KR20200123476A - In-situ caulking of heavy pitches and other feedstocks with high fouling tendency - Google Patents

Abstract

A process and system for in situ heating of heavy pitches in a caulking drum is disclosed. In-situ heating can provide processing of pure pitch, improved coking behavior and increased liquid yield.

Description

In-situ caulking of heavy pitches and other feedstocks with high fouling tendency

The upgrade of heavy pitch and other high fouling feedstocks through delayed coking is difficult, if not impossible, at best. Heavy pitch is derived from a variety of processes including solvent deasphalting, supercritical solvent deasphalting (such as Rose unit or LCFining), residual slurry hydrocracking, and also residual oil derived from tight oil. Can be. The difficulty in heavy pitch processing through delayed caulking is mainly due to operational reliability or some unreliability due to the rapid caulking of the combustion heater tube that slows down or shuts down the unit for mechanical heater tube decoking. do.

In processing heavy pitches and addressing the aforementioned problems, refiners design and/or operate the coker for high throughput rates to achieve acceptable heater operating lengths while vacuum residues, atmospheric residues and other lighter carbonizations. Mixing with the hydrogen stream makes the choice to process this pitch stream. Thus, mixing with other streams requires higher coker unit design or processing capacity with higher capital and operating costs. Higher recirculation rates to limit heater tube fouling and recirculation of light coker gas oil also increase unit size, leading to increased coke production and reduced liquid yield. The residual oil derived from the tight oil source is inherently highly paraffinic, which requires a higher heat input for conversion, thus accelerating heater tube fouling.

Examples herein are derived from residual oil from shale (tite) oil through solvent de-asphalting, supercritical solvent de-asphalting, residual hydrocracking, slurry hydrocracking and delayed coking process for the production of effluent and coke. It relates to a process for in-situ caulking of heavy pitch. The embodiment of the present application makes it possible to complete the coking reaction in a coke drum with the aid of a separate heating medium after heating the pure pitch or residual oil derived from shale oil to the initial coking temperature. At the end of the coking cycle, the coke drum will contain a partially converted pitch, after which it is further heated by the heating medium to the final reaction temperature to complete the reaction. Since it only heats the feed to the initial coking temperature, a lower heater coil outlet temperature will prevent rapid coking of the heater tube and significantly increase the heater and unit run length. In addition, the scheme proposed herein allows coking under a set of operating conditions that maximizes liquid yield from each feedstock. Further, the lower capital and operating costs associated with these processes and systems disclosed herein are in any case advantageous to the economics of a design or expansion project.

In one aspect, embodiments disclosed herein relate to a process for producing coke. The process comprises: heating the heavy pitch to an initial coking temperature to produce a heated coker feedstock; Supplying the heated coker feedstock to the coking drum; Heating the coker feedstock heated in the coking drum on site through direct heat exchange with the supercritical medium; And pyrolyzing the heated coker feedstock in a coking drum to produce cracked vapor products and coke products by cracking a portion of the heavy pitch.

In another aspect, embodiments disclosed herein relate to a process for producing coke. The process comprises: heating the heavy pitch to an initial coking temperature to produce a heated coker feedstock; Supplying the heated coker feedstock to the coking drum; Heating the heated coker feedstock with a supercritical medium, and pyrolyzing the heated coker feedstock in a coking drum to decompose a portion of the heavy pitch to produce decomposed vapor products and coke products. .

In another aspect, embodiments disclosed herein relate to a process for producing coke. The process comprises: heating the heavy pitch to an initial coking temperature to produce a heated coker feedstock; Mixing the heated coker feedstock with a superheated medium, and supplying the mixture to a coking drum; And pyrolyzing the heated coker feedstock in a coking drum to decompose a portion of the heavy pitch to produce decomposed vapor products and coke products.

In another aspect, embodiments disclosed herein relate to a process for producing coke. The process comprises: heating the heavy pitch to an initial coking temperature to produce a heated coker feedstock; Supplying the heated coker feedstock to the coking drum; Heating the heated coker feedstock in the coking drum in situ, and pyrolyzing the heated coker feedstock in the coking drum to decompose a portion of the heavy pitch to produce decomposed vapor products and coke products. have.

