KR100873653B1 - A method for treating pentachlorophenol treated wood - Google Patents

Abstract

A method for treating pentachlorophenol-treated wood is provided to recycle the treated wood, and reuse the recovered solvent as an extraction solvent by recovering a solvent from a pentachlorophenol extract. A method for treating pentachlorophenol-treated wood comprises the steps of: crushing the pentachlorophenol-treated wood, adding a solvent to the crushed wood, and performing solvent extraction and centrifugation; distilling the objected pentachlorophenol extract to separate the solvent and residues containing pentachlorophenol; and treating the separated residues containing pentachlorophenol with supercritical water oxidation at a pressure of 22.1 to 30 MPa, an excessive oxygen condition of 50 to 200%, and a temperature of 374 to 600 deg.C.

Description

Treatment method of contaminated fossil carbonized wood {A METHOD FOR TREATING PENTACHLOROPHENOL TREATED WOOD}

The present invention relates to a method of treating wood treated with pentachlorophenol (hereinafter referred to as "PCP"), and more particularly, to recycle wood by extracting PCP using a solvent from PCP treated wood, and including a solvent. The present invention relates to a method for separating a PCP-containing residue from an extracted PCP extract and recycling the solvent, and to completely treat the PCP-containing residue by supercritical water oxidation or hydrothermal decomposition.

Wood is by far one of the most widely used materials in various industries. Wood is perishable in nature, so long-term preservation is difficult. Corruption is mainly due to climatic factors and biological actions such as bacteria and pests.

PCP has been used as an antiseptic and insect repellent since the 1930s in order to extend the life of wood and to use and preserve it for a long time. PCP is a chemically very stable compound that does not separate chlorine even when heated at high temperature or boiled with acid. Since it shows strong antibacterial activity against bacteria and fungi, it is more than 100 times as effective as zinc chloride. Pure PCP is a dark gray powder or flake when it contains colorless crystals or impurities. It has a phenolic fragrance, but has an irritating fragrance only at high temperatures, and breaks down to produce hydrogen chloride, phenol chloride and carbon monoxide.

However, PCP presents a risk of fire and explosion when in contact with strong oxidizing agents, dangerous when mixed with acids, alkalis, oxidizing materials and organic materials, very hazardous to human exposure, especially eyes, nose, throat and eyes. It is irritating to skin and has very toxic properties when consumed. It can also cause headache, sweating, weakness, shortness of breath, high fever, chest pain, abdominal pain, long-term contact with skin rash, and acute symptoms. , Loss of appetite, vomiting, difficulty breathing, chest pain, sweating, headache, sweating, high fever, etc. In severe cases, bronchial and liver damage, peripheral neuropathy, sweating, weight loss, high fever . Therefore, since the late 1980s, where PCP is known to be a carcinogen and known to be very harmful to human body and the natural environment, it has been banned from production and use in various countries. This trend is currently banned under the Stockholm Convention, especially in developed countries such as the European Union and the United States.

After the harmfulness of these PCPs is known, many studies have been conducted to safely dispose of PCPs used in the past as preservatives and insect repellents. 5,378,323), chemical extraction (US Pat. No. 5,262,004), supercritical CO ₂ extraction (US Pat. No. 5,364,475), photolysis after supercritical CO ₂ extraction (US Pat. No. 5,698,829), microbial treatment using mold (US Patent Nos. 6,727,087 and 6,387,689) and the decomposition of PCP and halogenated phenols (US Pat. No. 5,512,478) using bacteria, and the removal of PCP by vaginal degrading microflora (Korea Patent No. 10-0282256) The treatment by white fungi is being studied.

However, incineration and landfilling are not a complete treatment method for releasing carcinogen dioxin, and when landfilling is not performed, landfill sites are limited or gradually reduced, and waste wood is fundamentally blocked, which is uneconomical. For pyrolysis and extraction with supercritical solvents, the apparatus is complex and energy consuming and therefore uneconomical. On the other hand, if the concentration is low, the microbial treatment method may be effective, but the PCP deposited inside the wood remains intact. Moreover, aerobic microorganisms are limited in oxygen and thus do not grow in the gaps, and anaerobic microorganisms can discard PCP in wood, but the treatment rate is low and the PCP and activated sludge concentrated in bacteria must be reprocessed.

