JPH1121573A - Process for dechlorinating rdf - Google Patents

Abstract

PROBLEM TO BE SOLVED: To convert chlorine gases into harmless chlorides to thereby prevent the formation of dioxins by bringing harmful chlorine gases produced from RDF(Refuse Derived Fuel) into contact with a dechlorinating agent comprising an alkali substance in a heated atmosphere. SOLUTION: Desirably the heated atmosphere has a temperature of 200-1,000 deg.C. RDF refers to a product prepared by treating a mixture of kitchen garbage, plastics, paper and other combustible materials so as to give combustibles. This is brought into contact with a dechlorinating agent such as sodium hydrogencarbonate. The system is composed of a heat treatment section 1, a metallic cylindrical member 2, a transfer screw 3 and a heating coil 4, is supported by a screw support member 8 and is revolved by a motor. RDF is mixed with 5-30 wt.%, based on the RDF, dechlorinating agent, and the mixture is introduced into the section 1. The coil 4 is energized, and the mixture is heat-treated until the RDF is carbonized. The RDF is withdrawn by a washing/separation means 6, and the produced gases are withdrawn from waste gas section 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the reprocessing of solidified fuel (hereinafter referred to as "RDF"), and more particularly to the reprocessing of RDF which is generally performed for reducing the volume of various wastes and converting it to fuel. The present invention relates to a dechlorination treatment method.

[0002]

2. Description of the Related Art The amount of objects to be treated such as municipal garbage is increasing year by year, and the disposal thereof has become a problem. Generally, municipal waste is discharged as a processed material from general households or offices and is mainly combustible. Recently, it has been considered that this flammable treated material is not simply incinerated but is effectively used as a resource. The treated material is once solidified into RDF (solidified fuel) and discarded in an incinerator. They are put together with goods and reused as fuel.

[0003]

However, in the object to be treated, various kinds of chemical substances in recent years, for example, plastics containing a large amount of vinyl chloride resin, and paper used in offices, such as chlorine bleach, are used. In addition, since substances containing a large amount of chlorine are mixed in, the materials to be treated are separated in advance to select only those that generate less chlorine components, or use chlorine removal means (addition of slaked lime, calcium, etc.) Attempts have been made to convert the RDF into RDF, but at present it is not sufficient.

[0004] Accordingly, when RDF is burned, chlorine-based gas is generated, which causes the generation of dioxin, and it is not environmentally preferable to release it directly into the atmosphere.

On the other hand, according to the guidelines of the Ministry of Health and Welfare in January 1997, there is a policy to promote RDF at a plurality of RDF facilities, and to collect these in large continuous operation incineration facilities for centralized incineration. However, the continuous operation incinerator is a facility that contributes to the prevention of dioxin, and although it is improved over the past, it is not always sufficient.

Accordingly, an object of the present invention is to provide a processing method for effectively dechlorinating this RDF.

[0007]

Means for solving the above-mentioned problems in the present invention is to contact a harmful chlorine-based gas generated from RDF with a dechlorinating agent consisting of an alkaline substance in a heated atmosphere. The RDF is dechlorinated by reacting with harmful chlorine gas to generate harmless chloride.

[0008] As described above, the RDF generating chlorine-based gas
Is not directly used as a fuel, but is dechlorinated and reprocessed, so that the volume can be further reduced and the residual carbide can be used as a new harmless fuel.

The following are the alkaline substances used as the dechlorinating agent used in the present invention.

(1) A simple substance or a mixture of plural alkali metal compounds.

(2) The alkali metal compound is a hydroxide,
Carbonate substance.

(3) Hydroxides and carbonates are sodium-based and potassium-based substances.

(4) The dechlorinating agent is (a) sodium bicarbonate. Also known as acidic sodium carbonate, sodium bicarbonate, and sodium bicarbonate.

(B) sodium carbonate. Also known as soda carbonate, soda, soda ash, washing soda, crystal soda.

(C) Sodium sesquicarbonate. Also known as sodium bicarbonate, sodium tricarbonate, and sodium sesquicarbonate.

(D) Natural soda. Another name, Trona.

(E) potassium carbonate, potassium hydrogen carbonate,
It is used as a simple substance selected from sodium potassium carbonate, sodium hydroxide and potassium hydroxide, or as a mixture of plural kinds.

Further, in order to enhance the contact effect between the RDF and the dechlorinating agent, the RDF and the dechlorinating agent are mixed and heated.

