Patent Application
20240101911
This application claims the priority of Chinese Patent Application No. CN202211183505.7, filed Sep. 27, 2022. The disclosure of that application is incorporated here by reference.
The present application relates to a catalytic cracking reaction system for crude oil, in particular, a method for reducing or preventing coking in a catalytic cracking reaction system and a device thereof, belonging to the petrochemical field.
Producing light olefins by directly cracking crude oil no longer depends on the steam cracking feedstock produced in the oil refining process, so the process is short, investment is small, and energy consumption is low. For the production of equivalent amounts of ethylene from the same crude oil, compared with oil refining combined with steam cracking, it results in a reduction in crude oil consumption of 60% or above by direct cracking of crude oil to produce light olefins. Greatly reducing the consumption of crude oil in olefin production will greatly alleviate the demand for crude oil.
There are two technical routes for the direct cracking of crude oil to produce light olefins. One is that the crude oil is preheated in a convection section of a cracking furnace and enters a flash tower, and light oil that is distilled off enters a radiant section for steam cracking. The other is that catalytic cracking occurs under the action of a catalyst. The former is essentially not different from steam cracking, except that the heat from the convection section of the cracking furnace is used as a heat source for crude oil flashing. Theoretically this process has no requirements on the nature of the crude oil, and in fact the heavier the crude oil, the less light oil, and heavy oil that is distilled off still relies on a traditional oil refining process for processing. Thus, for businesses that do not want to produce oil, by using a technical route of crude oil steam cracking, it is obvious that the lighter the crude oil processed, the better. The catalytic cracking of crude oil has much broader requirements on the nature of the crude oil, the crude oil can be light or heavy. For the heavier the crude oil, the yield of light olefins is lower, and the yield of aromatics is higher.
Steam cracking of crude oil and catalytic cracking of crude oil have significant differences in coking in the device and heat exchange cooling of high temperature oil gas. Steam cracking of crude oil is little different from steam cracking of light hydrocarbons and naphtha from reaction to separation. The coking phenomenon exists in a cracking furnace tube, and a heat exchange tube where high temperature oil gas generates high pressure steam. The continuous operation of the whole system can be maintained by successively burning coke in multiple sets of cracking furnaces at regular intervals. Whereas for a crude oil catalytic cracking device, coking is occurred in a reactor and a disengager will coke. If the same solution as steam cracking is adopted, heat exchange of high temperature oil gas is used in generating high pressure steam for cooling, and the heat exchange tube will surely coke. Once coking affects the operation of the device, it is impossible to switch several sets of reaction systems for burning coke like steam cracking to maintain the stable operation of the whole system.
A first object of the present application is to reduce or prevent the coking phenomena in are action system for producing light olefins from crude oil by catalytic cracking, particularly the coking phenomenon in a disengager is significantly reduced.
A second object of the present application is to reduce or prevent the coking phenomena in a disengager, a heat exchange device and the like of the reaction system for producing light olefins from crude oil by catalytic cracking, so as to prolong the operation period of the entire device.
A third object of the present application is to fully utilize the heat of high temperature oil gas in a reactor while reducing the heat loss of a high temperature spent catalyst in the reaction system for producing light olefins from crude oil by catalytic cracking. Waste of energy is reduced as much as possible, while coking of the system is also reduced.
In one aspect, a method for preventing coking on a device in the reaction system for producing light olefins from crude oil by catalytic cracking includes: cooling the temperature of high temperature oil gas discharged from a reactor, and adsorbing a liquid-phase oil condensed on a spent catalyst; and allowing the oil gas cooled to enter a disengager for gas-solid separation, and directly delivering most of the spent catalyst to the disengager.
By the anti-coking method of the present application, the high temperature oil gas is cooled before entering the disengager. The substances with high-boiling-point and being easily condensed are converted from a gaseous state to a liquid state, and liquid oil is adsorbed on the spent catalyst. Thus, the components of liquefaction coking on the walls and being included in the oil gas entering the disengager are reduced, and in turn, reducing or preventing coking in the disengager of the reactor.
In another aspect, a reaction device for producing light olefins from crude oil by catalytic cracking includes a reactor, a disengager, and a heat exchanger, wherein the heat exchanger is connected with the reactor and the disengager, respectively.
