JP4124103B2 - Waste incineration method and incinerator - Google Patents

Description

  The present invention relates to a waste incineration method and an incineration apparatus, and more particularly to a technique for reusing waste incineration ash as construction / civil engineering materials.

  In order to recycle waste incineration ash as construction and civil engineering materials, it is necessary to suppress elution of certain metals (mainly heavy metals) contained in incineration ash from the environmental viewpoint. There is "Environmental standards for soil contamination" (Heisei 3,8.23, notice 46).

As a method for suppressing elution of heavy metals from the incinerated ash, a technique for melting the incinerated ash at about 1300 ° C. or more to form slag is generally known.
However, melting treatment of incineration ash is difficult in terms of performance with existing waste incinerators, and it is often necessary to add melting equipment. Moreover, even if the equipment can be melted, the energy cost is high because a high temperature treatment of 1300 ° C. or higher is required.

Thus, as a treatment technique for incineration ash, a technique has been proposed in which elution of heavy metals from the incineration ash is suppressed by heat treatment at a relatively low temperature by controlling the oxygen concentration in the furnace (see, for example, Patent Document 1). ).
JP 2003-190910 A

  Although the technology for controlling the oxygen concentration in the furnace described above can reduce the processing temperature compared to the technology for melting incineration ash, it can more reliably suppress elution of heavy metals when applied to existing incineration facilities. Is desired. In particular, in the heat treatment technology of incineration ash at low temperatures, the elution amount of lead (Pb) is likely to change depending on the treatment temperature, so that the elution of lead (Pb) can be reliably suppressed to meet environmental standards. Technology development is desired.

  The present invention has been made in view of the above circumstances, and a waste incineration method and incineration capable of suppressing elution of heavy metals from incineration ash, in particular, elution of lead (Pb), by heat treatment at a low temperature. An object is to provide an apparatus.

An object of the present invention described above is to add a substance containing Si and Ca to a waste to be incinerated, thereby suppressing a mineral phase containing Ca to suppress elution of heavy metals from the waste in the treated product being incinerated. It is achieved by a waste incineration method characterized by developing

Thereby, it becomes possible to suppress elution of heavy metals from incineration ash, in particular, elution of lead, by heat treatment at a low temperature.

In the waste incineration method, the mineral phase containing Ca includes, for example, Gehlenite (SiCa ₂ Al ₂ O ₇ ).

  In this case, the substance preferably contains Si, Ca, and Al in a molar ratio of Si: Ca: Al = 1: 2: 2.

Further, in the waste incineration method, a mineral having a mineral phase containing the Ca as the substance may be generated in advance, and the generated mineral may be added to the waste to be incinerated.

In this case, as the minerals generated in advance, for example, gehlenite _{(SiCa 2 Al 2 O 7)} .

In the incineration method of the waste, a substance containing Si and Ca that develops a mineral phase containing Ca that suppresses elution of heavy metals from the waste in the treatment object being incinerated is thrown into the waste to be incinerated. It can be implemented by a waste incinerator characterized by having an inlet for the purpose.

Further, the method for incinerating waste includes a mineral phase containing Ca as a substance containing Si and Ca that develops a mineral phase containing Ca that suppresses elution of heavy metals from the waste in the treated product being incinerated. It can also be implemented by a waste incineration apparatus comprising a mineral generating device for generating a mineral having

In this case, examples of the mineral include gehlenite (SiCa ₂ Al ₂ O ₇ ).

  According to the incineration method and the incineration apparatus of the present invention, the elution of heavy metals from incineration ash by heat treatment at low temperature, particularly lead ( It becomes possible to suppress elution of Pb).

The present invention will be described below.
The present inventors paid attention to the technique described in the above-mentioned document (Japanese Patent Laid-Open No. 2003-190910), and as a result of research on low-temperature heat treatment of incinerated ash, As a result of elucidating that it is possible to reduce the amount of elution of heavy metals from incineration ash, in particular, the amount of elution of lead (Pb), and as a substance that promotes the growth of the mineral phase or the core of this mineral phase The present invention was completed by adding substances containing Si and Ca to the waste to be incinerated.

  That is, in the waste incineration method of the present invention, a mineral phase containing Ca is developed in the treated product during incineration by adding a substance containing Si and Ca to the waste before or during the incineration treatment. As a result, the incineration ash of the waste is reduced in elution of heavy metals, in particular, elution of lead (Pb).

  In the present invention, heavy metal elution is suppressed in the incineration ash during the waste incineration process. That is, it is not always necessary to separately heat the incineration ash after the waste incineration. This is advantageous in simplifying the process and the apparatus configuration. Needless to say, the same suppression effect can be obtained by adding a substance containing Si and Ca (including a mineral containing Ca) to the incinerated ash of the waste, and subjecting it to heat treatment.