In this heat treatment, the crushed RDF and the dechlorinating agent are mixed and heated. As described above, the surface area is increased by crushing, the chlorine-based gas is easily deposited, and the mixing with the dechlorinating agent is made sufficient to enhance the contact effect with the dechlorinating agent.

Further, a chlorine-based gas generated from the RDF is contacted with a dechlorinating agent. The site of this contact reaction is not limited to the contact in the heat treatment section, but may be a flue portion of exhaust gas.

The atmosphere in which the chlorine-based gas is brought into contact with the dechlorinating agent may be any of a pyrolysis atmosphere, a dry distillation atmosphere, and a low oxygen atmosphere, and is a "steaming" state in which the treated ash is not burned. Any atmosphere may be used as long as the heating atmosphere can be maintained.

The form of the dechlorinating agent may be any of a lump, a plate, a porous, a powder, a solution, and a suspension, or a combination thereof. decide.

The heated atmosphere is 200 ° C. to 1 ° C.
The temperature is set to 000 ° C., and is determined according to the operating conditions such as the shape of the heating furnace, the processing amount, and the processing time.

Here, RDF (solidified fuel) refers to a substance that has been treated so as to be combustible. In a broad sense, (a) kitchen waste (meat, fish head / bone, eggshell, vegetables, fruits, etc.) Leftovers) (b) Plastics (polyethylene, polypropylene, polystyrene, polyvinylidene chloride, etc.) (c) Papers (tissue paper, newspaper, advertising paper, bags, boxes, beverage packs, etc.) (d) Other flammable A mixture of objects (fibers such as cloth, wood chips, rubber, leather, etc.).

In a narrow sense, (b), (c) and (d) are referred to.

However, recently, solidified materials such as plastics and rubbers for the purpose of combustion and the like have been included.

Under the above conditions, R containing chlorine component
When a heat treatment is performed by adding a dechlorinating agent made of an alkali substance to DF, for example, in the case of sodium hydrogen carbonate, (NaHCO ₃ ) + (HCl) → (NaCl) + (H
₂₀ ) + (CO ₂ ) In the case of potassium hydrogen carbonate (KHCO ₃ ) + (HCl) → (KCl) + (H ₂₀ ) +
(CO ₂ ) In the case of sodium hydroxide (NaOH) + (HCl) → (NaCl) + (H ₂₀ ) In the case of potassium hydroxide (KOH) + (HCl) → (KCl) + (H ₂₀ ) Harmful sodium chloride (NaCl) and potassium chloride (KCl) are generated by reacting with chlorinated gas, and harmful chlorine component (HCl) is eliminated.

From this, detoxification treatment can be realized by adding an alkali substance and treating.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a system configuration diagram of one embodiment of the present invention. In FIG.
The heat treatment section 1 includes a metal cylindrical member 2 and a screw 3 provided inside the cylindrical member 2 for transferring an object to be processed.
And a heating coil 4 provided on the outer periphery of the cylindrical member 2. The screw 3 is supported by a screw support member 8,
It is rotated by a driving force not shown.

5 is a crushing / mixing means, which crushes and mixes RDF, which is an object to be processed, and a dechlorinating agent, and supplies the RDF from one end side in the cylindrical member 2. Reference numeral 6 denotes a washing / separating means, which is provided on the other end side of the cylindrical member 2 and takes out the residue subjected to the heat treatment for washing and solid-liquid separation. Reference numeral 7 denotes an exhaust gas take-out section for taking out gas generated in the cylindrical member 2 during the heat treatment from the discharge pipe 7a. Reference numeral 7b denotes a pipe for utilizing the heat of the exhaust gas, and a part of the exhaust gas from the discharge pipe 7a is discharged through a hollow screw support member 8 provided in the cylindrical member 2.

The dechlorination treatment of RDF will be described below. RDF and a dechlorinating agent, for example, sodium hydrogen carbonate (NaHCO ₃ ) are charged into the crushing / mixing means 5 and mixed. At this time, the RDF depends on the size of the shape,
Alternatively, use one that has been crushed in advance.

As the dechlorinating agent, powder is usually used, but other forms may be used as described above. In addition, a dechlorinating agent is added in an amount of 5 to 30% by weight based on the weight of RDF.

