Sludge treatment process and device based on flash evaporation

Abstract

The invention relates to a sludge treatment process and device based on flash evaporation, and the device comprises a first-stage flash evaporation system, and also comprises any one of a hydrolysis tank and a second-stage flash evaporation system. According to the method, the sludge is subjected to resourceful treatment in a flash evaporation and pyrohydrolysis and / or secondary flash evaporation mode, cell walls in the sludge can be fully and effectively broken under the low-temperature condition through the flash evaporation technology, moisture and solutes in cells are released, the dewatering performance of the sludge is improved, and the sludge can be recycled. The wall-broken sludge is conveyed to the hydrolysis tank for hydrolysis and / or the second flash evaporation tank for flash evaporation and drying, and the wall-broken sludge is more easily hydrolyzed and / or dried. The problems of high energy consumption, large heat loss and long treatment time in the sludge drying process are solved, and the productivity is greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of sludge treatment, and in particular relates to a sludge treatment process and device based on flash evaporation. Background Art

[0002] With the acceleration of urbanization and the development of industrialization, the sludge output of sewage treatment plants is increasing. Sludge contains a large amount of organic matter, heavy metals, pathogenic microorganisms and other harmful substances. If the sludge is not properly treated and disposed of, it will cause serious harm to the environment and human health, and will also cause waste of resources and economic losses. Sludge hydrolysis, as a sludge treatment technology, can decompose the complex organic matter in the sludge into small molecular organic matter, and in the hydrolysis process, it can destroy the cell structure of the sludge, release the water in the cells, reduce the water content of the sludge, and significantly improve the dewatering performance and subsequent treatment effect of the sludge. Therefore, it has received widespread attention. However, the current sludge hydrolysis and subsequent dehydration process usually require a long reaction time and low treatment efficiency. In order to maintain a suitable reaction temperature and environment, a large amount of energy is often consumed. The operation and maintenance of the hydrolysis and subsequent dehydration equipment are relatively complicated and labor-intensive. Therefore, it is of great significance to develop a process with low energy consumption and high efficiency. Summary of the invention

[0003] The present invention aims to provide a sludge treatment device based on flash evaporation, which adopts flash evaporation technology to improve the sludge hydrolysis and drying efficiency, and can solve the technical problems of low sludge treatment efficiency and high energy consumption in the prior art.

[0004] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0005] A sludge flash thermal hydrolysis drying process comprises the following steps:

[0006] Step 1, heating the sludge;

[0007] Step 2, the heated sludge is subjected to a first-stage flash evaporation, which uses negative pressure to remove part of the water and break the microbial cells; the steam after the flash evaporation is subjected to a first pressure relief condensation treatment, and the uncondensed part is returned to step 1 for further heating treatment;

[0008] Step 3, the sludge obtained by the primary flash evaporation treatment is subjected to hydrolysis treatment or secondary flash evaporation treatment.

[0009] When step 3 uses a hydrolysis tank for hydrolysis treatment: in step 1, the heating treatment temperature is greater than 50°C and the insulation is greater than 0.1h, in step 2, the pressure in the first-stage flash evaporation system is 0.05-0.08MPa; the sludge heating temperature during hydrolysis is greater than 50°C and the insulation is greater than 0.1h.

[0010] When step 3 adopts a two-stage flash evaporation system for secondary flash evaporation treatment: in step 1, the temperature of the heating treatment is greater than 50°C; in step 2, the pressure in the first-stage flash evaporation system is 0.05-0.08MPa; and the pressure in the second-stage flash evaporation system is 0.06-0.09MPa.

[0011] After the sludge is heated, the interior of the equipment for primary flash evaporation is negatively pressurized, so that the sludge is transported to the equipment for primary flash evaporation in the form of a jet through the siphon effect formed by the pressure difference.

[0012] A flash evaporation-based sludge treatment device includes a primary flash evaporation system and also includes any one of a hydrolysis tank or a secondary flash evaporation system;

[0013] The primary flash evaporation system is used to flash sludge;

[0014] The hydrolysis tank is used to hydrolyze the sludge after being treated by the primary flash evaporation system;

[0015] The secondary flash evaporation system is used to flash dry the sludge treated by the primary flash evaporation system;

[0016] The primary flash evaporation system and the secondary flash evaporation system are respectively connected with negative pressure equipment for generating negative pressure in the flash evaporation system.

