阅读说明：本技术 一种促进重质石油污染土壤热处理修复的方法 (Method for promoting thermal treatment restoration of heavy petroleum polluted soil ) 是由 谷庆宝 刘钰钦 马福俊 李晓东 马传博 孙宗全 沈佳伦 于 2021-08-24 设计创作，主要内容包括：一种促进重质石油污染土壤热处理修复的方法,包括将重质石油污染土壤进行风干、破碎、去除杂质,得到预处理的重质石油污染土壤；将预处理的重质石油污染土壤与强化剂进行充分混合,其中,强化剂能与重质石油烃分子中的杂原子结合,使重质石油烃分子中的碳原子与杂原子之间的化学键键能减弱；将预处理的重质石油污染土壤与强化剂的混合物在氮气气氛中进行热处理；将热处理后的土壤冷却至室温,以及将热处理产生的尾气进行冷凝回收,再经过活性炭吸附以去除未冷凝的尾气。该方法技术工艺简单,节能降耗、高效修复,修复后的土壤中石油烃浓度低于土壤质量风险管控值,具有复垦价值,并且可以降低尾气处理成本。(A method for promoting the thermal treatment restoration of heavy petroleum polluted soil comprises the steps of carrying out air drying, crushing and impurity removal on the heavy petroleum polluted soil to obtain pretreated heavy petroleum polluted soil; fully mixing the pretreated heavy petroleum polluted soil with a reinforcing agent, wherein the reinforcing agent can be combined with heteroatoms in heavy petroleum hydrocarbon molecules, so that the chemical bond energy between carbon atoms and heteroatoms in the heavy petroleum hydrocarbon molecules is weakened; carrying out heat treatment on the mixture of the pretreated heavy petroleum polluted soil and the reinforcer in a nitrogen atmosphere; and cooling the soil after the heat treatment to room temperature, condensing and recovering tail gas generated by the heat treatment, and adsorbing by using activated carbon to remove uncondensed tail gas. The method has the advantages of simple technical process, energy conservation, consumption reduction and high-efficiency restoration, the concentration of petroleum hydrocarbon in the restored soil is lower than the soil quality risk control value, the method has reclamation value, and the tail gas treatment cost can be reduced.)

1. A method for promoting the thermal treatment restoration of heavy petroleum polluted soil is characterized by comprising the following steps:

s1, air-drying, removing impurities and crushing heavy petroleum polluted soil to obtain pretreated heavy petroleum polluted soil;

s2, fully mixing the pretreated heavy petroleum polluted soil with a reinforcing agent, wherein the reinforcing agent can be combined with heteroatoms in heavy petroleum hydrocarbon molecules, so that chemical bond energy between carbon atoms and heteroatoms in the heavy petroleum hydrocarbon molecules is weakened, and the removal of the heavy petroleum hydrocarbon molecules is promoted;

s3, carrying out heat treatment on the mixture of the pretreated heavy petroleum polluted soil and the enhancer in a nitrogen atmosphere;

and S4, cooling the soil after the heat treatment to room temperature, condensing and recovering tail gas generated by the heat treatment, and adsorbing by using activated carbon to remove uncondensed tail gas.

2. The method for promoting the thermal treatment remediation of soil contaminated with heavy petroleum according to claim 1, wherein the fortifier is selected from the group consisting of Fe₂O₃、K₂CO₃、CaO、Al₂O₃HZSM-5 and red mud.

3. The method for promoting the thermal treatment remediation of soil contaminated with heavy petroleum according to claim 1, wherein the fortifier is Fe₂O₃。

4. The method for promoting the thermal treatment remediation of heavy petroleum-contaminated soil according to claim 1, wherein in step S2, the addition amount of the enhancer is 0.2-10% of the mass of the pretreated heavy petroleum-contaminated soil.

5. The method for promoting the thermal treatment remediation of soil contaminated by heavy petroleum according to claim 4, wherein the addition amount of the enhancer is 5% of the mass of the pretreated soil contaminated by heavy petroleum.

6. The method for promoting heat treatment remediation of heavy petroleum-contaminated soil according to claim 1, wherein in step S3, the mixture of the pre-treated heavy petroleum-contaminated soil and the fortifier is subjected to heat treatment at 200-500 ℃ in a nitrogen atmosphere with a carrier gas flow rate of 0.2-1L/min for 10-120 min.

