Esterificatfon of n-Butanol with Acetic Acid Catalyzed by a Cation Exchange Resin

The kinetics of the esterification of n-butanol with acetic acid have been studied in a batch and in a tubular reactor. The best model for obtaining the esterification rate with a partially wet ion exchanger (270/o water contents) is obtained by assuming a pseudohomogeneous system, while the kinetics of dry ion exchangers is best represented by a model derived from assumptions based on a heterogeneous system. A separate study of the induction period in a tubular reactor shows the considerable influence of the water content on reaction kinetics. This is manifested by a change of the catalytic activity during the reaction. Change of the catalytic activity can lead to erroneous interpretation of experimental results and to derivations of inadequate kinetic expression. It is shown that change of ion exchanger activity in the induction period is caused by diffusion of reactants into resin particle

High-shear vs. Fluid-bed Granulation Process of Dolomite: Process Modeling

High-shear and fluid-bed processes were used for granulation of dolomite powder into agrochemical product. In this paper, comparative study of the granulation process focuses on the observation of granule size distribution (GSD). Considerable difference between high-shear and fluid-bed GSDs is analyzed with process kinetics. Simulation of dynamic development of GSD is achieved with application of a 1-D discretized population balance and Equi-Partition of Kinetic Energy (EKE) coalescence model. The used approach indicates for both processes (high-shear and fluid-bed granulation) the presence of coalescence growth as a dominant mechanism in the dolomite granulation process. Deviations between simulated and real GSDs signify the probable existence of other granulation mechanism(s). A posteriori approach by the integral method was used for coalescence rate constant estimation. The generated kinetic considerations represent a valuable step towards a comprehensive perspective of dolomite granulation and implementing the acquired knowledge in real-life agrochemical granulation

4-Lump kinetic model for hydrotreated gas oil catalytic cracking

This study has monitored the influence of one of the hydrodesulphurisation process parameters - H2/CH ratio on the properties of three catalytic cracking products (gas, petrol, light cyclic oil, and heavy cyclic oil ). The microactivity test (MAT) was applied to all kinetic measurements. A 4-lump, non-isothermal and non-stationary kinetic model for the fixed, plug-flow MAT reactor was developed to model catalytic cracking of hydrotreated gas oil. Kinetic constants were estimated by the Nelder Mead method. The product yields predicted by the model showed good confirmity with experimental data

Esterificatfon of n-Butanol with Acetic Acid Catalyzed by a Cation Exchange Resin

The kinetics of the esterification of n-butanol with acetic acid have been studied in a batch and in a tubular reactor. The best model for obtaining the esterification rate with a partially wet ion exchanger (270/o water contents) is obtained by assuming a pseudohomogeneous system, while the kinetics of dry ion exchangers is best represented by a model derived from assumptions based on a heterogeneous system. A separate study of the induction period in a tubular reactor shows the considerable influence of the water content on reaction kinetics. This is manifested by a change of the catalytic activity during the reaction. Change of the catalytic activity can lead to erroneous interpretation of experimental results and to derivations of inadequate kinetic expression. It is shown that change of ion exchanger activity in the induction period is caused by diffusion of reactants into resin particle

Chronic cardiovascular and respiratory symptoms in aluminium workers

Na osnovi vlastitih istraživanja kao i ispitivanja ostalih autora u radu je analiziran. problem kroničnih pulmonalnih smetnji i kardijalnih simptoma u radnika zaposlenih u elektrolitskoj ekstrakciji aluminija. Medicinski su pregledane dvije skupine radnika, koje su različito dugo izložene iritansima. Funkcionalni i klinički respiracijski nalazi kao i medicinska anamneza upućuju da postoji povezanost izloženosti štetnim tvarima iz elektrolitskih peći i pojave kronične plućne bolesti. U pregledanih radnika nije nađen direktan učinak dužine izloženosti iritansima na učestalost kardijalnih simptoma.The subject of chronic respiratory and cardiovascular symptoms in exposure to irritants in a plant for the electrolytic extraction of aluminium is discussed on the basis of the results of own investigation and of those of other authors. Two groups of workers with a different length of exposure to irritants were medically examined. The workers\u27 histories and clinical and functional respiratory findings point to the existence of a correlation between potroom exposure and the development of chronic respiratory disease. No direct relationship was established between the duration of exposure and the occurrence of cardiovascular symptoms in the examined worker

Analysis and Modeling of Curing Polyester Resin in Cylindrical Moulds Heated by Air

