MXPA01004997A - A process for blending petroleum oils to avoid being nearly incompatible - Google Patents

Abstract

The present invention includes a process for blending two or more petroleum oils, any component of which may be an unprocessed crude oil or a processed oil derived from petroleum, in a manner to minimize fouling and coking of refinery process equipment. The blending method includes the steps of determining the insolubility number, I, for each oil, determining the solubility blending number, S, for each oil, and combining the petroleum oils in the proportions in order to keep the solubility blending number of the mixture higher than 1.4 times the insolubility number of any oil in the mixture. The present invention also includes selecting petroleum oils to minimize fouling.

Description

PROCESS TO COMBINE OILS TO AVOID BEING ALMOST INCOMPATIBLE BACKGROUND OF THE INVENTION The present invention relates to a process for mixing two or more oils in order to mitigate the fouling of refinery equipment, especially heat exchangers, avoiding almost incompatible mixtures. It is known that crude oils and petroleum containing asphaltenes derived from crude oils has a tendency to form solid organic deposits, which is known as dirt and coke in equipment refining processes that are in contact with oil. Such processing equipment includes, but is not limited to, tubes, tanks, heat exchangers, boiler tubes, fractionators and reactoxes. Even small amounts of dirt or coke result in a large loss of energy due to a much lower heat transfer through dirt and coke as opposed to the transfer obtained in the metal walls alone. Moderate amounts of dirt and coke cause significant pressure drops and interfere with the processing equipment and cause such processing equipment to operate inefficiently. Finally, large amounts of dirt or ccque that clog the processing equipment which impedes the flow or otherwise makes the operation ineffective, requiring the equipment to be closed and cleaned of dirt and coke. It is also known that petroleum derivatives, which contain asphaltenes that have been subjected to reaction at high temperatures above 350 ° C, have a tendency to quickly soil the processing equipment, either during cooling or through mixing with a further oil. paraffinic Such processed oils include, but are not limited to, the highest boiling distillation fraction after the catalytically hydrothermal thermal conversion of atmospheric or vacuum crude oil residues and the highest boiling fraction of the liquid decomposition product. Fluid catalytic, which is known as catalytic disintegrator bottoms or catalyst paste oil. This fouling is caused by asphaltenes that become insoluble when cooled or mixed with a more paraffinic oil. Here, the asteinols are defined as the fraction of the soluble oil when the oil is mixed with 40 volumes of toluene but insoluble when the oil is mixed with 40 volumes of n-heptane. If the asphaltenes become insoluble at high temperatures above 350 ° C, they rapidly form insoluble coke in toluene (see I.A., Industrial Engineering, Vol. 32, 2447-2454). The previous patent application of Wiehe and Kennedy disclosed that the simple mixing of two or more unprocessed crude oil oils can cause the precipitation of insoluble asphaltenes that can quickly soil the processing equipment or when such mixtures of crude oil are heated quickly above 350 ° C, insoluble asphaltenes can form coke in distillation boiler tubes. If the mixture of oils causes the precipitation of asphaltenes, it is said that the oils are incompatible unlike the compatible oils that do not cause the precipitation of asphaltenes when mixed. Thus, incompatible petroleum mixtures have a much greater tendency to soil and coke than compatible oils. Once a mixture of incompatible oils is obtained, the rapid fouling and the rapid coke formation that results usually requires the closure of the short-term refining process. This results in significant economic damage since large volumes of oil can not be processed during the equipment cleaning process. In the past most refineries have learned through trial and error to avoid certain crude oils either not combining certain processed oils or reducing the severity of the processing in order to make the processing oils more combinable. The combination of oils in a refinery is very common, especially in the case of crude oils, and consequently, few refineries, if any, can be economically viable without combining oils. This is done both to produce the most economical range of products and to handle multiple source products in a refinery that arrive at the same time with a limited number of storage tanks. It has now been discovered that compatible but nearly incompatible oil combinations can soil metal surfaces, especially heated metal surfaces, at a higher rate than the individual oils in the combination. While the speed of fouling is greater in the case of incompatible combinations, this speed is high for the almost incompatible combinations but decreases as proportions of the combination are selected in such a way that they are increasingly distant from the proportions that result. in incompatibility. It has also been discovered that the same compatibility model that allowed predicting oil proportions in a combination that avoid incompatibility, as taught in the previous application, also allows predicting the proportions of oils in a combination that avoid an almost incompatible, even when they use a different criterion. SUMMARY OF THE INVENTION The present invention includes a process for combining two or more oils, which complement may be an unprocessed crude oil or a processed petroleum derived from crude oil, in such a way as to minimize fouling and the formation of coke in the refinery processing equipment. The combination method includes the steps of determining the insolubility index I, for each oil, determining the insolubility combination index S, for each oil and combining said oils in the proportions that allow maintaining the combination index of insolubility of the mixture. greater than 1.4 times the insolubility index of any oil in the mixture. The present invention also includes the selection of oils to minimize fouling. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a measurement of the thermal fouling data using a thermal fouling test unit for a mixture of oils in example 1. BRIEF DESCRIPTION OF THE INVENTION In the present invention, it has been found that two or more tests of each oil with a test liquid containing different proportions of a non-polar asphaltene solvent and a non-polar asphaltene non-solvent can predict whether a given mixture of oils is almost incompatible. This is based on the determination of the insolubility index and the insolubility combination index for each oil in the combination using oil tests. Here we employ non-polar when the molecular structure of the liquid includes only carbon, hydrogen and sulfur atoms. Once again, it has been learned that almost incompatible oils can be processed cor. little dirt or coke formation to the extent that certain proportions of the oils in the combination are avoided, as can also be predicted from the insolubility index and the combination index of insolubility of each oil in the combination as determined by the oil tests. The first step in determining the insolubility index and the insolubility combination index for a petroleum is to establish whether the oil contains insoluble asbestos in n-heptanes. This is achieved by the combination of a volume of oil with five volumes of n-heptane and by determining whether asphaltenes are insoluble. Any convenient method can be used. One possibility is to observe a drop of the oil and test liquid mixture between a glass plate and a glass cover using the light transmitted with an optical microscope with a magnification of 50 to 600 times. If the asphaltenes are in solution, few or no dark particles will be observed. If the asphaltenes are insoluble, many dark particles will be observed, usually of brown color, usually of a size of 0.5 to 10 microns. Another possible method is to place a drop of the mixture of test liquid and oil on a piece of filter paper and let it dry. If the asphaltenes are insoluble, a ring or dark circle will be observed around the center of the yellow-brown oil stain. If the asphaltenes are insoluble, the color of the stain left by the oil will be relatively uniform in color. If the oil contains insoluble asphaltenes in n-heptane, the procedure described in the following three paragraphs is followed to determine the insolubility index and the indi.ee of insolubility combination. If the oil does not contain insoluble asphaltenes in n-heptane, the insolubility index receives a zero value and the index of insolubility combination is determined through the procedure described in the section marked "oils without asphaltenes". Petrophils containing asphaltenes The determination of the insolubility index and the index of the insolubility combination for an oil containing asphaltenes requires the oil solubility test in test liquid mixtures with a minimum ratio of two volumes of oil in relation to the test liquid mixture. Mixtures of the test liquid are prepared by mixing two liquids in various proportions. A liquid is non-polar and is a solvent for asphaltenes in petroleum while the other liquid is non-polar and non-solvent for asphaltenes in petroleum. Since asphaltenes are defined as insoluble in n-heptane and soluble in toluene, it is more convenient to select the same n-heptane as the non-solvent for the test liquid and toluene as the solvent for the test liquid. Even though the selection of many other non-test solvents and test solvents can be made, their use does not provide a better definition of the petroleum mixing process than the use of n-heptane and toluene described herein. A convenient volumetric ratio between oil and test liquid mixture is selected for the first test, for example, 1 ml of oil for 5 ml of test liquid mixture. Several test liquid mixture mixtures are then prepared by mixing n-heptane and toluene in various known ratios. Each of these mixtures is mixed with the oil in the volumetric ratio selected between the oil and the test liquid mixture. Then it is determined for each of these if the asphaltenes are soluble or insoluble. Any convenient method can be used. One possibility is to observe a drop in the mixture of test liquid and oil between a glass slide and a glass cover using the light transmitted with an optical microscope with a magnification of 50 to 600 times. If the asphaltenes are in solution, few or no dark particles will be observed. If the asphaltenes are insoluble, many dark particles, usually brown, usually 0.5 to 10 microns in size, will be observed. Another possible method is to place a drop of the combination of the test liquid mixture and oil on a piece of filter paper and let it dry. If the asphaltenes are insoluble, a ring or dark circle will be observed around the center of the