CN112694908B

CN112694908B - Efficient petroleum hydrocarbon cracking method

Info

Publication number: CN112694908B
Application number: CN202011478948.XA
Authority: CN
Inventors: 杨遥; 郭高顺; 余云波; 阳永荣; 王靖岱; 蒋斌波; 黄正梁; 孙婧元; 廖祖维
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2020-12-15
Filing date: 2020-12-15
Publication date: 2022-03-25
Anticipated expiration: 2040-12-15
Also published as: CN112694908A

Abstract

The invention relates to a high-efficiency cracking method of petroleum hydrocarbon. The method introduces one or more auxiliary agents in the thermal cracking process to initiate, induce and catalyze the cracking of petroleum hydrocarbon, improve the reaction depth, reduce the reaction temperature and regulate and control the product distribution. According to the invention, the best effect of the auxiliary agent for promoting cracking is achieved by optimizing the number of the filling ports, the positions of the filling ports, the flow rate of each filling port, the type of the auxiliary agent of each filling port, the concentration of the auxiliary agent of each filling port and the like. The auxiliary agent added in the method comprises water-soluble hyperbranched polymers such as polyether, polyamide, polyimide, imine polymers and the like and hyperbranched polymers which are modified by groups and have oil solubility.

Description

Efficient petroleum hydrocarbon cracking method

Technical Field

The invention relates to a thermal cracking process of petroleum hydrocarbon, belonging to the field of petrochemical industry. In particular, the present invention promotes thermal cracking of petroleum hydrocarbons by adding an additive and enhances this promotion by optimizing the convection section of the cracking furnace.

Background

Currently, thermal cracking of petroleum hydrocarbons is the primary source of ethylene. In the field of petrochemical industry, hydrocarbons such as ethane, propane, butane and naphtha are cracked in a cracking furnace to prepare low-carbon olefins such as ethylene and propylene under the conditions that the weight percentage of water and oil is about 30-70% and the temperature is about 700-900 ℃. The yields of ethylene and propylene vary between 24-55% and 15-18% due to the type of feed and the operating conditions, respectively. The cracking furnace includes a radiant section for heating a mixture of petroleum hydrocarbons and steam to thermally crack the petroleum hydrocarbons using radiant heat transfer generated by burning fuel in a burner, and a convection section for preheating reaction materials by convective heat transfer generated by combustion exhaust gas from the radiant section.

Although many improvements have been made to the disadvantages of high reaction temperature, high energy consumption, and severe coking in the process after decades of development, thermal cracking is still the most energy consuming process in the petrochemical industry. And the coke and carbon deposition need to be stopped for removing the coke after reaching a certain degree, thereby seriously restricting the production capacity of the cracking furnace. A series of technologies are used industrially to save energy and increase efficiency, physical means include three-dimensional reaction tube technology and ultrasonic tube cracking furnace system, and chemical means include coking inhibitor, catalytic cracking, initiation cracking and the like.

The Chinese patent CN101353590B uses a novel ultrasonic tubular thermal cracking system, at least one group of ultrasonic devices are installed in series outside a thermal cracking reaction furnace tube, and on the premise of not changing the existing device in a large scale, the high attached yield of an ethylene device can be improved by adding simple equipment, the occurrence of side reactions is reduced, and the selectivity of the cracking reaction and the economic benefit of the device are improved. The device can prolong the running period of the device, but does not change the reaction network of petroleum hydrocarbon thermal cracking, and has no obvious influence on the yield of olefins such as ethylene, propylene and the like.

Chinese patent CN107474869B is a catalyst for cracking oxide of hydrocarbon by filling in some or all of the area of the tubes arranged in the heating part of the tube furnace. In the steam cracking of hydrocarbons for the production of olefins, it is possible to improve the yield and selectivity of olefins, reduce fuel consumption due to excellent heat transfer efficiency, and extend decoking intervals by reducing the amount of coke deposited on the inner walls of tubes. The mixed catalyst is effective in increasing propylene selectivity, but thereby reducing the ethylene/propylene yield ratio.

The Chinese patent CN104611001B, the Chinese patent CN201710954641.4 and the Chinese patent CN110156554B all achieve the technical effects of improving the conversion rate of petroleum hydrocarbon, improving the yield of low-carbon olefin and inhibiting coking by adding auxiliary agents (such as alkali-containing aqueous solution, dendritic branched polymer, metal organic framework material loaded with polymer and the like).

