Microwave-based drying and sterilization system for sludges based on screw conveyor system

Abstract

The present invention relates to a continuous, integrated drying and sterilization system for transforming wet sludge into a dry, pathogen-free, and chemically neutral output. The system combines mechanical transport, microwave-induced dielectric heating, and vapor-phase sterilization to achieve complete sludge stabilization. Microwave radiation penetrates the sludge, inducing volumetric heating and evaporation of water, while destroying pathogens and deactivating aflatoxins. The system may incorporate natural agricultural biomass materials to enhance thermal distribution, absorb aflatoxins, and improve energy efficiency. A plasma-based sterilization step ensures the exhaust is non-toxic and odor-free. The fully dried and sterilized sludge is significantly reduced in volume and weight, rendered biologically inert, and may be repurposed as a biofuel, soil conditioner, or safely disposed of. The system provides an efficient and environmentally safe solution for sludge treatment.

Description

Microwave-Based Drying and Sterilization System for Sludges Based on Screw Conveyor System

[0001] The present invention relates to the field of waste treatment, particularly to a system and method for drying and sterilizing sewage sludge using microwave technology. This innovation is intended for use in wastewater treatment centers , enabling rapid, energy-efficient, and hygienic processing of sludge.

[0002] Traditional methods of sludge treatment include the followings.

[0003] Thermal drying using gas or electric heaters:Conventional sludge treatment techniques frequently utilize thermal drying systems powered by gas or electric heaters. In such configurations, dewatered sludge is subjected to elevated temperatures via direct or indirect contact with heated air streams or thermal surfaces. While this approach facilitates moisture reduction and volume minimization, it is associated with numerous technical and operational limitations. Foremost among these is the excessive energy consumption, as these systems require substantial amounts of fuel or electricity to achieve the desired drying effect, resulting in elevated operating costs. Additionally, the process tends to emit noxious odors and airborne contaminants, including volatile organic compounds (VOCs) and fine particulates, thereby necessitating the integration of complex air treatment and filtration systems to comply with environmental regulations.

[0004] Furthermore, thermal drying methods inherently rely on surface heat transfer, which often results in non-uniform drying, particularly in the inner mass of the sludge, thereby compromising both efficiency and hygiene. The systems typically do not ensure complete sterilization, thereby permitting the survival of pathogenic microorganisms, which can pose risks during downstream handling, transport, or reuse of the treated sludge. Maintenance requirements are also substantial, given the reliance on multiple moving mechanical components such as blowers, heaters, and conveyors, all of which are prone to wear and operational failure. Moreover, these installations demand considerable spatial footprint, rendering them unsuitable for decentralized, modular, or mobile deployments. They are also characterized by prolonged start-up and cool-down times, which limits operational flexibility, especially in batch or intermittent processing environments.

[0005] Belt dryers and rotary dryers:Another category of conventional sludge drying systems includes belt dryers and rotary dryers, both of which operate through the indirect application of thermal energy to sludge conveyed across heated surfaces. In belt dryer systems, sludge is distributed in a thin layer over a continuously moving perforated belt while heated air is passed over or through the material. Rotary dryers, on the other hand, utilize a rotating cylindrical drum that agitates and tumbles the sludge while exposing it to heated gases. Despite their widespread adoption, both technologies exhibit significant technical and practical shortcomings.

[0006] Primarily, these systems are energy-intensive, often requiring substantial thermal input to evaporate moisture effectively, which leads to high operational costs. Their drying efficiency is limited by the thermal conductivity of the sludge and the dependence on convective heat transfer, resulting in prolonged drying times and uneven moisture removal. The physical design of rotary and belt dryers also makes them susceptible to dust generation, odorous emissions, and the release of airborne biological contaminants, necessitating additional treatment infrastructure such as scrubbers or biofilters.

