A plasma melting pretreatment system and method for hazardous waste incineration ash

Abstract

The present invention discloses a plasma melting pretreatment system and method for hazardous waste incineration ash, including a fly ash pretreatment system, a bottom ash pretreatment system, a mixing device, a multi-point distribution device and a plasma furnace. The fly ash pretreatment system includes a fly ash bin, a grinder, a temporary storage bin and a granulator. The bottom ash pretreatment system includes a bottom ash bin, a dryer, an iron removal device and a crusher. The fly ash in the fly ash bin enters the temporary storage bin through the grinder, and then enters the mixing device through the granulator. The bottom ash in the bottom ash bin passes through the dryer, the iron removal device and the crusher in turn and enters the mixing device. The mixed material in the mixing device enters the plasma furnace through the multi-point distribution device. The present invention adopts dry grinding to reduce the heavy metal content in the secondary fly ash, so that more heavy metals are solidified by the glass body; the addition of calcium oxide reduces the water content of the fly ash and increases the hardness of the fly ash particles after granulation; the multi-point distribution form reduces the melting time of a single furnace, so that the formed glass body is more uniform.

Description

Technical Field

[0001] The invention belongs to the technical field of plasma melting pretreatment of hazardous waste ash, and in particular relates to a plasma melting pretreatment system and method for hazardous waste incineration ash. Background Art

[0002] Incineration is the main method of hazardous waste disposal. A large amount of bottom slag and fly ash will be produced during the incineration process, accounting for about 30% of the incineration volume. The slag produced is still a hazardous waste. The main method of slag disposal at present is landfilling. Landfilling is a temporary storage method, which still poses certain environmental risks and occupies a large amount of land. At present, the resource utilization of slag is a popular disposal method. The preparation of thermal insulation cotton and microcrystalline glass after plasma melting is one of the most promising methods. The main components of bottom slag are silicon, aluminum, calcium and magnesium, and the main components of fly ash are calcium, aluminum, silicon, chlorine, potassium, sodium, etc. The melting of fly ash and bottom slag separately requires additional additives (generally calcium oxide) to make the alkaline and acidic metal oxides meet a certain ratio. The coordinated disposal of fly ash and bottom slag can achieve the purpose of element complementarity and greatly reduce the amount of additives.

[0003] Fly ash contains a large amount of heavy metals and dioxins. Dioxins will be decomposed at high temperature during the melting process. A large amount of heavy metals will solidify in the glass during the slag discharge process. However, there are still a large amount of heavy metals in the fly ash that volatilize and overflow at high temperature. The main reason is that the chlorine content in the fly ash is high. The heavy metals exist in the form of chlorides, which will greatly increase their high-temperature overflow performance. Fly ash grinding can change the existence of heavy metals in fly ash, and convert the heavy metals in the fly ash in the form of chlorides into heavy metals in the form of oxides, thereby greatly reducing the overflow of heavy metals during the melting process. The particle size of fly ash is less than 200 meshes and the density is about 0.5g / cm3. It is easy to be carried by the airflow in the furnace and escape, becoming secondary fly ash. Therefore, the fly ash needs to be granulated before entering the furnace. In order to avoid the particles being worn and squeezed and broken during the subsequent transportation process, the formed particles must have a certain strength. At the same time, the particle size of the granulation will affect the melting time. If the particle size is too large, the melting time will be prolonged. If the particle size is too small, the fly ash will become secondary fly ash and escape.

[0004] Hazardous waste incineration bottom ash is the largest secondary toxic waste produced during the incineration process. It contains water, metallic iron, etc., and is generally in block form in the initial state. Before melting, the bottom ash generally needs to be dried, iron-removed, crushed, and mixed. The purpose of the mixing process is to mix the fly ash and bottom ash, and add them to the furnace for melting after mixing them as evenly as possible. Because the fluidity of the molten pool in the furnace is relatively low, a multi-point distribution method is used before entering the furnace to reduce the melting time of a single furnace and improve the uniformity and quality of the generated glass.

[0005] The patent application number is 202010530638.1, and its name is "A fly ash stabilization granulation system and working method". This patent proposes a fly ash stabilization granulation system and working method. This patent chelates the fly ash and then granulates it, which can reduce dust during the fly ash disposal process. However, the fly ash chelation disposal is a temporary disposal method and does not completely eliminate the environmental risks of fly ash.

