Plasma fly ash melting furnace and fly ash harmless treatment method thereof

Abstract

The invention relates to the technical field of fly ash treatment, and particularly discloses a plasma fly ash melting furnace and a fly ash harmless treatment method thereof.The plasma fly ash melting furnace comprises a furnace body and a furnace cover, the furnace body is formed by communicating a vertical section furnace body and a horizontal section furnace body, and the furnace cover is arranged at the top of the vertical section furnace body; a plasma electrode extending into the vertical section furnace body is arranged on the furnace cover, and a bottom electrode is arranged on the bottom wall of the horizontal section furnace body under the plasma electrode; a plurality of pneumatic feeding wells are uniformly arranged on the vertical section furnace body above the bottom of the plasma electrode in the circumferential direction, a slag discharge port is formed in the bottom of the horizontal section furnace body far away from one side of the vertical section furnace body, and a flue gas discharge port is formed in the upper end of the end surface of the vertical section furnace body above the slag discharge port; according to the method, the characteristics of high temperature and Joule heat of the plasma are fully utilized, and harmless treatment of the waste incineration fly ash is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fly ash treatment, and specifically discloses a plasma fly ash melting furnace and a fly ash harmless treatment method thereof. BACKGROUND

[0002] Garbage incineration fly ash mainly refers to the flue dust collected by the flue gas system of a garbage incineration boiler and other hazardous waste incineration boilers, and is a hazardous waste containing toxic and harmful components such as dioxins and heavy metals. The existing fly ash treatment technology mainly adopts chemical stabilization and solidification treatment and then implements landfill, which has many shortcomings such as incomplete treatment of toxic and harmful substances, great risk of secondary environmental pollution, the need to enter an industrial waste landfill site, and occupation of a large amount of land resources.

[0003] Glass treatment of fly ash by using a melting furnace is an important means to realize complete harmless treatment of fly ash. For example, the utility model patent with the application number 201620967663.5 discloses a garbage incineration fly ash composite plasma melting furnace, which comprises a hearth, a furnace lining, and a water-cooled sleeve pipe between the hearth and the furnace lining. A star-shaped hopper and a water vapor exhaust port are arranged on the top of the melting furnace and are in communication with the hearth. A conventional fuel burner with a downward spray port is arranged on the upper part of the melting furnace. An equal plasma torch with a downward spray port is arranged on the lower part of the melting furnace. A slag discharge port is arranged on the bottom of the melting furnace. A discharge pipe is arranged on the side of the bottom of the hearth. An exhaust gas discharge pipe is arranged in communication with the inlet of the discharge pipe. The garbage incineration fly ash composite plasma melting furnace disclosed by the utility model patent uses conventional fuel as the first heat source, effectively reduces the operation cost, and uses plasma as the reinforced melting heat source, thereby improving the melting efficiency.

[0004] However, the above-mentioned waste incineration fly ash composite plasma melting furnace still has some shortcomings. First, the melting furnace is limited to disposing of lighter quality waste incineration fly ash and cannot dispose of the added silicon-based additives in the fly ash. This is because the silicon-based additives are heavy and have a high melting temperature. When they are put into the melting furnace together with the fly ash, they will quickly fall to the bottom of the furnace. Even if they are heated by the conventional fuel burner and the plasma torch in turn, they cannot be fully melted. Since the silicon-based content in the fly ash is relatively low, the glass phase content in the single fly ash melt cannot meet the requirement of more than 85% in GB / T 41015-2021 "Solid Waste Glassification Treatment Product Technical Requirements" implemented on July 1, 2022, that is, the output fly ash melt cannot be called harmless glass body. Second, after the fly ash and the silicon-based additives are put in from the top, they quickly fall by gravity. On the one hand, the heating time cannot be prolonged, and on the other hand, the materials cannot be stirred, resulting in uneven heating and affecting the melting treatment effect. Third, the sensible heat generated during the fly ash melting process is directly discharged from the top of the melting furnace, and the sensible heat cannot be utilized, so the energy utilization rate is not high. Based on this, the present application proposes a plasma fly ash melting furnace and a fly ash harmless treatment method which can effectively solve the above technical problems. SUMMARY

[0005] The purpose of the present application is to provide a plasma fly ash melting furnace and a fly ash harmless treatment method to solve the technical problems and deficiencies that the existing plasma melting furnace cannot fully melt the mixture of fly ash and silicon-based additives to achieve fly ash harmless treatment, and the fly ash has a short heating time during the falling process, uneven heating, and low energy utilization rate of the melting furnace.