Meanwhile, drinking water based on the PCP of the US Environmental Protection Agency (EPA) is less than 1ppb, workplace allowable concentration is 0.5mg / m ^3, Korea has also apply the same criteria. There is no recycling standard for waste wood treated with PCP in Korea, but Germany and Europe are tightening PCP regulations by limiting PCP concentration to 5mg per kg of dry wood. In particular, the US Army used a large amount of chemically treated ammunition boxes in the past, and about 80% of them were treated with PCP, but the current method of treating waste ammunition boxes with PCP treatment has not been established. to be. Korea also revised its defense standards and banned the use of PCP after 1986 and used safer ammunition box protection. However, all the packaging wood of storage coal was chemically treated with PCP according to US standards. Ammunition crates will continue to occur in the disposal of stored coal and insoluble coals, so there is an urgent need for safe treatment and recycling of wood in ammunition crates produced in the past.

In order to solve such a problem, there is a method of extracting PCP from a PCP treated wood using a solvent such as methanol, reusing the wood from which the PCP has been removed, and distilling the solvent off again (Korea Patent Registration No. 10-726704). ). However, there is a problem that the final remaining PCP after distillation of the extraction solvent cannot be processed. In addition, PCP material extracted from wood is a diverse and complex isomer of PCP with some components, such as lignin, which make up wood, and its purity is low, and it is not suitable for recrystallization. Recycling of PCP-containing residues is not economical because it is prohibited. Therefore, PCP extracted from wood should be finally converted to completely harmless substance, but impurities and isomers contained in PCP after treatment are the main cause of dioxin formation when incinerated or landfilled, and general incineration is prohibited and solidified If it is landfilled, it cannot be regarded as complete. Another method is hot melting or plasma using, but they consume large amounts of energy as the apparatus is huge and use high temperature heat, and there is a risk of regeneration of dioxins unless rapid cooling after incineration.

The present invention has been made to solve the problems of the prior art as described above, the object of the present invention is to construct a commercial or simple device, by removing the PCP from the wood preservative and insectproof treated with PCP to a safe level to the human body, In addition to allowing wood to be recycled, the extraction solvent from the PCP extract can be recovered and reused for solvent extraction, and the final PCP-containing residue extracted from the wood can be recovered and completely recovered by supercritical water oxidation or hydrothermal decomposition. By converting them into harmless materials, they provide a safe way to treat PCP treated wood.

In order to achieve the above object, the PCP treated wood treatment method of the present invention,

(1) crushing the PCP treated wood, adding a solvent to the crushed wood, solvent extraction and centrifuging;

(2) distilling the PCP extract obtained in step (1) to separate the solvent and the PCP-containing residue; And

(3) treating the PCP by supercritical water oxidation or hydrothermal decomposition of the PCP-containing residue separated in step (2);

Characterized in that it comprises a.

Hereinafter, with reference to Figure 1 will be described in detail the treatment method of PCP treated wood of the present invention.

In step (1), the wood may be of any type, including wood preserved and insectproofed with PCP, such as a box, pallet, wire pole, sleeper and the like.

Wood treated with PCP is shredded using a shredding device (A1), and can be shredded into chips or sawdust depending on the purpose of the wood being recycled, and shredded to a size of 1 mm or less in consideration of extraction efficiency. It is desirable to be.

If the PCP treated wood contains metals such as nails and hinges, the wood may be classified into wood and non-wood through a metal sorter (A2). In addition, since the ammunition crates generally consist of wood, nails, hinges, outer wrap strips (metal bands) and grabbing straps (fibers), the outer wrap strips and grabbing straps are preferably separated before shredding.

PCP treated wood is analyzed for PCP concentration before extraction with solvent. In the present invention, if the PCP concentration of the PCP treated wood in accordance with the European standard exceeds 100mg per kg dry wood, it can be treated as a designated waste and treated according to the procedure of the present invention shown in FIG.