[0007] Moreover, the mechanical complexity of these systems introduces challenges related to maintenance and reliability. Rotary drums and conveyor belts are subject to abrasion, corrosion, and mechanical wear, requiring frequent inspections and part replacements, which increase downtime and maintenance costs. The sludge feed must also be carefully preconditioned to avoid clogging or material buildup, which can cause operational inefficiencies or shutdowns. Another key drawback is the large spatial footprint of these systems, as both rotary and belt dryers require extensive floor area and support structures, making them unsuitable for space-constrained or mobile applications. Furthermore, like other conventional dryers, they do not guarantee complete sterilization, leaving potential pathogenic organisms viable in the output, thus compromising biosafety.

[0008] Solar drying beds:Solar drying beds represent a passive sludge dewatering method commonly employed in small- to medium-scale wastewater treatment facilities. In this approach, dewatered sludge is manually or mechanically spread over sand and gravel layers in open-air basins, where solar radiation, natural convection, and evaporation facilitate gradual moisture reduction. While this method is considered energy-efficient due to its reliance on natural sunlight, it is associated with several critical limitations that undermine its scalability, hygiene standards, and operational reliability.

[0009] First and foremost, solar drying beds are extremely time-consuming, often requiring several days to weeks to achieve significant moisture reduction, depending heavily on ambient weather conditions, temperature, humidity, and sunlight availability. Consequently, the process is unpredictable and unsuitable for continuous or large-scale operations, especially in regions with limited solar exposure or during cold and rainy seasons. Additionally, the large surface area required to construct functional drying beds imposes severe land-use constraints, rendering the method impractical in urban or industrial zones with limited real estate.

[0010] Moreover, the open nature of these beds exposes the sludge to external contaminants, such as dust, insects, and animal activity, resulting in potential cross-contamination and public health concerns. The method also fails to achieve pathogen inactivation, as the surface-level solar heating does not uniformly penetrate the sludge mass. Odor emissions during the drying period can further lead to nuisance complaints and environmental violations. In addition, solar drying beds demand intensive manual labor for loading, turning, and removal of dried sludge, which increases labor costs and reduces automation potential. Overall, while low in energy input, solar drying beds are inefficient, unsanitary, space-demanding, and incapable of meeting modern industrial or regulatory standards for biosolids treatment.

[0011] Composting or lime stabilization:alternative biological and chemical approaches to sludge stabilization include composting and lime stabilization, both of which are intended to reduce the pathogenic load and organic activity in wastewater sludge. In composting, organic sludge is blended with carbon-rich materials (e.g., wood chips or straw) and allowed to undergo aerobic microbial degradation, generating heat as a byproduct to assist in pathogen reduction. In lime stabilization, quicklime (CaO) or hydrated lime (Ca(OH)₂) is added to sludge to raise the pH above 12, creating an environment inhospitable to microbial life. While both methods have found use in small-scale or agricultural settings, they are accompanied by substantial limitations in terms of process control, efficiency, safety, and environmental impact.

[0012] Composting processes are time-intensive, often requiring several weeks to months for stabilization and pathogen reduction. The method depends heavily on ambient temperature, humidity, and aeration conditions, making it difficult to standardize and scale for industrial use. The process generates unpleasant odors, bioaerosols, and methane emissions, and it requires large land areas and regular mechanical turning, contributing to high labor and operational costs. Moreover, composting does not guarantee the complete elimination of pathogens, especially in the absence of stringent temperature control, raising public health concerns if the product is reused as soil amendment.

[0013] Lime stabilization, while faster, introduces chemical handling hazards and corrosive byproducts. The addition of lime significantly increases the weight and volume of the treated sludge, thereby raising transport and disposal costs. The process does not reduce the moisture content of the sludge, thus failing to minimize volume effectively. Furthermore, lime-treated sludge may exhibit high alkalinity, which can be detrimental to soil quality and restricts its application in agriculture without further conditioning. Both methods also lack automation capability, are incompatible with closed-loop systems, and are unsuitable for decentralized or compact facility integration.

[0014] Several prior art documents disclose the use of microwave-based technologies for sludge treatment and drying. However, none incorporate the specific configuration, continuous sterilization mechanisms, or integrated advanced plasma treatment found in the present invention. Notable examples include:

[0015] The US Patent No. US5421061A, entitled Microwave Sludge Treatment System, discloses an early system for drying sewage sludge using microwave energy, primarily in batch mode. The sludge is placed in a confined microwave chamber and exposed to radiation over a fixed cycle. Limitations of this system include:

[0016] Discontinuous operation, which limits processing throughput and scalability.