7. The method for promoting the thermal treatment remediation of soil contaminated with heavy petroleum according to claim 6, wherein the thermal treatment temperature is 400 ℃.

8. The method for promoting thermal treatment remediation of soil contaminated with heavy petroleum according to claim 6, wherein the thermal treatment time is 30 min.

9. The method for promoting the thermal treatment remediation of soil contaminated with heavy petroleum according to claim 6, wherein the carrier gas flow rate of the nitrogen gas is 1L/min.

10. The method for promoting thermal treatment remediation of heavy petroleum-contaminated soil according to claim 1, wherein in step S1, the excavated heavy petroleum-contaminated soil is air-dried to a moisture content of less than 5% and crushed to a particle size of less than 24 mesh.

Technical Field

The invention relates to the technical field of polluted soil treatment, in particular to a method for promoting heat treatment restoration of heavy petroleum polluted soil.

Background

According to survey bulletin of national soil pollution conditions issued by the 2014 ministry of environmental protection and the ministry of national soil resources, the total overproof rate of soil pollution in China is as high as 16.1%. Among them, organic pollutants, especially petroleum pollutants, have become one of the important factors causing soil safety problems, and have serious adverse effects on soil ecology, crops and human health in polluted areas. Once entering the soil environment, the petroleum pollutants can undergo natural weathering to some extent, light hydrocarbons in the petroleum are removed through the weathering such as volatilization, diffusion, microorganism and photodegradation, and heavy petroleum hydrocarbon pollutants which are mainly difficult to biodegrade and remain in the soil. Furthermore, the interaction between the contaminants and the soil particles increases gradually with increasing weathering time. Therefore, the weathering/heavy petroleum polluted soil is difficult to restore, and is a difficult problem in the current soil restoration industry.

The heat treatment technology has the obvious advantages of high restoration efficiency, good adaptability to the types and concentrations of organic pollutants in soil and the like, and is widely applied to the restoration of the petroleum-polluted soil. Among them, the pyrolysis technology refers to a process of converting a compound into gas, liquid and coke at a relatively low temperature by thermochemical conversion under the condition of isolating air or a small amount of air. During pyrolysis, heavy petroleum hydrocarbon contaminants can be converted to stable and non-toxic coke at temperatures below their boiling point, improving soil fertility. However, for weathered/heavy petroleum polluted soil, the pyrolysis technology still has the defects of high energy consumption, great damage to the physicochemical properties of the soil, large tail gas release amount, high treatment cost and the like.

Disclosure of Invention

The invention provides a method for promoting heat treatment remediation of heavy petroleum polluted soil, which saves energy, reduces consumption, efficiently repairs and can reduce tail gas release amount, and solves the technical problems of high energy consumption, great damage to soil physicochemical properties, great tail gas release amount, high treatment cost and the like in the prior pyrolysis technology.

In order to solve the technical problems, the technical scheme of the invention is as follows:

the method for promoting the heat treatment remediation of the heavy petroleum polluted soil comprises the following steps: s1, air-drying, removing impurities and crushing heavy petroleum polluted soil to obtain pretreated heavy petroleum polluted soil; s2, fully mixing the pretreated heavy petroleum polluted soil with a reinforcing agent, wherein the reinforcing agent can be combined with heteroatoms in heavy petroleum hydrocarbon molecules, so that chemical bond energy between carbon atoms and heteroatoms in the heavy petroleum hydrocarbon molecules can be weakened, and the removal of the heavy petroleum hydrocarbon molecules is promoted; s3, performing heat treatment on the mixture of the pretreated heavy petroleum polluted soil and the reinforcer in a nitrogen atmosphere; and S4, cooling the soil after the heat treatment to room temperature, condensing and recovering tail gas generated by the heat treatment, and adsorbing by using activated carbon to remove uncondensed tail gas.

Preferably, in the method for promoting the thermal treatment remediation of the heavy petroleum polluted soil, the strengthening agent is selected from Fe₂O₃、K₂CO₃、CaO、Al₂O₃HZSM-5 and red mud.

Preferably, in the method for promoting the heat treatment remediation of the heavy petroleum polluted soil, the enhancer is Fe₂O₃。

Preferably, in the method for promoting the heat treatment remediation of the heavy petroleum-polluted soil, in the step S2, the addition amount of the reinforcing agent is 0.2-10% of the mass of the pretreated heavy petroleum-polluted soil

Preferably, in the method for promoting the thermal treatment remediation of the heavy petroleum-polluted soil, the addition amount of the enhancer is 5% of the mass of the pretreated heavy petroleum-polluted soil.

