Sludge drying system and control method thereof

Abstract

The present application provides a kind of sludge drying system and its control method, belong to sludge drying technical field.System includes: sludge drying mechanism, for carrying out drying to sludge;Heat supply mechanism, heat supply mechanism is connected between sludge drying mechanism by heat source circulation pipeline;The cooling medium inlet of heat supply mechanism is connected the cooling medium outlet of sludge drying mechanism by first supply pipeline;Cooling mechanism, the cooling medium inlet of cooling mechanism is connected the cooling medium outlet of sludge drying mechanism by first input pipeline, is connected the cooling medium outlet of heat supply mechanism by second input pipeline, the cooling medium outlet of cooling mechanism is connected the cooling medium inlet of sludge drying mechanism by second supply pipeline;The cooling medium outlet of heat supply mechanism is also connected with second supply pipeline by third supply pipeline.This application has the advantages of simple structure, system high thermal efficiency, is not affected by seasonal temperature variation, stable production capacity.

Description

Technical Field

[0001] This invention relates to the field of sludge drying technology, specifically to a sludge drying system and a control method for the sludge drying system. Background Technology

[0002] With economic development, the total amount of various types of sludge is gradually increasing, and the requirements for sludge treatment are becoming increasingly stringent. Leveraging the technological advantages of high-temperature combustion and ultra-low emissions in coal-fired power plants, technologies for the co-processing and disposal of sludge in coal-fired power plants to achieve sludge reduction, stabilization, harmlessness, and resource utilization are gradually maturing. When co-firing sludge in coal-fired boilers within thermal power plants, wet sludge with a moisture content of 60-80% is typically dried to a moisture content of 30-40% before co-firing. This reduction in sludge volume before co-firing reduces the sludge co-firing ratio, lowers the sludge moisture content, and minimizes the impact of sludge co-firing on the stable operation of the boiler unit.

[0003] Current technologies typically employ belt dryers for sludge drying; however, the following problems exist:

[0004] (1) The existing low-temperature belt drying process uses heat exchangers for indirect heat exchange between steam and heat source circulating water. The steam thermal efficiency cop < 1, resulting in high steam consumption for sludge drying.

[0005] (2) When the temperature is low in winter, the cooling water temperature of the belt dryer decreases, which causes the temperature of the circulating air inside the dryer to decrease, the sludge drying temperature inside the drying chamber to decrease, the sludge dewatering capacity to decrease, and the system capacity to decrease; when the temperature is high in summer, the cooling water temperature of the belt dryer increases, which cannot reduce the temperature of the circulating air inside the dryer to the design value, the cooling water condensation and dehumidification capacity of the circulating air to decrease, the relative humidity of the circulating air inside the dryer to be high, the ability of the circulating air to remove moisture from the sludge to decrease, and the system capacity to decrease.

[0006] (3) When the summer temperature is high, the cooling water temperature of the belt dryer increases, resulting in insufficient cooling capacity supplied to the belt dryer system. This causes the temperature of the circulating air inside the dryer to rise, which in turn increases the sludge drying temperature. The release rate of ammonia nitrogen during sludge drying increases with the temperature, leading to poor quality of condensed wastewater in summer, with ammonia nitrogen, COD, etc. exceeding the design values ​​of the wastewater treatment system.

[0007] (4) The cooling water system is open and does not use softened water or demineralized water, which causes scale to form in the pipes and heat exchangers, affecting the heat exchange efficiency and causing the drying unit to experience a decrease in production capacity. Summary of the Invention

[0008] The purpose of this invention is to provide a sludge drying system and its control method to solve the problems of existing sludge drying systems, such as low heat exchange efficiency, high steam consumption, reduced output in winter / summer, reduced quality of condensate wastewater in summer (increased ammonia nitrogen and COD content in wastewater), and reduced production capacity.

[0009] To achieve the above objectives, embodiments of the present invention provide a sludge drying system, the system comprising:

[0010] Sludge drying equipment is used to dry sludge;

[0011] A heating mechanism is connected to the sludge drying mechanism via a heat source circulation pipeline. The heating mechanism continuously supplies heated heat source medium to the sludge drying mechanism through the heat source circulation pipeline and heats the heat source medium from the sludge drying mechanism. The cooling medium inlet of the heating mechanism is connected to the cooling medium outlet of the sludge drying mechanism through a first supply pipeline, for using the heat in the cooling medium to heat the heat source medium.

