Method and system for mechanical drying of sludge at normal temperature, and two-stage system for dewatering and mechanical drying of sludge at normal temperature comprising said system

Abstract

The present application relates to a method and system for mechanical drying of sludge at normal temperature, and a two-stage system for dewatering and mechanical drying of sludge at normal temperature comprising said system. The method for mechanical drying of sludge at normal temperature comprises the following steps: step one, uniformly mixing sludge to be dried with an auxiliary material having a drainage effect in an amount of 3-10% by weight of the sludge to be dried, so that the auxiliary material completely adheres to the surface of the particles of the sludge to be dried; and step two, in a mechanical sludge drying device, performing pressure filtration on the sludge auxiliary material mixture treated in step one. Within a set pressure filtration time period, the operating pressure is gradually increased from an initial pressure until the pressure reaches a maximum set pressure of at least greater than 1.5 Mpa / cm^2. Compared with the existing sludge drying processes that require the consumption of a large amount of auxiliary heat sources, the present application can completely release the moisture inside sludge particles, greatly reducing the moisture content of the sludge; and mechanical drying of the sludge is achieved without the need for drying by a heat source, resulting in low energy consumption, simple operation, and high efficiency.

Description

A method and system for ambient temperature mechanical drying of sludge, and a two-stage ambient temperature sludge dewatering and mechanical drying system including this system. Technical Field

[0001] This application relates to the field of sludge treatment technology, and in particular to a method and system for ambient temperature mechanical drying of deeply dewatered sludge, as well as a two-stage ambient temperature sludge dewatering and mechanical drying system that includes this system in its drying process stage. Background Technology

[0002] A crucial step in wastewater treatment is separating water from sludge to reduce its volume and alleviate the sludge volume load on subsequent treatment processes. Different treatment processes are employed depending on the sludge's moisture content. When reducing the sludge moisture content from over 90% to 60-70%, sludge dewatering is used, traditionally achieved through mechanical filtration. When further reducing the moisture content from 60-70% to as low as 10%, drying processes are employed, typically utilizing gas-fired boilers or heat pump units that convert electrical energy into heat. Regardless of the energy source, sludge drying ultimately relies on thermal energy.

[0003] In sludge dewatering processes, the initial sludge moisture content is approximately 97%-99%. Depending on the mechanical filtration method, the moisture content of the sludge after primary dewatering varies: taking screw presses, centrifugal dewatering machines, and conventional belt filter presses as examples, sludge is dewatered from 97%-99% to around 80%, resulting in a primary dewatering sludge moisture content of approximately 80%, which is high. In contrast, sludge treated by deep dewatering equipment such as plate and frame filter presses and high-pressure belt filter presses has a lower moisture content, dewatering from 97%-99% to around 60%-70%, resulting in a primary dewatering sludge moisture content of approximately 60%-70%. To further reduce the moisture content of the primary dewatering sludge under these primary dewatering conditions, it is possible to add a large amount of lime powder during plate and frame filter press operation, thereby achieving a lower moisture content for the primary dewatered sludge. However, the sludge treated with added lime powder cannot be rendered harmless or utilized as a resource. Even if incineration is chosen, the addition of a large amount of lime powder necessitates a large amount of auxiliary heat source for combustion, leading to increased disposal costs.

[0004] In order to obtain sludge with a moisture content meeting the requirements of backend treatment, in current sludge treatment, a two-stage sludge treatment method is partially adopted, mainly including a spiral press, a belt filter press or a plate and frame filter press combined with subsequent thermal drying technologies such as low-temperature drying or steam drying. However, whether it is low-temperature drying or steam drying, a large amount of auxiliary heat sources are consumed during operation, the operation cost is relatively high, and the thermal energy reuse efficiency is low. Therefore, the sludge drying process has become the main energy-consuming link in the sludge treatment system and is also the focus of energy conservation and consumption reduction in the sludge treatment system. Moreover, there is a risk of spontaneous combustion of sludge dust during the drying process, resulting in great drawbacks in these thermal drying treatment methods during the sludge treatment process. Summary of the Invention

[0005] In the research on sludge drying treatment for the above technical problems, the inventors found that: 1) In sludge with a moisture content of 60%-70% after deep dehydration, in addition to the internal water within the sludge particles, there is still external water outside the sludge particles. At room temperature, this external water is tightly adsorbed on the outer surface of the sludge particles and forms a pressure balance with the internal water within the sludge particles. This is one of the important reasons why it is difficult to filter out more water through ordinary mechanical filtration methods in the sludge drying process to effectively reduce the moisture content of the sludge; 2) In the above situation, by uniformly mixing an auxiliary material with a drainage effect with the sludge with a moisture content of 60%-70% and slightly applying pressure through filtration, when the external pressure reaches 1.5 Mpa / cm^2, the water output suddenly increases, and the pressure can be continuously increased after this breaking pressure to mechanically dry the deeply dehydrated sludge to the extent required by the backend sludge treatment method. Based on the above findings, the inventors summarized and constructed the following principle of sludge normal-temperature drainage differential pressure breaking, that is: by uniformly mixing an auxiliary material with a drainage effect with the sludge with a moisture content of 60%-70% and entering a mechanical drying device to slightly apply pressure through filtration, under the drainage effect of the auxiliary material, the external water, especially the external water tightly adsorbed on the outer surface of the sludge particles, will be discharged, thereby breaking the balance between the internal water and the external water within the sludge particles, resulting in a pressure difference inside and outside the sludge particles. However, the pressure difference at this time is relatively small; subsequently, after the external pressure acts, the pressure difference inside and outside the sludge particles increases until the sludge particles rupture, producing a breaking effect and discharging the internal water. Based on the above principle of sludge normal-temperature drainage differential pressure breaking, this application provides a sludge normal-temperature mechanical drying method, system and a two-stage normal-temperature sludge dehydration and mechanical drying system including this system, which can filter out most of the water in the sludge from the deeply dehydrated sludge (with a moisture content of 60%-70%) and further reduce its moisture content to the extent required by the backend sludge treatment method (such as incineration, composting, etc.). Its drying process is carried out at room temperature, without the need for heat sources, with low energy consumption, simple operation and high efficiency.

