Method for upgrading a hydrocarbon feed

A method for upgrading a hydrocarbon feed is disclosed. The method may be carried out in a pyrolysis furnace that may have at least two coils and at least two thermal zones. The method may include two operating or run modes that may be repeated in a cycle. In one run, upgrading may be carried out in one coil while decoking may be carried out in the other coil. After a predetermined amount of time, the streams of the two coils may be switched for a second run, such that decoking may be carried out in the coil in which upgrading was done in the first run and upgrading may be carried out in the coil in which decoking was done in the first run. The first and the second run are cyclically repeated one after the other.

TECHNICAL FIELD

The present disclosure generally relates to the upgrading of hydrocarbon feeds, and particularly to a method and a pyrolysis furnace for upgrading hydrocarbon feeds, such as light, heavy, and waste hydrocarbons.

BACKGROUND

In order to upgrade and improve heavy oil compounds, a heating or catalytic, method may be used. In thermal processing, or delayed coking, hydrocarbon feedstock along with steam may enter a reactor tube placed in the radiant zone of a furnace. The feedstock may be heated by the burners of the furnace and they may be converted into lighter products. Along with the liquid and gas products, unwanted solid products (coke) may form inside the reactor tube or coil. A part of the formed coke may be routed out of the reactor, while some parts may remain on the walls of reactor tubes or coils.

Coke accumulation on the walls of the reactor increases the pressure and temperature of the process over time. Therefore, in predetermined intervals, the working furnace may be taken out of service for decoking the coils, and a replacement furnace may be used. The decoking process may be carried out at high-temperatures by steam and oxygen.

Upgrading processes of hydrocarbon feeds may require an additional furnace or a replacement furnace to allow for off-line decoking of the working furnace. This may have disadvantages that may include but are not limited to higher costs for building the additional furnace. Therefore, there is a need in the art for a method of upgrading that does not require an additional furnace. Moreover, in upgrading processes for hydrocarbon feeds, a better control over the temperature distribution in the thermal zones is needed.

SUMMARY

In one general aspect, the present disclosure is directed to a method for upgrading a hydrocarbon feed in a pyrolysis furnace. The method includes associating at least a first coil with a first thermal zone of the pyrolysis furnace, associating at least a second coil with a second thermal zone of the pyrolysis furnace, the second thermal zone being spaced apart from the first thermal zone, and operating the pyrolysis furnace in a first mode. The first mode can involve upgrading a first hydrocarbon feed in the second coil, feeding a first steam stream to the first coil, thereby heating the first steam stream, and decoking the first coil.

The above general aspect may include one or more of the following features. For example, operating the pyrolysis furnace in the first mode may further include mixing the first steam stream from the first coil with the first hydrocarbon feed in the first thermal zone, thereby producing a combined first hydrocarbon/steam stream; and feeding the first hydrocarbon/steam stream to the second coil in the second thermal zone. In addition, the method can comprise operating the pyrolysis furnace in a second mode, the second mode including upgrading a second hydrocarbon feed in the first coil; feeding a second steam stream to the second coil, thereby heating the second steam stream; and decoking the second coil. As another example, operating the pyrolysis furnace in the second mode may further include mixing the second steam stream from the second coil with the second hydrocarbon feed in the second thermal zone, thereby producing a combined second hydrocarbon/steam stream; and feeding the second, hydrocarbon/steam, stream to the first coil, in the first thermal zone. In some cases, the first thermal zone may operate as a radiant zone in the first mode and as a convection zone in the second mode. In other cases, the second thermal zone may operate as a convection zone in the first mode and as a radiant zone in the second mode. The method can further include switching the first thermal zone from the first mode to the second mode by turning off or decreasing the output of a first burner in the first thermal zone and opening a first stack in the first thermal zone. In addition, the method may include switching the second thermal zone from the first mode to the second mode by turning on a second burner in the second thermal zone and closing a second stack in the second thermal zone. In some cases, the method may include operating the pyrolysis furnace in the first mode and then the second mode in a series of repeating cycles. The method may include mixing the first steam stream with an oxidizing agent, wherein the oxidizing agent is selected from the group consisting of oxygen, air, H2O2, an alcohol, and combinations thereof. In other cases, the method, may further include feeding the first steam stream to the first coil from a first line, and feeding the first hydrocarbon/steam stream to the second coil from a second line during the first mode. In addition, the method may include feeding the second, steam stream to the second coil from the second line, and feeding the second hydrocarbon/steam, stream to the first coil from the first line during the second mode.

