Fluid-dynamic behavior of flaxseed fluidized and spouted bed / Comportamento fluidodinâmico de sementes de linhaça em leito fluidizado e jorro

ABSTRACT: Processing of particles in a moving bed, such as a fluidized bed or a spouting bed, is commonly used in the operations of drying, coating, and granulation of particulate systems. This process has applications in the chemical, pharmaceutical and, presently, agronomical industries, especially for seed treatment/coating. This research aimed to analyze the fluid-dynamic behavior of fluidized and spouting beds with different air temperatures and loads of flaxseeds (Linum usitatissimum L.), with estimates of the fluid-dynamic parameters correlated to each process. The parameters were compared with the values obtained from classical correlations in the literature, with indications of associated percentages of deviation. Influence of fluid dynamics on the physiological quality of seeds was assessed by germination tests and the germination speed index. An analysis of the results indicated that seed processing was adequate for processing in dynamically active beds; however, temperatures above 50ºC in both beds caused significant reductions in the physiological quality of the seeds. Processing in a fluidized bed presented a smaller reduction of the physiological properties of the flaxseed.

RESUMO: O processamento de partículas em leitos móveis, como o leito fluidizado e o leito de jorro, são comumente empregados em secagem, recobrimento e granulação de sistemas particulados, com aplicações nas indústrias química, farmacêutica, e atualmente na agronômica, em especial no tratamento/revestimento de sementes. Este trabalho tem como objetivo analisar o comportamento fluidodinâmico, em leito fluidizado e jorro, das sementes de linhaça (Linum usitatissimum L.), para diferentes cargas de sementes. Obter as curvas fluidodinâmicas dos leitos: fluidizado e de jorro, estimando os parâmetros fluidodinâmicos correlacionados a cada processo. No leito fluidizado foram determinados: a velocidade de mínima fluidização, queda de pressão na máxima e mínima fluidização, expansão do leito e, porosidade de mínima fluidização e, para o leito de jorro, foram estimados a velocidade de mínimo jorro, queda de pressão máxima e queda de pressão no mínimo jorro. Estes parâmetros foram comparados com os valores obtidos de correlações clássicas da literatura, sendo observados baixos desvios percentuais para os mesmos. Avaliou-se a influência da fluidodinâmica sobre a qualidade fisiológica das sementes através dos testes da germinação e do índice de velocidade de germinação.

Incidence of Posterior Capsular Opacification Based on Low and High Fluid-dynamic Parameters

PURPOSE: To compare the incidence of posterior capsular opacification (PCO) based on low and high fluid-dynamic parameters during cataract surgery and evaluate the importance of these findings. METHODS: This retrospective study included 125 eyes in 73 patients with senile cataract who received a cataract surgery between September 2013 and March 2014. Patients were divided into 2 groups: those with low (vacuum: 180 mm Hg, aspiration flow: 18 mL/min, bottle height: 55 cm) and high (vacuum: 400 mm Hg, aspiration flow: 22 mL/min, bottle height: 90 cm) fluidic parameters during the nucleus was removal. We measured the total surgery time, ultrasound time, and balanced salt solution consumption during phacoemulsification. Best corrected visual acuity (BCVA), PCO score, PCO percentage and severity were measured at 3, 6 and 12 months postoperatively. Endothelial cell density (ECD) was measured preoperatively and 12 months postoperatively. RESULTS: The study included 20 eyes of 13 patients with low parameters and 20 eyes of 15 patients with high parameters. There was no statistically significant difference in the mean total surgery time, ultrasound time or fluid consumption between the two groups. BCVA and ECD were not significantly different between the two groups during the postoperative follow-up. PCO score, percentage and severity were higher in the low parameter group at 3, 6 and 12 months postoperatively. CONCLUSIONS: Surgery with low fluid-dynamic parameters is equally effective as with high parameters in terms of surgical time and postoperative BCVA. However, the incidence of PCO was higher in the low fluid-dynamic parameter group up to 12 months. Surgical efforts to reduce remnant lens epithelial cells are needed during low fluidic-dynamic parameter surgery.

Comparison of Clinical Outcomes between High and Low Fluid-Dynamic Parameters during Phacoemulsification

PURPOSE: To compare the clinical outcomes between high and low fluid-dynamic parameter settings during phacoemulsification. METHODS: In this retrospective study we analyzed 183 consecutive eyes with senile cataracts that underwent cataract surgery between October 2010 and January 2015. The phacoemulsifications were performed with high and low fluidic parameter settings, which were designated by different fluid heights, aspiration flow rates, and vacuum settings. We measured and compared the intraoperative factors including fluid consumption, cumulative dissipated energy (CDE), ultrasound time, intraoperative complications, and pupil size changes during the phacoemulsification. Central corneal thickness (CCT), endothelial cell density (ECD), uncorrected visual acuity (UCVA), and best corrected visual acuity (BCVA) were measured and compared preoperatively and postoperatively. RESULTS: There was no statistically significant difference in the fluid consumption, CDE, or ultrasound time during phacoemulsification between the 2 groups. The frequencies of intraoperative complications were not statistically significant. UCVA, BCVA, and ECD were not statistically significantly different between the 2 groups during the postoperative follow-up. The low parameter group showed the lower increase in CCT on postoperative day 30. CONCLUSIONS: The phacoemulsifications with low fluid-dynamic parameter resulted in less damage to intraocular tissue without any significantly different postoperative findings. The phacoemulsification with low fluid-dynamic parameter setting is more advantageous due to stable and safe aspects.