JP2005114223A - Granularity adjustment method in boiler furnace bottom ash processing and granularity adjustment device used therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To process furnace bottom ash discharged from a boiler at low cost such that the furnace bottom ash is easy to effectively use. <P>SOLUTION: In this granularity adjustment method, the furnace bottom ash discharged from a clinker hopper 1 provided in a boiler furnace bottom part is put into an inclination type continuous screen sorter 3 by hydraulic power transport, the furnace bottom ash of small grain diameter, transporting water and the furnace bottom ash of large grain diameter are separated, the furnace bottom ash of the small grain diameter and the transporting water falling from a screen plate 6 are stored in a dewatering tank 4 to settle and separate the furnace bottom ash, the transporting water is extracted from an upper part of the dewatering tank, and the furnace bottom ash is extracted from a lower part thereof. The furnace bottom ash of the large grain diameter left on the screen plate is stored in a cushion tank 5. A lattice-like screen plate of 0.5-10 mm mesh size is suitable for the screen plate. A minute particle, a carbon component or the like checking the effective use to a roadbed material or the like is effectively separated. The method is suitable for the boiler of an electric power plant or the like. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

    TECHNICAL FIELD The present invention relates to a particle size adjusting apparatus and method for boiler bottom ash treatment for separating and processing bottom ash (also referred to as clinker ash or bottom ash) discharged from the lower part of a combustion furnace such as a boiler. . It is particularly suitable for treating bottom ash discharged from boilers in coal-fired power plants.

    The amount of ash discharged from a boiler in a thermal power plant or the like varies depending on the fuel used, the place of production, the brand, etc., but usually, the fuel coal contains 5 to 30% by weight of ash. And about 10-20% of the total ash amount becomes furnace bottom ash and falls to the boiler bottom. The rest is discharged as fly ash (called fly ash) together with the combustion waste gas, and is collected by an electric dust collector or the like. There are several methods for discharging the bottom ash, but in many cases in Japan, a clinker hopper filled with water is provided at the bottom of the combustion furnace to drop the bottom ash and quench and crush it. Further, a method is adopted in which the ash-flow gate at the bottom of the hopper is intermittently opened and hydraulically transported to the dehydration tank by transport water, and the remaining bottom ash is discharged by separating and recovering the transport water. A clinker crusher is installed downstream of the ash flow gate, and large lump of mixed bottom ash is pulverized to about 40 mm or less, about 10 to 20 mm. It is sent to the dehydration tank by hydropower transportation. The transport water and the bottom ash are settled and separated in the dewatering tank, the transport water is recycled for hydraulic transport, and the bottom ash is discharged out of the system.

    It is an important task to increase the proportion of effective utilization of residual ash by treating boiler bottom ash. The bottom ash discharged from the dehydration tank is effectively used as a drainage material that makes use of water permeability. However, if there are many fine particles, there are problems such as inability to impart sufficient water permeability to the soil, and there are problems such as inhibiting the uniformity of quality due to the large amount of impurities such as carbon components, and some landfills It was disposed of as industrial waste. Therefore, an attempt has been made to adjust the particle size by separately providing a wet or dry sieving apparatus. However, the bottom ash that is effectively used has extremely low prices for competing products, and needs to be competitive in price as well as improving quality. The biggest problem in the effective utilization of the bottom ash is to improve the quality without cost as in the effective utilization of many industrial wastes. The present invention has been completed as a result of studying how to treat furnace bottom ash so that it can be effectively used at low cost.

    In order to solve the above-mentioned problem, the present invention introduces furnace bottom ash (clinker ash) discharged from a clinker hopper provided at the bottom of a boiler furnace into an inclined continuous screen separator by hydraulic transportation, The bottom ash and small sized bottom ash and transport water are separated, and the large sized bottom ash is removed from the screen plate. Disclosed is a method for adjusting the particle size in boiler furnace bottom ash treatment, wherein the furnace bottom ash is settled and separated in a water tank, and transport water is extracted from the upper part of the dewatering tank and the furnace bottom ash is extracted from the lower part.