In another aspect, embodiments disclosed herein relate to a system for coke production. The system comprises: a heater for heating the heavy pitch to an initial coking temperature to produce a heated coker feedstock; A flow line for supplying the heated coker feedstock to the coking drum; A heater for heating the superheated medium to produce a heated superheated medium; A flow line for supplying the heated superheated medium to the coking drum in order to heat the heated coker feedstock in the site through direct heat exchange with the superheated medium; A flow line for recovering the cracked vapor product from the coking drum while pyrolyzing the heated coker feedstock in the coking drum to crack a portion of the heavy pitch to produce cracked vapor product and coke product.

In another aspect, embodiments disclosed herein relate to a system for coke production. The system comprises: a heater for heating the heavy pitch to an initial coking temperature to produce a heated coker feedstock; A flow line for supplying the heated coker feedstock to the coking drum; A flow line for pyrolyzing the resulting heated coker feedstock in a coking drum to supply a superheated medium for heating the heated coker feedstock and to decompose a portion of the heavy pitch to produce decomposed vapor products and coke products. Can include.

In another aspect, embodiments disclosed herein relate to a system for coke production. The system comprises: a heater for heating the heavy pitch to an initial coking temperature to produce a heated coker feedstock; Mixer for mixing the heated coker feedstock with superheated medium and the mixture to a coking drum to pyrolyze the heated coker feedstock in a coking drum to decompose a portion of the heavy pitch to produce decomposed vapor products and coke products. It may include a flow line for feeding.

In another aspect, embodiments disclosed herein relate to a system for coke production. The system includes: heating the heavy pitch to an initial coking temperature to produce a heated coker feedstock; A heater for supplying the heated coker feedstock to the coking drum; Includes a control system for controlling the on-site heating of the heated coker feedstock in the coking drum and a coking drum for pyrolyzing the heated coker feedstock to produce decomposed vapor products and coke products by decomposing a portion of the heavy pitch. can do.

In another aspect, embodiments disclosed herein relate to a process for coke production. The process comprises: heating the heavy pitch to an initial coking temperature to produce a heated coker feedstock; Supplying the heated coker feedstock to the coking drum; Heating the coker feedstock heated in the coking drum on site through direct heat exchange; And pyrolyzing the heated coker feedstock in a coking drum to decompose a portion of the heavy pitch to produce decomposed vapor products and coke products.

In another aspect, embodiments disclosed herein relate to a process for coke production. The process comprises: heating the heavy pitch to an initial coking temperature to produce a heated coker feedstock; Mixing the heated coker feedstock with a superheated medium; Supplying the mixture to a caulking drum; Heating the mixture in situ in a coking drum through direct heat exchange with a superheated medium; And thermally decomposing the mixture in a coking drum to decompose a portion of the heavy pitch to produce decomposed vapor products and coke products.

In another aspect, embodiments disclosed herein relate to a system for coke production. The system comprises: a heater for heating the heavy pitch to an initial coking temperature to produce a heated coker feedstock; A flow line for supplying the heated coker feedstock to the coking drum; A heater for heating the superheated medium to produce a heated superheated medium; A flow line for supplying the heated superheated medium to heat the heated coker feedstock on site in the coking drum through direct heat exchange with the superheated medium; It may comprise a flow line for recovering the cracked vapor product from the coking drum.

Other aspects and advantages will become apparent from the following description and the appended claims.

1 is a simplified diagram of a caulking process and apparatus according to an embodiment disclosed herein.

Embodiments herein relate to systems and processes for in-situ coking of heavy pitch and other high fouling feedstock via a delayed coking process. The heavy pitch feedstock may economically include any number of purification process streams that cannot be processed otherwise to make further distillation, catalytic cracking, or fuel-grade mixed streams. Typically, these materials are not suitable for catalysis due to catalytic fouling and/or deactivation by ash and metals. Examples herein are heavy pitch or other high fouling feed as coker feedstock comprising heavy pitch derived from residual oil from solvent deasphalting, ROSE unit, residual hydrocracking, slurry hydrocracking and shale (tite) oil. It relates to the use of raw materials.

