Hot in-place recycling asphalt pavement construction flue gas multiple purification device and hot in-place recycling asphalt pavement construction flue gas multiple purification method

Abstract

The invention discloses a hot in-place recycling asphalt pavement construction flue gas multi-purification device which comprises a catalytic reaction chamber, a cooling chamber, an absorption chamber and an adsorption chamber which are sequentially connected, a gas inlet pipeline is arranged on the catalytic reaction chamber, a heating device and a composite metal catalyst are arranged in the catalytic reaction chamber, the cooling chamber is used for reducing the flue gas temperature, and the absorption chamber is used for absorbing the flue gas. A mixed absorption solution of lauryl sodium sulfate and urea is contained in the absorption chamber, a silica gel particle layer and a Y-type zeolite molecular sieve layer are arranged in the adsorption chamber, and an exhaust pipeline is further arranged on the adsorption chamber. The asphalt flue gas is gradually purified through catalytic combustion, chemical absorption and physical adsorption, harmful substances in the flue gas are effectively removed, purified products are harmless substances, and secondary pollution is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of waste treatment, and particularly relates to a multi-stage purification device and method for the construction flue gas of in-situ hot recycling asphalt pavement. Background Art

[0002] The in-situ hot recycling technology for asphalt pavement is a newly emerging pavement maintenance process in recent years. It is a pavement maintenance process that uses professional equipment to perform a series of processes such as heating, milling, adding new materials and recycling agents, mixing, paving, and compaction on the old pavement, realizing a new technology for solving pavement diseases at one time. Due to the advantages of 100% utilization rate of old materials, no need for repeated transportation, and simple construction steps, in-situ hot recycling is widely used in the maintenance of old pavements and has broad market prospects.

[0003] The heating methods of the in-situ hot recycling technology usually include common methods such as open flame heating, infrared heating, microwave heating, and hot air circulation. During the heating process, the surface temperature of the road surface is relatively high. After exceeding 145°C, a large amount of asphalt fumes will be generated, including volatile organic compounds (VOCs), dust, harmful gas pollutants, etc., including many toxic and difficult-to-treat substances such as organic substances, sulfides, and nitrogen oxides, usually presenting gas-phase and liquid-phase states. The fine particles formed after the oxidation and reaction of organic substances lead to the generation of secondary organic aerosols, affecting the visibility of the air and causing serious harm to human health.

[0004] At present, due to technical reasons, the flue gas generated during the in-situ hot recycling construction process is difficult to popularize and is directly discharged, causing serious air pollution and endangering the personal safety of construction workers and residents at the same time. According to relevant reports, the number of people suffering from diseases caused by inhaling asphalt fumes has been increasing year by year, and the air pollution caused by the emission of asphalt fumes has become more and more serious. Therefore, there is an urgent need for a purification treatment device for the construction flue gas of in-situ hot recycling pavement to improve the air pollution caused by asphalt fumes and problems such as endangering the personal safety of construction workers. Summary of the Invention

[0005] Object of the Invention: Aiming at the above-mentioned shortcomings, the present invention provides a multi-stage purification device and method for the construction flue gas of in-situ hot recycling asphalt pavement, which crystallizes harmful substances in the asphalt fumes to avoid direct air pollution by the fumes and endanger the safety of construction workers and residents.

[0006] Technical solution: To solve the above problems, the present invention adopts a multi-purification device for the construction flue gas of in-situ hot recycled asphalt pavement, which includes a catalytic reaction chamber, a cooling chamber, an absorption chamber, and an adsorption chamber connected in sequence. An intake pipe is provided on the catalytic reaction chamber. A heating device and a composite metal catalyst are provided in the catalytic reaction chamber. The cooling chamber is used to reduce the temperature of the flue gas. A mixed absorption solution of sodium dodecyl sulfate and urea is contained in the absorption chamber. A silica gel particle layer and a Y-type zeolite molecular sieve layer are provided in the adsorption chamber, and an exhaust pipe is also provided on the adsorption chamber.

[0007] Further, the composite metal catalyst is in a honeycomb shape, and the base material is cordierite honeycomb ceramic. Pt and CeO 2 are loaded on the surface as active components. The mass fraction of Pt is 0.5-3wt%, and CeO 2 The mass fraction of is 5-15wt%.

[0008] Further, a nano-cobalt oxide solution is sprayed on the surface of the composite metal catalyst. The mass fraction of cobalt oxide in the nano-cobalt oxide solution is 1-5wt%, and the solvent is ethanol.

