System and method for fly ash and sludge co-cycling and reuse

Abstract

This invention discloses a system and method for the co-recycling and reuse of fly ash and sludge. The system uses a screening unit to recover the finest fly ash with the highest effective component content. The fly ash is then crushed and ground in a crushing unit to expose ultrafine fly ash with fully exposed effective reactants. This ultrafine fly ash is then screened again in a negative pressure conveying unit. A quantitative amount of the ultrafine fly ash is then added to a sludge drying unit, mixed and dried with the sludge in a specific ratio, and then co-incinerated with waste in a furnace. This process pre-treats acidic substances in the sludge. Furthermore, the hydrated lime in the ultrafine fly ash reacts with acidic gases in the flue gas, purifying the flue gas. This system allows for multiple desulfurization and acid removal processes in the co-incineration of sludge and waste, ensuring more thorough contact and reaction between the hydrated lime and acidic substances. This system significantly reduces the pressure on fly ash chelation solidification and its byproduct landfill through effective recycling, improves the comprehensive utilization rate of hydrated lime, and reduces steam consumption in the co-processing of sludge and waste.

Description

Technical Field

[0001] This invention belongs to the technical field of fly ash recycling equipment, specifically relating to a system and method for the co-circulation and reuse of fly ash and sludge. Background Technology

[0002] The flue gas generated during waste-to-energy incineration requires purification treatment to meet emission standards. Semi-dry deacidification is currently the mainstream method for flue gas purification in waste-to-energy incineration plants. It typically uses slaked lime as the reactant for acidic gases in the flue gas. The slaked lime is prepared into a lime slurry solution and sprayed into the reaction tower through a high-speed rotating atomizer to fully contact and react with the flue gas. The deacidification rate is very high, with SO2 removal at 85% and HCl removal at 99%. However, the utilization rate of the slaked lime is only about 35%. Excess slaked lime and other dust after the reaction are collected by fly ash scrapers at the bottom of the reaction tower and the bottom of the bag filter. These are then transported by a collecting scraper to the fly ash silo for chelation and solidification before being centrally transported to a landfill for disposal. Testing shows that the slaked lime content in the fly ash ranges from 29% to 34%, resulting in significant material waste and increasing the pressure on both the in-plant fly ash solidification and the off-site landfill treatment. Wastewater treatment plant sludge contains sulfur (S) and chloride (Cl). When this sludge is co-burned in a waste incinerator, it produces SO2 and HCl acidic gases, increasing the concentration of these gases in the flue gas and consequently increasing the consumption of deacidification materials. Currently, in sludge-waste incineration co-processing projects, the sludge is dried before co-burning. This drying process is entirely physical, without any pre-treatment for deacidification. The deacidification reaction is completed entirely in the downstream flue gas treatment stage, resulting in a higher deacidification load compared to waste-to-energy plants that do not co-burn sludge. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a system and method for the co-recycling and reuse of fly ash and sludge with high recovery rate and low energy consumption, which addresses the shortcomings of the existing technology.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A fly ash and sludge co-recycling system includes a screening unit, a crushing unit, a negative pressure conveying unit, a quantitative feeding unit, a sludge drying unit and a rotary dispersion unit connected in sequence.

[0006] The screening unit is used to screen the original fly ash into coarse ash and fine ash. The particle size of the coarse ash is >75μm, and the particle size of the fine ash is ≤75μm. The fine ash enters the crushing unit.

[0007] The crushing unit is used to crush fine ash to obtain ultrafine ash, the particle size of which is ≤15μm;

[0008] The negative pressure conveying unit is used to convey the ultrafine ash to the quantitative feeding unit;

[0009] The quantitative feeding unit is used to quantitatively add ultrafine ash to the sludge drying unit;

[0010] The sludge drying unit is used to mix and dry the ultrafine ash and sludge to obtain ash-sludge mixture;

[0011] The rotary dispersion unit disperses the sludge mixture onto the waste to be incinerated through rotation.

[0012] Preferably, in the aforementioned fly ash and sludge co-recycling system, the screening unit includes a coaxial gravity multi-stage screener, and adjacent coarse ash hoppers and fine ash hoppers. The coaxial gravity multi-stage screener includes a multi-stage screen cylinder, a rotating shaft, and a motor. The rotating shaft passes through the axis of the multi-stage screen cylinder, and a support is provided on the rotating shaft. The multi-stage screen cylinder is fixed to the rotating shaft by the support. One end of the rotating shaft is connected to the motor. The first end of the multi-stage screen cylinder has an ash inlet, and the second end has an ash outlet. The multi-stage screen cylinder is installed at an inclination on the opening end of the fine ash hopper, so that the second end is higher than the first end. The ash outlet is located on the opening end of the coarse ash hopper. The bottom of the coarse ash hopper has a coarse ash discharge port, and the bottom of the fine ash hopper has a fine ash discharge port, which is connected to the crushing unit.

[0013] In the aforementioned fly ash and sludge co-circulation and reuse system, preferably, the multi-stage screen cylinder includes a primary screen cylinder, a secondary screen cylinder, and a tertiary screen cylinder, which are sequentially nested from the inside out. The screen apertures of the multi-stage screen cylinder decrease in size from the inside out. One end of each multi-stage screen cylinder is open, and the other end is closed. The open end of the primary screen cylinder extends beyond the open end of the secondary screen cylinder, and the open end of the secondary screen cylinder extends beyond the open end of the tertiary screen cylinder. The open end of each screen cylinder is the ash outlet of that stage. The closed ends of each screen cylinder are flush. The closed end of the primary screen cylinder is connected to the ash inlet through a primary ash hopper.