[0017] Lack of integrated sterilization of vapor, allowing the potential release of airborne pathogens and volatile compounds.

[0018] Manual handling requirements, increasing labor and safety risks.

[0019] No automated control system for monitoring moisture content or temperature.

[0020] The US Patent Application No. US20070193733A1 entitled Continuous Microwave Sludge Drying System introduces a continuous belt-based microwave dryer for sludge processing. Although it improves upon batch systems by enabling steady material flow, several drawbacks remain:

[0021] Mechanical complexity due to reliance on conveyor belts susceptible to fouling, misalignment, and corrosion in harsh sludge environments.

[0022] No active sterilization of moisture-laden exhaust air or condensate.

[0023] Limited adaptability to high-pathogen-load environments, such as those found in medical or industrial wastewater facilities.

[0024] The EPO Patent No. EP1303432A1 entitled Dielectric Heating of Wet Biomass addresses the use of dielectric (RF or microwave) heating for drying biomass materials, including food waste and agricultural sludge. While it highlights volumetric heating advantages, its focus remains on:

[0025] General biomass, rather than sewage sludge or pathogenic materials.

[0026] No vapor management, thus presenting potential health and environmental risks.

[0027] No integrated continuous sterilization measures.

[0028] The system for continuously drying and sterilizing sewage sludge is a cutting-edge technology that provides an efficient and effective solution for wastewater treatment. This innovative system comprises a feed inlet, a helical screw conveyor, at least one microwave radiation source, a sludge outlet, a vapor outlet, and a plasma-based vapor sterilization unit. The system is designed to transport the sludge in a continuous flow along a defined axis, while exposing it to microwave energy that causes dielectric heating and evaporation of moisture. The resulting dried and sterilized sludge is discharged through the outlet, making it suitable for reuse as biofuel or soil amendment.

[0029] The system's screw conveyor is a crucial component, rotatably driven by an electric motor and constructed from corrosion-resistant and heat-resistant materials. This design ensures reliable operation in harsh sludge environments, allowing for efficient transportation of the sludge through the processing chamber. Additionally, the microwave radiation sources, typically magnetrons operating at 2.45 GHz, provide the necessary energy to induce internal heating and evaporation of moisture within the sludge. With a power level of at least 1 kW each, these sources ensure rapid and effective drying and sterilization.

[0030] The processing chamber itself is designed with safety and efficiency in mind, featuring a metallic or reflective housing that contains microwave energy, dielectric microwave windows for isolation, and embedded temperature and moisture sensors for real-time monitoring. This setup enables precise control over the drying and sterilization process, ensuring optimal conditions are maintained throughout. Furthermore, the system can be equipped with a controller that adjusts the speed of the screw conveyor, modulates the microwave power, activates or adjusts the plasma sterilization unit, and processes input from various sensors to maintain optimal conditions.

[0031] The introduction of natural agricultural biomass materials into the system enhances its performance, allowing for improved thermal uniformity, reduced aflatoxin content, and enhanced biological inactivation. These materials can include tea waste, rice husk, pistachio shells, hazelnut shells, and walnut shells, which function as microwave sensitizers, adsorbents, or anti-fungal agents. The nano TiO₂ plasma vapor sterilization unit is another key component, comprising a catalyst bed coated with nano-crystalline TiO₂, a dielectric barrier discharge or corona plasma generator, and a reaction chamber that facilitates photocatalytic oxidation of airborne contaminants.

[0032] The system's ability to produce high-quality dried sludge makes it an attractive solution for wastewater treatment. The final product has a moisture content below 10% and is free from detectable pathogenic microorganisms and regulated aflatoxin levels, making it suitable for reuse as biofuel or soil amendment. The entire apparatus can be mounted on a modular frame, allowing for containerized or mobile deployment in decentralized wastewater treatment environments. This flexibility enables the system to be easily integrated into existing infrastructure, providing a reliable and efficient solution for wastewater treatment.

