KR20220040109A - Method for Treating Wastes - Google Patents

Abstract

The present invention relates to a waste treatment method in which a specific type of additive is mixed into waste, pulverized, dried, and pyrolyzed. The present invention can remove harmful halogen compounds with high efficiency by suppressing particle aggregation during a process.

Description

Method for Treating Wastes

The present invention relates to a method for efficiently treating waste containing hazardous chlorine compounds.

Chloride is a chemical substance used in various product fields such as pesticides, pesticides, plastics (PVC, PVDC or Teflon, etc.) and flame retardants, and the process for manufacturing these products in the industrial field is a waste containing chlorine compounds. must be accompanied by However, chlorine compounds that may be included in the discharged wastes are often harmful to the human body, and polycyclic organochlorine compounds such as dioxins are known to be particularly harmful to the human body. Therefore, in the process of manufacturing a product containing chlorine compounds, it is necessary to properly process and discharge chlorine compounds that may be contained in waste, and research on related methods is active.

In general, methods known as waste treatment methods include incineration, landfill, plasma treatment, high-temperature base reaction, subcritical water treatment, and the like. In the case of incineration, wastes with a high concentration of organic chlorine compounds are mixed with other wastes with a low concentration of organic chlorine compounds, put into an incineration facility, and the organic chlorine compounds in the waste are treated by incineration. The advantage of the incineration method is that the volume of waste can be greatly reduced and some of the energy used can be recovered, but in the incineration step, compounds such as dioxins cannot be removed smoothly or can be resynthesized afterwards, and the size of the incineration facility There is a problem in that it is difficult to deal with a large amount of waste because of the limitations in the process, and in particular, it cannot easily meet the increased standards due to the recent increase in social demand for environmental protection. Landfilling is also a commonly used method because it is simple, but compounds such as dioxins are thermochemically stable, so they cannot be decomposed when buried, and they dissolve well in fat, etc. there is.

The remaining plasma treatment, high-temperature base reaction, subcritical water treatment, etc. also have problems in that high concentration of dioxin cannot be treated, the cost of equipment operation is high, and the decomposed dioxin is resynthesized. In addition, as a method of removing dioxin, there is also a method of using activated carbon adsorption, bag filter, scrubbing, etc. in the terminal process, but since dioxin is physically removed rather than chemically decomposed, there is no significant change in the total amount of dioxin. , there is a problem that the removal efficiency is also low.

Therefore, there is a need for research on a waste treatment method capable of reducing the emission of harmful chlorine compounds with high efficiency.

KR 10-2011-0129845 A KR 10-2014-0039647 A

The present invention is to solve the problems of the prior art described above, and to provide a waste treatment method capable of reducing the emission of harmful chlorine compounds with high efficiency.

The present invention comprises the steps of mixing an additive into the waste (S1), crushing and drying the waste (S2), and pyrolyzing the dried waste (S3), wherein the additive is i) an oxide of a Group 2 metal; Hydroxides and carbonates, ii) oxides, hydroxides and carbonates of transition metals, iii) organic amines with a boiling point of 250° C. or higher, and iv) antioxidant organic compounds with a boiling point of 250° C. or higher. Provide a waste treatment method do.

The waste treatment method of the present invention suppresses the waste from becoming large particles in the subsequent crushing and drying step by incorporating the additive into the waste, so that efficient heat treatment in the subsequent pyrolysis step can be performed, and as a result, the overall waste treatment process efficiency can be improved.

Hereinafter, the present invention will be described in more detail.

The terms or words used in the present specification and claims should not be construed as being limited to their ordinary or dictionary meanings, and the inventor may properly define the concept of the term in order to best describe his invention. Based on the principle that there is, it should be interpreted as meaning and concept consistent with the technical idea of the present invention.

Waste treatment methods

The present invention comprises the steps of mixing an additive into the waste (S1), crushing and drying the waste (S2), and pyrolyzing the dried waste (S3), wherein the additive is i) an oxide of a Group 2 metal; Hydroxides and carbonates, ii) oxides, hydroxides and carbonates of transition metals, iii) organic amines with a boiling point of 250° C. or higher, and iv) antioxidant organic compounds with a boiling point of 250° C. or higher. Provide a waste treatment method do.

Hereinafter, the waste treatment method of the present invention will be described step by step.

Additive mixing step (S1)

The waste treatment method of the present invention incorporates an additive into the waste prior to crushing and drying the waste. In a chemical process, since hazardous chlorine compounds to be discharged are dissolved directly in water or the like or are present in a solid state in a wastewater mixed with water, it is necessary to first remove water from the wastewater for more efficient waste treatment. Therefore, it is common to coagulate harmful chlorine compounds by adding a coagulant to wastewater, and to separately discharge the wastewater of the filtrate. As a waste to be used, it may be one containing a coagulant.

