Carbonized product manufacturing method and carbonization treatment equipment

Abstract

To provide a manufacturing method of a carbonized product, which is capable of manufacturing a carbonized product having excellent hydrogen sulfide adsorption performance.SOLUTION: There is provided a manufacturing method of a carbonized product, in which drying treatment of a dehydrated sludge obtained by dehydrating an organic substance-containing sludge is performed using a dryer 16 until the sludge has a predetermined moisture, to obtain a dried sludge, and the dried sludge is heated in a carbonization furnace 28 under an oxygen-free or low-oxygen condition to perform carbonization treatment. The manufacturing method of a carbonized product comprises: a carbonization treatment step of performing carbonization treatment on the dried sludge at an ultra-high temperature of finally 1000°C or higher; and a sieving step of sieving a carbide obtained by the carbonization treatment to have a predetermined upper limit size or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a carbonized product and a carbonization treatment facility, and more particularly to a method for producing a carbonized product and a carbonization treatment facility suitable for producing a carbonized product having excellent hydrogen sulfide adsorption performance. [Background technology]

[0002] Wastewater containing organic matter discharged from homes and other places is generally treated in sewage treatment facilities, and this wastewater treatment generates sewage sludge containing organic matter. When disposing of sewage sludge, the sludge contains a large amount of water and cannot be disposed of as is, so various treatments are currently being carried out to reduce the volume, such as concentration and dehydration, or further incineration or melting.

[0003] However, while incineration of sewage sludge reduces its volume and makes it harmless, it is difficult to recycle it by utilizing the energy and active ingredients contained in the sludge. Therefore, carbonization is being used as a treatment method for sewage sludge, which is expected to enable a variety of effective uses for the products. Since sewage sludge contains approximately 45% by mass of carbon in its matrix, this carbonization process does not consume the carbon in the sludge as in incineration or melting processes, but rather involves thermally decomposing (carbonizing) the sludge in an oxygen-free or low-oxygen environment, leaving the carbon behind and generating a carbonized material (carbonized product) with a new composition.

[0004] Specifically, such charcoal is produced as granulated charcoal, for example, to a size of about several millimeters, using carbonization equipment such as that shown in Patent Document 1 below. The charcoal thus obtained has physical properties similar to those of charcoal, and is currently used for applications such as fuel, fertilizer (soil conditioner), and cement aggregate. To further expand its use in the future, carbonized products with new functions and properties are in demand, and one example being considered is its use as a deodorizing material that adsorbs hydrogen sulfide.

[0005] The following Patent Documents 2 and 3 are related arts of the present invention. These patent documents disclose that dewatered sludge containing organic matter is dried to a predetermined moisture content to produce dried sludge, and this dried sludge is then carbonized at a temperature of 1000°C or higher. However, it is still difficult to stably obtain sufficient hydrogen sulfide adsorption performance from the carbonized product obtained in this manner. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-089567 [Patent Document 2] Japanese Patent Application Publication No. 2019-157076 [Patent Document 3] Japanese Patent Publication No. 2020-122079 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made against the background of the above circumstances, with an object to provide a method for producing a carbonized product that can produce a carbonized product having excellent hydrogen sulfide adsorption performance, and carbonization treatment equipment that can be suitably used for the method. [Means for solving the problem]

[0008] The carbonized product obtained by carbonizing organic matter-containing sludge has many pores on the surface and functions as activated carbon that adsorbs impurities. The present inventors have made the following discoveries while pursuing a hydrogen sulfide adsorption performance higher than that of conventional carbonized products. (1) The carbonization process of sludge (sludge containing organic matter) is generally carried out at temperatures below 900°C. However, by performing ultra-high temperature carbonization, in which the carbonization temperature is increased to 1000-1200°C, the specific surface area of ​​the carbonized product is increased, and the hydrogen sulfide adsorption performance is improved. (2) However, if the sludge used contains ash containing components with melting points lower than the carbonization temperature (e.g., 1100°C), these will melt and produce slag. Such slag does not have the ability to adsorb hydrogen sulfide, and the presence of slag reduces the hydrogen sulfide adsorption capacity of the carbonized product as a whole. (3) Because the slag melts and coarsens during the ultra-high temperature carbonization process, the particle size of the carbide containing slag is larger than that of the normal carbide without slag. By utilizing this property, it is possible to separate the carbide without slag from the carbide produced by the carbonization process. The present invention was made based on this finding.