[0033] The method of continuously drying and sterilizing sewage sludge using this system is a complex process that involves introducing sludge into the feed inlet, transporting it via the rotating screw conveyor through the microwave chamber, exposing it to microwave radiation, incorporating agricultural biomass materials, directing the generated vapor through a TiO₂ plasma-based sterilization unit, and discharging the dried and sterilized sludge through the outlet port. By operating the system in this manner, it is possible to achieve a moisture content in the final dried sludge of less than 10% and a reduction in pathogenic microorganisms and regulated aflatoxin levels to below detectable limits. This ensures that the resulting product is safe for reuse and meets the required standards for environmental sustainability.

[0034] Overall, the system and method for continuously drying and sterilizing sewage sludge provide an innovative solution for wastewater treatment, offering improved efficiency, effectiveness, and environmental sustainability. By leveraging microwave radiation, plasma-based vapor sterilization, and agricultural biomass materials, this technology enables the production of high-quality dried sludge that can be reused as biofuel or soil amendment, reducing waste and promoting a more circular economy..

[0035] The present invention replaces belt movement with a robust rotating screw mechanism that is better suited to handling high-viscosity sludge. Additionally, it uniquely integrates a nano TiO₂ plasma sterilization unit at the vapor outlet, which utilizes photocatalytic and plasma-based oxidation to neutralize pathogens, volatile organics, and odors present in the exiting vapors.

[0036] Also, the present invention is specifically engineered for wastewater sludge, taking into account its pathogen load, odor profile, and variable moisture content. The inclusion of a plasma-assisted nano TiO₂ module represents a novel and non-obvious advancement by ensuring that even the vapor phase exiting the system is rendered biologically and chemically inert before environmental release.

[0037] Moreover, the present invention operates on a continuous flow basis, utilizing a helical screw conveyor to feed and move sludge through a microwave-active zone. It incorporates real-time sensor feedback and process automation to optimize drying efficiency and safety.

[0038] So, unique advantages of the present invention are as follow:

[0039] Continuous and sealed operation, reducing environmental contamination risks.

[0040] Hybrid drying and sterilization mechanism, combining microwave heating and nano TiO₂ plasma for dual-phase decontamination (solid and vapor).

[0041] No belts or filters that require regular maintenance or replacement.

[0042] Compact and modular design, enabling deployment in decentralized, mobile, or containerized treatment units.

[0043] Smart monitoring system with sensors and automated controls to manage moisture, temperature, and vapor composition in real-time.

[0044] Enhanced biosafety, especially important for sludge from hospital, industrial, or pandemic-related wastewater streams.

[0045] Faster drying than conventional thermal dryers (up to 80% time reduction).

[0046] Lower energy consumption due to direct heating mechanism.

[0047] Complete sterilization reducing biological hazards.

[0048] Compact footprint suitable for mobile or containerized units.

[0049] Automation and sensor feedback allow for process control and energy savings.

[0050] Reduces final sludge mass by over 60–80%, decreasing transport and disposal costs.

[0051] Can operate using renewable power sources including solar panels.

[0052] In the Drawings, identical reference numbers identify same elements. The size and shape and relative position of elements are not necessarily drawn to scale. Further, the shapes of the elements as drawn, are not exactly as the actual shape of particular elements and are schematic and have been selected for ease of recognition in the drawings. The drawing figures depict one or more implementations in accordance to the present disclosure, by way of example only, not by way of limitation.Fig.1

[0053] shows the perspective cross-sectional view of the invention, illustrating the various components and their inter relationships.

[0054] In the following description, certain specific details are set forth in order to provide a comprehensive understanding of various implementation of this disclosed invention. A skilled person in relevant art could realize an embodiment of this invention may be practiced with parts of these specific details, or with other methods, circuits, components, materials, etc. In other instance, well-known structures associated with electronic systems, or details of circuit design have not been shown or described in detail to avoid unnecessarily obscuring descriptions of implementation and the focus of this disclosure is on core inventive concept including novelty, inventive step and applicability of the invention.