In the step (1), the process of extracting the crushed and sorted wood (A3) with a solvent (A4), adding a solvent to the crushed and sorted wood, stirring for a predetermined time, the PCP concentration in the wood It is preferable to repeat until the recycling standard is reached.

It is preferable to use 10-30 ml of extraction solvent with respect to 1 g of wood weight, extraction temperature is preferable at normal temperature, and extraction time is the best when the extraction time is 2 hours or more, Preferably it is 2-4 hours.

As the extraction solvent, one or more solvents having a large difference in boiling point from PCP having a boiling point of 310 ° C., such as methanol, ethanol and acetonitrile, can be used, and preferably methanol.

About 95% of PCP is extracted by the first extraction, so if the initial concentration of PCP is 1000ppm, the first extraction can meet below the designated waste standards (100mg / 1kg dry wood) in the US and Germany. have. However, in order to satisfy PCP concentration 5 mg / kg dry wood, which is the standard for wood recycling in Germany and Europe, the extraction sample is centrifuged (A5) after extraction to separate the wood and the extract, and the extraction solvent is satisfied until the above criteria are met. To the extraction apparatus in the same proportion as described above, and repeat the solvent extraction (A4) and centrifugation (A5) two or more times. Treated wood is allowed to air dry once the recycling criteria for wood are met.

Treated wood (chips or sawdust) can be recycled for proper use, which can be used for gardening, farming or composting, or for making plywood for particle boards. It can also be used to make.

In step (2), the PCP extract is distilled (A6) to separate the extraction solvent and PCP-containing residue. In the present invention, since a solvent having a large difference in boiling point from PCP is used as the extraction solvent, the extraction solvent and the PCP-containing residue can be easily separated using a simple distillation apparatus.

The solvent recovered in the distillation apparatus can be reused as an extraction solvent (A7), and the PCP-containing residue remaining in the distillation apparatus is recovered and then subjected to the next step (3).

Between the step (2) and the following step (3), optionally may further comprise the step of drying the PCP-containing residue. The reason for such a drying process is that if a solvent is contained in the PCP-containing residue, these solvents are not preferable because they act to inhibit PCP decomposition in the supercritical water oxidation process.

Step (3) is a process of completely treating the PCP-containing residue, in which a supercritical water oxidation or hydrothermal decomposition process is used.

Supercritical water oxidation of the present invention is preferably carried out at a pressure of 22.1 ~ 30MPa, preferably 25MPa, 50 ~ 200% oxygen excess conditions and a temperature of 374 ~ 600 ℃, preferably 400 ~ 550 ℃.

The supercritical water oxidation process carried out under these conditions shows the decomposition rate of PCP containing residues of 95% or more within a few seconds to several minutes, specifically 10 seconds.

The supercritical water oxidation process is a chemically stable and difficult to decompose harmful organic substance under supercritical water oxidation conditions (temperature 374 ℃, pressure 22.1MPa or more) using an oxidizing agent to completely decompose carbon dioxide and water.

In general, the time required for complete decomposition of organic matter in the supercritical water oxidation process is from a few seconds to several minutes, and is a high efficiency process compared with other processes. In particular, the PCP concentration of the ammunition box exemplified by the present invention is classified as hazardous waste with an average of about 1000 ppm as a result of analysis, but since the residual concentration is not large (first preservative concentration of 5% by weight), it is suitable to be treated by supercritical water oxidation process. Do.

Therefore, in order to finally process the PCP residual material to be completely harmless, a small-scale supercritical water oxidizer which is easy to operate is introduced into the final processing system A8 of FIG. 1 to construct a continuous processing system for the complete processing of PCP wood. Can be.

The supercritical water oxidizer includes a raw material supply unit including a PCP-containing residue storage tank 10, a hydrogen peroxide aqueous solution storage tank 20, and high pressure pumps 11 and 21, and a preheating and feed temperature of a feed solution. Electric heaters 31 and 32 and preheater 22, mixing tank 12 for mixing feed material, supercritical water oxidation reactor 30, heat exchanger 33 for rapid cooling of reactants, solid phase generated during the reaction The material removal filter 34, the pressure reducer 35, and the gas / liquid separator 36 may be configured as a sampling part (not shown) of the generated gas and liquid material.

