KR20120121122A - Solidifying agent for sewage sludge - Google Patents

Abstract

PURPOSE: A functional solidifying material for sewage sludge is provided to solidify sewage sludge, to reduce bad smell, to restrain eruption of heavy metal, to recycle sewage sludge as waste cover material, and to reduce environmental contamination. CONSTITUTION: A functional solidifying material for sewage sludge comprises 5-30 weight% of portland cement, 10-30 weight% of quicklime, 50-80 weight% of pozzolan material, and 0.5-10 weight% of a deodorizing agent. The sterilizer is that a metal composite is dipped in a calcium-phosphate compound represented by chemical formula 1: Ca_(10-x)(HPO4)_x(PO4)_(6-x)(OH)_(2-x) · nH2O. In chemical formula 1, x is 0 or 1. The pozzolan material is one or more selected from paper ash, fly ash, incinerate material, ground granulated blast-furnace slag, fly ash micropowder, volcano ash, chaff meal, diatomite, silica fume and zeolite.

Description

Functional solid fire for sewage sludge {Solidifying agent for sewage sludge}

The present invention relates to a functional solidified material for sewage sludge, and more specifically, to solidify so that it can be quickly recycled for the cover material (artificial soil) by removing the moisture of the sewage sludge, and used to solidify and cover the bad smell The present invention relates to a sewage sludge functional solidified material which has long-term stability so as not to be easily detached and also can suppress the leaching of heavy metals of solids.

Domestic sewage sludge has been rapidly increasing from 7,631 tons / day in 2007 to 10,259 tons / day in 2011 due to improvement in people's living standards and conditions. Therefore, the government recognizes the seriousness of this and establishes a treatment plan by installing treatment facilities for each city and province for sewage sludge treatment.

However, in the case of marine discharges (68.5% of total sewage sludge in 2010), which is one of the sewage sludge disposal methods, the total ban is scheduled for 2012 from the London Convention. In case of incineration and landfill, We are reluctant to worry about material outbreaks and to curb greenhouse gas emissions and promote recycling. In the recycling of sewage sludge, the Ministry of Agriculture is opposed to composting because the harmful substances contained in the sludge can harm the human body through crops. Therefore, there is a growing expectation for the recycling of sewage sludge as a cover material, but this also faces various problems.

Constituents of the sewage sludge is mostly _{SiO 2, Al 2 O 3,} Fe 2 O 3 a possible use of boktojae as it consists of inorganic materials such, it generally forms a sponge-like structure dehydrated with water contained by capillary forces It is very difficult to use as a soil material and it is likely to cause public health problems by providing habitat of pathogens, flies and mosquitoes due to moisture and organic substances contained in the sewage sludge, And it generates secondary pollutants such as ground water pollution and odor due to leachate.

In order to solve the above-mentioned problems, it is indispensable to develop a fire which can reduce the water content and sterilize by self-heating.

On the other hand, most of the currently used fires are mainly due to the use of CaO-based alkaline materials or FeSO ₄ -based acidic materials that induce absorption and heat generation, and thus they are vulnerable to the odor reduction part which is most problematic in sewage sludge treatment in recent years.

When analyzing the odor of sewage sludge having a water content of about 80%, about 50 kinds of substances are detected. Among them, the substances having relatively high concentration and low minimum detection value are shown in Table 1. As shown in Table 1, the sulfur compound, the aldehyde compound and the nitrogen compound are generated in a complex manner, and the odor is attributed to their odor.

Table 1 shows the percentage of contribution by the minimum detection value of the odor component to the actual generated substance. This contribution rate is a method of selecting the substance to be removed, and it is the main data for determining the ratio of the deodorant inside the deodorant when the odor is not caused by a single substance. It is a major object to remove acidic and basic systems.

No. Substance density
(ppm) Detection value
(ppm) Theoretical dilution Odor contribution rate
(%) One Hydrogen sulfide 0.26 0.00041 634 0.5 2 Methyl mercaptan 4.81 0.00007 68,714 51.1 3 Dimethyl sulfide 3.09 0.003 1,030 0.8 4 Dimethyl disulfide 0.62 0.0022 282 0.2 5 Acetaldehyde 0.51 0.0015 340 0.3 6 Acrolein 0.32 0.0085 38 0.03 7 Propionaldehyde 0.16 0.001 160 0.1 8 Benzaldehyde 0.02 0.028 One - 9 Trimethylamine 2 0.000032 62,500 46.5 10 ammonia 98 0.15 653 0.5

As shown in Table 1 above, methyl mercaptan and trimethylamine are considered to be the main odor substances. Considering the working environment in the workplace and taking into account the characteristics of the malodorous substance, hydrogen sulfide in the acidic substance and ammonia in the methylmercaptan And trimethylamine in an amount equal to the amount of generation of trimethylamine. Hydrogen sulfide and ammonia have a high volatility, and the amount of generation varies greatly depending on conditions such as temperature and pH in the presence of moisture, and above all, it must be removed to determine whether or not to improve odor because it is a substance that can sense severe stimuli. .

