JP5023510B2 - Fly ash treatment method - Google Patents

Description

  The present invention relates to a method for treating fly ash containing harmful substances such as dioxins, and more specifically, fly ash that is separated and collected from exhaust gas generated during incineration of dust and contains the harmful substances. Relates to the processing method.

  When incinerating garbage at municipal waste incineration facilities, etc., the incineration exhaust gas contains burning husks and acid gases typified by hydrogen chloride, sulfur dioxide, etc., and water is neutralized to neutralize the acid gases. An exhaust gas treatment agent such as calcium oxide is sprayed into the flue. The soot generated along with this, that is, the waste incineration fly ash, is separated from the exhaust gas stream by a dust collector such as a bag filter. The fly ash is generated by the reaction of calcium hydroxide and hydrogen chloride. It contains not only calcium chloride and unreacted calcium hydroxide, but also harmful substances such as dioxins.

  In recent years, the toxicity of dioxins generated during incineration of waste has been pointed out, the content of dioxins contained in exhaust gas is regulated by the Air Pollution Control Law, and dioxins contained in waste incineration fly ash It is regulated to 3 ng / g or less by the Act on Special Measures against Dioxins.

  In order to reduce such dioxins in the fly ash, the fly ash is dechlorinated by a fly ash heat dechlorination apparatus such as a Hagenmeier apparatus.

  However, the fly ash heated inside the heat dechlorination device solidifies inside the device and adheres to the inside of the device, thereby causing troubles that hinder the operation of the heat dechlorination device or damage the device. However, there is a problem that hinders the operation of fly ash treatment.

  As a technique for eliminating the solidification and adhesion of fly ash inside such a heat dechlorination apparatus, slaked limes can be directly applied to the fly ash collected by the dust collector or directly upstream of the apparatus. Has been proposed in which about 25 wt% or more of the fly ash is added to raise the melting point of the fly ash to a temperature higher than the temperature inside the apparatus (see, for example, Patent Document 1).

In this way, it is essential to raise the melting point of the fly ash to a temperature higher than the temperature in the apparatus, in response to the fly ash-containing components are a wide variety Hey et loose, stable target temperature of the melting point of fly ash It was not easy to raise. Further, even if the melting point can be raised, it is a little over 400 ° C., so the temperature inside the apparatus has to be suppressed to 350 to 380 ° C. which is lower than that. However, it cannot be said that the reaction rate of the dechlorination reaction is sufficiently high at such a temperature in the apparatus, and the decomposition efficiency of dioxins and the like is not necessarily sufficient. In addition, in this method, the amount of slaked lime added is determined on the basis of the amount of fly ash, so considering that the components contained in the fly ash vary depending on the type of waste, depending on the type of waste, There were also variations in the effect of preventing adhesion, and there was room for improvement in the stability of the effect.

JP 2005-246280 A

  Therefore, in view of the above-mentioned situation, the present invention intends to solve the problem that fly ash can be stably and smoothly operated without burning and sticking inside the heat dechlorination apparatus, and maintaining and managing the apparatus. It is in the point which provides the fly ash processing method which becomes easy.

  The present invention relates to calcium chloride produced when the causative substance of fly ash solidification and adhesion in the heat dechlorination apparatus neutralizes the acidic gas contained in the exhaust gas, and in the exhaust gas for the neutralization treatment. It is CaClOH generated by the reaction of the following formula (1) with the unreacted calcium hydroxide added in advance, and this CaClOH is heated to a high temperature (for example, 300 ° C. or higher) to be baked and hardened, thereby being dense and strong. This is based on the knowledge that a large sintered body becomes a cause of adhesion in the heat dechlorination apparatus.

That is, the present invention makes calcium carbonate by reacting the unreacted calcium hydroxide causing CaClOH generation with a specific treatment agent serving as a carbonic acid source, thereby suppressing the generation of CaClOH. even generated are those that reduce its hardness, after decomposing the dioxins was treated heating dechlorination fly ash containing dioxins, a fly ash treatment method of cooling, alkali metal carbonate A fly ash treatment agent comprising at least one of a salt and an alkali metal bicarbonate, calcium hydroxide contained in the fly ash is measured, and based on the measurement result, the calcium hydroxide and the treatment agent Add to the fly ash so that the substance ratio (fly ash treatment agent / calcium hydroxide) is 0.5 or more, and heat the calcium hydroxide contained in the fly ash. The fly ash treatment method is characterized in that the fly ash is dechlorinated and then cooled while reacting with the treatment agent in a chlorinator to form calcium carbonate.