In the reaction device, the high temperature oil gas and the spent catalyst discharged from the reactor are cooled in the heat exchanger, and the condensed oil is absorbed by the spent catalyst so as to reduce or prevent coking in the disengager after the oil gas enters the disengager.
In yet another aspect, a reaction device for producing light olefins from crude oil by catalytic cracking includes, a reactor, a disengager, a primary separator, and a heat exchanger, wherein the reactor is connected with the primary separator, the primary separator is connected with the heat exchanger, and the disengager is connected with the primary separator and the heat exchanger, respectively.
In the reaction device, the high temperature oil gas and the spent catalyst discharged from the reactor are subjected to gas-solid separation by the primary separator, the separated high temperature oil gas is delivered to the heat exchanger for cooling, and the separated spent catalyst is directly delivered to the disengager. The cooled oil gas is delivered to the disengager for gas-solid separation. The high temperature oil gas entering the heat exchanger carries a suitable amount of spent catalyst, the spent catalyst cannot only adsorb the condensed liquid-phase oil, but also rub against the wall of the heat exchanger, so that it is achieved to in time wipe off an oil coking precursor or coke and the like from the wall. Therefore, coking in the heat exchanger and the disengager is effectively prevented. In addition, since most of the spent catalyst does not enter the heat exchanger for cooling, the energy consumption in the regeneration process is reduced.
The anti-coking reaction system for producing light olefins from crude oil by catalytic cracking according to the present application is described in further detail below. The protection scope of the present application is not limited, and is defined by the claims.
The term “gas-solid separation efficiency” refers to the mass fraction of the catalyst that is separated from gas in the total catalyst entering a separator.
“Light olefins” generally refer to olefins having 2 to 4 carbon atoms, such as a generic term for small molecule olefins such as ethylene, propylene, and butylene.
“Crude oil” generally refers to unprocessed petroleum and is a mixture of various liquid hydrocarbons, such as alkanes, cycloalkanes, and aromatics, the main components of which are carbon and hydrogen having 83-87% and 11-14%, respectively.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Furthermore, any methods and materials similar or equivalent to those described can be used in the method of the present application. The preferred embodiments and materials described herein are exemplary only.
There are three main problems that need to be solved in the technology of producing light olefins (such as ethylene, propylene and the like) from crude oil by catalytic cracking: 1) the yield and selectivity of ethylene and propylene; 2) the device of the reaction system can be operated for a long period of time, the most prominent of which is how to avoid coking on the device; and 3) efficient recycling of the energy of high temperature oil gas. The yield and selectivity of light olefins such as ethylene, propylene, and the like are influenced primarily by such factors as composition and nature of feedstock, reactor structure and operating conditions, and catalyst performance. The yield and selectivity of light olefins have not been the bottleneck that has restricted the catalytic cracking of crude oil towards industrialization. What is urgently needed is the problem of affecting long cycle operation due to device coking and recycling of the energy of high temperature oil gas. The present application primarily solves these two problems.
In one aspect, a method for preventing coking in a reaction system for producing light olefins from crude oil by catalytic cracking includes: reducing the temperature of oil gas discharged from a reactor, and adsorbing condensed liquid-phase oil by a spent catalyst; and allowing the cooled oil gas to enter a disengager for gas-solid separation, and directly delivering most of the spent catalyst to the disengager.
In some embodiments, the oil gas and the spent catalyst discharged from the reactor are first subjected to gas-solid separation in a primary separator, and a separated oil gas carries a portion of the spent catalyst to enter a heat exchanger for heat exchange to reduce the temperature.
The primary separator is arranged outside a tank of the disengager and the reactor of the reaction system. The primary separator includes a separator body, an inlet, an outlet, and a discharging inclined pipe, wherein the outlet end of the discharging inclined pipe is located inside the tank of the disengager. The outlet of the primary separator is connected with an inlet of the heat exchanger, and the inlet of the primary separator is connected with an outlet of the reactor.
The high temperature oil gas carries the spent catalyst to enter the heat exchanger through the outlet of the primary separator for heat exchange. High pressure steam is generated.
