High-free calcium oxide fly ash wet modification deamination device and slurry preparation system and method

Abstract

A device for wet-process modification and deamination of high-free calcium oxide fly ash comprises a shell and a central guide tube, a guide device, an air distribution device, and a water distribution device disposed therein; the central guide tube is disposed vertically, suspended above and below, and is internally provided with a push-flow agitator, causing the water flow inside the tube to rise and the water flow outside the tube to descend, forming a circular flow; the guide device is in the shape of an inverted cone, disposed directly below the central guide tube, with both the top and bottom of the cone open, and the lower end of the central guide tube extending into the interior of the inverted cone, with a gap between the central guide tube and the inner wall; the air distribution device is disposed at the lower portion of the shell for distributing air upward, and the water distribution device is disposed at the upper portion of the shell for distributing water downward. The present invention also provides a system and method for preparing a slurry for wet-process modification and deamination of high-free calcium oxide fly ash, the system comprising a slurry concentrating device and the modified deamination device; the present invention can simultaneously complete the modification and deamination of high-calcium fly ash within a single processing unit, thereby realizing its resource utilization.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial solid waste resource utilization and coal filling mining, and particularly relates to a high-free calcium oxide fly ash wet modification and deamination device and a slurry preparation system and method. Background Art

[0002] The main nitrogen oxides (NO X To control nitrogen oxide emissions, coal-fired power plants are generally equipped with denitrification equipment. Currently, selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) flue gas denitrification technologies are widely used. Ammonia escape from the denitrification reactor is unavoidable. Fly ash is a byproduct of power plants. Some of this escaped ammonia mixes with the flue gas and is discharged from the chimney, some adheres to the surface of the fly ash, and some reacts with the SO2 or SO3 produced by combustion to form ammonium salts NH4HSO4 and (NH4)2SO4, which remain in the denitrified fly ash.

[0003] Fly ash, the main solid waste from power plants, is emitted in huge quantities. These fly ash accumulations occupy land and often cause dust problems, causing environmental problems. To address the fly ash accumulation problem, researchers have proposed fly ash paste backfill mining technology. This technology uses fly ash produced by coal-fired power plants as the main backfill material, mixed with other materials in a certain ratio to form a paste. This paste is then transported to the goaf through pipelines under the action of gravity or pumps. This technology not only effectively controls ground subsidence and protects the ecological environment, but also allows for on-site disposal of fly ash, solving the problems of fly ash storage and environmental pollution in coal-fired power plants. However, due to the quality issues of fly ash itself, there are still some difficulties in its application.

[0004] First, there is the quality issue of fly ash with high free calcium oxide. Studies have found that when fly ash with high free calcium oxide is used to prepare filling paste, the filling will crack and become brittle during the curing process, causing the filling strength to fail. This is because when free calcium oxide and free magnesium oxide come into contact with water, a chemical reaction occurs to generate calcium hydroxide and magnesium hydroxide, which wrap around the surface of the free calcium oxide / magnesium particles to form a gel layer, delaying the further reaction of water and free calcium oxide / magnesium. When this fly ash / magnesium slag is used to prepare filling paste, since water gradually reacts with free calcium oxide / magnesium during the curing process of the paste, and the generated calcium hydroxide and magnesium hydroxide will increase in volume, expansion stress is generated inside the filling paste, which ultimately leads to the breakage of the paste material and failure of strength. Therefore, the national standards "Magnesium Slag Portland Cement" (GB23933-2009) and "Fly Ash for Cement and Concrete" (GB1596-2017) clearly stipulate the free calcium oxide and magnesium oxide content when fly ash and magnesium slag are used as cementitious materials, requiring that the maximum free calcium oxide content shall not exceed 4% and the free magnesium oxide content shall not exceed 8%.

[0005] Secondly, the ammonium salts (NH4HSO4 and (NH4)2SO4) contained in fly ash cause ammonia to be released during the filling process, which has a negative impact on the underground filling air environment and limits the utilization of fly ash. As one of the main raw materials for coal mine filling paste, the composition and structure of fly ash have a direct impact on the performance of the filling paste. As the main material for mine filling, the amount of fly ash used is far greater than the amount of fly ash used in concrete. The residual ammonia in the denitrified fly ash will release ammonia due to hydration reaction, and the release may become more intense with stirring. It will escape in the relatively closed space underground, posing a threat to the health of underground construction workers.

[0006] Therefore, solving the self-expansion and ammonia release problems of high-free calcium oxide fly ash-based filling pastes during the curing process is of great significance for promoting the large-scale resource utilization of fly ash. At present, to solve the problem of ammonia release during the curing process of high-free calcium oxide fly ash-based filling pastes, methods such as alkali addition, oxidation, and heating are used to remove the ammonium salts (NH4HSO4 and (NH4)2SO4) contained in the fly ash through physical and chemical reactions, thereby reducing the ammonia content in the fly ash and meeting the requirements for normal use of the fly ash. However, since the alkali addition and oxidation methods require the addition of reagents and the subsequent heating and drying of the deaminated fly ash, and the heating method has high requirements for the heat source, the high cost makes these methods not widely used in the deammoniation treatment of high-free calcium oxide fly ash-based filling pastes.