In another general aspect, the present disclosure is directed to a pyrolysis furnace for upgrading a hydrocarbon feed. The pyrolysis furnace can include a plurality of thermal zones, including a first thermal zone and a second thermal zone, where the second thermal zone is spaced apart from the first thermal zone. In addition, the first thermal zone includes a first stack and a first burner, the second thermal zone includes a second stack and a second burner, and the first thermal zone is configured to provide convection in, a first mode and radiation in a second mode.

The above general aspect may include one or more of the following features. For example, the pyrolysis furnace may further include a plurality of intermediate thermal zones disposed between the first thermal zone and the second thermal zone. In some cases, the first thermal zone may operate in the first mode when the first burner is turned off or decreased and the first stack is opened, and the first thermal zone may operate in the second mode when the first burner is turned on and the first stack is closed. The second thermal zone may be configured to provide radiation in the first mode and convection in the second mode. In addition, the second thermal zone may operate in the first mode when the second burner is turned off or decreased and the second stack is opened, and the second thermal zone may operate in the second mode when the second burner is turned on and the second stack is closed. The pyrolysis furnace may also include at least a first coil and a second coil in the pyrolysis furnace, the first coil being associated with the first thermal zone and the second coil being associated with the second thermal zone. In some cases, the pyrolysis furnace may include a first valve, the first valve configured to open or close the first stack. The first thermal zone and the second thermal zone may be separated by at least one refractory wall

DETAILED DESCRIPTION

Upgrading processes of hydrocarbon feeds may require an additional furnace or a replacement furnace to allow for off-line decoking of the working furnace. This may have disadvantages that may include but are not limited to higher costs for building the additional furnace. The present disclosure describes an apparatus and a method of upgrading that does not require an additional furnace. Moreover, some implementations of the apparatus and method disclosed herein can provide improved control over the temperature distribution in the thermal zones.

Disclosed herein is a pyrolysis furnace and a method for upgrading a hydrocarbon feed in a cyclic process in which upgrading and decoking may continuously and periodically be performed in a number of coils in the pyrolysis furnace. The pyrolysis furnace of the present disclosure may include a number of thermal zones, for example, a first thermal zone and a second thermal zone, as well as a number of thermal zones in between. The pyrolysis furnace can also be associated with a number of coils, such as a first coil and a second coil that may enter the pyrolysis furnace and pass through the thermal zones. The first coil and the second coil may provide reactors in which the upgrading process may be carried out. A hydrocarbon feed may be fed to the first coil and steam or water may be fed to the second coil. The hydrocarbon feed in the first coil may be upgraded while the water or steam fed to the second coil may decoke the second coil. The hydrocarbon feed in the first coil may first enter a convection zone to be preheated and then it may flow through other thermal zones that may function as radiant zones (i.e., radiation heat-energy) for the upgrading process to occur. In the pyrolysis furnace of the present disclosure, the first and the second thermal zones may be symmetrically arranged at either ends of the pyrolysis furnace and may be designed such that their functionality may be switched between a convection zone and a radiant zone. Benefits from these features may include, but are not limited to, allowing the upgrading process to be carried out in the first coil, while decoking can occur in the second coil. In addition, after a predetermined amount of time the hydrocarbon feed and the steam streams may be switched between the coils and the upgrading process may be carried out in the second coil and steam may be fed to the first coil for decoking the first coil.

