KR20220029068A - Method for Disposing of Solid Wastes with Low Emissions of Harmful Compounds - Google Patents

Abstract

The present invention relates to a waste treatment method including a low-temperature pyrolysis step and a high-temperature pyrolysis step. When the present invention is used, harmful compounds such as dioxin can be removed with high efficiency.

Description

Method for Disposing of Solid Wastes with Low Emissions of Harmful Compounds

The present invention relates to a waste treatment method capable of minimizing the amount of harmful compounds discharged during the treatment process by treating the waste with two-stage heat treatment under specific conditions.

As modern society is advanced, various types of products are being developed and produced together, and in the production process of products such as chemical processes, not only products but also a large amount of industrial waste are generated. In addition, products that are produced and sold are also collected as waste after the end of their lifespan. Therefore, in the modern society where numerous products are produced and discarded, the amount of waste generated every year is enormous, and in particular, since waste generally contains compounds harmful to the human body such as dioxin, it must be properly treated and discharged.

Methods widely known as waste treatment methods include incineration, landfill, plasma treatment, high-temperature base reaction, subcritical water treatment, and the like. Although incineration is a generally preferred method in that it can significantly reduce the volume of waste and recover some of the energy used, compounds such as dioxins cannot be removed smoothly in the incineration step or can be resynthesized afterwards. , in particular, there is a problem in that it cannot easily meet the increased standards as social demands for environmental protection have recently increased. In the case of landfill, it is a method commonly used because it is simple, but compounds such as dioxins are thermochemically stable, so they cannot be decomposed when landfilled, and they dissolve well in fat, etc. There is a problem.

The remaining plasma treatment, high-temperature base reaction, subcritical water treatment, etc. also have problems in that high concentrations of dioxins cannot be treated, the cost of equipment operation is high, and the decomposed dioxins are 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 decomposed, there is no significant change in the total amount of dioxin, removed There is also a problem in that the efficiency of the

Therefore, while chemically decomposing harmful compounds such as dioxin completely, the resynthesis of dioxin can be suppressed, and there is a need for research on a waste treatment method that can be performed simply because it does not require complicated facilities.

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

The present invention is to solve the problems of the prior art described above, can completely decompose harmful compounds such as dioxins, can suppress the resynthesis of harmful compounds, and can be easily applied to existing processes without requiring complicated facilities. To provide a waste treatment method.

The present invention relates to a step of pulverizing and drying waste in the form of sludge to produce it in particle form (S1), classifying the waste in particle form and selecting only particles having a particle diameter of 2 mm or less (S2), and separating the selected particles in an oxygen-free atmosphere. To provide a waste treatment method comprising the step (S3) of low-temperature pyrolysis at a temperature of 500 ° C. and the step (S4) of high-temperature pyrolysis at a temperature of 650 to 850 ° C. of the pyrolysis gas generated in the low-temperature pyrolysis step.

The waste treatment method of the present invention employs a two-stage pyrolysis step of low temperature and high temperature so that harmful compounds such as dioxins in the waste can be completely decomposed, and the efficiency of the overall waste treatment process by appropriately pre-treating the waste to maximize the efficiency of thermal decomposition 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 relates to a step of pulverizing and drying waste in the form of sludge to produce it in particle form (S1), classifying the waste in particle form and selecting only particles having a particle diameter of 2 mm or less (S2), and separating the selected particles in an oxygen-free atmosphere. To provide a waste treatment method comprising the step (S3) of low-temperature pyrolysis to a temperature of 500 ° C. and the step (S4) of high-temperature pyrolysis of the pyrolysis gas generated in the low-temperature pyrolysis step to a temperature of 650 to 850 ° C.

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

Pre-processing step (S1)

In the waste treatment method of the present invention, the waste in the form of sludge to be treated is preferentially pulverized and dried to produce particles in the form of particles.

Waste to be treated in the present invention may be in the form of sludge having a moisture content of 40 to 50%. The waste obtained in the chemical process field has the form of sludge in which solid particles and moisture generated during the process are mixed. Specifically, the waste to be treated in the present invention is ethylene dichloride, vinyl chloride monomer (Vinyl) from ethylene. chloride monomer), etc. may include solid precipitates generated while treating waste liquid and waste water generated during the manufacturing process. In addition, the waste contains harmful chlorine components such as polychlorinated biphenyl, polychlorinated dibenzo-p-dioxin, polychlorinated dibenzofuran, and chlorophenol. may be included in a concentration of about 10,000 to 20,000 ppm. In addition, the waste may include an organic material and an inorganic material in an almost 1:1 ratio.