[0014] In the aforementioned fly ash and sludge co-circulation and reuse system, preferably, the original ash hopper is provided with a spiral ash feeding scraper that rotates with the rotating shaft; the inner wall of the primary screen cylinder is provided with a primary spiral blade extending axially; the inner wall of the secondary screen cylinder is provided with a secondary spiral blade extending axially; and the inner wall of the tertiary screen cylinder is provided with a tertiary spiral blade extending axially.

[0015] In the aforementioned fly ash and sludge co-recycling system, preferably, the primary screen cylinder is used to screen particles with a diameter greater than 300 μm, the secondary screen cylinder is used to screen particles with a diameter greater than 150 μm, and the tertiary screen cylinder is used to screen particles with a diameter greater than 75 μm.

[0016] In the aforementioned fly ash and sludge co-recycling system, preferably, the negative pressure conveying unit includes a buffer tank, a first negative pressure pipe, and a second negative pressure pipe. The top of the buffer tank is provided with an air inlet and an air outlet. The air inlet is connected to the output end of the crushing unit through the first negative pressure pipe, and the air outlet is connected to the primary air inlet of the waste incinerator through the second negative pressure pipe. The bottom of the buffer tank is provided with an ultrafine ash discharge port, which is connected to a quantitative feeding unit.

[0017] In the aforementioned fly ash and sludge co-recycling system, preferably, the sludge drying unit is a thin-layer dryer, which has a steam inlet at the top and a drainage outlet at the bottom.

[0018] In the aforementioned fly ash and sludge co-recycling system, preferably, the rotary dispersion unit includes a buffer chamber and a dispersion disc. The input end of the buffer chamber is connected to the output end of the thin-layer dryer. The dispersion disc is rotatably installed at the bottom of the buffer chamber. A motor is provided at the top of the buffer chamber. The motor is connected to the dispersion disc via a rotating shaft. The dispersion disc has dispersion ports circumferentially.

[0019] In the aforementioned fly ash and sludge co-recycling system, preferably, the crushing unit is a ball mill; the quantitative feeding unit includes a disc feeder and multiple quantitative feeders, the disc feeder has multiple discharge ports, one discharge port is connected to one quantitative feeder, and one quantitative feeder is connected to one sludge drying unit.

[0020] As a general inventive concept, this invention also provides a method for the co-recycling and reuse of fly ash and sludge based on the above system, comprising the following steps:

[0021] S1. The original fly ash is screened into coarse ash and fine ash using a screening unit;

[0022] S2. The fine ash is conveyed to the crushing unit for crushing to obtain ultrafine ash;

[0023] S3. The ultrafine ash is conveyed to the quantitative feeding unit by a negative pressure conveying unit. The amount of ultrafine ash added to the sludge drying unit is controlled by the quantitative feeding unit so that the ultrafine ash and sludge are mixed and dried in proportion to obtain ash-sludge mixture.

[0024] S4. The ash mixture is evenly dispersed onto the waste to be incinerated using a rotary dispersion unit, and then the mixed waste is put into the furnace for combustion.

[0025] In step S3, the mass ratio of the ultrafine ash to the sludge is 1:3 to 5.

[0026] In step S3, the mass ratio of the ultrafine ash to the sludge is 1:3.

[0027] Compared with the prior art, the advantages of the present invention are as follows:

[0028] (1) The fly ash and sludge co-recycling system of the present invention uses a screening unit to screen and recover the fine ash with the highest effective component Ca(OH)2 content. The ash is then crushed and ground in a crushing unit to obtain ultrafine ash with fully exposed effective reactant Ca(OH)2. This ultrafine ash is then screened again in a negative pressure conveying unit and quantitatively added to a sludge drying unit. After mixing and drying with the sludge in a specific ratio, the ash is fed into a furnace for co-firing with waste. This achieves the pretreatment effect of acidic substances in the sludge. Furthermore, the hydrated lime in the ultrafine ash reacts with acidic gases in the furnace and flue, achieving the effect of purifying the flue gas. Therefore, the system of the present invention can perform multiple desulfurization and acid removal processes in the co-firing of sludge and waste, ensuring more thorough contact and reaction between the hydrated lime and acidic substances. The present invention significantly reduces the pressure on fly ash chelation solidification and its byproduct landfill through effective recycling, improves the comprehensive utilization rate of hydrated lime, and reduces the consumption of hydrated lime as a deacidification material in the tail flue gas purification system by approximately 29%.

