A method of recycling asphalt from road asphalt waste

Abstract

The present application relates to a kind of road asphalt waste recycling asphalt, the method is that road asphalt waste is broken respectively after sodium oxide mixing, hydrochloric acid washing filter residue obtained after filtering is immersed by trichloroethylene extraction, and the mixture of trichloroethylene and asphalt obtained by filtering is distilled at 120~150 ℃ Separation obtains the asphalt product after separation.This method is simple to operate, can realize the effective extraction separation of asphalt in road asphalt waste, is convenient for large-scale industry directly used, improves the utilization of RAP, the extraction temperature of this method is controllable, effectively avoids the secondary aging of asphalt, can more completely retain the actual parameter performance of asphalt, and the subsequent application of the product obtained by this method is also more simple and efficient.

Description

Technical Field

[0001] This invention belongs to the field of asphalt technology, specifically relating to a method for recycling asphalt from road asphalt waste. This method can quickly separate and recycle asphalt from road asphalt waste and has high industrial application value. Background Technology

[0002] Throughout the entire process of asphalt pavement construction, prolonged exposure to sunlight, ultraviolet radiation, wind, rain, and temperature fluctuations, coupled with external factors such as heating and mixing during construction, paving and compaction, and traffic loads after completion, leads to the gradual aging of asphalt. Aged asphalt gradually loses its binding capacity and ductility, exhibiting reduced viscosity and ductility, resulting in decreased road performance. This causes problems such as loosening and cracking of the asphalt pavement, and it loses its ability to resist shear and impact. Asphalt aging directly affects the service performance and lifespan of the pavement. In asphalt mixtures, aged asphalt pavements exhibit increased high-temperature rutting resistance, decreased low-temperature crack resistance and water stability, and significantly reduced fatigue performance. Since waste asphalt pavement materials (RAP) contain aged asphalt, aggregates, and other non-renewable resources, their recycling value is significant. Therefore, the recycling of waste asphalt has become a very important research topic. Currently, commonly used recycling technologies for asphalt concrete pavement resurfacing include cold recycling and hot recycling. Hot recycling can be further divided into in-situ hot recycling and plant-mixed hot recycling. Cold recycling can be further divided into plant-mixed cold recycling, in-situ cold recycling, and full-depth recycling based on the recycling method. Plant-mixed hot recycling involves milling the original pavement, transporting the old mixture back, designing the mix proportions, adding asphalt, recycling agents, and new aggregates, mixing it again, and then transporting it back to the road to repave asphalt pavement. Currently, asphalt pavement recycling includes two production processes: cold recycling and hot recycling. Cold recycling is only suitable for minor road repairs with low requirements, and its application scope and significance are not very large. Hot recycling is mainly used for highway asphalt pavement maintenance and has a wide range of applications. However, the stability and recovery rate of the asphalt recovered by traditional hot recycling processes are not ideal, and the recycling process generates waste gas, polluting the environment. Currently, the mixing state of new and old asphalt in hot recycled asphalt mixtures remains a black box issue. When designing the performance of asphalt and asphalt mixtures, the degree and state of mixing of new and old asphalt have direct guiding significance for improving the recycling rate and the admixture rate in recycled asphalt mixtures. If the old asphalt and new asphalt are not completely mixed, a layer of new asphalt will coat the surface of the RAP, resulting in an increase in the thickness of the asphalt film on the RAP surface, while the asphalt film of the new aggregate becomes thinner. Moreover, there is a difference in the concentration of asphalt components at the interface between the old and new asphalt, forming a weak surface on the aggregate surface. Therefore, the performance of recycled asphalt mixtures cannot reach the level of the assumed complete mixing of old and new asphalt, which has a significant impact on its water stability, low-temperature crack resistance, and fatigue durability.