The reason that the waste in the form of sludge is pulverized and dried at this stage to produce particles in the form of particles is that if the waste in the form of sludge is subjected to low-temperature pyrolysis and high-temperature pyrolysis as it is, heat transfer to hazardous compounds in the waste to be decomposed due to the relatively high moisture content is difficult. Because it can be hindered. 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 that facilitates heat transfer, so that the subsequent low-temperature and high-temperature pyrolysis steps Efficiency can be further improved.

As a method of the pulverization, a general method known that can be used to pulverize a material in the form of a sludge may be used, for example, it may be carried out using a general pulverizer. Likewise in the case of drying, drying in this step may be performed using a method or apparatus known to be used for drying.

Classification step (S2)

The waste treatment method of the present invention includes the step of classifying the waste produced in the form of particles through pulverization and drying in the previous step, and selecting only particles having a particle diameter of 2 mm or less.

When the waste in the form of sludge passes through the preceding crushing and drying steps, the waste has a particle form with a moisture content of 1 to 20%, and the waste particles exhibit various sizes. In this step, only particles having a particle diameter of 2 mm or less are selected from the waste particles having various sizes as described above, and then subjected to low-temperature and high-temperature pyrolysis.

The reason for selecting only particles with a particle diameter of 2 mm or less in this step is that when the particle diameter is too large, the surface area becomes relatively small, making it difficult to conduct heat smoothly, and also to make it difficult to transfer heat to the inner center of the particles, and discharge of treated harmful chlorine compounds This is because it may indicate a problem in mass transfer in the process, and in particular, the effect of such a difference in particle size may be larger based on a particle size of 2 mm. On the other hand, if the particle size standard in this step is made smaller than 0.2 mm, and only particles with a particle diameter of 0.2 mm or less are selected, and this is used as the target for the subsequent step, the amount of selected particles among wastes manufactured in the form of particles is very small, so that the overall The economic feasibility of the treatment process may be lowered, and dust may be blown away by gas flow during heat treatment, and harmful chlorine compounds may be adsorbed to the dust in this process, so that it may not be treated.

In this step, as a specific method of performing classification to separate particles by size, a general method known to those skilled in the art may be used, and may be performed using a general apparatus used for classification.

Meanwhile, in this step, wastes in the form of particles having a particle diameter exceeding 2 mm may undergo additional pulverization and drying, that is, may be subjected to step S1. The economic feasibility of the overall process can be improved by pulverizing and drying the particles that have not been selected in this step again to become a selection target.

Low-temperature pyrolysis step (S3)

The waste produced in the form of particles in the previous step is then subjected to low-temperature pyrolysis.

The low-temperature pyrolysis in this step is 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 3% or less, preferably 1% or less, and oxygen is not present at all. It includes an atmosphere that is not present, that is, an oxygen concentration of 0%. The reason that low-temperature pyrolysis during this step is performed under an anoxic atmosphere is that under low-temperature pyrolysis and anoxic conditions, dechlorination reaction in which the C-Cl bond of harmful chlorine compounds in the waste is broken or the 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 may occur in the condition in which oxygen is present in excess of 3%. 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.

The temperature condition of low-temperature pyrolysis in this step may be 350 to 500 ℃, preferably 350 to 450 ℃. When the temperature of the low-temperature pyrolysis is within the above-mentioned range, the final removal rate of harmful compounds may be higher in terms of connection with the high-temperature pyrolysis step described later. In particular, when the temperature of low-temperature pyrolysis is lower than the above range, sufficient removal of harmful compounds may not occur. It may increase significantly, which may deteriorate the economics of the overall process.

The low-temperature pyrolysis time in this step may be 2 to 6 hours, preferably 3 to 5 hours. When the execution time of low-temperature pyrolysis is too short, sufficient thermal decomposition of harmful compounds cannot be achieved, and when the execution time of low-temperature pyrolysis is too long, the synergistic effect of the removal rate of harmful compounds is insignificant compared to the increase in energy consumption.

High-temperature pyrolysis step (S4)

In the previous low-temperature pyrolysis step, harmful compounds in waste particles are decomposed to form gas, and some of the gas components formed are still harmful. Therefore, it is necessary to additionally thermally decompose harmful compounds in a gaseous state to remove them. Through high-temperature thermal decomposition in this step, harmful compounds in the gas phase remaining may be further decomposed.

