WO2007040318A1

WO2007040318A1 - Method of and apparatus for drying sludge

Info

Publication number: WO2007040318A1
Application number: PCT/KR2006/003889
Authority: WO
Inventors: Dea Sik Jang
Original assignee: Jeongwoo Ms Co., Ltd.
Priority date: 2005-10-04
Filing date: 2006-09-28
Publication date: 2007-04-12
Also published as: KR100539413B1

Abstract

Disclosed are a method of and an apparatus for drying sludge. Sludge to be dried is supplied into one ends of a plurality of screws, which are disposed in parallel one after another such that pitches of rotary blades are off-set from one another. The screws are rotated such that the sludge is transferred to the other ends of the screws by means of the rotary blades of the screws. Magnetrons are disposed at certain predetermined intervals along the transferring direction of the sludge and operated such that microwave acts towards the screw. Fore infrared lamps are disposed between the magnetrons one after another and operated such that fore infrared rays act toward the screw, wherein the sludge is heated and dried by means of the microwave and for infrared rays while the sludge is crushed, stirred and transferred by means of the plurality of crews. The sludge drying apparatus includes a frame, a chamber, multiple crews, magnetrons and fore infrared lamps. Separate components such as crusher or stirrer are not necessitated to provide a relatively simplified structure. Further, the treating efficiency can be further improved and maintenance cost can be reduced, as compared with the conventional techniques.

Description

METHOD OF AND APPARATUS FOR DRYING SLUDGE

Technical Field

[1] The present invention relates to a method of and an apparatus for drying sludge.

More specifically, the invention relates to a method of and an apparatus for drying sludge, in which wet-sludge such as industrial waste, household waste, livestock waste and the like can be dried and treated. Background Art

[2] In recent years, treatment of waste containing moisture (hereinafter, referred to as

"sludge"), among other wastes produced from various fields, takes an increasing interest. Such sludge includes foul waste water from foul and waste water treating facilities, highly-wet waste from industries such as food and paper factories, food waste from households, livestock feces and urines from livestock farms. Typically the sludge contains moisture of up to 80%. Therefore, in general, such sludge is not treated through incinerating facilities, but through landfilling. However, the sludge treatment through landfilling has risen some problems such that secondary contamination of underground water or the like due to extraction water, ground weakening, securing of landfills, and the like. Thus, an alternative technology is needed.

[3] Therefore, in order to solve the above problems, many technologies for treating sludge have been proposed and filed for patents. For example, Korean Patent Laid- Open publication No. 2002-0005917 discloses a multi-step screw drying apparatus, in which multiple drying drums having screws are disposed in parallel adjacent to each other. Materials to be dried are charged into the uppermost drying drum, continuously transferred downwards, and discharged through the lowermost drying drum. Hot air is injected into the lowermost drying drum, continuously flown upwardly, and exhausted through the uppermost drying drum.

[4] In addition, Korean Patent Registration Publication No. 10-0407828 discloses a moisture drying method using infrared and high-frequency, in which a conveyor belt is rotatably installed. A magnet is installed at the upper side of the inlet of the conveyor belt to remove metallic foreign matters contained in charged sludge or food waste. Anode and cathode plates of a high-frequency generator are installed at the upper side of the conveyor belt to apply high-temperature heat to the sludge or food waste. A ventilator for discharging vapor generated by heating is installed in a drying container. A infrared drying furnace is provided, where infrared rays are radiated at the sludge or food waste passing through a discharge hole.

[5] Korean Utility Model Registration No. 20-0280671 proposes a waste drying apparatus associated with a waste incinerator. A driving means as a power source and a burner as a heating source are installed at both sides of a housing respectively. A waste charge hopper and a crusher are disposed on top of the housing. A drying chamber is provided for drying wasted being charged through the charge hopper and removing moisture. The drying chamber is provided with a screw conveyor, which is rotated by a driving means to transfer waste. A passageway and a gate are provided for discharging dried waste to outside or transferring it to an incinerator. The waste within the drying chamber is dried using waste heat of gas discharged from the incinerator. Korean Patent Laid-Open Publication No. 2003-0079397 discloses a food waste and livestock waste drying apparatus. This apparatus is composed of a heating device, which includes a plurality of spaces having a spiral shape, a rotating blade having a protrusion for rotating food waste into the space, a heating plate fixed onto a second fixing frame and having a hole formed at the center and one side thereof, a fore infrared lamp fixed onto a first fixing frame and generating radiant heat, and a bracket supporting the fore infrared lamp. Disclosure of Invention Technical Problem

[6] As described above, the conventional methods and apparatuses proposed for treating sludge in a dry mode use a conveyor belt or screw and various heat sources to perform a drying process while transferring sludge.