After sufficient mixing, the mixture is put into a heat treatment section 1 such as a heat treatment furnace. The heat treatment in the heat treatment section 1 is performed by energizing the heating coil 4, and the heat treatment is sufficiently performed until the RDF is fired. (For example, about 1 hour at 600 ° C.) This time and temperature are determined by the condition of the heating furnace (size,
Conditions depending on the furnace, such as heating means), processing amount, processing time,
The amount of power supply to the heating coil 4 and the rotation speed of the screw 3 are determined in consideration of the processing temperature.

The RDF subjected to the heat treatment in the heat treatment section 1 is
It is taken out by the washing / separating means 6 and separated into a liquid and a solid in which sodium chloride is dissolved by the washing / separating means. On the other hand, gas generated during the heat treatment is taken out from the exhaust gas take-out section 7. At this time, part of the pipe 7
From b, the heat of the exhaust gas is reused by heating the screw support member 8 in the cylindrical member 2 through the hollow space of the member.

The heat treatment in the heat treatment section 1 is not by combustion or incineration but by steaming and pyrolysis, so that the deposited harmful chlorine-based gas and the dechlorinating agent are effectively contacted and reacted. Harmful chlorine-based gas can be replaced with harmless chloride.

Therefore, in order to maintain the reaction environment, in part, the entire environment must be in a stable state necessary for maintaining the reaction, for example, in a stable state in a low oxygen atmosphere. It is necessary that the amount of air does not newly enter only around the object to be treated during the treatment, and if it enters, the periphery of the object to be treated starts burning, and the reaction may become unstable. There is.

Further, it has been found from an experiment that the reaction can be maintained by blowing fresh air so that the air can flow through the entire inside of the pulverized object under the condition that the unburned state can be maintained.

The harmful chlorine-based gas generated in the above process is reacted with a dechlorinating agent and replaced with harmless chloride, and contains no harmful chlorine-based gas (hydrogen chloride, chlorine gas). The exhaust gas can be used for various purposes, for example, as fuel (gas engine, turbine) for various facilities and heat exchanger (heating, etc.).

In the case of discharge, post-processing (secondary combustion, exhaust gas treatment) is carried out as required, and discharge is performed in conformity with various air pollution prevention standards.

After the treated residue is taken out, it is washed and separated with water or the like, and harmless chloride (eg, sodium chloride) is discharged as a solution.

On the other hand, by separating and drying, valuable carbides are taken out as solids.

When a harmful chlorine-based gas generated from an RDF containing a chlorine component is brought into contact with a dechlorinating agent made of an alkali substance that reacts in a heated atmosphere, the harmful chlorine-based gas reacts with the harmful chlorine-based gas to cause harmlessness. The formation of chloride was revealed by the following experimental investigation.

In the experiment, a low-oxygen atmosphere was created in a closed vessel equipped with an exhaust pipe and having an open / close door.
And heated in an electric furnace from 250 ° C to 600 ° C.
At 50 ° C intervals at each temperature for 5 minutes.
At the time of keeping, the exhaust pipe was opened to measure the concentration (ppm) of hydrogen chloride gas (HCl). In addition, the measurement was also performed at 600 ° C to 1000 ° C.

The gas concentration was measured using a detector tube specified in JIS-K0804.

Table 1 shows the measurement results. The hydrogen chloride gas concentration is a measured value in ten experiments, Examples 1 and 2 show the highest values, and Comparative Examples 1 and 2 show the lowest values.

Note that "ND" represents "not detected",
It shows that none was detected in 10 experiments.

In the experiment, first, as a comparative example, a sample of 40 g of RDF to which no dechlorinating agent was added was prepared, and the crushed one was designated as Comparative Example 1, and the lump without crushing was designated as Comparative Example 2.

Next, a sample was prepared by adding 10 g of sodium bicarbonate, which is the dechlorinating agent of the present invention, to 40 g of crushed RDF.
An experiment was performed as Example 2 using a sample in which sodium hydrogen carbonate was added to 0 g. Table 1 shows the results.

Note that a generally known processed RD
The content of chlorine component in F
DF contains 0.29 to 0.89% by weight of a chlorine component. Waste paper RDF contains 0.2% by weight of a chlorine component.

The chlorine content of the RDF used in this experiment was analyzed to be 0.7% by weight.

[0052]

[Table 1]

From the experimental results shown in Table 1, the following is considered.

(1) In the case of only RDF without using a dechlorinating agent, (a) In the case of lump, as shown in Comparative Example 2, at 350 ° C.
It can be seen that a considerable amount of hydrogen chloride is generated at about 450 ° C.