[0006] The present application is realized by the following technical solutions: A plasma fly ash melting furnace, comprising a furnace body and a furnace cover, the furnace body is L-shaped and is composed of a vertical section furnace body and a horizontal section furnace body in communication, the furnace cover is arranged at the top of the vertical section furnace body, and a plasma electrode extending into the vertical section furnace body is arranged on the furnace cover, and a bottom electrode is arranged on the bottom wall of the horizontal section furnace body directly below the plasma electrode; A gas feeding type feeding well is arranged above the bottom of the plasma electrode in the vertical section furnace body, and the material blown by gas can make counterclockwise rotational motion in the vertical section furnace body under the action of the gas feeding type feeding well, a slag discharge port is arranged at the bottom of the horizontal section furnace body away from one side of the vertical section furnace body, and a flue gas discharge port is arranged at the end of the horizontal section furnace body above the slag discharge port.

[0007] As a further arrangement of the above-mentioned scheme, the gas feeding type feeding well arranged on the vertical section furnace body is 1-4, and when there are not less than two gas feeding type feeding wells, they are arranged in a ring array.

[0008] As a further arrangement of the above-mentioned scheme, the air-feeding type feeding well is arranged to be inclined downward by 10-30° in the vertical direction and to be eccentrically inclined by 5-30° in the horizontal direction.

[0009] As a further arrangement of the above-mentioned scheme, a refractory material flow guide ring block is arranged on the inner wall of the vertical section furnace body below the plasma electrode, the upper end of the refractory material flow guide ring block is connected with the inner wall of the vertical section furnace body, and the lower end is arranged in a shape of a section converging to the middle.

[0010] As a further arrangement of the above-mentioned scheme, a resistance wire heating layer is arranged in the refractory outer wall of the horizontal section furnace body and in the end surface outer wall of the horizontal section furnace body at the flue gas discharge port.

[0011] As a further arrangement of the above-mentioned scheme, the bottom wall of the horizontal section furnace body is arranged to be inclined by an angle of 2-6°, and the slag discharge port is arranged at the lower inclined end of the bottom wall of the horizontal section furnace body.

[0012] The application further discloses a fly ash harmless treatment method using the above-mentioned plasma fly ash melting furnace. (1) the adding proportion of the required silicon-based additive is calculated according to the composition of the fly ash, and then the fly ash and the silicon-based additive are mixed in proportion for standby; (2) the plasma electrode and the bottom electrode are turned on, so that the bottom electrode and the plasma electrode generate plasma arc in the initial stage; (3) after the inside of the furnace body has feeding conditions, the mixture obtained in the step (1) is sent into the vertical section furnace body from the air-feeding type feeding well in a gas blowing conveying mode, so that the mixture rotates counterclockwise and falls in the vertical section furnace body, then the high-temperature arc generated by the plasma electrode heats the mixture, so that the fly ash in the mixture is heated and melted, the fly ash melt flows into the horizontal section furnace body to gather, and after the fly ash melt covers the bottom electrode, the electric current generates Joule heat through the bottom electrode; (4) with the continuous input of the mixture, the fly ash is rapidly melted by the high-temperature arc radiation heat generated by the plasma electrode, the silicon-based additive falls into the horizontal section furnace body and is continuously heated, melted and heat-insulated by the Joule heat generated by the bottom electrode, and when the mixed melt in the molten pool reaches a certain amount, the mixed melt is discharged by opening the slag discharge port; (5) in the whole melting treatment process, the gas flow for feeding the mixture and the flue gas generated in the melting process are discharged from the flue gas discharge port, and then are treated by flue gas treatment equipment and discharged after reaching the standard.

