MXPA06012948A - Delayed coking process for producing free-flowing coke using an overbased metal detergent additive. - Google Patents

Abstract

A delayed coking process for making substantially free-flowing coke, preferably shot coke. A coker feedstock, such as a vacuum residuum, is heated in a heating zone to coking temperatures then conducted to a coking zone wherein volatiles are collected overhead and coke is formed. An overbased alkaline earth metal detergent additive is added to the feedstock prior to it being heated in the heating zone, prior to its being conducted to the coking zone, or both.

Description

DELAYED COQUIFICATION PROCESS TO PRODUCE FREE FLOW COKE USING ADDITIVE METAL DETERGENT OF OVERBASES FIELD OF THE INVENTION The present invention relates to a delayed coking process for making substantially free flow coke, preferably coke firing. A coking raw material such as a vacuum residue is heated in a heating zone to coking temperatures then it is conducted to a coking zone where the volatile components are collected and the coke is formed. An overbased alkaline earth metal detergent additive is added to the raw material before being heated in the heating zone, before it is conducted to the coking zone, or both.

DESCRIPTION OF THE RELATED ART Delayed coking comprises the thermal decomposition of petroleum residues (residues) to produce gas, liquid streams of different boiling scales, and coke. The delayed coking of petroleum residues, from heavy crude oil and very sulphurous (high sulfur content) is carried out mainly through the disposal of these low value raw materials by converting part of the petroleum residues to gaseous and liquid products more valuable Although it is generally thought that the resulting coke is a low-value by-product, it may have some value, depending on its degree, as a fuel (fuel-grade coke), for electrodes to make aluminum (anode-grade coke), etc. . In the delayed coking process, the raw material is quickly heated in a heated heater or tubular furnace. The heated raw material is then passed to a coking drum which is maintained under conditions under which coking takes place, generally at temperatures above 400 ° C under pressures above atmospheric. The waste feed heated in the coker drum also forms volatile components that are removed at the top and passed to a fractionator, leaving behind the coke. When the coker drum is filled with coke, the heated feed is changed to another drum and the hydrocarbon vapors are purged from the coker drum with steam. Then the drum is rapidly cooled with water to lower the temperature to less than 149 ° C (300 ° F) after which the water is emptied. When the cooling and draining steps are completed, the drum is opened and the coke is removed after drilling and / or cutting using high-speed water jets.

For example, a hole is typically made through the center of the coke bed using high pressure water jet at high pressure from the nozzles located in a drilling tool. The nozzles oriented horizontally on the head of a cutting tool then cut the coke from the drum. The step of removing the coke considerably increases the production time of the total process. Therefore, it is desirable to be able to produce a free-flowing coke in a coker drum that does not require the cost and time associated with conventional coke removal. Although it may appear that the coker drum is completely cold, some areas of the drum do not completely cool. This phenomenon, sometimes called "hot drum", may be the result of a combination of coke morphologies present in the drum, which may contain a combination of more than one type of solid coke product, ie needle coke , coke sponge and coke shot. Since the non-agglomerated coke shot can be cooled more rapidly than other cokes of different morphology, such as coke sponge or large shot coke masses, it is desirable to predominantly produce substantially free-flowing coke, preferably coke shot, in a delayed coker, in order to avoid or reduce the hot drums.

SUMMARY OF THE INVENTION In one embodiment, a delayed coking process is provided comprising: (a) heating an oil residue in a first heating zone, at a temperature below the coking temperatures, but at a temperature at which the waste is a liquid that can be pumped; (b) conveying the hot residue to a second heating zone where it is heated to coking temperatures; c) conveying the hot residue from the second heating zone to a coking zone where the vapor products are collected from above and a solid coke product is formed; (d) introducing into the waste at least one overbased alkaline earth metal detergent additive which is effective for the formation of substantially free-flowing coke, wherein the metal-containing additive is introduced into the waste at a point upstream from the second heating zone, between the second heating zone and the coking zone, or both. In a preferred embodiment, the coking zone is in a delayed coker drum, and a substantially free flow coke product is formed.