[0006] The application number is 201810430783.5, and the name is "A fly ash granulation device and granulation incineration system". The patent proposes a fly ash granulation system, and the fly ash is directly added to the plasma furnace after granulation. The patent does not further propose a way to put fly ash into the furnace, such as reducing the melting time of a single furnace and improving the quality of the glass body. Summary of the invention

[0007] Technical problems to be solved: In response to the above technical problems, the present invention provides a hazardous waste incineration ash plasma melting pretreatment system and method, which can effectively solve the shortcomings of the above-mentioned large amount of additives leading to high cost, failure to completely eliminate the environmental risks of fly ash, and long single melting time.

[0008] Technical solution: A plasma melting pretreatment system for hazardous waste incineration ash, including a fly ash pretreatment system, a bottom ash pretreatment system, a mixing device, a multi-point distribution device and a plasma furnace. The fly ash pretreatment system includes a fly ash silo, a grinder, a temporary storage bin and a granulator. The bottom ash pretreatment system includes a bottom ash silo, a dryer, an iron removal device and a crusher. The fly ash in the fly ash silo enters the temporary storage bin through the grinder and then enters the mixing device through the granulator. The bottom ash in the bottom ash silo passes through the dryer, the iron removal device and the crusher in turn and enters the mixing device. The mixed material in the mixing device enters the plasma furnace through the multi-point distribution device.

[0009] Preferably, the grinder is provided with an additive inlet, the additive is calcium oxide, and the mass ratio of fly ash to calcium oxide is 2:1 to 1.2.

[0010] Preferably, the grinder is a ball grinder, the grinding balls are stainless steel balls with a diameter of 1 to 5 cm, the mass ratio of fly ash to grinding balls is 1:0.2 to 0.3, the ball milling time is 40 to 60 min, and the grinder speed is 500 to 600 rpm.

[0011] Furthermore, the volume of the temporary storage bin is 1.2 to 1.3 times the volume of the fly ash ground once.

[0012] Preferably, the granulator is a dry roller granulator, the roller pressure is 12-20 MPa, the granulation is spherical, and the particle size is 1 cm-2 cm.

[0013] Preferably, the moisture content of the bottom ash in the bottom ash bin after being dried by a dryer is 5-10%.

[0014] Preferably, the crusher is a jaw crusher or a roller crusher, and the particle size after crushing is less than 1 cm.

[0015] Preferably, the mass ratio of fly ash to bottom ash in the mixing equipment is 2:8.

[0016] Preferably, the distribution angle interval of the multi-point distribution equipment is 120°.

[0017] A method for plasma melting pretreatment of hazardous waste incineration ash comprises the following steps:

[0018] S1. Fly ash pretreatment: The fly ash in the fly ash silo is transferred to a grinder, calcium oxide is added to the grinder, the mixture of fly ash and calcium oxide is ground, and then transferred to a temporary storage bin, and then granulated by a granulator to obtain fly ash particles with a particle size of 1 to 2 cm for standby use;

[0019] S2. Bottom slag pretreatment: drying and iron removal of the bottom slag in the bottom slag silo and then crushing the bottom slag to obtain bottom slag particles with a particle size of less than 1 cm for later use;

[0020] S3, batching: the fly ash particles obtained in step S1 and the bottom ash particles obtained in step S2 are measured and mixed evenly to obtain a mixture;

[0021] S4, distribution: the mixed material obtained in step S3 is distributed to the plasma furnace through a multi-point distribution device.

[0022] Beneficial effects: 1. The present invention utilizes a dry grinding process and uses calcium oxide as a grinding agent. By changing the combination form of lead and chlorine, the volatilization of heavy metals during the melting process is inhibited, the heavy metal content in the secondary fly ash is reduced, and more heavy metals are solidified by the glass body;

[0023] 2. During the grinding process, calcium oxide reacts with the free water in the fly ash to reduce the water content of the fly ash and increase the hardness of the fly ash particles after granulation, thereby reducing the wear and breakage of the fly ash particles during transportation and reducing the amount of secondary fly ash;

