CN117946714A

CN117946714A - Method for treating waste material and application thereof

Info

Publication number: CN117946714A
Application number: CN202211324251.6A
Authority: CN
Inventors: 蒋冰; 李蔚; 张利军; 周丛; 石莹; 李宏光; 刘京川
Original assignee: Sinopec Beijing Chemical Research Institute Co ltd; China Petroleum and Chemical Corp
Current assignee: Sinopec Beijing Chemical Research Institute Co ltd; China Petroleum and Chemical Corp
Priority date: 2022-10-27
Filing date: 2022-10-27
Publication date: 2024-04-30

Abstract

The invention relates to the field of plastic and rubber recovery treatment, and discloses a treatment method and application of waste materials, wherein the method comprises the following steps: (1) Carrying out thermal cracking or catalytic cracking on the waste materials to obtain degraded oil; (2) In a steam cracking furnace, carrying out steam cracking reaction on the degraded oil to obtain low-carbon olefin; the steam cracking furnace comprises a convection section and a radiation section, wherein the degraded oil enters the radiation section to carry out steam cracking reaction after being mixed and heated to cross temperature by the convection section and dilution steam; wherein the cross temperature is 280-500 ℃ lower than the temperature of steam cracking reaction; the waste material is waste plastic and/or waste rubber. The treatment method of the waste material provided by the invention has the advantages of high production efficiency, difficult coking of equipment, contribution to the recycling utilization of waste plastics and waste rubber and provision of a new way for the preparation of low-carbon olefin.

Description

Method for treating waste material and application thereof

Technical Field

The invention relates to the field of plastic and rubber recovery treatment, in particular to a treatment method of waste materials and application thereof.

Background

Lower olefins such as ethylene, propylene and butadiene are important base stocks for the petrochemical industry. Currently, the process for producing low-carbon olefins is mainly a tube furnace petroleum hydrocarbon steam cracking process. The core equipment of the tube furnace petroleum hydrocarbon steam cracking process is a tube furnace (hereinafter referred to as a "cracking furnace"), and when cracking raw materials such as ethane, propane, naphtha and hydrogenated tail oil are heated to high temperature in the cracking furnace, carbon chain breaking chemical reaction occurs to generate low-carbon olefins such as ethylene, propylene, butadiene and the like.

Waste plastics and waste tires have a hydrogen content of about 13.5%, and are a very valuable resource in the situation of the current gradual shortage of fossil fuels. However, the main treatment modes of the existing waste plastics include landfill or discharge to natural environment (72%), incineration (14%), recycling (14%), and the like, but the problems of land pollution, air pollution and the like caused by the rough recycling mode still exist. Degradation oil produced in the chemical recovery process of waste plastics or waste tires has the characteristic of easy coking, and tends to coke in the convection section of the cracking furnace, namely in a relatively low-temperature area. Once the convection section is coked, the convection section cannot be removed by an on-line coking method, and the furnace is usually stopped for manual coke cleaning, so that the on-line time of the cracking furnace is greatly influenced, and the production efficiency and the yield are reduced. Therefore, although a series of waste plastics or waste tire pyrolysis technologies are developed in the prior art to generate the degradation oil of the waste plastics/waste tires, most of the produced degradation oil is directly burnt out as raw materials, and a large amount of resources are difficult to be effectively utilized.

Therefore, how to recycle and convert the waste plastics into products with high added value has very broad application prospect.

Disclosure of Invention

The invention aims to solve the problems of low recycling utilization rate of waste plastics or waste rubber and low production efficiency of a cracking furnace in conventional chemical recovery, and provides a waste material treatment method and application thereof.

In order to achieve the above object, an aspect of the present invention provides a method for treating waste materials, comprising the steps of:

(1) Carrying out thermal cracking or catalytic cracking on the waste materials to obtain degraded oil;

(2) In a steam cracking furnace, carrying out steam cracking reaction on the degraded oil to obtain low-carbon olefin;

The steam cracking furnace comprises a convection section and a radiation section, wherein the degraded oil enters the radiation section to carry out steam cracking reaction after being mixed and heated to cross temperature by the convection section and dilution steam;

Wherein the cross temperature is 280-500 ℃ lower than the temperature of steam cracking reaction;

the waste material is waste plastic and/or waste rubber.

In a second aspect the invention provides the use of the above process in the preparation of olefins.

