Spectroscopic characterization of lithium combustion
- PDF / 776,473 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 43 Downloads / 224 Views
EXPERIMENTAL DETAILS Spectroscopy Methods Spectra of the characteristic luminescence of the lithium atom around 670 nm were detected via spectrograph (Princeton Instruments, Acton Research 750) and CCD-camera (Princeton Instruments, Pixis 256) [1,2]. The line positions were calibrated by Hg- and Nereference lamps. The detection was focused on the middle of the sample holder, where – especially in case of combustion in air – a stationary reaction from ignition over red-hot combustion to extinction was observed. The intensity of the emission lines is correlated to the amount of molecules in the gaseous phase, which in turn is increasing sharply by evaporation due to the heat release of the combustion. Low Pressure Reactor A stainless steel container with a heated sample holder was used to study lithium combustion under controlled conditions (Figure 1). Lithium pellets with a weight up to 1 g were molten and ignited by a high voltage spark. Once the reaction started, the electric wire was moved out of the reaction zone. For experiments under different conditions, the reactor was evacuated. After that, the desired gas mixture of oxidizing and inert gases was added and the pressure was adjusted. In addition to spectroscopic measurement of the chemiluminescence emissions, reaction progress was monitored by probing the gas composition with online mass spectrometry. Once reaction was complete, the atmosphere in the reactor was replaced by air. Solid reaction products were removed and investigated by various techniques like elemental analysis and quantitative titration.
Figure 1. Reactor for lithium combustion under reduced pressure.
Reactor for Lithium Spray Combustion For power plant usability of the discharging process of the energy carrier lithium, the combustion of lithium spray like in a conventional combustion process has to be characterized. Therefore, the atomization process as well as the ignition and combustion of the lithium spray need to be analyzed. Atomization and spray formation of metals such as tin and some alloys are discussed in the literature [3-5] but to the knowledge of the authors no information about atomization of lithium can be found. The atomization experiments took place in a stainless steel reactor shown in figure 2a). The lithium was heated up in an atomizer to 900 K. With argon pressure it was pushed through a nozzle and atomized. Two different nozzles were tested: a pressure swirl nozzle and a twocomponent nozzle. To analyze the particle size and distribution, atomization experiments in inert argon atmosphere were carried out. The lithium particles were collected and measured under mineral spirits by using optical microscope. With a relative argon pressure of 4 bar the lithium particle in the spray have a mean diameter of 130 µm at a distribution from 50 µm to 250 µm (inset of figure 2b)). The particles have a round shape as can be seen in figure 2b). Unlike in the low-pressure experiments, the lithium spray was ignited using thermal energy by pre-heating the reaction gas. The solid react
Data Loading...