The waste to be treated according to the present invention may include a coagulant, and the coagulant may be at least one selected from the group consisting of polyaluminum chloride, iron chloride, iron sulfide, aluminum chloride, and a polymer-based coagulant. The polymer-based coagulant is a polyacrylamide-based polymer, poly(meth)acryloyloxyethyl trimethyl ammonium chloride-based polymer, polyacrylamide propyl trimethyl ammonium chloride-based polymer, polydiallyldimethylammonium chloride-based polymer, polyamidine and poly It may be at least one selected from the group consisting of (meth)acrylooxyethylbenzyl dimethylammonium chloride-based polymers. The coagulants listed above are coagulants commonly used in wastewater treatment processes, and as will be described later, they may rather cause agglomeration between particles in the pulverization step.

In this step, the waste may be in the form of sludge having a moisture content of 30 to 70% by weight. As described above, waste can be obtained from wastewater, and even if the filtrate is separated after the coagulant is added, some moisture remains mixed with the waste particles, and accordingly, the waste is in the form of sludge in which solid waste particles and water are mixed. and the moisture content may be a typical 30 to 70% by weight.

In this step, the waste may contain 1 to 10% by weight of chlorine, and specifically, the chlorine may include both organic and inorganic chlorine. An object of the present invention is to treat waste containing harmful organochlorine compounds, and it is common for wastes that have undergone coagulant input and filtrate removal to have a chlorine content in the above-mentioned range. In particular, the chlorine is polychlorinated biphenyl in waste, polychlorinated dibenzo-p-dioxin (polychlorinated dibenzo-p-dioxin), polychlorinated dibenzofuran (polychlorinated dibenzofuran), such as chlorophenol (chlorophenol) It may be present in the form of an organic compound or in the form of an inorganic compound such as iron chloride or polyaluminum chloride. In addition, the waste has an organic/inorganic carbon content of 5 to 20 wt%, an organic/inorganic oxygen content of 10 to 55 wt%, an organic/inorganic iron content of 5 to 15 wt%, and an organic/inorganic aluminum content of 1 to 5 wt% can

In this step, additives are incorporated into wastes such as those described above. When the waste contains a coagulant, in the subsequent pulverization step, rather than the coagulant component, the waste particles agglomerate larger due to shear force, which may cause a phenomenon that is difficult to pulverize, and the additive incorporated in this step is to solve this problem.

The amount of additives incorporated in this step may be 0.1 to 10%, preferably 0.1 to 5%, particularly preferably 1 to 5%, based on the mass of the waste. When the amount of the additive is too small, the aggregation inhibitory effect of the additive decreases, and when the amount of the additive is too large, the improvement in the aggregation inhibitory effect is insignificant compared to the increased amount of the additive, which is uneconomical.

The additives incorporated in this step include i) oxides, hydroxides and carbonates of Group 2 metals, ii) oxides, hydroxides and carbonates of transition metals, iii) organic amines having a boiling point of 250°C or higher, and iv) a boiling point of 250°C or higher. One or more selected from the group consisting of antioxidant organic compounds may be used.

The i) oxides, hydroxides and carbonates of the Group 2 metal are Ca(OH) ₂ , CaCO ₃ , CaO, MgO, Mg(OH) ₂ , MgCO ₃ , BaO and Ba(OH) ₂ 1 selected from the group consisting of It may include the above, and ii) the oxides, hydroxides and carbonates of the transition metal are Bi ₂ O ₃ , MnO ₂ , La ₂ O ₃ , CuO and Cu(OH) ₂ At least one selected from the group consisting of may include.

In the case of using the above-described oxides, hydroxides and/or carbonates of Group 2 metals or transition metals as additives, the phenomenon of hardening (hardening) by temporarily combining moisture with the additives in the waste when it is mixed with waste and then pulverized It can be induced, which prevents the aggregation of waste particles and enables the grinding to be performed densely and evenly. Furthermore, it is possible to suppress the amount of dust generated during the pulverization process due to moisture in the waste, and even in the subsequent pyrolysis step, the additives remaining in the waste can adsorb the by-product gas generated during the pyrolysis process, so organic chlorine compounds that are not decomposed It is possible to suppress the release before vaporization. In addition, when a hydrogen halide such as hydrochloric acid is included in the by-product gas, a metal halide may be formed by direct reaction with the strong acid hydrogen halide, thereby delaying the direct emission of harmful hydrogen halide.