[0029] (2) The fly ash and sludge co-recycling system of the present invention directly mixes and dries ultrafine ash with sludge. The Ca(OH)2 in the ultrafine ash reacts with the acidic components in the sludge. Furthermore, when the dried sludge containing ultrafine ash is co-incinerated with waste, the unreacted Ca(OH)2 in the ultrafine ash continues to react with the acidic components in the flue gas generated from the incineration of sludge and waste. Compared with the existing method of desulfurization and acid removal by contacting flue gas with lime slurry spray, this system allows for more sufficient contact and reaction time between Ca(OH)2 and acidic substances. Furthermore, the effective components are more thoroughly exposed after the fine ash is crushed, and the specific surface area is increased, which can further improve the efficiency and utilization rate of subsequent reactions with acidic substances in sludge and flue gas. The ultrafine ash is fed through a quantitative feeding unit, which can adjust the ratio of ultrafine ash to sludge and control the dryness and chemical reaction of the downstream sludge. The advantages are: the mixing and drying of ultrafine ash and sludge can make the mixing more thorough, which on the one hand improves the dryness of the mixture, and on the other hand, the initial acid-base neutralization reaction of the ash-sludge mixture occurs and the reaction is exothermic, which raises the temperature of the mixture, which can reduce the energy consumption of drying sludge to a certain extent and save energy.

[0030] (3) The fly ash and sludge co-recycling system of the present invention can be directly connected to the existing fly ash collection equipment through the ash inlet at the front end, and the ash and sludge mixture can be directly rotated and dispersed to the feed inlet of the waste incinerator that is feeding in the plant through the rotary dispersion unit at the back end, so as to disperse and co-burn immediately without the need to add a separate sludge and waste mixing equipment, saving space and cost, and facilitating the transformation of existing equipment.

[0031] (4) The fly ash and sludge co-recycling and reuse method of the present invention has the above-mentioned advantages because it has specific technical features corresponding to the system of the present invention. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of the fly ash and sludge co-recycling system in Embodiment 1 of the present invention.

[0033] Figure 2 This is a schematic diagram of the coaxial gravity multi-stage sieve in Embodiment 1 of the present invention.

[0034] Figure 3 for Figure 2 Enlarged diagram of point A in the middle.

[0035] Figure 4 for Figure 2 Cross-sectional view along line AA.

[0036] Figure 5 This is a schematic diagram of the disassembled structure of the multi-stage screen cylinder in Embodiment 1 of the present invention.

[0037] Figure 6 This is an enlarged schematic diagram of the ball mill in Embodiment 1 of the present invention.

[0038] Figure 7 This is an enlarged schematic diagram of the negative pressure conveying unit in Embodiment 1 of the present invention.

[0039] Figure 8 This is a schematic diagram illustrating the reaction principle of ultrafine ash and sludge in a thin-layer dryer in Embodiment 1 of the present invention.

[0040] Figure 9 This is a schematic diagram comparing the treatment of ash-sludge mixture and pure sludge by the rotary separation unit in Embodiment 1 of the present invention.

[0041] Legend: 1. Screening unit; 01. Rotating shaft; 011. Support; 02. Motor; 03. Ash inlet; 04. Ash outlet; 05. Raw ash hopper; 051. Spiral ash conveying scraper; 06. Steel ball; 11. Coaxial gravity multi-stage screener; 111. Primary screen cylinder; 1111. Primary spiral blade; 112. Secondary screen cylinder; 1121. Secondary spiral blade; 113. Tertiary screen cylinder; 1131. Tertiary spiral blade 12. Rotary vane; 13. Coarse ash hopper; 2. Fine ash hopper; 3. Crushing unit; 4. Negative pressure conveying unit; 5. Buffer tank; 6. Air inlet; 7. Air outlet; 8. First negative pressure pipe; 9. Second negative pressure pipe; 10. Quantitative feeding unit; 11. Disc feeder; 12. Quantitative feeder; 13. Dispersion disc; 14. Dispersion port; 15. Rotary dispersion unit; 16. Buffer chamber; 17. Dispersion disc; 18. Dispersion port; 19. Floating vane; 20. Coarse ash hopper; 10. Fine ash hopper; 21. Crushing unit; 22. Negative pressure conveying unit; 33. Buffer tank; 34. Air outlet; 35. First negative pressure pipe; 36. Second negative pressure pipe; 47. Quantitative feeding unit; 48. Disc feeder; 49. Quantitative feeder; 20. Floating sludge drying unit; 20. Rotary dispersion unit; 21. Buffer chamber; 22. Dispersion disc; 33. Dispersion port; 44. Quantitative feeder; 5. Floating sludge drying unit; 65. Rotary dispersion unit; 66. Buffer chamber; 67. Dispersion disc; 68. Dispersion port; 19. Rotary vane; 20. Coarse ash hopper; 10. Fine ash hopper; 21. Crushing unit; 22. Negative pressure conveying unit; 33. Buffer tank; 44. Air inlet; 55. Floating sludge dispersion unit; 66. Rotary dispersion unit; 77. Buffer chamber; 68. Dispersion disc; 69. Dispersion port; 20 Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0043] Example 1

[0044] Figure 1 This invention illustrates a specific embodiment of the fly ash and sludge co-recycling system, which includes a screening unit 1, a crushing unit 2, a negative pressure conveying unit 3, a quantitative feeding unit 4, a sludge drying unit 5, and a rotary dispersion unit 6 connected in sequence.

[0045] Screening unit 1 is used to screen the original fly ash into coarse ash and fine ash. The particle size of coarse ash is >75μm and the particle size of fine ash is ≤75μm. The fine ash enters crushing unit 2.

