Refractory materials are important foundation materials for high temperature technology. With the rapid development of high-temperature furnace technology, especially steel metallurgy technology, refractory materials must meet the increasingly demanding conditions and requirements, resulting in a wide variety of refractory products with different properties. Different types of refractory production methods also have their own characteristics due to the raw materials used and the quality requirements of the products.
Usually for inorganic substances with a refractoriness of not less than 1580 ° C- non-metallic ores are used as raw materials for refractory materials. The method of producing refractory materials varies depending on the type. However, the production of refractory materials is common. From the point of view of the production process, they must undergo the main processes of raw material calcination, crushing, fine grinding, sieving, batching, mixing, forming, drying and baking.
Calcination of raw materials for processing raw materials
Most of the primary ore cannot be used directly for brick making, because they will undergo a series of physical and chemical reactions (decomposition, compounding and sintering) under high temperature, and the weight and volume will change, that will change the volume of the brick, and even A large amount of deformation and cracking of waste appeared. If these changes can be completed (or substantially completed) when the raw material is calcined, it is guaranteed to obtain a finished product that meets certain quality requirements. The ultimate goal of raw material calcination is to achieve sintering, the basic principle of which is achieved by material migration under surface tension.
There are two main types of calcining equipment, shaft kiln and rotary kiln. In actual calcination, pure materials are difficult to sinter. For example, high-purity dolomite sintering requires a high temperature of 1,700 degrees, and high-purity magnesia can be sintered at 1900-2000 °C. Light burning activation can produce high-purity, high-density sintered magnesia below 1600 °C, with MgO content up to 99.9% and density up to 3.4g/cm3.Light burning activation is to lightly burn the material at a certain temperature, so that the lattice defects are increased, the activity is increased, and then the dead burning, the step is light burning - pressure ball or briquetting - dead burning, also known as two-step calcinations.
Infrared pyrometers are widely used in refractory plants because of their high temperature measurement accuracy. Among the key tunnel kiln, there are more temperature measurement points. The infrared pyrometer has the characteristics of many temperature measuring points and long working time. If the temperature parameter is not well controlled, it will bring significant economic losses to the production enterprise. Therefore, Choosing the right temperature measurement method is an important part of ensuring the normal operation of the kiln. There are two traditional methods of temperature measurement in tunnel kiln: one is to measure temperature with a thermocouple. This method is characterized by high temperature measurement accuracy and can be connected to a recorder or a control system for closed-loop control. The disadvantage is that the service life is short, especially the high-temperature kiln above 1300 °C has a large consumption of electric coupling, the price is also very expensive, and the equipment operating cost is high; The second method is an optical pyrometer. the method measures the temperature according to the color of the object to be measured. Because it does not directly contact the high temperature zone, the service life is long, but the measurement accuracy is low, no electrical signal is output, and the automatic recording cannot be performed. There are also human factors, and the authenticity is poor. The series infrared pyrometer from Dikai photoelectric can effectively overcome the above shortcomings. The meter has high measurement accuracy (up to ±0.5%), and can output electrical signals like thermocouples for automatic recording and control, and has a long service life (more than five years), simple operation, and small human error. etc. Therefore, Dikai Photoelectric Series Infrared pyrometer is the ideal temperature measuring instrument for high temperature tunnel kiln. Dikai photoelectric series infrared pyrometer in tunnel kiln application, there are two common methods of single point temperature measurement and multi-point switching temperature measurement according to different user requirements.
Introduced as follows:
Single point temperature measurement system: each temperature measurement point is composed of one probe and one instrument box.
The temperature measuring unit will performs temperature collection. Then connect the 4-20mA analog signal output from each unit's instrument box to the multi-point recorder or control actuator, And it can also communicate with computers, printers and other devices through the RS-232 port. The temperature measurement unit in this system usually uses WRIRP426 type instrument with high precision and strong function.
Switching temperature measurement system: The system is connected to a WRIRP426 multi-point pyrometer for signal processing by connecting the infrared probe signals installed at each temperature measurement point. It can output 1~5V temperature signals corresponding to each temperature measurement point separately for recording by multi-point recorder. At the same time, the temperature data can be directly input into the computer through the RS232 port, and the date will be analyzed and processed by the computer, The printer can print the temperature data directly.
Among the above two schemes, the single-point temperature measurement system has independent temperature measurement and signal processing system for each temperature measurement point, so the analog and digital signals of the output are real-time continuous signals, and the response speed is fast, which can be used as control execution.
For multi-point switching temperature measurement system, although the analog signal of the output is continuous, it has a certain hysteresis with the real-time temperature value, so it can only be used as data acquisition record, not as a control signal. The advantage is that the cost performance is better, and the equipment cost can be reduced when the usage requirements are not too high.
In other refractory kiln, such as downdraft kiln and prismatic kiln, the use of single point temperature measurement scheme is more because of the less temperature measurement point.
There are also DKHIRT handheld infrared pyrometers, but the meter can only intermittently measure the temperature of the furnace. Each measurement record must be manually operated, and automatic continuous measurement cannot be realized.