[0055] The present invention discloses an integrated, continuous-flow microwave-based drying and sterilization device for treating sludge in wastewater treatment facilities. The system is designed to reduce moisture content, inactivate pathogens, and sterilize exhaust vapors, thereby offering a compact, efficient, and hygienic solution for sludge management. The invention comprises four integrated subsystems: (1) a mechanical conveyance and feeding unit, (2) a microwave drying and sterilization chamber, (3) a vapor treatment unit employing nano TiO₂ plasma technology, and (4) Control and Automation System.

[0056] 1. Mechanical Conveyance and Feeding Subsystem:This subsystem ensures the controlled and uniform transport of sludge material through the system:

[0057] Inlet Hopper: The semi-solid sludge enters the system via a feed hopper, which may optionally be fitted with a valve or pump (not shown) for flow regulation.

[0058] Helical Screw Conveyor :A central helical shaft rotates within a cylindrical chamber, moving the sludge forward along the axial direction. The screw is fabricated from corrosion-resistant alloy suitable for high-moisture and high-temperature environments.

[0059] Bearings and Support Housing: ensure axial stability of the rotating shaft, and prevent axial play and secure the shaft assembly under load.

[0060] Electric Drive Motor: Provides rotational force to the screw shaft. A speed-reducing gearbox may be optionally coupled to regulate conveyor velocity.

[0061] Frame and Mounting Base: The entire assembly is mounted on a reinforced steel or composite base to absorb vibration and ensure structural integrity during continuous operation.

[0062] 2. Microwave Drying and Sterilization Chamber:This is the core processing zone where sludge is exposed to microwave energy for rapid internal heating and moisture evaporation:

[0063] Microwave Chamber Housing :A metallic, reflective enclosure surrounds the screw conveyor path. Constructed from stainless steel with waveguide shielding, this chamber confines and reflects microwave energy.

[0064] Magnetrons: Multiple microwave emitters (2.45 GHz, 1 kW each) are radially arranged around the chamber, ensuring uniform exposure. Magnetrons are placed in waveguide compartments shielded from the sludge path.

[0065] Teflon materials or Fused Quartz Inserts: High-transmission dielectric windows (optional) separate the magnetron ports from the chamber to avoid contamination.

[0066] Temperature and Moisture Sensors: Embedded along the chamber walls and outlet to monitor sludge core temperature and remaining water content.

[0067] Insulation Layer: Thermal and microwave-reflective insulation is applied externally to reduce energy loss and protect surrounding components.

[0068] Sludge Outlet Port: The dried and sterilized sludge is discharged continuously from the chamber’s distal end, ready for reuse or disposal.

[0069] 3. Nano TiO₂ Plasma Vapor Sterilization Unit:One of the key innovations of the present invention is the integrated sterilization of vapors produced during the drying process:

[0070] Vapor Outlet Duct: Moisture-laden air and volatile compounds generated during microwave drying are directed through a sealed exhaust channel.

[0071] Nano TiO₂-Coated Catalyst Bed: The interior surface of the vapor duct is coated with nano-crystalline titanium dioxide (TiO₂), which functions as a photocatalyst under plasma activation.

[0072] Plasma Discharge Unit: A low-temperature cold plasma generator (e.g., corona or dielectric barrier discharge type) activates ambient oxygen molecules, generating reactive oxygen species (ROS) such as O⁻, OH⁻, and ozone in low concentrations.

[0073] Photocatalytic Oxidation: The ROS interact with nano-TiO₂, producing highly oxidative radicals that decompose VOCs, bacteria, viruses, and odor-causing compounds present in the exhaust stream.

[0074] Sterile Venting Port: The treated vapor is safely released into the atmosphere or redirected to a condensation unit, ensuring compliance with biosafety and air quality standards.

[0075] 4. Control and Automation System:the system is governed by a programmable logic controller (PLC) or microcontroller-based interface featuring:

[0076] Real-time feedback from temperature, moisture, and vapor sensors.

[0077] Control of motor speed, microwave power level, and plasma generator intensity.

[0078] Automated safety interlocks to halt operation in case of overheating, magnetron failure, or pressure buildup.

