KR20040084025A - Photocatalytic reactor for wastewater treatment - Google Patents

Abstract

PURPOSE: A reactor for photocatalytic degradation of wastewater is provided in which ultraviolet light sources and photocatalyst-coated tubes are geometrically arranged in shell, and wastewater flows in the shell so that wastewater is photocatalytically degraded on the surface of the photocatalyst-coated tubes by irradiation of the ultraviolet light sources. CONSTITUTION: The reactor comprises a wastewater inflow part; a photocatalyst layer comprising a plural ultraviolet light sources(150) and a plural photocatalyst-coated tubes(140) arranged in such a structure that the photocatalyst-coated tubes surround the respective ultraviolet light sources; a fixing member for fixing the photocatalyst-coated tubes and the ultraviolet light sources to the reactor; and a treated wastewater discharge part, wherein the ultraviolet light sources and the photocatalyst-coated tubes of the photocatalyst layer are positioned in such a way that a longitudinal direction of the ultraviolet light sources and the photocatalyst-coated tubes is perpendicular to a wastewater flow direction, wherein the reactor further comprises a dispersion plate mounted between the wastewater inflow part and the photocatalyst layer, and a prefilter(130) mounted on the front part of the photocatalyst-coated tubes, wherein the photocatalyst-coated tubes are aluminum tubes coated with photocatalyst, wherein the photocatalyst-coated tubes are formed in a simple tube shape, a tube shape on the surface of which pins are formed or a mesh tube shape, wherein the fixing member comprises first perforated mesh and second perforated mesh, wherein the ultraviolet light sources ultraviolet lamps or ozone lamps having central wavelength of 180 to 370 nm, and wherein the photocatalyst-coated tubes are arranged in a distance of 5 to 10 mm.

Description

Photocatalytic Reactor for Wastewater Treatment {PHOTOCATALYTIC REACTOR FOR WASTEWATER TREATMENT}

The present invention relates to a photocatalytic cracking reactor for wastewater treatment, and more specifically, an ultraviolet light source and a photocatalyst coating tube are geometrically arranged inside the shell, and the waste water flows inside the shell to irradiate the ultraviolet light source with the surface of the photocatalyst coating tube. A photocatalytic reactor for wastewater treatment, wherein the photocatalytic decomposition is in a phase.

To date, various methods have been used to treat wastewater containing chromatic and hardly degradable substances. By taking into account the chemical oxidation treatment ozone, H ₂ O _2, the chroma and the recalcitrant substances using a strong oxidizing agent such as NaOCl purposes shown to complete oxidation of water and CO ₂ but the simple oxidation method has color and recalcitrant There is a limitation in processing the materials, there is a problem that the economic point is large. Advanced Oxidation Process (AOP), which has been studied a lot recently among these chemical oxidation methods, is widely used as an advanced water treatment technology that decomposes organic substances in water by generating an intermediate product, hydroxide (-OH) radical. It is a complex oxidation method for increasing the oxidative power by combining each other ozone, hydrogen peroxide, photocatalyst, ultraviolet light and the like. The common feature of these complex oxidation methods is the method of relying on the strong oxidizing power of the hydroxide (-OH) radicals produced as intermediates rather than expecting the treatment effect from the directly injected oxidant, and the existing oxidants such as chlorine, chlorine dioxide, potassium permanganate, etc. In addition to having a much stronger oxidizing power, there is an advantage that it is more economical and efficient than using each oxidant alone, the basic concept of this method is to maximize the production of hydroxyl (-OH) radicals.

Among these, the Fenton oxidation method that decomposes hardly decomposable substances in wastewater by using strong oxidizing power of hydroxide (-OH) radicals generated by reaction between hydrogen peroxide and divalent iron ions is caused by iron hydroxide due to iron used as a catalyst of the reaction. There is a problem that a large amount of sludge is generated.

On the other hand, the wastewater treatment method by the photooxidation method is irradiated with ultraviolet (UV) by using an ultraviolet lamp to activate a photocatalyst such as titanium dioxide (TiO ₂ ) and using an oxidizing agent such as hydrogen peroxide, after the reaction titanium dioxide (TiO ₂ ) There are the same problems as removing the sludge and treating the sludge.

Slurry reactors widely used in photocatalytic reaction research have been able to maximize the contact efficiency between reactants and catalysts by dispersing fine catalyst particles in wastewater (see Korean Patent Application No. 96-702419). Due to the blocking phenomenon, there has been a problem in using light energy efficiently. In order to solve this problem, the efficiency of the reactor could be increased by strongly mixing the reaction slurry, but the slurry type reactor basically requires a filtration process for recovery of fine catalyst particles, which is difficult to install in a continuous process. have.