[0009] Further, the heating device is arranged on the inner wall of the catalytic reaction chamber to heat the flue gas entering from the intake pipe. The heating device includes a magnetron and a waveguide connected to the magnetron. One end of the magnetron not connected to the waveguide is fixed on the inner wall of the catalytic reaction chamber.

[0010] Further, a condenser tube is provided in the cooling chamber, and the condenser tube is arranged in a U-shaped reciprocating bend.

[0011] Further, in the mixed absorption solution of sodium dodecyl sulfate and urea, the volume fraction of sodium dodecyl sulfate is 0.3-0.8%, the volume fraction of urea solution is 2-4%, and the solvent is water.

[0012] Further, the silica gel particle layer and the Y-type zeolite molecular sieve layer are arranged in two layers and are isolated by a partition grille in the middle. The silica gel particle layer includes a number of high-temperature resistant nylon mesh bags filled with silica gel particles, and the Y-type zeolite molecular sieve layer includes a number of high-temperature resistant nylon mesh bags filled with Y-type zeolite molecular sieve particles.

[0013] The present invention also provides a purification method for the multi-purification device for the construction flue gas of in-situ hot recycled asphalt pavement, including the following steps:

[0014] S1. Catalytic combustion: Introduce the asphalt flue gas to be treated into the intake pipe and enter the catalytic reaction chamber. Turn on the heating device to heat the flue gas to the catalytic combustion temperature, so that the flue gas undergoes a catalytic reaction under the action of the composite metal catalyst;

[0015] S2. Flue gas cooling: The flue gas enters the cooling chamber to be cooled to the outlet temperature;

[0016] S3. Solution absorption: The cooled flue gas is introduced into the mixed absorption solution of sodium dodecyl sulfate and urea in the absorption chamber for absorption and purification treatment.

[0017] S4. Physical adsorption: The flue gas enters the adsorption chamber and is successively subjected to adsorption treatment through a silica gel particle layer and a Y-type zeolite molecular sieve layer, and the treated flue gas is discharged from the exhaust pipe.

[0018] Furthermore, the catalytic combustion temperature is 300 °C.

[0019] Furthermore, the outlet temperature is 50 - 60 °C.

[0020] Beneficial effects: Compared with the prior art, the significant advantages of the present invention are: (1) The asphalt fume is gradually purified through catalytic combustion, chemical absorption, and physical adsorption, effectively removing harmful substances in the flue gas, and the purified products are all harmless substances, avoiding secondary pollution; (2) The heating device and the composite metal catalyst are combined to improve the catalytic reaction efficiency, and the composite metal catalyst has a lower cost compared with the noble metal catalyst, reducing the economic cost of flue gas treatment; (3) By spraying nano cobalt oxide on the surface of the composite metal, the stability and purification efficiency of the catalyst are further improved, and the service life of the catalyst is extended; (4) The silica gel particle layer and the Y-type zeolite molecular sieve layer in the adsorption chamber can be reused after regeneration treatment, further reducing the cost of flue gas treatment. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of the catalytic reaction chamber and the cooling chamber of the present invention;

[0022] Figure 2 It is a schematic external structure diagram of the absorption chamber and the adsorption chamber of the present invention;

[0023] Figure 3 It is a cross-sectional view of the interior of the absorption chamber and the adsorption chamber of the present invention. Detailed Embodiments

[0024] As Figures 1 to 3As shown in the figure, a multi - purification device for the flue gas in the construction of in - situ hot - recycled asphalt pavement in this embodiment includes a catalytic reaction chamber 1, a cooling chamber 2, an absorption chamber 3, and an adsorption chamber 4 connected in sequence. An intake pipe 11 is provided at the top of the catalytic reaction chamber 1. Inside the catalytic reaction chamber 1, there is a heating device 12 and a composite metal catalyst. The heating device 12 is installed on the upper part inside the catalytic reaction chamber 1, and the composite metal catalyst is placed in the cavity of the catalytic reaction chamber 1. Specifically, the heating device 12 includes a magnetron and a waveguide. The magnetron is directly connected to the waveguide through a port. A plurality of mounting holes are evenly opened on the inner wall of the reaction chamber, and the aperture is matched with the outer diameter of the magnetron and the output - end flange. The output - end flange of the magnetron is fixed to the mounting hole of the reaction chamber through high - conductivity oxygen - free copper bolts. The magnetrons are arranged at equal intervals on the inner wall, and the distance between adjacent magnetrons is 0.4D, where D is the diameter of the catalytic reaction chamber. The single - tube power of the magnetron is 1.5 - 3 kW. The waveguide is a rectangular waveguide, with the specific model being WR340 and the frequency being 2.45 GHz.