[0017] It also includes: a first pressure relief tank and / or a second pressure relief tank, which are respectively connected to the primary flash evaporation system and the secondary flash evaporation system, and are respectively used to perform pressure relief treatment on the steam generated by the primary flash evaporation system and the secondary flash evaporation system.

[0018] It also includes: a first sludge heating tank and / or a second sludge heating tank, which are respectively connected to the primary flash evaporation system and the secondary flash evaporation system, and are respectively used to heat the sludge entering the primary flash evaporation system and the secondary flash evaporation system.

[0019] At least part of the area on the pipeline between the first sludge heating tank and the primary flash evaporation system, and / or between the second sludge heating tank and the secondary flash evaporation system is provided with water inlet holes, and a sleeve is provided on the outside to form a cavity between the sleeve and the pipeline, and the cavity is connected to the water inlet pipeline.

[0020] The non-condensable gas outlet of the first pressure relief tank is connected to the primary flash evaporation system, and the condensate in the second pressure relief tank is discharged through the discharge port.

[0021] A screen is provided inside the first flash evaporation system and / or the second flash evaporation system to prevent sludge from entering the pressure relief tank; a pressure gauge is also provided in the first flash evaporation system and the second flash evaporation system respectively.

[0022] The hydrolysis tank is provided with a steam release valve.

[0023] Beneficial Effects

[0024] (1) In the sludge treatment method of the present invention, flash evaporation treatment is utilized to effectively improve the sludge treatment efficiency. At the same time, high temperature disinfection and cell wall breaking of microorganisms in the sludge can release water and solutes in the cells, improve the dehydration performance of the sludge, and then flash evaporation dehydration is performed to achieve the harmlessness, volume reduction, and resource utilization of the sludge. The sludge flash evaporation drying process has a simple structure, simple operation, low energy consumption, small footprint, high degree of automation control, rapidity and high efficiency, and is suitable for sludge treatment in municipalities, sewage treatment plants, etc. (2) Through the cell wall breaking effect, the volume of the sludge can be significantly reduced, which helps to reduce the cost of subsequent treatment and disposal; during the flash evaporation process, the flash evaporation waste heat can be effectively recovered.

[0025] (3) After the cell wall is broken, the organic matter in the sludge is more easily degraded, reducing the amount of odor and pathogens, thereby improving the stability of the sludge.

[0026] (4) Due to the setting of air pressure, the sludge can flow between different structures by controlling the air pressure difference, without the need for conveying equipment, thus saving overall operating energy consumption; and through the action of the negative pressure device, the continuity of the negative pressure state during the treatment process can be guaranteed.

[0027] (5) The sludge after wall breaking is easier to hydrolyze, thus saving energy consumption in the hydrolysis process; after hydrolysis, the sludge changes from solid to liquid.

[0028] (6) After drying, the volume and mass of the sludge are greatly reduced. The sludge becomes more stable, easier to package and transport, and can be reused as fertilizer, fuel or building material. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the process flow of the present invention.

[0030] Figure 2 It is a structural schematic diagram of the present invention.

[0031] The numbers in the figure represent: 1. discharge port; 2. heating tank body; 3. first stirring blade; 4. integrated control mechanism; 5. supporting mechanism; 6. stirring motor; 7. stirring shaft; 8. second stirring blade; 9. discharge port; 10. pipeline; 11. supporting mechanism; 12. feed port; 13. flash tank; 14. screen; 15. steam vent; 16. discharge port; 17. vacuum pump; 18. pipeline; 19. pipeline; 20. air inlet; 21. pressure relief tank; 22. discharge port; 23. supporting mechanism; 24. stirring motor; 25. hydrolysis tank; 26. first stirring blade; 27. stirring shaft; 28. discharge port; 29. ​​supporting mechanism; 30. integrated control mechanism; 31. double sleeve. DETAILED DESCRIPTION

[0032] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0033] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0034] like Figure 1 A sludge flash drying process is shown, wherein the flash system comprises a primary flash system, a hydrolysis tank and / or a secondary flash system.