[0009] The method for producing a carbonized product of the present invention includes dehydrating organic matter-containing sludge, passing the dehydrated sludge through a dryer to a predetermined moisture content to produce dried sludge, and heating the dried sludge under oxygen-free or low-oxygen conditions to carbonize the sludge and produce a carbonized product, the method comprising the steps of: a carbonization treatment step in which the dried sludge is finally carbonized at an ultra-high temperature of 1000°C or higher; a sieving step of sieving the carbonized material obtained by the carbonization treatment into a predetermined upper limit size or less; The present invention is characterized by the following features.

[0010] According to the method for producing a carbonized product specified in this way, the specific surface area of ​​the carbonized material is increased by performing an ultra-high temperature carbonization treatment at 1000°C or higher, and as a result, the hydrogen sulfide adsorption performance can be improved. Furthermore, even if the low-melting-point ash in the sludge melts during the ultra-high-temperature carbonization process and slag that does not have the ability to adsorb hydrogen sulfide is produced, a screening process is installed downstream to separate and extract charcoal that does not contain slag (having high hydrogen sulfide adsorption capacity) from the carbonized charcoal, making it possible to produce carbonized products with excellent hydrogen sulfide adsorption capacity.

[0011] Furthermore, in the sieving step, the carbide can be further sieved to a predetermined lower limit size or larger. The particle size of the carbide obtained by ultra-high temperature carbonization varies. Fine powder carbide with an excessively small particle size causes problems in handling, such as dust flying during use. Therefore, in the sieving step, sieving is performed by specifying a lower limit size of the carbide in addition to an upper limit size of the carbide, and by separating out fine powder carbide with an excessively small particle size, a carbonized product that has excellent hydrogen sulfide adsorption performance and is also easy to handle can be produced.

[0012] Furthermore, the method for producing a carbonized product of the present invention can further include a pellet forming step of adding lignin to the sieved carbonized material, extruding the lignin-added carbonized material through through holes formed in a mold, cutting it, and forming it into pellets. By pelletizing the carbonized material in this manner, the dimensional variation in the carbonized product can be reduced, further improving the handling properties.

[0013] The carbonization treatment equipment of the present invention includes: a dryer that dehydrates organic matter-containing sludge to a predetermined moisture state to produce dried sludge; a carbonization furnace having a retort as a dry distillation vessel made of a rotary drum inside a furnace body, the retort being rotated while the dried sludge is moved in an axial direction, and the dried sludge being carbonized by a carbonization process during the movement, the carbonization furnace including a first retort as the retort, and a second retort located downstream of the first retort in the sludge transport direction and containing a ceramic material; a sieving device that has a sieve with a predetermined mesh size and sieves the carbonized material discharged from the carbonization furnace according to its particle size; The present invention is characterized by the following features. The carbonization treatment equipment thus defined makes it possible to suitably carry out the above-described method for producing a carbonized product.

[0014] In addition, the carbonization treatment equipment of the present invention includes: a chemical addition device that adds lignin to the carbonized material; a pellet molding device that extrudes the lignin-added carbonized material through through holes formed in a mold, cuts it, and molds it into cylindrical pellets; can be provided downstream of the sieving device in the direction of transport of the carbide. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a diagram showing the configuration of a carbonization treatment facility according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing a schematic configuration of the dryer in FIG. [Figure 3] FIG. 2 is a diagram showing a schematic configuration of the carbonization furnace in FIG. [Figure 4] 4(A) is a view showing the upper half of the carbonization furnace including the first carbonization chamber and the gas combustion chamber in FIG. 3. FIG. 4(B) is a view taken along the line BB in FIG. [Figure 5] FIG. 2 is a diagram showing the configuration of the carbonization treatment equipment downstream in the carbonized material transport direction, continuing from FIG. [Figure 6] FIG. 6 is a diagram showing a schematic configuration of the sieving device of FIG. 5. [Figure 7] FIG. 6 is a diagram showing a schematic configuration of the pellet molding device of FIG. [Figure 8] FIG. 1 is a diagram showing the specific surface area and hydrogen sulfide adsorption amount of charcoal and pellets obtained by sieving charcoal that has been subjected to ultra-high temperature carbonization treatment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Next, an embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 shows the configuration of a carbonization treatment facility 1 according to one embodiment of the present invention. In the figure, reference numeral 10 denotes a receiving hopper (dewatered sludge storage tank), and dewatered sludge, which is sewage sludge containing organic matter dewatered to a moisture content of about 70 to 85% (usually about 80%), is first received in this receiving hopper 10. The dewatered sludge received here is sent via intermediate storage tank 12 to dryer 16 by constant volume feeder 14 and conveyor 15, where it is dried to a moisture content of about 35 to 45% (usually about 40%).

