KR20120023276A - The method for preparing solid fuel using the sludge - Google Patents

Abstract

PURPOSE: A method for manufacturing solid fuel using sewage sludge is provided to economically manufacture solid fuel of constant sizes and high intensity by drying sewage sludge and pelletizing the dried sewage sludge. CONSTITUTION: A method for manufacturing solid fuel using sewage sludge includes the following: sewage sludge is dehydrated such than the water content of the sewage sludge become lower than or equal to 10 weight%(S102, S103); water is supplied to the sewage sludge such that the water content of the sewage sludge is in a range between 13 and 17 weight%; the sludge is ground and mixed; the mixed sludge is pelletized(S106); and the pelletized sludge is dried such than the water content of the pelletized sludge become lower than or equal to 10 weight%(S107). If the organic material content of the sludge in a mixing process is lower than or equal to 30 weight%, combustible waste is added to the sludge.

Description

The method for preparing solid fuel using the sludge

The present invention relates to a method for producing solid fuel using sewage sludge, and more particularly, to a method for producing high strength solid fuel in an economical manner using sewage sludge.

Sediment that accumulates in sewage pipes during sewage treatment is called sewage sludge. In Seoul, about 1,800 tons of sewage sludge is generated per day, and in Korea, landfill and ocean dumping account for 30% of landfill, 45% of marine dumping, 20% of incineration, and 5% of recycling. . The offshore dumping will be banned under the London Convention from 2012, and it is urgent to develop alternative fuels that can be replaced by rising oil prices.

As part of the development of the alternative fuel, when the solid fuel is made by using sewage sludge, the calorific value of the microorganisms that eat organic matter such as food waste and manure contained in the sewage is dehydrated, dried, and molded. Organic fuels similar to lower coal can be produced at or around 3500 mW / kg.

However, organic fuel sludge has a high amount of calories due to a large amount of organic matter, but its high moisture content is not suitable for use as a fuel. However, when the moisture content of the organic fuel sludge is dried to 10% by weight or less, it can be used as an excellent renewable energy.

Currently, the amount of sewage sludge generated in the whole country is estimated to be about 7000 tons per day, and if the toner is dried at 1000 tons, 200 tons of dry sludge having a water content of 10% by weight or less is produced. Although the heat required to obtain 1 kg of dry sludge is 2,600 kPa, the calorie obtained from this dry sludge is about 3500 kW / kg, which is useful as an auxiliary fuel.

Dry sludge has the following advantages when used in a solidified state rather than in a powdered state.

First, when used in a solid state rather than a powder state will reduce the volume.

Secondly, the solidified state is not scattered by heat and wind during combustion than the powdered state, so it can reduce fuel loss and clean the surrounding environment.

Third, the solidified state lasts a long burning time as compared to the powdered state, and heat efficiency per unit weight is higher, thereby improving the efficiency of the combustion device.

Fourth, the solidified state is capable of quantitative supply because the particle size and specific gravity are constant.

Fifth, the solidified state reduces the volume and reduces equipment costs.

Sixth, in the solidified state compared to the powder, the air gap between the solid fuel becomes large, and the air supply is easy, and combustion is better.

On the other hand, in the conventional screw extruder-type pellet molding machine (see Patent Document 1), in order to mold in pellet form, the water content of the sewage sludge is 30 to 50% by weight, so that extrusion can be performed by reducing the resistance during extrusion. Therefore, after molding, the strength is weak due to residual moisture, it is difficult to maintain the pellet form. Therefore, in order to maintain the pellet form, it must be further dried using a hot air dryer after extrusion molding. Pellet sludge thus dried tends to break easily during transportation and handling, since the pores are formed in the interior while the moisture is dried, thereby decreasing the compressive strength.

In addition, in Patent Documents 2 and 3, in order to facilitate the formation of pellet sludge, sewage sludge having a high moisture content must be added as a raw material, so that the strength of the finished final product is weak and the moisture content is high. If you do not cut by the cutting machine or there is a disadvantage that the cut surface is not clean.

