负载型多分散气溶胶在管道内的传输规律

放射性气溶胶的传输一直是倍受关注的环境问题。为研究放射性气溶胶在管道内的传输规律，首先自制了能够产生稳定的、多分散气溶胶的发生器。主要考察了稀释气流速（5~25 L/min）、气溶胶颗粒粒径（多分散体系）及固体颗粒密度（土壤、石英砂）对气溶胶在管道内传输的影响。即考察了粒径多分散的石英砂、土壤颗粒形成的气溶胶及表面负载Ag的石英砂颗粒模拟负载型放射性气溶胶，在不同稀释气流速作用下进入管道内的传输，针对每一节管道内的沉积物进行收集分析，从而得到气溶胶在管道内的传输及沉降规律。研究结果表明：密闭管道内，在一定流速范围内，沉积物最高频度粒径随着管道距离的增长而先增大后减小；小粒径的颗粒在传输过程中自重沉降，且由于布朗运动吸附在大粒径颗粒物表面加速其沉降速率，即减小了其在管道内的传输距离；表面负载Ag的石英砂颗粒形成的气溶胶随着稀释气吹扫导致Ag和石英砂颗粒之间有不同程度的分凝，气流速率越大，分凝现象越明显。

Complicated Multi-Particles-Dispersed Aerosol Transportation in Tube

Transportation of radioactive aerosol is a concerned environment problem. In order to study the law of radioactive aerosol transportation in tube, an aerosol generator which can produce stable, multi-disperse and high concentration aerosol was set up.The main factors such as the gas flow rate（5-25 L/min）, the diameter of aerosol-particles(multi-dispersed particles), and the density of the solid-particles(soil and SiO₂) were considered. Three kinds of aerosol respectively formed by multi-particles-dispersed soil system, multi-particles-dispersed SiO₂ system and Ag coated multi-particles-dispersed SiO₂ system(imitating radioactive aerosol), were taken into the tube under different gas flow rate. Then samples of each section in the tube were analyzed, from that, the law of the transportation and deposition of aerosol in the tube can be deduced. Gravity and the particle size are the key factors, especially. At first, the particle sizes of sedimentation increase along the tube, then decrease. The small particles, which adsorbed on the surface of the large ones, fasten the sedimentation of the particles, and shorten the transportation distance. The Ag-SiO₂ sample data show that the fractionation of Ag from the SiO₂-carrier is more obvious as the gas flow rate is faster.