Investigation of effective dimensionless numbers on initiation of instability in combustion of moisty organic dust

In this work, the effect of various effective dimensionless numbers and moisture contents on initiation of instability in combustion of moisty organic dust is calculated. To have reliable model, effect of thermal radiation is taken into account. One- dimensional flame structure is divided into three zones： preheat zone, reaction zone and post-flame zone. To investigate pulsating characteristics of flame, governing equations are rewritten in dimensionless space-time （（, r/, ~） coordinates. By solving these newly achieved governing equations and combining them, which is completely discussed in body of article, a new expression is obtained. By solving this equation, it is possible to predict initiation of instability in organic dust flame. According to the obtained results by increasing Lewis number, threshold of instability happens sooner. On the other hand, pulsating is postponed by increasing Damk6hler number, pyrolysis temperature or moisture content. Also, by considering thermal radiation effect, burning velocity predicted by our model is closer to experimental results.

Investigation over the recirculation influence on the combustion of micro organic dust particles

This paper investigates the role of recircnlation and non-unity Lewis number on the combustion of organic dust particles. Since recirculation effect is more noticeable in micro-combustors, it is necessary to propose a modeling approach of this phenomenon to better simulate the performance of micro-combustors. In this research, in order to model the combustion of organic dust particles, it is assumed that the dust particles va- porize first to yield a known chemical structure which is oxidized in the gas phase, and the chemical structure of this gaseous fuel is assumed methane. To study the flame structure and solve the governing equations, it is considered that the flame structure consists of three zones titled the preheat-vaporization zone, the narrow reaction zone and finally the post flame zone. The recirculation phenomenon is evaluated by entering the exhausted heat from the post flame zone into the preheat zone. The solution is based on the follow- ing approach. First, the governing equations in each zone are nondimensionalized. Then the needed boundary and matching conditions are applied in each zone. After that, these equations and the required boundary and matching conditions are simultaneously solved with the analytical model. Consequently, the remarkable effects of recirculation and non- unity Lewis number on the combustion characteristics of the organic dust particles such as burning velocity and temperature profiles for different particle radii are obtained. The results show reasonable agreement with published experimental data.

Mutagenic activity in Salmonella typhimurium mutants of the dust organic extract and its five fractions derived from an aluminum electrolytic plant

The dust derived from an aluminum electrolytic plant was collected on a filter, then extracted with benzene. The benzene soluble material was separated into five fractions, namely organic acid, organic alkali, aliphatic hydrocarbon, polycyclic aromatic hydrocarbon and polar compounds. The mutagenic activities of these fractions were examined with two strains of Salmonella typhimurium mutants. It was demonstrated that the dust organic extract showed a very strong mutagenic activity. Among the five fractions tested, three fractions, namely organic acid, polycyclic aromatic hydrocarbon and polar compounds, played an important role in the mutagenic activity of the dust organic extract. The other two fractions, organic alkali and aliphatic hydrocarbon had no mutagenic activities. Therefore, dust abatement is an important measure in aluminum plants for controlling carcinogens, mutagens and protecting the environment and human health.