A method for capturing and converting CO2 generated by pyrolysis of waste rubber

Abstract

A method for capturing and converting CO2 generated by pyrolysis of waste rubber, comprising the following steps: (1) pyrolyzing pretreated waste tires at high temperature to generate gas and solid products; (2) the gas generated during the pyrolysis process passes through a gas-solid separator and a fractionation tower in sequence to obtain a gas phase component, a gasoline fraction, a diesel fraction, and tar; (3) the gas phase component is purified by a gas condenser and a selective adsorption unit to remove impurities to obtain a purified gas phase component, and an organic alcohol amine absorbent is used to capture the CO2 in the purified gas phase component, and the separated gaseous hydrocarbons are collected; (4) at least 30-50% of the captured CO2 is converted into methanol by a thermal catalytic hydrogenation method; (5) the remaining CO2 is reinjected into the bottom of the pyrolysis reactor. The method solves the CO2 emission problem in the prior art and significantly improves the yield of light oil products, and realizes the resource utilization of CO2.

Description

Technical Field

[0001] The invention relates to the technical field of waste tire resource utilization, and in particular to a system and method for capturing and converting CO2 generated during the pyrolysis of waste rubber. Background Art

[0002] With the continuous growth of global tire consumption, the treatment of waste tires has become an urgent problem to be solved. The main component of waste tires is rubber, which has the characteristics of stable chemical properties, heat resistance, cold resistance, and high biological tolerance. It is difficult to decompose naturally in nature. At present, the main treatment methods for waste tires include retreading, incineration, pyrolysis treatment, etc. Among them, pyrolysis technology, as one of the main means of resource utilization of waste tires, can minimize the emission of pollutants and convert waste tires into usable liquid fuels, solid carbon black and gas. It has been widely used.

[0003] However, a large amount of CO2 is produced during the pyrolysis of waste tires, which not only affects the environmental friendliness of the pyrolysis process, but also wastes precious carbon resources.

[0004] In the existing technology, CO2 capture and conversion technology has been applied in some industrial fields, but CO2 capture and conversion in the waste tire pyrolysis process still faces technical and economic challenges. Therefore, it is urgent to develop an efficient CO2 capture and conversion system that can capture CO2 in the waste tire pyrolysis process and convert it into valuable chemicals or energy.

[0005] CN117957296A discloses a method and system for recovering recycled carbon dioxide, wherein pyrolysis flue gas and / or pyrolysis gas from pyrolysis of waste plastics can be treated in an absorption system to form a recovered CO2 stream containing recycled carbon dioxide, and at least part of the CO2 stream can be introduced into a gasification facility as a raw material.

[0006] CN117980058A discloses a method and system for recovering recycled carbon dioxide, which can reduce the carbon footprint and global warming potential of chemical recovery facilities. More particularly, pyrolysis gases from waste plastic pyrolysis can be processed in an absorption system to form a recovered CO2 stream containing recycled carbon dioxide. The carbon dioxide recovery method and system help alleviate global warming. Summary of the invention

[0007] The purpose of the present invention is to provide a system and method for capturing and converting CO2 in the process of pyrolysis of waste tires to solve the CO2 emission problem in the prior art and significantly improve the yield of light oil products, and realize the resource utilization of CO2.

[0008] It is generally believed that the pyrolysis reaction is a reaction in which a solid phase decomposes into a gas phase. According to the principle of chemical reaction equilibrium, low pressure conditions are conducive to the pyrolysis reaction. However, the pyrolysis reaction of polymer compounds is a complex reaction system. In the reaction system, a cracking reaction occurs in which the polymer macromolecules are decomposed into hydrocarbon molecules with longer carbon chains. At the same time, the generated hydrocarbon molecules or long-chain hydrocarbon radicals are further decomposed into low-molecular hydrocarbons with lower carbon chains. In addition, the low-carbon chain hydrocarbon radicals undergo isomerization reactions. The inventors of the present application have found that the yield of hydrocarbon products with specific carbon chain lengths can be increased by controlling the concentration of carbon dioxide in the pyrolysis reaction system within a specific range and adjusting the reaction temperature and pressure. Based on the above findings, the inventors propose a method for capturing and converting CO2 produced by pyrolysis of waste rubber to increase the yield of diesel fractions.

