Induction heating of material for drying and method for drying

Abstract

The application discloses an inductive heating material drying device and a drying method thereof. An electromagnetic induction heating coil is wound outside a conveying pipeline. The coil is connected with a medium frequency or high frequency power supply. The conveying pipeline is provided with a heat preservation layer made of a high-temperature resistant material. When the conveying pipeline is a non-metal pipeline without electromagnetic shielding capability and conductivity, a plurality of small metal balls or iron powder is prearranged in the pipeline. The induction heating coil performs electromagnetic induction heating on the metal balls or iron powder in the pipeline through the non-metal pipeline wall. The metal balls or iron powder heated by electromagnetic induction transfer heat to the surrounding material to be dried, so that the material to be dried is heated and water is evaporated. The application has a scientific structure, a high heating speed for sludge treatment and a high water vapor removal efficiency.

Description

Technical Field

[0001] This invention relates to a drying technology for water-containing materials such as sludge. Background Technology

[0002] Sludge drying refers to the process of removing most of the water content from sludge through processes such as leaching or evaporation. Currently, the main drying methods used include:

[0003] (1) Rotary drum drying process. Using natural gas or biogas as energy and air as the heat transfer medium, wet sludge and partially dried sludge particles are mixed in a mixer. The mixture is then carried into the rotary drum dryer by airflow. The sludge rotates at a stable speed within the dryer, moving from the inner drum to the outer drum, gradually drying into particles. This process is divided into direct heating and indirect heating types. Direct heating rotary drum dryers require a very complex monitoring system for operation. Indirect heating rotary drum dryers operate under strict inertia conditions. Due to uneven internal temperature and heat distribution, dust accumulation and overheating in the microenvironment can easily occur, posing significant safety hazards.

[0004] (2) The sludge is directly fed into the fluidized bed dryer. Fluidizing gas is uniformly blown into the entire bottom cross-section of the fluidized bed dryer to form a fluidized layer inside. As the sludge gradually dries, its density decreases, it rises to the top, and is then extracted from the fluidized bed along with the gas being drawn away from the top. Because the composition of the sludge determines its fluidization characteristics, this treatment system is very sensitive to changes in the composition of the sludge, which often leads to poor heat exchange within the fluidized bed, severe wear on the fluidized bed and pipes, and high energy consumption of the system.

[0005] (3) Disc drying process. An oil furnace is first heated by an external heat source, and then the heat is transferred to the drying discs through the oil. Disc dryers are divided into horizontal disc dryers and vertical multi-disc dryers. Horizontal disc dryers can only use steam as the standard heating medium. The disadvantage of this method is that the dried product has a very high dust content, requiring a separate granulation system, and the equipment is extremely prone to wear.

[0006] These drying methods have disadvantages such as long drying cycles, large equipment, high energy consumption, and high pollution.

[0007] Patent application number 2013100613082 relates to heating devices for injection molding machines, and more particularly to an electromagnetic induction heating energy-saving system for pipelines. It includes a button-type heating coil, a thermal sensor, and a monitoring module. The thermal sensor is mounted on the button-type heating coil, and its output is connected to the monitoring module. The button-type heating coil includes a button-type high-temperature wire and an insulating layer. The button-type high-temperature wire is wrapped in the insulating layer, and both ends of the button-type high-temperature wire are plug-in connectors. This structure pre-forms the insulation material and the button-type high-temperature wire into a button-type heating coil. However, this invention only heats the injection molding machine pipeline, not the material inside the pipeline, resulting in insufficient material heating efficiency. Summary of the Invention

[0008] Purpose of the invention:

[0009] This invention provides an induction heating material drying device and method that are scientifically designed, have high drying efficiency, and simultaneously pulverize materials during drying.

