Screening and recycling method for pile foundation mud

Abstract

The invention discloses a pile foundation mud screening and recycling method, and relates to the technical field of solid waste treatment. The method mainly solves the problems of low solid-liquid separation efficiency, insufficient recovery of useful components and poor performance of recycled aggregate in traditional pile foundation mud treatment. According to the technical scheme, the method comprises the steps that pile foundation mud is input into a high-frequency vibrating screen to separate coarse aggregate, medium particles and primary mud; grading the primary slurry to intercept fine sand and powder particles, and outputting superfine slurry; the superfine slurry is input into a slurry storage tank to be regulated and controlled according to the viscosity and the specific gravity value monitored in real time; mixing the coarse aggregate, the medium particles, the fine sand, the powder particles and solid cakes generated by filter pressing with an aluminate activator and silica fume to form a solid mixture; and finally, calcining the solid mixture in a rotary calcining kiln to generate the recycled aggregate. The method is mainly used for efficient resource recycling of pile foundation engineering waste mud, recycled aggregate capable of replacing natural aggregate is produced, and environmental pollution and resource waste are remarkably reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid waste treatment. More particularly, the present application relates to a pile foundation mud screening and recycling method. BACKGROUND

[0002] The waste mud generated in the process of building pile foundation construction usually contains a large amount of sand, clay and water, and its efficient recycling faces multiple technical bottlenecks. First, the separation precision of the traditional screening process for mud components is insufficient. Due to the characteristics of high viscosity and wide particle size distribution (0.1-5 mm) of pile foundation mud, the following defects are easy to occur in the conventional single-layer vibrating screen or fixed aperture screen: (1) coarse aggregate (>2 mm) and medium particles (0.5-2 mm) are mixed due to screen hole blockage or adhesion, resulting in a decrease in the aggregate recovery rate; (2) fine particles (<0.5 mm) cannot be effectively intercepted, and are lost with the mud, causing subsequent processing burden. This problem is due to the non-Newtonian fluid characteristics of mud. The viscous resistance makes small particle size particles easily adhere to the surface of large particles, and a wide range of particle size distribution requires multi-stage screening cooperation, but the existing equipment is difficult to balance the separation efficiency and anti-blocking requirements.

[0003] Secondly, the running stability of the cyclone separation unit is significantly affected by the fluctuation of the solid phase concentration of the mud. In actual construction, the mud concentration often changes in the range of 15%-35%, and the separation efficiency of the cyclone is highly dependent on the inlet pressure. When the solid phase concentration increases, the rheological properties of the mud change (such as increased viscosity), and if the fixed pumping pressure is maintained, the following problems will occur: (1) when the concentration is >25%, the underflow port is blocked, and fine sand (0.18-0.52 mm) is not intercepted; (2) when the concentration is <20%, the overflow port "runs coarse", and the target powder particles (0.065-0.22 mm) enter the ultra-fine mud. Historical attempts to solve the problem include manually adjusting the pump pressure or adding a concentration detector, but due to the fast dynamic change of the mud concentration (fluctuating ±5% per minute) and the lag of manual response, real-time matching of pressure and concentration cannot be achieved, resulting in a separation efficiency fluctuation of >30%.

[0004] Furthermore, material circulation during pressure regulation causes secondary damage. During the pressure switching stage of the cyclone system (such as 0.7→1.3 MPa), if a step change in pressure is directly performed: (1) the sudden change in pressure causes the flow field in the cyclone to be disturbed, and the separated particles are mixed again; (2) fine sand and powder particles collide at high speed with the wall of the cyclone under high pressure difference, causing breakage (the amount of micro-powder with a particle size <0.1 mm increases by about 15%). Although a buffer bin has been used to temporarily store the material, re-pumping is required during reprocessing. The high shear force of the conventional centrifugal pump (impeller linear velocity >10 m / s) further aggravates the breakage of particles, resulting in a loss of 8%-12% in the strength of the recycled aggregate. The root cause of this problem lies in the contradiction between the compressive strength of brittle mineral particles (such as quartz sand) (≤50 MPa) and the pumping mechanical force, and the existing technology lacks a low-damage circulation means.

[0005] The above problems jointly restrict the pile foundation mud resource utilization efficiency: the coarse aggregate recovery rate is insufficient, the fine component (fine sand, powder particle) loss rate is high, and the recycled aggregate is deteriorated due to high content of micro powder and poor grading, and the crushing index is worse than that of natural aggregate. How to realize high-precision separation of wide-particle-size mud, stable control of cyclone under dynamic concentration, and integrity protection of material circulation has become a technical difficulty that the industry has been unable to break through for a long time. SUMMARY

[0006] An object of the present application is to provide a pile foundation mud screening and recycling method for efficient resource recycling of pile foundation engineering waste mud, producing recycled aggregate that can replace natural aggregate, and significantly reducing environmental pollution and resource waste.

[0007] In order to achieve these objects and other advantages of the present application, according to one aspect of the present application, the present application provides a pile foundation mud screening and recycling method, comprising the following steps: Step one, input the pile foundation mud into a high-frequency vibrating screen equipped with an upper layer of 1.8-2.2 mm aperture screen and a lower layer of 0.45-0.55 mm aperture screen, separate out coarse aggregate with particle size greater than 1.8 mm, medium particles with particle size of 0.45-2.2 mm, and primary mud passing through the lower layer screen; Step two, pressurize the primary mud to 0.7-1.3 MPa by a centrifugal pump and pump it into a three-stage series cyclone separation unit; wherein the underflow port of the primary cyclone traps fine sand with particle size of 0.18-0.52 mm, the underflow port of the secondary cyclone traps powder particles with particle size of 0.065-0.22 mm, and the overflow port of the tertiary cyclone outputs ultra-fine mud; Step three, input the ultra-fine mud into a slurry storage tank, and monitor in real time by an online viscosity sensor and an online specific gravity sensor: When the Marsh funnel viscosity value is in the range of 16-24 s and the specific gravity value is in the range of 1.12-1.22 g / cm 3 , output recycled mud; When the viscosity value is less than 16 s, add a colloidal enhancer compounded by sodium bentonite, nano-silicon dioxide and poly-anionic cellulose in a mass ratio of (14-16):(1.8-2.2):1 to the slurry storage tank; When the specific gravity value is greater than 1.22 g / cm 3 , enable a plate-and-frame filter press to dewater 15%-35% of the ultra-fine mud in the slurry storage tank, and return the filtrate to the slurry storage tank; Step four, input the coarse aggregate obtained in step one and the medium particles, the fine sand and the powder particles obtained in step two, and the pretreated solid cake produced by the plate and frame filter press in step three into a vertical mixer, add 2.5% to 3.5% of aluminate activator and 4% to 6% of silica fume to the total mass of the solid phase, and mix to form a solid mixture; Step five, transport the solid mixture to a rotary calcining kiln, calcine at a temperature of 620 to 780°C for 25 to 35 minutes to generate recycled aggregate.

[0008] Preferably, in step two, pressure dynamic regulation is performed between the centrifugal pump and the three-stage series cyclone separation unit; the solid phase concentration of the primary mud is detected in real time by an electromagnetic flowmeter, when the concentration is in the range of 15% to 20%, the output pressure of the centrifugal pump is controlled to 1.1 to 1.3 MPa; when the concentration is in the range of 20% to 25%, the output pressure is controlled to 0.9 to 1.1 MPa; when the concentration is in the range of 25% to 35%, the output pressure is controlled to 0.7 to 0.9 MPa.

[0009] Preferably, in the process of pressure dynamic regulation, pressure gradual control is performed on the centrifugal pump; When the solid phase concentration change triggers the pressure interval switching is detected, the output pressure of the centrifugal pump is linearly transitioned to the target pressure interval at a rate of 0.1 to 0.2 MPa / s; At the same time in the pressure gradual control stage, the fine sand intercepted by the bottom flow port of the primary cyclone and the powder particles intercepted by the bottom flow port of the secondary cyclone are combined and introduced into a temporary buffer bin, and after the pressure stabilizes to the target interval, the materials in the temporary buffer bin are re-input into the three-stage series cyclone separation unit for processing.

[0010] Preferably, the reprocessing of the materials in the temporary buffer bin is performed with anti-crushing control; The materials in the temporary buffer bin are pumped back to the three-stage series cyclone separation unit by a screw pump, and the output pressure of the screw pump is controlled to 0.2 to 0.3 MPa; Before the materials are pumped, a silicone-based lubricant is added to the temporary buffer bin, and the amount of addition is 0.05% to 0.1% of the total mass of the materials; The lubricant and the materials are mixed by a double-shaft mixer at a speed of 30 to 50 r / min for 1 to 2 minutes.

[0011] Preferably, in step four, the solid cake produced by the plate and frame filter press in step three is pretreated: the solid cake is input into a crusher and crushed to particles with a particle size of 1 to 3 mm; the crushed particles are input into a perforated drum dryer and dried using the waste heat flue gas discharged from the rotary calcining kiln in step five to reduce the moisture content to 16% to 18%; the dried particles and the coarse aggregate obtained in step one, the medium particles, and the fine sand and the powder particles obtained in step two are simultaneously input into a vertical mixer.

[0012] Preferably, in step four, the moisture content of the coarse aggregate obtained in step one and the medium particles, the fine sand obtained in step two and the powder particles are adjusted simultaneously: the coarse aggregate, the medium particles, the fine sand and the powder particles are input into the perforated drum dryer, and the waste heat flue gas discharged from the rotary calcining kiln in step seven is used for drying to reduce the moisture content of the materials to 16% to 18%; the dried materials and the pretreated solid cake are input into the vertical mixer simultaneously.

