Production method of low-grade road asphalt

Abstract

The invention discloses a production method of low-grade road asphalt. The method comprises the following steps: (1) pretreating waste plastics to obtain pretreated waste plastics; (2) mixing ethylene tar with the pretreated waste plastics, heating and stirring to obtain a premix; (3) carrying out shearing circulation on the premix in the step (2); and (4) performing countercurrent contact on the material obtained in the step (3) and an extraction solvent for supercritical extraction, wherein the obtained raffinate heavy component is used as low-grade asphalt. According to the method, high value-added utilization of the ethylene tar and the waste plastics can be realized, and the produced low-grade road asphalt has the advantages of high low-temperature ductility and good storage stability.

Description

Technical Field

[0001] The invention relates to a method for preparing low-grade road asphalt from ethylene tar, and belongs to the field of high value-added utilization of low-value resources. Background Art

[0002] Data from the transportation industry show that high temperatures and heavy loads have caused increasing damage to asphalt pavements year by year, and the requirements for asphalt application performance on highways have tended to be harder to improve the final performance of asphalt pavements. In order to adapt to market development trends, improve the service functions of asphalt pavements, and improve their high-temperature stability, low-grade asphalt has become the first choice for road construction in some areas. Compared with the currently commonly used No. 70 asphalt, No. 50 asphalt has high viscosity, high softening point, low penetration, better high-temperature stability and water stability. Asphalt pavements in Guangdong, Hainan and other provinces in China have begun to use low-grade No. 50 asphalt.

[0003] The research and application of low-grade asphalt in roads is still in its infancy. Among them, 50#A grade asphalt is difficult to produce. The commonly used vacuum deep drawing process has the problem of unqualified low-temperature ductility before film; the blending process of hard asphalt and soft asphalt can slightly improve the low-temperature ductility before film, but the surplus is not large and there is a problem of uneven product properties; by adding polymers, polymer-modified low-grade asphalt is prepared, which can improve the low-temperature ductility before film, but the cost of polymer modification is relatively high. For example, CN103554926B discloses a low-grade high-grade road asphalt and its preparation method, which uses vacuum residue oil, deoiled asphalt and solvent refined extracted oil to prepare low-grade high-grade road asphalt that meets 50#A grade, but its 10°C ductility before film is not large.

[0004] Ethylene tar is a byproduct produced during the high-temperature condensation of raw materials in the production of ethylene. It accounts for about 15% of the ethylene output. China has abundant ethylene tar resources. Ethylene tar is mainly composed of C and H elements, with a high aromatic content. It is composed of a variety of single-ring, double-ring, and multi-ring cyclic structure compounds, from C9 fraction to C90 fraction. Its distillation range spans nearly 600°C and its components are relatively complex. Due to the lack of awareness of the use of low-quality resources in the past, ethylene tar was only used as fuel oil for combustion, resulting in a huge waste of resources.

[0005] At present, various forms of disposable plastic products are widely used, and waste plastics have caused new pressure on resources and the environment. Waste plastics are difficult to degrade and decompose very slowly under natural conditions. Irregular treatment of plastic waste poses environmental risks. The recycling of waste plastics has always been a topic of concern. It can turn industrial waste into valuable industrial production raw materials and realize resource recycling and reuse, which is of great significance that cannot be ignored. Summary of the invention

[0006] In order to overcome the problems of low-grade road asphalt pre-film low-temperature ductility and high price of polymer modification in the prior art, the present invention provides a method for producing low-grade road asphalt. The method can not only realize the high added value utilization of ethylene tar and waste plastics, but also the produced low-grade road asphalt has the advantages of high low-temperature ductility and good storage stability.