If only high temperature oil gas or oil gas containing a very small amount of catalyst enters the heat exchanger for heat exchange, the oil gas is liable to coke in the heat exchanger during the heat exchange. Thereby the amount of steam generation is reduced and the pressure drop is increased, even resulting in unintended shutdown of the device. The present application uses the oil gas to carry the spent catalyst to pass through the heat exchanger together. On one hand, the catalyst is used to adsorb a liquid phase generated in the cooling process of the oil gas, reducing or even avoiding the liquid from adhering to the wall of a heat exchange and affecting the heat transfer; on the other hand, the friction between the spent catalyst and the wall of the heat exchange is used to “rub” off oil, a coking precursor and coke adsorbed onto the wall of the heat exchange in time. This ensures that the device can operate for a long period of time.
In order to efficiently and reasonably utilize the energy of the high temperature oil gas, reduce the energy consumption of a regenerated catalyst, and at the same time reduce the coking on the heat exchanger and the disengager, and the like, the high temperature oil gas discharged from an outlet of the primary separator is controlled to contain a proper amount of the catalyst.
In some embodiments, the total amount of the catalyst contained in the high temperature oil gas separated by the primary separator is 40% or below, preferably 5-25% of the total amount of the catalyst carried by the oil gas at the outlet of the reactor. That is, in the primary separator, most of the catalyst (60% or more of the total amount of the catalyst carried by oil gas at an outlet of a riser) can naturally settle.
The proportion of the catalyst that settles down in the primary separator can be controlled by adjusting the superficial gas velocity in the primary separator below the outlet of the reactor (i.e. below the inlet of the primary separator). The lower the gas velocity, the higher the proportion of the catalyst that settles down.
In some embodiments, the superficial gas velocity below the inlet of the primary separator is not more than 2 m/s, preferably not more than 0.5 m/s. It is ensured that most of the catalyst entering the primary separator (60% or more of the total amount of the catalyst carried by the oil gas at the outlet of the riser) can naturally settle.
On one hand, the proportion of the catalyst carried by the high temperature oil gas at the outlet of the primary separator is influenced by the superficial gas velocity below the inlet of the primary separator, and the lower the gas velocity, the lower the proportion. On the other hand, the proportion is also influenced by the superficial gas velocity above the inlet of the primary separator, and the higher the gas velocity, the higher the proportion. Thus, the proportion of the catalyst carried by the oil gas entering the heat exchanger is jointly influenced by the superficial gas velocities above and below the inlet of the primary separator. Further, the superficial gas velocity above the inlet of the primary separator is not less than 0.5 m/s, preferably not less than 2 m/s, ensuring that the oil gas carries a sufficient amount of catalyst to enter the oil gas heat exchanger.
The total amount of the catalyst carried by the high temperature oil gas entering the heat exchanger is 40% or below, preferably 5-25% of the total amount of the catalyst carried by the oil gas at the outlet of the reactor. The high temperature oil gas is subjected to heat exchange with low-temperature water gas in the heat exchanger to cool the high temperature oil gas, while high pressure steam is generated to drive the steam turbine. Carrying a small portion of the catalyst in the heat exchanger serves to avoid coking of the wall surface of the heat exchange. If the oil gas and the catalyst from the outlet of the reactor are all allowed to pass through the heat exchanger, in the case of cooling the oil gas to the same temperature, on one hand, the temperature of all the spent catalysts will be lowered, and more fuel will be consumed to raise the temperature of the catalysts after entering a regenerator; on the other hand, since the catalyst-oil ratio of crude oil catalytic cracking is very large, the amount of high pressure steam generated by the heat exchange with the high temperature oil gas and the catalyst in the heat exchanger will far exceed the demand of the whole system, so that the utilization of energy is unreasonable.
The superficial gas velocities at various locations in the primary separator defined in the present application are directed to the physical and mechanical properties of existing generally applicable catalysts for catalytic cracking to produce light olefins. That is, within the proposed superficial gas velocity range, most of the catalyst can be separated from the oil gas.
In some embodiments, in the vertical direction, the outlet end of the discharging inclined pipe is located in the middle and upper portion of an expanding section within the tank of the disengager.