[0017] As shown in Fig. 2, the dryer 16 has an agitator shaft 20 inside a rotating drum 18. The agitator shaft 20 is provided at a position eccentric to the center of the rotating drum 18, and a plurality of agitator blades 22 extend radially from the agitator shaft 20.

[0018] Meanwhile, a plurality of plate-shaped lifters 24 are provided at predetermined intervals around the inner circumferential surface of the rotating drum 18, and rotate integrally with the rotating drum 18. As a result, the sludge (dewatered sludge) inside the rotating drum 18 is lifted upward from the bottom by the lifters 24 as the rotating drum 18 rotates, and then falls under its own weight near the top. The fallen sludge is finely pulverized by the high-speed rotation of the agitating blades 22 located below it, and falls to the bottom side of the rotating drum 18.

[0019] While undergoing this agitation, the sludge inside the rotating drum 18 is exposed to the hot drying air introduced into the interior of the drum, and is dried, gradually reducing its moisture content. In the dryer 16, the sludge is gradually sent axially inside the rotating drum 18 due to the inclination of the rotating drum 18 and the crushing and scattering caused by the agitating blades 22.

[0020] As shown in FIG. 1, the dried sludge after being dried in the dryer 16 is then transported by a transport device 26 to a carbonization furnace 28, where the sludge is carbonized by a carbonization process. This carbonization furnace 28 is a furnace that dehydrates and pyrolyzes dried sludge in an oxygen-free or low-oxygen atmosphere, and as will be described in detail later, cylindrical retorts 32 and 34 are provided inside a furnace body 30 as dry distillation containers, and the sludge introduced into the first retort 32 gradually moves through the first retort 32 and then the second retort 34, and finally the dry distillation residue (carbonized material) is discharged from the outlet 36 at the left end of the second retort 34 in the drawing, i.e., from the carbonization furnace 28. Through this carbonization operation, the dried sludge is converted into a carbonized product with fine pores, with approximately 30 to 50% carbon and the remainder being inorganic matter.

[0021] In Fig. 1, 40 is a hot air generating furnace, and the hot air generated here is supplied to the dryer 16. The hot air supplied to the dryer 16 passes through this and a dust collector 42, and is further circulated by a circulation fan 44 to the hot air generating furnace 40 via a carbonization furnace exhaust gas heat exchanger 46 and a hot air furnace exhaust gas heat exchanger 47.

[0022] In this circulation system, a portion of the hot air generated in the hot air generating furnace 40 is extracted through a branch passage 48 extending from the hot air generating furnace 40, passes through a hot air furnace exhaust gas heat exchanger 47, and is released to the outside through a chimney 50 by a hot air furnace exhaust gas fan 49. On the other hand, an exhaust gas treatment chamber 31 is provided on the side of the furnace body 30 of the carbonization furnace 28, and the exhaust gas from the carbonization furnace 28 is led therein, and unburned gas in the exhaust gas is subjected to secondary combustion. An exhaust gas passage 52 extends from the exhaust gas treatment chamber 31, and the exhaust gas from the carbonization furnace 28 is passed through the exhaust gas passage 52 by a carbonization furnace exhaust gas fan 54 and then discharged to the outside from a chimney 50 via a carbonization furnace exhaust gas heat exchanger 46.

[0023] Next, the carbonization furnace 28 of this embodiment will be described in detail. A sludge supply device 64 equipped with a screw conveyor 64a and a hopper 64b is attached to the front end side of the carbonization furnace 28, i.e., one end side (left side in the figure) of the first retort 32, and dried sludge fed into the hopper 64b is fed into the inside of the first retort 32 by the screw conveyor 64a.

