Organic sludge treatment device and treatment method

Abstract

[Problem] To treat organic sludge while maintaining stable operation and reducing thermal loss and a fraction amount. [Solution] An apparatus for treating organic sludge, the apparatus comprising: a fractioning device 5 that acquires a fraction of a preheated material R1 from a calcination furnace 3 of a cement-firing device 1; a mixing device 8 that mixes organic sludge S with the preheated material R2 acquired by the fractioning device, and dries the organic sludge using sensible heat of the preheated material; and a supply device that supplies a mixture M discharged from the mixing device to a raw material supply system of the cement-firing device. The fractioning device is a screw conveyor having a casing, of which an upper half portion has been removed. An opening edge portion in a longitudinal direction of the casing can be extended along a wall surface of a raw material flow part of the calcination furnace. An introduction device that introduces an exhaust gas containing dust, odor, and water vapor from the mixing device into a gas outlet of a lowermost cyclone 4A2 of the cement-firing device may be provided.

Description

[Technical Field]

[0001] The present invention relates to a treatment device and a treatment method for organic sludge such as sewage sludge, and to an apparatus for effectively utilizing organic sludge as fuel or the like. [Background technology]

[0002] Since it is becoming difficult to bury organic sludge such as sewage sludge discharged from sewage treatment plants on land, various methods have been proposed for effectively utilizing it as fuel. For example, Patent Document 1 discloses a technology in which organic sludge such as sewage sludge is converted into fuel by directly charging it in the form of a water-containing slurry into the kiln end or calciner of a cement manufacturing facility.

[0003] Meanwhile, Patent Document 2 discloses a technique in which sewage sludge is mixed with quicklime, the sewage sludge is dehydrated, and the resulting solids are fed into a cement kiln to be converted into cement together with other cement raw materials. Patent Documents 3 and 4 disclose techniques for drying sewage sludge using quicklime from the preheater bottom raw material and quicklime from bypass dust.

[0004] However, in the method described in Patent Document 1, the organic sludge is fed in the form of a water-containing slurry into the cement kiln at the section where the cement raw materials undergo the decarbonation reaction (from the end of the kiln to the inlet of the lowest cyclone), which poses problems such as a large amount of heat required to evaporate the sludge water, the location and time at which the water evaporates not being constant, fluctuations in the amount of exhaust gas, and a sudden drop in the firing temperature, which reduces cement production efficiency.

[0005] Furthermore, when drying is performed using the reaction heat of quicklime as in Patent Document 2, quicklime is expensive and the drying requires a long time because the heat generated after hydration of quicklime is used for drying.

[0006] Drying using the heat of hydration of quicklime in cement raw materials, as in Patent Documents 3 and 4, is less expensive than using commercially available quicklime, but it must be dehydrated again before being used as a cement raw material, and the heat loss required is 1.5 to 2 times the theoretical value required for the dehydration reaction, which is a large heat loss.

[0007] Therefore, in Patent Document 5, the present applicant proposed a method for treating organic sludge, in which preheated raw material is separated from preheater cyclones excluding the lowest cyclone of a cement calciner, organic sludge is mixed with the separated preheated raw material, the sensible heat of the preheated raw material is used to dry the mixed sludge, and the dried organic sludge is supplied to the calciner of the cement calciner or to a duct between the end of the cement kiln and the calciner.

[0008] According to the invention described in Patent Document 5, organic sludge is dried using the sensible heat of the preheated raw material, and the dried sludge is supplied together with the preheated raw material to a calciner or a duct between the end of a cement kiln and the calciner, thereby making it possible to effectively use the dried sludge as a fuel alternative, and the heat source can efficiently contribute to the decarbonation of cement raw materials in the calciner, etc., so that the organic sludge can be treated while minimizing equipment costs and decreases in cement production efficiency and clinker production volume. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent No. 3933194 [Patent Document 2] Japanese Patent No. 2803855 [Patent Document 3] Japanese Patent No. 4106449 [Patent Document 4] Japanese Patent Publication No. 2015-66477 [Patent Document 5] International Publication No. WO2019 / 193938 Brochure Summary of the Invention [Problem to be solved by the invention]

[0010] However, in the invention described in Patent Document 5, the dried sludge dried using the sensible heat of the preheated raw material has a temperature of about 100°C and emits an odor, so it cannot be returned to the cement raw material system and is returned together with the preheated raw material to the calciner or to a duct between the end of the cement kiln and the calciner, resulting in heat loss.