[0024] 3. Through the multi-point distribution form, the melting time of a single furnace is reduced, making the formed glass more uniform. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the hazardous waste incineration ash plasma melting pretreatment system of the present invention;

[0026] Figure 2 It is a flow chart of the plasma melting pretreatment method of hazardous waste incineration ash of the present invention;

[0027] Figure 3is an XRD analysis diagram of the glass body after cooling in Example 1 of the present invention;

[0028] Figure 4 is the XRD analysis diagram of the glass body in Example 2;

[0029] Figure 5 This is the XRD analysis diagram of the glass body after melting for 2 hours in Example 3;

[0030] The serial numbers in the figure are: 1. fly ash silo, 2. grinder, 3. temporary storage silo, 4. granulator, 5. bottom slag silo, 6. dryer, 7. iron removal equipment, 8. crusher, 9. mixing equipment, 10. multi-point distribution device, 11. plasma furnace. DETAILED DESCRIPTION

[0031] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments:

[0032] Example 1

[0033] The composition of fly ash and bottom ash from hazardous waste incineration is shown in Table 1.

[0034] Table 1: Chemical composition of fly ash and bottom ash after incineration of hazardous waste

[0035]

[0036] The fly ash with the composition in Table 1 is first dry ground, and then added to the ball mill, and calcium oxide is added at the same time. Calcium oxide is used as a grinding aid and additive, and the ratio of fly ash to calcium oxide is 2:1.2. The diameter of the small ball in the ball mill is 1.5cm, the small ball is made of stainless steel, and the rotation speed is 600rpm. After ball milling for 40min, the fly ash that has been ball milled is transported to the temporary storage bin. The fly ash in the temporary storage bin is added to the granulation equipment for granulation, the granulation pressure is 15Mpa, the particle size of the formed particles is 1cm, and the strength of the formed particles is tested to be 82N.

[0037] The bottom ash is added to the drum dryer for drying, and the moisture content after drying is about 8%. The dried bottom ash is deironed by the belt deironing process, and then added to the roller crusher for crushing. The particle size of the crushed particles is less than 1 cm. The crushed bottom ash and fly ash are batched, and the batching ratio is 8:2 for bottom ash to fly ash using a static batching scale. After the batching is completed, the ingredients are stirred to make the two evenly distributed. After the stirring is completed, a multi-point distribution device is added. The multi-point distribution device consists of three bins, and three ports are added to the plasma furnace. The distribution angle interval of the three bins is 120°. After melting in the plasma furnace, the melting time of a single furnace is 2h. The composition of the secondary fly ash collected by the bag is shown in Table 2. After quantitative detection, the amount of secondary fly ash accounts for about 6% of the original material.

[0038] Table 2: Composition of secondary fly ash

[0039]

[0040] The cooled glass was subjected to XRD analysis, and the results were as follows: Figure 3 As shown in the figure, it can be seen that there is no obvious crystal diffraction peak in the formed glass body, and the glassification rate is 92.33% after statistics by software.

[0041] Example 2

[0042] Compare with Example 1 after canceling the grinding operation

[0043] The fly ash and bottom ash components shown in Table 1 of Example 1 were used for the test. In this example, the fly ash was directly granulated without a grinding process, and the calcium oxide additive was added during the batching, and the amount added was exactly the same as in Example 1. The subsequent process steps and operating conditions were the same as in Example 1. After the melting was completed, the secondary fly ash was quantitatively analyzed and the components were shown in Table 3 below.

[0044] Table 3: Composition of secondary fly ash after elimination of grinding operation

[0045]

[0046] As shown in Table 3, after the grinding process is cancelled, the content of volatile heavy metal Pb in the secondary fly ash increases significantly, which is 4 times higher than that in Example 1, and the content of Zn increases by 1.5 times. This shows the beneficial effect of adding calcium oxide to grind. In addition, due to the lack of water and reaction of calcium oxide during the grinding process, the strength of the formed fly ash particles is reduced. After testing, the strength is 69N, which is a decrease of about 15.8%, and a large amount of powder appears during the transportation process. After quantitative testing of the secondary fly ash, the amount of secondary fly ash accounts for about 6.55% of the original material, which is an increase of about 9.1%.

[0047] The results of XRD test on the molded glass are as follows Figure 4 As shown, the glass transition rate is 90.12%.

