09,22,2026 16 views
With the development of social economy and the continuous improvement of people's living standards, chlorides will occupy an increasingly important position in the fields of medicine, chemical industry, dyes, etc. The chloride flow rate parameter is an important measurement and control data in the production process. However, due to the strong corrosiveness, low conductivity, easy blockage of pipelines, and low flow rate in the process of chloride, there have been many problems in the measurement and control of chloride flow rate for many years.
1. Electromagnetic flowmeter
Due to the technical requirements of the electromagnetic flowmeter for the measured liquid, that is, the conductivity of the measured liquid cannot be lower than the threshold specified by the electromagnetic flowmeter, otherwise it cannot be measured normally. The threshold for the conductivity of the measured liquid specified by the universal electromagnetic flowmeter varies depending on the model, generally ranging from 5 × 10-6 to 10-4S/cm; It also depends on the length and distribution of flow signal lines between sensors during use. Considering that chlorides belong to low conductivity liquids, an electromagnetic flowmeter was selected by a certain electrochemical plant, but it still cannot work properly in practical use, with readings often fluctuating significantly or flow rates sometimes missing. After inspection, the installation of the flowmeter meets the requirements, the liquid equipotential grounding is good, and there are no problems with cable insulation. Due to the inability to find conductivity data for chlorides, the analysis mainly focuses on chloride conductivity being below or close to the specified threshold, leading to the above-mentioned problem. Although electromagnetic flow meters have no movable components inside the sensor and are good flow meters for measuring conductive fluids, they are still not suitable for measuring the flow rate of fluids with low conductivity or critical states such as chlorides.
2. Remote float flowmeter
Float flowmeter, also known as rotor flowmeter, although its measurement accuracy is low, it is suitable for low Reynolds number and small flow measurement. A certain shape of float even requires a minimum Reynolds number of 40 for the fluid. These two technical characteristics are more suitable for the characteristics of chloride fluids. Considering the strong corrosiveness of the medium, a certain electrochemical plant once used a remote float flowmeter lined with polytetrafluoroethylene to measure the chloride flow rate. However, due to the fact that chloride is a fluid containing multiple components that are prone to clogging, and the float flowmeter requires the measured fluid to be clean, problems such as the float getting stuck in the conical tube cavity still occurred during use. Although the flowmeter can still be used after disassembly, cleaning, and reassembly, it will soon become clogged again. Moreover, online disassembly and cleaning also require the installation of bypass pipelines and valves in the process pipeline, which are not only limited by on-site space and cost, but also have issues such as production impact and operational inconvenience. Due to the presence of movable components in the sensor of the float flowmeter, it is prone to blockage when measuring fluids that are prone to blockage. Therefore, using a float flowmeter cannot meet the needs of continuous and stable production measurement.
3. Mass flow meter
The mass flowmeter based on the Coriolis principle is a direct mass flowmeter with high accuracy, wide range ratio, no straight pipe requirements, and no need for compensation. Although it is expensive, in order to find a suitable instrument for measuring chloride flow rate, a certain electrochemical plant has also selected a mass flowmeter for measurement experiments. In order to prevent corrosion of the flowmeter by the medium, the supplier provided a quality flowmeter lined with PFA, but problems still occurred during use. Although PFA lining has played a certain role in preventing medium corrosion, due to the small diameter of the sensor and the need for the sensor to be installed facing downwards for liquid flow measurement and control, the chloride fluid in production is sometimes in an intermittent flow state, which leads to the problem of local blockage and indication error caused by the deposition of scale in the flow tube of the sensor during actual use. Therefore, it was ultimately eliminated when choosing to measure chloride flow.
4. Differential pressure flowmeter
Differential pressure flowmeter is the most diverse type of flow instrument in the flowmeter category. A certain electrochemical plant has used V-cone flowmeter, Annubar flowmeter, etc. Due to the fact that differential pressure instruments are limited by Reynolds number, it is necessary to first check whether they meet the technical requirements of the instrument. Analyze whether the instrument meets the requirements with a maximum chloride flow rate of 8m3/h and a minimum flow rate of 0.5-1m3/h for DN50 pipe diameter. According to the minimum flow rate of 0.5-1m3/h mentioned above, the corresponding Reynolds number is calculated to be 4000-6800 (viscosity μ=1.5mPa · s). Although the V-cone flowmeter is an instrument with lower lower requirements, its lower Reynolds number must reach ≥ 8000 to work properly. However, the lower limit required by Annubar is much higher than that of the V-cone flowmeter. So when the flow rate is low, the DN50 pipeline is limited by the Reynolds number, and the differential pressure flowmeter cannot work properly.
5. Ultrasonic flowmeter
Based on the above-mentioned problems in chloride flow measurement and control, after extensive technical exchanges with Jiake, a manufacturer of ultrasonic flow meters, it was preliminarily understood that for the difficulties in chloride flow measurement and control, ultrasonic flow meters that are not affected by fluid properties and characteristics and have no movable parts inside the sensor can be used for measurement.
When ultrasound propagates in a flowing fluid, the velocity of the sound wave increases in the downstream direction and decreases in the upstream direction, resulting in different propagation times for the same propagation distance. The difference between the time of forward propagation and backward propagation is related to the flow velocity of the measured fluid, and the flow velocity of the fluid can be calculated based on this.
For the measurement of chloride flow rate, considering that we have received multiple promises of reliable products from other flowmeter manufacturers in the past, we have decided to first use a handheld ultrasonic flowmeter for on-site measurement and control tests. If the measurement and control effect and data are reliable, we will gradually modify it. After about half a year of on-site actual measurement and testing, the flow measurement and control parameters are stable and reliable, meeting the needs of the production process. Based on this situation, multiple fixed ultrasonic flow meters have been gradually adopted in production, which have achieved stable measurement and automatic ratio adjustment of chlorine reactor parameters. After verification, ultrasonic flow meters have also been used for flow measurement of chloride reactant liquids in other devices, achieving good measurement results.
