A system and method for continuous and efficient hydrolysis of municipal sludge

Abstract

This invention discloses a system and method for continuous and efficient hydrolysis of municipal sludge. The system includes a sludge receiving and storage device, a slurry tank, a heat exchange device, a preheating tank, and a multi-stage hydrolysis flash evaporation unit connected in sequence, as well as a product collection unit. The multi-stage hydrolysis flash evaporation unit is connected to the heat exchange device, which is connected to the product collection unit via a condenser. The multi-stage hydrolysis flash evaporation unit includes a primary flash tank, a hydrolysis reactor, and a secondary flash tank connected in sequence. Both the primary and secondary flash tanks are connected to the steam inlet of the heat exchange device. Using this system to hydrolyze municipal sludge, the moisture content of the dewatered sludge cake reaches 17%, which is 43% lower than that of existing technologies. The COD value, ammonia nitrogen value, and total nitrogen value of the sludge hydrolysate are increased by an average of approximately 65% ​​compared to existing technologies. This system has a high degree of automation, good stability, and low operating costs, effectively improving the hydrolysis efficiency and degree of hydrolysis of municipal sludge.

Description

Technical Field

[0001] This invention relates to a system and method for continuous and efficient hydrolysis of municipal sludge, belonging to the field of sludge treatment and disposal technology. Background Technology

[0002] Sludge, a byproduct of wastewater treatment, is an extremely complex heterogeneous body composed of organic fragments, bacterial cells, inorganic particles, and colloids. Sludge thermal hydrolysis technology, with its unique functions, demonstrates significant advantages in the field of sludge treatment. This technology effectively disrupts the colloidal and capillary structures of sludge, causing sludge cell breakage and converting the originally tightly bound water within the cells and the water adsorbed on the cell surface into free water, significantly improving the sludge's fluidity and making it easier to transport and process. Simultaneously, this transformation greatly improves the sludge's settling and dewatering properties. Furthermore, sludge thermal hydrolysis technology promotes the release of intracellular organic matter, further decomposing large organic molecules into smaller molecules. This transformation facilitates the transfer of organic matter from the solid phase to the liquid phase, reducing the content of organic matter in the solid phase, thus benefiting the stabilization of the solid phase and subsequent treatment and disposal. This technology provides strong support for the subsequent degradation and dewatering of sludge organic matter and has been widely applied in practical engineering.

[0003] Sludge hydrolysis units are mainly classified into two types: batch and continuous. Currently, batch sludge hydrolysis units are widely used due to their higher technological maturity. The batch sludge hydrolysis process typically involves the following steps: First, a fixed amount of sludge is fed into the hydrolysis tank, and then the reaction takes place under specific high temperature and high pressure conditions to complete the hydrolysis process. Finally, the treated sludge is discharged from the tank and transferred to subsequent processing steps.

[0004] However, this batch processing method typically has some limitations, such as relatively complex operation and high energy consumption, resulting in low overall treatment efficiency. Furthermore, high investment and operating costs are also a factor limiting its widespread application in large-scale sludge thermal hydrolysis processes. Summary of the Invention

[0005] Purpose of the invention: The first purpose of the present invention is to provide a system for continuous and efficient hydrolysis of municipal sludge, and the second purpose of the present invention is to provide a method for hydrolyzing municipal sludge using the system for continuous and efficient hydrolysis of municipal sludge.

[0006] Technical Solution: The present invention discloses a continuous and efficient system for hydrolyzing municipal sludge, comprising a sludge receiving and storage device, a slurry tank, a heat exchange device, a preheating tank, and a multi-stage hydrolysis flash evaporation unit connected in sequence, as well as a product collection unit; the multi-stage hydrolysis flash evaporation unit is connected to the heat exchange device, and the heat exchange device is connected to the product collection unit through a condensation device; the multi-stage hydrolysis flash evaporation unit includes a primary flash tank, a hydrolysis reactor, and a secondary flash tank connected in sequence; the steam outlets of the primary flash tank and the secondary flash tank are both connected to the steam inlet of the heat exchange device, and the primary flash tank, the secondary flash tank, and the product collection unit are all connected to the outside environment.