The existing research shows that the petroleum hydrocarbon reaction network can be further modulated on the basis of a free radical cracking mechanism by introducing a free radical mode, and the free radical generated by cracking of an external auxiliary agent attacks the petroleum hydrocarbon to start a free radical chain reaction before the petroleum hydrocarbon self-cracks to generate the free radical, so that the technical effects of promoting the thermal cracking of the petroleum hydrocarbon, improving the yield of the low-carbon olefin and reducing the cracking reaction temperature are achieved.

Although the prior literature discloses the technical effect of generating free radicals to assist hydrocarbon cracking by thermal cracking of tree-like branched polymers or hyperbranched polymers, the thermal decomposition temperature difference of different polymers is obvious, different hydrocarbon cracking networks and polymer thermal cracking networks have matching relationship, and when the matching is not proper, the assistant can be failed. One of the mismatching can be described as: when the thermal decomposition temperature of one auxiliary agent is lower, the auxiliary agent is filled into a stream at a convection section (such as 300 ℃) with relatively low temperature for mixing, the auxiliary agent is thermally cracked to generate free radicals, but the hydrocarbons mixed with the auxiliary agent do not reach higher temperature, so that the free radicals cannot take effect; when the mixture is heated to the hydrocarbon thermal cracking temperature, the assistant is thermally decomposed, and the free radicals are annihilated, so that the assistant is finally ineffective.

Therefore, parameters such as the additive filling position and the additive filling concentration matched with petroleum hydrocarbon are determined according to the thermodynamic characteristics such as the thermal decomposition temperature of each additive, and the like, so as to realize the optimal matching of each petroleum hydrocarbon and each additive.

Therefore, it is necessary to design the material filling system in the convection section so that the additive cracking network and the petroleum hydrocarbon cracking network are matched with each other. This is the key to the implementation of the cracking technology of petroleum hydrocarbon promoted by the aid of the auxiliary agent, and the problem is solved by the patent.

Disclosure of Invention

The invention relates to a high-efficiency cracking method of petroleum hydrocarbon, wherein materials are filled in batches in a convection section of a cracking furnace, a cracking reaction is carried out in a radiation section after vaporization and preheating, gas-liquid separation is carried out on products through a cooling separation section, and cracking gas is led to a purification and refining section. The materials are divided into water, petroleum hydrocarbon, a mixture of water and an auxiliary agent and a mixture of petroleum hydrocarbon and an auxiliary agent, one or more auxiliary agents can be used simultaneously, and the substance type of the auxiliary agent and the concentration of the auxiliary agent can be adjusted.

In an alternative scheme of the invention, the convection section of the cracking furnace is modified, and one or more material auxiliary filling ports are added, so that auxiliary material filling can be realized on the premise of not changing the conventional device in a large scale, and the yield of low-carbon olefins such as ethylene in the petroleum hydrocarbon cracking furnace is further improved.

The auxiliary agent in the material comprises water-soluble hyperbranched polymers such as polyether, polyamide, polyimide, imine polymers and the like, and hyperbranched polymers which are modified by groups and have oil solubility.

The invention can achieve the technical effects of improving the conversion rate of petroleum hydrocarbon, improving the yield of low-carbon olefin and inhibiting coking, and the target products of the invention are low-carbon olefin such as ethylene.

Preferably, the filling position of the main filling material corresponds to an area of the convection section of the cracking furnace from normal temperature to 150 ℃; the filling position of the auxiliary filling material corresponds to the area with the temperature of 200-600 ℃ in the convection section of the cracking furnace. Typically, but not by way of limitation, in one embodiment of the invention, the plurality of material auxiliary charging ports distributed in the convection section of the cracking furnace may correspond to temperatures of 200, 300, 400, 500, 600 ℃ and the like in the convection section. Further, the fill ports at other temperature locations may be added for specific additives.

The invention has the advantages that:

on the premise of not changing the existing device on a large scale, the yield of the low-carbon olefins such as ethylene of the petroleum hydrocarbon cracking furnace can be improved by adding the auxiliary filling port of the convection section material and the auxiliary agent.

Can reduce the coking reaction rate and prolong the operation period of the cracking furnace.

Can reduce the cracking temperature, reduce the proportion of the deep cracking process and improve the utilization rate of materials.

Aiming at different petroleum hydrocarbons, the method can flexibly change the feeding mode by selecting a proper auxiliary agent and matching with the optimal auxiliary agent filling scheme, thereby achieving the technical effects of promoting the conversion rate of the petroleum hydrocarbons, reducing the cracking temperature and changing the product distribution and increasing the yield of target products, particularly ethylene.