[0006] To achieve the above objectives, according to a first aspect of this application, a method for mechanically drying sludge at room temperature is provided, comprising the following steps:

[0007] Step 1: Mix the sludge to be dried with an auxiliary material that has a flow-guiding effect at a weight of 3-10% of the sludge to be dried, so that the auxiliary material completely adheres to the surface of the sludge particles.

[0008] Step 2: The sludge mixture processed in Step 1 is subjected to pressure filtration in a sludge mechanical drying device; within the set pressure filtration time, the working pressure is slowly increased from the initial pressure until the pressure reaches the maximum set pressure, which is at least greater than 1.5 MPa / cm^2.

[0009] According to this application, in step two, under the slight action of the initial external pressure applied by the sludge mechanical drying equipment and the guiding effect of the auxiliary material, the external water of the sludge particles to be dried is rapidly discharged, creating a small pressure difference between the inside and outside of the sludge particles. Subsequently, after the external water is discharged and the pressure balance between the internal and external water of the sludge particles is disrupted, the pressure difference between the inside and outside of the particles gradually increases as the system pressure increases, eventually causing the particles to rupture, producing a cell-wall breaking effect, and releasing the water inside the particles.

[0010] "Cell wall disruption" generally refers to a method that causes cell walls to rupture under the interference of external factors. In this application, it refers to a method that, under the combined action of external pressure and auxiliary materials, breaks the pressure balance between the inside and outside of sludge particles, thereby releasing the water inside the sludge particles.

[0011] According to this application, the sludge mechanical drying equipment belongs to physical pressing, which is a purely mechanical pressing method powered by, for example, a hydraulic system. It can dry sludge with a moisture content of 60% to 70% to the degree required for the sludge downstream disposal method, such as usually below 40% moisture content. Moreover, in addition to the power consumption of the equipment itself, the equipment does not require a large amount of auxiliary heat source to dry the sludge during operation.

[0012] According to this application, the sludge to be dried does not refer to any sludge that requires broad dewatering treatment (i.e., reducing the moisture content of the sludge), but rather refers to a type of dewatered sludge that, like the sludge dewatered to 60%-70% as used in the aforementioned industry classification of drying processes, is granular, has certain solid characteristics, and can better solidify and shape when mixed and pressed with the auxiliary material. The moisture content of the sludge to be dried is preferably 60%-70%. In contrast, sludge with high moisture content, such as the aforementioned dewatered sludge with a moisture content of around 80%, has a certain degree of fluidity. When the same proportion of the auxiliary material is added, sludge leakage is likely to occur during the pressing process, making it impossible to apply the sludge room temperature flow pressure difference cell breaking principle described in this application. Moreover, due to its excessively high moisture content, the mechanical drying method of this application cannot be used to further reduce its moisture content to the level required for the sludge's downstream disposal.

[0013] In some embodiments according to this application, the sludge to be dried can also be sludge treated by a deep sludge dewatering device. This deep sludge dewatering device is preferably a high-pressure belt integrated deep sludge dewatering device, which can continuously and deeply dewater wastewater with a moisture content of 96%–98% to 60%–70%. Plate and frame filter presses are also types of deep sludge dewatering devices, but they operate intermittently and have a low degree of automation.

[0014] According to this application, the auxiliary material has a diversion function. After a layer of auxiliary material adheres to the surface of the sludge particles to be dried, it can form water-permeable channels, which can quickly divert water from the outside of the sludge particles and water from the inside of the particles that is subsequently filtered out from the inside of the sludge particles, thereby achieving the purpose of rapid mechanical drying. Optionally, the auxiliary material can be non-water-soluble solid powder waste and / or biomass waste. Optionally, the non-water-soluble solid powder waste can be one or more of wood ash, biochar, fly ash, and sludge incineration residue. Depending on the back-end disposal method of the sludge, different materials of auxiliary materials can be selected. For example, if the back-end disposal method is incineration, biomass waste such as sawdust or leaves from street sweepings can be added to increase the calorific value of the sludge. Biochar, fly ash, and sludge incineration residue after sludge carbonization can also be used. For another example, if the back-end disposal method is aerobic composting, wood ash can be added to supplement potassium fertilizer, thereby achieving comprehensive resource utilization of waste.

