Photocatalytic reactor and method for treating gaseous pollutants using the same

The present invention provides a photocatalytic reactor and a method for treating gaseous pollutants using the same, which can decompose and remove gaseous pollutants such as volatile organic compounds (VOCs), odors, etc. as well as liquid pollutants using an environmentally friendly photocatalytic reaction. To this end, the present invention provides a photocatalytic reactor including: a solution tank to which a fluid containing gaseous pollutants to be treated is supplied through an inlet; a solution injector installed at the top of the inlet and injecting a gaseous pollutant solution into the fluid to be treated such that the gaseous pollutants of the fluid are dissolved; and a liquid photocatalytic treatment device receiving the gaseous pollutant solution, in which the gaseous pollutants of the fluid are dissolved and liquefied, from the solution tank and decomposing the liquefied gaseous pollutants of the fluid.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No. 10-2011-0074322, filed Jul. 26, 2011, under 35 U.S.C. §119(a). The entire content of the aforementioned application is incorporated herein by reference in its entirety.

BACKGROUND

(a) Technical Field

The present invention relates to a photocatalytic reactor. More particularly, it relates to a photocatalytic reactor and a method for treating gaseous pollutants using the same, which decomposes and removes gaseous pollutants such as volatile organic compounds (VOCs), odors, etc., as well as liquid pollutants using an environmentally friendly photocatalytic reaction.

(b) Background Art

With the rapid development of the global industry, the problem of environmental pollution has become more serious requiring strict regulations for pollution treatment. Moreover, the diversification in the types of pollution sources, and continued generation of new pollutants has created various approaches to more effectively solve the pollution problem.

A recently developed method includes a method for treating pollutants using a photocatalytic reaction, which is relatively unaffected by temperature, pH, etc., and does not require strict treatment conditions. Moreover, the method for treating pollutants using the photocatalytic reaction can use clean energy such as the light of the sun, etc., and thus has the advantages of being environment-friendly and energy efficient.

The currently used photocatalytic reaction will be discussed briefly below. When light energy from the sun or any other light source is applied to a photocatalyst, electrons and holes are generated in the photocatalyst and migrate to the surface of the photocatalyst. The electrons and holes migrating to the surface of the photocatalyst come into contact with pollutants to be treated and cause chemical oxidation-reduction reactions, thereby decomposing the pollutant molecules.

An organic pollutant decomposition device using the photocatalytic reaction is a nature-friendly pollution reduction device and has enormous potential for development, and thus the interest in the photocatalytic reactor has increased.

Conventional photocatalytic reactors are classified as a suspended photocatalytic reactor as shown inFIG. 1and a fixed photocatalytic reactor as shown inFIG. 2.

The suspended photocatalytic reactor10is a device for decomposing liquid pollutants and, as shown inFIG. 1, comprises a light source11for supplying light energy, a photoreactive treatment tank12for accommodating a fluid14to be subjected to pollutant removal treatment such as wastewater, dye solution, etc., and a photocatalytic powder13introduced and dispersed into the fluid14to be treated in the photoreactive treatment tank12.

The suspended photocatalytic reactor10can utilize much larger surface area of the photocatalytic powder10in the photocatalytic reaction and thus has the advantage of high treatment efficiency compared to the fixed photocatalytic reactor. However, the photocatalytic powder10is not fixed to gaseous pollutants such as volatile organic compounds (VOCs), odors, etc., during treatment. Therefore, treatment of gaseous pollutants is not possible with a suspended photocatalytic reactor10.

The fixed photocatalytic reactor20is a device for decomposing liquid and gaseous pollutants and, as shown inFIG. 2, comprises a light source21for supplying light energy, a photoreactive treatment tank22through which a fluid26to be subjected to pollutant removal treatment, including gaseous pollutants such as VOCs, odors, etc., and liquid pollutants such as wastewater, dye solution, etc., passes, and a photocatalyst-coated tube25on which a photocatalyst is coated and fixed.

The photoreactive treatment tank22includes an inlet23through which the fluid26to be treated is introduced and an outlet24through which the fluid26being in contact with the photocatalyst is finally discharged such that the fluid26introduced through the inlet23is in contact with the photocatalyst fixed on the photocatalyst-coated tube25to be decomposed and then discharged through the outlet24.