[0013] Preferably, dynamic temperature compensation is performed on the waste heat flue gas input into the perforated drum dryer, including the following steps: a high-temperature buffer tank and a low-temperature buffer tank are connected in parallel at the outlet of the calcining kiln, the volume ratio of the two is 1:2 to 1:3, and the output pipelines of the high-temperature buffer tank and the low-temperature buffer tank finally converge into the same main pipeline, which is connected with the perforated drum dryer through a bag-type dust collector; the flue gas temperature T at the outlet of the calcining kiln is monitored in real time by a thermocouple: When T>110℃, the high-temperature flue gas treatment path is executed, the flue gas is introduced into the high-temperature buffer tank for temporary storage for 5 to 8 minutes, and then mixed with 20 to 30℃ ambient air in the outlet pipeline of the high-temperature buffer tank at a volume ratio of flue gas:ambient air= (75 to 85):(15 to 25) ; When T<80℃, the low-temperature flue gas treatment path is executed, the flue gas is introduced into the low-temperature buffer tank for temporary storage for 3 to 5 minutes, and then mixed with the high-temperature flue gas output from the high-temperature buffer tank at a volume ratio of flue gas:high-temperature flue gas= (85 to 90):(10 to 15) in the outlet pipeline of the low-temperature buffer tank; When 80℃≤T≤110℃, the direct delivery path is executed, and the flue gas is directly delivered to the bag-type dust collector; The mixed flue gas is input into the bag-type dust collector, the filter bag material of the dust collector is PTFE-coated glass fiber with a filtration accuracy of 1 μm, and a 0.5 to 1 mm isolation layer is formed on the surface of the filter bag by pre-coating the regenerated mud in step three; and a clean gas stream with an output temperature of 85 to 95℃ is obtained after dust removal.

[0014] Preferably, a temperature sensor is installed in the clean gas chamber of the bag-type dust collector to monitor the temperature of the mixed flue gas in real time, and the target temperature range is set to 85℃ to 95℃; When the monitored temperature is higher than 95℃, the mixing ratio of ambient air is automatically increased by 2 to 3 vol% for every 1℃ exceeded, and the flue gas output of the high-temperature buffer tank is simultaneously reduced; When the monitored temperature is lower than 85℃, the mixing ratio of high-temperature flue gas is automatically increased by 1.5 to 2 vol% for every 1℃ decreased, and the flue gas output of the low-temperature buffer tank is simultaneously reduced; Temperature data is collected every 30 s, and if the temperature deviates from the target value by more than 5℃ for three consecutive times, an alarm is triggered and a backup burner is activated to supplement heat.

[0015] Preferably, the mixing ratio is adjusted by using a pneumatic regulating valve system, and the control valve opening degree change rate is in the range of 0.5% / s~1% / s; wherein the pneumatic regulating valve system includes four groups of independent valves: ambient air regulating valve, arranged at the node where the ambient air pipeline accesses the high-temperature path mixer; high-temperature flue gas branch regulating valve, arranged at the branch pipeline from the high-temperature buffer tank to the low-temperature path mixer; low-temperature flue gas output regulating valve, arranged at the low-temperature buffer tank output pipeline; high-temperature buffer tank main output regulating valve, arranged upstream of the high-temperature buffer tank main output pipeline convergence point; When the monitored temperature is >95℃: if the system is executing high-temperature path processing, increase the ambient air regulating valve opening degree; if the system is executing low-temperature path processing, decrease the high-temperature flue gas branch regulating valve opening degree; simultaneously decrease the high-temperature buffer tank main output regulating valve opening degree; When the monitored temperature is <85℃: if the system is executing low-temperature path processing, increase the high-temperature flue gas branch regulating valve opening degree; increase the low-temperature flue gas output regulating valve opening degree; simultaneously increase the high-temperature buffer tank main output regulating valve opening degree.

[0016] The present application at least includes the following beneficial effects: the present application significantly improves the retention efficiency of coarse aggregate and medium particles by the synergistic effect of hierarchical screening and multi-stage cyclone separation, and greatly reduces the loss of fine particle components; the pressure self-adaptive regulation mechanism based on the solid phase concentration of the slurry effectively maintains the stability of the cyclone separation process, avoiding the phenomena of underflow blockage and overflow coarse particles; the gradual control and buffer strategy in the pressure switching stage significantly reduces the risk of particle breakage and guarantees the integrity of the material circulation; the introduction of trace lubricant and low-speed mixing process significantly inhibits the fine particle pulverization tendency in the reprocessing process; the crushing and waste heat drying treatment of the solid cake significantly improves the moisture uniformity of the mixed material and improves the calcination reaction effect; the flue gas temperature dynamic compensation system significantly stabilizes the drying heat source temperature and reduces energy loss; the automatic valve linkage control quickly responds to temperature fluctuations and ensures drying continuity; finally, the performance of the recycled aggregate approaches that of natural aggregate, achieving the goal of efficient resource utilization and near-zero emission of slurry solid waste.

[0017] Other advantages, objects, and features of the application will be apparent to those skilled in the art from the following specification. DETAILED DESCRIPTION

[0018] The present application will be further described in detail below with reference to specific embodiments, so that those skilled in the art can implement it according to the description.

[0019] It should be understood that the terms such as "have", "contain" and "include" used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0020] The present application provides a pile foundation mud screening recycling method, comprising the following steps: Step one, input the pile foundation mud into the high-frequency vibrating screen equipped with upper layer 1.8~2.2 mm aperture screen and lower layer 0.45~0.55 mm aperture screen, separate out coarse aggregate with particle size greater than 1.8 mm, medium particles with particle size of 0.45~2.2 mm, and primary mud passing through the lower layer screen; Step two, pump the primary mud into a three-stage series cyclone separation unit after pressurizing to 0.7~1.3 MPa by centrifugal pump; wherein the fine sand with particle size of 0.18~0.52 mm is intercepted at the underflow port of the primary cyclone, the powder particles with particle size of 0.065~0.22 mm are intercepted at the underflow port of the secondary cyclone, and the overflow port of the tertiary cyclone outputs superfine mud; Step three, input the superfine mud into the slurry storage tank, and monitor in real time by online viscosity sensor and online specific gravity sensor: When the marshall funnel viscosity value is in the range of 16~24 s and the specific gravity value is in the range of 1.12~1.22 g / cm 3 , output the regenerated mud; When the viscosity value is less than 16 s, add the colloidal enhancer compounded by sodium bentonite, nano silicon dioxide and polyanionic cellulose in a mass ratio of (14~16):(1.8~2.2):1 to the slurry storage tank; When the specific gravity value is greater than 1.22 g / cm 3 , enable the plate and frame filter press to dewater 15%~35% volume of superfine mud in the slurry storage tank, and the filtrate is returned to the slurry storage tank; Step four, input the coarse aggregate and medium particles obtained in step one, the fine sand and powder particles obtained in step two, and the pretreated solid cake produced by the plate and frame filter in step three into the vertical mixer, add 2.5%~3.5% of aluminate activator and 4%~6% of silica fume according to the total mass of solid phase, and mix to form a solid mixture; Step five, deliver the solid mixture to the rotary calcination kiln, calcine at a temperature of 620~780℃ for 25~35 min to generate regenerated aggregate.

[0021] In the technical solution, the pile foundation mud is first input into a high-frequency vibrating screen. The upper layer screen mesh aperture of the device can be configured to be 1.8 mm, 2.0 mm or 2.2 mm, and the lower layer screen mesh aperture can be configured to be 0.45 mm, 0.50 mm or 0.55 mm. The vibrating screen can be selected to be a double-motor self-synchronous exciter type, and the screen frame material is 304 stainless steel. The separated primary mud is pressurized by a centrifugal pump, and the pressure can be set to 0.7 MPa, 1.0 MPa or 1.3 MPa. The pump body overflow part can be selected to be a high-chromium alloy material. The pressurized mud is pumped into a three-stage series cyclone separation unit. The first-stage cyclone underflow port traps fine sand with a particle size of 0.18-0.52 mm, the second-stage traps powder particles with a particle size of 0.065-0.22 mm, and the third-stage overflow port outputs ultra-fine mud. The cyclone group can be selected to be a standard hydraulic cyclone module, and the cylinder body material is a polyurethane composite material. The ultra-fine mud enters the mud storage tank, and the online viscosity sensor installed in the tank can be selected to be a Ma funnel electronic timing type, and the specific gravity sensor can be selected to be a nuclear density meter.

[0022] The viscosity sensor monitoring threshold is 16 seconds, 20 seconds or 24 seconds, and the specific gravity sensor threshold is 1.12 g / cm3, 1.18 g / cm3 or 1.22 g / cm3. When the viscosity of the ultra-fine mud is lower than 16 s due to excessive dilution, a colloidal enhancer needs to be added to restore its engineering performance. The sodium-based bentonite in the added colloidal enhancer can be selected to be a drilling grade calcium-based bentonite sodium modified product, nano silicon dioxide can be selected to be a precipitated white carbon black, and a poly anion cellulose can be selected to be an industrial grade carboxymethyl cellulose sodium. The mass ratio of the three can be 14:1.8:1, 15:2:1 or 16:2.2:1. When the specific gravity is greater than 1.22 g / cm3, a plate and frame filter press is enabled to dewater 20%, 25% or 30% of the volume of the ultra-fine mud in the mud storage tank, and the filter plate material of the filter press can be selected to be reinforced polypropylene. The solid cake after pressure filtration is mixed with the coarse aggregate (particle size > 1.8 mm), medium particles (particle size 0.45-2.2 mm) obtained by screening, and fine sand and powder particles obtained by cyclone. The added aluminate activator can be selected to be a CA50 cement clinker grinding product, and the silica powder can be selected to be a metallurgical grade microsilica powder.