[0003] If asphalt and inorganic materials such as aggregates can be effectively separated from RAP (Rich Asphalt Parts), the old asphalt can be directly processed, which will greatly improve the utilization efficiency of RAP and expand its application scenarios. Asphalt recycling can be achieved by heating to extract asphalt from waste asphalt mixtures. However, most asphalt recycling methods on the market simply involve heating, which results in uneven heating and incomplete recovery of waste asphalt, affecting subsequent work. Currently, there are three main methods for extracting old asphalt: reflux extraction, centrifugal extraction, and fat extractor method. The most commonly used method is centrifugal extraction, which uses trichloroethylene as the extraction solvent. A fully automated extractor is used to extract the milled material, obtaining a mixture of trichloroethylene and old asphalt. Then, a rotary evaporator is used to separate the trichloroethylene and asphalt, yielding the old asphalt. However, during the extraction of milled material, mineral powder remains in the trichloroethylene-old asphalt mixture. Furthermore, this method has a long operation time, making it unsuitable for large-scale RAP asphalt separation and recycling. CN115418107A discloses a method for recycling asphalt and its preparation. The method involves pouring waste asphalt mixture and trichloroethylene solvent into a centrifuge, starting the centrifuge, gradually increasing the speed to 3000 r / min, and centrifuging for 120 min. The extract is then poured into a crucible and heated in a hot bath until the solution turns dark black, thus obtaining the recycled aged asphalt. Due to the complex composition of the waste asphalt mixture and the slow dissolution of trichloroethylene, this recycling method is time-consuming and has low recovery efficiency. CN111266387A discloses a method for recycling road asphalt. This method separates the undersize material after crushing and separation by flotation, obtaining recycled asphalt products and fine aggregates, achieving separate recovery of coarse aggregates, fine aggregates, and asphalt in road asphalt. This method has a low asphalt recovery rate, is time-consuming, and has high energy consumption. CN116178786A discloses a method for rapidly recovering small amounts of aged asphalt. This method uses a wide-mouth bottle instead of a rotary flask for distillation and employs a rotary evaporator for two-stage recovery of aged asphalt. Compared to existing asphalt recycling methods, this method not only reduces the workload of testing but also effectively avoids trichloroethylene and mineral powder residues, ensuring the purity of the recycled asphalt and thus improving the accuracy of subsequent testing. However, this method is relatively complex, and due to the complex composition of asphalt and aggregates in waste asphalt mixtures and the slow dissolution of trichloroethylene, it still suffers from time-consuming and inefficient processes. Therefore, it is necessary to provide a simpler and more feasible method for recycling asphalt from asphalt road waste. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a method for recycling asphalt from road asphalt waste. This method is simple, time-saving, and has high recycling and separation efficiency. It can be used for large-scale and rapid recycling of asphalt from road asphalt waste, and can effectively avoid trichloroethylene and mineral powder residues, ensuring the purity of the recycled asphalt.

[0005] A method for recycling asphalt from road asphalt waste includes the following steps: Step 1: Weigh 1000g of road asphalt waste, crush it to a particle size of less than 10mm, wash it with water and dry it to obtain material A; Step 2: Put material A into a mixing tank and add 100g of sodium oxide powder, stir continuously for 3-24h, then add 1.25L of 2M hydrochloric acid to the mixing tank, stir continuously for 0.5-2h, filter and dry the filter residue to obtain material B. Step 3: After cooling material B to room temperature, place it in a mixing tank, add trichloroethylene to completely submerge material B, and continue stirring for 30 minutes. Filter to obtain a mixture of trichloroethylene and asphalt. Step 4: Place the mixture obtained in Step 3 into a distillation flask for distillation separation. Trichloroethylene begins to be distilled out at 80℃. To ensure the distillation separation rate and separation time, the distillation separation temperature is controlled between 120~150℃. Carbon dioxide gas is introduced throughout the distillation process, and the gas flow rate is controlled at 800-1300mL / min. After the trichloroethylene distillation is complete, the separated asphalt product is obtained.