Compression molding machines (see Patent Documents 4 and 5) of the coal briquette forming machine and the ball coal briquetting machine system of another prior art may use dry sewage sludge, so a separate drying device is not necessary after molding, but such a compression molding machine is simply It is not a pellet sludge because it is compressed and solid sludge, and the size of the product is so large that it can be used as fuel for special purpose combustors, but it can be used for automatic feeders that supply a fixed quantity used for ordinary combustors such as boilers. It is not suitable as a solid fuel.

Patent Document 1: Korean Patent No. 10-0908450

Patent Document 2: Korean Unexamined Patent Publication No. 2009-0045161

Patent Document 3: Korean Patent Publication No. 2005-0121785

Patent Document 4: Korea Patent No. 10-0700110

Patent Document 5: Korea Patent Registration No. 10-0914993

Therefore, in the present invention, as a result of extensive research to solve the above problems, when the water content of sewage sludge is dried to 10% or less, and then pelletized while supplying water, solidified solid fuel having a constant size and high strength Was prepared in an economical manner, and the present invention was completed based on this.

Accordingly, an object of the present invention is to provide a method for producing a high-strength solid fuel using sewage sludge which can automatically regulate the amount of supply through electric control in a screw or vibration metering feeder used in a large-scale combustion device such as a power plant. have.

Method for producing a solid fuel using sewage sludge according to the present invention for achieving the above object is as follows.

(One). Dewatering the sewage sludge and then drying to provide sewage sludge having a water content of 10% by weight or less; Grinding and mixing the sludge while supplying water to the sludge so that the water content of the sludge is in the range of 13 to 17 wt%; Pelletizing the mixed sludge by compression molding in a pellet molding machine having an extrusion die; And drying the pelletized sludge such that the water content of the sludge is 10% by weight or less.

(2). The method according to (1), wherein the method is characterized in that the sludge contains at least one combustible waste selected from the group consisting of carbon-based fossil fuels, waste paper, plastic waste and wood when the organic matter content in the sludge is 30% by weight or less. It further comprises the step of adding.

(3). The process according to (1) or (2), wherein the mixing step is performed in a conditioning mixer.

(4). (1), the extrusion die has a plurality of extrusion holes, the extrusion hole is a compression unit having a diameter of 3 ~ 10mm; A cooling unit extending from the end of the compression unit to an outer diameter of 1 to 2 mm with respect to the inner diameter of the compression unit to cool the extrudate in air; And an inclined portion extending from 1.5 ° to 30 ° in an inward direction of the extrusion die at an opposite end of the compression part in which the cooling part is formed, to induce extrusion, an inner diameter of the compression part from an end of the first inclination part. An injection unit extending from about 1 mm to 2 mm outside to induce the extrudate, and 10 ° to 30 ° in an inward direction of the extrusion die from an end of the injection unit to initially induce the compressed product. Characterized in that it comprises; an inlet portion consisting of two inclined portion.

(5). In (1), the drying step is characterized in that performed in a counter flow cooling dryer.

(6). The method of (1), characterized in that the method further comprises coating a colorant or a combustion catalyst on the surface of the pelletized sludge.

(7). (1) The pelletized sludge has a diameter of 3 to 10 mm, a length of 6 to 30 mm and an impact strength of 90 kg / cm 2 or more.

The present invention can produce sewage sludge into pellets of constant size and high strength. Therefore, in the screw-type or vibratory metering feeder used in a large-scale combustion device such as a power plant, it is possible to automatically regulate the amount of supply through electric control.

In addition, the pellet sludge of the present invention is not easily broken due to a certain impact strength or more, and does not require a drying device that additionally adds a separate heat source during the manufacturing process, thereby making it easier to produce pellet sludge that is economical and high in strength as compared with the prior art. In addition, the pelletized sludge of a certain size can reduce the size of the equipment, such as transport equipment, storage facilities, supply equipment, so that the facility cost, transportation costs, logistics costs and storage costs are inexpensive and easy to handle, thereby saving costs.

1 is a flowchart sequentially showing a manufacturing process of a solid fuel using sewage sludge according to the present invention.
2 is a process diagram schematically showing a manufacturing process of a solid fuel using sewage sludge according to the present invention.
Figure 3 is a side view schematically showing a continning mixer and pellet molding machine used in an embodiment of the present invention.
Figure 4 is a schematic diagram showing a molding process using a pellet molding machine used in an embodiment of the present invention.
Figure 5 is a schematic view showing the extrusion hole of the pellet molding machine used in one embodiment of the present invention.
6 is a schematic diagram of a cooling drying apparatus used in an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

1 and 2 show a method for producing a solid fuel using the sewage sludge of the present invention.