Preferably, in the method for promoting the thermal treatment remediation of the heavy petroleum-contaminated soil, in step S3, the mixture of the pre-treated heavy petroleum-contaminated soil and the strengthening agent is thermally treated at 200 to 500 ℃ in a nitrogen atmosphere with a carrier gas flow rate of 0.2 to 1L/min for 10 to 120 min.

Preferably, in the method for promoting the thermal treatment remediation of the heavy petroleum polluted soil, the thermal treatment temperature is 400 ℃.

Preferably, in the method for promoting the thermal treatment remediation of the heavy petroleum polluted soil, the thermal treatment time is 30 min.

Preferably, in the method for promoting the thermal treatment remediation of the heavy petroleum-contaminated soil, the flow rate of the carrier gas of the nitrogen gas is 1L/min.

Preferably, in the method for promoting the thermal treatment remediation of the heavy petroleum-contaminated soil, in step S1, the excavated heavy petroleum-contaminated soil is air-dried until the water content is less than 5% and is crushed until the particle size is less than 24 meshes.

The invention has the beneficial effects that:

according to the method for promoting the heat treatment restoration of the heavy petroleum polluted soil, the reinforcer is added into the heavy petroleum polluted soil before the heat treatment, the process operability is strong, only one stirring and mixing device for the polluted soil and the reinforcer is added in front of the pyrolysis treatment equipment, the technical process is simple, and the method can be widely used in engineering application; the method has the advantages that the pyrolysis technology is used for carrying out enhanced pyrolysis restoration on the heavy petroleum polluted soil, the concentration of petroleum hydrocarbon in the restored soil is lower than the soil quality risk control value, the heavy petroleum hydrocarbon pollutants are converted into stable and nontoxic coke at low temperature, the generated coke with a large number of pore structures is attached to the surface of soil particles, the phytogenic performance of the restored soil is improved, the fertility of the restored soil is improved, the restored soil has a reclamation value, and the aims of efficient restoration, energy conservation, consumption reduction and tail gas treatment cost reduction are fulfilled.

Drawings

In order to more clearly illustrate the detailed description of the invention or the technical solutions in the prior art, the drawings that are needed in the detailed description of the invention or the prior art will be briefly described below.

FIG. 1 is a flow chart of the method for promoting the thermal treatment remediation of heavy petroleum-contaminated soil according to the present invention.

FIG. 2 is a mechanism diagram of the method for promoting the thermal treatment remediation of heavy petroleum-contaminated soil according to the present invention.

FIG. 3 is a schematic view of a pyrolysis treatment apparatus used in the method for promoting thermal treatment remediation of heavy petroleum-contaminated soil according to the present invention.

FIG. 4 is a schematic diagram showing the relationship between the type and amount of the enhancer and the residual amount of total petroleum hydrocarbon pollutants in the heavy petroleum-contaminated soil in the method of the present invention.

FIG. 5 is a conventional pyrolysis without strengthening agent and Fe of the present invention₂O₃Energy consumption in the enhanced pyrolysis process is compared.

FIG. 6 is a conventional pyrolysis without strengthening agent and Fe of the present invention₂O₃And (3) enhancing the gas release type and content in the pyrolysis process.

Detailed Description

In order to more clearly illustrate the detailed description of the invention or the technical solutions in the prior art, the drawings that are needed in the detailed description of the invention or the prior art will be briefly described below.

The method for promoting the thermal treatment remediation of the heavy petroleum polluted soil, disclosed by the invention, comprises the following steps as shown in figure 1:

s1, air-drying, removing impurities and crushing the heavy petroleum polluted soil to obtain the pretreated heavy petroleum polluted soil. In a preferred embodiment, the excavated heavy petroleum-polluted soil is placed in a shade place to be air-dried until the water content is lower than 5%, large blocks of large stones and animal and plant residues are removed, and the soil is crushed until the particle size is smaller than 24 meshes.