  Here, the fly ash to be treated in the present invention refers to soot and dust containing harmful substances such as dioxins, and is typically separated and collected from the exhaust gas generated at the waste incineration facility. However, it is not limited to this.

  Further, the fly ash treatment agent is at least one of alkali metal carbonate and alkali metal bicarbonate, and measures calcium hydroxide contained in the fly ash, and based on the measurement result, the hydroxide It is preferable to add the treatment agent to the fly ash so that the mass ratio of calcium to the treatment agent (fly ash treatment agent / calcium hydroxide) is 0.5 or more.

  Furthermore, it is preferable to collect a fly ash sample for measuring calcium hydroxide contained in the fly ash in a transporting step before the fly ash is introduced into the heat dechlorination treatment apparatus.

  Moreover, it is preferable to add the said fly ash processing agent at the conveyance process before the said fly ash is introduce | transduced into a heat dechlorination processing apparatus.

  Furthermore, it is more preferable that the fly ash treatment agent is at least one of sodium carbonate and sodium bicarbonate.

  Moreover, it is preferable that the atmospheric temperature in a heat dechlorination apparatus shall be 400 degreeC or more.

  According to the fly ash treatment method according to the present invention as described above, the fly ash treatment agent comprising at least one selected from the group consisting of alkali metal carbonates, alkali metal bicarbonates, and carbon dioxide gas is used as a carbonate source. By adding calcium hydroxide contained in the ash and reacting the calcium hydroxide contained in the fly ash with the treatment agent in the heating dechlorination device to form calcium carbonate, the fly ash is dechlorinated, so that the fly ash A stable and smooth operation can be performed without burning and sticking inside the heating dechlorination apparatus, and maintenance and management of the apparatus are facilitated.

  Further, the fly ash treatment agent is at least one of alkali metal carbonate and alkali metal bicarbonate, and measures calcium hydroxide contained in the fly ash, and based on the measurement result, the hydroxide By adding the treatment agent to the fly ash so that the ratio of the amount of calcium to the treatment agent (fly ash treatment agent / calcium hydroxide) is 0.5 or more, any fly containing various components can be obtained. Corresponding to ash, the minimum amount of the fly ash treatment agent used can prevent the fly ash from sticking, and the processing cost can be reduced.

  Furthermore, a fly ash sample for measuring the calcium hydroxide contained in the fly ash can be easily sampled by collecting it in the transport process before the fly ash is introduced into the heat dechlorination treatment apparatus. At the same time, it becomes easy to add an appropriate amount of processing agent to the fly ash.

  Further, by adding a fly ash treatment agent comprising at least one of alkali metal carbonate and alkali metal bicarbonate in the transporting step before the fly ash is introduced into the heat dechlorination treatment apparatus, It becomes easy to mix the treating agent uniformly in the ash in advance and to make it react efficiently.

  Furthermore, the cost of this processing agent can be reduced by making the said fly ash processing agent into at least 1 sort (s) among sodium carbonate and sodium hydrogencarbonate.

  Alternatively, by using carbon dioxide as the fly ash treatment agent, fly ash can be treated while effectively using carbon dioxide that causes global warming.

  Furthermore, by directly introducing the carbon dioxide gas into the heat dechlorination treatment apparatus, it is not necessary to provide a separate heating apparatus, which is advantageous in terms of heating cost.

  In addition, by setting the atmospheric temperature in the heat dechlorination apparatus to 400 ° C. or higher, the treatment can be efficiently performed in an environment having a high dechlorination reaction rate.

  Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited to these examples.

  FIG. 1 is a schematic diagram showing the overall configuration of an apparatus for carrying out the fly ash treatment method according to the present invention, in which reference numeral 1 is an incineration exhaust gas flow path, 1a is a fly ash flow path, 1b is an exhaust gas flow path, 2 Is a post-treatment fly ash flow path, 11 is a dust collector, 12 is a conveying step, 13 is a heat dechlorination device, 14 is a cooling device, 21 is a fly ash treatment agent storage tank, 22 is a carbon dioxide gas inlet, and 23 is carbonic acid. Each gas outlet is shown.