[0024] 3, the carbonization furnace 28 is an externally heated rotary kiln type, and is provided with a first retort 32 and a second retort 34 as dry distillation containers. Inside the furnace body 30, a first carbonization chamber 56 and a second carbonization chamber 57 having a higher temperature than the first carbonization chamber 56 are formed, and a gas combustion chamber 58 is formed between the first carbonization chamber 56 and the second carbonization chamber 57.

[0025] In the first carbonization chamber 56, the dried sludge is heated to 700 to 900°C for carbonization. The first retort 32, which penetrates the first carbonization chamber 56, is made of heat-resistant steel. Examples of heat-resistant steel that can be used for the first retort 32 include austenitic stainless steel and alloy steel.

[0026] The first retort 32 has ring bodies 60 and 61 attached to the outer periphery of one end and the other end, which are supported by rollers (not shown), and a drive chain is suspended on a sprocket 63 attached to the outer periphery of one end to rotate the first retort 32.

[0027] The first retort 32 is slightly inclined downward toward the right in the figure, and the dried sludge sent from the dryer 16 side is sent toward the right as the first retort 32 rotates, and is discharged into the connected container 80 through the outlet 66 formed at the right end in the figure.

[0028] 4(A) is a diagram showing the upper half of the carbonization furnace 28, including the first carbonization chamber 56. Reference numeral 68 denotes an auxiliary burner provided in the first carbonization chamber 56. Fuel is supplied to the auxiliary burner 68 together with combustion air, and the atmosphere in the first carbonization chamber 56 is heated. When the atmosphere in the first carbonization chamber 56 is heated, the combustible gas contained in the dried sludge escapes through the outlet pipe 33 provided in the retort 32 into the external heating chamber, more specifically, the first carbonization chamber 56, and this combustible gas is ignited. Thereafter, the sludge in the first retort 32 is heated by combustion of the combustible gas.

[0029] Furthermore, an air inlet 70a is formed in the furnace body 30 surrounding the first carbonization chamber 56 to introduce combustion air into the first carbonization chamber 56, and the amount of air introduced through the air inlet 70a and the combustion of the auxiliary burner 68 are appropriately adjusted so that the temperature of the first carbonization chamber 56 matches a preset target temperature. In Fig. 4(A), 76 is a thermocouple, 75 is a control unit, 77 is a control valve provided on the air supply path 72, and 74 is an air supply fan. As a result, the moisture in the sludge supplied to the inside of the first retort 32 is efficiently evaporated on the upstream side of the retort, and after moving to the downstream side of the retort, the sludge is maintained at a temperature close to that of the atmosphere in the first carbonization treatment chamber 56 and carbonized.

[0030] Meanwhile, the gas atmosphere in the first carbonization chamber 56, which has been heated to a predetermined temperature, is sent to the gas combustion chamber 58. In this example, the first carbonization chamber 56 is located upstream in the gas flow direction, and the second carbonization chamber 57 is located downstream in the gas flow direction, and the high-temperature gas combusted in the first carbonization chamber 56 is sent to the gas combustion chamber 58 located between the first carbonization chamber 56 and the second carbonization chamber 57, where it is further heated to a temperature of 1000°C or higher (1100°C in this example).

[0031] As shown in Fig. 4(A), the gas combustion chamber 58 is partitioned from the first carbonization chamber 56 and the second carbonization chamber 57 by an upper partition wall 90 and a lower partition wall 91, respectively. As shown in Fig. 4(B), an upper communication port 90a is formed in the upper partition wall 90 to allow the gas in the first carbonization chamber 56 to flow in. The upper communication port 90a is spaced apart in the axial direction from the first retort 32 located directly above it, and is formed in a position not facing the first retort 32.

[0032] Further, the lower partition wall 91 is formed with a lower communication port 91a that allows the gas heated in the gas combustion chamber 58 to flow out into the second carbonization treatment chamber 57. As shown in Fig. 4(B), the lower communication port 91a is formed at a position opposite the upper communication port 90a in the width direction of the gas combustion chamber 58, and is configured so that the gas that flows into the gas combustion chamber 58 through the upper communication port 90a flows through the gas combustion chamber 58 in the width direction and then flows out from the lower communication port 91a toward the second carbonization treatment chamber 57.