Most of the catalyst enters the disengager after being separated by inertia in the primary separator, which causes many advantages for slowing down or even avoiding the coking of the disengager. The temperature in the upper part of the disengager is increased, and the condensation of the oil gas is reduced, thereby reducing the formation of soft coke. The catalyst is dispersed in the disengager and naturally settles, and can effectively adsorb macromolecular oil gas that is easily condensed. In this way, not only can the high temperature oil gas be appropriately cooled and generate high pressure steam, but also the energy can be used efficiently and reasonably, and the coking of the disengager can be slowed down or even avoided.
In some embodiments, a slide valve is arranged on the discharging inclined pipe of the primary separator, and the amount of the catalyst carried by the oil gas entering the heat exchanger is regulated by controlling the opening of the valve.
Preferably, a conveying medium driving the catalyst to enter the disengager is introduced into the discharging inclined pipe of the primary separator, and the amount of the catalyst carried by the oil gas entering the heat exchanger is adjusted by adjusting the opening of the slide valve and the amount of the conveying medium.
Increasing the opening of the slide valve and increasing the amount of the conveying medium cause the interface between the dilute and dense phases of the catalyst in the primary separator to move downwards and the proportion of the catalyst carried by the oil gas entering the heat exchanger is decreased. Otherwise the proportion of the catalyst carried by the oil gas entering the heat exchanger is increased. By closing the slide valve, all the catalysts can enter the heat exchanger with the oil gas.
In certain embodiments, the apparent linear velocity of the oil gas carrying the catalyst entering the heat exchanger is greater than 0.5 m/s, preferably in a range of 2-10 m/s, more preferably in a range of 3-5 m/s.
Through the method of the present application, the probability of coking in the heat exchanger and the disengager and the like is significantly reduced. On the other hand, the energy of the oil gas is fully used for generating high pressure steam for driving a turbine of a rich gas compressor. In a large-scale production device for preparation of ethylene by evaporative cracking, the rich gas compressor needs to drive the turbine by high pressure steam of 10 MPa or above. By using the high pressure steam of 10 MPa or above generated by the high temperature oil gas through the heat exchanger, not only the energy utilization is most reasonable, but also the rapid drop in the temperature of the oil gas contributes to the safe and stable operation of the subsequent system. The energy required for the regeneration process of the spent catalyst can also be reduced, and the energy utilization can be more reasonable.
The method for preventing coking in the reaction system for producing light olefins from crude oil by catalytic cracking of the present application may be carried out in any one of the following reaction devices.
In another aspect, a reaction device for producing light olefins from crude oil by catalytic cracking includes a reactor, a disengager, and a heat exchanger, wherein the heat exchanger is located outside the reactor and the disengager, an inlet of the heat exchanger is connected with an outlet of the reactor, and an outlet of the heat exchanger is connected with a cyclone separator in the disengager.
Compared with the conventional catalytic cracking system, the reaction system, namely a circulating fluidized bed reaction-regeneration system of the present application can be run with high reaction temperature, typically in the range of 600-750° C.; and low pressure, generally 1200 kPa (a) or below; and a regenerator requires supplemental fuel.
In the existing reaction system for producing light olefins from crude oil by catalytic cracking (e.g., the reactor is a riser), in order to ensure that crude oil is converted fully as much as possible in once-through and also to reduce oil not to be gasified in the reactor, a dense phase fluidization section is formed at the lower part of the riser by expanding (referring to
However, it is not completely avoided to coke in the reaction system by merely modifying the structure of the reactor. Since the temperature at the outlet of a riser reactor for producing light olefins from crude oil by catalytic cracking is controlled at about 700° C., the oil gas in the gas phase at this temperature still has the risk of liquefaction coking when entering the disengager, the cyclone separator, an oil gas pipeline, etc.
The present application proposes that the high temperature oil gas and the catalyst enter the oil gas heat exchanger together to generate high pressure steam, and the catalyst is used to adsorb oil condensed during cooling, thereby avoiding coking of the reaction system.
The heat exchanger of the present application is a shell and tube heat exchanger, which has a heat exchange tube and a shell, and the heat exchange tube is connected with a tube sheet and fixed by the shell. The oil gas and the catalyst enter the heat exchanger via either a shell side or a pipe side; and the pipe side is preferable to be selected.
In some embodiments, the inlet of the heat exchanger for feeding the oil gas and the catalyst is located above the outlet of the reactor, and preferably is located just above the outlet of the reactor.