[0011] Furthermore, when using preheated raw material collected from the chute of the third cyclone from the top of the preheater cyclone, the temperature of the preheated raw material is relatively low at around 650°C, which means that a large amount needs to be collected, resulting in increased processing costs.

[0012] Furthermore, because the material is separated using a screw conveyor installed in the center of the raw material chute of the preheater cyclone, the amount of material separated fluctuates, making it difficult to maintain stable operation.

[0013] Therefore, the present invention has been made in consideration of the problems in the above-mentioned prior art, and has as its object to treat organic sludge with less heat loss, a small amount of separated sludge, and while maintaining stable operation. [Means for solving the problem]

[0014] In order to achieve the above object, the present invention is an organic sludge treatment device comprising: a separation device that separates preheated raw material from a calciner of a cement calciner; a mixer that mixes organic sludge with the preheated raw material separated by the separation device and dries the organic sludge using the sensible heat of the preheated raw material; and a supply device that supplies the mixture discharged from the mixer to a raw material supply system of the cement calciner.

[0015] According to the present invention, a mixture of dried organic sludge and separated preheated raw material is returned to the raw material supply system of the cement firing apparatus, thereby reducing the heat loss that would occur if a conventional mixture were returned to the duct between the end of the cement kiln and the calciner. In addition, because the organic sludge is dried using high-temperature preheated raw material at approximately 800°C separated from the calciner, the amount of preheated raw material used can also be reduced.

[0016] In the organic sludge treatment apparatus, the fractionating device can be a screw conveyor with the upper half of the casing removed, and the longitudinal opening edge of the casing can be extended along the wall surface of the raw material flow section of the calciner, thereby preventing pulsation in the fractionating amount and maintaining stable operation.

[0017] The organic sludge treatment device can be equipped with an introduction device that introduces exhaust gas containing dust, odor, and water vapor from the mixer into the gas outlet of the lowest cyclone of the cement calciner, allowing the sludge to be treated while effectively utilizing the odorous gas generated by drying the sludge for denitrification of the cement kiln exhaust gas. Furthermore, while returning the exhaust gas to the calciner or cement kiln results in heat loss during calcination, in the present invention, the exhaust gas is returned to the gas outlet of the lowest cyclone (exhaust gas after calcination is completed), minimizing heat loss.

[0018] The temperature of the mixture at the outlet of the mixing device can be set to 100°C or higher, which allows the organic sludge to be dried to a moisture content of 5% by mass or less so that it does not produce an odor, and also prevents problems caused by condensation of moisture during transportation.

[0019] The present invention also provides a method for treating organic sludge, which comprises mixing the organic sludge with preheated raw material separated from a calciner of a cement calciner, drying the organic sludge using the sensible heat of the preheated raw material, and supplying the mixture to a raw material supply system of the cement calciner.

[0020] According to the present invention, a mixture of dried organic sludge and separated preheated raw material is returned to the raw material supply system of the cement firing apparatus, thereby reducing the heat loss that would occur if a conventional mixture were returned to the duct between the end of the cement kiln and the calciner. In addition, because the organic sludge is dried using high-temperature preheated raw material at approximately 800°C separated from the calciner, the amount of preheated raw material used can also be reduced.

[0021] In the above-described organic sludge treatment method, the exhaust gas containing dust, odor, and water vapor generated when the organic sludge is mixed with the preheated raw material can be introduced into the gas outlet of the lowest cyclone of the cement burning apparatus, and the ammonia component contained in the odorous gas generated by drying the sludge can be effectively utilized for denitrification of the cement kiln exhaust gas during treatment.

