Drying of paper by impinging jets of superheated steam was studied in an apparatus which closely simulates conditions for a potential industrial impingement dryer. / Drying was found to consist in a constant rate period, followed by a falling rate period where the drying rate decreases linearly with moisture content. The relation found between the constant rate and Reynolds number and temperature of the jet is consistent with a previous correlation for air impingement heat transfer, suitably modified for conditions in a steam environment. For a given mass flux, steam drying is slower than air drying below an inversion temperature of 175$ sp circ$C and faster above. The specific blower power for steam drying is much lower than for air drying at temperatures in the industrial range. / Equilibrium moisture content measurements showed that complete drying can be obtained at steam temperatures only slightly above the boiling point. Expressions for the critical moisture content in impingement drying in steam and in air were obtained. In steam drying, the falling rate period was found to be determined more by internal transport resistance than by adsorption of water on the fibers. / A new arrangement for drying paper, in which the first half of the drying is done by a conventional dryer to which steam is supplied from a steam impingement dryer handling the second half, was analyzed. In regions with low electricity cost, recirculation of steam around the impingement dryer circuit by a mechanical fan is much more economical than by a thermocompressor. However, this advantage is only marginal where electricity cost is high. The overall performance is optimized by using the highest temperature and lowest jet velocity possible. The drying cycle proposed is a realistic and attractive means to increase drying capacity and reduce energy consumption.

This study is concerned with the numerical analysis, formulation, programming and computation of solution of steady, 3D conservation equations of reacting laminar duct flow heat and mass transfer in ducts of arbitrary cross-sections. The non-orthogonal boundary-fitted coordinate transformation method is applied to the Cartesian form of overall-continuity, momenta, energy and species-continuity equations, parabolized in the axial direction. The boundary conditions are also transformed accordingly. / In the mathematical modelling of the system under consideration, variable physical and transport properties of fluid, viscous heat-dissipation and buoyancy effects are also considered. The non-Newtonian power-law constitutive equation is employed to express the rheology of the purely viscous fluid considered. / Applying a novel feature of the solution procedure, the contravariant velocity components are introduced into the transformed equations while the physical Cartesian velocity components are retained as dependent variables of the velocity field in the equations. This approach greatly simplifies the subsequent finite-difference formulation of the transformed equations. The latter equations are discretized by the control-volume finite-difference method in which a suitably-adopted staggered grid is employed using Patankar's B-type arrangement in the transformed plane. For discretization, the transformed equations are integrated over 3D control-volumes, followed by differencing the convective and diffusive terms employing upwind and central-difference schemes respectively. A modified version of the SIMPLER algorithm is introduced in the solution procedure and a line-by-line TDMA algorithm is employed for the solution of the discretization equations. / A computer-programme is developed for the generation of non-orthogonal grids corresponding to the B-type arrangement in the transformed plane. A general computer programme in Fortran is developed in this study for the solution of flow, heat and mass transfer problems for laminar reacting fluids in straight ducts of arbitrary cross-sections for Newtonian and purely viscous non-Newtonian fluids. The model and computer codes are validated by theoretical, experimental and numerical results from various sources. / The computer programmes are employed for studies in the analysis of hydrodynamics and heat transfer in the thermal entrance regions of ducts of arbitrary cross-sections for Newtonian and non-Newtonian fluids. Relevant results are documented for triangular, trapezoidal and pentagonal ducts. The computer programmes are ultimately employed for simulation of the production of polystyrene in arbitrary cross-sectional duct reactors.

A reversed micellar phase was studied using infrared spectroscopy and surface tension analysis. The effect of the organic phase composition and the type and concentration of salt were investigated. Two parameters were measured, the surfactant partition between the organic and aqueous phases and the amount of water solubilized. The organic phase consisted of a mixture of hexane and hexadecane containing dissolved Aerosol OT. The aqueous phase contained a postassium salt in a buffer solution. / The Aerosol OT partitioned essentially completely to the organic phase under conditions of high salt concentration or high hexane concentration. As the hexane:hexadecane ratio increased, the amount of water solubilized decreased. For all salts, except those of lanthanum, the water solubilized decreased considerably as the salt concentrations increased.

The partition behavior of aqueous and organic ternary solutions into two immiscible phases at ambient temperatures was studied. A classification system of the types of materials which phase partition water and organic solvents was developed and a comprehensive list of systems for which phase diagram information is available in the literature has been presented. / Systems in three different classes of materials were studied. Equilibrium phase diagrams, tie-lines and plait points were generated for the ternary systems: poly(ethylene glycol)-1,000/sodium sulfate/water at 28$ sp circ$C; poly(ethylene glycol)-3,350/sodium sulfate/water at 28$ sp circ$C and 35$ sp circ$C; poly(ethylene glycol)-8,000/sodium sulfate/water at 28$ sp circ$C; poly(vinyl alcohol)/methylcellulose/water at 25$ sp circ$C; and poly(propylene glycol)/polystyrene/cyclohexane at 25$ sp circ$C. All measurements were done at 1 atm. The influence of temperature and polymer molecular weight on the shape and location of the equilibrium phase cure and the location of the critical point was analyzed for the poly(ethylene glycol)/sodium sulfate/water system.

