With the improvement of cement production automation level and control system reliability requirements, the function of material level measurement control is increasingly prominent.
Level is one of the main measurement parameters in the cement industry production process. Raw materials, semi-finished products and finished products in cement production are all granular or powdery solid materials. There are many occasions for material level measurement, except raw meal and pulverized coal. , cement, mixed materials, grate cooler, shaft kiln unloading and other processes have applications. According to the production process requirements, there are two types of material level measurement devices.
One is the limit material level detection, that is, the level switch, which generally has two detection points, the upper and lower limits. Once the material level reaches the pre-set level, a control signal is sent to make the feeding or unloading equipment perform the corresponding action.
The second is continuous material level measurement. There are two kinds of working methods, which are timing measurement and measurement when needed, which can be used to accurately grasp the height of the material surface. In this mode of operation, bagged cement is generally transported to the loading location via a conveyor belt. To protect the interests of the supply and demand sides, accurate counting of cement bags during the transfer process is necessary for management.
In actual situations, many electronic counting methods have not been able to be used normally because of the harsh environment (dust and vibration).
Unlike other industries, the cement industry is mainly a level measurement of solid materials, and there are few liquid level measurements. There are many kinds of solid materials, such as blocks, granules and powders. The dielectric constant, bulk density, temperature and moisture content of these materials are also different. Contact measurement is the main means of measuring the material level in the past. Because the instrument and the material are in contact with each other during measurement, various problems often occur during use, such as the hanging of capacitors, the breaking of the hammer, the burying of the hammer, the blocking of the tuning fork, and the daily maintenance.
By the 1990s, the cement industry began to use non-contact level measurement. The earlier non-contact measurement technologies were ultrasonic technology and nuclear radiation (gamma ray). The nuclear radiation technology was affected by radioactive sources and was subjected to applications. limit. Ultrasonic technology has developed rapidly in recent years and is currently the most widely used non-contact measurement method, especially in liquid level measurement. Ultrasonic level measurement in cement plants has been more commonly used in raw material blending warehouses, raw coal reservoirs, clinker silos, etc., but ultrasonic waves must be transmitted by means of media. For example, measurement of the storage level in cement plants usually uses air as the medium of propagation. Changes in air temperature, humidity, composition, etc. will affect the speed of ultrasonic waves, and dust in the air will also attenuate the transmitted signals of ultrasonic waves.