Referring to Figures 1 and 2, looking at the method of the present invention, first, the sewage sludge concentrated in the sewage treatment plant is introduced into the dehydrator (S 101), and then the sewage sludge is dewatered from the dehydrator (S 102). The water content of the dewatered sludge thus dehydrated is generally in the range of 70 to 85% by weight. Then, it is transferred to a dryer and dried (S 103) to provide dried sewage sludge having a water content of 10% by weight or less, preferably 8 to 10% by weight, and supplying the dried sludge to the mixer (S 104). do. As the dehydrator and dryer used in the present invention, a commercially available dehydrator and dryer can be used.

In general, when sewage sludge is used as a fuel, the water content of the sludge is preferably 10% by weight or less. This means that when the moisture content of the dry sludge exceeds 10% by weight, the heat loss consumed during heating and evaporation by the moisture contained in the sludge increases, thereby reducing the efficiency of combustion, and when the moisture content is lower than 10% by weight, the fuel As a result, the combustion efficiency is increased, but it is expensive to dry, which causes a cost increase.

Therefore, in the present invention, the moisture content of the sludge in the drying step is maintained at 10% by weight or less, preferably 8 to 10% by weight, followed by molding by adding water in a subsequent process, and rebuilding the water content of the sludge to 10% by weight or less. We were able to maximize economics at the time of Josh.

On the other hand, in step 104, when the organic content of the sewage sludge is 30% by weight or less, it may be optionally mixed (S 201) by adding a flammable waste. If the dry sludge has an organic content of less than 30% by weight, the calorific value of the sludge decreases and the value as a fuel decreases. Therefore, if the organic content of the sludge is low, carbonaceous fossil fuel, waste paper, plastic waste and / or wood are present in the sludge. It is desirable to add flammable wastes such as, but not limited to, all other combustible organic additives to increase the pellet forming rate and the calorific value to increase the value as a fuel. The combustible waste may be added by grinding uniformly and finely, and the added combustible waste is uniformly mixed in the dry sludge and the mixer.

Then, the sludge is pulverized and mixed (S 105) while supplying water to the sludge so that the water content of the sludge is in the range of 13 to 17% by weight, preferably 15% by weight. In forming dry sludge having a water content of 10% by weight or less in the form of pellets, by adding appropriate moisture to the surface of the dry sludge particles, maintaining the mixing force with the respective sludge particles themselves or flammable waste, It is possible to increase the molding efficiency by increasing the binding force and bonding force. In this way, by supplying water to the surface of the slurry and molding, pellets having higher strength can be economically molded than when molding into a slurry having the same moisture content. Therefore, when the moisture content exceeds 17% by weight, the moisture content of the dry sludge is increased, so when molding in a pellet molding machine, the molding cost is good because the power ratio is low, but the moisture content of the final product should be 10% by weight or less, so the amount of water must be evaporated. This is disadvantageous due to the increased drying time and cost. If the water content of the sludge is less than 13% by weight, the molding of the sludge in the form of pellets during the pellet molding is not performed well, there is a disadvantage that the power cost increases.

In the present invention, the mixing process may be carried out in the conditioning mixer 300 (S 105), which is shown in FIG. Referring to the structure of the conditioning mixer 300 of FIG. 3 in detail, there is one rotary shaft 31 that rotates by an electric motor in the center of the cylindrical body, a plurality of blades 32 inclined by about 30 ° When the rotary shaft 31 is rotated at a high speed of about 350 to 450 revolutions per minute, the blade 32 is also rotated at a high speed with the rotary shaft 31, and the blade 32 inclined to dry sludge supplied from the feeder 200. By moving forward, by the centrifugal force of the end of the wing 32, the end of the wing 32 collides with the mass so that the process of movement, grinding and mixing is made in one device at the same time. If the rotation in the mixer 300 is slower than about 350 revolutions per minute, the centrifugal force is weak at the end of the blade, so that the grinding is not performed properly, and if the rotation is faster than about 450 revolutions per minute, the contents cannot be sufficiently mixed, so that the mixing is not performed properly. .

