Showing papers in "Industrial & Engineering Chemistry Process Design and Development in 1986"

Internal model control: PID controller design

Abstract: For a large number of single input-single output (SISO) models typically used in the process industries, the Internal Model Control (IMC) design procedure is shown to lead to PID controllers, occaslonally augmented with a first-order lag. These PID controllers have as their only tuning parameter the closedloop time constant or, equivalently, the closed-loop bandwidth. On-line adjustments are therefore much simpler than for general PID controllers. As a special case, PIand PID-tuning rules for systems modeled by a first-order lag with dead time are derived analytically. The superiority of these rules in terms of both closed-loop performance and robustness is demonstrated.

M2 forming - A process for aromatization of light hydrocarbons

Abstract: Effective aromatization processes for converting light hydrocarbons to BTX aromatics could improve the availability of aromatics as chemicals and high octane gasoline-blending components To this end, M2 forming offers a potential new route The process can convert olefins and paraffins to aromatics The aromatic yields are only limited by the stoichiometric constraint imposed by the hydrogen content of the feed and the products The heart of this process is the HZSM-5-type catalyst The process operates in the cyclic mode at about 538 /sup 0/C and 1-20 atm The reactions involved in the M2 forming process are complex, consecutive, acid-catalyzed reactions, including (1) conversion of olefinic and paraffinic molecules to small olefins via acidic cracking and hydrogen-transfer reactions, (2) formation of C/sub 2/-C/sub 10/ olefins via transmutation, oligomerization, cracking, and isomerization reactions, and (3) aromatic formation via cyclization and hydrogen transfer

Mixed-oxide sorbents for high-temperature removal of hydrogen sulfide

Abstract: Several pure and mixed oxides (ZnO, CuO, ZnO-Fe_2O_3, CuO-Fe_2O_3, CuO-AI_O_3, and CuO-Fe_2O_3-Al_2O_3) were investigated as regenerable sorbents for the removal of H_2S at high temperatures. A special technique was used to prepare the sorbents in highly porous form. The sorbents were subjected to successive sulfidation-regeneration cycles in a packed-bed microreactor. Sulfidation was carried out at 538-650 °C with H_2S-H_2O-H_2-N_2 mixtures, regeneration with O_2-N_2-H_2O mixtures. Fresh, sulfided, and regenerated sorbents were characterized by XRD, SEM-EDS, and BET surface area analysis. Solid conversion and the prebreakthrough exit concentration of H_2S are discussed in terms of physical structure and thermodynamic properties of the sorbents. The performance of the sorbents CuO-Fe_2O_3, CuO-Al_2O_3, and CuO-Fe_2O_3-AI_2O_3 is discussed in terms of changes in the oxidation state of copper during sulfidation.

Novel process for direct conversion of free energy of mixing into electric power

Abstract: Direct conversion of salinity gradients into electric power as well as production of an acid and a base, simultaneous to generation of electricity, was investigated. Devices that combined features of an electrodialytic pile with those of fuel cells or of electrochemical half cells were designed. Electrodes of the electrochemical half cells were restored to their initial condition by simple reversal of the flow pattern. Fuel cells in the investigated system used water as the fuel and air as the oxidant. Energy extracted from salinity gradients at power density of up to 1 W/m/sup 2/ of the membrane yields up to 0.6 MW of electric power per m/sup 3//s of river or brackish water. Sodium hydroxide is obtained in an amount which corresponds to the number of coulombs of electricity generated in the process. Part of the produced HCI is, however, lost.