In some embodiments, the aforementioned feedstock may be supplied purely (undiluted) to the coking unit for delayed coking. In other examples, the feedstock may be minimally diluted through the addition of up to 10% by weight of diluent. Diluents useful in the examples herein may include conventional coker feedstocks such as atmospheric distillation residues, vacuum distillation residues, catalytic cracker residual oils, hydrocracker residual oils, and residual oils from other refining units. The inclusion of a minimum level of diluent can improve the processability of heavy pitches and other high fouling feedstocks without significantly penalizing other benefits mentioned herein associated with equipment size and processing of pure or near pure heavy pitch. .

Feedstocks that may be used according to embodiments herein may have a high Conradson carbon content, such as greater than 35% by weight. Feedstocks that can be used according to the examples herein have high asphaltene contents, such as more than 15% by weight, more than 25% by weight, or even more than 35% by weight, such as an asphaltene content which can be as high as a Conradson carbon content. You can also have it.

As is known in the art, the coker feedstock can be processed upstream of the coking unit. For example, the coker feedstock may be subjected to a hydrotreating process, a desalting process, a demetallization process, a desulfurization process, or other pretreatment process useful to produce the desired coke product.

In a typical coking process, the coker feedstock is heated to a coking temperature and then can reside in a coke drum for completion of the coking/cracking reaction using the energy already imparted through the coking heater. Another design heats the feedstock upstream of the coke drum to a temperature higher than the coking temperature in order to accelerate decomposition and quench the feedstock. Conversely, the process herein heats the heavy pitch/high fouling feed to an initial coking temperature, which temperature is not adequate to drive the coking reaction to completion. The energy balance is then transferred to the heater effluent accumulated inside the coke drum, leading to the completion of the coking/decomposition reaction. The balance of energy can be transferred to the heater effluent directly upstream and/or inside the coke drum through superheated media introduced into the coke drum through the supply line after the filling cycle is complete and/or during the cycle in which the coke drum is being filled. . In addition to the coker heater, a separate energy source is required at sufficiently high temperatures. As far as the inventors are aware, in-situ heating of pure heavy pitch/high fouling feedstock in coke drums has not been performed so far.

In burned heaters, the heavy pitch/high fouling feed is heated only to the initial coking reaction temperature, not the full coking temperature that is practiced in conventional delayed coking. The initial coking reaction temperature may depend on the heavy pitch/high fouling feedstock or feedstock mixture used and may be different for different feedstocks. Completion of the coking reaction is achieved inside the coke drum with the aid of a separate heating medium that transfers energy directly to the coker heater effluent, leading to completion of the coking reaction. In-situ heating of the heavy pitch/high fouling feed may be continued for the length of time required for the coking reaction to approach completion, and this length of time may also vary depending on the type of heavy pitch/high fouling feedstock being used. . However, for each feedstock, a pilot test can be performed to determine the initial coking temperature, the duration of the coke drum field heating, and the preheated pitch level inside the coke drum as part of the unit's process design.

The examples herein relate to the processing of fouling feedstocks with 100% (pure) pitch/high Conradson carbon (>35% by weight) and asphaltene content which can be as high as the Conradson carbon content. Examples herein are 100% (pure) pitch/high fouling feeds from the sources mentioned above or residual oils derived from shale (tight) oil leading to severely limited unit run length and lower liquid yields under normal coking conditions. It allows a higher unit progression length when processing. The ability to process the pure pitch of the above mentioned feedstock categories: eliminates the need to mix significantly with other diluents making the unit capacity requirement higher; Increase the unit effective travel length; Increases liquid yield and reduces unit utility requirements.

Hereinafter, referring to FIG. 1, a coking process according to an embodiment disclosed herein is shown. The heavy pitch/high fouling feedstock 10 is introduced into the bottom portion of the coker fractionator 12, where it combines with condensed hydrocarbons from the coker vapor stream 14 (ie the resulting internal recycle stream). The heavy pitch/high fouling feedstock may be further heated in one or more preheat exchangers prior to flowing to the bottom of the main coker fractionator 12.

