WO2006118369A1

WO2006118369A1 - Hybrid-type apparatus for treating exhaust gas having a condenser

Info

Publication number: WO2006118369A1
Application number: PCT/KR2005/003234
Authority: WO
Inventors: In Seob Lee; Hern Kim; Mi Hye Yang
Original assignee: Dai Sung Engineering Environment Co., Ltd.
Priority date: 2005-04-30
Filing date: 2005-09-29
Publication date: 2006-11-09
Also published as: KR100639261B1

Abstract

The present invention relates to an apparatus for treating exhaust gas exhausted from thermal installations such as a hazardous substance drying apparatus, a municipal solid waste incinerator and a furnace. The apparatus for treating exhaust gas according to the present invention comprises a wet scrubbing means for primarily scrubbing acid exhaust gas by spraying an alkaline chemical solution to the exhaust gas, a dry scrubbing means for secondly scrubbing the primarily-scrubbed exhaust gas by passing the exhaust gas through a simple bag filter or a bag filter to which a release agent and lime powder are supplied, to remove hazardous substances remaining in the exhaust gas, a condenser for condensing moisture remaining in the exhaust gas, which has passed through the dry scrubbing means, to remove malodor and volatile organic compounds, and a second blower for introducing external air into the condenser. In the apparatus for treating exhaust gas according to the present invention, there is no need for installation of an additional combustion system for preventing generation of malodor or white smoke, and a simple bag filter is used or a bag of the bag filter to which a non-plasterized releasing agent and chemical powder such as lime are sequentially attached is used semi-permanently. Thus, construction and maintenance costs of facilities can be reduced. Further, since an air-cooling type condenser is installed at the rear of the dry scrubbing means, generation of malodor and white smoke is prevented. Therefore, various kinds of hazardous exhaust gas can be completely scrubbed and then exhausted to the atmosphere.

Description

HYBRID-TYPE APPARATUS FOR TREATING EXHAUST GAS

HAVING A CONDENSER

Technical Field

[1] The present invention relates to an apparatus for treating exhaust gas exhausted from thermal installations such as a hazardous substance drying apparatus, a municipal solid waste incinerator and a furnace. More particularly, the present invention relates to a hybrid- type apparatus for treating exhaust gas, wherein an alkaline chemical solution is first sprayed to exhaust gas so as to neutralize the exhaust gas, the exhaust gas is secondly passed through a bag filter or a bag filter with a release agent layer and a chemical layer adhering thereto so as to remove residual hazardous substances of the exhaust gas, and the exhaust gas is thirdly passed through a condenser so as to remove white smoke and malodor. Background Art

[2] Exhaust gas generated from an incinerator for incinerating municipal solid wastes or industrial wastes contains hazardous substances such as dust, acid gases (HCl, SOx, NOx, HF, etc.), heavy metals (Hg, Cd, Pb, As, Zn, etc.), and dioxin. Furthermore, exhaust gas exhausted upon drying of food garbage or hazardous substances also contains a large amount of dust or noxious gases and malodorous fine dust. Particularly, exhaust gas generated upon drying of food garbage or hazardous substances contains volatile organic compounds (VOCs) that generate smog through photochemical reaction and are the cause of malodor.

[3] Conventional methods for treating such hazardous exhaust gas include a method in which an alkaline solution is sprayed to exhaust gas to remove dust therefrom or neutralize the exhaust gas in a wet process and the exhaust gas is incinerated in a de- odorization furnace, subsequently dehydrated to remove moisture therefrom and then exhausted, and a method in which a lime slurry is supplied to exhaust gas to neutralize the exhaust gas in a semi-dry process, the neutralized exhaust gas is passed through a bag filter to remove dust therefrom and then exhausted. In order to prevent generation of malodor and white smoke by removing VOCs, additional equipment for burning the VOCs using a catalyst may be installed at the rear of a scrubber.

[4] On the other hand, Korean Patent Application No. 10-2004-0093768 filed in the name of the applicant and entitled Hybrid-type apparatus for treating exhaust gas discloses a method and apparatus for treating exhaust gas by wet-scrubbing acid exhaust gas containing dust and directly passing the wet-scrubbed exhaust gas through a bag filter (hereinafter, a method for treating exhaust gas by wet-scrubbing acid exhaust gas containing dust and directly passing the wet-scrubbed exhaust gas through a bag filter is referred to as a hybrid-type method for treating exhaust gas ). Furthermore, Korean Patent Application No. 10-2005-0026074 filed in the name of the applicant and entitled Wet type apparatus for scrubbing exhaust gas discloses a wet scrubbing apparatus capable of improving the efficiency of removal of dust, mist, moisture, condensate and the like from exhaust gas and preventing generation of wastewater and clogging of spray nozzles in a scrubbing chamber. All technical contents of the exhaust gas scrubbing apparatuses disclosed in the aforementioned patent applications are incorporated herein as a part of the present invention.