  Furthermore, the present invention provides a hydraulic transport piping system 2 for transporting the bottom ash discharged from the clinker hopper 1 provided at the bottom of the boiler furnace, and a large particle size bottom ash from the transported bottom ash slurry and transport water. An inclined continuous screen separator 3 to be separated, a cushion tank 5 for storing a large particle size furnace bottom ash separated on the screen plate, a small particle size furnace bottom ash falling from the screen plate of the separator, and Disclosed is a particle size adjusting device in boiler furnace bottom ash treatment, characterized in that it comprises a dewatering tank 4 that contains transport water and settles and separates the furnace bottom ash from the transport water.

  In the present invention, the inclined continuous screen separator is preferably attached to the upper surface of the dehydration tank so that the small-particle-size furnace bottom ash and transport water 21 fall directly from the screen plate into the tank. The opening of the screen plate mounted on the inclined continuous screen sorter is preferably in the range of 0.5 to 10 mm. In order to sort the bottom ash according to the size of the particle size, a plurality of inclined continuous screen sorters with different openings of the screen plate are arranged in the order of the opening size, The bottom ash and transport water that have fallen after passing through are supplied to the next-stage screen separator, and a cushion tank is provided for storing the bottom ash sorted on the screen plate for each stage. Disclosed is a particle size adjusting device in the above-mentioned boiler furnace bottom ash treatment.

    The present invention adjusts the boiler furnace bottom ash to a particle size that is easy to use effectively by using an inclined continuous screen separator, and at the same time, cleans and reduces the carbon component (carbon content) attached to the furnace bottom ash, Has a secondary effect. The inclined continuous screen sorter used in the present invention is a simple facility that does not require power equipment or a processing agent and only passes through a screen plate having an appropriate mesh opening, and in fact maintenance costs are generated. do not do. In addition, since it can be separated and washed in normal operation, no additional running costs are incurred. Further, it is not necessary to use new water from outside the system, and it is possible to operate without changing the water balance in the conventional process. By installing a simple and cost-effective slanted continuous screen sorter, fine particles in the bottom ash are removed to make the particle size uniform, or if necessary, a plurality of different particle sizes using multiple sorters Sorting into seed furnace bottom ash and removing impurities such as carbon components improves quality. It becomes an effective means for solving the above-mentioned problems, and it is possible to advantageously expand the use of boiler furnace bottom ash.

    The present invention will be specifically described with reference to the drawings. FIG. 1 is a flow sheet showing an example of a boiler furnace bottom ash treatment apparatus equipped with the particle size adjusting device of the present invention, FIG. 2 is a schematic diagram of the particle size adjusting device of the present invention and its peripheral devices, and FIG. It is a perspective view which shows an example of a machine.

  First, the furnace bottom ash from the boiler falls into the clinker hopper 1 provided at the bottom. The clinker hopper 1 is filled with water, and the bottom ash drain gate 7 is opened every predetermined time depending on the storage state of the furnace bottom ash so that the furnace bottom ash is intermittently discharged, and a large amount is passed through the clinker crusher 8. The lump is pulverized and the slurry-like furnace bottom ash 20 is transported through the hydraulic transport piping system 2. Hydropower transportation may be any of a suction type, a pressure type, and a combined type. A rotary ash pump 9, a jet pump, or the like can be used as a drive source for hydraulic transportation, but an ash pump having many advantages such as a small amount of water used and easy flow rate adjustment is recommended.

  The transported bottom ash slurry 20 is fed to the upper end of the inclined continuous screen separator 3. The screen plate 6 to be mounted on the inclined continuous screen sorter 3 may be a wire mesh. However, a wire (rod-like body) having a wedge-shaped cross section that is large on the upper surface side and becomes smaller toward the lower surface is provided at a predetermined interval (opened). A cocoon-like screen plate 6 (also referred to as a wedge wire screen) arranged in parallel is recommended because it is durable and less clogged. The mesh opening can be appropriately selected according to the usage of the furnace bottom ash, but preferably 0.5 to 10 mm, particularly 1.2 to 1 in consideration of the roadbed material which is the main application for the time being. About 8 mm is preferable.

