IRANIAN JOURNAL OF CHEMICAL ENGINEERING
Year:2008 | Volume:5 | Issue:3|Papers Count:6

The present work is concerned with the development of a new algorithm for determination of the equilibrium composition of gaseous detonations. The elements balance equations, and the second law of thermodynamics (i.e., the minimization of the Gibbs free energy of products), are used to determine the equilibrium composition of the detonation products. To minimize the Gibbs free energy with traditional deterministic methods one needs to solve a set of highly nonlinear equations. The numerical methods in the existing equilibrium codes suffer from several drawbacks such as the divergence possibility in some equivalent ratios, and the possibility of converging to a local relative minimum in the minimization process. To overcome these drawbacks, a genetic algorithm is presented in the present study. Converging to the global minimum of Gibbs function in all equivalent ratios, and having a reasonable CPU time are the notable aspects of the proposed algorithm.

Corn stalk can be used as an alternative non-wood raw material to produce cellulosic dissolving grade pulp. In this work, the potential of corn stalk in the production of dissolving pulp (alpha-cellulose) was investigated. It was collected from a corn stalk farm of Kermanshah, Iran. The sequences of experimental work were: water and acid prehydrolysis at 160oC for 30min, followed by Kraft pulping at 170oC for 90min, and bleached by HEH & HEHP sequences. The influence of active alkali (14-20%), and sulphidity (10-25%) on the pulp properties such as yield, kappa number, and degree of polymerization was investigated. In optimum conditions (water prehydrolysis; pulping with active alkali of 20%, sulphidity of 25%; and HEH bleaching sequence), the alphacellulose content, degree of polymerization, and ash content of the produced dissolving pulp were acceptable: 94.7%, 269 and 1% respectively. The properties of the produced pulp were comparable with the pulp obtained by other sources. Active alkali was the most important irifluent parameter, with respect to delignification, whereas the sulphidity had a minor effect.

An industrial ethane thermal cracking reactor was modeled assuming a molecular mechanism for the reaction kinetics coupled with material, energy, and momentum balances of the reactant-product flow along the reactor. To carry out the multi-objective optimization for two objectives such as conversion and ethylene selectivity, the elitist non-dominated sorting genetic algorithm was used. The Pareto optimum set was obtained successfully and finally the effect of the decision variable was discussed.

The removal of hydrogen sulfide (H2S) from airstreams was studied in a biotrickling filter packed with porous lava as a carrier of Thiobacillus thioparus (DSM5368) with counter current flows of the air and liquid streams. The effect of operating parameters on biotrickling filter performance was studied. Experiments were performed at different empty bed residence times (9-60 see), and moderate H2S concentrations (10-90 ppm) to assess the performance of biotrickling filter at different conditions of these parameters.The effect of superficial liquid velocity (0.98-1.95mh-1) on the performance of biotrickling filter was evaluated. Increasing superficial liquid velocity decreased removal efficiency of the BTF. The gradual change in the concentration of H2S in different heights of the BTF was investigated. Decreasing empty bed residence time lead to a slight increase in the homogeneity of the removal at different heights of the BTF; however the effect of change in the inlet concentration was insignificant.Complete removal was achieved in the first 85% of the bed. To gain a brief insight into the robustness of the biotrickling filter, its performance was investigated after several upsets in the system.

Lennard-Jones-Devonshire equation o/state is an old but theoretical based EOS. The concept of the nearest neighboring molecules or coordination number is proposed to be a function of temperature and volume, whereas it is a constant in the original. The dilute gas and hard sphere limits of molecules are employed to determine this function.Improvement of this modification is demonstrated by property calculations for Lennard- Jones fluid. Results of the modified LJD equation of state offer senior accord with simulation data of Lennard-Jones fluid than those of the original version.

Airborne particulate matter (PM10) was collected from the atmosphere of the city of Isfahan. The concentration of heavy metals and anions associated with airborne particulate matter were determined using atomic absorption spectrometric and ion chromatographic techniques. A comparison was made between the variation in the concentration of PM10 and that for heavy metals and CO. An excellent similarity was found between the variation model of PM10, heavy metals and CO. Due to the atmospheric concentrations of heavy metals, the enrichment factors were calculated and showed that the well-known toxic heavy metals are mostly released into the city atmosphere from anthropogenic sources.