Comparison of Measurement of Liquid Density in Tower by Mass Flow Meter and Pressure Transmitter

Abstract: This paper introduces two methods for measuring the liquid density in the absorption tower in the desulfurization project of thermal power plants: the density measurement method of Coriolis force mass flow meter and the density measurement method of diaphragm pressure transmitter, and compares the advantages and disadvantages of the two measurement methods . Keywords: Density measurement Mass flowmeter Diaphragm pressure transmitter Introduction: With the improvement of environmental protection requirements, domestic large-scale thermal power plants have basically launched flue gas desulfurization projects, and real-time online measurement is often required in wet desulfurization projects Liquid density in the absorption tower (such as limestone slurry, ammonium sulfate, etc.). This article will introduce 2 methods of measuring liquid density, and compare them in terms of installation and price. 1 Measure density with mass flowmeter 1.1 Introduction of mass flowmeter Coriolis force mass flowmeter is commonly used in various wet desulfurization projects at this stage. The mass flowmeter is a new type of measuring instrument that directly measures the mass flow of fluid in a closed pipeline manufactured according to the principle of Coriolis force. It generally consists of two parts: a signal measurement sensor and a signal converter. French physicist Coriolis discovered in 1832 when studying water turbines that when fluid flows in a rotating tube, it will generate a force on the tube wall, which is the Coriolis force, or Coriolis force for short. 1.2 Requirements for the installation of the mass flowmeter The installation of the mass flowmeter generally needs to consider the requirements of the necessary straight pipe sections before and after, and try to stay away from throttling devices such as valves and orifice plates. The mass flowmeter is often installed in a bypass mode. At this time, it is necessary to ensure that the flow rate of the medium flowing through the mass flowmeter cannot be lower than 1m/s, so as to prevent the medium from depositing in the mass flowmeter and cause blockage, and consider setting up automatic sewage and drainage on the installation pipeline. Flush the valve. Some manufacturers suggest to install the mass flowmeter vertically at the lowest point of the vertical pipeline downstream of the pump (to avoid being vacuumed). Since the medium flows from bottom to top, it often brings some inconvenience to the pipeline process design. Since the medium to be measured in the wet desulfurization project has acidity and high solid content, it will cause greater wear to the mass flowmeter at a slightly higher flow rate, so the material performance should be considered when selecting the type. Acid resistance and wear resistance (generally, Hastelloy can be considered). 1.3 Disadvantages of mass flowmeter It is found in the actual use process that Coriolis force mass flowmeter is generally more accurate and has high precision when it is first used. After being used for a period of time, the measurement pipeline may vibrate continuously due to the harsh operating environment, and its measurement value is often inaccurate; at the same time, it must be washed frequently during use, otherwise it is very easy to block. In addition, the price of the Coriolis mass flowmeter is very high, generally more than 100,000 yuan, and the cheaper one costs 50,000 to 60,000 yuan. 2 Measuring Density with Diaphragm Pressure Transmitter 2.1 Installation method and principle The pressure transmitter is used to indirectly measure the liquid density in the tower, which is easy to install and cheap, and can be used in occasions where the accuracy requirement is not particularly high. The measurement method is as follows: Install two diaphragm flange pressure transmitters at the upper and lower points relative to the bottom of the absorption tower. In order to prevent the medium from settling and coagulating in the tower, a large agitator is generally installed on the absorption tower. If the agitator keeps agitating, the medium will not condense, but at the bottom of the absorption tower, since the agitator does not work, as the solid particles of the medium continue to settle, it will definitely deposit and condense. Therefore, the installation position of the pressure transmitter should be a distance away from the bottom of the absorption tower, usually about 1.3m. The height difference Δh between the 2 pressure transmitters is a known value. According to Archimedes' law p=ρIt can be seen from gh that p1=ρgh1,p2=ρgh2, so there is Δp=p1-p2=ρgh1-ρgh2=ρg(h1-h2) =ρgΔh, getρ=Δp/(gΔh). In finding the medium densityρAfter that, you can pass h1=p1/(ρg), h=h1+h0 to obtain the actual liquid level in the tower. In the case of less demanding measurement accuracy, the density can be assumedρFor a known fixed value, the liquid level is measured directly with a pressure transmitter by this method. Since the liquid level in the absorption tower fluctuates relatively, the actual pressure value measured by the pressure transmitter itself has errors. The wet desulfurization project does not have very high requirements on the control accuracy of the liquid level in the tower. This error does not affect the system operation and can be ignored. However, the liquid level of the medium in the tower is an important parameter for the stable operation of the system.“choose one' or“Two out of three' redundant design.

Owing to its insertion ultrasonic flow meter and low flow turbine flow meter benefits, has become a buzzword in the coriolis density meter market.

Beijing Sincerity Automatic Equipment Co., Ltd will be known for our leadership edge, through our passion for high standards, our respect for diversity and our commitment to create exceptional opportunities for professional growth so that associates can fulfill their highest potential.

Beijing Sincerity Automatic Equipment Co., Ltd deems mass flow meter as evolutionary rather than revolutionary. We've always had these 'social commerce' marketplaces in some form.

Beijing Sincerity Automatic Equipment Co., Ltd is the best manufacturer which has rich experience on manufacturing.