skip to main content
Idioma:

Comparative analysis of different techniques to monitor liquid level in a cane diffuser bed

Angel, Diana Maritza Segura

Biblioteca Digital de Teses e Dissertações da USP; Universidade de São Paulo; Escola de Engenharia de São Carlos 2019-03-14

Acesso online

  • Título:
    Comparative analysis of different techniques to monitor liquid level in a cane diffuser bed
  • Autor: Angel, Diana Maritza Segura
  • Orientador: Seleghim Junior, Paulo
  • Assuntos: Testes A Escala Industrial; Pressão; Nível Do Líquido Observado; Impedância; Extração De Sacarose; Difusor; Condutância; Full-Scale Test; Impedance; Diffuser; Observed Liquid Level; Pressure; Sucrose Extraction; Conductance
  • Notas: Tese (Doutorado)
  • Descrição: The extraction of sucrose in a sugar cane diffuser depends on the percolation rate of juice through the cane bed. High percolation rates promote mass transfer and increase the wetness of the cane bed (i.e. liquid hold-up within the bed) thereby improving sucrose extraction. However, increasing the rate of juice applied to the surface of the cane bed above the maximum percolation rate results in flooding, causing uncontrolled mixing of juice, destruction of the brix profile and reduced extraction. Therefore, to avoid flooding, the liquid holdup in a stage-wise counter-current diffuser must be monitored and controlled through the automation of the spray position responsible for distributing the liquid onto the bed surface, according to the settings selected. Currently, the liquid level is controlled by inspecting of a group of sight glasses in the diffusers, this technique requires at least 12 operators working as long as the diffuser is under operation, as a result, this method is unfeasible in practice. In addition this measured is limited by the manual data acquisition and the short sampling time interval. Most of the conventional methods to measure liquid holdup are not suitable for this application, so new methodologies were introduced such as conductance measurements. Other researchers opted for using manometers to measure the pressure on a laboratory scale. Nevertheless, no satisfactory results were presented and the results from the experiments trials performed in a full scale have not been widely accepted; additionally, no subsequent work has validated or invalidates these results. Therefore, the aim of this study is to test the viability of using a manometers, conductivy meters and impedance meters to assess the observed liquid level in a cane diffuser bed, in order to provide the necessary information to control to adjust the spray position, which can optimise percolation rates. Electrical impedance has never been measured in a cane diffuser neither on a laboratory scale. Therefore, a new impedance measurement system capable of recording measurements over an adjustable impedance range has been designed and constructed to detect the fluctuations of capacitive and resistive effect in a cane bed. The results of the experimental trials of conductivity, impedance and pressure conducted on the Tongaat Hulett cane diffuser at the Maidstone factory in South Africa are reliable techniques to indirectly measure the level of the liquid within the cane bed. Reproducibility tests were performed to confirm the results presented in this research. The results of the test of impedance show that the capacitive effect is not significant and it is not related to the flooding of the cane bed neither with a specific characteristics of the sugarcane or the extraction process. In the same way, the conductance results show that the flow rate and the conductance only have the same fluctuations under special operating conditions such as when the diffuser is being fed and when the recirculation pumps are switched on and off. The relationships between variables such as conductance, piezometric level, and the liquid level were found through the development of mathematical models. Where the adjustment of the constants of a linear function of permeability permitted to validate the experimental data, in the case of the technique of pressure measurements. On the other hand, the mathematical models were created based on several equations such as second-order transfer equations and Darcy\'s equations.
  • DOI: 10.11606/T.18.2020.tde-05022020-113011
  • Editor: Biblioteca Digital de Teses e Dissertações da USP; Universidade de São Paulo; Escola de Engenharia de São Carlos
  • Data de criação/publicação: 2019-03-14
  • Formato: Adobe PDF
  • Idioma: Inglês
Links
Voltar para lista de resultados

  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

Buscando em bases de dados remotas. Favor aguardar.