[0025] The composite metal catalyst is processed into a honeycomb shape to increase its contact reaction area with the flue gas. The base material of the composite metal catalyst is cordierite (2MgO·2Al 2 O 3 ·5SiO 2 ) honeycomb ceramics, and Pt and CeO 2 are loaded on the surface as active components. The mass fraction of Pt is 0.5 - 3 wt%, and the mass fraction of CeO 2 is 5 - 15 wt%. And a nano - cobalt oxide (Co 3 O 4 ) solution is sprayed on the surface of the catalyst. The mass fraction of cobalt oxide in the nano - cobalt oxide solution is 1 - 5 wt%, and the solvent is ethanol. The composite metal catalyst is filled in multiple layers in the catalytic reaction chamber, and the distance between each layer is 10 mm to ensure the smooth flow of asphalt flue gas in the catalyst gap and avoid blockage.

[0026] At the bottom of the cooling chamber 2, there is a condensing pipe 21 for cooling the flue gas. The condensing pipe 21 is arranged in a U - shaped reciprocating bend to increase the laying length of the condensing pipe and improve the cooling effect. The cooling chamber 2 and the condensing pipe 21 are both made of 316L stainless steel, which has good high - temperature resistance and heat - conduction performance. The gas outlet end of the cooling chamber 2 is connected to the gas inlet end of the absorption chamber 3, and the flue gas is introduced into the absorption chamber 3 through an inlet pipe 31.

[0027] At the bottom of the absorption chamber 3, there is a solution absorption pool 32. The solution absorption pool 32 is filled with a mixed absorption solution of sodium dodecyl sulfate (SDS) and urea. And the absorption pool 32 is connected to a solution storage pool 33 through an infusion pipe. The solution storage pool 33 is filled with a large amount of mixed absorption solution, which is used to supplement the solution in the solution absorption pool 32 in time. In the mixed absorption solution of sodium dodecyl sulfate and urea, the volume fraction of sodium dodecyl sulfate is 0.3 - 0.8%, the volume fraction of urea solution is 2 - 4%, and the solvent is water. The intake pipe 31 directly introduces the flue gas into the solution absorption pool 32, and after being absorbed by the solution, it flows into the adsorption chamber 4.

[0028] In the adsorption chamber 4, the silica gel particle layer 41 and the Y-type zeolite molecular sieve layer 42 are respectively installed in the lower layer and the upper layer. The two layers are isolated by a partition grille to prevent the two layers from contacting each other and causing competitive adsorption. The partition grille is made of 316L stainless steel. Specifically, silica gel particles with a particle size of 3 - 5 mm and a specific surface area of 600 - 800 m 2 / g are loosely filled in a high-temperature resistant nylon mesh bag. The mesh holes of the high-temperature resistant nylon mesh bag are 0.5 - 1 mm, and the filling density is controlled at 0.4 - 0.6 g / cm 3 , and then the mesh bag is laid flat at the bottom of the adsorption chamber 4 to form the silica gel particle layer 41. Y-type zeolite molecular sieve layer particles with a particle size of about 0.74 nm are loaded into a high-temperature resistant nylon mesh bag. The molecular sieve particles of this size have a higher matching degree with benzene series compounds and can filter and catalyze benzene series compounds more effectively. The mesh holes of the high-temperature resistant nylon mesh bag are 0.5 - 1 mm, and then the mesh bag is laid flat on the partition grille. To prevent the air flow from bypassing the silica gel particle layer 41 and the Y-type zeolite molecular sieve layer 42, a rubber sealing ring or a ceramic fiber pad is installed at the contact between the inner wall of the adsorption tower and the silica gel particle layer and the Y-type zeolite molecular sieve layer to avoid the air flow from bypassing from the edge. An exhaust pipe 43 is provided at the top of the adsorption chamber.

[0029] The silica gel particle layer 41 and the Y-type zeolite molecular sieve layer 42 are installed in a detachable manner. After being used for a period of time, they can be regenerated and continue to be put into use after regeneration. The silica gel particles can be desorbed by low-pressure steam purging at a temperature of 100 - 120 °C and a pressure of 0.5 - 0.9 bar(g) (gauge pressure); or desorbed by hot nitrogen with the temperature controlled at 80 - 100 °C, and the regeneration period is 12 - 24 hours. After regeneration, it needs to be cooled to below 50 °C before being put back into use. The Y-type zeolite molecular sieve is desorbed by high-temperature hot air at a temperature of 250 - 300 °C to achieve the effect of regeneration and reuse.