Korean Patent Application No. 97-46135 discloses a method of treating wastewater by combining electrolysis and photocatalyst in order to more efficiently process the photocatalyst-using photooxidation method. The method hydroxide ions (OH ^-) is obtained through the electrolysis of water to the titanium dioxide (TiO ₂₎ removed by the photocatalyst was converted to the hydroxide (-OH) radical treatment of waste water and adsorption of heavy metal ions contained in the waste water In order to generate hydroxyl (-OH) radicals, ultraviolet rays (UV) are irradiated using an ultraviolet lamp. However, this method also has the disadvantage of having to remove titanium dioxide (TiO ₂ ) after the reaction and to treat the sludge and to frequently clean the scale due to the scale of the electrode plate.

Photocatalytic oxidation can be regarded as a catalytic oxidation process, but the difference is that the activation energy required for the reaction is supplied through light, not in the form of heat. Act as electron acceptors, and OH ^- and H ₂ O act as electron donors to produce OH radicals with strong oxidizing power, which oxidize the organic material to be treated and decompose it into CO ₂ , H ₂ O, HCl, etc. It is known.

These photocatalytic oxidation reactions do not use toxic chemicals or the like and can economically decompose hardly decomposable chemicals with only a few watts of ultraviolet lamps without using fossil fuels. In addition, the operating conditions are easy, the energy consumption is low, and the system configuration is simplified, there is an advantage that the initial investment costs are reduced.

In order to overcome the problems of this slurry reactor, a catalyst fixed reactor has been proposed in which a catalyst is immobilized by coating a photocatalyst such as titanium oxide on a suitable solid support. Such a catalyst-fixed reactor has the advantage that the continuous process is easy, but compared with the slurry reactor, the interface area between the wastewater and the catalyst is very small, thereby reducing the efficiency of the reaction. However, the introduction of a catalyst immobilized in such a coating form overcomes the photoreactor design and operational limitations inherent in particulate catalysts. This is very big. However, in order to increase the light efficiency of the immobilization reactor, not only the mutual arrangement relationship between the ultraviolet light source and the catalyst surface, but also methods of efficiently inducing the ultraviolet light source to the catalyst surface are essential, and maximize the area where the waste water to be treated actually contacts the catalyst. In order to facilitate the material transfer between the two phases, an important challenge has emerged.

In order to solve this problem, a reactor of an annular structure in which a catalyst is coated on a reactor wall and a reaction fluid flows between two concentric circles has been disclosed (see Korean Patent Application Laid-Open No. 2000-0017686). The reason why the reactor is used is that most of the ultraviolet rays are absorbed when the titanium oxide is coated, even though the material can transmit ultraviolet rays. Commercially available reactors, which have recently been reported, are also in a state that does not deviate significantly from these reactor type reactors. The major drawback of such an annular structure is that it is difficult to scale up and there is no suitable means to properly mix the reaction fluids.In order to solve this problem, it is possible to annularly rotate the reactants in the space (US patent). No. 5,069,885), attempts have been made to simultaneously fill the space with titanium oxide-coated beads to serve as a catalyst layer and to mix fluids (Sematech Technology Transfer 96023084A-ENG), but basically the reactor and large It was not a difference structure.

1 shows an annular reactor and its problems. As shown in FIG. 1, when the catalyst is coated on the inner wall of the reactor, the reaction fluid flows in a direction parallel to the ultraviolet light source, so that it is difficult to properly mix the reactants, and only the reaction fluid in the vicinity of the catalyst layer is decomposed. In addition, in order to maximize the amount of light irradiation, the catalyst layer and the ultraviolet light source are designed to be as close as possible, which reduces the irradiation area and causes a limit in throughput. One can also think of a modified annular reactor in which the catalyst is coated on the outer wall of the reactor and the reaction fluid contacts in a direction perpendicular to the lamp to properly mix the reaction fluid and impart a turbulent flow. It must be made of Pyrex or quartz, which can transmit UV light, which is not suitable for use in large-capacity reactors due to its low impact resistance. Recently, new types of reactors have been reported that are not pressed, but most of them require new types of lamps, new catalyst materials, or new types of coating technology.

In order to improve the decomposition efficiency of organic chemicals by photocatalysts, geometrically optimized mutual placement relationship between UV light source and photocatalyst and methods for efficiently irradiating UV light source are essential, and the area where the surface of photocatalyst structure is actually in contact with fluid Maximization and facilitating mass transfer are also very important.

