How to Greatly Improve Temperature Uniformity in a Box-Type Electric Furnace

How to Greatly Improve Temperature Uniformity in a Box-Type Electric Furnace

Box furnaces, due to inadequate sealing at the furnace opening and door, experience significant heat loss, resulting in a furnace temperature that is lower than the temperature at the center of the furnace chamber. If the temperature variation range for the workpieces being heated must be tightly controlled, the heating zone for each part will inevitably have to be reduced, which in turn necessitates a smaller effective furnace chamber area. Consequently, the furnace cannot operate at full load, leading to wasted energy and processing time, as well as increased specific consumption per unit of product. Therefore, it is essential to maximize the uniform-temperature zone within the box furnace.

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2024

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04

What are the design features of a box-type furnace?

What are the design features of a box-type furnace?

Box furnaces, also known as muffle furnaces, are heating furnaces with a box-shaped furnace chamber. They are easy to operate, simple to maintain, and equipped with a controllable chimney at the rear. These furnaces are suitable for a wide range of industrial and institutional applications, including chemical analysis of coal, coking products, and chemical raw materials, as well as in industries such as power generation, papermaking, petrochemicals, cement production, agriculture and animal husbandry, pharmaceutical research, and education and teaching. The design of box furnaces features a furnace chamber constructed from stainless steel plates, forming a sealed cavity for heating and hot-air circulation. The flow of hot air within the chamber significantly enhances temperature uniformity. The furnace chamber and the furnace frame are designed as separate components: the chamber rests on load-bearing rollers at the base of the frame and can slide freely back and forth. When heated, the chamber can expand freely along its length. In addition, to prevent heat leakage from the chamber, the door is fitted with a double-layer seal—inner and outer—and the door lock employs a multi-point handwheel mechanism for secure locking. A door-fixing device is mounted on the end face of the chamber and utilizes a movable double-hinge mechanism, allowing it to move in tandem with the chamber’s expansion and thereby ensuring a tighter seal. Box electric furnaces incorporate reliable integrated circuits, offering an excellent operating environment and strong anti-interference capabilities. At the maximum operating temperature, the outer surface temperature of the furnace body remains below 50°C, greatly improving working conditions. Equipped with microcomputer program control, these furnaces can store two sets of 16-step temperature profiles, enabling fully automatic heating and cooling. During operation, temperature-control parameters and programs can be adjusted, providing flexible, convenient, and straightforward operation. Moreover, both the temperature-control accuracy and the constant-temperature accuracy of box electric furnaces are ±1°C, with rapid heating rates—up to 45°C per minute. Their rational structural design, featuring double-layer inner and outer furnace casings and air-cooling heat dissipation, significantly shortens test cycles. In summary, both box furnaces and muffle furnaces are heating furnaces with a box-shaped chamber, suitable for a wide range of industrial and institutional applications. Box electric furnaces, in particular, utilize electric heating and offer superior operating conditions and more precise temperature control. These devices play an important role in scientific research, education, and industrial production. Box furnace: http://www.ctjzh.com/

07

2024

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04

What are the characteristics of a tubular electric furnace?

What are the characteristics of a tubular electric furnace?