[5]

Disclosure of Invention Technical Problem

[6] The present invention is conceived on an extension line of the aforementioned inventions of the Korean patent applications filed in the name of the applicant. An object of the present invention is to provide a hybrid-type apparatus for treating exhaust gas, wherein various kinds of hazardous exhaust gas can be completely scrubbed and then exhausted to the atmosphere. Particularly, an object of the prevent invention is to provide an apparatus for treating exhaust gas having a condenser, wherein VOCs or malodor can be removed and generation of white smoke can be prevented without installation of an additional catalytic combustion device. Furthermore, an object of the present invention is to provide a hybrid-type apparatus for treating exhaust gas, wherein releasing agent powder and chemical powder are supplied to a bag filter to completely remove hazardous substances of exhaust gas and the bag filter can be used semi-permanently, thereby improving economical efficiency due to low maintenance costs. Technical Solution

[7] A hybrid-type apparatus for treating exhaust gas according to the present invention comprises a wet scrubbing means including a wet scrubbing chamber that has an inlet through which exhaust gas is introduced, an outlet through which treated exhaust gas flows out, and a drain hole formed at a position in a side surface thereof spaced apart by a certain distance upwardly from the bottom thereof, and is disposed such that the exhaust gas introduced through the inlet horizontally flows toward the outlet, an eliminator that is disposed within the wet scrubbing chamber to divide the interior of the wet scrubbing chamber into an inlet-side space and an outlet-side space, has a plurality of bent blades arranged to form a passage for the exhaust gas, and is installed such that the bottom thereof is positioned below the drain hole, and a spray nozzle for spraying liquid into the inlet-side space of the wet scrubbing chamber; a dry scrubbing means including a duct having one end connected to the outlet of the wet scrubbing chamber, a bag filter connected to the other end of the duct, and a powder supply means connected to the duct so as to supply release agent powder and chemical powder to the bag filter through the duct; a condenser for receiving the exhaust gas exhausted from the bag filter and condensing moisture contained in the exhaust gas to remove the moisture therefrom; and a blower connected to the condenser to blow out the exhaust gas through a chimney, wherein the powder supply means supplies the release agent powder to the duct during operation of the blower to cause the release agent powder to adhere to a surface of a bag of the bag filter so as to form a release agent layer with a predetermined thickness and subsequently supplies the chemical powder to cause the chemical powder to adhere to a surface of the release agent layer so as to form a chemical layer with a predetermined thickness, and the spray nozzle sprays liquid into the wet scrubbing chamber, whereby the exhaust gas is primarily scrubbed in the wet scrubbing means, secondly scrubbed in the dry scrubbing means, thirdly passed through the condenser to remove the moisture, and then exhausted.

[8] The wet scrubbing means may further comprise an oil/water separation tank including a plurality of reservoirs to scrub liquid received from the drain hole by sequentially passing the liquid through the plurality of reservoirs; a concentrating tank for receiving sludge precipitated in the oil/water separation tank and concentrating the sludge therein; and a dehydrator for receiving the concentrated sludge from the concentrating tank, separating remaining liquid from the concentrated sludge, supplying the separated liquid to one of the reservoirs of the oil/water separation tank, and discharging a cake of sludge obtained through the separation of the remaining liquid. The spray nozzle may be installed to receive liquid from a final treatment reservoir of the reservoirs of the oil/water separation tank and to spray the liquid into the inlet-side space of the wet scrubbing chamber. Further, the wet scrubbing means may be adapted to supply an alkaline chemical to the oil/water separation tank to scrub acid exhaust gas. That is, the wet scrubbing means may further comprise a pH sensor installed at the oil/water separation tank; an alkali chemical storage tank; a chemical feed pump connected to the storage tank to feed an alkali chemical to the oil/water separation tank; and a controller for receiving a value measured by the pH sensor and supplying the chemical to the oil/water separation tank by operating the chemical feed pump if the measured value is in a predetermined range.

[9] Preferably, the bag filter includes a baffle installed between an inlet connected to the duct and the bag, and a rotary valve installed at a lower portion of the bag filter, the rotary valve includes a plurality of blades arranged at a predetermined interval along the circumference of the rotary valve, and the rotary valve is rotated at a predetermined speed to intermittently supply external air from the lower portion of the bag filter when the chemical spray means supplies the release agent powder and the chemical powder to the bag filter, so that the release agent powder and the chemical powder can uniformly adhere to the surface of the bag.

[10] Furthermore, the condenser preferably comprises a condensation chamber in which a plurality of cooling pipes are installed such that the exhaust gas supplied from the bag filter passes by the cooling pipes, and a second blower installed to suck external air and to cause the external air to pass by outer peripheries of the cooling pipes so that the external air can be exhausted together with the exhaust gas through the chimney.

[11] Moreover, it is preferred that the release agent comprise 90 to 99.5 wt% of porous expansion ceramic, 0.5 to 9 wt% of binder, and 0 to 1 wt% of thickener. The porous expansion ceramic is preferably prepared by calcining at least one rock component selected from the group consisting of obsidian, perlite, pitchstone, vermiculite, pumice and shale at a temperature range of 900 to l,600°C. Furthermore, lime or activated carbon powder may be used as the chemical powder. Brief Description of the Drawings

[12] Fig. 1 is a schematic view of a hybrid- type scrubbing apparatus having a condenser according to an embodiment of the present invention.

[13] Fig. 2 is a perspective view of an example of an eliminator used in the hybrid-type scrubbing apparatus having a condenser according to the present invention.

