Sludge treatment process based on ultrasonic hydrothermal carbonization technology

Abstract

The invention discloses a sludge treatment process based on an ultrasonic hydrothermal carbonization technology. The sludge treatment process comprises the following steps: intercepting and filtering out large impurities in biological sludge; carrying out solid-liquid separation on the intercepted sludge, and carrying out concentration treatment on the sludge to obtain concentrated sludge; discharging the concentrated sludge into an ultrasonic hydrothermal carbonization reaction kettle, adding water to adjust the concentration of the concentrated sludge to 10-20%, starting an ultrasonic generator, adding a composite catalyst when the temperature in the ultrasonic hydrothermal carbonization reaction kettle reaches 50 DEG C and the pressure reaches 0.8 Mpa, and converting to generate carbon slurry; wherein the composite catalyst is prepared from ferric oxide, platinum and activated carbon according to a preset proportion; carrying out primary solid-liquid separation on the carbonaceous slurry, separating solid-phase carbon mud and liquid-phase carbon mud in the sludge suspension, and carrying out filter pressing on the solid-phase carbon mud to obtain a mud cake; and drying the mud cake, and granulating in a granulator to obtain the hydrothermal carbon granules. According to the sludge treatment process based on the ultrasonic hydrothermal carbonization technology, the sludge treatment difficulty can be effectively reduced, and the sludge can be quickly treated.

Description

Technical Field

[0001] The invention relates to the technical field of sludge treatment, and in particular to a sludge treatment process based on ultrasonic hydrothermal carbonization technology. Background Art

[0002] With the sustained, rapid and stable economic development, the scale of urban sewage treatment is increasing, and the sludge production is also increasing accordingly. However, the phenomenon of "heavy water and light sludge" is widespread and serious. Sludge treatment has not been improved synchronously with sewage treatment, and the problem of sludge treatment and disposal has not been effectively solved. The situation is very serious. Among them, sewage treatment has a huge demand for sludge treatment, and because the sludge treatment process requires a lot of energy and funds, the cost of sludge treatment is very high.

[0003] Traditional sludge treatment methods are mainly landfill and incineration. Landfill will cause geological disasters, waste of land resources, and emit large amounts of greenhouse gases such as methane, causing serious environmental pollution; incineration will produce toxic and harmful substances such as sulfur dioxide, nitrogen oxides and dioxins, causing great harm to the environment and human health.

[0004] In order to solve the problems caused by traditional sludge treatment methods, new sludge treatment processes have emerged. For example, the biological solidification process can solidify the sludge to form a building material with mechanical strength and stability. However, the new sludge treatment process also has some problems, mainly the difficulty of treatment, the complex treatment process, the long treatment cycle and the high treatment cost. Therefore, it is very necessary to study a relatively simple, convenient and effective sludge treatment process. Summary of the invention

[0005] The embodiment of the present application provides a sludge treatment process based on ultrasonic hydrothermal carbonization technology, which can effectively reduce the difficulty of sludge treatment, quickly treat sludge, have a short treatment cycle, low treatment cost, and the sludge treatment product has strong availability.

[0006] The present application embodiment provides a sludge treatment process based on ultrasonic hydrothermal carbonization technology, which is used to treat biological liquid sludge, wherein the treatment process mainly includes the following steps:

[0007] S10, intercepts and removes large debris in biological sludge;

[0008] S20, performing solid-liquid separation on the sludge after the interception and filtration of large debris, and then concentrating the separated sludge to obtain concentrated sludge;

[0009] S30, discharging the concentrated sludge into an ultrasonic hydrothermal carbonization reactor, adding water to adjust the concentration of the concentrated sludge to 10%-20%, turning on the ultrasonic generator, and adding a composite catalyst when the temperature in the ultrasonic hydrothermal carbonization reactor reaches 50°C and the pressure reaches 0.8Mpa to convert it into a carbonaceous sludge, wherein the composite catalyst is composed of iron oxide, platinum and activated carbon in a predetermined ratio;

[0010] S40, performing preliminary solid-liquid separation on the carbonaceous sludge to separate the solid carbon sludge and the liquid phase in the sludge suspension, wherein the solid carbon sludge is filtered to obtain a sludge cake;

[0011] S50, drying the mud cake, and then granulating it in a granulator to obtain hydrothermal carbon particles.

