Application of non-orifice plate variable frequency air flow meter in formaldehyde production

Abstract: The application information of non-orifice variable frequency air flow meter in formaldehyde production is provided by excellent flow meter and flow meter manufacturers and quotation manufacturers. Abstract: The intelligent instrument can finely adjust the setting and modification of various parameters, and there is no adjustable movable element inside the instrument, so the reliability and stability are extremely high. The smart meter comes with temperature compensation and parameter power-off storage functions, and the single-chip computer automatically calculates and looks up the table. For more flowmeter manufacturers to select models and price quotations, you are welcome to inquire. The following is the application article details of the non-orifice variable frequency air flow meter in formaldehyde production. Abstract: The intelligent instrument can finely adjust the setting and modification of various parameters, and there is no adjustable movable element inside the instrument, so the reliability and stability are extremely high. The smart meter comes with temperature compensation and parameter power-off storage functions, and the single-chip computer automatically calculates and corrects by the look-up table method. It is a new generation of ideal products to replace traditional digital meters. 1. Sampling of air flow of variable frequency fans in formaldehyde production and energy saving of fans Many domestic formaldehyde manufacturers use orifice plates to“U”Type glass tube differential pressure gauge to observe or send to display through electronic accumulating instrument through differential pressure transmitter. Since the air supply duct is installed in the orifice plate, it will cause a system resistance of 1000~3000Pa, which will increase the energy consumption of the fan. The resistance power consumption of the two-blade fan is about 0.85kW/kPa, and the resistance power consumption of the three-blade fan is 0.8kW/kPa. The annual resistance power consumption of the two-blade fan is 7000kWh/kPa. Calculated based on the electricity price of 0.70 yuan/kWh, an additional electricity fee of about 5000 yuan/kPa is required every year. In order to reduce the resistance of the air duct system, the engineering and technical personnel of many enterprises have adopted secondary expansion processing to reduce the resistance of the orifice plate. There is even a method of increasing the thickness of the pipeline in the measurement section and installing a large-diameter orifice plate to reduce the pressure difference to below 300Pa. However, the investment of the orifice plate is as little as several thousand yuan, and the composition of the transmission unit and the flow meter will cost more than ten thousand yuan. We use frequency converter to control the fan speed to achieve the purpose of adjusting the air flow, which is economical and energy-saving and easy to operate. Harbin Zhengyanghe Adhesive Factory, Harbin Juye Chemical, Suihua Wuyuan Chemical Company, Hebei Hejian Xinli Chemical Factory, Jilin Juli Industry and Trade Company, Heilongjiang Langxiang Forestry Bureau Particleboard Factory and other units The formaldehyde production line is equipped with variable frequency governors, and the orifice pressure difference measurement method is canceled, and it can be remotely operated in the oxygen control room. When the annual average load is 70%, it can save 49% of electricity, and the annual electricity cost of the 30,000-ton formaldehyde plant is about 200,000 yuan. If the 300 sets of formaldehyde plants in the country are changed to use variable frequency speed governors to control fans, at least 30 million to 50 million yuan in electricity can be saved every year, and about 500 million yuan in ten years. In the 30,000-ton formaldehyde system of Harbin Juye Chemical Co., Ltd., a low pressure difference orifice plate of 120~250Pa was applied in the early stage, and the actual air flow with pressure compensation and temperature compensation was displayed through intelligent digital flowmeter. The three-year operation monitoring shows that the error is 0.3%, but the investment is relatively high, about 12,000 yuan (the price of imported similar devices is higher). The particleboard plant of Langxiang Forestry Bureau, Heilongjiang Province also has a 30,000-ton formaldehyde plant. The intelligent digital air flow meter of the frequency conversion frequency method described in this article is adopted. The flow signal comes from the frequency output terminal of the frequency converter. resistance. The air volume required for general formaldehyde production is 600m3/h·t, the error is±12m3/h·t, if the normal production of formaldehyde per hour is 4t, the impact of the error is only 0.050t/h. The application error of the instrument is 1.5%, and the investment is about 7,000 yuan. This method can fully meet the needs of the proportioning operation of the formaldehyde production process. 2 The importance of fan air flow calculation In the process of starting and normal production, it is the most concerned thing for each formaldehyde workshop technician to be able to accurately grasp the actual air supply volume of the fan or adjust it to the required air volume. But in fact, many formaldehyde factories only operate by experience.“U”If the differential pressure gauge is not on time, it often does not match the output of formaldehyde produced. In severe cases, it will cause process deviation and increase unit consumption. The introduction of alcohol into the tube is also a common phenomenon, and it is generally easy to handle. However, it is more troublesome to deal with the internal problems of the orifice plate, and it is even more difficult to find such problems. Starting from practice, this paper leads to the calculation method of air flow without orifice plate, which is a relatively new calculation theory of fan flow. On the basis of a large number of studies on the characteristic curves of two-blade and three-blade Roots blowers, it was found that fans of the same level of flow model, as long as the motors of different powers or motors of different series are replaced, will produce fans of different speed and rated pressure of different grades and models. This was also confirmed in the discussions with the manufacturers during the visit to the fan factory. According to the simplified air volume formula of the Roots blower, the calculation expression of the air volume of the variable frequency fan is: Qm=K×f1 (1) [When the inlet air temperature is 20°C] K in the formula is the inherent coefficient of the fan after finishing, and f1 is the frequency corresponding to the rotation speed. It can be seen from formula (1) that the air volume of the Roots blower has a linear relationship with the motor speed frequency. However, with the increase of the outlet pressure during the operation of the Roots blower, the air volume will decrease to a certain extent. When the outlet pressure of the fan is 1000mmH2O and 5000mmH2O, there is a deviation of about 6% of the air volume. When the high-pressure fan is at the outlet pressure of 1000mmH2O and 7000mmH2O, the air volume difference is about 12%.

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