A continuous sludge thermal hydrolysis reactor and a method for detecting sludge residence time thereof

Abstract

The application discloses a continuous sludge thermal hydrolysis reactor and a detection method of sludge residence time thereof, and the reactor comprises an outer heating jacket and an inner tank body, a sludge feeding port is arranged at the bottom of the tank body, a sludge discharging port is arranged at the upper portion of the tank body, and an inspection opening is formed in the middle portion of the tank body; a stirring paddle is arranged in the tank body and rotates by being controlled by a stirring motor at the top end of the tank body, three groups of fan blades are arranged on the stirring paddle, two groups of flow guide plates are arranged on the inner wall of the tank body, and the tank body is divided into three areas, i.e., upper, middle and lower areas, by the flow guide plates. Through the cooperation of the stirring paddle and the flow guide plates, the residence time of sludge in the reactor can be effectively ensured to be in the optimal range in the continuously-operated sludge thermal hydrolysis treatment system, and the sludge hydrolysis efficiency of the whole system is improved.

Description

Technical Field

[0001] This invention relates to a continuous sludge thermal hydrolysis reactor and a method for detecting sludge retention time, belonging to the field of sludge treatment and disposal technology. Background Technology

[0002] Sludge is a complex organic mixture containing a large amount of macromolecular proteins, carbohydrates, and lipids, as well as numerous microorganisms and pathogens. If sludge is not treated to render it harmless, it poses a significant threat to the environment. Hot water hydrolysis technology is a highly efficient hydrothermal treatment method that significantly improves the dewatering and anaerobic digestibility of sludge. It can maximize the resource utilization of sludge, effectively reduce the amount of sludge generated by municipal wastewater treatment plants, and alleviate the pressure on end-of-pipe sludge treatment.

[0003] The operation modes of sludge hydrolysis units are mainly divided into batch and continuous types. In existing continuous operation technologies, the hydrolysis reactor is limited by the tank structure design. Sludge is fed from the top of the tank. Since sludge has a higher specific gravity than water, it is difficult to ensure that the sludge in the tank has sufficient residence time to complete the hydrothermal reaction under the influence of gravity. Moreover, large sludge particles tend to settle at the bottom of the tank after entering the hydrolysis tank. If the mixing is uneven, dead zones of sludge with incomplete hydrolysis can easily appear in the hydrolysis reactor, resulting in a decrease in the overall sludge hydrolysis efficiency of the system. Summary of the Invention

[0004] Objective of the Invention: One objective of this invention is to provide a continuous sludge thermal hydrolysis reactor. Another objective of this invention is to provide a method for detecting sludge residence time using this continuous sludge thermal hydrolysis reactor.

[0005] Technical solution: The present invention provides a continuous sludge hot water hydrolysis reactor, including a tank body, a guide plate on the inner wall of the tank body, the guide plate having a structure that is narrow at the top and wide at the base, the upper and lower ends of the base of the guide plate having a certain curvature, the top of the guide plate having a conical structure with a hole at the top of the conical structure, and a stirring paddle extending vertically inward through the guide plate from the top of the tank body.

[0006] Furthermore, the upper end of the root of the guide plate has an arc r1 of 25-30°, and the arc length is 40-50% of the straight-line distance from the upper cross-section endpoint of the guide plate to the tank body; the lower end of the root of the guide plate has an arc r2 of 20-25°, and the arc length is 40-50% of the straight-line distance from the lower cross-section endpoint of the guide plate to the tank body. There are two or more sets of guide plates, the angle between the lower cross-section of the front end of the guide plate and the horizontal plane is 25-30°, and the radius of the hole is 20-30% of the radius of the reactor tank body. The tank body is equipped with a heating device, which is an outer heat conduction heating jacket fitted on the tank body. The upper end of the stirring paddle passes through the top of the tank body and is equipped with a stirring motor, and the stirring paddle is controlled by the stirring motor to rotate. The stirring paddle is equipped with multiple sets of fan blades. The bottom of the tank body is equipped with a sludge inlet, the upper part of the tank body is equipped with a sludge outlet, and the middle of the tank body is equipped with an inspection port. Both the sludge inlet and outlet are equipped with check valves. A pressure gauge and pressure sensor interface are located on the upper part of the tank, through which a pressure sensor and a pressure gauge are connected respectively. The angle β between the upper and lower ends of the guide plate near the orifice is 40-45°. The distance L between the outer diameter of the agitator and the guide plate is 15-30cm, and the angle γ between the fan blade and the agitator is 55-65°.