[0007] To address the self-expansion problem of fly ash-based pastes containing high free calcium oxide during curing, the following three methods are generally used to reduce the free calcium oxide content in high-calcium ash: 1. Mixing high-calcium ash with low-calcium ash to reduce the amount of free calcium oxide introduced, thereby ensuring the volume stability of the filling. 2. Grinding the high-calcium ash under water mist conditions and then allowing it to rest to dissolve the free calcium oxide in the fly ash, thereby reducing the free calcium oxide content. 3. Using a dedicated high-calcium ash concrete admixture can improve the strength and volume stability of fly ash-based pastes containing high free calcium oxide. However, the high processing costs of these methods limit their application in addressing the self-expansion problem of fly ash-based pastes containing high free calcium oxide. Summary of the Invention

[0008] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a high-free calcium oxide fly ash wet modification deamination device and a slurry preparation system and method, so as to solve the strength failure problems such as self-expansion and ammonia release problems of high-free calcium oxide fly ash-based filling paste during the curing process in a low-cost manner.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is:

[0010] A high-free calcium oxide fly ash wet modification and deamination device comprises a shell, a dry powder metering and dosing device, and a central guide tube, a guide device, an air distribution device, and a water distribution device arranged inside the shell.

[0011] The dry powder metering and adding device is connected to the shell one, and adds high-free calcium oxide fly ash into the interior of the shell one;

[0012] The central guide tube is vertically arranged and suspended above and below, and a plug-flow agitator is installed inside the central guide tube. The plug-flow agitator causes the water flow inside the tube to rise and the water flow outside the tube to fall, forming a circular flow.

[0013] The flow guide device is in the shape of an inverted cone and is arranged directly below the central flow guide cylinder. The top and bottom of the cone are both open. The lower end of the central flow guide cylinder extends into the interior of the inverted cone and there is a gap between the lower end and the inner wall of the inverted cone.

[0014] The gas distribution device is arranged at the lower part of the shell body and is used to distribute gas upward. During the gas distribution process, the fly ash slurry contacts with the bubbles in countercurrent, thereby strengthening the mass transfer process of ammonia in the slurry and maximizing its transfer from the liquid phase to the gas phase.

[0015] The water distribution device is arranged on the upper part of the shell body and is used for distributing water downward.

[0016] In one embodiment, the air distribution device is an annular air distribution pipe, which is arranged around the central guide tube and has air distribution holes and an air inlet on it; the water distribution device is an annular water distribution pipe, which is arranged above the central guide tube, and the inner ring diameter is larger than the outer diameter of the central guide tube, and has water distribution holes and a water inlet on it.

[0017] In one embodiment, the inner ring diameter of the annular air distribution pipe is 30 to 200 mm larger than the cone bottom diameter of the guide device, and two rows of air distribution holes are arranged at 90 degrees at the bottom of the annular air distribution pipe. The diameter of the air distribution holes is 0.5 to 1 mm, the spacing between adjacent holes is 10 to 50 mm, and the opening rate is 60 to 150% of the cross-sectional area of ​​the annular air distribution pipe; the annular water distribution pipe is installed close to the top of the shell, and a single row of water distribution holes is opened at a position of 135 degrees to the vertical direction. The diameter of the water distribution holes is 1 to 3 mm, the spacing between adjacent holes is 30 to 80 mm, and the opening rate is 60 to 150% of the cross-sectional area of ​​the annular air distribution pipe. 50 to 80% of the cross-sectional area of ​​the water pipe; the cylinder diameter of the central guide tube is 3 / 5 to 2 / 3 of the diameter of the shell, the blade diameter of the plug-flow agitator is 2 / 3 to 4 / 5 of the diameter of the central guide tube, and the rotation speed is 500 to 1500 rad / min; the height of the guide device is 1 / 2 to 3 / 4 of the diameter of the central guide tube, the cone top diameter is 2 to 3 times the slurry outlet diameter, the cone bottom diameter is 2 / 3 to 3 / 4 of the shell diameter, and the width of the gap between the central guide tube and the guide device in the vertical direction is 15 to 50 mm.

[0018] In one embodiment, the outlet of the dry powder metering and dosing device is arranged above the water distribution device, and has a dual-channel structure with built-in spiral meter 1 and spiral meter 2, which respectively quantitatively feed high-free calcium oxide fly ash and solid additives into shell 1, and the solid additives are sodium hydroxide, sodium carbonate or sodium sulfate.

