Nina Paula Gonçalves Salau

Adsorption Kinetics in Liquid Phase: Modeling for Discontinuous and Continuous Systems

Adsorption is one of the most widely applied unit operations to separate molecules that are present in a fluid phase using a solid surface. Adsorption kinetic aspects should be evaluated in order to know more details about its mechanisms, characteristics, and possibilities of application. These data can determine the residence time to reach the required concentration of the adsorbate, making possible the design and operation of an adsorption equipment and defining the performance in batch and continuous systems. This chapter presents the particularities of adsorption kinetics in liquid phase. Batch and fixed-bed systems are considered. For discontinuous batch systems, diffusional mass transfer models and adsorption reaction models are discussed. For fixed-bed systems, the shape of breakthrough curves is studied on the basis of mass balance equations and empirical models. Furthermore, the design and scale up of fixed-bed columns are detailed according to the length of unused bed (LUB) and bed depth service time (BDST) concepts. Several numerical methods are presented in order to solve the required models for batch and fixed-bed systems. Some parameter estimation techniques are discussed in order to obtain the fundamental parameters for adsorption purposes, like mass transfer coefficients and empirical parameters.

Mass transfer models for the adsorption of Acid Red 357 and Acid Black 210 by tannery solid wastes

Diffusional mass transfer models with and without external resistance were applied to represent the adsorption of Acid Red 357 (AR357) and Acid Black 210 (AB210) by tannery solid wastes. The mass transfer parameters, such as, external mass transfer coefficient (k f ), surface diffusion coefficient (D s ), and Biot number (B i ) were estimated and interpreted. It was found that the two models agreed with the experimental data and, very similar values of the parameters were obtained. This indicated that the external mass transfer mechanism can be neglected. Then, the model without external resistance, which is simpler, can be used. The D s values ranged from 5.01 × 10−13 to 1.30 × 10−12 m2 s−1 for AR357 and from 3.19 × 10−14 to 5.38 × 10−14 m2 s−1 for AB210. The high values of the B i number confirmed that the adsorption of AR357 and AB210 on tannery solid wastes was controlled by surface diffusion.

Implementation of an Indirect Control Structure for Composition in a Hybrid Distillation Column

In this paper a PID controller is proposed to ensure the fuel ethanol composition at desired value, above 92.5°INPM, at the same time as saving energy through the minimal use of reboiler power. Due to the fact that composition analyzers are expensive and have a high response time, an inference model was developed in which the product composition is inferred from the product temperature and thermodynamics equations, enabling the monitoring and the indirect control a posteriori of this variable. In addition, the inference of composition allows defining the reference value of the product temperature, which ensures the fuel ethanol production at the desired composition.

Online real-time inference of ethanol composition in a mixed distillation column

Abstract The main indicator of the distilled ethanol quality is its composition. In general, the online composition analyzers are not available due to their high cost. To overcome the lacking of devices to measure online and at real-time the process composition, we have proposed a soft-sensor to work as a virtual analyzer. Among the techniques available in the literature to achieve this goal, we have chosen the identification and neural networks. Both are used to infer online the ethanol composition through the real-time measured temperatures. According to our results, the neural networks have shown better performance in the composition inference. Further, this technique as soft-sensor was implemented in a SCADA (Supervisory Control And Data Acquisition) software in order to monitor the distilled ethanol composition.