[0007] A method for detecting the residence time of sludge in a continuous sludge hydrolysis reactor according to the present invention includes the following steps:

[0008] (1) Sludge preparation: Add calcium oxide powder to the sludge, add water and stir to prepare slurry;

[0009] (2) Sludge preheating: The sludge is preheated to obtain preheated sludge, and then various microcapsules with different rupture times at the same temperature are added to obtain preheated sludge;

[0010] (3) Sludge hydrolysis flash evaporation: The preheated sludge is fed into the continuous sludge hot water hydrolysis reactor. Under the synergistic action of the guide plate and the stirring paddle, the sludge undergoes hot water hydrolysis reaction, flash evaporation, dehydration and centrifugation.

[0011] Furthermore, in step (2), the preparation of the microcapsules includes the following steps:

[0012] (A1) Preparation of millimeter-sized paraffin templates: Paraffin wax is heated and melted, a detection agent is added to the paraffin wax, and the mixture is stirred and mixed; granulation is performed, solidification is carried out to form spheres, sieves are made, and drying is carried out to obtain paraffin template spheres;

[0013] (A2) PLA / DCM solution preparation: Weigh PLA with a molecular weight of 20kDa-100kDa and dissolve it in dichloromethane (DCM). Heat and stir in a water bath until the solution is completely transparent. Add nano SiO2, nano clay or glutaraldehyde and disperse by ultrasonication to obtain PLA / DCM solution.

[0014] (A3) Dip-coating to form a shell and control the wall thickness: ① Initial coating: Dip the paraffin template ball from step (A1) into the PLA / DCM solution and dry it to form the initial shell; ② Multi-layer thickening: Repeat the coating operation in step ① until the capsule wall thickness reaches the required thickness.

[0015] (A4) Template removal and enhanced drying: Immerse the capsules in silicone oil, stir in an oil bath, centrifuge, the upper layer is PLA microcapsules, the middle layer is silicone oil, and the lower layer is molten paraffin; then perform gradient drying on the upper PLA microcapsules.

[0016] Furthermore, different detection reagents were encapsulated in microcapsules of varying wall thicknesses. These microcapsules were then added to sludge slurry and thoroughly mixed before being introduced into a hydrolysis reactor for a hydrothermal reaction. At a predetermined heating temperature, as the sludge was heated for an extended period, the microcapsules of different wall thicknesses ruptured sequentially, releasing the encapsulated detection reagents into the sludge hydrolysate. Quantitative analysis of the different detection reagents present in the sludge hydrolysate was then performed to determine whether the residence time of the sludge in the hydrolysis reactor met the optimal experimental range.

[0017] Furthermore, the microcapsules are made of polylactic acid (PLA) with a particle size of approximately 1 mm, and the controlled rupture at different time ranges under specific conditions can be precisely achieved by adjusting the molecular weight and additives.

[0018] Furthermore, the test reagent needs to meet the following four conditions simultaneously:

[0019] (1) It is water-soluble and can be fully dissolved in sludge hydrolysate;

[0020] (2) It has thermal stability and can withstand high temperatures without changing when heated at this temperature for at least 2 hours;

[0021] (3) It has chemical stability, does not react chemically with different detection reagents, and does not react chemically with various substances in sludge;

[0022] (4) Easy to detect and analyze. Different detection reagents need to have a certain degree of differentiation in the detection methods used, and the characteristic elements in these detection reagents are not present or have very low content in the sludge.

[0023] Furthermore, different detection reagents and microcapsules with different wall thicknesses need to correspond one-to-one with the heating time points.

[0024] Furthermore, the factors that regulate the microcapsule wall thickness and rupture time are shown in the table below:

[0025]

[0026] Furthermore, the detection reagents used include, but are not limited to, strontium chloride, lanthanum chloride, lithium chloride, rubidium chloride, and cesium chloride.