Tube furnaces are all newly developed, high-performance, energy-efficient electric furnaces employing advanced technology. They come in various configurations, including single-tube, double-tube, horizontal, openable, vertical, single-zone, dual-zone, and triple-zone models. These furnaces are primarily used in colleges and universities, research institutes, and industrial and mining enterprises for laboratory experiments and small-batch production. They feature safety and reliability, simple operation, high temperature-control accuracy, excellent heat insulation, a wide temperature range, superior furnace-chamber temperature uniformity, multiple heating zones, and optional atmospheres or vacuum furnace configurations. Customers can choose either a single-setpoint controller or a 30-segment programmable controller. The energy-saving ceramic-fiber insulation and double-wall construction reduce the external surface temperature to ambient levels. With long uniform-heating zones, easy operation, reliable sealing, and overall high performance metrics, these furnaces are at the leading domestic level. The furnace tubes can be configured with materials such as heat-resistant steel, quartz glass, or ceramic tubing. Tube furnaces operate on a batch-cycle basis and are used in laboratories, industrial and mining enterprises, and research institutions for elemental analysis, as well as for quenching, annealing, tempering of small steel parts, and heating of new materials such as electronic ceramics. The complete equipment package includes temperature controllers, thermocouples, compensation leads, and other accessories. Temperature control is available in two modes: relay control and thyristor control. Given that these are intermittent-operation furnaces, most are equipped with a 40-segment PID programmable controller, which enables precise control over the firing process. Key features of tube furnaces: 1. Control accuracy: ±1°C; furnace temperature uniformity: ±1°C (depending on the size of the heating chamber). 2. Furnace tubes are made of quartz glass. 3. Stainless-steel metal flange seals with double O-rings. 4. The furnace body is finished with a high-quality, corrosion- and acid/alkali-resistant powder coating; the furnace wall is air-cooled to keep the outer surface temperature close to room temperature, effectively isolating the furnace body from the heating chamber. 5. Dual-loop protection system covering over-temperature, over-pressure, over-current, thermocouple failure, and power outages. 6. Imported refractory materials ensure excellent thermal insulation and high temperature resistance. 7. Vacuum gauge reading ranges from 0 to -0.1 MPa. 8. The furnace can be purged with various gases, including oxygen, nitrogen, argon, and hydrogen. 9. Available temperature ranges: 800°C, 1000°C, and 1200°C. 10. Utilizes reliable integrated circuitry for stable operation, strong anti-interference capability, and low external casing temperature—no higher than 50°C even at maximum operating temperatures—significantly improving the working environment. Microcomputer-based program control allows users to set up two sets of 16-step heating/cooling curves, enabling fully automatic heating and cooling. During operation, temperature-control parameters and programs can be adjusted, offering flexibility, convenience, and ease of use. Temperature-control accuracy: ±1°C; constant-temperature accuracy: ±1°C. Rapid heating rates of up to ≤5°C per minute are achievable. All furnace-chamber linings are made from imported Morgan fiber, providing high service temperatures, low heat storage, and excellent thermal insulation (energy-saving performance exceeds 80% compared with traditional electric furnaces). The rational design featuring an inner and outer double-layer furnace structure with air cooling significantly shortens test cycles. This product is an essential piece of equipment for testing and experimentation in fields such as refractories, electronics, ceramics, metallurgy, machinery, building materials, specialty materials, and new-material development. Tube furnace: http://www.ctjzh.com/

03

2024

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04

Introduction to the Selection of Heating Elements for Tubular Electric Furnaces

Introduction to the Selection of Heating Elements for Tubular Electric Furnaces

Tube-type electric furnaces are widely used in industries such as ceramics, metallurgy, electronics, glass, chemical engineering, machinery, refractory materials, new materials development, specialty materials, and building materials. Working principle of high-temperature tube-type electric furnaces: A thermocouple converts the furnace temperature into a voltage signal, which is then fed into a microcomputer-based temperature control regulator (as shown in Figure 1). The regulator compares this signal with the pre-programmed setpoint and outputs an adjustable control signal. This adjustable signal subsequently controls a trigger circuit, which in turn activates a voltage regulator, thereby adjusting the furnace voltage and, consequently, the furnace temperature.