[0007] Furthermore, a filter device is installed at the bottom of the discharge port of the primary flash tank, so that the material after primary flash evaporation can be separated into solid and liquid by the filter device, the hydrolysate is discharged outside the boundary, and the remaining sludge is fed into the hydrolysis reactor.

[0008] Furthermore, two guide plates are fixed inside the hydrolysis reactor to divide the interior of the hydrolysis reactor into three parts: upper, middle and lower. A stirring paddle is installed at the top of the hydrolysis reactor, extending inward through the guide plates. The stirring paddle has stirring blades in each of the three spaces separated by the two guide plates. The distance between the outer diameter of the stirring paddle and the guide plates is 15-30cm.

[0009] Furthermore, the guide plate is a circular baffle with the same radius as the inner diameter of the hydrolysis reactor. A hole is opened at the center of the guide plate, and the radius of the hole is 20-30% of the inner diameter of the hydrolysis reactor. The angle between the upper and lower ends of the guide plate near the hole is 25-35°.

[0010] Furthermore, the stirring blades are inclined from the top to the bottom of the hydrolysis reactor.

[0011] Furthermore, a motor is installed on the top of the hydrolysis reactor, and the stirring paddle is controlled by the motor to rotate.

[0012] Furthermore, the inlet of the first-stage flash tank is connected to the outlet of the preheating tank, the outlet of the first-stage flash tank is connected to the inlet of the hydrolysis reactor and the outside, the outlet of the hydrolysis reactor is connected to the inlet of the second-stage flash tank, and the outlet of the second-stage flash tank is connected to the outside.

[0013] Furthermore, both the top of the primary flash tank and the top of the secondary flash tank are equipped with pressure relief and exhaust valves, and the steam outlets of the primary flash tank and the secondary flash tank are connected to the steam inlet of the heat exchange device through the pressure relief and exhaust valves.

[0014] Furthermore, the product collection unit includes a liquid collection tank and a gas collection tank, which are connected by a check valve.

[0015] Furthermore, the inlet of the liquid collection tank is connected to the outlet of the condenser, the outlet of the liquid collection tank is connected to the outside, and the outlet of the liquid collection tank is connected to the inlet of the gas collection tank through a check valve.

[0016] Furthermore, the inner diameter of the connecting pipes between the primary flash tank, the secondary flash tank, and the heat exchange device is 20-100cm.

[0017] Furthermore, the inner layer of the heat exchange device is a spiral condenser tube, which contains high-temperature steam discharged during the flash evaporation and depressurization process. The outer layer is filled with a well-prepared slurry that exchanges heat with the high-temperature steam inside the spiral condenser tube, thereby enabling the recovery and utilization of the thermal energy of the high-temperature steam.

[0018] Furthermore, the outlet end of the condenser is below the liquid level inside the liquid collection tank.

[0019] Furthermore, the slurry tank is connected to a heat exchange device via a screw pump.

[0020] A method for continuously and efficiently hydrolyzing municipal sludge using the system described in this invention includes the following steps:

[0021] (1) Sludge preparation: municipal sludge from the sludge receiving and storage device is put into a pulping tank, and calcium oxide powder and water are added to the pulping tank to prepare the sludge into a slurry.

[0022] (2) Sludge preheating: The prepared sludge is fed into a heat exchange device to exchange heat with the high-temperature steam discharged from the first-stage and second-stage flash tanks in the multi-stage hydrolysis flash evaporation unit. The sludge is then fed into a preheating tank for heating to obtain preheated sludge.

