ES2353867T3 - METHOD FOR DETERMINING THE SOURCE OF ENSUCIATION IN UNITS OF THE THERMOCONVERSION PROCESS. - Google Patents

Abstract

A method for determining the source of coke deposits in the head equipment in a heavy hydrocarbon thermoconversion process unit that converts a heavy hydrocarbon feed into products of lower boiling point in a thermoconversion zone, the method comprising the steps of: (a) introducing an effective amount of at least one substantially non-volatile organic compound containing metal as a tracer in the feed to be converted, compound which is at least 90% soluble in said feed; b) convert at least a fraction of said feed containing said tracer into a product stream in the form of vapor of products of lower boiling point; c) passing said product stream in the form of steam through at least one element of the head unit, in which coke deposits are formed; (d) analyze said coke deposits to determine the presence of said tracer metal; and (e) differentiate, by reference to the measured amount of metal in coke deposits, if the source of coke deposits in said at least one element of the head equipment results from: (i) condensation of said product stream into vapor form, or (ii) feed droplets being carried into said product stream in the form of steam.

Description

FIELD OF THE INVENTION 5

The present invention relates to a method for determining the source of fouling in units of the oil heat conversion process. More particularly, the invention distinguishes whether the fouling occurs due to the feeding of small feed droplets or condensation of the vapor phase.

BACKGROUND OF THE INVENTION

 fifteen

Thermoconversion processes, such as coking, are commonly used in oil refineries to convert heavy hydrocarbon feeds into more valuable lower boiling products. Examples of two types of effective coking for this invention are short time contact coking, and fluidized bed coking. The short vapor contact time coke contains a short steam contact time reaction zone containing a horizontal mobile bed of recycled fluidized hot solids of a heating zone. The reaction zone is operated at a temperature of 450 ° C to 700 ° C (842-1292 ° F) and under conditions such that the residence time of the solids and the residence time of the steam are independently controlled. The 30

Conventional fluidized bed coking process units typically include a coking zone, a separation zone, a coke regeneration zone, and head equipment. In the coking zone, which contains a fluidized bed of hot solids, preferably coke, a heavy carbonaceous oil feed is introduced. The feed is distributed as uniformly as possible on the surfaces of said coke particles, in which it is cracked in vapors and carbonaceous material, which is deposited on hot solids. Vapors pass through cyclones, which remove entrained coke particles. The steam is then discharged into a washing zone where any remaining solid particles are removed, the heavier product is condensed, and the steam is then cooled to condensed products, which go to the fractionator. A suspension of heavy liquid and solid particles, which usually contain 1 to 3% by weight of coke particles, is recycled until extinction from the scrubber to the coking zone. twenty

During the coking process, thermally cracked feeds have a tendency to form solid, insoluble carbonaceous deposits that re-dress and seal the process equipment. The deposition of these deposits in the process equipment is called under-25, and the deposits are called the fouler. Coke plugs line and damage head equipment, such as cyclones. Even small amounts of co-deposited on the surface of the process equipment can greatly reduce the effectiveness of the re-30 equipment.

ducting heat transfer. Large amounts of coke deposited on the surface of the process equipment, for example the cyclone nozzles, can result in a high pressure drop, which reduces the performance so that the unit has to be turned off for Eliminate coke deposits. The fouling can be due to a variety of causes, including the entrainment of the feed and condensation of the vaporized feed on surfaces that then undergo a thermoconversion in coke. Unfortunately, when such fouling occurs, it could not be differentiated if the source of the fouling was due to the feeding of small droplets of feed or condensation of vaporized feeds. Therefore, there is a need in the art for a method to determine the source of such fouling so that process conditions or head equipment can be adjusted to reduce and / or mitigate coking.