[0033] A combustion burner 92 and an air introduction pipe 93 for introducing combustion air are attached to the gas combustion chamber 58. The combustion air introduced into the gas combustion chamber 58 through the tip opening (air introduction port) 93a of the air introduction pipe 93 burns unburned gas components contained in the gas in the gas combustion chamber 58, thereby further increasing the temperature of the gas in the gas combustion chamber 58. In addition, the temperature of the gas in the gas combustion chamber 58 can also be further increased by burning the combustion burner 92.

[0034] In Figure 4(A), 94 is a control valve provided on the air supply path 72, 95 is a control valve provided on the fuel supply path 96, and 97 is a control unit. A thermocouple 98 for measuring the gas temperature is provided near the lower communication port 91a in the second carbonization treatment chamber 57. The control unit 97 appropriately adjusts the amount of air introduced through the air inlet 93a and the combustion of the combustion burner 92 so that the gas temperature measured by the thermocouple 98 matches a preset target temperature (1100°C). The air inlet and combustion burner for increasing the temperature inside the furnace can also be provided in the second carbonization treatment chamber 57.

[0035] 3, a connected container 80 is provided on the right side of the first retort 32 in the drawing so as to surround the end of the first retort 32. The connected container 80 is a cylindrical, vertical container, and the right end in the drawing, including the outlet 66 of the first retort 32, is housed therein through a horizontal opening 81 formed in the upper part of the peripheral wall 80a. Meanwhile, a downward-facing opening 82 is formed in the lower end of the connected container 80, and sludge discharged into the connected container 80 from the outlet 66 of the first retort 32 falls by its own weight while being guided by the inner surface of the peripheral wall 80a, and is discharged downward through the opening 82 formed in the lower end.

[0036] The edge of the opening 81 of the connected container 80 is brought into sliding contact with the outer surface of the retort 32 via a heat-resistant sealing cloth so as not to interfere with the rotation of the first retort 32, and the downward opening 82 is connected to an opening 88c provided on the second retort 34 side via a rotary valve 83. In the connected container 80 configured in this way, the intrusion of outside air into the interior is suppressed, preventing the temperature of the sludge in the connected container 80 from dropping due to exposure to the outside air.

[0037] The second carbonization chamber 57 is provided below the first carbonization chamber 56 and the gas combustion chamber 58, and performs ultra-high temperature carbonization by heating the dried sludge with 1100°C gas supplied from the gas combustion chamber 58. The second retort 34, which is provided to penetrate the second carbonization chamber 57, is made of a ceramic material (silicon carbide in this example) and is arranged approximately parallel to the axial direction of the first retort 32.

[0038] The second retort 34 has rings 85 and 86 attached to the outer periphery of one end and the other end, which are supported by rollers (not shown), and a drive chain is suspended on a sprocket 87 attached to the outer periphery of the other end (left side in the drawing) to rotate it. A supply device 88 is provided on one end side (right side in the drawing) of the second retort 34 for supplying the second retort 34 with sludge that has passed through the first retort 32 and been heated to a predetermined temperature.

[0039] The supply device 88 is equipped with a screw conveyor 88a and a hopper 88b. As described above, the upward opening 88c of the hopper 88b is connected to the opening 82 of the connected container 80 via the rotary valve 83. The discharge end of the screw conveyor 88a is inserted into the second retort 34, and the sludge once contained in the hopper 88b is fed into the retort 34 by the screw conveyor 88a.

[0040] The second retort 34 is slightly inclined downward toward the left in Figure 3, and the sludge sent from the first retort 32 side is sent toward the left in the figure as the retort 34 rotates, and is discharged to the outside from a discharge port 36 formed at the end on the left side in the figure. During this time, the sludge supplied inside the second retort 34 is kept at a temperature close to that of the atmosphere in the second carbonization treatment chamber 57, i.e., approximately 1100°C, and the pore area (specific surface area) of the carbonized material increases. As a result, carbonized material with high hydrogen sulfide adsorption performance is discharged from the carbonization furnace 28.

[0041] As shown in Figure 3, a gas exhaust port 99 is formed in the furnace body 30 surrounding the second carbonization treatment chamber 57 near the outlet side of the second retort 34, which discharges the combusted gas toward the exhaust gas treatment chamber 31, and the gas inside the furnace body 30 is sequentially sent to the exhaust gas treatment chamber 31 by the suction action of the exhaust gas fan 54 (see Figure 1).