In addition, generally, wastewater sludge may contain some heavy metals due to the water quality characteristics of the treated water and the chemicals added to the water treatment process, and the pH of the wastewater sludge is solidified using a solidifying agent based on existing quicklime and cement. There is a concern that the increase of some heavy metal components in the elution increases. In general, solubility increases with increasing pH in Cr and Cu, but there is a fear of dissolution increase as the pH increases from about pH 9 in Cr and about 10.5 in Cu.

Accordingly, an object of the present invention is to reduce the environmental pollution by recycling the sewage sludge to a high quality landfill material by providing a functional solid material for sewage sludge that solidifies sewage sludge, reduces odor and suppresses heavy metal leaching.

In order to achieve the above object, the present invention is Portland cement 5 to 30% by weight; 10-30% by weight of quicklime; 50-80 weight percent of the pozzolanic material; And 0.5 to 10% by weight of a deodorant, wherein the deodorant provides a functional solidifying material for sewage sludge, characterized in that a metal complex is supported on a calcium-phosphate compound represented by Formula 1 below:

[Formula 1]

In Formula 1, x may be 0 or 1.

The portland cement serves to advance the first hydration reaction in contact with the sewage sludge moisture, and can be used differently depending on the application of one to five types of portland cement. At this time, when the content of the Portland cement exceeds 30% by weight, the water permeation coefficient of the solidified material is reduced by mixing with the sewage sludge after hydration reaction, and when the Portland cement content is less than 5% by weight, the hydration product is reduced. Due to this, the fire may not meet the required compressive strength or may cause problems of re-elution upon contact with water.

The quicklime is in contact with the sewage sludge moisture and evaporates the water of the sewage sludge by the capillary pores enlarged by the high heat and volume expansion caused by the hydration reaction at the beginning of the reaction, and determines the free water and hydrates the sewage sludge within a short time. Serves to dry. At this time, when the content of quicklime exceeds 30% by weight, it may cause an impairment of the mixing facility due to the high temperature reaction with water or increase ammonia generation due to the increase of pH, and when the quicklime content is less than 10% by weight, water vaporization may occur. The reduction of calories needed and the reduction of hydration product generation can cause problems in solidifying sewage sludge.

The pozzolan material plays a role of sustaining the long-term hydration reaction caused by the pozzolanic reaction through the chemical reaction with the hydrate produced by the first hydration reaction between the portland cement and sewage sludge moisture. In addition, any one or two or more selected from the group consisting of paper ash, fly ash, incineration ash, blast furnace slag powder, coal ash powder, volcanic ash, rice hull ash, diatomaceous earth, silica fume and zeolite may be used. At this time, if the content of the pozzolanic material exceeds 80% by weight, it does not have its own hydraulic properties and delays hardening or the solids do not satisfy the required compressive strength.If the pozzolanic material is less than 50% by weight, the ratio of cement and quicklime is increased. When mixed with sewage sludge, it may cause excessive hardening, which may cause a problem of decreasing the permeability coefficient of the solids.

The deodorant is physically or chemically adsorbed through a reaction between an odor component generated in sewage sludge, for example, amine / ammonia, a sulfur compound, and an inorganic support (calcium-phosphate) and an odor removing substance (metal complex), as shown in FIG. It is an environmentally friendly ingredient that does not cause secondary problems such as desorption and re-decomposition. In addition, by adding a deodorant having a neutral pH, the pH of the solid is maintained at 10 to 11, and coordination of heavy metals is performed. It plays a role of suppressing leaching out of cargo. If the content of the deodorant is out of the above range may cause a decrease in the solidification performance by changing the content of portland cement, quicklime and pozzolanic, it may lead to a cost increase of the solidified material.