S2, fully mixing the pretreated heavy petroleum polluted soil with a reinforcing agent, wherein the reinforcing agent can be combined with heteroatoms in heavy petroleum hydrocarbon molecules, so that the chemical bond energy between carbon atoms and heteroatoms in the heavy petroleum hydrocarbon molecules is weakened, and the heavy petroleum hydrocarbon molecules are promotedAnd (4) removing. In a preferred embodiment, the fortifier is selected from Fe₂O₃、K₂CO₃、CaO、Al₂O₃HZSM-5 (molecular sieve with an orthorhombic crystal system and MFI type structure) and red mud. In a preferred embodiment, the enhancer is Fe₂O₃. And the addition amount of the enhancer is 0.2-10%, preferably 0.2-5%, and more preferably 5% of the mass of the pretreated heavy petroleum-polluted soil.

And S3, carrying out heat treatment on the mixture of the pretreated heavy petroleum polluted soil and the reinforcer in a nitrogen atmosphere. In a preferred embodiment, the mixture of the pretreated heavy petroleum-polluted soil and the reinforcing agent is subjected to heat treatment at 200-500 ℃ for 10-120 min in a nitrogen atmosphere with a carrier gas flow rate of 0.2-1L/min, preferably, the carrier gas flow rate is 1L/min, the heat treatment temperature is 400 ℃, and the heat treatment time is 30 min.

And S4, cooling the soil after the heat treatment to room temperature, condensing and recovering tail gas generated by the heat treatment, and adsorbing by using activated carbon to remove uncondensed tail gas.

The mechanism for promoting the thermal treatment remediation of the soil polluted by the heavy petroleum is shown in fig. 2, wherein a functional group related to a heteroatom (for example, O, N, S in fig. 2) in a heavy petroleum hydrocarbon molecule is combined with a reinforcing agent, so that the chemical bond between a carbon atom and the heteroatom in the heavy petroleum hydrocarbon molecule is weakened, the functional group is broken and split, and in the process, the reinforcing agent reacts with the heavy petroleum hydrocarbon molecule in the soil to convert the heavy petroleum hydrocarbon molecule into stable and nontoxic coke, so that the remediation of the soil polluted by the heavy petroleum is promoted to promote the removal of the heavy petroleum hydrocarbon molecule.

The invention adopts the pyrolysis treatment equipment shown in figure 3 to carry out pyrolysis on the heavy petroleum polluted soil, and the device is tubular furnace pyrolysis equipment. The device comprises heat-preservation and heat-insulation quartz sand 1, an exhaust pipeline 2, a pyrolysis steel pipe 3, an intelligent adjusting screen 4, a thermocouple 5, a flange 6, an air inlet pipeline 7, a combustion boat push pipe 8, a combustion boat 9, a heating resistor 10, a power switch 11 and the like. The main operation procedures are as follows: and placing the soil sample mixed with the reinforcer to be pyrolyzed in a combustion boat 9, placing the combustion boat push pipe 8 in the middle of the pyrolysis steel pipe 3, and screwing down the flange 6 by using screws to seal the pyrolysis pipeline. Then, the whole pyrolysis system is aerated for 15min to exhaust the pyrolysis system air, wherein the carrier gas enters from the gas inlet pipeline 7 and is exhausted through the exhaust pipeline 2. Turning on a power switch 10, setting pyrolysis temperature and time through the intelligent adjusting screen 4, pressing a confirmation key, then starting heating the soil sample, cooling the soil in a heat treatment system after heat treatment to room temperature, and taking out the soil; after being discharged through the exhaust pipeline 2, the gas generated in the pyrolysis process firstly passes through the condensing device to recover light hydrocarbon in the tail gas, and then passes through the activated carbon adsorption device to remove uncondensed gas, and the gas after the tail gas treatment meets the requirements of the integrated emission standard of atmosphere and finally reaches the standard for emission. The method has strong process operability, only needs to add a stirring and mixing device of the heavy petroleum polluted soil and the reinforcing agent in front of the pyrolysis treatment equipment, and can be widely used in engineering application.