The method for processing waste materials provided by the invention degrades waste plastics or non-rubber through a chemical recovery method to obtain degraded oil, the degraded oil can be directly used as a cracking raw material or is used as a cracking raw material for steam cracking after being processed through a hydrogenation process to prepare low-carbon olefin, and meanwhile, the problem that a cracking furnace (especially a convection section) is easy to coke when the waste plastics or waste tire degraded oil is used as the cracking raw material for steam cracking to prepare olefin in the existing steam cracking flow method is solved, so that the problem of low online rate is caused, and the production efficiency is improved.

The treatment method of the waste material is beneficial to the resource utilization of waste plastics and waste rubber, and provides a new way for preparing low-carbon olefin.

Drawings

FIG. 1 is a schematic view showing the structure of a steam cracker used in example 1 of the present invention;

FIG. 2 is a schematic view showing the structure of a convection section in a steam cracker employed in example 1 of the present invention;

FIG. 3 is a schematic view showing the arrangement position of the side wall burner in embodiment 3 of the present invention.

Description of the reference numerals

1. Convection section 3 radiation furnace tube of fan 2

4. Quenching boiler of combustion system 5 radiation section 6

7. Water supply 9 dilution steam of oil degradation 8 boiler

10. High-pressure steam 11 raw material preheating section 12 boiler feed water preheating section

13. Mixing heating section of ultrahigh-pressure steam superheating section 15 of dilution steam superheating section 14

16. 18 Radiation section furnace tube of flue gas cross section 17 gasification separation device

19. Sidewall burner

Detailed Description

The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.

The first aspect of the present invention provides a method of treating waste material comprising the steps of:

the waste material is waste plastic and/or waste rubber.

At present, chemical recycling and chemical recycling methods are regarded as the only sustainable recycling method for waste plastics or rubber. However, the existing pyrolysis technology of waste plastics or waste rubber generates degradation oil of waste plastics/waste rubber, but most of the produced degradation oil is directly burnt out as raw materials, and the effective recycling utilization is lacked. If the waste materials can be recycled, the low-carbon olefin with high added value is produced, which is beneficial to recycling of waste plastics and waste rubber and provides a new way for preparing the low-carbon olefin.

However, the degraded oil obtained in the chemical recovery process of waste materials, such as waste rubber or waste plastics, has the characteristic of easy coking in the steam cracking process, so when the oil is used as a raw material for steam cracking, the steam cracking furnace convection section is often required to be stopped for decoking treatment, and the problem of low online rate exists when the oil is used for olefin production.

In general, the main functions of the convection section of a steam cracking furnace are: preheating, gasifying and overheating the cracking raw material to cross temperature, and then entering a radiation section for cracking reaction; and recovering the waste heat in the flue gas of the radiation section. Under the conventional condition, the convection section has different tube row arrangement modes according to different process requirements, and the convection section approximately comprises the following heat exchange sections: the device comprises a raw material preheating section, a boiler feed water preheating section, a steam superheating section and a mixed heating section, wherein a raw material and dilution steam mixture is heated to a crossing temperature at an outlet of the mixed heating section and then enters a radiation section. For the steam cracking furnace, after the radiation section cokes to a certain extent, the coke layer attached to the pipe wall is cleaned through on-line coking, and then the feeding operation is continued; if coking is serious in the convection section, the coke cleaning operation is performed manually after the furnace is stopped and cooled, so that a great amount of time is occupied and the operation cannot be performed, the online rate of the steam cracking furnace is reduced, and the energy consumption and the operation cost are increased due to the fact that the steam cracking furnace is stopped and started while maintenance cost is consumed.

The inventor of the present invention has skillfully found during the research process that coking in the convection section can be reduced and the online rate of the treatment system can be improved by properly reducing the temperature in the convection section.

In the present invention, the "crossover temperature" refers to the radiant section inlet temperature (XOT), and the "temperature of steam cracking reaction" refers to the radiant section outlet temperature (COT).

Preferably, according to the present invention, the cross-over temperature is between 350 and 600 ℃, preferably between 430 and 550 ℃.

The temperature at the outlet of the radiant section will vary depending on the pyrolysis feedstock. In order to obtain higher yield benefits of the cleavage product, the steam cleavage reaction is preferably carried out at a temperature of 750-850 ℃, preferably 790-820 ℃.