[7] With these conventional techniques, however, a thermal efficiency is low and thus the cost for drying sludge is high. Much time is consumed, as compared with incinerating methods. In addition, these conventional methods and apparatuses do not provide proper measures for dust or noise generated when treating sludge. For example, Korean Patent Laid-Open Publication No. 2002-0005917 "multi-step screw drying apparatus" and Korean Utility Model Registration No. 20-0280671 "waste drying apparatus associated with a waste incinerator" have proposed a sludge-drying technique using a multi-stage screw and hot air (or as a heat source using convection heat and waste heat of an incinerating furnace). However, these approaches consumes much time in drying sludge containing moisture of even less than 60%, and have a lower treating efficiency and a higher maintenance cost. In addition, with Korean Patent Laid-Open Publication No. 2003-0079397 "food waste and livestock waste drying apparatus", a rotary blade is installed in a treating apparatus of layered structure such that sludge is transferred from the upper layer to the lower layer, and a heating plate and a fore infrared lamp are used as a heat source to dry sludge through radiant heat and reflective heat. With this approach, however, the structure of apparatus becomes complicated, sludge crushing must be separately performed, and the sludge is dried at stacked state, so that the amount of treated sludge is limited, thereby leading to a low treating efficiency and high maintenance cost, similar to the before-mentioned apparatus. In addition, the "moisture drying method using infrared and high-frequency" disclosed in Korean Patent Registration No. 10-0407828 uses a high-frequency wave and a conveyor belt to dry sludge while transferring the sludge and radiating infrared rays at the discharge side. In such a method, however, similar to the aforementioned examples, the sludge crushing is separately carried out and the amount of treated sludge is limited, thereby resulting in a low treating efficiency and a high maintenance cost.

[8] As describe above, the conventional sludge drying methods and apparatuses do not provide a high thermal efficiency and a good practicality. In particular, when screws are involved, the sludge transfer is rarely performed so that sludge being transferred along the inner side can be hardly dried. That is, usually a sludge drying apparatus using a screw has been expected for sludge to be transferred and simultaneously crushed by means of the screw. In practice, however, the crushing process hardly occurs. Sludge being transferred along the surface is dried, but not in the inner side, consequently over load is exerted on the screw. Technical Solution

[9] Accordingly, the present invention has been made in view of the above-mentioned problems occurring in the prior art, and it is an object of the invention to provides a sludge drying method and apparatus, in which sludge is more efficiently treated, as compared with the conventional ones, to improve treating efficiency, and a relatively simplified structure is employed to reduce initial investment and maintenance cost.

[10] The sludge drying apparatus comprises a chamber having a closed internal space. A plurality of screws are disposed in parallel one after another across the chamber such that pitches of rotary blades are off-set from one another. Thus, sludge is crushed and stirred simultaneously while being transferred from one end to the other end, thereby enabling to efficiently avoid the improper transfer and drying of sludge, which may occur due to differently drying between the surface and inside of the sludge. Separate components such as crusher or stirrer are not necessitated to provide a relatively simplified structure.

[11] Particularly, the screw of the invention is configured such that sludge transfer is increased at the front portion of the screw to which the sludge is charged, and from the intermediate portion thereof the sludge is stirred and crushed through a mixing plate according to the degree of sludge-drying, thereby causing the sludge to be effectively dried in its surface and inside portions while being smoothly transferred. In addition, magnetrons are continuously installed along the sludge-transferring direction and fore infrared lamps are installed between the magnetrons. Thus, fore infrared rays remove surface moisture, which causes problems in case of application of microwave, so that its thermal efficiency can be maximized, thereby further improving the treating efficiency and reducing maintenance cost, as compared with the conventional techniques. Advantageous Effects

[12] According to the sludge drying method and apparatus, a chamber is provided to have a closed internal space. A plurality of screws are disposed in parallel one after another across the chamber such that pitches of rotary blades are off-set from one another. Thus, sludge is crushed and stirred simultaneously while being transferred from one end to the other end, thereby enabling to efficiently avoid the improper transfer and drying of sludge, which may occur due to differently drying between the surface and inside of the sludge. Separate components such as crusher or stirrer are not necessitated to provide a relatively simplified structure. In particular, the screw of the invention is configured such that sludge transfer is increased at the front portion of the screw to which the sludge is charged, and from the intermediate portion thereof the sludge is stirred and crushed through a mixing plate according to the degree of sludge- drying, thereby causing the sludge to be effectively dried in its surface and inside portions while being smoothly transferred. In addition, magnetrons are continuously installed along the sludge-transferring direction and fore infrared lamps are installed between the magnetrons. Thus, fore infrared rays remove surface moisture, which causes problems in case of application of microwave, so that its thermal efficiency can be maximized, thereby further improving the treating efficiency and reducing maintenance cost, as compared with the conventional techniques. Brief Description of the Drawings

[13] FlG. 1 explains the technical concept of a sludge drying method and apparatus according to the present invention.

