Experiment Research Of The PM2.5 Aerosol Preparation Based On Supercritical Method

Due to the uneven monitoring results of the PM2.5 monitors, it is urgent for a standard PM2.5 aerosol to test and calibrate the equipment. Therefore, we will carry out research work about the preparation of standard PM2.5 aerosol. And the research work carried out for PM2.5 monitors’ calibration, calibration is of great significance.In this paper, based on the PM2.5 aerosol generator designed by our research group, the research work about the preparation of standard PM2.5 aerosol was carried out respectly using PGSS method and SAS method. We determined the influence factors about using PGSS method for the preparation of polyethylene glycol aerosol particles, and the L9(34) orthogonal scheme was designed. The average particle diameter of aerosol particles were about at 1μm, 1.9μm, 2.3μm, 17μm, 20μm under different experimental conditions. Under the same conditions, the particle size distribution is nonuniform, and the aggregation is serious. According to the experimental results, the influence degree and trend of the experimental factors are analyzed, and the results showed that: Effects of experimental factors on the results from large to small is carbon dioxide flow, nozzle size, autoclave temperature, autoclave pressure. With the autoclave temperature too high or too low and the bigger of CO2 flow rate and nozzle size, the particle size is much bigger. With the higher of the autoclave pressure and the smaller nozzle size, the particle size is smaller. We determined the influence factors about using SAS method for the preparation of polystyrene aerosol particles, and the Box-Behnken scheme was designed. Aerosol particles collected under different experimental conditions were about at 1~10μm,and the particle size with a narrow and uniform distribution under the same conditions. According to the experimental results, the influence degree and trend of the experimental factors are analyzed, and the results showed that: Effects of experimental factors on the results from large to small is crystal kettle temperature, gas liquid ratio, solution concentration, crystal kettle pressure. With the higher of the solution concentration and the crystal kettle temperature, the particle size is much bigger. With the higher of the crystal kettle pressure and the bigger gas liquid ratio, the particle size is smaller. Through the analysis of experimental results, we find the SAS is better than PGSS, and also to verify the PM2.5 aerosol generator designed by our research group for the preparation of PM2.5 aerosol is feasible.In this paper, the preparation of standard PM2.5 aerosol also has some problems in particles size and uniform. Thus, it still needs to make a further optimization and improvement for the experimental equipments and parameters, in order to achieve the expected results.