Experimental modeling of tropospheric nucleation in a laminar flow tube reactor

A Laminar Flow Tube Reactor (LFTR) has been designed and constructed for study of nucleation of multi-component systems of particular tropospheric interest. The experimental device is based on the injection of certain vapor-gas mixtures of some of the typical tropospheric substances (water, sulfuric acid, ammonia, organics, etc.), which are presumed to be responsible for the tropospheric nucleation, into a thermostatted tube. Because the flow in the tube is laminar, all the thermodynamic parameters (space distributions of temperature, vapor concentrations, supersaturation) inside the tube can be calculated. The boundary conditions are defined by the temperature of the walls of the reactor tube. The initial conditions (the temperature of the flow and the concentration of compounds at the inlet) are well controlled also. Thus the parameters of nucleation zone can be determined and the nucleation volume and time can be obtained. The concentration of the particles formed in the reactor is measured by a condensation particle counter and consequently nucleation rate can be measured as a function of temperature, supersaturation and concentration of all the components injected into the system. An interface with a differential mobility analyzer and with a mass-spectrometer has been designed as well. The latter will allow obtaining information about particle size distribution and the composition analysis of the particles.

This work has supported by the Atmospheric Chemistry Program of the U.S. Department of Energy (DOE) under Contract DE-AC06-76RLO 1830. Pacific Northwest National Laboratory (PNNL) is operated for DOE by Battelle Memorial Institute.