[0046] Crushing unit 2 is used to crush fine ash to obtain ultrafine ash, the particle size of which is ≤15μm;

[0047] The negative pressure conveying unit 3 is used to convey ultrafine ash to the quantitative feeding unit 4;

[0048] The quantitative feeding unit 4 is used to quantitatively add ultrafine ash to the sludge drying unit 5;

[0049] The sludge drying unit 5 is used to mix and dry ultrafine ash and sludge to obtain ash-sludge mixture;

[0050] The rotating dispersion unit 6 disperses the sludge mixture onto the waste to be incinerated through rotation.

[0051] The working process of the fly ash and sludge co-recycling system in this embodiment is as follows:

[0052] In this embodiment, the fly ash collected after flue gas purification treatment at a waste-to-energy plant is screened into coarse and fine ash by a screening unit 1. The fine ash is then crushed and ground by a crushing unit 2 to remove CaSO4, CaSO3, CaCl2, and metal oxides from the surface of the fine ash particles, exposing the effective target substance Ca(OH)2 inside, resulting in ultrafine ash. This ultrafine ash is then screened a second time by a negative pressure conveying unit 3, and the ultrafine ash with high Ca(OH)2 content is conveyed to a quantitative feeding unit 4. The quantitative feeding unit 4 controls the ultrafine ash to enter the sludge drying unit 5, where the ultrafine ash and sludge are mixed in proportion and dried. Then, the ultrafine ash is evenly dispersed onto the waste by a rotary dispersion unit 6 and mixed with the waste before being incinerated in the furnace. The system in this embodiment recovers the effective components from fly ash, mixes them with sludge, and then co-incinerates them with waste. This achieves the effect of pre-treating the acidic components of sludge, significantly reduces the pressure of fly ash solidification and landfilling of its products, reduces the consumption of deacidification materials in the tail flue gas purification system by about 29%, and improves the comprehensive utilization rate of quicklime.

[0053] Tests revealed that the fine ash obtained contained the highest content of the effective target compound Ca(OH)2 compared to fly ash of other particle sizes. The test results are shown in the table below:

[0054] Table 1. Ca(OH)2 content and alkalinity in fly ash particles of different sizes

[0055]

[0056] In this embodiment, ultrafine ash is directly mixed with sludge and dried. The Ca(OH)2 in the ultrafine ash reacts with the acidic components in the sludge. Furthermore, when the dried sludge containing ultrafine ash is co-fired with waste, the unreacted Ca(OH)2 in the ultrafine ash continues to react with the acidic components in the flue gas produced during co-firing. Compared to existing methods that use lime slurry spray to contact flue gas for desulfurization and acid removal, this system allows for more sufficient contact and reaction time between Ca(OH)2 and acidic substances. Moreover, the effective components are more thoroughly exposed after the fine ash is crushed, and the increased specific surface area further improves the efficiency and utilization rate of subsequent reactions with acidic substances in sludge and flue gas. The ultrafine ash is fed through the quantitative feeding unit 4, which can adjust the ratio of ultrafine ash to sludge and control the dryness and chemical reaction of the downstream sludge. Specifically, the mixing and drying of ultrafine ash and sludge can make the mixing more thorough. On the one hand, it can improve the dryness of the mixture. On the other hand, the initial acid-base neutralization reaction of the ash-sludge mixture and the release of heat can raise the temperature of the mixture, which can reduce the energy consumption of drying sludge to a certain extent.

[0057] Further improvements, such as Figure 2 , Figure 3 As shown, in this embodiment, the screening unit 1 includes a coaxial gravity multi-stage screener 11, a coarse ash hopper 12, and a fine ash hopper 13 arranged adjacent to each other. The coaxial gravity multi-stage screener 11 includes a multi-stage screen cylinder, a rotating shaft 01, and a motor 02. The rotating shaft 01 passes through the axis of the multi-stage screen cylinder, and a bracket 011 is provided on the rotating shaft 01. The multi-stage screen cylinder is fixed on the rotating shaft 01 by the bracket 011. One end of the rotating shaft 01 is connected to the motor 02. The first end of the multi-stage screen cylinder is provided with an ash inlet 03, and the second end is provided with an ash outlet 04. The multi-stage screen cylinder is installed at an inclination on the open end of the fine ash hopper 13, so that the second end is higher than the first end. The ash outlet 04 is located on the open end of the coarse ash hopper 12. The bottom of the coarse ash hopper 12 is provided with a coarse ash discharge port, and the bottom of the fine ash hopper 13 is provided with a fine ash discharge port. The fine ash discharge port is connected to the crushing unit 2. The screening unit 1 in this embodiment adopts a multi-stage coaxial design and relies on gravity screening during screening. The multi-stage design can improve the purity of fine ash and make the proportion of particles that meet the size standard as large as possible. The coaxial design and gravity screening can save equipment space and reduce screening power consumption while extending screening time and improving screening effect.

[0058] Further improvements, such as Figure 3 , Figure 4As shown, in this embodiment, the multi-stage screen cylinder includes a first-stage screen cylinder 111, a second-stage screen cylinder 112, and a third-stage screen cylinder 113, which are sequentially installed from the inside to the outside. The screen holes of the multi-stage screen cylinder decrease in size from the inside to the outside. One end of the multi-stage screen cylinder is open, and the other end is closed. The open end of the first-stage screen cylinder 111 extends beyond the open end of the second-stage screen cylinder 112, and the open end of the second-stage screen cylinder 112 extends beyond the open end of the third-stage screen cylinder 113. The open end of each stage of the screen cylinder is the ash outlet 04 of that stage of the screen cylinder. The closed ends of each stage of the screen cylinder are flush. The closed end of the first-stage screen cylinder 111 is connected to the ash inlet 03 through an original ash hopper 05.