In another embodiment, a delayed coking process is provided which comprises: (a) contacting a vacuum residue with an effective amount of at least one overbased metal detergent additive at a temperature of from 70 ° C to 370 ° C during a sufficient time to disperse the additive substantially uniformly to the feed; (b) heating the vacuum residue contacted to an effective temperature to coke the residue; (c) feeding the hot treated residue to a coking zone at a pressure of 15 to 80 psig (103.42 to 551.58 kPa) during an effective coke time to allow the hot coke bed to form; and (d) rapidly cooling at least a portion of the hot coke bed with water. In another embodiment, a substantially free flow coke product is formed and removed from the coking zone. The coking zone preferably is a delayed coke drum. The additive can be incorporated and combined with the feed either before introducing the feed into the heating zone, which is a coker oven, or it can be introduced into the feed between the coker oven and the coker drum. It is also within the scope of the present invention to introduce the additive to the feed in both locations. The same additive, or additives, can be added independently at each location or a different additive or additives can be added at each location. The use of the terms "combine" and "make contact" are used in their broadest sense, that is, in some cases they may occur in the additive, the feed, or both when the additive is present in the feed. In other words, the invention is not restricted to cases in which the additive and / or feed do not undergo chemical and / or physical change after, or during contact and / or combination. An "effective amount" of additive is the amount of the additive (s) that when brought into contact with the feed results in the formation of free-flowing shot coke in the coking zones, preferably substantially free-flowing coke shot. An effective amount typically ranges from 100 to 100,000 ppm (based on the total weight of the metal in the additive and feed), and will depend on the additive species used and their physical and chemical form. While not wishing to join by any theory or model, it is believed that the amount is less for the additive species with a physical and chemical form that leads to a better dispersion in the feed than for the additive species that disperse with greater difficulty. It is because additives that are at least partially soluble in organic compounds, more preferably in the waste feed. The uniform dispersion of the additive in the waste feed is desirable to avoid homogeneous areas of coke morphology formation. That is, no locations are desired in the coker drum where the coke is substantially free flowing and other areas where the coke is not substantially free flow. The dispersion of the additive is effected by any suitable technique, preferably by introducing a lateral stream of the additive into the feed at the desired location. The additive can be added by solubilizing the additive in the waste feed or by reducing the viscosity of the waste before mixing in the additive, for example, by heating, adding solvent, etc. Mixing with high energy level or the use of static mixing devices can be used to assist the dispersion of the additive, it is especially useful for additives that have relatively low solubility in the feed stream. Preferably, all or substantially all of the coke formed in the process is substantially free-flowing coke, more preferably, substantially free-flowing coke. It is also preferred that at least a portion of the volatile species present in the coker drum during and after coking the formation of the coke be separated and removed from the process, preferably above the coker drum.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 thereof is an optical micrograph showing the coke formed from a sponge coke that makes the waste feed (Heavy Canadian Residue) that does not contain additive. The figure shows the flow domains that vary in size from 10 to 15 micrometers (typical of sponge coke), and a medium / coarse mosaic that varies from 3 to 10 micrometers (typical of sponge coke), and a mosaic of medium / coarse that varies from 3 to 10 micrometers (typically coke shot). Figure 2 shows the effect of the use of calcium in coke morphology. The figure is also an optical micrograph, but shows coke formed from the Heavy Canadian Residue containing 500 ppm (0.05% by weight) of calcium in the detergent form with calcium sulphonate overlays. The figure shows only a medium / rough mosaic in the range of 1 to 8 micrometers. Figure 3 shows the effect of the use of calcium in coke morphology. The figure is also an optical micrograph, but shows coke formed from the Heavy Canadian Residue containing 500 ppm (0.05% by weight) of calcium in the form of the detergent with calcium salicylate overlays. The figure shows only a medium / rough mosaic in the range of 1 to 9 micrometers. In all the photo-micrographs in these Figures, a polarized optical light microscope with a viewing area of 170 by 136 micrometers was used.

