A sludge drying and coal-fired boiler co-processing system

Abstract

The application discloses a sludge drying and coal-fired boiler collaborative treatment system, which comprises a boiler system, a molten salt system and a secondary sludge drying system; the boiler system comprises a boiler, and the boiler is provided with a flue gas outlet; the molten salt system is internally circulated with molten salt, and the inlet of the molten salt system is communicated with the flue gas outlet, so as to heat and store heat of the molten salt by using the flue gas of the boiler; the secondary sludge drying system is used for drying sludge; and the air blower is provided with an air outlet, which is communicated with the molten salt system and used for conveying the airflow exchanged with the molten salt system into the secondary sludge drying system. According to the sludge drying and coal-fired boiler collaborative treatment system, the stable heat transfer channel is established between the boiler system and the secondary sludge drying system through the molten salt system without directly introducing the dust-containing flue gas, the collaborative closed-loop treatment of the sludge drying and the boiler waste heat utilization is realized, and the heat exchange efficiency and the environmental protection emission requirement are considered.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization and comprehensive energy utilization technology, and in particular to a sludge drying and coal-fired boiler co-processing system. Background Technology

[0002] In the construction of a new power system guided by the "dual carbon" goal, the role of thermal power is undergoing a profound transformation, gradually shifting from the "main power source" that ensured power supply to a "regulatory power source" that supports grid stability and promotes the consumption of new energy. The core of this transformation lies in the fact that thermal power, with its massive installed capacity, mature operating experience, and abundant regulation capacity reserves, has become a key "ballast" and "stabilizer" in addressing the challenges of the intermittency and volatility of new energy sources. At the same time, thermal power units are playing an increasingly important role in reducing carbon emissions by co-firing biomass and solid waste (sludge).

[0003] Urban sewage sludge has a high water content and complex composition, and is typically disposed of through landfill, land application, composting, and incineration. Landfilling requires significant land resources and poses a long-term risk of groundwater contamination. Land application involves using sludge in farmland or urban greening, but carries risks of heavy metal and pathogen contamination. Composting, which only converts sludge into fertilizer through microbial fermentation, also requires a large land area and carries risks of odor and heavy metal contamination. Incineration can reduce sludge volume by over 90%, eliminate pathogens, and utilize some of the sludge's calorific value, but it suffers from low thermal efficiency and cannot effectively remove pollutants such as dioxins from the flue gas.

[0004] In existing technologies, solutions for the co-utilization of sludge drying and coal-fired boilers often employ a single high-temperature flue gas or extracted steam to provide a heat source for sludge drying, or directly co-fire sludge on the boiler side. The drying unit and the boiler body are mostly simply connected by piping. Furthermore, constrained by the unit's deep peak-shaving operation and denitrification temperature window, flue gas temperature and flow fluctuate significantly. There is a lack of a medium-temperature energy storage link to regulate and buffer between the boiler and drying sides, making it difficult to simultaneously meet the needs of a continuous and stable heat source for sludge drying and the unit's flexible adjustment requirements. Summary of the Invention

[0005] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a sludge drying and coal-fired boiler co-processing system, which establishes a stable heat transfer channel between the boiler system and the secondary sludge drying system through a molten salt system without directly introducing dust-laden flue gas. On the one hand, this improves the comprehensive utilization efficiency of the boiler's flue gas waste heat and reduces the secondary sludge drying system's dependence on additional fossil fuels. On the other hand, it reduces the risk of dust and corrosive substances entering the drying equipment, achieving a synergistic closed-loop treatment of sludge drying and boiler waste heat utilization, while taking into account both heat exchange efficiency and environmental emission requirements.

[0006] According to an embodiment of the present invention, a sludge drying and coal-fired boiler co-processing system includes: a boiler system comprising a boiler having a flue gas outlet; a molten salt system in which molten salt circulates, the inlet of the molten salt system being connected to the flue gas outlet for heating and storing heat using boiler flue gas; a secondary sludge drying system for drying sludge; and a blower having an air outlet connected to the molten salt system for conveying airflow that exchanges heat with the molten salt system to the secondary sludge drying system.

[0007] According to an embodiment of the present invention, a sludge drying and coal-fired boiler co-processing system is provided. The boiler has a flue gas outlet, and molten salt circulates within a molten salt system. The inlet of the molten salt system is connected to the flue gas outlet, used to heat and store the molten salt using boiler flue gas. A secondary sludge drying system is used to dry the sludge. A blower has an air outlet connected to the molten salt system, used to transport the airflow that has exchanged heat with the molten salt system to the secondary sludge drying system. This achieves a stable heat transfer channel between the boiler system and the secondary sludge drying system through the molten salt system without directly introducing dust-laden flue gas. On the one hand, this improves the comprehensive utilization efficiency of the boiler's flue gas waste heat and reduces the secondary sludge drying system's dependence on additional fossil fuels. On the other hand, it reduces the risk of dust and corrosive substances entering the drying equipment, achieving a synergistic closed-loop treatment of sludge drying and boiler waste heat utilization, while also considering heat exchange efficiency and environmental emission requirements.

[0008] In some embodiments of the present invention, the molten salt system includes a low-temperature molten salt storage tank, a medium-temperature molten salt storage tank, and a molten salt circulation pipeline connecting the low-temperature molten salt storage tank and the medium-temperature molten salt storage tank. The low-temperature molten salt storage tank, the medium-temperature molten salt storage tank, and the molten salt circulation pipeline constitute a first heat exchange flow path for transporting molten salt. The airflow path between the air outlet and the secondary sludge drying system constitutes a second heat exchange flow path. The first heat exchange flow path and the second heat exchange flow path exchange heat with each other.

[0009] In some embodiments of the present invention, the boiler system further includes an electrostatic precipitator system, the outlet of the molten salt system is connected to the electrostatic precipitator system, and the airflow path between the flue gas outlet, the inlet of the molten salt system and the outlet of the molten salt system constitutes a third heat exchange path, wherein the first heat exchange path and the third heat exchange path exchange heat with each other.