[0027] Further, in step (1), the amount of calcium oxide powder added is 2-5 wt% of the sludge mass, and the water content of the sludge is 90-95%; in step (2), the preheating temperature is 90-100℃, the preheating time is 10-20 min, and the amount of microcapsules added is 1-5 wt% of the sludge added; in step (3), the temperature of the hot hydrolysis reaction is 175-180℃, the hot hydrolysis reaction time is 55-65 min, the pressure inside the reaction vessel during the hot hydrolysis reaction is 1.5-2.0 MPa, and after flash evaporation, the pressure inside the flash evaporation vessel is released to atmospheric pressure within 1-30 s.

[0028] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The sludge hot water hydrolysis reactor of the present invention has a simple and reasonable structural design, is easy to operate and maintain, has a high degree of automation and good stability, and effectively reduces the cost and difficulty of sludge treatment. (2) The guide plate of the present invention is made of glass fiber composite material, which is lightweight, resistant to high temperature and high pressure, and resistant to acid and alkali corrosion; its structure is simple, easy to maintain, has a long service life and is not easily deformed; its root has a certain arc structure at the upper and lower ends, which can effectively reduce the dead zone of sludge deposition. (3) Through the synergistic effect of the stirring paddle and guide plate in the reactor, the present invention can effectively ensure that the residence time of sludge in the reactor can be kept in the optimal range in the continuously operating sludge hot water hydrolysis treatment system, so as to carry out hot water hydrolysis reaction and thus improve the sludge hydrolysis efficiency of the whole system. (4) The sludge residence time detection method of the present invention is simple to operate, efficient and fast, and can intuitively show the residence of sludge in the hot water hydrolysis reactor, thereby helping researchers to optimize the experimental scheme and reactor design parameters. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the continuous sludge thermal hydrolysis reactor in Example 1;

[0030] In the diagram, 1-heating device, 2-tank body, 3-stirring motor, 4-pressure gauge and pressure sensor interface, 5-thermometer and temperature sensor interface, 6-discharge port, 7-check valve, 8-guide plate, 9-stirring paddle, 10-stirring paddle blade, 11-feed inlet, 12-inspection port, 13-reactor base and support.

[0031] Figure 2 This is a flowchart of the process for detecting the residence time of Wuning water using a continuous sludge hot hydrolysis reactor in Example 1. Detailed Implementation

[0032] The municipal sludge described in this embodiment was taken from a municipal wastewater treatment plant in Nanjing, Jiangsu Province. Its water content was 67%, pH value was 7.2, TCOD was 95.28 g / L, C / N was 10.71, and VS / TS was 60.30%. The above values ​​are the average values ​​during this round of experiments.

[0033] Example 1

[0034] like Figure 1 As shown, the continuous sludge hot water hydrolysis reactor of the present invention includes a tank body 2. A heating device 1 is provided on the outside of the tank body 2, which is an outer heat conduction heating sleeve fitted onto the tank body 2. Two sets of guide plates 8 are provided on the inner wall of the tank body 2, dividing the interior of the tank body 2 into upper, middle, and lower regions. A stirring paddle 9 extends vertically inward from the top of the tank body 2 through the guide plates 8. A stirring motor 3 is located at the upper end of the stirring paddle 9, passing through the top of the tank body 2, and the stirring paddle 9 is controlled to rotate by the stirring motor 3. Three sets of fan blades 10 are provided on the stirring paddle 9. A sludge inlet 11 is provided at the bottom of the tank body 2, a sludge outlet 6 is provided at the top of the tank body 2, and an inspection port 12 is opened in the middle of the tank body 2. Check valves 7 are provided on both the sludge outlet 6 and the inlet 11. A pressure gauge and pressure sensor interface 4 are provided at the top of the tank body 2, and a pressure sensor and a pressure gauge are connected to the pressure gauge and pressure sensor interface 4, respectively.

[0035] The guide plate 8 is a glass fiber composite material partition with a certain thickness. It is narrow at the top and wide at the base, with both the upper and lower ends of the base having a certain curvature. The curvature r1 of the upper end of the base is 25-30°, and the arc length is 40-50% of the straight-line distance from the upper end of the guide plate 8 to the tank 2. The curvature r2 of the lower end of the base is 20-25°, and the arc length is 40-50% of the straight-line distance from the lower end of the guide plate 8 to the tank 2. A hole is opened at the conical tip of the guide plate 8, and the radius of the hole is 20-30% of the radius of the tank 2. The angle α between the lower section of the front end of the guide plate 8 and the horizontal plane is 25-30°, and the angle β between the upper and lower ends of the guide plate 8 near the hole is 40-45°. The distance L between the outer diameter of the agitator 9 and the guide plate 8 is 15-30cm, and the angle γ between the fan blade 10 and the agitator 9 is 55-65°.