[0012] The cooling mechanism has a cooling medium inlet connected to the cooling medium outlet of the sludge drying mechanism via a first input pipe and a cooling medium outlet of the heating mechanism via a second input pipe. The cooling medium outlet of the cooling mechanism is connected to the cooling medium inlet of the sludge drying mechanism via a second supply pipe. The cooling mechanism is used to continuously supply the sludge drying mechanism with cooled cooling medium and to cool the cooling medium from the sludge drying mechanism and the heating mechanism.

[0013] The cooling medium outlet of the heating mechanism is also connected to the second supply pipeline via a third supply pipeline.

[0014] Optionally, the sludge drying mechanism is a belt dryer.

[0015] Optionally, the heating mechanism is connected to a steam source via a steam delivery pipeline, and a desuperheating and pressure reducing device is installed on the steam delivery pipeline;

[0016] The heating mechanism is an absorption heat pump.

[0017] Optionally, a heat source medium circulation pump is installed on the heat source circulation pipeline;

[0018] A cooling medium circulation pump is installed on the second supply pipeline. The cooling medium circulation pump is located between the cooling medium inlet of the sludge drying mechanism and the connection point between the third supply pipeline and the second supply pipeline.

[0019] Optionally, the dry sludge outlet of the sludge drying mechanism is connected to a dry sludge storage silo;

[0020] The condensate outlet of the sludge drying unit is connected to a wastewater treatment device.

[0021] Optionally, valves are provided on the first input pipe, the second input pipe, the first supply pipe, and the third supply pipe.

[0022] Optionally, the cooling mechanism is a cooling water tower.

[0023] Optionally, both the heat source medium and the cooling medium can be demineralized water.

[0024] On the other hand, the present invention also provides a control method for a sludge drying system, applicable to the aforementioned sludge drying system, the method comprising:

[0025] Obtain the ambient temperature value;

[0026] The operating conditions are determined based on the ambient temperature value;

[0027] Based on the operating conditions, the on / off states of the first input pipe, the second input pipe, the first supply pipe, the second supply pipe, and the third supply pipe are controlled.

[0028] Optionally, determining the operating conditions based on the ambient temperature value includes:

[0029] If the ambient temperature value is less than or equal to the preset temperature threshold, then control the first supply pipe, the second input pipe and the second supply pipe to be connected, and control the first input pipe and the third supply pipe to be disconnected.

[0030] If the ambient temperature value is greater than the preset temperature threshold, the first input pipe, the first supply pipe, the second supply pipe and the third supply pipe are controlled to be connected, and the second input pipe is controlled to be disconnected.

[0031] This technical solution dries sludge through a sludge drying unit and continuously supplies heated heat source medium to the sludge drying unit through a heating unit, while also heating the heat source medium from the sludge drying unit. Simultaneously, a cooling unit continuously supplies cooled cooling medium to the sludge drying unit and cools the cooling medium from both the sludge drying unit and the heating unit. It has the advantages of simple structure, high system thermal efficiency, no impact from seasonal temperature changes, and stable production capacity.

[0032] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0033] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0034] Figure 1 This is a schematic diagram of the structure of the first sludge drying system provided by the present invention;

[0035] Figure 2 This is a schematic diagram of the structure of the second sludge drying system provided by the present invention;

[0036] Figure 3 This is a flowchart of the control method for the sludge drying system provided by the present invention.

[0037] Explanation of reference numerals in the attached figures

[0038] 1-Sludge drying unit; 2-Heating unit; 3-Cooling unit;

[0039] 4-Steam source; 5-Heat source medium circulation pump; 6-Cooling medium circulation pump;

[0040] 7-Dry sludge storage silo; 8-Wastewater treatment device; 9-Valve;

[0041] 11-Heat source circulation pipe; 12-First input pipe; 13-Second input pipe;

[0042] 14 - First supply pipeline; 15 - Second supply pipeline; 16 - Third supply pipeline;

[0043] 41-Steam transmission pipeline; 42-Desuperheater and pressure reducer. Detailed Implementation

[0044] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.

[0045] In the embodiments of the present invention, unless otherwise stated, directional terms such as "up," "down," "left," and "right" generally refer to the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use.