SUMMARY OF THE INVENTION 20

According to the present invention, a method is provided for determining the source of coke deposits in the head equipment in a heavy hydrocarbon thermoconversion process unit that converts a heavy hydrocarbon feed into products of lesser point of boiling in a thermoconversion zone, the method comprising the steps of:

(a) introducing an effective amount of at least one substantially non-volatile organic compound containing metal as a tracer in the feed to be converted, compound which is at least 90% soluble in said feed; 5

b) convert at least a fraction of said feed containing said tracer into a product stream in the form of steam of products of lower boiling point;

c) passing said product stream in the form of steam through at least one element of the head equipment, in which coke deposits are formed;

(d) analyze said coke deposits to determine the presence of said tracer metal; Y

(e) differentiate, by reference to the measured amount of the metal in the coke deposits, if the source of coke deposits in said at least one element of the head equipment results from: (i) condemnation of said current of product in the form of a va-by, or (ii) feed droplet drag in said product stream in the form of steam.

In a preferred embodiment, the metal-containing nonvolatile organic compound is selected from the group consisting of metalloporphyrins, metal acetylacetonates 25 and metal naphthenates.

In another preferred embodiment of the present invention, the metal-containing organic compound is copper naphthene.

 30

DETAILED DESCRIPTION OF THE INVENTION

The present invention is suitable for use in any heavy hydrocarbon thermoconversion process unit in which coke deposition of head equipment 5 is a problem. Preferred processes of thermo-conversion of heavy hydrocarbons include coking processes. Coking is generally carried out at relatively high temperatures, to which the coking tendencies of the feeds are revealed, for example at temperatures above 350 ° C (662 ° F), and more usually above 450 ° C (840ºF).

Suitable feeds of heavy hydrocarbons for use in the present invention include vacuum residual oils, atmospheric residual oils, heavy and reduced crude oil, pitch, asphalt, bitumen, coal sludge, coal liquefaction funds , the heaviest fractions of asphalt sand oil and shale oil, and mixtures thereof. Such feeds will typically have a Conradson carbon content of at least 5% by weight, generally 5 to 50% by weight. For the rest of Conrad-son's carbon, see ASTM test D 189-165.

A typical heavy hydrocarbon feed, suitable for the practice of the present invention, will typically have the composition and properties within the ranges set forth below.

 Conradson Carbon

 5 to 40% by weight

 Sulfur

 0.75 to 8% by weight

 Hydrogen

 9 to 12% by weight

 Nitrogen

 0.2 to 2% by weight

 Carbon

 80 to 88% by weight

 Metals

 1 to 2000 ppm by weight

 Boiling point

 340 ° C (644 ° F) to 650 ° C (1202 ° F)

 Specific density

 -10 to 35 ° API

This invention uses a metal-containing compound, soluble in hydrocarbons, which is substantially non-volatile at the temperature of the thermo-conversion process unit in which it is used as a tracer to distinguish the source of fouling in reactor head areas. The compound will preferably be 95% non-volatile, more preferably 98% non-volatile. Additionally, the compound will preferably be at least 90% soluble in said feed, more preferably at least 95% soluble in said feed, and most preferably at least 99% soluble in said feed. All percentages are by weight. The metal of the metal-containing compound will preferably be chosen to be different from metals that are typically inherent in the feed. Non-limiting examples of preferred metal-containing compounds, suitable for use herein, include metalloporphyrins, metal acetylacetonates or metal naphthenates, more preferably it is copper naphthenate. The volatility of the metal portion of the selected compound is a critical variable. For example, a thermogravimetric analysis (TGA) of copper naphthenate shows that, at around 600 ° C (1112 ° F), a residue of

11.23% by weight. The theoretical calculated residue for copper oxide, the product of the thermal decomposition of copper naphthenate, is 11.34% by weight. On the other hand, cobalt naphthenate leaves a cobalt oxide residue of 6.45% by weight versus the theoretical value of 10.6% by weight 5 for cobalt oxide, indicating that volatile cobalt material has evolved from this material. In this way, cobalt naphthenate would not be an acceptable tracer.

Non-limiting types of coking for which the present invention can be used include contact time coking in the form of short steam, and fluidized bed coking. A fluidized bed coking unit can be any unit of the conventional fluidized bed coking process that usually comprises a coking zone, a separation zone, a coke regeneration zone, and a head equipment.

