JP2006015174A - Method and apparatus for sludge treatment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for highly efficient and economical sludge treatment which can produce solid fuel having a proper calorific value by using dehydrated sewage sludge generated in a sewage treatment plant. <P>SOLUTION: The dehydrated sewage sludge prepared by dehydrating sewage sludge obtained in the sewage treatment plant to a moisture content of 70-85%, and crushed plastic prepared by crushing it to a size of 0.1-3 mm and/or crushed waste paper prepared by crushing it to a size of 1-5 mm are mixed so that a ratio of the total amount of the crushed plastic to the crushed waste paper is 0.1-0.7 pt.wt. with respect to 1 pt.wt. of the dehydrated sewage sludge. The mixture is molded in the form of a rod having a diameter of 4-10 mm and a length of 2-7 cm, and then dried with warm air of 60-180°C. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sludge treatment method and apparatus, and more particularly to a sludge treatment method and apparatus for effectively using sewage sludge discharged from a sewage treatment plant as a solid fuel.

  There is a demand for technology that promotes energy use of sewage sludge and contributes to global warming countermeasures, and attempts are being made to use dried sludge as fuel for thermal power plants. However, general sewage dry sludge has a low calorific value, so it is expected that the amount of power received by the power plant will be limited.

  On the other hand, a large amount of plastic is discarded from ordinary households and factories, but plastic does not rot even if it is landfilled, and its disposal is a big problem. Also, with regard to used paper, it is difficult to recycle and reuse paper-coated ones such as paper packs.

For this reason, after drying the organic sludge discharged from the paper mill to a moisture content of about 60%, the waste oil and plastic waste are added and dried while mixing, and then shaped into a predetermined shape. A method for solidifying the fuel into a solid fuel has been proposed (for example, see Patent Document 1).
JP 56-62891 A

  However, in the conventional method, after drying the organic sludge, the waste oil and waste plastic are mixed and dried while mixing them, so the energy required for drying becomes enormous and the equipment configuration is also complicated. It was expensive. Furthermore, since waste oil is used as a part of the raw material, there is a disadvantage that management and the like are troublesome.

  Accordingly, the present invention provides a sludge treatment method and apparatus that can produce a solid fuel having an appropriate calorific value using a sewage dewatering cake generated at a sewage treatment plant, and that is highly efficient and economical. It is aimed.

  In order to achieve the above object, the sludge treatment method of the present invention is characterized in that a sewage dewatered cake is mixed with a waste plastic pulverized material and / or waste paper crushed material, and dried after molding, particularly from a sewage treatment plant. A sewage dewatered cake obtained by dehydrating the water content of the obtained sewage sludge to 70 to 85%, a waste plastic pulverized product pulverized to a size of 0.1 to 3 mm and / or a waste paper crushed product crushed to 1 to 5 mm, The total amount of waste plastic crushed material and waste paper crushed material was mixed at a ratio of 0.1 to 0.7 parts by weight with respect to 1 part by weight of the sewage dewatered cake, and formed into a rod shape having a diameter of 4 to 10 mm and a length of 2 to 7 cm. Then, it is characterized by drying with hot air of 60 to 180 ° C.

  The sludge treatment apparatus of the present invention includes a mixer for mixing the sewage dewatered cake, the waste plastic pulverized product and / or the waste paper crushed material, a molding machine for forming the mixture mixed in the mixer into a rod shape, A dryer for drying the molded product molded by the molding machine with hot air, and the dryer supplies an air-permeable conveying belt disposed so as to cross the drying chamber, and supplies the hot air to the drying chamber. The hot air supply means, the means for stirring the warm air in the drying chamber, the hot air collecting means for collecting the warm air from the drying chamber, and the molded product placed on one end of the transport belt on the transport belt It is characterized by comprising a molded product placing part and a molded product recovery part for recovering a dried molded product from the other end of the conveyor belt.

  According to the present invention, waste paper or waste plastic is mixed with a sewage dewatered cake and then dried, so that the drying efficiency can be greatly improved, and a solid fuel having an appropriate calorific value can be produced efficiently. Can do. In particular, the drying efficiency can be further improved by using a specific dryer.

  FIG. 1 is an explanatory view showing a first embodiment of the sludge treatment method of the present invention. In this embodiment, waste plastic is mixed with a sewage dewatering cake to produce a solid fuel. In the sewage dewatering cake, the sewage sludge generated at the sewage treatment plant has a water content of 70 to 70 with a normal dehydrator. Use 85% dehydrated as it is.

