阅读说明：本技术 一种垃圾焚烧炉渣重金属固化方法 (Method for solidifying heavy metal in waste incineration slag ) 是由 谢海华 赵广林 于 2021-01-29 设计创作，主要内容包括：本发明涉及固废环保技术领域,具体涉及一种垃圾焚烧炉渣重金属固化方法,包括粉碎、涡电流分选、固化、养护几个步骤,炉渣粉碎后通过涡电流分选机筛选出重金属粉末,然后通过分子筛固化剂能够有效吸附重金属,再加上水和碱激发剂的作用,使得固化剂能够有效粘附、固定重金属粉末,然后经养护即可得到被固化的重金属。该固化方法固定的重金属放置一年只有极少量的金属浸出。(The invention relates to the technical field of solid waste environment protection, in particular to a heavy metal curing method for waste incineration slag, which comprises the steps of crushing, eddy current sorting, curing and maintaining, wherein heavy metal powder is screened out by an eddy current sorting machine after the slag is crushed, then heavy metal can be effectively adsorbed by a molecular sieve curing agent, and the curing agent can effectively adhere and fix the heavy metal powder under the action of water and an alkali activator, and then the cured heavy metal can be obtained through maintenance. The heavy metals fixed by the solidification method are only leached out with a very small amount of metals after being placed for one year.)

1. The method for solidifying the heavy metal in the waste incineration slag is characterized by comprising the following steps of sequentially executing:

grinding and crushing waste incineration slag to obtain slag powder;

step two, separating the slag powder by using an eddy current separator to obtain the slag powder with the conductivity of 1.5 to 10⁷S/m～3.8*10⁷S/m of waste aluminum to obtain non-aluminum slag powder;

thirdly, separating the non-aluminum slag powder by using an eddy current separator to obtain a substance with the conductivity more than 10S/m to obtain heavy metal powder;

step four, uniformly mixing the heavy metal powder obtained in the step three with a molecular sieve curing agent to obtain mixed powder;

step five, adding water and an alkali activator into the mixed powder obtained in the step four, and uniformly stirring at room temperature to obtain a mixture;

and step six, filling the mixture obtained in the step five into a mold for molding, demolding after 12 hours, and curing for 4-6 days to obtain the heavy metal solidified body.

2. The method for solidifying heavy metal in waste incineration slag according to claim 1, wherein the method comprises the following steps: in the first step, the grain size of the slag powder is 0.1-1 nm.

3. The method for solidifying heavy metal in waste incineration slag according to claim 1, wherein the method comprises the following steps: in the fourth step, the molecular sieve curing agent comprises the following raw materials in parts by weight:

4. the method for solidifying heavy metal in waste incineration slag according to claim 3, wherein the method comprises the following steps: in the fourth step, the molecular sieve curing agent further comprises the following raw materials in parts by weight:

1-2 parts of calcium oxide

11-15 parts of ferric oxide

5-10 parts of aluminum sulfate.

5. The method for solidifying heavy metal in waste incineration slag according to claim 1, wherein the method comprises the following steps: in the fourth step, the mass ratio of the heavy metal powder to the molecular sieve curing agent is (2-3): 1.

6. the method for solidifying heavy metal in waste incineration slag according to claim 1, wherein the method comprises the following steps: in the fifth step, the mass ratio of the water to the mixed powder is (0.3-0.4): 1.

7. the method for solidifying heavy metal in waste incineration slag according to claim 1, wherein the method comprises the following steps: in the fifth step, the alkali activator is one of potassium hydroxide, sodium hydroxide and strong alkali and weak acid salt.

8. The method for solidifying heavy metal in waste incineration slag according to claim 1, wherein the method comprises the following steps: in the fifth step, the mass ratio of the alkali activator to the mixed powder is (1-2): 10.

9. the method for solidifying heavy metal in waste incineration slag according to claim 1, wherein the method comprises the following steps: in the sixth step, the curing temperature is 20-30 ℃, and the relative humidity is 80-90%.

Technical Field

The invention relates to the technical field of solid waste environment protection, in particular to a method for solidifying heavy metal in waste incineration slag.