The present inventors have intensively researched to solve the problems of the conventional photocatalytic decomposition reactors. As a result, the present invention geometrically arranges the ultraviolet light source and the photocatalyst coating tubes and flows the reaction fluid in a direction perpendicular to the ultraviolet light source. A new photocatalytic reactor for wastewater treatment has been invented.

An object of the present invention is to overcome the above limitations of conventional photocatalytic cracking reactors by providing a photocatalytic cracking reactor system that facilitates mass transfer by maximizing the area where the surface of the photocatalyst structure is in contact with the fluid.

1 shows an annular reactor;

2A is a perspective view of a photocatalytic reactor according to the present invention;

FIG. 2B is a detailed view of the photocatalytic reactor inlet of FIG. 2A; FIG.

3 is a view showing the form of a metal support for a photocatalyst coated tube;

4A is a side cross-sectional view of a photocatalytic reactor according to the present invention;

4B is a view showing a first perforated network for supporting a photocatalyst coated tube;

4C is a diagram showing a second perforated network supporting an ultraviolet light source;

4D is an enlarged view of portion A of FIG. 4A;

5A is a top perspective view of a photocatalytic reactor according to the present invention;

5B is a detailed structural diagram of an ultraviolet light source shielding fixing flange;

<Brief description of the symbols in the drawings>

100 shell 110 inlet

120 Dispersion 130 Prefilter

140 Photocatalyst coated tube 141 First perforated network

150 Ultraviolet Light Source 151 Second Perforation Network

152 Flange 153 O-ring

160 outlet

The present invention wastewater inlet; A photocatalyst layer comprising a plurality of ultraviolet light sources and a plurality of photocatalyst coating tubes arranged in a structure surrounding each of the ultraviolet light sources; A fixing member for fixing the photocatalyst coating tube and the ultraviolet light source to the reactor; And a treatment wastewater discharge portion, wherein the ultraviolet light source and the photocatalyst coating tube of the photocatalyst layer are positioned so that their length direction is perpendicular to the direction of the fluid flow.

In the photocatalytic decomposition reactor for wastewater treatment according to the present invention, the wastewater flows in a direction perpendicular to the photocatalyst coating tube and the ultraviolet light source, thereby increasing the mixing effect and inducing turbulence to be formed.

In a preferred embodiment of the present invention, a plurality of photocatalyst coating tubes are geometrically arranged around each ultraviolet light source, such as honeycomb, to oxidize the photocatalyst in all parts of the photocatalyst coating tube through ultraviolet irradiation with the ultraviolet light source. Allow the reaction to occur.

In the photocatalytic decomposition reactor for wastewater treatment according to the present invention, the metal tube is used as the support for the photocatalyst coating, which is convenient for maintenance and can be molded into a complicated shape, thereby increasing the ultraviolet irradiation area considerably compared with the conventional reactor type reactor. You can.

Titanium oxide (TiO ₂ ) is most commonly used in the environmental field as a photocatalyst material, which has a rutile and anatase crystal structure. In the present invention, anatase titanium oxide is used.

In order to distribute the wastewater flowing into the reactor evenly in the reactor, a plurality of inlets of the wastewater may be installed, and it is preferable to install a distribution plate behind the inlet.

In addition, it is preferable to install a pre-filter in front of the photocatalyst coating tube in order to prevent solid impurities from entering the waste water and damaging the ultraviolet light source.

As an ultraviolet light source for ultraviolet irradiation, the germicidal lamp of wavelength 254 nm can be used normally, and the UV-A lamp of wavelength 365 nm can also be used. Preferably, ozone generated by using an ozone lamp may serve to assist the oxidation reaction occurring at the photocatalyst surface.

In particular, when using a conventional ultraviolet light source is a phenomenon that the photocatalyst is deactivated after a certain time after the start of the reaction occurs, in order to prevent the deactivation of the photocatalyst, an ozone lamp can be used as the ultraviolet light source.

The fixing member for fixing the photocatalyst coating tube and the ultraviolet light source to the reactor includes a first perforated network positioned inside the reactor to fix the photocatalyst coated tube and allowing the external light source to pass therethrough, and an ultraviolet light source penetrating the first perforated network outside the reactor. It is composed of a second perforated network which is fixed at the same time and sealed from the outside air.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

2A is a perspective view of a photocatalytic reactor according to the present invention. Reactor for photocatalyst decomposition of the present invention shown in Figure 2a comprises a shell (100); A plurality of inlets 110 for flowing wastewater into the shell 100; A dispersion plate 120 (shown in FIG. 2B) to evenly distribute the incoming wastewater; Pre-filter 130 is bonded to the stainless mesh installed in front of the photocatalyst coating tube in order to prevent the solid impurities flow into the lamp; An ultraviolet light source 150 and a photocatalyst coating tube 140 disposed around the light source 150; And a plurality of outlets 160 through which the reaction is completed and the generated fluid is discharged.

