Ricardo Amâncio Malagoni

Isoconversional Kinetic Analysis of Pyrolysis of Sugarcane Bagasse

This paper presents a kinetic study of pyrolysis of sugarcane bagasse from dynamic thermogravimetric experiments (TG). The methods of Kissinger, Ozawa, Starink, Kissinger-Akahira-Sunose and Friedman were used to estimate the activation energy. These methods consider the temperature shifts with increase of heating rate for a given conversion in dynamic TG tests. The activation energy values obtained by the isoconversional methods were in a range 182.8 192.4 kJ·mol-1, values very close to the other biomasses presented by literature.

Differential Evolution Algorithm and Response Surface Methodology Applied to Turning Process Optimization

Modern engineering problems are often composed by a large number of variables that must be chosen simultaneously for better design performance. The optimization of phenomenological model is an impossible task in terms of computational time. To improve this disadvantage, the Response Surface Methodology (RSM), defined as a collection of mathematical and statistical methods that are used to develop, to improve, or to optimize a product or process, is configured as important alternative to model real process. In the literature, different approaches based on optimization methods have been proposed to design system engineering. In this context, the Differential Evolution algorithm (DE) is a stochastic optimization method that is based on vector operations to improve a candidate solution with regard to a given measure of quality. For illustration purposes, in the present contribution the DE is applied to optimize multiple correlated responses in a turning process. As a case study, the turning process of the AISI 52100 hardened steel is examined considering three input factors: cutting speed, feed rate and depth of cut. The outputs considered were: the mixed ceramic tool life, processing cost per piece, cutting time, the total turning cycle time, surface roughness and the material removing rate. The optimization of cutting speed, feed rate and depth of cut indicate the better configuration of process to minimize the cost.

CINÉTICA DE CRISTALIZAÇÃO DE SACAROSE EM CRISTALIZADOR DE LEITO VIBRADO

A cristalizacao e a principal operacao unitaria no processo de fabricacao da sacarose comercial, este processo pode ocorrer naturalmente ou em equipamentos denominados cristalizadores. Este estudo teve como objetivo determinar a equacao de cinetica de crescimento de cristais de sacarose em um cristalizador batelada de leito vibrado. A fim de definir qual a melhor condicao operacional para simultaneamente obter maior produtividade e tamanho medio de cristais, seguiu-se um planejamento de experimentos no qual as variaveis supersaturacao, vibracao do meio e tempo de cristalizacao foram observadas. Apos a obtencao da condicao de resposta maxima para produtividade e diâmetro do cristal, acompanhou-se a variacao do crescimento cristalino em seis diferentes tempos, atraves da analise granulometrica dos cristais. Observou-se a alta influencia da supersaturacao aliada a vibracao do meio e o rapido crescimento no inicio do processo, com decaimento a partir do decimo quinto minuto de operacao, possibilitando a obtencao de cristais com granulometria semelhante aos comercialmente disponiveis.

Sucrose Crystallization in Vibrated Bed Process, Unusual Crystallizer Configuration

Through yield and Sauter mean diameter, the sucrose crystallization was studied in vibrated bed equipment, in which, supersaturation degree, dimensionless vibration number and crystallization time were independent variables. A central composite design with seventeen trials was performed in order to ascertain the influence of each variable in both responses, the crystallization temperature and the amount of seeds were kept constant. The crystallization vibration system differs from the usual configuration, consisting of two perforated discs made of stainless steel, one loop and three aluminum rings. By canonical analysis, it was obtained the operating condition which maximizes the yield and average crystal size. Surface responses were also obtained according to the relevance of each variable, in which were evidenced the high supersaturation and vibration influence for both factors, the high quadratic term of all variables on the crystal yield, and also highlights the great interaction between supersaturation and the dimensionless vibration number.

ANÁLISE DE SUPERSATURAÇÃO, INTENSIDADE DE VIBRAÇÃO E TEMPO DE OPERÇÃO NA PRODUÇÃO DE CRISTAIS DE ÁCIDO CÍTRICO E SACAROSE EM CRISTALIZADOR DE LEITO VIBRADO

A sacarose e o acido citrico sao amplamente estudados em pesquisas, devido a sua ampla utilizacao em produtos alimenticios, na industria quimica e na producao de farmacos. Atraves da analise canonica dos resultados provenientes de um planejamento de experimentos, este estudo analisou a influencia do indice de supersaturacao, da vibracao do meio cristalizante e do tempo de operacao no processo de cristalizacao do acido citrico e da sacarose, por meio das respostas produtividade e do tamanho medio final do cristal. Para o planejamento de experimentos, observou-se as diferencas em granulometria e regiao de metaestabilidade entre a sacarose e o acido citrico fazendo-se adaptacao ao procedimento experimental para os ensaios de sacarose, em comparacao ao procedimento adotado em Teixeira et al (2012) na cristalizacao do acido citrico. Os resultados para ambos os compostos demonstraram-se semelhantes ao exigirem altos graus de supersaturacao e baixos valores para o adimensional de vibracao, fazendo somente distincao ao tempo de operacao, sendo este ultimo maior na cristalizacao de acido citrico. Os altos indices alcancados para dimensao do cristal e rendimento, associado a confirmacao estatistica, demonstraram a eficiencia do equipamento no processo de separacao solido liquido.

Evaluation of Water Consumption and Neuro-Fuzzy Model of the Detergent Leavings Kinetics’ Removal in a Clean in Place System

This work has focused on describing the water consumption and the Neuro-Fuzzy model of the detergent leavings kinetics’ removal of a CIP System, based on the pH measured. The plant dynamics has been identified for different operational conditions. A flowrate value of 10.5 L.min−1 has been proved to be effective in order to provide the minimum required rinse water volume to execute the stage of the CIP system, which means that it is possible to optimize the process reducing energy, water and steam consumption as well as the time of unused machinery bringing productivity gains. The obtained models, allowed the prediction of the system dynamics behavior. The results were validated when compared with the experimental data. Three triangular membership functions for the input data modeled accordingly the pH dynamics with an error of 0.011 when comparing the validation data and the obtained model.