[0036] The method for detecting the residence time of sludge in the continuous sludge hydrolysis reactor using the above-mentioned method includes the following steps:

[0037] (1) Sludge preparation: Add calcium oxide powder to the sludge, add water and stir to prepare slurry;

[0038] (2) Sludge preheating: The sludge is heated to obtain preheated sludge, and then various microcapsules with different rupture times at the same temperature are added to obtain preheated sludge;

[0039] (3) Sludge hydrolysis flash evaporation: Preheated sludge is introduced into the above-mentioned sludge hot hydrolysis reactor. Under the synergistic action of the guide plate 8 and the stirring paddle 9, the sludge undergoes hot hydrolysis reaction in the reactor. Subsequently, flash evaporation is performed, and the remaining material is dehydrated and centrifuged. The entire process is as follows: Figure 2 As shown.

[0040] The microcapsule synthesis method is as follows:

[0041] (1) Preparation of millimeter-sized paraffin templates: ① Weigh appropriate amounts of paraffin and divide them into 5 equal groups. Heat the paraffin to 70℃ and melt it completely. Add 0.1%wt of different detection reagents (metal ion chlorides, namely strontium chloride, lanthanum chloride, lithium chloride, rubidium chloride, and cesium chloride) to the paraffins in groups 1-5 and stir to mix. Then add the liquid paraffin to the template granulation device and drop the droplets vertically into 0-5℃ ice water (the injection pump speed is 5mL / h, and the needle is 15cm away from the water surface) to solidify and form spheres. ② Pass the collected template spheres through a standard sieve of 16 mesh (1250μm) and 18 mesh (1000μm) in sequence, and collect template spheres of the required particle size (1000μm < template sphere particle size < 1250μm). Dry the collected template spheres in a drying oven at 40℃ for 2 hours for later use.

[0042] (2) PLA solution preparation: Weigh appropriate amounts of PLA with molecular weights of 20kDa-100kDa and dissolve them in dichloromethane (DCM). Control the solution concentration to 8%-12% w / v and label them as 1-5. Stir the solutions using a magnetic stirrer at 40℃ water bath and 500rpm until the solutions are completely transparent. Then add 0.5%wt of nano-SiO2, 1%wt of nano-SiO2, 0.5%wt of nano-clay, 1%wt of nano-clay and 0.2%wt of glutaraldehyde to solutions 1-5 respectively. Disperse solutions 1-4 ultrasonically in an ice bath (100W, 10min). Continue to stir solution 5 at 40℃ water bath and 500rpm for 30min to activate crosslinking.

[0043] (3) Dipping and coating to form a shell and control the wall thickness: ① Initial coating: Fix the five sets of paraffin template balls dried in step (1) into the rotating fixture (20 rpm), then immerse them in the PLA / DCM solution with the corresponding number for 10 s, and then slowly lift them above the liquid surface (speed 2 mm / s). After drying, the initial shell is formed; ② Multi-layer thickening: Repeat the above coating operation until the capsule wall thickness reaches the required thickness (each coating can thicken the capsule by about 10 μm).

[0044] (4) Template removal and enhanced drying: ① Melting and removing paraffin: After coating, the capsules are immersed in silicone oil in an oil bath at 60°C and mechanically stirred for 30 min (100 rpm). After stirring, they are centrifuged for 15 min (5000 rpm). After centrifugation, the upper layer is PLA microcapsules, the middle layer is silicone oil (reused after filtration), and the lower layer is molten paraffin (recycled); ② Gradient drying: First, air dry at 25°C for 6 h, then dry in nitrogen flow at 40°C for 12 h, and finally degas under vacuum at 60°C and -0.1 MPa for 2 h.

[0045] (5) Wall thickness verification: Fix the microcapsules obtained in step (4) onto the sample stage, use micro-CT scan to measure the wall thickness, and calculate the mean and dispersion (SD < 8% is acceptable).