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2024

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04

Introduction to Common Furnace Linings Used in Modern Tubular Heating Furnaces

Introduction to Common Furnace Linings Used in Modern Tubular Heating Furnaces

Tube-type atmosphere resistance furnaces are primarily used in industries such as metallurgy, glass manufacturing, heat treatment, lithium-ion battery cathode and anode materials, new energy, and abrasive tools as specialized equipment for determining material properties under specific atmospheric conditions. Modern tube-type heating furnaces commonly employ three types of furnace lining structures: brick construction, refractory fiber spray coating, and castable refractory lining. Brick Construction Brick-lined furnace linings are constructed using refractory bricks, including standard and shaped refractory bricks. The advantage is that different types, properties, and grades of refractory bricks and refractory mortars can be selected according to the varying operating temperatures, working conditions, and thermal loads of different sections of the furnace. The disadvantage is poor overall integrity and sealing performance, as well as low construction efficiency. Refractory Fiber Spray Coating Refractory fiber spray coating is applied using a dedicated fiber spraying machine that forcefully injects pre-treated loose fiber wool through a spray gun while simultaneously delivering an inorganic binder via several sets of specialized fluid delivery systems into the fiber wool through the outer annular nozzle of the spray gun. The two components mix externally and are then sprayed onto the inner wall of the furnace. The advantages of this construction technique include rapid installation, seamless lining, and excellent gas tightness, making it particularly suitable for complex or irregular furnace wall sections. Its disadvantages are: (1) Low lining strength, making it susceptible to mechanical damage during operation; (2) Poor resistance to airflow erosion; (3) Harsh working conditions, with quality heavily influenced by human factors, resulting in instability and difficulty in ensuring optimal performance during equipment operation. Castable Refractory Lining Castable refractory linings are primarily constructed from heat-resistant concrete, castables, and other refractory materials. Their main advantages are excellent structural integrity and gas tightness, long service life, ease of mechanized application, and high construction efficiency. However, the refractory materials must be used within their shelf life, and repairs to the lining are less flexible than those for brick-lined furnaces. Installation Steps Mixing with Water Castable refractories are supplied in packaged form, with each bag containing both the main material and a small sachet of additives. The main material and additives should be poured into a mixer. Before using a forced-action mixer, the castable should be dry-mixed for about 1–2 minutes, followed by the addition of clean tap water. For every 100 kg of castable, add approximately 77 ± 1 kg of tap water, gradually adding water while mixing until the mixture is uniform before discharging. The mixed wet material should be promptly transported to the construction site for pouring. (If the wet material is stored for too long, its workability will deteriorate; such material should be discarded and must never be returned to the mixer for re-watering and reuse.) Formwork and Pouring The formwork must be erected tightly and securely (large amounts of slurry leakage are strictly prohibited), and coated with oil or a release agent in a thin, even layer. After the formwork is in place, the material should be evenly distributed along the formwork, with a thickness of 200–400 mm, at which point the vibrator should be activated promptly. The vibrator should be operated with quick insertion and slow withdrawal, ensuring uniform vibration; prolonged vibration at a single spot is prohibited to prevent particle segregation. When slurry begins to surface and the number of bubbles decreases, it indicates that the pouring is complete. For pours thicker than 400 mm, layered construction is required, but each layer must be placed continuously without interruption. Demolding and Curing Formwork removal should only be carried out after the castable has developed sufficient strength (typically 12–24 hours at room temperature). Until the material reaches a strength capable of withstanding significant pressure, stepping on or impacting the surface should be avoided to prevent cracking and edge damage. If the ambient temperature is low, curing time should be appropriately extended, or insulation measures should be implemented (the curing temperature should ideally be maintained above 10°C). For shorter construction schedules, the ambient temperature can be raised to accelerate hardening. After formwork removal, the castable must continue to cure in a warm, humid environment for at least 12–24 hours before baking can proceed. Furnace Lining Baking The furnace lining should be baked according to the established baking plan and baking curve [1]. Precautions (1) Water addition must strictly adhere to the specified ratio; excessive water will severely reduce the strength and high-temperature performance of the castable. While ensuring adequate workability, water should be added as sparingly as possible. (2) The temperature of the mixing water should not fall below 5°C, and the curing temperature should also be maintained above 5°C. When temperatures are lower, curing time should be appropriately extended, or measures should be taken to raise the ambient temperature. It is strictly forbidden to expose uncured wet castable to environments below 0°C. (3) Mixed castable should be used within 25–30 minutes; otherwise, the mortar will lose its thixotropic flow properties. Castable that has lost its thixotropic flow cannot be diluted with water and reused.