[0007] The present invention provides a method for producing low-grade road asphalt, comprising the following steps:

[0008] (1) pre-treating waste plastics to obtain pre-treated waste plastics;

[0009] (2) mixing ethylene tar with pretreated waste plastics, heating and stirring to obtain a premix;

[0010] (3) subjecting the premix of step (2) to shear cycling;

[0011] (4) The material obtained in step (3) is contacted with an extraction solvent in countercurrent to perform supercritical extraction, and the heavy component of the residue obtained is used as low-grade asphalt.

[0012] In the method of the present invention, the waste plastics in step (1) are one or more of polypropylene (PP), polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC) and polyethylene terephthalate (PET). The molecular weight of the waste plastics is above 10,000, and can be 10,000 to 50,000.

[0013] In the method of the present invention, the waste plastic pretreatment method in step (1) is shallow thermal cracking. The conditions of the shallow thermal cracking are: temperature of 330-400°C and time of 30-90 minutes.

[0014] In the method of the present invention, the properties of the ethylene tar described in step (2) are as follows: density at 25°C is 1.0 to 1.2 g / cm 3 The residual carbon value is 10wt% to 20wt%, and the mass content of aromatic hydrocarbons is more than 70wt%.

[0015] In the method of the present invention, the mass ratio of the ethylene tar to the pretreated waste plastic in step (2) is 100:1-10, preferably 100:2-8.

[0016] In the method of the present invention, the conditions for heating and stirring in step (2) are: temperature of 130 to 160° C., and stirring time of 60 to 120 min.

[0017] In the method of the present invention, in step (3), the shearing temperature is 150-200° C., the number of cycles is 2-6 times, and the shearing time each time is 10-30 minutes. The shearing is preferably carried out in a colloid mill.

[0018] In the method of the present invention, in step (4), the extraction solvent is a C3-C5 alkane, such as at least one of propane, butane and pentane. The volume ratio of the extraction solvent to the material obtained in step (3) is 3-6:1.

[0019] In the method of the present invention, in step (4), the extraction temperature is 80-180° C. and the pressure is 4-6 MPa.

[0020] In the method of the present invention, in step (4), the light components of the extract obtained are separated to obtain light tar and solvent. The solvent can be recycled. The separation temperature is 200-250°C and the pressure is 5-10MPa.

[0021] In the method of the present invention, the properties of the low-grade road asphalt are as follows: needle penetration at 25°C is 40-600.1 mm, softening point is 60-90°C, elongation at 10°C before film is ≥30 cm, and storage stability is ≤0.5°C.

[0022] The present invention adopts a method combining waste plastic pretreatment with supercritical extraction to achieve efficient crosslinking of ethylene tar and waste plastic modifier and improve crosslinking stability. The two stages work synergistically to produce the following beneficial effects:

[0023] 1. In the method of the present invention, waste plastics are pretreated with shallow thermal cracking, which can moderately degrade the waste plastics, reduce the molecular weight of the waste plastics, and improve the compatibility with ethylene tar. The newly generated active sites in the pyrolysis process improve the cross-linking activity of ethylene tar and waste plastics. After high-temperature shearing and supercritical extraction processes, the inactive components in the system can be removed, and the active components of ethylene tar in the system can quickly cross-link with the waste plastics, which greatly promotes the swelling development of the waste plastics, and quickly forms a network structure in the ethylene tar, increasing the cross-linking depth. On the one hand, it significantly improves the ductility index of low-grade asphalt, and on the other hand, it can greatly improve the storage stability of low-grade asphalt.

[0024] 2. The present invention uses ethylene tar as raw material, which has a wide source and low price, and can achieve high added value utilization of low-value resources. Degrading waste plastics into oligomers through chemical recycling methods and using them as new chemical raw materials to replace polymer modifiers is also a very promising recycling method in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the process of the present invention;

[0026] Explanation of the reference numerals: 1-pretreatment tank, 2-premixing tank, 3-colloid mill, 4-extraction tower, 5-separator, 6-solvent tank, 7-waste plastic, 8-ethylene tar, 9-pretreated waste plastic, 10-premix, 11-sheared material, 12-residue, 13-extract, 14-light tar, 15-solvent. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described below in conjunction with embodiments, but is not limited to the following embodiments.