Background

Along with the enlargement of the urban scale of China, the improvement of the economic level and the living standard of people, the quantity of garbage generated by cities is increasing day by day, the clearing quantity of domestic garbage in China reaches 2.36 hundred million tons in 2017, the quantity is continuously increased at a speed of about 10 percent every year, the garbage incineration treatment has the capacity of quickly reducing volume, reducing quantity and removing harm, the treatment rate can reach 40 percent, slag generated after the incineration treatment accounts for about 25 to 30 percent of the weight of the garbage, and fly ash accounts for about 3 to 5 percent of the weight of the garbage. As the fly ash contains a certain amount of harmful substances, particularly heavy metals such as Cr, Pb, Cd, Ni, Zn, Cu and the like, and belongs to HW18 dangerous solid wastes, the fly ash needs to be solidified or stabilized, and the treated product can be landfilled and recycled. Although the leaching amount of heavy metals in the slag basically meets the requirements of hazardous waste identification standard-leaching toxicity identification (GB5085.3-2007), the leaching of the heavy metals is changed due to the accumulative nature of ion leaching and the possibility of environmental influence on the slag in the processes of storage, disposal and recycling, so that the surrounding environment and human health are threatened, and therefore, the slag is a hazardous waste with potential hazard and needs to be subjected to harmless disposal and resource utilization.

At present, the harmless treatment of the waste incineration ash is mainly directed at fly ash, and the potential pollution of heavy metal substances in the slag is ignored.

Disclosure of Invention

The invention aims to provide a method for effectively solidifying heavy metal in waste incineration slag aiming at the defects of the prior art, and the heavy metal fixed by the solidifying method is only leached out with a very small amount of metal when being placed for one year.

A method for solidifying heavy metal in waste incineration slag comprises the following steps of sequentially executing:

grinding and crushing waste incineration slag to obtain slag powder;

step two, separating the slag powder by using an eddy current separator to obtain the slag powder with the conductivity of 1.5 to 10⁷S/m～3.8*10⁷S/m of waste aluminum to obtain non-aluminum slag powder;

thirdly, separating the non-aluminum slag powder by using an eddy current separator to obtain a substance with the conductivity more than 10S/m to obtain heavy metal powder;

step four, uniformly mixing the heavy metal powder obtained in the step three with a molecular sieve curing agent to obtain mixed powder;

step five, adding water and an alkali activator into the mixed powder obtained in the step four, and uniformly stirring at room temperature to obtain a mixture;

and step six, filling the mixture obtained in the step five into a mold for molding, demolding after 12 hours, and curing for 4-6 days to obtain the heavy metal solidified body.

In the technical scheme, in the step one, the grain size of the slag powder is 0.1-1 nm.

In the above technical scheme, in the fourth step, the molecular sieve curing agent comprises the following raw materials in parts by weight:

in the above technical scheme, in the fourth step, the molecular sieve curing agent further comprises the following raw materials in parts by weight:

1-2 parts of calcium oxide

11-15 parts of ferric oxide

5-10 parts of aluminum sulfate.

In the above technical scheme, in the fourth step, the mass ratio of the heavy metal powder to the molecular sieve curing agent is (2-3): 1.

in the above technical scheme, in the fifth step, the mass ratio of the water to the mixed powder is (0.3-0.4): 1.

in the above technical scheme, in the fifth step, the alkali activator is one of potassium hydroxide, sodium hydroxide and strong alkali and weak acid salt.

In the above technical scheme, in the fifth step, the mass ratio of the alkali activator to the mixed powder is (1-2): 10.

in the technical scheme, in the sixth step, the curing temperature is 20-30 ℃, and the relative humidity is 80-90%.

The invention has the beneficial effects that:

according to the method for solidifying the heavy metal in the waste incineration slag, the slag is crushed and then screened out to obtain the heavy metal powder through an eddy current separator, then the heavy metal can be effectively adsorbed through a molecular sieve curing agent, and the curing agent can effectively adhere and fix the heavy metal powder under the action of water and an alkali activator, and then the solidified heavy metal can be obtained through maintenance. The heavy metals fixed by the solidification method are only leached out with a very small amount of metals after being placed for one year.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects solved by the present invention more apparent, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