[0009] A method for capturing and converting CO2 generated by pyrolysis of waste rubber, comprising the following steps:

[0010] (1) Pyrolyzing the pre-treated waste tires at high temperature to generate gas and solid products;

[0011] (2) The gas generated during the pyrolysis process passes through a gas-solid separator and a distillation tower in sequence to obtain gas phase components, gasoline fraction, diesel fraction, and tar;

[0012] (3) wherein the gas phase component is purified by a gas condenser and a selective adsorption unit to remove impurities, thereby obtaining a purified gas phase component, and an organic alcohol amine absorbent is used to capture CO2 in the purified gas phase component, and the separated gaseous hydrocarbons are collected;

[0013] (4) At least 30-50% of the captured CO2 is converted into methanol through thermal catalytic hydrogenation;

[0014] (5) The remaining CO2 is reinjected into the bottom of the pyrolysis reactor.

[0015] The pretreatment in step (1) includes cleaning, crushing, and separation of impurities; the particle size after crushing is less than 1 cm, preferably less than 0.5 cm, and more preferably less than 1 cm; the impurities include non-pyrolyzable stones and metal wires.

[0016] In step (1), the pyrolysis pressure is not less than 7.38 MPa, and the temperature is 300-600°C. More preferably, the pyrolysis pressure is 7.5-10 MPa, and the temperature is 350-500°C. The volume content of carbon dioxide in the pyrolysis atmosphere is not less than 20%, preferably 25-40%. The pyrolysis is carried out under CO2 and an inert atmosphere, and the inert gas introduced is one or more of nitrogen and argon.

[0017] The gas in step (1) includes hydrocarbons, sulfides and solid particles; the solid particles are carbon black and other incompletely burned solid residues; the adsorption material is activated carbon or molecular sieve.

[0018] The gas-solid separator in step (2) is one or more of a cyclone separator, an electrostatic separator, and a filter.

[0019] The gas phase component in step (3) is cooled in a gas condensation tower to remove water vapor therein, and then further removed from the gas phase component by a selective adsorption unit to remove harmful gases such as sulfides and trace hydrocarbons, thereby obtaining a purified gas phase component; the organic alcohol amine absorbent is one or more of monoethanolamine MEA and diethanolamine DEA.

[0020] The thermal catalytic hydrogenation method in step (4) is carried out under the action of a copper-based catalyst; the reaction conditions are 200-300°C, 3-5 MPa; the loading amount of the copper-based catalyst is 10-20wt%, and the carrier is activated carbon or molecular sieve.

[0021] The CO2 reinjected in step (5) needs to be pressurized to above 7.38 MPa using a compressor and heated to above 300°C before being injected into the pyrolysis reactor.

[0022] Beneficial technical effects of the present invention: The method of the present invention can significantly reduce the pyrolysis temperature, reduce excessive cracking of hydrocarbon substances, reduce the generation of gaseous hydrocarbons, and increase the yield of liquid hydrocarbon fractions, especially diesel fractions, in the pyrolysis products by partially refluxing the carbon dioxide generated by pyrolysis, which is beneficial to energy conservation and emission reduction and reduces CO2 emissions. The overall emission of CO2 in the method of the present invention can be reduced by more than 90%, effectively solving the problem of CO2 emissions generated during the pyrolysis of waste tires, utilizing CO2 as a resource, and reducing environmental pollution. Specific embodiments

[0023] Example 1

[0024] A method for capturing and converting CO2 generated by pyrolysis of waste rubber comprises the following steps:

[0025] (1) After cleaning and crushing the waste tires, the waste tires are cut into small pieces with an average particle size of 0.5 cm. After removing impurities such as steel wire and stones, the rubber particles are sent to a pyrolysis reactor, and inert gas and CO2 are introduced to perform pyrolysis at 400°C. The pyrolysis pressure is controlled to be 7.38 MPa, and the volume percentage of CO2 in the pyrolysis reactor is 35%, generating gas and solid products;

[0026] (2) The gas obtained by pyrolysis passes through a cyclone separator, an electrostatic precipitator, and a fractionating tower in sequence to obtain gas phase components, a gasoline fraction, a diesel fraction, and tar;

[0027] (3) The gas phase component is purified by a gas condenser and a selective adsorption unit to remove water vapor and sulfide to obtain a purified gas phase component, and an organic alcohol amine absorbent is used to capture CO2 in the purified gas phase component, and the separated gaseous hydrocarbons are collected; wherein the organic alcohol amine absorbent is monoethanolamine MEA;

[0028] (4) 70% of the captured CO2 is converted into methanol through thermal catalytic hydrogenation;

[0029] (5) The remaining CO2 is heated to 500°C and then injected back into the bottom of the pyrolysis reactor.

[0030] Example 2

[0031] A method for capturing and converting CO2 generated by pyrolysis of waste rubber comprises the following steps:

[0032] (1) After cleaning and crushing the waste tires, the waste tires are cut into small pieces with an average particle size of 1 cm. After removing impurities such as steel wire and stones, the rubber particles are sent to a pyrolysis reactor, and inert gas and CO2 are introduced. Pyrolysis is carried out at 350°C, and the pyrolysis pressure is controlled to be 7.5 MPa. The volume percentage of CO2 in the pyrolysis reactor is 25%, and gas and solid products are generated;

[0033] (2) The gas obtained by pyrolysis passes through a cyclone separator, an electrostatic precipitator, and a fractionating tower in sequence to obtain gas phase components, a gasoline fraction, a diesel fraction, and tar;

[0034] (3) The gas phase component is purified by a gas condenser and a selective adsorption unit to remove water vapor and sulfide to obtain a purified gas phase component, and an organic alcohol amine absorbent is used to capture CO2 in the purified gas phase component, and the separated gaseous hydrocarbons are collected; wherein the organic alcohol amine absorbent is monoethanolamine MEA;

[0035] (4) 50% of the captured CO2 is converted into methanol through thermal catalytic hydrogenation;

[0036] (5) The remaining CO2 is heated to 500°C and then injected back into the bottom of the pyrolysis reactor.

[0037] Example 3

[0038] A method for capturing and converting CO2 generated by pyrolysis of waste rubber comprises the following steps:

[0039] (1) After cleaning and crushing, the waste tires are cut into small pieces with an average particle size of 1 cm. After removing impurities such as steel wire and stones, the rubber particles are sent to a pyrolysis reactor, and inert gas and CO2 are introduced to perform pyrolysis at 500°C. The pyrolysis pressure is controlled to be 8.0 MPa, and the volume percentage of CO2 in the pyrolysis reactor is 30%, generating gas and solid products;

[0040] (2) The gas obtained by pyrolysis passes through a cyclone separator, an electrostatic precipitator, and a fractionating tower in sequence to obtain gas phase components, a gasoline fraction, a diesel fraction, and tar;

[0041] (3) The gas phase component is purified by a gas condenser and a selective adsorption unit to remove water vapor and sulfide to obtain a purified gas phase component, and an organic alcohol amine absorbent is used to capture CO2 in the purified gas phase component, and the separated gaseous hydrocarbons are collected; wherein the organic alcohol amine absorbent is monoethanolamine MEA;

[0042] (4) 60% of the captured CO2 is converted into methanol through thermal catalytic hydrogenation;

[0043] (5) The remaining CO2 is heated to 500°C and then injected back into the bottom of the pyrolysis reactor.

[0044] Comparative Example 1:

[0045] The rest is the same as Example 1, except that no CO2 reflux is performed, and all the separated CO2 is used for preparing methanol by hydrogenation.

