KR100347997B1 - Method of recycling sewage sludge as useful sources - Google Patents

Abstract

PURPOSE: A method for recycling sewage sludge as useful sources is provided. CONSTITUTION: The method includes the steps of blending 30 to 90 wt.% of dry sewage sludge, 10 to 70 wt.% of one binder selected from clay, clayish waste, bentonite; forming the mixture into a certain shape; and baking it at high temperatures, wherein the method is characterized in that the baking is performed at 800 to 1180°C for 10 to 30 min; temperature difference between a material input and baking zone is less than 200 deg.C; the time needed to transfer a mixture to be baked from the material input to the baking zone is in the range of 5 to 20 min; and 50 wt.% of less of a mixture including one or more materials selected from coal ash, incineration ash, blast furnace slag and waste mold sand, including 40 wt.% or more of SiO2 and 10 wt.% or more of Al2O3 is added to 100 wt.% of a total amount of sewage sludge and binder.

Description

Recycling of sewage sludge by internal heat generation sintering method.

The present invention stabilizes / solidifies sewage sludge by mixing sludge generated in sewage terminal treatment plant with appropriate inorganic material as internal heating element and directly sintering the mixture, and at the same time disposing of sewage sludge so that the product itself can be recycled. And a resourceization method.

In general, sewage sludge is a solid secondary environmental pollutant that is generated when the particulate, colloidal, and dissolved pollutants contained in the sewage are removed during sewage treatment. Currently, sewage sludge is 120 per year in 290 sewage treatment plants nationwide. Tens of thousands of tons are being generated, and sewage pipe maintenance and additional installation of sewage treatment facilities are being made continuously to protect the water resources, and the amount of generation is increasing day by day. In order to protect water resources and prevent secondary environmental pollution caused by sewage sludge, it is an urgent issue.

Recycling technology for conventional sewage sludge is currently the only method using sewage sludge directly as an organic fertilizer, but since the sewage sludge contains a considerable amount of harmful substances, its use is very limited, More than 90% of sewage sludge is being disposed of by simple landfill. However, the simple reclamation method is expected to be banned after 2001 because it is difficult to secure landfills and is likely to cause secondary environmental pollution.

Currently, fluidized-bed incineration is widely considered as an alternative technology for landfill disposal, but this method also has the advantages of reducing and stabilizing sewage sludge, but requires expensive facility and treatment costs and requires the disposal of incineration ash. . Therefore, the incineration method is effective as an intermediate treatment method for stabilization and reduction of sewage sludge, but it also has economic problems such as the huge construction cost and the increase of treatment cost of the incinerator. It does not fully meet the ultimate goal of waste disposal, both economic and complete disposal.

The purpose of the present invention is to dispose sewage sludge physically and chemically stably with a simple process in one step and not excessive facilities and treatment costs in order to solve the limitations and problems of the prior art and at the same time, the product is directly added value-added material To recycle

1 is a process chart for explaining the process of recycling sewage sludge by the internal heat generating sintering method of the present invention.

The present invention mixes sewage sludge and caking agent (clay, bentonite, etc.) in a dry weight ratio (hereinafter, the same) in the ratio of 30 to 90: 10 to 70, respectively, and the mixture is about 1 cm in diameter. After molding and drying in a spherical shape, it is baked at 800 ~ 1180 ℃ for 10 ~ 30 minutes, and the temperature difference between the product inlet and the firing section is within 200 ℃ and the time to reach the firing section from the inlet is within 5 minutes to 20 minutes. It provides a method for recycling sewage sludge by the internal heat generation sintering method characterized in that the firing.

When it is necessary to reinforce physical properties such as compressive strength, the physical property reinforcing agent may be added within 50 parts by weight based on 100 parts by weight of the basic composition.

Hereinafter, the present invention will be described in detail.

The present invention, unlike the existing disposal method that can be completely disposed only after the two-stage process of incineration ash for the purpose of simple disposal or after incineration, makes the sewage sludge environmentally harmless in one step of the firing process. At the same time, it is possible to solidify and recycle the waste product directly to the material resource without reprocessing process, thus enabling the complete disposal of sewage sludge, and at the same time, the co-disposal and recycling of coal ash or clay waste during the disposal process.