[14] FlG. 2 is an elevational view of a sludge drying apparatus according to a preferred embodiment of the invention.

[15] FlG. 3 is a side view of the sludge drying apparatus of FlG. 2.

[16] FIGS. 4 to 6 show details of the chamber in a sludge drying apparatus according to a preferred embodiment of the invention.

[17] FlG. 7 explains details of the screws in a sludge drying apparatus according to a preferred embodiment of the invention.

[18] FlG. 8 explains details of the screw installed in the upper chamber of a sludge drying apparatus according to a preferred embodiment of the invention.

[19] FlG. 9 explains details of the fore infrared lamp in a sludge drying apparatus according to a preferred embodiment of the invention. Best Mode for Carrying Out the Invention

[20] FlG. 1 shows the technical concept of a sludge drying method and apparatus according to the present invention.

[21] Referring to FlG. 1, the sludge drying method according to the present invention is configured such that sludge (wet-sludge) is supplied at one ends of multiple screws 40 arranged in parallel and transferred to the other ends of the screws 40 by rotation of the screws 40. Each screw 40 is provided with a rotary blade 44, the pitch of which is offset from those of rotary blades of adjacent screws 40. Magnetrons 70 are installed at regular intervals along the sludge transferring direction. The magnetron 70 is operated such that microwave is exerted in the direction of screw 40. Fore infrared lamps 80 installed between the magnetrons 70 operate such that fore infrared rays are exerted in the screw 40 direction.

[22] In the sludge drying method as described above, a wet-sludge is heated to be dried using fore infrared rays while crushing, stirring and transferring through a plurality of screws 40, which is installed such that pitches of the rotary blades 44 are off-set to one another, thereby forming a dried sludge.

[23] Referring to FlG. 1 again, the sludge drying apparatus 10 of the invention includes a frame 12 (see FlG. 2), a chamber 20, a plurality of screws 40, a magnetron 70 and a fore infrared lamp 80. As shown in FlG. 2, the frame 12 is a skeleton structure constructed of various rods, panels, profiles and the like, and supports various components constituting the sludge drying apparatus 10. Therefore, such frame 12 may be formed in various ways, depending upon the structure of the sludge drying apparatus 10. In addition, the sludge drying apparatus 10 is provided with a control unit 110, which controls various components such that the sludge drying process can be carried out in an automatic or semi-automatic mode. The control unit may employ electronic or hydraulic and pneumatic control and can control the whole apparatus using a PLC or computer.

[24] The chamber 20 is supported on the frame 12, and has a horizontally fluidically communicated internal space 22. The chamber 20 is provided at its front end with a charge hopper 50 for supplying sludge to be dried and at its rear end with a discharge hopper for discharging dried sludge. Such a chamber 20 forms a closed space where the sludge drying process can be performed, and in general is constructed by welding stainless panels or connecting the stainless panels using bolts and nuts. Of course, the chamber 20 may be constructed in the same way as in the preferred embodiment, which will be explained later.

[25] The sludge drying apparatus of the invention employs a plurality of screws 40. Of course, the sludge drying apparatus may employ a single screw in case of a small capacity of treatment. However, in order that crushing and stirring of sludge can be smoothly carried out while transferring the sludge, two or more screws 40 are disposed in parallel so that the sludge can be efficiently transferred through between the two screws 40. Such a screw 40 is supported in such a manner that its shaft is rotatably supported at both ends of the chamber 20. In addition, the screws 40a, 40b, 40c and 4Od are disposed in parallel one after another such that the pitches of rotary blades 44 are off-set from one another. The screw 40 is horizontally disposed in the internal space 22 and rotated by means of a driving unit 50, which is installed outside of the chamber 20.

[26] As described above, in the sludge drying apparatus 10 according to an embodiment of the invention, the screws 40a, 40b, 40c and 4Od are designed such that their rotary blades 44 are off-set from neighboring blades so as to be crossed with each other. Thus, sludge supplied through the charge hopper 60 is transferred along the rotary blade 44 towards the discharge hopper 62 while the sludge is crushed and stirred.

[27] The magnetron 70 operates such that microwave generated from a microwave generator 72 is exerted in the screw direction. That is, the magnetron 70 is disposed in the upper portion of the chamber 20 one after another in the horizontal direction of the chamber 20 such that the microwave is exerted towards the internal space 22 where the screw 40 is installed. The fore infrared lamp 80 is disposed in the upper portion of the chamber 20 one after another in the horizontal direction of the chamber 20 such that fore infrared rays are exerted towards the screw 40.