[0023] (3) Multi-stage hydrolysis flash evaporation of sludge: The preheated sludge is fed into the first-stage flash tank, and the pressure relief valve is opened to release the pressure. During this process, the pressure in the first-stage flash tank drops rapidly in a short time. After the pressure is released, the material is filtered by the filter device, the hydrolysate is discharged, and the remaining sludge is fed into the hydrolysis reactor. Under the action of the guide plate and the stirring paddle, the sludge has enough residence time in the hydrolysis reactor to complete the alkaline hot water hydrolysis reaction. The reacted sludge is then transported to the second-stage flash tank for flash evaporation. After the flash evaporation is completed, the material is discharged and dehydrated and centrifuged.

[0024] (4) Collection of sludge hydrolysis products: The gas discharged during the flash evaporation process is heat exchanged by the heat exchange device and then condensed by the condensation device before being discharged into the product collection unit. Water vapor is condensed and absorbs soluble gases into the liquid collection tank, while insoluble gases are discharged into the gas collection tank.

[0025] Furthermore, in step (1), the sludge has a moisture content of 90-95%, the municipal sludge is residual activated sludge with a moisture content of 80-85% from the urban domestic sewage treatment plant, and the amount of calcium oxide powder added is 18-22% of the dry weight of the sludge;

[0026] Furthermore, in step (2), after heat exchange, the temperature of the mud rises to 60-100℃, the temperature in the preheating tank is 160-200℃, and the pressure is 2.5-3.5MPa.

[0027] Furthermore, in step (3), the process of venting and depressurizing in the primary flash tank and the secondary flash tank is completed within 1-30 seconds, the temperature of the sludge in the hydrolysis reactor is 160-200℃, and the residence time is 2-4 hours.

[0028] Furthermore, in step (4), the condensate and soluble gas collected in the liquid collection tank can be mixed with the hydrolysate discharged from the first-stage flash tank and the second-stage flash tank and used as liquid fertilizer. The insoluble gas collected in the gas collection tank includes methane, which can be purified and used as fuel.

[0029] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0030] (1) The present invention adopts a continuous multi-stage hydrolysis flash evaporation process. By setting high-temperature and high-pressure resistant guide plates and stirring paddles in the hydrolysis reactor, the sludge is guaranteed to have sufficient residence time for alkaline hot water hydrolysis reaction. The hydrolysis reactor and flash tank are separated into independent units to ensure that the hot water hydrolysis and flash evaporation processes do not interfere with each other and operate stably. Alkaline hot water hydrolysis and multi-stage flash evaporation can completely destroy the cell walls of sludge cells, and release the contents of the cells into the hydrolysate to the maximum extent, thereby improving the degree of sludge hydrolysis, thereby reducing the water content in the final dewatered cake and improving the fertilizer efficiency of the hydrolysate.

[0031] (2) Through experimental simulation verification, the process of the present invention can achieve a subsequent dewatering cake moisture content of 17%, which is 43% lower than the subsequent dewatering cake moisture content of 60% in the prior art. The process of the present invention can also increase the COD value, ammonia nitrogen value and total nitrogen value of sludge hydrolysate by an average of about 65% compared with the prior art.

[0032] (3) This invention collects the gas discharged during the flash evaporation depressurization process and feeds it into a heat exchanger and a condenser. This not only allows the thermal energy of the steam to be recovered and utilized, but also allows the water vapor to absorb soluble gases after condensation and flow into a liquid collection tank. This liquid is then mixed with the hydrolysate discharged from the flash tank to create liquid fertilizer. Insoluble gases, such as methane, are fed into a gas collection tank and purified for use as fuel. Through these technical means, this invention achieves maximum recovery and utilization of the gas discharged during the flash evaporation depressurization process.