[0013] In addition, in the case of an emergency, the resistance wire heating layer can keep the temperature of the furnace body above 1100℃, so that the molten fly ash in the melting furnace is discharged from the furnace body, the bottom electrode at the bottom of the horizontal section furnace body is exposed, and the bottom electrode is convenient for use next time.

[0014] As a further provision of the above scheme, the amount of silicon-based additive in step (1) is controlled between 15% and 30% of the total amount of the mixture.

[0015] As a further feature of the above scheme, it also includes immediately stopping the feeding of the gas-feeding well and opening the slag discharge port to quickly discharge all the molten material inside the furnace body when encountering an emergency and determining that it cannot be resolved in a short time.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The fly ash plasma melting furnace disclosed in this invention organically combines the use of arc plasma radiation heat and the Joule heat generated by the electrode path formed in the molten state, thereby enabling the reaction of silicon-based additives and molten fly ash in the molten state to form a molten glass body after heating. It makes full use of the high temperature of plasma and the characteristics of Joule heat, and realizes the harmless treatment of waste incineration fly ash.

[0017] This invention designs the furnace body in an L-shape, consisting of a vertical section and a horizontal section. After entering the vertical section, fly ash and silicon-based additives are first melted by a plasma arc, then fall into the horizontal section where they converge and are subjected to Joule heating. This not only maintains a uniform temperature of the molten material but also utilizes energy more effectively, reducing energy consumption. Simultaneously, a resistance wire heating layer is installed in the furnace wall of the horizontal section, effectively maintaining the mixture of fly ash and additives in a molten state, ensuring smooth discharge from the slag outlet. Furthermore, it increases the flue gas temperature to above 1100℃, maintains saturated steam pressure, prevents the precipitation of harmful substances such as NaCl as the gas temperature decreases, and ensures smooth exhaust gas discharge.

[0018] This invention changes the traditional feeding method to pneumatic feeding using multiple circumferentially uniform and angled pneumatic feeding wells. This allows fly ash and silicon-based additives to rotate counterclockwise after entering the vertical section of the furnace. By changing the feeding posture of the mixture, it is beneficial to the uniform heating of each substance, prolongs the falling time of the mixture, increases the heating time of the mixture by the high-temperature electric arc, and creates agitation inside the molten pool in the horizontal section of the furnace, making the temperature inside the molten pool more uniform.

[0019] This invention provides a flue gas outlet at the upper end of the horizontal section of the furnace body on the side away from the vertical section. At the same time, the space above the molten material in the horizontal section of the furnace body can form a flue gas channel, which allows the feeding airflow and molten flue gas to flow in an orderly manner along the flue gas channel and finally be discharged from the flue gas outlet. This helps to reduce dust generation and reduce the load on the dust removal equipment in the subsequent tail gas purification. Attached Figure Description

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the description of the embodiments will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0021] Figure 1 It is a schematic view of the front internal plane structure of the present application. Figure 2 It is a schematic view of the plane structure of the present application. DETAILED DESCRIPTION

[0022] In order to make the person skilled in the art better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should be within the scope of protection of the present application.

[0023] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with the embodiments. Figures 1-2 The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0024] Embodiment 1

[0025] Embodiment 1 discloses a plasma melting furnace for treating waste incineration fly ash, referring to the drawings of Figure 1 and Figure 2 The melting furnace comprises an "L"-shaped furnace body 1 and a pneumatic feeding well 2. The furnace body 1 is divided into a vertical section furnace body 101 and a horizontal section furnace body 102. The upper surface end of the horizontal section furnace body 102 is connected with the lower end of the vertical section furnace body 101, and a furnace cover 3 is arranged at the top of the vertical section furnace body 101. A plasma electrode 4 is arranged in the furnace cover 3 and extends to the middle position of the vertical section furnace body 101. A bottom electrode 5 formed by laying a conductive material is arranged on the bottom wall of the horizontal section furnace body 102 directly below the plasma electrode 4. The bottom electrode 5 is connected with a switch through a wire, so that after the switch is closed, the bottom electrode 5 can generate plasma arc with the plasma electrode 4 in the initial stage to generate a large amount of radiation heat to heat the fly ash entering the furnace.