[0019] In one embodiment, the water inlet of the water distribution device is connected to the water supply main, the air inlet of the air distribution device is connected to the air supply device, and the water supply main is connected to the liquid additive metering device, and the liquid additive is sodium silicate, hydrochloric acid, or a liquid agent formed by mixing and dissolving one or more solid additives.

[0020] The present invention also provides a system for preparing a high-free calcium oxide fly ash wet-process modified deamination slurry, comprising a slurry concentration device and the high-free calcium oxide fly ash wet-process modified deamination device;

[0021] The slurry concentrating device comprises a second shell and a central tube vertically suspended in the second shell, wherein a concentrated slurry area is formed below the central tube in the second shell;

[0022] The slurry outlet of the high-free calcium oxide fly ash wet modification and deamination device is connected to the top end of the central pipe.

[0023] In one embodiment, a water collecting tank is provided at the upper portion of the second shell, and the water collecting tank is connected to a water storage tank that supplies water to the water distribution device; the concentrated slurry area is connected to a filling paste preparation system.

[0024] The present invention further provides a slurry preparation method based on the high free calcium oxide fly ash wet modified deamination slurry preparation system, comprising the following steps:

[0025] Startup phase: Based on the effective volume of the high-free calcium oxide fly ash wet modified deamination device and the selected mass concentration of the prepared slurry, the corresponding amount of water and liquid additives are injected into the shell 1, and then the plug-flow agitator is turned on to form an annular water flow inside and outside the central guide tube. Then, the air supply is turned on to enter the preparation phase;

[0026] Preparation stage: high free calcium oxide fly ash and solid additives corresponding to the amount of water are put into the high free calcium oxide fly ash wet modification and deamination device. After the preset mixing time is reached, the slurry outlet transports the modified slurry to the slurry concentration device. At the same time, high free calcium oxide fly ash, solid additives, liquid additives and water are added according to the preset mass concentration ratio to ensure that the slurry outflow and material addition reach a dynamic balance and continue to operate; after reaching the target preparation amount, the addition is stopped, and after all the modified slurry is emptied, the cleaning stage begins;

[0027] Cleaning stage: Turn on the water supply to fill the shell one with clean water, start the plug-flow agitator and the air distribution device at the same time and run for the set time, then drain the water; then turn off the plug-flow agitator and the air distribution device, and if 40-60% of the volume of clean water is filled into the shell one again, it will enter the standby stage, and the next time it is prepared, it will directly enter the preparation stage; if no water is added after the cleaning stage is completed, it will start from the startup stage the next time it is prepared.

[0028] In one embodiment, the mass concentration of the prepared slurry is 10% to 50%, the total mixing time of the materials in the high free calcium oxide fly ash wet modification and deamination device is 2 to 10 minutes, and the prepared modified slurry is concentrated to 40 to 65% by adjusting the supernatant reflux water intake in the slurry concentration device according to the ratio requirements of the filling paste.

[0029] In one embodiment, during the preparation stage, the air supply volume is 30 to 50 times the water supply volume by weight, and the air supply pressure is 2 to 3 times the effective water depth in the shell.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The device of the present invention simultaneously completes the modification of high-calcium fly ash and the removal of its adsorbed ammonia in one processing unit, expands the range of raw material selection for filling paste preparation, and better realizes the resource utilization of inferior fly ash.

[0032] 2. The present invention has simple operation, low processing cost and good processing effect.

[0033] 3. The device of the present invention has strong compatibility and can be used for new filling systems. It is also applicable to the transformation of existing fly ash-based filling paste preparation systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic structural diagram of the wet-process modification and deamination device of high-free calcium oxide fly ash of the present invention.

[0035] Figure 2 It is a top view of the wet-process modification and deamination device of high-free calcium oxide fly ash of the present invention.

[0036] Figure 3 It is a schematic structural diagram of the system for preparing the high-free calcium oxide fly ash wet modified deammoniation slurry of the present invention.

[0037] In the figure: 1 shell 1, 2 central guide tube, 3 high-speed motor, 4 plug-flow agitator, 5 guide device, 6 guide device bracket, 7 air inlet, 8 air distribution device, 9 air distribution hole, 10 water inlet, 11 water distribution device, 12 water distribution hole, 13 slurry outlet, 14 cover plate, 15 dry powder metering and adding device, 15-1 spiral metering device 1, 15-2 spiral metering device 2, 16 water storage tank, 17 metering water pump 1, 18 metering water pump 2, 19 check valve 1, 20 check valve 2, 21 water supply main pipe, 22 liquid additive metering and adding device, 23 dosing pipe, 24 air supply device, 25 shell 2, 26 central guide tube, 27 concentrated slurry area, 28 slurry screw pump, 29 sump, 30 supernatant reflux pump, 31 air supply check valve. DETAILED DESCRIPTION

[0038] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples.

[0039] like Figure 1 and Figure 2 As shown, the present invention first provides a high-free calcium oxide fly ash wet modification and deamination device, which mainly includes a shell 1, a dry powder metering and adding device 15, and a central guide tube 2, a guide device 5, an air distribution device 8 and a water distribution device 11 arranged inside the shell 1.