[0079] Optional remote monitoring interface for integration into smart treatment facilities.

[0080] Material and Construction Considerations

[0081] All parts in contact with sludge are fabricated from acid-resistant, high-temperature stainless steel (e.g., SS316L) or equivalent polymer composites.

[0082] Microwave components are shielded per IEC 60335 and FCC Part 18 standards to prevent leakage.

[0083] Bearings and seals are heat- and corrosion-resistant, suitable for continuous industrial use.

[0084] Operation Method

[0085] The operation of the present invention is characterized by a continuous, integrated drying and sterilization process that transforms wet sludge into a dry, pathogen-free, and chemically neutral output. The system combines mechanical transport, microwave-induced dielectric heating, and vapor-phase sterilization to achieve complete sludge stabilization. The operational sequence is as follows:

[0086] 1. Sludge Feeding:Dewatered sludge with high moisture content is introduced into the system via the inlet hopper and enters the feed chamber. Pre-conditioning (e.g., particle size reduction) may be optionally applied to ensure uniform consistency.

[0087] 2. Conveyance Through Microwave Chamber:A rotating helical screw conveyor continuously transports the sludge through the microwave-active zone. The speed of rotation is optimized to ensure sufficient dwell time for complete thermal penetration.

[0088] 3. Microwave Heating and Internal Evaporation:As the sludge advances through the chamber, it is subjected to microwave radiation (2.45 GHz), which penetrates the bulk material and induces volumetric heating. The microwaves cause the polar water molecules within the sludge to oscillate rapidly, leading to localized heating and evaporation of bound and free water.

[0089] 4. Pathogen and Aflatoxin Deactivation:Simultaneously, the generated thermal energy and electromagnetic field result in destruction of pathogenic microorganisms, including bacteria, viruses, and helminths. In a unique enhancement, the system may incorporate natural agricultural biomass materials—such as medical waste ,foods , tea, rice, pistachio and pistachio shell, hazelnut and hazelnut shell, and walnut shell powder—either as filter media, additives, or microwave absorbers, depending on the configuration. These materials, known for their absorptive and anti-fungal properties, assist in:

[0090] Absorbing and neutralizing aflatoxins, which may be present in the sludge or vapor phase;

[0091] Improving thermal distribution by acting as microwave sensitizers;

[0092] Contributing to the overall energy efficiency of the drying process;

[0093] Enhancing biodegradability and safety of the final product.

[0094] 5. Vapor Evacuation and Plasma-Based Sterilization:The steam and volatile organic compounds (VOCs) generated during drying are directed through a sealed vapor outlet, where they undergo advanced plasma and nano TiO₂ photocatalytic treatment. The cold plasma reactor activates nano-crystalline titanium dioxide, initiating oxidative decomposition of any remaining airborne pathogens, aflatoxins, and odor-producing compounds, thereby ensuring the exhaust is non-toxic, odor-free, and environmentally safe.

[0095] 6. Discharge of Treated Sludge:The fully dried and sterilized sludge exits the system via the discharge port. The product is significantly reduced in volume and weight, rendered biologically inert, and may be repurposed as a biofuel, soil conditioner, or safely disposed of, depending on the regulatory context and composition.Examples

[0096] In a part of exemplary embodiment of the invention,is a schematic diagram of the invention. According to thethe followings are the main elements of the exemplary embodiment:

[0097] 1. Discharge Outlet:The final discharge point of the dried material from the end of the spiral, with an anti-clogging design with a suitable slope. And reflection of the output waves

[0098] 2. Screw Conveyor:A spiral shaft made of wear-resistant and temperature-resistant steel that is responsible for continuous movement of materials in the heating path. Made of 304 steel

[0099] 3. Air Channel:A path designed for ventilation and exhaust of vapors produced from the drying process, can be connected to filters or energy recovery systems. With suction spiral fans and connection of a nano titanium dioxide plasma generator to disinfect exhaust gases and remove odors

[0100] 4. Waveguide Port:A standard opening for secure connection of the waveguide and directing microwave waves into the process chamber. With a Teflon wall to prevent materials from entering the waveguide

[0101] 5. Gearbox Flange:A place where the motor gearbox connects to the main shaft with a design resistant to mechanical stresses.