[0023] The mixed materials are input into a vertical mixer, which can be selected to be a double-shaft paddle type, and the paddle material is wear-resistant NM400 steel plate. The solid mixture is transported to a rotary calcination kiln, and the calcination temperature can be set to 620°C, 700°C or 780°C, and the time can be 25 minutes, 30 minutes or 35 minutes. The refractory lining of the calcination kiln can be selected to be high alumina castable. The regenerated aggregate generated after this treatment has a particle size distribution comparable to that of natural aggregate, and the mud content is significantly reduced, which can realize the resource utilization of the solid components in the pile foundation mud and reduce the amount of waste discharge.

[0024] The pile foundation mud is separated by grading screening and multi-stage cyclone separation, which significantly improves the interception efficiency of coarse aggregate and medium particles and reduces the loss of fine particle components; the ultra-fine mud is adjusted by real-time viscosity and specific gravity to ensure the stable and reliable performance of the recycled mud; the solid components are adjusted by colloid enhancer or pressure filtration dewatering, mixed with aluminate activator and silica fume, and calcined to generate recycled aggregate with low mud content and reasonable grade, which meets the engineering recycling requirements. This method realizes efficient recovery of useful solid phase in mud, reduces the demand for natural aggregate mining, and reduces the impact of waste discharge on the environment.

[0025] In conventional pile foundation mud treatment, a single layer vibrating screen is usually used for screening, and the screen aperture is fixed at 1.0 mm. After screening, coarse particles with a particle size greater than 1.0 mm are intercepted, and fine particles smaller than 1.0 mm enter the subsequent process with the mud. The coarse particles on the screen are directly used as low-quality aggregate without grading. The mud under the screen is pumped into a single-stage cyclone by a centrifugal pump at a fixed pressure of 0.8 MPa. The mixed sand particles (particle size 0.1-0.5 mm) are output from the underflow port of the cyclone, and the overflow port discharges wastewater containing fine mud. The wastewater after cyclone is input into an open-air sedimentation tank for natural sedimentation, which takes more than 48 hours. The sludge at the bottom of the sedimentation tank is excavated and dried in the open air. When the water content is reduced to 25%-30%, blocky sludge is formed. The sludge is mixed with the aforementioned coarse particles, ordinary Portland cement is added as a binder, and calcination is carried out in a simple sintering furnace at 500-600°C for 40-50 minutes to generate recycled aggregate.

[0026] In the prior art, the use of a single layer vibrating screen with a fixed aperture screen results in the mixing of medium particles with a particle size of 1.0-2.0 mm and coarse aggregate, and the complete loss of fine particles below 0.45 mm; the use of a single-stage cyclone with fixed pumping pressure cannot effectively separate fine sand and powder particles, resulting in a bottom flow product with a mud content exceeding 20%; mud treatment relies on open-air natural sedimentation, and the viscosity and specific gravity fluctuate in the range of 10-30 seconds and 1.05-1.30 g / cm3, respectively, resulting in uncontrollable performance of the recycled mud; the water content is not regulated when mixing solid components, and ordinary Portland cement is directly added for calcination, resulting in recycled aggregate with high mud content and significantly lower crushing value than the engineering standard. These defects collectively result in low recovery rate of useful solid phase, and recycled aggregate cannot meet the engineering recycling requirements, resulting in increased waste discharge.

[0027] In another technical solution, in step two, dynamic pressure regulation is performed between the centrifugal pump and the three-stage series cyclone separation unit; the solid phase concentration of the primary mud is detected in real time by an electromagnetic flowmeter, when the concentration is in the range of 15%-20%, the output pressure of the centrifugal pump is controlled to 1.1-1.3 MPa; when the concentration is in the range of 20%-25%, the output pressure is controlled to 0.9-1.1 MPa; when the concentration is in the range of 25%-35%, the output pressure is controlled to 0.7-0.9 MPa.

[0028] In the technical solution, an electromagnetic flowmeter is installed between the outlet pipeline of the centrifugal pump and the inlet of the three-stage series cyclone separation unit. The flowmeter can be selected from a wear-resistant electrode lining material, and the measuring pipe diameter is consistent with the main pipeline. The electromagnetic flowmeter detects the solid phase concentration of the primary slurry in real time, and the detection signal is transmitted to the PLC control system. The centrifugal pump can be selected from a variable frequency speed regulation type, and the motor power is matched with the pump head pressure range of 1.0-1.5 MPa working condition. The PLC system presets a concentration-pressure matching program: when the solid phase concentration is in the range of 15% to 20%, the centrifugal pump is maintained at an outlet pressure of 1.1 to 1.3 MPa by outputting a control instruction; when the concentration is in the range of 20% to 25%, the pressure is adjusted to 0.9 to 1.1 MPa; and when the concentration is in the range of 25% to 35%, the pressure is adjusted to 0.7 to 0.9 MPa.

[0029] When the primary slurry flows through the electromagnetic flowmeter, the solid phase concentration value is updated every second and input into the PLC system. If the detected concentration value is 18% (belonging to the interval of 15%-20%), the PLC sends an instruction to the centrifugal pump frequency converter to increase the pump speed to the output gear corresponding to 1.2 MPa. If the concentration value changes to 22% (entering the interval of 20%-25%), the PLC controls the frequency converter to reduce the speed at a rate of 0.5 Hz / s, so that the pressure is smoothly transitioned from 1.2 MPa to 1.0 MPa within 15 seconds. When the concentration suddenly increases to 28% (belonging to the interval of 25%-35%), the PLC immediately starts the pressure reduction program to control the pressure to decrease to 0.8 MPa within 20 seconds. The pressure data is fed back to the PLC in real time through the pressure transmitter at the pump outlet, forming a closed-loop control.

[0030] The installation position of the electromagnetic flowmeter is kept more than 5 times the pipe diameter away from the inlet of the cyclone unit to avoid flow field disturbance affecting the measurement accuracy. The centrifugal pump frequency converter can be selected from a vector control type to ensure that the pressure fluctuation range is less than ±0.05 MPa. When the concentration detection is abnormal (such as continuously exceeding 35% or being lower than 15% for 10 seconds), the PLC automatically switches to a safety mode: maintaining the pressure at 0.8 MPa, while triggering an audible and light alarm. A buffer tank is arranged in the inlet pipeline of the cyclone group, with a volume of 2 times the instantaneous flow rate of the pipeline, for absorbing water hammer impact during pressure adjustment.

[0031] The pressure dynamic regulation method effectively avoids the blockage of the underflow port of the cyclone under high concentration conditions and the overflow and coarse particle running under low concentration conditions by real-time matching of the solid phase concentration of the slurry and the pressure requirement of the cyclone separation. The closed-loop control mechanism narrows the pump pressure fluctuation range, ensuring the particle size classification accuracy of the three-stage cyclone separation unit. The self-adaptive pressure regulation reduces the invalid work of the centrifugal pump and reduces the energy consumption of the system. Ultimately, the retention efficiency of fine sand and powder particles is improved, providing stable solid raw materials for subsequent resource utilization.

[0032] In the conventional pile foundation mud slurry cyclone separation process, the centrifugal pump transports the primary mud slurry to the single-stage cyclone at a fixed pressure of 0.9 MPa. Regardless of the change of the solid phase concentration of the mud slurry (the measured concentration range is 15%-35%), the pumping pressure remains unchanged. When the mud slurry concentration rises to 28%, the cyclone underflow port is periodically blocked due to the increase of the fluid viscosity, and manual shutdown and cleaning are required, and each cleaning takes about 15 minutes; when the concentration decreases to 16%, the centrifugal force in the cyclone is insufficient, and the target fine sand with a particle size of 0.1-0.3 mm increases in loss rate from the overflow port. The fixed pressure mode also causes energy waste: the excess pumping pressure under low concentration conditions causes the useless power consumption to exceed 30%, and the insufficient pressure under high concentration conditions requires repeated start and stop of the pump.

[0033] In the existing fixed pressure cyclone separation process, the centrifugal pump transports the mud slurry at a constant pressure of 0.9 MPa, and when the solid phase concentration of the mud slurry fluctuates to 28%, the underflow port of the cyclone is frequently blocked due to the excessively high fluid viscosity, and manual shutdown and cleaning are required and each cleaning takes about 15 minutes; when the concentration decreases to 16%, the cyclone centrifugal force is insufficient, causing a large amount of target fine sand with a particle size of 0.1-0.3 mm to be lost from the overflow port. The fixed pressure mode also causes significant energy waste: the excess pumping pressure under low concentration conditions produces invalid power consumption, and the insufficient pressure under high concentration conditions forces the pump to be repeatedly started and stopped. Ultimately, the fine sand and powder particle mixed product has a high mud content of 18%-22%, and the cyclone separation efficiency fluctuates by more than 25%.