A method for solidifying heavy metal in waste incineration slag comprises the following steps of sequentially executing:

grinding and crushing waste incineration slag to obtain slag powder with the particle size of 0.1-1 nm;

step two, separating the slag powder by using an eddy current separator to obtain the slag powder with the conductivity of 1.5 to 10⁷S/m～3.8*10⁷S/m of waste aluminum to obtain non-aluminum slag powder;

thirdly, separating the non-aluminum slag powder by using an eddy current separator to obtain a substance with the conductivity more than 10S/m to obtain heavy metal powder;

step four, mixing the heavy metal powder obtained in the step three with a molecular sieve curing agent according to a mass ratio of (2-3): 1, uniformly mixing to obtain mixed powder, wherein the molecular sieve curing agent comprises the following raw materials in parts by weight:

step five, adding water and an alkali activator into the mixed powder obtained in the step four, wherein the mass ratio of the water to the mixed powder is (0.3-0.4): 1, the mass ratio of the alkali activator to the mixed powder is (1-2): 10, uniformly stirring at room temperature to obtain a mixture, wherein the alkali activator is one of potassium hydroxide, sodium hydroxide and strong alkali and weak acid salt;

and step six, filling the mixture obtained in the step five into a mold for molding, demolding after 12 hours, and curing for 4-6 days under the conditions that the temperature is 20-30 ℃ and the relative humidity is 80% -90%, so as to obtain the heavy metal solidified body.

The invention has the following effects in steps:

the particle size of the slag powder is selected to be 0.1-1 nm, so that the heavy metal powder can be well adsorbed and fixed by the nano molecular sieve; when the particle size is larger than 1nm, the particle size of the powder is larger than the diameter of the nanometer molecular sieve pore, so that the nanometer molecular sieve can not adsorb the powder; when the particle size of the powder is less than 0.1nm, the particle size of the powder is too small, and the powder is easy to migrate or leach after the powder is adsorbed and coated by the curing agent, so that the fixing effect is influenced.

The nano molecular sieve in the molecular sieve curing agent is a microporous crystal material with a framework structure, has huge specific surface area and numerous micropores, and crystal cavities and pore channels in the nano molecular sieve are communicated with each other, the volume of pores in the framework structure is 60-65% of the total volume, and the pore diameter is uniform and fixed, so that the nano molecular sieve has a strong adsorption effect on heavy metals.

The clay has heavy metal adsorbing effect.

The fly ash and the cement can generate hydration reaction under the action of water and an alkali activator to have cohesiveness, so that a large amount of heavy metal powder can be adhered; the carbide slag can adjust the pH of the mixture and enhance the action effect of the alkali activator; under the action of alkali activator and water, the active aluminosilicate phase contained in the fly ash, the cement and the carbide slag is dissolved into low-polymer aluminosilicate oligomer, the oligomer is condensed into n-aluminosilicate polymer through dehydroxylation reaction, and the generated n-aluminosilicate polymer is further condensed into a gelled matrix with a complex three-dimensional network structure, so that the effect of adsorbing and bonding heavy metal powder is achieved.

Calcium oxide, iron oxide and aluminum sulfate can generate a curing reaction under the action of water, and metal powder is wrapped and cured to prevent the metal powder from migrating or leaching; under the action of water, calcium oxide can adjust the pH of the mixture, iron oxide can generate iron hydroxide, and aluminum sulfate can generate flocculent aluminum hydroxide, so that heavy metals are adsorbed.

Example 1

A method for solidifying heavy metal in waste incineration slag comprises the following steps of sequentially executing:

grinding and crushing the waste incineration slag to obtain slag powder with the particle size of 0.5 nm;

step two, separating the slag powder by using an eddy current separator to obtain the slag powder with the conductivity of 1.5 to 10⁷S/m～3.8*10⁷S/m of waste aluminum to obtain non-aluminum slag powder;

thirdly, separating the non-aluminum slag powder by using an eddy current separator to obtain a substance with the conductivity more than 10S/m to obtain heavy metal powder;

step four, mixing the heavy metal powder obtained in the step three with a molecular sieve curing agent according to a mass ratio of 2.5: 1, uniformly mixing to obtain mixed powder, wherein the molecular sieve curing agent comprises the following raw materials in parts by weight:

step five, adding water and an alkali activator into the mixed powder obtained in the step four, wherein the mass ratio of the water to the mixed powder is 0.35: 1, the mass ratio of the alkali activator to the mixed powder is 1.5: 10, uniformly stirring at room temperature to obtain a mixture, wherein the alkali activator is one of potassium hydroxide, sodium hydroxide and strong alkali and weak acid salt;

and step six, filling the mixture obtained in the step five into a mold for molding, demolding after 12 hours, and curing for 5 days under the conditions that the temperature is 25 ℃ and the relative humidity is 85% to obtain the heavy metal solidified body.