Figure 2b shows the inlet of the photocatalytic reactor according to the invention in detail, the inlet of the reactor shell 100 may be provided with a plurality of inlets to flow so that the waste water is distributed evenly, in the present invention for the purpose of illustration Only two inlets 110 are shown. In order to more evenly distribute the wastewater introduced into the reactor through the inlet 110, a dispersion plate 120 having a hole of a certain size and shape was installed at the rear of the inlet, and solid impurities were mixed together and introduced into the wastewater. In order to prevent the light source from being damaged, a prefilter 130 having a stainless mesh bonded thereto was installed in front of the catalyst layer.

As an ultraviolet light source, a germicidal lamp having a wavelength of 254 nm (manufactured by Sankyo Electric Co., Ltd.) was used.

As shown in the drawing, the ultraviolet light source 150 and the photocatalyst coating tube 140 are formed in a honeycomb form in which one ultraviolet light source 150 is surrounded by six photocatalytic coating tubes 140. It is designed to have a larger irradiation area per unit ultraviolet light source than in the reactor.

3 is a view showing the form of a metal tube serving as a support for coating the photocatalyst in the photocatalyst coating tube 140. In the conventional reactor type reactor, it was common to use Pyrex glass as a support for coating a titanium oxide photocatalyst, but in the present invention, metal (preferably aluminum) is used instead of glass material to increase the stability of the reactor structure and to maintain it. It was convenient. Another advantage of using a metal support is that injection molding is possible in the desired form. Using this, it is possible to add fins to a general round tube to increase the applicable surface area of the catalyst and to impart vortices to the fluid. In this case, in the case of adding the fin in the direction perpendicular to the ultraviolet light source in order to ideally widen the ultraviolet irradiation area, the usable form of injection molding is to attach the fin in parallel with the lamp in the longitudinal direction and to coat the photocatalyst on the surface thereof. desirable. By doing so, even if the tube does not reach some ultraviolet rays, the irradiation area can be increased by 50% or more compared with the conventional reactor type reactor, and the final surface area of the coated tube can be increased by 2 times or more.

In addition, as the photocatalyst coating tube 140, instead of a simple tube form, it is also possible to use a coating of a photocatalyst on a mesh tube made by rolling a mesh several times in the form of a roll, in which case the reaction fluid passes not only inside the catalyst structure but also inside. As a result, the reaction area and residence time can be further increased.

The difference between the surface area, that is, the ultraviolet irradiation area, of the conventional reactor type reactor as shown in FIG. 1 and the wastewater treatment reactor of the present invention according to FIG. 2 is shown in Table 1 below.

Reactor Pipe diameter (cm) Tube circumference (cm) Tube length (cm) Tube number Surface area (m ² ) Annular reactor 100 314 1,130 50 17.7 Reactor of the present invention 45 226 1,130 160 40.6

4A is a side cross-sectional view of a photocatalytic reactor according to the present invention. There may be a number of methods for arranging the ultraviolet light source 150 and the photocatalyst coating tube 140 to support the inside of the shell, but on a stainless steel flat plate which does not cause hardening or corrosion by ultraviolet rays, As described above, the use of a perforated network in which a hole corresponding to the diameter of the photocatalyst coating tube and the ultraviolet light source is bored in a desired arrangement form is the cheapest and can support a precise geometrical arrangement. In the photocatalytic cracking reactor according to the present invention, the perforated network shown in FIG. 4B is referred to as a first perforated network, and as shown here, a portion indicated by a dotted circle is a portion where the photocatalyst coating tube 140 is supported, and is indicated by a black filled circle. The portion is the portion through which the ultraviolet light source 150 extends through it. The first perforated network 141 of FIG. 4B is mounted to the inner side edge of the shell 100 to support the photocatalyst coating tube and the ultraviolet light source. In order to increase the mixing effect of the reactants and minimize the pressure drop, the distance between the photocatalyst coating tubes is preferably 5 to 10 mm.

FIG. 4C shows a second perforated network 151 for fixing the ultraviolet light source 150 extending out of the shell past the first perforated network 141 inside the shell 100 of FIG. 4B to the outside of the reactor. The second perforated network 151 fixes the ultraviolet light source 150 to the outside of the reactor and at the same time seals the connection portion between the ultraviolet light source 150 and the reactor. The flange 152 was installed to fix the portion of the ultraviolet light source 150 extending outside the reactor and exposed to the outside while being fixed to the reactor so that the ultraviolet light source 150 was shielded and fixed.