[0026] The number of the air feeding type feeding well 2 can be set between 1 and 4. When the air feeding type feeding well 2 is provided with multiple air feeding type feeding wells 2, the multiple air feeding type feeding wells 2 are arranged in a ring array on the vertical section furnace body 101, and each air feeding type feeding well 2 is located above the bottom of the plasma electrode 4 at the communication position of the vertical section furnace body 101. In the embodiment 1, the air feeding type feeding well 2 is provided with at least three air feeding type feeding wells 2, and each air feeding type feeding well 2 is designed to be inclined downward by an angle α in the vertical direction, and the angle α can be set between 10° and 30° according to the actual situation, and each air feeding type feeding well 2 is designed to be inclined eccentrically by an angle β in the horizontal direction, and the angle β can be set between 5° and 30° according to the actual situation. Through the above arrangement of the angles of the air feeding type feeding well 2 and the air blowing during the material conveying, the falling fly ash and the silicon-based additive can make a counterclockwise rotating movement in the vertical section furnace body 101, which is beneficial to the uniform heating of the materials, prolongs the falling time of the fly ash and the silicon-based additive, and enables the fly ash and the silicon-based additive to be heated sufficiently by the plasma electrode 4, and enables the silicon-based additive falling into the horizontal section furnace body 102 to have a certain stirring kinetic energy, so as to realize the stirring of the molten material in the horizontal section furnace body 102.

[0027] A refractory material flow guide ring block 6 is arranged on the inner wall of the vertical section furnace body 101 below the plasma electrode 4. The upper end of the refractory material flow guide ring block 6 is connected with the inner wall of the vertical section furnace body 101, and the lower end is in the shape of a section converging to the middle. When the fly ash and the silicon-based additive are blown from the air feeding type feeding well 2, the fly ash and the silicon-based additive will make a counterclockwise rotating movement in the vertical section furnace body 101. At this time, since the melting point of the fly ash is low, the fly ash will become a molten slag state and adhere to the refractory material flow guide ring block 6 after being heated by the high-temperature arc generated by the plasma electrode 4, and the molten slag state fly ash will continuously adhere to the refractory material flow guide ring block 6 over time, and then the molten slag state fly ash will drop from the bottom section of the refractory material flow guide ring block 6 to the molten pool in the horizontal section furnace body 102 under the action of gravity. At the same time, since the silicon-based additive is heavy and has a high melting point, the silicon-based additive will not be completely melted after being heated by the high-temperature arc generated by the plasma electrode 4, and will fall into the molten pool in the horizontal section furnace body 102, and then the mixture of the fly ash and the silicon-based additive in the molten pool of the horizontal section furnace body 102 will continue to be heated by the joule heat generated by the bottom electrode 5, so that the mixture can be completely converted into a molten state while maintaining the uniformity of the temperature.

[0028] The electric resistance wire heating layer 7 is arranged in the refractory outer wall of the horizontal section furnace body 102, and the bottom wall of the horizontal section furnace body 102 is arranged to be inclined downward by about 2-6°, and then a slag discharge port 8 is arranged at the lower inclined end of the bottom wall of the horizontal section furnace body 102. The heating by the electric resistance wire heating layer 7 can maintain the high-temperature state in the molten pool, and ensure that the fly ash and the silicon-based additive mixture are always in a molten state in the horizontal section furnace body 102. As the molten material in the molten pool 10 becomes more and more, and the fly ash and the silicon-based additive mixture in the pneumatic feeding well 2 are continuously pneumatically fed, the feeding gas and the silicon-based additive with certain kinetic energy can effectively stir the molten material in the molten pool. On the one hand, the molten material is uniformly heated, and on the other hand, the flow of the molten material in the molten pool is accelerated, and then the flowing molten material runs towards the slag discharge port 8, so that the molten material is smoothly discharged from the slag discharge port 8 of the horizontal section furnace body 102.