FIG. 1illustrates a schematic view of an upgrading process carried out in a pyrolysis furnace100, according to one or more implementations of the present disclosure. As shown in the implementation presented inFIG. 1, the pyrolysis furnace100may include a plurality of thermal zones, including but not limited to a first thermal zone101, a second thermal zone102, and a number of thermal zones (“intermediate thermal zones”)103in between. The first thermal zone101may include a first substantially symmetrical stack (“first stack”)104and the second thermal zone102may include a second substantially symmetrical stack (“second stack”)105. The functionality of the first thermal zone101may be switched between a convection zone and a radiant zone by turning a first burner108on and off and opening and closing the first stack104. Similarly, the functionality of the second thermal zone102may be switched between a convection zone and a radiant zone by turning a second burner109on and off and opening and closing the second stack105. At least two coils (a first coil106and a second coil107) may enter or be disposed in the pyrolysis furnace100and pass through one or more of the thermal zones (inFIG. 1, the first thermal zone101, the second thermal zone102, and the intermediate thermal zones103).

In different implementations, the pyrolysis furnace100may operate in at least two modes, herein identified as a first mode of operation and a second mode of operation. During the first mode of operation, hydrocarbon feed may be fed to the first coil106and water or steam may be fed to the second coil107. In some implementations, in this first mode, the first burner108of the first thermal zone101may be turned off or down or be otherwise decreased. In addition, the first stack104of the first thermal zone101may be opened in order for the first thermal zone101to function as a convection zone. The hydrocarbon feed in the first coil106then enters the convection zone to be preheated, and subsequently flows through the first coil106to other thermal zones (such as the second thermal zone102and the intermediate thermal zones103) that function as radiant zones while the upgrading process occurs in the pyrolysis furnace for a predetermined amount of time, for example, at least 15 minutes. In one implementation, water or steam may flow through the second coil107. In addition, during the first mode, the second thermal zone102may function as a radiant zone by turning on the second burner109of the second thermal zone102and closing the second stack105of the second thermal zone102. Steam or water may be heated in the furnace in the second coil107and the flow of the steam in the second coil107may lead to a decoking of the second coil107. In some implementations, the heated steam from the second coil107may be mixed with the hydrocarbon of the first coil106prior the upgrading process.

During the second mode of operation, the streams of hydrocarbon feed and water or steam, may be switched, between the first coil106and the second coil107. The hydrocarbon feed may be fed to the second coil107, while the steam or water may be diverted to the first coil106. In some implementations, during the second mode, the second burner109of the second thermal zone102may be turned off or down or be otherwise decreased. In addition, the second stack105of the second thermal zone102may be opened in order for the second thermal zone102to function as a convection zone. The hydrocarbon feed in the second coil107may enter the convection, zone for preheating and may subsequently flow through the second coil107to other thermal zones (such as the first thermal zone101and the intermediate thermal zones103) that function as radiant zones for the upgrading process to occur in the furnace. In one implementation, the water or steam may flow through the first coil106. In addition, during the second mode, the first thermal zone101may function as a radiant zone by turning on the first burner108of the first thermal zone101and closing the first stack104of the first thermal zone101. The steam or water may be heated in the furnace in the first coil106and the flow of the steam in the first coil106may lead to the decoking of the first coil106. The heated steam from the first coil106may be mixed with the hydrocarbon of the second coil107prior the upgrading process in one implementation. In some implementations, two or more thermal zones may optionally be spaced apart or separated by one or more refractory walls110. Benefits of separating the thermal zones in the furnace may include but are not limited to: improved temperature distribution inside the furnace, increased efficiency of the radiant section of the furnace, and improved control over the temperature profile along the furnace.

In different implementations, it should be understood that the first mode and second mode may be repeated. In some implementations, the first mode and second mode can be run in a cycle, providing a cyclic process in which upgrading the hydrocarbon occurs in one coil while the other coil is being decoked by a stream of steam. During this cycle the streams of the two coils may be switched and the coil in which the upgrading process occurred can undergo the decoking process while the upgrading process occurs in the other coil.