[0046] The terms “first,” “second,” “third,” etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0047] The terms "parallel" and "perpendicular" do not mean that the components must be absolutely parallel or perpendicular, but rather that they can be slightly tilted. For example, "parallel" simply means that its direction is more parallel than "perpendicular," not that the structure must be completely parallel, but that it can be slightly tilted.

[0048] The terms "horizontal," "vertical," and "sag" do not imply that a component must be absolutely horizontal, vertical, or sagging, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," not that the structure must be completely horizontal, but can be slightly tilted.

[0049] Furthermore, terms like "roughly" and "basically" are used to indicate that the content does not require absolute precision, but rather allows for a certain degree of deviation. For example, "roughly equal" does not simply mean absolute equality; in actual production and operation, achieving absolute "equality" is difficult, and a certain degree of deviation is generally present. Therefore, besides absolute equality, "roughly equal to" also includes the aforementioned situation where a certain degree of deviation exists. Using this as an example, in other cases, unless otherwise specified, terms like "roughly" and "basically" have similar meanings.

[0050] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0051] Figure 1 This is a schematic diagram of the structure of the first sludge drying system provided by the present invention; Figure 2 This is a schematic diagram of the structure of the second sludge drying system provided by the present invention; Figure 3 This is a flowchart of the control method for the sludge drying system provided by the present invention.

[0052] like Figure 1 As shown, this embodiment provides a sludge drying system, the system comprising:

[0053] Sludge drying unit 1, used for drying sludge;

[0054] Heating mechanism 2 is connected to sludge drying mechanism 1 via heat source circulation pipe 11. Heating mechanism 2 continuously supplies heated heat source medium to sludge drying mechanism 1 via heat source circulation pipe 11 and heats the heat source medium from sludge drying mechanism 1.

[0055] The cooling mechanism 3 has a cooling medium inlet connected to the cooling medium outlet of the sludge drying mechanism 1 via a first input pipe 12 and a cooling medium outlet connected to the heating mechanism 2 via a second input pipe 13. The cooling medium inlet of the heating mechanism 2 is connected to the cooling medium outlet of the sludge drying mechanism 1 via a first supply pipe 14. The cooling medium outlet of the cooling mechanism 3 is connected to the cooling medium inlet of the sludge drying mechanism 1 via a second supply pipe 15. This mechanism is used to continuously supply the sludge drying mechanism 1 with cooled cooling medium and to cool the cooling medium from the sludge drying mechanism 1 and the heating mechanism 2.

[0056] The cooling medium outlet of the heating mechanism 2 is also connected to the second supply pipe 15 via the third supply pipe 16.

[0057] In this embodiment, the heating mechanism 2 can heat the heat source medium in the heat source circulation pipe 11 and then transport it to the sludge drying mechanism 1. In the sludge drying mechanism 1, the sludge is dried by heat exchange with the dry and cold internal circulation air. The temperature of the heat source medium itself will decrease. The low-temperature heat source medium returns to the heating mechanism 2 through the heat source circulation pipe 11 for heating, thereby realizing the recycling of the heat source medium.

[0058] During the sludge drying process, ammonia nitrogen, COD, and other pollutants are present in the circulating air. Therefore, wastewater is generated by condensing the circulating air with a cooling medium to achieve wastewater collection and treatment. As a result, the temperature of the cooling medium rises when condensing the circulating air. The heated cooling medium is then transported to the heating unit 2 for heat exchange, serving as a low-grade heat source for the heating unit 2 to improve energy efficiency. After heat exchange, it can be directly transported to the sludge drying unit 1. At the same time, the cooling medium can also be cooled directly through the cooling unit 3 before being transported to the drying unit 1.

[0059] The absorption heat pump is configured for series / parallel operation. The reason for this configuration is that the heat recovered by the absorption heat pump from the cooling water is a fixed value, meaning the flow rate of cooling water entering the absorption heat pump is constant. In summer, the cooling tower increases the cooling water flow rate to ensure sufficient cooling capacity, but the absorption heat pump requires a fixed flow rate. Since the flow rate is the same as in series operation, a parallel connection is established to bypass the excess cooling water. This configuration achieves the dual function of heat recovery from the cooling water and cooling capacity provided by the cooling tower in summer, effectively adapting to changes in ambient temperature.

[0060] Furthermore, the sludge drying mechanism 1 is a belt dryer.