[0010] In some embodiments of the present invention, a denitrification flue gas bypass is provided at the main flue outlet of the boiler, the outlet of the denitrification flue gas bypass forms the flue gas outlet, and a rotatable baffle is provided in the denitrification flue gas bypass for adjusting the flow rate of flue gas flowing through the denitrification flue gas bypass.

[0011] In some embodiments of the present invention, the secondary sludge drying system has an exhaust gas outlet connected to the furnace combustion zone of the boiler, for introducing the exhaust gas generated during the sludge drying process into the furnace combustion zone for incineration.

[0012] In some embodiments of the present invention, the system further includes: a primary sludge drying system for conveying sludge to the secondary sludge drying system; the primary sludge drying system includes a staggered turning assembly, the staggered turning assembly including a first chain plate and a second chain plate, wherein the two ends in a first direction are a first end and a second end, respectively; the first chain plate conveys sludge along the direction from the first end to the second end, and the second chain plate conveys sludge along the direction from the second end to the first end; in the direction from the first end to the second end, the second end of the first chain plate is inclined upward, and the second end of the second chain plate is inclined downward; in the vertical direction, the second end of the first chain plate is opposite to the second end of the second chain plate and is located above the second end of the second chain plate, and the first end of the first chain plate is opposite to the first end of the second chain plate and is located below the first end of the second chain plate.

[0013] In some embodiments of the present invention, the first chain plate is provided with a first tumbling tooth, the first tumbling tooth being a plurality of such teeth and arranged at intervals along the conveying direction of the first chain plate, for tumbling the sludge when the first chain plate conveys sludge; and / or, the second chain plate is provided with a second tumbling tooth, the second tumbling tooth being a plurality of such teeth and arranged at intervals along the conveying direction of the second chain plate, for tumbling the sludge when the second chain plate conveys sludge.

[0014] In some embodiments of the present invention, the angle between the extension direction of the first chain plate and the extension direction of the second chain plate is α, and satisfies: 30°≤α≤60°.

[0015] In some embodiments of the present invention, the primary sludge drying system further includes a drying zone, the top and sides of which are formed of a light-transmitting material to enclose a greenhouse-like drying space for accommodating the staggered turning assembly.

[0016] In some embodiments of the present invention, the top of the drying zone is provided with a reflector array, the reflector array having an extended state and a retracted state, the reflector array being used to reflect sunlight onto the sludge on the staggered overturning assembly; and / or, the primary sludge drying system further includes a forced ventilation system, the forced ventilation system being used to exhaust the humid air in the drying zone and introduce external dry air.

[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0018] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of a sludge drying and coal-fired boiler co-processing system according to an embodiment of the present invention. Figure 2 This is a schematic diagram of a staggered throwing and flipping assembly according to an embodiment of the present invention; Figure 3 This is a control schematic diagram of a sludge drying and coal-fired boiler co-processing system according to an embodiment of the present invention; Figure 4 This is a heat exchange schematic diagram of a sludge drying and coal-fired boiler co-processing system according to an embodiment of the present invention.

[0019] Figure label: 100. Sludge drying and co-processing system for coal-fired boilers; 1. Boiler system; 11. Boiler; 111. Denitrification flue gas bypass; 1111. Flue gas outlet; 112. Furnace combustion zone; 12. Electrostatic precipitator system; 13. Booster fan; 2. Molten salt system; 3. Secondary sludge drying system; 31. Exhaust gas outlet; 4. Blower; 41. Air outlet; 5. Primary sludge drying system; 51. Staggered turning assembly; 511. First chain plate, 5111. First turning tooth; 512. Second chain plate, 5121. Second turning tooth; 513. Viscosity sensor; 52. Drying zone; 521. Reflector array; 6. Dried sludge storage system; 7. Wastewater purification system. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0021] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, features defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more. In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" 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 mechanical connection or an electrical 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.

[0022] The following description, with reference to the accompanying drawings, describes a sludge drying and coal-fired boiler co-processing system 100 according to an embodiment of the present invention.

[0023] like Figure 1 As shown, the sludge drying and coal-fired boiler co-processing system 100 according to an embodiment of the present invention includes a boiler system 1, a molten salt system 2, a secondary sludge drying system 3, and a blower 4. The boiler system 1 includes a boiler 11 with a flue gas outlet 1111. Molten salt circulates within the molten salt system 2, and the inlet of the molten salt system 2 is connected to the flue gas outlet 1111 for heating and storing heat in the molten salt using boiler flue gas. The secondary sludge drying system 3 is used to dry the sludge. The blower 4 has an air outlet 41 connected to the molten salt system 2 for conveying the airflow that exchanges heat with the molten salt system 2 to the secondary sludge drying system 3.

[0024] Specifically, boiler system 1 is a coal-fired boiler system. During the operation of the unit, the high-temperature flue gas generated is discharged through flue gas outlet 1111. Molten salt system 2 is located downstream of flue gas outlet 1111. Molten salt circulates within molten salt system 2 and exchanges heat with the incoming flue gas, storing the heat in the flue gas in the molten salt. Among them, the high-temperature flue gas with a temperature of over 300℃ drawn from the denitrification system outlet of boiler 11 serves as the main heat source for molten salt system 2. The molten salt is preferably a molten salt mixture suitable for the medium temperature range, such as a binary nitrate system (60% NaNO3 + 40% KNO3), with a melting point of approximately 220℃ and an operating temperature range of approximately 250℃ to 550℃, to adapt to the high-temperature flue gas conditions of the boiler and ensure stable energy storage and release of the molten salt in the medium temperature range.

[0025] Meanwhile, the blower 4 draws in air from the outside or the plant's air source and sends it through the air outlet 41 into the air-side heat exchange channel of the molten salt system 2, so that the air exchanges heat with the molten salt after heat storage and is heated into a high-temperature airflow. The heated airflow is further transported to the secondary sludge drying system 3 as a drying heat source to dry the sludge with high-temperature hot air.