[0015] In a preferred embodiment of this application, in step one, the uniform mixing of the sludge to be dried and the auxiliary material is achieved by initial mixing during the sludge conveying process followed by crushing and stirring.

[0016] According to this application, the slow increase in working pressure in step two can be a continuous slow increase in working pressure, or it can be a process of setting multiple stage pressure values ​​and increasing them step by step. In a preferred embodiment of this application, in step two, the slow increase in working pressure means that after each stage's set pressure value is reached, the pressure is held for 1-3 minutes, and after this holding operation is completed, the next pressure stage begins. Further, in a preferred embodiment of the application, one of the set pressure values ​​in each stage is 1.5 MPa / cm^2.

[0017] In a preferred embodiment of this application, in step two, the maximum set pressure range of the working pressure is greater than 1.5 MPa / cm^2 and up to 2.8 MPa / cm^2 (i.e., the preferred pressure range is 1.5-2.8 MPa / cm^2, but not including 1.5 MPa / cm^2). More preferably, the pressure range is 2-2.8 MPa / cm^2, so that a sludge drying effect with a lower working pressure can be achieved that is not significantly different from that under a higher working pressure, thereby further reducing energy consumption.

[0018] According to a second aspect of this application, a sludge ambient temperature mechanical drying system is provided, which is applicable to the above-mentioned sludge ambient temperature mechanical drying method, and includes at least a sludge conveying device and a sludge mechanical drying device, wherein the sludge conveying device is configured to mix the sludge to be dried with the auxiliary material and then send it to the downstream sludge mechanical drying device.

[0019] In a preferred embodiment of the present application, the sludge ambient temperature mechanical drying system further includes a crushing device disposed between the sludge conveying device and the sludge mechanical drying equipment, and configured to further and fully mix the sludge to be dried with the auxiliary material by stirring and crushing.

[0020] In a preferred embodiment of the present application, the sludge ambient temperature mechanical drying system may further include an auxiliary material storage and addition device configured to store and provide auxiliary materials required for sludge mechanical drying.

[0021] According to a third aspect of this application, a two-stage ambient temperature sludge dewatering and mechanical drying system is provided, comprising at least, in sequence, a sludge deep dewatering device, an auxiliary material storage and addition device, a mixing device, and a sludge mechanical drying device. The sludge deep dewatering device is configured to deeply dewater initial sludge into sludge to be dried. The auxiliary material storage and addition device is configured to store auxiliary materials with a guiding effect and add the auxiliary materials, at a weight of 3-10% of the weight of the sludge to be dried, to the sludge to be dried. The mixing device includes at least a sludge conveying device, which is configured to mix the sludge to be dried with the added auxiliary materials and convey it to the downstream sludge mechanical drying device. The sludge mechanical drying device is configured to perform pressure filtration on the mixture of sludge to be dried and auxiliary materials processed by the mixing device. During a set pressure filtration time, the working pressure is slowly increased from the initial pressure until the pressure reaches a maximum set pressure of at least 1.5 MPa / cm².

[0022] In a preferred embodiment according to this application, the mixing device may further include a crushing device disposed between the sludge conveying device and the sludge mechanical drying equipment, and configured to further and fully mix the sludge to be dried with the auxiliary material by stirring and crushing.

[0023] According to this application, the sludge to be dried is sludge that has been treated by the sludge deep dewatering equipment, and its characteristics are as described above, and will not be repeated here.

[0024] In a preferred embodiment according to this application, the sludge deep dewatering equipment is configured to continuously and integrally dewater the initial sludge to a moisture content of 60%–70%, preferably, for example, a high-pressure belt integrated sludge deep dewatering equipment. Plate and frame filter presses also belong to the category of sludge deep dewatering equipment, but they operate intermittently and have a low degree of automation.

[0025] According to this application, the slow increase in working pressure in the sludge mechanical drying equipment can be a continuous slow increase in working pressure, or it can be a step-by-step increase of multiple set pressure values. In a preferred embodiment of this application, the slow increase in working pressure means that after each set pressure value is reached, the pressure is held for 1-3 minutes, and after this holding operation is completed, the next pressure stage begins. Further, in a preferred embodiment of this application, one of the set pressure values ​​in each stage is 1.5 MPa / cm^2.

[0026] In a preferred embodiment of the present application, the preferred pressure range of the maximum set pressure of the working pressure is greater than 1.5 MPa / cm^2 and up to 2.8 MPa / cm^2 (i.e., the preferred pressure range is 1.5-2.8 MPa / cm^2, but not including 1.5 MPa / cm^2). More preferably, the pressure range is 2-2.8 MPa / cm^2, so as to achieve a sludge drying effect that is not significantly different from that under a higher working pressure at a lower working pressure, thereby further reducing energy consumption.