Example 2

A method for solidifying heavy metal in waste incineration slag comprises the following steps of sequentially executing:

grinding and crushing the waste incineration slag to obtain slag powder with the particle size of 0.1 nm;

step two, separating the slag powder by using an eddy current separator to obtain the slag powder with the conductivity of 1.5 to 10⁷S/m～3.8*10⁷S/m of waste aluminum to obtain non-aluminum slag powder;

thirdly, separating the non-aluminum slag powder by using an eddy current separator to obtain a substance with the conductivity more than 10S/m to obtain heavy metal powder;

step four, mixing the heavy metal powder obtained in the step three with a molecular sieve curing agent according to a mass ratio of 2: 1, uniformly mixing to obtain mixed powder, wherein the molecular sieve curing agent comprises the following raw materials in parts by weight:

step five, adding water and an alkali activator into the mixed powder obtained in the step four, wherein the mass ratio of the water to the mixed powder is 0.3: 1, the mass ratio of the alkali activator to the mixed powder is 1: 10, uniformly stirring at room temperature to obtain a mixture, wherein the alkali activator is one of potassium hydroxide, sodium hydroxide and strong alkali and weak acid salt;

and step six, filling the mixture obtained in the step five into a mold for molding, demolding after 12 hours, and curing for 4 days under the conditions that the temperature is 20 ℃ and the relative humidity is 80% to obtain the heavy metal solidified body.

Example 3

A method for solidifying heavy metal in waste incineration slag comprises the following steps of sequentially executing:

grinding and crushing waste incineration slag to obtain slag powder with the particle size of 1 nm;

step two, separating the slag powder by using an eddy current separator to obtain the slag powder with the conductivity of 1.5 to 10⁷S/m～3.8*10⁷S/m of waste aluminum to obtain non-aluminum slag powder;

thirdly, separating the non-aluminum slag powder by using an eddy current separator to obtain a substance with the conductivity more than 10S/m to obtain heavy metal powder;

step four, mixing the heavy metal powder obtained in the step three with a molecular sieve curing agent according to a mass ratio of 3: 1, uniformly mixing to obtain mixed powder, wherein the molecular sieve curing agent comprises the following raw materials in parts by weight:

step five, adding water and an alkali activator into the mixed powder obtained in the step four, wherein the mass ratio of the water to the mixed powder is 0.4: 1, the mass ratio of the alkali activator to the mixed powder is 2: 10, uniformly stirring at room temperature to obtain a mixture, wherein the alkali activator is one of potassium hydroxide, sodium hydroxide and strong alkali and weak acid salt;

and step six, filling the mixture obtained in the step five into a mold for molding, demolding after 12 hours, and curing for 6 days under the conditions that the temperature is 30 ℃ and the relative humidity is 90% to obtain the heavy metal solidified body.

Comparative example 1

A method for solidifying heavy metal in waste incineration slag comprises the following steps of sequentially executing:

grinding and crushing the waste incineration slag to obtain slag powder with the particle size of 0.5 nm;

step two, separating the slag powder by using an eddy current separator to obtain the slag powder with the conductivity of 1.5 to 10⁷S/m～3.8*10⁷S/m of waste aluminum to obtain non-aluminum slag powder;

thirdly, separating the non-aluminum slag powder by using an eddy current separator to obtain a substance with the conductivity more than 10S/m to obtain heavy metal powder;

step four, mixing the heavy metal powder obtained in the step three with a molecular sieve curing agent according to a mass ratio of 2.5: 1, uniformly mixing to obtain mixed powder, wherein the molecular sieve curing agent comprises the following raw materials in parts by weight:

step five, adding water and an alkali activator into the mixed powder obtained in the step four, wherein the mass ratio of the water to the mixed powder is 0.35: 1, the mass ratio of the alkali activator to the mixed powder is 1.5: 10, uniformly stirring at room temperature to obtain a mixture, wherein the alkali activator is one of potassium hydroxide, sodium hydroxide and strong alkali and weak acid salt;

and step six, filling the mixture obtained in the step five into a mold for molding, demolding after 12 hours, and curing for 5 days under the conditions that the temperature is 25 ℃ and the relative humidity is 85% to obtain the heavy metal solidified body.