[28] On the other hand, the sludge drying method and apparatus of the invention may be further provided with an exhaust unit 90 and an exhaust gas inlet passage 92 to maximize heat efficiency. That is, the sludge drying apparatus 10 of the invention is operated at a high temperature of around 600 C during the sludge drying process. During this course of process, hot exhaust gas generated is flown into the inside of the chamber 20 to be used as an auxiliary heat source. This technological construction, by which exhaust gas is flown again inside of the chamber 20 and used as an auxiliary heat source, may be achieved by the preferred embodiment of the invention, which will be hereafter explained. In addition, the sludge drying method and apparatus of the invention may be provided with a hot air supply unit 100, through which a heated dry air (hot dry air) of high temperature and high pressure can is supplied into the internal space 22 of the chamber 20 to thereby maximize the efficiency of drying. The hot air being supplied into the internal space 22 of the chamber 20 is co-operated with the afore-mentioned microwave and fore infrared rays to further improve drying efficiency.

[29] Hereinafter, preferred embodiments of the invention will be explained in details, with reference to the accompanying FIGS. 2 to 8. In FIGS. 1 to 9, components performing a same function are denoted by a same reference numeral. On the other hand, each figure omits or provides a brief explanation for common sludge drying techniques, which is considered as an easy appreciation for those skilled in the art, but focuses on details related to the present invention. In addition, in those figures, assembled components and connected components shows different shapes and dements, which are only for the purpose of convenient illustration and explanation of the invention and not to be construed as limiting the technical spirit of the invention.

[30] FlG. 2 is an elevational view of a sludge drying apparatus according to a preferred embodiment of the invention. FlG. 3 is a side view of the sludge drying apparatus of FlG. 2. FIGS. 4 to 6 show details of the chamber in a sludge drying apparatus according to a preferred embodiment of the invention. FlG. 7 explains details of the screws in a sludge drying apparatus according to a preferred embodiment of the invention. FlG. 8 explains details of the screw installed in the upper chamber of a sludge drying apparatus according to a preferred embodiment of the invention. FlG. 9 explains details of the fore infrared lamp in a sludge drying apparatus according to a preferred embodiment of the invention. Here, FIGS. 2 and 3 depict the sludge drying apparatus of this embodiment such that feature components thereof can be viewed.

[31] Referring to FIGS. 2 and 3, in order to treating sludge containing relatively high moisture of up to 80%, the sludge drying apparatus 10 according to a preferred embodiment of the invention includes a multi-stage frame 12 (three-stage frame in this embodiment), chambers 20, 20' and 20" installed in each stage of the frame 12, screws 40, 40 and 40 in each chamber 20, a magnetron 70 and a fore infrared lamp 80.

[32] The frame 12 according to this embodiment is designed to enable to adjust hori- zontality with respect to the ground and stably support various elements including the chambers 20, 20' and 20". In addition, although not illustrated, in case where the entire height of the sludge drying apparatus 10 increases, a railing is further provided along the periphery of the apparatus for easy maintenance.

[33] The sludge drying apparatus of this embodiment includes three chambers 20, which are disposed one on top of another. Sludge is supplied from the outside through a charge hopper 60 installed at the left end portion of the upper chamber 20. Although not illustrated, the sludge may be supplied through the charge hopper 60 using various types of conveyors and suppliers. Thus, the three chambers 20, 20' and 20" are connected through intermediate hoppers 64 and 66. Thus, the sludge is supplied through the charge hopper 60 into one end of the upper chamber 20 and transferred into the other end of the upper chamber 20. Then, the sludge is flown into one end of the intermediate chamber 20 through the intermediate hopper 64 and transferred to the other end of the intermediate chamber 20'. Thereafter, the sludge is introduced into one end of the lower chamber 20 through the intermediate hopper 66 and discharged to the outside through the discharge hopper 62. The dried sludge, discharged through the discharge hopper 62 to the outside, is stored in a storage container.

[34] As described above, the chambers 20, 20' and 20" are structured as shown in FIGS.

4 and 5. That is, referring to FIGS. 2 to 6, the chambers 20, 20' and 20" is basically supported on a frame 12 so as to have an internal space 22 horizontally fluidically communicated. At this time, each chamber 20, 20 and 20 includes a lower case 24, an upper case 26 and a partition plate 30. The lower case 24 forms the lower side of the chamber 20, 20' and 20". The upper case 26 is combined to the upper portion of the lower case 24 to form an internal space 22 with the lower case 24 while forming the upper side of the chamber 20, 20' and 20". As shown in FIGS. 4 to 5, the partition plate 30 is disposed inwards of the lower case 24 in horizontal direction to form the bottom of the internals space 22 and form a sub-space 23 at the lower side of the internal space 22. Thus, exhaust gas (180~200°C) generated during the sludge drying process in the internal space 22 is supplied into the sub-space 23 formed by the partition plate 30 using an exhaust unit 90 having a blower and so on. The exhaust gas is used as a heat source for heating the internal space 22, where the sludge drying process is carried out.