[0012] In one possible implementation, in step S10, large debris is intercepted and filtered out by a grid funnel, wherein the grid spacing is 5-10 mm, wherein the upper portion of the grid funnel is a mechanical grid composed of one or more groups of parallel metal bars, and the lower portion of the grid funnel is provided with a pneumatic lock chamber, using compressed air as a power source.

[0013] In a possible implementation, step S20 is specifically as follows: the sludge from which large debris is intercepted and filtered out is discharged into a flotation thickening tank, in which tiny bubbles are attached to the sludge particles so as to force the sludge particles to float upward, and at the same time, the flotation thickening tank is axially stirred from bottom to top by the stirring shaft to separate the solid and liquid, wherein the separated sludge is concentrated to obtain concentrated sludge, and the separated liquid enters the sewage treatment plant for treatment.

[0014] In a possible implementation, in step S30, the operating frequency of the ultrasonic generator is 20-100kHz, the power is 200-1000W, the processing time is 10-30min, and the ratio of the composite catalyst is: 15-25 parts of iron oxide, 8-12 parts of platinum, and 25-35 parts of activated carbon, by mass.

[0015] In a possible implementation, in step S30, the water environment for converting and generating carbonaceous mud is: the power of the ultrasonic generator is 300-1000W, the temperature is 180°C-250°C, and the pressure is 2-5MPa.

[0016] In one possible implementation, in step S40, the carbonaceous slurry is subjected to preliminary solid-liquid separation by a horizontal screw sedimentation centrifuge, wherein the solid phase carbon sludge is filtered into a cake by a plate and frame filter press, and the liquid phase is collected by a filtrate tank, and a part of the collected filtrate is used for ultrasonic hydrothermal carbonization reactor, and the other part is discharged to a sewage treatment plant for treatment.

[0017] In a possible implementation, in step S50, the mud cake is dried by a paddle dryer, wherein the paddle dryer dries the mud cake by conductive heating, wherein the paddle dryer is provided with a hollow rotating shaft, and the hollow rotating shaft is densely covered with wedge-shaped hollow blades, and a heat medium flows through the hollow rotating shaft through the wedge-shaped hollow blades, and the mud cake is stirred by the hot surface of the wedge-shaped hollow blades.

[0018] In a possible implementation, in step S50, a flocculant and a binder are added during the granulation process of the granulator, the granulation time is 10-30 minutes, and the particle size of the hydrothermal carbon particles is 3-15 mm.

[0019] Beneficial effects: Compared with the prior art, the sludge treatment process based on ultrasonic hydrothermal carbonization technology provided by the present application adopts a multi-stage collaborative treatment mode. From sludge collection, pretreatment, ultrasonic enhancement, hydrothermal carbonization reaction to solid-liquid separation and drying granulation, each stage is closely coordinated, which can greatly improve the sludge treatment efficiency, short treatment cycle, low treatment difficulty, and at the same time, the various equipment involved in the treatment process can be integrated in the same container, which can maximize the use efficiency of the treatment process. It has the significant advantages of being simple, effective, portable and recyclable, and is particularly suitable for sludge treatment problems with flexible deployment, strong temporaryity and strong mobility;

[0020] The special composite catalyst ratio can ensure that the organic matter in the sludge can quickly undergo a series of reactions such as hydrolysis, condensation, and carbonization under the ultrasonic enhancement, high temperature and high pressure water environment, and finally be converted into carbonaceous sludge. At the same time, the final hydrothermal carbon particles have excellent performance in terms of solid carbon content, ash content, specific surface area, copper ion adsorption performance and other indicators.

[0021] These and other objects, features and advantages of the present invention will be fully reflected in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The schematic diagram of the process of sludge treatment based on ultrasonic hydrothermal carbonization technology of the present application is shown. DETAILED DESCRIPTION

[0023] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art can think of other obvious variations. The basic principles of the present invention defined in the following description can be applied to other embodiments, variations, improvements, equivalents, and other technical solutions that do not deviate from the spirit and scope of the present invention.