Example 1

Heavy petroleum polluted soil in a Shandong victory oil field polluted site is collected, and the concentration of total petroleum hydrocarbon is 119 g/kg. Air-drying the soil sample at a shady and cool ventilation position until the water content is lower than 5%, crushing the massive soil, removing massive major stones and animal and plant residues, and crushing until the particle size is smaller than 24 meshes; taking the enhancer Fe₂O₃、K₂CO₃、CaO、Al₂O₃HZSM-5 and red mud, and preparing soil samples with the mass percentages of 0.2 percent, 0.5 percent, 1 percent, 2 percent and 5 percent of the polluted soil respectively; 15g of the soil sample mixed with the enhancer is placed in a combustion boat and transferred into pyrolysis treatment equipment, the heat treatment condition is 400 ℃, the heat treatment time is 30min, and the carrier gas flow rate is 1L/min. The soil is cooled to room temperature in a heat treatment system after being subjected to heat treatment and then taken out, the generated tail gas recovers light hydrocarbon in the tail gas through a condensing device, uncondensed gas is removed through activated carbon adsorption, and the gas after tail gas treatment meets the requirements of the 'comprehensive emission standard for atmosphere'.

The total petroleum hydrocarbon residual concentration in the treated soil is shown in FIG. 4. As can be seen from FIG. 4, the addition of the fortifier before the heat treatment significantly promoted the improvementRemoval of heavy petroleum hydrocarbon contaminants, wherein K₂CO₃CaO and Fe₂O₃The three heat treatments are best, and the Total Petroleum Hydrocarbon (TPH) concentration is lower than the risk control target value. Taking the addition amount of the enhancer as 5 percent as an example, the physicochemical properties of the soil before and after heat treatment are shown in Table 1, K₂CO₃And after the CaO strengthening heat treatment, the pH value of the soil is strong alkalinity, and the soil reclamation is obviously influenced. Comprehensively considering the cost, the removal efficiency and the influence on the physical and chemical properties of the soil, Fe is preferably selected₂O₃The addition amount of the fertilizer is 5 percent of the mass of the polluted soil.

TABLE 1 variation of physicochemical Properties of the soil before and after pyrolysis of different fortifiers

Example 2

Heavy petroleum polluted soil in a Shandong victory oil field polluted site is collected, and the concentration of total petroleum hydrocarbon is 119 g/kg. Air-drying the soil sample at a shady and cool ventilation position until the water content is lower than 5%, crushing the massive soil, removing massive major stones and animal and plant residues, and crushing until the particle size is smaller than 24 meshes; fe₂O₃The addition amount of the enhancer is 5% of the mass of the polluted soil, 15g of the mixed soil is placed in a combustion boat and transferred to pyrolysis treatment equipment, the heat treatment temperature is set to be 400 ℃, and the heat treatment time is set to be 30 min. And after the soil is heated for a preset time, cooling the soil to room temperature in a pyrolysis treatment device and taking the soil out. The removal rate of the total petroleum hydrocarbon in the treated soil reaches 95.8 percent, the concentration of the total petroleum hydrocarbon in the soil is 4.99g/kg, which is lower than the risk control value of soil environment quality standard, and the energy consumption can be reduced by 34.7 percent.

Fe₂O₃The reinforcer is a substance contained in the soil, is cheap and wide in source, generates no pollutant after pyrolysis, and is harmless to the soil. Fe₂O₃In the process of strengthening the pyrolysis of the soil polluted by the heavy petroleum, most of the heavy petroleum hydrocarbon pollutants are converted into stable and nontoxic coke, the discharge amount of the tail gas of heat treatment is reduced, the treatment cost of the tail gas is reduced, and the generated coke has the advantages ofA large amount of coke with pore structures is attached to the surface of soil particles, so that the planting performance of the soil after remediation is improved.

Under the same treatment condition, the concentration of total petroleum hydrocarbon in the treated soil is 35.1g/kg when no reinforcing agent is added, and is obviously higher than the risk control value of soil environmental quality standard.

Example 3

The collected heavy petroleum polluted soil and the content are the same as those of the heavy petroleum polluted soil in the example 2, and the heavy petroleum polluted soil is subjected to the same air drying and crushing treatment conditions, and Fe₂O₃The adding amount of the reinforcer is 5% of the mass of the polluted soil, 15g of the mixed soil is placed in a combustion boat and transferred into pyrolysis treatment equipment, the heat treatment temperature is set to be 500 ℃, the heat treatment time is respectively 10 min, 20min and 30min, the removal rates of total petroleum hydrocarbons in the treated soil are respectively 94.17%, 97.21% and 99.57%, and the concentrations of the total petroleum hydrocarbons in the soil are respectively 6.94g/kg, 3.32g/kg and 0.51 g/kg. And when the treatment time is 20min and 30min respectively, the concentration of the total petroleum hydrocarbon remained in the soil is lower than the risk control value of soil environmental quality standard.