[0026] In actual operation, considering that the blower 4 of boiler 11 is often limited to minimum output under deep load, and the secondary air volume is usually higher than the air volume required for combustion, a bypass duct can be added to the outlet side of blower 4 to draw part of the secondary air out from the outlet of blower 4 and introduce it into molten salt system 2 for heat exchange. After this part of the secondary air is heated to about 200℃~220℃ by the heating of medium temperature molten salt, it is sent into the secondary sludge drying system 3 as hot air. Under the mechanical action of hot air and the stirring and fluidization of the secondary sludge drying system 3 itself, the sludge is further dried to the target moisture content of about 20%.

[0027] Therefore, the waste heat from the flue gas of boiler system 1 is first stored in molten salt system 2, and then the heat released from the molten salt is sent to the secondary sludge drying system 3 in the form of hot air by blower 4. This allows the heat energy generated on the boiler side to be effectively utilized for the deep drying of sludge. Thus, without directly introducing dust-laden flue gas, a stable heat transfer channel is established between boiler system 1 and secondary sludge drying system 3 through molten salt system 2. On the one hand, this improves the comprehensive utilization efficiency of waste heat from the flue gas of boiler 11 and reduces the dependence of secondary sludge drying system 3 on additional fossil energy. On the other hand, it reduces the risk of dust and corrosive substances entering the drying equipment, realizing the synergistic closed-loop treatment of sludge drying and boiler waste heat utilization, while taking into account both heat exchange efficiency and environmental emission requirements.

[0028] In addition, the sludge dried by the secondary sludge drying system 3 can be further sent to the dried sludge storage system 6 for temporary storage, and then sent to the pulverizing system in a preset ratio to be mixed with raw coal and burned together according to the operation and co-firing requirements of the boiler 11, so as to realize the resource utilization of the calorific value of the sludge.

[0029] The sludge drying and coal-fired boiler co-processing system 100 according to an embodiment of the present invention includes a boiler 11 with a flue gas outlet 1111, a molten salt system 2 with circulating molten salt, the inlet of the molten salt system 2 being connected to the flue gas outlet 1111 for heating and storing the molten salt using boiler flue gas, a secondary sludge drying system 3 for drying sludge, and a blower 4 with an air outlet 41 connected to the molten salt system 2 for transporting the airflow that exchanges heat with the molten salt system 2 to the secondary sludge drying system 3. This achieves a stable heat transfer channel between the boiler system 1 and the secondary sludge drying system 3 through the molten salt system 2 without directly introducing dust-laden flue gas. On the one hand, this improves the comprehensive utilization efficiency of the waste heat from the boiler 11's flue gas and reduces the secondary sludge drying system 3's dependence on additional fossil fuels. On the other hand, it reduces the risk of dust and corrosive substances entering the drying equipment, achieving a synergistic closed-loop treatment of sludge drying and boiler waste heat utilization, while also considering heat exchange efficiency and environmental emission requirements.

[0030] In some embodiments of the present invention, such as Figure 1 and Figure 4 As shown, the molten salt system 2 includes a low-temperature molten salt storage tank, a medium-temperature molten salt storage tank, and a molten salt circulation pipeline connecting the low-temperature molten salt storage tank and the medium-temperature molten salt storage tank. The low-temperature molten salt storage tank, the medium-temperature molten salt storage tank, and the molten salt circulation pipeline constitute the first heat exchange flow path for transporting molten salt. The airflow path between the air outlet 41 and the secondary sludge drying system 3 constitutes the second heat exchange flow path. The first heat exchange flow path and the second heat exchange flow path exchange heat with each other.

[0031] Specifically, the molten salt stored in the low-temperature molten salt storage tank first absorbs heat from the flue gas of boiler 11 when circulating in the first heat exchange flow path. The heated molten salt is then collected in the medium-temperature molten salt storage tank and continues to circulate in the first heat exchange flow path. The air delivered by the blower 4 enters the second heat exchange flow path through the air outlet 41. In the second heat exchange flow path, the air flows along the air-side channel adjacent to the first heat exchange flow path and exchanges heat with the high-temperature molten salt in the first heat exchange flow path through the heat exchange wall. This allows the air to carry away the heat released by the molten salt from the second heat exchange flow path and be heated into a high-temperature airflow. The molten salt then cools down after releasing heat and returns to the low-temperature molten salt storage tank.

[0032] Thus, the first heat exchange flow path is responsible for completing the heat absorption, storage and release processes of the molten salt inside the molten salt system 2, while the second heat exchange flow path is responsible for transferring the heat obtained from the first heat exchange flow path to the airflow supplied to the secondary sludge drying system 3. The two heat exchange flow paths exchange heat indirectly with each other through the heat exchange wall, so that the waste heat of the boiler flue gas can be stably and efficiently transferred to the hot air for sludge drying through the molten salt system 2. At the same time, direct contact between the flue gas and the drying air is avoided. Moreover, due to the high specific heat and stable characteristics of the molten salt in the medium temperature range, the influence of the flue gas load of the boiler 11 and the fluctuation of solar irradiance on the system can be effectively mitigated, so that the secondary sludge drying system 3 can still maintain a nearly constant hot air temperature and continuous drying capacity when external conditions fluctuate.

[0033] In some embodiments, the medium-temperature molten salt storage tank directly heats the dry air taken from the outlet of the blower 4, raising the temperature of this air to about 200°C to 220°C, and then uses it as the heat source for the secondary sludge drying system 3. The cooled molten salt is then returned to the low-temperature molten salt storage tank in a closed loop, realizing the heat storage and release process of molten salt in the low-temperature molten salt storage tank - medium-temperature molten salt storage tank - air heat exchange - low-temperature molten salt storage tank.

[0034] In some embodiments of the present invention, such as Figure 1 and Figure 4 As shown, the boiler system 1 also includes an electrostatic precipitator system 12. The outlet of the molten salt system 2 is connected to the electrostatic precipitator system 12. The airflow path between the flue gas outlet 1111, the inlet of the molten salt system 2 and the outlet of the molten salt system 2 constitutes a third heat exchange path. The first heat exchange path and the third heat exchange path exchange heat with each other.