DETAILED DESCRIPTION OF THE INVENTION The raw materials of remains (residues) are suitable for delayed coking. Such petroleum residues are often obtained after removing the distillates from the crude raw materials under vacuum and they are characterized because they comprise components of great weight and molecular size, generally containing: (a) asphaltenes and other aromatic structures of high molecular weight that inhibit the hydrotreatment / thermal decomposition regime and cause catalyst deactivation; (b) metal contaminants as found in nature in crude oil or resulting from the previous treatment of crude oil, whose contaminants tend to deactivate the catalysts by hydrotreating / thermal decomposition and interfere with catalyst regeneration; and (c) a relatively high content of nitrogen and sulfur compounds that give rise to objectionable amounts of SO2, SO3 and NOx after combustion of the petroleum residue. The nitrogen compounds present in the petroleum residues have a tendency to deactivate the catalysts by catalytic thermal decomposition. In one embodiment, the raw materials of petroleum residues include, but are not limited to, residues from vacuum distillation and atmospheric distillation of petroleum crudes, or vacuum or atmospheric distillation of heavy oils, visco-reduced residues, liquid coal, shale oil, pitting of deasphalting units or combinations of these materials. Heavy tars can also be used that are finished in vacuum or at atmospheric conditions. Typically, such raw materials are high-boiling hydrocarbonaceous materials having an initial boiling point of 538 ° C or higher, an API gravity of 20 ° or less, and a content of Conradson Coal Residue from 0 to 40 percent by weight. weight. The waste feed is subjected to delayed coking. Typically, in delayed coking, a waste fraction, such as a petroleum residue raw material, is pumped to a heater at a pressure of 50 to 550 psig (344.74 to 3792.12 kPa) where it is heated to a temperature of 480 ° C to 520 ° C. It is then discharged to a coking zone, typically a vertically oriented isolated coker drum, through an inlet in the base of the drum. The pressure in the drum is relatively low, such as 15 to 80 psig (103.42 to 551.58 kPa) to allow volatile products to be removed overhead. Typical operating temperatures of the drum will be between 410 ° C and 475 ° C. The hot raw material breaks down thermally for a period (the "coking time") in the coker drum, releasing the volatile products that are mainly composed of hydrocarbon products that continuously rise through the coke mass (bed) and are collected from above. The volatile products are sent to a coke fractionator for the distillation and recovery of fractions of heavy gas oil, light gas oil, coking gas, naphtha. In one embodiment, a small portion of the thick coking gas oil in the product stream introduced into the coking fractionator can be captured for recycling and combined with the fresh feed (coke feed component), thereby forming the feed of the coke oven. coking or coking heater. In addition to volatile products, delayed coking also forms a solid coke product. There are generally three different types of solid retarded coke products that have different values, appearance and properties, ie, needle coke, sponge coke and coke shot. The coke of needle is the one that has the best quality of the three varieties. The needle coke, after the additional thermal treatment, has high electrical conductivity (and a low coefficient of thermal expansion) and is used in the production of electric arc steel. It has a relatively low content of sulfur and metals and is often produced from some of the highest quality coking raw materials that include the most aromatic raw materials such as mud oils and decanting catalytic disintegrating stills and decomposition tars. thermal It is not typically formed by delayed coking of waste feeds. Sponge coke, a coke of inferior quality, is very often formed in refineries. Low quality refinery coking raw materials that have significant amounts of asphaltenes, heteroatoms and metals produce this lower quality coke. If the sulfur and metals content is low enough, the coke sponge can be used for the manufacture of electrodes for the aluminum industry. If the sulfur and metals content is very high, then the coke can be used as fuel. The name "coque sponge" is derived from its porous appearance similar to that of sponges. Conventional delayed coking processes, using the preferred void waste feedstock of the present invention, typically produce coke sponge, which is produced as an agglomerated mass that requires an extensive removal process including jet water and drilling technology. . As mentioned, this considerably complicates the process by increasing the cycle time. The coke shot is considered the coke of lower quality. The term "coke shot" is derived from its shape similar to that of BB balls sized [from .16 to .95 centimeters (from 1/16 of an inch to 3/8 of an inch)]. Coke shot, like other types of coke, has a tendency to agglomerate, especially when mixed with coke sponge in larger masses, sometimes greater than 30.48 centimeters (1 foot) in diameter. This can cause problems in the refinery equipment and processing. The coke shot is usually made from feeds with high content of resin-asphaltene of the lowest quality and is a good supply of fuel with high sulfur content, particularly for use in the manufacture of steel and cement kilns. There is another coke called transition coke and it refers to a coke that has a morphology between that of coke sponge and coke shot or that is composed of a mixture of coke shot linked to coke sponge. For example coke that has a physical appearance very similar to that of a sponge, but with evidence of small firing spheres that begin to form as discrete shapes.