[14] Fig. 3 shows various arrangement states of spray nozzles and eliminators in the hybrid-type scrubbing apparatus having a condenser according to the present invention.

[15] Fig. 4 is a detailed view of a bag filter of a dry scrubbing means in the hybrid- type scrubbing apparatus having a condenser according to the present invention.

[16] <Brief Explanation of Reference Numerals in the Drawings>

[17] 10: Wet scrubbing chamber 11: Eliminator

[18] 20: Oil/water separation tank 50: Concentrating tank

[19] 70: Dehydrator 80: Chemical tank

[20] 81 : pH sensor 90: Bag filter

[21] 91 : B affle 95 : Releasing agent hopper

[22] 96: Lime hopper 100: Condenser

[23]

Best Mode for Carrying Out the Invention

[24] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[25] Fig. 1 is a schematic view of a hybrid-type scrubbing apparatus having a condenser according to an embodiment of the present invention. [26] The apparatus for scrubbing exhaust gas according to this embodiment comprises a wet scrubbing means A for primarily scrubbing acid exhaust gas by spraying an alkaline chemical solution to the exhaust gas; a dry scrubbing means B for secondly scrubbing the primarily scrubbed exhaust gas to remove hazardous substances remaining therein by passing the exhaust gas through a bag filter to which releasing agent and lime powder are supplied; a condenser C for scrubbing the exhaust gas, which has passed through the dry scrubbing means B, to malodor and VOCs by condensing moisture remaining in the exhaust gas; and a blower connected to the condenser C to blow out the exhaust gas through a chimney.

[27] The wet scrubbing means A comprises a wet scrubbing chamber 10 provided with an inlet 17 through which exhaust gas is introduced and an outlet 12 through which treated exhaust gas flows out; a pair of eliminators 11 disposed within the wet scrubbing chamber to divide the interior of the wet scrubbing chamber into an inlet- side space and an outlet-side space; an oil/water separation tank 20 comprising a plurality of reservoirs for scrubbing liquid containing dust and the like discharged from the wet scrubbing chamber 10; a concentrating tank 50 for concentrating sludge precipitated in the oil/water separation tank 20; and a dehydrator 70 for separating remaining liquid from the concentrated sludge. Furthermore, the wet scrubbing means A comprises spray nozzles 18 installed to spray liquid into the inlet-side space of the wet scrubbing chamber 10.

[28] An installation stand 14 is fixed at a lower portion of the wet scrubbing chamber 10 so as to install the eliminators such that the eliminators are spaced apart by a predetermined distance from the bottom of the wet scrubbing chamber. Furthermore, the wet scrubbing chamber 10 is disposed such that exhaust gas introduced into the wet scrubbing chamber through the inlet 17 flows horizontally toward the outlet 12, and the eliminators 11 are installed perpendicularly to the flow of the exhaust gas. Furthermore, a drain hole 13 for drainage of liquid collected on the bottom of the wet scrubbing chamber 10 is formed at a position on a side wall of the wet scrubbing chamber 10, which corresponds to a level higher than that of the bottoms of the eliminators 11. Furthermore, a drainpipe 15 for cleaning is connected to the bottom of the wet scrubbing chamber 10, and a valve 16 for closing the drainpipe 15 upon use of the wet scrubbing chamber is installed at the drainpipe 15.

[29] The eliminators 11 installed in the wet scrubbing chamber 10 are disposed within the wet scrubbing chamber 10 to divide the scrubbing chamber 10 into the inlet-side space and the outlet-side space. The eliminators 11 are installed such that the bottoms thereof are mounted on the installation stand 14 positioned below the drain hole 13 and side surfaces of the eliminators 11 except the bottoms thereof are in close contact with an inner surface of the wet scrubbing chamber 10. Therefore, moisture separated from exhaust gas, which passes through the eliminators 11, flows to and is collected at the lower portion of the wet scrubbing chamber 10, and the collected moisture is discharged to a first reservoir 20a of the oil/water separation tank 20 through a drainpipe 19 connected to the drain hole 13. Since the bottoms of the eliminators 11 are positioned below the drain hole 13, water or a chemical solution is always filled in a space between the bottoms of the eliminators 11 and the bottom of the wet scrubbing chamber 10 so that the exhaust gas cannot pass through the space. Therefore, the exhaust gas is exhausted through the outlet 12 in a state where moisture is always removed from the exhaust gas through the eliminators 11.

[30] Fig. 2 a perspective view of an example of an eliminator used in the hybrid-type scrubbing apparatus according to the present invention. Referring to Fig. 2, the eliminator 11 comprises an upper plate l la with handles installed thereon, a frame 1 Id for receiving a plurality of blades 1 Ib, a lower plate 1 Ic, and the plurality of blades 1 Ib installed at the upper plate l la and the lower plate 1 Ic. The plurality of blades 1 Ib are vertically disposed so that moisture or dust removed from the exhaust gas falls onto the bottom of the wet scrubbing chamber 10 by gravity. Furthermore, the respective blades 1 Ib are bent so that particulates can be removed by guiding a flow direction of the exhaust gas. Moreover, installation grooves 1 Ic-I in which the blades 1 Ib are installed are formed in the upper plate l la and the lower plate l ie.