[0046] The types of microcapsules obtained are shown in Table 1 below:

[0047] Table 1. Relevant parameters of microcapsules

[0048]

[0049] Example 2

[0050] The residence time of sludge in the continuous sludge hydrolysis reactor described in Example 1 was detected, as follows:

[0051] The upper end of the root has an arc r1 of 30°, and its arc length is 50% of the straight-line distance from the upper end of the guide plate 8 to the tank 2. The lower end of the root has an arc r2 of 25°, and its arc length is 50% of the straight-line distance from the lower end of the guide plate 8 to the tank 2. The radius of the hole in the guide plate 8 is 20% of the radius of the reactor tank 2. The angle α between the lower section of the guide plate and the horizontal plane in the sludge thermal hydrolysis reactor is 30°, the angle β between the upper and lower end of the guide plate near the hole is 45°, the distance L between the outer diameter of the agitator and the guide plate is 15cm, and the angle γ between the fan blade and the agitator is 60°.

[0052] (1) Sludge preparation: municipal sludge with a moisture content of 67% is put into a slurry tank, then calcium oxide powder with a ratio of 2% of the sludge mass is added, and water is added to prepare a slurry with a moisture content of 95%.

[0053] (2) Sludge preheating: The sludge is fed into a preheating tank and heated to 100°C to obtain preheated sludge. At this time, five kinds of microcapsules are added to the preheating tank. The amount of each kind of microcapsule added is the same and is 1 wt% of the amount of sludge added.

[0054] (3) Sludge hydrolysis flash evaporation: The preheated sludge is fed into the sludge hot hydrolysis reactor. Under the synergistic action of the guide plate 8 and the stirring paddle 9, the sludge is kept in the reactor at 180°C for 1 hour to complete the alkaline hot hydrolysis reaction. After the reaction, the sludge is transported to the flash tank for flash evaporation. The pressure inside the flash tank is 1.8 MPa according to the pressure gauge reading. The pressure relief valve is opened to release the pressure. The pressure inside the flash tank drops to atmospheric pressure within 20 seconds. After the flash evaporation is completed, the material inside the flash tank is discharged and dehydrated and centrifuged.

[0055] After dehydration and centrifugation of the material discharged from the flash tank in step (3), the moisture content of the cake was determined. Then, the COD, ammonia nitrogen, and total nitrogen of the remaining hydrolysate were measured. The results are as follows: the moisture content of the cake was 34%, the COD of the hydrolysate was 75500 mg / L, the ammonia nitrogen was 2177 mg / L, and the total nitrogen was 6588 mg / L. After pretreatment of the hydrolysate to eliminate interference, the concentration ratio of the five detection reagents in the hydrolysate was detected using atomic absorption spectrometry (AAS). The results are shown in Table 2 below.

[0056] Table 2. Detection percentage of different reagents in sludge hydrolysate from Example 2

[0057]

[0058] Table 2 shows that all detection reagents ① through ④ were detected, but the detection rate of reagent ④ was extremely low. The detection rates of reagent ③ were close to those of reagents ① and ②, indicating that the first three microcapsules completely ruptured and released their contained detection reagents during the hot water hydrolysis reaction, while microcapsules ④ and ⑤ hardly underwent rupture. This suggests that the residence time of the sludge in the hot water hydrolysis reactor in this round of experiments was concentrated within 60 minutes (the optimal residence time).

[0059] Comparative Example 1

[0060] The only difference between Comparative Example 1 and Example 2 is that the angle α between the lower section of the guide plate inside the sludge thermal hydrolysis reactor and the horizontal plane is 0°.

[0061] After dehydration and centrifugation of the material discharged from the flash tank in step (3), the moisture content of the cake was determined. Then, the COD, ammonia nitrogen, and total nitrogen of the remaining hydrolysate were measured. The results are as follows: the moisture content of the cake was 42%; the COD of the hydrolysate was 65000 mg / L, the ammonia nitrogen was 1893 mg / L, and the total nitrogen was 5766 mg / L. After pretreatment of the hydrolysate to eliminate interference, the concentration ratio of the five detection reagents in the hydrolysate was detected using atomic absorption spectrometry (AAS). The results are shown in Table 3 below.

[0062] Table 3 shows the detection percentage of different reagents in the sludge hydrolysate of Comparative Example 1.