yellow-brown oil stain. If the asphaltenes are insoluble, the color of the stain left by the oil will be relatively uniform in color. The results of the oil combination with all the test liquid mixtures are classified according to the increasing percentage of toluene in the test liquid mixture. The desired value will be between the minimum percentage of .cluen that dissolves the asphaltenes and the maximum percentage of toluene that precipitates the asphaltenes. Other test liquid mixtures are prepared with the percentage of toluene between these limits, they are combined with petroleum in the volumetric proportion selected between oil and test liquid mixture, and it is determined if the asphaltenes are soluble or insoluble. The desired value will be between the minimum percentage of toluene that dissolves the asphaltenes and the maximum percentage of toluene that precipitates the asphaltenes. This process continues until the desired value is determined within the desired precision. Finally, the desired value is taken as the average of the minimum percentage of toluene that dissolves the asphaltenes and the maximum percentage of toluene that precipitates the asphaltenes. It is the first data point T :, in the volumetric ratio selected between oil and test liquid mixture, R:. The second data point can be determined by the same process as the first data point, only by selecting a different volumetric ratio between the oil and the test liquid mixture. Alternatively, a percentage of toluene below that determined for the first data point can be selected and this test liquid mixture can be added to a known volume of oil until the asphaltenes start to precipitate. At this point, the volumetric ratio between the oil and the test liquid mixture R2 / in the selected percentage of toluene in the test liquid mixture, T :, becomes the second data point. Since the precision of the final figures increases the longer the distance between the second data point and the first data point, the preferred mixture of the test liquid to determine the second data point is 0% toluene or 100% of n-heptane. The index of insolubility, I is obtained by: and the solubility ccmbination index,?, is provided by: Petroles without asphaltenes If the oil does not contain asphaltenes, the insolubility index is 0. However, the erythrite. The combination of solubility index for a petroleum that does not contain asphaltenes requires the use of a petroleum ie test that contains asphaltenes for the ote. The insolubility index and the insolubility combination indexes and the solubility combination indexes have been previously determined using the procedure just described. First, a volume of test oil is combined with 5 volumes of oil. The insoluble asphaltenes can be detected by the microscope or by the stain technique, described above. If the highly viscous oils (more than 100 centipcises), they can be heated to a temperature of 100 ° C during the combination and then cooled to room temperature before looking for the insoluble asphaltenes. Likewise, the spot test can be carried out in a combination of viscous oils in an oven at a temperature of 50-70 ° C. If insoluble asphaltenes are detected, the oil is not a solvent for the test oil and the procedure presented in the following paragraph. However, if insoluble asphaltenes are not detected, the oil is a solvent for the test oil and the procedure presented in the paragraph following the next paragraph must be followed. If insoluble asphaltenes were detected when a volume of test oil was combined with 5 volumes of petroleum, small volumetric increments of oil are added to 5 ml of the test oil until insoluble asphaltenes are detected. The volume of non-solvent oil V-.so is equal to the average of the total volume of oil added for the volumetric increase just before the detection of the insoluble asphaltenes and the aggregate volume when the insoluble asphaltenes were detected for the first time. The volumetric increment size can be reduced to that required for the desired accuracy. Yes S7_. is the solubility combination index of the test oil and ITo is the oil insolubility index test / then the petroleum solubility combination index. _or r_: so_vente is procporcí ee.iar.te: If the inscrutable asphaltenes were not detected when a volume of the test oil was corroborated. 5 volumes of oil, oil is solvent oil for test oil. The same volumetric ratio between oil and test liquid mixture ?:, that used to measure the insolubility index and the solubility combination index for the test oil is selected. However, now several mixtures of the test liquid are prepared by the combination of different known proportions of petroleum and n-heptane instead of toluene and n-heptane. Each one mixes with the • test oil in a volumetric relationship between the oil and the test liquid mixture equal to R-_. Then it is determined for each whether the asphaltenes are soluble or insoluble, as for example by means of the microscope or stain test methods discussed previously. The results of the oil combination with all test liquid mixtures are classified in accordance with an increasing percentage of oil in the test liquid mixture. The desired value is between the minimum percentage of oil that dissolves the asphaltenes and the maximum percentage of oil that precipitates asphaltenes. More mixtures of test liquid are prepared with percentage of oil between these limits, mixed with the test oil in the volumetric proportion selected between test oil and test liquid mixture (R: - and it is determined if the asphaltenes are soluble The desired value will be between the minimum percentage of oil that dissolves the asphaltenes and the maximum percentage of oil that precipitates the asphaltenes.This process continues until the desired value is determined within the desired precision., the desired value is taken as the mean of the minimum percentage of the oil that dissolves the asphaltenes and the maximum percentage of oil that precipitates the asphaltenes. Is the data point, T¿_, in the volumetric ratio selected between oil and test liquid mixture,? .t. If T- is the peak of cate previously measured in the volumetric ratio- between test oil and test liquid mixture, R:, in the test oil with test liquids composed of different proportions of toluene and n-heptane, then the index of oil combination and solubility, S, is provided by: T- S = 100 TO LTsoj Blends of cetrólecs. Once the solubility combination index for each component has been determined, the Soiubiii___d Combination Index. for a mixture of n oils, S -.-, is provided by: S -. V? S1 + V2S2 + V3S3 + + vnsn m "~ v1 + v2 + v3 + + vn where V: is the volume of component 1 in the mixture. Document No. 763,652 now issued) indicates that the criterion for the compatibility of a petroleum mixture is that the solubility combination index of the petroleum mixture is greater than the index of insolubility of any component in the mixture. In this application the criterion for low fouling is that the solubility combination index of the oil mixture is greater than 1.3 times, and preferably greater than 1.4 times, the rate of insolubility of any component in the mixture. The highest fouling velocity is when the blend solubility index of the mixture is less than the insolubility index of at least one er component. the mixture, consequently incompatible oils. However, surprisingly, it has been found that even in the case of combinations of compatible oils a high fouling can be observed if the combination index of solubility of the oil mixture is less than 1.3 times the rate of insolubility of at least one component in the mix. Only when the solubility combination index of the petroleum mixture is greater than 1.4 times the insolubility index of any component in the mixture, is the fouling velocity approximately what is expected based on a linear combination of fouling velocities of the individual components of the combination. If the lowest solubility combination index of all the components in the combination is greater than the highest insolubility index of all the components in the combination, the order of combination is not important. Otherwise, the combination order taught by the previous patent must be followed to obtain a low fouling speed. If none of the oils in the proposed combination have a solubility combination index greater than 1.3, preferably 1.4 times the maximum solubility combination index of the components in the combination, clearly no proportion of the oils in the combination will comply with the criterion to obtain a low fouling, insofar as all the oils are present. In this case, the choice is obvious to remove the oil with the highest index of insolubility from the combination or to add a petroleum to the combination that has a solubility combination index greater than 1.3, preferably greater than 1.4 times, the index of maximum insolubility of the component in the combination. EXAMPLE The soiling of the Forties and Souedie oils and several mixtures of these two oils was measured on heated surfaces. First, the insolubility index and the solubility combination index of each oil were cleaned following the procedure for asphaltene containing oils. The minimum percentage of toluene in the test liquid to keep the asphaltenes in solution, T, was determined as 7.5 for Forties and 33 for Souedie to 1 gram of oil and 5 ml of test liquid composed of mixtures of toluene and n-heptane . Since the density of Forties is 0.791 g / ml and for Souedie it is 0.874 g / ml, R: is l / [(.791) 5 .252 for Forties and 1 / [í .87 5] = 0.229 for Souedie . The maximum amount of n-heptane that could be added to 5 ml of petroleum without precipitating the allyhenes was determined as 6.9 ml in the case of Forties and 3.1 ml in the case of Souedie. Thus, T_ is zero at R equal to 5 / 6.9 = 0.725 for Forties and 5 / 3.1 = 1.61 for Souedie. Therefore: I = 11.5 for Forties; I = 38.5 for Souedie S = 11.5 1 + -1 S = 38.5 .725 J 1 + - 0 .725 '1.61 1.61 S = 27 for Forties; S = 62 for Souedie Since the insolubility index for Souedie crude is higher than the solubility combination index of the Forties crude, these two crude oils are potentially incompatible. The onset of incompatibility occurs when: vF = 0.69 VF + VS Thus any mixture of Forties and Scuedie, e is greater than 69% by volume of Forties, will precipitate when combined. For a solubilization combination index: e is 1.3 vets the insolubility index: _, - _ v. sF v. s. vF + vs vF + vs = 1.3. = 50.0 For a solubility combination index that is 1.4 times, the insolubility index: 15 VFSF V, is $ m? - = 1.41 = 53.9 V. = 0.27 vF + vs 20 The relative fouling velocity of Forties crude oil, Souedie crude oil and Forties and Souedie crude oil blends was measured using a test unit _D thermal laboratory fouling manufactured by Alcor. In each case the oil, under a nitrogen pressure of 492,172 kg / mr (700 psig) to prevent boiling, was pumped at 3 ml / min through a ring where a carbon steel rod in the center was heated at a constant temperature of 404 ° C (760 ° F). As the dirt accumulated on the surface of the rod, the insulating effect of the dirt reduced the heating capacity of the oil flow and caused the temperature drop at the exit of the ring. Accordingly, the decrease in the temperature of the oil flow at the outlet of the ring over a period of 3 hours is a measurement of the oil fouling velocity. The data appear in the Table and in the Figure and show how this measurement of fouling velocity showed variation with the volumetric percentage of Forties crude when combined with Souedie crude. Volume% index index index com¬ Forties insolubility bination of solubility solubility rate index of insolubility 0 38.5 62 1.61 25 38.5 53 1.38 50 38.5 44 1.14 75 38.5 36 0.93 100 11.5 27 2.35% volume Decrease in linear decrease Forties temperature ° F temperature 0 7 -7 25 19 12.8 50 46 18.5 75 72 24.2 100 30 30 Decrease in temperature ° C 3.9 10.6 25.6 40 16.7 The fouling velocity with 25% Forties crude is only slightly higher than expected from a line drawn through the 0% points Forties (only Souedie) and 100% Forties. Since at 75% Forties the combination is incompatible (more than 69% Forties), it is not surprising that the fouling rate is the largest measure for this set. The surprise is that the speed of fouling with 50% Forties is greater than the fouling speed of any component of the combination even when this combination is compatible. If the Forties and Souedie mixes were controlled at a mixture solubility mix index greater than 1.3 times the insolubility index, the combinations should always be less than 35% Forties. This would represent a large reduction in fouling velocity compared to 69% Forties at the incompatibility limit (blend solubility combination index = insolubility index). In addition, the fouling velocity would never be much greater than the fouling velocity that the Forties crude alone. However, if the Forties and Souedie mixtures were controlled at a mixture solubility mix index greater than 1.4 times the insolubility index, the mixtures would always be less than 27% Forties. This would be a fouling speed close to the linear prediction based on the fouling of the pure components. Thus, the control of the solubility combination index of ur. Petroleum mixture to be greater than 1.4 times the insolubility combination index should maintain the rate of organic fouling almost as low as can be expected, given the fouling rate of the pure components of the mixture.

Claims (1)

CLAIMS A process to combine two or more oils, any component of said combination can be an unprocessed crude oil or a processed petroleum derivative, in such a way as to minimize fouling and coke formation in the refinery processing equipment, which includes: (a) the determination of the insolubility index I, for each oil; (b) the determination of the solubility combination index S, for each oil, (c) the combination of said oils in such a way that the combination index of solubility of the mixture is always greater than 1.4 times the index of insolubility of the oil. oil in the mixture The process of claim 1, wherein the proportions between the oils in the blend are selected to maintain the mix solubility index greater than 1.3 times the insolubility index of any oil in the blend. The method according to claim 1, wherein the insolubility index and the solubility combination index are determined from the toluene equivalency test and the heptane dilution test for each oil containing asphaltenes. according to claim 1, wherein the insolubility index is zero and the solubility combination index is de either the solvent equivalence test or the non-solvent oil dilution test for each oil that does not contain asphaltenes. The method according to claim 1, wherein said solubility combination index of the mixture is determined by S _ V? S1 + V2S2 + V3S3 + + vns V1 + V2 + V3 + + vn where V: is the volume of oil 1 and S-_ is the combination index of insolubility of oil 1. A method to select a petroleum for its combination with a petroleum or a mixture of oils that would otherwise be almost incompatible for minimize fouling and coke formation in subsequent processing, which comprises the selection of said oil to be combined in such a way that it has a solubility combination index greater than 1.4 times the insolubility index of any oil in the mixture and an index of insolubility less than at least one other oil in the mixture. The method of compliance with claim 6, wherein said oil to be combined has a solubility combining index greater than 1.3 times the index and the insolubility of any mixture. The method according to claim 6, wherein said selected combination oil has the highest solubility combination index for the oils under consideration, a lower index and insolubility than at least one other oil in the mixture. The method according to claim 6, wherein said rate of combination of solubility of the mixture is determined by v1s, + v2s2 + v3s3 + + vnsn S-, = v1 + V2 + V3 + + Vn wherein V-_ _ is oil volume 1 and S-_ is the oil solubility combination index

1. The method according to claim 6, wherein the insolubility index and the solubility combination index are determined from the toluene equivalency test and the heptane dilution test for each oil containing asphaltenes. The method according to claim 6, wherein the insolubility index is zero and the solubility combination index is determined from the solvent oil equivalence test or the non-solvent oil dilution test for each oil that It does not contain asphaltenes.