Comparative example 2

A method for solidifying heavy metal in waste incineration slag comprises the following steps of sequentially executing:

grinding and crushing the waste incineration slag to obtain slag powder with the particle size of 0.5 nm;

step two, separating the slag powder by adopting an eddy current separatorConductivity of 1.5 x 10⁷S/m～3.8*10⁷S/m of waste aluminum to obtain non-aluminum slag powder;

thirdly, separating the non-aluminum slag powder by using an eddy current separator to obtain a substance with the conductivity more than 10S/m to obtain heavy metal powder;

step four, mixing the heavy metal powder obtained in the step three with a molecular sieve curing agent according to a mass ratio of 2.5: 1, uniformly mixing to obtain mixed powder, wherein the molecular sieve curing agent comprises the following raw materials in parts by weight:

step five, adding water and an alkali activator into the mixed powder obtained in the step four, wherein the mass ratio of the water to the mixed powder is 0.35: 1, the mass ratio of the alkali activator to the mixed powder is 1.5: 10, uniformly stirring at room temperature to obtain a mixture, wherein the alkali activator is one of potassium hydroxide, sodium hydroxide and strong alkali and weak acid salt;

and step six, filling the mixture obtained in the step five into a mold for molding, demolding after 12 hours, and curing for 5 days under the conditions that the temperature is 25 ℃ and the relative humidity is 85% to obtain the heavy metal solidified body.

Comparative example 3

A method for solidifying heavy metal in waste incineration slag comprises the following steps of sequentially executing:

grinding and crushing the waste incineration slag to obtain slag powder with the particle size of 0.5 nm;

step two, separating the slag powder by using an eddy current separator to obtain the slag powder with the conductivity of 1.5 to 10⁷S/m～3.8*10⁷S/m of waste aluminum to obtain non-aluminum slag powder;

thirdly, separating the non-aluminum slag powder by using an eddy current separator to obtain a substance with the conductivity more than 10S/m to obtain heavy metal powder;

step four, mixing the heavy metal powder obtained in the step three with a molecular sieve curing agent according to a mass ratio of 2.5: 1, uniformly mixing to obtain mixed powder, wherein the molecular sieve curing agent comprises the following raw materials in parts by weight:

step five, adding water and an alkali activator into the mixed powder obtained in the step four, wherein the mass ratio of the water to the mixed powder is 0.35: 1, the mass ratio of the alkali activator to the mixed powder is 1.5: 10, uniformly stirring at room temperature to obtain a mixture, wherein the alkali activator is one of potassium hydroxide, sodium hydroxide and strong alkali and weak acid salt;

and step six, filling the mixture obtained in the step five into a mold for molding, demolding after 12 hours, and curing for 5 days under the conditions that the temperature is 25 ℃ and the relative humidity is 85% to obtain the heavy metal solidified body.

Comparative example 4

A method for solidifying heavy metal in waste incineration slag comprises the following steps of sequentially executing:

grinding and crushing the waste incineration slag to obtain slag powder with the particle size of 0.5 nm;

step two, separating the slag powder by using an eddy current separator to obtain the slag powder with the conductivity of 1.5 to 10⁷S/m～3.8*10⁷S/m of waste aluminum to obtain non-aluminum slag powder;

thirdly, separating the non-aluminum slag powder by using an eddy current separator to obtain a substance with the conductivity more than 10S/m to obtain heavy metal powder;

step four, mixing the heavy metal powder obtained in the step three with a molecular sieve curing agent according to a mass ratio of 2.5: 1, uniformly mixing to obtain mixed powder, wherein the molecular sieve curing agent comprises the following raw materials in parts by weight:

step five, adding water and an alkali activator into the mixed powder obtained in the step four, wherein the mass ratio of the water to the mixed powder is 0.35: 1, the mass ratio of the alkali activator to the mixed powder is 1.5: 10, uniformly stirring at room temperature to obtain a mixture, wherein the alkali activator is one of potassium hydroxide, sodium hydroxide and strong alkali and weak acid salt;

and step six, filling the mixture obtained in the step five into a mold for molding, demolding after 12 hours, and curing for 5 days under the conditions that the temperature is 25 ℃ and the relative humidity is 85% to obtain the heavy metal solidified body.