In broad terms, the operation of the fluidized bed coking unit proceeds as follows in the present invention: a heavy hydrocarbon feed meets an effective amount of a substantially non-volatile, soluble metal-containing compound. in hydrocarbons, preferably copper naphthenate. By "effective amount" is meant the minimum amount of metal-containing compound that will result in a measurable amount of metal from the compound in the deposits resulting from the thermo-conversion process. Such amount will typically range from 10 ppm by weight to 1000 ppm by weight, preferably from 25 ppm 30

by weight at 500 ppm by weight, and more preferably from 50 ppm by weight to 200 ppm by weight of said compound. The doped feed is then passed to the thermoconversion zone of a thermoconversion process unit, which is preferably a coking zone that has a fluidized bed of solids, or the so-called "seeding" particles. , which are typically coke particles. A fluidizing gas, for example water vapor, is admitted at the base of the coking zone, in an amount sufficient to obtain a surface fluidization rate. Such speed is typically in the range of 0.5 to 5 feet / s. Coke, coming from a heating regeneration zone, at a temperature above the coking temperature, for example at a temperature of 40 ° C to 200 ° C, preferably from 15 65 ° C to 120 ° C in excess of the actual operating temperature of the coking zone is admitted in an amount sufficient to maintain the coking temperature in the range of 450 ° C to 600 ° C. The pressure in the coking zone is maintained in the range of 0 to 10 20 kg (0 to 150 psig), preferably in the range of 0.34 to 3.1 barg (5 to 45 psig). The lower portion of the coking zone serves as a separation zone, to remove occluded hydrocarbons from the coke. From the separation zone, a separate coke stream is removed, and circulated to a heating zone. In the heating zone, the separated coke is introduced into a fluidized bed of hot coke particles, in which the coke deposits are burned from the coke particles. The bed is heated by passing a 30

combustible gas in the heating zone together with the coke particles. The gaseous effluent from the heating zone, including entrained solids, is passed through one or more cyclones, in which separation of the larger entrained solids occurs. The larger separated solids are returned to the heating zone. The gaseous effluent from the cyclones is removed from the process unit. Conversion products from the coking zone are passed through a cyclone to remove entrained solids that are returned to the coking zone through an aspiration tube. Vapors leave the cyclone and go to a washing area. The washed stream of materials and heavy solids is recycled to the coking zone. Washing products of the coker's version are removed from the washing zone for fractionation in a conventional manner.

Although the above invention has been described in relation to a fluid coking process, it can also be practiced in contact time coking in short steam. In short-term steam contact coking, the feed in the present invention is doped with the non-volatile hydrocarbon soluble metal-containing compound, preferably copper naphthenate, as previously described. This doped feed is then fed into a short-time contact time reactor, which contains a horizontal mobile bed of fluidized hot particles, which are received from a heating zone. The particles can be fluidized by any suitable means, such as by use.

of fluidized gas, preferably water vapor, a mechanical medium, and by use of vapors resulting from the vaporization or cracking of a fraction of the feed. It is preferred to use a mechanical means, and that the mechanical means is a mechanical mixing system characterized by having a relatively high mixing efficiency with only small amounts of axial back-mixing. Such a mixing system acts as a piston flow system, with a flow pattern that ensures that the residence time is almost the same for all particles. The most preferred mechanical mixing system is the type described in U.S. Pat. No. 5,919,352.

Such a mixing system comprises a plurality of horizontally oriented rotating screws 15 that help fluidize the particles. Although it is preferred that the solid particles be coke particles, they can be any other suitable refractory material. Non-limiting examples of such other suitable refractory materials include those selected from the group consisting of silica, alumina, zirconia, magnesia, or muli-ta, synthetically prepared or naturally occurring material such as pumice, clay, kieselguhr, diatomaceous earth or bauxite. The solids will have an average particle size of 40 to 1000 micrometers, preferably 25 to 500 to 800 micrometers.