[0033] (4) The continuous and efficient hydrolysis method and system for municipal sludge of the present invention has a high degree of automation and good stability while continuously feeding and discharging sludge, reducing operating costs, effectively improving the hydrolysis efficiency and degree of hydrolysis of municipal sludge, and improving the solid-liquid separation efficiency and fertilizer effect of the end product. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of a continuous and efficient hydrolysis system for municipal sludge according to the present invention;

[0035] Figure 2 This is a schematic diagram of the hydrolysis reactor described in this invention;

[0036] In the diagram: 1-Sludge receiving and storage device, 2-Pulping tank, 3-Screw pump, 4-Heat exchange device, 5-Preheating tank, 6-Multi-stage hydrolysis flash unit, 601-First-stage flash tank, 602-Hydrolysis reactor, 603-Second-stage flash tank, 604-Pressure relief valve, 605-Filter device, 606-Baffle plate, 607-Agitator, 608-Agitator blade, 609-Motor, 7-Product collection unit, 701-Liquid collection tank, 702-Gas collection tank, 703-Check valve, 8-Condensation device. Detailed Implementation

[0037] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0038] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0039] The municipal sludge was taken from a municipal wastewater treatment plant in Nanjing, Jiangsu Province. Its water content was 85%, pH value was 7.5, TCOD was 94.12 g / L, C / N ratio was 12.56, and VS / TS ratio was 65%. The above values ​​are the average values ​​during this round of experiments.

[0040] Example 1

[0041] like Figure 1-2As shown, the present invention discloses a continuous and efficient system for hydrolyzing municipal sludge. The system includes a sludge receiving and storage device 1, a slurry tank 2, a heat exchange device 4, a preheating tank 5, and a multi-stage hydrolysis flash evaporation unit 6 connected in sequence, as well as a product collection unit 7. The multi-stage hydrolysis flash evaporation unit 6 is connected to the heat exchange device 4, and the heat exchange device 4 is connected to the product collection unit 7 through a condensation device 8. Both the multi-stage hydrolysis flash evaporation unit 6 and the product collection unit 7 are connected to the outside.

[0042] The multi-stage hydrolysis flash evaporation unit 6 includes a primary flash tank 601, a hydrolysis reactor 602, and a secondary flash tank 603 connected in sequence. The inlet of the primary flash tank 601 is connected to the outlet of the preheating tank 5, and the outlet of the primary flash tank 601 is connected to both the inlet of the hydrolysis reactor 602 and the outside environment. The outlet of the hydrolysis reactor 602 is connected to the inlet of the secondary flash tank 603. Both the top of the primary flash tank 601 and the top of the secondary flash tank 603 are equipped with pressure relief valves 604. The steam outlets of both the primary flash tank 601 and the secondary flash tank 603 are connected to the steam inlet of the heat exchange device 4 through the pressure relief valves 604. The outlet of the secondary flash tank 603 is connected to the outside environment. A filter device 605 is installed at the bottom of the discharge port of the primary flash tank 601, allowing the material after primary flash evaporation to achieve solid-liquid separation through the filter device 605. The hydrolysate is discharged externally, and the remaining sludge is fed into the hydrolysis reactor 602. Two guide plates 606 are fixedly installed inside the hydrolysis reactor 602, dividing the hydrolysis reactor 602 into upper, middle, and lower parts. The guide plate 606 is a circular baffle with a radius the same as the inner diameter of the hydrolysis reactor 602, and an opening is made at the center of the guide plate 606. The reactor 602 has holes with a radius of 20-30% of its inner diameter. The angle α between the upper and lower ends of the guide plate 606 near the holes is 25-35°. An agitator 607 extends inward from the top of the reactor 602 through the guide plate 606. The agitator 607 has multiple stirring blades 608 within the three spaces separated by the two guide plates 606, and the stirring blades 608 slope from the top to the bottom of the reactor. The distance L between the outer diameter of the agitator 607 and the upper end of the guide plate 606 is 15-30 cm. The inner diameter of the pipes connecting the primary flash tank 601, the secondary flash tank 603, and the heat exchange device 4 is 20-100 cm to ensure that the venting and depressurization process of the two flash tanks can be achieved in a very short time. A motor 609 is installed at the top of the reactor 602, and the agitator 607 is controlled to rotate via the motor 609. The primary flash tank 601, the secondary flash tank 603, and the product collection unit 7 are all connected to the outside world.