According to the invention, the source of the waste plastics or rubber is not particularly required, and can be from waste plastics, waste tires and the like. Preferably, the waste plastics include, but are not limited to, one or more of polyethylene, polypropylene and polystyrene. The waste rubber can be from rubber products such as waste tires, waste gloves, waste sponges and the like.

In the invention, the waste material is subjected to thermal cracking or catalytic cracking, and the complex macromolecules are broken into small molecules, so that gaseous small molecules and degraded oil are obtained. In the present invention, the specific method and conditions for the thermal cracking or catalytic cracking are not particularly limited, and may be carried out by conventional methods known in the art. Preferably, the conditions of the catalytic cracking include: the reaction temperature is 100-500 ℃, the reaction pressure is 0.1-3MPa, and the mass airspeed of the waste material is 500-2000h ^-1.

The present invention is not particularly limited, and a catalyst which can be used for catalytic cracking reaction, which is well known to those skilled in the art, may be used. For example, alumina carrier supported metal Cr and/or Ni catalysts.

Preferably, the conditions of thermal cracking include: the reaction temperature is 300-700 ℃ and the reaction pressure is 0.1-5MPa.

The degraded oil obtained by adopting the preferred embodiment is subjected to steam cracking, so that the higher oil yield of waste materials is obtained, and the overall benefit of steam cracking is improved.

In the present invention, the catalytic cracking or thermal cracking apparatus is not particularly limited, and a reactor conventional in the art, such as a fixed bed reactor or a fluidized bed reactor, preferably a fixed bed reactor, may be employed.

In order to further reduce coking in the convection section of the steam cracking furnace and improve the online rate of the steam cracking furnace, according to a preferred embodiment of the present invention, the degraded oil may remove the non-gasified heavy components during the heating and gasification of the convection section in the steam cracking furnace (through the gasification separation device arranged in the convection section), and the remaining light components are gasified and heated to cross temperature to enter the radiation section. The present invention is not particularly limited as long as it is capable of removing the heavy components of the degraded oil which are not gasified in the heating gasification process in the convection section, so that the light components therein are heated to cross the temperature and enter the radiation section.

In the invention, the heavy component refers to a component with a vaporization temperature of more than 400 ℃ in the degraded oil, and the light component refers to a component with an initial boiling point of about 400 ℃ in the degraded oil.

In the present invention, the mixing mode of the degradation oil and the dilution steam is not particularly limited, and may be adjusted according to actual production requirements, for example, the dilution steam may be introduced into the convection section at one time in a one-stage injection mode to be mixed with the degradation oil; the convection section can also be introduced by means of sectional injection and mixed with the degraded oil step by step.

According to a preferred embodiment of the invention, the dilution steam is mixed with the degraded oil in a single injection, the dilution steam having a temperature of 400-700 ℃, preferably 450-650 ℃.

According to the invention, the degradation oil is preferably used in a weight ratio to the dilution steam of 1-4:1, preferably 1.5-2.5:1. Under the preferable condition, coking of the degraded oil in the steam cracking process is reduced, and the yield of the low-carbon olefin is improved.

According to the invention, preferably, the method further comprises: and preheating the degraded oil in the convection section before mixing the dilution steam with the degraded oil to obtain the preheated degraded oil.

Preferably, the temperature of the preheated degraded oil is 200-400 ℃, more preferably 250-350 ℃.

To further reduce coking in the convection section when the degraded oil of the waste material is subjected to steam cracking, preferably dilution steam may be mixed with the degraded oil in the convection section by means of two-stage injection. The two-stage injection mode is to inject dilution steam into the convection section twice, and mix the dilution steam with degraded oil: the method comprises the steps of injecting high-temperature dilution steam for one time, diluting and preheating degraded oil, mixing the diluted degraded oil with ultrahigh-temperature steam, heating to cross temperature, and then delivering to a radiation section.

Preferably, the two-stage injection method comprises the following steps:

(1-1) mixing high temperature steam with the degraded oil, and diluting and preheating the degraded oil;

(1-2) mixing ultra-high temperature steam with the product of step (1-1).

According to the invention, the high temperature steam preferably has a temperature of 150-450 ℃, preferably 180-350 ℃.

According to the invention, the ultra-high temperature steam preferably has a temperature of 400-700 ℃, preferably 450-650 ℃.

Preferably, the weight ratio of the high temperature steam to the amount of the degradation oil is 0.3-1:1.

