Application of mass flowmeter to measure the density of limestone slurry

Due to the corrosiveness and abrasiveness of the desulfurization system slurry and the high solid content (up to 30%), the density cannot be measured by conventional detection methods, which limits the selection of the density meter. At present, there are three main methods for measuring the density of slurry in domestic desulfurization systems, namely differential pressure method, γ-ray radiation absorption measurement method and Coriolis force mass flowmeter method.

The Coriolis force mass flowmeter measures the density of the limestone slurry in the desulfurization system because the structure of the flowmeter is similar to the structure of the vibrating tube density meter. The measuring tube continuously vibrates at a certain resonance frequency, because the resonance frequency is a function of the density of the fluid. When fluids of different densities fill the vibration tube, the vibration frequency of the vibration tube will also change. Therefore, measuring the frequency change of the vibration tube completes the density measurement. This method is the current mainstream measurement method of slurry density. This method is accurate and reliable, and it is suitable for a wide range of slurry density. Can fully meet the requirements of on-site use. To use the product better, you must pay attention to the following issues.

1: When installing vertically or horizontally, the measuring tube should be upward to protect the measuring tube from changes in the frequency of the measuring tube caused by the accumulation of solid residues, thereby affecting the accuracy of its density measurement.

2: When the manufacturer uses the Coriolis force mass flowmeter to measure the density, it often ignores the impact of the flow rate or flow rate on the mass flowmeter. The flow through the mass flowmeter medium does not have a direct effect on the density accuracy of the flowmeter, but the high-speed flowing limestone slurry is very weary on the measuring tube of the mass meter, thus affecting its service life. Therefore, the flow rate through the mass meter should not be too high to increase its service life and reduce costs. The specific method is that if the flow rate of the main pipeline is too large, the mass meter can be installed in the bypass and the flow rate can be controlled by the valve.

3: Do not install directly at the outlet of the vertical vent tube, but on the pressure side of the pump (to prevent low pressure).

4: The mechanical structure of the measuring tube has changed due to material accumulation, wear and corrosion after a long period of use. Its resonance frequency has been affected by these factors, resulting in a reduction in density measurement accuracy. On-site re-calibration adjustment must be performed.

5: Rinse the pipeline with clean water before it is stopped for a long time to prevent the limestone from adhering to the wall of the measuring pipe or even blocking the pipe.

The differential pressure method is an indirect measurement method, that is, the pressure difference between the slurry of different heights is measured by a differential pressure transmitter, and the slurry density is calculated according to ρ = P / gH, where ρ is the slurry density and P is the differential pressure transmitter Out pressure, H is a fixed distance, g is a constant.

The main advantage is that it is cheap and does not require a separate measurement piping system. However, the measuring probe is easy to be blocked, and the instrument data will remain unchanged when severe, and the monitoring function will be lost. In addition, the measurement accuracy is low. Because the density of the slurry is not uniform at every point, it causes a deviation.

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