On the other hand, it may be considered to use Group 1 metals, that is, oxides, hydroxides and/or carbonates of alkali metals as additives, but oxides, hydroxides, and carbonates of alkali metals have relatively high solubility in water, so It can be directly dissolved, and as a result, the temperature of the waste is increased, which is not suitable for application in the present invention. In particular, sodium hydroxide or sodium carbonate may corrode or foul the subsequent grinding and drying equipment, and when the additive compound reacts directly with chlorine in the waste to form sodium chloride or potassium chloride, etc., the temperature below the melting point/boiling point It can also cause equipment corrosion. Therefore, oxides, hydroxides and carbonates of Group 1 metals are not suitable as additives of the present invention.

iii) the organic amine having a boiling point of 250° C. or higher may include at least one selected from the group consisting of polyethyleneimine, polyallylamine, polyaniline, polymethylaniline, triethanolamine, dopamine, triethylenetetramine, urea and dimethylurea. and iv) the antioxidant organic compound having a boiling point of 250° C. or higher may include at least one selected from the group consisting of ascorbic acid, sucrose, trehalose, polyethylene glycol, glycerol, benzoic acid, oxalic acid and citric acid.

Organic amines or antioxidant organic compounds with a boiling point of 250° C. or higher are not removed in the drying step prior to pyrolysis, but may be decomposed at the temperature at which the pyrolysis process is performed to form radicals. Halogen can be replaced with hydrogen to decompose harmful halogen compounds. In particular, organic amines easily form hydrogen radicals to promote decomposition of organic halogen compounds, and antioxidant organic compounds can form hydrogen bonds with moisture in waste at room temperature. Hydrogen bonding between the antioxidant organic compound and the moisture in the waste can suppress the temperature rise of the waste. can be expanded On the other hand, if the boiling point of the organic amine and the antioxidant organic compound is less than 250 ° C, it is vaporized and decomposed at the time before the pyrolysis starts, so that it cannot sufficiently contact the organochlorine compound in the waste. It can be removed along with moisture in the process.

The additives of i) to iv) described above may be used alone or in combination with each other. In addition, additives in each group may be mixed and used, or additives of different groups may be mixed and used. For example, when a group 2 metal-based additive and an antioxidant organic compound are mixed and used as an additive, there is an advantage in that the process margin can be further expanded as described above.

Grinding and drying step (S2)

The waste mixed with the additive in the previous step may be subjected to a subsequent grinding and drying step, and the waste that has passed through the above step may be in the form of particles. The reason that waste is pulverized and dried in this step to produce particles in the form of particles, when waste containing moisture, such as waste in the form of sludge, is pyrolyzed as it is, hydrogen halide that may be generated by halogen compounds in the waste during the pyrolysis process exists in moisture. This is because it can cause a problem of corrosion of equipment by being strongly oxidized under it. For example, if chlorine compounds are present in the waste, hydrogen chloride may be generated during the pyrolysis process. When moisture is present during this process, hydrogen chloride is dissolved in moisture to form hydrochloric acid, a strong acid, and the formed hydrochloric acid is pyrolyzed. It may cause corrosion of equipment by direct contact with it.

In addition, on the basis of the same mass, the particle-type waste inevitably has a larger surface area than the sludge-type waste, and this large surface area becomes a factor for smooth heat transfer, further increasing the efficiency of the subsequent pyrolysis step. can be raised

As a method of the pulverization, a general method known that can be used to pulverize a material in the form of sludge may be used, and for example, it may be carried out using a general pulverizer.

The particle diameter of the waste produced in the form of particles through pulverization in this step may be 10 mm or less, preferably 1 to 5 mm, particularly preferably 1 to 3 mm. If the pulverization step is performed so that the particle size of the waste is larger than this, sufficient heat transfer in the subsequent pyrolysis step may not be achieved, so that the decomposition of harmful compounds may not be performed smoothly. If the particle size of the waste is too small, the pulverization cost increases and , the storage volume is large compared to the weight, and a large amount of dust may be generated.

Drying in this step may be carried out at 60 to 130 ℃ moisture can be removed smoothly. In addition, the moisture content in the waste dried in this step may be 0.01 to 10% by weight. When the moisture content is within the above-mentioned range, problems such as equipment corrosion can be minimized.

Pyrolysis step (S3)

The pulverized and dried waste in the previous step is then subjected to a pyrolysis step, and harmful compounds in the waste may be removed in the pyrolysis step.