Preferably, the weight ratio of the ultra-high temperature steam to the amount of the product of step (1-1) on the basis of the degraded oil quality is 0.2 to 0.6:1.

According to the invention, the degradation oil obtained from waste plastics or waste rubber has larger degradation oil property difference due to different raw material components, and partial raw materials with poor quality cannot be directly used as steam cracking raw materials and need to be hydrotreated. Preferably, the method further comprises: and (3) contacting the degraded oil with a hydrogenation catalyst to carry out hydrogenation reaction to obtain a fraction after hydrogenation of the degraded oil, and then sending the fraction into a steam cracking furnace.

In the present invention, the hydrogenation reaction may be performed by a method conventional in the art, and the hydrogenation catalyst may be selected by a person skilled in the art according to actual needs, as long as the catalyst capable of catalyzing the hydrogenation reaction is applicable to the present invention, and the hydrogenation catalyst may be a noble metal catalyst, for example, the hydrogenation catalyst is a platinum and/or palladium catalyst supported on an alumina carrier.

The invention has a wide selection range of specific conditions for the hydrogenation reaction, and the person skilled in the art can select the specific conditions according to actual needs. Preferably, the hydrogenation reaction conditions include: the reaction temperature is 200-400 ℃, preferably 250-350 ℃; the reaction pressure is 2-4MPa, preferably 2.5-3.5MPa, and the hydrogen-oil ratio is 100-400:1, preferably 150-350:1. by adopting the preferred embodiment, coking of the degraded oil in the steam cracking process is reduced, and the yield of the low-carbon olefin is improved.

According to a preferred embodiment of the invention, wherein the method further comprises: and cooling and separating the steam-cracked product to obtain the low-carbon olefin.

Preferably, the reacted material is cooled and separated in a quench boiler.

In the present invention, the method may further include: the material obtained after steam cracking in the radiation section is cooled in a quenching device and separated into cracking gas and steam. The separated steam enters a steam drum to carry out gas-liquid separation, the separated high-pressure steam can enter a convection section to be heated so as to obtain ultrahigh-pressure steam, and the separated water can be used as cooling water of a quenching heat exchanger; the pyrolysis gas enters a subsequent separation device through a pyrolysis gas main pipe to separate out a target product. High-temperature flue gas generated by combustion in the radiation section enters the convection section through the flue gas crossing section.

According to a preferred embodiment of the invention, the method further comprises: in the radiation section, heat supply is added to the first-pass furnace tube part. The method of increasing heating may include providing an enhanced heat transfer element (in the radiant section) and/or providing an enhanced heating device (in the first pass furnace section of the radiant section). If the radiation section book is provided with a certain number of enhanced heat transfer elements, the heat supply can be increased by increasing the number of the enhanced heat transfer elements or replacing the heat transfer elements with better enhanced heat transfer effect.

Preferably, the enhanced heat transfer element increases the heat transfer coefficient of the furnace tube at the location where the enhanced heat transfer element is mounted by 50-800% compared with the light tube. The light pipe refers to a furnace tube without an enhanced heat transfer element. That is, after the reinforced heat transfer element is installed, the heat transfer coefficient of the installation part on the furnace tube is 1.5-9 times that of the heat transfer coefficient before installation.

In the present invention, the enhanced heat transfer element is not particularly limited as long as it facilitates heat transfer from the radiation section. For example, the enhanced heat transfer element may be a spiral flight insert, a twisted ribbon insert, a cross-zigzag insert, a coil core insert, a wire wound porous body, a spherical matrix insert, or the like. The same enhanced heat transfer elements can be arranged at different positions of the radiant section furnace tube, and different enhanced heat transfer elements can be respectively arranged at different parts of the furnace tube.

In the invention, the enhanced heat supply device is used for improving the heat transfer efficiency of the primary furnace tube, and any enhanced heat supply device capable of achieving the purpose can be suitable for the invention.

Preferably, the enhanced heating device enhances the heat supply of the raw materials after entering the radiant section one-pass furnace tube. More preferably, the enhanced heating device increases the heat supply of the corresponding position of the primary pipe by 1-50% compared with the case of not arranging the enhanced heating device.

In the invention, in order to achieve the purpose of enhancing heat supply of the primary furnace tube, an enhanced heat supply device can be additionally arranged on the side wall of the hearth of the primary furnace tube. The furnace wall of the primary furnace tube can be modified and designed to enhance the heat supply of the primary furnace tube, for example, a reflection enhancing element can be arranged on the furnace wall, or the reflection angle of the furnace wall can be changed, so that the radiation heat supply of the primary furnace tube is enhanced.