[0035] Specifically, the high-temperature flue gas generated by the combustion of boiler 11 is discharged through flue gas outlet 1111 and enters the flue gas side channel of molten salt system 2. In the third heat exchange flow path, it flows sequentially through the inlet of molten salt system 2, the internal section for heat exchange with molten salt, and the outlet of molten salt system 2, and finally enters electrostatic precipitator system 12 from the outlet of molten salt system 2 for dust removal. During this process, the molten salt in the first heat exchange flow path and the flue gas in the third heat exchange flow path exchange heat through the heat exchange wall. The molten salt absorbs the sensible heat of the flue gas from the third heat exchange flow path and heats up and stores heat, while the flue gas is cooled to a temperature range suitable for the operation of electrostatic precipitator system 12.

[0036] Therefore, the third heat exchange flow path is responsible for transferring the waste heat of the boiler flue gas to the molten salt in the first heat exchange flow path. The first heat exchange flow path then transfers the obtained heat to the hot air supplied to the secondary sludge drying system 3 through heat exchange with the second heat exchange flow path, realizing a multi-stage energy transfer chain of flue gas-molten salt-hot air. On the one hand, it improves the comprehensive utilization efficiency of the waste heat of the flue gas, and on the other hand, it reduces the temperature of the flue gas entering the electrostatic precipitator system 12, which is conducive to improving the dust removal effect and reducing the heat load of the electrostatic precipitator equipment.

[0037] In addition, under high load conditions of boiler 11, the flue gas first heats the initial molten salt or the molten salt that has released heat in the low temperature molten salt storage tank, so that the temperature of the molten salt gradually increases before entering the medium temperature molten salt storage tank. The molten salt in the medium temperature molten salt storage tank is kept in a medium-high temperature range suitable for heating the air. The temperature of the flue gas after heat exchange is reduced to about 180℃~200℃ or below before entering the downstream electrostatic precipitator system 12. This is conducive to the stable operation of the electrostatic precipitator system 12 within a suitable temperature window.

[0038] In some embodiments of the present invention, such as Figure 1 and Figure 4 As shown, a denitrification flue gas bypass 111 is provided at the outlet of the main flue of boiler 11. The outlet of the denitrification flue gas bypass 111 forms a flue gas outlet 1111. A rotatable baffle is provided inside the denitrification flue gas bypass 111. The baffle is used to regulate the flow rate of flue gas flowing through the denitrification flue gas bypass 111.

[0039] Specifically, the denitrification flue gas bypass 111 is located at the outlet of the denitrification device in the main flue of boiler 11, serving as a branch pipe of the main flue. Its outlet is connected to the inlet of the molten salt system 2, forming the flue gas outlet 1111. By installing a rotatable baffle inside the denitrification flue gas bypass 111, the flow rate of flue gas flowing through the denitrification flue gas bypass 111 can be adjusted according to the current load of boiler system 1, the heat storage status of molten salt system 2, and the heat demand of secondary sludge drying system 3. When it is necessary to increase the molten salt temperature or provide more heat for sludge drying, the baffle is opened appropriately to allow more flue gas to enter the molten salt system 2 through the denitrification flue gas bypass 111 and participate in the heat exchange of the third heat exchange flow path. When the molten salt temperature has reached the set upper limit or it is necessary to limit the amount of flue gas entering the molten salt system 2, the baffle opening is reduced to decrease the bypass flow. Thus, by adjusting and controlling the flue gas flow of the third heat exchange flow path through the denitrification flue gas bypass 111 and the internal baffle, the heat generation of the boiler-side flue gas and the heat demand of the molten salt system 2 and the secondary sludge drying system 3 can be flexibly matched, making the heat exchange process between the first and third heat exchange flow paths more stable and controllable, while also taking into account the operating conditions of the downstream electrostatic precipitator system 12 and the flue gas purification device in the main flue.

[0040] In some embodiments, for example, when the boiler unit 11 is under high load and the flue gas temperature in the denitrification section is not lower than about 350°C, the damper opening can be controlled at about 30% to 50%, and the corresponding extraction volume can be in the range of about 2000 to 3000 m³ / h, so as to ensure that a sufficient high-temperature flue gas heat source is provided for the molten salt system 2, without significantly affecting the denitrification reaction temperature window (about 300°C to 400°C) in the main flue. When the peak load is deep and the flue gas temperature is lower than about 300°C, the damper opening can be controlled at less than 10% or closed, so that the limited high-temperature flue gas can prioritize the normal operation of the denitrification system and reduce the impact on the denitrification efficiency.

[0041] In some embodiments, such as Figure 1 As shown, the boiler system 1 may also include a booster fan 13, which is located downstream of the molten salt system 2 and is used to transport the flue gas after heat exchange and cooling by the molten salt system 2 to the subsequent electrostatic precipitator system 12 and flue gas purification device.

[0042] In some embodiments of the present invention, such as Figure 1 As shown, the secondary sludge drying system 3 has an exhaust gas outlet 31 that is connected to the furnace combustion zone 112 of the boiler 11, for introducing the exhaust gas generated during the sludge drying process into the furnace combustion zone 112 for incineration.

[0043] Specifically, the secondary sludge drying system 3 is equipped with an exhaust gas outlet 31, which is connected to the furnace combustion zone 112 of the boiler 11 via a pipeline. When the sludge is dried by high-temperature hot air in the secondary sludge drying system 3, exhaust gas containing water vapor, volatile organic compounds, and odorous components is generated. This exhaust gas is collected through the exhaust gas outlet 31 and directly sent to the furnace combustion zone 112, where it is incinerated and decomposed together with the coal burned in the boiler 11 under a high-temperature, oxygen-rich environment. Specifically, pollutants such as VOCs, water vapor, and odors generated during the sludge drying process are introduced into the furnace combustion zone 112 along with the heat-exchanged hot air for secondary combustion and high-temperature decomposition, thereby achieving the harmless and reduced-volume treatment of the exhaust gas.

[0044] Therefore, by incorporating the waste gas generated from sludge drying into the boiler combustion system for unified treatment, on the one hand, the existing high-temperature combustion conditions of the boiler are utilized, which is conducive to destroying VOCs and malodorous substances and reducing harmful gas emissions; on the other hand, it avoids setting up a separate complex waste gas treatment device, reduces the environmental protection treatment cost of the sludge drying system, and reduces additional exhaust chimneys and land occupation, so that sludge drying and boiler combustion processes can achieve synergy in exhaust gas treatment.