Drawings

FIG. 1 is a schematic view of a pyrolysis furnace for thermal cracking of petroleum hydrocarbons.

Detailed Description

The hyperbranched polymer is a highly branched three-dimensional macromolecule, has multiple branching points, is not easy to tangle molecular chains, generally has rich terminal functional groups, and is easy to modify. The water-soluble hyperbranched polymer means that the hyperbranched polymer has better water solubility, and can be one or more of polyether, polyamide, polyimide and imine polymers; the hyperbranched polymer with oil solubility after group modification can be modified by groups to enable the hyperbranched polymer to show oil solubility.

The implementation process of the high-efficiency petroleum hydrocarbon cracking method generally comprises the following steps:

a. adding a main filling material into a zone of a convection section of the cracking furnace corresponding to the temperature of between normal temperature and 150 ℃; optionally, one or more auxiliary charging materials are not added or added in the zone of the convection section of the cracking furnace corresponding to the temperature of 200-600 ℃;

b. when materials are injected, the materials are introduced into the convection section to be vaporized and preheated according to any one of the following matching schemes, and then enter the radiation section to carry out cracking reaction:

scheme 1: filling all water required for cracking and 85-95 wt% of petroleum hydrocarbon required for cracking as main filling materials, and fully mixing the rest 5-15 wt% of petroleum hydrocarbon with a cracking auxiliary agent to be used as one or more main filling materials and/or auxiliary filling materials for filling;

scheme 2: all petroleum hydrocarbon required by cracking and 85-95 wt% of water required by cracking are used as main filling materials for filling, and the rest 5-15 wt% of water is mixed with a cracking auxiliary agent and then used as one or more main filling materials and/or auxiliary filling materials for filling;

c. and carrying out gas-liquid separation on the product through a cooling separation section, and leading the gas-phase product to a purification and refining section.

In one embodiment of the invention, a plurality of material auxiliary filling ports distributed in the convection section of the cracking furnace correspond to the temperature of the convection section and can be 200, 300, 400, 500, 600 ℃ and the like. One typical arrangement is shown in figure 1.

In a preferred embodiment, the mixture of water and adjuvant or the mixture of petroleum hydrocarbon and adjuvant is injected as one or more main and/or auxiliary charges according to the following flow distribution principles:

a. the mixture flow rate in the main filling material is not lower than 50% of the total mixture flow rate;

b. the auxiliary agent used simultaneously can be one or more, the selected auxiliary agent can be singly dissolved in water or petroleum hydrocarbon or a plurality of auxiliary agents can be dissolved in water or petroleum hydrocarbon together, and the mixture of each auxiliary agent and the water or petroleum hydrocarbon oil can be divided into one or more auxiliary filling materials.

As another preferable mode, when a mixture of water and an auxiliary agent or a mixture of petroleum hydrocarbon and an auxiliary agent is injected as an auxiliary injection material, the mixture may be injected directly in a liquid phase state or may be injected after being vaporized in advance, preferably, in a liquid phase.

Preferably, when the mixture of water and adjuvant or the mixture of petroleum hydrocarbon and adjuvant is injected in the gas phase, the vaporization temperature should not be higher than the thermal decomposition temperature of the adjuvant.

In a preferred embodiment, the mixing effect is enhanced by an enhancing mixing means such as stirring, heating, ultrasonic wave or the like when water or petroleum hydrocarbon is mixed with the auxiliary.

As a preferred mode, the auxiliary agent mixed and injected with water is a water-soluble hyperbranched polymer, and the auxiliary agent mixed and injected with petroleum hydrocarbon comprises a hyperbranched polymer which is modified by groups and has oil solubility; the content of the added auxiliary agent relative to the total petroleum hydrocarbon per unit time is between 100 and 2000 ppm.

Further preferably, the auxiliary agent is an oil-soluble hyperbranched polymer, 100 wt% of water and 95 wt% of petroleum hydrocarbon are used as main filling materials, and a petroleum hydrocarbon mixture dissolved with 5 wt% of the oil-soluble hyperbranched polymer is used as an auxiliary filling material.