[0040] The dry powder metering device 15 is connected to the shell 1 and is used to add high-free calcium oxide fly ash, as well as necessary solid additives and other solid substances, into the shell 1. The bottom of the shell 1 is provided with a slurry outlet 13. In the present invention, the solid additive can be a paste-based admixture such as sodium hydroxide, sodium carbonate, or sodium sulfate, and the weight concentration of the added additive is generally 1-5%.

[0041] The central flow guide tube 2 is a vertically mounted, suspended structure, and can be installed by connecting its outer wall to the inner wall of the shell 1 via brackets. A plug-flow agitator 4 is installed inside the tube. The rotation of the plug-flow agitator 4 causes the water inside the tube to rise and the water outside the tube to fall, forming a circular flow. It can also operate at extremely high speeds, using high-speed hydraulic shear to exfoliate the calcium hydroxide gel.

[0042] The flow guide device 5 is an inverted cone structure, which is arranged directly below the central flow guide tube 2. The top and bottom of the cone are open. The lower end of the central flow guide tube 2 extends into the interior of the inverted cone and there is a gap between it and the inner wall.

[0043] The gas distribution device 8 is arranged at the lower part of the shell 1 and is used to distribute gas upward. During the gas distribution process, the fly ash slurry contacts with the bubbles in countercurrent, strengthening the mass transfer process of ammonia in the slurry and maximizing its transfer from the liquid phase to the gas phase.

[0044] Water distribution device 11 is disposed at the top of housing 1 and is used to distribute water downward. It can also mix a liquid additive with the water and deliver it. For example, the liquid additive of the present invention can be sodium silicate, hydrochloric acid, or a liquid agent formed by dissolving one or more of the aforementioned solid additives. The weight concentration of the added additive is generally 1-5%.

[0045] According to this device, by utilizing the high-speed rotation of the plug-flow agitator 4, the water flow in the central guide tube 2 can be caused to rise rapidly. Correspondingly, a downward flow is formed outside the tube. On the one hand, a circular flow is formed inside and outside the central guide tube 2, continuously stripping the calcium hydroxide gel on the surface of the free calcium oxide particles in the fly ash, accelerating the reaction process between the free calcium oxide particles and water. On the other hand, the fly ash slurry outside the central guide tube 2 is in countercurrent contact with the air bubbles released from the bottom of the device, increasing the transfer rate of ammonia molecules dissolved in water from the liquid phase to the gas phase, thereby achieving rapid deammoniation of the fly ash slurry. At the same time, the shearing effect between the bubbles and the liquid and solid phases can enhance the stripping effect of the calcium hydroxide gel on the surface of the free calcium oxide particles, further enhancing the reaction rate of the free calcium oxide with water.

[0046] The present invention provides preferred implementation parameters for the central draft tube 2: its diameter is 3 / 5 to 2 / 3 of the diameter of the housing 1, and the diameter of the plug-flow agitator 4 is 2 / 3 to 4 / 5 of the diameter of the central draft tube 2. Driven by a high-speed motor 3 mounted on the cover plate 14, it can achieve an extremely high speed of 500 to 1500 rad / min. Friction and shear between the calcium hydroxide gel layer formed on the surface of the free calcium oxide particles in the fly ash upon contact with water and the high-speed rotation of the plug-flow agitator blades promotes the release of calcium hydroxide from the surface of the free calcium oxide particles, thereby increasing the reaction rate of the free calcium oxide with water.

[0047] For example, the top end of the central guide tube 2 is a flared structure to facilitate water flow to overflow from the inside to the outside.

[0048] The present invention provides a preferred implementation parameter of the guide device 5: its height is 1 / 2 to 3 / 4 of the diameter of the central guide tube 2, the diameter of the cone top is 2 to 3 times the diameter of the slurry outlet 13, the diameter of the cone bottom is 2 / 3 to 3 / 4 of the diameter of the shell 1, and the width of the gap between the central guide tube 2 and the guide device 5 in the vertical direction is 15 to 50 mm, so that the slurry maintains a high flow rate at the position where it passes through the gap, preventing particle sedimentation during the slurry circulation process.

[0049] For example, the guide device 5 can be fixed to the bottom of the shell 1 through the guide device bracket 6, and the water flows into the guide device 5 from the gap between the bottom of the shell 1 and the outer wall of the guide device 5, and rises into the central guide tube 2.

[0050] In some embodiments of the present invention, the air distribution device 8 adopts an annular air distribution pipe structure and is arranged around the central guide tube 2. Air distribution holes 9 and air inlets 7 are opened on it. The air distribution holes 9 can be opened downward, and the air inlet 7 can be opened at any suitable position according to the layout and extend to the outside of the shell 1.