Predložen je i izveden matematički model očvršćivanja poliesterskih smola u kalupima valjkastog oblika koji se griju zrakom. Model pretpostavlja konvektivni prijenos topline sa zraka na stijenku kalupa te vođenje topline kroz smolu. Temperatura unutar uzorka mijenja se tijekom očvršćivanja, što je posljedica egzotermnosti reakcije i procesa prijenosa topline. Dodatkom punila u smolu mijenjaju se toplinska svojstva smjese kao i iznos topline koja nastaje reakcijom u istom volumenu uzorka, što vodi do nižih temperaturnih maksimuma u centru simetrije valjkastog kalupa. Model je provjeren mnogobrojnim eksperimentima u kojima je mjerena temperatura uzorka smole unutar kalupa tijekom očvršćivanja. Nezavisnim eksperimentima u kojima je umjesto uzorka smole u kalupu bio glicerol te uz različite brzine strujanja zraka oko kalupa procijenjen je koeficijent prijenosa topline zrak - stijenka kalupa. Dobivene vrijednosti uspoređene su s poznatim korelacijama i dobiveno je dobro slaganje. Predloženim modelom vrlo dobro se može simulirati proces očvršćivanja u valjkastim kalupima te procijeniti utjecaje prijenosa topline i brzine reakcije na maksimalno moguće temperature unutar kalupa.The mathematical model of the cure of unsaturated polyester resin in cylindrical mould heated with warm air was suggested and derived. The model assumes convective heat transfer through air on the wall of the mould and conductive heat transfer through the resin. The temperature within the sample changes during the cure process, which is the result of the reaction being exothermal and the process of heat transfer. The addition of the filler changes the thermal properties of the mixture and reduces the amount of heat generated during the reaction in the sample of the same volume, which leads to lower temperature maximums in the center of the cylindrical mould. The model was tested with multiple experiments in which the temperature of the resin inside the mould during the cure process was measured. The heat transfer coefficients between the air and wall of the mould with different speeds of air flow were estimated using independent experiments where the glycerol was used instead of resin. Estimated values were compared with known correlations and good agreement was obtained. Using the suggested model, the cure process in the cylindrical mould can be simulated accurately and influents of the heat transfer and reaction rate on the temperature maximums can be studied

Chronic cardiovascular and respiratory symptoms in aluminium workers

Na osnovi vlastitih istraživanja kao i ispitivanja ostalih autora u radu je analiziran. problem kroničnih pulmonalnih smetnji i kardijalnih simptoma u radnika zaposlenih u elektrolitskoj ekstrakciji aluminija. Medicinski su pregledane dvije skupine radnika, koje su različito dugo izložene iritansima. Funkcionalni i klinički respiracijski nalazi kao i medicinska anamneza upućuju da postoji povezanost izloženosti štetnim tvarima iz elektrolitskih peći i pojave kronične plućne bolesti. U pregledanih radnika nije nađen direktan učinak dužine izloženosti iritansima na učestalost kardijalnih simptoma.The subject of chronic respiratory and cardiovascular symptoms in exposure to irritants in a plant for the electrolytic extraction of aluminium is discussed on the basis of the results of own investigation and of those of other authors. Two groups of workers with a different length of exposure to irritants were medically examined. The workers\u27 histories and clinical and functional respiratory findings point to the existence of a correlation between potroom exposure and the development of chronic respiratory disease. No direct relationship was established between the duration of exposure and the occurrence of cardiovascular symptoms in the examined worker

High-shear vs. Fluid-bed Granulation Process of Dolomite: Process Modeling

High-shear and fluid-bed processes were used for granulation of dolomite powder into agrochemical product. In this paper, comparative study of the granulation process focuses on the observation of granule size distribution (GSD). Considerable difference between high-shear and fluid-bed GSDs is analyzed with process kinetics. Simulation of dynamic development of GSD is achieved with application of a 1-D discretized population balance and Equi-Partition of Kinetic Energy (EKE) coalescence model. The used approach indicates for both processes (high-shear and fluid-bed granulation) the presence of coalescence growth as a dominant mechanism in the dolomite granulation process. Deviations between simulated and real GSDs signify the probable existence of other granulation mechanism(s). A posteriori approach by the integral method was used for coalescence rate constant estimation. The generated kinetic considerations represent a valuable step towards a comprehensive perspective of dolomite granulation and implementing the acquired knowledge in real-life agrochemical granulation

4-Lump kinetic model for hydrotreated gas oil catalytic cracking

This study has monitored the influence of one of the hydrodesulphurisation process parameters - H2/CH ratio on the properties of three catalytic cracking products (gas, petrol, light cyclic oil, and heavy cyclic oil ). The microactivity test (MAT) was applied to all kinetic measurements. A 4-lump, non-isothermal and non-stationary kinetic model for the fixed, plug-flow MAT reactor was developed to model catalytic cracking of hydrotreated gas oil. Kinetic constants were estimated by the Nelder Mead method. The product yields predicted by the model showed good confirmity with experimental data

A Design of Experiments Investigation of Adsorptive Desulfurization of Diesel Fuel

Adsorptive desulfurization of diesel fuel was investigated applying two Design of Experiments (DOE) methods. The experiments were carried out in a batch adsorption system using Chemviron Carbon SOLCARBTM C3 activated carbon as adsorbent. The first DOE method employed was a full factorial with three factors on two levels and five center points, and the second was Box-Behneken design with the same three factors but on three levels. The effects of individual factors and their interactions on sulfur concentration and sorption capacity were determined, and statistical models of the process developed. The first-order models predict the behavior of the system rather well but significant curvature was detected. Subsequently developed second-order models were able to give reasonably well descriptions of the system. The lowest achieved output sulfur concentration was 7.6 mg kg–1 with relatively low sorption capacity of 0.0861 mg g–1