[0034] In another technical solution, during the pressure dynamic regulation process, the centrifugal pump is controlled to gradually change the pressure; When the change of the solid phase concentration is detected to trigger the pressure interval switching, the centrifugal pump output pressure is linearly transitioned to the target pressure interval at a rate of 0.1-0.2 MPa / s; At the same time, during the pressure gradual change stage, the fine sand intercepted by the underflow port of the primary cyclone and the powder particles intercepted by the underflow port of the secondary cyclone are combined and introduced into the temporary buffer bin, and after the pressure is stabilized to the target interval, the materials in the temporary buffer bin are re-input into the three-stage series cyclone separation unit for processing.

[0035] In the technical solution, the centrifugal pump is equipped with a variable frequency speed regulation motor, and the speed thereof is accurately regulated by a PLC system through a PID algorithm. When the electromagnetic flowmeter detects a solid phase concentration change triggering pressure interval switching (for example, the concentration increases from 18% to 23%, crossing the 20% threshold), the PLC controls the centrifugal pump to transition to the target pressure interval at a linear rate of 0.1 MPa / s, 0.15 MPa / s or 0.2 MPa / s. The specific execution process is as follows: if the pressure needs to be reduced from 1.2 MPa to 1.0 MPa (a reduction of 0.2 MPa), the transition is completed in 20 seconds at a rate of 0.1 MPa / s, and in 10 seconds at a rate of 0.2 MPa / s. The pressure transmitter feeds back the actual pressure value to the PLC in real time, and automatically compensates for the adjustment amount when the deviation exceeds ±0.03 MPa.

[0036] During the pressure transition stage, the pneumatic three-way valve at the bottom flow port of the primary cyclone and the bottom flow port of the secondary cyclone is switched synchronously, and the trapped fine sand (particle size 0.18-0.52 mm) and powder particles (particle size 0.065-0.22 mm) are combined and introduced into a temporary buffer bin. The bin can be of a vertical conical bottom structure, with a volume of 2.5 times the single-minute processing capacity of the cyclone unit, and the inner wall is lined with an ultra-high molecular weight polyethylene wear-resistant layer. A radar level gauge is provided in the bin, and an audible and visual warning is triggered when the material accumulation height reaches 60% of the bin capacity. After the pressure stabilizes to the target interval (confirmed by a pressure transmitter with a 10-second continuous fluctuation of <±0.02 MPa), the three-way valve switches back to the original path, and the discharge valve at the bottom of the buffer bin is opened.

[0037] The material in the buffer bin is pumped back to the inlet manifold of the tertiary series cyclone separation unit by a screw pump at an output pressure of 0.25 MPa. Before pumping, a silicon oil-based lubricant is added to the buffer bin, and the amount of addition is 0.08% of the total mass of the material, and the bin is stirred by a double-shaft paddle mixer installed at the top of the bin at a speed of 40 rpm for 90 seconds. A static mixer is provided at the inlet of the cyclone unit to uniformly mix the backflow material with the primary mud. During the reprocessing period, the particle size distribution of the product at the bottom flow port is monitored in real time, and if the proportion of >0.6 mm particles in the fine sand exceeds 5%, the mixing time is automatically extended by 30 seconds.

[0038] The pressure transition control method adjusts the pump pressure transition rate linearly, avoiding flow field turbulence and particle mixing caused by pressure sudden change; the temporary buffer bin mechanism temporarily stores fine sand and powder particles during pressure switching, ensuring material circulation continuity; the silicon oil lubricant and low-speed mixing process significantly reduce the risk of particle breakage during the reprocessing process. Ultimately, the cyclone separation process is smoothly transitioned, the fine component retention integrity is improved, and stable solid raw materials are provided for subsequent resource utilization.

[0039] In the traditional pile foundation slurry cyclone separation process, when the slurry solid phase concentration changes are detected and the output pressure of the centrifugal pump needs to be adjusted, the system will directly and stepwise switch the pressure. For example, if the concentration increases and the pressure needs to be reduced, the pump pressure will instantly drop from a high pressure value (such as 1.2 MPa) to a target low pressure value (such as 0.8 MPa). This sudden pressure change seriously disturbs the stable flow field state inside the cyclone, causing the coarse particles (such as fine sand) and fine particles (such as powder) that have been successfully separated to mix together again, destroying the classification accuracy. At the same time, during the entire unstable period of pressure switching, the material discharged from the underflow port of the cyclone (i.e. the fine sand and powder that needs to be recovered) does not take any caching or isolation measures, but continues to be directly transported to the subsequent processing process. This brings two serious problems: on the one hand, in the cyclone with a large pressure fluctuation, particles (especially brittle minerals such as quartz sand) will hit the wall at high speed under the drive of high pressure difference, causing significant physical breakage, resulting in a significant increase (about 15%) in the content of micropowder with a particle size of less than 0.1 mm; on the other hand, these mixed broken particles directly enter the downstream, and the quality does not meet the requirements. When these materials contaminated or broken by pressure switching need to be reprocessed, the existing technology usually directly uses a high-shear centrifugal pump to pump them back to the cyclone unit inlet. The high-speed rotation (linear speed exceeds 10 m / s) of the centrifugal pump impeller produces strong mechanical shear force, which causes secondary damage to the particles, further aggravating the pulverization phenomenon. The final result is that the proportion of micropowder in the recovered solid material is too high, directly leading to the deterioration of the performance of the recycled aggregate produced by using these materials, and the compressive strength loss can reach 8% to 12%. In addition, the entire pressure step switching and subsequent system recovery process takes a long time (usually 5 to 8 minutes), during which the cyclone separation function is basically lost, and the target powder is lost in large quantities from the overflow port (loss rate exceeds 30%), and a single pressure switching event can cause the overall separation efficiency to decrease by more than 25%. In actual engineering, problems such as equipment blockage, frequent shutdown for cleaning (such as a bottom flow port blockage rate of 40%, cleaning time of about 15 minutes), and final product (recycled aggregate) crushing value exceeding standard (>28%, much higher than the engineering standard of ≤20%) often occur, which seriously affects the processing efficiency and resource utilization effect.

[0040] In another technical solution, the reprocessing process of the material in the temporary buffer bin is controlled to prevent breakage; The material in the temporary buffer bin is pumped back to the three-stage series cyclone separation unit by a screw pump, and the output pressure of the screw pump is controlled to be 0.2-0.3 MPa; Before pumping the material, a silicone-based lubricant is added to the temporary buffer bin, and the amount of addition is 0.05%-0.1% of the total mass of the material; The lubricant and the material are mixed by a double-shaft mixer at a speed of 30-50 r / min for 1-2 min.

[0041] In order to reduce the risk of particle breakage during the reprocessing of the material in the temporary storage bin, the following specific measures are taken. When the material is pumped back to the three-stage series cyclone separation unit from the temporary storage bin, a single screw pump can be used for transportation. The output pressure of the screw pump is set in the lower range of 0.2 MPa to 0.3 MPa, for example 0.25 MPa. This pump type can be installed on the bottom outlet pipe of the temporary storage bin, and its low shear characteristic helps to protect the particle integrity.

[0042] Before the material is pumped, a silicon oil-based lubricant needs to be added to the temporary storage bin. The lubricant can be an industrial-grade low-viscosity silicon oil liquid. The amount added is controlled to be 0.05% to 0.1% of the total mass of the material in the storage bin, for example 0.08%. The inlet for adding the lubricant can be set above the top or sidewall of the temporary storage bin.

[0043] After adding the lubricant, a double-shaft paddle mixer installed inside the temporary storage bin or connected to the bin body is started. The mixer operates at a low speed, with a speed range set between 30 rpm and 50 rpm, for example 40 rpm. The mixing time is controlled between 1 minute and 2 minutes, for example 1.5 minutes. Through this low-speed mixing, the silicon oil lubricant can be more evenly coated on the surface of the material particles, reducing the friction between particles and between particles and equipment.

[0044] When working, after confirming that the pressure has stabilized in the target interval, the operator or automatic system first adds a specified amount of silicon oil-based lubricant to the temporary storage bin. Then the double-shaft mixer is started and runs at a set low speed for a specified time to mix the lubricant with the fine sand and powder particles temporarily stored in the bin. After mixing is complete, the low-pressure screw pump at the outlet of the storage bin is started, its output pressure is adjusted and maintained between 0.2 MPa and 0.3 MPa (such as 0.25 MPa), and the mixed material is smoothly pumped back to the total inlet pipe of the three-stage series cyclone separation unit to participate in the subsequent re-separation process.

[0045] The present technical solution reduces the mechanical stress applied to the particles during the pumping process by using a low-shear screw pump and strictly controlling its low output pressure. The addition of an appropriate amount of silicon oil-based lubricant and the low-speed mixing to form a lubricating layer on the surface of the particles effectively reduces the friction and collision intensity between particles and between particles and the pipe wall during the transportation and recirculation of the material. The low-speed mixing process itself also avoids additional impact or extrusion damage to the material. These measures work together to help maintain the original particle size and integrity of the particles to the greatest extent during the reprocessing of the material, reduce the generation of fine particle level fines, and benefit the performance stability of the subsequent recycled aggregate product.

