CN114481749B - Hot plant-mixing, regenerating, pre-mixing and step-by-step mixing control method for old asphalt materials - Google Patents

Abstract

The invention discloses a plant-mixing hot-recycling premixed step-by-step mixing control method for old asphalt materials, which solves the problem of asphalt aging in the existing process. The method comprises two important improvement steps of pre-cooling and cutting carbon fiber yarns, wherein old asphalt materials are put into a cold water tank, the old asphalt materials and the cold water are subjected to cold exchange by soaking in the cold water, and the temperature of the old asphalt materials is reduced to be within the range of 0-5 ℃; heating the new aggregate in a No. 1 rotary kiln, wherein the temperature of the heated new aggregate is not lower than 200 ℃, the optimal temperature is 220 ℃, heating the RAP in a No. 2 rotary kiln, wherein the temperature of the heated RAP is not higher than 80 ℃, adding a regenerated SBS modified old asphalt material modifier and a cut carbon fiber yarn into the No. 2 rotary kiln, and mixing; the invention realizes the purpose of premixed step-by-step mixing by mixing in the mixing pot, heat-preserving spiral conveying mixing and mixing in the mixing plant, improves the mixing uniformity, reduces the high-temperature time period of asphalt, and is beneficial to the maintenance state of high performance of asphalt.

Description

Hot plant-mixing, regenerating, pre-mixing and step-by-step mixing control method for old asphalt materials

Technical Field

The invention relates to the technical field of plant-mixed thermal regeneration production of old asphalt materials.

Background

The regeneration technology of old asphalt material is that after milling, recovering, crushing and sieving, the old asphalt pavement is re-mixed with regenerant, new asphalt material, new aggregate, etc. in certain proportion to form mixed material with certain road performance, and the mixed material is re-paved on pavement.

The technical route comprises in-situ regeneration and plant-mix regeneration, and can also be divided into hot regeneration and cold regeneration. The plant heat regeneration is the key point of research and development of various units at present, and the development of the plant heat regeneration technology is also an important subject related to the highway maintenance technology and the recycling rate of renewable resources in China.

Four difficulties are present regarding the application of the hot mix plant regeneration technology:

firstly, in the process of breaking old asphalt materials obtained by milling, jaw crushers, impact crushers or hammer crushers are adopted at present, and the efficiency of the equipment is high, but in the breaking process, the existing shearing force can cause the temperature rise of the old asphalt materials, meanwhile, the uniformity of broken particles is poor, and the damage to the particles is caused.

Secondly, the problem of heating RAP (reclaimed materials) in the old asphalt materials. In the production process of plant-mixed heat regeneration, RAP needs to be heated, and the heating process generally adopts a fuel nozzle heating mode to exchange heat. In theory, the uniform heating process is more beneficial to asphalt stabilization, and in practice, factors such as the height of the heating temperature of the RAP in the rotary kiln, the selection of a heating mode, whether a heating structure is reasonable or not and the like greatly influence the stability of the final product material, the running reliability of equipment and the continuity. Therefore, in the process of making the process, the heating mode and the type selection of the heating equipment are particularly important.

Thirdly, the RAP bonding problem is a derivative problem of the hot-mix plant recycling technology, and the bonding problem restricts the whole production process from the moment the RAP temperature is increased. The adhesion problem exists in both rotary kilns and temporary storage bins and conveying channels. Asphalt recycling adhesion has a bi-directional positive side and a negative, negative side. Wherein, after asphalt is heated, the adhesiveness of asphalt is reduced, and the mechanism and chemical components of asphalt are changed after repeated heating, so that the adhesiveness is reduced. Meanwhile, the dust pollution and impurity introduction in the production site can reduce the adhesive property of the adhesive. Therefore, in the process of making the process, the problem of the decrease of the adhesive property of the waste asphalt material is especially solved.

Fourth, asphalt smoke can be generated after asphalt reclaimed materials are heated, and influence factors are numerous, wherein the heating temperature is a main factor influencing the chemical components of the asphalt smoke. The asphalt fume pollutes the environment, and the collection and treatment of the asphalt fume are very difficult. At present, the common collection and treatment methods include an incineration method, a mechanical separation method, a spray tower water film washing method, an activated carbon adsorption method, an electric dust removal method and the like. In the current engineering practice, several methods are adopted and used for reducing the emission of asphalt smoke to the greatest extent, but no method is adopted to reduce the generation of asphalt smoke from the source.