Preferably, the enhanced heating device comprises a burner and/or a reflection enhancing element arranged on the side wall of the upper furnace chamber of the primary furnace tube.

On the other hand, the steam cracking furnace adopted in the method also belongs to the protection scope of the invention. The steam cracking furnace comprises: a convection section and a radiation section connected in series;

In the invention, the temperature of the material at the outlet of the convection section is lower due to the reduction of the cross temperature, and after the material enters the radiation section, the material entering the radiation section can reach the reaction temperature after being heated for a longer time. The inventor of the invention also discovers in the research process that in order to reduce the influence of lower temperature of the outlet material of the convection section on the reaction process, the heat supply efficiency of the radiation section can be improved by arranging a reinforced heat supply device in the radiation section of the steam cracking furnace, so that the temperature rising rate of the material of the radiation section is improved, and the material reaches the reaction temperature as soon as possible.

According to a preferred embodiment of the invention, the radiant section comprises 2-6 pass furnace tubes, wherein a portion of one pass furnace tube is provided with enhanced heating means. The features of the enhanced heating device are as described above and will not be described in detail herein.

According to a preferred embodiment of the invention, the radiant section adopts a two-pass furnace tube.

Preferably, the two-pass furnace tube is a type 2-1 radiation furnace tube or a type 4-1 radiation furnace tube. Namely, in the two-pass furnace tube, the first pass is two parallel vertical inlet tubes, and the second pass is a vertical outlet tube, so that a 2-1 type radiation furnace tube is formed. Or the first pass is four parallel vertical inlet pipes, and the second pass is a vertical outlet pipe, so that a 4-1 type radiation furnace tube is formed.

According to a preferred embodiment of the present invention, the ratio of the inner diameter of the outlet tube to the inner diameter of the inlet tube of the radiant section furnace tube is greater than 1 and less than or equal to 2.5.

Preferably, the inlet tube has an inner diameter of 25-70mm, more preferably 40-65mm.

Preferably, the outlet tube has an inner diameter of 45-120mm, more preferably 60-95mm.

In order to further enhance the heat transfer of the radiant section, according to a preferred embodiment of the present invention, the radiant section further comprises an enhanced heat transfer element mounted to the radiant section furnace tube. The features of the enhanced heat transfer element are as described above and will not be described in detail herein.

In order to further reduce the coking in the convection section, in particular in the case of steam cracking with heavy cracking raw materials (such as waste plastics or degradation oils produced in total in the course of chemical recovery of waste tires), according to a preferred embodiment of the invention the pyrolysis furnace is further provided in the convection section with a gasification separation device for removing the non-gasified heavy components of the degradation oils in the convection section. The present invention is not particularly limited as long as it is capable of removing the heavy components of the degraded oil which are not gasified in the heating gasification process in the convection section, so that the light components therein are heated to cross the temperature and enter the radiation section.

According to a preferred embodiment of the present invention, the steam cracker further comprises a high pressure drum, a combustion system and a quench boiler. The material obtained after the radiation section pyrolysis can be cooled in a quenching boiler and separated into pyrolysis gas and steam. The separated steam enters a steam drum to carry out gas-liquid separation, the separated high-pressure steam can enter a convection section to be heated so as to obtain ultrahigh-pressure steam, and the separated water can be used as cooling water of a quenching heat exchanger; the pyrolysis gas enters a subsequent separation device through a pyrolysis gas main pipe to separate out a desired target product. High-temperature flue gas generated by combustion in the radiation section enters the convection section through the flue gas crossing section.

In the present invention, in order to make full use of the heat of the high-temperature flue gas from the radiant section, the convection section of the pyrolysis furnace may be provided with a plurality of sections for recovering heat. Typically, the convection section may be provided with a feed preheating section, a boiler feedwater preheating section, a dilution steam superheating section, an ultra-high pressure steam superheating section, and a hybrid heating section. The feedstock preheating stage is typically used to preheat the pyrolysis feedstock. The boiler feed water preheating section is typically used to preheat the boiler feed water supplied to the drum. The dilution steam superheating section is typically used to preheat dilution steam (e.g., steam). The super-high pressure steam superheating section is typically used to heat high pressure steam from a drum to obtain super-high pressure steam. The hybrid heating section is typically used to heat the degraded oil to a cross-over temperature. In the preferred embodiment, in the convection section, a mixed heating section, an ultrahigh pressure steam superheating section, a dilution steam superheating section, a boiler feed water preheating section, and a raw material preheating section are preferably provided in this order along the flow direction of the high-temperature flue gas.