[0045] Furthermore, the ash residue after high-temperature combustion in the furnace and subsequent dust removal and purification can be utilized as a resource according to current standards. The entire process has no leachate discharge or fugitive emissions, which meets the requirements of solid waste resource utilization and strict environmental protection.

[0046] In some embodiments of the present invention, such as Figure 1 As shown, the sludge drying and coal-fired boiler co-processing system 100 is also connected to the dried sludge storage system 6 and the wastewater purification system 7. The sludge dried by the secondary sludge drying system 3 can be further sent to the dried sludge storage system 6 for temporary storage. According to the operation and co-firing requirements of the boiler system 1, it is sent to the pulverizing system in a preset ratio to be mixed with raw coal and burned together, so as to realize the synergistic utilization of the calorific value of the sludge. The wastewater generated in the sludge drying and subsequent treatment process is introduced into the wastewater purification system 7 for centralized purification treatment, so as to realize the synergistic treatment of the solid and liquid phases of the sludge.

[0047] In some embodiments of the present invention, such as Figure 1 , Figure 2 and Figure 4 As shown, the sludge drying and coal-fired boiler co-processing system 100 also includes a primary sludge drying system 5, which is used to transport sludge to the secondary sludge drying system 3. The primary sludge drying system 5 includes a staggered turning assembly 51, which includes a first chain plate 511 and a second chain plate 512. The two ends in the first direction are a first end and a second end, respectively. The first chain plate 511 transports sludge from the first end to the second end, and the second chain plate 512 transports sludge from the second end to the first end. In the direction from the first end to the second end, the second end of the first chain plate 511 is inclined upward, and the second end of the second chain plate 512 is inclined downward. In the vertical direction, the second end of the first chain plate 511 is opposite to the second end of the second chain plate 512 and is located above the second end of the second chain plate 512. The first end of the first chain plate 511 is opposite to the first end of the second chain plate 512 and is located below the first end of the second chain plate 512.

[0048] Specifically, the wet sludge is first conveyed to the feed end of the primary sludge drying system 5 and falls onto the first chain plate 511 near its first end. The first chain plate 511 moves at a preset speed from the first end to the second end, slowly pushing the sludge to the higher second end while spreading it during the conveying process. When the sludge moves with the first chain plate 511 to the vicinity of its second end, because the second end of the first chain plate 511 is vertically offset from and above the second end of the second chain plate 512, the sludge falls from the second end of the first chain plate 511 to the middle area of ​​the second chain plate 512 under the action of gravity, achieving a single drop and flip.

[0049] Subsequently, the second chain plate 512 runs in the opposite direction to the first chain plate 511, from the second end to the first end, conveying the received sludge to a lower position. During the conveying process, the sludge is further dispersed and spread. When the sludge moves with the second chain plate 512 to its first end, the sludge height is reduced, and the moisture has been initially evaporated and lost through the long path, multiple turning and exposure processes. It can then be sent to the secondary sludge drying system 3 for further drying by the subsequent conveying mechanism. Through the arrangement of the staggered turning components 51, the sludge moves back and forth along a path with opposite directions and multiple height differences and is turned and thrown multiple times in the primary sludge drying system 5. This significantly increases the contact area and contact time between the sludge and air and solar radiation, which is beneficial for reducing the sludge moisture content at the front end, thereby reducing the heat load of the secondary sludge drying system 3 and improving the energy efficiency of the entire co-processing system.

[0050] In some embodiments, a height difference of about 60 cm is provided between the first chain plate 511 and the second chain plate 512, and the linear velocity of the first chain plate 511 is 1.5:1 with the linear velocity of the second chain plate 512, so that the conveying speed of the upper layer is slightly higher than that of the lower layer or vice versa, in order to enhance the shearing and loosening effect of sludge during the falling and receiving process.

[0051] In some embodiments of the present invention, such as Figure 2 As shown, the first chain plate 511 is provided with a first tumbling tooth 5111, and there are multiple first tumbling teeth 5111 arranged at intervals along the conveying direction of the first chain plate 511, for tumbling the sludge when the first chain plate 511 conveys sludge; and / or, the second chain plate 512 is provided with a second tumbling tooth 5121, and there are multiple second tumbling teeth 5121 arranged at intervals along the conveying direction of the second chain plate 512, for tumbling the sludge when the second chain plate 512 conveys sludge.

[0052] Specifically, the first throwing teeth 5111 are disposed on the conveying surface of the first chain plate 511, and can be arranged in a strip-shaped or tooth-shaped structure along the width direction of the first chain plate 511. Multiple first throwing teeth 5111 are evenly spaced along the conveying direction of the first chain plate 511. When wet sludge accumulates on the first chain plate 511 and moves towards the second end, the first throwing teeth 5111 scrape, lift and cut the sludge layer, causing the sludge to be lifted on the surface of the first chain plate 511 and fall back down, thereby forming a tumbling and dispersing effect.

[0053] The second throwing and turning teeth 5121 are disposed on the conveying surface of the second chain plate 512, and multiple second throwing and turning teeth 5121 are also arranged at intervals along the conveying direction of the second chain plate 512. When the sludge falls from the first chain plate 511 to the second chain plate 512, it comes into contact with the second throwing and turning teeth 5121 again during the conveying process of the second chain plate 512. The second throwing and turning teeth 5121 agitate and turn the sludge a second or multiple times, so that the already broken sludge is further broken, spread thinner and evenly spread.

[0054] This allows the primary sludge drying system 5 to achieve a higher frequency of turning and a larger specific surface area within a limited layout length, providing more adequate pretreatment conditions for subsequent solar and hot air drying.

[0055] Furthermore, to prevent the turning teeth from adhering to and scaling during long-term contact with sludge with high water content, a hydrophobic coating can be provided on the surface of the first turning tooth 5111 and the second turning tooth 5121. By reducing the adhesion between the sludge and the metal surface, a dense sludge layer is avoided, ensuring that the first turning tooth 5111 and the second turning tooth 5121 maintain effective turning ability for a long time.