[0006] Preferably, the particle size of the crushed product in step one is 0.5-5mm, more preferably 1-3mm. The specific crushing particle size is determined according to the properties of the road asphalt waste being processed, ensuring that the asphalt is fully exposed and separated within this particle size. Crushing is carried out using crushing machinery, such as hammer crushers, impact crushers, jaw crushers, cone crushers, and roller crushers. More preferably, a rotor centrifugal crusher is used. Its working principle is to use centrifugal force to give the feed particles maximum acceleration in the rotor. After the material is thrown out, it collides with the crushing plate, which is usually composed of annular liners or a sand bed, relying on impact force to crush the material. The rotor centrifugal crusher can selectively impact and crush the aggregate particles, and at the same time, it can maximize the separation of aggregates and maintain the integrity of the particle size when crushing and recycling asphalt pavement materials.

[0007] Preferably, the drying in step one is carried out in a drying oven at a temperature of 80-100℃. To avoid secondary aging of the asphalt, the drying temperature should not exceed 100℃.

[0008] Preferably, the mixing tank in step two has an acid and alkali resistant lining, and the drying temperature in step two is 50-70℃.

[0009] Preferably, the filtration in step three is any one of vacuum filtration, suction filtration, or centrifugal filtration.

[0010] Preferably, the distillation separation temperature in step four is 130℃, and the carbon dioxide gas flow rate is controlled at 1000mL / min.

[0011] Compared with the prior art, the beneficial effects of the technical solution of this application are as follows:

[0012] This invention employs a simple method to effectively extract and separate asphalt from road asphalt waste. The operation is simple and easy to implement, enabling large-scale asphalt separation and extraction from road asphalt waste. The extraction temperature is controllable, effectively preventing secondary aging of the asphalt and preserving its actual parameters and properties relatively completely.

[0013] This method can separate and extract road asphalt waste in a single step, eliminating the need for separate extraction based on material particle size ranges. The resulting asphalt product exhibits better consistency with waste asphalt. The method incorporates crushing treatment before asphalt separation and extraction, which improves the separation of asphalt and aggregates to some extent. It also has lower requirements for road asphalt waste, reducing the need for RAP recycling.

[0014] Before extracting asphalt using trichloroethylene, the mixture is sequentially treated with sodium oxide and hydrochloric acid. This effectively promotes the separation of asphalt and aggregates, further improving the efficiency of the extraction process and facilitating the large-scale industrial separation of asphalt waste to obtain asphalt aggregates. This method effectively separates asphalt and aggregates from road asphalt waste, producing asphalt products without any residual mineral powder particles. Compared to directly regenerating RAP (Rich Asphalt Particulate Epoxy) to prepare asphalt materials, the aggregates obtained by this method can be used directly as new aggregates, and the obtained asphalt can be reused through simple activation and regeneration. The subsequent application of the products is simpler and more effective. Detailed Implementation

[0015] To make the technical problems solved by this invention, the technical solutions adopted, and the technical effects achieved clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0016] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "front end," "rear end," "both ends," "one end," and "the other end," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the text, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "comprising" and "having," and any variations thereof, in the embodiments of this application are intended to cover non-exclusive inclusion.

[0017] Example 1

[0018] This embodiment discloses a method for recycling asphalt from road asphalt waste. The method includes the following steps: Step 1: Weigh 1000g of road asphalt waste, crush it to a particle size distribution between 0.5mm and 5mm using a hammer crusher, wash it with water, and dry it at 80℃ to obtain material A; Step 2: Put material A into a mixing tank and add 100g of sodium oxide powder, stir continuously for 3 hours, then add 1.25L of 2M hydrochloric acid to the mixing tank, stir continuously for 2 hours, filter, and dry the filter residue at 50℃ to obtain material B; Step 3: Cool material B to room temperature and put it into a mixing tank, add trichloroethylene to completely immerse material B, stir continuously for 30 minutes, and filter to obtain a mixture of trichloroethylene and asphalt; Step 4: Put the mixture obtained in Step 3 into a distillation flask for distillation separation. The distillation separation temperature is controlled at 130℃, and carbon dioxide gas is introduced throughout the distillation process at a gas flow rate of 1000mL / min. After the trichloroethylene is distilled, the separated asphalt product is obtained.