Since the photocatalyst is fixed on the photocatalyst-coated tube25in the fixed photocatalytic reactor20, it is not necessary to recover the photocatalyst separately. Moreover, even in the case where a sealed space for maintaining the contact between the photocatalyst and the gaseous pollutants to be treated or the flow rate of the fluid26to be treated is small, it is possible to treat the gaseous pollutants. However, compared to the suspended photocatalytic reactor10, the reaction area of the photocatalyst is limited to the coated area of the photocatalyst-coated tube25. Thus, when liquid and gaseous pollutants having high flow rate and velocity are treated (e.g., in a factory), the reaction time between the photocatalyst and the gaseous pollutants is very short, which makes it difficult to treat the pollutants, thereby reducing the treatment efficiency.

The current invention addresses the current drawbacks by providing an apparatus to treat gaseous pollutants in an effective, efficient, and environmentally friendly manner.

SUMMARY OF THE DISCLOSURE

The present invention provides a photocatalytic reactor and a method for treating gaseous pollutants using the same, which can decompose and remove gaseous pollutants as well as liquid pollutants, by dissolving the gaseous pollutants and allowing the dissolved gaseous pollutant to react with a photocatalyst.

In one aspect, the present invention provides a photocatalytic reactor comprising: a solution tank to which a fluid containing gaseous pollutants to be treated is supplied through an inlet; a solution injector installed at a top of the inlet which injects a gaseous pollutant solution into the fluid to be treated such that the gaseous pollutants of the fluid are dissolved; and a liquid photocatalytic treatment device receiving the gaseous pollutant solution, in which the gaseous pollutants of the fluid from the solution tank, are dissolved and liquefied, then the liquefied gaseous pollutants are decomposed.

In one embodiment, the photocatalytic reactor further comprises a porous filler provided at a bottom of the solution injector which increases contact time between the gaseous pollutants of the fluid and the gaseous pollutant solution.

In another embodiment, the photocatalytic reactor further comprises a circulation means provided between the liquid photocatalytic treatment device and the solution injector, which circulates the gaseous pollutant solution.

In still another embodiment, the gaseous pollutant solution may comprise hydrogen peroxide or dissolved oxygen.

In another aspect, the present invention provides a method for treating gaseous pollutants, the method comprising the steps of: (i) adding a fluid containing gaseous pollutants to be treated to a solution tank; (ii) injecting a gaseous pollutant solution into the solution tank such that the gaseous pollutant solution comes into contact with the gaseous pollutants of the fluid; and (iii) allowing the gaseous pollutant solution of step (ii), in which the gaseous pollutants of the fluid are dissolved and liquefied, to react with a photocatalyst such that the liquefied gaseous pollutants of the fluid are decomposed.

In one embodiment, the method further comprises the step wherein, in step (ii), in the injecting of the gaseous pollutant solution into the solution tank, the gaseous pollutant solution injected into the solution tank is allowed to pass through a porous filler to increase the contact time between the gaseous pollutants of the fluid and the gaseous pollutant solution.

In another embodiment, the method further comprises the step of wherein, in step (iii), the liquefied decomposed gaseous pollutants of the fluid are circulated to an injector of the solution tank to be injected again into the solution tank.

In certain embodiments, the gaseous pollutant solution comprises hydrogen peroxide or dissolved oxygen.

DETAILED DESCRIPTION

The present invention provides a photocatalytic reactor and a method for treating gaseous pollutants using the same, wherein the reactor can decompose and remove gaseous pollutants such as volatile organic compounds (VOCs), odors, etc. as well as liquid pollutants by allowing a fluid (to be subjected to pollutant removal treatment or odor removal treatment) to react with a photocatalyst using light energy.

In particular, the photocatalytic reactor of the present invention is obtained in part by improving a conventional suspended photocatalytic reactor (seeFIG. 1), which is not readily able to decompose gaseous pollutants because the photocatalyst is not fixed. In certain embodiments, the invention provides a photocatalytic reactor wherein gaseous pollutants of a fluid to be treated are dissolved and liquefied in a gaseous pollutant solution, and the resulting solution is treated using a liquid photocatalytic treatment device having high removal efficiency of liquid pollutants. The reactor of the invention provides the advantage of using a photocatalytic reaction between the photocatalyst and the gaseous pollutants of a fluid having high flow rate and velocity, providing for the treatment of gaseous non-biodegradable pollutants.