[0027] In a preferred embodiment according to this application, corresponding to the aforementioned integrated continuous operation sludge deep dewatering equipment, the sludge mechanical drying equipment is configured to operate intermittently in batches, and a material storage tank is provided between the sludge deep dewatering equipment and the sludge mechanical drying equipment. The initial continuous sludge processing capacity of the sludge deep dewatering equipment, the storage capacity of the material storage tank, and the single processing capacity of the intermittent operation of the sludge mechanical drying equipment are matched to achieve the effect of overall continuous operation.

[0028] In a preferred embodiment of the present invention, the auxiliary material storage and addition device is provided with a control module configured to control the addition ratio of the auxiliary material, and a flow detection module configured to detect the addition ratio.

[0029] The sludge ambient temperature mechanical drying method and system according to this application, as well as the two-stage ambient temperature sludge dewatering and mechanical drying system including this system, achieve the following beneficial effects:

[0030] 1. The sludge room temperature mechanical drying method and system based on the principle of room temperature flow and pressure difference cell breaking according to this application, and the two-stage room temperature sludge dewatering and mechanical drying system including the system, can completely release the internal moisture of the sludge particles by breaking the pressure balance inside and outside the sludge particles at room temperature through the combined action of the added auxiliary materials with flow-guiding effect and external pressure, thereby significantly reducing the moisture content of the sludge to be dried (preferably 60%-70%).

[0031] 2. Compared with existing drying processes that require a large amount of auxiliary heat source, the sludge ambient temperature mechanical drying method and system according to this application, as well as the two-stage ambient temperature sludge dewatering and mechanical drying system including the system, achieve mechanical drying of the sludge to be dried without the need for a heat source, resulting in low energy consumption, simple operation, and high efficiency.

[0032] 3. By selecting the type of auxiliary material and / or the working pressure, the moisture content of different dried sludge can be adjusted and controlled during the drying process according to different requirements of downstream sludge disposal, making the implementation more flexible and convenient.

[0033] 4. The two-stage ambient temperature sludge dewatering and mechanical drying system according to this application can significantly reduce the moisture content of the sludge after deep dewatering through mechanical drying during the sludge drying stage;

[0034] 5. Furthermore, this two-stage ambient temperature sludge dewatering and mechanical drying system can operate fully automatically 24 hours a day without human intervention, is odorless, and reduces deodorization costs. Attached Figure Description

[0035] Figure 1 is a schematic diagram of the sludge ambient temperature mechanical drying system according to this application, which is used in conjunction with an integrated sludge deep dewatering system.

[0036] Figure 2 is a schematic diagram of the two-stage ambient temperature sludge dewatering and mechanical drying system according to this application.

[0037] Among them, 1-integrated sludge deep dewatering system, 11-sludge pump, 12-fully automatic dosing tank, 3-sludge deep dewatering equipment, 4-sludge conveying device, 5-sludge mechanical drying equipment, 6-conditioning tank, 7-auxiliary material storage and addition device, 8-crushing device, 9-sludge transport vehicle.

[0038] Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description of the sludge room-temperature mechanical drying method, through embodiments and in conjunction with the accompanying drawings, is provided. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0040] Figure 1 illustrates a sludge ambient temperature mechanical drying system according to this application, used in conjunction with an integrated sludge deep dewatering system 1 equipped with a sludge deep dewatering device 3. This sludge ambient temperature mechanical drying system mainly includes: a sludge conveying device 4, a crushing device 8, and a sludge mechanical drying device 5. The sludge conveying device 4 is configured to mix the sludge to be dried with the auxiliary materials and then convey it to the downstream sludge mechanical drying device 5. The crushing device 8 is disposed between the sludge conveying device 4 and the sludge mechanical drying device 5 to further and thoroughly mix the sludge to be dried with the auxiliary materials through stirring and crushing.

[0041] Preferably, the sludge ambient temperature mechanical drying system may further include an auxiliary material storage and addition device 7 to store and provide the auxiliary materials required for sludge mechanical drying.

[0042] As mentioned above, the sludge to be dried can be, but is not limited to, sludge with a moisture content of 60-70% that has been treated by the sludge deep dewatering equipment 3. The sludge to be dried is granular and has certain solid characteristics. When it is mixed and pressed with the auxiliary material, the sludge to be dried can be better solidified and shaped.

[0043] The term "deep sludge dewatering equipment 3" refers to a general term for dewatering equipment that dewaters initial sludge to 60%-70%, which can include plate and frame filter presses, high-pressure belt presses, etc.

[0044] Those skilled in the art should understand that the configuration of the sludge ambient temperature mechanical drying system according to this application is not limited to Figure 1 above. This sludge ambient temperature mechanical drying system can be configured independently or used in conjunction with a sludge dewatering process system capable of reducing sludge moisture content to 60-70%. Furthermore, this sludge dewatering process system capable of reducing sludge moisture content to 60-70% is not limited to a deep sludge dewatering system; it can be any existing sludge dewatering process system capable of reducing sludge moisture content to 60-70%.