[0063]

[0064] Table 3 shows that all detection reagents ①-③ were detected, with the detection rate gradually decreasing. Detection reagents ④ and ⑤ were not detected, indicating that microcapsules ① were almost completely pyrolyzed, microcapsules ② and ③ were only partially pyrolyzed, and microcapsules ④ and ⑤ did not pyrolyze. This suggests that the residence time of sludge in the hydrothermal hydrolysis reactor in this round of experiments was concentrated within 30 minutes, which is less than the optimal residence time. The reason for this phenomenon may be that, compared to Example 1, the α angle of the guide plate in Comparative Example 1 was smaller, resulting in an excessively high sludge lifting rate in the reactor. Most of the sludge was lifted to the outlet by the agitator before undergoing sufficient hydrothermal reaction and then entered the flash tank.

[0065] Comparative Example 2

[0066] The only difference between Comparative Example 2 and Example 2 is that the angle α between the lower section of the guide plate inside the sludge thermal hydrolysis reactor and the horizontal plane is 60°.

[0067] After the experiment, a sludge deposition dead zone was found at the guide plate and the inner wall of the tank through the inspection port of the reactor. The material discharged from the flash tank in step (3) was dehydrated and centrifuged to determine the moisture content of the sludge cake. Then, the COD, ammonia nitrogen and total nitrogen of the remaining hydrolysate were determined. The results are as follows: the moisture content of the sludge cake was 55%; the COD value of the hydrolysate was 48500 mg / L, the ammonia nitrogen value was 1414 mg / L, and the total nitrogen value was 4277 mg / L. After the hydrolysate was pretreated to eliminate interference, the concentration ratio of the five detection reagents contained in the hydrolysate was detected by atomic absorption spectrometry (AAS). The detection results are shown in Table 4 below.

[0068] Table 4 shows the detection percentage of different reagents in the sludge hydrolysate of Comparative Example 2.

[0069]

[0070] Table 4 shows that all detection reagents ①-⑤ were detected, and the detection rates of reagents ①-③ were consistent, indicating that microcapsules ①-③ had completely ruptured and released their contained detection reagents, some microcapsules ④ ruptured, and a small portion of microcapsules ⑤ ruptured. This suggests that the residence time of sludge in the hot hydrolysis reactor in this round of experiments was concentrated at 75 minutes, which is longer than the optimal residence time. The reason for this phenomenon may be that the α angle of the baffle plate in Comparative Example 2 was relatively large, resulting in insufficient sludge rise rate in the reactor, causing the material entering the flash tank to be mainly water; and the cross-section of the baffle plate and the inner wall of the reactor formed a sludge dead zone, where a large amount of sludge was deposited and continuously heated. Excessive heating of the sludge led to the Maillard reaction, which significantly reduced the overall hydrolysis efficiency of the system.

[0071] Comparing the results of Example 2 with those of Comparative Examples 1 and 2, it was found that the moisture content of the sludge cake in Example 2 was reduced by 8% and 21% compared to Comparative Examples 1 and 2, respectively. The COD, ammonia nitrogen, and total nitrogen values ​​of the hydrolysate in Example 2 were increased by 16.15%, 15.00%, and 14.26% compared to Comparative Example 1, and by 55.67%, 53.96%, and 54.03% compared to Comparative Example 2, respectively. In Example 2, the sludge retention time was concentrated within the optimal reaction time (60 min), while in Comparative Example 1, the sludge retention time was shorter than the optimal reaction time, and in Comparative Example 2, the sludge retention time was much longer than the optimal reaction time. The optimal parameter for the angle α between the lower section of the baffle plate inside the sludge hot hydrolysis reactor and the horizontal plane should be 30°.

[0072] In summary, the continuous sludge hydrolysis reactor of this invention, within a continuously operating sludge hydrolysis treatment system, effectively ensures sufficient residence time for the sludge in the reactor to undergo hydrolysis, thereby improving the overall sludge hydrolysis efficiency and degree. It exhibits excellent performance in treating municipal sludge, achieving both volume reduction and resource recovery. The sludge residence time detection method disclosed in this invention is simple to operate, highly efficient, and rapid, providing a direct visual representation of sludge residence in the hydrolysis reactor, thus helping researchers optimize experimental procedures and reactor design parameters.