[0043] Product collection unit 7 includes a liquid collection tank 701 and a gas collection tank 702, which are connected by a check valve 703. The inlet of liquid collection tank 701 is connected to the outlet of condenser 8, and the outlet of liquid collection tank 701 is connected to the outside. The outlet of liquid collection tank 701 is connected to the inlet of gas collection tank 702 via check valve 703. The end of the outlet of condenser 8 should be below the liquid level in liquid collection tank 701.

[0044] The discharge port of the sludge receiving and storage device 1 is connected to the inlet of the slurry tank 2. The discharge port of the slurry tank 2 is connected to the sludge inlet of the heat exchange device 4 via a screw pump 3. The sludge discharge port of the heat exchange device 4 is connected to the inlet of the preheating tank 5. The liquid outlet of the heat exchange device 4 is connected to the liquid inlet of the condenser 8. The inner layer of the heat exchange device 4 is a spiral condenser tube, which contains high-temperature steam discharged during the flash evaporation and depressurization process. The outer layer is filled with prepared sludge, which exchanges heat with the high-temperature steam in the spiral condenser tube to achieve the recovery and utilization of the thermal energy of the high-temperature steam.

[0045] The method for hydrolyzing municipal sludge using the above-mentioned continuous and efficient hydrolysis system includes the following steps:

[0046] (1) Sludge preparation: municipal sludge in sludge receiving and storage device 1 is put into pulping tank 2, calcium oxide powder and water are added to pulping tank 2 to prepare sludge into mud.

[0047] (2) Sludge preheating: The prepared sludge is fed into the heat exchange device 4 through the screw pump 3 to exchange heat with the high-temperature steam discharged from the first flash tank 601 and the second flash tank 603 in the multi-stage hydrolysis flash unit 6. The sludge is then fed into the preheating tank 5 for heating to obtain preheated sludge.

[0048] (3) Multi-stage hydrolysis flash evaporation of sludge: The preheated sludge is fed into the first-stage flash tank 601, and the pressure relief valve 604 is opened to release the pressure. During this process, the pressure in the first-stage flash tank 601 drops rapidly in a short time. After the pressure is released, the material is filtered by the filter device 605, the hydrolysate is discharged, and the remaining sludge is fed into the hydrolysis reactor 602. Under the action of the guide plate 606 and the stirring paddle 607, the sludge has enough residence time in the hydrolysis reactor 602 to complete the alkaline hot water hydrolysis reaction. The reacted sludge is then transported to the second-stage flash tank 603 for flash evaporation. After the flash evaporation is completed, the material is discharged and dehydrated and centrifuged.

[0049] (4) Collection of sludge hydrolysis products: The gas discharged during the flash evaporation process is heat exchanged by the heat exchange device 4 and then condensed by the condensation device 8 before being discharged into the product collection unit 7. The water vapor is condensed and absorbs the soluble gas, which flows into the liquid collection tank 701, while the insoluble gas is discharged into the gas collection tank 702.

[0050] In step (1), the sludge has a moisture content of 90-95%, and the municipal sludge is residual activated sludge with a moisture content of 80-85% from an urban sewage treatment plant. The amount of calcium oxide powder added is 18-22% of the dry weight of the sludge. In step (2), after heat exchange, the temperature of the sludge rises to 60-100℃, the temperature in preheating tank 5 is 160-200℃, and the pressure is 2.5-3.5MPa. In step (3), the primary flash tank 60 The process of venting and depressurizing in the first and second flash tanks 603 is completed within 1-30 seconds. The temperature of the sludge in the hydrolysis reactor 602 is 160-200℃ and the residence time is 2-4 hours. In step (4), the condensate and soluble gas collected in the liquid collection tank 701 are mixed with the hydrolysate discharged from the first flash tank 601 and the second flash tank 603 and can be used as liquid fertilizer. The insoluble gas collected in the gas collection tank 702 includes methane, which can be purified and used as fuel.