[0059] Motor 02 and shaft 01 drive the multi-stage screen cylinders to rotate. The original fly ash enters the original ash hopper 05 through the ash inlet 03. When passing through the rotating first-stage screen cylinder 111, fly ash particles smaller than the first-stage screen mesh fall into the second-stage screen cylinder 112 under gravity, while the remaining fly ash particles fall into the coarse ash hopper 12 from the opening end of the first-stage screen cylinder 111. During rotation, fly ash particles smaller than the second-stage screen mesh fall into the third-stage screen cylinder 113 under gravity, while the remaining fly ash particles fall into the coarse ash hopper 12 from the opening end of the second-stage screen cylinder 112. During rotation, fly ash particles smaller than the third-stage screen mesh fall into the fine ash hopper 13 under gravity, while the remaining fly ash particles fall into the coarse ash hopper 12 from the opening end of the third-stage screen cylinder 113. This achieves three-stage screening of the original fly ash particles, which can greatly improve the screening rate of fine ash. Of course, more stages of screen cylinders can be designed if necessary.

[0060] Further improvements, such as Figure 5 As shown, in this embodiment, the original ash hopper 05 is equipped with a spiral ash-feeding scraper 051 that rotates with the rotating shaft 01; the inner wall of the first-stage screen cylinder 111 is equipped with a first-stage spiral blade 1111 extending axially; the inner wall of the second-stage screen cylinder 112 is equipped with a second-stage spiral blade 1121 extending axially; and the inner wall of the third-stage screen cylinder 113 is equipped with a third-stage spiral blade 1131 extending axially. The spiral ash-feeding scraper 051 and the spiral blades extending axially at each stage can effectively push the fly ash particles in each stage of the screen cylinder to move upward along the screen to the ash outlet 04 during the rotation of the multi-stage screen cylinders, causing fly ash particles of different sizes to quickly disperse in the corresponding screen cylinders, which is beneficial to improving screening efficiency.

[0061] In a further improvement, in this embodiment, the primary screen cylinder 111 is used to screen particles with a diameter greater than 300 μm, the secondary screen cylinder 112 is used to screen particles with a diameter greater than 150 μm, and the tertiary screen cylinder 113 is used to screen particles with a diameter greater than 75 μm. The screen aperture design of each stage of the screen cylinder in this embodiment is reasonable, and the proportion of fine ash obtained from screening reaches 93.45% of the original ash mass, resulting in a high yield of fine ash.

[0062] Further improvements, such as Figure 6As shown in this embodiment, the crushing unit 2 is a ball mill. Using a ball mill for crushing can more effectively remove impurities such as CaSO4, CaSO3, CaCl2 and metal oxides from the surface of the particles, resulting in a better crushing effect.

[0063] Further improvements, such as Figure 7 As shown, in this embodiment, the negative pressure conveying unit 3 includes a buffer tank 31, a first negative pressure pipe 32, and a second negative pressure pipe 33. The top of the buffer tank 31 is provided with an air inlet 311 and an air outlet 312. The air inlet 311 is connected to the output end of the crushing unit 2 through the first negative pressure pipe 32, and the air outlet 312 is connected to the primary air inlet of the waste incinerator through the second negative pressure pipe 33. The bottom of the buffer tank 31 is provided with an ultrafine ash discharge port, which is connected to the quantitative feeding unit 4. Fine ash enters the crushing unit 2, and ultrafine ash is output from the crushing unit 2, both of which are conveyed through the negative pressure air source at the inlet of the primary air fan, thereby reducing the power consumption of the newly added equipment in this system.

[0064] In a further improvement, in this embodiment, the sludge drying unit 5 is a thin-layer dryer, such as a cylindrical thin-layer dryer. The thin-layer dryer has a steam inlet at the top and a drainage outlet at the bottom. The ultrafine ash mixes with the sludge inside the thin-layer dryer, which can improve the dryness of the sludge. Furthermore, the ultrafine ash is in full contact with the sludge inside the thin-layer dryer, which is beneficial for the initial acid-base neutralization reaction, such as… Figure 8 As shown.

[0065] In a further improved embodiment, the rotary dispersion unit 6 includes a buffer chamber 61 and a dispersion disk 62. The input end of the buffer chamber 61 is connected to the output end of the thin-layer drying machine. The dispersion disk 62 is rotatably mounted on the bottom end of the buffer chamber 61. A motor 02 is provided on the top of the buffer chamber 61. The motor 02 is connected to the dispersion disk 62 via a rotating shaft 01. The dispersion disk 62 has dispersion ports 621 circumferentially arranged. Figure 9 As shown, compared to pure sludge, the ash-sludge mixture has relatively lower viscosity, a looser texture, and better separation effect. During rotational separation, it can break into small clumps, which are thrown out over a larger area and are more widely and evenly distributed on the waste, making it less likely to clump together.

[0066] In a further improvement, in this embodiment, the quantitative feeding unit 4 includes a disc feeder 41 and multiple quantitative feeders 42. The disc feeder 41 has multiple discharge ports, one discharge port is connected to one quantitative feeder 42, and one quantitative feeder 42 is connected to one sludge drying unit 5. In this embodiment, by cooperating with the disc feeder 41 and multiple quantitative feeders 42, ultrafine ash can be mixed and dried with sludge in multiple thin-layer dryers, improving overall work efficiency.