The inlet of the heat exchanger for feeding the oil gas and the catalyst is lower than the outlet of the heat exchanger.
In certain embodiments, the upper part of the reactor has a bend, such that the outlet of the reactor faces downwards and the outlet of the reactor is connected to the inlet of the heat exchanger for feeding the oil gas and the catalyst.
The inlet of the heat exchanger for feeding the oil gas and the catalyst is higher than the outlet of the heat exchanger.
Alternatively, the inlet of the heat exchanger for feeding the oil gas and the catalyst is connected with the outlet of the reactor by a bent pipe. For example, the bent pipe may be a U-shaped pipe of which an opening faces downwards, and is connected with the outlet of the reactor and the inlet of the heat exchanger for feeding the oil gas and the catalyst, respectively.
The oil gas and the catalyst discharged from the outlet of the reactor enter the heat exchanger from the top down, so the pressure drop is relatively small. In addition, the catalyst moves downward by gravity in the heat exchanger, regardless of catalyst lifting, so the range of a flow rate can be wide.
In all embodiments, the outlet of the heat exchanger for the oil gas and the catalyst is connected with a cyclone separator within the reaction disengager.
The reaction device for producing light olefins from crude oil by catalytic cracking further includes a primary separator and a disengager. The primary separator is arranged between the heat exchanger and the reactor, and is respectively connected with the heat exchanger and the reactor.
The disengager includes a disengager tank, a cyclone separator arranged in the disengager tank. The primary separator is arranged outside the disengager tank and the reactor. The primary separator includes a separator body, an inlet, an outlet, and a discharging inclined tube, the outlet end of the discharging inclined tube is located in the disengager tank, the outlet of the primary separator is connected with the inlet of the heat exchanger, and the outlet of the heat exchanger is connected with the cyclone separator.
The inlet of the primary separator is connected with the outlet of the reactor. The oil gas and the catalyst in the reactor enter the primary separator through the inlet.
Most of the catalyst discharged from the reactor is first separated from the gas by the primary separator, and the high temperature oil gas carries a small portion of the catalyst to enter the heat exchanger.
The heat exchanger is connected with the primary separator in the same manner as that the heat exchanger is connected to the outlet of the reactor.
The inlet of the heat exchanger for feeding the oil gas and the catalyst is above the outlet of the primary separator, and preferably is just above the outlet of the primary separator.
The inlet for the oil gas and the catalyst of the heat exchanger is lower than the outlet.
Alternatively, the upper part of the primary separator has a bend such that the outlet of the primary separator faces downwards, and the outlet of the primary separator is connected with the inlet of the heat exchanger for feeding the oil gas and the catalyst.
The inlet of the heat exchanger for feeding the oil gas and the catalyst is higher than the outlet.
Alternatively, the inlet of the heat exchanger for feeding the oil gas and the catalyst is connected with the outlet of the primary separator by a bent pipe. For example, the bent pipe may be a U-shaped pipe of which an opening faces downwards, and is connected to the outlet of the primary separator and the inlet of the heat exchanger for feeding the oil gas and the catalyst, respectively.
In order to control the amount of the catalyst carried by the oil gas entering the heat exchanger, the size of the separator body and the size of the outlet of the reactor are limited to achieve control of the content of the catalyst carried in the oil gas.
The reactor can be of various configurations, such as an equal-diameter riser, a variable diameter riser, or the like.
In some embodiments, the cross-section of the separator body is a circular, and the diameter of the separator body is larger than the diameter of the outlet of the reactor.
By adjusting the size of the diameter of the separator body and the size of the diameter of the bent pipe, the amount of the catalyst carried by the oil gas from the outlet of the primary separator into a primary cyclone separator is controlled.
In addition, by the arrangement of the bent pipe it can be ensured that the oil gas smoothly flow into the cyclone separator without the problem of catalyst deposition; and on the other hand, the velocity of the oil gas is adjusted, and the deposited rate of the catalyst or the amount of the catalyst carried by the oil gas into a rough-cut cyclone is adjusted.