[0051] The present invention provides preferred implementation parameters for an annular air distribution duct: the inner diameter of the annular air distribution duct is 30 to 200 mm larger than the conical base diameter of the flow guide device 5. Two rows of air distribution holes 9 are arranged at a 90-degree angle at the bottom of the annular air distribution duct. The diameter of the air distribution holes 9 is 0.5 to 1 mm, the spacing between adjacent holes is 10 to 50 mm, and the opening ratio is 60 to 150% of the cross-sectional area of ​​the annular air distribution duct 8. This ensures uniform gas pressure and bubble release within the air distribution duct.

[0052] For example, the annular air distribution pipe 8 is located above the air guide device 5 , and the gap between the inner wall of the air guide device 5 and the lower end of the central air guide tube 2 is used to allow the air distribution to pass through and enter the central air guide tube 2 .

[0053] In some embodiments of the present invention, the water distribution device 11 also adopts an annular water distribution pipe structure and is arranged above the central guide tube 2. The inner ring diameter is larger than the outer diameter of the central guide tube 2, and a water distribution hole 12 and a water inlet 10 are opened on it. Obviously, the water distribution hole 12 should be opened downward, and the water inlet 10 can be opened at any suitable position according to the layout and extend to the outside of the shell 1.

[0054] The present invention provides preferred implementation parameters for an annular water distribution pipe: the annular water distribution pipe is installed close to the top of the housing 1, with a single row of water distribution holes 12 formed at a 135° angle to the vertical. The diameter of the water distribution holes 12 ranges from 1 to 3 mm, the spacing between adjacent holes is 30 to 80 mm, and the porosity is 50 to 80% of the cross-sectional area of ​​the annular water distribution pipe. This ensures sufficient water pressure within the water distribution pipe, allowing water to be sprayed into the housing through the water distribution holes, ensuring uniform and impactful water distribution, thereby achieving flushing of the interior of the housing.

[0055] In some embodiments of the present invention, the dry powder metering and adding device 15 adopts a dual-channel structure, and the two channels contain high-free calcium oxide fly ash and solid additives respectively, which are separated by a partition and a cone at the bottom. The two channel outlets are respectively provided with a spiral metering device 15-1 and a spiral metering device 15-2. The dry powder metering and adding device 15 is installed on the cover plate 14, and the outlet is provided above the water distribution device 11. The high-free calcium oxide fly ash and the solid additive are quantitatively added into the shell 1 through the spiral metering device 15-1 and the spiral metering device 15-2.

[0056] In some embodiments of the present invention, a water reservoir 16 is provided to supply water. Water supply metering pump 17 and water supply metering pump 2 18 are installed in parallel within water reservoir 16. Check valves 19 and 20 are installed on the outlet pipes of water supply metering pump 17 and water supply metering pump 2 18, respectively, and flow into a water supply main 21. Water supply main 21 is connected to the water inlet 10 of the water distribution device 11. The two water supply metering pumps serve as backup for each other and can also enhance the temporary slurry configuration water supply capacity to meet the needs of adjusting the slurry moisture content during the process. A liquid additive metering device 22 is connected to the water supply main 21 via a dosing pipe 23, through which the agent is added to the housing 1 via the water supply main 23. The air inlet 7 of the air distribution device 8 is connected to the air supply device 24 via an air supply pipeline, with an air supply check valve 31 installed between the two.

[0057] refer to Figure 3 The present invention also provides a high-free calcium oxide fly ash wet modified deamination slurry preparation system, which mainly includes a slurry concentration device and the high-free calcium oxide fly ash wet modified deamination device;

[0058] The slurry concentrating device includes a second shell 25 and a central tube 26 vertically suspended in the second shell 25 . A concentrated slurry area 27 is formed below the central tube 26 in the second shell 25 .

[0059] The slurry outlet 13 of the high free calcium oxide fly ash wet modification and deamination device is connected to the top of the central pipe 26. The heavy fly ash particles in the slurry are diverted from the central pipe and then precipitated from bottom to top in the concentrating device. After concentration, they are stored in the concentrated slurry area 27 at the bottom.

[0060] In some embodiments of the present invention, the bottom end of the central tube 26 is a flared structure to facilitate the slurry to diffuse and flow out from the inside to the outside.

[0061] Furthermore, in the present invention, a water collection tank 29 is provided above the shell 25, and the water collection tank 29 is connected to the water storage tank 16 that supplies water to the water distribution device 11, and is used to collect the supernatant separated from the heavy fly ash particles and lift it to the water storage tank 16 via the supernatant reflux pump 30.

[0062] The concentrated slurry area 27 of the present invention is connected to the filling paste preparation system, and the concentrated slurry finally obtained can be transported to the filling paste preparation system by means of a slurry screw pump 28.