[0042] After the carbonization process is completed, the bone-dry carbonized material discharged from the carbonization furnace 28 is sent to a cooler (not shown) to cool it down to near room temperature, and then sieved.

[0043] Fig. 5 is a diagram showing the configuration of the carbonization treatment equipment following Fig. 1. The carbonized material discharged from the carbonization furnace 28 and cooled to near room temperature is transported to a sieving device 102 by a transport device 101, as shown in Fig. 5.

[0044] 6 shows a schematic configuration of the sieving device 102. The sieving device 102 sieves the transported carbide into predetermined particle sizes, and is equipped with a casing 104 into which the carbide is fed, a trough 105 provided on the bottom surface of the casing 104 for vibrating and transporting the carbide, and a linear motor 106 fixed to the casing 104.

[0045] The casing 104 is a box-shaped member supported so as to be able to slide horizontally by rollers 109 provided at the upper end of the support body 108, and an inlet 110 through which the carbide is introduced is formed on the upper surface of one end of the longitudinal direction (left side in the figure). The internal space of the casing 104 is divided vertically into three areas: a first area 112, a second area 113, and a third area 114, by a first screen 115 and a second screen 116. Discharge outlets 112a, 113a, and 114a that open downward are formed at the other end of each area (the right side in the figure).

[0046] In the sieving device 102 configured in this manner, when the linear motor 106 is vibrated, the casing 104 and the trough 105 are vibrated, and the carbides C on the screen 115 are sieved in such a way that smaller particle sizes fall to a lower area according to the mesh size of the screen. A sieving device configured in this manner is described, for example, in JP 2010-277895 A.

[0047] The primary reason for providing the sieving device 102 downstream of the carbonization furnace 28 is to separate the ultra-high-temperature carbonized char into char containing slag and char without slag (high hydrogen sulfide adsorption capacity). If the sludge contains ash containing components with melting points lower than the carbonization temperature (e.g., 1100°C) (e.g., sodium sulfate, whose melting point is 884°C), these components melt during the ultra-high-temperature carbonization process, producing slag. Such char containing slag has no or very low hydrogen sulfide adsorption capacity. According to the inventors' research, most slag fuses and coarsens at ultra-high temperatures, resulting in particles with a diameter of 10 mm or more. In this example, the mesh size of the first screen 115 is set to 5 mm to separate the char containing slag.

[0048] The second reason for providing the sieving device 102 is to separate fine powder carbonized material that would otherwise fly around as dust during use from the carbonized material that has been subjected to ultra-high temperature carbonization. In this example, the openings of the second screen 116 are set to 1 mm in order to separate the fine powder carbonized material.

[0049] As a result, in the screening device 102 of this example, carbides including large particle size slag that did not pass through the first screen 115 are discharged from the discharge outlet 112a of the first area 112, carbides of medium particle size that passed through the first screen 115 but not the second screen 116 (carbides with excellent hydrogen sulfide adsorption performance and handleability) are discharged from the discharge outlet 113a of the second area 113, and carbides of small particle size that passed through the first screen 115 and the second screen 116 (carbides with problems in handleability) are discharged from the discharge outlet 114a of the third area 114.

[0050] As shown in Figure 5, the small particle size charcoal discharged from the sieving device 102 is returned by the conveying device 120 to the sewage treatment process, such as a settling tank in the sewage treatment facility, and the medium particle size charcoal is sent by the conveying device 121 to a bagging machine as charcoal with good hydrogen sulfide adsorption properties and easy handling. The large particle size charcoal is collected by the conveying device 122 via a route separate from the medium particle size charcoal. The collected large particle size charcoal is packed with fucose or the like and disposed of, or can be used for purposes other than as a deodorizing agent. The small particle size charcoal can also be packed into flexible containers or disposed of without being returned to the sewage treatment process.

[0051] The carbide particles can be further pelletized, which reduces the variation in shape and further improves handling. In this case, the carbonized material in the particle size is sent to the pellet forming device 140 via the chemical adding device 125 shown in Fig. 5. When pelletizing, it is preferable to subject the pellets to a drying treatment before sending them to the bagging machine.