According to the mixer 300 of the present invention, the water supplied by supplying the moisture as described above between the blade 32 and the feeder 200 simultaneously rotating and moving while rotating at about 350 to 450 revolutions / minute is supplied. It is mixed evenly with dry sludge. The water supply can be used as long as a conventional water supply such as a spray nozzle 33, and as shown in Figure 2, supply the water using a water tank connected to the spray nozzle 33 (S 202) You may.

According to the present invention, the mixed sludge is pelletized by compression molding in a pellet molding machine having an extrusion die (S 106). Then, the pelletized sludge is dried (S 107) such that the water content of the sludge is 10% by weight or less. Optionally, a colorant or a combustion catalyst may be coated on the surface of the pelletized sludge (S 203). Through the above process, a sewage sludge pellet fuel having a final moisture content of 10% by weight is manufactured (S 108).

According to the present invention, in the compression molding step, the sludge containing the water content of 13 to 17% by weight, preferably about 15% by weight, is introduced into the pellet forming machine 400 having the compression die so as to have an impact strength of 90 kg / cm 2 or more. It is compressed to high pressure and compression molded into a compressed pellet shape.

In the present invention, dry sludge can be compression molded using a commercially available pellet molding machine. Referring to Figure 4 describes the compression molding process of the present invention, the compression die or rotary wheel 41 located in the casing 45 is rotated by an electric motor and supplied to the interior of the compression die or rotary wheel 41 The sludge 46 is rotated in the same direction as the compression die or the rotary wheel 41 by the rotational force of the compression die or the rotary wheel 41. Compression rollers 42 and 43 do not rotate because the central axis is fixed to the fixed plate, only the outer roller (rollacell) is to idle (idle rotation). At this time, when the dry sludge 46 rotating along the inner wall of the rotary wheel 41 meets the compression rollers 42 and 43, the rotating dry sludge 46 is stopped by the compression rollers 42 and 43. . The dry sludge 46 stopped by the compression rollers 42 and 43 is compressed to a high pressure and discharged to the extrusion hole 50 of the compression die 41. The compressed sludge discharged in this way is compressed and becomes a solid solid and is discharged to the outside of the rotary wheel 41. The sludge discharged in this way is cut into a predetermined size by the cutter (44). The pelletized sludge 47 has a diameter of about 3 mm to 10 mm, a length of about 6 mm to 30 mm, and a high strength solid fuel having an impact strength of 90 kg / cm 2 or more. This means that the pellet molding machine 400 is excellent in producing a solid fuel having a high strength while maintaining a constant size and shape as compared to other extruders, compression molding machines and the like.

With reference to FIG. 5, the extrusion hole 50 of the compression die 41 of the pellet molding machine provided with the said extrusion die 41 is demonstrated. The extrusion die 41 has a plurality of extrusion holes 50. The extrusion hole 50 is composed of a compression unit 51, a cooling unit 52 and the inlet portion 56 having a diameter of 3 ~ 10mm. The cooling unit 52 extends outwardly 1 to 2 mm with respect to the inner diameter of the compression unit 51 from the end where the compression unit 51 ends and serves to cool the extrudate in the air.

The inlet part 56 includes a first inclination part 53, an injection part 54, and a second inclination part 55. The first inclined portion 53 is formed to be inclined to extend in an inward direction of the extrusion die 50 to 1.5 ° ~ 30 ° at the opposite end of the compression unit 51 in which the cooling unit 52 is formed to induce extrusion do. The injection part 54 extends from the end of the first inclination part 53 to an outer diameter of 1 to 2 mm with respect to the inner diameter of the compression part 51 to induce the extrudate. Finally, the second inclined portion 55 is formed at an angle of 10 ° to 30 ° in the inward direction of the extrusion die from the end of the injection portion 54 to initially guide the compressed material.