[35] Further, in the sludge drying apparatus 10 of this embodiment, a bottom prominence 32 is installed on the partition plate 30 and a lateral prominence 38 is installed at both side walls of the lower case 24. In this embodiment, the partition plate 30 is extended in lateral direction and the lateral prominence 38 is installed at the upper side of the extended side face. Referring to FlG. 5, the bottom prominence 32 is formed between the screws 40a and 40b, 40b and 40c, and 40c and 4Od so as to be protruded towards the internal space 22 while not being interfered with the screws. The lateral prominence 38 is formed at the upper portion of both inner side walls of the lower case 24 so as to be inwardly protruded while not being interfered with the screws 40a and 4Od. Such bottom and lateral prominences are for enabling smooth transportation of sludge. That is, the sludge being transferred by means of the rotary blade 44 of the screw 40 can be smoothly performed, without being stagnant or blocked.

[36] On the other hand, in this embodiment, the bottom prominence 32 is provided with a hot-air passage 37 horizontally formed along the longitudinal direction of the screw 40. A crevice 34 is formed at regular internals between the bottom prominence 32 and the partition plate 30 such that the internal space 22 and the hot-air passage 37 are fluidically communicated through the crevice 34. In this embodiment, an angle constituting the bottom prominence 32 is welded onto a stainless plate to form the bottom prominence 32 and the crevice 34 in the partition plate 30. The crevice 34 is formed by forming a welding point 36 at regular intervals during the welding of the bottom prominence 32. With the above-constructed bottom prominence 32, a hot-air supply unit 100 (see FlG. 1) having a blower and the like supplies a dried hot-air of high temperature and pressure into the hot-air passage 37. This hot-air is flown into the internal space 22 through the crevice 34 to thereby further improve the efficiency of drying. Although the figures of this embodiment do not illustrate the structure for supplying hot-air, the hot-air supply into the hot-air passage can be achieved in various ways.

[37] The external faces of the above-constructed chambers 20, 20' and 20" are finished with a separate cover 28.

[38] The sludge drying apparatus 10 according to this embodiment includes four screws

40a, 40b, 40c and 4Od in each chamber 20, 20' and 20". These screws 40a, 40b, 40c and 4Od are combined in such a way that their shafts 42 are rotatably supported on both ends of the chamber 20. As shown in FlG. 6, neighboring screws 40a and 40b, 40b and 40c, and 40c and 4Od are disposed in parallel one after another in such a manner that the pitches of their rotary blades 44 are off-set from one another. As shown in FlG. 2, the screws 40, 40 and 40 installed in each chamber 20, 20' and 20" are horizontally disposed in the internal space 22 so as to fit the length of each chamber 20, 20' and 20". The screws are rotated by means of a motor 52 installed outside, so that the sludge supplied through the charge hopper 60 is transferred towards the discharge hopper 62 while being stirred and crushed. In the sludge drying apparatus 10 of this embodiment, each screw 40, 40', 40" is operated by means of a driving unit especially designed, to thereby simplify its driving structure. That is, as shown in FIGS. 2 and 3, in this embodiment, the driving unit 50 (see FlG. 1) is installed in such a way to be placed at one end of each of four screws 40a, 40b, 40c and 4Od. The driving unit 50 includes a motor connected with any one of the four screws 40a, 40b, 40c and 4Od through a chain 55, 55 to transfer its driving force, and a gear 58 connected to other end of the four screws 40a, 40b, 40c and 4Od respectively and engaged with each other. That is, a drive sprocket 54, 54 is installed in the motor and a driven sprocket 56, 56 is installed in one end of any one of the four screws 40a, 40b, 40c, and 4Od, such that the driving force of the motor 52 is transferred through the chain 55 and 55'. In addition, the other end of the screw 40 is engaged by means of a gear 59 such as a spur gear or the like such that a same rotation speed can be achieved on the whole. At this time, unexplained reference numeral 51 denotes a motor support frame to be combined to the frame 12 and thus support the motor 52.