[0045] Figure 2 illustrates a two-stage ambient temperature sludge dewatering and mechanical drying system according to this application. This two-stage ambient temperature sludge dewatering and mechanical drying system, from the initial sludge inlet to the dried sludge outlet, sequentially includes a sludge pump 11, a fully automatic dosing tank 12, a conditioning tank 6, a deep sludge dewatering device 3, an auxiliary material storage and addition device 7, a sludge conveying device 4, a crushing device 8, a sludge mechanical drying device 5, and a sludge transport vehicle 9. The sludge pump 11, the fully automatic dosing tank 12, the conditioning tank 6, and the deep sludge dewatering device 3 constitute the deep sludge dewatering process section of the system, while the auxiliary material storage and addition device 7, the sludge conveying device 4, the crushing device 8, and the sludge mechanical drying device 5 constitute the mechanical sludge drying process section of the system.

[0046] According to this application, the term "system" refers to an organic whole with specific functions, composed of several interacting components. Therefore, it should be understood that the two sections of the system according to this application—the sludge deep dewatering process section and the sludge mechanical drying process section—can be physically separated into different sites, or, as shown in Figure 1, placed together in the same site to form an integrated sludge treatment system. This arrangement in physical space does not affect the composition of the "system" according to this application.

[0047] In the sludge mechanical drying process section, the auxiliary material storage and addition device 7 is configured to store auxiliary materials with a guiding effect and add the auxiliary materials, with a weight of 3-10% of the weight of the sludge to be dried, to the sludge to be dried. The auxiliary material storage and addition device 7 includes a control module configured to control the addition ratio of the auxiliary materials, and a flow detection module configured to detect the addition ratio, so as to control the weight of the added auxiliary materials.

[0048] The sludge conveying device 4 connects the outlet of the sludge deep dewatering equipment 3 and the crushing device 8, as well as the outlet of the sludge mechanical drying equipment 5 and the sludge transport vehicle 9. It conveys the sludge to be dried during the mechanical drying stage, and after the sludge to be dried is initially mixed with auxiliary materials with a guiding effect at a weight of 3-10% of the sludge to be dried, it is conveyed to the crushing device 8. After the mechanical drying of the sludge is completed, the dried sludge is conveyed to the sludge transport vehicle 9.

[0049] In the embodiment shown in Figure 2, the crushing device 8 is positioned above the sludge mechanical drying equipment 5, enabling further and thorough mixing of the sludge to be dried and the auxiliary materials through agitation and crushing. Preferably, a material storage tank (not shown in the figure) is also provided between the crushing device 8 and the sludge mechanical drying equipment 5. During the intermittent operation of the sludge mechanical drying equipment, the material storage tank can temporarily store the mixture of sludge to be dried and auxiliary materials that has been thoroughly mixed by the crushing device 8 and loaded into it, and during the operation of the sludge mechanical drying equipment, the temporarily stored mixture of sludge to be dried and auxiliary materials is fed into the sludge mechanical drying equipment 5.

[0050] It should be understood that Figure 2 only shows one possible arrangement of the pulverizing device 8 and the material storage tank according to this application between the sludge deep dewatering equipment 3 and the sludge mechanical drying equipment 5. Those skilled in the art can choose the arrangement method according to actual needs. For example, the pulverizing device 8 and the material storage tank can be arranged independently or in combination. In the case of combined arrangement, the pulverizing device 8 and the material storage tank can be arranged independently of the sludge mechanical drying equipment 5 and connected to it via the sludge conveying device 4, or they can be combined with the sludge mechanical drying equipment 5.

[0051] As mentioned above, the sludge to be dried after being treated by the sludge deep dewatering equipment 3 can be, but is not limited to, sludge with a moisture content of 60-70%. The sludge to be dried is granular and has certain solid characteristics. When it is mixed and pressed with the auxiliary material, the sludge to be dried can be better solidified and shaped.

[0052] The sludge deep dewatering equipment 3 refers to a general term for dewatering equipment that dewaters initial sludge to 60%-70%, and can be a plate and frame filter press, a high-pressure belt press, etc. In a preferred embodiment according to this application, the sludge deep dewatering equipment is configured to continuously and integrally dewater the initial sludge to a moisture content of 60%-70%, preferably, for example, a high-pressure belt integrated sludge deep dewatering equipment.

[0053] In the embodiment shown in Figure 2, the sludge mechanical drying equipment 5 is a top-feed sludge filter press powered by a hydraulic system, which can mechanically dry sludge with a moisture content of 60% to 70% to the degree required for the sludge post-disposal method, such as typically below 40% moisture content.

[0054] Corresponding to the aforementioned integrated and continuously operating sludge deep dewatering equipment 3, the sludge mechanical drying equipment 5 operates intermittently in batches. By matching the initial continuous sludge processing capacity of the sludge deep dewatering equipment 3, the storage capacity of the material storage tank, and the intermittent single-cycle processing capacity of the sludge mechanical drying equipment 5, the effect of integrated and continuous operation of the system is achieved. Example 1

[0055] Based on the above-mentioned sludge ambient temperature mechanical drying system, the sludge ambient temperature mechanical drying method according to this application includes the following steps:

[0056] Step 1: The sludge dewatered to a moisture content of 60-70% by the integrated sludge deep dewatering system 1 equipped with a belt filter press is initially mixed with auxiliary materials provided from the auxiliary material storage and addition device 7 by the sludge conveying device 4, and then crushed by the crushing device 8 to ensure that the sludge to be dried is fully mixed with the auxiliary materials. The auxiliary materials are biochar produced by sludge carbonization or biomass waste such as sawdust and leaves from street sweeping, which are 5-10% of the weight of the sludge to be dried, in order to increase the calorific value of the sludge during the subsequent incineration process.