[0028] Combine the following Figure 1 The method of the present invention is described in detail. The present invention provides a method for producing low-grade road asphalt, comprising: waste plastic 7 is subjected to shallow thermal cracking to obtain pretreated waste plastic 9, ethylene tar 8 and pretreated waste plastic 9 enter premixing tank 2 for mixing, heating and stirring to obtain premix 10; premix 10 enters colloid mill 3 for shearing circulation to obtain sheared material 11, sheared material 11 is contacted with extraction solvent 15 in countercurrent in extraction tower for supercritical extraction, and the obtained raffinate heavy component 12 is used as low-grade asphalt, extract 13 enters separator, light tar 14 is obtained at the bottom, solvent 15 is obtained at the top, solvent 15 enters solvent tank, and the solvent can be recycled.

[0029] The relevant parameter testing method of the present invention:

[0030] The penetration and penetration index PI were measured according to the Ministry of Transportation Standard T0604, the softening point (ring and ball method) was measured according to the Ministry of Transportation Standard T0606, the ductility was measured according to the Ministry of Transportation Standard T0605, the dynamic viscosity at 60°C was measured according to the Ministry of Transportation Standard T0620, the polymer modified asphalt segregation test was carried out according to the Ministry of Transportation Standard T0661, and the thin film heating test (TFOT) was carried out according to the Ministry of Transportation Standard T0609.

[0031] Example 1

[0032] In this example, Figure 1The process is as follows, the waste plastic is polyethylene (PE) with a molecular weight of 15,000, the extraction solvent is propane, and the properties of ethylene tar are shown in Table 1. The waste plastic is thermally cracked at 380°C for 50 minutes to obtain pretreated waste plastic. Ethylene tar and pretreated waste plastic are mixed at a mass ratio of 100:5, heated to 150°C and stirred for 80 minutes to obtain a premix; the premix is ​​sheared and cycled at 160°C, the number of cycles is 4, and the shearing time for each time is 20 minutes. The sheared material is countercurrently contacted with the extraction solvent for supercritical extraction, and the extraction conditions are as follows: the extraction temperature is 90°C, the pressure is 5MPa, the volume ratio of the extraction solvent to the sheared material is 4, and the heavy component of the extract obtained after extraction is used as low-grade asphalt, and the properties are shown in Table 2. The light component of the obtained extract is separated, and the separation conditions are: temperature 200°C, pressure 8MPa, to obtain light tar and solvent. The solvent can be recycled.

[0033] Example 2

[0034] In this example, Figure 1 The process is as follows, the waste plastic is polypropylene (PP) with a molecular weight of 20,000, the extraction solvent is propane, and the properties of ethylene tar are shown in Table 1. The waste plastic is thermally cracked at 390°C for 60 minutes to obtain pretreated waste plastic. Ethylene tar and pretreated waste plastic are mixed at a mass ratio of 100:6, heated to 150°C and stirred for 60 minutes to obtain a premix; the premix is ​​sheared and cycled at 180°C, the number of cycles is 4, and the shearing time for each time is 30 minutes. The sheared material is countercurrently contacted with the extraction solvent for supercritical extraction, and the extraction conditions are as follows: the extraction temperature is 100°C, the pressure is 5MPa, the volume ratio of the extraction solvent to the sheared material is 5, and the heavy component of the extract obtained after extraction is used as low-grade asphalt, and the properties are shown in Table 2. The light component of the obtained extract is separated, and the separation conditions are: temperature 200°C, pressure 9MPa, to obtain light tar and solvent. The solvent can be recycled.