  In the fly ash treatment method according to the present invention, the fly ash separated from the incineration exhaust gas by the dust collector 11 is introduced into the dechlorination treatment device 13 through the transport step 12, and harmful substances such as dioxins contained in the fly ash Is reduced to a fly ash treatment method that is cooled by the cooling device 14, and the carbonic acid source is at least one selected from the group consisting of alkali metal carbonates, alkali metal bicarbonates, and carbon dioxide. The fly ash treatment agent is added to the fly ash from the fly ash treatment agent storage tank 21 or the carbon dioxide gas inlet 22, and the calcium hydroxide contained in the fly ash reacts with the treatment agent in the heat dechlorination apparatus 13. The fly ash is dechlorinated while making calcium carbonate.

  Examples of the alkali metal carbonate include lithium carbonate, sodium carbonate, and potassium carbonate. Examples of the alkali metal bicarbonate include lithium hydrogen carbonate, sodium hydrogen carbonate, and potassium hydrogen carbonate. Of these, sodium carbonate and sodium hydrogen carbonate are particularly preferable because the cost of the treatment agent can be kept low.

The mechanism by which the fly ash treatment method according to the present invention can prevent fly ash sticking troubles in the heat dechlorination apparatus will be described in more detail below, taking as an example the case where sodium carbonate is used as the treatment agent. First, calcium hydroxide in fly ash, which is considered to be a raw material of the causative agent, is carbonated by adding sodium carbonate to form calcium carbonate. Further, the sodium hydroxide generated at the same time by the reaction of sodium carbonate and calcium hydroxide, and calcium chloride in fly ash is considered another raw material reacts causative agent, sodium chloride that generates. Through the reaction described above, the amount of CaClOH, which is a causative agent of sticking, is reduced, and an impure component with respect to the CaClOH is produced, thereby preventing the production of a sticking causative substance having high hardness.

  When alkali metal carbonate or alkali metal bicarbonate is used as the fly ash treatment agent, unreacted calcium hydroxide contained in fly ash is measured, and the calcium hydroxide is measured based on the measurement result. And the treatment agent is added to the fly ash so that the substance ratio (fly ash treatment agent / calcium hydroxide) is preferably 0.5 or more and 20 or less, more preferably 1.0 or more. 10 or less. Of course, when two or more of alkali metal carbonate and alkali metal bicarbonate are used in combination, the substance amount ratio is calculated based on the total amount of the treating agent. By setting the fly ash treatment agent / calcium hydroxide substance amount ratio to 0.5 or more, the sintered body hardness can be prevented from being baked and hardened by the heat dechlorination treatment, that is, transport in the apparatus. It can be reduced to a level that collapses with the force of. Furthermore, by setting the substance amount ratio to 1.0 or more, the hardness of the sintered body can be further reduced, and a more stable and smooth heat dechlorination process can be achieved. If the substance amount ratio is too large, the amount of fly ash treatment agent to be used increases and costs increase, and the amount of fly ash generated after treatment tends to increase. Preferably it is 10 or less.

As an addition method in the case of using alkali metal carbonate or alkali metal bicarbonate, it may be added directly from the fly ash treatment agent storage tank 21 into the heat dechlorination apparatus 13, or fly ash is added to the apparatus 13. In the process before being introduced into the ash, it may be previously added and mixed in the fly ash, and the mixture may be introduced into the heat dechlorination apparatus. It is simple and preferable that the fly ash is added in the transporting step 12 before being introduced into the heat dechlorination processor 13. In order to prevent sintering more effectively, it is preferable to add a treatment agent and mix it uniformly in the process before the fly ash sintering is started in the heat dechlorination apparatus 13. By uniformly mixing in advance in this way, the calcium hydroxide in the fly ash introduced into the device 13 can be reacted uniformly with the treatment agent, and calcium carbonate can be efficiently produced, thereby preventing sticking. Can be further increased. In order to mix uniformly, it is preferable to add alkali metal carbonate or alkali metal bicarbonate to the fly ash in the form of powder, and a mixing means (not shown) such as a screw conveyor is provided in the conveying step 12. More preferably, an alkali metal carbonate or an alkali metal bicarbonate is added to the fly ash introduced into the mixing means. When using 2 or more types together among alkali metal carbonate and alkali metal bicarbonate, the processing agent which mixed 2 or more types beforehand may be added from the storage tank 21, and each processing agent is stored. A separate storage tank may be provided and added by another route. In the case where alkali metal carbonate or alkali metal bicarbonate is added and mixed in the step before fly ash is introduced into the apparatus 13, the atmospheric temperature in the step is preferably 100 ° C. or less, and more preferably Is 60 ° C. or lower, more preferably 40 ° C. or lower. The advantage of adding and mixing the treatment agent consisting of alkali metal carbonate or alkali metal bicarbonate at a low temperature is that it can be uniformly mixed with fly ash before the carbonation reaction starts. If the temperature at the time is too high, the carbonation reaction tends to occur locally, and the sticking prevention effect tends to be reduced.