[0057] Step two: The mixture of sludge to be dried and auxiliary material is fed into the sludge mechanical drying equipment 5 via the sludge conveying device 4 for pressure filtration. Within the set pressure filtration time (the specific time can be selected as needed), the working pressure is slowly increased from the initial pressure of 0.45 MPa / cm^2. At the same time, the pressure is held for 1-3 minutes after each set pressure value is reached. After the pressure holding is completed, the next pressure stage begins. One of the set pressure values ​​is 1.5 MPa / cm^2, until the pressure reaches the maximum set pressure of about 2.5 MPa / cm^2. The moisture content of the dried sludge is reduced to about 40%, thereby reducing the amount of auxiliary fuel added during the incineration process and reducing the incineration cost.

[0058] Step 3: After mechanical drying, the sludge is loaded into a sludge transport vehicle 9 via a sludge conveying device 4 and transported to the downstream treatment site for incineration. Example 2

[0059] Based on the above-mentioned sludge ambient temperature mechanical drying system, the sludge ambient temperature mechanical drying method according to this application includes the following steps:

[0060] Step 1: The sludge with a moisture content of 65-70% is initially mixed with the auxiliary materials through the sludge conveying device 4, and then crushed by the crushing device 8 to ensure that the sludge to be dried is fully mixed with the auxiliary materials. The auxiliary materials are wood ash, which accounts for 3-5% of the weight of the sludge to be dried, in order to increase the potassium fertilizer content in the sludge during the subsequent composting process.

[0061] Step two: The mixture of sludge to be dried and the auxiliary material is fed into the sludge mechanical drying equipment 5 via the sludge conveying device 4 for pressure filtration. During the set pressure filtration time, the working pressure is slowly increased from the initial pressure of 0.45 MPa / cm^2. At the same time, the pressure is maintained for 1-3 minutes after each set pressure value is reached. After the pressure holding is completed, the next pressure stage begins. One of the set pressure values ​​is 1.5 MPa / cm^2, until the pressure reaches the maximum set pressure of about 2 MPa / cm^2. The moisture content of the dried sludge is controlled at about 55%-60% to prevent the moisture content from being too low or too high, which would affect the composting effect.

[0062] Step 3: After mechanical drying, the sludge is loaded into a sludge transport vehicle 9 via a sludge conveying device 4 and transported to a downstream processing site for composting. Example 3

[0063] In this embodiment, the initial sludge is deeply dewatered and mechanically dried at room temperature using a two-stage ambient temperature sludge dewatering and mechanical drying system according to this application, reducing the sludge moisture content to approximately 40% for subsequent incineration. The specific operation process is as follows:

[0064] In the sludge deep dewatering process section (i.e., section 1) of this system, the initial sludge with a moisture content of 96% to 98% is continuously pumped from the gravity thickener to the sludge deep dewatering equipment 3 via sludge pump 1. At the same time, the conditioning agent prepared by the fully automatic dosing tank 2 is delivered to the conditioning tank 6 via the dosing pump and fully mixed with the sludge. Then, the conditioning sludge is dewatered to a moisture content of about 85% by the thickener and dewatering machine. Then, iron salt is added and mixed, and the sludge is continuously dewatered to a moisture content of 60% to 70% by the belt filter press (i.e., sludge deep dewatering equipment 3). The iron salt has two functions: first, to neutralize the negative charge of the sludge and reduce electrostatic repulsion; second, to catalyze the degradation of PAM, reduce its water-binding properties, and facilitate the squeezing out of the water between the sludge particles, thus achieving the purpose of deep dewatering.

[0065] In the sludge mechanical drying process section (i.e., the second stage) of this system, sawdust, weighing 5%-10% of the sludge weight, is added to the deeply dewatered sludge to be dried via the auxiliary material storage and addition device 7. The sludge to be dried is then thoroughly mixed with the sawdust via a sludge scraper conveyor (i.e., sludge conveying device 4) and a crushing device 8, and then fed into the sludge mechanical drying equipment 5 for pressure filtration. Within the set pressure filtration time (the specific time can be selected as needed), the working pressure is slowly increased from the initial pressure of 0.45 MPa / cm^2. At the same time, the pressure is held for 1-3 minutes after each set pressure value is reached. After the pressure holding is completed, the next pressure stage begins. One of the set pressure values ​​is 1.5 MPa / cm^2, until the pressure reaches the maximum set pressure of about 2.5 MPa / cm^2, reducing the moisture content of the dried sludge to about 40%. After mechanical drying, the dried sludge is loaded into sludge transport vehicle 9 via sludge conveying device 4 and transported to the downstream treatment site for incineration.