Further preferably, for the auxiliary agent with lower thermal decomposition temperature, the auxiliary agent is preferably added in the zone with the corresponding temperature of 400-600 ℃ in the convection section of the cracking furnace; for the auxiliary agent with higher thermal decomposition temperature, the auxiliary agent is preferably added in the convection section of the cracking furnace corresponding to the area with the temperature of 200-400 ℃. More preferably, the auxiliary agent with the temperature lower than 400 ℃ corresponding to the maximum weight loss rate in the thermal decomposition process in the auxiliary agent is preferably added in the convection section of the cracking furnace corresponding to the area with the temperature of 400-600 ℃. The auxiliary agent with the temperature higher than 400 ℃ corresponding to the maximum weight loss rate in the thermal decomposition process in the auxiliary agent is preferably added in the zone with the temperature of 200-400 ℃ corresponding to the convection section of the cracking furnace.

The following examples are offered to those of ordinary skill in the art to make and evaluate the present invention, and are intended to be merely exemplary of the disclosure and not to limit the scope thereof. Although efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), some errors and deviations should be accounted for. The listed methods are exemplary only, and temperature, catalyst, concentration, reactant composition, and other process conditions may vary.

The expressions given in the examples for the thermodynamic characteristics of the auxiliaries, such as (180-: the thermal decomposition temperature range of the auxiliary agent, the temperature corresponding to the maximum weight loss rate in the thermal decomposition process of the auxiliary agent and the residual mass ratio of the auxiliary agent when the auxiliary agent is weightless to 600 ℃.

Example 1

Weighing water-soluble hyperbranched polymer polyamide (230-420, 370, 0), stirring and dissolving in water at 40 ℃ to prepare 1 wt% solution. Introducing water and mixed oil (the mass ratio of n-hexane, cyclohexane, 2-methylpentane and toluene is 3:3:3:1) into the device at normal temperature through a main material filling port according to the ratio of 1:2, and injecting a mixture of the water and the auxiliary agent into the device at 400 ℃ through an auxiliary filling port according to 10 wt% of the water at the main filling port. The conversion rate at 800 ℃ is 67%, the ethylene proportion in the product is 29%, the conversion rate of a comparison group with main and auxiliary materials filled from a main filling port is 64%, and the ethylene proportion is 28%.

Example 2

Weighing oil-soluble hyperbranched polymer polyamide (240-520, 450, 5%), stirring strongly at 40 ℃, dissolving in mixed oil (the mass ratio of n-hexane, cyclohexane, 2-methylpentane and toluene is 3:3:3:1) by auxiliary means such as ultrasonic waves and the like to prepare 1.5 wt% solution. Introducing water and mixed oil (the mass ratio of n-hexane, cyclohexane, 2-methylpentane and toluene is 3:3:3:1) into the device at normal temperature through a main material filling port according to the ratio of 1:2, and injecting a mixture of the oil and the auxiliary agent into the device at 200 ℃ according to 6 wt% of the mixed oil at the main filling port. The conversion rate at 800 ℃ is 69 percent, the ethylene proportion in the product is 30 percent, the conversion rate of a comparison group which is filled with the same amount of mixed oil without the added hyperbranched polymer through an auxiliary filling port is 61 percent, and the ethylene proportion is 27 percent.

Example 3

Oil-soluble hyperbranched polyether ester (150-340, 240, 0) is weighed and stirred at 40 ℃ to be dissolved in mixed oil (the mass ratio of n-hexane, cyclohexane, 2-methylpentane and toluene is 3:3:3:1) to prepare a 1.8 wt% solution. Introducing water and mixed oil (the mass ratio of n-hexane, cyclohexane, 2-methylpentane and toluene is 3:3:3:1) into the device at normal temperature through a main material filling port according to the ratio of 1:2, and injecting a mixture of the oil and the auxiliary agent into the device at 500 ℃ according to 10 wt% of the mixed oil at the main filling port. The conversion rate at 820 ℃ is 75%, the ethylene proportion in the product is 34%, the conversion rate of the comparative group, which adjusts the filling temperature of the auxiliary filling material from 500 ℃ to 200 ℃, is 68%, and the ethylene proportion is 31%.