[0067] To fully illustrate the solution and advantages of this embodiment, the working process of the fly ash and sludge co-recycling system of this embodiment is further described below:

[0068] The raw fly ash enters the coaxial multi-stage gravity screen 11 through the ash inlet 03. Driven by the motor 02, the rotating shaft 01 drives the ash-feeding scraper, the primary screen cylinder 111, the primary spiral blade 1111, the secondary screen cylinder 112, the secondary spiral blade 1121, the tertiary screen cylinder 113, and the tertiary spiral blade 1131 to rotate synchronously. Power transmission and structural support are achieved by the bracket 011. After the raw fly ash enters the raw ash hopper 05, it enters the primary screen cylinder under the action of the spiral ash-feeding scraper 051. In section 111, particles with a diameter greater than 300 μm in the original fly ash cannot pass through the primary screen cylinder 111. Driven by the primary spiral blades 1111, they spiral forward and eventually fall from the ash outlet 04 into the coarse ash hopper 12. Particles with a diameter less than or equal to 300 μm pass through the primary screen cylinder 111 under the action of gravity and fall into the secondary screen cylinder 112. Particles with a diameter greater than 150 μm that fall into the secondary screen cylinder 112 are driven by the secondary spiral blades 1121 and fall out of the ash outlet 04. Particles with a diameter of 150 μm or less are fed into the coarse ash hopper 12. Under the influence of gravity, they pass through the secondary screen cylinder 112 and fall into the tertiary screen cylinder 113. Particles with a diameter greater than 75 μm that fall into the tertiary screen cylinder 113 are then fed into the coarse ash hopper 12 through the ash outlet 04 by the action of the tertiary spiral blades 1131. Particles with a diameter of 75 μm or less pass through the tertiary screen cylinder 113 and fall into the fine ash hopper 13 under the influence of gravity. This process achieves multi-stage screening of the original fly ash, resulting in... The mass ratio of fine ash particles to original fly ash reaches 93.45%. The fine ash in fine ash hopper 13 enters the ball mill under the action of wind. Inside the ball mill, the steel balls 06 collide with each other and grind and crush the fine ash into ultrafine ash. The CaSO4, CaSO3, CaCl2 and metal oxides on the surface of the crushed ultrafine ash are removed, exposing the effective target substance Ca(OH)2 inside. At the same time, the ultrafine ash has a smaller particle size and a larger specific surface area, which is more conducive to the subsequent reaction process. The buffer tank 31, the first negative pressure pipe 32, and the second negative pressure pipe 33 constitute a negative pressure conveying system. The inlet of the primary blower provides a negative pressure head. The ultrafine ash after grinding enters the buffer tank 31. Lighter dust, metal oxides, and other finer particles enter the incinerator through the second negative pressure pipe 33 under the negative pressure of the primary blower. Slightly larger particles containing the effective target substance Ca(OH)2 settle to the bottom of the buffer tank 31. The bottom of the buffer tank 31 is equipped with a disc feeder 41, which distributes the ultrafine ash to four quantitative feeders 42. Each quantitative feeder 42 is connected to a thin-layer dryer. The feeding frequency of the quantitative feeder 42 is adjusted according to the amount of sludge fed into the thin-layer dryer to ensure a proper ratio of sludge to ash. After being quantitatively fed, the ultrafine ash enters the thin-layer dryer and mixes with the sludge inside. Because the ultrafine ash does not contain moisture, it can increase the dryness of the mixture after mixing with the sludge. At the same time, the alkaline substances such as Ca(OH)2 in the ultrafine ash react with the acidic substances in the sludge in a neutralization reaction, which releases heat and raises the temperature of the mixture.The fully mixed sludge mixture enters the buffer chamber 61. The motor 02 drives the dispersing disc 62 to rotate through the rotating shaft 01. The sludge mixture falls from the buffer chamber 61 onto the dispersing disc 62 and rotates with the dispersing disc 62. Under the action of centrifugal force, it separates from the dispersing disc 62, spreads out in all directions, and falls onto the garbage, spreading evenly on the garbage.

[0069] The system advantages of this invention can be further demonstrated by the following data:

[0070] (1) Investigation on saving the amount of hydrated lime

[0071] In this embodiment, the changes in total mass and Ca(OH)2 content when the system crushes fine fly ash into ultrafine fly ash are negligible. Therefore, assuming the Ca(OH)2 content in the ultrafine fly ash is 31.65%, the mass of Ca(OH)2 obtained from recovering 1 ton of raw fly ash is...

[0072] m=1*93.45%*31.65%=0.29t

[0073] When this portion of Ca(OH)2 is mixed with and dried with sludge, it reacts with acidic substances in the sludge. The sludge mixture then reacts with acidic substances in the incinerator flue gas. Its utilization rate is no less than that of the quicklime added to the flue gas purification system (35%). Conservatively estimated, the amount of quicklime that can be saved is at least [amount missing].

[0074] M = 0.29 * 35% / 35% = 0.29t

[0075] It is understood that the system of the present invention can reduce the consumption of quicklime, a deacidification material, in the tail flue gas purification system by about 29% by recycling the original fly ash.