[31] Fig. 3 shows various arrangement states of the spray nozzles and the eliminators in the hybrid-type scrubbing apparatus according to the present invention. The spray nozzles 18 may be installed (contrary to those shown in Fig. 1) such that a liquid spray direction of the spray nozzles faces in a downstream direction of the flow of exhaust gas (a direction designated by arrows) as shown in Fig. 3a, pairs of spray nozzles 18 may be installed such that spray directions thereof are opposite to each other as shown in Fig. 3b, or spray nozzles may be installed between the plurality of eliminators 11 as shown in Fig. 3c.

[32] Natural flow piping or a pump 40 for discharging the precipitated sludge is connected to the bottoms of the respective reservoirs of the oil/water separation tank 20. In case of the pump 40, the pump sucks the sludge and feeds it to the concentrating tank 50. The sludge concentrated in the concentrating tank 50 is sent to the dehydrator 70 through a pump 60 connected to a pipe 61. The dehydrator 70 separates remaining liquid from the sludge and sends it to the reservoir 2Of of the oil/water separation tank 20, and separately discharges a cake of sludge that is to be disposed of.

[33] For neutralization of acid exhaust gas, the wet scrubbing means A of this embodiment further comprises a device for spraying an alkaline solution through the spray nozzles 18 into the wet scrubbing chamber 10.

[34] In case of acid exhaust gas, the exhaust gas contains SOx, NOx, HCl, dioxin, and/or other hazardous substances. In order to treat the acid exhaust gas, the wet scrubbing means A neutralizes the acid exhaust gas by spraying an alkaline chemical into the wet scrubbing chamber, and passing the exhaust gas through the eliminators to remove moisture and dust from the exhaust gas. Although a calcium based (Ca(OH) , CaO and CaCO ) solution and a sodium based (NaHCO , NaOH and Na CO ) solution can be

3 3 2 3 used as the alkaline chemical, the sodium based solution is preferably used since upon use of the calcium based solution, a reaction product has low solubility as compared with the sodium based solution, resulting in formation of a great deal of scale in a reactor due to precipitation.

[35] If sodium hydroxide (NaOH) is used as a chemical in the wet treatment process, acid exhaust gas is neutralized according to the following reaction equations 1 to 4. Although sulfur dioxide or hydrogen chloride easily dissolved in water or an alkaline solution is easily removed in the wet treatment process, NO, dioxin and other hazardous gases that are not easily dissolved in water or an alkaline solution are hardly removed in the wet treatment process but exhausted as they are. Thus, there is a need for an additional treatment process. Dust is removed by inertial impaction with droplets of a sodium hydroxide solution sprayed from the nozzles in the wet scrubbing chamber or interception by particles of the droplets, and fine particles are removed while passing through the eliminators by colliding with the droplets due to diffusion resulting from Brownian movement, and other gravity, electrostatic force, and the like.

[36] [Reaction Equation 1]

[37] SO + 2NaOH => Na SO + H O

2 2 3 2

[38] [Reaction Equation 2]

[39] SO 2 + NaOH ^ NaHSO 3

[40] [Reaction Equation 3]

[41 ] HCl + 2NaOH => NaCl + H O

[42] [Reaction Equation 4]

[43] NO + 2NaOH + 1/20 2 => Na 2 (NO 3 ) 2

[44] The wet scrubbing means A of this embodiment comprises installations for injecting a controlled alkaline chemical such as sodium hydroxide (NaOH) so that a solution in the reservoir 2Of, which has been previously sprayed by the spray nozzles 18 to neutralize the acid exhaust gas and to remove hazardous particle substances such as dust contained in the exhaust gas, can be maintained at a proper pH value. That is, the wet scrubbing means further comprises a chemical storage tank 80 for storing an alkaline chemical therein, a pH sensor 81 installed in the reservoir 2Of of the oil/water separation tank 20, and a chemical feed pump 83 and pipes 82 and 84 for feeding the chemical stored in the chemical storage tank 80 to the reservoir 2Of. Moreover, although not shown in the figure, the wet scrubbing means further comprises a controller for receiving a value measured by the pH sensor 81 and supplying the chemical to the reservoir 2Of by operating the chemical feed pump if the measured value is in a predetermined range. Typically, a programmable logic controller (PLC) can be used as the controller. However, a general-purpose computer may be used as the controller.

[45] The wet scrubbing means A of this embodiment is constructed such that dust or moisture removed by the eliminators 11 fall into the first reservoir 20a of the oil/water separation tank 20 through the drain hole 13 of the wet scrubbing chamber 10. The oil/ water separation tank 20 comprises the plurality of reservoirs 20a to 2Of of which partitions walls are formed with penetration holes such that supernatant and subnatant alternately flow from one of the reservoirs to a neighboring reservoir through the penetration holes so as to precipitate sludge. Therefore, particles such as dust are all precipitated in intermediate reservoirs so that scrubbed clean supernatant can flow into the final reservoir 2Of. A pump 30 is connected to the final reservoir 2Of through a pipe 31, and the pump supplies a scrubbed solution to the spray nozzles 18 installed in the wet scrubbing chamber 10. Accordingly, the spray nozzles 18 are prevented from being clogged.