The resulting mixture 16 (heater charge stream) is then pumped through a coker heater 18, where the temperature is increased to the initial coking temperature of the stream, such as 500°F to 750°F. The temperature of the heater effluent stream 20 can be measured and controlled by the use of a temperature sensor 24 that sends a signal to the control valve 26 to regulate the amount of fuel 28 supplied to the heater 18. I can. If desired, steam or boiler feed water 30 may be injected into the heater to reduce coke formation in tube 32.

The heater effluent stream 20 may be recovered from the coker heater 18 for supply to the coking drum 36. Two or more drums 36 can be used in parallel, as known in the art, to provide continuous operation during operation cycles (coke generation, coke recovery (decoking), preparation for the next coke generation cycle, repetition). have. A switch valve 38, for example a 3-way or 4-way valve, diverts the heater effluent stream to the desired caulking drum 36 in a fill mode of operation.

The coke drum 36 in fill mode can hold the feed until the material reaches a certain safety level inside the coke drum. At this point, the feed can be routed to another coke drum ready to fill.

When the coke drum is filled with the heater effluent (heavy pitch heated to the initial coking temperature), the contents of the coke drum are further heated through injection of a suitable superheated medium. The superheated medium may be injected into the coke drum 36 through a flow line 76 which may be connected to the heater effluent transfer line intermediate the diverter valve 38 and the coking drum 36. Alternatively or additionally, the superheated medium may be injected directly into the caulking drum through one or more inlets (not shown) at or near the bottom of the caulking drum, such as through or near the bottom head 48. In some embodiments, superheated medium may be supplied with the heater effluent during the fill cycle.

Superheated media useful in the examples herein include steam, carbon dioxide, nitrogen and other inert gases as well as lighter hydrocarbons that are relatively stable at coking temperatures. In some embodiments, the superheated medium may have sufficient heat capacity to directly heat the pitch, may not condense under coke drum operating conditions, and may not react with heavy pitch or decomposed products.

The superheated medium may be mixed with the heater effluent or heated in a separate heater (not shown) before being supplied to the coke drum 18. In another embodiment, overheating of the superheated medium may occur in one zone of the heater 18, and the heavy pitch is heated to the initial coking temperature in the other zone of the heater. After the filling cycle is complete and/or during the filling cycle, the superheated medium may be introduced into the coke drum via the supply line.

The coking drum 36 is provided with sufficient on-site heating and residence time to allow the thermal decomposition and coking reaction to be completed. In this way, the heavy pitch feedstock is pyrolyzed in the coking drum 36 to produce lighter hydrocarbons, which are vaporized and discharged from the coke drum via flow line 40. Petroleum coke and some residues (eg, cracked hydrocarbons) remain in the coking drum 36. When the coking drum 36 is sufficiently filled with coke and the field heating has sufficiently driven the coking reaction to completion, the coking cycle is ended. After completion of the coking cycle, a decoking cycle is initiated in the first coking drum.

In the decoking cycle, the contents of the coking drum 36 are cooled, the remaining volatile hydrocarbons are removed, the coke is drilled or otherwise removed from the coking drum, and the coking drum 36 is ready for the next coking cycle. Cooling of coke generally consists of three distinct stages. In the first step, the coke is cooled and stripped by steam or other stripping medium 42 to economically maximize the removal of recoverable hydrocarbons that are entrained or otherwise left in the coke. In the second stage of cooling, water or other cooling medium 44 is injected to reduce the coking drum temperature while avoiding thermal shock to the coking drum. The water vaporized from this cooling medium further promotes the removal of additional vaporizable hydrocarbons. In the final cooling step, the coking drum is quenched by water or other quenching medium 46 to quickly lower the coking drum temperature to conditions favorable for safe coke removal. After quenching is complete, the bottom and top heads or slide valves 48 and 50 of the caulking drum 36 are removed or opened, respectively. Thereafter, the petroleum coke is cut, for example by means of a hydraulic water jet, and removed from the coking drum. After coke removal, the caulking drum head or slide valves 48 and 50 are replaced or closed, respectively, and the caulking drum 36 is preheated and otherwise ready for the next filling and caulking cycle.