[0061] Specifically, belt dryers are typically waste heat type belt dryers. The process flow is as follows: municipal and industrial sludge with a moisture content of 80% (wet sludge) or 60% (semi-dry sludge) from wastewater treatment plants is transported to a wet sludge silo via a sealed transfer vehicle. Then, via a sludge hopper and a wet sludge conveyor, it is fed into the belt dryer. The wet sludge is separated into dry sludge and condensate wastewater by the belt dryer. Typically, a heat source water circulation system is installed outside the belt dryer to provide heat to the dryer, and the heat source water is supplied to the belt dryer. The system provides heat, which is exchanged with the dry and cool internal circulating air inside the dryer, heating the circulating air into dry and hot circulating air. The heat source water is cooled into low-temperature hot water, which is then heated to high-temperature hot water through a heat exchanger and re-enters the belt dryer for circulation. In addition, a cooling water system is installed outside the belt dryer. The low-temperature cooling water provides cooling capacity to the belt dryer and exchanges heat with the humid and hot internal circulating air inside the dryer, cooling the humid and hot internal circulating air and condensing the wastewater into dry and cool circulating air, thus preventing pollutants from being emitted to the outside.

[0062] Furthermore, such as Figure 2 As shown, the heating mechanism 2 is connected to the steam source 4 through a steam conveying pipe 41, and a desuperheating and pressure reducing device 42 is installed on the steam conveying pipe 41.

[0063] The heating mechanism 2 is an absorption heat pump.

[0064] In this embodiment, an absorption heat pump is used as the heating mechanism 2, which ensures a stable temperature of the heat source medium supplied to the belt dryer. Simultaneously, using steam from the power plant as the heat source reduces steam consumption during the sludge drying process and improves steam thermal efficiency. The desuperheater and pressure reducer 42 lowers the steam temperature and pressure to within the design range allowed by the absorption heat pump 2. The steam serves as the high-level driving heat source for the absorption heat pump, undergoes heat exchange and condensation, and the steam condensate is collected and utilized comprehensively.

[0065] Furthermore, such as Figure 2 As shown, a heat source medium circulation pump 5 is installed on the heat source circulation pipeline 11;

[0066] A cooling medium circulation pump 6 is installed on the second supply pipe 15. The cooling medium circulation pump 6 is located between the cooling medium inlet of the sludge drying mechanism 1 and the connection position of the third supply pipe 16 and the second supply pipe 15.

[0067] Specifically, the heat source medium circulation pump 5 can overcome the resistance of the heat source medium in the heat source circulation pipeline 11 and realize the transportation of the heat source medium; the cooling medium circulation pump 6 can overcome the resistance of the cooling medium in the pipeline and realize the transportation of the cooling medium.

[0068] Furthermore, such as Figure 2As shown, the dry sludge outlet of the sludge drying mechanism 1 is connected to the dry sludge storage bin 7;

[0069] The condensate outlet of the sludge drying unit 1 is connected to the wastewater treatment device 8.

[0070] In this embodiment, the dry sludge storage bin 7 is connected to the dry sludge outlet of the sludge drying mechanism 1 through a conveyor belt, pipeline, etc., so that the dried sludge enters the dry sludge storage bin 7 for storage, and is then transported to the boiler to be mixed with pulverized coal when boiler co-combustion is required.

[0071] Furthermore, such as Figure 2 As shown, valves 9 are provided in the first input pipe 12, the second input pipe 13, the first supply pipe 14, and the third supply pipe 16.

[0072] In this embodiment, valve 9 can be configured as a pneumatic or electric valve, which can automatically open and close according to a control signal.

[0073] Furthermore, the cooling mechanism 3 is a cooling water tower.

[0074] In this embodiment, a cooling tower is used for heat exchange and cooling, which can stabilize the cooling water at the design value, ensure a stable cooling capacity provided by the system, and ensure that the system output is not affected by seasonal temperature changes.

[0075] Furthermore, both the heat source medium and the cooling medium are demineralized water.

[0076] In this embodiment, both the heat source medium and the cooling medium are in closed-loop circulation, and neither the heat source medium nor the cooling medium comes into contact with the outside world. The initial water is demineralized water, which can prevent scaling in the pipelines and heat exchangers, improve the heat exchange efficiency of the equipment, and ensure the system output.

