KR100799261B1 - Sludge Recycling Method Using Titanium Salt as Dehydration Aid - Google Patents

Abstract

A sludge dewatering method is provided to produce sludge with a low water content by using a titanium salt as a dewatering aid, and improve dewatering of sludge and enable sludge to be recycled by incinerating the produced sludge with a low water content and recovering incineration ash containing titanium dioxide that exhibits photocatalytic activities. A sludge recycling method using a titanium salt as a dewatering aid comprises the steps of: (a) adding a titanium salt as a dewatering aid into sludge to be treated; (b) applying sludge obtained in the step(a) to a dewatering equipment to perform a dewatering process; (c) removing filtrate and obtaining a sludge cake by the dewatering process of the step(b); and (d) incinerating the sludge cake in a temperature range of 500 to 1000 deg.C to recover incineration ash containing titanium dioxide having photocatalytic activities. The sludge recycling method further comprises the step of drying the sludge cake between the steps (c) and (d). The dewatering process of the step(b) is carried out by injecting sludge obtained in the step(a) between filter fabrics and applying a predetermined pressure to the filter fabrics to separate sludge into filtrate and sludge cake.

Description

Sludge recycling method using titanium salt as dehydration aid {METHOD FOR DEWATERING SLUDGE TO ENHANCE ITS RECYCLING USABILITY WITH TITANIUM SALTS AS DEWATERING COAGULANT AID}

1 is a schematic diagram of a process showing a preferred embodiment of the method for dewatering sludge according to the invention.

Figure 2 is a graph showing the water content change of the sludge after dehydration according to the addition amount of titanium salt as a dehydration aid.

Figure 3 is a graph comparing the size of the sludge cake according to the type of inorganic dehydrating aid for the purpose of comparison.

4 is an XRD pattern of titanium sintered powder obtained by sintering at a temperature of 500 ° C.

5 is a SEM photograph of titanium oxide finally obtained by the method of the present invention.

6 is a mapping photograph of titanium oxide finally obtained by the sludge recycling method according to the present invention.

7 is a graph showing the experimental results of acetaldehyde gas phase decomposition reaction of the final by-product obtained by the sludge recycling method according to the present invention.

The present invention relates to a sludge recycling method using titanium salts. More specifically, the present invention uses a titanium salt as a dehydration aid to produce sludge of low water content, incinerate it to recover an incineration material containing titanium oxide (TiO ₂ ) exhibiting photocatalytic activity, and as a dehydration aid, titanium salt. The present invention relates to a method for dewatering sludge with improved dewatering efficiency and recycling.

Substances formed by separating solids from liquids during water purification and wastewater treatment are widely referred to as sludge. The sludge includes sludge generated from sewage and water treatment plants, sludge discharged from industrial wastewater treatment plants such as chemical plants, steel mills, dyeing plants, and paper mills, and sludge generated from livestock and manure facilities. As the importance of the environment is increasingly emphasized, various studies on the reduction of sludge have been conducted.

In particular, organic sludge is difficult to dehydrate as micronized sludge. Generally, the water content of these sludges is about 95% or more. Therefore, in order to treat sludge solids more efficiently, it is concentrated (gravity and flotation), stabilized (anaerobic, aerobic, wet oxidation, impregnated tank), improved (washing, chemical treatment, heat treatment), dehydration (vacuum filtration, pressurization). Sludge is processed by filtration, centrifugation, drying), incineration (multi-stage type, fluidized bed incinerator), and disposal (soil spraying, landfill, ocean dumping, composting). Sludge disposal is currently being treated as 24% landfill and 43% ocean dumping, with about 12% being recycled. However, since the disposal of sludge has been limited to sludge with a water content of 75 wt% or less since 2003, marine dumping has been banned since 2010 under the London Dumping Treaty.

Sludge improvement is used to increase dewatering properties and is one of the most efficient sludge treatment methods. Rinsing cleans the sludge with water to remove fine solids components that consume a large amount of chemicals when using inorganic salts such as bicarbonate and the like. Heat treatment is mainly used to improve waste activated sludge, and heat treatment is used to destroy microorganisms, dissociate and release water between cells with high water content. As one of the methods for the efficient improvement of the sludge, dehydration aids have been used. For examples of sludge dewatering methods using dehydration aids, see Korean Patent Publication Nos. 2004-80643 and 2005-38948. Dehydration aids are largely classified into organic dehydration aids and inorganic dehydration aids. Organic polymers are mainly used as organic dehydration aids. However, these organic polymers are difficult to recycle and have a problem of causing environmental pollution by organic polymers. As inorganic dehydration aids, aluminum inorganic compounds such as Al ₂ (SO ₄ ) ₃ · 8H ₂ O or Al (OH) ₂ Cl), iron inorganic compounds (eg FeCl ₃ · H ₂ O, FeSO ₄ · H ₂ O) Or Fe ₂ (SO ₄ ) ₃ · H ₂ O) or calcium inorganic compounds (eg Ca (OH) ₂ ). However, these dehydration aids do not provide satisfactory results.