In the present invention, when an alkali metal carbonate or alkali metal bicarbonate is used as a fly ash treatment agent, it can also be subjected to a heat dechlorination treatment in an oxygen-existing atmosphere or a heat dechlorination treatment in a reducing atmosphere. By processing, as described above, the fly ash can be prevented from being baked and hardened. Here, the oxygen-existing atmosphere is an atmosphere containing oxygen, for example, in the air.

  When carbon dioxide gas is used as the fly ash treatment agent, it may be introduced directly into the heat dechlorination apparatus 13 through the carbon dioxide gas inlet 22, or transport before fly ash is introduced into the apparatus 13. In step 12, a carbon dioxide gas inlet (not shown) may be provided for introduction. Among these, in consideration of heating cost, a method of directly introducing into the heating dechlorination apparatus 13 from the carbon dioxide gas inlet 22 is more preferable. The atmospheric temperature at the time of introduction of carbon dioxide is set to 100 ° C. or higher, preferably 200 ° C. or higher, more preferably 300 ° C. or higher, in order to allow calcium hydroxide and carbon dioxide to react more efficiently. The amount of carbon dioxide supplied is preferably 150 ml or more, more preferably 300 ml or more, with respect to 1 g of fly ash to be treated, so that calcium hydroxide in the fly ash is carbonated and heat dechlorinated. The amount is sufficient to prevent sticking in the apparatus. In addition, as an atmosphere when the calcium hydroxide and the carbon dioxide gas are reacted, it is preferable to supply a gas composed of 100% carbon dioxide, but a carbon dioxide gas and a gas not containing a carbon dioxide source (carbon dioxide) are mixed. When supplying carbon dioxide gas in a volume ratio, carbon dioxide gas and calcium hydroxide in fly ash are efficiently supplied by supplying a gas containing carbon dioxide gas by 10% or more, preferably 25% or more, more preferably 50% or more. It can be reacted well and has a carbon dioxide gas concentration sufficient to prevent sticking in the heat dechlorination apparatus. The advantage of using carbon dioxide gas in this way is that carbon dioxide, which is the cause of global warming, can be used effectively. The gas discharged from the carbon dioxide discharge port 23 is circulated and introduced again from the introduction port 22. In the case of adopting the method, the carbon dioxide gas can be recycled, which is further advantageous in terms of cost.

Of course, carbon dioxide can be introduced from the inlet 22 while adding the alkali metal carbonate or alkali metal bicarbonate from the storage tank 21 as the fly ash treatment agent. Further, it is possible to more effectively prevent fly ash from being baked and solidified in the dechlorination apparatus 13.

  In the present invention, the measurement of calcium hydroxide and calcium chloride contained in the fly ash may be performed by a conventional chemical analysis method, and is not particularly limited. For example, it can be measured as follows. .

  First, fly ash samples for measuring calcium hydroxide and calcium chloride contained in the fly ash are collected. Here, the fly ash sample may be collected in the process before the fly ash is introduced into the heat dechlorination treatment apparatus, and can be easily sampled by collecting in the transport process 12 and Therefore, it becomes easy to add an appropriate amount of the processing agent.

  The fly ash sample collected in this manner is dissolved in distilled water, and the alkali is quantified by performing neutralization titration (pH = 9) using hydrochloric acid, and the obtained alkali content is used as the amount of calcium hydroxide. . Furthermore, the sample after the neutralization titration is subjected to solid-liquid separation by filtration. EDTA chelate titration is performed on the filtrate side to quantify calcium. The obtained amount of Ca material is the sum of the amounts of calcium hydroxide and calcium chloride. By the above operation, calcium hydroxide and calcium chloride contained in the fly ash can be respectively measured.