[0046] In the traditional pile foundation slurry treatment process, when the cyclone separation system needs to be reprocessed due to pressure adjustment, a high-output pressure centrifugal pump is generally used to pump the fine sand and powder particles in the temporary buffer bin back to the cyclone unit. Such centrifugal pumps usually work in a high pressure range, for example, 0.8 MPa to 1.0 MPa. During pumping, the high-speed rotating impeller exerts significant mechanical shear force on the material, which easily causes brittle mineral particles to break. Before the material is discharged from the buffer bin for reprocessing, no lubricant is usually added. The granular material directly enters the pumping system in a dry or slightly wet state, resulting in intense friction and collision between particles and between particles and the inner wall of the pump body and pipeline. In addition, if the material needs to be mixed (even if no lubricant is added), the traditional process often uses a high-speed mixing device, and the rotational speed is often set to more than 100 rpm. This high-speed stirring action further exacerbates the impact and wear between material particles.

[0047] In another technical solution, in step four, the solid cake produced by the plate-and-frame filter press in step three is pretreated: the solid cake is input into a crusher to be crushed to particles with a particle size of 1-3 mm; the crushed particles are input into a perforated drum dryer to be dried using the waste heat flue gas discharged from the rotary calcination kiln in step six, so that the water content is reduced to 16%-18%; and the dried particles are synchronously input into a vertical mixer with the coarse aggregate obtained in step one, the medium particles, and the fine sand and powder particles obtained in step two.

[0048] In the technical solution, when the solid cake is input into the crusher, a double-roller crusher can be selected, the roller surface material can be high-chromium alloy cast iron, and the roller gap adjustment range can be set to 1-3 mm. The crushed particles are transported to the perforated drum dryer, the dryer cylinder can be lined with 304 stainless steel screens with a screen hole diameter of 5 mm. The waste heat flue gas pipeline of the rotary calcination kiln can be configured with a high-temperature-resistant flexible joint, and the interface flange can be selected as a PN16 standard flange. The vertical mixer can be selected as a double-shaft paddle type structure, and the paddle can be made of NM400 wear-resistant steel plate.

[0049] The crusher can be located below the discharge port of the plate-and-frame filter press and connected through a sealed chute, and the inner wall of the chute can be lined with ultra-high molecular weight polyethylene wear-resistant plate. The perforated drum dryer can be installed downstream of the calcination kiln flue gas discharge pipeline, and the inlet end can be equipped with an expansion joint to compensate for thermal displacement. The dryer and the vertical mixer can be connected through a bucket elevator, and the elevator hopper can be made of engineering plastic. The flue gas pipeline insulation layer can be made of aluminum silicate fiber felt with a thickness of 80 mm.

[0050] The solid cake discharged from the plate-and-frame filter press (moisture content about 35-40%) falls into the double-roller crusher through the chute. The operator adjusts the roller gap according to the hardness of the cake: 3 mm for clayey cake and 1 mm for cake with high sand content. The 1-3 mm particles after crushing are fed into the perforated drum dryer through the vibrating feeder. At the same time, the waste heat flue gas (temperature fluctuation range 80-150°C) discharged from the rotary calcining kiln is introduced into the dryer inlet through the pipeline. The dryer operates at a speed of 4-6 rpm, and the residence time of the material is controlled at 15-20 minutes, so that the moisture content is reduced to 16-18%. After drying, the particles are transported to the feed inlet of the vertical mixer through the bucket elevator, and the coarse aggregate, medium particles separated by the high-frequency vibrating screen, and fine sand and powder particles obtained by cyclone separation are simultaneously fed into the mixing process.

[0051] The present technical solution forms uniform particles by crushing the solid cake, avoids clumping during subsequent mixing, uses waste heat flue gas for drying to reduce the moisture content of the material to the target range, improves mixing uniformity, and synchronously inputs various solid components to ensure the consistency of the timing of the material entering the mixer. This pretreatment process creates favorable conditions for the subsequent addition of aluminate activator and silica fume mixing and calcination.

[0052] In the conventional pile foundation mud treatment process, a single-layer vibrating screen is first used for solid-liquid separation, and the screen aperture is fixed at 1.0 mm. After screening, coarse particles with a particle size greater than 1.0 mm are trapped, while fine particles with a particle size less than 1.0 mm pass into the subsequent process with the mud. Due to unclassified treatment, a large amount of medium particles with a particle size of 0.5-1.0 mm are mixed in the coarse particles on the screen, and fine particles with a particle size less than 0.45 mm are completely lost. The mud below the screen is pumped into a single-stage cyclone by a centrifugal pump at a fixed pressure of 0.9 MPa. When the solid phase concentration of the mud fluctuates to 28%, the viscosity is too high, causing the underflow port of the cyclone to frequently block, requiring manual shutdown for cleaning, which takes about 15 minutes each time. When the concentration decreases to 16%, the centrifugal force of the cyclone is insufficient, causing the loss rate of target fine sand with a particle size of 0.1-0.3 mm to increase from the overflow port. The fluctuation range of the cyclone separation efficiency is more than 25%, and the mud content of the underflow product is 22%. The waste water after cyclone separation is input into an open-air sedimentation tank for natural sedimentation for more than 48 hours, and a blocky sludge with a moisture content of 30% is formed at the bottom of the sedimentation tank. This sludge is directly mixed with the coarse particles from the screen, ordinary Portland cement is added as a binder, and calcination is carried out in a simple sintering furnace at 550°C for 45 minutes. The regenerated aggregate has high mud content, a crushing value that is more than 15% lower than that of natural aggregate, and uneven particle size distribution, which cannot meet the engineering grading requirements.

[0053] In another technical solution, the water content of the coarse aggregate obtained in step one and the medium particles, and the fine sand and powder particles obtained in step two are controlled simultaneously in step four: the coarse aggregate, medium particles, fine sand and powder particles are input into a perforated drum dryer, and the waste heat flue gas discharged from the rotary calcining kiln is used for drying to reduce the water content of the materials to 16-18%; the dried materials and the pretreated solid cake are simultaneously input into a vertical mixer.

[0054] In the technical solution, the coarse aggregate, medium particles, fine sand and powder particles can be input into the perforated drum dryer by using a belt conveyor. The drum body of the dryer can be lined with carbon steel and provided with a 304 stainless steel screen plate, the screen hole diameter can be set to 5 mm, and the inclination angle of the drum body can be adjusted to 2-5 degrees. The waste heat flue gas pipeline of the rotary calcining kiln can be connected to the air inlet cover of the dryer through an expansion joint, and the outer wall of the pipeline can be wrapped with an 80 mm thick aluminum silicate fiber insulation layer. The discharge port of the dryer can be connected to a bucket elevator through a sealed chute, the elevator can be of a ring chain structure, and the hopper material can be nylon 66. The finally dried materials and the pretreated solid cake can be simultaneously input into a double-shaft paddle vertical mixer.

[0055] The coarse aggregate and medium particles separated by the high-frequency vibrating screen fall into the belt conveyor through a vibrating feeder, and the fine sand and powder particles intercepted by the three-stage cyclone separation unit are collected into the same conveyor belt through a closed screw conveyor. The mixture is continuously input into the feeding end of the perforated drum dryer at a flow rate of 1.5-2 tons / hour. The waste heat flue gas discharged from the rotary calcining kiln is introduced into the dryer through a main flue branch, and the flue gas inlet temperature is monitored in real time by a thermocouple. The dryer operates at a speed of 4-6 revolutions per minute, and the material is repeatedly thrown up by the lifting plates arranged on the inner wall of the drum body, so that the flue gas penetrates the material layer. After the dried materials are screened by the discharge end grid to remove impurities, they are conveyed to the vertical mixer by the bucket elevator and are simultaneously input into the mixing process with the solid cake dried by crushing.

[0056] The temperature of the waste heat flue gas entering the dryer is controlled in the range of 85-95°C, and the residence time of the materials in the dryer is set to 18-22 minutes. Every 30 minutes, a sample is taken from the discharge port of the dryer for detection: 200 g of the sample is placed in a 105°C oven and dried to constant weight, and the water content is calculated. When the detection value is higher than 18%, the residence time is automatically extended to 25 minutes; when the detection value is lower than 16%, the residence time is shortened to 15 minutes. The dried materials are stored in a moisture-proof bin, the humidity in the bin is maintained below 45%, and the water content is stabilized in the range of 16-18% when input into the mixer. By adjusting the speed of the dryer or the partition temperature control, materials with different initial water contents D can be simultaneously controlled to reach the target value of 16-18%.

[0057] The technical scheme realizes the synergistic regulation of the moisture content of multi-component materials through waste heat flue gas drying, avoids uneven mixing caused by moisture differences, prevents moisture absorption of dried materials through a closed conveying system, and ensures stable moisture content through constant temperature control and residence time adjustment. It provides a basic condition for the uniform mixing of subsequent solid-phase mixture and activator.

[0058] In the conventional pile foundation mud resource utilization process, the coarse aggregate separated by high-frequency vibrating screen and the medium particles are stored outdoors, and the moisture content fluctuates by 8%-30% due to weather. The fine sand and powder particles separated by cyclone separation are treated by natural air drying, which takes 48 hours in summer and more than 72 hours in winter to reduce the moisture content to below 20%. The solid cake produced by plate and frame filter pressing is directly crushed into block-shaped materials with a particle size of 5-10 mm without drying treatment. When the above components are put into a double-shaft mixer by a forklift, the moisture content is significantly different (8% for coarse aggregate, 22% for fine sand, and 35% for solid cake), and the added aluminate activator and silica ash are easily adsorbed on the surface of the high-moisture material to form clumps. The mixing process needs to be extended to more than 15 minutes, and 10%-15% of the activator is still not uniformly dispersed. When the mixed material is input into the rotary kiln for calcination, the uneven moisture content causes local overheating or underfiring: the high-moisture area needs to absorb more heat, extending the calcination time to 40 minutes; the low-moisture area has already sintered at 620℃. In the generated recycled aggregate, 5%-8% of the particles have insufficient strength due to underfiring, and the crushing value is 12%-18% lower than that of natural aggregate.