(B) In the case of crushing, as shown in Comparative Example 1, hydrogen chloride was generated in the same temperature range as Comparative Example 2. It can be seen that this has occurred.

(2) In the case of RDF and dechlorinating agent: (a) In the case of lump, as shown in Example 2, at 350 ° C.
At about 450 ° C., hydrogen chloride is slightly generated.

(B) It was found that when crushed, no generation of hydrogen chloride was observed.

In the above experiment, sodium bicarbonate was found to be very effective as a dechlorinating agent.
Experiments were conducted for similar harmless chloride-producing substances.

This experiment was performed in the same manner as described above.

In the experiment, first, a preliminary test was performed using only 4 g of polyvinylidene chloride containing a large amount of a chlorine component. The results are shown in Comparative Example 1 of Table 2.

Next, an experiment was conducted by adding 20 g each of slaked lime and calcium carbonate powder conventionally known as dechlorinating agents. The results are shown in Comparative Examples 2 and 3.

Next, polyvinylidene chloride and vinyl chloride, which generate a large amount of hydrogen chloride when heated, are selected as the objects to be treated. Table 2 shows the dechlorinating agents based on the alkaline substance of the present invention. Experiments were performed with several substances selected and added.

In Examples 1 and 2, when 20 g of the sodium hydrogencarbonate powder of the present invention was added to 4 g of polyvinylidene chloride and 4 g of vinyl chloride to be treated, Examples 3 to 5 were the same. In the case where 10 g of potassium hydrogencarbonate, 20 g of sodium hydroxide, and 20 g of potassium hydroxide of the present invention were added to 4 g of polyvinylidene chloride as a treated material, respectively, the treated material and the dechlorinating agent were mixed in each of the examples. Was done. Table 2 shows the results.

[0064]

[Table 2]

From the experimental results shown in Table 2, the following is considered.

First, when polyvinylidene chloride containing a large amount of a chlorine component is used as an object to be treated, a large amount of hydrogen chloride gas is generated over each temperature by heat treatment in Comparative Example 1 in which a dechlorinating agent is not added. . In Comparative Example 2 in which slaked lime, which is a conventional dechlorinating agent, was added to the object to be treated, and in Comparative Example 3 in which calcium carbonate was added, the generation of hydrogen chloride gas was considerably suppressed as compared with Comparative Example 1. Not enough.

On the other hand, in the present invention, a very small amount (1 ppm, 2 ppm) at 450 ° C. of Examples 4 and 5 was used.
pm) of hydrogen chloride gas was detected, but other than that, it was not detected at all over the entire temperature range, and very good results were obtained.

In addition, when sodium bicarbonate is added to the material to be treated using vinyl chloride, as shown in Example 2, the production of hydrogen chloride is completely suppressed in any temperature range. .

According to the above experimental investigation, when RDF is dechlorinated, an alkali substance (particularly an alkali metal compound) which reacts with a chlorine-based gas to produce harmless chloride is added, and then treated. It was confirmed that detoxification treatment was possible.

The reason why the harmful hydrogen chloride is replaced with a harmless chloride has been clarified from the following reaction.

(1) In the case of sodium hydrogen carbonate (NaHCO ₃ ) + (HCl) → (NaCl) + (H
( ₂₀ ) + (CO ₂ ) (2) In the case of potassium hydrogen carbonate (KHCO ₃ ) + (HCl) → (KCl) + (H ₂₀ ) +
(CO ₂₎ (3) the case of sodium hydroxide (NaOH) + (HCl) → (NaCl) + (H 2 0) (4) if the potassium hydroxide (KOH) + (HCl) → (KCl) + ( H ₂ 0) NaCl and KCl produced as described above are harmless chlorides.
There are the following sodium-based and potassium-based substances that produce, and similar effects can be obtained.

Sodium carbonate Potassium carbonate Sodium potassium carbonate Sodium carbonate hydrate Sodium sesquicarbonate Natural soda Next, the obtained residue was analyzed, and the chlorine-based substances after the dechlorination treatment were confirmed. No gas components were detected, and harmless chlorides sodium chloride and potassium chloride were detected. Further, the residue was stirred for 10 minutes and washed with water, so that sodium chloride and potassium chloride were dissolved in water and a carbide remained, but no harmful chlorine-based gas component was detected in the carbide.