[0056] In some embodiments of the present invention, such as Figure 2As shown, the angle between the extension direction of the first chain plate 511 and the extension direction of the second chain plate 512 is α, and satisfies: 30°≤α≤60°.

[0057] Specifically, the first chain plate 511 and the second chain plate 512 are arranged in a cross shape in the planar projection, forming an angle α between their extension directions. When the angle α is in the range of 30° to 60°, on the one hand, it can ensure that the second end of the first chain plate 511 has a suitable height difference in the vertical direction relative to the second end of the second chain plate 512, so that the sludge has sufficient drop and horizontal displacement when falling from the first chain plate 511 to the second chain plate 512, which is conducive to forming a significant scattering and tumbling effect; on the other hand, it avoids the situation where the angle α is too small, resulting in an excessively long cross area of ​​the chain plates and an excessively large equipment footprint, or the situation where the angle α is too large, resulting in an excessively high overall height and a significant increase in the requirements for driving power and structural strength.

[0058] Therefore, by limiting the angle between the extension direction of the first chain plate 511 and the extension direction of the second chain plate 512 to within the range of 30° to 60°, the staggered turning component 51 achieves a balance between turning effect, equipment compactness and operating energy consumption, ensuring that the primary sludge drying system 5 can achieve full turning and is also easy to arrange reasonably inside the drying zone 52.

[0059] In some embodiments of the present invention, such as Figure 1 As shown, the primary sludge drying system 5 also includes a drying zone 52, the top and sides of which are formed of a light-transmitting material to enclose a greenhouse-like drying space that accommodates the staggered overturning assembly 51.

[0060] Specifically, the drying zone 52 can be enclosed with a steel frame and glass or transparent plastic panels. Its top and side walls are entirely made of translucent materials, allowing sunlight to directly penetrate the drying zone 52 and reach the staggered turning assembly 51 inside and the surface of the sludge it supports. The greenhouse-like drying space enclosed by the drying zone 52 creates a significant greenhouse effect under sunlight, making the internal air temperature significantly higher than the external environment, while simultaneously slowing down the loss of internal heat to the outside.

[0061] In addition, the top and sides of the entire drying zone 52 are covered with light-transmitting material to form a greenhouse-like enclosed space. Sunlight can directly shine on the surface of the sludge that is repeatedly turned over on the staggered turning component 51, providing continuous radiant heat energy to the sludge and promoting the evaporation of surface moisture. The greenhouse effect causes the overall air temperature inside the drying zone 52 to rise, thereby accelerating the process of moisture migrating and evaporating from the inside of the sludge to the outside.

[0062] Meanwhile, the sludge is continuously turned, spread, and falls along the paths of the first chain plate 511 and the second chain plate 512 on the staggered turning component 51, and is continuously exposed to the warming air and solar radiation inside the greenhouse during the movement. With the help of the greenhouse-like drying space provided by the drying zone 52, the surface temperature and evaporation driving force of the sludge in the primary sludge drying system 5 can be increased without increasing or with minimal increase in external fossil energy consumption, and the moisture content of the sludge before entering the secondary sludge drying system 3 can be reduced, thereby reducing the heat load of the subsequent high-temperature hot air drying section.

[0063] In some embodiments, the residence time of sludge in the primary drying section can be controlled to about 40 min to 60 min by the combined effect of the staggered turning component 51 and the solar radiation of the drying zone 52. This allows most of the free water in the sludge to be removed before it enters the secondary drying section, significantly reducing the heat required for subsequent high-temperature drying.

[0064] In some embodiments of the present invention, such as Figure 1 As shown, a reflector array 521 is provided on the top of the drying zone 52. The reflector array 521 has an extended state and a retracted state. The reflector array 521 is used to reflect sunlight onto the sludge on the staggered throwing assembly 51.

[0065] Specifically, the reflector array 521 may include multiple flat or curved reflectors arranged along the top of the drying zone 52. Each reflector is rotatably connected to the support structure via a pivot and can switch between an extended and retracted state under the action of a drive mechanism or control system. On sunny days with sufficient sunlight, the reflector array 521 extends to a preset angle, reflecting and converging some of the sunlight that would not normally directly illuminate the sludge surface into the staggered throwing assembly 51 area inside the drying zone 52, thereby increasing the solar radiation intensity per unit area of ​​the sludge surface. In cloudy or rainy weather or when wind loads are high, the reflector array 521 can be retracted to reduce wind pressure and structural stress, while avoiding ineffective shading under low light conditions. Through the adjustable extension / retraction of the reflector array 521, the primary sludge drying system 5 can adaptively optimize the solar energy utilization effect according to different seasons, different solar altitude angles, and different meteorological conditions.

[0066] Furthermore, the reflector array 521 can adopt a light-concentrating surface liftable structure, and the reflectivity of the reflector surface can be no less than about 92%. By changing the tilt angle and unfolding height of the reflector, the sunlight that was originally incident on the top periphery or non-effective area of ​​the drying zone 52 can be reflected and focused on the area where the staggered throwing component 51 is located. Under sunny conditions, the effective light intensity acting on the sludge surface can be increased by about 40%.

[0067] In some embodiments of the present invention, the primary sludge drying system 5 further includes a forced ventilation system for discharging humid air from the drying zone 52 and introducing external dry air.

[0068] Understandably, the forced ventilation system may include exhaust fans installed at the top or side walls of the drying zone 52, and ventilation ducts connected to fresh air openings at the bottom or sides of the drying zone 52. When the exhaust fans are operating, humid air rich in water vapor inside the drying zone 52 is exhausted from the top or higher position, while relatively dry air from outside is introduced into the drying zone 52 through the fresh air openings, forming a bottom-up ventilation path. As the sludge is continuously turned and tossed on the staggered turning assembly 51 and comes into contact with hot air and solar radiation, the moisture in the sludge continuously evaporates and is promptly carried away by the forced ventilation system, preventing excessive humidity in the greenhouse space from inhibiting the evaporation process.

