A review is presented of recent work in the field of solvent extraction of metal ions by chelating compounds with particular reference to the metals iron, copper, cobalt and nickel. The preparation, and purification via its copper complex, of a substituted biguanide is described together with details of its preparation for use as a cation-exchange extractant. The extraction of copper, nickel and cobalt with this complexant is described and its inability to extract either iron(II) or iron (III) confirmed. From the results of various extraction and distribution experiments, and using published theory, the structure of the extracted biguanide-copper complex is shown to be of the type MA2(HA)6; similarly the average structure of the extractant in the organic phase is determined as the tetramer (HA)4. The effects of sulphate ions and ammonium ions on the extraction of all three metals were determined and the results are discussed. Ammonia was found not to hinder appreciably the extraction of the three metals tested but the presence of sulphate ions is found so to enhance the extraction of nickel, whilst slightly hindering cobalt extraction, that appreciable separation of these metals is possible by the preferential extraction of nickel. The separation of copper from iron is a desirable characteristic shown by this complexant and the possibilities for its use as an industrial extractant are discussed.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

Fluid catalytic cracking (FCC) is one of the most important processes in the petroleum refining industry for the conversion of heavy gasoil to gasoline and diesel. Furthermore, valuable gases such as ethylene, propylene and isobutylene are produced. The performance of the FCC units plays a major role on the overall economics of refinery plants. Any improvement in operation or control of FCC units will result in dramatic economic benefits. Present studies are concerned with the general behaviour of the industrial FCC plant, and have dealt with the modelling of the FCC units, which are very useful in elucidating the main characteristics of these systems for better design, operation, and control. Traditional control theory is no longer suitable for the increasingly sophisticated operating conditions and product specifications of the FCC unit. Due to the large economic benefits, these trends make the process control more challenging. There is now strong demand for advanced control strategies with higher quality to meet the challenges imposed by the growing technological and market competition. According to these highlights, the thesis objectives were to develop a new mathematical model for the FCC process, which was used to study the dynamic behaviour of the process and to demonstrate the benefits of the advanced control (particularly Model Predictive Control based on the nonlinear process model) for the FCC unit. The model describes the seven main sections of the entire FCC unit: (1) the feed and preheating system, (2) reactor, (3) regenerator, (4) air blower, (5) wet gas compressor, (6) catalyst circulation lines and (7) main fractionators. The novelty of the developed model consists in that besides the complex dynamics of the reactorregenerator system, it includes the dynamic model of the fractionator, as well as a new five lump kinetic model for the riser, which incorporates the temperature effect on the reaction kinetics; hence, it is able to predict the final production rate of the main products (gasoline and diesel), and can be used to analyze the effect of changing process conditions on the product distribution. The FCC unit model has been developed incorporating the temperature effect on reactor kinetics reference construction and operation data from an industrial unit. The resulting global model of the FCC unit is described by a complex system of partial-differential-equations, which was solved by discretising the kinetic models in the riser and regenerator on a fixed grid along the height of the units, using finite differences. The resulting model is a high order DAE, with 942 ODEs (142 from material and energy balances and 800 resulting from the discretisation of the kinetic models). The model offers the possibility of investigating the way that advanced control strategies can be implemented, while also ensuring that the operation of the unit is environmentally safe. All the investigated disturbances showed considerable influence on the products composition. Taking into account the very high volume production of an industrial FCC unit, these disturbances can have a significant economic impact. The fresh feed coke formation factor is one of the most important disturbances analysed. It shows significant effect on the process variables. The objective regarding the control of the unit has to consider not only to improve productivity by increasing the reaction temperature, but also to assure that the operation of the unit is environmentally safe, by keeping the concentration of CO in the stack gas below a certain limit. The model was used to investigate different control input-output pairing using classical controllability analysis based on relative gain array (RGA). Several multi-loop control schemes were first investigated by implementing advanced PID control using anti-windup. A tuning approach for the simultaneous tuning of multiple interacting PID controllers was proposed using a genetic algorithm based nonlinear optimisation approach. Linear model predictive control (LMPC) was investigated as a potential multi-variate control scheme applicable for the FCCU, using classical square as well as novel non-square control structures. The analysis of the LMPC control performance highlighted that although the multivariate nature of the MPC approach using manipulated and controlled outputs which satisfy controllability criteria based on RGA analysis can enhance the control performance, by decreasing the coupling between the individual low level control loops operated by the higher level MPC. However the limitations of using the linear model in the MPC scheme were also highlighted and hence a nonlinear model based predictive control scheme was developed and evaluated.

Flexible pipes are commonly used for connecting seabed flow-lines to floating production facilities. The general riser design consists of an internal carcass for collapse resistance, a polymer fluid barrier, carbon steel interlocked circumferential pressure armour layer for resisting internal pressure loads, helically wound carbon steel tensile armour layers to resist axial loads and a watertight external sheath. Much of the analytical work that has been carried out on flexible composite pipe is based on the early stress analyses of wire ropes, and this is primarily because of the helical geometry of many of the metallic elements such as pressure armour and tensile armour layers of a flexible riser. The general design philosophy of the layer is defined in API 17J (American Petroleum Institute) in terms of the stress "utilisation" factor that specifies the maximum allowable average hoop stress in the layer, which is conventionally produced by the elastic stress analysis. The layers are subjected to severe cyclic bending and twisting deformation during manufacturing of the pipe which makes the material to exceed the yield point. Consequently, residual stresses are developed in the pipe material and variable amounts of non zero stresses exist in the metallic layers of the newly manufactured pipes. An attempt has been made to model the amount of residual stress evolved during manufacturing stage for two different metallic layers, namely; pressure armour and tensile armour layers and its effects on overall pipe's performance while in service. The strategy is to apply the finite element (FE) method by creating a3 dimensional wire model of the segment of pipe. Solid structural elements with plasticity were employed for the analyses. Kinematic hardening with Baushinger effect, contact and friction effects were also taken into account. Precise boundary conditions were applied to the model for elastic-plastic bending. The resulting residual stresses have been transferred to 3D axisymmetric model to investigate the internal and external pressure effects. This new procedure was carried out for both layers satisfying equilibrium and compatibility conditions for the pressure and tensile armours to find the common interface pressure and contact loading. FAT (Factory Acceptance Test) condition is simulated to investigate the level of residual stress variation. Experimental measurements of residual stress by X-Ray diffraction are in well agreement with FE results.