Prediction of molecular-type analysis of petroleum fractions and coal liquids

Abstract: Different sets of correlations for prediction of composition of petroleum fractions and coal liquids in terms of readily available parameters are proposed. Paraffinic, naphthenic, and aromatic portions of olefin-free fractions can be predicted from the knowledge of either specific gravity, refractive index, and viscosity or molecular weight, refractive index, and carbon to hydrogen weight ratio. The proposed correlations may be used for fractions with molecular weights of 70-600. For coal liquids or highly aromatic fractions, correlations in terms of molecular weight, refractive index, and density are proposed to predict monoaromatic and polyaromatic portions of the fraction. These correlatlons are applicable to fractions with molecular weights up to 250. Petroleum fractions are mixtures of different hydrocarbons from different homologous groups. When the pseudocompound method is used for prediction of thermophysical properties of undefined petroleum fractions (Huang and Daubert 1974; Riazi, 1979), knowledge of the paraffin, olefin, naphthene, and aromatic content of the fraction is necessary. However, most petroleum fractions for which data on their composition are available are free from olefins, and most coal liquids are highly aromatic (80-90% aromatic). The n-d-M method of Van Nes and Van Westen (1951) for estimating the percentage carbon as an aromatic, naphthenic, or paraffinic structure from measured values of density, refractive index, and molecular weight is based on limited and mainly saturated data. Riazi (1979) has shown that the method gives high errors in the prediction of the composition of petroleum fractions. Riazi and Daubert (1980) developed a set of correlations for molecular-type analysis which required viscosity, specific gravity, density, and refractive index as input parameters. The fractions were divided into light (M C 200) and heavy (M > 200) molecular weight ranges, and the correlations were in terms of the refractivity intercept (RI) and viscosity gravity relation (VG). These two characterizing parameters were defined as

Improved equation for the calculation of minimum fluidization velocity

Abstract: Classement des particules solides en trois categories selon leur forme, et determination pour chaque categorie des valeurs optimales des constantes figurant dans les equations de calcul de la vitesse minimale. Obtention de trois equations qui minimisent l'erreur de calcul de la vitesse minimale

Heat integration in batch processing

Abstract: En un certain temps, dans un procede discontinu, certains recipients necessitent du chauffage et d'autres du refroidissement. Probleme de la determination de l'integration de chaleur maximale entre les reservoirs, afin de reduire la consommation d'utilites. Selon les exigences du procede, l'echange de chaleur peut presenter trois profils de temperature distincts au cours du temps, semblables aux profils de temperature a cocourant, a contre-courant et a une combinaison cocourant/contre-courant

Review of experimental methods for studying the hydrodynamics of gas-solid fluidized beds

Abstract: A state-of-the-art review of experimental methods for studying the hydrodynamics of gas-solids fluidization is presented. Techniques applied by various investigators to obtain statistically representative properties of bubble behavior and particle mixing in the dense region and particle dynamics in the region above the bed surface are described. Measurement principles, descriptions of the experimental setups, and accuracy of the measurements are presented. Guidelines for measurement system selection are given.

Design for multiloop SISO controllers in multivariable processes

Abstract: Methode de conception logique, systematique, qui produit un systeme SISO a boucles multiples. Application a une colonne a distiller d'un melange ternaire

Optimal temperature profile for an ammonia reactor

Abstract: A = cross-sectional area of bed, cm2 Bi = Langmuir constant, atm-’ or psi-’ 2 = heat capacity of adsorbed phase, cal/mol/K <: = heat capacity of solid carbon, cal/mol/K d = diameter of the tube, cm d , = diameter of particle, cm h = overall heat-transfer coefficient, cal/cm2/K/s L = length of bed, cm n = constant p = pressure, atm q = amount adsorbed, L STP/g qm = monolayer amount adsorbed, L STP/g R = gas constant t = time, s T = temperature, K To = ambient temperature (= 20 O C ) u = gas velocity, mol/s V, = molar volume at STP (= 22.4 L/mol) z = height of bed (=O at the feed end), cm = heat capacity of gas, cal/mol/K Greek Symbols c = fractional void in bed p = bed density, g/cm3 bed

Spiral distributor for fluidized beds

Abstract: Evaluation des caracteristiques de performance d'un distributeur spirale en fonction du nombre de fentes utilisees dans la spirale et de la fraction d'aire ouverte Mesure de la qualite de fluidisation, des caracteristiques de perte de charge et des coefficients de transfert de chaleur entre le distributeur et le lit, et correlation avec la geometrie de l'unite Comparaison avec les distributeurs a plaque frittee