[0029] Finally, the end face of the horizontal section furnace body 102 away from the vertical section furnace body 101 is provided with a flue gas discharge port 9, and the liquid level of the molten pool in the horizontal section furnace body 102 is always lower than the horizontal height of the flue gas discharge port 9. At the same time, the electric resistance wire heating layer 7 is also arranged on the outer wall of the end face of the horizontal section furnace body 102 at the flue gas discharge port 9, so as to avoid the formation of salt plugging in the flue gas discharge port 9 due to the cooling of flue gas. Through the above design of the flue gas discharge port 9, the molten fly ash and silicon-based additive mixture in the horizontal section furnace body 102 flows towards the slag discharge port 8, and the gas conveying fly ash and silicon-based additive and the tail gas generated in the melting process all flow towards the flue gas discharge port 9 along the space above the molten pool in the horizontal section furnace body 102, and then are discharged from the flue gas discharge port 9 in time. Finally, the discharged flue gas is treated by subsequent flue gas treatment equipment and discharged after reaching the standard.

[0030] In addition, when an emergency occurs and it is determined that it cannot be solved for a short time, the electric resistance wire heating layer 7 maintains the temperature of the furnace body to maintain the fly ash in a molten state, and at the same time, the feeding of the pneumatic feeding well 2 is immediately stopped, and the slag discharge port 8 is immediately opened, so as to ensure that the molten fly ash in the melting furnace is discharged from the furnace body, and the bottom electrode 5 at the lower part of the furnace body is exposed, facilitating the reuse next time the furnace is started.

[0031] Embodiment 2

[0032] Embodiment 2 discloses a method for harmless treatment of fly ash using the plasma melting furnace in embodiment 1, which mainly comprises the following steps: S1: calculating the required addition ratio of the silicon-based additive according to the composition of the fly ash, and then mixing the fly ash and the silicon-based additive for standby. When calculating, the addition amount of the silicon-based additive is controlled to be between 15-30% of the total amount of the fly ash and the silicon-based additive mixture.

[0033] S2: open the circuit of the plasma electrode 4 and the bottom electrode 5, so that the bottom electrode 5 can generate plasma arc with the plasma electrode 4 in the initial stage.

[0034] S3: when the melting furnace has the feeding conditions, the fly ash and the silicon-based additive mixture are sent into the multiple pneumatic feeding wells 2 by using the pneumatic conveying mode, so that the mixture can make counterclockwise rotating motion and fall in the vertical section furnace body 101, and then the high-temperature arc generated by the plasma electrode 4 heats the mixture by using the radiant heat.

[0035] The fly ash in the mixture is melted due to small particle size and low melting point, and is first attached to the refractory material flow guide ring block 6, and then starts to flow downward as the attached fly ash melt increases, and then drips from the bottom of the refractory material flow guide ring block 6 to gather in the horizontal section furnace body 102, and after the fly ash melt covers the bottom electrode 5, the current passes through the bottom electrode 5 to generate Joule heat to continuously heat the fly ash melt and the silicon-based additive.

[0036] S4: with the continuous input of the fly ash and the silicon-based additive mixture, the fly ash is first rapidly melted by the high-temperature arc generated by the plasma electrode 4, and then the silicon-based additive is gathered in the molten pool in the horizontal section furnace body 102 and is continuously heated, melted and heat-insulated by the Joule heat generated by the bottom electrode 5.

[0037] When the mixed melt in the molten pool reaches a certain amount and flows to the lower slag outlet 8, the resistance wire heating layer 7 on the outer wall of the horizontal section furnace body 102 continuously heats to ensure that the mixed melt does not condense during the flowing process, and then the slag outlet 8 is opened to discharge the mixed melt to obtain the fly ash harmless glass body. At the same time, the continuous heating of the resistance wire heating layer 7 increases the flue gas temperature to above 1100°C, maintains the saturated steam pressure, prevents harmful substances such as Nacl from precipitating when the gas temperature decreases, and ensures the smooth discharge of the tail gas.

[0038] S5: during the entire melting process of the fly ash and the silicon-based additive mixture, the gas flow for feeding the mixture and the flue gas generated during the melting process all flow through the space above the molten pool in the horizontal section furnace body 102 to the flue gas discharge port 9 side, and are finally discharged from the flue gas discharge port 9 and discharged after being treated by the flue gas treatment equipment.

