Measurement Study Of The Sparse Solid Phase Concentration In Gas-Solid Two Phase Flow

In coal-fired power plant, the uniformity of first wind mass flow rate and coal powder concentration in burners are directly related to the security and economy of boiler combustion, so the online measurement of coal powder concentration has very important engineering significance and many practical benefits. In the first wind powder pipelines, the ratio of first wind and coal powder is about 1.8～2.0 kg/kg in the normal operation condition, the coal powder concentration is about 0.4 kg/kg～0.8 kg/kg, the volume percentage is about 0.5‰～1‰, the velocity of first wind is about 20m/s～30m/s and the wind powder conveying system is a typical thin gas-solid two phase flow.In this paper, it focus on the measurement of sparse solid concentration in gas-solid two phase flow, based on light extinction method, make systematical research through theoretical analysis, experimental verification and simulation analysis. The main research content is as follows:(1) From the basic principle of extinction method, make a summary analysis of the measurement characteristics, accuracy and measuring devices of the extinction method, calculate and derive the theory linear equation of voltage value and powder concentration.(2) Based on the theory of gas-solid two-phase flow, set up large closed cycle test bench, use visible light as the measurement source and larger beam section, design anti-stain window structure and make solid concentration measurement research with floating beads particle. In addition, by repeating the experiment demonstration, the relationship between voltage and powder concentration curve is obtained. The results showed that:in powder concentration about 0.5 kg/kg～0.7 kg/kg range, both have good linear relation, coefficient of fitting error is 15%～20% and repeated measurement error is less than 5%.(3) Combined with the experimental data, make simulation studies under different working conditions by Fluent software. Make some analysis about the two phase fluid resistance pressure drop along the pipe wall, powder concentration distribution in the direction of along the optical path, etc.The extinction method adopt in this experiment has better feasibility of pulverized coal concentration, it can be used the relative measurement of coal conveying pipelines in the coal-fired power plant, or absolute measurement of powder concentration in some pneumatic conveying without high precision.