In addition, sewage sludge itself is a combustible material composed of more than 50% of organic material, and can produce an average calorific value of about 2500 ㎉ / ㎏ · DS, which brings about the effect of offsetting the temperature difference between inside and outside caused by the difference in heat transfer during firing. Rather, by raising the internal temperature to melt and sinter the interior first under the same temperature conditions and at the same time generate a large amount of gas to prevent shrinkage due to melting and to act as an internal heating agent-foaming agent to encourage foaming, It lowers the firing temperature for sintering and shortens the firing time, thereby reducing fuel costs. Second, the toxic sintered heavy metals in the sewage sludge are not completely solidified. Fully immobilized can be achieved, which can lead to environmental harmlessness of sewage sludge.

Examples of the caking agent usable in the present invention include clay, kaolin, clay, clay waste, bentonite, and the like, and any material may be used as long as it has an inorganic material having a predetermined level or higher caking force. It is possible.

Examples of physical reinforcing agents usable in the present invention include coal ash, paper ash, blast furnace slag, waste foundry sand, and the like, and any inorganic material containing 40 wt% or more of SiO ₂ and 10 wt% or more of Al ₂ O ₃ may be used. It can be used. Among them, the use of coal ash (fly ash) is most preferable in consideration of light weight and ease of use.

1 is a process chart for solidifying and recycling the sewage sludge by the internal heat generation sintering method of the present invention, the base material in the manufacturing process is sewage sludge and a binder, and a physical property reinforcing agent for selectively increasing the compressive strength is added thereto. do. Each mixing ratio is 30 to 90% of sewage sludge and 10 to 70% of binder in terms of dry weight, and the physical property enhancer may be added up to 50 parts by weight based on 100 parts by weight of the total amount of sewage sludge and the binder.

Within this mixing composition ratio, each material is appropriately taken and mixed with a refiner or blender, and then molded into a sphere having a diameter of about 1 cm and dried. The dried mixture is put into a kiln having a temperature condition of an inlet temperature of 800 to 1100 ° C., a heating rate of 10 to 30 ° C./min, and a firing temperature of 1100 to 1180 ° C., and then fired for 10 to 30 minutes (total time required). A sintered compact is manufactured. The specific gravity of the final product depends on the type of mixed material, the mixing composition and the firing temperature conditions, and varies from 0.5 to 1.6 depending on their combination.

In order to impart lightness to the obtained product, it is preferable that the temperature difference between the product inlet and the firing section is within 400 ° C, preferably within 200 ° C. In the case of a general rotary firing furnace for mass production, the temperature of the product inlet is about 500 to 600 ° C. lower than the firing temperature. When the method of the present invention is applied using such a conventional rotary firing furnace, the sintering of the product is incomplete and the absorption rate is increased. It is difficult to achieve the purpose of the present invention efficiently, such as the strength is weakened or shrinkage sintered to increase the specific gravity to 1.7 or more.However, when the product inlet temperature is adjusted upward so as not to be lower than 400 ° C. above the firing temperature, the internal foaming is effective. Induced, the specific gravity of the product is lowered.

Embodiments of the present invention are as follows.

<Example 1>

90% by weight of sewage sludge (heating amount 2500-3100 ㎉ / ㎏, DS, ignition loss 40-47% by weight) in Chuncheon (10% by weight of clay produced in Muan area as a binder) In addition, the mixture was molded into a sphere having a diameter of about 1 cm, dried sufficiently to have a water content of 10% by weight or less, and then charged into a firing furnace having an inlet temperature of 800 ° C. and raised to 1,140 ° C. at a temperature rising rate of 20 ° C./min, and 1,140 ° C. It was calcined for 10 minutes at. Physical properties of the resulting fired body are shown in Table 1 below (the same applies).

<Example 2>

The dried molded product of Example 1 was put into a firing furnace having an inlet temperature of 1,000 ° C., raised to 1,140 ° C. at a temperature rising rate of 20 ° C./min, and calcined at 1,140 ° C. for 10 minutes.

<Example 3>

3 parts by weight of bentonite was added as a caking reinforcing agent to 100 parts by weight of the mixture of Example 1 in the same manner as in Example 1, followed by molding, drying and firing.

Comparative Example 1

The dried molded product of Example 1 was put into a firing furnace having an inlet temperature of 700 ° C., raised to 1,140 ° C. at a temperature rising rate of 20 ° C./min, and calcined at 1,140 ° C. for 10 minutes.