  In the present invention, as described above, the heat dechlorination treatment is for decomposing harmful substances such as dioxins contained in the fly ash. This is performed by the apparatus 13 equipped with a conveyor or the like as appropriate.

  In the present invention, the atmospheric temperature during the heat dechlorination treatment of fly ash is, for example, 300 ° C. or higher as in the prior art, and is not particularly limited. This is preferable because it can be efficiently processed in an environment with a high speed.

  The heat dechlorination treatment time may be set to such an extent that dioxins are not re-synthesized. For example, it is preferably 60 minutes or more at 300 ° C. and 30 minutes or more at 400 ° C.

  In the present invention, the cooling after the heat dechlorination treatment is performed in the same manner as in the past, and is not limited at all. For example, the cooling is performed in the cooling device 14, and dioxins are re-synthesized. In order to prevent this, it is preferable to rapidly cool to 250 ° C. or lower.

  The fly ash after being treated by the fly ash treatment method according to the present invention is usually discharged from the flow path 2 in FIG. 1 and then solidified by kneading with cement or the like.

  According to the fly ash treatment method according to the present invention, the fly ash approaches neutrality (pH = 7) from alkalinity by carbonated calcium hydroxide contained in the fly ash to form calcium carbonate. When fly ash is solidified by kneading with cement in a later step, elution of heavy metals such as lead from the solidified product can be suppressed. Therefore, as a further effect of the fly ash treatment method of the present invention, an effect of reducing the amount of heavy metal immobilization agent such as a chelating agent can be expected.

(Examples 1 and 2, Comparative Example 1)
Calcium chloride dihydrate (Wako Pure Chemical Industries, special grade calcium chloride dihydrate) and calcium hydroxide (Okutama Kogyo, JIS special slaked lime), and sodium carbonate (Japanese A predetermined amount of plastic bag (made by Kojun Pharmaceutical Co., Ltd., special grade sodium carbonate) was taken in each of the plastic bags and mixed well to make a sample, which was placed in a ceramic bakeware. Next, the sample placed in a bakeware was heated for 1 hour in an electric furnace (KM-420, manufactured by Advantech Toyo Co., Ltd.) set at 500 ° C. in an oxygen-existing atmosphere (in air). In this embodiment, under an oxygen-existing atmosphere (air), a part of the electric furnace is opened within a range in which the ambient temperature can be maintained so that external air can be taken in without supplying air at a predetermined flow rate. The experiment was conducted under the condition.
After heating, the sample was taken out, and the hardness was measured using a Yamanaka type soil hardness meter manufactured by Fujiwara Seisakusho Co., Ltd. in order to see the hardness of the sintered sample.

  In the hardness measurement method, a sample that was sintered and formed into a lump was subjected to a load by the hardness meter, and the load when the sample was broken was defined as a hardness value.

The pass / fail judgment is based on the hardness level at which the sintered body collapses due to the force of conveyance in a general heat dechlorination apparatus, and passes if the sintered sample hardness is 40 N / cm ² or less. The case where “◯” was satisfied and the value exceeding 40 N / cm ² was determined as “NG”.

As shown in Table 1, by setting the sodium carbonate / calcium hydroxide substance amount ratio to 0.5 or more, the sample properties were partially agglomerated, but the sample hardness was 29.4 N / cm ² or less. In the heat dechlorination treatment apparatus, the hardness level is lower than the hardness level at which the baked and solidified material is adhered, and the result is “good”. In particular, in Example 1 in which the substance amount ratio was 1.0, the sample hardness was reduced to 4.9 N / cm ² . On the other hand, in Comparative Example 1 in which no sodium carbonate was added, the sample hardness was 196 N / cm ² , which was rejected “x”.

(Examples 3 and 4, Comparative Example 2)
Experiments of Examples 3 and 4 and Comparative Example 2 were performed in the same manner as in Examples 1 and 2 and Comparative Example 1 except that the temperature set for the electric furnace when heating the sample was 380 ° C. .