FIG. 4D is an enlarged view of portion A of FIG. 4A. Referring to FIG. 4D, the wastewater flowing through the inlet 110 and passing through the prefilter comes into contact with the ultraviolet light source 150 and the photocatalyst coating tube 140 in a direction perpendicular to the longitudinal direction thereof. Reaction on the surface of the photocatalyst coated tube 140 by irradiation of 150).

The photocatalytic layer of the photocatalytic cracking reactor of the present invention is installed and maintained in an appropriate arrangement, preferably two rows of ultraviolet light sources 150 and three rows of photocatalytic coating tubes 140 arranged around them. Can make it simpler.

FIG. 5A is a plan perspective view of a photocatalytic reactor according to the present invention, and FIG. 5B is a perspective view of the photocatalytic reactor in which the ultraviolet light source 150 is fixed to the reactor at a connection point between the ultraviolet light source 150 extending outside the reactor and the second perforated network. The detailed structure of the flange 152 is shown to prevent exposure. As the screw of the flange 152 is rotated, the O-ring 153 inserted between the ultraviolet light source 150 and the flange 152 tightens to block the ultraviolet light source 150 from the outside air while fixing the reactor to the reactor. Will be Since the photocatalyst coating tube 140 is fixed by the first perforation network 141 mounted on the wall inside the reactor, no separate sealing is necessary. The photocatalytic decomposition reactor for wastewater treatment of the present invention can minimize the loss of ultraviolet rays by directly shielding the ultraviolet light source 150 with the flange 152, and when ozone lamp is used, ozone generated from the lamp can be used as a direct oxidation aid. There is this.

In order to increase the performance of the reactor, the contact between the fluid and the catalyst tube should be maximized. For this purpose, it is preferable to use the catalyst tube and the ultraviolet lamp as a blocking plate to change the path of the fluid.

The photocatalytic decomposition reactor for wastewater treatment according to the present invention is convenient to use and maintain using a metal such as aluminum as a catalyst support, and can increase the irradiation area of the wastewater by increasing the number of ultraviolet light sources. It can be enlarged, and by coating a photocatalytic material on a metal tube, it is possible to manufacture and use a complex tube in addition to a circular shape to maximize the UV irradiation area. In addition, since the waste water flows in a direction perpendicular to the photocatalyst coating tube and the ultraviolet light source, the photocatalyst coating tube itself acts as an obstacle to maximize the contact effect of the fluid.

Claims (9)

Wastewater inlet; A photocatalyst layer comprising a plurality of ultraviolet light sources and a plurality of photocatalyst coating tubes arranged in a structure surrounding each of the ultraviolet light sources; A fixing member for fixing the photocatalyst coating tube and the ultraviolet light source to the reactor; And a treatment wastewater discharge portion, wherein the ultraviolet light source and the photocatalyst coating tube of the photocatalyst layer are positioned such that their longitudinal direction is perpendicular to the flow direction of the wastewater. The method of claim 1, Dispersion plate is further provided between the wastewater inlet and the photocatalyst layer, wastewater treatment photocatalytic reactor. The method of claim 1, The precatalyst is further equipped with a front end of the photocatalyst coating tube, wastewater treatment photocatalytic reactor for treatment. The method of claim 1, The photocatalytic coating tube is characterized in that the photocatalyst is coated on the aluminum tube, wastewater treatment photocatalytic reactor. The method of claim 1, The photocatalyst coating tube is characterized in that the simple tube form, the tube form having a pin on the surface or a mesh tube form, wastewater treatment photocatalytic reactor. The method of claim 1, The fixing member is located inside the reactor to fix the photocatalyst coated tube and pass through the ultraviolet light source, and the second perforated network to fix the ultraviolet light source penetrating the first perforated network to the outside of the reactor and to seal it from the outside air. Characterized in that the photocatalytic reactor for wastewater treatment. The method of claim 1, The ultraviolet light source is an ultraviolet lamp or ozone lamp having a central wavelength of 180 to 370 nm, wastewater treatment photocatalytic reactor. The method of claim 1, The photocatalytic coating tube is characterized in that disposed at intervals of 5 to 10 mm, wastewater treatment photocatalytic reactor. The method of claim 6, A photocatalytic reactor for wastewater treatment, characterized in that a flange equipped with an O-ring is used to shield the portion of the ultraviolet light source extending outward from the second perforated network.