Example 4

Weighing oil-soluble hyperbranched polymer polyamide (240-520, 450, 5%), stirring at 40 ℃, dissolving in mixed oil (the mass ratio of n-hexane, cyclohexane, 2-methylpentane and toluene is 3:3:3:1) to prepare 0.5 wt% solution which is used as an auxiliary filling material 1. Oil-soluble hyperbranched polymer polyimide (150-280,250,0) is weighed and stirred at 40 ℃ to be dissolved in mixed oil (the mass ratio of n-hexane, cyclohexane, 2-methylpentane and toluene is 3:3:3:1) to prepare 1.0 wt% solution which is used as an auxiliary filling material 2. Introducing water and mixed oil (the mass ratio of n-hexane, cyclohexane, 2-methylpentane to toluene is 3:3:3:1) into the device through a main material filling port at normal temperature according to the ratio of 1:2, injecting an auxiliary filling material 1 into the device through an auxiliary material filling port at 300 ℃ according to 10 wt% of the mixed oil at the main filling port, and injecting an auxiliary filling material 2 into the device at 500 ℃ according to 2 wt% of the mixed oil at the main filling port. The conversion rate at 800 ℃ is 67%, the ethylene proportion in the product is 28%, the conversion rate of a comparison group which is filled with the same amount of mixed oil without the added hyperbranched polymer through two auxiliary filling ports is 61%, and the ethylene proportion is 26%.

Claims

1. A method for efficiently cracking petroleum hydrocarbon is characterized by comprising the following steps:

a. adding a main filling material into a zone of a convection section of the cracking furnace corresponding to the temperature of between normal temperature and 150 ℃; and adding one or more auxiliary filling materials into the convection section of the cracking furnace corresponding to the region with the temperature of 200-600 ℃;

scheme 1: injecting all water required for cracking and 85-95 wt% of petroleum hydrocarbon required for cracking as main injection materials, and fully mixing the rest 5-15 wt% of petroleum hydrocarbon with an auxiliary agent to be used as one or more main injection materials and/or auxiliary injection materials for injection; the auxiliary agent mixed and injected with the petroleum hydrocarbon comprises an oil-soluble hyperbranched polymer prepared by modifying a water-soluble hyperbranched polymer by groups, and the content of the auxiliary agent added in unit time relative to the total petroleum hydrocarbon is between 100-2000 ppm;

scheme 2: all petroleum hydrocarbon required by cracking and 85-95 wt% of water required by cracking are used as main filling materials for filling, and the rest 5-15 wt% of water is mixed with an auxiliary agent and then used as one or more main filling materials and/or auxiliary filling materials for filling; the assistant mixed with water is water-soluble hyperbranched polymer, and the content of the assistant added in unit time relative to the total petroleum hydrocarbon is between 100 and 2000 ppm;

c. performing gas-liquid separation on the product through a cooling separation section, and leading the gas-phase product to a purification and refining section;

in the step b, the auxiliary agent with the temperature lower than 400 ℃ corresponding to the maximum weight loss rate in the thermal decomposition process in the auxiliary agent is added in the area with the temperature of 400-600 ℃ corresponding to the convection section of the cracking furnace; the auxiliary agent with the temperature higher than 400 ℃ corresponding to the maximum weight loss rate in the thermal decomposition process is added in the zone with the temperature of 200-400 ℃ corresponding to the convection section of the cracking furnace.

2. A method according to claim 1, wherein the mixture of water and adjuvant or the mixture of petroleum hydrocarbon and adjuvant is injected as one or more of the main and/or auxiliary charges with the flow distribution criteria as follows:

b. the auxiliary agents used simultaneously are one or more, the selected auxiliary agents can be singly dissolved in water or petroleum hydrocarbon or a plurality of auxiliary agents can be dissolved in water or petroleum hydrocarbon together, and the mixture of each auxiliary agent and the water or the petroleum hydrocarbon can be divided into one or more auxiliary filling materials.

3. The method of claim 1, wherein when the mixture of water and the adjuvant or the mixture of the petroleum hydrocarbon and the adjuvant is injected as the auxiliary injection material, the mixture may be directly injected in a liquid phase state or may be injected after being vaporized in advance.

4. The method of claim 1 or 3, wherein when the mixture of water and adjuvant or the mixture of petroleum hydrocarbon and adjuvant is injected in the gas phase, the vaporization temperature is not higher than the thermal decomposition temperature of the adjuvant.

5. The method of claim 1, wherein the water or petroleum hydrocarbon is mixed with the adjunct in a manner that enhances mixing by enhancing mixing means.

6. The method of claim 1, wherein the water-soluble hyperbranched polymer to be mixed with water for injection is one or more of polyether, polyamide, polyimide, and imine-based polymers.

7. The method of claim 1, wherein the adjuvant is an oil soluble hyperbranched polymer, and wherein 100 wt% water and 95 wt% petroleum hydrocarbon are used as the main fill material, and 5 wt% petroleum hydrocarbon mixture with the oil soluble hyperbranched polymer dissolved therein is used as the auxiliary fill material.