In some implementations, the steam may be mixed with an oxidizing agent, such as oxygen, air, H2O2, and/or an alcohol such as methanol, or combinations thereof. In some implementations, the oxidizing agent has a concentration of 0 to 100 weight percent of the mixture. In other implementations, the steam may be mixed with hydrogen. In one implementation, the concentration of hydrogen is between 0 to 100 weight percent of the mixture. The upgrading process may include but is not limited to thermal cracking, steam cracking, pyrolysis, or catalytic versions of the aforementioned processes. Furthermore, in some implementations, the first and the second coils include a catalyst for catalytic upgrading of the hydrocarbon feed.

FIG. 2illustrates a method200for upgrading a hydrocarbon feed according to one or more implementations of the present disclosure. As represented inFIG. 2, in one implementation, the method200includes a first step201of associating at least a first coil with, a first thermal zone of the pyrolysis furnace and associating at least a second coil with a second thermal zone of the pyrolysis furnace. In some implementations, the second thermal zone is spaced apart or otherwise separated from the first thermal zone. A second step202can involve operating the pyrolysis furnace in a first mode. In one implementation, the first mode comprises upgrading a first hydrocarbon feed in the second coil, feeding a first steam stream to the first coil, thereby heating the first steam, stream, and decoking the first coil.

Additional steps in the first mode can include a third step203of mixing the first steam, stream from the first coil with the first hydrocarbon feed in the first thermal zone, thereby producing a combined first hydrocarbon/steam stream, and a fourth step204of feeding the first hydrocarbon/steam stream to the second coil in the second thermal zone. Furthermore, a fifth step205may include operating the pyrolysis furnace in a second mode. In one implementation, the second mode can include upgrading a second hydrocarbon feed in the first coil, feeding a second steam stream to the second coil, thereby heating the second steam, stream, and decoking the second coil. A subsequent sixth step206involves mixing the second steam stream from the second coil with the second hydrocarbon feed in the second thermal zone, thereby producing a combined second hydrocarbon/steam stream, and a seventh step207of feeding the second hydrocarbon/steam stream to the first coil in the first thermal zone.

In other implementations, the method can comprise other or alternative steps. It should be understood that one of more steps identified in the following method can be substituted for any of the steps described above for method200or added to the method200. For example, in other implementations of the method, a first step comprises providing a pyrolysis furnace having a number of coils, for example a first coil and a second coil; a second step of feeding a steam stream, to the first coil in order to be heated in the pyrolysis furnace; a third step of combining the heated steam from the first coil with the hydrocarbon feed to obtain a combined hydrocarbon/steam stream; a fourth step of feeding the hydrocarbon/steam stream to the second coil for upgrading in the pyrolysis furnace for a predetermined period; a fifth step of diverting the steam stream to the second coil; a sixth step of combining the heated steam from the second coil with the hydrocarbon feed to obtain a combined hydrocarbon/steam stream; and a seventh step of feeding the combined hydrocarbon/steam stream to the first coil in order to be upgraded in the pyrolysis furnace for a predetermined period. In some implementations, the cycle from the second step to the seventh step is repeated, where the hydrocarbon feed may first be upgraded in the second coil, while the first coil may be decoked by the steam and then the streams of the first and the second coils, may be switched, such that hydrocarbon feed may be upgraded in the first coil, while the second coil may be decoked by the steam. This cycle may be continued to form a cyclic process in which upgrading and decoking may continuously and periodically be performed in a number of coils in the pyrolysis furnace.

Furthermore, with reference toFIG. 2, in one implementation, in first step201of method200the pyrolysis furnace may be associated with, be provided with, or otherwise include a number of thermal zones, for example a first thermal zone and a second thermal zone. The pyrolysis furnace may also include a number of coils, for example a first coil and a second coil, that may pass through or be disposed within the first and the second thermal zones. As noted above, in one implementation, the first and the second thermal zones may be capable of functioning as convection zones or radiant zones and the functionality of the thermal zones may be switched between a convection zone and a radiant zone.

