JPH07114957B2 - Firing method of sludge containing leachate calcium - Google Patents

Description

TECHNICAL FIELD The present invention is directed to calcining calcium-containing sludge generated in a leachate treatment facility in a general waste final disposal site, and calcining the calcium obtained by the calcining in a fluidized bed type incinerator or the like. The present invention relates to a method for firing sludge containing leachate calcium for reuse.

Conventional technology Conventionally, in the incinerator, the method of removing hydrogen chloride generated by incineration of plastics is a dry method, a semi-dry method,
It is roughly divided into wet methods. The dry method and the semi-dry method use slaked lime [Ca
(OH) ₂ ] or the like is used as an absorbing agent, and caustic soda [NaOH] is used in the wet method. However, since the maintenance cost is higher than that of the dry method, such as the expensive medicine, the cleaning method in recent years often uses the dry method or the semi-dry method.

Also, by removing hydrogen chloride, chlorine in the waste is in the form of being concentrated in fly ash and incineration residues, and calcium is also in the concentration process by incineration and slaked lime etc. is added as a hydrogen chloride absorbent. It has an extremely high content rate.
If chlorine and calcium are accumulated in the landfill, no problem will occur, but there is a problem that most of chlorine and 20 to 30% of calcium are eluted into the leachate.

Therefore, the method disclosed in Japanese Patent Laid-Open No. 63-258692 has been proposed as a method for treating organic wastewater containing calcium ions such as leachate. This method will be described.

The raw water of the organic sewage is sent directly or from a storage tank to the adjustment tank to stir and homogenize it, and then the raw water is sent to the reaction tank to adjust the neutrality or weak alkalinity while adding a calcium removing agent in an amount equal to or more than Ca ^2+. , Stir to react. Furthermore, after the reaction is complete, the treated water is sent to a settling tank to precipitate water-insoluble calcium salts such as calcium carbonate [CaCO ₃ ] which is a reaction product for solid-liquid separation, and the supernatant water is transferred to a biological treatment facility. In addition to performing ordinary biological treatment, the precipitated sludge containing water-insoluble calcium salt is treated through the steps of concentrating, dehydrating and drying.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As described above, in one incinerator, calcium compounds such as slaked lime [Ca (OH) ₂ ] are used when the dry method and the semi-dry method are used to remove hydrogen chloride. It must be used as an absorbent, and in the other leachate treatment facility, there is a problem that a large amount of sludge containing water-insoluble calcium salt is generated.

The present invention is to solve the above-mentioned problems, and recovers quicklime from sludge generated in a treatment facility for leachate, and uses the recovered quicklime to remove hydrogen chloride in an incineration facility. The purpose is to provide.

Means for Solving the Problems In order to solve the above problems, the present invention forms sludge containing a water-insoluble calcium salt produced in a treatment facility for leachate into a cake having an appropriate water content by concentrating and dehydrating. The cake is put into an incinerator which is in a high temperature combustion state and fired, and the quicklime produced in the fired product is reacted with hydrogen chloride contained in the combustion gas in the incinerator.

Action With the above-described configuration, in the leachate treatment facility, the calcium removing agent is added to the raw water containing calcium ions in an amount equal to or more than Ca ²⁺ to produce a water-insoluble calcium salt such as calcium carbonate [CaCO ₃ ]. The sludge containing this calcium salt is concentrated by gravity settling and dehydrated by centrifugal force to form a cake having an appropriate water content. This cake is put into an incinerator in a high temperature combustion state and fired to produce quicklime in the fired product. On the other hand, in the incineration facility, hydrogen chloride is generated along with the incineration of plastics, and quicklime in the burned material reacts with hydrogen chloride contained in the combustion gas as an absorbing agent to remove hydrogen chloride.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. First
In the figure, raw water 1 is organic sewage containing a large amount of calcium ions such as leachate, and the raw water 1 is once sent to the adjusting tank 2 from the storage tank or the like to be uniformly stirred. In this case, mechanical stirring is preferable in order to prevent the occurrence of scaling.

Then, the raw water 1 that has passed through the adjusting tank 2 is sent to the reaction tank 3,
Neutral to weakly alkaline (pH =
While adjusting to 7 to 10), the calcium removing agent 5 is added in an amount equal to or more than Ca ²⁺ and stirred to react. As the calcium remover, compounds such as water-soluble carbonates, sulfates and phosphates which react with Ca ²⁺ to form water-insoluble calcium salts are used, and carbonates such as sodium carbonate are generally used. A reaction time of about 10 to 20 minutes is sufficient.