When the doped feed is contacted with the hot solids, which will preferably be at a temperature of 450 ° C to 700 ° C, more preferably 500 ° C to 600 ° C, an important portion of the feed 30

It will crack and vaporize. The residence time of the steam in the thermal zone of short contact time will be an effective amount of time so that substantial secondary cracking does not occur. This amount of time will typically be less than 5 seconds, preferably less than 4 seconds, more preferably less than 3 seconds. That portion of the feed that does not vaporize immediately upon contact with the hot solids will form a thin film on the hot solids in which cracking reactions occur. This results in the formation of additional steam products, and a small amount of carbonaceous material that is deposited on hot solids. The residence time of the solids in the short steam contact time reactor will be 5 to 60 seconds, preferably 10 to 30 seconds. It is preferred that the short steam contact time reactor is operated so that the ratio of solids to feed is 20 to 1, preferably 10 to 1. It will be understood that the precise ratio of solids to feed 20 will depend mainly on the thermal balance requirement of the short contact time reactor. The association of the ratio of oil to solids with the requirements of thermal balance is within the skill of those who have a normal skill in the art, and thus will not be elaborated here anymore. A small amount of the food will be deposited on the particles in the form of combustible carbonaceous material. The metal components will also be deposited on the particles. Consequently, the vaporized portion leaving the unit of 30

The process will have substantially less amount of both Conradson carbon and metals, when compared to the original feed.

Deposits in the head equipment associated with a thermoconversion unit are analyzed for metallic re-5 of the metal of the organic compound containing non-volatile metal, which most preferably will be copper. Non-limiting types of head equipment in which coke deposition is a problem include reactor head areas or cyclones. Cyclones are usually analyzed first because the cyclone is the first place to condense heavy liquids after leaving the heat conversion zone.

Coke deposits may be due to a variety of causes, including entrainment of feed 15 or condensation of vaporized feed. The copper oxide residue in the reactor head areas identifies the source of the coke deposits. If there are low levels of copper remaining in the head areas, then coke deposits are due to the condensation of vapors. If the head areas contain high levels of copper remaining, then coke deposits are due to feed drag. If both mechanisms work, then intermediate copper levels will be observed. 25

Based on the determination of the coking source, process conditions or head equipment can be adjusted to reduce or mitigate coking. When coke deposits are due to condensation of vapors, an adjustment may be overheating.

steam with coke or steam at a heater temperature of 620-630 ° C, or reduce the temperature of the thermoconversion process unit, for example the fluidized bed coking unit can be reduced to 510 ° C, and the unit Short time contact coking can be reduced up to 550 ° C.

When coke deposits are due to feed drag, mechanical changes can be made to the spray size of the feed nozzle droplet and / or to the mixer, to obtain a better mixing and capture Effective of small feeding go-titas.

EXAMPLE 1

 fifteen

An assay was conducted to verify the ability to prevent copper from volatilizing, and was carried out with the volatile feed components and products in the present invention.

A vacuum oil feed was doped under vacuum with 192 ppm of copper as copper naphthenate. A short distance vacuum distillation was carried out. Several boiling fractions of the product, as well as the coke resulting from the pyrolysis of these fractions, were analyzed to determine copper retention. The balance 25 of resulting material (Table 1) essentially indicates that there is no volatility of copper.

EXAMPLE 2

 30

A trial was performed to demonstrate the source of fouling in the head unit.

To analyze whether the deposits above the cyclone were formed by feed entrainment or by steam condensation, a coking unit of the pi-5 lotus plant capable of making a replica of the fouler formed in a commercial unit was used. A typical experiment of the pi-lotus plant consisted of an operating period of 8 hours at a temperature of about 585 ° C and a pressure of 1.0 bar. The feed rate of the dual vacuum resi-10 oil was maintained at 1.2 kg / h, and the coke circulation rate was maintained at 20 kg / h. The coke used in the circulation typically came from the commercial unit, which has an average Sauter diameter of about 700 µm. fifteen

The vacuum residual oil feed was doped with 150 ppm of copper as copper naphthenate before the feed was sprayed onto a bed of coke particles in a double screw coking pilot plant. After the pilot experiment, the cyclone deposits 20 were analyzed for copper. The cyclone tank contained 80 ppm by weight of copper, compared to about 1000 ppm by weight expected if the tank was formed by feed drag. The 80 ppm by weight of copper could be attributed to 25 coke fines. Coke fines contained copper because it was derived from the feed, which contained 150 ppm by weight of copper.