[0024] Those skilled in the art should understand that, in the disclosure of the specification, the orientation or position relationship indicated by the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the orientation or position relationship shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0025] It is to be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the element may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0026] refer to Figure 1 The present invention provides a sludge treatment process based on ultrasonic hydrothermal carbonization technology for treating biological liquid sludge, wherein the treatment process mainly includes the following steps:

[0027] S10, intercepting and filtering out large pieces of debris in biological sludge, wherein the biological sludge may come from a sewage treatment plant, is a product of sewage treatment, is a heterogeneous body mainly composed of organic debris, bacterial cells, inorganic particles, colloids, etc., has a high organic matter content, is easy to rot and stink, and has fine particles, a small specific gravity, and is in a colloidal liquid state with a water content of more than 85%. The large pieces of debris can be intercepted and filtered out by a grid funnel, wherein the grid spacing is 5-10mm, and the spacing can also be adaptively adjusted according to actual needs, wherein the grid The upper part of the funnel is a mechanical grid, which is composed of one or more groups of parallel metal bars. It is mainly used to intercept large debris such as branches and plastics in the sludge to achieve the pretreatment process. The lower part of the grid funnel is provided with a pneumatic lock chamber, which uses compressed air as the power source. The pneumatic actuator in the pneumatic lock chamber controls the lifting and lowering of the internal gate, thereby realizing the opening and closing operation of the valve, which can realize remote control and automatic operation. The grid funnel that receives the sludge is equipped with an ultrasonic level meter, which can alarm when it is at a low level to ensure the stable delivery of sludge raw materials;

[0028] S20, performing solid-liquid separation on the sludge after the interception and filtration of large debris, and then concentrating the separated sludge to obtain concentrated sludge; specifically: the sludge after the interception and filtration of large debris is discharged into an air flotation concentrating tank, a large number of tiny bubbles in the air flotation concentrating tank are attached to the sludge particles, so that the bubbles and the sludge are fully mixed, the particle specific gravity is reduced, and the sludge particles are forced to float, thereby achieving solid-liquid separation, and at the same time, the stirring shaft of the air flotation concentrating tank is axially stirred from bottom to top through the spiral auger blade, wherein the separated sludge is concentrated to obtain concentrated sludge, wherein the water content of the concentrated sludge is about 75%, and the separated liquid enters the sewage treatment plant for treatment;

[0029] S30, discharge the concentrated sludge into the ultrasonic hydrothermal carbonization reactor, add water to adjust the concentration of the concentrated sludge to 10%-20%, turn on the ultrasonic generator, the working frequency of the ultrasonic generator is 20-100kHz, the power is 200-1000W, the processing time is 10-30min, and at the same time, when the temperature in the ultrasonic hydrothermal carbonization reactor reaches 50°C and the pressure reaches 0.8Mpa, add the composite catalyst, the ratio of the composite catalyst is: by mass, 15-25 parts of iron oxide (Fe2O3), 8-12 parts of platinum (Pt), and 25-35 parts of activated carbon. Under this special composite catalyst ratio and water environment, organic matter such as biomass in the sludge will quickly undergo a series of reactions such as hydrolysis, condensation, and carbonization to transform into carbonaceous mud;

[0030] S40, the carbonaceous slurry is subjected to preliminary solid-liquid separation by a horizontal screw sedimentation centrifuge to separate the solid carbon sludge and the liquid phase in the sludge suspension. Specifically, after the suspension enters the drum of the horizontal screw sedimentation centrifuge, under the centrifugal force generated by high-speed rotation, the solid phase particles with high density settle to the drum wall, and the liquid phase with low density forms an inner liquid ring and is discharged through the overflow port or feed pipe on the drum, which is the liquid phase. The screw pusher pushes the solid phase particles settled on the drum wall to the slag discharge port at the small end of the drum for discharge, which is the solid carbon sludge; wherein the plate and frame filter press is used The solid phase carbon sludge is filtered into a cake to obtain a mud cake. When the plate and frame filter press is in operation, the plates and frames cooperate with each other to generate a strong squeezing force, forcing the water in the sludge to penetrate the filter cloth. The solid particles cannot pass through the filter cloth and gradually accumulate in the filter chamber to eventually form a filter cake. The moisture content of the filter cake is maintained at about 30%, which can efficiently treat the sludge and significantly reduce the moisture content of the mud cake. The liquid phase is collected by the filtrate tank, and part of the collected filtrate is used for the ultrasonic hydrothermal carbonization reactor, and the other part is discharged to the sewage treatment plant for treatment and reaches the discharge standard after purification.