[0052] As shown in Figure 5, the chemical additive device 125 includes a screw conveyor 126, a hopper 127 provided at the inlet of the screw conveyor 126, a mixing tank 128 for storing a mixed liquid obtained by mixing lignin and water, a pipe 129 as a spraying means for spraying the mixed liquid toward the carbonized material in the hopper 127 or the conveyor 126, a liquid feed pump 130, and a spray nozzle 131. The mixed liquid containing lignin in the mixing tank 128 is sent by the liquid feed pump 130 to the spray nozzle 131 attached to the top of the hopper 127, and is sprayed into the hopper 127, specifically toward the carbonized material in the hopper 127 or the conveyor 126. In this way, lignin is added to the carbonized material in the hopper 127 or the conveyor 126. The addition of lignin increases the strength of the carbonized material when it is pelletized, making it less likely for the pellet shape to collapse. The amount of lignin added is preferably in the range of 0.5 to 2.0% of the solid weight of the carbonized material.

[0053] 7 is a diagram showing the schematic configuration of a pellet forming apparatus 140 into which the carbonized material to which lignin has been added is fed. The pellet forming apparatus 140 shown in the figure includes a die 141, a rotary shaft 143, and a press roller 144 and a cutter 145 attached to the rotary shaft 143. The mold 141 has a disk-like overall shape and is formed with a large number of through-holes 142 that penetrate vertically. The outer peripheral edge of the mold 141 is supported by a frame 146. The pressing rollers 144 are disposed above the die 141 and roll over the through holes 142 to press the carbide on the die 141 into each of the through holes 142 . The cutter 145 is disposed below the mold 141 and rotates around the axis of the rotary shaft 143 to cut the compact extruded downward from the through-hole 142 to a predetermined length.

[0054] In the pellet molding device 140 configured in this manner, carbide material is fed through an upper feed port 148, pushed into each through-hole 142 by a push roller 144, compressed, and then extruded downward from the lower end of the through-hole 142 as a compact. The continuously extending compact is then cut by a cutter 145 into cylindrical pellets P of a predetermined length (see partial enlarged view). The cut pellets P are thrown radially outward by a discharge disc 150 that rotates together with the rotary shaft 143 below the cutter 145, and are discharged from a discharge port 152. A drying device for drying the discharged pellets may also be provided separately.

[0055] [Example] The specific surface area and hydrogen sulfide adsorption capacity of carbides and pellets with different particle sizes obtained by sieving carbides that had been subjected to ultra-high temperature carbonization were investigated. Three types of carbides were investigated: (1) carbides with medium particle size (1 mm to 5 mm), (2) pellets obtained by molding carbides with medium particle size, and (3) carbides with large particle size (greater than 5 mm). The carbonization conditions are a carbonization temperature of 1000 to 1100°C, a residence time of 45 minutes or more, and a kiln (retort) filling rate of 30%. When forming the pellets in (2) above, lignin was added in an amount of 1.5% of the weight of the solid matter in the carbonized material, and pellets of Φ4×10 mm were formed.

[0056] The specific surface area of ​​the charcoal (or pellet) was measured by the N2-BET method. To measure the amount of hydrogen sulfide adsorption, 0.2 g of sample was placed in a breathable bag, which was then attached to a Witt filter and filled with 100 ppm of hydrogen sulfide. After two hours, 25 mL of gas was removed from the filter and the hydrogen sulfide concentration was measured. The amount of hydrogen sulfide adsorption was calculated from the measurement results. Additionally, for comparison, the amount of hydrogen sulfide adsorption was also investigated for commercially available activated carbon PG-S (manufactured by Asahi Filter Materials Co., Ltd.). These results are shown in FIG.

[0057] The results in Figure 8 reveal the following: After ultra-high temperature carbonization, the carbonized material was sieved to particles of 1mm to 5mm in size, and it was found to have a hydrogen sulfide adsorption capacity approximately 1.5 times that of commercially available activated carbon, making it suitable for use as a deodorizing material. On the other hand, pellets obtained by molding carbonized material into particles show a slightly lower hydrogen sulfide adsorption capacity than carbonized material of the same particle size, but still show a hydrogen sulfide adsorption capacity equal to or greater than that of commercially available activated carbon. Therefore, pelletization is effective when you want to improve the handleability of carbonized products. On the other hand, carbides that are sieved to particles larger than 5 mm and contain a large amount of slag have a significantly low hydrogen sulfide adsorption capacity and are therefore unsuitable as deodorizing materials.

