JP5029453B2 - Transportation method of landfill ash - Google Patents

Description

  The present invention relates to a method for transporting landfill ash when excavating incineration ash such as municipal waste that has been disposed of in landfill and recycling it as a cement raw material.

  Various types of incineration ash, including municipal waste incineration ash, are generally disposed of in landfills.Recently, the capacity of the landfills has been tightened, and this landfill has been difficult due to the difficulty in securing new land. It has been studied to extend the life of the disposal site by excavating the ground and recycling the landfilled incineration ash (hereinafter referred to as landfill ash) as a raw material for cement.

  Since landfill ash may contain harmful dioxins, it is necessary to transport the landfill ash in a sealed manner so that the landfill ash does not scatter. In addition, landfill ash is exposed to rain or the like outdoors and contains 15 to 35% by weight of water. For this reason, when transporting pneumatically, landfill ash adheres from the bent portion of the transport pipe, and there is a problem that the transport becomes difficult due to troubles such as blockage of the pipe. In particular, when the transport distance is 20 to 50 meters or more, the influence is remarkable, and the piping may be blocked in a short time.

  As the landfill ash transporter, generally, a transporter such as a closed chain conveyor or a vertical belt conveyor is often used. However, these transport aircraft require a large space for restrictions on placement and installation. In addition, there are problems such as concern about troubles due to adhesion of landfill ash to belts and other transportation equipment.

As an improvement in handling properties in the transportation process of incineration ash, etc., Patent Document 1 describes a technique for improving the handling property by mixing with incineration ash in a state in which waste plastic is heated and melted to improve handling and taking measures against dust generation Yes. However, a process of applying heat is required. Patent Document 2 discloses that a large amount of water is mixed, that is, slurryed and transported over a long distance by a pump. However, landfill ash needs to be treated at a high temperature, so it is put directly into the high temperature part of the kiln kiln, so if a large amount of water is used, the heat loss required for water evaporation and heating increases. There were still operational problems in transportation such as deterioration of the operation of the equipment.
JP 2002-66499 A JP 2004-97865 A

  An object of the present invention is to reduce adhesion and blockage in an air transport pipe and improve transport efficiency when air transporting landfill ash mainly composed of incinerated ash.

  As a result of intensive studies on the conditions for pneumatically transporting the landfill ash, the present inventors have found that if waste plastic is accompanied with the landfill ash as a fluidity aid, adhesion and blockage of the landfill ash inside the air transport pipe will be reduced. The headline and invention were completed. That is, the present invention digs up the landfill ash, and when transporting the dug up landfill ash to the bottom of the kiln of the cement kiln, the landfill ash is accompanied by waste plastic and is transported by air. Is the method. The waste plastic preferably has a longest portion of 5 to 20 mm. In addition, it is preferable that 10 to 30 parts by weight of the waste plastic is accompanied by pneumatic transportation with respect to 100 parts by weight of landfill ash.

  According to the present invention, it is possible to reduce the phenomenon that landfill ash adheres to the piping for pneumatic transportation and clogging, and landfill ash can be continuously charged into the kiln. As a result, the cement kiln can be operated continuously and stably, and the productivity is improved.

  Landfills as final disposal sites mainly composed of municipal waste incineration ash, sewage sludge incineration ash, and water sewage sludge incineration ash can be recycled as raw materials for cement clinker. Excavate and dig up this landfill. At the excavated site, large foreign substances such as resin burning glass, stones, concrete, and non-magnetic metals are removed by a wind separator, and magnetic metals such as iron are removed by a magnetic separator. Next, the size is sieved to 40 mm or less by a sieving device to form a granular material having a size that can be used as a raw material for cement clinker as landfill ash. The landfill ash 1 preferably has a longest side of 40 mm or less and an average size of 5 to 15 mm. This landfill ash is loaded onto a vehicle such as a dump truck and carried into a cement factory.

  As shown in FIG. 1, landfill ash 1 received in a storage facility such as a receiving tank 4 of a cement factory is extracted with waste plastic 2 stored in a separate waste plastic tank 3 at an optimum blending ratio. Mixed. Here, the waste plastic 2 is mainly composed of soft fluffy resins made of polyethylene, polypropylene, polystyrene, PET, nylon, etc., but it contains flammable waste such as rubber, wood chips, paper, fiber, and oil. You may do it.

The waste plastic 2 is preferably crushed in advance, passes through the entire 40 mm sieve, and has a longest side of 5 to 20 mm and an average size of about 10 mm.
Further, it is desirable that dice-like hard resin composed of a lump having a sharp surface of about 10 to 30% by weight as a whole is mixed. This is because if it exceeds 30% by weight, there is a possibility of causing accumulation or clogging in the piping at the rising portion or the upward inclined portion of the piping that is being transported to the kiln bottom 9 within the air transport tube 8.