  The screen separator 3 is preferably attached directly to the upper surface of the dehydration tank 4 so that the small particle size furnace bottom ash and the transport water 21 pass through the screen plate 6 and fall directly into the dehydration tank 4. The bottom ash slurry 20 thus transported is separated by the screen separator 3 into a large bottom ash, a small bottom ash and transport water 21. It should be noted that, at that time, the carbon component of the impurity that has adhered to the large particle size furnace bottom ash on the screen plate 6 and has become an obstacle to the reuse of the furnace bottom ash is washed and removed. The furnace bottom ash having a large particle size slides down on the screen plate 6 and is thrown into the cushion tank 5 from the lower end to be stored. The stored large particle size furnace bottom ash is transported out of the system by opening the ash removal gate 10 provided at the bottom of the cushion tank 5 at appropriate times. FIG. 1 shows an example of carrying out the large particle size furnace bottom ash 12 after being dropped on the draining conveyor 11 and drained.

  On the other hand, the furnace bottom ash and transport water 21 having a small particle size fall into the dehydration tank 4 and are stored. The stored transport water and furnace bottom ash are separated in the dehydration tank 4 into settling small bottom furnace ash and supernatant transport water. The transported water separated and settled is usually extracted from the upper part 13 of the dewatering tank 4, and is returned and recycled for hydraulic transport through the ash settling tank 15 and the water storage tank 16 as the return transport water 14. The furnace bottom ash 17 having a small particle size is conveyed outside the system by opening the ash removal gate 18 provided at the bottom of the dehydration tank 4. In the example of FIG. 1, the ash discharge gate 18 is opened at an appropriate time when it does not mix with the large particle size furnace bottom ash 12, the furnace bottom ash is dropped onto the draining conveyor 14, and the drained small particle size bottom ash 17 is removed. Transport outside the system.

  In addition, for example, in the bottom ash slurry stored in the upper part of the clinker hopper, the bottom ash of large particle size settles in the lower part and is hardly contained in the upper part. Direct storage in the dehydration tank does not cause any serious trouble, and it is practical to use the pipe 19 that bypasses the inclined continuous screen separator and reaches the dehydration tank. Moreover, a plurality of screen separators can be arranged according to the flow of the liquid passing through the screen plate, and can be separated and collected into a plurality of types of furnace bottom ash having different particle sizes. The screen plates may be arranged in the vertical direction in the order of the size of the openings.

    In a coal-fired power plant boiler in operation, the particle size adjusting apparatus according to the present invention was installed in a boiler furnace bottom ash treatment apparatus using an ash pump, and the confirmation test of the present invention was carried out. The analytical test method used is described below.

Permeability JIS A 1218 [Soil permeability test] compliant Carbon component JIS A 1226 [Ignition loss test] compliant Particle size distribution JIS A 1204 [Soil particle size test] compliant The present invention has the same configuration as shown in FIG. 1 by attaching a screen separator and a cushion tank having a discharge promoting mechanism such as a water injection port and a vibrator as a receiving tank for the furnace bottom ash remaining on the screen plate. Modified to a combustion furnace clinker ash treatment system. A slanted screen sorter was fitted with a scissor-shaped screen plate having a width of 1 m, a length of 3.8 m, and an opening of 1.5 mm with an inclination angle of 30 degrees.

Close the gate valve of the hydraulic transport pipe connected to the dewatering tank, open the gate valve on the screen separator side, and use the ash pump to feed 440 m ³ / h boiler bottom ash slurry from the clinker hopper to the screen separator. Washed away. Then, the draining conveyor was started, the ash removal gate at the bottom of the cushion tank was opened, and the state of discharge of the separated large particle size furnace bottom ash was confirmed. As a result, there was no stagnation at the tip of the screen plate, which was a concern, and the separated large particle size furnace bottom ash was also good from the inside of the cushion tank without the need to operate a discharge promotion mechanism such as an air vibrator or backwash water injection device. The operation was successfully completed for 3 days.

  The particle size distribution was measured for the separated large particle size furnace bottom ash (also referred to as granular ash (coarse)) and raw ash 22 (solid content contained in the slurry before entering the screen sorter). 4 shows the removal rate of fine particles in the grain ash (coarse particles) (= estimated passing weight by particle size at the time of fractionation / raw ash weight of each particle size). Further, an ignition loss test was performed to evaluate the cleaning effect of the residual carbon content, and the results are shown in Table 2. Furthermore, since the water permeability test of soil was implemented in order to confirm the water permeability improvement effect, the result was shown in Table 3.