[0077] In another implementation, such as Figure 2As shown, the cooling medium inlet of the cooling mechanism 3 is connected to the cooling medium outlet of the heating mechanism 2 through the second input pipe 13; the cooling medium outlet of the drying mechanism 1 is connected to the second input pipe 13 through the first input pipe 12; and a three-way valve is installed at the connection position of the first input pipe 12 and the second input pipe 13 to realize the on / off and flow control of each pipe; the cooling medium inlet of the heating mechanism 2 is connected to the first input pipe 12 through the first supply pipe 14; and a three-way valve is installed at the connection position of the first supply pipe 14 and the first input pipe 12 to realize the on / off and flow control of each pipe; the cooling medium outlet of the cooling mechanism 3 is connected to the cooling medium inlet of the sludge drying mechanism 1 through the second supply pipe 15; one end of the third supply pipe 16 is connected to the second input pipe 13, and the other end is connected to the second supply pipe 15; and a three-way valve is installed at each connection position to realize the on / off and flow control of each pipe. When this connection method is adopted, the valve installed on the first input pipe 12 is located between the connection position of the first input pipe 12 and the first supply pipe 14 and the connection position of the first input pipe 12 and the second input pipe 13; the valve installed on the second input pipe 13 is located between the connection position of the first input pipe 12 and the second input pipe 13 and the connection position of the second input pipe 13 and the third supply pipe 16.

[0078] Through the above approach, my solution can achieve the following beneficial effects:

[0079] 1. A belt dryer coupled with an absorption heat pump recovers heat from the cooling water, improving the system's thermal efficiency. The steam thermal efficiency COP is 1.6 to 1.8, which can reduce steam consumption by 30 to 40%.

[0080] 2. The heat source water supplied to the belt dryer has a stable temperature and is not affected by changes in environment or operating conditions.

[0081] 3. The drying temperature inside the dryer is stable at around 70℃, which is low-temperature drying. The quality of the dried sludge wastewater is good. At this temperature, the volatilization rate of organic matter in the sludge is low, avoiding the generation of malodorous gases. It is also unaffected by changes in the environment and operating conditions. The quality of the condensate wastewater fluctuates very little, which reduces the burden on the subsequent wastewater treatment system and also reduces wastewater treatment costs.

[0082] 4. Both the cooling medium and the heat source medium are in closed-loop circulation, and the medium does not come into contact with the outside world. The initial medium is demineralized water to avoid scaling in the pipelines and heat exchangers, which helps to improve the heat exchange efficiency of the equipment and ensure the system output.

[0083] 5. The cooling system uses a cooling tower for heat exchange, which can stabilize the cooling water at the design value, ensure a stable cooling capacity provided by the system in case of water shortage, and ensure that the system output is not affected by seasonal temperature changes.

[0084] 6. The circulating cooling medium system is designed for two operating conditions. One of the operating conditions is designed for high-temperature environments in summer, which can ensure that the system can operate normally under extreme temperatures and that production capacity is not affected.

[0085] like Figure 3 As shown, this embodiment also provides a control method for a sludge drying system, applied to the above-mentioned sludge drying system, the method comprising:

[0086] Step 101: Obtain the ambient temperature value;

[0087] Step 102: Determine the operating conditions based on the ambient temperature value;

[0088] Step 103: Based on the operating conditions, control the on / off state of the first input pipe, the second input pipe, the first supply pipe, the second supply pipe, and the third supply pipe.

[0089] Further, determining the operating conditions based on the ambient temperature value includes:

[0090] If the ambient temperature value is less than or equal to the preset temperature threshold, then control the first supply pipe, the second input pipe and the second supply pipe to be connected, and control the first input pipe and the third supply pipe to be disconnected.

[0091] If the ambient temperature value is greater than the preset temperature threshold, the first input pipe, the first supply pipe, the second supply pipe and the third supply pipe are controlled to be connected, and the second input pipe is controlled to be disconnected.

[0092] Specifically, in this embodiment, the pipeline on / off control is carried out according to the changes in the external ambient temperature, which can improve energy utilization while ensuring the stability of the cooling capacity provided by the cooling medium, so that the system output is not affected by seasonal temperature changes, and ensure that the ammonia nitrogen and COD content in the belt dryer does not exceed the design value.

[0093] More specifically, the opening and closing of the pipelines is achieved by controlling the opening and closing of valves 9 installed on the first input pipeline 12, the second input pipeline 13, the first supply pipeline 14, and the third supply pipeline 16. The valves 9 are connected to the controller, which determines the operating conditions based on the ambient temperature value and controls the valves accordingly.