An object of the present invention is to provide a sludge recycling method using titanium salt as a dehydration aid. More specifically, an object of the present invention is to use a titanium salt as a dehydration adjuvant, to produce a sludge of low water content, to incinerate it to recover the incineration material containing titanium oxide (TiO ₂ ) exhibiting photocatalytic activity, to improve the dehydration and It is to provide a sludge dewatering method that allows the recycling of resources.

According to a preferred embodiment of the present invention, a) adding a sludge dehydration aid to the sludge to be treated, b) applying the sludge obtained in step a) to a dehydration apparatus to perform a dehydration process, c) step titanium salt, comprising the step of removing the filtrate by dehydration of b) to obtain a sludge cake, and d) recovering the incineration ash containing titanium oxide having photocatalytic activity by incineration of the sludge cake. A sludge recycling method is provided. Here, it is preferable that the titanium salt used as a dehydration adjuvant is a hydrolysable titanium salt. Examples of titanium salts that can be used include titanium trichloride, titanium tetrachloride, titanyl sulfate, titanium sulfate, titanium oxysulfate and titanium iron sulfate.

According to a more preferred embodiment of the invention, the incineration process of step d) is carried out at 500-1000 ° C., more preferably at 500-650 ° C. This incineration forms titanium oxide having an anatase crystal structure. At this time, the titanium oxide, carbon (C), phosphorus (P), trace amounts of Si, Fe, S, Al, V, Ca, Na, Cr and Cl, depending on the organic / inorganic content contained in the sludge Doped titanium oxide doped with organic / inorganic elements maintains photocatalytic activity.

1 is a process chart showing a preferred embodiment of the sludge dewatering method according to the present invention. First, titanium salt is added to the sludge to be treated as a dehydration aid. The titanium salt dehydration aid is preferably added to have a titanium content of 3 mg / L-9 mg / L, based on the total volume of the sludge. Preferred examples of titanium salts are hydrolyzable titanium salts. Examples of titanium salts that can be used include titanium trichloride, titanium tetrachloride, titanyl sulfate, titanium sulfate, titanium oxysulfate and titanium iron sulfate. The titanium salt may be added together with other dehydration aids. Other dehydration aids include conventional organic dehydration aids and inorganic dehydration aids. Preferably it is an inorganic dehydration adjuvant. Organic dehydration aids are decomposed and removed upon incineration. The inorganic dehydration aid is present in which the inorganic compound is doped with titanium oxide. Examples of preferred inorganic dehydration aids are iron dehydration aids and aluminum dehydration aids. The combination of the titanium salt dehydration adjuvant and the iron dehydration adjuvant showed relatively low initial adsorption, but the decomposition performance of acetaldehyde showed relatively high activity. Most preferably, the titanium dehydration aid is used alone. The combination of titanium salt dehydration adjuvant and aluminum dehydration adjuvant showed relatively high initial adsorption, but the resolution was relatively low. The pH of the sludge is adjusted in the range of 1-13, preferably 3-8, most preferably 7-8. In order to properly adjust the pH of the sludge and to further enhance the dehydration effect, a basic compound may be used together. Examples of sludge to which the present invention is applicable are not particularly limited, and water, sewage, and industrial wastewater sludge are all applicable. It is especially suitable for the treatment of organic sludge. Generally, the sludge obtained in the settling tank is further concentrated in the thickening tank and preliminarily stored in the storage tank. Then, with the help of the pump, it is applied to the dehydrator. At this time, the titanium salt as said dehydration adjuvant is normally supplied to a storage tank. If necessary, a mixing tank may be added between the concentration tank and the storage tank, or between the storage tank and the dehydration device, and a dehydration aid may be added thereto. Most preferably, a mixing tank is provided between the concentration tank and the storage tank, and a dehydration adjuvant is supplied thereto.