[39] On the other hand, installed in the screw 40 (installed in the upper chamber 20 in this embodiment) is a mixing plate 46, 46', which is increased more and more towards the rear section. This technical feature of the invention is for preventing the problem that, if sludge containing a large amount of moisture and thus having a high viscosity is stirred and crushed at the earlier stage, the charged sludge may be over-flown towards the upstream of the screw 40. Thus, when the surface of the sludge is dried more or less, the stirring and crushing operation is progressively applied, to thereby achieve efficient drying while smoothly transferring the sludge. Referring to FIGS. 1 and 8, such a screw 40 includes a front section nearing to the charge hopper 60, a rear section nearing to the discharge hopper 62, and an intermediate section between the front and rear sections. In the intermediate section, the screw 40 is provided with a first mixing plate 46 installed one after another at regular intervals so as to be protruded in one direction horizontally with the pitch direction of the screw 40. In the rear section, a second mixing plate 46 is installed at certain predetermined intervals in both directions horizontally with the pitch direction of the screw 40.

[40] The above-constructed sludge drying apparatus 10 of this embodiment is provided with a magnetron 70 and a fore infrared lamp 80 to enable to dry sludge efficiently.

[41] The magnetron 70 makes microwave from the microwave generator 72 to be exerted towards the screws. That is, the magnetron 70 is installed horizontally one after another in the upper portion of the chamber 20 such that the microwave is exerted towards the internal space 22 where the screw 40 is installed. In particular, in this embodiment, as shown in FIGS. 2 and 3, in order that the microwave acts on the sludge efficiently, a waveguide 74 is installed and the shape of the upper case 26 is made so as to correspond to the advancing direction of the microwave, thereby maximize the efficiency of the microwave.

[42] The fore infrared lamp 80 is disposed horizontally one after another in the upper side of the chamber 20 such that fore infrared rays are directed towards the screws 40. In particular, the fore infrared lamp 80 is disposed between the magnetrons 70 so as not to be interfered with the magnetrons 70, to thereby prevent damage of the fore infrared lamp 80 and not to block traveling of the microwave. Furthermore, in the sludge drying apparatus 10 of this embodiment, as shown in FlG. 9, the fore infrared lamp 80 is formed in a way that a fore infrared heating element 82 is inserted into a transparent quartz tube 84 and the upper outer circumference is finished with a plating 86 for fore infrared rays to be directed downwardly. In this way, the direction of fore infrared rays can be controlled and possible damage of the fore infrared heating element 82 by the microwave can be prevented.

[43] While the present invention has been described with reference to several preferred embodiments, the description is illustrative of the invention and is not to be construed as limiting the invention. Various modifications and variations may occur to those skilled in the art, without departing from the scope and spirit of the invention, as defined by the appended claims. Mode for the Invention [44] According to one aspect of the invention, there is provided a method of drying sludge. The method of the invention comprises: supplying sludge to be dried into one ends of a plurality of screws, which are disposed in parallel one after another such that pitches of rotary blades are off-set from one another, and rotating the screws such that the sludge is transferred to the other ends of the screws by means of the rotary blades of the screws; operating magnetrons disposed at certain predetermined intervals along the transferring direction of the sludge such that microwave acts towards the screws; and operating fore infrared lamps disposed between the magnetrons one after another such that fore infrared rays act toward the screws, wherein the sludge is heated and dried by means of the microwave and for infrared rays while the sludge is crushed, stirred and transferred by means of the plurality of crews.

[45] In the above method, exhaust gas generated during drying of the sludge is re-flown into a sub-space formed at lower side of an internal space where the screw is installed, such that the exhaust gas serves as an auxiliary heat source for heating the internal space, and dried hot-air of high-pressure and high-temperature flows through a hot-air passage, which is formed at lower side of the internal space and between the screws, and fluidically communicated with the internal space through a crevice.

[46] According to another aspect of the invention, there is provided an apparatus for drying sludge. The apparatus of the invention comprises: a frame; a chamber supported on the frame, the chamber including an internal space horizontally fluidically communicated, the chamber being provided at its front end with a charge hopper for supplying sludge to be dried and at its rear end with a discharge hopper for discharging dried sludge; a plurality of screws rotatably supported at both ends of the chamber and having a rotary blade, the crews being disposed in parallel one after another such that pitches of the blades are off-set from one another, the screws being installed horizontally in the internal space of the chamber such that sludge supplied through the charge hopper is transferred along the blade towards the discharge hopper, the screws being rotated by a driving unit installed outside of the chamber; a plurality of magnetrons disposed at the upper side of the chamber horizontally one after another such that microwave acts towards the internal space where the screw is installed; and a plurality of fore infrared lamps disposed at upper side of the chamber horizontally one after another such that fore infrared rays act towards the screw.