02

2024

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04

Applications of Tube Furnaces in Industrial Production

Applications of Tube Furnaces in Industrial Production

Tube furnaces are primarily used in industries such as metallurgy, glass manufacturing, heat treatment, lithium-ion battery cathode and anode materials, new energy, and abrasive tools, serving as specialized equipment for determining material properties under specified temperature conditions. The furnace design is simple, operation is straightforward, control is convenient, and continuous production is possible. All tube furnaces are newly developed, high-performance, energy-efficient electric furnaces employing advanced international technologies, available in various configurations, including single-tube, double-tube, horizontal, openable, vertical, single-zone, dual-zone, and triple-zone models. They are mainly used in colleges and universities, research institutes, and industrial and mining enterprises for laboratory experiments and small-batch production. These furnaces feature safety and reliability, simple operation, high temperature-control accuracy, excellent thermal insulation, a wide temperature range, uniform furnace temperature distribution, multiple heating zones, and optional atmosphere control or vacuum furnace configurations. Users can choose between a single-setpoint controller or a 30-segment programmable controller. Energy-saving ceramic fiber insulation combined with a double-layer structure reduces the external surface temperature to ambient levels. With long uniform heating zones, easy operation, reliable sealing, and superior overall performance, these furnaces are at the leading domestic level. The furnace tubes can be configured with heat-resistant steel, quartz glass, ceramic tubes, or other materials. Applications of Tube Furnaces in Industrial Production 1. Chemical Industry: Tube furnaces are used in chemical reactions, steam distillation, evaporation, and material heating, among other processes. 2. Food Industry: Tube furnaces are employed for food heating, holding, sterilization, and other operations. 3. Electronics Industry: Tube furnaces are utilized for heat treatment of semiconductor materials and soldering of electronic components. 4. Glass Industry: Tube furnaces are used for glass heating and forming, as well as quenching and strengthening processes. 5. Ceramics Industry: Tube furnaces are applied to ceramic heating and sintering. In addition, tube furnaces are widely used in many other industrial applications. Due to their simple structure, ease of maintenance, and long service life, they have become indispensable in numerous industrial sectors. In summary, as a type of heating equipment, tube furnaces offer broad application prospects and significant room for development. In industrial production, their unique structure and operating principles provide robust support for manufacturing processes. Advantages: Mature technology; Simple furnace design; Easy operation, convenient control, and capability for continuous production; High ethylene and propylene yields with high product concentrations; Low power consumption and high thermal efficiency; Most pyrolysis gas and flue gas can be recovered; The range of applicable feedstocks is steadily expanding with advances in pyrolysis technology; Multiple furnaces can be combined for large-scale production. Disadvantages: (1) Limited applicability to heavy feedstocks: When processing heavy feedstocks, coking tends to occur more readily, necessitating shorter operating cycles and reduced cracking depth. This often results in lighter coke formation, shortening the effective annual production time and reducing the service life of both the cracking furnace and its tubes. Moreover, lower cracking depths lead to lower feedstock utilization rates, increased yields of low-value products such as heavy oil, and higher utility costs. (2) The process requirements of high temperature, short residence time, and low hydrocarbon partial pressure inevitably increase the surface heat flux on the furnace tubes, thereby demanding high-temperature-resistant alloy tubing and advanced casting technologies. Tube furnaces are classified by furnace type into vertical furnaces, cylindrical furnaces, and large square furnaces; and by application into chemical reaction furnaces, liquid-heating furnaces, gas-heating furnaces, and mixed-phase-flow heating furnaces. Tube furnaces are further categorized as follows: 1. Vacuum tube furnaces and atmosphere-controlled tube furnaces; 2. Conventional tube furnaces, rotary tube furnaces, and multi-station tube furnaces; 3. Split-type tube furnaces, integrated-type tube furnaces, vertical tube furnaces, and horizontal tube furnaces; 4. Single-zone tube furnaces, dual-zone tube furnaces, and triple-zone (multi-zone) tube furnaces.