[0030] The purification process of the on-site thermal regeneration asphalt pavement construction flue gas multi-purification device of the present invention is as follows:

[0031] S1. Catalytic combustion. Introduce the asphalt fume to be treated into the intake pipe 11. The main harmful substances in the fume are volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), particulate matters, etc. After the fume enters the catalytic reaction chamber 1, turn on the heating device 12 to heat the fume to 300 °C to reach the catalytic combustion temperature. Under the catalysis of the composite metal catalyst, purify PAHs and VOCs in the asphalt fume, especially hydrocarbons, aldehydes and benzene series. In this process, improve the reaction activity through microwave heating, and make the asphalt fume catalytically combust to generate CO 2 and H 2 O without generating other harmful substances additionally. Make Pt and CeO 2 compounded into a honeycomb shape to make the fume fully contact with the composite metal catalyst. As a noble metal, Pt has high activity, provides active sites for the fume reaction, and promotes the oxidation of complex organic substances; CeO 2 as a transition metal has good oxygen storage and release functions, which helps to maintain the oxygen concentration during the reaction and enhance the stability of the reaction. Uniformly spray nano cobalt oxide (Co 2 ) on the composite metal catalyst Pt-CeO 3 O 4 . Through the strong redox ability of Co 3 O 4 , enhance the activation of oxygen in the catalytic reaction, and then promote the oxidation reaction of VOCs. At the same time, improve the anti-poisoning property of the catalyst, enhance the stability and long-term efficiency of the catalyst, and extend the service life.

[0032] S2. Fume cooling. The fume after catalytic combustion enters the cooling chamber, and the fume is cooled through the condensing pipes laid at the lower part to reach the reaction temperature of the subsequent absorption and adsorption steps. Based on the principle of countercurrent heat exchange, the water flow direction of the condensing pipes is opposite to the fume flow direction. The inlet temperature of the cooling water ≤ 25 °C. When the fume temperature is too high, an ice car group can be used to make the inlet temperature of the cooling water ≤ 15 °C and increase the water flow rate in the condensing pipes. After being cooled by the condensing pipes, the outlet temperature of the fume is 50 - 60 °C to ensure good effects of subsequent solution absorption and physical adsorption.

[0033] S3. Solution absorption. The cooled flue gas is introduced into the solution absorption tank 32 through the intake pipe 31 and undergoes absorption and purification treatment in the mixed absorption solution of sodium dodecyl sulfate (SDS) and urea. By utilizing the solubilization effect of SDS as an anionic surfactant, non-polar or weakly polar VOCs are encapsulated into micelles, especially showing a significant absorption effect on benzene series and PAHs in the flue gas. When the concentration of SDS exceeds the critical micelle concentration (CMC) (about 8 mM, i.e., 8 mmol / L), a micelle core is formed to encapsulate non-polar VOCs (such as benzene series, etc.) therein, achieving solubilization. While urea enhances the solubility of VOCs as a co-solvent, it can also capture aldehydes in the asphalt fume and achieve neutralization with sulfides. The waste liquid generated after the absorption solution contacts the harmful substances in the asphalt fume can be filtered through an activated carbon filter element, without generating hazardous waste and secondary pollution.

[0034] S4. Physical adsorption. After the flue gas undergoes solution absorption, it enters the adsorption chamber and successively passes through a silica gel particle layer filled with high-temperature resistant nylon mesh bags, a partition grille, and a Y-type zeolite molecular sieve filled with high-temperature resistant nylon mesh bags. Due to the characteristic that the surface of silica gel is rich in hydroxyl groups (-OH), it preferentially adsorbs alcohols and water molecules through hydrogen bonding and dipole interactions, especially showing a significant adsorption effect on small molecule alcohols such as methanol and ethanol. Through the size screening effect of the Y-type zeolite, benzene series are selectively adsorbed. The remaining VOCs in the flue gas are further filtered out through physical adsorption, and the treated flue gas is discharged from the exhaust pipe 43.

[0035] Table 1 shows the atmospheric pollutant emission content of the specific implementation cases of the present invention. The asphalt fume treated by the device of the present invention is analyzed by gas chromatography-mass spectrometry (GC-MS), and the pollutant emissions are detected by a Test 350 flue gas analyzer.

[0036] Table 1 Content of volatile organic compounds before and after treatment

[0037]

[0038] As can be seen from Table 1, the content of volatile organic compounds in the flue gas emitted during the construction process of the asphalt pavement is greatly reduced before and after being treated by the device of the present invention, and the purification effect is good.