[47] The apparatus of the invention may further comprise: a lower case forming lower side of the chamber; an upper case combined to upper side of the lower case to form upper side of the chamber and an internal space with the lower case; a partition plate horizontally combined inside of the lower case to form a bottom face of the internal space, the partition plate forming at lower side of the internal space a sub-space separated from the internal space; and an exhaust unit for supplying into the sub-space exhaust gas generated when sludge drying process is carried out in the internal space. At this time, the partition plate is provided with a bottom prominence protruded towards the internal space between the crews so as not to be interfered with the screws; and the lower case is provided with a lateral prominence protruded at upper side of both inner sidewalls so as not to be interfered with the screws, wherein the bottom prominence is provided internally with a hot-air passage horizontally formed along the longitudinal direction of the screw, and a crevice is formed between the bottom prominence and the partition plate so that the internal space and the hot-air passage are fluidically communicated through the crevice.

[48] In the above apparatus for drying sludge, the screw may include a front section near the charge hopper, a rear section near the discharge hopper, and an intermediate hopper between the front section and the rear section, the intermediate section is provided with first mixing plate installed at certain predetermined intervals one after another so as to be protruded in one direction horizontally with the pitch direction of the screw, and the rear section is provided with a second mixing plate installed at certain predetermined intervals one after another so as to be protruded in both directions horizontally with the pitch direction of the screw.

[49] In the above apparatus of the invention, the fore infrared lamp is disposed between the magnetrons so as not to be interfered with the magnetron, the fore infrared lamp is formed in such away to insert a fore infrared generating element into a transparent quartz tube, and the upper outer circumferential face is finished with a plating so as to radiate fore infrared rays downwardly.

[50] In the above apparatus of the invention, the driving unit includes a motor disposed at one end of the plurality of crews and connected with any one of the screws by means of a chain to thereby transfer a driving force, and a gear connected to the other end of each of the screws and engaged with each other.

[51] In the sludge drying method according to the present invention, a chamber having a closed internal space is provided. A plurality of screws are disposed in parallel one after another across the chamber such that pitches of rotary blades are off-set from one another. Thus, sludge is crushed and stirred simultaneously while being transferred from one end to the other end. Thus, the sludge drying method and apparatus is configured such that the sludge stirring and crushing along with the sludge transfer are effectively carried out only by means of the screws, thereby enabling to efficiently avoid the improper transfer and drying of sludge, which may occur due to differently drying between the surface and inside of the sludge. Separate components such as crusher or stirrer are not necessitated to provide a relatively simplified structure. In addition, in the sludge drying method and apparatus, magnetrons are continuously installed along the sludge-transferring direction and fore infrared lamps are installed between the magnetrons. Thus, fore infrared rays remove surface moisture (water vapor), which causes problems in case of application of heating mechanism of microwave oven and microwave, so that its thermal efficiency can be maximized. Therefore, the treating efficiency can be further improved and maintenance cost can be reduced, as compared with the conventional techniques.

[52] Microwave is generated through a particular electron tube, klystron, magnetron, maser or the like. Its transmission uses a microwave circuit, where a sharp directionality is provided to an electron flare and a parabola antenna to transmit. Such microwave has a strong sterilizing power and is well absorbed in plants or water to produce heat. Typically microwave ovens employ this property. In the present invention, such microwave is used to dry sludge. Thus, the preset invention illustrates a microwave generator, a magnetron, a waveguide, or the like as components for microwave applications. However, various other common techniques may be employed as long as they generates microwave so as to be acted on sludge.

[53] Dissimilar to other infrared rays that acts near an object, fore infrared rays penetrates inside of an object to act to produce heat. Such heat has many effects on sterilization and disinfection. The present invention uses these fore infrared rays as a heating source, which avoids insufficient drying to improve drying efficiency. The insufficient drying may be caused when only microwave is used, as described below.

[54] Microwave used in common microwave ovens oscillates water molecules of an object (sludge) to produce heat for heating the object. Here, water molecules oscillating by such microwave travels from inside to inside of an object. During this course of action, the abject is surrounded by moisture to degrade drying efficiency. Thus, in the sludge drying method and apparatus, fore infrared lamps are continuously installed between magnetrons, which operate microwave to be acted on sludge, such that moisture surrounding the sludge particles (subject to be treated) can be removed, thereby performing heating through microwave and fore infrared rays effectively to maximize the efficiency of drying sludge. Industrial Applicability