[0063] Therefore, the slurry preparation method of the high-free calcium oxide fly ash wet modified deamination slurry preparation system of the present invention, that is, the operation procedure of the preparation device, includes four stages: startup, preparation, cleaning, and standby. The method steps are as follows:

[0064] Start-up phase: Based on the effective volume of the high-free calcium oxide fly ash wet modification and deamination device and the selected mass concentration of the prepared slurry, under the joint action of the liquid additive dosing device 22 and the water supply metering pump, the corresponding amount of water and liquid additives are injected into the shell 1, and then the plug-flow stirring blade 4 is turned on to form an annular water flow inside and outside the central guide tube 2, and then the air supply is turned on to enter the preparation phase; generally speaking, in the present invention, the selected mass concentration of the prepared slurry is 10% to 50%.

[0065] Preparation stage: Turn on the spiral metering device and put the high free calcium oxide fly ash and solid additives corresponding to the amount of water into the high free calcium oxide fly ash wet modification and deamination device. After the preset mixing time is reached, the slurry outlet 13 transports the modified slurry to the slurry concentration device. The prepared modified slurry is concentrated to 40-65% by adjusting the supernatant reflux water intake in the slurry concentration device according to the ratio requirements of the filling paste.

[0066] Simultaneously, the spiral metering device, liquid additive dosing device 22, and water metering pump are activated to add high-free calcium oxide fly ash, solid additives, liquid additives, and water according to the preset mass concentration ratios, ensuring that the slurry outflow and material addition reach a dynamic balance and continue to operate. Once the target preparation volume is reached, dosing is stopped, and the spiral metering device, liquid additive dosing device 22, and water metering pump are turned off. Once all the modified slurry is emptied, the cleaning phase begins.

[0067] For example, the air supply volume is 30 to 50 times the water supply volume by weight, and the air supply pressure is 2 to 3 times the effective water depth in the shell 1.

[0068] Generally speaking, in the present invention, the total mixing time of the materials in the high free calcium oxide fly ash wet modification and deamination device is 2 to 10 minutes.

[0069] Cleaning Phase: Only the water metering pump is activated, filling the housing 1 with clean water. The push-flow agitator 4 and the air distributor 8 are simultaneously activated and run for a set time, after which the water is drained. Generally, the cleaning time is 1 to 3 minutes, and this process may be repeated 1 to 2 times depending on the cleaning effect. The push-flow agitator 4 and the air distributor 8 are then turned off. If 40 to 60% of the volume of the housing 1 is refilled with clean water, the system enters the standby phase, and the next batch will proceed directly to the preparation phase. If no water is added after the cleaning phase, the next batch will begin at the startup phase.

[0070] The principle of the present invention is:

[0071] High-free calcium oxide fly ash is first prepared into a low-mass concentration slurry. The reaction products of the fly ash particles with water are exfoliated from the particle surfaces under high hydraulic shear conditions, enhancing the rate and process of the fly ash-water reaction and dissolution. This also allows ammonia adsorbed on the fly ash particle surfaces to dissolve in the water. Subsequently, air bubbles released from the bottom of the device interact with the slurry in countercurrent flow, achieving rapid deammonification of the fly ash slurry. The shearing action of the bubbles further enhances the exfoliation of the calcium hydroxide gel on the surface of the free calcium oxide particles. Next, under the combined action of the central draft tube 2 and the plug-flow impeller 4, a circular flow pattern is formed along the inside and outside of the central draft tube 2. Dissolved ammonium ions in the slurry and the gel on the surface of the fly ash particles are continuously and repeatedly mass-transferred and disturbed by the air bubbles, ultimately achieving wet-process modification of the fly ash and ammonia removal. Finally, the low-mass concentration fly ash slurry is concentrated to a suitable concentration, and then aggregate, cementitious materials, and admixtures are added to prepare a filling paste.

[0072] In a specific embodiment of the present invention, the diameter of the shell 1 is 1500mm, the diameter of the plug-flow agitator 4 is 500mm, the rotation speed is 800rad / min, and the diameter of the central guide tube 2 is 700mm; the height of the guide device 5 is 350mm, the diameter of the cone top section is 900mm, the diameter of the cone bottom section is 300mm, and the width of the gap between the central guide tube 2 and the guide device 5 in the vertical direction is 30mm; the diameter of the annular air distribution pipe is 350mm, and two rows of air distribution holes 9 are arranged at 90° at the bottom of the pipe, with an aperture of 0.5mm, a spacing of 15mm, and an opening rate of 120% of the cross-sectional area of ​​the air distribution pipe; the annular water distribution pipe is installed close to the inner side of the top of the equipment, and a single row of holes is opened at a position of 135° to the vertical direction, with an aperture of 1mm, a spacing of 40mm, and an opening rate of 60% of the cross-sectional area of ​​the water distribution pipe; a blower is used as the air supply device, and the air supply volume is 8m 3 / min, wind pressure is 59kpa.