[46] Further, in the wet scrubbing means of this embodiment, the entire exhaust gas containing the sprayed moisture passes through the eliminators and is then exhausted through the outlet in a state where the moisture has been removed from the exhaust gas, thereby preventing excessive loss of moisture. Therefore, there is a little need for replenishment of a solution to be sprayed. Moreover, in the wet scrubbing means of this embodiment, clogging of the nozzles due to sludge is prevented by completely scrubbing the sludge in the oil/water separation tank. Further, since the sludge is separately concentrated and discharged in a form of a cake and a solution is circulated and then reused, wastewater is not discharged, resulting in a contribution to environmental conservation.

[47] Next, the dry scrubbing means B will be described. The dry scrubbing means B removes hazardous substances remaining in the exhaust gas while the exhaust gas is passed through a chemical layer and a releasing agent layer attached to the surface of a bag of a bag filter. In a case where the exhaust gas is not acid exhaust gas, the exhaust gas may be passed through a bag of the bag filter of which the surface has no releasing agent and chemical powder attached thereto. Lime powder, activated carbon powder, zeolite powder, diatomite powder or a mixture thereof obtained by mixing them at a proper mixing ratio can be used for the chemical layer according to the type and concentration of the exhaust gas. It is preferred that lime be used to scrub acid exhaust gas. The release agent layer formed of powder of a composition comprising porous expansion ceramic, a binder and a thickener is not solidified or plasterized on the surface of the bag even though the exhaust gas containing a large amount of moisture passes through the release agent layer. Therefore, even though the lime layer (chemical layer) for removing the hazardous components remaining in the exhaust gas is plasterized, application of pulsed air under high pressure within the bag allows the lime layer to be easily separated along with an outer lime layer of the bag. Accordingly, hazardous exhaust gas containing a large amount of moisture or sticky particulate matters can be filtered to collect dust from the exhaust gas, thereby scrubbing the exhaust gas.

[48] If a chemical layer formed of lime powder is used in the bag filter 90 of the dry scrubbing means B, acid exhaust gas is removed through neutralization according to the following reaction equations 5 to 9.

[49] [Reaction Equation 5]

[50] Ca(OH) 2 + SO 2 => CaSO 3 + H 2O

[51] [Reaction Equation 6]

4

[53] [Reaction Equation 7]

[54] Ca(OH)₂ + 4NO + 3O₂ => 2Ca(NO₃) + 2H₂O

[55] [Reaction Equation 8]

[56] Ca(OH)₂ + 2HCl => CaCl₂ + 2H₂O

[57] [Reaction Equation 9]

[58] Ca(OH) + 2HF => CaF + 2H O

[59] Furthermore, certain hazardous substances (HAPs) such as dioxin and heavy metals are collected and removed while passing through the lime layer, the release agent layer and the bag of the bag filter by means of inertial impaction, direct interception or diffusion in a state that some of the hazardous substances are adsorbed by the lime layer, and some of them are adsorbed by dust. In addition, some of the HAPs that are not removed through a reaction with the lime layer may be adsorbed and removed by activated carbon injected in front of the bag filter. Furthermore, if NaClO as an additive is injected in front of the bag filter to improve the efficiency of removal of NO, scrubbing treatment is performed according to the following reaction equations 10 and 11. Similarly to the exhaust gas passing through the wet scrubbing means A, dioxin and dust are removed by inertial impaction and interception while passing through the lime layer, the release agent layer and the bag, and fine particles are removed by diffusion due to Brownian movement, and other gravity, electrostatic force and the like.

[60] [Reaction Equation 10]

[61] 4NO + NaClO 2 + 2Ca(OH)2 => 2Ca(NO 2 )2 + NaCl + 2H 2O

[62] [Reaction Equation 11] [63] 2SO 2 + NaClO 2 + 2Ca(OH) 2 => 2CaSO 4 + NaCl + 2H 2 O

[64] The dry scrubbing means B of this embodiment comprises a duct 2 with one end connected to the outlet 12 of the wet scrubbing chamber 10, a bag filter 90 connected to the other end of the duct 2, and a powder supply means connected to the duct 2 to supply release agent powder and lime powder to the bag filter 90 through the duct 2. The powder supply means comprises a releasing agent hopper 95 for storing a releasing agent therein and a lime hopper 96 for storing lime therein. The respective hoppers are installed such that they are connected to the duct 2 to independently supply releasing agent powder and lime powder. Although not shown in the figures, it is preferred that screw conveyors for crushing and transferring powder be installed on pipes 97 and 98, respectively.