Titanium salt dehydration adjuvant forms titanium hydrate in water and adsorbs on the negative charge of sludge to destabilize the water to agglomerate small sludges to form agglomerates of large substances. At this time, the larger the size of the aggregate, the better the dehydration effect. According to a specific experimental example of the present invention, the titanium salt dehydrating adjuvant formed an aggregate of about 47.54 μm, and provided an improved aggregation effect than the same amount of aluminum-based aggregates 16.91 μm and iron-based aggregates 42.50 μm. Sludge added with a dehydration aid is applied to a dehydration device to perform a dehydration process. The dehydration process is usually carried out by pressurization. Specifically, the sludge to which the dehydration aid is added is injected between the filter cloths and a predetermined pressure is applied to the filter cloths to separate the sludge into water (filtrate) and solids (sludge cake). Specific examples of the pressurized dewatering device include a belt press, a filter press, a screw decanter or a centrifugal separator. The belt press dewatering device is the most widely used dehydration equipment. It is a dehydration device that moves and compresses the superfiling fabric and subfoam with a roller, and injects and filters sludge therebetween. The filter press dewatering device compresses a plurality of filter plates having a certain constitution with a hydraulic cylinder, and then inserts sludge into the space to compress and concentrate the sludge sludge cake inside the filter plate and discharge the filtrate. When the screw decanter is continuously fed into the rotating bowl through feed pipe without sludge and flocculant at the same time, centrifugal consolidation force is applied to thousands of times of gravity to separate solids and water, and solids It is a dewatering device discharged to the cake by the action of the pressing force. In addition, the centrifugal separator uses the principle of centrifugal separation and is widely used when continuously dehydrating a relatively small volume. The sludge cake obtained affects treatment costs and treatment efficiency depending on the moisture content. The titanium salt dehydration aid, which forms an average size of 47.54 μm, provided a cohesive effect higher than that of the conventional aluminum-based dehydration aid 16.91 μm and the iron-based dehydration aid 42.50 μm, which provides improved water content and improved treatment efficiency. .

The sludge cake obtained after the dehydration process is subjected to the incineration process. If necessary, the sludge cake may be added a drying process between the dehydration process and the incineration process. The drying process may be natural drying at room temperature. Preferably the drying process is a drying process is carried out at a temperature of 90 ℃-150 ℃, most preferably 100 ℃-120 ℃.

According to a preferred embodiment according to the invention, the incineration process is carried out at 500 ° C. or higher, preferably 500-1000 ° C., more preferably 500-650 ° C. By the incineration step, excess water and organic compounds are decomposed and removed to obtain an incineration ash. At this time, the incineration ash contains titanium oxide having photocatalytic activity. That is, an incineration ash containing titanium oxide having photocatalytic activity is finally obtained, and these are used as building materials requiring photocatalytic activity, or they are embedded in a landfill or soil polluted area, and organic and pathogenic microorganisms are formed by photocatalytic activity using sunlight. It can be used for the removal of. This means that the product obtained by the incineration process can be recycled.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, these examples are presented for understanding the present invention, it should be understood that the scope of the present invention is not limited by these examples.

Example

Example 1: Moisture Content Measurement

The water content of the sludge was tested using the sludge generated in the sewage treatment plant. Titanium chloride (TiCl ₄ ) of different concentrations was administered to the sewage sludge having a solid content of 5%, and the water content was measured after dehydration by a belt press. The results are shown in FIG. 2. As shown in FIG. 2, as the concentration of titanium oxide was increased, the water content of the sludge decreased, and the water content was reduced up to 70%.

Example 2: Comparative experiment with other inorganic dehydration aids

After adding the inorganic dehydrating aids Alum, FeCl ₃ , TiCl ₄ to 13 mg / L, respectively, to 1L of sewage sludge with 5% solids, the size of the resulting slurry cake was LS 230 (Beckman Coulter, Inc., Great British), and the results are shown in FIG. 3. As shown in FIG. 3, the titanium salt dehydration aid, the iron dehydration aid and the aluminum dehydration aid had sizes of 47.54 μm, 42.50 μm, and 16.91 μm, respectively. This means that the dehydration efficiency of the titanium salt dehydration aid is further improved.

Example 3 Preparation of Titanium Oxide from Sludge Aggregates

Titanium chloride (TiCl ₄ ) was administered to a Ti salt content of 13 mg / L in a sewage sludge having a solid content of 5%, dehydrated by a belt press, dried at 105 ° C., and incinerated to obtain a titanium oxide incinerator. The XRD pattern of the obtained titanium oxide was measured, and the results are shown in FIG. As the temperature increased, the sintered powder changed from black to white powder. At 500 ° C., the XRD pattern showed anatase crystals. This indicates that organic / inorganic elements are doped independently of TiO ₂ without being formed independently in oxide form. At that temperature, amorphous powder formed. The elemental content was measured and the results are shown in Table 1 below.