In some embodiments, the discharging inclined tube of the primary separator is extended into the disengager tank through the wall of the disengager tank, and the discharging inclined tube in the disengager is substantially perpendicular to the wall of the tank. The discharging inclined tube in the disengager tank is as short as possible, thereby the catalyst discharged through the discharging inclined tube can touch with a greater area of the wall of the disengager.
The catalyst entering the disengager from the primary separator spreads from top to bottom to the bottom of the disengager, thereby causing to flush the discharging inclined tube of the cyclone separator and the wall of the disengager, and avoiding long-term accumulative coking of freshly condensed oil gas and the adhered catalyst on these assemblies. At the same time, some coking components which are easy to adsorb and condense in the disengager are also adsorbed.
In certain embodiments, the discharging inclined tube of the primary separator includes a horizontal section and a vertical section, wherein the horizontal section is located below the vertical section, the vertical section is connected to the bottom of the separator body, and the horizontal section is extended at least partially into the disengager tank. The horizontal section is substantially parallel to a horizontal plane, and the vertical section is a pipeline for conveying the catalyst downward.
The disengager tank includes an expanding section and a stripping section, wherein the expanding section is located above the stripping section. The cross section of the disengager tank is preferably circular, and the diameter of the expanding section is larger than the diameter of the stripping section in a plane perpendicular to the central axis of the disengager tank.
In some embodiments, the discharging inclined tube of the primary separator is extended into the disengager tank through the tank wall of the expanding section of the disengager tank.
The temperature of the catalyst directly entering the expanding section of the disengager (the middle of the disengager) from the discharging inclined tube of the primary separator is higher than the temperature of the catalyst discharged through a discharging tube of the cyclone separator during the settling period. The catalyst with the relatively high temperature and entering in the middle of the disengager raises the temperature within the disengager and prevents the oil gas from condensing and coking on a disengager housing or the discharging tube of the cyclone separator.
The discharging inclined tube is circular in cross section and of equal diameter.
In some embodiments, a gas distributor is arranged within the separator body of the primary separator. Preferably, the gas distributor is located in the separator body near the discharging inclined tube.
The gas distributor may be of a structure commonly used in the field of catalytic petroleum cracking or catalytic cracking, such as an annular tube provided with vent holes uniformly formed in the wall of the tube.
A stripping medium enters the separator body through the gas distributor. The catalyst passing through the primary separator is degassed by the stripping medium to remove entrained oil gas, and the catalyst degassed enters the discharging inclined tube. Thus, the oil gas entrained in the catalyst discharged through a conveying pipe of the discharging inclined tube is greatly reduced.
The stripping medium includes dry gas, nitrogen, or water vapor. Water vapor is preferred.
Preferably, the gas velocity of the stripping medium at the outlet of the gas distributor is in a range of 0.5-50 m/s, preferably in a range of 0.8-30 m/s.
In order to increase the stripping effect, multiple layers of baffles are arranged within the separator body of the primary separator. The baffles are positioned above the gas distributor.
Stripping stream enters in the primary separator from the lower portion to strip the oil gas off the catalyst, thereby minimizing the amount of the oil gas carried by the catalyst entering the disengager. The stripped catalyst enters the disengager from the upper middle part of the disengager through the vertical section, the slide valve, and the horizontal section of the discharging inclined tube. In order to improve the effect of the catalyst to absorb the condensed oil gas in the disengager, in the horizontal section of the discharging inclined tube may be fed with a conveying medium which causes the catalyst to disperse and naturally settle in the disengager. The conveying medium is selected one or more from a group consisting of dry gas, nitrogen and water vapor, preferably water vapor.
In the present application, the primary separator is arranged outside the disengager tank, and arranged between the reactor (e.g., a riser reactor) and the disengager tank. The oil gas and the catalyst from the outlet of the reactor enter the primary separator. Most of the oil gas carrying a small amount of catalyst after primary separation enters the cyclone separator in the disengager from the upper part of the primary separator. Most of the catalyst in the primary separator is stripped again during the falling process to remove entrained oil gas, and then enters the disengager, thereby reducing the concentration of the oil gas entering the disengager to prevent from coking in the disengager.
In some embodiments, the cyclone separator of the present application includes a first stage cyclone separator and a second stage cyclone separator, and the outlet of the primary separator is connected with the first stage cyclone separator.
