claims (19)

1. REJECTED 1. A method for determining the corrosivity of naphthenic acid in a fluid, comprising the steps of providing a fluid containing naphthenic acid; providing hiexxo powder having a surface area of at least 0.01 m2 / g; to contact the illuid and poxvo for a period of time, to provide a portion of the iron as dissolved iron dissolved in the fluid, and to measure the iron concentration of the fluid contained in the dissolved iron, to provide a measure of the potential of corrosion of naphthenic acid during the period of time.
2. 2. A method of compliance with claim U wherein the hiexxo powder has an average particle size of less than or equal to about 50 μm.
3. 3. A method of confounding x On Xa claim- L, _ where the contact stage comprises- ^ put. in contact the j l v and the diluted in - a molar ratio of iron to naphthenic acid in the fluid of at least about 1: 2.
4. 4. A compliance method xx > n Xa claim 1, wherein the contact step comprises contacting the powder and the defined one in an oLax ratio of iron to naphthenic acid in the fluid of at least about 80: 1.
5. 5. A method according to claim 1, wherein the contacting step further provides a stable portion, the solid as solid, which did not react in the fluid, and further comprises the step of removing solid iron that did not react before the stage. measurement.
6. 6. A method of confounding x: On Xa claim ^ 5, wherein the step of removing the unreacted solid iron comprises liornageneizax and filtxax the fluid, by means of which the unreacted solid iron is separated from the fluid.
7. 7. A method according to claim 1, wherein J the contact stage comprises. mix the powder and the fluid to provide a substantially homogeneous mixture of the powder and the fluid
8. 8. A method of compliance with Xa claim L, wherein the contact step is carried out under an inert atmosphere.
9. 9. A method according to claim, JL, wherein the fluid comprises a stream-e-fluid.
10. 10. A method according to claim Xa.1, wherein the fluid comprises a hydrocarbon.
11. 11. A method according to claim 1, wherein the fluid is a refinery stream.
12. 12- In method according to claim 11, wherein the refinery stream is selected from the group gue cx > n3Xs of distilled discharges at atmospheric pressure, vacuum distilled fluids and mixtures thereof.
13. 13. A method according to claim JL, wherein the Fugue is a crude pefxole.
14. 14. A method according to claim. 13, where the crude oil is selected from the gxupo that x or s-l ^ X of viscous oil, light oil and combinations thereof.
15. 15. A method according to claim L, wherein the Rout is a 50 ° cut C - 500 ° C of a coring extracted from any point of a refinery.
16. 16. A method according to claim 1, wherein the fluid has a total acid number (.TAN) of cexca entity of D and cexx: a of 2J1D mg of KOH / g.
17. 17. A method according to claim 1, wherein the step of measuring comprises the concentration of .hiexx or the measurement of iron naphthenate in the fluid.
18. 18. A method according to claim 1, wherein the contacting step is carried out at a known temperature, and the enhancing, corrosion is provided for the known temperature.
19. 19. A method of confounding with Xa claim.1, where the iron powder has a supexficial area between 0-5 and about 2 m2 / g.