[65] Moreover, as shown in Fig. 4, the bag filter 90 comprises a plurality of bags 92 installed therein, and a baffle 91 installed between the bags 92 and an inlet with the duct 2 connected thereto. A release agent layer 92a and a lime layer 92b respectively formed of the release agent powder and lime powder supplied through the duct 2 adhere to each of the bags 92. It is preferred that the release agent powder be neutral, have a low specific gravity of 0.12 ton/D and a porosity of 85 to 95%, and be hardly plasterized even though moisture is absorbed into the release agent powder, and components thereof comprise silica (SiO ) as a drying/damp-proofing agent, alumina (Al O ) as an adsorbing/dehydrating agent, potassium oxide (K O) as a catalyst reacting with water, sodium oxide (Na O) as a reducer/catalyst, calcium oxide (CaO) as a moisture capturing/drying agent, and iron oxide (Fe O ) as a moisture adsorbent. The release agent comprising the aforementioned components preferably has the following composition: 69 to 79.5 wt% of silica, 10.9 to 17 wt% of alumina, 0.5 to 6.4 wt% of potassium oxide, 1.5 to 3.7 wt% of sodium oxide, 0.1 to 1.0 wt% of calcium oxide and 0.1 to 2.0 wt% of iron oxide. Further, the lime layer 92b is formed of a mixture of lime and at least one selected from activated carbon, silica gel, starch, bentonite, alumina, diatomite, zeolite, perlite, and ceramic powder according to air pollutants. Furthermore, since particles of the release agent powder are larger than those of lime powder as shown in Fig. 4, pores of the release agent layer 92a are larger than those of the lime layer 92b.

[66] In addition, a discharge port is formed at a lower portion of the bag filter 90 to drain the release agent and lime removed from the bags, and a rotary valve 93 is installed at the discharge port. The rotary valve 93 comprises a plurality of blades 93a formed at a predetermined interval along the circumference of the rotary valve 93, and discharges the release agent and lime removed in the bag filter to the outside by rotation of the plurality of blades 93a. Particularly, the rotary valve 93 and the baffle 91 enable uniform formation of the release agent layer 92a and the lime layer 92b when the blower 110 sucks air from the interior of the bag filter 90 to form a vacuum state therein and the release agent and the lime powder are sequentially supplied through the duct 2 to form the release agent layer 92a and the lime layer 92b in the bag 92. That is, when the release agent powder or the lime powder is sequentially supplied into the bag filter, the rotation of the rotary valve 93 at a constant speed allows the powder supplied to the lower portion of the bag filter due to the baffle 91 to be entrained by and raised along with external air intermittently supplied through a clearance C by means of the rotation of the rotary valve 93, so that the release agent powder or the lime powder can uniformly adhere to the plurality of bags 92. Reference numeral 93b designates a resin blade that adjusts a gap between a housing of the bag filter and the blade 93a and is installed to be simply exchanged when the blade 93b is worn out.

[67] Next, the condenser C will be described. The condenser C of this embodiment prevents generation of malodor and white smoke by condensing and removing moisture and impurities such as VOCs remaining in the exhaust gas that has passed through the bag filter 90. The condenser C comprises a condensation chamber 100, and a plurality of cooling pipes 101 installed in the condensation chamber 100 such that the exhaust gas passes by the cooling pipes 101. Furthermore, the condenser C comprises a second blower 106 for sucking external air and causing the external air to pass by outer peripheries of the cooling pipes and exhausting the external air together with the exhaust gas through the chimney. Although not shown in the figure, a filter for removing dust introduced from the outside is installed at an inlet pipe 102 through which the external air is introduced by the second blower 106, and an outlet pipe 105 is connected to the condensation chamber 100 such that the external air introduced into the condensation chamber 100 comes into contact with and passes by the outer peripheries of the cooling pipes 101 and is then exhausted through the chimney via the outlet pipe 105. A pipe 103 for discharging condensate is connected to a lower portion of the condensation chamber 100, and a valve 104 is installed on the pipe 103.

[68] Hereinafter, the operation of the apparatus for scrubbing exhaust gas according to this embodiment will be described.

[69] First, vacuum lower than the atmospheric pressure is formed in the condensation chamber 100 and the bag filter 90 by operating the blower 110 and the second blower 106 connected to the condensation chamber 100 to blow out exhaust gas to the outside through the chimney. Next, a predetermined amount of releasing agent powder is supplied to the duct 2 from the releasing agent hopper 95 to form the releasing agent layer 92a on the surface of the bag 92. Then, a predetermined amount of lime powder is supplied to the duct 2 from the lime hopper 96 to form the lime layer 92b on the releasing agent layer of the surface of the bag 92. At this time, the rotary valve 93 is simultaneously operated to intermittently supply external air into the bag filter through the clearances C between the housing of the bag filter and the blades 93a so that the powder can uniformly adhere to the surface of the bag 92. In addition, there is an advantage in that the rotation of the rotary valve 93 supplies the external air so that the supplied powder can fly upward, thereby causing all the supplied powder to adhere to the bag 92 of the bag filter 90.