The first stage cyclone separator includes a body and a discharging pipe. The discharging pipe includes a discharging pipe degassing section and a discharging pipe conveying section, an upper end of the discharging pipe degassing section is connected to a lower end of the body, and a lower end of the discharging pipe degassing section is connected to an upper end of the discharging pipe conveying section.
A gas distributor is arranged within the discharging pipe degassing section of the first stage cyclone separator.
A stripping medium enters in the discharging pipe degassing section through the gas distributor, the catalyst separated in the body of the first stage cyclone separator is degassed by the stripping medium to remove entrained oil gas, and the degassed catalyst enters in the discharging pipe conveying section. Thus, the oil gas entrained in the catalyst discharged through the conveying pipe of the discharging pipe is greatly reduced.
The stripping medium is selected from nitrogen or water vapor.
Preferably, the gas velocity of the stripping medium at the outlet of the gas distributor is in range of 0.5-50 m/s, preferably in range of 0.8-30 m/s.
In order to achieve further good gas-solid separation, the catalyst and the oil gas pass through the first stage cyclone separator and enter the second stage cyclone separator, and the first stage cyclone separator and the second stage cyclone separator are connected by a straight pipe.
Each of the first stage cyclone separator or the second stage cyclone separator includes a separator body and a discharging leg arranged below the separator body.
The oil gas and the catalyst cooled in the heat exchanger enter in the first stage cyclone separator. Since most of the catalyst already enters in the disengager directly and a small amount of the catalyst enters in the first stage cyclone separator after being separated for gas oil in the primary separator, the load of the first stage cyclone separator is substantially reduced. So it is advantageous to reduce the concentration of the catalyst containing in the oil gas entering the second stage cyclone separator and reduce catalyst run-off during system fluctuations.
In some embodiments, a stripping distributor is arranged at the discharging leg of the first stage cyclone separator. The amount of the oil gas carried by the catalyst entering in the disengager via the first stage cyclone separator is reducing, and further the coking tendency in the disengager is reduced.
The reactor of the present application may be a common riser, a dual riser, or a riser reactor with an expanded diameter.
The main technical advantage of the present application is that the catalyst is used to absorb the oil condensed during cooling in the heat exchanger arranged between the reactor and the disengager tank, and it is reduced that the oil gas is liquefied and coked in the disengager. Thereby reducing or avoiding coking in the disengager is achieved, and the energy during cooling can also be used to generate steam.
On the other hand, the oil gas and the catalyst are separated by the primary separator before entering the disengager. The coking phenomenon on the disengager, the heat exchanger, etc. is significantly reduced, and the energy utilization of the whole system is reasonable to achieve the effect of saving energy.
The reaction system for producing olefins from crude oil by catalytic cracking according to the present application is further described below with reference to specific examples.
As shown in
As shown in
Another example is shown in
Referring to
The primary separator 18 includes a separator body 21, a discharging inclined tube 22, an inlet and an outlet. The discharging inclined tube of the primary separator 18 is extended into the disengager 3, and most of the separated catalyst enters in the disengager along the discharging inclined tube 22. The outlet of the primary separator is connected with the inlet of the heat exchanger 17 for feeding the oil gas and the catalyst, and the oil gas carries part of the catalyst to enter in the heat exchanger 17. The inlet of the primary separator is connected with the outlet of the riser 1, and the catalyst and the oil gas in the riser reactor enter the primary separator through the inlet. The outlet of the heat exchanger 17 for discharging the oil gas and the catalyst is connected with the first stage cyclone separator 7 within the disengager 3.
The outlet of the primary separator is connected with the inlet of the heat exchanger 17 for feeding the oil gas and the catalyst as shown in
Alternatively, as shown in
The separator body 21 is a tank body of a cylindrical structure. The discharging inclined tube 22 is located below the separator body 21 and is connected with the separator body 21. An annular gas distributor 19 is arranged in the separator body 21 for allowing a stripping gas to enter in the separator body 21 to strip the catalyst, thereby reducing the amount of the oil gas carried by the catalyst entering the disengager.
Preferably, baffles are arranged above the gas distributor in the separator body 21. Each of the baffles includes two plates, the side of one plate is connected to the side of the other plate at an angle, or one plate is bent to form a baffle with an opening downwards.