  The waste plastic is pulverized to an appropriate size, preferably 0.1 to 3 mm, more preferably about 1 mm, in the pulverizing step in the pulverizer 11 and then mixed with the sewage dewatered cake. If the size of the waste plastic pulverized product is too small, problems such as scattering may occur, and the cost required for pulverization also increases. On the other hand, if the waste plastic pulverized product is too large, mixing with the sewage dewatering cake or molding after mixing with the sewage dewatering cake becomes difficult. The pulverizer 11 may be any type of pulverizer as long as it can pulverize various types of waste plastics to the size described above.

  The mixing ratio of the sewage dewatering cake and the pulverized waste plastic in the mixer 12 that performs the mixing step can be set in consideration of the properties of the sewage dewatering cake, the type of the waste plastic, and the heat generation amount of both, May be a ratio of 0.1 to 0.7 parts by weight, preferably about 0.4 parts by weight of the waste plastic pulverized product with respect to 1 part by weight of the sewage dewatered cake. At this time, if the proportion of waste plastic is too small, the desired heat generation may not be obtained, and if the proportion of waste plastic is too large, the amount of wastewater dewatered cake processed becomes small and the original purpose can be achieved. Disappear. The mixer 12 only needs to be able to sufficiently mix the sewage dewatering cake and the pulverized waste plastic, and either a batch type or a continuous type may be used.

  The molding machine 13 that performs the molding process is to mold a mixture of sewage dewatered cake and waste plastic into a shape and size suitable for use as a solid fuel, and use a general molding machine or the like. Can do. The shape and size of the molded product can be appropriately set, but if it is too small, it may be difficult to handle, and if it is too large, a problem occurs during drying or combustion. Is a rod having a diameter of 6 to 8 mm, and a length of 2 to 7 cm, preferably about 5 to 6 cm is optimal. The molding machine 13 may be integrated with the mixer 12.

  The dryer 14 which performs a drying process can use the dryer of various structures of a batch type and a continuous type, if a molding can be dried. The drying temperature can be set according to the type of waste plastic and the desired drying state, but is usually in the range of 60 to 130 ° C., and a preliminary drying step at a low temperature and a drying step at a high temperature. Can also be combined.

  By drying the molded product in this way, a solid fuel (RDF) using sewage dewatered cake and waste plastic as raw materials can be obtained. This solid fuel can obtain a calorific value equivalent to that of coal, heavy oil, etc. by appropriately setting the mixing ratio of the sewage dehydrated cake with low organic content and low calorific value and waste plastic with high calorific value. There is no problem that the calorific value is low as in the case of a conventional solid fuel obtained by drying a sewage dewatered cake, and there is no problem of an excessive calorific value when only waste plastic is burned.

  FIG. 2 is an explanatory view showing a second embodiment of the sludge treatment method of the present invention. In this embodiment, a solid fuel is produced by mixing waste paper with a sewage dewatering cake, and the sewage dewatering cake has a moisture content of sewage sludge generated at a sewage treatment plant in the same manner as described above. Is dehydrated to 70-85% and used as it is.

  The waste paper is preliminarily crushed so as to be a piece of paper of an appropriate size, preferably about 1 to 3 mm, in the crushing process in the crusher 21, and then mixed with the sewage dewatered cake. When the size of the waste paper crushed material is too small, problems such as scattering may occur, and the cost required for crushing also increases. On the other hand, if the waste paper crushed material is too large, mixing with the sewage dewatering cake or molding after mixing with the sewage dewatering cake becomes difficult. The crusher 21 may be any type of crusher as long as it can crush used paper to the size described above. Also, as the used paper, a resin-coated paper can be used.

  Since the following mixing process, molding process, and drying process can be performed by the same operation using the mixer 12, the molding machine 13, and the dryer 14 similar to those when the above-described waste plastic is used, Detailed description is omitted here. In the drying process in the case of waste paper, it is preferable to dry at a temperature of 100 to 180 ° C., which is higher than that of waste plastic.

  FIG. 3 is a schematic view showing an example of a dryer that is optimal for carrying out the drying step. The dryer 31 includes an air-permeable conveying belt 33 disposed so as to horizontally traverse the inside of the drying chamber 32, hot air supply means 34 that supplies hot air or hot air into the drying chamber 32, and the drying chamber 32. A circulating fan 35 that is a means for stirring the warm air or hot air inside, a hot air collecting means 36 that collects the warm air from the inside of the drying chamber 32, and a molding 37 placed on one end of the transport belt 33 on the transport belt And a molded product collecting unit 39 that collects a dried molded product 37 from the other end of the conveyor belt 33.

  The drying chamber 32 has hot air introduction portions 41a to 41d and hot air derivation portions 42a to 42d, and is connected to tunnel-shaped drying chamber units 32a to 32d in which a circulation fan 35 is disposed. The molded product placing portion 38 and the molded product collecting portion 39 are coupled to each other, and the sprockets 43 and 43 provided in the molded product placing portion 38 and the molded product collecting portion 39 are hung on the conveyor belt 33 having a predetermined length. It is formed so that the number of drying chamber units can be increased or decreased in accordance with the dry state and the processing amount of the molded product 37.