[0022] The mixing ratio of the organic sludge to the separated preheated raw material can be set to 1:3 to 1:4, which allows stable evaporation of water in a short time. Furthermore, by diluting the combustible content of the organic sludge with the separated preheated raw material, which is non-combustible, the risk of dust explosions can be reduced, and the handling of the highly viscous organic sludge can be improved. [Effects of the Invention]

[0023] As described above, according to the present invention, heat loss is small, the amount of separated sludge is small, and stable operation can be maintained while treating organic sludge. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a schematic diagram showing an embodiment of an organic sludge treatment apparatus according to the present invention. [Figure 2] 2 is a schematic cross-sectional view showing an example of installation of a fractionation device in the organic sludge treatment device shown in FIG. 1. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0025] Next, embodiments of the present invention will be described in detail with reference to the drawings.

[0026] Fig. 1 shows a cement calcination apparatus equipped with an organic sludge treatment apparatus according to the present invention. In addition to typical cement calcination apparatus components such as a cement kiln 2, a calciner 3, and a preheater 4, the cement calcination apparatus 1 also includes a fractionator 5 that fractionates a portion of the preheated raw material R1 descending through the calciner 3, and a mixer 8 that mixes the fractionated preheated raw material R2 with organic sludge S supplied from an organic sludge supply device 6 while drying the organic sludge S. The preheater 4 has four or five cyclones, but Fig. 1 does not show the equipment above the three-stage cyclones 4C1 and 4C2. The organic sludge S refers to sewage sludge, paper sludge, building pit sludge, food sludge, etc.

[0027] The fraction collection device 5 can be, for example, a screw conveyor with the upper half of the casing 5a (the upper half of a cylindrical casing) removed and the top open. As shown in Figure 2, the fraction collection device 5 has the longitudinal opening edge 5b of the casing 5a that penetrates the calciner 3 extending along the wall surface 3a of the calciner 3 where the preheated raw material R1 flows. Since the preheated raw material R1 flowing along the wall surface 3a is smoothly introduced into the fraction collection device 5, the amount of fraction collection does not pulsate, and stable operation can be maintained. Note that fraction collection devices with configurations other than those described above can also be used.

[0028] 1, the mixer 8 is a pug mill or the like having a horizontal shaft 8a to which multiple blades 8b are attached, and which rotates as the horizontal shaft 8a rotates, and which simultaneously mixes, dries, and transports the organic sludge S and the separated preheated raw material R2. This mixer 8 is not limited to the above, and other types of equipment that can dry the organic sludge S using the sensible heat of the separated preheated raw material R2 can also be used.

[0029] Although not shown, the mixer 8 is provided with an introduction device that introduces the exhaust gas G containing dust, odor, and water vapor from the mixer 8 into the gas outlet of the lowest cyclone (lowest cyclone 4A2 in the illustrated example).

[0030] Next, a method for treating organic sludge according to the present invention using the cement burning apparatus 1 having the above-described configuration will be described with reference to FIG.

[0031] During operation of the cement burning apparatus 1, organic sludge S is supplied to the mixer 8 via the organic sludge supply device 6, and a portion of the preheated raw material R1 descending in the calciner 3 is separated by the separation device 5, and the separated preheated raw material R2 is introduced into the mixer 8 to dry the organic sludge S.

[0032] The amount of preheated raw material R2 dispensed can be instantly adjusted by changing the rotation speed of the screw conveyor of the dispensing device 5, and even if the supply amount of organic sludge S changes, the amount of preheated raw material R2 dispensed can be instantly adjusted to accommodate the change, enabling stable processing.

[0033] It is preferable to adjust the mixing ratio of the organic sludge S and the separated preheated raw material R2 in the mixer 8 to organic sludge S (solids excluding moisture):separated preheated raw material R2 = 1:3 to 1:4. This allows for stable and rapid evaporation of moisture. Furthermore, diluting the combustible content of the organic sludge S with the non-combustible preheated raw material R2 reduces the risk of dust explosions and improves the handleability of the highly viscous organic sludge.

[0034] In the mixer 8, the organic sludge S and the preheated raw material R2 are conveyed while being mixed and stirred, preferably for about 1 to 5 minutes, and the organic sludge S is heated and dried using the sensible heat of the separated preheated raw material R2. Note that the preheated raw material R1 that has not been separated is decarbonated in the calciner 3 and the lowest cyclones 4A1 and 4A2 as usual, and then burned in the cement kiln 2 to produce cement clinker.

[0035] Table 1 shows the relationship between the moisture content (mass %) and odor of the mixture M of the organic sludge S and the preheated raw material R2 dried as described above.

