JP2002263609A - Treatment process of alkali fly ash and facilities for the same process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkali fly ash treatment process which is used treating fly ash having a high alkali content so as to prevent heavy metals in the fly ash from being eluted from the fly ash and by which an amount on an industrial production scale of such fly ash can be treated and also to provide treatment facilities for the process. SOLUTION: This treatment process comprises: cooling a flue gas discharged from a dust collector communicating with an incinerator for incinerating nonindustrial and/or industrial solid waste, to a required temperature, to form condensed water due to dew condensation; then, adding a part of the condensed water to the alkali fly ash and mixing them together, to obtain a mixture of the alkali fly ash and the condensed water; also, passing a part of the flue gas cooled to the required temperature through the mixture; and further, adding a heavy metal fixation agent to the mixture and mixing them together.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a facility for treating fly ash containing a large amount of alkali in order to prevent heavy metals contained therein from being eluted.

[0002]

2. Description of the Related Art When household waste and industrial waste are incinerated in an incinerator, exhaust gas containing fly ash is generated. Therefore, the exhaust gas is released into the atmosphere after the fly ash is captured by the dust collector. One of the fly ash is dust captured by a dust collector after neutralization by adding alkali powder such as slaked lime to strong acid gas in exhaust gas, and alkali powder such as unreacted (excess) slaked lime etc. There is a substance called alkaline fly ash that is contained and shows strong alkalinity. This alkali fly ash contains a large amount of harmful heavy metals such as lead and cadmium, so if alkali fly ash is effectively used for landfill or ground construction as waste treatment,
Heavy metals contained therein may elute and pollute the environment, which may adversely affect the human body. Therefore, in disposing of the alkaline fly ash, it is necessary to take measures to prevent the elution of heavy metals.

[0003]

However, conventionally, alkali fly ash has been treated to prevent the elution of heavy metals contained therein, and the treatment method and treatment equipment are suitable for industrial production. There is almost no
This kind of industry has demanded the appearance of an alkaline fly ash treatment method and equipment that meet the industrial production base.

[0004] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method and equipment capable of treating alkaline fly ash on an industrial production basis.

[0005]

In order to achieve the above object, a method for treating alkali fly ash according to the present invention prevents fly ash containing a large amount of alkali from eluting heavy metals contained therein. A part of the dew condensation water generated by lowering the exhaust gas discharged from the dust collector communicating with the incinerator for incineration of general waste and industrial waste to the required temperature to the alkaline fly ash While adding and mixing the alkali fly ash and dew water, a part of the exhaust gas lowered to the required temperature is allowed to flow through a mixture of the alkali fly ash and the dew water, and further, the alkali fly ash and the dew water Characterized in that a heavy metal fixing agent is added to and mixed with the above mixture.

In the present invention, when the exhaust gas flows through the alkaline fly ash, slaked lime in the alkaline fly ash reacts with carbon dioxide in the exhaust gas to neutralize the alkali component. And by setting the temperature of the exhaust gas to 10 to 80 ° C. (normal temperature),
The reaction between slaked lime in alkali fly ash and carbon dioxide in exhaust gas can be promoted. Furthermore, by adding liquid dew water to the alkali fly ash and mixing them, the exhaust gas flows through this mixture to ensure the reaction between the slaked lime in the alkali fly ash and the carbon dioxide gas in the exhaust gas. Can be

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an alkaline fly ash treatment facility to which the present invention is applied will be described below in detail with reference to FIG. The treatment equipment includes a dust collector 1 communicating with an incinerator (not shown) for incinerating general waste and industrial waste, a heat exchanger 2 for lowering a part of exhaust gas discharged from the dust collector 1 to a required temperature, A mixer 3 as mixing means for mixing the alkali fly ash discharged from the dust collector 1 with the exhaust gas, the dew water and the heavy metal fixing agent, Condensed water supply means 4 for supplying, exhaust gas flow-through means 5 for flowing exhaust gas discharged from the heat exchanger 2 into the mixer 3, and heavy metal fixing agent supply means for supplying a heavy metal fixing agent to the mixer 3. It comprises a chemical addition unit 6 with a pump / tank and exhaust gas control means 7 for controlling the exhaust gas discharged from the dust collector 1 to required conditions.