As shown in Table 1, even when the ambient temperature was set to 380 ° C., the sample property was partially agglomerated by setting the sodium carbonate / calcium hydroxide substance amount ratio to 0.5 or more. The sample hardness was 19.6 N / cm ² or less, which was lower than the hardness level at which the sample was baked and solidified in the heat dechlorination treatment apparatus, and was a pass “◯”. In particular, in Example 3 where the substance amount ratio was 1.0, the sample hardness was reduced to 4.9 N / cm ² . On the other hand, in Comparative Example 2 in which no sodium carbonate was added, the sample hardness was 196 N / cm ² , which was rejected “x”.

(Example 5, Comparative Example 3)
Experiments of Example 5 and Comparative Example 3 were performed in the same manner as in Example 1 and Comparative Example 1, except that nitrogen gas was introduced into the electric furnace (2.0 L / min) and the atmosphere was reduced.

As shown in Table 1, in Example 5 where the sodium carbonate / calcium hydroxide substance amount ratio was 1, even in a reducing atmosphere, the sample properties were partially agglomerated, but the sample hardness was 4.9 N. / Cm ² , which was lower than the hardness level at which the baked and solidified material was deposited in the heat dechlorination treatment apparatus, and the test was “good”. On the other hand, in Comparative Example 3 in which no sodium carbonate was added, the sample hardness was 196 N / cm ² , which was rejected “x”.

(Examples 6 to 8)
As fly ash treatment agent, sodium bicarbonate (made by Wako Pure Chemical Industries, Ltd., special grade sodium bicarbonate), potassium carbonate (made by Wako Pure Chemical Industries, Ltd., special grade potassium carbonate) or potassium bicarbonate, respectively, instead of sodium carbonate Experiments of Examples 6 to 8 were performed in the same manner as in Example 1 except that Wako Pure Chemical Industries, Ltd. (special grade potassium hydrogen carbonate) was used.

As shown in Table 2, even when sodium bicarbonate, potassium carbonate or potassium bicarbonate is used as the fly ash treatment agent, the sample property can be obtained by setting the treatment agent / calcium hydroxide substance amount ratio to 1. Although the sample was partially agglomerated, its sample hardness was 14.7 N / cm ² or less, which was lower than the hardness level at which it was baked and stuck in the heat dechlorination treatment apparatus, and passed “◯”.

(Examples 9 and 10, Comparative Example 4)
The experiment was conducted as follows using the fly ash actually discharged in the incineration plant. First, in order to measure the content of calcium chloride and calcium hydroxide in the fly ash, 10 g of the fly ash was taken, dissolved in 100 cm ³ of distilled water, and neutralized with 1N hydrochloric acid (pH = 9). Went. Phenolphthalein was used as an indicator at this time. The suspension after neutralization titration was filtered, and the calcium ion was quantified by EDTA chelate titration of the filtrate.

  As a result, it was found that 3.4 g (0.023 mol) of calcium chloride dihydrate and 1.5 g (0.020 mol) of calcium hydroxide were present in 10 g of fly ash.

  To such fly ash, sodium carbonate was added so as to have a predetermined sodium carbonate / calcium hydroxide substance amount ratio shown in Table 3, and the mixture was used as a sample and placed in a ceramic bakeware. Next, the sample placed in a bakeware was placed in an electric furnace (KM-420, manufactured by Advantech Toyo Co., Ltd.) set at 500 ° C. and heated for 1 hour as an oxygen-existing atmosphere (air). After heating, the sample was taken out and the hardness of the sintered sample was measured as described above.

As shown in Table 3, by setting the sodium carbonate / calcium hydroxide substance amount ratio to 0.5 or more, the sample properties were partially agglomerated, but the sample hardness was 29.4 N / cm ² or less. In the heat dechlorination treatment apparatus, the hardness level is lower than the hardness level at which the baked and solidified material is adhered, and the result is “good”. In particular, in Example 10 in which the substance amount ratio was 1.0, the sample hardness was reduced to 4.9 N / cm ² . On the other hand, in Comparative Example 4 in which no sodium carbonate was added, the sample hardness was 196 N / cm ² , which was rejected “x”.