[0102] 6. Thrust Bearing:A mechanical element to withstand the axial force applied to the shaft and prevent looseness and damage.

[0103] 7. Shaft Support Flange:Holds the shaft in the correct position for smooth, vibration-free rotation.

[0104] 8. Fan Guard Metal:guard to prevent foreign objects from entering the fan and increase operational safety.

[0105] 9. Shaft Bearing:Reinforced bearings to support smooth shaft rotation at high temperatures.

[0106] 10. Drainage Screw:Manually drains material or residues from the tank or auger, can be opened and closed.

[0107] 11. Water Drain Outlet:Special path for the exit of condensed liquid moisture, resistant to corrosion.

[0108] 12. Rear Thrust Bearing:Axial support at the end of the shaft to reduce friction and increase the life of the device.

[0109] 13. Magnetron cooling fan

[0110] 14. Main Frame:The robust metal structure of the device on which all functional components are mounted. 12 cm x 12 cm 4 mil thick steel profile

[0111] 15. Tilting Base Bearing:Special bearing to provide angular rotation capability in the bases to adjust the position of the device.

[0112] 16. Adjustable Tilt Frame:Mechanical mechanism to adjust the overall height of the device and the tilt angle for better material discharge.

[0113] 17. Height Adjustment Column:Adjustable metal columns that allow the height of the system to be changed to adapt to different processing lines.

[0114] 18. Height Locking Pin:Pin mechanism to stabilize the adjusted height and prevent unwanted movement.

[0115] 19. Magnetron:Source of industrial frequency microwaves (2.45GHz) for internal heating and effective sterilization of materials.

[0116] 20. Motor-Reducer Unit:Electric motor connected to the gearbox to provide uniform spiral rotation power with controlled torque and optimal energy consumption.

[0117] The discharge outlet (1) is located at the end of the spiral, providing a final point for the dried material to exit the device. The anti-clogging design and suitable slope of the discharge outlet (1) ensure smooth material flow and prevent blockages. The output waves from the drying process are also reflected at this point.

[0118] The screw conveyor (2), made of 304 steel, is a spiral shaft that continuously moves materials through the heating path. The screw conveyor (2) is connected to the gearbox flange (5), which securely attaches to the main shaft and withstands mechanical stresses.

[0119] Air channel (3) provides a path for ventilation and exhaust of vapors produced during the drying process. The air channel (3) can be connected to filters or energy recovery systems, and features suction spiral fans and a connection for a nano titanium dioxide plasma generator to disinfect exhaust gases and remove odors.

[0120] The waveguide port (4) is a standard opening that securely connects the waveguide and directs microwave waves into the process chamber. A Teflon wall surrounds the waveguide port (4), preventing materials from entering the waveguide.

[0121] The gearbox flange (5) connects to the motor-reducer unit (20), which provides uniform spiral rotation power with controlled torque and optimal energy consumption. The thrust bearing (6) withstands axial forces applied to the shaft, preventing looseness and damage.

[0122] The shaft support flange (7) maintains the shaft in the correct position for smooth, vibration-free rotation. The shaft bearing (9) is a reinforced bearing that supports the shaft's rotation at high temperatures.

[0123] The fan guard (8) is a metal guard that prevents foreign objects from entering the fan, increasing operational safety. The drainage screw (10) allows for manual draining of material or residues from the tank or auger and can be opened and closed as needed.

[0124] The water drain outlet (11) provides a special path for condensed liquid moisture to exit, resistant to corrosion. The rear thrust bearing (12) offers axial support at the end of the shaft, reducing friction and increasing the device's lifespan.

[0125] The magnetron cooling fan (13) cools the magnetron (19), which is the source of industrial frequency microwaves (2.45GHz) for internal heating and effective sterilization of materials.

[0126] The main frame (14) is a robust metal structure that supports all functional components, measuring 12 cm x 12 cm with a 4 mil thick steel profile. The tilting base bearing (15) provides angular rotation capability in the bases, allowing adjustment of the device's position.