Referring to FIG. 2, the process of treating the PCP-containing residue by the supercritical water oxidizer will be described briefly. The aqueous hydrogen peroxide solution stored in the hydrogen peroxide aqueous solution storage tank 20 as an oxidizing agent is a high pressure pump 21 and a preheater 22. The PCP-containing residue stored in the PCP-containing residue storage tank 10 is introduced into the mixing tank 12 through the high-pressure pump 11 through an oxidation reactor together with an aqueous hydrogen peroxide solution. (30), after the oxidation reaction proceeds in supercritical water conditions, the result of the oxidation reaction is cooled while passing through the heat exchanger (33), and then passed through the filter (34) to the corrosion during the supercritical water oxidation reaction Due to the solid particles that may have been generated is removed, and then passed through the pressure reducer 35, and finally the gas and liquid are separated through the gas / liquid separator 36.

The supercritical water oxidation process as described above is a highly efficient oxidation process compared to other processes, but in the present invention, by adding caustic soda under anoxic conditions in which no oxidant is used in place of the supercritical water oxidation process in step (3), Hydrothermal cracking processes can be applied to operate the same equipment used in supercritical water oxidation processes.

Preferred reaction conditions for the hydrothermal decomposition process are pressures of 22.1 to 30 MPa, anoxic conditions, temperatures of 300 to 420 ° C., preferably around 400 ° C., and 5 to 10 moles of caustic soda per mole of contaminated fossil carbonate. The addition is carried out under the conditions.

This hydrocracking process can not only reduce the cost of oxidant, which accounts for about one third of the operating cost of supercritical water oxidation, but can also greatly reduce the corrosion of the device by neutralizing the PCP-containing residues in advance. There is an advantage.

The PCP processing apparatus used to apply the above method can be easily systemized by purchasing or combining a commercial or commercial apparatus into a unit process, and finally, the remaining PCP can be processed by constructing a small supercritical water treatment apparatus. Therefore, installation and operation are very simple and economically it can be treated as completely harmless material.

As described in detail above, according to the processing method of the PCP treated wood of the present invention, it is possible to build a recycling and recycling system of hazardous waste wood resources using a commercial or simple practical device, by using such a system to the PCP The complete treatment of the chemically treated wood is also economical in that the treated wood can be recycled while the solvent can be recovered from the PCP extract and reused as the extraction solvent.

Example

One. PCP  Crushing of treated wood and PCP  Concentration measurement

After dismantling the 81mm mortar shell box (manufactured in the US in April 1971), which is the most used in the military, separating the non-wood such as metal, handles and strings, the wood was chipped (10mm wide x 5mm long). It was ground in the form of 3mm height x), and the PCP concentration was measured (PCP concentration of chip 1297ppm).

2. Solvent Extraction

(1) Test by type of solvent

1 g of the chip obtained in 1. was added to a glass container, and 50 ml of methanol, ethanol, and acetonitrile were added to each other, followed by extraction with a 150 rpm left and right reciprocating shaker at room temperature for 4 hours, followed by centrifugation to separate the chip and PCP extract. It was. The extraction effect for each solvent was in the order of methanol> ethanol> acetonitrile.

(2) Test by amount of methanol

Methanol was mixed by 5 ml, 10 ml, 20 ml and 30 ml, respectively, and extracted in the same manner as in (1). Extraction effect of methanol by use amount was minimal when 5ml was used, but similar extraction effect was shown in 10ml, 20ml and 30ml.

(3) Test by extraction temperature

10 ml of methanol was mixed and extracted in the same manner as in (1) at room temperature and 50 ° C. The extraction effect was increased within 1% at 50 ℃ compared to room temperature extraction. However, as a result of analyzing the extract quality by gas chromatography-mass spectrometry (GC-MS), various substances (wood components, tar-like components, etc.) It was found that it is more preferable to extract at room temperature.