[0051] Example 2

[0052] The specific steps for hydrolyzing municipal sludge using the continuous and efficient hydrolysis system for municipal sludge described in Example 1 are as follows:

[0053] (1) Sludge preparation: municipal sludge with a moisture content of 85% in sludge receiving and storage device 1 is put into pulping tank 2, and then calcium oxide powder with a ratio of 20% of the dry weight of sludge is added, and water is added to prepare sludge with a moisture content of 95%.

[0054] (2) Sludge preheating: The sludge is pumped into the heat exchange device 4 through the screw pump 3 to exchange heat with the high-temperature steam discharged from the first-stage flash tank 601 and the second-stage flash tank 603 in the multi-stage hydrolysis flash unit 6, so that the sludge temperature rises to 85°C. Then the sludge is fed into the preheating tank 5 and heated to 200°C. The pressure inside the preheating tank 5 is increased to 3.0 MPa by reading the pressure gauge, and preheated sludge is obtained.

[0055] (3) Multi-stage hydrolysis flash evaporation of sludge: The preheated sludge is fed into the first-stage flash tank 601. The pressure relief valve 604 is opened to release the pressure. Within 20 seconds, the pressure in the first-stage flash tank 601 drops to atmospheric pressure. After the pressure is released, the material in the first-stage flash tank 601 is filtered by the filter device 605. The hydrolysate is discharged, and the remaining sludge enters the hydrolysis reactor 602. Under the action of the guide plate 606 and the stirring paddle 607, the sludge is kept at 200°C for 2 hours to complete the alkaline hot water hydrolysis reaction. The reacted sludge is then transported to the second-stage flash tank 603 for flash evaporation. The pressure gauge reading shows that the pressure in the second-stage flash tank 603 is 2.7 MPa. The pressure relief valve 604 is opened to release the pressure. Within 20 seconds, the pressure in the second-stage flash tank 603 drops to atmospheric pressure. After the flash evaporation is completed, the material in the second-stage flash tank 603 is discharged and dehydrated and centrifuged.

[0056] (4) Collection of sludge hydrolysis products: The gas discharged during the flash evaporation process is heat exchanged by the heat exchange device 4 and then condensed by the condensation device 8 before being discharged into the product collection unit 7. At this time, water vapor is condensed and absorbs soluble gases into the liquid collection tank 701, while insoluble gases are discharged into the gas collection tank 702.

[0057] After dehydration and centrifugation of the material discharged from the secondary flash tank 603 in step (3), the moisture content of the mud cake was determined, and the COD, ammonia nitrogen and total nitrogen of the remaining hydrolysate were determined. The results are as follows: the moisture content of the mud cake is 17%; the COD value of the hydrolysate is 87500 mg / L, the ammonia nitrogen value is 2519 mg / L, and the total nitrogen value is 6834 mg / L.

[0058] Comparative Example 1

[0059] The continuous sludge thermal hydrolysis system and process disclosed in CN112094015A, which enables efficient and complete thermal hydrolysis, includes the following steps:

[0060] (1) Put municipal sludge with a moisture content of 85% into the pulping tank, and pass some of the sludge filtrate and the heat of the steam discharged from the flash tank into the pulping tank through the heat exchange tube to increase the sludge moisture content to 90% and the temperature to 60℃.

[0061] (2) The sludge is pumped from the pulping tank into the preheating tank by a screw pump and heated. The sludge is stirred and held for 40 minutes to raise the temperature of the sludge to 125°C. Then the sludge is pumped from the preheating tank into the hydrolysis tank for hot hydrolysis at 180°C. The sludge is stirred and held for 40 minutes at a pressure of 2.8 MPa.