The thermal decomposition in this step may be performed under an oxygen-free atmosphere. The oxygen-free atmosphere in the present invention means an atmosphere in which oxygen is not substantially present in the gas constituting the atmosphere, and specifically refers to an atmosphere in which the concentration of oxygen is 2% or less, preferably 1% or less, and oxygen is not present at all. It includes an atmosphere that is not present, ie, the oxygen concentration is substantially 0%. The reason that low-temperature pyrolysis is performed under an anoxic atmosphere during this step is that under low-temperature pyrolysis and anoxic conditions, a dechlorination reaction in which the C-Cl bond of harmful chlorine compounds in waste is broken or a self-decomposition reaction of harmful chlorine compounds can occur smoothly. , because oxygen reacts with organic matter and harmful chlorine compounds in the waste to form another harmful chlorine compound, or a problem in which decomposed harmful chlorine compounds are resynthesized under the conditions in which oxygen is present in excess of 2%. The oxygen-free atmosphere may specifically be a nitrogen atmosphere, an inert atmosphere, or a vacuum atmosphere. The inert atmosphere may be an argon atmosphere or a helium atmosphere. Among them, in particular, when a nitrogen atmosphere is applied as an oxygen-free atmosphere, nitrogen having a relatively low price can be used, which is economical and has the advantage of easy atmosphere composition. Meanwhile, when the oxygen-free atmosphere is a low-oxygen atmosphere having a low oxygen content, carbon dioxide may be used as a carrier gas.

The temperature conditions for thermal decomposition in this step may be 250 to 650 °C, preferably 300 to 400 °C. When the temperature of pyrolysis is lower than the above range, sufficient removal of harmful compounds may not occur, and when the temperature of pyrolysis is higher than the above range, there is little improvement in the removal efficiency of harmful chlorine compounds, while only energy consumption is greatly increased The economics of the process may deteriorate.

The pyrolysis time in this step may be 0.5 to 12 hours, preferably 2 to 6 hours. When the time for pyrolysis is too short, sufficient pyrolysis of harmful compounds cannot be achieved, and when the time for pyrolysis is too long, the synergistic effect of the removal rate of harmful compounds is insignificant compared to the increase in energy consumption.

By-product gas treatment step

The waste treatment method of the present invention may further include the step (S4) of incinerating the by-product gas generated in the pyrolysis, or pyrolyzing the by-product gas generated in the pyrolysis again together with the waste dried in the step S3.

Harmful chlorine compounds that have not been decomposed may remain in the by-product gas generated in the pyrolysis step, and the amount of harmful chlorine compounds discharged from the process can be further reduced by further processing the by-product gas.

For example, the by-product gas may be incinerated. The incineration may be carried out in an oxygen atmosphere, and may be carried out at a temperature higher than the temperature at which pyrolysis was performed. In addition, the by-product gas may be further pyrolyzed by inputting the by-product gas into a heat treatment furnace in which the dried waste is pyrolyzed again.

Hereinafter, examples and experimental examples will be described in more detail to describe the present invention in detail, but the present invention is not limited by these examples and experimental examples. Embodiments according to the present invention may be modified in various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those of ordinary skill in the art.

Example 1

After adding polyaluminum chloride as a coagulant to wastewater generated in the process of chlorinating ethylene, the filtrate was removed to obtain 100 parts by weight of waste in the form of sludge, and the chlorine content in the waste was measured by combustion IC. After mixing 5 parts by weight of calcium hydroxide in the waste, pulverization for 10 seconds at room temperature with a grinder - 5 seconds pause was repeated 3 times to pulverize. After confirming that the temperature of the waste before and after pulverization was maintained, it was dried at 120° C. for one day to remove moisture, and then pyrolyzed at 300° C. and under a nitrogen atmosphere for 1 hour, and the chlorine content remaining in the waste after pyrolysis was measured.

Example 2

In Example 1, the chlorine content in the waste before treatment and the chlorine content in the waste after treatment were checked in the same manner except that 5 parts by weight of oxalic acid was added instead of 5 parts by weight of calcium hydroxide.

Example 3

In Example 1, except that 5 parts by weight of sucrose was added instead of 5 parts by weight of calcium hydroxide, the chlorine content in the waste before treatment and the chlorine content in the waste after treatment were checked in the same manner.

Comparative Example 1

In Example 1, the same procedure was performed except that 1 part by weight of sodium hydroxide was added instead of 5 parts by weight of calcium hydroxide. However, in the case of Comparative Example 1, the temperature of the waste increased by 10° C. or more after pulverization, and corrosion of the equipment occurred, so that the thermal decomposition could not be completely performed. On the other hand, the reason why the amount of sodium hydroxide used in Comparative Example 1 was lower than that of calcium hydroxide was because when sodium hydroxide was used in the same weight part as calcium hydroxide, severe equipment corrosion occurred and equipment damage was expected.