[0069] In addition, the primary solar drying stage mainly relies on the light-transmitting greenhouse structure, the reflector array 521 for light concentration, and the forced ventilation system working together. Based on the large specific surface area of ​​the staggered overturning component 51, it accelerates the migration of sludge moisture into the air, so that the primary drying stage can significantly reduce the sludge moisture content without consuming additional fuel, creating favorable conditions for subsequent treatment.

[0070] In some embodiments, a viscosity sensor 513 can be used to monitor the accumulation pressure or running resistance of sludge on the chain plate, and the running speed and turning frequency of the first chain plate 511 and the second chain plate 512 can be dynamically adjusted accordingly to match the turning intensity with the viscosity and moisture content of the sludge, so as to avoid problems such as clumping or insufficient turning.

[0071] Furthermore, during the primary drying process, the high-moisture-content sludge, pretreated at the wastewater treatment plant, is evenly spread at the inlet end of the upper first chain plate 511. The upper drive shaft rotates slowly, driving the first chain plate 511 and its throwing teeth to continuously transport and turn the sludge, exposing it to air and solar radiation. When the sludge is turned to the upper end, it naturally falls from the staggered position to the lower second chain plate 512. The lower drive shaft rotates in the opposite direction, transporting and turning the sludge again in the opposite direction. Through the staggered falling and interleaved transport of the upper and lower layers, the sludge is turned and loosened multiple times within a limited arrangement length. Under the combined effect of solar energy and ambient wind, the moisture content of the sludge can be significantly reduced in the primary drying stage, reducing the burden on the subsequent secondary high-temperature drying stage.

[0072] In some embodiments, such as Figure 3As shown, the sludge drying and coal-fired boiler co-processing system 100 also includes a control system, which is electrically connected to the drive mechanisms of the boiler system 1, the molten salt system 2, the primary sludge drying system 5, the secondary sludge drying system 3, the dried sludge storage system 6, the blower 4, and the booster blower 13.

[0073] Specifically, the control system acquires parameters such as the unit load of boiler 11, the flue gas temperature in the denitrification section, and the molten salt temperature in the molten salt system 2. Based on the molten salt temperature and the heat load requirements of the secondary sludge drying system 3, it adjusts the opening of the baffle in the denitrification flue gas bypass 111 and the air volume of the blower 4 and the booster fan 13 in a coordinated manner. When the secondary sludge drying system 3 needs to increase the hot air temperature or air volume, the control system appropriately increases the baffle opening and increases the air volume of the blower 4, so that more high-temperature flue gas enters the molten salt system 2 to store heat and release heat to the hot air side. When the molten salt temperature or hot air temperature reaches the upper limit, or when boiler 11 needs to prioritize the denitrification temperature window, the bypass flow and air volume are reduced, thereby utilizing the heat storage buffering capacity of molten salt to mitigate the impact of boiler operating condition fluctuations on the drying heat source.

[0074] In the primary sludge drying system 5, the control system receives signals from the viscosity sensor 513 arranged on the staggered turning assembly 51 and the temperature and humidity detection device in the drying zone 52. When the sludge viscosity is high, the turning resistance is increased, or the humidity in the drying zone 52 is too high, the operating speed and turning frequency of the first chain plate 511 and the second chain plate 512 are increased, and the exhaust volume of the forced ventilation system is increased. When the sludge is relatively loose and the temperature and humidity are close to the target value, the chain plate speed and fan frequency are reduced accordingly to reduce energy consumption and dust escape risk while ensuring the primary drying effect.

[0075] In the secondary sludge drying system 3, the control system adjusts the hot air temperature, hot air volume, and sludge feed rate into the secondary sludge drying system 3 in a coordinated manner based on the deviation between the sludge outlet moisture content detected online and the set target value: when the moisture content is too high, the hot air parameters are increased or the feed rate is reduced; when the moisture content is significantly lower than the target and the molten salt heat storage is sufficient, the hot air parameters are appropriately reduced and the processing capacity is increased, so that the secondary sludge drying system 3 can stably output dried sludge that meets the co-firing requirements.

[0076] Furthermore, in the boiler co-utilization stage, the control system also controls the flow rate of dried sludge fed into the pulverizing system based on the inventory in the dried sludge storage system 6 and the current permissible sludge co-firing ratio of boiler 11, so that the sludge co-firing ratio is dynamically optimized under the constraints of emission compliance and safe unit operation. Through the above control logic, the entire process of coordinated control between staggered mechanical turning, solar primary drying, low-to-medium temperature molten salt energy storage, boiler flue gas waste heat, and sludge co-firing utilization is achieved, enabling the system to balance drying efficiency, energy cascade utilization, and environmental emission requirements under different operating conditions.

[0077] In summary, the sludge drying and coal-fired boiler co-processing system 100 of the present invention has the following advantages in terms of energy cascade utilization and operational economy: On the one hand, by making full use of solar energy through the drying zone 52 and the staggered turning component 51 in the primary sludge drying system 5, most of the moisture in the sludge is evaporated in the primary drying stage, significantly reducing the external heating source required for the secondary sludge drying system 3; on the other hand, by coupling the molten salt system 2 with the high-temperature flue gas generated by the boiler 11 in the boiler system 1, the sensible heat of the flue gas that could originally be directly emitted is converted into stable medium-temperature heat storage in the form of molten salt in the molten salt system 2, and then the heat is transported to the secondary sludge drying system 3 in the form of hot air by the blower 4 and its air outlet 41 for secondary drying, thereby reducing the impact of solar irradiance and unit load fluctuations on the system, and improving the overall energy utilization efficiency and operational reliability.

[0078] In terms of drying efficiency, the staggered turning component 51 in the primary sludge drying system 5, through the staggered arrangement of the first chain plate 511 and the second chain plate 512 and the turning action of the first turning tooth 5111 and the second turning tooth 5121, allows the sludge to fully contact the air and solar radiation in the drying zone 52 during multiple falls and rolls. This helps prevent sludge clumping and promotes the migration of moisture from the interior of the sludge to the surface. On this basis, the secondary sludge drying system 3 uses high-temperature hot air provided by the coupling of the molten salt system 2 and the blower 4 to deeply dry the sludge after primary drying, forming a multi-stage drying path of "primary solar drying + secondary high-temperature hot air drying". Compared with the traditional single-stage hot air drying method, the overall drying efficiency is higher, and the sludge moisture content can be reduced from about 80% to 85% to below 20%.