  The landfill ash 1 and the waste plastic 2 are mixed with an optimum blending ratio by weighing each of the landfill ash from each storage tank with a weighing machine. The optimum blending ratio of the waste plastic 2 is 10 to 30% by weight, preferably 20 to 30% by weight, with respect to 100 parts by weight of landfill ash. If the hard plastic contains a large amount of the hard resin, the ratio of waste plastic to landfill ash can be qualitatively small.

  As shown in FIGS. 1 and 2, after the landfill ash 1 and the waste plastic 2 are blended, the air from the sealed pneumatic feeder 7 is transported to the kiln bottom 9 of the cement kiln 14 by the dedicated air transport pipe 8. Is done. Finally, it is ejected from a dedicated cylindrical tube 11 attached to the kiln butt portion 9 and put into a cement kiln 14. In the cement kiln 14, the combustion heat from the kiln burner 19 is discharged from the exhaust gas fan 20, so that the atmosphere temperature in the kiln bottom 9 is generally 1000 to 1200 ° C. For this reason, the waste plastic that has been put in burns immediately, and the water in the landfill ash also evaporates immediately. The landfill ash charged into the cement kiln 14 is combined with the cement raw material supplied from the cement raw material inlet 10 at the kiln bottom 9 and fired while gradually raising the temperature by the combustion heat of the kiln burner 19, The cement kiln outlet 16 becomes a part of the cement clinker 15. Moreover, although dioxin etc. may exist in some landfill ash, it can be made harmless by the high temperature process of the kiln bottom part 9. FIG.

  The input position of the landfill ash mixed with waste plastic may basically be an atmosphere region of 800 ° C. or higher. However, if the structure of the furnace is such that a relatively large size of landfill ash falls within the furnace and lands on the furnace bottom 9 after the landfill ash is physically injected, the bottom cyclone chute 17 or The rising duct 12 or the calcining furnace burner 18 may be put into the calcining furnace 13 where it burns. Preferably, it is best to directly put into the kiln bottom 9 of the cement kiln 14. If it is introduced into the temperature range of an atmosphere of less than 800 ° C, the burning speed of combustible and unburned materials that are partly present in the input is slowed down and exhausted to the exhaust fan 20 before it burns out. It is wasted without being used effectively. The shape of the charging portion into the furnace is preferably a horizontal cylindrical tube 11 having the same diameter as the air transport tube 8 but may be in a range of 0 to 60 degrees in the downward direction from the horizontal.

The mechanism that can improve the fluidity of landfill ash by carrying waste plastic with the landfill ash is not necessarily clear, but it is presumed as follows.
In many cases, landfill ash contains about 10 to 35% by weight of water containing or adhering to particles, which are incineration ash that occupies most of it. For this reason, the particles easily adhere to each other and are likely to become a particle group in a dumpling state, which is not preferable as an object for pneumatic transportation. Moreover, since the material of the air transport pipe 8 for performing air transport is generally an iron metal, particles of the incinerated ash to which moisture has adhered are likely to adhere to the inner wall of the air transport pipe 8. For this reason, the air transport pipe 8 is likely to be blocked. Moreover, if the material of the pneumatic transport pipe 8 is lined with an abrasion-resistant resin, it is relatively small in terms of adhesion to the inner wall, but there is a drawback in that the equipment cost is high and it is not perfect.
The solid-gas mixing action in the pipe is promoted mainly by the water-repellent action of fluffy flakes of waste plastic, and the high adhesion characteristics inherent in landfill ash are reduced, making it easier to disperse. . In addition, it is estimated that the sharp shape of hard resin causes the phenomenon of scraping landfill ash on the inner wall of the pipe, reducing the adhesion in the pipe, thereby improving the fluidity of landfill ash and promoting the solid-gas mixing action. ing.

  Moreover, when the weight ratio of the said hard resin increases, it is guessed as follows that fluidity | liquidity can be improved further. Since the waste plastic has high water repellency, it not only collides with the particles of landfill ash and crushes the particles, but also disperses the particles due to the property that the surface of the waste plastic and the landfill ash are difficult to adhere. It is estimated that it contributes to making it. The hard resin having a relatively large inertial force has an effect of reducing adhesion between particles because the force for crushing the particle group is larger than that of the soft fluffy waste plastic.

  And in waste plastic, the crushing surface crushed with the crusher of the previous process is often sharp. Therefore, after being blended with landfill ash, when being pumped by the air transport pipe 8, the landfill ash adhering to the inner wall portion of the air transport pipe 8 at the tip of the hard plastic is scraped off and adhered. There is a characteristic that does not progress. If the mixing ratio of the waste plastic 2 to the landfill ash 1 is less than 10% by weight, the amount of the landfill ash adhering in the air transport pipe 8 increases, and if it exceeds 30% by weight, the volume of the waste plastic 2 increases. It becomes larger and the transport capacity of landfill ash decreases.

