In line with Anglo American’s asset optimization and environmental policies, the coal burning flash dryer operations at its smelters have been identified for potential optimization by means of advanced process control. For this project, the process and related literature were studied in detail and a revised control philosophy, which includes modifications to the existing basic control structure as well as a hybrid rule and model-predictive advanced control layer, was developed, installed and tested on one of these flash drying operations. Since commissioning of the APC, the flash dryer’s average throughput has increased by more than 6 %, despite higher feed moistures. Furthermore, even though coal consumption has increased slightly, the operation efficiency has improved by almost 5 %. This was made possible by improving the stability of the drying column outlet temperature by approximately 40 %, which in turn enabled the selection of a more optimal setpoint. Recent data has shown that APC utilization now exceeds 95 %. This is indicative of a successful controller installation with good site acceptance. / Dissertation (MEng)--University of Pretoria, 2011. / Chemical Engineering / unrestricted

Made available in DSpace on 2014-12-17T15:01:26Z (GMT). No. of bitstreams: 1 LuzianyACF_DISSERT.pdf: 949661 bytes, checksum: 3ac9543ca6f7961fb8c420391d30326b (MD5) Previous issue date: 2011-07-08 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / In this work, a pneumatic dryer has been designed and assembled in laboratory scale in order to study and evaluate configurations more efficient for application in drying of important materials of Northeast region in Brazil. The equipment was tested with drying of corn and rice grains, in conditions of temperature and air velocity at 80 oC and 35 m/s, respectively. For this type of dryer, it is recommended to work at temperatures above 200 ?C and air velocity with higher dynamic pressure. However, even under operating conditions below what it is recommended, the results obtained with the pneumatic dryer were satisfactory. In addition, experiments of drying were performed by using a cabinet dryer (batch dryer) under the same conditions used in the pneumatic dryer. Flash one curves for the corn were fitted satisfactorily by applying of the Lewis model, while a better agreement was found for rice by using the Page model. The data obtained with both drying processes allowed to compare the performance between pneumatic and batch dryers. In respect to drying rate, the pneumatic dryer presented a similar performance to the batch dryer during processing with corn and a superior performance to the last one during processing with rice. Therefore, it was possible to verify that the pneumatic dryer assembled in this preliminar study can be applied for different materials and under different operating conditions / Este trabalho tem como objetivo principal ? concep??o, montagem e opera??o de um secador pneum?tico do tipo flash com o prop?sito de avaliar novas configura??es de secadores, apresentando uma import?ncia regional no contexto da produ??o agr?cola de gr?os. O equipamento operou com temperaturas na ordem de 80?C e velocidade do ar de secagem igual a 35 m/s. Para este tipo de secador recomenda-se temperaturas superiores a 200?C e velocidades com alta press?o din?mica. O equipamento operou com um bom desempenho na secagem do milho e arroz. Para efeito comparativo, tamb?m foi utilizado um secador de bandejas para secagem do milho e do arroz com casca em condi??es operacionais similares as praticadas com secador pneum?tico do tipo flash. Os resultados experimentais demonstraram que na secagem do milho ambos secadores responderam com desempenho an?logo no que ser refere ? taxa de secagem. J? na secagem do arroz com casca, o secador pneum?tico apresentou um desempenho superior ao secador de bandejas. Portanto, a partir dos dados experimentais as curvas para a secagem do milho foram melhor correlacionadas com o modelo de Lewis, enquanto que as curvas de secagem do arroz com casca foram melhor ajustadas com o modelo de Page. Assim, pode-se concluir que a configura??o montada apresenta aspectos promissores que podem ser estudados utilizando-se materiais com diferentes caracter?sticas e em diferentescondi??es operacionais