In more detail, the deodorant may carry 0.1 to 20 parts by weight of the metal complex based on 100 parts by weight of the calcium-phosphate compound, and the calcium-phosphate compound may have a nonstoichiometric hydroxyapatite structure. . At this time, the metal composite is not carried in excess of 20 parts by weight, even if it is carried in excess of 20 parts by weight may cause a problem that causes a change in physical properties when applied to the material.

The metal complex includes two or more selected from the group consisting of a copper (Cu) compound, a manganese (Mn) compound, a silver (Ag) compound, a zinc (Zn) compound, a platinum (Pt) compound, and a molybdenum (Mo) compound And preferably a complex between a copper compound and a manganese compound.

Preparing a calcium-phosphate compound represented by Chemical Formula 1 by reacting the deodorant by adding calcium salt and phosphate to purified water (first step); Adding a calcium-phosphate and a metal complex to purified water to support the metal complex on the calcium-phosphate (second step); And filtering and drying the reactant (third step).

In the first step, the calcium-phosphate compound manufacturing process is performed by adding calcium salt, for example, 5 to 30 parts by weight of calcium nitrate and phosphate, for example, 2 to 25 parts by weight of disodium hydrogen phosphate, to 100 ° C based on 100 parts by weight of purified water. Stirring up; Lowering the reaction temperature to 50 to 80 ° C. and then adding sodium hydroxide to stir; And cooling to room temperature, followed by filtration and drying.

In the second step of supporting the metal complex, 10 to 60 parts by weight of calcium-phosphate and 0.1 to 12 parts by weight of the metal complex may be added to 100 parts by weight of purified water to support the metal complex on the calcium-phosphate.

On the other hand, the solidification principle of the solidified material according to the present invention is as follows.

(1) Solidification by Formation of Ettringite in Portland Cement

When water is added to Portland cement, the reaction between the constituents in the cement and water, the so-called hydration reaction, begins, and upon contact with water, C ₃ A (aluminate) and gypsum (CaSO ₄ –2H ₂₎ The reaction of O) produces a large amount of Ettringite (3CaO? Al ₂ O ₃ -3CaSO ₄ -32H ₂ O). Ethrinzite absorbs a large amount of water as binding water and grows finely into a needle bed as shown in the following formula, thereby lowering the water content of the solidified material and at the same time, the effect of consolidation is suppressed, constraining the movement of the granules, thereby promoting solidification.

3CaO? Al ₂ O ₃ + 3CaSO ₄ + 32H ₂ O → 3CaO? Al ₂ O ₃ ? 3CaSO ₄ ? 32H ₂ O

(C ₃ A + 3CS + 32H → C ₃ A? 3CS? 32H)

(2) Aggregation and solidification of calcium hydroxide [Ca (OH) ₂ ]

Portland cement and quicklime produce large amounts of calcium hydroxide by hydration. The CaO component in cement and quicklime reacts with water to produce calcium hydroxide in crystalline form. Ca ²⁺ ions eluted from calcium hydroxide, calcium silicate, and the like, which are produced as described above, agglomerate and solidify the sludge particles to lower the plasticity index, thereby making the sludge silicide.

CaO + H ₂ O → Ca (OH) ₂

(3) Enhancement of Curing by Calcium Silicate Hydrate Production

Portland cement and quicklime produce large amounts of calcium hydroxide by hydration. The silicate phases (C ₃ S, C ₂ S) in cement react with water to produce calcium silicate hydrate (CSH) in gel form or in microcrystalline form. Calcium silicate formation reaction is as follows.

2 (3CaO? SiO ₂ ) + 6H ₂ O → 3CaO? 2SiO ₂ ? 3H ₂ O + 3Ca (OH) ₂

(2C ₃ S + 6H → C ₃ S ₂ H ₃ + 3CH)

2 (2CaO? SiO ₂ ) + 4H ₂ O → 3CaO? 2SiO ₂ -3H ₂ O + Ca (OH) ₂

(2C ₃ S + 4H → C ₃ S ₂ H ₃ + CH)

As such, calcium silicate requires almost the same amount of water for hydration, but the resulting hydrate produces about two times more hydrate C ₃ S than C ₂ S. Complete cement hydration consists of about 60% by weight of calcium silicate and 30% by weight of calcium hydroxide. As the hydration proceeds, the structure becomes dense, resulting in increased bonding between particles and increased strength.