[0035] Example 3

[0036] In this example, Figure 1The waste plastic is polystyrene (PS) with a molecular weight of 15,000, the extraction solvent is butane, and the properties of ethylene tar are shown in Table 1. The waste plastic is thermally cracked at 370°C for 40 minutes to obtain pretreated waste plastic. Ethylene tar and pretreated waste plastic are mixed at a mass ratio of 100:4, heated to 130°C and stirred for 100 minutes to obtain a premix; the premix is ​​sheared and cycled at 160°C for 3 times, and each shearing time is 20 minutes. The sheared material is countercurrently contacted with the extraction solvent for supercritical extraction. The extraction conditions are as follows: the extraction temperature is 150°C, the pressure is 5MPa, the volume ratio of the extraction solvent to the sheared material is 4, and the heavy component of the extract obtained after extraction is used as low-grade asphalt. The properties are shown in Table 2. The light component of the obtained extract is separated under the separation conditions: temperature 220°C, pressure 6MPa, and light tar and solvent are obtained. The solvent can be recycled.

[0037] Example 4

[0038] In this example, Figure 1 The waste plastic is polystyrene (PS) with a molecular weight of 25,000, the extraction solvent is butane, and the properties of ethylene tar are shown in Table 1. The waste plastic is thermally cracked at 380°C for 50 minutes to obtain pretreated waste plastic. Ethylene tar and pretreated waste plastic are mixed at a mass ratio of 100:3, heated to 140°C and stirred for 80 minutes to obtain a premix; the premix is ​​sheared at 180°C for 3 times, and each shearing time is 30 minutes. The sheared material is countercurrently contacted with the extraction solvent for supercritical extraction. The extraction conditions are as follows: the extraction temperature is 140°C, the pressure is 4MPa, the volume ratio of the extraction solvent to the sheared material is 3, and the heavy component of the extract obtained after extraction is used as low-grade asphalt. The properties are shown in Table 2. The light component of the obtained extract is separated under the separation conditions: temperature 220°C, pressure 6MPa, and light tar and solvent are obtained. The solvent can be recycled.

[0039] Example 5

[0040] In this example, Figure 1The process, the waste plastic is polyvinyl chloride (PVC), the molecular weight is 30000, the extraction solvent is pentane, and the properties of ethylene tar are shown in Table 1. The waste plastic is thermally cracked at 340℃ for 40min to obtain the pretreated waste plastic. Ethylene tar and pretreated waste plastic are mixed in a mass ratio of 100:6, heated to 140℃ and stirred for 80min to obtain a premix; the premix is ​​sheared and cycled at 170℃, the number of cycles is 5, and the shearing time is 20min each time. The sheared material is contacted with the extraction solvent in countercurrent for supercritical extraction. The extraction conditions are as follows: the extraction temperature is 170℃, the pressure is 5MPa, the volume ratio of the extraction solvent to the sheared material is 4, and the heavy component of the extract obtained after extraction is used as low-grade asphalt. The properties are shown in Table 2. The light component of the obtained extract is separated, and the separation conditions are: temperature 250℃, pressure 5MPa, to obtain light tar and solvent. The solvent can be recycled.

[0041] Example 6

[0042] In this example, Figure 1 The waste plastic is polyethylene terephthalate (PET) with a molecular weight of 25,000, the extraction solvent is pentane, and the properties of ethylene tar are shown in Table 1. The waste plastic is thermally cracked at 330°C for 80 minutes to obtain pretreated waste plastic. Ethylene tar and pretreated waste plastic are mixed at a mass ratio of 100:8, heated to 150°C and stirred for 80 minutes to obtain a premix; the premix is ​​sheared at 160°C for 4 cycles and each shearing time is 20 minutes. The sheared material is countercurrently contacted with the extraction solvent for supercritical extraction. The extraction conditions are as follows: the extraction temperature is 180°C, the pressure is 4MPa, the volume ratio of the extraction solvent to the sheared material is 3, and the heavy component of the extract obtained after extraction is used as low-grade asphalt. The properties are shown in Table 2. The light component of the obtained extract is separated under the separation conditions of temperature 240°C and pressure 6MPa to obtain light tar and solvent. The solvent can be recycled.