02

2024

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04

Analysis and Usage Precautions for Safe and Reliable Atmospheric Tube Furnaces

Analysis and Usage Precautions for Safe and Reliable Atmospheric Tube Furnaces

Atmosphere tube furnaces, as a common type of industrial heating equipment, play an important role in many fields. However, due to their unique characteristics and operating procedures, there are sometimes concerns about their safety and proper usage. This article provides a detailed overview of the working principle, operating guidelines, and essential precautions for atmosphere tube furnaces, ensuring that users can operate them safely and reliably. I. Understanding Atmosphere Tube Furnaces 1. Introduction to Atmosphere Tube Furnaces: These are specialized high-temperature heating devices that primarily rely on internal control systems to regulate parameters such as temperature, humidity, and pressure. 2. Working Principle: Heating Method: Advanced radiation and conduction heating technologies are employed, with appropriate diluent or reactive substances—such as inert gases or reducing agents—added to create the desired process environment. Temperature Control: Precise temperature regulation is achieved through temperature-sensing elements (e.g., nickel-chromium alloy or aluminum alloy) and temperature-control instruments. II. Operating Guidelines Preparatory Work: 1. Ensure that there are no flammable or explosive materials in the vicinity of the equipment. 2. Verify that the power and gas supplies are functioning properly and make any necessary adjustments. Correct Operating Procedures: 1. Open the furnace door and place the object to be heated in the appropriate position. 2. Set the desired heating temperature and duration, paying close attention to the usage limitations specified in the product manual. 3. Turn on the power and adjust the gas flow to meet the requirements of the process environment. 4. Close the furnace door and start the heating program. Precautions: 1. Carefully read the product manual before use and follow the instructions accordingly. 2. It is strictly forbidden to open the furnace door while the power is still on or when the furnace is at high temperature, to prevent burns or other accidental injuries. 3. During prolonged continuous operation, regularly inspect the safety performance of the equipment and associated pipelines. Through this detailed analysis of the working principle and proper usage of atmosphere tube furnaces, we believe readers now have a deeper understanding of this equipment. In actual operation, it is essential to strictly adhere to safety regulations, closely monitor the equipment’s performance, and ensure both safe operation and effective heating. By doing so, you can extend the service life of the equipment and improve operational efficiency.

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2024

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04

What are the key points for temperature control during the heating process in a muffle furnace?

What are the key points for temperature control during the heating process in a muffle furnace?

The key points for temperature control during the heating process in a muffle furnace include the following: Control of the heating rate: Heating too rapidly can cause the furnace temperature to exceed the desired range, potentially damaging both the furnace chamber and the experimental samples. Therefore, during heating, the heating power and duration should be appropriately adjusted to ensure a controlled and appropriate rate of temperature rise.

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2024

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04

Guide to the Use of Muffle Furnaces and Safety Precautions

Guide to the Use of Muffle Furnaces and Safety Precautions

The muffle furnace is a critical piece of heat-treatment equipment that must be operated in accordance with the relevant guidelines. Strict procedures govern equipment inspection, preheating, sample placement, temperature and time settings, monitoring during the experiment, and post‑experiment handling. Safety precautions include adherence to operating procedures, fire and explosion prevention, protection against burns and electric shock, regular maintenance, and emergency response protocols. Users are advised to refer to this document to ensure the safe operation of the equipment.

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Operating Procedures and Precautions for Muffle Furnaces

Operating Procedures and Precautions for Muffle Furnaces

Guide to the Use of Muffle Furnaces and Safety Precautions I. Operating Instructions for Muffle Furnaces Check the Power Connection: Ensure that the muffle furnace’s power plug is securely inserted into the power outlet and that the power cord is free from damage or exposed conductors to prevent the risk of electric shock. Set the Heating Temperature: Use the control panel or rotary knob to set the desired heating temperature. Make sure that the set temperature does not exceed the muffle furnace’s rated temperature. Start Heating and Monitor: Turn on the muffle furnace to begin heating. During the heating process, regularly observe temperature changes and conditions inside the furnace to ensure a stable heating operation. Inspect Item Placement: Before heating, ensure that items inside the furnace are arranged neatly, avoiding contact or stacking to promote uniform heating. Shut Down After Heating: Once the desired temperature or heating time has been reached, turn off the muffle furnace and allow it to cool naturally to a safe temperature before removing the items.

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