Therefore, the harmful chlorine components are sodium chloride (NaCl) and potassium chloride (K
Cl), water (H ₂ O), and gas (CO ₂ ), and do not generate hydrogen chloride, which causes the generation of dioxins.

From the above, it has been found that it is better to use RDF after dechlorination and detoxification, instead of reusing RDF as fuel as it is.

The dechlorinating agents used in the dechlorination treatment include: (1) a simple substance of an alkali metal compound, a mixture of plural kinds thereof, and (2) the alkali metal compound is a substance of hydroxide or carbonate. ) Hydroxides and carbonates are sodium-based and potassium-based substances. (4) Dechlorinating agents are sodium bicarbonate, sodium carbonate, sodium sesquicarbonate, natural soda, potassium carbonate, potassium bicarbonate, sodium potassium carbonate, water It was also found that a single substance selected from sodium oxide and potassium hydroxide, and a mixture of plural kinds thereof were suitable.

Therefore, the harmful chlorine-based gas generates harmless chlorides (NaCl, KCl) by the contact reaction between the generated harmful chlorine-based gas and the added dechlorinating agent. Moreover, these harmless chlorides can be effectively removed by a washing treatment with a solution such as water, and after the washing, reusable carbides and the like remain.

Further, before and after the washing treatment, each substance can be separated by an arbitrary separation means, and the separated substance can be dried and solidified to be effectively used as fuel or the like.

Although the treatment liquid after washing contains harmless chlorides, it contains almost no harmful substances, and can be subjected to wastewater treatment as required and discharged into rivers or the ocean.

[0079]

As is clear from the above experimental results, it was found that when the solidified RDF was subjected to heat treatment as it was, hydrogen chloride was generated, and if this was used as a fuel, it would be a cause of dioxin generation. There was found.

According to the present invention, instead of using RDF as it is as fuel, dechlorination is performed using the dechlorinating agent of the present invention, and harmful chlorine-based gas is replaced with harmless chloride. Detoxification of both exhaust gas and residue was achieved. As a result, an excellent effect that dioxin generation can be effectively prevented can be obtained.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Heat treatment part 2 ... Cylindrical member 3 ... Screw 4 ... Heating coil 5 ... Crushing / mixing means 6 ... Cleaning / separation means 7 ... Exhaust gas part 8 ... Screw support member

Claims (11)

[Claims] 1. A harmful chlorine-based gas generated from an RDF is brought into contact with a dechlorinating agent composed of an alkali substance in a heated atmosphere to react with the harmful chlorine-based gas to generate harmless chloride. A method for dechlorination of RDF. 2. The alkali substance is a simple substance of an alkali metal compound or a mixture of plural kinds thereof.
The method for dechlorination of RDF described in the above. 3. The method for dechlorination of RDF according to claim 1, wherein the alkali metal compound is a substance of hydroxide or carbonate. 4. The hydroxide and carbonate are sodium-based,
The method for dechlorination of RDF according to any one of claims 1 to 3, wherein the method is a potassium-based substance. 5. The dechlorinating agent may be a simple substance selected from the group consisting of sodium bicarbonate, sodium carbonate, sodium sesquicarbonate, natural soda, potassium carbonate, potassium bicarbonate, sodium potassium carbonate, sodium hydroxide, and potassium hydroxide. 2. The method for dechlorination of RDF according to claim 1, wherein the method is a mixture. 6. The method for dechlorination of RDF according to claim 1, wherein the RDF and the dechlorination agent are mixed and heated. 7. The R according to claim 1, wherein the crushed RDF and the dechlorinating agent are mixed and heated.
DF dechlorination treatment method. 8. The method according to claim 1, wherein a chlorine-based gas generated from the RDF is contacted with a dechlorinating agent.
Or the method for dechlorination of RDF according to 7. 9. The dechlorination treatment of RDF according to claim 1, wherein the contact atmosphere between the chlorine-based gas and the dechlorinating agent is any one of a pyrolysis atmosphere, a dry distillation atmosphere, and a low oxygen atmosphere. Method. 10. The dechlorinating agent may be in the form of lump, plate, porous,
The RDF dechlorination treatment method according to any one of claims 1 to 9, wherein the method is a powder, a solution, a suspension, or a combination thereof. 11. The heated atmosphere is at 200 ° C. to 10 ° C.
10. R according to claim 1 or 9, wherein the temperature is 00 ° C.
DF dechlorination treatment method.