[0035] Example 1 Flash thermal hydrolysis treatment

[0036] like Figure 2 As shown. The specific operation steps are: first, add the sludge to the first sludge heating tank for preheating, set the preheating temperature to 90°C, and the speed to 150rmp. At the same time, turn on the vacuum pump connected to the flash tank, keep the first-stage flash system at room temperature, and make the pressure in the first-stage flash system reach 0.06MPa. When the sludge is heated to 90°C, open the throttle valve between the first sludge heating tank and the vacuum pump, and send the sludge in the sludge heating tank to the flash tank for flash evaporation through siphon action. Before the sludge enters the flash tank from the sludge heating tank, it is also transported by a double sleeve. The inner tube of the double sleeve is a sludge delivery pipe, and the outer tube is a negative pressure water pipe. There is a cavity between the inner tube and the outer tube. The surface of the outer tube is provided with a water inlet and a pressure valve. The flow rate of water from the outer tube into the inner tube is achieved by controlling the pressure valve. During transportation, the sludge moves forward in the sludge pipe, passes through the cavity between the inner and outer pipes, and the pressurized water flows from the outer pipe into the inner pipe from the cavity, moistening the sludge surface, forming a water film on the sludge surface, and reducing the adhesion between the sludge and the inner wall of the sludge pipe. During the flash evaporation process, the throttle valve between the primary flash evaporation system and the first pressure relief tank is opened to discharge the large amount of steam generated through the pipeline into the first pressure relief tank.

[0037] The sludge in the primary flash system is pumped into the hydrolysis tank, and at the same time, the high-temperature steam in the first pressure relief tank is discharged into the hydrolysis tank as a heat source. The hydrolysis process here adopts the hot water hydrolysis method, and the working temperature of the hydrolysis tank is set to 120℃ and the speed is 150rmp. When the temperature rises to 120℃, it is kept warm for 30 minutes, and then the steam relief valve on the hydrolysis tank is opened to release steam, and finally the sludge is discharged.

[0038] In this embodiment, the sludge used comes from a sewage treatment plant in Nanjing. Its basic parameters, sludge property parameters after flash evaporation, and property parameters after hydrolysis are shown in the following table.

[0039] Basic parameters Raw sludge Flash steam wall breaking High temperature hydrolysis SS(%) 65.35 38.12 28.43 VSS(%) 65.82 48.31 29.53 COD(mg / L) 69840 84350 97120

[0040] Example 2: Secondary flash distillation

[0041] The sludge in the sludge storage tank is transported to the first sludge heating tank through the sludge conveying device. The operating temperature of the first sludge heating tank is set to 90℃ and the stirring shaft speed is set to 100rmp through the control mechanism, and the temperature starts to rise. At the same time, the throttle valve between the first sludge heating tank and the primary flash evaporation system and between the primary flash evaporation system and the first pressure relief tank is closed, and the vacuum pump connected to the primary flash evaporation system is opened to reduce the pressure in the primary flash evaporation system to 0.06MPa. The sludge temperature in the first sludge heating tank is observed by the detection mechanism. When the temperature rises to 90℃, the heating is stopped immediately, and the throttle valve between the first sludge heating tank and the primary flash evaporation system is opened. The sludge in the heating tank is ejected through the pipeline jet to the primary flash evaporation system for flash evaporation; after opening the throttle valve between the first sludge heating tank and the primary flash evaporation system, the throttle valve between the primary flash evaporation system and the first pressure relief tank is immediately opened to discharge a large amount of water vapor in the primary flash evaporation system to the first pressure relief tank. After the first-stage flash evaporation wall breaking is completed, the sludge in the first flash evaporation system is transported to the second sludge heating tank through the sludge pump, and the hot steam in the first pressure relief tank is refluxed to the first sludge heating tank as a heat source. The operating temperature of the second sludge heating tank is set to 100°C by the control mechanism, and the speed of the stirring shaft is 100rmp, and the temperature starts to rise. At the same time, the throttle valve between the second sludge heating tank and the secondary flash evaporation system and between the secondary flash evaporation system and the second pressure relief tank is closed, and the vacuum pump connected to the secondary flash evaporation system is opened to reduce the pressure in the secondary flash evaporation system to 0.08MPa. The sludge temperature in the second sludge heating tank is observed by the detection mechanism. When the temperature rises to 100°C, the heating is stopped immediately, the throttle valve between the second sludge heating tank and the secondary flash evaporation system is opened, and the sludge in the second sludge heating tank is ejected through the pipeline jet to the secondary flash evaporation system for flash evaporation. After opening the throttle valve between the second sludge heating tank and the secondary flash evaporation system, the throttle valve between the secondary flash evaporation system and the second pressure relief tank is immediately opened to discharge a large amount of water vapor in the flash tank to the pressure relief tank. After the secondary flash drying is completed, the sludge in the secondary flash system is discharged to the dry sludge pool, the high-temperature steam in the pressure relief tank flows back to the second sludge heating tank as a heat source, and the condensate is discharged. Water inlet holes are distributed on at least part of the pipeline between the first sludge heating tank and the primary flash system, and / or between the second sludge heating tank and the secondary flash system (for example, at the upstream position of the pipeline), and a sleeve is provided on the outside, a cavity is formed between the sleeve and the pipeline, and the cavity is connected to the water inlet pipeline. Before the sludge enters the flash tank from the sludge heating tank, it is transported through the double sleeve. Due to the negative pressure of the flash equipment, the sludge moves to the flash system through the siphon effect. Usually, due to the poor fluidity of the sludge, if water is added to dilute it to improve the fluidity, it will lead to an increase in energy consumption in the subsequent drying process. However, due to the openings on the sleeve, the water in the chamber can wet the outer surface of the sludge during the negative pressure siphon process, thereby improving its fluidity in the pipeline. Moreover, since the wetting only occurs on the wall, it will not cause excessive energy consumption in the subsequent drying process.