As shown in Table 1, functional titanium oxide doped with various organic elements (C, P, S, Cl, Br, etc.) and inorganic elements (Si, Fe, Al, V, Ca, Na, Cr, Ni) Formed. 5 and 6 show SEM and mapping pictures of the prepared titanium oxide, respectively. As a result of the characteristics of the titanium oxide, nanoparticles having a size of about 10 nm were formed, and it was confirmed that organic and inorganic element components were evenly doped in TiO ₂ .

Example 4 Organic Photolysis of Titanium Oxide Prepared from Sludge Aggregates

TiO ₂ powder obtained by administering titanium chloride (TiCl ₄ ) to 13 mg / L of titanium in a sewage sludge having a solid content of 5%, dehydrated and calcined, and titanium chloride (TiCl ₄ ) of 6.5 mg / L in titanium TiO obtained by administering aluminum dehydration aid (Al ₂ (SO ₄ ) ₃ · 8H ₂ O) and iron dehydration adjuvant (FeCl ₃ ) mixed with Al and Fe contents each to 6.5 mg / L. Acetaldehyde gas phase decomposition was conducted to investigate the photodegradability of ₂ -Al and TiO ₂ -Fe powders. 7 is a graph showing the experimental results of acetaldehyde gas phase decomposition reaction. 0.5 g of titanium oxide powder was added to a sealed photocatalytic gas phase reactor, 2000 ppm of acetaldehyde was injected, adsorbed for 1 hour, and a plurality of samples were taken while irradiating a UV lamp.

As a result of analyzing the concentration of acetaldehyde contained in the samples, the dehydration aid (TiO ₂ ) of TiO ₂ alone, the dehydration aid (TiO ₂ -Al) consisting of TiO ₂ and aluminum inorganic compounds, TiO ₂ and iron inorganic compounds Dehydration adjuvant (TiO ₂ -Fe) consisting of a combination of all showed satisfactory photocatalytic activity. In particular, TiO ₂ powder decomposed acetaldehyde up to several tens of ppm in about 40 minutes after UV irradiation.

The present invention proposed a new sludge dewatering aid that can solve the water content and disposal, which are the main problems in sludge treatment. After reducing the sludge moisture content by using titanium salt as a dehydration aid, incineration material containing titanium oxide, which is a commercially useful material, can be incinerated to be used as a building material, or used as a building material, or recycled to environmental purification by spraying to landfills or soil-contaminated areas. Can be.

Claims (9)

a) adding titanium salt to the sludge to be treated as a dehydration aid, b) performing the dehydration process by applying the sludge obtained in step a) to the dehydration apparatus, c) removing the filtrate by the dehydration process of step b) to obtain a sludge cake, and d) recovering the incineration material containing titanium oxide having photocatalytic activity by incineration of the sludge cake, wherein the sludge recycling method using titanium salt as a dehydration aid. According to claim 1, Between the step c) and the step d), characterized in that it further comprises the step of drying the sludge cake, sludge recycling method using titanium salt as a dehydration aid. The sludge recycling method using titanium salt as a dehydration aid according to claim 1, wherein the titanium salt is a hydrolyzable titanium salt. The titanium salt as a dehydration aid according to claim 3, wherein the titanium salt is selected from the group consisting of titanium trichloride, titanium tetrachloride, titanyl sulfate, titanium sulfate, titanium oxalate and titanium iron sulfate. Sludge Recycling Method The sludge recycling method using titanium salt as a dehydration aid according to claim 1, wherein the titanium salt dehydration aid of step a) is added together with an organic dehydration aid or an inorganic dehydration aid. The sludge recycling method using titanium salt as a dehydration aid according to claim 5, wherein the inorganic dehydration aid is an iron dehydration aid or an aluminum dehydration aid. The sludge recycling method using titanium salt as a dehydration adjuvant according to claim 6, wherein the incineration of step d) is performed at 500-1000 ° C. The sludge recycling method of claim 1, wherein the dehydration process of step b) is performed by pressurization. The method of claim 1, wherein the dehydration process of step b) is carried out by injecting the sludge obtained in step a) between the filter cloth and applying a constant pressure to the filter cloth to separate the sludge into the filtrate and the sludge cake. , Sludge recycling method using titanium salt as dehydration aid.

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