[0059] In another technical scheme, dynamic temperature compensation is performed on the waste heat flue gas input into the perforated drum dryer, including the following steps: a high-temperature buffer tank and a low-temperature buffer tank are connected in parallel at the outlet of the calcination kiln, the volume ratio of the two is 1:2~1:3, and the output pipelines of the high-temperature buffer tank and the low-temperature buffer tank finally converge into the same main pipeline, which is connected with the bag-type dust collector and the perforated drum dryer; the flue gas temperature T at the outlet of the calcination kiln is monitored in real time by a thermocouple: When T>110℃, the high-temperature flue gas treatment path is executed, the flue gas is introduced into the high-temperature buffer tank for temporary storage for 5~8 min, and then mixed with 20~30℃ ambient air in the outlet pipeline of the high-temperature buffer tank at a flue gas:ambient air volume ratio of (75~85):(15~25); When T<80℃, the low-temperature flue gas treatment path is executed, the flue gas is introduced into the low-temperature buffer tank for temporary storage for 3~5 min, and then mixed with the >110℃ high-temperature flue gas output from the high-temperature buffer tank in the outlet pipeline of the low-temperature buffer tank at a flue gas:high-temperature flue gas volume ratio of (85~90):(10~15); When 80℃≤T≤110℃, the direct conveying path is executed, and the flue gas is directly conveyed to the bag-type dust collector; The mixed flue gas is input into a bag filter, the filter bag material of the bag filter is PTFE coated glass fiber, the filtering precision is 1 μm, and a 0.5-1 mm isolation layer is formed on the surface of the filter bag by pre-coating the regenerated mud of step three; and a clean gas stream with a temperature of 85-95℃ is output after dust removal.

[0060] In the technical solution, a K type armored thermocouple (temperature measurement range 0-400℃) is installed at the outlet of the calcination kiln flue gas, and the flue gas temperature T is monitored in real time. The flue gas main pipeline is divided into three paths: the first path is connected to a high-temperature buffer tank through a DN200 pipeline, the tank can be selected as a vertical carbon steel storage tank (volume 15 m 3 ), lined with 310S stainless steel, and covered with an 80 mm aluminum silicate insulation layer; the second path is connected to a low-temperature buffer tank through a DN250 pipeline, which can be selected as a horizontal carbon steel storage tank (volume 30 m 3 ), lined with 304 stainless steel; and the third path is a straight pipeline (DN300). The output pipelines of the high-temperature buffer tank and the low-temperature buffer tank are merged into a DN350 main pipeline, which is connected to the inlet of a perforated drum dryer through a bag filter (filter bag material is PTFE coated glass fiber, filtering precision is 1 μm). A static mixer is installed on the outlet pipeline of the high-temperature buffer tank, an environmental air pipeline (DN100) is connected to the upstream of the mixer through a centrifugal fan, and a pneumatic regulating valve is arranged at the mixing node. A three-way mixer is installed on the outlet pipeline of the low-temperature buffer tank, and a high-temperature buffer tank output pipeline (DN150) is connected thereto through a branch, and a pneumatic butterfly valve is arranged at the branch node.

[0061] When the thermocouple detects T>110℃ (such as 120℃), the pneumatic three-way valve is switched to the high-temperature path: the flue gas is introduced into the high-temperature buffer tank for temporary storage for 6 minutes, and then mixed with 25℃ environmental air at a volume ratio of 80:20 in the outlet static mixer. When T<80℃ (such as 70℃), the low-temperature path is switched: the flue gas is introduced into the low-temperature buffer tank for temporary storage for 4 minutes, and then mixed with 115℃ flue gas output from the high-temperature buffer tank at a volume ratio of 88:12 in the outlet three-way mixer. When T is between 80-110℃ (such as 95℃), the flue gas is directly connected to the bag filter. Before the mixed flue gas enters the bag filter, the regenerated mud (specific gravity 1.18 g / cm 3 ) of step three is circulated and sprayed on the surface of the filter bag to form a 0.8 mm isolation layer; and a 90℃ clean gas stream is output after dust removal to the dryer.

[0062] Pt100 temperature sensor is installed in the clean chamber of the bag-type dust collector, and the target temperature is set to 90°C (with an allowable deviation of ±5°C). If the monitored temperature reaches 97°C (>95°C), the opening of the PLC-controlled ambient air regulating valve is increased by 5% (2.5 vol% per 1°C), and the opening of the high-temperature buffer tank main output valve is reduced by 10%. If the temperature drops to 83°C (<85°C), the opening of the high-temperature flue gas branch regulating valve is increased by 7% (1.8 vol% per 1°C), and the opening of the low-temperature flue gas output valve is increased by 8%. Temperature data is collected every 30 seconds; if the temperature is ≤85°C or ≥95°C (such as 84°C, 83°C, and 82°C) for three consecutive times, an audible and light alarm is triggered, and a natural gas backup burner is started to supplement heat.

[0063] The technical solution stabilizes the fluctuating flue gas (70-150°C) to a dry heat source of 85-95°C through double-buffer tank staging and mixing ratio adjustment; the filter bag pre-coated regeneration mud isolation layer effectively intercepts fine dust, reducing filter bag plugging; automatic valve linkage responds to temperature fluctuations, ensuring continuous operation of the drying process. Ultimately, it improves the utilization rate of waste heat, reduces drying energy consumption, and prolongs the service life of the filter bag.

[0064] In the traditional pile foundation mud resource utilization process, the waste heat flue gas discharged from the calcination kiln is directly introduced into the perforated drum dryer to dry solid materials. Due to the fluctuation of the calcination kiln working condition (such as changes in the amount of material added, differences in fuel heat value), the outlet temperature of the flue gas fluctuates sharply, and the actual measured temperature range can reach 80-150°C. When high-temperature flue gas (>110°C) directly enters the dryer, the material in the cylinder is locally overheated and forms a hard crust on the surface, and the internal moisture cannot be effectively evaporated, resulting in uneven moisture content distribution in the dried material (part of the area <10%, part of the area >25%); at the same time, high-temperature flue gas accelerates the deformation and cracking of the dryer screen, increasing the maintenance frequency. When low-temperature flue gas (<80°C) is input, the drying efficiency drops sharply, and the moisture content of the material cannot be reduced to below 20%, forcing the use of electric heaters to assist in temperature rise, increasing energy consumption by more than 30%.

[0065] The dust (mainly containing alumina powder) in the flue gas directly enters the dryer without pretreatment, forming an ash covering layer (accounting for 3%-5%) on the surface of the material, which deteriorates the purity of the recycled aggregate. To alleviate temperature fluctuations, some projects use simple buffer tanks to temporarily store flue gas, but the single-tank structure cannot be adjusted and controlled in stages: during high-temperature periods, only cold air can be mixed manually to cool down, and operators need to continuously observe the thermometer and manually adjust the valve, with a response lag of more than 5 minutes; during low-temperature periods, an external burner is needed to supplement heat, and during the heating process, local overheating (>200℃) occurs due to uneven mixing of flue gas and flame, burning ordinary fiberglass filter bags in the downstream bag-type dust collector (replaced 12 times per year on average). The dust collector does not have a pre-coating layer, and fine dust (particle size <5μm) penetrates the filter bag into the drying system, polluting the material and causing the filter bag to harden and fail, with abnormal fluctuations in system negative pressure up to ±500Pa. The final drying heat source temperature is out of control (60℃-130℃), resulting in recycled aggregate with excessive moisture content (>20%) and high impurity content, increased energy consumption in the calcination process, and a product qualification rate of less than 70%.

[0066] In another technical solution, a temperature sensor is installed in the clean gas chamber of the bag-type dust collector to monitor the mixed flue gas temperature in real time, and the target temperature range is set to 85℃~95℃; When the monitored temperature is higher than 95℃, the proportion of ambient air is automatically increased by 2~3 vol% for every 1℃ over, and the flue gas output of the high-temperature buffer tank is reduced; When the monitored temperature is lower than 85℃, the proportion of high-temperature flue gas is automatically increased by 1.5~2 vol% for every 1℃ decrease, and the flue gas output of the low-temperature buffer tank is reduced; Temperature data is collected every 30 seconds, and if the temperature deviates from the target value by more than 5℃ for three consecutive times, an alarm is triggered and a backup burner is activated to supplement heat.

[0067] In this technical solution, the real-time temperature monitoring device installed in the clean gas chamber of the bag-type dust collector can be a Pt100 thermistor temperature sensor, which is assembled in the middle section of the airflow channel at the center position of the clean gas chamber, avoiding the pipe wall disturbance area. The alarm device can be an audible and visual alarm installed on the central control cabinet panel; the backup heat source compensation device can be a natural gas burner assembled in the bypass of the bag-type dust collector inlet main pipeline, connected to the main pipeline through a flange. The data acquisition module is integrated into the PLC control system, with a sampling period of 30 seconds per time, and the control signal transmission uses a 4-20mA current loop.