[0042] In this embodiment, the sludge used comes from a sewage treatment plant in Nanjing. Its basic parameters, sludge property parameters after primary treatment, and property parameters after secondary treatment are shown in the following table.

[0043] Basic parameters Raw sludge First-stage flash steam wall breaking Secondary flash drying SS(%) 65.35 37.66 29.39 COD / (mg / L) 69840 81460 85370

[0044] Comparative Example 1

[0045] This example compares flash hydrolysis with traditional high-temperature hot water hydrolysis. The sludge was placed in a high-pressure reactor and heated to 120°C for 2 hours. The results are shown in the following table. The traditional high-temperature hot water hydrolysis method does not pre-treat the cell walls in the sludge. The organic matter in the sludge is wrapped by the cell walls. The treatment process not only requires more energy and time, but also has poor treatment effects.

[0046] Basic parameters Raw sludge High temperature hydrolysis SS(%) 65.35 40.36 VSS(%) 65.82 42.71 COD(mg / L) 69840 78450

[0047] Comparative Example 2

[0048] This example investigates the effect of different flash pressures on the flash cell breaking effect. The difference between this example and Example 1 is that the negative pressure of the primary flash system is adjusted to 0.08 MPa, and the other parameters are the same. The results are shown in the following table. The results of the example show that when the negative pressure of the flash tank is 0.08 MPa, it will have an adverse effect on the cell wall breaking effect in the sludge. When the flash pressure is lower than 0.06 MPa, the energy required is relatively large, and the flash pressure of 0.06 MPa is the optimal processing pressure.

[0049] Basic parameters Raw sludge Flash steam wall breaking hydrolysis SS(%) 65.35 41.13 32.05 VSS(%) 65.82 43.11 32.79 COD(mg / L) 69840 72140 79510

[0050] Comparative Example 3

[0051] This example compares the flash drying method of sludge with the traditional flash drying method without wall breaking. The difference between this example and Example 2 is that the flash drying method does not undergo the first-stage flash evaporation, but directly adopts the second-stage flash evaporation. The other parameters are the same, and the results are shown in the following table. Although the traditional flash drying method has a certain dehydration effect on the sludge, the sludge moisture content is only reduced by 24.87%, while the second-stage flash drying method reduces the sludge moisture content by 35.96%.

[0052] Basic parameters Raw sludge Secondary flash drying SS(%) 65.35 40.48 COD(mg / L) 69840 80600

[0053] Comparative Example 4

[0054] This example investigates the effect of different temperatures of the second sludge heating tank on the flash evaporation wall breaking effect. The difference between this example and Example 2 is that the operating temperature of the second sludge heating tank is 80°C, and the other parameters are the same. The results are shown in the following table. The results of the example prove that when the temperature in the second sludge heating tank is too low, the heating tank cannot produce enough steam, resulting in low pressure in the heating tank, which in turn leads to a small pressure difference between the heating tank and the negative pressure flash tank, thereby causing less evaporation of water in the sludge.