[0046] Comparative Example 2:

[0047] The rest is the same as Example 1, the only difference is that the CO2 reflux is relatively low, wherein the volume content of carbon dioxide in the pyrolysis atmosphere is 16%.

[0048] Comparative Example 3:

[0049] The rest is the same as Example 1, the only difference is that the CO2 reflux is higher, wherein the volume content of carbon dioxide in the pyrolysis atmosphere is 45%.

[0050] Comparative Example 4:

[0051] The other steps are the same as those in Example 1, except that the pyrolysis pressure is 5 MPa.

[0052] The pyrolysis products of Example 1 and Comparative Examples 1-5 were analyzed, and the results are shown in Table 1:

[0053] Table 1

[0054] Light hydrocarbon yield Gasoline yield Diesel yield <![CDATA[CO2 recovery rate]]> Example 1 5.6% 18.1% 32.5% 3.5% Comparative Example 1 8.1% 13.2% 11.6% 5.2% Comparative Example 2 7.3% 15.3% 23.0% 2.8% Comparative Example 3 3.8% 14.7% 26.3% 2.6% Comparative Example 4 7.1% 19.2% 21.0% 3.2%

[0055] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention specification, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for capturing and converting CO2 produced by pyrolysis of waste rubber, comprising the following steps: (1) Pyrolyzing the pretreated waste tires at high temperature in a pyrolysis reactor to generate gas and solid products; (2) The gas generated during the pyrolysis process passes through a gas-solid separator and a distillation tower in sequence to obtain gas phase components, gasoline fraction, diesel fraction, and tar; (3) wherein the gas phase component is purified by a gas condenser and a selective adsorption unit to remove impurities, thereby obtaining a purified gas phase component, and an organic alcohol amine absorbent is used to capture CO2 in the purified gas phase component, and the separated gaseous hydrocarbons are collected; (4) At least 30-50% of the captured CO2 is converted into methanol through thermal catalytic hydrogenation; (5) Reinjecting the remaining CO2 back into the bottom of the pyrolysis reactor; In step (1), the pyrolysis pressure is not less than 7.38 MPa, and the temperature is 300-600°C; the volume content of carbon dioxide in the pyrolysis atmosphere is 25%-35%; the pyrolysis is carried out under CO2 and an inert atmosphere, and the inert gas introduced is one or more of nitrogen and argon.

2. The method according to claim 1, characterized in that The pretreatment in step (1) includes cleaning, crushing, and separation of impurities; the particle size after crushing is less than 0.5 cm; the impurities include non-pyrolyzable stones and metal wires.

3. The method according to claim 1, characterized in that The pyrolysis pressure in step (1) is 7.5-10 MPa and the temperature is 350-500°C.

4. The method according to claim 1, characterized in that The gas in step (1) includes hydrocarbons, sulfides and solid particles; the solid particles are carbon black and other incompletely burned solid residues.

5. The method according to claim 1, characterized in that The gas-solid separator in step (2) is one or more of a cyclone separator and an electrostatic separator.

6. The method according to claim 1, characterized in that The gas phase component in step (3) is cooled in a gas condensation tower to remove water vapor therein, and then further removed from the gas phase component by a selective adsorption unit to remove harmful gases such as sulfides and trace hydrocarbons, thereby obtaining a purified gas phase component; the organic alcohol amine absorbent is one or more of monoethanolamine MEA and diethanolamine DEA.

7. The method according to claim 1, characterized in that The thermal catalytic hydrogenation method in step (4) is carried out under the action of a copper-based catalyst.

8. The method according to claim 7, characterized in that The reaction conditions are 200-300° C. and 3-5 MPa; the copper loading in the copper-based catalyst is 10-20wt%, and the carrier is activated carbon or molecular sieve.

9. The method according to claim 1, characterized in that The CO2 reinjected in step (5) needs to be pressurized to above 7.38 MPa using a compressor and heated to above 300°C before being injected into the pyrolysis reactor.