Claims

1. A method for detecting the residence time of sludge in a reactor, characterized in that, Includes the following steps: (1) Sludge preparation: Add calcium oxide powder to the sludge, add water and stir to prepare slurry; (2) Sludge preheating: The sludge is preheated, and then various microcapsules with different rupture times at the same temperature are added to obtain preheated sludge; (3) Sludge hydrolysis flash evaporation: The preheated sludge is fed into a continuous sludge hot water hydrolysis reactor. Under the synergistic action of the guide plate (8) and the stirring paddle (9) in the continuous sludge hot water hydrolysis reactor, the sludge undergoes hot water hydrolysis reaction, flash evaporation, dehydration and centrifugation. In step (2), the preparation of microcapsules includes the following steps: (A1) Preparation of millimeter-sized paraffin templates: heating and melting paraffin, adding a detection agent to the paraffin, stirring and mixing; granulating, solidifying to form spheres, sieving, drying to obtain paraffin template spheres; (A2) PLA / DCM solution preparation: Weigh PLA and dissolve it in dichloromethane. Heat and stir in a water bath until the solution is completely transparent. Add nano SiO2, nano clay or glutaraldehyde, and disperse by ultrasonication to obtain PLA / DCM solution. (A3) Dip-coating to form a shell and control the wall thickness: ① Initial coating: Dip the paraffin template ball from step (A1) into the PLA / DCM solution and dry it to form the initial shell; ② Multi-layer thickening: Repeat the coating operation in step ① above until the capsule wall thickness reaches the required thickness; (A4) Template removal and enhanced drying: Immerse the capsules in silicone oil, stir in an oil bath, centrifuge, the upper layer is PLA microcapsules, the middle layer is silicone oil, and the lower layer is molten paraffin; then perform gradient drying on the upper PLA microcapsules.

2. The method according to claim 1, characterized in that, In step (3), the continuous sludge hot water hydrolysis reactor used includes a tank (2), characterized in that: a guide plate (8) is provided on the inner wall of the tank (2), the guide plate (8) has a structure that is narrow at the top and wide at the root, the upper and lower ends of the root have a certain curvature, the top of the guide plate (8) is a conical structure, the top of the conical structure has a hole, and the top of the tank (2) extends vertically inward through the guide plate (8) and is provided with a stirring paddle (9).

3. The method according to claim 2, characterized in that, The upper arc of the root of the guide plate (8) is 25-30°, and the arc length is 40-50% of the straight distance from the upper section endpoint of the guide plate (8) to the tank (2).

4. The method according to claim 2, characterized in that, The lower end of the root of the guide plate (8) has an arc of 20-25° and an arc length of 40-50% of the straight distance from the lower end of the guide plate (8) to the tank (2).

5. The method according to claim 2, characterized in that, There are two or more sets of guide plates (8). The angle (α) between the lower section of the front end of the guide plate (8) and the horizontal plane is 25-30°. The radius of the hole is 20-30% of the radius of the tank body (2).

6. The method according to claim 2, characterized in that, The upper end of the stirring paddle (9) passes through the tank body (2) and is equipped with a stirring motor (3). The stirring paddle (9) is controlled to rotate by the stirring motor (3). Multiple sets of fan blades (10) are provided on the stirring paddle (9).

7. The method according to claim 2, characterized in that, The tank (2) is equipped with a heating device (1) on the outside, a sludge inlet (11) at the bottom of the tank (2), a sludge outlet (6) at the top of the tank (2), and an inspection port (12) in the middle of the tank (2).

8. The method according to claim 7, characterized in that, The angle (β) between the upper and lower cross-sections of the guide plate (8) near the hole is 40-45°; the distance (L) between the outer diameter of the agitator (9) and the guide plate (8) is 15-30cm; and the angle (γ) between the fan blade (10) and the agitator (9) is 55-65°.

9. The method according to claim 1, characterized in that, In step (1), the amount of calcium oxide powder added is 2-5 wt% of the sludge mass, and the water content of the sludge is 90-95%; in step (2), the preheating temperature is 90-100℃, the preheating time is 10-20 min, and the amount of microcapsules added is 1-5 wt% of the sludge mass; in step (3), the temperature of the hot hydrolysis reaction is 175-180℃, the hot hydrolysis reaction time is 55-65 min, the pressure inside the reaction vessel during the hot hydrolysis reaction is 1.5-2.0 MPa, and after flash evaporation, the pressure inside the flash evaporation vessel is released to atmospheric pressure within 1-30 s.

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