Preferably, the mixer 3 is a Plowshare mixer manufactured by Taiheiyo Kiko Co., Ltd. Also,
A rotary valve 8 is attached to a lower end of the dust collector 1, and a discharge port of the rotary valve 8 faces a supply port of the mixer 3 via a first screw conveyor 9 and a fly ash storage tank 10 with a vibrator 30. Out, mixer 3
The discharge port of the second screw conveyor 11 faces the supply port of the second screw conveyor 11. The dew condensation water supply means 4 communicates with a dew condensation water storage tank 14 connected to an induction pipe 12 connected to an exhaust port of the heat exchanger 2 via an electromagnetic on-off valve 13, and the dew condensation water storage tank 14. Water injection unit 1 with pump and tank
5 and.

The exhaust gas passing means 5 includes a first blower 16 communicating with the guide tube 12, an induction tube 17 and a first butterfly valve 18 connecting the first blower 16 to the mixer 3, and the dust collector 1. , And a second butterfly valve 20 and an induction pipe 21 for connecting the mixer 3 to the second blower 19. A small dust collector 22 is disposed between the guide tube 21 and the second blower 19.

Further, the exhaust gas control means 7 is provided with the first
First measurement unit 23 for measuring the temperature, flow rate, and carbon dioxide concentration of exhaust gas discharged from blower 16 respectively.
A second measuring unit 24 for measuring the temperature, flow rate and carbon dioxide concentration of the exhaust gas discharged from the mixer 3 respectively, and the mixer based on the measurement results of the first measuring unit 23 and the second measuring unit 24. The first and second blowers 16 are calculated by calculating the required supply amount of exhaust gas to the third blower 16.
And a computer 25 for issuing a command to 19. The first and second measurement units 23 and 24 are electrically connected to the computer 25. Also,
The first measuring unit 23 is arranged between the first blower 16 and the guide pipe 17, and the second measuring unit 24 is arranged between the small dust collector 22 and the second blower 19, respectively. . Further, the guide pipe 17 is a branch pipe 26,
The third butterfly valve 27 and the branch pipe 28 communicate with the guide pipe 21 via the branch pipe 28 in this order. Further, a tank 29 for receiving dew condensation water generated by a decrease in the temperature of the exhaust gas is connected to the exhaust port side of the small dust collector 22.

In the above-described structure, the rotary valve 8 and the first screw conveyor 9 are appropriately driven to supply alkali fly ash from the dust collector 1 to the fly ash storage tank 10. Then, the vibrator 30 of the fly ash storage tank 10 is driven for a required time to introduce a predetermined amount of the alkali fly ash in the fly ash storage tank 10 into the mixer 3, and then the dust collector is incinerated by incineration of general refuse and industrial waste. Part of the condensed water generated by lowering the exhaust gas discharged from 1 to a required temperature (10 to 80 ° C.) is converted into alkaline fly ash in the mixer 3 by driving the required time of the water injection unit 15 with a pump and a tank. Added. In addition, by adding the dew water, it is possible to prevent the scattering of the alkaline fly ash when mixing, and to ensure the reaction between the slaked lime in the alkaline fly ash and the carbon dioxide gas in the exhaust gas in the subsequent process. Can be.

Next, the mixer 3 is driven to mix the alkaline fly ash and the dew water. Further, while continuing this mixing process, the first butterfly valve 18 and the second butterfly valve 20 are opened for a required time, and the heat exchanger 2 is opened. Part of the exhaust gas whose temperature has been lowered to 10 to 80 ° C. by passing through
The mixture is supplied into the mixer 3 to flow through the mixture of the alkali fly ash and the dew condensation water. Subsequently, the phosphoric acid-based heavy metal fixing agent is added to the mixture in the mixer 3 by driving the required time of the drug addition unit 6 with a pump and a tank. Addition of the alkali fly ash, dew water, and the phosphoric acid heavy metal fixing agent is continued.