During the filling, in situ heating and coking cycles, the superheated medium comprising lighter hydrocarbon vapors and decomposed products are recovered from the coking drum 36 as overhead fraction 40. The overhead fraction 40 is then conveyed as a coker vapor stream 14 to a coker fractionator 12, where the recovered components are separated into two or more fractions and recovered. For example, the heavy coker gas oil (HCGO) fraction 52 and the light coker gas oil (LCGO) fraction 54 may be discharged from the separator in a desired boiling temperature range. . HCGO may contain hydrocarbons that boil, for example, in the range of 650-870 °+F. LCGO may contain hydrocarbons that boil, for example, in the range of 400-650 °F. In some embodiments, other hydrocarbon fractions such as quench oil fraction 56 and/or wash oil fraction 57, which may contain hydrocarbons similar to or heavier than HCGO, may also be recovered from the coker fractionator 12. I can. The fractionator overhead stream, coker wet gas fraction 58, passes to a separator 60 where it is separated into a wet gas fraction 62, a water/aqueous fraction 64 and a naphtha fraction 66. A portion of the naphtha fraction 66 may be returned to the separator as reflux 68.

In another embodiment, the superheated medium may comprise a heavier hydrocarbon stream such as hydrocarbons having a normal boiling point in the range of about 400°F to about 650°F, such as LCGO stream 54. For example, the LCGO fraction 54 may be recovered from the coker fractionator 12 and may be partially vaporized in a heater (not shown). The portion that has not been vaporized can be collected and returned to the coker separator 12. The vapor portion can then be superheated in the same or different heaters and then introduced into the coke drum for on-site caulking.

The coking system according to an embodiment of the present application may also comprise a device for recovery and recycling of superheated medium, if necessary. Such a system may be included in the coker fractionator 12 and associated equipment. For example, the superheated medium recovery apparatus may include a side discharge for recovery of a particular temperature cut associated with the superheated medium, or may simply include condensation from the water/aqueous fraction 64. Alternatively, other equipment may be placed upstream or downstream of the coker fractionator 12 for recovery and recycling of superheated medium.

The temperature of the steam leaving the coke drum through the flow line 40 can be an important control parameter used to represent the temperature of the material in the coking drum 36 during the coking process. Conditions can be controlled in such a way as to produce a large variety of coke with a volatile combustible material (VCM) content ranging from about 3% to about 25% by weight, as measured by ASTM D3175t, for example. have.

The type of coke product produced can also be influenced by the temperature and the type of superheated medium as well as the duration of the in-situ heating. Accordingly, the control system used in the embodiments herein may be varied to control the temperature of the superheated medium supplied to the coke drum for on-site heating.

As described above, an embodiment of the present application provides a system and process for on-site coking of heavy pitches through a delayed coking process for the production of distillate and coke. The embodiment of the present application makes it possible to complete the coking reaction in a coke drum with the aid of a separate heating medium after heating the pure pitch or residual oil derived from shale oil to the initial coking temperature. At the end of the filling cycle, the coke drum will contain a partially converted pitch, which is then further heated by the heating medium to the final reaction temperature to complete the reaction. The lower heater coil outlet temperature will prevent rapid caulking of the heater tube because it only heats the feed to the initial caulking temperature, and significantly increases the heater and unit run length. In addition, the scheme proposed herein allows coking under a set of operating conditions that maximizes liquid yield from each feedstock. Further, the lower capital and operating costs associated with these processes and systems disclosed herein are in any case advantageous to the economics of a design or expansion project. In addition, the embodiments disclosed herein enhance or increase the preference of delayed cokers by processing difficult feedstocks at lower volumes (CPAEX), higher on-stream coefficients, higher liquid yields, and lower utility consumption (OPEX). I can make it. Examples herein are also from paraffinic feedstocks such as supercritical solvent deasphalting (such as LCFining), residue hydrocracking (such as LC-MAX), residual slurry hydrocracking, or shale (tite) oil feedstock. It allows an attractive combination of different techniques, such as the processing of the resulting high fouling residual oil.