Disclosure of Invention

The invention mainly aims to provide a plant-mixed hot-regenerated premixed step-by-step mixing control method for old asphalt materials, and provides a new process route under the condition of keeping the asphalt cohesiveness not reduced as much as possible, so as to solve the defects and the shortcomings in the technical background.

The technical scheme adopted for solving the technical problems is as follows:

the plant-mixing hot-recycling pre-mixing step-by-step mixing control method for the old asphalt materials comprises the following steps of:

s1: the old asphalt material is put into a cold water tank, a scraper type conveyer belt is arranged in the cold water tank, the scraper type conveyer belt is arranged along the length direction of the cold water tank, the old asphalt material obtained by milling is put into the cold water tank and is put onto the scraper type conveyer belt, the scraper type conveyer belt is partially immersed in cold water and slowly runs, the old asphalt material and the cold water are subjected to cold exchange through immersing in the cold water, and the temperature of the old asphalt material is reduced to be within the range of 0-5 ℃;

s2: the old asphalt materials with low temperature are put into a centrifugal impact crusher, the centrifugal acceleration of the centrifugal impact crusher is not lower than 5G, the speed of the materials after acceleration is not lower than 100 m/s, as the brittleness of the old asphalt materials in a low temperature state is obviously increased, the impact crushing effect can be realized, and then the crushed materials are screened to obtain RAP materials with different granularity specifications;

s3: the RAP materials with different granularity specifications are respectively stacked in different bins and are in a standby state;

s4: randomly sampling and detecting new aggregate, new asphalt and asphalt regenerated SBS modified old asphalt material modifier;

s5: designing mineral aggregate grading, wherein grading parameters meet related pavement construction technical specifications, and expanding the process based on data obtained in a laboratory and technical specification requirements;

s6: heating in a rotary kiln, putting the new aggregate into a No. 1 rotary kiln for heating, wherein the temperature of the new aggregate after heating is not lower than 200 ℃, the optimal temperature is 220 ℃, putting RAP into a No. 2 rotary kiln for heating, the temperature of the RAP after heating is not higher than 80 ℃, adding a regenerated SBS modified old asphalt material modifier and a cut carbon fiber yarn into the No. 2 rotary kiln, and mixing;

s7: putting the new aggregate and RAP generated in the step S3 into a mixing pot according to the grading proportion for pre-mixing, wherein the pre-mixing time is strictly controlled in the pre-mixing process, and the mixing time is controlled within 1 minute;

s8: before entering a mixing plant, adding new asphalt into a conveying path of a heat-preserving spiral elevator, and realizing secondary step mixing of materials by utilizing a spiral lifting process;

s9: after being mixed in the mixing plant, the mixture is transported to a paving site for paving operation in a heat preservation state.

The mixing plant and the mixing pot are designed into inert gas space, so that the generation amount of asphalt smoke is reduced from the source.

The cold water tank is provided with a circulating filtering and purifying system.

The cold water in the cold water tank is in an ice-water mixture state.

Asphalt is extracted from the asphalt tank by a heat-preserving three-screw pump and is sent into a conveying path of a heat-preserving spiral elevator.

The centrifugal impact crusher can be arranged in series in sequence.

The centrifugal impact crusher has a dehydration function for crushing and generating RAP.

The beneficial effects of the invention are as follows:

according to the invention, the recycled blocky old asphalt materials are cooled and centrifugally crushed by using the centrifugal impact crusher for the first time, so that the mechanical damage of the traditional jaw crusher to particles in the old pavement materials is avoided, the integrity of the particles is kept, and the performance of the new raw materials is kept.

And in addition, the invention effectively reduces the generation amount of asphalt smoke from the source by carrying out far infrared heating transformation and inert environment transformation on the rotary kiln, and is more environment-friendly.

And thirdly, the invention realizes the aim of premixed step-by-step mixing by mixing in the mixing pot, insulating and spiral conveying mixing and mixing in the mixing plant, improves the uniformity of mixing, reduces the high-temperature time period of asphalt and is beneficial to the maintenance state of high performance of asphalt.