Under the same treatment conditions, the concentrations of total petroleum hydrocarbon in the soil after treatment without the strengthening agent are respectively 24.78g/kg, 18.57g/kg and 14.43g/kg, which are higher than the risk control value of soil environmental quality Standard.

Under the above conditions, the heat treatment conditions are 600 ℃ and 700 ℃ respectively without reinforcing agent, the heat treatment time is 30min, and the total petroleum hydrocarbon concentration in the treated soil is 5.42 g/kg and 2.17g/kg respectively. The condition shows that the heat treatment temperature is at least 600 ℃ without reinforcing agent, and the concentration of the residual total petroleum hydrocarbon in the soil can be lower than the risk control value of the soil environment quality standard.

Example 4

Collecting heavy petroleum polluted soil in a polluted field of an oil field in Daqing Liaoning, wherein the concentration of total petroleum hydrocarbon is 173g/kg, air-drying a soil sample at a shady and ventilated place until the water content is lower than 5%, crushing large pieces of soil, removing large pieces of large stones and animal and plant residues, and crushing until the particle size is smaller than 24 meshes; fe₂O₃The addition amount of the enhancer is 5% of the mass of the polluted soil, 15g of the mixed soil is placed in a combustion boat and transferred to a pyrolysis treatment deviceIn the preparation, the heat treatment temperature is set to be 450 ℃ and the heat treatment time is set to be 30 min. And after the soil is heated for a preset time, cooling the soil to room temperature in a pyrolysis treatment device and taking the soil out. The removal rate of the total petroleum hydrocarbon in the treated soil reaches 96.4 percent, and the concentration of the total petroleum hydrocarbon in the soil is 6.23g/kg, which is lower than the risk control value of soil environment quality standard.

Under the same conditions, Fe is not added₂O₃And the total petroleum hydrocarbon concentration of the reinforcer in the soil after heat treatment at the temperature of 450 ℃ for 30min is 40.57 g/kg.

Test 1

For a conventional pyrolysis process (500 ℃, 30min) without strengthening agent with the same removal efficiency and 5% Fe according to the invention₂O₃The energy consumption of the intensified pyrolysis process (400 ℃, 30min) is calculated, and 5 percent of Fe is found₂O₃The energy consumption of the intensified pyrolysis can be reduced by 34.7% compared with the energy consumption of the traditional pyrolysis, and the result is shown in figure 5.

Test 2

Heavy petroleum polluted soil in a Shandong victory oil field polluted site is collected, and the concentration of total petroleum hydrocarbon is 129 g/kg. Air-drying the soil sample at a shady and cool ventilation position until the water content is lower than 5%, crushing the massive soil, removing massive major stones and animal and plant residues, and crushing until the particle size is smaller than 24 meshes; fe₂O₃The adding amount of the enhancer is 5% of the mass of the polluted soil, 20-50 mg of the mixed soil is weighed, and the gas product detection in the process of the enhanced pyrolysis of the heavy petroleum polluted soil is carried out by Py-GC/MS in a pyrolysis gas mass spectrum at 400 ℃.

Under the same conditions, Fe is not added₂O₃Weighing 20-50 mg of the enhancer, and detecting a gas product in the enhanced pyrolysis process of the heavy petroleum polluted soil by utilizing Py-GC/MS at 400 ℃ in a pyrolysis gas mass spectrum.

The results are shown in FIG. 6, which shows that Fe was added₂O₃When the enhancer is pyrolyzed, the release amount of various types of gas products is obviously reduced, and the tail gas treatment cost is further reduced.

According to the method for promoting the heat treatment restoration of the heavy petroleum polluted soil, the reinforcer is added into the heavy petroleum polluted soil before heat treatment, so that the heavy petroleum hydrocarbon pollutants are converted into stable and nontoxic coke at low temperature, the restoration of the heavy petroleum polluted soil is strengthened, the soil fertility after restoration is improved, and the purposes of efficient restoration, energy conservation, consumption reduction and tail gas treatment cost reduction are achieved.

Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art will understand that: any person skilled in the art can modify or easily conceive the technical solutions described in the foregoing embodiments or equivalent substitutes for some technical features within the technical scope of the present disclosure; such modifications, changes or substitutions do not depart from the spirit and scope of the embodiments of the present invention, and they should be construed as being included therein. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.