Here, there are two possible reasons why elution of heavy metals is suppressed by the development of the mineral phase containing Ca.
(1) When the mineral phase develops, heavy metals in the processed material are taken into the mineral phase. And the elution of a heavy metal is suppressed because the heavy metal is fixed as a structure | tissue of a mineral phase.
(2) When the mineral phase develops, an alkaline earth or alkali metal typified by Ca in the treated product is taken into the mineral phase. By fixing the alkaline earth or alkali metal as a mineral phase structure, elution of the alkaline earth or alkali metal is suppressed. As a result, an increase in pH of the eluate is suppressed, and the pH of the eluate is inclined to be acidic. When the pH of the eluate is inclined to be acidic, the solubility of heavy metals is lowered and elution of heavy metals is suppressed.

Examples of the mineral phase containing Ca include gehlenite (SiCa ₂ Al ₂ O ₇ ).
By adding a substance containing Si, Ca, and Al to waste before incineration or during incineration, as the temperature of the waste during incineration increases, the treated material contains gehlenite (SiCa ₂ Al ₂ O ₇ ) Nuclei and a gehlenite phase can be developed in the processed material. In this case, in order to satisfactorily develop the gehlenite phase, it is preferable that Si, Ca, and Al are included in the substance in a molar ratio of Si: Ca: Al = 1: 2: 2. Since waste generally contains a large amount of Al, and the incineration space contains oxygen, the substance to be added may not contain Al. That is, by adding a substance containing at least Si and Ca to the waste, it is possible to develop a gehlenite phase in the treated product during incineration.

Further, in the waste incineration method of the present invention, a mineral containing Ca such as gehlenite is generated in advance, and the mineral is input / added to the waste to be incinerated, so that the treatment during incineration can be performed more reliably. It is possible to develop a mineral phase containing Ca (Gelenite phase, etc.) in the object. The gehlenite can be generated based on, for example, the following formulas (1) and (2).
SiO ₂ + 2CaO + Al ₂ O ₃ → SiCa ₂ Al ₂ O ₇ (1)
SiO ₂ + 2CaCO ₃ + Al ₂ O ₃ → SiCa ₂ Al ₂ O ₇ + 2CO ₂ (2)

Next, an incinerator capable of implementing the waste incineration method of the present invention will be described.
As the waste incinerator, for example, a rotary stoker furnace or a moving bed stoker furnace can be used. The configuration of the rotary stoker furnace is described in, for example, JP-A-11-257616. The configuration of the moving bed stoker furnace is described in, for example, Japanese Patent Application Laid-Open No. 2002-181311.
FIG. 1 is a diagram schematically showing an example in which the waste incinerator according to the present invention is applied to a rotary stoker furnace.

  In FIG. 1, an incinerator 1 has a cylindrical combustion furnace 2 disposed rotatably, a boiler 3 into which combustion gas generated in the combustion furnace 2 is introduced, and exhaust gas discharged from the boiler 3 is introduced. The economizer 4 and the mineral generator 20 for generating the mineral added to the waste W are configured.

  A supply hopper 5 for temporarily storing the waste W and a screw feeder 6 for appropriately sending the waste W from the supply hopper 5 into the combustion furnace 2 are installed in the introduction part 2 a of the combustion furnace 2. The supply hopper 5 is provided with an input port 5a for supplying the mineral generated by the mineral generating device 20 into the waste W. Moreover, the discharge part 2b of the combustion furnace 2 is connected to the drop resister 7 for discharging the combustion ash. The cylindrical combustion furnace 2 is disposed with the rotation axis inclined so that the discharge part 2b is lower than the introduction part 2a. A plurality of air blowing portions 10 a to 10 d for supplying combustion air into the combustion furnace 2 are disposed on the lower side surface of the combustion furnace 2. Each of the plurality of air blowing portions 10a to 10d is connected to a combustion air generating device 15 that appropriately adjusts the composition of the combustion air, and the air blown from the plurality of air blowing portions 10a to 10d is the waste W Depending on the type, the combustion conditions of the combustion furnace 2, etc., the oxygen concentration, the supply amount, etc. are individually controlled. The mineral generator 20 includes a heat treatment furnace for raising the temperature of the raw material, and the temperature and environmental conditions in the heat treatment furnace are appropriately controlled.

In the incinerator 1 having the above-described configuration, first, the mineral generating device 20 generates Ca-containing mineral, in this example, gehlenite (SiCa ₂ Al ₂ O ₇ ). The gehlenite can be produced, for example, by putting a mixture of SiO ₂ , CaO (or CaCO ₃ ), and Al ₂ O ₃ into the heat treatment furnace 21 and raising the temperature. The produced gehlenite is added to the waste W before incineration through the inlet 5a of the supply hopper 5. The addition of gehlenite may be performed automatically or by an operator. Further, the addition amount of gehlenite is set according to the type of waste W, the combustion conditions of the combustion furnace 2, and the like.

  Then, the waste W to which gelenite is added is introduced into the incinerator 2, and the waste W is incinerated. When the waste W is incinerated, combustion air is supplied into the combustion furnace 2 through the plurality of air blowing portions 10a to 10d. Exhaust gas (combustion gas) generated by the combustion is introduced into the boiler 3 from the discharge part 2b, recovered by heat, and further guided to the economizer 4.