[0039] The present invention gradually purifies asphalt fumes through catalytic combustion, chemical absorption, and physical adsorption, effectively removing harmful substances in the fumes. The purified products are all harmless substances, avoiding secondary pollution. By using a heating device in cooperation with a composite metal catalyst, the catalytic reaction efficiency is improved, and the composite metal catalyst has a lower cost compared with noble metal catalysts, reducing the economic cost of fume treatment. By spraying nano cobalt oxide on the surface of the composite metal, the stability and purification efficiency of the catalyst are further improved, and the service life of the catalyst is extended. The silica gel particle layer and Y-type zeolite molecular sieve layer in the adsorption chamber can be reused after regeneration treatment, further reducing the cost of fume treatment.

Claims

1. A multiple purification device for flue gas during hot-in-situ asphalt pavement regeneration, characterized in that: It comprises a catalytic reaction chamber, a cooling chamber, an absorption chamber and an adsorption chamber connected in sequence. The catalytic reaction chamber is provided with an air intake pipe, a heating device and a composite metal catalyst are arranged in the catalytic reaction chamber, the cooling chamber is used to reduce the flue gas temperature, the absorption chamber is filled with a mixed absorption solution of sodium dodecyl sulfate and urea, the adsorption chamber is provided with a silica gel particle layer and a Y-type zeolite molecular sieve layer, and the adsorption chamber is also provided with an exhaust pipe.

2. The multiple purification device for flue gas during hot-in-situ asphalt pavement construction as claimed in claim 1, characterized in that: The composite metal catalyst is in a honeycomb shape, the base material is cordierite honeycomb ceramic, Pt and CeO2 are loaded on the surface as active components, the mass fraction of Pt is 0.5-3wt%, and the mass fraction of CeO2 is 5-15wt%.

3. The multiple purification device for flue gas during hot-in-situ asphalt pavement construction as claimed in claim 2, characterized in that: The surface of the composite metal catalyst is sprayed with a nanometer cobalt oxide solution, the mass fraction of cobalt oxide in the nanometer cobalt oxide solution is 1-5wt%, and the solvent is ethanol.

4. The multiple purification device for flue gas during hot-in-situ asphalt pavement construction as claimed in claim 1, characterized in that: The heating device is arranged on the inner wall of the catalytic reaction chamber to heat the flue gas entering from the air intake duct. The heating device includes a magnetron and a waveguide connected to the magnetron. The end of the magnetron not connected to the waveguide is fixed on the inner wall of the catalytic reaction chamber.

5. The multiple purification device for flue gas during hot-in-situ asphalt pavement construction as claimed in claim 1, characterized in that: The cooling chamber is provided with a condenser tube, which is arranged in a U-shaped reciprocating bending manner.

6. The multiple purification device for flue gas during hot-in-situ asphalt pavement construction as claimed in claim 1, characterized in that: In the mixed absorption solution of sodium dodecyl sulfate and urea, the volume fraction of sodium dodecyl sulfate is 0.3-0.8%, the volume fraction of urea solution is 2-4%, and the solvent is water.

7. The multiple purification device for flue gas during hot-in-situ asphalt pavement construction as claimed in claim 1, characterized in that: The silica gel particle layer and the Y-type zeolite molecular sieve layer are arranged in two layers, separated by a partition grid in the middle. The silica gel particle layer includes a plurality of high temperature resistant nylon mesh bags filled with silica gel particles, and the Y-type zeolite molecular sieve layer includes a plurality of high temperature resistant nylon mesh bags filled with Y-type zeolite molecular sieve particles.

8. A purification method for flue gas from hot-in-situ asphalt pavement construction using a multiple purification device according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1, catalytic combustion; introducing the asphalt flue gas to be treated into the air intake pipe, entering the catalytic reaction chamber, turning on the heating device to heat the flue gas to the catalytic combustion temperature, so that the flue gas undergoes a catalytic reaction under the action of the composite metal catalyst; S2, flue gas cooling; The flue gas enters the cooling chamber and is cooled to the outlet temperature; S3, solution absorption: the flue gas after cooling is passed into the mixed absorption solution of sodium dodecyl sulfate and urea in the absorption chamber for absorption and purification treatment; S4, physical adsorption; The flue gas enters the adsorption chamber and passes through the silica gel particle layer and the Y-type zeolite molecular sieve layer in turn for adsorption treatment. The treated flue gas is discharged from the exhaust duct.

9. The purification method according to claim 8, characterized in that: The catalytic combustion temperature is 300°C.

10. The purification method according to claim 8, characterized in that: The outlet temperature is 50-60°C.

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