Drawings

FIG. 1 is a process diagram of the present invention.

Fig. 2 is a system diagram of the present invention.

Detailed Description

Conventional mixing in the traditional process refers to a process route of mixing RAP, new aggregate, new asphalt and the like in one time, and has the defects of long heating time, long mixing process, poor uniformity, asphalt performance reduction, more asphalt smoke and the like.

In order to improve the bonding performance of the mixture, reduce the generation amount of asphalt smoke and avoid degradation and delamination of waste asphalt pavement materials, the invention provides a plant-mixing thermal regeneration process for regenerating old asphalt materials, and the bonding comprehensive performance is improved by adopting effective control of pre-mixing and step-by-step mixing.

The premixed step-by-step mixing in this embodiment means that the original mixing process is divided into several sub-steps, the mixing objects and the mixing environments in each step are different, and the fine screening of the mixture is improved through the design of the sub-steps. And by reasonably arranging an inert gas supplementing system, the generation amount of asphalt smoke is reduced from the source, the subsequent asphalt smoke treatment investment is reduced, and the environment is protected.

The old asphalt material recovered by milling or the like is mainly composed of asphalt, coarse aggregate, fine aggregate, mineral powder, a small amount of impurities (including but not limited to dust, sand and the like), and the old asphalt material is referred to as the old asphalt material in this embodiment. Since various materials in the old asphalt material are uniformly distributed, the pure recovery of the old asphalt material cannot be directly used here. The process comprises the steps of carrying out fine screening, impurity removal and other pre-mixing on the raw materials, or carrying out step-by-step mixing on the raw materials with new aggregate, new asphalt and cut carbon fiber yarns to form a regenerated old asphalt material meeting the engineering paving requirements.

After the premixed step-by-step mixing process of the embodiment, the mixing components of a specific recycled old asphalt material comprise the following components in percentage by mass: 71-75% of RAP, 20-25% of new aggregate, 7-8% of new asphalt, 0.01-0.3% of cut carbon fiber yarn and 0.1-0.2% of regenerated SBS modified old asphalt material modifier; the amount of each component can be selected in a given range according to actual needs, and the total sum is 100%, wherein the length of the segmented carbon fiber is controlled between 2 cm and 8 cm. The segmented carbon fiber is obtained from various industrial products recycled from the existing waste, such as various disassembled carbon fiber fan blades and the like, and is obtained through full cracking and segmentation, and the implementation of the process also increases a carbon fiber waste utilization channel and is environment-friendly. If the conditions do not allow, the cut carbon fiber filaments can be omitted.

The RAP in this embodiment is a material that is recycled in stages by the crushing and sieving process of the crushing and sieving device in the mixing station, and the RAP obtained by the process contains asphalt, coarse aggregate, fine aggregate, mineral powder, a small amount of impurities (including but not limited to dust and sand). In the process, a low-temperature cracking process is adopted, adverse effects on asphalt performance in RAP are avoided through introduction of the low-temperature cracking process, and the maintenance of granularity is facilitated, and the specific process is elaborated in the subsequent implementation process.

The new aggregate is an aggregate for common roads, and the proper particle size is selected according to the actual engineering requirements.

The new asphalt is used as an additive to make up the defect of the reduction of the RAP adhesive property.

The regenerated SBS modified old asphalt material modifier mainly comprises SBS, a tackifying component, a compatibilizer component and the like and is used for improving the adhesive property of the old asphalt material. For example, as a conventional option, the SBS modified old asphalt modifier may be a high viscosity asphalt additive of the Xiang-Chemicals GN-01 family or a RMA thermal regeneration composite modifier, just by way of example, without undue limitation to the manufacturer and brand.