[0079] In terms of system stability and continuous operation, the introduction of molten salt system 2 effectively mitigates fluctuations in flue gas conditions and solar irradiance on the boiler system 1 side caused by random load and weather changes. This allows the secondary sludge drying system 3 to obtain a continuous and stable hot air source over a longer timescale under diurnal and seasonal variations. Simultaneously, the secondary sludge drying system 3 introduces the waste gas containing VOCs and water vapor generated during the drying process into the furnace combustion zone 112 of the boiler 11 for secondary combustion via waste gas outlet 31. The waste gas is further purified in the downstream electrostatic precipitator system 12 and the existing flue gas purification device of the boiler system 1. This, combined with the dried sludge storage system 6, enables stable storage and subsequent co-firing of dried sludge. Thus, while achieving sludge reduction and resource utilization, it effectively controls secondary pollutant emissions, meeting the comprehensive requirements of solid waste resource utilization and environmental protection.

[0080] This application utilizes a staggered overturning component 51 to promote moisture evaporation and uniform heating, uses solar energy as the primary drying energy source, uses the high-temperature flue gas from the boiler 11 as the main stable heat source, and introduces a molten salt system 2 to overcome the problems of flue gas fluctuation and solar energy intermittency, thereby achieving continuous, efficient, and energy-saving sludge drying.

[0081] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0082] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A sludge drying and coal-fired boiler co-processing system, characterized in that, include: A boiler system, the boiler system including a boiler having a flue gas outlet; A molten salt system, in which molten salt circulates, and the inlet of the molten salt system is connected to the flue gas outlet, for heating and storing the molten salt using boiler flue gas. Secondary sludge drying system, the secondary sludge drying system being used for drying sludge; A blower, the blower having an air outlet connected to the molten salt system, is used to transport the airflow that exchanges heat with the molten salt system to the secondary sludge drying system.

2. The sludge drying and coal-fired boiler co-processing system according to claim 1, characterized in that, The molten salt system includes a low-temperature molten salt storage tank, a medium-temperature molten salt storage tank, and a molten salt circulation pipeline connecting the low-temperature molten salt storage tank and the medium-temperature molten salt storage tank. The low-temperature molten salt storage tank, the medium-temperature molten salt storage tank, and the molten salt circulation pipeline constitute a first heat exchange flow path for transporting molten salt. The airflow path between the air outlet and the secondary sludge drying system constitutes a second heat exchange flow path. The first heat exchange flow path and the second heat exchange flow path exchange heat with each other.

3. The sludge drying and coal-fired boiler co-processing system according to claim 2, characterized in that, The boiler system also includes an electrostatic precipitator system. The outlet of the molten salt system is connected to the electrostatic precipitator system. The airflow path between the flue gas outlet, the inlet of the molten salt system, and the outlet of the molten salt system constitutes a third heat exchange path. The first heat exchange path and the third heat exchange path exchange heat with each other.

4. The sludge drying and coal-fired boiler co-processing system according to claim 3, characterized in that, A denitrification flue gas bypass is provided at the outlet of the main flue of the boiler. The outlet of the denitrification flue gas bypass forms the flue gas outlet. A rotatable baffle is provided in the denitrification flue gas bypass. The baffle is used to regulate the flow rate of the flue gas flowing through the denitrification flue gas bypass.

5. The sludge drying and coal-fired boiler co-processing system according to claim 1, characterized in that, The secondary sludge drying system has an exhaust gas outlet connected to the furnace combustion zone of the boiler, which is used to introduce the exhaust gas generated during the sludge drying process into the furnace combustion zone for incineration.

6. The sludge drying and coal-fired boiler co-processing system according to claim 1, characterized in that, Also includes: A primary sludge drying system is provided for conveying sludge to a secondary sludge drying system. The primary sludge drying system includes a staggered turning assembly, which comprises a first chain plate and a second chain plate. Wherein, the two ends of the first direction are a first end and a second end, the first chain plate conveys sludge along the direction from the first end to the second end, the second chain plate conveys sludge along the direction from the second end to the first end, in the direction from the first end to the second end, the second end of the first chain plate is inclined upward and the second end of the second chain plate is inclined downward, along the vertical direction, the second end of the first chain plate is opposite to the second end of the second chain plate and is located above the second end of the second chain plate, the first end of the first chain plate is opposite to the first end of the second chain plate and is located below the first end of the second chain plate.

7. The sludge drying and coal-fired boiler co-processing system according to claim 6, characterized in that, The first chain plate is provided with a first tumbling tooth, and there are multiple first tumbling teeth arranged at intervals along the conveying direction of the first chain plate, which are used to tumble the sludge when the first chain plate conveys the sludge. And / or, the second chain plate is provided with a second tumbling tooth, and there are multiple second tumbling teeth arranged at intervals along the conveying direction of the second chain plate, for tumbling the sludge when the second chain plate conveys the sludge.

8. The sludge drying and coal-fired boiler co-processing system according to claim 6, characterized in that, The angle between the extension direction of the first chain plate and the extension direction of the second chain plate is α, and satisfies: 30°≤α≤60°.

9. The sludge drying and coal-fired boiler co-processing system according to claim 6, characterized in that, The primary sludge drying system also includes: The drying zone, the top and sides of which are formed of a light-transmitting material, encloses a greenhouse-like drying space to accommodate the staggered overturning assembly.

10. The sludge drying and coal-fired boiler co-processing system according to claim 9, characterized in that, The top of the drying zone is equipped with a reflector array, which has an extended state and a retracted state. The reflector array is used to reflect sunlight onto the sludge on the staggered overturning assembly. And / or, the primary sludge drying system further includes a forced ventilation system for discharging humid air from the drying zone and introducing external dry air.

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