(Examples 11 and 12, Comparative Examples 5 and 6)
Calcium chloride dihydrate (Wako Pure Chemical Industries, Ltd., special grade calcium chloride dihydrate) and calcium hydroxide (Okutama Kogyo Co., Ltd., JIS special name slaked lime) each shown in Table 4 in the specified amount of vinyl Taken in a bag, mixed well, and placed in a ceramic crucible. In order to change the atmosphere in the electric furnace while stirring the mixture in the crucible with the stirring blade set in the laboratory stirrer BL600 manufactured by Shinto Kagaku Co., Ltd., a predetermined gas as shown in Table 4 was used. Alternatively, heating was performed for 1 hour in an electric furnace KM-420 manufactured by Advantech Toyo Co., Ltd. set at 380 ° C. while supplying a mixed gas at a predetermined flow rate. After heating, the sample was taken out and the hardness of the sintered sample was measured as described above.

As shown in Table 4, in Example 11 treated in a carbon dioxide atmosphere, although the sample properties were partially agglomerated, the sample hardness was 4.9 N / cm ² or less, and the heat dechlorination treatment apparatus The hardness level was lower than the hardness level at which baked and stuck inside, and the result was “good”. Also in Example 12, in which nitrogen in the supplied mixed gas was reduced to 75% by volume and the atmosphere was reduced, while carbon dioxide was supplied as a fly ash treatment agent in the mixed gas to 25% by volume. Similarly, the sample hardness was 4.9 N / cm ² or less, which was a pass “◯”. On the other hand, in Comparative Example 5 and Comparative Example 6 in which carbon dioxide gas was not supplied, the sample hardness was a level at which the sample was baked and stuck in the heat dechlorination treatment apparatus, and was rejected as “x”.

(Example 13, Comparative Example 7)
The same amount of fly ash as that used in Example 9 was placed in a predetermined amount of plastic bag shown in Table 5 and placed in a ceramic crucible. While stirring the fly ash in the crucible with a stirring blade set in a laboratory stirrer BL600 manufactured by Shinto Kagaku Co., Ltd., supplying a predetermined gas at a predetermined flow rate as shown in Table 5, 380 ° C. Was heated in an electric furnace KM-420 manufactured by Advantech Toyo Co., Ltd. for 1 hour. After heating, the sample was taken out and the hardness of the sintered sample was measured as described above.

As shown in Table 5, in Example 13 treated in a carbon dioxide atmosphere, although the sample properties were partially agglomerated, the sample hardness was 4.9 N / cm ² or less, and the heat dechlorination treatment apparatus The hardness level was lower than the hardness level at which baked and stuck inside, and the result was “good”. On the other hand, in Comparative Example 7 treated in an oxygen-existing atmosphere (air), the sample hardness was 98 N / cm ² , which was rejected “x”.

Schematic which shows the whole structure of the apparatus which implements the fly ash processing method which concerns on this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Incineration exhaust gas flow path 1a Fly ash flow path 1b Exhaust gas flow path 11 Dust collector 12 Conveyance process 13 Heat dechlorination apparatus 14 Cooling apparatus 21 Fly ash treatment agent storage tank 22 Carbon dioxide gas inlet 23 Carbon dioxide gas outlet

Claims (5)

After decomposing dioxins by treating heating dechlorination fly ash containing dioxins, a fly ash treatment method for cooling,
A fly ash treatment agent comprising at least one of alkali metal carbonate and alkali metal bicarbonate, calcium hydroxide contained in the fly ash, and based on the measurement result, the calcium hydroxide and the treatment Is added to the fly ash so that the substance amount ratio with the agent (fly ash treatment agent / calcium hydroxide) is 0.5 or more, and the calcium hydroxide contained in the fly ash is heated in the heating dechlorination apparatus. A fly ash treatment method, wherein the fly ash is dechlorinated and then cooled while reacting with a treating agent to form calcium carbonate.   The fly ash treatment method according to claim 1, wherein a fly ash sample for measuring calcium hydroxide contained in the fly ash is collected in a transport step before the fly ash is introduced into the heat dechlorination treatment apparatus. .   The fly ash treatment method according to claim 1 or 2, wherein the fly ash treatment agent is added in a transport step before the fly ash is introduced into a heat dechlorination treatment apparatus.   The fly ash treatment method according to claim 1, wherein the fly ash treatment agent is at least one of sodium carbonate and sodium hydrogen carbonate.   The fly ash treatment method according to any one of claims 1 to 4, wherein the atmospheric temperature in the heat dechlorination apparatus is 400 ° C or higher.

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