[0031] S50, conveying the mud cake to a paddle dryer for drying, wherein the paddle dryer dries the mud cake by conduction heating, wherein the paddle dryer is provided with a hollow shaft, the hollow shaft is densely covered with wedge-shaped hollow paddles, the heat medium flows through the wedge-shaped hollow paddles through the hollow shaft, and the mud cake is stirred by the hot surface of the wedge-shaped hollow paddles, the wedge-shaped hollow paddles are in full contact with the sludge, the thermal efficiency is higher, the energy consumption is low, the cost is low, the operation is simple, the maintenance is easy, the sludge with high humidity and high viscosity can be effectively treated, and the drying effect is good; then the dried mud cake is granulated in a granulator, and the rotation of the disc is utilized. When the disc diameter, the inclination angle and the rotation speed are constant, the aperture or gap size of the granulator mold determines the initial size of the particles, the smaller the aperture, the smaller the particles, and the larger the aperture, the larger the particles, so that the material can roll and agglomerate into particles in the disc under the action of centrifugal force, friction and gravity, so as to obtain hydrothermal carbon particles.

[0032] In one embodiment, in step S30, the water environment for converting to generate carbonaceous mud is: the power of the ultrasonic generator is 300-1000W, the temperature is 180°C-250°C, and the pressure is 2-5MPa.

[0033] In one embodiment, in step S50, flocculants and binders are added during the granulation process of the granulator to promote the coagulation of sludge particles, while also making the particles more uniform and having a good molding effect. The granulation time is 10-30 minutes, and the particle size of the hydrothermal carbon particles is 3-15 mm, wherein the flocculant is a conventional agent in the field of water treatment.

[0034] The sludge carbonization product obtained through this treatment process, namely hydrothermal carbon particles, can be returned to the source of sewage treatment, realizing the circularity of the entire process, that is, recycling. Hydrothermal carbon has rich pore structure and surface functional groups, and can adsorb heavy metal ions in sewage, such as lead, mercury, cadmium, etc., through ion exchange and complexation. For organic pollutants in sewage, such as dyes and phenols, hydrothermal carbon can absorb heavy metal ions such as lead, mercury, cadmium, etc., with its large specific surface area (100-500m 2 / g) and hydrophobic effects. After ultrasonic hydrothermal carbonization reaction, the carbon content of hydrothermal carbon is significantly increased relative to the raw material, up to 50%-70%. It has good carbon material properties and better adsorption and catalytic effects. It can also be used as a catalyst or microbial carrier to provide a good living environment and a place for nutrient exchange for microorganisms, promote the metabolic activities of microorganisms, and improve their ability to degrade pollutants. It can also be used as solid fuel, soil conditioner, etc., which can effectively improve the utilization efficiency of sludge and reduce dependence on traditional energy.

[0035] In the specific implementation process, the same batch of biological sludge with a moisture content of 80% was used as the test object to ensure the consistency of the carbonization process. The frequency of the ultrasonic generator was set to 80kHz, the power was 400W, and the treatment time was 25min. According to the addition ratio of the composite catalyst, the experimental group and the control group were set in terms of mass fraction as follows:

[0036] Test group 1: 15 parts of iron oxide (Fe2O3), 8 parts of platinum (Pt), and 25 parts of activated carbon;

[0037] Test group 2: 15 parts of iron oxide (Fe2O3), 8 parts of platinum (Pt), and 35 parts of activated carbon;

[0038] Test group 3: 15 parts of iron oxide (Fe2O3), 12 parts of platinum (Pt), and 25 parts of activated carbon;

[0039] Test group 4: 15 parts of iron oxide (Fe2O3), 12 parts of platinum (Pt), and 35 parts of activated carbon;