Comparative Example 2

Example 1 was carried out in the same manner except that calcium hydroxide was not used. In the case of Comparative Example 2, it was confirmed that as the pulverization step progressed, the waste particles were again weakly aggregated to form large particles with a particle diameter of 10 mm or more.

Experimental Example 1. Confirmation of chlorine removal rate in Examples and Comparative Examples

In the Examples and Comparative Examples, the chlorine content of the waste before and after treatment was confirmed by combustion IC, and is summarized in Table 1 below.

Chlorine content before treatment (ppm) Chlorine content after treatment (ppm) Chlorine removal rate (%) Example 1 26837 2964 88.96 Example 2 27195 2778 89.78 Example 3 26849 2125 90.67 Comparative Example 1 27146 - - Comparative Example 2 28178 5972 78.81

Specifically, 10 to 30 mg of a sample is weighed and placed in a crucible dedicated to combustion ion chromatography (Ion Chromatography, IC), the entire sample is covered with WO ₃ powder, which is a superflammant, and then put into the equipment to produce an Ar/O ₂ gas atmosphere. was oxidized at 100 °C. After collecting the volatile products generated at this time in an aqueous hydrogen peroxide-based absorption solution, the generated ions were separated by an IC ion exchange column, and then IC analysis was performed.

From the above results, it was confirmed that, using the waste treatment method of the present invention, when a specific type of coagulant is added to the waste and then pyrolyzed, the chlorine removal rate is excellent compared to the case where other additives or no additives are mixed.

In particular, in the case of Comparative Example 1 using a hydroxide of a Group 1 metal as an additive, heat and equipment corrosion occurred during the mixing of the additive, so waste treatment itself was not easy, and in Comparative Example 2 where the additive was not used, the chlorine removal rate was not sufficient. On the other hand, it was confirmed that 88% or more of chlorine could be removed in Examples 1 to 3 of the present invention.

Claims (15)

Incorporating an additive into the waste (S1);
pulverizing and drying the waste (S2); and
and thermally decomposing the dried waste (S3);
The additive consists of i) oxides, hydroxides and carbonates of Group 2 metals, ii) oxides, hydroxides and carbonates of transition metals, iii) organic amines having a boiling point of 250° C. or higher, and iv) an antioxidant organic compound having a boiling point of 250° C. or higher. One or more waste disposal methods selected from the group.
The method of claim 1,
The waste is a waste treatment method in the form of sludge having a moisture content of 30 to 70% by weight.
The method of claim 1,
The waste treatment method comprising at least one coagulant selected from the group consisting of polyaluminum chloride, iron chloride, iron sulfide, and a polymer-based coagulant.
According to claim 1,
Wherein the additive is added at 0.1 to 10% of the mass of the waste.
The method of claim 1,
The i) oxides, hydroxides and carbonates of the Group 2 metal are Ca(OH) ₂ , CaCO ₃ , MgO, Mg(OH) ₂ , MgCO ₃ , BaO and Ba(OH) ₂ At least one selected from the group consisting of A waste treatment method comprising:
The method of claim 1,
The ii) oxides, hydroxides and carbonates of transition metals include at least one selected from the group consisting of Bi ₂ O ₃ , MnO ₂ , La ₂ O ₃ , CuO and Cu(OH) ₂ .
The method of claim 1,
iii) the organic amine having a boiling point of 250° C. or higher includes at least one selected from the group consisting of polyethyleneimine, polyallylamine, polyaniline, polymethylaniline, triethanolamine, dopamine, triethylenetetramine, urea and dimethylurea Phosphorus waste treatment method.
The method of claim 1,
Wherein iv) the antioxidant organic compound having a boiling point of 250° C. or higher includes at least one selected from the group consisting of ascorbic acid, sucrose, trehalose, polyethylene glycol, glycerol, benzoic acid, oxalic acid and citric acid.
The method of claim 1,
The waste treatment method, wherein the waste comprises 1 to 10% by weight of chlorine.
The method of claim 1,
The particle size of the waste pulverized in step S2 is less than 10mm waste treatment method.
The method of claim 1,
The pyrolysis is a waste treatment method that is performed in an oxygen-free atmosphere.
12. The method of claim 11,
The anaerobic atmosphere is a waste treatment method of which the oxygen concentration is 2% or less.
According to claim 1,
The pyrolysis is a waste treatment method that is carried out at 250 to 650 ℃.
The method of claim 1,
Incinerating the by-product gas generated in the thermal decomposition (S4); Waste treatment method comprising a further.
The method of claim 1,
The waste treatment method of pyrolyzing the by-product gas generated in the pyrolysis with the waste dried in step S3 again.