[0094] In this embodiment, such as Figure 2As shown, both the heat source medium and the cooling medium are demineralized water. The heat source water circulation system: The heat source water circulates between the belt dryer, the heat source medium circulation pump, the absorption heat pump, and back to the belt dryer. The heat source water, at approximately 90°C, enters the belt dryer for heat exchange and cooling to approximately 70°C. The heat source medium circulation pump then pressurizes the water, sending it to the absorption heat pump. There, it exchanges heat with steam and is heated to approximately 90°C before re-entering the belt dryer for circulation. The initial water used in this system is demineralized water.

[0095] Cooling water circulation system: Cooling water circulates between the belt dryer, absorption heat pump, closed-loop cooling tower, cooling medium circulation pump, and back to the belt dryer. The cooling water circulation system operates under two conditions:

[0096] Operating Condition 1: Series Operation, adaptable to spring, autumn, and winter temperatures. When the ambient temperature is less than or equal to the preset temperature threshold, 27°C low-temperature cooling water enters the belt dryer for heat exchange and is heated to 40°C. The 40°C high-temperature cooling water serves as a low-grade heat source for the absorption heat pump, providing some heat energy to the absorption heat pump. The 40°C high-temperature cooling water is cooled to 35°C medium-temperature cooling water after heat exchange by the absorption heat pump. The 35°C medium-temperature cooling water is cooled to 27°C by a closed cooling tower. A cooling medium circulation pump is set up to pressurize and overcome system resistance, sending the cooling water into the belt dryer to form a circulation, such as: abcdga.

[0097] Operating Condition 2: Parallel Operation, adapted to high summer temperatures (due to high wet-bulb temperatures in summer, the cooling tower cannot lower the cooling water to 27℃; the design temperature for cooling water is set at 34℃). When the ambient temperature exceeds the preset temperature threshold, the 34℃ low-temperature cooling water enters the belt dryer for heat exchange and is heated to 40℃. The 40℃ high-temperature cooling water is divided into two paths: one path serves as a low-grade heat source for the absorption heat pump, providing some heat energy; the 40℃ high-temperature cooling water is cooled to 35℃ after heat exchange by the absorption heat pump; the other path enters the closed cooling tower for cooling to 32℃. The two paths merge into one 34℃ cooling water. A cooling medium circulation pump is set up to pressurize and overcome system resistance, sending the cooling water into the belt dryer to form a circulation, such as: abcfga and aedga.

[0098] The absorption heat pump is configured for series / parallel operation. This is because the heat recovered by the absorption heat pump from the cooling water is a fixed value, meaning the flow rate of cooling water entering the absorption heat pump is constant. In summer, the cooling tower increases the cooling water flow rate to ensure sufficient cooling capacity, but the absorption heat pump requires a fixed flow rate. Since the flow rate is the same as in series operation, a parallel connection is used to bypass the excess cooling water. This configuration allows for the dual function of heat recovery from the cooling water and cooling capacity provision from the cooling tower in summer, effectively adapting to changes in ambient temperature.

[0099] In another embodiment, the opening of the valves on the first input pipe and the third supply pipe is adjusted by obtaining the temperature value of the cooling medium at the cooling medium inlet of the belt dryer, so that the temperature value of the cooling medium at the cooling medium inlet of the belt dryer is kept within a set range.

[0100] Through the above approach, my solution can achieve the following beneficial effects:

[0101] 1. A belt dryer coupled with an absorption heat pump recovers heat from the cooling water, improving the system's thermal efficiency. The steam thermal efficiency COP is 1.6 to 1.8, which can reduce steam consumption by 30 to 40%.

[0102] 2. The heat source water supplied to the belt dryer has a stable temperature and is not affected by changes in environment or operating conditions.

[0103] 3. The drying temperature inside the dryer is stable at around 70℃, which is low-temperature drying. The quality of the dried sludge wastewater is good. At this temperature, the volatilization rate of organic matter in the sludge is low, avoiding the generation of malodorous gases. It is also unaffected by changes in the environment and operating conditions. The quality of the condensate wastewater fluctuates very little, which reduces the burden on the subsequent wastewater treatment system and also reduces wastewater treatment costs.