As shown inFIG. 3, the photocatalytic reactor of the present invention comprises a solution tank100to which a fluid from which gaseous and liquid pollutants are to be removed is supplied, a solution injector103for injecting a gaseous pollutant solution into the fluid to be treated in the solution tank100, and a liquid photocatalytic treatment device105in which the pollutants of the fluid are reacted with a photocatalyst and decomposed.

The solution tank100is provided with an inlet101through which the fluid to be treated is introduced and an outlet102through which the fluid, from which gaseous and liquid pollutants are decomposed and removed by the reaction with the photocatalyst, is discharged.

The solution tank100is a liquefaction treatment tank, in which the gaseous pollutants contained in the fluid supplied through the inlet101are liquefied, and the solution injector103is installed at the top of the inlet101.

The solution injector103comprises an injection nozzle, for example, and injects the gaseous pollutant solution into the fluid introduced through the inlet101from the top of the inlet101such that the gaseous pollutants of the fluid to be treated are in contact with the gaseous pollutant solution.

Thus, the gaseous pollutants of the fluid to be treated are dissolved and liquefied in the gaseous pollutant solution.

In certain embodiments, the gaseous pollutant solution is a liquid containing a compound which can produce OH radicals. In certain embodiments, the liquid is water. In other embodiments, the compound that produces OH radicals is hydrogen peroxide, dialkyl peroxide, alkyl aryl peroxide, diaryl peroxide, or dissolved oxygen. In certain embodiments, the gaseous pollutant solution is a liquid containing hydrogen peroxide or dissolved oxygen which can produce OH radicals.

In a further embodiment, the gaseous pollutant solution is oxygenated water or oxygen-enriched water. In certain embodiments, the oxygenated water comprises about 99.00 to about 99.99 wt % water and 0.01 to 1.00 wt % hydrogen peroxide. In certain embodiments, the oxygenated water comprises about 99.00 to about 99.25 wt % water and 0.75 to 1.00 wt % hydrogen peroxide. In certain embodiments, the oxygenated water comprises about 99.25 to about 99.50 wt % water and 0.50 to 0.75 wt % hydrogen peroxide. In certain embodiments, the oxygenated water comprises about 99.50 to about 99.75 wt % water and 0.25 to 0.50 wt % hydrogen peroxide. In certain embodiments, the oxygenated water comprises about 99.75 to about 99.99 wt % water and 0.01 to 0.25 wt % hydrogen peroxide.

In other embodiments, the oxygen-enriched water may contain 99.99 to 99.00 wt % water and 0.01 to 1.00 wt % dissolved oxygen. In certain embodiments, the oxygenated water comprises about 99.00 to about 99.25 wt % water and 0.75 to 1.00 wt % dissolved oxygen. In certain embodiments, the oxygenated water comprises about 99.25 to about 99.50 wt % water and 0.50 to 0.75 wt % dissolved oxygen. In certain embodiments, the oxygenated water comprises about 99.50 to about 99.75 wt % water and 0.25 to 0.50 wt % dissolved oxygen. In certain embodiments, the oxygenated water comprises about 99.75 to about 99.99 wt % water and 0.01 to 0.25 wt % dissolved oxygen.

In another embodiment, the OH radicals cause an additional oxidation reaction along with the oxidation reaction of the photocatalyst in the liquid photocatalytic treatment device. Moreover, when the hydrogen peroxide or dissolved oxygen of the gaseous pollutant solution produces OH radicals, the OH radicals act as electron acceptors of the photocatalyst to inhibit the recombination of electrons and holes produced. As a result, OH radical production is greatly increased by holes, which significantly promotes the oxidation reaction of the photocatalyst.

In various embodiments, a porous filler104is provided at the bottom of the solution injector103in the solution tank100.

The porous filler104is disposed between the solution injector103and the inlet101such that the gaseous pollutant solution injected from the solution injector103passes through the porous filler104before contacting the gaseous pollutants of the fluid to be treated, increasing the contact time between the gaseous pollutants of the fluid to be treated and the gaseous pollutant solution.