[0076] In practical applications, taking the applicant's plant's daily processing capacity as an example, recycling 50 tons of raw fly ash daily can save at least [amount missing] tons of hydrated lime.

[0077] 50 * 0.29 = 14.5t

[0078] The plant operates four waste incinerators simultaneously, each processing 850 tons of waste per day. Each ton of waste generates flue gas that requires 12 kg of quicklime for purification. Therefore, the total daily consumption of quicklime is 850 * 12 * 4 = 40.8 tons. By recycling 50 tons of raw fly ash daily, 14.5 tons of quicklime can be saved. This savings amount to 14.5 tons / 40.8 tons = 35.5%, which is equivalent to reducing the daily consumption of quicklime, a deacidification material, in the tail flue gas purification system by approximately 35.5%.

[0079] (2) Investigation on steam consumption of dried sludge

[0080] Taking the mixing of ultrafine ash and sludge at a mass ratio of 1:3 as an example, the sludge dryness before mixing is 20%, and the ultrafine ash dryness is 100%. The dryness after mixing is...

[0081] (20% * 3 + 100% * 1) / (1 + 3) = 40%

[0082] Therefore, mixing sludge at a mass ratio of 1:3 can increase the dryness of the sludge from 20% to 40%.

[0083] Based on experimental data, the temperature rises after mixing ultrafine ash and sludge. When mixed at a mass ratio of 1:3, the temperature increases by 11℃. The experimental results are shown in the table below:

[0084] Table 2. Temperature changes before and after mixing ultrafine ash and sludge.

[0085] Initial temperature (°C) Dosage (g) Dosage (g) sludge 23.5 150 150 ultrafine ash 41 30 50 The mixing ratio of ultrafine ash and sludge —— 1∶3 1∶5 Temperature before mixing and reaction (°C) 23.5 23.5 Temperature after mixing and reaction (°C) —— 31.5 34.5 Temperature rise of mortar mixing material (°C) —— 8 11

[0086] Note: The temperature before the mixing reaction is the temperature at which the ultrafine ash and sludge have not yet undergone a chemical reaction after mixing; the temperature after the mixing reaction is the temperature at which the ultrafine ash and sludge have undergone a chemical reaction after mixing.

[0087] When pure sludge enters the dryer, steam heats the sludge from 30℃ to 95℃. The steam consumption per ton of sludge is approximately 0.45t / t. The steam consumption for utilizing 1 ton of ultrafine ash is...

[0088] 3 * 0.45 = 1.35

[0089] The steam required to raise the sludge temperature by 1°C is...

[0090] 1.35 / (95-30)=0.0207

[0091] Based on the fact that the temperature rises by 11°C after mixing ultrafine ash and sludge at a mass ratio of 1:3, the amount of steam saved is:

[0092] 0.0207 * 11 = 0.228

[0093] Steam consumption reduced

[0094] 0.228 / 1.35 * 100% = 16.9%

[0095] Using the system of this invention, 16.9% of steam can be saved for every ton of ultrafine ash recycled. Therefore, 16.9% * 93.45% = 15.8% of steam can be saved for every ton of raw fly ash recycled.

[0096] Example 2

[0097] A method for the co-recycling and reuse of fly ash and sludge based on the system of Example 1 includes the following steps:

[0098] S1. The original fly ash is screened into coarse ash and fine ash using screening unit 1;

[0099] S2. The fine ash is conveyed to the crushing unit 2 for crushing to obtain ultrafine ash;

[0100] S3. The ultrafine ash is conveyed to the quantitative feeding unit 4 by the negative pressure conveying unit 3. The amount of ultrafine ash added to the sludge drying unit 5 is controlled by the quantitative feeding unit 4 so that the ultrafine ash and sludge are mixed and dried in proportion to obtain ash-sludge mixture.

[0101] S4. The ash and sludge mixture is uniformly mixed with the waste using a rotary dispersion unit 6, and then the mixed waste is put into the furnace for combustion.

[0102] This embodiment separates unreacted quicklime and reacts it with SO2 and HCl acidic gases in the sludge. This not only recovers excess quicklime from the fly ash and reduces the consumption of deacidification materials in the tail flue gas purification system by about 29%, thus improving the comprehensive utilization rate of quicklime, but also reduces the treatment pressure of fly ash chelation solidification and landfill.

[0103] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the spirit and technical essence of the invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, shall still fall within the scope of protection of the present invention.

