%0 Journal Article
%T Test Gas Generation from Pure Liquids: An Application-Oriented Overview of Methods in a Nutshell
%A Yue Li
%A Tim T£¿ffner
%A Michael Bischoff
%A Bernd Niemeyer
%J International Journal of Chemical Engineering
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/417029
%X The generation of test gas from pure liquids has a wide variety of applications in laboratory and field experiments, for which the quality of the test gas is of significance. Therefore, various methods for test gas generation have been designed. Each method has unique advantages and disadvantages. Thus, a short overview is presented within the scope of this paper. Furthermore, a common bubbler system is presented, which was built to generate test gas from volatile organic compounds for experimental usage in laboratory applications. An analysis is conducted with respect to the generated concentrations at different temperatures and flow rates of the diluting gas. Accuracy and stability of this method are investigated. 1. Introduction The generation of test gas from pure liquids, for example, volatile organic compounds (VOCs), is of great importance for laboratory and field experiments. There are several major applications for it:(i)Adsorption analysis of isotherms, breakthrough, and kinetics.(ii)Standard gas for calibration of analytical instruments, for example, gas chromatography (GC).(iii)Safety system verification/calibration.(iv)Calibration of air quality analysis and pollution control systems.(v)Chemical vapour deposition (CVD). Various methods have been developed for the generation of test gas. They can be divided into two categories: static and dynamic methods [1¨C4]. The injection of liquid and its evaporation in an enclosed container with defined volume of diluting gas constitute the functional principles of all static methods. The metal, glass, or plastic container could be employed without any other complex apparatus, which is simple and inexpensive. However, one of the crucial drawbacks of these methods is the appearance of adsorption and condensation on the wall of the container [2]. Therefore, the concentration of the test gas cannot be reliable at higher concentrations. Another drawback is that only a limited amount of test gas is generated once. Moreover, leakages and pressure changes exert an effect. Compared with static methods, dynamic methods are based on a continuous diluting gas flow through the generation system and the mixture with the vapour at a known generation rate [2]. Though these methods are more complex and expensive, but they show important advantages, such as a negligible effect of the adsorption and condensation at the state of equilibrium, continuous test gas generation without volume limit, continuous dilution providing a wide concentration range, and possible control of test gas condition for temperature, relative
%U http://www.hindawi.com/journals/ijce/2012/417029/