[0062] (3) The sludge after hot hydrolysis is sequentially fed from the hydrolysis tank into the first-stage flash tank, the second-stage flash tank and the third-stage flash tank to achieve multi-stage flash evaporation; specifically, during the multi-stage flash evaporation process, the temperature in the first-stage flash tank is 150℃ and the pressure is 2.0MPa, the temperature in the second-stage flash tank is 110℃ and the pressure is 1.14MPa, and the temperature in the third-stage flash tank 403 is 70℃ and the pressure is atmospheric pressure;

[0063] (4) The sludge after flash evaporation is fed into a heat exchanger. After the heat exchanger cools the sludge, it is fed into an automatic filter press system. After the automatic filter press system is used for filtration, dewatered cake and sludge filtrate are produced. The dewatered cake is transported out, and the sludge filtrate enters the sludge filtrate collection tank.

[0064] The moisture content of the dewatered cake obtained in step (4) and the COD, ammonia nitrogen and total nitrogen of the sludge filtrate were determined. The results are as follows: the moisture content of the cake was 50%; the COD of the hydrolysate was 52000 mg / L, the ammonia nitrogen was 1575 mg / L and the total nitrogen was 4146 mg / L.

[0065] Comparing the measurement results of Example 2 and Comparative Example 1, it was found that the moisture content of the mud cake in Example 2 was reduced by 33% compared with that in Comparative Example 1. Compared with the 60% moisture content of the subsequent dewatering cake in the prior art, the process of the present invention reduced the moisture content of the subsequent dewatering cake by 43%. The COD value, ammonia nitrogen value and total nitrogen value of the hydrolysate in Example 1 were increased by 68.27%, 59.93% and 64.83% respectively compared with those in Comparative Example 1.

[0066] In summary, the method and system for continuous and efficient hydrolysis of municipal sludge disclosed in this invention can control the continuous feeding and discharging of sludge, has a high degree of automation and good stability, reduces operating costs, and can effectively improve the hydrolysis efficiency and degree of hydrolysis of municipal sludge, thereby improving the solid-liquid separation efficiency and the fertilizer effect of the end product.

[0067] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A system for continuous and efficient hydrolysis of municipal sewage sludge, characterized in that, It includes a sludge receiving and storage device (1), a slurry tank (2), a heat exchange device (4), a preheating tank (5), and a multi-stage hydrolysis flash evaporation unit (6) connected in sequence, as well as a product collection unit (7); the multi-stage hydrolysis flash evaporation unit (6) is connected to the heat exchange device (4), and the heat exchange device (4) is connected to the product collection unit (7) through a condensation device (8); the multi-stage hydrolysis flash evaporation unit (6) includes a primary flash tank (601), a hydrolysis reactor (602), and a secondary flash tank (603) connected in sequence; the primary flash tank ( The steam outlets of the primary flash tank (601) and the secondary flash tank (603) are both connected to the steam inlet of the heat exchange device (4). The primary flash tank (601), the secondary flash tank (603), and the product collection unit (7) are all connected to the outside. Two guide plates (606) are fixedly installed inside the hydrolysis reactor (602) to divide the hydrolysis reactor (602) into three parts: upper, middle, and lower. The top of the hydrolysis reactor (602) extends inward through the guide plates (606) and is equipped with a stirring paddle (607). The stirring paddle (607) is positioned between the two guide plates. Each of the three spaces separated by the plate (606) is equipped with a stirring blade (608). The distance (L) between the outer diameter of the stirring blade (607) and the guide plate (606) is 15-30 cm. The guide plate (606) is a circular baffle with the same radius as the inner diameter of the hydrolysis reactor (602). A hole is opened at the center of the guide plate (606), and the radius of the hole is 20-30% of the inner diameter of the hydrolysis reactor (602). The angle (α) between the upper and lower cross-sections of the guide plate (606) near the hole is 25-35°. The discharge port of the first-stage flash tank (601) is equipped with a filter device (605), which allows the material after the first-stage flash to pass through the filter device (605) to achieve solid-liquid separation. The hydrolysate is discharged outside the boundary, and the remaining sludge is fed into the hydrolysis reactor (602). The sludge after the hydrolysis reaction is then transported to the second-stage flash tank (603) for flash evaporation. The product collection unit (7) includes a liquid collection tank (701) and a gas collection tank (702). The liquid collection tank (701) and the gas collection tank (702) are connected by a check valve (703).