Claims

1. A system for the co-recycling and reuse of fly ash and sludge, characterized in that, It includes a screening unit (1), a crushing unit (2), a negative pressure conveying unit (3), a quantitative feeding unit (4), a sludge drying unit (5), and a rotary dispersion unit (6) connected in sequence. The screening unit (1) is used to screen the original fly ash into coarse ash and fine ash. The particle size of the coarse ash is >75μm and the particle size of the fine ash is ≤75μm. The fine ash enters the crushing unit (2). The crushing unit (2) is used to crush fine ash to obtain ultrafine ash, wherein the particle size of the ultrafine ash is ≤15μm; The negative pressure conveying unit (3) is used to convey the ultrafine ash to the quantitative feeding unit (4). The quantitative feeding unit (4) is used to quantitatively add ultrafine ash to the sludge drying unit (5). The sludge drying unit (5) is used to mix and dry the ultrafine ash and sludge to obtain ash-sludge mixture; The rotary dispersion unit (6) disperses the sludge mixture onto the waste to be incinerated through rotation. The screening unit (1) includes a coaxial gravity multi-stage screener (11), an adjacent coarse ash hopper (12), and a fine ash hopper (13); the coaxial gravity multi-stage screener (11) includes a multi-stage screen cylinder, a rotating shaft (01), and a motor (02). The rotating shaft (01) passes through the axis of the multi-stage screen cylinder, and a bracket (011) is provided on the rotating shaft (01). The multi-stage screen cylinder is fixed on the rotating shaft (01) by the bracket (011). One end of the rotating shaft (01) is connected to the motor. The machine (02) is connected. The first end of the multi-stage screen cylinder is provided with an ash inlet (03), and the second end is provided with an ash outlet (04). The multi-stage screen cylinder is installed at an inclination on the opening end of the fine ash hopper (13), so that the second end is higher than the first end. The ash outlet (04) is located on the opening end of the coarse ash hopper (12). The bottom of the coarse ash hopper (12) is provided with a coarse ash discharge port, and the bottom of the fine ash hopper (13) is provided with a fine ash discharge port. The fine ash discharge port is connected to the crushing unit (2). The multi-stage screen cylinder includes a first-stage screen cylinder (111), a second-stage screen cylinder (112), and a third-stage screen cylinder (113) that are sequentially fitted from the inside to the outside. The screen holes of the multi-stage screen cylinder decrease in size from the inside to the outside. One end of the multi-stage screen cylinder is open and the other end is closed. The open end of the first-stage screen cylinder (111) extends beyond the open end of the second-stage screen cylinder (112), and the open end of the second-stage screen cylinder (112) extends beyond the open end of the third-stage screen cylinder (113). The open end of each stage of the screen cylinder is the ash outlet (04) of that stage of the screen cylinder. The closed ends of each stage of the screen cylinder are flush. The closed end of the first-stage screen cylinder is connected to the ash inlet (03) through a primary ash hopper (05). The original ash hopper (05) is provided with a spiral ash feeding scraper (051) that rotates with the rotating shaft (01); the inner wall of the first-stage screen cylinder (111) is provided with a first-stage spiral blade (1111) extending axially; the inner wall of the second-stage screen cylinder (112) is provided with a second-stage spiral blade (1121) extending axially; the inner wall of the third-stage screen cylinder (113) is provided with a third-stage spiral blade (1131) extending axially.

2. The fly ash and sludge co-recycling system according to claim 1, characterized in that, The primary screen cylinder (111) is used to screen particles with a diameter greater than 300 μm, the secondary screen cylinder (112) is used to screen particles with a diameter greater than 150 μm, and the tertiary screen cylinder (113) is used to screen particles with a diameter greater than 75 μm.

3. The fly ash and sludge co-recycling system according to claim 1 or 2, characterized in that, The negative pressure conveying unit (3) includes a buffer tank (31), a first negative pressure pipe (32), and a second negative pressure pipe (33). The top of the buffer tank (31) is provided with an air inlet (311) and an air outlet (312). The air inlet (311) is connected to the output end of the crushing unit (2) through the first negative pressure pipe (32). The air outlet (312) is connected to the primary air inlet of the waste incinerator through the second negative pressure pipe (33). The bottom of the buffer tank (31) is provided with an ultrafine ash discharge port. The ultrafine ash discharge port is connected to the quantitative feeding unit (4).

4. The fly ash and sludge co-recycling system according to claim 1 or 2, characterized in that, The sludge drying unit (5) is a thin-layer dryer, which has a steam inlet at the top and a drain outlet at the bottom.

5. The fly ash and sludge co-recycling system according to claim 4, characterized in that, The rotating dispersion unit (6) includes a buffer chamber (61) and a dispersion disk (62). The input end of the buffer chamber (61) is connected to the output end of the thin-layer dryer. The dispersion disk (62) is rotatably mounted at the bottom of the buffer chamber (61). A motor (02) is provided at the top of the buffer chamber (61). The motor (02) is connected to the dispersion disk (62) through a rotating shaft (01). The dispersion disk (62) is provided with a dispersion port (621) in the circumferential direction.

6. The fly ash and sludge co-recycling system according to claim 1 or 2, characterized in that, The crushing unit (2) is a ball mill; the quantitative feeding unit (4) includes a disc feeder (41) and multiple quantitative feeders (42). The disc feeder (41) is provided with multiple discharge ports. One discharge port is connected to a quantitative feeder (42), and the quantitative feeder (42) is connected to a sludge drying unit (5).

7. A method for the co-recycling and reuse of fly ash and sludge based on the system described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. The original fly ash is screened into coarse ash and fine ash using a screening unit (1); S2. The fine ash is conveyed to the crushing unit (2) for crushing to obtain ultrafine ash; S3. The ultrafine ash is conveyed to the quantitative feeding unit (4) by the negative pressure conveying unit (3). The amount of ultrafine ash added to the sludge drying unit (5) is controlled by the quantitative feeding unit (4) so ​​that the ultrafine ash and sludge are mixed and dried in proportion to obtain ash-sludge mixture. S4. The ash mixture is evenly dispersed onto the waste to be incinerated using a rotary dispersion unit (6), and then the mixed waste is put into the furnace for combustion.

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