Industry new

Description of the method for measuring the flow rate of high temperature fluid by electromagnetic flowmeter

For industrial measuring instruments, different types have their own specified high temperature range. For example, the thermometer is in the range of 1500 to 2000 ° C for the high temperature range. For valves such as regulating valves and switching valves, when referring to high temperatures, it refers to temperatures of 400 to 500 ° C or higher. The flowmeter also defines different high temperature ranges according to the principle structure. The practical industrial temperature upper limit is about 540 °C for the differential pressure flowmeter of the throttle mechanism, about 200 °C for the volumetric flowmeter, and about 400 °C for the area flowmeter. High-temperature gas, high-temperature steam as a heat transfer medium or energy source, strong heat transfer coal for high-speed proliferation reactors, liquid metal sodium, etc.; molten iron and molten steel in the steel industry. It is these three fluids that differ in the accuracy and the materials used, and the points required for the flow measurement are also different. It is difficult to describe the common points in common. Therefore, in this chapter, the flow rate measurement of the high-temperature fluid is described centering only on the practical problem of the throttling flowmeter used for the high-temperature gas and the high-temperature vapor, and the electromagnetic flowmeter for measuring the liquid metal.
There are two methods for measuring the flow rate of molten iron and molten steel: one is the method of measuring the cross-sectional area of the flow trough using the high-frequency skin effect; the other is the way of the electromagnetic flowmeter. Both of these methods can be used in continuous steelmaking equipment. In order to carry out direct, non-contact measurement, various researches and discussions have been carried out, but in practice, batch processing is generally performed by converting the flow rate into liquid column *** or weight. In addition, when measuring the flow rate of liquid metal sodium, an ultrasonic method in which a detector is mounted outside the pipe was tested, and it will soon be put into practical use.
The departments that use high-temperature fluids are mainly in the power, steel, and chemical industries, and they have a wide range of fluids. When measuring the flow rate of liquid, water vapor, gas, etc., people from various types of flowmeters with different principle structures, firstly studied whether the differential pressure flowmeter of the throttle mechanism is applicable, but actually applied more. This is because it is simple in structure and has a wealth of data and practical experience. As a result, the throttling device acts as a process instrumentation, and its reliability is more important than any other instrument.
The company uses power generation and power generation units for various plants to reduce the steam temperature and pressure of the boiler to critical temperatures and pressures with the goal of avoiding efficiency and large capacity. This vapor is a high temperature, high pressure superheated vapor having a temperature of 568 ° C and a pressure of 240 kgf / cm 2 . The flow rate of the high pressure vapor flowing from the boiler to the steam turbine is generally measured by a throttling device such as a nozzle.
In steel making and iron making, the temperature of the combustion air is increased and then blown into a furnace such as a furnace, a converter, or a sintering furnace. The flow rate of these combustion air can be measured by a throttling device such as a venturi tube. In addition, the gas discharged from these furnaces is also in the high temperature range, and the flow rate can be measured by a venturi tube.
Since the discharged gas is a high-temperature gas, it is corrosive and contains dust. When selecting materials, these characteristics and conditions of use should be considered, and materials suitable for the purpose of use and corrosion resistance should be selected. In the chemical and petrochemical industries, for example, a hydrogen production unit and a reforming furnace using a steam reforming method, the temperature in the reaction tube is also increased by about 800-900 °C. The petroleum refined contact modification device has a temperature of 420-580 ° C and a pressure of 15-50 kg/cm 2 . The furnace temperature in these devices is high temperature, but because it measures and controls the flow before entering the furnace, so. Do not measure fluids as high as they are. When considering the flow rate of the high-temperature fluid by the throttling device, as with the selection of the valve-like material, it is important to pay attention to the pressure while paying attention to the temperature.
With the right material selected, you can measure the flow in the high temperature range. However, in terms of material strength, tensile strength and yield point decrease with increasing temperature. When the temperature reaches above 400 °C, creep occurs. Therefore, this temperature can be regarded as the high temperature in the throttling device. .

PREVIOUS：Some unknown installation details of the elecNEXT：How to solve the problem of the vortex flowme