The method for controlling the plant-mixed hot recycling premixed step-by-step mixing of the old asphalt material is illustrated for the convenience of further understanding of the technical scheme of the invention:

example 1

Referring to fig. 1 and 2, the process of the embodiment is described from the beginning of milling and the end of the recycled asphalt mixture:

(1) Precooling, first a loading hopper 10, uses a truck to discharge used material into the loading hopper 10. A step of cooling the recovered bulk material is added, specifically, a rectangular cold water tank 20 is added, a scraper type conveyer belt 21 is installed in the cold water tank, the scraper type conveyer belt is arranged along the length direction of the cold water tank, the bulk material obtained by milling is thrown onto the scraper type conveyer belt in the cold water tank through a storage bin, the scraper type conveyer belt is partially immersed in cold water, the cold water exchanges cold with the bulk material through immersing in the cold water, the temperature of the bulk material is reduced to be in the range of 0-5 ℃, and the cold water is in an optimal ice-water mixture state. The low-temperature state is more beneficial to crushing of the block pavement materials. The waste asphalt material in a low-temperature state has stronger brittleness, and the crushing effect is easier to generate in the process of impacting the inner wall in the centrifugal impact crusher, so that the crushing efficiency is improved, and the original granularity and viscosity of asphalt and massive materials in the waste asphalt material are kept.

The cold water soaking process can further clean the blocky materials, improve the cleanliness of RAP materials and improve the bonding performance of construction pavement.

The cold water is circularly filtered and purified, and the turbid cold water can enter the filtering system 22 for recycling, and a water purifying system is introduced into the system, so that wastewater is basically not discharged.

Through implementation of the pre-cooling process, the problem that centrifugal crushing equipment cannot be applied to RAP material treatment with high efficiency is synchronously solved.

(2) Centrifugal crushing and screening

A centrifugal impact crusher 30 is installed at the discharge end of the cold water tank for crushing the cooled material. The centrifugal acceleration of the centrifugal impact crusher is up to 10G, and the speed of the accelerated material is up to 200 meters per second, so that the massive material can be completely cracked at one time. The specific process is that the material of low temperature gets into this equipment from the top blanking mouth of breaker, then the material is accelerated by high-speed rotatory centrifugal flywheel to throw away the impact equipment inner wall, form effectual rupture. In the process, the centrifugal impact crusher replaces the traditional jaw crusher, the breaking hammer and the like, and the impact between the materials and the equipment is utilized to generate crushing, so that the crushing process does not generate heat or generates little heat, and the influence on the physical properties of the materials is minimal.

Meanwhile, in the centrifugal cracking process, the temperature is raised naturally along with low-temperature materials, and the temperature raising range is limited and is generally lower than the ambient temperature.

Further, if the crushing effect of one centrifugal impact crusher is not ideal, secondary centrifugal crushing can be performed according to the design requirement, so that particles generated by centrifugal crushing are finer, and the technical requirement of secondary use is met.

Further, after preliminary impact, screening is carried out to form 1#RAP, 2#RAP and powder with the diameters of 16 mm-30 mm, 1-16 mm and 0-1 mm, and the screened materials are basically in a normal temperature state.

For the treatment of RAP, it is also conceivable to use more screens for classification after crushing in a mixing plant, for example to screen crushed material into multiple stages. Crushing and sieving, and the grading of the materials meets the production requirement, and then the materials can be sent to a mixing plant for production, or can be stacked and stored for standby.

The centrifugal crushing process is combined with the cold water soaking process, so that the temperature of materials is low, the problem of heating of RAP materials in the crushing process of a traditional crusher is solved, the problem that RAP materials are easy to agglomerate again under the combined action of dead weight, temperature and old asphalt is solved, and the centrifugal crushing process has positive significance for improving the quality of RAP. Meanwhile, the method has positive significance for preventing asphalt from being aged continuously, segregation, hardening or caking of the old material grading and ensuring the stability of the quality of the old material.

The centrifugal crushing process also realizes the primary dehydration of the RAP, so that the RAP is in a basically dehydrated state.

(3) Separate warehouse stacking

And (3) uniformly stacking the 1#RAP, the 2#RAP and the powder obtained in the step (2) in different bins respectively, wherein the temperature of the RAP material is mainly affected by the air temperature and the fluctuation is small during the storage period in a standby state. Wherein, the design of feed bin satisfies conventional design.

Further 1#rap, 2#rap and powder mentioned above are lifted by different lifts 40 respectively and stored in dedicated bins 41 for use.