[0040] Test group 5: 25 parts of iron oxide (Fe2O3), 8 parts of platinum (Pt), and 25 parts of activated carbon;

[0041] Test group 6: 25 parts of iron oxide (Fe2O3), 8 parts of platinum (Pt), and 35 parts of activated carbon;

[0042] Test group 7: 25 parts of iron oxide (Fe2O3), 12 parts of platinum (Pt), and 25 parts of activated carbon;

[0043] Test group 8: 25 parts of iron oxide (Fe2O3), 12 parts of platinum (Pt), and 35 parts of activated carbon;

[0044] Control group: 0 part of iron oxide (Fe2O3), 0 part of platinum (Pt), and 0 part of activated carbon;

[0045] The results of the biochar produced by the above 8 experimental groups and 1 blank control group were analyzed, with solid carbon content, ash content, specific surface area, and copper ion adsorption as the result evaluation indicators. The data results are shown in the following table:

[0046]

[0047] There is no absolutely unified best indicator for the evaluation of hydrothermal carbon. The above four indicators involve three aspects, namely the chemical properties, physical properties and adsorption performance of hydrothermal carbon.

[0048] Among them, solid carbon content and ash content are used as indicators of chemical properties. Generally, it is hoped that the fixed carbon content reaches more than 40% to improve its value as a fuel or adsorbent.

[0049] The ash content should be as low as possible, generally less than 30%, to reduce adverse effects on subsequent applications;

[0050] Specific surface area is an indicator of physical properties and usually reaches 100-500m 2 / g or more, the sludge carbon can have good adsorption performance;

[0051] The adsorption capacity of copper ions is used as an indicator of adsorption performance. It is generally hoped that the adsorption capacity of copper ions can reach 30-80 mg / g or above.

[0052] Through the analysis of the data results in the above table, it was found that under the conditions of ultrasonic frequency of 80kHz, power of 400W and treatment for 25min, the 8 test groups with the addition of composite catalysts had better chemical, physical and adsorption performance than the control group without any catalyst. Especially for test group 6, when 25 parts of iron oxide (Fe2O3), 8 parts of platinum (Pt) and 35 parts of activated carbon were added, the solid carbon content, ash content, specific surface area and copper ion adsorption performance were relatively better.

[0053] On the basis of test group 6 (adding composite catalyst and turning on ultrasonic generator), control group 2 and control group 3 were set up, where control group 2 added composite catalyst (mass fraction as test group 6) and turned off ultrasonic generator, and control group 3 did not add composite catalyst and turned off ultrasonic generator. The results of the biochar produced were analyzed, with solid carbon content, ash content, specific surface area, and copper ion adsorption as the evaluation indicators. The data results are shown in the following table:

[0054]

[0055] Through the analysis of the data results in the above table, it is found that compared with the control group 2 without ultrasound and only adding catalyst and the control group 3 without ultrasound and without catalyst, the experimental group 6 with both ultrasound and catalyst performed better. Under the parameter conditions of ultrasound frequency of 80kHz, power of 400W, treatment of 25min and addition of composite catalyst iron oxide (Fe2O3) 25 parts, platinum (Pt) 8 parts, and activated carbon 35 parts, the performance was more obvious, reflecting the important role of ultrasound and catalyst in increasing fixed carbon content, reducing ash content, optimizing pore structure and specific surface area, and enhancing the adsorption and catalytic properties of carbonization products. By changing the parameters, the performance of the carbonization product can be adjusted to make it more in line with the needs of different application fields, such as preparing activated carbon materials with specific functions for water treatment, gas purification and other fields.

[0056] It should be noted that the terms "first, second" in the present application are only used for descriptive purposes and do not indicate any order. They cannot be understood as indicating or implying relative importance. These terms can be interpreted as names.

[0057] It should be understood by those skilled in the art that the embodiments of the present invention described above and shown in the accompanying drawings are only examples and do not limit the present invention. The advantages of the present invention have been fully and effectively achieved. The functional and structural principles of the present invention have been demonstrated and explained in the embodiments, and the embodiments of the present invention may be deformed or modified in any way without departing from the principles.