The convection section preferably comprises a first tube group of the convection section (comprising a raw material preheating section, a boiler feed water preheating section, a dilution steam superheating section, an ultrahigh pressure steam superheating section and a mixed heating section) and a second tube group of the convection section (comprising a mixed heating section). The degradation oil is fully gasified in the first tube group of the convection section, so that the steam cracking effect is effectively improved.

In order to further improve the heat transfer efficiency of the radiant section (one-pass furnace), the radiant section furnace tubes of the steam cracking furnace can be arranged in a plurality of large groups, wherein each large group comprises a plurality of multi-pass furnace tubes. When the radiant section furnace tubes are arranged, one-pass tubes of the same group of furnace tubes are arranged in a concentrated mode. The radiant heat transfer to the primary tube is increased over the 1/3 height of the radiant section from the inlet to the upper portion.

Preferably, the radiation furnace tube is vertically arranged in the radiation section.

The present invention will be described in detail by examples.

The product gas composition gases in the examples were measured by gas chromatography.

The structure of the steam cracking furnace adopted in the embodiment is shown in fig. 1, and the steam cracking furnace comprises: the device comprises a fan 1, a convection section 2, a radiation furnace tube 3, a combustion system 4, a radiation section 5 and a quenching boiler 6, wherein a material outlet of the convection section 2 is connected with a material inlet of the radiation section 5. The convection section of the steam cracking furnace comprises a raw material preheating section, a boiler feed water preheating section, a dilution steam superheating section, an ultrahigh pressure steam superheating section and a mixed heating section. Referring to fig. 2, in the pyrolysis furnace, after the high-pressure steam from the steam drum is heated by the super-pressure steam superheating section 14, high-pressure steam 10 is generated, and the separated high-pressure steam can enter the convection section for heating; the degraded oil 7 (namely cracking raw material) enters a convection section, is preheated in a raw material preheating section 11, enters a mixing heating section 15 for preheating, and then enters a radiation section; the boiler feed water 8 enters a boiler feed water preheating section 12, enters a steam drum after being preheated, the dilution steam 9 is mixed with the preheated degradation oil after being preheated by a dilution steam superheating section 13, the degradation oil is gasified and passes through a gasification separation device 17, wherein the light fraction of the gas phase enters a mixing heating section 15 together with the dilution steam, and the heavy fraction of the liquid phase is sent to other device units (not shown in fig. 2). In the hybrid heating section 15, the preheated degraded oil is heated to a cross-over temperature. The radiation section is connected with the quenching boiler through a pipeline and is used for conveying the cracking product to the quenching boiler and cooling and separating the cracking product to obtain the low-carbon olefin.

Example 1

(1) And (3) performing thermal cracking of the waste plastics by taking the tubular fixed bed as a reactor to obtain waste plastic degradation oil. The waste plastic comprises mixed plastic with polypropylene, polystyrene and polyvinyl chloride as main components, wherein the three main components account for 30wt%, 30wt% and 30wt% respectively, and the rest plastics account for 10wt%. The thermal cracking reaction temperature is 520 ℃, the reaction pressure is 2MPa, and the oil yield is 78%. Then, the obtained degraded oil is hydrotreated to obtain a hydrogenated fraction of the waste plastic degraded oil, wherein the hydrogen-oil ratio is 300:1, reaction pressure 3.5MPa, reaction temperature 330 ℃, hydrogenation catalyst used is 3wt% Pt/Al ₂O₃, and the basic property pair of the fraction after the waste plastic degradation oil is hydrogenated is shown in Table 1.

(2) In the steam cracking furnace shown in fig. 1, the fraction after the degradation oil is hydrogenated is subjected to steam cracking reaction. The radiation furnace tube 3 adopts a two-pass 2-1 furnace tube, the inlet tube diameter of the furnace tube is 51mm, and the tube length of the furnace tube is 13.3m; the outlet pipe diameter of the furnace pipe is 73mm, and the length of the furnace pipe is 13.3m.

