Set Point Weighted PID Controllers for Integrating Systems with Time Delay

-- C V Nageswara Rao and R Padma Sree

To improve the servo response of the system, a set point weighted Proportional Integral and Derivative (PID) controller is used. Two methods of calculating set point weighting parameter is proposed for integrating systems with time delay in this paper. First method is based on numerical optimization of Integral Square Error (ISE), Integral Absolute Error (IAE) and Integral Time Weighted Absolute Error (ITAE) for the closed loop servo problem. Second method is the extension of equating coefficient method for integrating systems. A simulink block diagram is generated using the process transfer function and the PID controller with set point weighting parameter which is updated by a MATLAB program using lsqnonlin/fminunc routines with ISE/IAE/ITAE as the objective functions. Optimum set point weighting parameter is obtained by minimizing these objective functions numerically. In the equating coefficient method, set point weighting parameter is obtained by matching the corresponding coefficients of s in the numerator with that of the denominator of the closed loop transfer function. The above set point weighted PID controllers are applied to various transfer function models and nonlinear models of integrating systems to show the efficiency of the proposed set point weighted PID controllers.

© 2011 IUP. All Rights Reserved.

Evaluation of MATCONT of MATLAB for Constructing Bifurcation Diagrams
of Chemical Process Systems

-- Jason R Picardo and Anand V P Gurumoorthy

As the study of nonlinear system dynamics and bifurcation theory percolate into applied engineering and biological disciplines, the need for a user friendly, flexible and robust bifurcation analysis software is evident. MATCONT is a MATLAB toolbox with a Graphical User Interface (GUI) for the continuation of static and dynamic equilibria of nonlinear systems. This software is relatively recent and has certain advantages over existing continuation software which include its MATLAB foundation, in addition to new features. In this paper, this toolbox is evaluated via a well-studied illustrative example of an ethanol fermentor which shows rich nonlinear behavior. Some computed results are displayed and a discussion of the basic workflow in MATCONT is provided. A few difficulties encountered while studying nonlinear systems with MATCONT are highlighted. Nevertheless, due to its merits and future scope, as is discussed, this software is recommended for bifurcation analysis of nonlinear systems in research as well as in the classroom.

© 2011 IUP. All Rights Reserved.

Studies on Pressure Drop and Bed Porosity in Liquid Fluidized Beds with Twisted Tape Internals

--B S Subramanyam, M S N Murty, B Surendra Babu and K V Ramesh

Pressure drop and bed porosity data have been obtained in a liquid fluidized bed in the presence of a twisted tape internal. Glass spheres of diameters 3.13, 4.57 and 6.29 mm were employed as bed material. Tape width varied from 2 to 4 cm and the tape pitch from 11 cm to ¥. The modified friction factor increased with increasing particle diameter. Increase in tape pitch caused a decrease in modified friction factor. The bed porosity decreased with increase in particle diameter. The influence of tape pitch and tape width on bed porosity was observed to be insignificant.

© 2011 IUP. All Rights Reserved.

‘Foam Over’ Temperatures Using Glass Coker Experimentation: A Case Study

-- Pradipta Chattopadhyay

In petroleum refineries, excessive foaming in process equipments leads to inefficiency and higher maintenance cost. A very relevant aspect of current petroleum refinery operations is the heating up of vacuum resid in a coke drum and the subsequent generation of unwanted foam. This research paper describes the foam produced by heating vacuum resid in a glass coker experimental set up in terms of foam over temperature. The vacuum resids for analysis were obtained from major US oil companies like Chevron, Shell, Petrobras, etc. Run data are provided that illustrate the variation of foam over temperature for different vacuum resids and at what time the foam over phenomenon started during the glass coker run. Also the production of white vapors (an intermediate stage for foam generation), in terms of the first incidence of white vapor temperature have been reported. The experimental results clearly lead to the fact that foaming during a glass coker run is dependent on the resid (feedstock) properties and run operating conditions.

© 2011 IUP. All Rights Reserved.

Studies on Characterization and Leaching of Malachite Ore

-- Pravas Ranjan Behera, Barsha Dash, Prodip Kumar Sen,
Tondepu Subbaiah and Raj Kishore Paramguru

The present study reports development of a process to extract copper from malachite ore available at Congo region. The ore was subjected to X-Ray Diffractograms (XRD) and Scanning Electron Microscope (SEM) tests along with the chemical analysis. The major phases found were malachite and chalcocite. The major gangue was quartz. The total copper content was estimated to be 19% and a relative (not fully quantitative) estimation of malachite and chalcocite were found to be 16.31% and 2.68% respectively. Leaching of malachite using 0.6 molar sulphuric acid was completed for both 10% and 20% of pulp density and 5 min was sufficient to extract all the copper values into the solution. Most of the chalcocite and gangue stayed back in the residue. The recovery of copper was close to 75%.

© 2011 IUP. All Rights Reserved.