[0068] The temperature sensor sets the target range to 85-95℃, and the monitoring data is updated every 30 seconds. When the detected temperature is higher than 95℃ (e.g. 97℃), the system automatically adjusts the ambient air mixing ratio: increase 2.5 vol% of ambient air for every 1℃ over (e.g. 5 vol% for every 2℃ over), and simultaneously reduce the high-temperature buffer tank main output regulating valve opening by 10%. When the detected temperature is lower than 85℃ (e.g. 83℃), increase 1.75 vol% of high-temperature flue gas for every 1℃ under (e.g. 3.5 vol% for every 2℃ under), and simultaneously reduce the low-temperature buffer tank output regulating valve opening by 8%. If the detected temperature deviates from the target value by more than 3 times in a row (e.g. 100℃, 101℃, 102℃ or 80℃, 79℃, 78℃), trigger the audible-light alarm, and start the backup natural gas burner, with the burner output set to increase by 5% of the rated power for every 1℃ deviation.

[0069] Through real-time temperature monitoring and dynamic proportional adjustment, the flue gas temperature is maintained within the set range, ensuring the stability of the drying heat source; the alarm mechanism and backup heat source respond to avoid drying interruption caused by abnormal temperature; closed-loop control reduces the need for manual intervention, ensuring the reliability of continuous system operation.

[0070] In the existing pile foundation slurry resource utilization process, the waste heat flue gas discharged from the calcination kiln is directly introduced into the perforated drum dryer to dry the solid materials. Due to the fluctuation of the calcination kiln feed quantity and the difference in fuel heat value, the flue gas temperature varies greatly, and the actual measured outlet temperature range can reach 80-150℃. When the high-temperature flue gas exceeds 110℃ and directly enters the dryer, the material surface rapidly hardens and forms a crust due to local overheating, and the internal moisture cannot be effectively evaporated, resulting in a serious uneven distribution of moisture content in the dried material, with some areas below 10% and some areas above 25%. At the same time, high temperature accelerates the thermal deformation and cracking of the dryer screen, significantly increasing the frequency of equipment maintenance. When the low-temperature flue gas is below 80℃, the drying efficiency drops sharply, and the moisture content of the material cannot be reduced below 20%, forcing the use of electric heaters to assist in temperature rise, increasing the additional energy consumption cost by more than 30%. The alumina powder and other dust carried in the flue gas directly contact the material without pretreatment, forming a 3-5% ash coating layer on the particle surface, which deteriorates the purity of the recycled aggregate.

[0071] To alleviate temperature fluctuations, some projects use simple single-tank buffer structure to temporarily store flue gas, but there are fundamental flaws: during high temperature period, only rely on operator manual observation of thermometer and manual adjustment of cold air valve, response lag more than 5 minutes, during which high temperature flue gas has caused material crust; low temperature period needs to connect external burner to supplement heat, but due to uneven mixing of flue gas and flame, local area over temperature to above 200℃, frequently burning ordinary glass fiber filter bag of downstream bag type dust collector, average replacement frequency is 12 times per year. The dust removal system does not set the pre-coating process, and the fine dust with particle size less than 5 microns penetrates the filter bag into the dryer, which not only pollutes the material but also causes the filter bag to be solidified and fail, and the system negative pressure abnormally fluctuates ±500 Pa. The whole drying process lacks real-time temperature feedback and automatic compensation mechanism, and the operator can only estimate the adjustment amount by experience, and cannot accurately match the dynamic demand. The final drying heat source temperature is out of control in the range of 60℃ to 130℃, the moisture content of the regenerated aggregate exceeds 20%, the impurity content increases, the calcination process energy consumption increases, and the product qualified rate is less than 70%.

[0072] In another technical solution, a pneumatic regulating valve system is used to perform mixed proportion adjustment, and the control valve opening degree change rate is in the range of 0.5% / s~1% / s; wherein the pneumatic regulating valve system includes four independent valves: ambient air regulating valve, provided at the node where the ambient air pipeline accesses the high-temperature path mixer; high-temperature flue gas branch regulating valve, provided in the branch pipeline from the high-temperature buffer tank to the low-temperature path mixer; low-temperature flue gas output regulating valve, provided in the output pipeline of the low-temperature buffer tank; high-temperature buffer tank main output regulating valve, provided upstream of the convergence point of the high-temperature buffer tank main output pipeline; When the monitored temperature >95℃: if the system is executing high-temperature path processing, increase the ambient air regulating valve opening degree; if the system is executing low-temperature path processing, decrease the high-temperature flue gas branch regulating valve opening degree; simultaneously decrease the high-temperature buffer tank main output regulating valve opening degree; When the monitored temperature <85℃: if the system is executing low-temperature path processing, increase the high-temperature flue gas branch regulating valve opening degree; increase the low-temperature flue gas output regulating valve opening degree; simultaneously increase the high-temperature buffer tank main output regulating valve opening degree.

[0073] In the technical solution, the ambient air regulating valve in the pneumatic regulating valve system can be a butterfly valve structure, assembled at the flange interface of the ambient air pipeline accessing the high-temperature path static mixer. The high-temperature flue gas branch regulating valve can be a ball valve structure, installed in the middle section of the branch pipeline from the high-temperature buffer tank to the low-temperature path three-way mixer. The low-temperature flue gas output regulating valve can be a plug valve, located at the outlet pipeline of the low-temperature buffer tank 1.5 meters away from the tank body. The high-temperature buffer tank main output regulating valve can be a gate valve, assembled in the straight pipe section before the main output pipeline of the high-temperature buffer tank merges into the main pipeline, 2 meters upstream of the merging point. The valve actuator can be a cylinder-driven type, with a gas source pressure set to 0.6 MPa.

[0074] The valve body material can be 304 stainless steel, and the sealing material can be graphite-filled polytetrafluoroethylene. The valve position opening degree change rate is controlled by PLC programming and set to 0.75% / s (within the range of 0.5-1% / s). The temperature sensor can be a Pt100 platinum resistor, installed at the central axis position of the bag-type dust collector clean gas chamber, with a temperature measurement response time of less than 3 seconds. When the monitored temperature is higher than 95°C (such as 97°C), the PLC calculates the opening degree increment by increasing the ambient air proportion by 2.5% for every 1°C exceeded; when the monitored temperature is lower than 85°C (such as 83°C), the opening degree increment is calculated by increasing the high-temperature flue gas proportion by 1.8% for every 1°C decreased.

[0075] When the bag-type dust collector clean gas chamber temperature sensor detects 97°C (target range 85-95°C) during operation, the PLC determines the current system running path: if it is in the high-temperature path processing state (i.e. the flue gas is mixed with ambient air through the high-temperature buffer tank), the ambient air regulating valve opening degree is increased by 5%, and the high-temperature buffer tank main output regulating valve opening degree is simultaneously reduced by 8%; if it is in the low-temperature path processing state (i.e. the flue gas is mixed with high-temperature flue gas through the low-temperature buffer tank), the high-temperature flue gas branch regulating valve opening degree is reduced by 6%. The valve opening degree is linearly adjusted at a rate of 0.75% / s, and the action is completed within 20 seconds. After adjustment, the flue gas temperature drops to 93°C, re-entering the target range. This system responds to temperature fluctuations through multi-valve linkage, maintains the stability of dry heat source temperature, avoids the decrease of drying efficiency caused by over-temperature leading to material crust or low temperature, and ensures the uniformity of recycled aggregate moisture content.

[0076] In the traditional pile foundation slurry resource utilization process, the waste heat flue gas discharged from the calcination kiln is directly introduced into the perforated drum dryer to dry the solid materials. Due to the fluctuation of the feeding amount of the calcination kiln and the difference in fuel heat value, the temperature of the flue gas changes dramatically, and the actual measured outlet temperature ranges from 80 to 150 DEG C. When the high-temperature flue gas exceeds 110 DEG C and directly enters the dryer, the surface of the material rapidly hardens and forms a crust due to local overheating, and the internal moisture cannot be effectively evaporated, resulting in a serious uneven distribution of the moisture content of the dried material, with some areas below 10% and some areas above 25%. At the same time, high temperature accelerates the thermal deformation and cracking of the dryer screen, and the frequency of equipment maintenance increases significantly. When the low-temperature flue gas is below 80 DEG C, the drying efficiency drops sharply, and the moisture content of the material cannot be reduced below 20%, so an electric heater is forced to be used to assist in temperature rise, and the additional energy consumption cost increases by more than 30%. The alumina powder and other dust carried in the flue gas directly contact the material without pretreatment, forming a 3 to 5% ash coating layer on the surface of the particles, which deteriorates the purity of the recycled aggregate. To alleviate the temperature fluctuations, some projects use simple single-tank buffer structures to temporarily store the flue gas, but there are fundamental defects: during the high-temperature period, only the operator manually observes the thermometer and adjusts the cold air valve, with a response lag of more than 5 minutes, during which the high-temperature flue gas has caused the material to crust; during the low-temperature period, an external burner is needed to supplement the heat, but due to uneven mixing of the flue gas and the flame, the local area overheats to more than 200 DEG C, frequently burning out the ordinary glass fiber filter bags of the downstream bag-type dust collector, with an average replacement frequency of 12 times per year. The dust collection system does not have a pre-coating process, and fine dust with a particle size of less than 5 microns penetrates the filter bag into the dryer, polluting the material and causing the filter bag to harden and fail, with an abnormal negative pressure fluctuation of ± 500 Pa. The entire drying process lacks real-time temperature feedback and automatic compensation mechanism, and the operator can only estimate the adjustment amount by experience, and cannot accurately match the dynamic demand. The final drying heat source temperature is out of control in the range of 60 to 130 DEG C, the moisture content of the recycled aggregate exceeds 20%, the impurity content increases, the calcination process energy consumption increases, and the product qualification rate is less than 70%.