[0066] In this embodiment, the first-stage sludge deep dewatering equipment 3 continuously discharges sludge, while the second-stage sludge mechanical drying equipment 5 operates intermittently in batches, with each batch lasting approximately 20-30 minutes. A material storage box installed on the second-stage sludge mechanical drying equipment 5 can temporarily store materials for 20-30 minutes. The continuous processing capacity of the first-stage sludge deep dewatering equipment 3, the storage capacity of the material storage box, and the intermittent single-batch processing capacity of the second-stage sludge mechanical drying equipment 5 are matched to achieve an overall continuous operation effect. Example 4

[0067] In this embodiment, the initial sludge is deeply dewatered and mechanically dried at room temperature using a two-stage ambient temperature sludge dewatering and mechanical drying system according to this application, reducing the sludge moisture content to approximately 55%-60% for subsequent composting. The specific operation process is as follows:

[0068] In the sludge deep dewatering process section (i.e., the first stage) of the system, the sludge tank continuously pumps the initial sludge with a moisture content of 96% to 98% from the gravity thickener to the sludge deep dewatering equipment 3 in the first stage via sludge pump 1. At the same time, the conditioner prepared by the fully automatic dosing tank 2 is delivered to the conditioning tank 6 via the dosing pump and fully mixed with the sludge. Then, the conditioned sludge is dewatered to about 85% by the thickener and dewatering machine. Then, iron salt is added and mixed, and the sludge is continuously dewatered to 65% to 70% by the belt filter press, thus completing the deep dewatering of the sludge.

[0069] In the mechanical drying process section (stage two) of this system, 3%-5% by weight of wood ash is added to the deeply dewatered sludge to be dried via the auxiliary material storage and addition device 7. The dried sludge and wood ash are thoroughly mixed by the sludge scraper conveyor and crushing device 8, and then transported to the mechanical drying equipment 5 in stage two for pressure filtration. During the set pressure filtration time, the working pressure is slowly increased from an initial pressure of 0.45 MPa / cm², and pressure is maintained for 1-3 minutes after each set pressure value is reached. After the pressure holding period, the next pressure stage begins, with one stage set at 1.5 MPa / cm², until the pressure reaches the maximum set pressure of approximately 2 MPa / cm². The moisture content of the dried sludge is controlled at approximately 55%-60%. After mechanical drying, the dried sludge is loaded into sludge transport vehicles 9 via the sludge conveying device 4 and transported to the downstream processing site for composting.

[0070] In this embodiment, the first-stage sludge deep dewatering equipment 3 continuously discharges sludge, while the second-stage sludge mechanical drying equipment 5 operates intermittently in batches, with each batch lasting approximately 10-20 minutes. A material storage box located on the second-stage sludge mechanical drying equipment 5 can temporarily store materials for 10-20 minutes. The continuous processing capacity of the first-stage sludge deep dewatering equipment 3, the storage capacity of the material storage box, and the intermittent single-batch processing capacity of the second-stage sludge mechanical drying equipment 5 are matched to achieve an overall continuous operation effect. Example 5

[0071] In this embodiment, based on the above embodiments 2 or 4, the maximum set pressure value of the working pressure in the sludge mechanical drying equipment 5 in step two is changed (as shown in Table 1 below) to show how the maximum set pressure value adjusts and controls the moisture content of the mechanically dried sludge.

[0072] Table 1: Comparison of pressure per unit area:

[0073] Serial Number | Unit | Pressure (MPa / cm^2) | Moisture Content of Dried Sludge | 12 | 55% -60% | 22.5 | 40% -45% | 32.8 | 38% -45%

[0074] As shown in Table 1 above, the moisture content of mechanically dried sludge can be adjusted by regulating the maximum set pressure. The pressure value of 2.8 MPa / cm² is the preferred maximum set pressure from the perspective of system energy saving and consumption reduction. This is because, during the experiment, it was found that when the maximum set pressure was adjusted from 2.5 MPa / cm² to 2.8 MPa / cm², the change in sludge moisture content was only 2%. Increasing the pressure to above 2.8 MPa / cm² improved the sludge drying effect somewhat, but not significantly.

[0075] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0076] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for mechanically drying sludge at room temperature, comprising the following steps: Step 1: Mix the sludge to be dried with an auxiliary material that has a flow-guiding effect at a weight of 3-10% of the sludge to be dried, so that the auxiliary material completely adheres to the surface of the sludge particles. Step 2: The sludge mixture processed in Step 1 is subjected to pressure filtration in a sludge mechanical drying device; within the set pressure filtration time, the working pressure is slowly increased from the initial pressure until the pressure reaches the maximum set pressure, which is at least greater than 1.5 MPa / cm^2.

2. The method for mechanically drying sludge at room temperature according to claim 1, characterized in that, The sludge to be dried is granular and has solid characteristics. When it is mixed and pressed with the auxiliary materials, the sludge to be dried can be better solidified and shaped.

3. The method for mechanically drying sludge at room temperature according to claim 1, characterized in that, The moisture content of the sludge to be dried is 60-70%.

4. The method for mechanically drying sludge at room temperature according to claim 1, characterized in that, The auxiliary materials are non-water-soluble solid powder waste and / or biomass waste.

5. The method for mechanically drying sludge at room temperature according to claim 4, characterized in that, The non-water-soluble solid powder waste is one or more of the following: wood ash, biochar, fly ash, and sludge incineration residue.