Referring now toFIGS. 3A and 3B, two schematics of a pyrolysis furnace300configured to operate according to the method ofFIG. 2is illustrated. The pyrolysis furnace300may include a first thermal zone301and a second thermal zone302. In some implementations, the first thermal zone301includes a first burner303and a first stack304that may be controlled by valve V11. In addition, in some implementations, the second thermal zone302may include a second burner305and a second stack306that may be controlled by valve V12.

As noted earlier, in order for each thermal zone to function as a convection zone, the respective burner of that thermal zone may be turned off or alternatively operate at a lower capacity, and the respective stack of that zone may be opened. For example, in order for the first thermal zone301to function as a convection zone, first burner303may be turned off or alternatively the first burner303may operate at a lower capacity, and the first stack304may be opened by valve V11.

Furthermore, in order for each thermal zone to function as a radiant zone, the respective burner of that zone may be turned on and the respective stack of that zone may be closed. For example, in order for the first thermal zone301to function as a radiant zone, first burner303may be turned on and the first stack304may be closed by valve V11.

With further reference toFIG. 3A, in one implementation, pyrolysis furnace300may include a first coil307and a second coil308. In some implementations, the first coil307may be supplied from a first line309and the second coil308may be supplied from a second line310. References to “lines” herein can refer to any kind of fluid transportation, feed, or supply system or network, including but not limited to lines, pipes, tubes, or other fluid transfer vessels or components. The pyrolysis furnace300may operate in two modes: in a first mode, the hydrocarbon feed is upgraded in the second coil308while the first coil307is decoked by a stream of steam fed through the first coil307; and, in a second mode, the steam stream is diverted to the second coil308in order to decoke the second coil308while the hydrocarbon feed is upgraded in the first coil307. The hydrocarbon feed that is to be upgraded in each coil may be mixed prior entering the pyrolysis furnace300with the heated steam or water in the other coil in some implementations.

Referring again toFIG. 3A, in one implementation of the first mode, hydrocarbon feed may be supplied from a third line311that may be controlled or otherwise managed by valve V9and water or steam may be supplied from a fourth line312that may be controlled by valve V5. During the first mode, in one implementation, valves V2, V5, V8, V9, and V10may be opened while valves V1, V3, V4, V6, and V7may be closed. Hydrocarbon feed supplied from a third line311may flow through a fifth line313and then through a sixth line314to node315. Water or steam supplied from fourth line312may flow through first line309that supplies the first coil307. Water or steam supplied from first line309to the first coil307may first enter the first thermal zone301, which in this mode functions as a radiant zone (whereby the first burner303may be turned on and the first stack304may be closed by valve V11).

Afterwards, the steam may continue to flow in the first coil307to the second thermal zone302, which in this mode function as a convection zone (whereby the second burner305may be turned off or operate at a lower capacity and the second stack306may be opened by valve V12). The heated steam from the first coil307may flow through a seventh line316that may be controlled by valve V2to the node315, where the heated steam may be mixed with, the hydrocarbon feed. The mixture of the hydrocarbon and steam may then be fed to the second coil308via second line310. The mixture (i.e., hydrocarbon/steam mixture) may initially enter the second thermal zone302. The second thermal zone302functions as a convection zone in this mode and the hydrocarbon/steam mixture may be preheated in the second thermal zone302before it enters the first thermal zone301(i.e., at this time a radiant zone). The upgrading process may occur in the second coil308while it is being heated in the first thermal zone301(i.e., at this time a radiant zone).

In other implementations, the pyrolysis furnace300may include more than one radiant zone. The upgraded or partially upgraded hydrocarbon from the second coil308may flow through an eighth line317that may be controlled by valve V8to a coke drum318for further separation in some implementations. In one implementation, the first thermal zone301and the second thermal zone302are separated by a refractory wall326.

Referring now toFIG. 3B, it can be seen that in one implementation of the second mode, hydrocarbon feed may be supplied from a ninth line319that is controlled by valve V7and water or steam may be supplied from a tenth line320that is controlled by valve V6. In some implementations of the second mode, valves V1, V3, V4, V6, and V7are opened while valves V2, V5, V8, V9, and V10are closed. Hydrocarbon feed supplied from ninth line319may flow through fifth line313and then through an eleventh line321to node322. Water or steam supplied from tenth line320may flow through second line310that supplies the second coil308. Water or steam supplied from second line310to the second coil308may first enter the second thermal zone302, which in this mode functions as a radiant zone (whereby the second burner305is turned on and the second stack306is closed by valve V11).