For example, on the inner diameter side of the compression die 41, the 14 mm hole (second inclined portion) is 15 mm lowered (injection portion) while narrowing to 12 mm in a trumpet shape with a depth of 2 mm. The diameter is narrowed to 10 mm again to a depth of mm, and 35 mm is straight down (compression part), and at the end, the diameter is increased to 12 mm and 15 mm is lowered (cooling part) to the outer diameter side of the compression die 41. It consists of a discharge process. Here, the 14 mm diameter portion (second inclined portion) functions as an induction furnace, and has a larger size to facilitate entry of the dry sludge into the 12 mm hole, and the thus-induced dry sludge is a 12 mm hole injection portion. In (54), the first compression is performed by passing the length of 15 mm, and the compressed sludge, first compressed to 30 kg / cm 2, is a 10 mm hole through the inclined hole once again to easily enter the hole of the next stage. The final compression process is performed while passing through the compression section 51 by 35 mm length, and the compression force is compressed to reach 90 kg / cm 2 or more. The compression sludge temperature is 80 ° C. to 90 ° C. by compression and frictional heat. This leads to. Since the high-temperature high-pressure compressed sludge is discharged without any further increase in temperature at 80-90 ° C because no further friction or compression is applied while passing the length of 15 mm through the 12 mm hole, the end of which the hole diameter is expanded, the cooling part 52 ).

On the other hand, the size of the hole and the length shown in Figure 5 is an example, the diameter and the length can be changed proportionally, the hole diameter is 12mm in proportion to the 10mm compression hole diameter of the illustrated figure All other dimensions are also proportionally larger, and when the hole diameter is 5 mm, all other dimensions are proportionally smaller. If the compression hole diameter is larger than 10 mm, the compression length should be 35 mm, and all other dimensions will be proportionally larger. If the compression part is short, the compressive strength is less than 90㎏ / ㎠ and it breaks well during transportation or handling after molding into pellets. If the compression part is long, the compression strength is higher than 90㎏ / ㎠ and it is not broken, There is a disadvantage that the risk of damage to the rotating wheels and increased power consumption. The hole diameter of the compression part may be larger or smaller than 10 mm. However, when the diameter of the hole is too small, it is difficult to cut and drill the hole of the rotating wheel by a machine.

The pelletized sludge subjected to the above process is subjected to high pressure while passing through the extrusion die, thereby raising the temperature of the pelletized sludge discharged due to the high pressure and the frictional heat to 80 ° C to 90 ° C. At this time, the high temperature is generated by drying at least 2% by weight of moisture from 13 to 17% by weight of the discharged pelletized sludge and releasing it into the air, resulting in a water content of 11 to 15% by weight of the discharged pelletized sludge. Lower it to.

That is, the pelletized sludge cut to a constant length by the cutter 44 has a temperature of 80 ° C to 90 ° C and has an average water content of about 13% by weight. The sludge is then cooled to dryness so as to have a water content of 10% by weight or less. Any device may be used as long as it is a cooling drying device capable of cooling the sludge to dry the water content to 10% by weight or less.

However, the counter flow cooling apparatus is shown in FIG. 6 as a preferred embodiment of the cooling drying apparatus of the present invention. Referring to Figure 6, the cooling dryer 600 is provided with a main body 61 of the square-shaped cooling dryer made of steel, the upper portion of the main body 61 while pelletizing the 80 ℃ to 90 ℃ while blocking the outside air The rotary airlock 62 is made to supply only the sludge, and the lower part of the main body 61 is automatically operated when the sludge pelletized to a certain height (about 800 mm) is stacked on the main body to cool the pelletized material. The sludge 63 is provided with a motor-driven reciprocating ejector 64 for discharging all or part of the sludge 63 below the main body 61 by free fall. Since the counter flow cooling dryer 600 is an air-cooled drying method, the dried pellet maintains its shape and high strength as compared to a drying apparatus that is dried by heat by applying heat, and the cost is reduced when drying, and the pelletized sludge There is an advantage that can be easily cooled and dried.

In addition, the turbo fan 65 having a role to suck the outside air into the main body 61 as a secondary equipment and the sucked air passes through the main body to separate fine dust and particles, so that only filtered air is discharged into the atmosphere. It is provided with a cyclone dust collector (66) to discharge the dust and dust collected when a certain amount of dust, such as dust collected.

