Application and development prospects of vortex gas flowmeter in cement industry

Various flow meters are widely used in industries such as chemical, petrochemical, steel, electricity, heating and water treatment to measure the flow of various liquids and gases. With the increasing requirements for flow measurement in the industrial field, various new flow meters are no longer new in the market. They are given different modified terms according to the measurement mechanism, such as Coriolis, ultrasonic, electromagnetic, and vortex flow meters. Compared with traditional volumetric, venturi, and mechanical orifice flow meters, new flow meters have more novel features and are significantly different from old flow meters in terms of accuracy, reliability, repeatability, and maintainability. In these devices, there are few or no moving parts that are prone to wear; most of the flow meters are non-invasive components with smaller pressure drops and better safety; many meters are equipped with microprocessors that can perform self-diagnosis and other functions, thereby providing users with real-time feedback and historical data collection.

Application of vortex gas flowmeter in cement industry

Compared with other industries, various flowmeters are less used in cement industry. This is because the main media in the production process are material flow and air flow, and the material flow is mainly powder and granules. There is almost no liquid flow in the main process flow, and the air flow still carries a certain amount of dust, and it passes through a large pipe, which brings great difficulty to flow measurement. Although at some process points such as the air volume of each room of the cooler, since the high-pressure air flow is measured and the diameter of the pipe is not large, the traditional Venturi tube is generally used to measure it through differential pressure, but due to the low measurement accuracy, the flow value can only be used as a reference, and it is difficult to use it to adjust the opening of the damper, and the constant air volume is also difficult. At present, some 5000t/d no longer measure the flow of high-pressure air, but estimate the flow by measuring the electric power output of the high-pressure Roots blower. Therefore, flow measurement was almost a blank in the cement industry in the past, and automation technicians often only knew about temperature, pressure, level and other metering sensors. With the increase in cement production scale and the continuous updating of process, flow measurement and new flow meters have also begun to be used in the cement industry, which is reflected in the following aspects:

1. Measurement of gas flow in large pipelines

For some dry cement production lines introduced in the early days, foreign companies proposed to detect gas flow at the outlet of the kiln tail and in the large pipelines for waste gas treatment and adjust the relevant valves accordingly. Orifice plate flowmeters and flute-shaped average velocity tube flowmeters were used, but they were too difficult to use. Since flow measurement does not affect cement production, they have not been used since then. With the continuous updating of cement technology and scale, large vertical mills have been widely used. In the process flow of vertical mills, it is required to measure the inlet and outlet air volume of the mill and keep the circulating air volume constant. For example, the 3300t/d cement production line exported to Oman in China uses the vertical mill of Feifan Company. This requirement is included in the list of measuring points. The outlet air duct diameter of the raw mill of the 3000t/d cement production line is generally around 800mm. In the flow measurement specification, pipelines with a diameter greater than 200mm are considered large-diameter flow measurements. For example, when using a traditional orifice flowmeter, during operation, due to the wear of the sharp edge of the orifice, contamination of the plate surface, and accumulation of condensed dust in the pipeline, it needs to be replaced after wear; the orifice flowmeter also has the disadvantages of small range ratio, low accuracy, and large irrecoverable pressure loss; large flanges are required for large-diameter pipelines, and its price, installation cost and maintenance are also issues worthy of attention. In addition, the flow measurement of gas is affected by changes in temperature and pressure, which will have a serious impact on the flow measurement of gas, mainly in terms of accuracy and repeatability; in the cement industry, most of the measured process gases contain dust, and the measuring sensors generally have small holes, and dust can easily cause the measuring sensors to be blocked. Therefore, it is difficult to measure the gas flow in large pipelines in the cement industry, and there are many problems to be solved.

With the emergence of the new differential pressure average velocity tube flowmeter, the problem of measuring the gas flow in large pipelines has been solved. It has the characteristics of large range ratio, high accuracy, and small irrecoverable pressure loss. Various measures can also be taken to prevent dust in the gas from clogging the measuring sensor. This article will focus on the working principle, basic structure, performance characteristics and application of the new differential pressure average velocity tube flowmeter.

2. The measurement mechanism of the vortex gas flowmeter is used for material measurement

In the cement process, the raw materials, intermediate products and final products are all solid, and are mainly granular and powdery materials. The flow measurement of these materials is achieved in cement plants by electronic belt scales and various solid flow meters. They are both process equipment and automation equipment, but they do not belong to flow meters. In recent years, some foreign companies have used the measurement mechanism of new flow meters such as Coriolis and ultrasonic for metering scales. The most typical example is the Coriolis scale developed by the German Schenck Company using the mechanism of Coriolis force to measure fluid quality. It is used to measure coal powder. Compared with other coal powder metering scales, it has the characteristics of simple structure, high control accuracy, integrated metering and transportation, etc. It is now widely used in China's cement industry. Some domestic companies also use Coriolis to develop metering scales, but the indicators in various aspects are not as good as Schenck's products.

3. Use new flowmeters in auxiliary processes and low-temperature waste heat power generation The

auxiliary processes in the cement industry are mainly used to improve the equipment operation rate and protect the equipment. For example, the humidification water spray in the waste gas treatment process is to increase the resistivity of the dust, thereby improving the efficiency of the electrostatic precipitator. In the new dry cement plant, there is an automatic water spray adjustment loop. In the water volume control, each plant has set up an electromagnetic flowmeter, and some are also equipped with a bundled ultrasonic flowmeter, which plays a good monitoring role and enables the normal operation of the automatic water spray adjustment loop.

The cement industry has generally used waste gas low-temperature waste heat to generate electricity, and many new flowmeters, such as ultrasonic and vortex, have been applied in the waste heat power generation system.

III. Conclusion

With the increase in the scale of cement production and the continuous updating of the process, the vortex gas flowmeter has also begun to be used in the cement industry, and the development trend is promising. In the automation system of the cement plant, if it is used for adjustment and monitoring, the differential pressure average velocity tube flowmeter can be used first for the measurement of large pipeline gas flow. Because the gas in large pipelines in cement technology contains dust, when selecting, it is necessary to confirm every detail of "tailor-made" and direct installation with the differential pressure type velocity averaging tube manufacturer. Some necessary accessories must be determined in the order. (end)