[0048] Example 3

[0049] Single point fabric form

[0050] The test was conducted according to the fly ash and bottom ash compositions shown in Table 1 of Example 1. Example 3 adopted a single-point distribution method, and the remaining steps were the same as those of Example 1. After 2 hours of melting, part of the melt was slag-out and cooled. The XRD analysis of the cooled glass was as follows: Figure 5 As shown in the figure, the glass still has some crystal diffraction peaks. After calculation, its glassification rate is 82.1%.

[0051] The materials in this batch were continued to be melted, and the slag was cooled after melting for 2.5 hours. The glass slag was tested by XRD. From the test results, it can be seen that the diffraction peak basically disappeared and the glass transition rate reached 89.99%. When the glass transition rate was similar, the melting time of a single furnace was extended by half an hour, which shows the beneficial effect of multi-point distribution.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A hazardous waste incineration ash plasma melting pretreatment system, characterized by: The invention comprises a fly ash pretreatment system, a bottom ash pretreatment system, a mixing device (9), a multi-point distribution device (10) and a plasma furnace (11), wherein the fly ash pretreatment system comprises a fly ash silo (1), a grinder (2), a temporary storage silo (3) and a granulator (4), and the bottom ash pretreatment system comprises a bottom ash silo (5), a dryer (6), an iron removal device (7) and a crusher (8). The fly ash in the fly ash silo (1) enters the temporary storage silo (3) through the grinder (2), and then enters the mixing device (9) through the granulator (4). The bottom ash in the bottom ash silo (5) passes through the dryer (6), the iron removal device (7) and the crusher (8) in sequence and enters the mixing device (9). The mixed material in the mixing device (9) passes through the multi-point distribution device (10) and enters the plasma furnace (11); the grinder (2) is provided with an additive inlet, the additive is calcium oxide, and the mass ratio of fly ash to calcium oxide is 2:1-1.2; the grinder (2) is a ball grinder, the grinding balls are stainless steel balls, the ball diameter is 1-5 cm, the mass ratio of fly ash to grinding balls is 1:0.2-0.3, the ball milling time is 40-60 min, and the rotation speed of the grinder (2) is 500-600 rpm; the granulator (4) is a dry roller granulator, the roller pressure is 12-20 MPa, the granulation is spherical, and the particle size is 1 cm-2 cm.

2. The hazardous waste incineration ash plasma melting pretreatment system according to claim 1, characterized in that: The volume of the temporary storage bin (3) is 1.2 to 1.3 times the volume of the fly ash ground once.

3. The hazardous waste incineration ash plasma melting pretreatment system according to claim 1, characterized in that: The moisture content of the bottom slag in the bottom slag bin (5) after being dried by the dryer (6) is 5-10%.

4. The hazardous waste incineration ash plasma melting pretreatment system according to claim 1, characterized in that: The crusher (8) is a jaw crusher or a roller crusher, and the particle size after crushing is less than 1 cm.

5. The hazardous waste incineration ash plasma melting pretreatment system according to claim 1, characterized in that: The mass ratio of fly ash to bottom ash in the mixing device (9) is 2:

8.

6. The hazardous waste incineration ash plasma melting pretreatment system according to claim 1, characterized in that: The distribution angle interval of the multi-point distribution device (10) is 120°.

7. A method for plasma melting pretreatment of hazardous waste incineration ash using the pretreatment system according to any one of claims 1 to 6, characterized in that: The steps include: S1. Fly ash pretreatment: The fly ash in the fly ash silo (1) is transferred to a grinder (2), calcium oxide is added to the grinder (2), the mixture of fly ash and calcium oxide is ground, and then transferred to a temporary storage bin (3), and then granulated in a granulator (4) to obtain fly ash particles with a particle size of 1 to 2 cm for standby use; S2, bottom slag pretreatment: drying and removing iron from the bottom slag in the bottom slag bin (5) and then crushing the bottom slag to obtain bottom slag particles with a particle size of less than 1 cm for later use; S3, batching: the fly ash particles obtained in step S1 and the bottom ash particles obtained in step S2 are measured and mixed evenly to obtain a mixture; S4, distribution: the mixed material obtained in step S3 is distributed to the plasma furnace (11) via a multi-point distribution device (10).

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