Study On Sampling And Separating Performance Of Fly-ash In Power Plant

With thoroughly development of Low-Carbon Economy, higher requirements for energy-saving and emission-reducing have been put forward in power plants. As a major economical and technical indicator of coal-fired boiler, carbon content in fly-ash is of important significance for the power plants to carry out a reasonable energy-saving plan. Sampling and separating performance of fly-ash was studied in this paper, and the main work and result are summarized as follows.Through the pressure loss theoretical study of the sampling nozzle, the inner compensation structure of fly-ash sampling nozzle was determined. Numerical simulation method was used to analyze the influence of inner compensation structure on the static pressure. The results showed that in 10-20m/s isokinetic sampling conditions, static pressure was compensated at the distance of 0.015m from sampling nozzle, therefore the location of inner static pressure test hole was determined. A study was carried out to track the trajectory of fly-ash particles, and the results show that small particles are highly impacted by non-isokinetic sampling rate, but there is little effect to the particles whose equivalent diameters are larger than 20μm. An experiment of the fly-ash sampling was carried out in a power plant, and the results show that it is almost identical of the fly-ash particle size distribution by the sampling nozzle used in this paper and automatic isokinetic sampling device and the real components of fly-ash particles can be reflected.In this paper, the dynamics of airflow in the cyclone separation was studied by the method of numerical simulation. And its internal velocity distribution, pressure distribution and turbulence structure were analyzed systematically. It is found that:the center of the cyclone separation is a forced upward rotation vortex; the external is a quasi-free downward rotation vortex.Study on the trajectory of fly-ash particles and the separation performance found that separation efficiency of less than 3μm particles are low due to effects of the exhaust pipe short-circuit flow and second back-mixing of dust port. The separation efficiency of cone and ET exhaust pipe was improved by about 20% than Dχ=60mm cylindrical exhaust pipe, while the pressure dropped only increases by about 4%.Isokinetic sampling device this paper designed has been used in fly-ash sampling equipment of some plants. The study on law of fly-ash separation performance provides guidance for the structure and performance improvement of cyclone separation.