The discharging inclined tube 22 of the primary separator includes a horizontal section 221 and a vertical section 222, and the horizontal section 221 is located below the vertical section 222. The vertical section 222 is connected to the bottom of the separator body 18, and the horizontal section 221 is extended at least partially into the disengager tank. The horizontal section 221 is substantially parallel to a horizontal plane, and the vertical section 222 is a pipeline for conveying the catalyst downward.
The reactor disengager 3 includes an expanding section 31 and a stripping section 32, wherein the expanding section 31 is located above the stripping section 32. In this example, both the expanding section 31 and the stripping section 32 have a cross section which circular shape and are straight tubes, and the diameter of the expanding section 31 is greater than the diameter of the stripping section 32. A first stage cyclone separator 7 and a second stage cyclone separator 23 are arranged in the reactor disengager 3. A main body of the first stage cyclone separator and a main body of the second stage cyclone separator are located in the expanding section of the disengager, and the outlets of the discharging pipes of the first stage cyclone separator and the second stage cyclone separator are located at the junction of the expanding section 31 and the stripping section 32 or in the stripping section.
As shown in
In this example, the reaction process carried out in the reaction device includes: a reaction feedstock 11 being subject to reaction under the action of the catalyst in a dense phase section of the riser 1. The catalyst and the oil gas from the reaction device enter in the body through the inlet of the primary separator 18. After gas-solid separation, the separated catalyst is sprayed into the disengager 3 through the discharging inclined tube 22 under the pushing force caused by a conveying medium 20 introduced in the horizontal section 221 of the discharging inclined tube 22. The separated oil gas carrying part of the catalyst enters in the pipe side through the inlet of the heat exchanger 17 for feeding the oil gas and the catalyst, and a heat exchange medium (typically water, generating high pressure steam) is introduced in the shell side of the heat exchanger. The oil gas and the catalyst after heat exchanged enter the first stage cyclone separator 7 in the disengager 3, and the oil gas from the first stage cyclone separator 7 enters the second stage cyclone separator 23 for further gas-solid separation. The separated catalyst enters in a degassing section of the first stage cyclone separator 7 in which a gas distributor 14 is arranged. Oil gas 15 separated in the first stage cyclone separator and the second stage cyclone separator is discharged from the disengager through an oil gas outlet.
The catalyst going down in the reactor disengager 3 is stripped by a stripping medium 13 and enters in a regenerator 2 through a spent inclined tube 6, and the catalyst is transported by a conveying medium 12 near the regenerator 2 in the spent inclined pipe 6. Air and fuel 10 are introduced into the bottom of the regenerator 2 to combust the catalyst. Flue gas 16 and the catalyst enter in a regenerator disengager 4 for gas-solid separation through a cyclone separator 8. The regenerated catalyst enters in a reactor riser 1 through a regeneration inclined pipe 5 and moves upward under the action of a pre-lifting medium 9 to enter in the dense phase section of the riser 1. The catalyst is in contact with the feedstock 11 for a reaction. The flue gas 16 is discharged from the top of the regenerator disengager 4.
Zhongyuan crude oil having a density of 862 kg/m 3 and a carbon residue of 6.0 was used, and the cracking catalyst prepared in Example 8 of a patent CN202010022024.2 was used.
A test was carried out on a catalytic cracking industrial device for a fifty thousand ton/year crude oil according to the solution in
The test was carried out continuously for one month. During the test, the device operated stably, and the temperature of the oil gas entering and exiting the heat exchanger as well as the amount, temperature and pressure of steam generated were essentially unchanged. After the test, the device was opened for inspection, the result showed that the oil gas heat exchanger, the disengager, the primary separator, the first stage cyclone separator, the second stage cyclone separator and the oil gas pipe line had no obvious coking phenomenon.
This comparative example refers to Example 1 for other process conditions except that the arrangement of a separator of a reactor disengager is different. As shown in
With the reaction device in the comparative example, the heat of the high temperature oil gas is reasonably utilized. But the high temperature oil gas enters in the heat exchanger and is soon coked in the heat exchanger, which gradually blocks the heat exchanger while affecting the heat exchange effect. The reaction system may fail to operate within one month of operation, and there is significant coking in the disengager.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202211183505.7 | Sep 2022 | CN | national |
