JP2013053261A - Method and apparatus for treating cca timber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To treat a chromated copper arsenate (CCA) timber (a timber in which CCA wood antiseptic agent is pressure-injected) with lower energy and at low cost.SOLUTION: The CCA timber is exposed in a reaction chamber 1 to superheated steam from a steam generator 2, thereby carbonizing the CCA timber without causing hexavalent chrome.

Description

  The present invention relates to wood treatment technology, and in particular, harmful hexavalent chromium in non-treated materials containing wood (hereinafter referred to as CCA wood) into which CCA (chromium, copper, arsenic compound-based wood preservative) has been pressure-injected. The present invention relates to a wood processing technique for carbonization and volume reduction without being generated.

  CCA timber is obtained by pressure-injecting CCA into the timber for the purpose of preserving and protecting timber. In Japan, CCA timber has been used as a building material for utility poles and foundations since the 1960s. Currently, it is hardly produced domestically due to its toxic and wastewater standards, but it is expected that CCA wood will be discharged in large quantities as waste due to the dismantling of buildings.

It has been pointed out that when CCA wood is improperly incinerated, generation of harmful gases containing arsenic and incineration ash contain hexavalent chromium and arsenic, which are harmful substances. For this reason, CCA wood must be properly incinerated or landfilled.
In particular, chromium is fixed to wood in a trivalent state in wood, but in ordinary incineration treatment, it is oxidized to hexavalent, which is easy to dissolve, so it is dangerous to elute in residues and ash at a high concentration. It is considered to be. Therefore, it has been a problem to safely treat the discarded CCA wood without changing the trivalent chromium to hexavalent chromium.

  On the other hand, as described in Patent Document 1, a method using superheated steam has been proposed as a method for carbonizing food waste and the like. The use of superheated steam enables efficient carbonization and suppresses the generation of dioxins.

JP 2002-194362 A

However, such a carbonization method for food waste and the like using superheated steam cannot be directly applied to waste wood treatment.
The present invention is for solving such problems, and an object of the present invention is to provide a wood treatment technique capable of treating CCA wood with low energy and low cost.

In order to achieve such an object, the CCA wood treatment method according to the present invention heats water to generate superheated steam, and CCA (chrome, copper, arsenic compound wood preservative) is pressurized and injected into the inside. The CCA wood is exposed to superheated steam so that the CCA wood is carbonized without producing hexavalent chromium.
At this time, a superheated steam having a temperature of 300 ° C. or higher may be used.

In the CCA wood treatment apparatus according to the present invention, a superheated steam generator for heating water to generate superheated steam and CCA (chrome, copper, arsenic compound wood preservative) are injected under pressure. A reaction vessel that contains CCA wood and exposes CCA wood to superheated steam generated by a superheated steam generator to carbonize CCA wood without producing hexavalent chromium, and a product obtained by carbonization in the reaction vessel A recovery container.
Under the present circumstances, you may use what has the temperature of 300 degreeC or more as superheated steam introduce | transduced in a reaction container from a superheated steam generator.

  According to the present invention, CCA wood containing trivalent chromium can be carbonized without using a chemical substance at a relatively low temperature without producing hexavalent chromium, and the volume of CCA wood can be reduced. In the present invention, since CCA wood can be carbonized at a relatively low temperature using environmentally friendly water, a special device is unnecessary and energy required for harmless volume reduction can be reduced. The cost required for processing can also be reduced.

It is a block diagram which shows the structure of a CCA wood processing apparatus. It is a flowchart which shows the CCA wood processing method.

Next, an embodiment of the present invention will be described with reference to the drawings.
First, a CCA wood processing apparatus 10 according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a block diagram showing the configuration of the CCA wood processing apparatus. FIG. 2 is a flowchart showing a CCA wood processing method.

  As shown in FIG. 1, the CCA wood processing apparatus 10 according to the present embodiment includes, as a main structure, a reaction container 1 that contains a workpiece containing CCA wood to be decomposed, and heats water to a predetermined temperature. A superheated steam generator 2 that generates superheated steam, a warmer 3 that heats the steam and air in the reaction vessel 1, and a cooler that cools and liquefies the gas and superheated steam that are decomposition products of the hydrolysis treatment 4. A recovery container 5 for recovering the solid and liquid obtained by the treatment and a recovery container 6 for recovering the liquefied product are provided.

Moreover, the CCA wood processing method concerning this Embodiment has carbonization processing and a fraction collection process. Of these, carbonization heats water to a predetermined temperature to generate superheated steam, exposes the workpiece to this superheated steam, and carbonizes the wood without oxidizing the trivalent chromium contained in the workpiece. This is a process for reducing the volume. On the other hand, the separation and recovery process is a process for separating and recovering the decomposition products resulting from the process into gas, liquid, and solid.
Examples of CCA wood to which this CCA wood treatment can be applied include utility poles and house waste. Moreover, even if waste wood having these materials is mixed, the treatment is possible.