While this disclosure includes a limited number of embodiments, those skilled in the art having the advantage of the disclosure will understand that other embodiments may be devised without departing from the scope of the disclosure. Accordingly, its scope should be limited only by the appended claims.

Claims (25)

As a process for producing coke,
Heating the heavy pitch to an initial coking temperature to produce a heated coker feedstock;
Supplying the heated coker feedstock to a coking drum;
Further heating the heated coker feedstock in the field in the coking drum through direct heat exchange; And
And pyrolyzing the heated coker feedstock in the coking drum to crack a portion of the heavy pitch to produce cracked vapor products and coke products. The method of claim 1,
Wherein the direct heat exchange takes place through contact of the heated coker feedstock with a superheated medium. The method of claim 1,
The process, wherein the heating and thermal decomposition through the direct heat exchange are performed simultaneously. The method of claim 1,
The process, wherein the initial coking temperature is between 500°F and 750°F. The method of claim 1,
The process further comprising feeding the cracked vapor product to a coker separator for recovery of one or more light hydrocarbon fractions. The method of claim 1,
Stopping supply of the heated coker feedstock to the coking drum and removing coke products from the coking drum. The method of claim 2,
The superheated medium is in contact with the heated coker feedstock through at least one of a supply inlet upstream of the coking drum, a superheated medium heater upstream of the coking drum, or a supply inlet for directly introducing the superheated medium into the coking drum, process. The method of claim 2,
The process, wherein the superheated medium does not condense at coke drum operating conditions during a coking cycle. The method of claim 8,
Wherein the superheated medium is one or more of steam, carbon dioxide, nitrogen and other inert gases, or one or more light hydrocarbons. The method of claim 2,
The process, wherein superheated medium is supplied to the coking drum during a filling cycle, during a coking cycle, or both. The method of claim 1,
Wherein the heating in situ of the heated coker feedstock continues for a length of time necessary for the thermal decomposition to approach completion. The method of claim 1,
Wherein the heavy pitch is 100% heavy pitch. The method of claim 1,
Wherein the heavy pitch comprises up to 10% by weight of diluent. The method of claim 1,
The process, wherein the heavy pitch has a Conradson carbon content of 35% by weight or more and an asphaltene content of 15% by weight or more. As a process for producing coke,
Heating the heavy pitch to an initial coking temperature to produce a heated coker feedstock;
Mixing the heated coker feedstock with a superheated medium;
Supplying the mixture to a caulking drum;
Heating the mixture in situ in a coking drum through direct heat exchange with the superheated medium; And
And pyrolyzing the mixture in the coking drum to decompose a portion of the heavy pitch to produce decomposed vapor products and coke products. The method of claim 15,
Wherein the superheated medium is one or more of steam, carbon dioxide, nitrogen and other inert gases, or one or more light hydrocarbons. The method of claim 15,
Wherein the heating in situ of the heated coker feedstock continues for a length of time necessary for the thermal decomposition to approach completion. The method of claim 15,
Wherein the heavy pitch is 100% heavy pitch. The method of claim 15,
Wherein the heavy pitch comprises up to 10% by weight of diluent. The method of claim 15,
Wherein the heavy pitch has a Conradson carbon content of 35% by weight or more and an asphaltene content of 15% by weight or more. As a system for coke production,
A heater for heating the heavy pitch to an initial coking temperature to produce a heated coker feedstock;
A flow line for supplying the heated coker feedstock to a coking drum;
A heater for heating the superheated medium to produce a heated superheated medium;
A flow line for supplying the heated superheated medium to heat the heated coker feedstock in the field in the coking drum through direct heat exchange with the superheated medium;
And a flow line for recovering cracked vapor products from the coking drum. The method of claim 21,
A mixer for mixing the heated coker feedstock with the superheated medium and a flow line for supplying a mixture to the coking drum. The method of claim 21,
And the flow line for supplying the heated superheated medium is connected to the caulking drum. The method of claim 21,
Wherein the heater for heating the heavy pitch and the heater for heating the superheated medium are disposed in different zones of a common heater. The method of claim 21,
The system further comprising a control system for controlling in situ heating of the heated coker feedstock in the coking drum.

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