[70] Next, the exhaust gas introduced into the wet scrubbing chamber 10 by the operation of the blower 110 is neutralized by reacting with a solution into which an alkaline chemical sprayed from the spray nozzles 18 is dissolved, according to the reaction equations 1 to 4. The neutralized exhaust gas passes through the eliminators 11 where dust or moisture is removed therefrom, and is then exhausted through the outlet 12. Dust, neutralized salts, moisture and condensate contained in the exhaust gas, which have been removed by the eliminators 11, are collected on the bottom of the wet scrubbing chamber 10. A solution with the chemical dissolved therein is always filled in the space between the bottoms of the eliminators 11 and the bottom of the wet scrubbing chamber 10 so that the exhaust gas cannot pass through the space. Therefore, the exhaust gas is exhausted through the outlet 12 in a state where dust or moisture is always removed from the exhaust gas through the eliminators 11. The moisture, which flows to and is collected on the bottom of the wet scrubbing chamber 10, is discharged to the first reservoir 20a of the oil/water separation tank 20 through the drainpipe 19 connected to the drain hole 13. Dust and reaction salts contained in the solution are precipitated onto the bottom of the oil/water separation tank 20 while the solution is sequentially scrubbed in the oil/water separation tank 20. Sludge precipitated onto the bottom of the oil/water separation tank 20 is sent to the concentrating tank 50 through the pump 40, and the sludge is concentrated in the concentrating tank. The concentrated sludge is dehydrated in the dehydrator 70, and a cake of sludge is then discharged and disposed of. Liquid collected through dehydration in the dehydrator 70 is sent to and reused in the oil/water separation tank 20. If a value measured by the pH sensor 81 installed at the oil/water separation tank 20 is out of a predetermined range, a controller (not shown) operates the pump 83 so that the chemical stored in the tank 80 can be supplied to the oil/water separation tank 20.

[71] The exhaust gas, which has been primarily scrubbed by the wet scrubbing means A and supplied to the bag filter 90 of the dry scrubbing means B is secondly scrubbed by passing through the lime layer 92b such that residual acid gas is neutralized and dust or other impurities are adsorbed onto the lime layer or trapped in pores of the lime layer 92b. If pressure loss in the filter 92 increases due to clogging of the pores of the release agent layer and the lime layer as the bag filter 90 is continuously used for exhaust gas treatment, high-pressure air is supplied into the bag 92 to separate the release agent layer and the lime layer from the bag. Since the release agent layer is not plasterized even though it absorbs moisture, the release agent layer is easily separated from the bag when the high-pressure air is applied in a pulse manner to the bag for the separation of the release agent layer. Therefore, the lime layer adhering to the release agent layer is also easily separated from the bag. Accordingly, when the bag is cleaned and a fresh release agent and lime are then caused to adhere to the bag as described above, the bag of the bag filter can be used semi-permanently. Since technical contents of a dedusting means for removing dust adhering to the bag 92 of the bag filter 90 are known in the art, detailed descriptions thereof will be omitted.

[72] Finally, residual impurities including fine dust and VOCs remaining in the exhaust gas, which has been secondly scrubbed in the dry scrubbing means B, are removed together with condensate while the exhaust gas passes through the condenser C, and the exhaust gas is then exhausted to the atmosphere through the chimney without generation of malodor and white smoke. Industrial Applicability

[73] According to the present invention, there is provided a hybrid-type apparatus for treating exhaust gas having a condenser, wherein exhaust gas containing hazardous substances is primarily neutralized by spraying an alkaline chemical solution to the exhaust gas, secondly passed through a simple bag filter or a bag filter to which a releasing agent layer and a chemical layer are attached to remove residual hazardous substances from the exhaust gas, and thirdly passed through the condenser to remove white smoke and malodor.

[74] In the scrubbing apparatus according to the present invention, the drain hole is formed at a position higher than the bottoms of the eliminators installed in the wet scrubbing chamber, so that moisture and dust of exhaust gas can be more efficiently removed. Furthermore, a solution containing the dust removed from the exhaust gas is scrubbed in the oil/water separation tank comprising a plurality of treatment reservoirs, thereby preventing the nozzles from being clogged. Furthermore, remaining liquid contained in sludge discharged from the oil/water separation tank is separated by the dehydrator and then reused. Thus, wastewater is not discharged, resulting in a contribution to environmental conservation.

[75] Further, in the scrubbing apparatus according to the present invention, primarily wet-scrubbed exhaust gas is subjected to secondary dry scrubbing by being supplied directly to a simple bag filter or a bag filter with a bag to which a non-plasterized releasing agent and chemical powder such as lime are sequentially attached, thereby effectively scrubbing the exhaust gas and simultaneously reducing construction and maintenance of facilities.

[76] Moreover, in the scrubbing apparatus according to the present invention, instead of an additional combustion device for preventing generation of malodor and white smoke, an air-cooling type condenser is installed at the rear of the dry scrubbing means to avoid the generation of malodor and white smoke, thereby enabling various kinds of hazardous exhaust gas to be completely scrubbed and exhausted to the atmosphere. [77] It should be understood that the technical spirit of the present invention is not limited to the embodiments of the present invention described above and illustrated in the drawings. The scope of the present invention should be defined only by the appended claims. It is apparent to those skilled in the art that various modifications and changes can be made thereto within the technical spirit of the invention. Therefore, the modifications and changes will fall within the scope of the present invention so long as they are apparent to those skilled in the art.