On the other hand, the present invention and other compression molding technology uses a sewage sludge of 30 to 50% by weight in order to facilitate the compression molding in the molding machine, but after the compression molding is necessarily a heating dryer, but in the present invention compression molding In order to achieve the characteristics, dry sludge with a moisture content of 11-15 wt% is used as a basic raw material, and dry pellets of high-pressure pelletized sludge are dried at room temperature, and pellets are heated by heat of 80-90 ° C. by compression and friction heat generated during pellet molding. At least 2% by weight of moisture is evaporated into the air while the pellet is discharged from the molding machine, and the remaining water is cooled by air at room temperature in the air cooler to evaporate to dry. It is characterized in that the water content is suitable for use as fuel.

According to the present invention, after the sewage sludge is prepared into pelletized sludge, the surface of the pelletized sludge may further include coating a colorant or a combustion catalyst with a suitable coater. This may improve the appearance and coat the color of the particles differently according to the fuel components to enable the naked eye to distinguish the fuel, or to increase the combustion efficiency when the combustion catalyst is coated.

As an example, when the fine charcoal powder is rotated while being put into the coating machine, such as pelletized sludge, the black charcoal powder is physically bonded to the surface of the pelletized sludge, and the charcoal powder itself is colored. Since it is a combustible material, it also serves as a combustion catalyst. Various non-toxic paint pigments on the market may be mixed with charcoal powder to pre-color charcoal powder, and then put into a coating machine and contacted with pelletized sludge to be colored in various desired colors.

In addition, it is difficult to prepare a mixed fuel when the raw material in the powder form and the fuel of various shapes and sizes are mixed together, but it is difficult to prepare a mixed fuel, but the powder is pulverized to a uniform size as in the present invention, and then mixed uniformly and compression molded. The solid fuels made can be mixed in the right proportions to produce mixed fuels that are evenly mixed.

200: feeder
300: mixer 33: spray nozzle
400: pellet molding machine or pellet mill 41: compression die or rotary wheel
50: extruder
600: cooler 62: rotary airlock

Claims (7)

Dewatering the sewage sludge and then drying to provide sewage sludge having a water content of 10% by weight or less;
Grinding and mixing the sludge while supplying water to the sludge so that the water content of the sludge is in the range of 13 to 17 wt%;
Pelletizing the mixed sludge by compression molding in a pellet molding machine having an extrusion die; And
Drying the pelletized sludge such that the water content of the sludge is 10% by weight or less;
Solid fuel production method using sewage sludge, characterized in that it comprises a.
The method according to claim 1,
The method further comprises the step of adding at least one combustible waste selected from the group consisting of carbonaceous fossil fuel, waste paper, plastic waste and wood when the organic content in the sludge is 30% by weight or less in the mixing step. Solid fuel production method using sewage sludge, characterized in that.
The method according to claim 1 or 2,
The mixing step is a solid fuel production method using sewage sludge, characterized in that carried out in a conditioning mixer.
The method according to claim 1,
The extrusion die has a plurality of extrusion holes,
The extrusion hole is a compression unit 15 having a diameter of 3 ~ 10mm;
A cooling unit (16) extending from the end of the compression unit to an outer diameter of 1 to 2 mm with respect to the inner diameter of the compression unit to cool the extrudate in air; And
A first inclined portion 11 formed to be inclined at an angle of 1.5 ° to 30 ° in an inward direction of the extrusion die at an opposite end of the compression portion in which the cooling portion is formed, and inducing the extrusion from the end of the first inclined portion; The injection part 12 is extended to the outer diameter 1 ~ 2mm with respect to the inner diameter diameter and is formed in 10 ° ~ 30 ° in the inward direction of the extrusion die from the end of the injection portion to form the compressed material An inlet portion 14 composed of a second inclined portion 13 for initial induction;
Solid fuel production method using sewage sludge, characterized in that provided with.
The method according to claim 1,
The drying step is a method for producing solid fuel using sewage sludge, characterized in that carried out in a counter flow cooling dryer.
The method according to claim 1,
The method further comprises the step of coating a colorant or a combustion catalyst on the surface of the pelletized sludge, the method for producing solid fuel using sewage sludge.
The method according to claim 1,
The pelletized sludge has a diameter of 3 ~ 10 mm, a length of 6 ~ 30 mm and an impact strength of 90 kg / ㎠ or more, solid fuel using sewage sludge.

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