It has been found that substantially free flow coke can be produced by treating the waste feedstock with one or more alkaline earth metal detergent additives of the present invention. The additives are those that improve the production of coke shot during delayed coking. A feed of the waste is subjected to treatment with one or more additives, at effective temperatures, that is, at temperatures that will promote the dispersion of the additives in the raw material. Such temperatures will normally be from 70 ° C to 500 ° C, preferably from 150 ° C to 370 ° C, more preferably from 185 ° C to 350 ° C. Alkali metal and alkaline earth metal containing detergents are used as the additive of the present invention. These detergents are exemplified by basic salts soluble in oil or dispersible in oil of the alkaline earth metals with one or more of the following acidic substances (or mixtures thereof): (1) sulfonic acids, (2) carboxylic acids, (3) alicyclic acids, (4) alkylphenols, (5) sulfurized alkylphenols, (6) organic phosphorous acids characterized by at least one direct carbon to phosphorus connection. Such organic phosphorous acids include those prepared by treating an olefin polymer (eg, polyisobutene having a molecular weight of 1000) with a phosphorizing agent such as phosphorous trichloride, phosphorous heptasulfide, phosphorous pentasulfide, phosphorous trichloride and sulfur, white phosphorus. and a sulfur halide, or phosphorothio chloride. The most commonly used salts of such acids are those of calcium and magnesium. Salts for use in this embodiment are preferably basic salts having a TBN of at least 50, preferably over 100, and more preferably over 200. In this regard, the TBN is determined in accordance with ASTM D-2896-88. The term "basic salt" is used to designate metal salts wherein the metal is present in stoichiometrically greater amounts than the organic acid radical. The methods commonly employed to prepare the basic salts involve heating a mineral oil solution of an acid with a stoichiometric excess of a metal neutralizing agent such as metal oxide, hydroxide, carbonate, bicarbonate or sulfide at a temperature of 50 ° C and filtering the resulting mass. The use of a "promoter" in the neutralization stage to assist in the incorporation of a large excess of metal is also known. Examples of compounds useful as the promoter include phenolic substances such as phenol, naphthol, alkylphenol, thiophenyl, sulfurized alkylphenol and condensation products of formaldehyde with a phenolic substance; alcohols such as methanol, 2-propanol, octyl alcohol, Cellosolve alcohol, Carbitol alcohol, ethylene glycol, stearyl alcohol and cyclohexyl alcohol; and amines such as aniline, phenylenediamine, phenothiazine, phenyl-beta-naphthylamine, and dodecylamine. A particularly effective method for preparing the basic salts comprises mixing an acid with an excess of a basic alkaline earth metal neutralizing agent and at least one alcohol promoter, and carbonizing the mixture at an elevated temperature such as 60 ° C to 200 ° C. Examples of suitable alkaline earth metal-containing detergents include, but are not limited to, the base or base salts of such substances as calcium phenates, magnesium phenates, sulfurized calcium phenates and sulphurized magnesium phenates, wherein each aromatic group has one or more aliphatic groups imparting hydrocarbon solubility; calcium sulphonates and magnesium sulphonates wherein each portion of sulfonic acid is attached to an aromatic nucleus which in turn usually contains one or more aliphatic substituents that impart the hydrocarbon solubility; calcium salicylates and magnesium salicylates wherein the aromatic portion is usually replaced by one or more aliphatic substituents that impart hydrocarbon solubility; the calcium and magnesium salts of the hydrolyzed phospho-sulfurized olefins having 10 to 2,000 carbon atoms or of hydrolyzed phosphosulfurized alcohols and / or aliphatic substituted phenolic compounds having 10 to 2,000 carbon atoms; calcium and magnesium salts of aliphatic carboxylic acids and aliphatic substituted cycloaliphatic carboxylic acids; and many other similar alkaline earth metal salts of oil soluble organic acids. Mixtures of basic or overbased salts of two or more different alkaline earth metals can be used. Likewise, basic or overbasing salts of mixtures of two or more different acids or two or more different types of acids (for example, one or more calcium phenates with one or more calcium sulfonates) may also be used. As is well known, overbased metal detergents are generally considered to contain amounts of inorganic base-based bases, probably in the form of microdispersions or colloidal suspensions. Thus, the terms "oil-soluble" and "oil-dispersible" are applied to these metal-containing detergents so that metallic detergents are included wherein the inorganic bases are presented that are not necessarily soluble in complete oil or correctly in the strict sense of the term, since since such detergents when mixed in base oils behave by much of the same mucus when they are completely and completely dissolved in the oil. Collectively, the various basic or overbased detergents referred to hereinbefore, have been sometimes called, quite simply, organic acid salts containing alkali metal or alkaline earth metal. The precise conditions in which the raw material of the waste is treated with the additive is fed and is dependent on the additive. That is, the conditions to which the feed is treated with the additive are dependent on the composition and properties of the coked feed and the additive used. These conditions can be determined conventionally. For example, several tests would be done with a particular feed containing an additive at different times and temperatures followed by coking in an experimental scale reactor such as the Microcarbon Residue Test Unit (MCRTU). The resulting coke is then analyzed by the use of an optical and / or polarized light microscope as set forth herein. The preferred coke morphology (ie, one that will produce substantially free-flowing coke) is a coke microstructure of discrete microdomains having an average size of 0.5 to 10 μm, preferably 1 to 5 μm, somewhat similar to mosaic shown in Figures 1, 2 and 3 thereof. The coke microstructure representing a coke microstructure that is substantially composed of substantially large, non-discrete flow domains up to 60 μm or greater in size, typically 10 to 60 μm.