Comparative example 5

A method for solidifying heavy metal in waste incineration slag comprises the following steps of sequentially executing:

grinding and crushing the waste incineration slag to obtain slag powder with the particle size of 0.5 nm;

step two, separating the slag powder by using an eddy current separator to obtain the slag powder with the conductivity of 1.5 to 10⁷S/m～3.8*10⁷S/m of waste aluminum to obtain non-aluminum slag powder;

thirdly, separating the non-aluminum slag powder by using an eddy current separator to obtain a substance with the conductivity more than 10S/m to obtain heavy metal powder;

step four, mixing the heavy metal powder obtained in the step three with a molecular sieve curing agent according to a mass ratio of 2.5: 1, uniformly mixing to obtain mixed powder, wherein the molecular sieve curing agent comprises the following raw materials in parts by weight:

step five, adding water and an alkali activator into the mixed powder obtained in the step four, wherein the mass ratio of the water to the mixed powder is 0.35: 1, the mass ratio of the alkali activator to the mixed powder is 1.5: 10, uniformly stirring at room temperature to obtain a mixture, wherein the alkali activator is one of potassium hydroxide, sodium hydroxide and strong alkali and weak acid salt;

and step six, filling the mixture obtained in the step five into a mold for molding, demolding after 12 hours, and curing for 5 days under the conditions that the temperature is 25 ℃ and the relative humidity is 50% to obtain the heavy metal solidified body.

Comparative example 6

A method for solidifying heavy metal in waste incineration slag comprises the following steps of sequentially executing:

grinding and crushing the waste incineration slag to obtain slag powder with the particle size of 0.5 nm;

step two, separating the slag powder by using an eddy current separator to obtain the slag powder with the conductivity of 1.5 to 10⁷S/m～3.8*10⁷S/m of waste aluminum to obtain non-aluminum slag powder;

thirdly, separating the non-aluminum slag powder by using an eddy current separator to obtain a substance with the conductivity more than 10S/m to obtain heavy metal powder;

step four, mixing the heavy metal powder obtained in the step three with a molecular sieve curing agent according to a mass ratio of 2.5: 1, uniformly mixing to obtain mixed powder, wherein the molecular sieve curing agent comprises the following raw materials in parts by weight:

step five, adding water and an alkali activator into the mixed powder obtained in the step four, wherein the mass ratio of the water to the mixed powder is 0.35: 1, the mass ratio of the alkali activator to the mixed powder is 1.5: 10, uniformly stirring at room temperature to obtain a mixture, wherein the alkali activator is one of potassium hydroxide, sodium hydroxide and strong alkali and weak acid salt;

and step six, filling the mixture obtained in the step five into a mold for molding, demolding after 12 hours, and curing for 5 days under the conditions that the temperature is 35 ℃ and the relative humidity is 85% to obtain the heavy metal solidified body.

Test results and analysis

The leaching concentrations (mg/L) of heavy metals after one year of storage of the same batch of incineration slag after the curing treatment of examples 1 to 3 and comparative examples 1 to 6 are shown in Table 1.

TABLE 1

As can be seen from the comparison between example 1 and comparative examples 1-4, the lack of the nano molecular sieve or the clay can obviously reduce the adsorption effect of the heavy metal powder, so that the heavy metal powder is easy to migrate; the lack of calcium oxide, iron oxide and aluminum sulfate or the lack of fly ash, carbide slag and cement can obviously reduce the curing effect of the heavy metal powder, so that the heavy metal powder is easy to leach. Therefore, the leaching concentration of the heavy metal powders of comparative examples 1 to 4 was significantly higher than that of example 1.

As is clear from comparison of example 1 with comparative examples 5 to 6, the increase in curing temperature or the decrease in ambient humidity both reduce the adhesion and curing effect of the curing agent to the heavy metal powder, resulting in leaching of the heavy metal powder.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.