[0104] 4. Both the cooling medium and the heat source medium are in closed-loop circulation, and the medium does not come into contact with the outside world. The initial medium is demineralized water to avoid scaling in the pipelines and heat exchangers, which helps to improve the heat exchange efficiency of the equipment and ensure the system output.

[0105] 5. The cooling system uses a cooling tower for heat exchange, which can stabilize the cooling water at the design value, ensure a stable cooling capacity provided by the system in case of water shortage, and ensure that the system output is not affected by seasonal temperature changes.

[0106] 6. The circulating cooling medium system is designed for two operating conditions. One of the operating conditions is designed for high-temperature environments in summer, which can ensure that the system can operate normally under extreme temperatures and that production capacity is not affected.

[0107] The optional embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above embodiments. Within the scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the protection scope of the embodiments of the present invention.

[0108] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the embodiments of the present invention will not describe the various possible combinations separately.

[0109] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. This program is stored in a storage medium and includes several instructions to cause a microcontroller, chip, or processor to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0110] Furthermore, various different implementations of the present invention can be combined arbitrarily, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed in the present invention.

Claims

1. A control method for a sludge drying system, characterized in that, The sludge drying system includes: Sludge drying unit (1), used for drying sludge; A heating mechanism (2) is connected to the sludge drying mechanism (1) via a heat source circulation pipe (11). The heating mechanism (2) continuously supplies heated heat source medium to the sludge drying mechanism (1) via the heat source circulation pipe (11) and heats the heat source medium from the sludge drying mechanism (1). The cooling medium inlet of the heating mechanism (2) is connected to the cooling medium outlet of the sludge drying mechanism (1) via a first supply pipe (14) for heating the heat source medium using the heat in the cooling medium. The cooling mechanism (3) has a cooling medium inlet connected to the cooling medium outlet of the sludge drying mechanism (1) via a first input pipe (12) and a cooling medium outlet connected to the cooling medium outlet of the heating mechanism (2) via a second input pipe (13). The cooling medium outlet of the cooling mechanism (3) is connected to the cooling medium inlet of the sludge drying mechanism (1) via a second supply pipe (15). The cooling mechanism (3) is used to continuously supply the sludge drying mechanism (1) with cooled cooling medium and to cool the cooling medium from the sludge drying mechanism (1) and the heating mechanism (2). The cooling medium outlet of the heating mechanism (2) is also connected to the second supply pipe (15) through the third supply pipe (16); the heating mechanism (2) is connected to the steam source (4) through the steam transmission pipe (41), and the steam transmission pipe (41) is equipped with a de-cooling pressure reducer (42); the heating mechanism (2) is an absorption heat pump. A heat source medium circulation pump (5) is installed on the heat source circulation pipe (11); a cooling medium circulation pump (6) is installed on the second supply pipe (15), and the cooling medium circulation pump (6) is located between the cooling medium inlet of the sludge drying mechanism (1) and the connection position of the third supply pipe (16) and the second supply pipe (15). The method includes: Obtain the ambient temperature value; Determining operating conditions based on the ambient temperature value includes: If the ambient temperature value is less than or equal to the preset temperature threshold, the first supply pipe (14), the second input pipe (13), and the second supply pipe (15) are controlled to be connected, and the first input pipe (12) and the third supply pipe (16) are controlled to be disconnected. If the ambient temperature value is greater than the preset temperature threshold, the first input pipe (12), the first supply pipe (14), the second supply pipe (15) and the third supply pipe (16) are controlled to be turned on, and the second input pipe (13) is controlled to be turned off.

2. The control method for the sludge drying system according to claim 1, characterized in that, The sludge drying mechanism (1) is a belt dryer.

3. The control method for the sludge drying system according to claim 1, characterized in that, The dry sludge outlet of the sludge drying unit (1) is connected to the dry sludge storage bin (7). The condensate outlet of the sludge drying unit (1) is connected to the wastewater treatment device (8).

4. The control method for the sludge drying system according to claim 1, characterized in that, Valves (9) are provided on the first input pipe (12), the second input pipe (13), the first supply pipe (14) and the third supply pipe (16).

5. The control method for the sludge drying system according to claim 1, characterized in that, The cooling mechanism (3) is a cooling water tower.

6. The control method for the sludge drying system according to claim 1, characterized in that, Both the heat source medium and the cooling medium are demineralized water.

Images