(4) Raw material detection

The materials such as the selected new aggregate, new asphalt and the like are randomly sampled and tested for quality, and all indexes are required to meet the requirements of the Highway asphalt pavement regeneration technical Specification (JTG/T5521-2019) and the Highway asphalt pavement construction technical Specification (JTG F40-2004).

Selecting two RAPs and powder materials in the step (2), extracting and screening, and respectively performing performance test on the extracted and recovered old asphalt and old aggregate, wherein each index is required to meet the requirements of the Highway asphalt pavement regeneration technical Specification (JTG/T5521-2019);

and screening the old aggregate to obtain mineral aggregate grading. The more the number of steps is, the more stable the gradation of the regenerated mixture is, and the step of the step number of 2 to 5 is also carried out according to the step.

And (3) performing performance test on the selected new asphalt and the regenerated SBS modified old asphalt material modifier, wherein the new asphalt can be common SBS modified asphalt or high-viscosity asphalt. The new asphalt selected at this time is SBS modified asphalt, the regenerated SBS modified old asphalt material modifier is GN-01 asphalt high-viscosity additive of Xiang cross, and each index is required to meet the requirements of the Highway asphalt pavement regeneration technical Specification (JTG/T5521-2019) and the Highway asphalt pavement construction technical Specification (JTG F40-2004).

(5) Grading design

According to specific engineering requirements, mineral aggregate grading is designed, grading parameters meet relevant pavement construction technical specifications, and the process is developed based on data obtained by a laboratory and technical specification requirements.

(6) Heating the rotary kiln, firstly selecting RAP materials in 1#RAP and 2#RAP bins and new aggregates (broken stone, gravel, sand, slag and the like) in new aggregate bins for mixing according to grading requirements, wherein the number of mixing places is two, the rotary kiln 50 is used for mixing, the new aggregates and the RAP are heated in advance before mixing, the temperature of the heated new aggregates is slightly higher than 220 ℃ (the optimal temperature range is between 200 ℃ and 230 ℃), and the temperature of the RAP is slightly lower than 80 ℃. The RAP with low temperature has certain fluidity, is not adhered to the wall of the hopper, and effectively solves the adhesion effect caused by the overhigh RAP temperature in the traditional process.

In the heating process, the temperature of the new aggregate is obviously higher than 220 ℃, more heat energy is reserved in the new aggregate, the new aggregate does not contain asphalt components, and in the subsequent mixing process of the new aggregate and the RAP, heat exchange can occur between the new aggregate and the RAP, so that the new aggregate achieves the heat balance again, and meanwhile, the new aggregate with higher temperature has the effect of local fast melting on asphalt on the surface layer of the RAP material.

Wherein, above-mentioned heating process, new aggregate adopts 1# rotary kiln to heat, and the RAP adopts 2# rotary kiln to heat, forms different heating temperature, adds the modified old pitch material modifier of regeneration SBS in 2# rotary kiln and mixes evenly, mixes cut carbon fiber silk and RAP in 2# rotary kiln, takes place adhesion effect at 2# rotary kiln inscription section carbon fiber silk and RAP surface, and the temperature control of RAP is below 80 ℃, consequently, cut carbon fiber silk adheres to the RAP granule surface.

After the segmented carbon fiber yarn is added into asphalt, the segmented carbon fiber yarn is directly contacted with new aggregate with higher temperature, so that the flexibility of the segmented carbon fiber yarn is increased, and the tensile property of the asphalt is improved under the adhesion state of the asphalt on the surface.

The optimal cutting length of the cutting section in the embodiment is within 10 cm, for example 3 cm and 5 cm.

The original state of the asphalt used material is granular, the asphalt used material is still in a non-sticky state of the granules at 80 ℃, the asphalt used material has good trafficability in a rotary kiln, and the adhesion defect of the asphalt used material in a No. 2 rotary kiln is overcome.

(7) Mixing in a mixing pot

And (3) putting the new aggregate and RAP generated in the step (6) into a mixing pot (60) according to the grading proportion for pre-mixing, wherein the pre-mixing time is strictly controlled in the pre-mixing process, the total mixing time is controlled within 1 minute, and the heat exchange between the high-temperature new aggregate and the secondary high-temperature RAP material occurs in the mixing process, so that the mixing pot is not required to be heated, the temperature of the mixed material is controlled to be 120-140 ℃ after mixing, and the mixed material is randomly conveyed to a subsequent process.