In this step, a separate gas is not input because pyrolysis is performed instead of combustion, and high-temperature pyrolysis can be performed in the same atmosphere as the previous low-temperature pyrolysis. On the other hand, the temperature of high-temperature pyrolysis may be 650 to 850 °C, preferably 700 to 800 °C. If the high-temperature pyrolysis temperature is lower than this, the residual gaseous harmful compounds cannot be sufficiently decomposed.

The time of high-temperature pyrolysis in this step may be 5 to 60 minutes, preferably 15 to 30 minutes. When the high-temperature pyrolysis time is too short, sufficient decomposition cannot be performed, and when it is too long, as in the case of temperature, the amount of energy used for high-temperature pyrolysis is excessive, which may deteriorate the economic feasibility of the overall treatment process.

Cooling step (S5)

In addition to the above-described steps S1 to S4, the waste treatment method of the present invention may further include a step (S5) of cooling the gas generated by high-temperature pyrolysis in step S4. Even through the preceding steps S1 to S4, harmful compounds that are not completely decomposed and removed may remain, and only partially decomposed harmful compounds may be re-synthesized into harmful compounds thereafter. Therefore, in order to prevent such resynthesis, it is necessary to cool the pyrolysis gas in which undecomposed harmful compounds may remain to remove energy that can be used for resynthesis.

The cooling may be performed by a method generally used, for example, using cooling water, and it is preferable that the cooling is rapid in order to suppress resynthesis to the maximum.

Post-processing steps (S6-1 and S6-2)

The gas cooled in the preceding cooling step may still contain a trace amount of harmful gas and acid gas, and in order to further remove it, the waste treatment method of the present invention includes the step of passing the pyrolysis gas cooled in step S5 through a scrubber ( S6-1) or the step of passing the pyrolysis gas cooled in step S5 through the dust collector (S6-2) may be further included. Either one or both of steps S6-1 and S6-2 may be included.

In this post-treatment step, most harmful compounds can be removed, and in the case of passing through the scrubber (S6-1), an organic solvent scrubber for removing organic gas and a base solution scrubber for removing acid gas are included. can do. The pyrolysis gas may be passed through an organic solvent scrubber and then through a base solution scrubber. A toluene scrubber may be used as the organic solvent scrubber, and a sodium hydroxide scrubber may be used as the base solution scrubber. When using the scrubber described above, the effect of removing harmful compounds can be maximized.

Meanwhile, in the case of passing the dust collector through the dust collector (S6-2), the dust collector may include a bag filter or the like.

In this post-treatment step, when both the step of passing through the scrubber and the step of passing through the dust collector are included, the order is not particularly limited, and the cooled pyrolysis gas is passed through the dust collector and then passed through the scrubber, or the cooled The pyrolysis gas can be passed through the scrubber and then through the dust collector. From the viewpoint of removing harmful gases, it may be more preferable to pass through the scrubber and the dust collector first.

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.

Examples and Comparative Examples

After pulverizing a waste sample in the form of sludge with a toxic concentration of 64,000 pg I-TEQ/g of hazardous compounds into a waste sample in the form of particles, the waste sample in the form of particles is subjected to low-temperature pyrolysis and high-temperature pyrolysis under different temperature and time conditions. After thermal decomposition, cooling and scrubbing with toluene and sodium hydroxide were performed in the same manner to confirm the residual toxic concentration of harmful compounds. Specifically, in low-temperature pyrolysis, residual toxicity in the particles remaining after pyrolysis was confirmed, and in high-temperature pyrolysis, residual toxicity in gas discharged after pyrolysis was confirmed, and the residual toxicity was evaluated based on the entire system. Specifically, the toxic concentration of the entire system was calculated by adding the residual toxic concentration of the solid and the residual toxic concentration of the gas, and the toxic removal rate was calculated for the entire system based on the initial toxic concentration of 64,000 pg I-TEQ/g. On the other hand, low-temperature pyrolysis was performed under a nitrogen atmosphere.