In the convection section 2, the fraction after the hydrogenation of the degraded oil at 60 ℃ is mixed with high-temperature steam at 400 ℃ for dilution and preheating, and the dosage weight ratio of the high-temperature steam to the degraded oil is 0.6:1; the preheated degradation oil is 180 ℃; then injecting ultra-high temperature steam at 600 ℃, wherein the weight ratio of the ultra-high temperature steam to the degradation oil is 0.3:1; and heating to cross the temperature, and then entering the radiation furnace tube 3 to carry out steam cracking reaction. The crossover temperature (XOT) was 450 ℃. The outlet temperature (COT) of the radiation section of the steam cracking furnace was 790 ℃, namely, the cross temperature was 340 ℃ lower than the temperature of the steam cracking reaction, the feeding amount of the degraded oil was 58000kg/h, the dilution steam amount (total amount of high temperature steam and ultra-high temperature steam) was 52200kg/h, and the main composition of the cracking product was shown in Table 2.

The operation of the cracking furnace was carried out in accordance with example 1, with a period of 60 days, 5 times a year with an on-line coke burn time of 2 days each. In the embodiment, the cross temperature of the materials is reduced, so that the cracking reaction in the convection section is effectively reduced, the coking is reduced, and the decoking of the convection section is not required, thereby prolonging the on-line time.

TABLE 1

Project	Waste plastic degradation oil	Waste plastic degradation oil hydrogenation product
			Density (20 ℃ C.) kg/m ³	833.6	824.0
Distillation range, DEG C	140-600	84-530
			S，μg/g	360	108
N，μg/g	630	192
			Si，μg/g	46	＜1
Cl，μg/g	284	＜0.5
			Metal content, μg/g
Fe	1.0	＜1
			Ca	1.0	＜1
Mass composition
			Paraffin wt%	28.4	38.8
Total naphthene/olefin wt%	55.3	38.9
			Total arene wt%	26.3	22.3

TABLE 2

Comparative example 1

According to the same method as that in example 1, except that the radiation furnace tube 3 adopts a two-pass type 2-1 furnace tube, the inlet tube of the furnace tube is 51mm, and the length of the furnace tube is 12.8m; the outlet pipe diameter of the furnace pipe is 73mm, and the length of the furnace pipe is 12.8m. The cross temperature (XOT) was 520 ℃, the radiant section outlet temperature (COT) of the steam cracker was 790 ℃, and the cross temperature was 270 ℃ lower than the cracking temperature of the radiant section.

According to the operation of the comparative example 1, the operation period of the cracking furnace is 60 days, the convection section is decoked once in one year (7 days, the furnace is additionally stopped and opened once respectively), and the on-line coke burning is carried out for 5 times.

As can be seen from a comparison of example 1 and comparative example 1, example 1 reduced the cross-over temperature of the feed, and the reduction in cross-over temperature effectively reduced coking in the convection section compared to comparative example 1 (520 ℃). In order to ensure that the raw materials acquire enough heat in the radiant section, the lengths of the inlet pipe and the outlet pipe of the radiant furnace pipe 3 are respectively increased by 0.5 meter.

Example 1 compared with comparative example 1, the on-line time of the cracking furnace is increased by 7 days within one year, and the yield of a large amount of products is increased, and the yield of only triene (ethylene, propylene and butadiene) products is increased by 3696 tons. For example, according to the average product unit price of 7000 Yuan-ren-nationality/ton, the yield of the triene product is increased to 2587 Yuan-ren-nationality. In addition, example 1 also saves a lot of starting, stopping and maintenance costs compared to comparative example 1.

Example 2

The procedure of example 1 was followed, except that the pyrolysis feedstock used in step (2) was a degraded oil of waste plastics which had not been hydrotreated. The main composition of the cleavage product is shown in Table 2.

Example 3

The same processing system as in example 1 was used, except that side wall burners 19 (see FIG. 3) were arranged 3 meters from the top of the radiant section at positions corresponding to the one pass tube row of radiant section tubes 18. The radiation furnace tube 3 adopts a two-pass 2-1 furnace tube, the inlet tube diameter of the furnace tube is 49mm, and the tube length of the furnace tube is 13.5m; the outlet pipe diameter of the furnace pipe is 71mm, and the length of the furnace pipe is 13.5m. The ratio of the inner diameter of the outlet pipe to the inner diameter of the inlet pipe of the furnace pipe in the radiation section is 1.45.