In the traditional process, the theoretical heating temperature (discharging temperature) of the RAP is between 120 and 140 ℃, the embodiment breaks through the limitation, the old asphalt material is pre-softened in a temperature reducing mode, after the pre-softened old asphalt material is mixed with new aggregate up to 220 ℃, heat exchange is completed in the mixing process, so that the temperature of the mixed old asphalt material reaches the optimal 120 to 140 ℃ temperature range, the high-temperature time period of the old asphalt material is shortened through direct mixing of the two materials with different temperatures, and the high-temperature aging of asphalt can be effectively prevented.

In the process, the proportion of various materials is controlled through the opening degree of the gate and the matching of the metering meter.

Then, a heat-insulating spiral elevator with a heat-insulating function is used for carrying out high lifting, wherein the heat-insulating spiral elevator is a measure of adding a heat-insulating layer outside a conveying cylinder of a conventional spiral conveyor. In the conveying process, the internal materials are in a heat preservation state.

In the mixing process, the RAP temperature is increased, and the segmented carbon fiber filaments are further attached between RAP particles and new aggregate particles, so that the adhesion enhancing effect is achieved.

(8) Spiral lifting and mixing

Before entering the mixing plant, the process of adding the asphalt and the new asphalt in the conveying path of the heat-insulating spiral lifter 70 fully utilizes the spiral lifting process to realize secondary step mixing of materials, and simultaneously, the implementation of the process effectively reduces the mixing time in the mixing plant process, and the reduction of the mixing time has positive significance for reducing asphalt aging.

For example, asphalt is pumped from an asphalt tank by a heat-insulating three-screw pump and is fed into an asphalt metering scale to meter new asphalt, and the new asphalt is uniformly added into a conveying path of a heat-insulating spiral elevator until the new asphalt is conveyed to a mixing plant and uniformly mixed.

Meanwhile, the new asphalt is added into the heat-preserving spiral lifting channel in proportion to be fully mixed with the mixture, and compared with the traditional mode of directly adding the new asphalt into the mixing plant, the method has positive significance in shortening the mixing time of the mixing plant.

(9) Mixing plant for mixing

To the mixing plant 80, the process is compressed to about 1 minute, and the continuous mixing plant equipment with continuous mixing function is preferably used in the process because the mixing time is compressed in the step, so that the continuous production can be realized. Shortening the mixing time can avoid the defect caused by asphalt aging reduction, and has positive significance for maintaining the performance of asphalt materials.

And finally, transporting the material to a paving site for paving operation under the heat preservation state.

Example two

The rotary kiln in the embodiment adopts countercurrent heating, and comprises a rotary kiln and a far infrared heating rod, wherein the far infrared heating rod is arranged at the discharge end of the rotary kiln, and the rolling and cloud infrared heating modes are adopted to heat the old asphalt material. The heating mode has the advantages that the heat exchange efficiency is extremely high, the temperature of the regenerated material can be quickly increased, electric heating is adopted, open fire does not exist, the content of asphalt smoke is reduced, and a large amount of radiant heat can be fully utilized.

Further, the inside of the 2# rotary kiln is dynamically sealed, a set of nitrogen supplementing device is additionally arranged outside the rotary kiln, nitrogen is supplemented into the 2# rotary kiln by the nitrogen supplementing device, an inert environment is formed, the oxidation reaction of asphalt and oxygen is avoided or reduced, the reduction of the oxidation of asphalt is facilitated, and the generation amount of asphalt smoke is reduced from the source.

Further, the mixing pot and the mixing plant are dynamically sealed, a nitrogen supplementing device is additionally arranged outside the rotary kiln, nitrogen is supplemented into the 2# rotary kiln by the nitrogen supplementing device, an inert environment is formed, the activity of asphalt is reduced, and the generation amount of asphalt smoke is reduced from the source.

A batching conveying system based on the process: comprises a centrifugal impact crusher, a storage bin, a belt feeder, a belt conveyor, a Leng Zhenshai, a rotary kiln, a heat preservation spiral elevator, a metering weighing hopper, a mixing pot, a mixing plant, a tail gas treatment module and an electric control system.