  The conveyor belt 33 is made of a wire mesh having heat resistance and flexibility, and is formed so that warm air flows around the molded product through the mesh and through holes. In addition, as described above, by molding the molded product into a columnar shape or a cylindrical shape, the surface area of the molded product is increased as compared with other shapes, so that heat transfer is good and drying efficiency can be improved. Further, since the molded product 37 is dried while being transported in a state where it is placed on the conveyor belt 33, the molded products are not rubbed against each other, and the molded product 37 is not damaged or dust is not generated. .

  The hot air supply means 34 supplies the hot air generated by the heater 44 with the fan 45, and distributes the hot air whose flow rate has been adjusted by the dampers 46a to 46d to the hot air introducing portions 41a to 41d. Is formed. Further, the hot air collecting means 36 is formed so that the fan 48 sucks the hot air whose flow rate is adjusted by the dampers 47a to 47d of the hot air derivation sections 42a to 42d. Therefore, by appropriately adjusting each of the dampers 46a to 46d and 47a to 47d, an optimum amount of hot air corresponding to the situation of each molding 37 being dried in each drying chamber unit 32a to 32d is supplied to each drying chamber. It is possible to circulate in the units 32a to 32d.

  The molded product placement unit 38 is formed so that the molded product 37 mixed by the mixer 12 and molded by the molding machine 13 is uniformly placed on the transport belt 33. By uniformly depositing the molded product 37 in this way, it is possible to prevent a short path of warm air and uniformly heat the entire molded product, and to improve the drying efficiency.

  Since the dried molded product 37 recovered from the molded product recovery unit 39 is molded in advance and then dried, it can be used as it is as a solid fuel and has an appropriate hardness. Therefore, it can be easily conveyed by a belt conveyor or the like.

  By treating sewage dewatered cake in this way, sewage sludge, waste plastic, or waste paper, which has been previously landfilled, can be used effectively as fuel, so the final disposal cost of waste can be greatly reduced, and the power plant Can be used as a substitute for fossil fuels such as coal and heavy oil.

  In addition, it is also possible to mix waste plastic and waste paper in an arbitrary ratio to the sewage dewatering cake. In this case, the total amount of waste plastic and waste paper is 1 part by weight of the sewage dewatering cake. What is necessary is just to make it become 0.1-0.7 weight part.

It is explanatory drawing which shows the 1st form example of the processing method of the sludge of this invention. It is explanatory drawing which shows the 2nd form example of the processing method of the sludge of this invention. It is the schematic which shows one example of a dryer optimal for implementation of a drying process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Crusher, 12 ... Mixer, 13 ... Molding machine, 14 ... Dryer, 21 ... Crusher, 31 ... Dryer, 32 ... Drying room, 32a-32d ... Drying room unit, 33 ... Conveyor belt, 34 ... Warm air supply means, 35 ... circulating fan, 36 ... warm air collecting means, 37 ... molded product, 38 ... molded product placing section, 39 ... molded product collecting section, 41a-41d ... warm air introducing section, 42a-42d ... Hot air derivation section, 43 ... sprocket, 44 ... heater, 45 ... fan, 46a-46d, 47a-47d ... damper, 48 ... fan

Claims (3)

  A method for treating sludge, comprising mixing a dewatered sewage cake, a pulverized waste plastic and / or a crushed waste paper, and drying after molding.   Sewage dewatered cake dehydrated to 70-85% water content of sewage sludge obtained from the sewage treatment plant, waste plastic crushed material crushed to a size of 0.1-3 mm and / or waste paper crushed to 1-5 mm The total amount of waste plastic crushed material and waste paper crushed material is mixed at a ratio of 0.1 to 0.7 parts by weight with respect to 1 part by weight of the sewage dewatered cake, and the diameter is 4 to 10 mm and the length is 2 to 7 cm. A sludge treatment method comprising forming into a rod shape and drying with hot air of 60 to 180 ° C.   A mixer that mixes the sewage dewatered cake with the waste plastic pulverized product and / or waste paper crushed material, a molding machine that forms the mixture mixed in the mixer into a rod shape, and a molded product molded by the molding machine with hot air A dryer for drying, the dryer having an air-permeable conveying belt disposed across the drying chamber, hot air supply means for supplying hot air into the drying chamber, and a temperature in the drying chamber. Means for stirring the air, hot air collecting means for collecting the warm air from the drying chamber, a molded product placing portion for placing the molded product on the transport belt at one end of the transport belt, and A sludge treatment apparatus, comprising: a molded product recovery unit that recovers a molded product dried from the other end.

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