EXAMPLE 3 30

Based on the successful demonstration that steam condensation was responsible for the coke deposits of the fouler in the cyclone of the small pilot plant, 50 ppm by weight of copper as naphte-5 copper was added to the feed of residual vacuum oil before spraying the feed onto a bed of coke particles in a larger double screw coking unit. The unit was operated at about 1.2 bar pressure. After four days of operation, three samples of the head soiling were taken, which showed copper levels of 18, 14 and 12 ppm by weight for the three different samples, as compared to about 350 ppm Cu expected if feed drag is the main fouling mechanism. In addition, samples of deposits taken near the reactor outlet were analyzed for a result of 13 and 17 ppm by weight of copper. These results confirm the results of the small pilot plant.

 twenty

EXAMPLE 4

A detailed analysis of the metals was carried out in coke samples of Example 3 taken at the outlet of the mixer, before the cyclone. These results, summarized in Table 2, show that as the surface of the coal coal of calcined starting coal is displaced by the coke of the product, there is a decrease in the level of chromium present in the coke of original coal tar, but absent in Ali-30

Mention Nickel and vanadium levels both increase over the short period of time of the experiment, approaching equilibrium levels after four days. The copper level gradually increases to 345 ppm, the expected level in coke. 5

TABLE 1

 DISCUSSION OF SHORT SHORT (DISTAC) OF VACUUM RESIDUAL OIL OF THE THERMAL CONTACT TIME PROCESS UNIT IN SHORT STEAM GIVEN WITH COPPER

 Dest Weights (1)

 Distillation Fraction Party Feed (PPM) Head (PPM) Mi-crocar-bonus Remainder Test (a) Head (% by weight) Coke (PPM) Mi-crocar-bonus Remainder Test (a) Coke (% by weight) Comments (3)

 100.0

 Feeding of Vacuum Residual Oil Doped with 78.4 18.9 Theoretical:

 Cu 192.0 <0.11 1030.0 Cu, 1015 ppm

 V 793 1.84 444.0 V, 420

 Ni 50.4 4.77 291.0 ppm Ni, 267 ppm

 61.0

 Residual Vacuum Oil of Dis- 66.0 26.4 Theoretical:

 tac,

 1200 ° F +

 Cu 306.0 <0.40 933.0 Cu, 1159 ppm

 V 121.0 1.25 439.0 V, 459 ppm

 Ni 84.8 23.5 304.0

 24.2

 Vacuum Residual Oil Distillate, 92.2 3.6 Theoretical:

 1100-1200 ° F

 Cu 3.75 0.55 47.9 (2) Cu, 104

 V 56.6 3.71 52.9 (2) ppm V, 1573

 ppm

 Ni - 33.8 35.7 27.0 (2)

 14.8

 Vacuum Distilled Start - 1100ºF 90.7 1.7 There is not enough sample to make metals in coke. The coke should be:

 Cu 0.04 0.32 N.D. Cu, 2.4 ppm

 V 15.7 2.79 N.D. V, 923 ppm

 Ni 11.4 17.8 N.D.

 (1) Calculated from distillation cuts for residual oil feed: Cu 188.5 ppm V 89.8 ppm Ni 61.6 ppm (2) Coke sample too small for exact metal analysis

 (3) Calculated from the analysis of coke and metal yields, using the approximation that all metals pass to coke; not performed for Ni for experiments with high Ni content in liquids. (4) ASTM microcarbon residue test No. 4530-93.

