US-20260125605-A1 - Anti-Coking Method for Production of Light Olefins from Crude Oil by Catalytic Cracking and Device Thereof

US20260125605A1US 20260125605 A1US20260125605 A1US 20260125605A1US-20260125605-A1

Abstract

A method for preventing coking in a reaction system for producing light olefins from crude oil by catalytic cracking includes: reducing temperature of oil gas discharged from a reactor, adsorbing a condensed liquid-phase oil by a spent catalyst, allowing a cooled oil gas to enter a disengager for gas-solid separation, and delivering most of the spent catalyst to the disengager. The above method is taken to avoid coking of the reaction system and to ensure stable operation of a device for a long period of time; and the high-temperature potential heat of the oil gas is fully utilized, making the energy utilization of the whole system more reasonable, and achieving the effects of energy saving and emission reduction.

Inventors

Chunyi Li

Assignees

CHINA UNIVERSITY OF PETROLEUM (EAST CHINA)

Dates

Publication Date: 20260507
Application Date: 20251222
Priority Date: 20220927

Claims (10)

1 . A method for preventing coking in a reaction device for producing light olefins having 2 to 4 carbon atoms from crude oil by catalytic cracking, including: oil gas and a spent catalyst discharged from a reactor entering into a primary separator for gas-solid separation, the oil gas carrying less than 40% of a total amount of the spent catalyst discharged from an outlet of the primary separator entering a heat exchanger for heat exchange to reduce temperature of the oil gas discharged from a reactor and adsorb a condensed liquid-phase oil by the spent catalyst, allowing a cooled oil gas from the heat exchanger to enter a disengager for gas-solid separation, and delivering more than 60% of the total amount of the spent catalyst from a discharging inclined tube of the primary separator to the disengager, wherein the reaction device includes: the reactor, the disengager including a disengager tank and a cyclone separator arranged in the disengager tank, wherein the disengager tank includes a stripping section and an expanding section located above the stripping section, the primary separator, located outside the disengager tank and reactor, and including a separator body, an inlet, the outlet, and the discharging inclined tube, wherein the discharging inclined tube is arranged below and connected with the separator body, and the heat exchanger located outside the reactor and the disengager, wherein the discharging inclined tube includes a vertical section and a horizontal section arranged below the vertical section, the horizontal section having an outlet opening of the discharging inclined tube is extended at least partially into an upper portion of the expanding section of the disengager tank, and the horizontal section is substantially parallel to a horizontal plane, 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, and an outlet of the heat exchanger is connected with the cyclone separator in the disengager.
2 . The method according to claim 1 , wherein, an amount of the spent catalyst carried in the oil gas from the outlet of the primary separator is in range of 5-25% of the total amount of the spent catalyst carried in the oil gas from the reactor.
3 . The method according to claim 1 , wherein, a superficial gas velocity below an inlet of the primary separator is not more than 2 m/s.
4 . The method according to claim 1 , wherein, a superficial gas velocity above an inlet of the primary separator is not less than 0.5 m/s.
5 . The method according to claim 1 , wherein, a slide valve is arranged on the discharging inclined pipe of the primary separator, and an amount of the spent catalyst carried by the oil gas entering the heat exchanger is regulated by controlling opening state of the valve.
6 . The method according to claim 5 , wherein, a conveying medium driving the spent catalyst to enter the disengager is introduced into the discharging inclined pipe of the primary separator, and the amount of the spent catalyst carried by the oil gas entering in the heat exchanger is adjusted by adjusting the opening state of the slide valve and an amount of the conveying medium.
7 . The method according to claim 1 , wherein, the inlet of the heat exchanger for feeding the oil gas and the spent catalyst is located above the outlet of the reactor, and the inlet of the heat exchanger for feeding the oil gas and the spent catalyst is lower than the outlet of the heat exchanger.
8 . The method according to claim 1 , wherein the vertical section is a pipeline for conveying the spent catalyst downward.
9 . The method according to claim 1 , wherein, a gas distributor is arranged within the separator body of the primary separator, the gas distributor is an annular pipe with vent holes uniformly formed in a wall of the pipe.
10 . The method according to claim 9 , wherein, the gas distributor is located in the separator body near the discharging inclined tube.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a division of U.S. patent application Ser. No. 18/314,564, filed on May 9, 2023, which claims priority to Chinese patent application No. 202211183505.7, filed on Sep. 27, 2022, each of which is incorporated herein by reference in its entirety. TECHNICAL FIELD 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. BACKGROUND 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 hasmuch 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. SUMMARY 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