[0127] The adjustable tilt frame (16) is a mechanical mechanism that adjusts the overall height of the device and the tilt angle for better material discharge. The height adjustment column (17) allows the system's height to be changed to adapt to different processing lines.

[0128] The height locking pin (18) stabilizes the adjusted height, preventing unwanted movement. The motor-reducer unit (20) connects to the gearbox flange (5), providing power to the screw conveyor (2).

[0129] In summary, the various components of the device work together to provide a comprehensive system for drying and sterilizing materials using microwave energy. The relationships between these components ensure efficient material flow, effective heating and sterilization, and safe operation.

Claims

A system for continuously drying and sterilizing sewage sludge, comprising:a feed inlet configured to receive dewatered sludge;a helical screw conveyor enclosed within a processing chamber, wherein the screw conveyor is operable to transport the sludge in a continuous flow along a defined axis;at least one microwave radiation sources arranged around the processing chamber, each source being configured to emit microwave energy into the chamber at a frequency sufficient to cause dielectric heating of the sludge;a sludge outlet for discharging dried and sterilized sludge;a vapor outlet for evacuating vapors generated during microwave heating; anda plasma-based vapor sterilization unit positioned at the vapor outlet, the unit comprising a nano-crystalline titanium dioxide (TiO₂) catalyst bed and a cold plasma generator operable to neutralize volatile organic compounds, airborne pathogens, and aflatoxins within the vapor stream.The system of Claim 1, wherein the screw conveyor is rotatably driven by an electric motor and is constructed from a corrosion-resistant and heat-resistant material suitable for use in sludge environments.The system of Claim 1, wherein the microwave radiation sources are magnetrons operating at a frequency of approximately 2.45 GHz and a power level of at least 1 kW each.The system of Claim 1, wherein the processing chamber comprises:a metallic or reflective housing configured to contain microwave energy;dielectric microwave windows composed of Teflon, fused quartz, or alumina ceramic, the windows being configured to isolate the magnetrons from the sludge path; andembedded temperature and moisture sensors for real-time monitoring and process control.The system of Claim 1, further comprising a controller configured to:adjust the speed of the screw conveyor;modulate the microwave power;activate or adjust the plasma sterilization unit; andprocess input from temperature, moisture, and vapor sensors to maintain optimal drying and sterilization conditions.The system of Claim 1, wherein natural agricultural biomass materials are introduced into the system, the materials being selected from a group consisting of:tea waste;rice husk;pistachio shells;hazelnut shells; andwalnut shells,wherein the materials function as at least one of the following:microwave sensitizers to enhance thermal uniformity;adsorbents to reduce aflatoxin content;anti-fungal agents for enhanced biological inactivation.The system of Claim 1, wherein the nano TiO₂ plasma vapor sterilization unit comprises:a catalyst bed coated with nano-crystalline TiO₂;a dielectric barrier discharge or corona plasma generator; anda reaction chamber configured to facilitate photocatalytic oxidation of airborne contaminants, including aflatoxins, bacteria, and volatile organic compounds.The system of Claim 1, wherein the final dried sludge discharged from the outlet has a moisture content below 10% and is free from detectable pathogenic microorganisms and regulated aflatoxin levels, making it suitable for reuse as biofuel or soil amendment.The system of Claim 1, wherein the entire apparatus is mounted on a modular frame suitable for containerized or mobile deployment in decentralized wastewater treatment environments.A method for continuously drying and sterilizing sewage sludge using the system of Claim 1, comprising:introducing sludge into the feed inlet;transporting the sludge via the rotating screw conveyor through the microwave chamber;exposing the sludge to microwave radiation to induce internal heating and evaporation of moisture;incorporating agricultural biomass materials during processing to enhance aflatoxin removal and drying efficiency;directing the generated vapor through a TiO₂ plasma-based sterilization unit to neutralize airborne toxins and pathogens; anddischarging the dried and sterilized sludge through the outlet port.The method of Claim 10, wherein the system is operated to achieve a moisture content in the final dried sludge of less than 10% and a reduction in pathogenic microorganisms and regulated aflatoxin levels to below detectable limits.

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