화학공학소재연구정보센터
Chemical Engineering Science, Vol.55, No.12, 2203-2212, 2000
Measurements of solid contaminant emission rates from boiling pools
An experimental study was performed to measure release rates of solid particles from boiling pools. Sensitivity studies were conducted to reveal the dependence of the particle carry-over rate on the pool depth, the boiling rate and the vertical distance from the pool surface. Experimental data on particle concentrations as a function of size at the pool surface are also provided. The study was conducted in a nucleate boiling regime. Tests were performed with distilled water and solid nickel particles ranging in size from 5 to 40 mu m. The test apparatus was made of a cylindrical vessel, 30 cm in diameter and 120 cm in height. Slurry particle concentrations were on the order of milligrams per cubic centimeter of slurry. Heat fluxes on the order of 100 kW/m(2) were attained by electrical bottom heating. Corresponding superficial vapor velocities were on the order of several centimeters per second. The phenomenon of particle emission from the surface of boiling pools pauses major environmental and industrial problems. Such particles are often undesirable contaminants, especially if toxic or radioactive. Exploration of this subject is of considerable importance to the chemical, nuclear, and power generation industries. The current study provides important data to support safety analyses and development of analytical tools. Surface contamination concentrations and particle emission rates are essential data for environmental contamination evaluations of spills and boiling, respectively. The study indicates, among other things, that emission rates intensify as pools get shallower. A released particle Aux is strongest near the surface; and at a decreasing pace, diminishes tu a constant rate as the distance from the surface is increased. Decontamination factors of the boiling process were found to be in a range of 10(3)-10(4).