A novel method for the metering of mass flow rate of solid in gas-solid two-phase flow was presented in this paper. A number of industrial prototype capacitance concentration meter have been developed for plant testing in a number of iron-steel factories' pneumatic conveying system of pulverized coal (PC) on blast furnace. Under the conditions of normal operation and safe pneumatic conveying of PC for blast furnace, the slip of mean velocity between suspending PC and air in pneumatic conveying pipe line was not large when compared with the magnitude of the mean air velocity. So the mean velocities of PC and air were very close, and therefore, the ratio of mean velocity of PC to air was approximately constant and had a value near unity. By deduction we can conclude that the mass loading ratio of PC to air in pneumatic conveying pipe is of an approximately linear relationship to the concentration (ratio of mass to volume in which the mass dispersed) of PC and in inverse proportion to air density. We have developed a number of capacitance transducer -capacitance concentration transducer-for the measurement of PC concentration in conveying pipe, and have them calibrated under plant operation. The air density can be easily calculated according to the temperature and pressure detected in pipe using routine technology. So we can get the mass loading ratio by use of capacitance transducer. The mass flow rate of air can be conveniently measured before pulverized coal was introduced into pipe. Combining the air muss flow rate and solid-to-gas mass loading ratio the mass flow rate of pulverized coal can be measured. To assess the performance of this gauge in determining the mass flow rate of pulverized coal for on-line use. the results from the gauge were compared with electronic weighing system. The comparing data were collected under the conditions that the electronic weighing system could be run without any disturbance so that reliable mass flow rate of pulverized coal can be calculated by weighing. The corresponding pulverized coal mass flow rate of the gauge and electronic weighing system was calculated by averaging over 2 minutes separately. The solid-to-gas mass flow rate calculated by electronic weighing system range from 4.27 to 9.1. Taking the value from electronic weighing system as standard, errors of mass flow rate of this gauge were less than 5%. Although this plant trial was conducted by use of capacitance concentration meter, this method is applicable by use of other kind of concentration meter, for example, radioactive absorption, and higher accuracy may be obtained.
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