[0010] Technical solution:

[0011] The induction heating material drying device of the present invention has a conveying pipeline (in this document, including fixed pipelines, containers, or rotary kilns) for conveying or storing materials to be dried, or is equipped with a power device for conveying materials, driving the materials to be dried forward or backward (which can both regulate the movement of materials to prevent long-term stagnation and compaction, and also has the function of repeated heating to improve the drying effect); the front section of the conveying pipeline is the inlet and the end is the outlet, and the upper side wall of the conveying pipeline may have an air vent (so that sludge will not leak), and the conveying pipeline may have an insulation layer made of high-temperature resistant material (the thickness of which should be greater than the pipe wall thickness). An electromagnetic induction heating coil (insulated from or not in contact with the pipeline) is located outside the conveying pipeline or the insulation layer, and the coil is connected to a medium-frequency or high-frequency power supply (and also has a control switch for heating or stopping the heating of the coil). The materials to be dried for conveying or storing in the pipeline include solutions, suspensions, emulsions, colloids, etc., such as mud, sludge, rice containing moisture, etc.

[0012] The conveying pipeline is a steel pipe or a non-metallic pipe (ceramic pipe, high-temperature resistant plastic pipe, FRP pipe).

[0013] When the conveying pipeline is a steel pipe, when the electromagnetic induction heating coil is connected to a medium-frequency or high-frequency power supply, the pipe wall is heated by electromagnetic induction due to the eddy current formed on the surface of the pipe by the electromagnetic field. The heated pipe wall transfers heat to the material to be dried, causing the temperature of the material to rise. The water vapor is evaporated and discharged from the discharge port, air outlet, or feed port. After the material is dehydrated and dried, it is discharged from the discharge port.

[0014] When the conveying pipeline is a non-metallic pipe (including ceramic pipe, high-temperature resistant plastic pipe, or FRP pipe) without electromagnetic shielding capability and conductivity, many small metal balls (including spherical, ellipsoidal, cylindrical, and conical steel objects, preferably steel balls) or iron powder are pre-placed inside the pipe. An induction heating coil provides electromagnetic induction heating to the internal metal balls or iron powder through the non-metallic pipe wall. The heated metal balls or iron powder transfer heat to the surrounding material to be dried, causing the material to heat up and moisture to evaporate, exiting from the vent or discharge port. After dehydration and drying, the material is discharged from the discharge port. The metal balls or iron powder are discharged along with the sludge. After discharge, they are separated by sorting machinery and then sent back into the pipeline for reuse.

[0015] The preferred metal spheres are hollow or porous. The mass of a hollow metal sphere is equivalent to the mass of the material to be dried (ensuring the sphere mixes well with the material and doesn't float or settle on its surface). An induction heating coil heats the internal metal sphere through a non-metallic tube wall (which doesn't shield the electromagnetic field and ensures insulation). The heated sphere transfers heat to the surrounding material, causing it to heat up and evaporate moisture, which is then released through the vent. The material is dehydrated and dried before exiting through the discharge port. The metal spheres can also be discharged together with the material. After discharge, they are separated by a sorting machine and then returned to the pipeline for reuse.

[0016] In this invention, the material to be dried can be a viscous solid-liquid material such as sludge, chemical raw materials, or food raw materials.

[0017] The metal balls are heated and rolled and ground inside, which can also crush dried materials, making the dried materials into small fragments or granules.

[0018] Preferably, a screen plate is provided at the discharge port, and the diameter of the metal ball is larger than the screen hole on the screen plate. The dried crushed or granular material leaks out, but the metal ball cannot leak out. It is blocked by the screen plate and remains in the material pipeline to be dried. The metal ball can be reused for heating and grinding. The heat of the metal ball will not be dissipated and wasted, and there is no need for manual or mechanical sorting and separation, which reduces the amount of labor and improves efficiency.

[0019] The preferred conveying pipeline is inclined, with the outlet slightly higher than the inlet, so that the metal balls automatically roll back into the material to be dried. Since the inlet or pipeline has a conveying device that provides conveying power, it pushes the material to be dried forward. The inclined pipeline causes the metal balls to flow backward under the action of gravity. The combined effect of these two actions allows the metal balls to be distributed at any position in the pipeline, continuing to perform the function of induction heating of the material to be dried.