[0058] As described above, according to the method for producing a carbonized product in this embodiment, the specific surface area of ​​the carbonized product is increased by performing ultra-high temperature carbonization treatment at 1000°C or higher, and as a result, the hydrogen sulfide adsorption performance can be improved. Furthermore, even if the low-melting-point ash in the sludge melts during the ultra-high temperature carbonization process and slag that has no hydrogen sulfide adsorption capacity is produced, a sieving process is installed downstream to sieve the carbonized material to a specified upper limit size or less, and carbonized material that does not contain slag and has high hydrogen sulfide adsorption capacity can be separated and extracted from the carbonized material, making it possible to produce carbonized products with excellent hydrogen sulfide adsorption capacity.

[0059] Furthermore, in the screening process, by specifying the lower limit size of the carbonized material in addition to the upper limit size of the carbonized material and performing screening, it is possible to produce a carbonized product that has excellent hydrogen sulfide adsorption performance and is also easy to handle.

[0060] In the method for producing a carbonized product in this embodiment, lignin is added to the sieved carbonized material, and the carbonized material to which the lignin has been added is extruded through through-holes 142 formed in a mold 141 and cut, thereby forming the carbonized material into cylindrical pellets. By pelletizing the carbonized material in this manner, dimensional variation in the carbonized product can be reduced, further improving handleability.

[0061] Although the embodiments of the present invention have been described in detail above, these are merely examples. For example, in the above embodiment, the char obtained by the carbonization process is sieved into three types of particle size: large, medium, and small. However, in some cases, it may be sieved into two types: char containing slag (large particle size char) and char not containing slag (small particle size char). Furthermore, the mesh size of the screen (sieve) used to sieve the char can be changed as appropriate depending on the properties of the sludge used. For example, the present invention can be configured in various modified forms without departing from the spirit of the invention. [Explanation of symbols]

[0062] 1 Carbonization treatment facility 16 Dryer 28 Carbonization furnace 32 First Retort 34 Second Retort 102 Sieving device 115 First Screen 116 Second Screen 125 Chemical Addition Device 140 Pellet molding equipment 141 Mold 142 Through hole

Claims

1. The dehydrated sludge obtained by dehydrating organic matter-containing sludge is passed through a dryer to dry it to a predetermined moisture state to obtain dried sludge, and the dried sludge is heated under anoxic or low-oxygen conditions to carbonize it to produce a carbonized product, a carbonization treatment step in which the dried sludge is finally carbonized at an ultra-high temperature of 1000 to 1200°C to melt the ash contained in the dried sludge and produce slag; a sieving step of sieving the carbide obtained by the carbonization treatment into coarse carbides that did not pass through the first screen and carbides that passed through the first screen, using a first screen having openings that can sieve out coarse carbides having a particle size of 10 mm or more, including the slag; A method for producing a carbonized product, comprising:

2. 2. The method for producing a carbonized product according to claim 1, wherein in the sieving step, a second screen having a mesh size smaller than that of the first screen is used to further sieve the carbonized material that has passed through the first screen to a predetermined lower limit size or larger.

3. A method for producing a carbonized product described in either one of claims 1 and 2, characterized in that it further comprises a pellet forming process in which lignin is added to the sieved carbonized material, and the lignin-added carbonized material is extruded through a through hole formed in a mold, cut, and formed into pellets.

4. a dryer for drying the dehydrated sludge obtained by dehydrating the organic matter-containing sludge to a predetermined moisture state to produce dried sludge; a carbonization furnace having a retort as a dry distillation vessel made of a rotary drum inside a furnace body, the retort being rotated while the dried sludge is moved in an axial direction, and the dried sludge being carbonized by a carbonization process during the movement, the carbonization furnace including a first retort as the retort, and a second retort located downstream of the first retort in the sludge conveying direction and containing a ceramic material; a sieving device that has a sieve with openings that can separate carbides having particle sizes of 1 mm to 5 mm from coarse carbides having particle sizes of 10 mm or more, and sieves the carbides discharged from the carbonization furnace according to their particle sizes; A carbonization treatment facility comprising:

5. A chemical addition device that adds lignin to the carbonized material; a pellet molding device that extrudes the lignin-added carbonized material through through holes formed in a mold, cuts it, and molds it into pellets; 5. The carbonization treatment facility according to claim 4, further comprising a sieving device disposed downstream of the sieving device in the carbonized material transport direction.

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