Claims

1. A sludge treatment process based on ultrasonic hydrothermal carbonization technology for treating biological liquid sludge, characterized in that: The following steps are involved: S10, intercepts and removes large debris in biological sludge; S20, performing solid-liquid separation on the sludge after the interception and filtration of large debris, and then concentrating the separated sludge to obtain concentrated sludge; S30, discharging the concentrated sludge into an ultrasonic hydrothermal carbonization reactor, adding water to adjust the concentration of the concentrated sludge to 10%-20%, turning on the ultrasonic generator, and adding a composite catalyst when the temperature in the ultrasonic hydrothermal carbonization reactor reaches 50°C and the pressure reaches 0.8Mpa to convert it into a carbonaceous sludge, wherein the composite catalyst is composed of iron oxide, platinum and activated carbon in a predetermined ratio; S40, performing preliminary solid-liquid separation on the carbonaceous sludge to separate the solid carbon sludge and the liquid phase in the sludge suspension, wherein the solid carbon sludge is filtered to obtain a sludge cake; S50, drying the mud cake, and then granulating it in a granulator to obtain hydrothermal carbon particles.

2. The sludge treatment process based on ultrasonic hydrothermal carbonization technology according to claim 1, characterized in that: In step S10, large debris is intercepted and filtered out by a grid funnel, wherein the grid spacing is 5-10 mm, wherein the upper part of the grid funnel is a mechanical grid composed of one or more groups of parallel metal bars, and the lower part of the grid funnel is provided with a pneumatic lock chamber, using compressed air as a power source.

3. The sludge treatment process based on ultrasonic hydrothermal carbonization technology according to claim 1, characterized in that: Step S20 specifically includes discharging the intercepted and filtered sludge with large debris into a flotation thickening tank, wherein tiny bubbles in the flotation thickening tank are attached to the sludge particles, forcing the sludge particles to float upward, and at the same time, the flotation thickening tank is axially stirred from bottom to top by the stirring shaft to separate the solid and liquid, wherein the separated sludge is concentrated to obtain concentrated sludge, wherein the separated liquid enters the sewage treatment plant for treatment.

4. The sludge treatment process based on ultrasonic hydrothermal carbonization technology according to claim 1, characterized in that: In step S30, the operating frequency of the ultrasonic generator is 20-100kHz, the power is 200-1000W, the processing time is 10-30min, and the ratio of the composite catalyst is: 15-25 parts of iron oxide, 8-12 parts of platinum, and 25-35 parts of activated carbon, by mass.

5. The sludge treatment process based on ultrasonic hydrothermal carbonization technology according to claim 4, characterized in that: In step S30, the water environment for converting into carbonaceous mud is: the power of the ultrasonic generator is 300-1000W, the temperature is 180°C-250°C, and the pressure is 2-5MPa.

6. The sludge treatment process based on ultrasonic hydrothermal carbonization technology according to claim 1, characterized in that: In step S40, the carbonaceous slurry is subjected to preliminary solid-liquid separation by a horizontal screw sedimentation centrifuge, wherein the solid phase carbon sludge is filtered into a cake by a plate and frame filter press, and the liquid phase is collected by a filtrate tank, and a part of the collected filtrate is used for ultrasonic hydrothermal carbonization reactor, and the other part is discharged to a sewage treatment plant for treatment.

7. The sludge treatment process based on ultrasonic hydrothermal carbonization technology according to claim 1, characterized in that: In step S50, the mud cake is dried by a paddle dryer, wherein the paddle dryer dries the mud cake by conductive heating, wherein the paddle dryer is provided with a hollow rotating shaft, on which wedge-shaped hollow blades are densely distributed, and a heat medium flows through the hollow rotating shaft through the wedge-shaped hollow blades, and the mud cake is stirred by the hot surface of the wedge-shaped hollow blades.

8. The sludge treatment process based on ultrasonic hydrothermal carbonization technology according to claim 1 or 7, characterized in that: In step S50, flocculants and binders are added during the granulation process of the granulator, the granulation time is 10-30 minutes, and the particle size of the hydrothermal carbon particles is 3-15 mm.

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