(4) Enhancement of Strength by Pozzolan Reaction

Pozzolan materials such as paper ash do not have their own hydrophobic properties such as silica (SiO ₂ ) and alumina (Al ₂ O ₃ ), but when they are finely pulverized, they are chemically treated with cement hydroxide, calcium hydroxide, at room temperature. It reacts and has the pozzolanic activity which exhibits hydraulic property like cement. Such pozzolanic properties are gradually combined with calcium hydroxide produced by the hydration reaction of cement and quicklime at room temperature, thereby producing insoluble stable calcium silicate, thereby increasing the compressive strength by keeping the internal voids of the solidified in a long term.

The functional solidified material for sewage sludge according to the present invention is solidified so as to quickly remove moisture from the sewage sludge and to be recycled for covering soil (artificial soil), and to prevent the odor causing substances from being easily detached when used for solidifying and covering soil. It can be very useful for recycling the sewage sludge as a good landfill material because it has stability and can suppress the leaching of heavy metals of solids.

Figure 1 shows the pH change with time of the cover material sample including the solidified material according to the present invention,
Figure 2 shows the temperature change with time of the cover material sample including the solidified material according to the present invention,
Figure 3 shows the moisture content change with time of the cover material sample containing a solid fire according to the present invention,
Figure 4 shows the ICP analysis equipment used in the heavy metal dissolution test of the cover material sample containing a solid fire according to the present invention,
5 is a schematic diagram showing the principle of bonding with heavy metals contained in the sewage sludge by the deodorant contained in the solidified material according to the present invention,
Figure 6 is a schematic diagram showing the principle of removing the odor component contained in the sewage sludge by the deodorant contained in the solidified material according to the present invention.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the present invention is not limited by these examples.

Example 1 Preparation of Deodorant

1. Calcium-phosphate preparation

To 4 L of purified water, 494 g of Ca (NO ₃ ) _{2 and} 392 g of Na ₂ HPO ₄ were added and stirred. The reaction temperature was raised to 100 ° C and reacted for 3 hours with stirring. Thereafter, the reaction temperature was lowered to 80 ° C., and 40 g of NaOH was added thereto, followed by stirring for 12 hours. Thereafter, when the temperature dropped to room temperature, the resultant was washed with 1 L of water while filtration, and the product was dried to prepare calcium-phosphate.

2. Supporting metal complexes on calcium-phosphate

1.5 kg of calcium-phosphate, 5 g of copper nitrate, and 20 g of manganese chloride were added to 3 L of purified water, followed by complete dissolution. At this time, the reaction temperature was stirred for 4 hours at 50 ℃. After the reaction was terminated, a white solid powder was obtained through filtration and drying.

Example 2 Manufacture of Fire A

A solid fire A was prepared by mixing 10.0 wt% of Portland cement, 20.0 wt% of quicklime, and 70.0 wt% of paper ash using an ultrafast shear omni mixer. The ultra-fast shear omni mixer used was made in Japan CHIYODA OMH-30NA, and was mixed at 350 RPM for 3 minutes at 20 ℃. At this time, the characteristics of the raw materials used are shown in Table 2.

division manufacturer product name Powder figure density cement Dongyang Cement Portland Class 1 3397㎠ / g 3.15 g / cm 3 quicklime Taeyoung EMC Quicklime Express 200MESH or more 2.65 g / cm 3 Paper ash Daehan Paper - 3850㎠ / g 2.80g / cm3

Example 3 Manufacture of Fire F

Solidified material B was prepared by mixing 10.0 wt% of Portland cement, 18.0 wt% of quicklime, 70.0 wt% of paper ash, and 2.0 wt% of the deodorant prepared above using an ultrafast shear omni mixer. The mixer, mixing method, and raw material characteristics used at this time are the same as in Example 2.

Example 4 Preparation of Cover Material

       Sewage sludge used in this example is as follows. Wastewater from the sewage treatment plant and Seongseo Industrial Wastewater Treatment Plant in Dalseocheon, Western, Northern, Sincheon, Hyeonpung, and Seongseo Industrial Complexes in Daegu area is treated by advanced treatment or combination of anaerobic, anaerobic, and aerobic treatment. The sludge from the sewage treatment plant sediment was separated and dehydrated at a water content of 80% using a centrifugal dehydrator. 1000 g of the concentrated sludge obtained as described above was put in a container, and 500 g of the solidified material prepared in Examples 2 and 3 were put in a container containing the concentrated sludge, respectively, mixed for 10 minutes, and then dried naturally for 24 hours. (A, B) was prepared.