[0077] Although the embodiments of the present application have been disclosed as above, they are not limited to the application listed in the specification and the embodiments, and can be fully applied to various fields suitable for the present application, and additional modifications can be easily realized by those skilled in the art, and therefore the present application is not limited to the specific details and the embodiments shown and described herein, without departing from the general concept defined by the claims and the equivalent scope.

Claims

1. A method for screening and recycling pile foundation mud, characterized in that, Includes the following steps: Step 1: Input the pile foundation mud into a high-frequency vibrating screen equipped with an upper 1.8~2.2 mm aperture screen and a lower 0.45~0.55 mm aperture screen to separate coarse aggregate with a particle size greater than 1.8 mm, medium particles with a particle size of 0.45~2.2 mm, and primary mud that passes through the lower screen. Step 2: The primary slurry is pressurized to 0.7~1.3 MPa by a centrifugal pump and then pumped into a three-stage series hydrocyclone separation unit; wherein, the underflow port of the first-stage hydrocyclone retains fine sand with a particle size of 0.18~0.52 mm, the underflow port of the second-stage hydrocyclone retains powder particles with a particle size of 0.065~0.22 mm, and the overflow port of the third-stage hydrocyclone outputs ultrafine slurry; Step 3: Input the ultrafine slurry into the storage tank and monitor it in real time using online viscosity sensors and online specific gravity sensors. When the viscosity of the Martens funnel is in the range of 16~24 s and the specific gravity is in the range of 1.12~1.22 g / cm³ 3 When within the specified range, output regenerated mud; When the viscosity value is less than 16 s, add a colloidal reinforcing agent composed of sodium bentonite, nano silica and polyanionic cellulose in a mass ratio of (14~16):(1.8~2.2):1 to the slurry storage tank; When the specific gravity is greater than 1.22 g / cm³ 3 At that time, the plate and frame filter press is used to dewater 15% to 35% of the volume of ultrafine slurry in the storage tank, and the filtrate is returned to the storage tank. Step 4: Input the coarse aggregate and medium particles obtained in Step 1, the fine sand and powder obtained in Step 2, and the pretreated solid cake produced by the plate and frame filter press in Step 3 into a vertical mixer. Add 2.5%~3.5% aluminate activator and 4%~6% silica fume according to the total mass of solid phase, and mix to form a solid mixture. Step 5: The solid mixture is transported to a rotary kiln and calcined at 620~780℃ for 25~35 minutes to generate recycled aggregate.

2. The method for screening and recycling pile foundation mud as described in claim 1, characterized in that, In step two, dynamic pressure control is performed between the centrifugal pump and the three-stage series cyclone separator. The solid concentration of the primary slurry is detected in real time by an electromagnetic flowmeter. When the concentration is in the range of 15% to 20%, the output pressure of the centrifugal pump is controlled to 1.1 to 1.3 MPa; when the concentration is in the range of 20% to 25%, the output pressure is controlled to 0.9 to 1.1 MPa; and when the concentration is in the range of 25% to 35%, the output pressure is controlled to 0.7 to 0.9 MPa.

3. The method for screening and recycling pile foundation mud as described in claim 2, characterized in that, During the dynamic pressure regulation process, gradual pressure control is implemented on the centrifugal pump; When a change in solid concentration is detected that triggers a pressure range switching, the centrifugal pump output pressure is controlled to linearly transition to the target pressure range at a rate of 0.1~0.2 MPa / s. Meanwhile, during the pressure gradual change phase, the fine sand retained at the underflow port of the first-stage hydrocyclone and the powder retained at the underflow port of the second-stage hydrocyclone are combined and introduced into a temporary buffer bin. After the pressure stabilizes to the target range, the material in the temporary buffer bin is re-input into the three-stage series hydrocyclone separation unit for processing.

4. The method for screening and recycling pile foundation mud as described in claim 3, characterized in that, The reprocessing of materials in the temporary buffer warehouse is subject to anti-breakage control. The material in the temporary buffer bin is pumped back to the three-stage series cyclone separator unit by a screw pump, and the output pressure of the screw pump is controlled at 0.2~0.3 MPa; Before material pumping, add silicone oil-based lubricant to the temporary buffer bin at a rate of 0.05% to 0.1% of the total material mass. The lubricant and materials are mixed for 1 to 2 minutes using a twin-shaft mixer at a speed of 30 to 50 r / min.

5. The method for screening and recycling pile foundation mud as described in claim 1, characterized in that, In step four, the solid cake produced by plate and frame filter press in step three is pretreated: the solid cake is fed into a crusher and crushed into particles with a diameter of 1-3 mm; the crushed particles are fed into a perforated drum dryer and dried using the waste heat flue gas discharged from the rotary kiln in step five, so that the moisture content is reduced to 16%-18%; the dried particles, coarse aggregate and medium particles obtained in step one, and fine sand and powder obtained in step two are simultaneously fed into a vertical mixer.

6. The method for screening and recycling pile foundation mud as described in claim 5, characterized in that, In step four, the moisture content of the coarse aggregate and medium particles obtained in step one, and the fine sand and powder obtained in step two are simultaneously controlled: the coarse aggregate, medium particles, fine sand and powder are fed into a perforated drum dryer and dried using the waste heat flue gas discharged from the rotary kiln in step five, so that the moisture content of the material is reduced to 16%~18%; the dried material and the pretreated solid cake are simultaneously fed into a vertical mixer.

7. The method for screening and recycling pile foundation mud as described in claim 6, characterized in that, Dynamic temperature compensation is applied to the waste heat flue gas input to the perforated drum dryer, including the following steps: A high-temperature buffer tank and a low-temperature buffer tank are connected in parallel at the flue gas outlet of the calcining kiln, with a volume ratio of 1:2 to 1:

3. The output pipes of the high-temperature buffer tank and the low-temperature buffer tank eventually merge into the same main pipe, which is then connected to the perforated drum dryer via a bag filter. The flue gas temperature T at the flue gas outlet of the calcining kiln is monitored in real time using thermocouples. When T > 110℃, the high-temperature flue gas treatment path is executed, and the flue gas is introduced into the high-temperature buffer tank for temporary storage for 5~8 min, and then mixed with ambient air at 20~30℃ in its outlet pipe at a volume ratio of flue gas:ambient air = (75~85):(15~25). When T < 80℃, the low-temperature flue gas treatment path is executed, and the flue gas is introduced into the low-temperature buffer tank for temporary storage for 3~5 min, and then mixed with the high-temperature flue gas output from the high-temperature buffer tank at >110℃ in its outlet pipe at a volume ratio of flue gas: high-temperature flue gas = (85~90):(10~15). When 80℃≤T≤110℃, the direct conveying path is implemented to directly convey the flue gas to the bag filter. After mixing, the flue gas is fed into a bag filter. The filter bag is made of PTFE-coated glass fiber with a filtration accuracy of 1 μm. The regenerated slurry from step three is pre-coated on the surface of the filter bag to form a 0.5~1 mm isolation layer. After dust removal, a clean airflow with a temperature of 85~95℃ is output.

8. The method for screening and recycling pile foundation mud as described in claim 7, characterized in that, The clean air chamber of the bag filter is equipped with a temperature sensor to monitor the temperature of the mixed flue gas in real time, and the target temperature range is set to 85℃~95℃. When the monitored temperature is higher than 95℃, the mixing ratio of ambient air is automatically increased by 2~3 vol% for every 1℃ increase, while the flue gas output of the high temperature buffer tank is reduced. When the monitored temperature is below 85℃, the mixing ratio of high-temperature flue gas is automatically increased. For every 1℃ decrease, the proportion of high-temperature flue gas increases by 1.5~2 vol%, while the flue gas output of the low-temperature buffer tank is reduced. Temperature data is collected every 30 seconds. If the temperature deviates from the target value by more than 5°C for three consecutive times, an alarm is triggered and the backup burner is activated to supplement the heat.

9. The method for screening and recycling pile foundation mud as described in claim 8, characterized in that, A pneumatic control valve system is used to perform mixed proportional regulation, controlling the valve opening change rate within the range of 0.5% / s to 1% / s; the pneumatic control valve system includes four sets of independent valves: An ambient air conditioning valve is located at the node where the ambient air duct connects to the high-temperature path mixer. High-temperature flue gas branch regulating valve is installed in the branch pipeline from the high-temperature buffer tank to the low-temperature path mixer; A low-temperature flue gas output regulating valve is installed on the output pipeline of the low-temperature buffer tank; The main output regulating valve of the high-temperature buffer tank is located upstream of the junction of the main output pipeline of the high-temperature buffer tank. When the monitored temperature is >95℃: if the system is performing high-temperature path processing, increase the opening of the ambient air regulating valve; if the system is performing low-temperature path processing, decrease the opening of the high-temperature flue gas branch regulating valve; simultaneously decrease the opening of the high-temperature buffer tank main output regulating valve. When the monitored temperature is <85℃: if the system is performing low-temperature path processing, increase the opening of the high-temperature flue gas branch regulating valve; increase the opening of the low-temperature flue gas output regulating valve; and simultaneously increase the opening of the high-temperature buffer tank main output regulating valve.