The specific treatment method comprises the following steps:

(1) The procedure was followed as in example 1.

(2) In the convection section 2, the degraded oil fraction at 60 ℃ is mixed with high-temperature steam at 400 ℃ for dilution and preheating, and the weight ratio of the high-temperature steam to the degraded oil is 0.6:1; the preheated degradation oil is 180 ℃; then injecting ultra-high temperature steam at 600 ℃, wherein the weight ratio of the ultra-high temperature steam to the degradation oil is 0.3:1; and heating to cross the temperature, and then entering the radiation furnace tube 3 to carry out steam cracking reaction. The crossover temperature (XOT) was 430 ℃. The outlet temperature (COT) of the radiation section of the steam cracking furnace is 790 ℃, and the radiation furnace tube 3 is additionally provided with an enhanced heat transfer element, so that the heat transfer coefficient of the installation part is improved by 500 percent compared with that of a light pipe. The main composition of the cleavage product is shown in Table 2.

It can be seen from comparison that by enhancing the heating device, the radiation heat transfer of the upper part of the primary tube is enhanced (the heat supply of the corresponding position of the primary tube is increased by 20% compared with that of the primary tube when no burner is arranged), the temperature of the primary tube is quickly raised after the material enters the radiant section, and the same residence time of a high temperature region is reached under the conditions that the tube length of the primary tube is the same as that of the comparative example 1 and the temperature of a crossing section is lower, so that the equivalent product yield and the burning period of the radiant section are obtained.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.

Claims

1. A method of disposing of waste material comprising the steps of:

the waste material is waste plastic and/or waste rubber.

2. A method according to claim 1, wherein the cross-over temperature is 350-600 ℃, preferably 430-550 ℃;

preferably, the steam cracking reaction is carried out at a temperature of 750-850 ℃, preferably 790-820 ℃.

3. The method according to claim 1 or 2, wherein the waste plastic is selected from at least one of polyethylene, polypropylene and polystyrene;

preferably, the catalytic cracking comprises: under the condition of catalytic cracking reaction, waste materials are contacted with a catalytic cracking catalyst to obtain degraded oil;

Preferably, the conditions of the catalytic cracking include: the reaction temperature is 100-500 ℃, the reaction pressure is 0.1-3MPa, and the mass airspeed of the waste material is 500-2000h ^-1;

4. A method according to any one of claims 1-3, wherein the dilution steam is mixed with the degraded oil by means of a one-stage injection, the dilution steam having a temperature of 400-700 ℃, preferably 450-650 ℃.

5. The method according to claim 4, wherein the weight ratio of the amount of degraded oil to dilution steam is 1-4:1, preferably 1.2-2.5:1.

6. The method of claim 4, wherein the method further comprises: preheating the degraded oil in a convection section before mixing dilution steam with the degraded oil to obtain preheated degraded oil;

Preferably, the temperature of the preheated degraded oil is 180-400 ℃, more preferably 150-350 ℃.

7. A method according to claims 1-3, wherein the dilution steam is mixed with the degraded oil in a two-stage injection;

preferably, the two-stage injection method comprises the following steps:

(1-2) further heating the mixture of ultra-high temperature steam and step (1-1);

Preferably, the temperature of the high temperature steam is 150-450 ℃, preferably 180-400 ℃;

Preferably, the temperature of the ultra-high temperature steam is 400-700 ℃, preferably 450-650 ℃;

preferably, the weight ratio of the high-temperature steam to the amount of the degradation oil is 0.3-1:1, a step of;

preferably, the weight ratio of the ultra-high temperature steam to the amount of the degradation oil is 0.2-0.6:1.

8. The method of claim 7, wherein the method further comprises: the degraded oil is contacted with a hydrogenation catalyst to carry out hydrogenation reaction to obtain a fraction after the hydrogenation of the degraded oil, and then the fraction is sent into a steam cracking furnace;

Preferably, the hydrogenation reaction conditions include: the reaction temperature is 200-400 ℃, preferably 250-350 ℃; the reaction pressure is 2-4MPa, preferably 2.5-3.5MPa, and the hydrogen-oil ratio is 100-400:1, preferably 150-350:1.

9. The method according to any one of claims 1-8, wherein the method further comprises: and separating the product after steam cracking to obtain the low-carbon olefin.

10. Use of the process of any one of claims 1-9 in the preparation of olefins.