[0020] When the medium being induction heated is iron powder, the iron powder is discharged from the outlet along with the dry powder of the material to be dried. After discharge, the iron powder is separated by a magnet and then flows back into the inlet for reuse. However, in this case, some iron powder is lost because the separation between the iron powder and the dry mud powder is incomplete. Moreover, during induction heating, the wall of the metal ball is a complete and continuous surface, which can form more eddy currents, resulting in high thermal efficiency of electromagnetic induction heating. Iron powder cannot achieve such efficient processing.

[0021] Beneficial effects:

[0022] The equipment design of this invention conforms to scientific principles, features a compact structure, reasonable manufacturing costs, and a powerful ability to dry sludge. During induction heating, the sludge and other materials awaiting drying heat up rapidly. The heat transferred through the metal pipes, or even more heat transferred through induction heating of metal balls or iron powder in non-metallic pipes, results in rapid temperature rise and high water and air removal efficiency. With the metal balls capable of being rolled back for reuse, there is almost no external heat discharge, leading to energy conservation and reduced consumption. The metal balls can be reused for a long time, reducing the consumption of auxiliary materials and lowering operating costs. The widespread application of this invention can bring significant economic and environmental benefits to industries such as sludge drying treatment. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a longitudinal cross-sectional structure of the present invention;

[0024] In the diagram, 1-medium frequency or high frequency power supply; 2-electromagnetic induction coil; 3-transportation pipeline; 4-sludge; 5-steel ball;

[0025] 6-Insulation layer. Detailed Implementation

[0026] like Figure 1 The induction heating drying device shown has a conveying pipe for conveying or storing materials to be dried, or is equipped with a power device for conveying materials. The front end of the conveying pipe is an inlet and the end is an outlet. The side wall of the conveying pipe may have an air vent. An electromagnetic induction heating coil is wound around the outside of the conveying pipe. The coil is connected to a medium-frequency or high-frequency power supply. The outside of the conveying pipe may have a heat insulation layer made of high-temperature resistant material.

[0027] The conveying pipeline is a non-metallic pipe without electromagnetic shielding and conductivity. Many small metal balls or iron powders are pre-placed inside the pipeline. The induction heating coil electromagnetically heats the metal balls inside through the non-metallic pipe wall. The metal balls or iron powders heated by electromagnetic induction transfer heat to the surrounding material to be dried, causing the material to heat up and the moisture to evaporate and be discharged from the vent or discharge port. After the material is dehydrated and dried, it is discharged from the discharge port.

[0028] The metal balls are discharged along with the sludge. After discharge, they are separated by sorting machinery and then sent into the pipeline for reuse.

Claims

1. An inductive heating drying material device, having a conveying pipe for conveying or storing the material to be dried, the conveying pipe being a non-metal pipe without electromagnetic shielding ability and electrical conductivity, the front section of the conveying pipe being an inlet and the end section being an outlet, the side wall of the conveying pipe having air outlet holes, the conveying pipe being externally wound with an electromagnetic induction heating coil, the coil being connected to a medium frequency or high frequency power source, and the conveying pipe externally having a heat insulation layer made of high temperature resistant material; characterized in that: the material to be dried is sludge or rice containing moisture, and a plurality of small metal balls are prearranged inside the pipe; the metal balls are hollow metal balls or metal balls with through holes, and the mass of the metal balls is equivalent to the mass of the same volume of the material to be dried; the conveying pipe is provided with a slope, and the outlet is slightly higher than the inlet, so that the metal balls automatically roll back into the sludge material to be dried; the induction heating coil performs electromagnetic induction heating on the metal balls inside the non-metal pipe, the metal balls heated by electromagnetic induction transfer heat to the surrounding material to be dried, causing the material to be dried to heat up, the water is evaporated and discharged from the air outlet holes or the outlet, and the dehydrated and dried material is discharged from the outlet. The outlet is provided with a sieve plate, the size of the metal balls is larger than the aperture of the sieve holes on the sieve plate, the dried crushed or granular material leaks out, and the metal balls are blocked by the sieve plate and still remain in the material pipe to be dried. ​ ​ 2. The inductively heated material drying apparatus of claim 1, wherein: ​

Images