The results are shown in Table 1 below.

low temperature pyrolysis high temperature pyrolysis system-wide atmosphere particle size
(mm) temperature
(℃) hour
(hr) Solid Residual Toxic Concentration
(pg I-TEQ/g) temperature
(℃) Gas Residual Toxic Concentration
(pg I-TEQ/g) Toxic concentration
(pg I-TEQ/g) Toxic removal rate
(%) Comparative Example 1-1 N ₂ ≤2 200 4 23834 700 402 24236 62.1 Comparative Example 1-2 250 4 17649 700 352 18001 71.9 Comparative Example 1-3 300 4 1370 700 313 1683 97.4 Example 1-1 350 4 89 700 138 227 99.6 Example 1-2 400 4 25 700 160 185 99.7 Examples 1-3 450 4 12 700 148 160 99.7 Examples 1-4 500 4 6.1 700 137 143 99.8 Comparative Example 1-4 550 4 4.6 700 136 141 99.8 Examples 1-5 350 One 852 700 365 1217 98.1 Examples 1-6 350 2 566 700 173 739 98.8 Examples 1-7 350 6 64 700 164 228 99.6 Examples 1-8 350 8 42 700 165 207 99.7 Comparative Example 1-5 350 4 95 500 2531 2626 95.9 Comparative Example 1-6 350 4 87 600 1358 1445 97.7 Examples 1-9 350 4 94 800 115 209 99.7 Comparative Example 1-7 350 4 93 900 104 197 99.7 Comparative Example 2 ≤4 350 4 3645 700 422 4067 93.6 Comparative Example 3 Air ≤2 350 4 69510 700 5833 75343 -17.7

From the results in Table 1, it was confirmed that when the waste treatment method of the present invention is used, toxicity can be removed with high efficiency while using less energy.

Specifically, in the case of Comparative Examples 1-1 to 1-3, in which a temperature lower than the temperature range of the present invention was employed in the low-temperature pyrolysis step, a lower toxicity removal rate than in Examples of the present invention was shown, and in the low-temperature pyrolysis step, the present invention In the case of Comparative Example 1-4 employing a temperature higher than the temperature range of , a toxicity removal rate similar to that of Example 1-4 employing a lower temperature appeared, confirming that energy was used unnecessarily.

In addition, in the case of Comparative Examples 1-5 and 1-6 employing a temperature lower than the temperature range of the present invention in the high-temperature pyrolysis step, a lower toxicity removal rate than in Example -1-9 of the present invention was shown, and the high-temperature pyrolysis step In Comparative Examples 1-7 employing a temperature higher than the temperature range of the present invention, a toxicity removal rate similar to that of Examples 1-9 employing a lower temperature appeared, confirming that energy was used unnecessarily.

Finally, in the case of Comparative Example 2, in which the particle size is larger than 2 mm based on the present invention, smooth mass transfer and heat transfer were not performed, so the toxicity removal rate was low, and in Comparative Example 3 where the thermal decomposition condition was not an anoxic atmosphere, air Due to heavy oxygen, the resynthesis of organochlorine compounds occurred, resulting in increased toxicity.

Claims (12)

Grinding and drying the waste in the form of sludge to prepare particles in the form of particles (S1);
Classifying the waste in the form of particles and selecting only particles having a particle diameter of 2 mm or less (S2);
Low-temperature thermal decomposition of the selected particles at a temperature of 350 to 500 ℃ in an oxygen-free atmosphere (S3); and
A waste treatment method comprising a; high-temperature pyrolysis of the pyrolysis gas generated in the low-temperature pyrolysis step at a temperature of 650 to 850 °C (S4).
The method of claim 1,
The waste treatment method of the sludge form having a moisture content of 40 to 50%.
The method of claim 1,
The waste treatment method of the waste in the form of particles having a moisture content of 1 to 20%.
The method of claim 1,
The oxygen concentration of the anaerobic atmosphere is 3% or less waste treatment method.
The method of claim 1,
The oxygen-free atmosphere is a nitrogen atmosphere, an inert atmosphere, or a vacuum atmosphere.
The method of claim 1,
The waste treatment method that the particles having a particle diameter of more than 2mm separated in step S2 are pulverized and dried again in step S1.
The method of claim 1,
The pyrolysis time in step S3 is a waste treatment method of 2 to 6 hours.
The method of claim 1,
The waste treatment method further comprising a; cooling the gas generated by high-temperature pyrolysis in step S4 (S5).
9. The method of claim 8,
The waste treatment method further comprising a; passing the gas cooled in step S5 through the scrubber (S6-1).
10. The method of claim 9,
The scrubber is a waste treatment method comprising an organic solvent scrubber and a base solution scrubber.
9. The method of claim 8,
The waste treatment method further comprising a; passing the gas cooled in step S5 through the dust collector (S6-2).
12. The method of claim 11,
The dust collector is a waste treatment method comprising a bag filter.