As the contact time between the gaseous pollutants of the fluid to be treated and the gaseous pollutant solution is increased by the porous filler104in the above-described manner, the dissolution efficiency of the gaseous pollutants is increased, thereby increasing the removal efficiency of the gaseous pollutants of the fluid to be treated.

In certain embodiments, the porous filler104comprises a typical filler material having a plurality of pores.

In another embodiment, the gaseous pollutant solution (in which the fluid to be treated is mixed and the gaseous pollutants of the fluid to be treated are dissolved) placed at the bottom of the solution tank100is treated by the liquid photocatalytic treatment device105to reduce the pollutants.

In certain embodiments, the liquid photocatalytic treatment device105is connected to the solution tank100through a pipe, etc. to receive the gaseous pollutant solution placed at the bottom of the solution tank100or may be mounted in the solution tank100to receive the solution at the bottom of the solution tank100.

Here, the gaseous pollutant solution introduced into the liquid photocatalytic treatment device105is a mixed solution of the gaseous pollutants dissolved and liquefied in the solution and the fluid introduced into the solution tank100.

As mentioned above, the liquid photocatalytic treatment device105is a type of pollutant removal device for decomposing the pollutants of the fluid to be treated by the reaction with the photocatalyst, and functions to decompose and reduce the gaseous pollutants of the fluid dissolved and liquefied in the gaseous pollutant solution, as well as the liquid pollutants of the fluid to be treated.

In the present invention, the liquid photocatalytic treatment device105may be any device capable of reducing the liquid pollutants of the fluid to be treated and may preferably be a liquid photocatalytic treatment device having a high efficiency as shown inFIG. 4.

The gaseous pollutant solution from which the pollutants are removed by the photocatalyst in the liquid photocatalytic treatment device105is circulated to the solution injector103by a circulation means.

The circulation means is interposed between the liquid photocatalytic treatment device105and the solution injector103and may comprise a circulation pump106connected to (an inlet of) the liquid photocatalytic treatment device105and circulates the gaseous pollutant solution by the operation of the pump and a pipe107, which is connected between the circulation pump106and the solution injector103.

The gaseous pollutant solution (mixed with the fluid to be treated) from which the pollutants are reduced, is circulated by the circulation means to be reused to dissolve the gaseous pollutants. As a result, it is possible to decompose a fluid newly introduced to be treated and, at the same time, to re-treat the fluid treated and, as the circulation process is performed several times (i.e., as the process of treating the fluid is repeatedly performed), it is possible to increase the reaction time for reducing the pollutants between the fluid and the photocatalyst, thereby increasing the removal efficiency of the pollutants of the fluid.

The gaseous pollutant solution from which the pollutants are sufficiently removed by the repeated pollutant removal treatment may be recovered through the outlet102of the solution tank100by the circulation means and discharged to the outside or may be treated by the liquid photocatalytic treatment device105and directly discharged to the outside through an outlet112of the liquid photocatalytic treatment device105.

Otherwise, after the gaseous pollutant solution from which the pollutants are sufficiently removed is treated by the liquid photocatalytic treatment device105to remove the pollutants, a portion of the gaseous pollutant solution may be discharged to the outside through the outlet112of the liquid photocatalytic treatment device105and the other portion may be recovered to the solution injector103of the solution tank100through the circulation means to be reused and re-treated.

Referring toFIGS. 4 and 5, the liquid photocatalytic treatment device105may comprise a photoreactive treatment tank110through which the fluid supplied through an inlet111passes through the inner space and is then discharged through the outlet112, a side-emitting optical fiber120fixed in the photoreactive treatment tank110by a support means, a photocatalyst (not shown) coated on the surface of the side-emitting optical fiber120, and a light source130for supplying light to the inside of the side-emitting optical fiber120such that light is emitted from the side of the optical fiber120.

The inlet111of the photoreactive treatment tank110is provided at one end and the outlet112is provided at the other end. A plurality of optical fibers120are arranged parallel to each other at regular intervals and fixed between the inlet111and the outlet112.

Preferably, a plurality of side-emitting optical fibers120are arranged at regular intervals in the photoreactive treatment tank110in such a manner that one end of each optical fiber is fixed toward the inlet111and the other end is fixed toward the outlet112.

A partial partition140is provided in the photoreactive treatment tank110as a support means for supporting the optical fibers120.