  In this way, as a result of performing the test with the simple continuous type particle size adjusting device of the present invention attached to the field device, the clinker having a particle size of less than 1.5 mm is shown in FIG. From the results shown in Table 1, it was confirmed that the estimated removal rate of less than 1.5 mm was approximately 90%. Further, from the results of the ignition loss test (Table 2), it was confirmed that the residual carbon content in the granular ash (coarse particles) was significantly reduced as compared with the carbon content contained in the raw ash. Furthermore, the soil permeability test removes most of the silt and clay particles with a particle size of less than 75 μm that impede the permeability from the grain ash (coarse grains). It was also found that it was greatly improved compared to ash and improved to the medium water permeability seen in sand and gravel in general soil (Table 3). It has been confirmed that the apparatus according to the present invention has an excellent particle size adjusting function and at the same time has a residual carbon cleaning effect as a secondary effect.

    Compared with conventional wet or dry particle size adjusting means, the simple particle size adjusting means for boiler bottom ash according to the present invention is equivalent to or more fine particles that impair the effective use of boiler bottom ash, Carbon components and the like can be effectively separated. This is extremely useful in large boilers that use various types of coal as fuel to recycle the bottom ash. In particular, it is preferably used in coal-fired power plants that emit a large amount of furnace bottom ash.

Flow sheet showing an example of a boiler furnace bottom ash treatment device equipped with the particle size adjustment device of the present invention Schematic diagram of the present invention particle size adjusting device and its peripheral equipment Perspective view showing an example of an inclined continuous screen sorter The graph which shows the particle size distribution measurement result of grain ash (coarse grain) and raw ash

Explanation of symbols

1: Clinker hopper 2: Hydraulic transport piping system for furnace bottom ash transport 3: Inclined continuous screen separator 4: Dehydration tank 5: Cushion tank 6: Screen plate 7: Ash sink gate 8: Clinker crusher 9: Ash pump 10: Ash discharge gate 11: Draining conveyor 12: Large particle size furnace bottom ash (grained ash (coarse))
13: Clear water outlet at the top of the dehydration tank 14: Return transport water 15: Ash precipitation tank 16: Water tank 17: (Fine granule) Furnace bottom ash 18: Ash discharge gate 19: Screen separator bypass pipe 20: Furnace bottom ash And transport water 21: Small particle size furnace bottom ash and transport water 22: Raw ash slurry before separation

Claims (5)

    Furnace bottom ash (clinker ash) discharged from the clinker hopper provided at the bottom of the boiler furnace is put into an inclined continuous screen sorter by hydraulic transportation, Separated into transport water, take out the large particle size furnace bottom ash from the screen plate, store the small particle size furnace bottom ash and transport water falling from the screen plate in a dehydration tank, settling and separating the bottom ash, A particle size adjustment method in boiler furnace bottom ash treatment, characterized in that transport water is extracted from the upper part of the dehydration tank and furnace bottom ash is extracted from the lower part.     Hydropower transport piping system (2) for transporting the bottom ash discharged from the clinker hopper (1) provided at the bottom of the boiler furnace, and separating the bottom ash with a large particle size from the transported bottom ash slurry and transport water An inclined continuous screen separator (3), a cushion tank (5) for storing a large particle size furnace bottom ash separated on the screen plate, and a small particle size furnace falling from the screen plate of the separator A dehydration tank (4) that contains bottom ash and transport water and settles and separates the bottom ash from transport water, and a particle size adjusting device in boiler furnace bottom ash treatment.     3. A boiler furnace bottom according to claim 2, wherein an inclined continuous screen separator is attached to the upper surface of the dewatering tank so as to drop the small particle size furnace bottom ash and water directly from the screen plate into the tank. Particle size adjustment device in ash treatment.     The boiler furnace bottom ash treatment according to claim 2 or 3, wherein the screen plate (6) attached to the inclined continuous screen separator is a hook-like screen having an opening of 0.5 to 10 mm. Grain size adjusting device. A plurality of inclined continuous screen sorters with different screen plate openings are arranged in the order of the size of the openings, and then the bottom ash and transport water that have fallen through the previous screen plate are sequentially transferred. The cushion tank for storing the bottom ash supplied to the stage screen separator and separated on the screen plate for each stage is provided. Particle size adjustment device in boiler furnace bottom ash treatment.

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