[0039] The above is only a preferred embodiment of the present application, and is not used to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A plasma fly ash melting furnace, comprising a furnace body and a furnace cover, characterized in that, The furnace body is L-shaped and is composed of a vertical section and a horizontal section connected together. The furnace cover is located on the top of the vertical section and a plasma electrode extending into the vertical section is provided on the furnace cover. A bottom electrode is provided on the bottom wall of the horizontal section directly below the plasma electrode. A pneumatic feeding well is provided on the vertical section of the furnace body located above the bottom of the plasma electrode. The material blown in by the pneumatic feeding well can rotate counterclockwise inside the vertical section of the furnace body. A slag discharge port is provided at the bottom of the horizontal section of the furnace body on the side away from the vertical section of the furnace body. A flue gas discharge port is provided at the upper end of the horizontal section of the furnace body above the slag discharge port.

2. The plasma fly ash melting furnace according to claim 1, characterized in that, The vertical section of the furnace body is equipped with 1 to 4 pneumatic feeding wells, and when there are no fewer than two pneumatic feeding wells, they are arranged in a ring array.

3. The plasma fly ash melting furnace according to claim 2, characterized in that, The pneumatic feeding well is set at a downward inclination of 10~30° in the vertical direction and at an eccentric inclination of 5~30° in the horizontal direction.

4. The plasma fly ash melting furnace according to claim 1, characterized in that, A refractory material guiding ring block is provided on the inner wall of the vertical section furnace located below the plasma electrode. The upper end of the refractory material guiding ring block is connected to the inner wall of the vertical section furnace, and the lower end is set in a cross-sectional shape that tapers towards the middle.

5. The plasma fly ash melting furnace according to claim 1, characterized in that, Resistance wire heating layers are provided in the refractory outer wall of the horizontal section of the furnace body and in the outer wall of the end face of the horizontal section of the furnace body at the flue gas outlet.

6. The plasma fly ash melting furnace according to claim 1, characterized in that, The bottom wall of the horizontal section of the furnace body is inclined at an angle of 2 to 6 degrees, and the slag discharge port is located at the lower inclined end of the bottom wall of the horizontal section of the furnace body.

7. A method for harmlessly treating fly ash using the plasma fly ash melting furnace according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Calculate the required proportion of silicon-based additives based on the composition of fly ash, and then mix fly ash and silicon-based additives in proportion for later use. (2) Turn on the plasma electrode and the bottom electrode to generate a plasma arc in the initial stage; (3) After the furnace body is ready for feeding, the mixture obtained in step (1) is fed into the vertical section furnace body from the air-pumped feeding well by air-blowing conveying, so that the mixture rotates counterclockwise and falls in the vertical section furnace body. Then, the high temperature arc generated by the plasma electrode heats the mixture, so that the fly ash in the mixture is heated and melted. The molten fly ash then flows into the horizontal section furnace body and accumulates. After the molten fly ash covers the bottom electrode, the current passes through the bottom electrode to generate Joule heat. (4) As the mixture is continuously fed in, the fly ash is first rapidly melted by the high-temperature electric arc radiation heat generated by the plasma electrode, and the silicon-based additive falls into the horizontal section of the furnace body and is continuously heated, melted and kept warm by the Joule heat generated by the bottom electrode. When the mixed molten material in the molten pool reaches a certain amount, the slag discharge port is opened to discharge the mixed molten material. (5) During the entire melting process, the gas flow fed into the mixture and the flue gas generated during the melting process are discharged together from the flue gas outlet, and then treated by the flue gas treatment equipment to meet the standards before being discharged.

8. The method for harmless treatment of fly ash according to claim 7, characterized in that, In step (1), the amount of silicon-based additive is controlled between 15% and 30% of the total amount of the mixture.

9. The method for harmless treatment of fly ash according to claim 7, characterized in that, It also includes immediately stopping the feeding of the pneumatic feed well and opening the slag discharge port to quickly discharge all molten material inside the furnace when encountering an emergency and determining that it cannot be resolved in a short time.

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