Experimental Example 1 pH Experiment

As a control, take the concentrated sludge itself treated by aerobic microorganisms in the sewage treatment plant and 10 g of the cover material samples (A, B) prepared in the previous example in a 50 mL beaker, add 25 mL of distilled water, stir well, and leave for at least 30 minutes. Was measured as a sample solution and the glass electrode was measured to measure the pH value, and the results are shown in FIG. 1.

Experimental Example 2 Temperature Experiment

In order to examine the exothermic characteristics generated during the sludge mixing of the solid material, the temperature change with time of the cover material samples (A, B) prepared in the previous embodiment was measured, and the results are shown in FIG. 2.

Experimental Example 3 Moisture Content Experiment

In order to examine the drying characteristics of the solidified material, the moisture content over time of the cover material samples (A, B) prepared in the previous embodiment was measured, and the result is that the cover material samples (A, B) as shown in FIG. It was confirmed that the decrease.

Experimental Example 4 Heavy Metal Dissolution Experiment

Heavy metal leaching analysis was carried out according to the method specified in the waste process test method. At this time, the analysis equipment used ICP analysis equipment (Liberty Series II, Varian) shown in FIG.

As a result of the heavy metal dissolution test, as shown in Table 3, in the case of the cover material sample A without deodorant, the concentration of Cu was higher than that of the existing sewage sludge, and the dissolution caused by the solidified material was detected. In the case of the cover material sample B, it can be seen that the Cu content and the overall heavy metal concentration are low due to the effect of the deodorant. At this time, the principle of binding the heavy metal by the deodorant is shown in Figure 5, n.d in Table 3 means that it is not detected.

Item Analytical component (mg / L) Cr ⁶⁺ Cu CD Pb As Hg CN Sewage sludge (control) n.d 3.324 n.d 0.06 n.d n.d n.d Cover material Sample A n.d 4.130 n.d 0.09 n.d n.d n.d Cover material sample B n.d 2.524 n.d 0.05 n.d n.d n.d

Experimental Example 5 Deodorization Characteristic Analysis

In order to analyze the deodorization characteristics, 100 g of sewage sludge and 100 g of cover material (A, B) prepared in the previous example were placed in a 5L Tedler bag and allowed to stand at room temperature for 30 minutes, and then the deodorization characteristics were analyzed by a detection tube and GC-PFPD. It was.

As a result, as shown in Table 4, when applying the sewage sludge, the ammonia and trimethylamine components were detected more than the control group. As a result, the nitrogen compounds dissolved in the sewage sludge due to the high pH of the sewage sludge were high. It is a phenomenon that is emitted by. On the other hand, since the solidified material of the cover material sample B is similar to the cover material sample A, but contains a deodorant, it can be confirmed that these odor components have been removed by the deodorant. In this case, TMA in Table 4 means trimethylamine.

H ₂ S CH ₃ SH NH ₃ TMA density
(ppm) Removal rate
(%) density
(ppm) Removal rate
(%) density
(ppm) Removal rate
(%) density
(ppm) Removal rate
(%) Sewage Sludge
(Control group) 0.26 - 4.81 - 54 - 2 - Cover material Sample A 0.15 42.31 2.56 46.78 200 over 5 over Cover material sample B 0.05 80.77 0.78 83.78 17 68.52 0.5 75

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It is to be understood that various modifications and changes may be made without departing from the scope of the appended claims.

Claims (4)

Portland cement 5-30% by weight; 10-30% by weight of quicklime; 50-80 weight percent of the pozzolanic material; And 0.5 to 10% by weight of a deodorant, wherein the deodorant is a functional solidifying material for sewage sludge, characterized in that a metal complex is supported on a calcium-phosphate compound represented by the following Chemical Formula 1:
[Formula 1]

In Formula 1, x is 0 or 1. The sewage material according to claim 1, wherein the pozzolanic material is any one or two selected from the group consisting of paper ash, fly ash, incineration ash, blast furnace slag powder, coal ash powder, volcanic ash, rice hull ash, diatomaceous earth, silica fume and zeolite. Functional solid fire for sludge. The functional solidifying material for sewage sludge according to claim 1, wherein the deodorant carries 0.1 to 20 parts by weight of the metal composite with respect to 100 parts by weight of the calcium-phosphate compound. The method of claim 3, wherein the metal complex is in the group consisting of copper (Cu) compound, manganese (Mn) compound, silver (Ag) compound, zinc (Zn) compound, platinum (Pt) compound and molybdenum (Mo) compound Functional solid fire for sewage sludge, characterized in that it comprises at least two selected.

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