[0036] [Table 1]

[0037] The moisture content was measured according to JIS Z 7302-3 "Refuse-derived fuel - Part 3: Moisture content test method." Specifically, the sample was heated and dried at 107±2°C for 1 hour, and the difference in mass before and after drying was taken as the mass percentage of the sample.

[0038] On the other hand, the odor intensity was measured by the following procedure. (1) Seal 100g of sample in a 1L plastic container. (2) Let it stand for 1 hour in a constant temperature environment of 30°C. (3) Using a flex pump, collect the gas from the plastic container containing the sample into a 3L gas bag. (4) The odor intensity of the gas in the collected gas bag is measured using an odor sensor (Neo Sigma, manufactured by Calmor Co., Ltd.).

[0039] The odor intensity that humans can tolerate as unpleasant, based on the odor sensor readings, is 600 or less. From Table 1, the moisture content at which the odor intensity becomes 600 is 5% by mass, and in order to keep the moisture content of mixture M at 5% by mass or less, the temperature of mixture M at the outlet of mixer 8 is set to 100°C or higher. This allows the organic sludge (mixture M) to be dried to a moisture content that does not produce an odor, and also improves handling during transportation.

[0040] Because mixture M has been dried to a moisture content of 5% by mass or less, which does not produce an odor, it can be returned to the raw material supply system of the cement burning apparatus 1, that is, from the raw material storage area to the raw material supply device to the preheater 4. This reduces the heat loss that would occur if mixture M were conventionally returned to a duct or the like between the end of the cement kiln 2 and the calciner 3 by about 50 kJ / kg-cli. In addition, because the organic sludge is dried using high-temperature preheated raw material at about 800°C taken from the calciner, the amount of preheated raw material used can also be reduced.

[0041] Meanwhile, exhaust gas G containing dust, odor, and water vapor from mixer 8 is returned to the gas outlet of lowest cyclone 4A2 of cement burning apparatus 1, where odorous gases produced by drying organic sludge S are effectively utilized for denitrification of the cement kiln exhaust gas. Furthermore, while returning exhaust gas G to calciner 3 or cement kiln 2 results in heat loss during calcination, in the present invention, heat loss is minimized by returning it to the gas outlet of lowest cyclone 4A2 (exhaust gas after calcination is completed). 1. Cement baking equipment 2. Cement kiln 3. Calciner 4 Preheater 5 Preparation device 6. Organic sludge supply device 8 Mixing device G. Exhaust gas M mixture R1, R2 Preheat raw materials S Organic sludge

Claims

1. a sampling device that samples preheated raw materials from a calciner of the cement burning device; a mixer that mixes the organic sludge with the preheated raw material separated by the separation device and dries the organic sludge using the sensible heat of the preheated raw material; a supply device for returning the mixture discharged from the mixer from the raw material storage area to the raw material supply device for the preheater,

2. 2. The organic sludge treatment apparatus according to claim 1, wherein the separation device is a screw conveyor with the upper half of the casing removed, and the longitudinal opening edge of the casing extends along the wall surface of the raw material flow section of the calciner.

3. 3. The organic sludge treatment apparatus according to claim 1, further comprising an introducing device that introduces the exhaust gas containing dust, odor, and water vapor from the mixing device into a gas outlet of the lowest cyclone of the cement burning apparatus.

4. 4. The organic sludge treatment apparatus according to claim 1, wherein the temperature of the mixture at the outlet of the mixer is set to 100° C. or higher.

5. A method for treating organic sludge, comprising mixing organic sludge with preheated raw material separated from a calciner of a cement calciner, drying the organic sludge using the sensible heat of the preheated raw material, and returning the mixture from a raw material storage area to a raw material supply device for a preheater.

6. 6. The method for treating organic sludge according to claim 5, wherein exhaust gas containing dust, odor, and water vapor generated when the organic sludge and the preheated raw material are mixed is introduced into a gas outlet of a lowermost cyclone of the cement burning apparatus.

7. 7. The method for treating organic sludge according to claim 5 or 6, wherein the mixing ratio of the organic sludge to the separated preheated raw material is organic sludge (solid content excluding water): separated preheated raw material = 1:3 to 1:4.

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