  Thus, waste plastic is mixed with landfill ash, and the wind speed is preferably about 15 to 30 meters / second. When the wind speed exceeds 30 meters / second and is thrown into the kiln bottom 9, a large amount of the cement raw material flowing toward the kiln 14 through the kiln bottom 9 is re-scattered, the ventilation of the cement kiln 14 becomes worse and oxygen is insufficient. There is a risk of becoming. As a result, unburned gas is generated in the kiln bottom 9 and there is a possibility that the cement kiln 14 is deteriorated in combustion.

  A specific experimental example will be described with reference to FIGS. 1 and 2. The cement production apparatus in which the experiment was conducted is a cement production plant in which the preheating process of the input raw material has a five-stage cyclone, the cement raw material is calcined in the calcining furnace 13, and the clinker is calcined in the cement kiln 14.

  The landfill ash 1 having a moisture content of 23% by weight and a longest side size of 40 millimeters or less was charged into the receiving tank 4 at a supply rate of 1.0 t / hr (bulk specific gravity of 1.4). Further, the waste plastic 2 was extracted from the waste plastic tank 3 at a flow rate of 0.2 t / hr (bulk specific gravity 0.2) and simultaneously introduced into the receiving tank 4. The particle size distribution of the landfill ash at this time is as shown in Table 1. The waste plastic 2 is a crushed product having a longest side of 20 mm or less, mainly a soft and fluffy material centered on a polyethylene film or a polypropylene film, but an ABS resin comprising a lump with a sharp surface. About 5% by weight of a dice-like hard resin centering on is mixed.

  In the receiving tank 4, a stirring blade 5 is installed, and stirring and mixing in the receiving tank 4 are performed by a method of revolving around the inner wall of the cone portion of the receiving tank 4 while the screw rotates. ing.

  A mixture of landfill ash and waste plastic was supplied from the lower part of the receiving tank 4 to the pneumatic transport pipe 8 via the double rotary feeder 6. The double rotary feeder 6 is highly airtight so that the compressed air in the pneumatic transport pipe 8 is less likely to leak into the receiving tank 4. Roots blower 7 was used as the compressed air inside the pneumatic transport pipe 8, the amount of air in the pipe was 74 cubic meters / minute, and the wind speed in the pipe was 25 meters / second.

  The pneumatic transport pipe 8 has a tip connected to the cylindrical pipe 11 in the horizontal direction toward the hollow core of the cement kiln 14 at the position of the kiln bottom 9. The mixture of landfill ash and waste plastic was introduced toward the center of the cement kiln 14 at the bottom of the kiln. The blockage state was detected by detecting the pressure of each part in the pipe. By this method, the landfill ash was transported pneumatically, so that continuous and stable operation was possible without causing the landfill ash to adhere to the air transport tube 8 or to block the air transport tube 8.

  In addition, as an experiment to be compared under conditions in which pneumatic transportation is difficult, the same experiment as described above was performed with no waste plastic 2 being supplied. As a result, the inside of the piping was blocked in about 60 minutes. Moreover, waste plastic was supplied at 0.1 t / hr, and the piping was clogged in about 240 minutes even when the same experiment was repeated under other conditions.

  The present invention can be used in all industries that use landfill ash based on incinerated ash as raw fuel, such as waste that may contain waste plastic such as various contaminated soil, construction residual soil, and various sludge. Can be used for pneumatic transportation.

The schematic of the pneumatic transportation method of landfill ash in the present invention is shown. It is the schematic which shows the injection | throwing-in position to the cement kiln of this invention.

Explanation of symbols

1 Landfill Ash 2 Waste Plastic 3 Waste Plastic Tank 4 Receiving Tank 5 Stirring Blade 6 Double Rotary Feeder 7 Pneumatic Feeder (Roots Blower)
8 Pneumatic transport pipe 9 Kiln bottom 10 Cement raw material inlet 11 Cylindrical pipe 12 Rising duct 13 Calciner 14 Cement kiln 15 Cement clinker 16 Cement kiln outlet 17 Lowermost cyclone chute 18 Calciner burner 19 Kiln burner 20 Exhaust gas fan

Claims (3)

A method for transporting landfill ash, characterized in that when landfill ash is dug up and the landfill ash dug up is transported pneumatically to the bottom of a kiln of a cement kiln, waste plastic is accompanied with the waste plastic. The method for transporting landfill ash according to claim 1, wherein the waste plastic has a longest portion of 5 to 20 mm. The method for transporting landfill ash according to claim 1 or 2, wherein 10 to 30 parts by weight of the waste plastic is accompanied by air transport with respect to 100 parts by weight of the landfill ash.

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