Next, the decomposition and recovery method according to the present embodiment will be described in detail with reference to FIG.
First, an object to be treated such as waste wood containing CCA wood is put into the reaction vessel 1 (step 100). Subsequently, as the carbonization treatment, superheated steam heated to a treatment temperature of 300 ° C. or higher by the superheated steam generator 2 is introduced into the reaction vessel 1 through the valve 7A, and is covered in a steam atmosphere filled with superheated steam. The processed material is exposed to heat the CCA wood contained in the processed material (step 101). At this time, the water vapor and air in the reaction vessel 1 are heated to a set temperature of 300 ° C. or higher by the heater 3 provided in the reaction vessel 1.

As a result of the thermal reaction by such carbonization treatment, the product carbonized from the CCA wood contained in the object to be treated and the contained metals such as copper, trivalent chromium and arsenic are recovered. Types of decomposition products include gas, liquid, and solid.
Next, the decomposition product obtained by the carbonization is subjected to a separate collection process corresponding to each of gas, liquid and solid (step 102).

  First, the gas in the decomposition product is introduced into the cooler 4 from the reaction vessel 1 through the valve 7B together with the superheated steam, and is cooled and liquefied by the cooler 4 (step 110). The liquid obtained by liquefaction is recovered from the cooler 4 to the recovery container 5 via the valve 7C (step 111). Since this liquid is a mixture of ash, fine particles of contained metal and water, the contained metal can be recovered by fractional distillation.

Further, the liquid of the decomposition product is recovered into the recovery container 6 via the valve 7D (step 120). Further, some of the decomposition products are also recovered into the recovery container 6 via the valve 7D in the same manner as the liquid (step 130).
In the separation and recovery process, the solid remaining in the reaction vessel 1 is a residue that could not be decomposed by the hydrolysis process, so that it can be recovered by an operator or a recovery operation by a carry-out device (not shown) provided in the reaction vessel 1. , Unloaded from the reaction vessel 1 and collected.

Actually, in order to confirm the CCA wood treatment method according to the present embodiment, an electric pole made of CCA wood as a raw material was put into the reaction vessel 1 as a treatment object, and the treatment object was exposed to superheated steam. At this time, the set temperature of the heater 3, that is, the set temperature in the reaction vessel 1 capable of storing superheated steam was set to 350 ° C.
Thereafter, the gas collected together with the water vapor was liquefied by the cooler 4 and recovered by the recovery container 5, and the obtained liquid was analyzed by ICP mass spectrometry. As a result, it was confirmed that arsenic was present in a trace amount. Similarly, copper, arsenic, and chromium were detected from the liquid recovered in the recovery container 6. Furthermore, the solid residue which became ash was recovered from the reaction vessel 1.

  As described above, in the present embodiment, the CCA wood is carbonized in the reaction vessel 1 without being produced hexavalent chromium by exposing the CCA wood to superheated steam from the steam generator 2. At a relatively low temperature, carbonization can be performed without using hexavalent chromium without using chemical substances, and the volume of CCA wood can be reduced. In addition, according to the present embodiment, since CCA wood can be carbonized at a relatively low temperature using environmentally friendly water, a special device is unnecessary and energy required for harmless volume reduction is reduced. Therefore, the cost required for processing can be reduced.

[Extended embodiment]
The present invention has been described above with reference to the embodiments, but the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

  INDUSTRIAL APPLICABILITY The present invention can be applied to a technique for reducing waste volume without producing hexavalent chromium in an object to be treated containing CCA wood.

  DESCRIPTION OF SYMBOLS 10 ... CCA wood processing apparatus, 1 ... Reaction container, 2 ... Superheated steam generator, 3 ... Heater, 4 ... Cooler, 5, 6 ... Recovery container.

Claims (4)

  By heating water to generate superheated steam, CCA wood into which CCA (chromium, copper, arsenic compound-based wood preservative) has been injected under pressure is exposed to the superheated steam. CCA wood processing method characterized by carbonizing without producing valent chromium. In the CCA wood processing method of Claim 1,
The CCA wood treatment method, wherein the superheated steam has a temperature of 300 ° C or higher. A superheated steam generator that heats water to generate superheated steam;
By containing CCA wood in which CCA (chromium, copper, arsenic compound-based wood preservative) is pressure-injected, and exposing the CCA wood to the superheated steam generated by the superheated steam generator, A reaction vessel for carbonizing without producing hexavalent chromium in the CCA wood;
A CCA wood processing apparatus, comprising: a recovery container for recovering a product obtained by carbonization in the reaction container. In the CCA wood processing apparatus of Claim 3,
The CCA wood processing apparatus, wherein the superheated steam introduced from the superheated steam generator into the reaction vessel has a temperature of 300 ° C or higher.

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