[0055] Basic parameters Raw sludge First-stage flash steam wall breaking Secondary flash drying SS(%) 65.35 42.65 38.34 COD(mg / L) 69840 74320 77650

[0056] In general, although the secondary negative pressure flash treatment increases energy consumption, it improves the quality of sludge drying. You can choose the sludge treatment process of negative pressure flash thermal hydrolysis treatment or secondary negative pressure flash treatment to dry the sludge according to your needs. Both treatment methods have significant improvements in reducing energy consumption and improving efficiency of sludge treatment.

Claims

1. A sludge treatment process based on flash evaporation, characterized in that: The following steps are involved: Step 1, heating the sludge; Step 2, the heated sludge is subjected to a first-stage flash evaporation, which uses negative pressure to remove part of the water and break the microbial cells; the steam after the flash evaporation is subjected to a first pressure relief condensation treatment, and the uncondensed part is returned to step 1 for further heating treatment; Step 3, the sludge obtained by the primary flash evaporation treatment is subjected to hydrolysis treatment or secondary flash evaporation treatment.

2. The sludge treatment process based on flash evaporation according to claim 1, characterized in that: When step 3 uses a hydrolysis tank for hydrolysis treatment: in step 1, the heating treatment temperature is greater than 50°C and the insulation is greater than 0.1h, in step 2, the pressure in the first-stage flash evaporation system is 0.05-0.08MPa; the sludge heating temperature during hydrolysis is greater than 50°C and the insulation is greater than 0.1h.

3. The sludge treatment process based on flash evaporation according to claim 1, characterized in that: When step 3 adopts a two-stage flash evaporation system for secondary flash evaporation treatment: in step 1, the temperature of the heating treatment is greater than 50°C; in step 2, the pressure in the first-stage flash evaporation system is 0.05-0.08MPa; and the pressure in the second-stage flash evaporation system is 0.06-0.09MPa.

4. The sludge treatment process based on flash evaporation according to claim 1, characterized in that: After the sludge is heated, the interior of the equipment for primary flash evaporation is negatively pressurized, so that the sludge is transported to the equipment for primary flash evaporation in the form of a jet through the siphon effect formed by the pressure difference.

5. A sludge treatment device based on flash evaporation, characterized in that: including a primary flash system and also including either a hydrolysis tank or a secondary flash system; The primary flash evaporation system is used to flash sludge; The hydrolysis tank is used to hydrolyze the sludge after being treated by the primary flash evaporation system; The secondary flash evaporation system is used to flash dry the sludge treated by the primary flash evaporation system; The primary flash evaporation system and the secondary flash evaporation system are respectively connected with negative pressure equipment for generating negative pressure in the flash evaporation system.

6. The flash evaporation-based sludge treatment device according to claim 5, characterized in that: Also includes: The first pressure relief tank and / or the second pressure relief tank are respectively connected to the primary flash evaporation system and the secondary flash evaporation system, and are used for respectively performing pressure relief treatment on the steam generated by the primary flash evaporation system and the secondary flash evaporation system.

7. The flash evaporation-based sludge treatment device according to claim 5, characterized in that: It also includes: a first sludge heating tank and / or a second sludge heating tank, which are respectively connected to the primary flash evaporation system and the secondary flash evaporation system, and are respectively used to heat the sludge entering the primary flash evaporation system and the secondary flash evaporation system.

8. The flash evaporation-based sludge treatment device according to claim 5, characterized in that: At least part of the area on the pipeline between the first sludge heating tank and the primary flash evaporation system, and / or between the second sludge heating tank and the secondary flash evaporation system is provided with water inlet holes, and a sleeve is provided on the outside to form a cavity between the sleeve and the pipeline, and the cavity is connected to the water inlet pipeline.

9. The flash evaporation-based sludge treatment device according to claim 5, characterized in that: The non-condensable gas outlet of the first pressure relief tank is connected to the primary flash evaporation system, and the condensate in the second pressure relief tank is discharged through the discharge port.

10. The flash evaporation-based sludge treatment device according to claim 5, characterized in that: The first flash evaporation system and / or the second flash evaporation system is provided with a screen inside to prevent sludge from entering the pressure relief tank; the first flash evaporation system and the second flash evaporation system are also provided with a pressure gauge respectively; the hydrolysis tank is provided with a steam relief valve.

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