Conventional coke processing aids, including an antifoaming agent, may be employed in the process of the present invention. Although the coke shot has been produced by conventional methods, it usually agglomerates to such an extent that the water technology is still necessary for its removal. In one embodiment of the present invention, the raw material of the waste is first treated with an additive that promotes the formation of substantially free-flowing coke. By keeping the coker drum at relatively low pressures, many of the volatile products in development can be collected from above, which prevents the formation of mesophase and undesired agglomeration. The recycling ratio ("CRF") is the volume ratio of the furnace charge (fresh feed plus recycled oil) to fresh feed to the operation of the continuous delayed coker. Delayed coking operations typically use recycled from 5% by volume to 25% by volume (CFRs from 1.05 to 1.25). In some cases, there is 0 recycling and sometimes the recycling of special applications of up to 200%. The CFRs must be low to assist the formation of free-flowing shot coke and preferably no recycling should be used. Although it is not desired to join any specific theory or model, the additive or mixture of additives employed is believed to work through one or more of the following trajectories: a) as dehydrogenation and cross-linking agents when metals are present in the feed are they convert into metal sulfides which are catalysts for dehydrogenation and the formation of coke shot; b) agents that add metal-containing species within the feed that influence or direct the formation of coke shot or are converted to species, for example, metal sulfides, which are catalysts for coke firing; c) as particles that influence the formation of coke firing by acting as microscopic seed particles for the coke shot that forms around, such as cracking and crosslinking catalysts of Lewis acid and the like. The additives can alter or build viscosity of the plastic mass of reaction components so that the shear forces in the coker oven, the transfer line and the coke drum wind the plastic mass into small spheres. Even if different additives and mixtures of additives can be used, similar methods can be used by contacting the additive (s) with the feed. Normally, the additive or additives are conducted to the coking process in a continuous mode. If necessary, the additive could be dissolved or saturated within an appropriate transfer fluid, which will normally be the solvent that is compatible with the waste and in which the additive is substantially soluble. The fluid mixture or slurry is then pumped into the coking process at a rate to achieve the desired concentration of additives in the feed. The point of introduction of the additive may be, for example, in the discharge of the feed loading pumps of the furnace, or near the outlet of the coker transfer line. There may be a pair of mixing vessels operated in a manner so that there is a continuous introduction of the additives into the coking process. The speed of introduction of the additive can be adjusted according to the nature of feeding the waste to the coker. The feeds that are in the threshold to produce coke firing may require less additive than those which are farther from the threshold. For additives that are difficult to dissolve or disperse in waste feeds, the additive or additives are transferred into the mixing / slurry vessel and mixed with a slurry medium that is compatible with the feed. Non-limiting examples of suitable grout media include heavy gas oil from the coker, water, etc. The energy may be provided within the container, for example, by a mixer to disperse the additive. For additives which can be more readily dissolved or dispersed in waste feeds, the additive or additives are transferred into the mixing vessel and mixed with a fluid transfer medium which is compatible with the feed. Non-limiting examples of suitable fluid transfer media include hot residues (temperature between 150 ° C to 300 ° C), coke heavy gas oil, light cycle oil, heavy reformate and mixtures thereof. Catalytic slurry oil (CSO) can also be used, although under some conditions it can inhibit the ability of the adhesive to produce loose shot coke. The energy may be provided within the container, for example, by a mixer, to disperse the additive within the fluid transfer medium. The present invention will be better understood for reference to the following non-limiting examples that are presented for illustrative purposes.