<p> Laboratory tests were performed to investigate the trajectory of the Particulate Matters (PMs) after a pressure gradient is imposed. Later, field tests were performed next to a rail track upstream of a building with local wind, to confirm the laboratory results. In the current investigations, field tests are in compliance with the laboratory experiments. It is concluded that PM concentration is correlated with the wind velocity, wind direction and the imposed pressure gradient. Near the building within a distance equivalent to the building height, where the blockage is present, the effects of the imposed pressure gradient become more evident and PM concentration increases significantly. The wind direction may also lead to increase or decrease in PM concentration, depending on the urban aerodynamics. By increasing the wind velocity, the PM concentration drops in the blockage region, which can be associated to the vortex stretching phenomena.</p>

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The dynamics and control of a catalytic bubbling fluidized-bed reactor were investigated. The reaction chosen was the selective oxidation of benzene to maleic anhydride. This highly exothermic reaction proceeds according to a parallel-consecutive scheme. / The study of reaction kinetics showed that the reaction rate expressions based on the oxido-reduction mechanism could be used to describe the benzene conversion and maleic anhydride yield. A fluidized bed reactor model using bubble assemblage concepts combined with the reaction rate expressions gave accurate predictions of the benzene conversion and maleic anhydride yield for a wide range of temperature, feed rate, inlet benzene concentration, and catalyst mass. / A phenomenological model of the dynamic behaviour based on the steady-state model was formulated and validated with experimental data. The model predicted accurately the responses of temperature and product concentrations. / The study of the reactor steady-state and dynamic behaviour showed that benzene conversion and maleic anhydride production rate could be used as controlled variables to optimize the yield. System identification techniques were used to obtain input-output linear models of the benzene conversion and maleic anhydride production rate as a function of feed rate and temperature set-point. The models were used to design a multivariable controller based on the internal model control approach. The performance of different controller designs was studied through simulation.

The objective of this study was to examine the possibility of producing white liquor directly from kraft black liquor using a single stage plasma reactor. An Atomized Suspension Technique Reactor was designed in which a fine spray of concentrated black liquor was fed co-currently with a jet of high-temperature steam, generated using plasma technology. The pilot scale reactor processed up to 23 kg/h black liquor solids on a dry basis during the experimental programme. / The most successful experiment simulated the case where the product gas from the plasma reactor would be recycled and used as the plasma gas. A high quality green liquor was produced: over 99% of the black liquor carbon was gasified, over 99% of the total sulphur was reduced to Na$ sb2$S, and near-complete sulphur recovery was achieved. / It is postulated that white liquor similar to that obtained in the conventional kraft recovery process would form in a plasma reactor following certain reactor modification including the elimination of alumina-containing refractory walls and the recycle of reactor effluent gases.

Radial gas holdup profiles were determined in 50 cm and 91 cm dia. flotation columns. The local gas holdup was measured using an electrical conductivity technique, which is described in detail. The effect of gas rate and axial location on the profiles was investigated. The relative variation in gas holdup was about 20%. The profiles were axially symmetric but of complex shape: parabolic, saddle and 'W' shapes were observed. For the case of a parabolic profile, the shear stress model was solved to give liquid circulation velocity profiles; no solution was found for the other gas holdup profile shapes. / Measurement of radial gas holdup profiles may prove useful in evaluating sparger systems. For example, in the pilot column, one off-centre sparger gave a non-symmetrical shape but nevertheless did distribute the gas relatively evenly. / Liquid residence time distributions (RTD) were measured for various operating and design conditions using the pulse tracer technique. Application of the one-dimensional plug flow axial dispersion model and the use of the vessel dispersion number $N sb{ rm d}$ to quantify the degree of mixing was evaluated. A numerical solution to the axial dispersion model with closed-closed boundary conditions using the finite difference method is recommended for column RTD studies. Compartment models were also evaluated: the N perfect tanks-in-series model did not fit the data but a backflow compartment model was successful. / The effect of gas rate, liquid rate, column length, feed percent solids and column verticality on $N sb{ rm d}$ was studied. It was found that $N sb{ rm d}$ increased with gas rate and decreased with liquid rate and column length. Percent solids and verticality had a minor effect on $N sb{ rm d}.$ New correlations to predict $N sb{ rm d}$ were developed and compared with previous correlations.

Thermoplastics injection molding involves plastication followed by the injection of the melt into a cold cavity. Packing is employed to compensate for shrinkage due to cooling. Ultimately, the solidified part is ejected from the mold without damage. The successful operation of an injection molding machine requires control of the process variables during each of the consecutive stages in addition to correctly identifying the points of transition from one stage to the next. / Pressure and its variation during the injection molding cycle play an important role with regard to productivity, product quality, and product reproducibility. From the practical point of view, it is necessary to consider simultaneously hydraulic pressure, nozzle pressure, and the distribution of pressure in the cavity. Control of each phase of the injection molding process is best achieved by controlling one or a combination of the above pressure parameters. The present work describes a comprehensive study of the dynamics and control of pressure during each stage of the injection molding cycle. / Deterministic models were obtained for cavity gate pressure during the filling and packing stages. Dynamic model predictions were in good agreement with experimental data. The response of cavity gate pressure exhibited nonlinear behavior which was investigated and rectified by a gain scheduling control strategy. Stochastic models were obtained for cavity gate pressure response in the filling stage for the purpose of comparison and future design of more advanced control algorithms / The dynamic models were employed to design and evaluate control schemes for the injection molding cycle. Nozzle and cavity pressures were used in conjunction with PI, PID and Dahlin controllers. The hydraulic system of the injection molding machine was redesigned to incorporate two servovalves in order to achieve control over the cavity pressuretime profile during the packing stage as well as over peak cavity and hold pressures. The control loops were designed through a simulation study which also gave good indications of system limitations. / On the basis of this study, very good and reliable integrated control over the filling, packing, and holding stages was achieved by a general control scheme which allows the transfer of control from one variable to another during the various stages of the process.