In addition, when the waste W is burned, in the incinerated processed material (waste W, the carbide of the waste W, combustion ash, etc.), the added gehlenite (SiCa ₂ Al ₂ O ₇ ) is used as the core for the waste. While taking in Si, Ca, Al, and heavy metals (such as Pb) contained in W or combustion ash, the gehlenite phase develops. Due to the development of the gehlenite phase, the incineration ash discharged from the discharge part 2b becomes one with less elution of heavy metals, in particular, lead (Pb). Combustion ash is collected through the fall shield 7 and reused as construction / civil engineering materials (eg aggregate).

  In this example, mineral (gerenite) is added to the waste W before being introduced into the combustion furnace 2, but gehlenite may be charged / added into the combustion furnace 2. In this case, in order to secure the time for the development of the gehlenite phase, the galenite charging position is preferably a position close to the introduction part 2a of the combustion furnace 2 and upstream of the maximum temperature point of the combustion furnace 2. Is preferred.

[Gelenite addition test by laboratory test]
A commercially available reagent was mixed so as to have a composition corresponding to real ash shown in the lower part of Table 1, and a simulated ash (hereinafter referred to as Sample 1) shown in the upper part of Table 1 was prepared. In addition, a sample (hereinafter referred to as sample 2) was prepared by mixing gehlenite and a mixture of commercially available reagents at a weight ratio of 1: 4 so as to have a composition corresponding to real ash shown in the lower part of Table 1.

Gehlenite was created as follows.
Each reagent of SiO ₂ , CaCO ₃ , and Al ₂ O ₃ is mixed at a molar ratio of 1: 2: 1, heated to 1500 ° C. at 10 ° C./min in a muffle furnace, then held for 3 hours, and then allowed to cool naturally. did. It was confirmed that gehlenite (SiCa ₂ Al ₂ O ₇ ) was generated by an X-ray diffractometer.

  Next, the sample 1 and the sample 2 were heated to a predetermined processing temperature (800 ° C., 900 ° C., 1000 ° C., 1100 ° C.) at 10 ° C./min, held for 1 hour, taken out, and allowed to cool to the atmosphere. The treated product was subjected to a dissolution test in accordance with Test No. 46, and the pH and Pb concentration of the eluate were analyzed. The test results are shown in FIG.

  As shown in FIG. 2, the result that lead elution amount decreased to 1/10 or more by the addition of gehlenite was obtained. In addition, under the condition where gehlenite was added, the development of the amount of minerals was noticeable as the treatment temperature increased. In addition, the pH value of the eluate was significantly reduced by the addition of gehlenite.

  Thus, in the test using simulated ash, it was confirmed that the elution amount of lead can be suppressed by adding gelenite.

  As described above, the preferred embodiments according to the present invention have been described with reference to the accompanying drawings, but the present invention is not limited to the examples. Various shapes, combinations, and the like of the constituent members shown in the above-described examples are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

It is a figure which shows typically the example which applied the incinerator of the waste which concerns on this invention to a rotary stoker furnace. It is a graph which shows the result of having tested the lead elution inhibitory effect by addition of a mineral (gerenite) using simulated ash.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Incinerator, 2 ... Combustion furnace, W ... Waste, 20 ... Mineral production | generation apparatus, 5 ... Supply hopper, 5a ... Input port.

Claims (8)

In a method for incineration of waste , a mineral containing Ca that suppresses elution of heavy metals from the waste in the incinerated waste by adding a substance containing Si and Ca to the waste to be incinerated Waste incineration method characterized by developing phases . The waste incineration method according to claim 1 , wherein the Ca-containing mineral phase includes gehlenite (SiCa ₂ Al ₂ O ₇ ). 3. The waste according to claim 1, wherein the substance contains Si, Ca, and Al in a molar ratio of Si: Ca: Al = 1: 2: 2. Incineration method. The waste according to any one of claims 1 to 3 , wherein a mineral having a mineral phase containing Ca as the substance is generated in advance, and the generated mineral is added to the waste to be incinerated. Incineration method. The waste incineration method according to claim 4 , wherein the mineral produced in advance is gehlenite (SiCa ₂ Al ₂ O ₇ ). In a device for incineration of waste, a substance containing Si and Ca that develops a mineral phase containing Ca that suppresses the elution of heavy metals from the waste in the incinerated waste is input to the incinerated waste An incinerator for waste, comprising an inlet for carrying out the process. In an apparatus for incinerating waste , a mineral phase containing Ca as a substance containing Si and Ca that develops a mineral phase containing Ca that suppresses elution of heavy metals from the waste in the incinerated waste. A waste incineration apparatus comprising a mineral generation apparatus for generating a mineral having the same . The waste mineral incineration method according to claim 7 , wherein the mineral is gehlenite (SiCa ₂ Al ₂ O ₇ ).

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