No abstract

Citric acid is one of the organic acids of which world market is growing every year. This paper proposes reactive extraction of citric acid with trioctylamine as an alternative to the classical method [1]. An experimental setup with solvent recycling is presented. As organic solvents were used: octanol, cyclohexanol, iso-butyl alcohol and paraf®n oil. The removal ef®ciency is enhanced when the reactive extraction is accompanied by back-extraction using sodium carbonate as stripping agent.

The extraction-back extraction column of low concentration species by means of an organic closed loop flow, considered as liquid membrane, was modelled then simulated, using some simplifying assumptions. The main hypotheses are: the aqueous phase is perfectly mixed, the drops of the organic phase are lumped into a plug-flow inner cylinder co-axial with the aqueous phase, and the organic phases under the sieve and on the top of the column are perfectly mixed also. The dynamic model of the extraction-back extraction column is, then, applied to the recovery of the hydrocarboxylic acids. The mathematical model, reduced through orthogonal collocation to a system of ordinary differential equations, was solved using a self-adaptive (RK)-type method. Its validation was done based on batch experimental data; the optimal model parameters (the specific mass transfer coefficients for both extraction and back-extraction zones), ensuring the agreement with the experiment, were found by means of a modified genetic algorithm technique. Then, a sensitivity analysis was done, to grasp the behaviour of the system with respect to the main operating parameters - the organic flow in the closed loop, the partition coefficient and the buffer volume.

Petrochemical complexes include high risk interconnected plants processing large quantities of dangerous/flammable substances, complex reactors of high thermal sensitivity operated under severe conditions of high productivity and associated equipment, vessels or separation units operating at intense temperature and pressures. Such plant design/operation problems contribute quite frequently to the occurrence of small incidents or rare major accidents including domino effects. The study applies classical boiling liquid expanding vapour explosion fire and toxic puff release models to evaluate the effects and consequences of different accident scenarios involving two neighbouring risk plants, with exemplifications for the aniline and maleic anhydride synthesis plants. A proposed joint probability index of human casualties, related to thermal radiation doses and toxic material released around plants, points out the influence of production capacity and plant proximity on the severity of accident consequences and domino‐effect occurrence. © 2013 Curtin University of Technology and John Wiley & Sons, Ltd.

Chitin extraction from crab shells was studied experimentally and optimized aiming to obtain chitosan with predefined deacetylation degree and molecular mass. To find out the optimum operating conditions that ensure the obtaining of a chitosan with highest deacetylation degree and specific molecular mass four parameters were varied: the concentration of NaOH and the temperature for deproteinization step, respectively HCl concentration and the number of acidic treatments for the demineralization stage. The experiment was carried on following Taguchi orthogonal array L9, and the best combination of factors was found using the desirability function approach. The optimization results showed that 5% NaOH concentration and low temperatures lead to a chitosan with high deacetylation degree. High molecular mass chitosan is obtained when a single step acidic treatment is used, while a chitosan with low molar mass is obtained for multiple acid contacts and higher HCl concentration.