1) It shows atypical uniaxial compressive strength measured using spherical sintered body directly.

* Uniaxial compressive strength = σ / 0.19, σ = destructive load / (volume )

As can be seen from Table 1, internal foaming effectively occurred when the inlet temperature was higher than 800 ° C, but when the temperature was lower than 700 ° C, the firing temperature was the same, but the total firing time was longer. In spite of many, it is difficult to effectively carry out the pursuit of the present invention, such as sintering incomplete or shrinkage sintering. This is because the internal calorific value did not work intensively.

<Example 4>

10 weight of clay (hereinafter equal) calculated in Gunsan area as a binder for 50% by weight of sewage sludge (heating amount 2800-3300㎉ / ㎏ · DS, ignition loss 34 ~ 37wt.%) In Anyang-si %, 40% by weight of coal ash (non-fly ash, same as below) discharged from Honam thermal power plant as a strength reinforcing material reinforcing agent was mixed, molded and dried in the same manner as in Example 1, and the dried molded body was subjected to an inlet temperature of 1,000 It was put into a calcination furnace and raised to 1,140 degreeC by the temperature increase rate of 20 degreeC / min, and baked at 1,140 degreeC for 10 minutes. The physical properties of the obtained sintered compact are shown in Table 2 (hereinafter same).

Example 5

The dried molded product of Example 4 was put into a firing furnace having an inlet temperature of 1080 ° C., raised to 1,180 ° C. at a temperature rising rate of 15 ° C./min, and calcined at 1,180 ° C. for 10 minutes.

Comparative Example 2

The dried molded product of Example 4 was introduced into a firing furnace having an inlet temperature of 600 ° C., raised to 1,140 ° C. at a temperature rising rate of 20 ° C./min, and calcined at 1,140 ° C. for 10 minutes.

Comparative Example 3

The dry molded product of Example 4 was put into a firing furnace having an inlet temperature of 600 ° C., raised to 1,180 ° C. at a temperature rising rate of 15 ° C./min, and calcined at 1,180 ° C. for 10 minutes.

1) It shows atypical uniaxial compressive strength measured using spherical sintered body directly.

Although Example 4 was calcined under the same conditions as in Example 2, which is the optimum foaming temperature condition, the inside of the mixture was not completely melt-foamed, and only the mixed sewage sludge component was melted to fuse the surrounding particles, thereby forming a high-strength sintered body. Obtained. This is due to the decrease in the internal temperature rise rate of the mixture due to the internal calorific value increase as the total melting point of the mixture and the sewage sludge mixing ratio is relatively reduced due to the increased content of the auxiliary agent having a higher melting point than the sewage sludge. Therefore, in order to overcome this and obtain a complete internal melt foam, the internal temperature of the mixture is fully melted by adjusting the firing temperature conditions as in Example 5, but the ultra-light sintered compact having a specific gravity of 1 or less although the compressive strength is lower than that of Example 4 Could be induced.

In addition, the results of Table 2 shows that the compressive strength of Example 5 is more than doubled as compared with the resultant products of Examples 1 to 3 showing the same internal structure and specific gravity, indicating that the role of coal ash as a strength reinforcing aid is very effective. Prove that. On the other hand, Comparative Examples 2 and 3 only lowered the inlet temperature, and the same heating rate and final firing temperature as those of Examples 4 and 5, and despite firing for a longer time, the sintering is incomplete, showing a high absorption rate or shrinkage sintered specific gravity It was difficult to achieve the object of the present invention, such as this increase.

<Example 6>

50% by weight of sewage sludge in Anyang City was mixed with 20% by weight of clay as a caking agent and 30% by weight of ash with a reinforcing agent for strength reinforcement in the same manner as in Example 4.

<Example 7>

50% by weight of sewage sludge in Anyang-si was mixed with 30% by weight of clay as a caking agent and 20% by weight of coal ash with a property reinforcing agent for strength reinforcement in the same manner as in Example 4.

<Example 8>

40 wt% of sewage sludge in Anyang-si was mixed with 30 wt% clay as a caking agent and 30 wt% coal ash with a physical reinforcing agent for strength reinforcement in the same manner as in Example 4.

Example 9

40 wt% of sewage sludge in Anyang-si was mixed with 20 wt% clay as a caking agent and 40 wt% coal ash with a physical reinforcing agent for strength reinforcement in the same manner as in Example 4.