After the reaction is completed, the treated water 6a is sent to the flocculation tank 7, and ferric chloride,
A flocculating agent 8 such as a sulphate sulfate is added to cause a flocculation reaction.
After that, the treated water 6b is sent to the floc forming tank 9, and the polymer flocculant 10 is added to promote the growth of flocs. Next, the treated water 6c is sent to the settling tank 11, and the water-insoluble calcium salt of the reaction product is allowed to settle to perform solid-liquid separation. Then, the supernatant water 12 is sent to the neutralization tank 13, [H ₂ SO ₄ ] 14 and [NaOH] 15 are added to adjust the pH (pH≈7), and then transferred to a biological treatment facility for normal biological treatment. I do.

Then, the sludge 16 containing the water-insoluble calcium salt settled in the settling tank 11 is sent to the sludge thickening tank 17 and concentrated by gravity settling. Furthermore, the concentrated sludge 18 that has been concentrated is once stored in a sludge storage tank.
After being stored in 19, it is sent to a dehydrator 20 to form a cake 21 having a water content of 30 to 50%. This cake 21 contains 75 [CaCO ₃ ].
% Is included. Further, the cake 21 becomes better when it is dried to a water content of 5 to 10%.

Then, the cake 21 of the sludge 16 generated in the above-mentioned organic wastewater treatment step is put into a fluidized bed type incinerator 22 in a high temperature combustion state of about 900 ° C. and fired to produce quicklime in the fired product. To do.

Here, the component ratio at the firing temperature and time when the sludge 16 is fired on a trial basis will be described.

Table 1 shows the result of component analysis of the calcium-removed sludge discharged from the leachate treatment facility, and FIG. 2 is a graph showing the result of calcium-removed sludge component test.
The figure is a graph showing the proportions of the main components in Table 1. As is clear from Table 1, FIG. 2 and FIG. 3, the proportion of Ca is greatly increased, with the firing temperature of 900 ° C. and the firing time of 30 minutes as the critical values. For this reason, [Ca
CO ₃ ] is about 20% and [CaO] is about 55%.

On the other hand, in the incinerator 22, hydrogen chloride is generated as the plastics are burned, and the raw materials in the burned material are generated. Lime reacts with hydrogen chloride contained in the combustion gas as an absorbent, and hydrogen chloride is removed by the reaction of 2HCl + CaO → CaCl ₂ + H ₂ O.

Therefore, in the hydrogen chloride removing device of the incinerator 22, the amount of chemicals added from the chemical silo 23 can be reduced. The exhaust gas 24 discharged from the incinerator 22 is the gas cooling chamber 25.
The dust 27 in the exhaust gas 24 sent to the electrostatic precipitator 26 through the electric dust collector 26 and collected in the electrostatic precipitator 26, etc.
The exhaust gas 24, which is exhausted at 28 and is dedusted, is exhausted to the chimney 30 through the induced air blower 29.

Then, the incineration residue is landfilled in a landfill, where the leachate contains
Although it can be a Ca component, it becomes Ca sludge in the Ca removal process of the leachate treatment facility and again serves as an absorbing agent for removing hydrogen chloride in the incinerator 22.

Effects of the Invention As described above, according to the present invention, a cake containing a water-insoluble calcium salt is put into an incinerator in a high-temperature combustion state and fired to produce quicklime in the fired product.
Hydrogen chloride contained in the exhaust gas of the incinerator can be removed by using quicklime in the burned material as an absorbent.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention, FIG. 2 is a graph diagram showing results of calcium removal sludge component test, and FIG.
The figure is a graph showing the results of calcium removal sludge component analysis. 1 ... Raw water, 2 ... Adjustment tank, 3 ... Reaction tank, 11 ... Sedimentation tank, 16 ... Sludge, 20 ... Dehydrator, 22 ... Incinerator.

Claims (1)

[Claims] 1. A sludge containing a water-insoluble calcium salt produced in a leachate treatment facility is formed into a cake having an appropriate water content by concentration and dehydration, and the cake is placed in an incinerator in a high temperature combustion state. A method for calcination of sludge containing leachate calcium, characterized in that the lime is put into a calcination and calcinated, and the quicklime produced in the calcination is reacted with hydrogen chloride contained in the combustion gas in the incinerator.