The partial partition140is arranged in a direction perpendicular to the longitudinal direction of the optical fibers120between the inlet111and the outlet112in the photoreactive treatment tank110. Preferably, a plurality of partial partitions140are arranged at regular interval in the longitudinal direction of the optical fibers120such that the optical fibers120are inserted and fixed through holes of the partial partitions140. As a result, the optical fibers120laterally penetrate the partial partitions140.

Here, one end of each partial partition140is fixed to one side of the photoreactive treatment tank110and the other end has an opening through which the fluid to be treated passes. Preferably, the openings of the partial partitions140are arranged alternately in the longitudinal direction of the optical fibers120such that a zigzag flow path is formed in the photoreactive treatment tank110.

As a result, the zigzag flow path is formed from the inlet111to the outlet112in the inner space of the photoreactive treatment tank110, and each partial partition140acts as a support means for supporting the optical fibers120, as a spacing means for spacing the optical fibers120, and as a flow path forming means for forming the flow path through which the fluid to be treated flows.

When the partial partitions140are arranged in a direction perpendicular to the longitudinal direction of the optical fibers120in the above-described manner, the fluid to be treated passes through the optical fibers120in a direction perpendicular to the longitudinal direction of the optical fibers120and moves along the zigzag flow path in the inner space of the photoreactive treatment tank110. Thus, it is possible to increase the flow path of the fluid under treatment and, at the same time, to make the best use of the large area of the optical fibers120, which increases the reaction time between the fluid under treatment and the photocatalyst, thereby maximizing the treatment efficiency.

Since the optical fibers120are arranged lengthwise between the inlet111and the outlet112, the fluid introduced through the inlet111sequentially passes through and makes contact with the photocatalyst-coated optical fibers120in the longitudinal direction, while flowing along the predetermined flow path in the photoreactive treatment tank110toward the outlet112, thereby maximizing the reaction area.

Next, a method for treating gaseous pollutants using the photocatalyst reactor in accordance with another preferred embodiment of the present invention will be described.

First, a fluid containing gaseous pollutants to be treated is supplied to a solution tank100. Before the fluid supplied to the solution tank100is introduced into a liquid photocatalytic treatment device105or at the same time when the fluid is introduced into the solution tank100, a gaseous pollutant solution is injected into the solution tank100using a solution injector103.

The gaseous pollutant solution injected into the solution tank100passes through a porous filler104before contacting the gaseous pollutants of the fluid to be treated, wherein the contact time between the injected gaseous pollutant solution and the gaseous pollutants of the fluid under treatment is increased such that the gaseous pollutants are efficiently dissolved and liquefied in the gaseous pollutant solution.

In such a step, the gaseous pollutant solution injected into the solution tank100comes into contact with the gaseous pollutants of the fluid to be treated such that the gaseous pollutants of the fluid are dissolved and liquefied.

The liquefied gaseous pollutants are mixed with the gaseous pollutant solution and the fluid to be treated and is introduced into the liquid photocatalytic treatment device105.

The liquid photocatalytic treatment device105decomposes the liquefied gaseous pollutants by allowing the gaseous pollutant solution (mixed with the liquefied gaseous pollutants and the fluid to be treated) fed from the solution tank100, to react with the photocatalyst, thereby removing the gaseous and liquid pollutants.

The gaseous pollutant solution (from which the pollutants are removed) discharged through an outlet of the liquid photocatalytic treatment device105may be recovered from the solution injector103through a circulation means and injected into another fluid to be treated introduced into the solution tank100, thereby liquefying the gaseous pollutants of the corresponding fluid.

The fluid, from which the gaseous and liquid pollutants are sufficiently removed by repeating the pollutant removal treatment, is discharged to the outside through the outlet112of the liquid photocatalytic treatment device105or through the discharge102of the solution tank100.

As described above, according to the photocatalytic reactor and the method for treating gaseous pollutants using the same of the present invention, it is possible to significantly increase the removal efficiency of pollutants, especially, gaseous pollutants, and thus it is possible to efficiently decompose and remove the gaseous non-biodegradable pollutants from the fluid having high flow rate and velocity as well as the liquid pollutants contained in the fluid.

The contents of all references (including literature references, issued patents, published patent applications, and co-pending patent applications) cited throughout this application are hereby expressly incorporated herein in their entireties by reference.