EXAMPLES General Procedures for the Addition of Additives within Vacuum Residue Feeds The residue feed is heated to 70-150 ° C to lower its viscosity. The additive (in parts by weight per million, wppm) is then added slowly, mixing for a sufficient time to disperse and / or solubilize the additive (s) (a "dispersion time"). For laboratory experiments, it is generally preferred to dissolve and / or first disperse the additive in a solvent, for example, toluene, tetrahydrofuran or water and mix it with agitation inside the heated residue, or within the residue to which some solvent has been added for reduce its viscosity. The solvent can then be removed. In a refinery, the additive contacts the waste when it is added to or combined with the waste feed. As discussed, the contact of the additive and the feed can be achieved by mixing a kind of additive containing feed fraction (including feed fractions naturally containing such species) into the feed. To ensure maximum dispersion of the additive within the feed of the vacuum residue, the reaction mixture can be soaked hot. The following tests were conducted using various additives to a waste feed. The concentration of additives, the time of hot soaking, and the resulting coke morphology as determined from optical micrographs are set forth in Tables 1 below. The control samples of the residue without additive were used as a comparison.

TABLE 1

Claims (11)

1. CLAIMS 1. A delayed coking process, comprising: (a) heating a petroleum residue in a first heating zone, at a temperature below the coking temperatures, but at a temperature where the waste is a pumpable liquid; (b) conveying the heated waste to a second heating zone to a coking zone wherein the steam products are collected from above and a coke product is formed; and (d) introducing into the waste at least one overbased metal detergent additive which is effective for the formation of substantially free-flowing coke, wherein the overbasin metal detergent additive is introduced into the waste at an upstream point of the second heating zone, upstream of the coking zone, or both. 2. A delayed coking process, comprising: (a) contacting a vacuum residue with an effective amount of at least one alkaline earth metal-based detergent additive at a temperature from 70 ° C to 370 ° C for a time sufficient to disperse the agent uniformly within the feed; (b) heating the treated residue to an effective temperature for coking the feed, (c) heating the heated treated waste to a coking zone at a pressure from 15 to 80 psig (103.42 to 551.58 kPa) for a coking time to form a bed of hot coke; and (d) quenching at least a portion of the hot coke bed with water. 3. The process of claim 1, wherein the waste feed is a vacuum waste. 4. The process of any preceding claim, wherein at least a portion of the additive is soluble in the raw material. The process of any preceding claim, wherein the additive is one or more of calcium phenate, magnesium phenate, sulfurized calcium phenate and magnesium phenate, wherein each aromatic group has one or more aliphatic groups that impart solubility of hydrocarbon. The process of any preceding claim, wherein the additive is one or more of the calcium sulphonates and magnesium sulphonates, wherein each portion of sulfonic acid is attached to an aromatic nucleus which in turn usually contains one or more substituents that impart hydrocarbon solubility. 7. The process of any preceding claim, wherein the additive is one or more of the calcium salicylates and magnesium salicylates, wherein the aromatic portion is replaced by one or more aliphatic substituents that impart hydrocarbon solubility. The process of any preceding claim, wherein the additive is selected from calcium and magnesium salts of hydrolyzed phospholusized olefins having 10 to 2,000 carbon atoms or hydrolyzed phosphosulfurized alcohols and / or aliphatic substituted phenolic compounds having 10 to 2,000 carbon atoms. The process of any preceding claim, wherein the additive is one or more of the calcium and magnesium salts of aliphatic carboxylic acids and aliphatic substituted cycloaliphatic carboxylic acids. 10. The process of any preceding claim, wherein the produced coke is substantially a coke shot. The process of claim 1, wherein the metal base detergent additive is introduced into the vacuum residue at a point upstream of the first heating zone, upstream of the second heating zone, or both.