[55] As described above, according to the sludge drying method and apparatus, a chamber is provided to have a closed internal space. A plurality of screws are disposed in parallel one after another across the chamber such that pitches of rotary blades are off-set from one another. Thus, sludge is crushed and stirred simultaneously while being transferred from one end to the other end, thereby enabling to efficiently avoid the improper transfer and drying of sludge, which may occur due to differently drying between the surface and inside of the sludge. Separate components such as crusher or stirrer are not necessitated to provide a relatively simplified structure. In particular, the screw of the invention is configured such that sludge transfer is increased at the front portion of the screw to which the sludge is charged, and from the intermediate portion thereof the sludge is stirred and crushed through a mixing plate according to the degree of sludge-drying, thereby causing the sludge to be effectively dried in its surface and inside portions while being smoothly transferred. In addition, magnetrons are continuously installed along the sludge-transferring direction and fore infrared lamps are installed between the magnetrons. Thus, fore infrared rays remove surface moisture, which causes problems in case of application of microwave, so that its thermal efficiency can be maximized, thereby further improving the treating efficiency and reducing maintenance cost, as compared with the conventional techniques.

Claims

[1] A method of drying sludge, the method comprising: supplying sludge to be dried into one ends of a plurality of screws, which are disposed in parallel one after another such that pitches of rotary blades are off-set from one another, and rotating the screws such that the sludge is transferred to the other ends of the screws by means of the rotary blades of the screws; operating magnetrons disposed at certain predetermined intervals along the transferring direction of the sludge such that microwave acts towards the screws; and operating fore infrared lamps disposed between the magnetrons one after another such that fore infrared rays act toward the screws, wherein the sludge is heated and dried by means of the microwave and for infrared rays while the sludge is crushed, stirred and transferred by means of the plurality of crews.

[2] The method according to claim 1, wherein exhaust gas generated during drying of the sludge is re-flown into a sub-space formed at lower side of an internal space where the screw is installed, such that the exhaust gas serves as an auxiliary heat source for heating the internal space, and dried hot-air of high- pressure and high-temperature flows through a hot-air passage, which is formed at lower side of the internal space and between the screws, and fluidically communicated with the internal space through a crevice.

[3] An apparatus for drying sludge, the apparatus comprising: a frame; a chamber supported on the frame, the chamber including an internal space horizontally fluidically communicated, the chamber being provided at its front end with a charge hopper for supplying sludge to be dried and at its rear end with a discharge hopper for discharging dried sludge; a plurality of screws each rotatably supported at both ends of the chamber and having a rotary blade, the crews being disposed in parallel one after another such that pitches of the blades of the screws are off-set from one another, the screws being installed horizontally in the internal space of the chamber such that sludge supplied through the charge hopper is transferred along the blades towards the discharge hopper, and being rotated by a driving unit installed outside of the chamber; a plurality of magnetrons disposed at the upper side of the chamber horizontally one after another such that microwave acts towards the internal space where the screw is installed; and a plurality of fore infrared lamps disposed at upper side of the chamber horizontally one after another such that fore infrared rays act towards the screw.

[4] The apparatus according to claim 3, further comprising: a lower case forming lower side of the chamber; an upper case combined to upper side of the lower case to form upper side of the chamber and an internal space with the lower case; a partition plate horizontally combined inside of the lower case to form a bottom face of the internal space, the partition plate forming at lower side of the internal space a sub-space separated from the internal space; and an exhaust unit for supplying into the sub-space exhaust gas generated when sludge drying process is carried out in the internal space.

[5] The apparatus according to claim 4, wherein the partition plate is provided with a bottom prominence protruded towards the internal space between the crews so as not to be interfered with the screws; and the lower case is provided with a lateral prominence protruded at upper side of both inner sidewalls so as not to be interfered with the screws, wherein the bottom prominence is provided internally with a hot-air passage horizontally formed along the longitudinal direction of the screw, and a crevice is formed between the bottom prominence and the partition plate so that the internal space and the hot-air passage are fluidically communicated through the crevice.

[6] The apparatus according to any one of claims 3 to 5, wherein the screw includes a front section near the charge hopper, a rear section near the discharge hopper, and an intermediate hopper between the front section and the rear section, the intermediate section is provided with first mixing plate installed at certain predetermined intervals one after another so as to be protruded in one direction horizontally with the pitch direction of the screw, and the rear section is provided with a second mixing plate installed at certain predetermined intervals one after another so as to be protruded in both directions horizontally with the pitch direction of the screw.

[7] The apparatus according to any one of claims 3 to 5, wherein the fore infrared lamp is disposed between the magnetrons so as not to be interfered with the magnetron, the fore infrared lamp is formed in such away to insert a fore infrared generating element into a transparent quartz tube, and the upper outer circumferential face is finished with a plating so as to radiate fore infrared rays downwardly.

[8] The apparatus according to any one of claims 3 to 5, wherein the driving unit includes a motor disposed at one end of each of the plurality of crews and connected with any one of the screws by means of a chain to thereby transfer a driving force, and a gear connected to the other end of each of the screws and engaged with each other.