During the mixing step, the first measuring unit 23 of the exhaust gas control means 7 measures the temperature, flow rate and carbon dioxide concentration of the exhaust gas discharged from the first blower 16 of the exhaust gas flow-through means 5, respectively. The second measuring unit 24 of the exhaust gas control means 7 measures the temperature, the flow rate and the carbon dioxide concentration of the exhaust gas discharged from the mixer 3 respectively. The first measuring unit 23 and the second measuring unit 2
4, the computer 25 calculates the required supply amount of exhaust gas to the mixer 3 and the first and second blowers 5.
The number of rotations and the drive time of 18 are calculated and transmitted to the first and second blowers 16 and 19, respectively. Thereby, the first
The second blowers 16 and 19 can allow a constant flow of exhaust gas to flow through the mixture in the mixer 3 for a required time.

Thus, when the alkali fly ash and the phosphate-based heavy metal fixing agent are mixed while flowing a constant flow of exhaust gas, unreacted slaked lime and the like in the alkali fly ash react with carbon dioxide gas in the exhaust gas to cause unreacted slaked lime. And neutralize
By reducing the temperature of the exhaust gas to 10 to 80 ° C,
The reaction between unreacted slaked lime and carbon dioxide is promoted,
The heavy metal is fixed by the heavy metal fixing agent.

For example, alkali fly ash scattered from the mixer 3 due to excessive air supply from the first blower 16 is captured by the small dust collector 22. The alkali fly ash and the like thus treated are discharged from the mixer 3 and then transferred to a predetermined place by the second screw conveyor 11.

[0016]

As is apparent from the above description, the present invention relates to a method for treating fly ash containing a large amount of alkali in order to prevent the elution of heavy metals contained therein. A part of the dew condensation water generated by lowering the exhaust gas discharged from the dust collector communicating with the incinerator for incineration of garbage and industrial waste to the required temperature is added to the alkali fly ash, and the alkali fly ash and the dew water are added. While mixing, a part of the exhaust gas lowered to the required temperature is allowed to flow through the mixture of the alkali fly ash and the dew water, and further, a heavy metal fixing agent is added to the mixture of the alkali fly ash and the dew water and mixed. Therefore, it is necessary to treat alkaline fly ash on an industrial production basis to prevent the elution of heavy metals contained in it, since dew water and exhaust gas generated by lowering the temperature of exhaust gas can be used effectively. It exhibits an excellent practical effect of such is possible.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dust collector 2 Heat exchanger 3 Mixer 4 Condensed water supply means 5 Exhaust gas flow-through means 6 Chemical addition unit with pump and tank

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Hirofumi Asai 3-1 Honohara, Toyokawa-shi, Aichi F-term (reference) in Shintoh Kogyo Co., Ltd. 4D004 AA37 AB03 BA02 CA15 CA35 CB05 CB21 CB42 CC06 CC20 DA03 DA06

Claims (3)

[Claims] 1. A method for treating fly ash containing a large amount of alkali in order to prevent the elution of heavy metals contained therein, which is in communication with an incinerator for incinerating general waste and industrial waste. A part of the dew water generated by lowering the exhaust gas discharged from the dust collector to the required temperature is added to the alkali fly ash to mix the alkali fly ash and the dew water, and the exhaust gas reduced to the required temperature A part of the alkaline fly ash and the condensed water are allowed to flow through the mixture, and a heavy metal fixing agent is added to and mixed with the mixture of the alkali fly ash and the condensed water. . 2. The method for treating alkali fly ash according to claim 1, wherein the temperature of the exhaust gas blown into said alkali fly ash is set to 10 to 80 ° C. 3. A facility for treating fly ash containing a large amount of alkali to prevent elution of heavy metals contained therein, which is in communication with an incinerator for incinerating general waste and industrial waste. A dust collector, a heat exchanger for lowering the exhaust gas discharged from the dust collector to a required temperature, an alkali fly ash discharged from the dust collector and dew condensation water and a heavy metal fixing agent generated by lowering the exhaust gas to a required temperature. Mixing means for mixing, condensed water supply means for supplying the dew water to the mixing means, exhaust gas flowing means for flowing exhaust gas discharged from the heat exchanger into the mixing means, and heavy metal fixed to the mixing means And a heavy metal fixing agent supplying means for supplying an agent.