[0073] 3m3 is pumped into the water supply metering pump 17, the check valve 19 and the water supply main pipe 21. 3Water is supplied into the shell 1. After the plug-flow agitator 4 is activated, 0.8 tons of fly ash raw material containing 12.6% free calcium oxide and 24.1% calcium oxide is added into the shell 1 using a screw meter 15-1. The initial fly ash slurry has a mass concentration of approximately 21%. Simultaneously, hydrochloric acid is added to the slurry from a liquid reagent dosing device 22 at a concentration of 1%. After stirring for 1 minute, 0.5% sodium hydroxide and 0.5% sodium sulfate admixtures are added and stirring continues. The entire mixing process lasts for 1 minute. During the slurry stirring process, the calcium hydroxide gel layer formed on the surface of the free calcium oxide particles in the fly ash when exposed to water and the high-speed rotating plug-flow agitator blades creates friction and shear, causing the calcium oxide to peel from the surface of the free calcium oxide particles and increasing the reaction rate of the free calcium oxide with water.

[0074] In addition, the plug-flow agitator causes the water flow to rise rapidly in the central tube, and a corresponding downward flow is formed outside the tube. On the one hand, a circulation is formed inside and outside the central tube of the fly ash modification device, which continuously peels off the calcium hydroxide gel on the surface of the free calcium oxide particles in the fly ash, and accelerates the reaction process between the free calcium oxide particles and water. On the other hand, the fly ash slurry outside the central tube is in countercurrent contact with the air bubbles released from the bottom of the device, which increases the transfer rate of ammonia molecules dissolved in water from the liquid phase to the gas phase, and realizes the rapid deamination of the fly ash slurry; at the same time, the shearing effect between the bubbles and the liquid phase and the solid phase can enhance the peeling effect of the calcium hydroxide gel on the surface of the free calcium oxide particles, and further enhance the reaction rate of the free calcium oxide with water.

[0075] After stirring for 2 minutes, the modified slurry is prepared and flows into the concentration device; 2.1m 3 After the water content is reduced, the mass concentration of the slurry reaches 47%. Subsequently, 1.6 tons of crushed coal gangue with a particle size range of 5 to 15 mm and 0.16 tons of 425 Portland cement are added to the concentrated slurry and mixed evenly. Finally, a filling paste with a solid content of 74% is made for coal mine filling. After 28 days of curing, the appearance of the filling specimen is intact and there is no crack development. The compressive strength is tested to be 5.36MPa, which meets the filling requirements.

[0076] In summary, the present invention has simple operation, low processing cost and good processing effect. It simultaneously completes the modification of high-calcium fly ash and the removal of its adsorbed ammonia in a single processing unit, expands the range of raw material selection for filling paste preparation, and better realizes the resource utilization of inferior fly ash.

Claims

1. High free calcium oxide fly ash wet modification deamination device, characterized in that: It comprises a housing (1), a dry powder metering and adding device (15), and a central guide tube (2), a guide device (5), an air distribution device (8), and a water distribution device (11) arranged inside the housing (1); The dry powder metering and adding device (15) is connected to the shell one (1) and adds high-free calcium oxide fly ash into the interior of the shell one (1); The central guide tube (2) is vertically arranged and suspended in the air, and a plug-flow stirring paddle (4) is installed inside the central guide tube. The plug-flow stirring paddle (4) causes the water flow inside the tube to rise and the water flow outside the tube to fall, thereby forming a circular flow. The flow guide device (5) is in the shape of an inverted cone and is arranged directly below the central flow guide tube (2). The top and bottom of the cone are both open. The lower end of the central flow guide tube (2) extends into the interior of the inverted cone and has a gap with the inner wall thereof. The air distribution device (8) is arranged at the lower part of the housing (1) and is used to distribute air upwards; The water distribution device (11) is arranged on the upper part of the shell (1) and is used to distribute water downward.

2. The high free calcium oxide fly ash wet modification and deamination device according to claim 1 is characterized in that: The air distribution device (8) is an annular air distribution pipe, which is arranged around the central guide tube (2) and is provided with air distribution holes (9) and an air inlet (7); the water distribution device (11) is an annular water distribution pipe, which is arranged above the central guide tube (2) and has an inner ring diameter greater than the outer diameter of the central guide tube (2), and is provided with water distribution holes (12) and a water inlet (10).