[0019] Example 2

[0020] This embodiment discloses a method for recycling asphalt from road asphalt waste. The method includes the following steps: Step 1: Weigh 1000g of road asphalt waste, crush it to a particle size distribution between 1mm and 3mm using a rotor centrifugal crusher, wash it with water, and dry it at 80℃ to obtain material A; Step 2: Put material A into a mixing tank and add 100g of sodium oxide powder, stir continuously for 10h, then add 1.25L of 2M hydrochloric acid to the mixing tank, stir continuously for 2h, filter, and dry the filter residue at 70℃ to obtain material B; Step 3: Cool material B to room temperature and put it into a mixing tank, add trichloroethylene to completely submerge material B, stir continuously for 30min, and filter to obtain a mixture of trichloroethylene and asphalt; Step 4: Put the mixture obtained in Step 3 into a distillation flask for distillation separation. The distillation separation temperature is controlled at 120℃, and carbon dioxide gas is introduced throughout the distillation process, with a gas flow rate controlled at 1300mL / min. After the trichloroethylene is distilled, the separated asphalt product is obtained.

[0021] Example 3

[0022] This embodiment discloses a method for recycling asphalt from road asphalt waste. The method includes the following steps: Step 1: Weigh 1000g of road asphalt waste, crush it to a particle size distribution between 0mm and 5mm using a jaw crusher, wash it with water, and dry it at 100℃ to obtain material A; Step 2: Put material A into a mixing tank and add 100g of sodium oxide powder, stir continuously for 15h, then add 1.25L of 2M hydrochloric acid to the mixing tank, stir continuously for 0.5h, filter, and dry the filter residue at 60℃ to obtain material B; Step 3: Cool material B to room temperature and put it into a mixing tank, add trichloroethylene to completely submerge material B, stir continuously for 30min, and filter to obtain a mixture of trichloroethylene and asphalt; Step 4: Put the mixture obtained in Step 3 into a distillation flask for distillation separation. The distillation separation temperature is controlled at 150℃, and carbon dioxide gas is introduced throughout the distillation process, with a gas flow rate controlled at 800mL / min. After the trichloroethylene is distilled, the separated asphalt product is obtained.

[0023] Comparative Example 1

[0024] This comparative example discloses a method for recycling asphalt from road asphalt waste. The method includes the following steps: Step 1: Weigh 1000g of road asphalt waste, crush it to a particle size distribution between 1mm and 5mm using a rotor centrifugal crusher, wash it with water, and dry it at 110℃ to obtain material A; Step 2: Put material A into a mixing tank and add 100g of sodium oxide powder, stir continuously for 10h, then add 1.25L of 2M hydrochloric acid to the mixing tank, stir continuously for 2h, filter, and dry the filter residue at 80℃ to obtain material B; Step 3: Cool material B to room temperature and put it into a mixing tank, add trichloroethylene to completely submerge material B, stir continuously for 30min, and filter to obtain a mixture of trichloroethylene and asphalt; Step 4: Put the mixture obtained in Step 3 into a distillation flask for distillation separation. The distillation separation temperature is controlled at 160℃, and carbon dioxide gas is introduced throughout the distillation process, with a gas flow rate controlled at 1300mL / min. After the trichloroethylene is distilled, the separated asphalt product is obtained.

[0025] Comparative Example 2

[0026] The difference between Comparative Example 2 and Example 1 is that step one is omitted, and existing RAP is directly selected. No crushing treatment is performed on the raw material, and other parameter settings are the same as in Example 1.

[0027] Comparative Example 3

[0028] The difference between Comparative Example 3 and Example 1 is that step two is modified to "Step two: put material A into a mixing tank and add 100g of sodium oxide powder, stir continuously for 3 hours, then add 1.25L of deionized water into the mixing tank, stir continuously for 2 hours, filter, and dry the filter residue at 50°C to obtain material B". All other parameter settings are the same as in Example 1.

[0029] Comparative Example 4

[0030] The difference between Comparative Example 4 and Example 1 is that step 2 is modified to "Step 2: Put material A into a mixing tank and stir continuously for 3 hours, then add 1.25L of 2M hydrochloric acid into the mixing tank and stir continuously for 2 hours, filter and dry the filter residue at 50°C to obtain material B". All other parameter settings are the same as in Example 1.