6. The method for mechanically drying sludge at room temperature according to claim 1, characterized in that, In step one, the uniform mixing of the sludge to be dried and the auxiliary materials is achieved by initial mixing during the sludge transportation process followed by crushing and stirring.

7. The method for mechanically drying sludge at room temperature according to claim 1, characterized in that, In step two, the slow increase in working pressure means that the pressure is held for 1-3 minutes after each set pressure value is reached, and the next pressure stage is entered after the pressure holding operation is completed.

8. The method for mechanically drying sludge at room temperature according to claim 7, characterized in that, One of the set pressure values ​​for each stage is 1.5 MPa / cm^2.

9. The method for mechanically drying sludge at room temperature according to claim 1 or 7, characterized in that, In step two, the pressure range of the maximum set pressure is 2-2.8 MPa / cm^2.

10. A sludge ambient temperature mechanical drying system, applicable to the sludge ambient temperature mechanical drying method as described in any one of claims 1-9, characterized in that, The sludge ambient temperature mechanical drying system includes at least a sludge conveying device and a sludge mechanical drying device, wherein the sludge conveying device is configured to mix the sludge to be dried with the auxiliary materials and then send it to the sludge mechanical drying device at the rear end.

11. The sludge ambient temperature mechanical drying system according to claim 10, characterized in that, The sludge ambient temperature mechanical drying system also includes a crushing device, which is located between the sludge conveying device and the sludge mechanical drying equipment, and is configured to further and fully mix the sludge to be dried with the auxiliary materials through stirring and crushing.

12. The sludge ambient temperature mechanical drying system according to claim 10, characterized in that, The sludge ambient temperature mechanical drying system also includes an auxiliary material storage and addition device configured to store and provide the auxiliary materials required for sludge mechanical drying.

13. A two-stage ambient temperature sludge dewatering and mechanical drying system, characterized in that, This includes a sludge ambient temperature mechanical drying system as described in any one of claims 10-12, specifically comprising at least, in sequence, a sludge deep dewatering device, an auxiliary material storage and addition device, a mixing device, and a sludge mechanical drying device. The sludge deep dewatering equipment is configured to deeply dewater the initial sludge into sludge awaiting drying. The auxiliary material storage and addition device is configured to store auxiliary materials with a diversion function and add the auxiliary materials, which account for 3-10% of the weight of the sludge to be dried, to the sludge to be dried. The mixing device includes at least a sludge conveying device, which is configured to mix the sludge to be dried with the added auxiliary materials and convey it to the downstream sludge mechanical drying equipment. The sludge mechanical drying equipment is configured to perform pressure filtration on the mixture of sludge to be dried and auxiliary materials that has been treated by the mixing device. Within the set filtration time, the working pressure is slowly increased from the initial pressure until the pressure reaches the maximum set pressure, which is at least greater than 1.5 MPa / cm^2.

14. The two-stage ambient temperature sludge dewatering and mechanical drying system according to claim 13, characterized in that, The mixing device also includes a crushing device, which is disposed between the sludge conveying device and the sludge mechanical drying equipment, and is configured to further and fully mix the sludge to be dried with the auxiliary materials by stirring and crushing.

15. The two-stage ambient temperature sludge dewatering and mechanical drying system according to claim 13, characterized in that, The sludge to be dried is granular and has solid characteristics. When it is mixed and pressed with the auxiliary materials, the sludge to be dried can be better solidified and shaped.

16. The two-stage ambient temperature sludge dewatering and mechanical drying system according to claim 15, characterized in that, The moisture content of the sludge to be dried is 60-70%.

17. The two-stage ambient temperature sludge dewatering and mechanical drying system according to claim 13, characterized in that, The auxiliary materials are non-water-soluble solid powder waste and / or biomass waste.

18. The two-stage ambient temperature sludge dewatering and mechanical drying system according to claim 17, characterized in that, The non-water-soluble solid powder waste is one or more of the following: wood ash, biochar, fly ash, and sludge incineration residue.

19. The two-stage ambient temperature sludge dewatering and mechanical drying system according to claim 13, characterized in that, The maximum set pressure range is 2-2.8 MPa / cm^2.

20. The two-stage ambient temperature sludge dewatering and mechanical drying system according to claim 13, characterized in that, The sludge deep dewatering equipment is configured to operate continuously as an integrated unit.

21. The two-stage ambient temperature sludge dewatering and mechanical drying system according to claim 20, characterized in that, The sludge mechanical drying equipment is configured to operate intermittently in batches, and a material storage tank is provided between the sludge deep dewatering equipment and the sludge mechanical drying equipment. The initial continuous sludge processing capacity of the sludge deep dewatering equipment, the storage capacity of the material storage tank, and the single processing capacity of the intermittent operation of the sludge mechanical drying equipment are matched to achieve the effect of continuous overall operation.

22. The two-stage ambient temperature sludge dewatering and mechanical drying system according to claim 13, characterized in that, The auxiliary material storage and addition device is equipped with a control module configured to control the addition ratio of the auxiliary material, and a flow detection module configured to detect the addition ratio.

Images