3. The high free calcium oxide fly ash wet modification and deamination device according to claim 2 is characterized in that: The inner ring diameter of the annular air distribution pipe is 30 to 200 mm larger than the cone bottom diameter of the flow guide device (5). Two rows of air distribution holes (9) are arranged at 90 degrees at the bottom of the annular air distribution pipe. The diameter of the air distribution holes (9) is 0.5 to 1 mm, the distance between adjacent holes is 10 to 50 mm, and the opening rate is 60 to 150% of the cross-sectional area of ​​the annular air distribution pipe. The annular water distribution pipe is installed close to the top of the shell (1). A single row of water distribution holes (12) is opened at a position of 135 degrees to the vertical direction. The diameter of the water distribution holes (12) is 1 to 3 mm, the distance between adjacent holes is 30 to 80 mm, and the opening rate is 50% of the cross-sectional area of ​​the annular water distribution pipe. ~80%; the diameter of the cylinder of the central guide tube (2) is 3 / 5~2 / 3 of the diameter of the shell (1), the diameter of the blade of the plug-flow stirring paddle (4) is 2 / 3~4 / 5 of the diameter of the central guide tube (2), and the rotation speed is 500~1500 rad / min; the height of the guide device (5) is 1 / 2~3 / 4 of the diameter of the central guide tube (2), the diameter of the cone top is 2~3 times the diameter of the slurry outlet (13), the diameter of the cone bottom is 2 / 3~3 / 4 of the diameter of the shell (1), and the width of the gap between the central guide tube (2) and the guide device (5) in the vertical direction is 15~50mm.

4. The high free calcium oxide fly ash wet modification and deamination device according to claim 1, 2 or 3, characterized in that: The outlet of the dry powder metering and adding device (15) is arranged above the water distribution device (11), and is a double-channel structure with a built-in spiral metering device (15-1) and a spiral metering device (15-2), which respectively quantitatively feed high-free calcium oxide fly ash and solid additives into the shell (1), wherein the solid additives are sodium hydroxide, sodium carbonate or sodium sulfate.

5. The high free calcium oxide fly ash wet modification and deamination device according to claim 1, 2 or 3, characterized in that: The water inlet (10) of the water distribution device (11) is connected to a water supply main pipe (21), the air inlet (7) of the air distribution device (8) is connected to an air supply device (24), and the water supply main pipe (21) is connected to a liquid additive metering device (22), wherein the liquid additive is sodium silicate, hydrochloric acid, or a liquid agent formed by mixing and dissolving one or more solid additives.

6. High free calcium oxide fly ash wet modified deammoniation slurry preparation system, characterized by: It comprises a slurry concentration device and a high-free calcium oxide fly ash wet modification and deamination device as claimed in claim 1, 2, 3, 4 or 5; The slurry concentrating device comprises a second shell (25) and a central tube (26) vertically suspended in the second shell (25), wherein a concentrated slurry area (27) is formed below the central tube (26) in the second shell (25); The slurry outlet (13) of the high-free calcium oxide fly ash wet modification and deamination device is connected to the top end of the central pipe (26).

7. The system for preparing high-free calcium oxide fly ash wet modified deammoniation slurry according to claim 6, characterized in that: A water collecting tank (29) is provided at the upper portion of the second shell (25), and the water collecting tank (29) is connected to a water storage tank (16) that supplies water to the water distribution device (11); the concentrated slurry area (27) is connected to a filling paste preparation system.

8. The slurry preparation method based on the high free calcium oxide fly ash wet modified deamination slurry preparation system according to claim 6 is characterized in that: The steps include: Startup phase: according to the effective volume of the high free calcium oxide fly ash wet modified deamination device and the selected mass concentration of the prepared slurry, a corresponding amount of water and liquid additives are injected into the shell (1), and then the push-flow agitator (4) is turned on to form an annular water flow inside and outside the central guide tube (2), and then the air supply is turned on to enter the preparation phase; Preparation stage: high free calcium oxide fly ash and solid additives corresponding to the amount of water are put into the high free calcium oxide fly ash wet modification deamination device. After the preset mixing time is reached, the slurry outlet (13) transports the modified slurry to the slurry concentration device. At the same time, high free calcium oxide fly ash, solid additives, liquid additives and water are added according to the preset mass concentration ratio to ensure that the slurry outflow and the material addition reach a dynamic balance and continue to operate; after reaching the target preparation amount, the addition is stopped, and after all the modified slurry is emptied, the cleaning stage is entered; Cleaning stage: start the water supply, fill the shell one (1) with clean water, start the push-flow stirring blade (4) and the air distribution device (8) at the same time and run for a set time, then drain the water; then turn off the push-flow stirring blade (4) and the air distribution device (8), and if 40-60% of the volume of clean water is filled into the shell one (1) again, the standby stage will be entered, and the preparation stage will be directly entered when preparing next time; If no water is added after the cleaning phase is completed, the next preparation will start from the start-up phase.

9. The slurry preparation method according to claim 8, characterized in that: The mass concentration of the prepared slurry is 10% to 50%, the total mixing time of the materials in the high-free calcium oxide fly ash wet modification and deamination device is 2 to 10 minutes, and the prepared modified slurry is concentrated to 40 to 65% by adjusting the supernatant reflux water intake in the slurry concentration device according to the ratio requirements of the filling paste.

10. The slurry preparation method according to claim 8, characterized in that: During the preparation stage, the air supply volume is 30 to 50 times the water supply volume by weight, and the air supply pressure is 2 to 3 times the effective water depth in the shell 1 (1).

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