2. The system for continuous and efficient hydrolysis of municipal sludge according to claim 1, characterized in that, The top of the primary flash tank (601) and the top of the secondary flash tank (603) are both equipped with pressure relief valves (604). The steam outlets of the primary flash tank (601) and the secondary flash tank (603) are connected to the steam inlet of the heat exchange device (4) through the pressure relief valves (604). The inner diameter of the connecting pipes between the primary flash tank (601), the secondary flash tank (603) and the heat exchange device (4) is 20-100cm.

3. The system for continuous and efficient hydrolysis of municipal sludge according to claim 1, characterized in that, The inlet of the liquid collection tank (701) is connected to the outlet of the condenser (8), the outlet of the liquid collection tank (701) is connected to the outside, and the outlet of the liquid collection tank (701) is connected to the inlet of the gas collection tank (702) through the check valve (703).

4. The system for continuous and efficient hydrolysis of municipal sludge according to claim 1, characterized in that, The inner layer of the heat exchange device (4) is a spiral condenser tube, and the end of the liquid outlet of the condenser (8) is below the liquid level in the liquid collection tank (701).

5. A method for hydrolyzing municipal sludge using a continuous and efficient hydrolysis system according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Sludge preparation: municipal sludge in sludge receiving and storage device (1) is put into pulping tank (2), calcium oxide powder and water are added to pulping tank (2) to prepare sludge into mud; (2) Sludge preheating: The prepared sludge is fed into the heat exchange device (4) to exchange heat with the high-temperature steam discharged from the first-stage flash tank (601) and the second-stage flash tank (603) in the multi-stage hydrolysis flash unit (6). The sludge is then fed into the preheating tank (5) for heating to obtain preheated sludge. (3) Multi-stage hydrolysis flash evaporation of sludge: The preheated sludge is fed into the first-stage flash tank (601), and the pressure relief valve (604) is opened to release the pressure. During this process, the pressure in the first-stage flash tank (601) drops rapidly in a short time. After the pressure is released, the material is filtered by the filter device (605), the hydrolysate is discharged, and the remaining sludge is fed into the hydrolysis reactor (602). Under the action of the guide plate (606) and the stirring paddle (607), the sludge has enough residence time in the hydrolysis reactor (602) to complete the alkaline hot water hydrolysis reaction. The sludge after the reaction is then transported to the second-stage flash tank (603) for flash evaporation. After the flash evaporation is completed, the material is discharged and dehydrated and centrifuged. (4) Collection of sludge hydrolysis products: The gas discharged during the flash evaporation process is heat exchanged through the heat exchange device (4) and then condensed through the condensation device (8) before being discharged into the product collection unit (7). The water vapor is condensed and absorbs the soluble gas, which flows into the liquid collection tank (701), while the insoluble gas is discharged into the gas collection tank (702).

6. The method according to claim 5, characterized in that, In step (1), the sludge has a moisture content of 90-95%, and the municipal sludge is residual activated sludge with a moisture content of 80-85% from an urban sewage treatment plant. The amount of calcium oxide powder added is 18-22% of the dry weight of the sludge. In step (2), after heat exchange, the temperature of the sludge rises to 60-100℃, the temperature in the preheating tank (5) is 160-200℃, and the pressure is 2.5-3.5MPa. In step (3), the primary flash tank (601) and the secondary flash tank... The process of venting and depressurizing in the tank (603) is completed within 1-30 seconds. The temperature of the sludge in the hydrolysis reactor (602) is 160-200℃ and the residence time is 2-4 hours. In step (4), the condensate and soluble gas collected in the liquid collection tank (701) can be mixed with the hydrolysate discharged from the first-stage flash tank (601) and the second-stage flash tank (603) and used as liquid fertilizer. The insoluble gas collected in the gas collection tank (702) includes methane, which can be purified and used as fuel.

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