[0043] Comparative Example 1

[0044] The difference from Example 1 is that the waste plastic polyethylene (PE) is directly mixed with ethylene tar without pretreatment. The results are shown in Table 3.

[0045] Comparative Example 2

[0046] The difference from Example 1 is that the sheared material is not subjected to supercritical extraction, but low-grade asphalt is obtained by deep drawing. The results are shown in Table 3.

[0047] Table 1 Properties of ethylene tar

[0048] Analyze Project data Density at 25℃, g / cm 1.103 Kinematic viscosity at 60℃, cst 194.3 Carbon residue,% 16.31 Aromatic content, wt% 78.23 Ash content, % 0.034 Elemental composition, % C 92.56 H 7.30 S 0.05 N 0.03 O 0.06

[0049] Table 2 Product test results of each embodiment

[0050]

[0051]

[0052] Table 3 Test results of products in various comparative examples

[0053]

[0054] The embodiments of the present invention are only detailed descriptions of the technical solutions of the present invention, but the present invention is not limited to the above embodiments, that is, the present invention can be implemented without relying on the steps described in the above embodiments. In summary, any improvements made to the present invention by those skilled in the art, as long as they do not deviate from the content of the technical solutions of the present invention, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention, shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for producing low-grade road asphalt, comprising the following steps: (1) pre-treating waste plastics to obtain pre-treated waste plastics; (2) mixing ethylene tar with pretreated waste plastics, heating and stirring to obtain a premix; (3) subjecting the premix of step (2) to shear cycling; (4) The material obtained in step (3) is contacted with an extraction solvent in countercurrent to perform supercritical extraction, and the heavy component of the residue obtained is used as low-grade asphalt.

2. The preparation method according to claim 1, characterized in that: The waste plastics in step (1) are one or more of polypropylene, polyethylene, polystyrene, polyvinyl chloride and polyethylene terephthalate; preferably, the molecular weight of the waste plastics is above 10,000, preferably 10,000 to 50,000.

3. The preparation method according to claim 1, characterized in that: The waste plastic pretreatment method in step (1) is shallow thermal cracking, and the conditions of the shallow thermal cracking are: temperature of 330-400° C. and time of 30-90 min.

4. The preparation method according to claim 1, characterized in that: The properties of the ethylene tar in step (2) are as follows: density at 25°C is 1.0-1.2 g / cm 3 The residual carbon value is 10wt% to 20wt%, and the mass content of aromatic hydrocarbons is more than 70wt%.

5. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of the ethylene tar to the pretreated waste plastic is 100:1-10, preferably 100:2-8.

6. The preparation method according to claim 1, characterized in that: The heating and stirring conditions in step (2) are: temperature of 130-160° C., and stirring time of 60-120 min.

7. The preparation method according to claim 1, characterized in that: In step (3), the shearing temperature is 150-200° C., the number of cycles is 2-6 times, and the shearing time each time is 10-30 minutes.

8. The preparation method according to claim 1, characterized in that: In step (4), the extraction solvent is C3-C5 alkane, and the volume ratio of the extraction solvent to the material obtained in step (3) is 3-6:

1.

9. The preparation method according to claim 1, characterized in that: In step (4), the extraction temperature is 80-180° C. and the pressure is 4-6 MPa.

10. The preparation method according to claim 1, characterized in that: In step (4), the light components of the obtained extract are separated to obtain light tar and solvent. Preferably, the solvent is recycled.

11. The preparation method according to claim 10, characterized in that: The separation temperature is 200-250° C. and the pressure is 5-10 MPa.

12. The preparation method according to claim 10, characterized in that: The properties of the low-grade road asphalt are as follows: needle penetration at 25°C is 40-60 0.1 mm, softening point is 60-90°C, elongation at 10°C before film is ≥30 cm, and storage stability is ≤0.5°C.

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