<Example 10>

30% by weight of sewage sludge in Anyang-si was mixed with 40% by weight of clay as a binder and 30% by weight of ash with a reinforcing agent for strength reinforcement in the same manner as in Example 4.

<Example 11>

30% by weight of sewage sludge in Anyang-si was mixed with 30% by weight of clay as a caking agent and 40% by weight of coal ash with a property reinforcing agent for strength reinforcement in the same manner as in Example 4.

<Example 12>

30% by weight of sewage sludge in Anyang City was mixed with 20% by weight of clay as a caking agent and 50% by weight of coal ash with a property reinforcing agent for strength reinforcement in the same manner as in Example 4.

<Comparative Example 4>

10 wt% of sewage sludge in Anyang-si was mixed with 20 wt% of clay as a caking agent and 70 wt% of coal ash with a physical reinforcing agent for strength reinforcement in the same manner as in Example 4.

Comparative Example 5

20% by weight of sewage sludge in Anyang City was mixed with 20% by weight of clay as a caking agent and 60% by weight of coal ash with a property reinforcing agent for strength reinforcement in the same manner as in Example 4.

The physical properties of the resultant products obtained in Examples 6 to 12 and in Comparative Example 5 and Comparative Example 6 were as shown in Table 3.

1) It shows atypical uniaxial compressive strength measured using spherical sintered body directly.

As can be seen from Table 3, when the amount of sewage sludge mixed is less than 30% by weight, specific gravity and water absorption are increased, and the quality of the lightweight aggregate is lowered, making it difficult to efficiently achieve the object of the present invention. In particular, in the case of Comparative Examples 5 and 6, unlike the other examples, no internal melt foaming was performed even under the firing conditions of Example 5, and only a solid sintered body having a specific gravity of 1.65 was obtained, which was 1240 ° C close to the melting point of the entire mixture. Only when the internal melt foaming was possible. However, in this case, due to the rupture of the surface layer of the product or the serious melting of the surface, the sintered bodies were fused to the furnace walls or the sintered bodies were frequently fused to each other.

The present invention is the same as the incinerator or melting furnace method in terms of burning sewage sludge at a high temperature, but after mixing and molding a binder or caking additive and a physical reinforcing agent in the sewage sludge and put the molded body at a high temperature (below melting point) By burning sewage sludge and concentrating the calorific value inside the molded body, the inside is melted and sintered, and the processed product can be calculated as intentionally shaped sintered body according to the purpose of recycling instead of burning ash or irregular shaped slag. At the same time, it is possible to freely control the specific gravity and the compressive strength of the final product by changing only the input temperature condition even in the same mixing composition and by changing the mixing ratio of the strength reinforcing agent (physical reinforcing agent) even under the same firing temperature condition. Has an effect.

In addition, as can be seen through the above examples and comparative examples, the porous sintered body of the present invention is for structural and non-structural lightweight building materials (lightweight aggregate, lightweight brick, soundproofing and insulation lightweight panels, base materials, roban materials, etc.) As it is widely used, it is not only useful for diversifying, multiplying and adding value of waste sewage sludge and coal ash, but also using other sewage sludge as internal heat generating agent and accompanying other inorganic wastes (various ash and clay waste, etc.). Not only can it be disposed of, but it can also be applied as a disposal method for stabilizing / solidifying other wastes containing a large amount of organic matter, such as sewage sludge, and as a resourceization technology for creating value added.

Claims (2)

Sewage sludge (dry weight basis) 30 to 90% by weight of one or more selected from clay, clay waste, and bentonite as a caking agent 10 to 70% by weight is mixed and molded, and then sintered at high temperature to recycle sewage sludge In The molded product was fired at a firing temperature of 800 to 1180 ° C. for a total of 10 to 30 minutes, A method for recycling sewage sludge by the internal heating sintering method, wherein the temperature difference between the product inlet and the firing section is within 200 ° C., and the baking time is reached within 5 minutes to 20 minutes. The method of claim 1, wherein at least one selected from coal ash, incineration ash, blast furnace slag, and waste foundry sand containing at least 40% by weight of SiO ₂ and at least 10% by weight of Al ₂ O ₃ as a physical property reinforcing agent is a sum of sewage sludge and a binder. A method for recycling sewage sludge by the internal heat generating sintering method, which is added within 50% by weight relative to the weight%.