Claims

[1] A hybrid- type apparatus for treating exhaust gas having a condenser, the apparatus comprising: a wet scrubbing means including a wet scrubbing chamber having an inlet through which exhaust gas is introduced, an outlet through which treated exhaust gas flows out, and a drain hole formed at a position in a side surface thereof spaced apart by a certain distance upwardly from the bottom thereof, an eliminator disposed within the wet scrubbing chamber to divide the interior of the wet scrubbing chamber into an inlet-side space and an outlet-side space and having a plurality of bent blades arranged to form a passage for the exhaust gas, and a spray nozzle for spraying liquid into the inlet-side space of the wet scrubbing chamber, the wet scrubbing chamber being disposed such that the exhaust gas introduced through the inlet horizontally flows toward the outlet, the eliminator being installed such that the bottom thereof is positioned below the drain hole; a dry scrubbing means including a duct having one end connected to the outlet of the wet scrubbing chamber, and a bag filter connected to the other end of the duct; a condenser for receiving the exhaust gas exhausted from the bag filter and condensing moisture contained in the exhaust gas to remove the moisture therefrom; and a blower connected to the condenser to blow out the exhaust gas through a chimney, whereby the exhaust gas is primarily scrubbed in the wet scrubbing means, secondly scrubbed in the dry scrubbing means, thirdly passed through the condenser to remove the moisture, and then exhausted.

[2] The apparatus according to Claim 1, wherein the wet scrubbing means further comprises: an oil/water separation tank including a plurality of reservoirs to scrub liquid received from the drain hole by sequentially passing the liquid through the plurality of reservoirs; a concentrating tank for receiving sludge precipitated in the oil/water separation tank and concentrating the sludge therein; a dehydrator for receiving the concentrated sludge from the concentrating tank, separating remaining liquid from the concentrated sludge, supplying the separated liquid to one of the reservoirs of the oil/water separation tank, and discharging a cake of sludge obtained through the separation of the remaining liquid; a pH sensor installed at the oil/water separation tank; an alkali chemical storage tank; a chemical feed pump connected to the storage tank to feed an alkali chemical to the oil/water separation tank; and a controller for receiving a value measured by the pH sensor and supplying the chemical to the oil/water separation tank by operating the chemical feed pump if the measured value is in a predetermined range, and wherein the spray nozzle is installed to receive liquid from a final treatment reservoir of the reservoirs of the oil/water separation tank and to spray the liquid into the inlet-side space of the wet scrubbing chamber.

[3] The apparatus according to Claim 2, wherein the dry scrubbing means further includes a powder supply means connected to the duct connected to the bag filter so as to supply release agent powder and chemical powder to the bag filter through the duct, and the powder supply means supplies the release agent powder to the duct during operation of the blower to cause the release agent powder to adhere to a surface of a bag of the bag filter so as to form a release agent layer with a predetermined thickness and subsequently supplies the chemical powder to cause the chemical powder to adhere to a surface of the release agent layer so as to form a chemical layer with a predetermined thickness, whereby the exhaust gas is primarily scrubbed in the wet scrubbing means, secondly scrubbed in the dry scrubbing means, thirdly passed through the condenser to remove the moisture, and then exhausted.

[4] The apparatus according to Claim 3, wherein the bag filter includes a baffle installed between an inlet connected to the duct and the bag, and a rotary valve installed at a lower portion of the bag filter, the rotary valve includes a plurality of blades arranged at a predetermined interval along the circumference of the rotary valve, and the rotary valve is rotated at a predetermined speed to intermittently supply external air from the lower portion of the bag filter when the chemical spray means supplies the release agent powder and the chemical powder to the bag filter, so that the release agent powder and the chemical powder can uniformly adhere to the surface of the bag.

[5] The apparatus according to Claim 3 or 4, wherein the condenser comprises a condensation chamber in which a plurality of cooling pipes are installed such that the exhaust gas supplied from the bag filter passes by the cooling pipes, and a second blower installed to suck external air and to cause the external air to pass by outer peripheries of the cooling pipes so that the external air can be exhausted together with the exhaust gas through the chimney.

[6] The apparatus according to Claim 5, wherein the plurality of blades of the eliminator are vertically disposed such that moisture or dust removed from the exhaust gas falls onto the bottom of the wet scrubbing chamber by gravity.

[7] The apparatus according to Claim 6, wherein a plurality of eliminators are provided and installed to be spaced apart from one another at a predetermined interval, and a plurality of nozzles are provided and at least one of the nozzles is installed between the eliminators.

[8] The apparatus according to Claim 7, wherein the bag filter includes a baffle installed between an inlet connected to the duct and the bag, and a rotary valve installed at a lower portion of the bag filter, the rotary valve includes a plurality of blades arranged at a predetermined interval along the circumference of the rotary valve, and the rotary valve is rotated at a predetermined speed to intermittently supply external air from the lower portion of the bag filter when the chemical spray means supplies the release agent powder and the chemical powder to the bag filter, so that the release agent powder and the chemical powder can uniformly adhere to the surface of the bag.

[9] The apparatus according to any one of Claims 6 to 8, wherein the release agent comprises 90 to 99.5 wt% of porous expansion ceramic, 0.5 to 9 wt% of binder, and 0 to 1 wt% of thickener.

[10] The apparatus according to Claim 9, wherein the porous expansion ceramic is prepared by calcining at least one rock component selected from the group consisting of obsidian, perlite, pitchstone, vermiculite, pumice and shale at a temperature range of 900 to l,600°C.

[11] The apparatus according to Claim 9, wherein the chemical powder is lime powder.

[12] The apparatus according to Claim 11, wherein the chemical powder is powder of at least one selected from activated carbon, silica gel, starch, bentonite, alumina, diatomite, zeolite, perlite, and ceramic.