The above examples are provided for illustrating the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and those skilled in the art should not depart from the spirit of the present invention in all kinds of modifications and improvements that fall within the scope of the present invention as defined in the appended claims.

Claims (6)

1. The plant-mixed hot-regenerated pre-mixed step-by-step mixing control method for the old asphalt material is characterized by sequentially carrying out the following steps:

s1: the old asphalt material is put into a cold water tank, a scraper type conveyer belt is arranged in the cold water tank, the scraper type conveyer belt is arranged along the length direction of the cold water tank, the old asphalt material obtained by milling is put into the cold water tank and is put onto the scraper type conveyer belt, the scraper type conveyer belt is partially immersed in cold water and slowly runs, the old asphalt material and the cold water are subjected to cold exchange through immersing in the cold water, and the temperature of the old asphalt material is reduced to be within the range of 0-5 ℃;

s2: feeding the low-temperature old asphalt material into a centrifugal impact crusher, wherein the centrifugal acceleration of the centrifugal impact crusher is not lower than 5G, the speed of the material after acceleration is not lower than 100 m/s, and then screening the crushed material to obtain RAP materials with different granularity specifications, so as to form 1#RAP, 2#RAP and powder with the particle sizes of 16 mm-30 mm, 1-16 mm and 0-1 mm;

s3: the RAP materials with different granularity specifications are respectively stacked in different bins and are in a standby state;

s4: randomly sampling and detecting new aggregate, new asphalt and asphalt regenerated SBS modified old asphalt material modifier;

s5: designing mineral aggregate grading, wherein grading parameters meet related pavement construction technical specifications, and expanding the process based on data obtained in a laboratory and technical specification requirements;

s6: heating the rotary kiln, namely heating the rotary kiln in a countercurrent way, wherein the rotary kiln comprises a rotary kiln and a far infrared heating rod, the far infrared heating rod is arranged at the discharge end of the rotary kiln, the rolling and far infrared heating modes are adopted to heat the old asphalt material, new aggregate is put into the No. 1 rotary kiln for heating, the temperature range of the heated new aggregate is 220-230 ℃, RAP is put into the No. 2 rotary kiln for heating, the temperature of the heated RAP is slightly lower than 80 ℃, and the regenerated SBS modified old asphalt material modifier and the cut carbon fiber filaments are added into the No. 2 rotary kiln for mixing;

s7: putting the new aggregate and RAP generated in the step S3 into a mixing pot according to the grading proportion for pre-mixing, wherein in the pre-mixing process, the mixing time is controlled within 1 minute;

s8: before entering a mixing plant, adding new asphalt into a conveying path of a heat-preserving spiral elevator, and realizing secondary step mixing of materials by utilizing a spiral lifting process; filling inert gas into the mixing space of the mixing plant and the mixing pot,

s9: after being mixed in the mixing plant, the mixture is transported to a paving site for paving operation in a heat preservation state.

2. The method for controlling plant-mixed hot recycling premixed step-by-step mixing of old asphalt materials according to claim 1, wherein the method comprises the following steps of: the cold water tank is provided with a circulating filtering and purifying system.

3. The method for controlling plant-mixed hot recycling premixed step-by-step mixing of old asphalt materials according to claim 1, wherein the method comprises the following steps of: the cold water in the cold water tank is in an ice-water mixture state.

4. The method for controlling plant-mixed hot recycling premixed step-by-step mixing of old asphalt materials according to claim 1, wherein the method comprises the following steps of: asphalt is extracted from the asphalt tank by a heat-preserving three-screw pump and is sent into a conveying path of a heat-preserving spiral elevator.

5. The method for controlling plant-mixed hot recycling premixed step-by-step mixing of old asphalt materials according to claim 1, wherein the method comprises the following steps of: the centrifugal impact crusher is formed by two centrifugal impact crushers which are sequentially arranged in series.

6. The method for controlling plant-mixed hot recycling premixed step-by-step mixing of old asphalt materials according to claim 1, wherein the method comprises the following steps of: the centrifugal impact crusher has a dehydration function for crushing and generating RAP.