Following this step, the steam may continue to flow in the second coil308to the first thermal zone301, which in this mode functions as a convection zone (whereby the first burner303is turned off or operates at a lower capacity and the first stack304is opened by valve V12). The heated steam from the second coil308may flow through a twelfth line323that may be controlled by valve V1to the node322, where the heated steam may be mixed with the hydrocarbon feed. The mixture of the hydrocarbon and steam may then be fed to the first coil307via first line309. The mixture (i.e., hydrocarbon/steam mixture) may first enter the first thermal zone301. The first thermal zone301functions as a convection zone in the second mode and the hydrocarbon/steam mixture may be preheated in, the first thermal zone301before it enters the second thermal zone302(i.e., at this time a radiant zone). The upgrading process may occur in the first coil307while it is being heated in the second thermal zone302(i.e., at this time a radiant zone).

In other implementations, the pyrolysis furnace300may include more than one radiant zone. The upgraded or partially upgraded hydrocarbon from the first coil307may flow through a thirteenth line324that may be controlled by valve V4to a coke drum325for further separation.

Referring now toFIG. 4, a pyrolysis furnace400with a plurality of thermal zones is illustrated according to an implementation of the present disclosure. In some implementations, the pyrolysis furnace400may include two thermal zones disposed at either end of the pyrolysis furnace400. For example, a first thermal zone401may be disposed along a first end and a second thermal zone402may be disposed along a second end. In one implementation, the first thermal zone401may include a first burner403and a first stack404and the second thermal zone402may include a second burner405and a second stack406. In some implementations, the first thermal zone401and the second thermal zone402may be symmetrically arranged.

According to some implementations, the first thermal zone401and the second thermal zone402may be capable of functioning as both a convection zone and a radiant zone. In order for each thermal zone to function as a convection zone, the respective burner of that zone may be turned off or alternatively operate at a lower capacity and the respective stack of that zone may be opened. For example, in order for the second thermal, zone402to function as a convection zone, the second burner405is turned off or alternatively the second burner405operates at a lower capacity, and the second stack406is opened by valve V11. In order for each thermal zone to function as a radiant zone, the respective burner of that zone is turned on and the respective stack of that zone is closed. For example, in order for the second thermal zone402to function as a radiant zone, second burner405may be turned on and the second stack406may be closed by valve V11.

With further reference toFIG. 4, at least one thermal zone may be provided between the first thermal zone401and the second thermal zone402. For example, in, the implementation shown inFIG. 4, there may be three thermal zones407disposed between the first thermal zone401and the second thermal zone402. In other implementations, thermal zones407can comprise one thermal zone, two thermal zones, or more than three thermal zones. In some implementations, pyrolysis furnace400may include, for example 3 to 10 thermal zones. Thermal zones407may include burners408and may function as radiant zones. In some implementations, thermal zones can be separated by refractory walls409.

In different implementations, the system can include other features to facilitate the operation of the thermal zones. For example, in some exemplary implementations, the heated steam is combined with the hydrocarbon feed, with a steam to hydrocarbon ratio of between 0.1 and 3, In addition, in some implementations, the temperature of steam and/or the hydrocarbon feed at the outlets of the first coil and the second coil can be between 300 and 900 degrees Celsius. In one exemplary implementation, the absolute pressure of steam and the hydrocarbon feed at the outlet of the first and the second coils is between 0.1 bar-abs and 300 bar-abs.

According to some implementations, the method and the pyrolysis furnace as disclosed herein may be utilized in catalytic versions of hydrocarbon upgrading processes, in which catalysts may be provided inside the coils in the form of, for example, catalyst pellets, internal coating of the coil with the catalyst, etc. In this implementation, the steam may be mixed with a catalyst regeneration agent.