TABLE 2

METAL ANALYSIS (ICPS) * OF SAMPLES OF EXIT OF THE REACTOR OF THE UNIT OF THE THERMAL CONTACT TIME PROCESS IN SHORT VAPOR DOPED IN PPM 5

(AVERAGE TEMPERATURE 592ºC [1098ºF])

 Sample Description

 Co Cr Cu Ni V

 VGO Reactor Output (R.O.), 590 ° C

 - 27.6 - 23.9 8.39

 R.O. of Residual Oil Vacuum, 1 h. at ½ of the Feed Speed

 - - 103 39.6 48.9

 R.O. of Vacuum Residual Oil, 1 h at ½ of the Feed Rate, Filter Sample, without N2 under the Stored Box.

 - 22.4 71.7 47.2 35.1

 R.O. of Residual Oil to Vac. 20 h.

 - 10.7 191 153 201

 R.O. of Residual Oil to Vac. 25.5 h

 - - 158 136 181

 R.O. of Residual Oil to Vac. 593 ° C, 87.5 h

 5.38 - 319 293 383

 R.O. of Residual Oil to Vac. 588 ° C, 90 h

 6.02 - 345 322 422

 * Inductively Coupled Plasma Emission Spectroscopy

Claims (11)

1.- A method to determine the source of coke deposits in the head unit in a heavy hydrocarbon thermoconversion process unit that converts a heavy hydrocarbon feed into products of lower boiling point in a thermoconversion zone , the method comprising the steps of: (a) introducing an effective amount of at least one substantially non-volatile organic compound containing metal as a tracer in the feed to be converted, compound which is at least 90% soluble in said feed; b) convert at least a fraction of said feed containing said tracer into a product stream in the form of steam of products of lower boiling point; c) passing said product stream in the form of steam through at least one element of the head equipment 20, in which coke deposits are formed; (d) analyze said coke deposits to determine the presence of said tracer metal; Y (e) differentiate, by reference to the measured amount of metal in coke deposits, if the source of coke deposits in said at least one element of the head equipment results from: (i) condemnation of said current of product in the form of a va-by, or (ii) droplet of feed droplets into said product stream in the form of steam. 30 2. Method of claim 1, wherein the thermoconversion process unit is a fluidized bed coking unit. 3. Method of claim 2, wherein the organic compound containing non-volatile metal is selected from metalloporphyrins, metal acetylacetonates, and metal naphthenates. 4. Method of claim 1, wherein at least one element of the head unit is a cyclone. 10 5. Method of claim 3 or 4, wherein the organic compound containing non-volatile metal is copper naphthenate. 6. Method of claim 1 or 5, wherein the heavy hydrocarbon feed is selected from the group consisting of vacuum residual oils, atmospheric residual oils, heavy and reduced crude oil, pitch, asphalt, bitumen, coal sludge, coal liquefaction funds, and heavier fractions of asphalt sand oil and shale oil. 7. Method of claim 1, 2 or 6, wherein 10 to 1000 ppm by weight of copper naphthenate are introduced into a heavy hydrocarbon feed. 8.- Procedure for thermoconverting a feed of heavy hydrocarbons into products with a lower boiling point, a procedure which comprises the steps of: (A) introduce 10 to 1000 ppm by weight of the tracer; 30 (B) injecting the hydrocarbon feed containing said non-volatile organic compound containing metal through the feed nozzle into said thermoconversion process unit; and then determine the source of the coke deposits 5 using the method of determination according to any one of claims 1 to 6; (C) reduce the temperature of said thermoconversion process unit, or increase the temperature of said product stream in the form of steam by an effective amount when the coke deposits in said at least one element of the head equipment are due to condensation of vapors; or (D) adjust the feed nozzles or mixers by an effective amount when the coke deposits in said at least one element of the head equipment result from the feed drag. 9. The method of claim 8, wherein at least one element of the head unit is a cyclone. 10. The method of claim 8, wherein the heavy hydrocarbon feed is selected from the group consisting of vacuum residual oils, atmospheric residual oils, heavy and reduced crude oil, pitch, asphalt, bitumen, coal sludge, coal liquefaction funds, and heavier fractions of asphalt sand oil and shale oil. 30 11. The method of claim 8, wherein the thermoconversion process unit is a fluidized bed coking unit.