3. PCP  Distillation of Extract

10 ml of methanol was added to 1 g of the chip obtained in 1., and the PCP extract obtained by extraction under the same conditions as 2. was separated using a distillation machine to separate methanol and PCP-containing residue.

4. PCP  contain Residue Fully disassembled

(1) supercritical water oxidation

On the supercritical water oxidation system as shown in FIG. 2, 1.02 g of PCP-containing residue was dissolved in water in a 1 L container, prepared at 1,000 mg / L, and stored in a PCP-containing residue storage tank. As an oxidizing agent, 35% w / v aqueous hydrogen peroxide solution was diluted with distilled water and used.

Supercritical water oxidation was performed under the oxidation conditions of PCP as shown in Table 1, and it was confirmed that more than 98% of PCP was decomposed.

variable Condition pressure 25 MPa Temperature 500 ℃ Residence time 10 sec Required oxygen 150%

(2) hydrothermal decomposition

On the same system as in (1) above, 1.02 g of PCP-containing residue and 1.61 g of NaOH were dissolved in water in a 1 L container to prepare 1,000 mg / L and stored in a PCP-containing residue storage tank. Hydrothermal decomposition of the PCP was carried out under the conditions shown in Table 2 without the addition of an oxidizing agent to confirm that more than 99% of the PCP was decomposed.

variable Condition pressure 25 MPa Temperature 400 ℃ Residence time 20 seconds

1 is a schematic diagram showing a process of completely processing the PCP from wood treated with PCP.

2 shows a supercritical water oxidation apparatus for decomposing PCP containing residues.

<Description of the code>

10 --- PCP containing residue storage tank, 20 --- hydrogen peroxide aqueous storage tank,

11, 21 --- high pressure pump, 12 --- mixing tank,

22 --- preheater, 30 --- oxidation reactor,

31, 32 --- electric heater, 33 --- heat exchanger,

34 --- filter, 35 --- decompressor,

36 --- Gas / Liquid Separator

Claims (11)

A process for treating contaminated fossil carbonate treated wood comprising the following steps: (1) crushing the contaminated fossil carbonate treated wood, adding a solvent to the crushed wood, solvent extraction and centrifuging; (2) distilling the contaminated fossil carbonate extract obtained in step (1) to separate the solvent and the contaminated fossil carbonate-containing residue; And (3) Treating the contaminated fossil carbonate-containing residue separated in step (2) by supercritical water oxidation at a pressure of 22.1-30 MPa, an excess of 50-200% oxygen and a temperature of 374-600 ° C. Steps. A process for treating contaminated fossil carbonate treated wood comprising the following steps: (1) crushing the contaminated fossil carbonate treated wood, adding a solvent to the crushed wood, and then extracting and centrifuging the solvent; (2) distilling the contaminated fossil carbonate extract obtained in step (1) to separate the solvent and the contaminated fossil carbonate-containing residue; And (3) The contaminated fossil carbonate-containing residue isolated in step (2) is a pressure of 22.1 ~ 30MPa, anoxic conditions, temperature of 300 ~ 420 ℃ and 5-10 moles of caustic soda per 1 mole of contaminated fossil carbonate. Treating with hydrothermal decomposition under the condition of adding; The method of claim 1 or 2, further comprising the step of drying the contaminated fossil carbonate containing residues between the step (2) and step (3). The method of claim 1 or 2, wherein the crushed wood of step (1) is 1 mm or less in diameter. The method of claim 1 or 2, wherein the solvent of step (1) is at least one selected from the group consisting of methanol, ethanol and acetonitrile. The method of claim 5, wherein the solvent is added to 10 ~ 30ml per 1g of crushed wood. The method of claim 1 or 2, wherein the solvent extraction of step (1) is carried out at room temperature. The method of claim 1 or 2, wherein the solvent extraction and centrifugation in step (1) is repeated two or more times. The method of claim 1 or 2, wherein the wood separated by step (1) is recycled. The process according to claim 1 or 2, wherein the solvent distilled from step (2) is recycled to the solvent in step (1). delete

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