[0031] The asphalt reclaimed materials obtained in the above embodiments and comparative examples were tested, and the test results are shown in the table below.

[0032] Table 1: Product performance test results in the examples and comparative examples

[0033]

[0034] As can be seen from the table above, the asphalt properties obtained in Examples 1-3 are quite similar. The asphalt yields in these examples are similar, indicating that the asphalt in the asphalt waste is basically completely recovered and separated, resulting in a high asphalt recovery rate. A comparison of the examples and comparative examples shows that the method of this invention can achieve a high asphalt recovery rate from asphalt waste. When crushing is not performed before recovery, or when the crushed material is not pre-stirred with sodium oxide, or when sodium oxide is stirred but not acid-washed, the asphalt recovery rate decreases. This may be because the asphalt in the asphalt waste is coated on the surface of the aggregate, with uneven thickness and relatively dense coating, causing the asphalt in the waste to not completely dissolve in trichloroethylene within the soaking time set in the examples, leading to a lower asphalt recovery rate. Comparative Example 1 shows that higher drying or distillation temperatures during asphalt recovery easily lead to secondary aging of the asphalt, which to some extent affects the performance of the asphalt and its performance after modification and recycling to prepare road asphalt. Comparative Example 3 shows that when sodium oxide is introduced into the asphalt but not removed, the excess inorganic oxides remaining in the asphalt product greatly reduce the ductility of the asphalt, reducing the high-temperature stability of the road surface when using this asphalt material for paving.

[0035] The foregoing has provided a detailed description of a method for recycling asphalt from road asphalt waste, as disclosed in the embodiments of this application. The above description, in conjunction with specific preferred embodiments, further illustrates the present invention and should not be construed as limiting the specific implementation of the invention to these descriptions. For those skilled in the art, the structural form of this invention can be flexibly varied without departing from its concept, and a series of products can be derived. Any simple deductions or substitutions should be considered as falling within the patent protection scope defined by the submitted claims.

Claims

1. A method for recycling asphalt from road asphalt waste, comprising the following steps: Step 1: Weigh 1000g of road asphalt waste, crush it to a particle size of less than 10mm, wash it with water, and dry it at 80-100℃ to obtain material A; Step 2: Put material A into a mixing tank, add 100g of sodium oxide powder, and stir continuously for 3-24h. Then add 1.25L of 2M hydrochloric acid to the mixing tank, stir continuously for 0.5-2h, filter, and dry the filter residue to obtain material B; Step 3: Cool material B to room temperature and put it into a mixing tank, add trichloroethylene to completely submerge material B, stir continuously for 30min, and filter to obtain a mixture of trichloroethylene and asphalt; Step 4: Put the mixture obtained in Step 3 into a distillation flask for distillation separation. The distillation separation temperature is controlled between 120~150℃, and carbon dioxide gas is introduced throughout the distillation process. The gas flow rate is controlled at 800-1300mL / min. After the trichloroethylene is distilled, the separated asphalt product is obtained.

2. The method for recycling asphalt from road asphalt waste according to claim 1, characterized in that, In step one, the particle size of the crushed product is 0.5-5mm, and the crushing is carried out using a rotor centrifugal crusher.

3. The method for recycling asphalt from road asphalt waste according to claim 1, characterized in that, In step one, the particle size of the crushed product is 1-3mm, and the crushing is carried out using a rotor centrifugal crusher.

4. The method for recycling asphalt from road asphalt waste according to claim 1, characterized in that, The drying in step one is carried out in a drying oven.

5. The method for recycling asphalt from road asphalt waste according to claim 1, characterized in that, The mixing tank in step two has an acid and alkali resistant lining, and the drying temperature in step two is 50-70℃.

6. The method for recycling asphalt from road asphalt waste according to claim 1, characterized in that, The filtration in step three can be any one of vacuum filtration, suction filtration, or centrifugal filtration.

7. The method for recycling asphalt from road asphalt waste according to claim 1, characterized in that, In step four, the distillation separation temperature is 130℃, and the carbon dioxide gas flow rate is controlled at 1000mL / min.

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