Equipment Scale-up Research Articles

Scale-Up of Mixing Equipment for Suspensions

This paper deals with the scale-up of equipment for the mixing of suspensions. The measurement of just-suspended agitator speeds was carried out with standard, pitched, four-blade turbines and folded, four-blade turbines in three vessels (290 mm, 600 mm, and 800 mm in diameter) for several particle sizes and concentrations. The results of measurements confirmed that scale-up based on dimensionless Froude number dependence, on the relative particle size and concentration, can be used. On the basis of the results, a scale-up rule for agitator speeds in a given suspension and equipment geometry was recommended, and various conclusions reported by different investigators were discussed.

Catalytic Degradation of Textile Wastewater Effluent by Peroxide Oxidation Assisted by UV Light Irradiation

Textile industries produce a complex wastewater which is difficult to be treated. In this work, a catalytic degradation of wastewater effluent composed of sulphur black coloring agent discharged by industry was studied. UV lamp power, peroxide concentration, pH, and iron oxide catalyst were varied to determine the best conditions for oxidative treatment. Kinetic parameters were evaluated based on the reaction model proposed. In the absence of iron oxide catalyst, chemical oxygen demand (COD) and biological oxygen demand (BOD) degradation of up to 80% and 75%, respectively, were observed as resulting from using an H2O2 concentration of 0.61 moles/L, UV lamp power of 30 watts, and pH of 6. When using an iron oxide catalyst combined with UV light irradiation, the degradation rate could be increased significantly, while similar final COD and BOD degradation percentages resulted. It is found that the reaction rate order was shifted from first order to second order when using an H2O2/UV/Fe2O3 system. The results could be an alternative for treating textile industry wastewater, and the parameters obtained can be used for equipment scale-up.

A preliminary study of pilot-scale electrolytic reduction of UO 2 using a graphite anode

Abstract Finding technical issues associated with equipment scale-up is an important subject for the investigation of pyroprocessing. In this respect, electrolytic reduction of 1 kg UO 2 , a unit process of pyroprocessing, was conducted using graphite as an anode material to figure out the scale-up issues of the C anode-based system at pilot scale. The graphite anode can transfer a current that is 6–7 times higher than that of a conventional Pt anode with the same reactor, showing the superiority of the graphite anode. UO 2 pellets were turned into metallic U during the reaction. However, several problems were discovered after the experiments, such as reaction instability by reduced effective anode area (induced by the existence of Cl 2 around anode and anode consumption), relatively low metal conversion rate, and corrosion of the reactor. These issues should be overcome for the scale-up of the electrolytic reducer using the C anode.

Nuclear-based hydrogen production with a thermochemical copper-chlorine cycle and supercritical water reactor: equipment scale-up and process simulation

SUMMARY Issues related to equipment scale-up and process simulation are described for a thermochemical cycle driven by nuclear heat from Canada's proposed Generation IV reactor (Super-Critical Water-Cooled Reactor; SCWR), which is a CANDU derivative using supercritical water cooling. The copper–chlorine (Cu-Cl) cycle has been identified by Atomic Energy of Canada Limited as the most promising cycle for thermochemical hydrogen production with SCWR. Water is decomposed into hydrogen and oxygen through intermediate Cu-Cl compounds. This article outlines the challenges and design issues of hydrogen production with a Cu-Cl cycle coupled to Canada's nuclear reactors. The processes are simulated using the Aspen Plus process simulation code, allowing the cycle efficiency and possible efficiency improvements to be examined. The results are useful to assist the development of a lab-scale cycle demonstration, which is currently being undertaken at the University of Ontario Institute of Technology in collaboration with numerous partners. Copyright © 2010 John Wiley & Sons, Ltd.

Diffusion of gaseous products through a particle surface layer in a fluidized bed reactor

This paper examines a solid conversion process during hydrolysis and decomposition of cupric chloride in a thermochemical copper–chlorine (Cu–Cl) cycle of hydrogen production. Reaction rate constants and the time required for complete solid conversion are determined by a shrinking-core model. Diffusion of gaseous reactant occurs through a film surrounding the particle, after which the reactant penetrates and diffuses through a layer of ash to the surface of the unreacted core. The shrinking-core model for spherical particles predicts the reaction of gaseous reactant with solid at the particle surface, and diffusion of gaseous products through the ash, back to the exterior surface of the solid. The hydrolysis reaction is also analyzed with respect to chemical equilibrium conversion and required heat input. Effects of varying operating parameters are examined, including the temperature, pressure, excess steam, inert gas and hydrogen chloride (HCl) in the steam. At a temperature of 375 °C, complete conversion of CuCl 2 can be achieved by controlling the excess steam, operating pressure and inert gas supply. Addition of HCl in the steam supply increases the excess steam requirement for conversion of cupric chloride solid, and the upper limit for HCl concentration increases with temperature and inert gas composition. The addition of inert gas may also reduce the excess steam requirement, thereby reducing the heat requirement. These new results have valuable utility for equipment scale-up in the thermochemical Cu–Cl cycle of hydrogen production.

Multilevel Modelling of Dispersed Multiphase Flows

Dispersed multiphase flows are frequently encountered in a variety of industrially important processes in the petroleum, chemical, metallurgical and energy industries. Scale-up of equipment involving dispersed multiphase flows is quite difficult which is mainly due to the inherent complexity of the prevailing flow phenomena (formation of bubbles and clusters in gas-particle flows). Especially during the last decade significant research efforts have been made in both academic and industrial research laboratories to study dispersed multiphase flows using detailed microbalance models (1 to 3). Despite current limitations it has become clear that this approach offers a powerful complementary strategy parallel to careful experimentation and it is therefore anticipated that the role of modelling based on detailed microbalance models for design and operation of multiphase chemical reactors will significantly expand in the near future. In this paper the concept of multilevel modelling will be highlighted with which

20. Rechnergestützte Problemlösungsstrategien in der mechanischen Flüssigkeitsabtrennung

The decision-making process in an expert group involved in solid-liquid separations cannot be covered by a monolithic methodology or software. The analysis of typical problem-solving processes shows the experts' knowledge requirements and turnover. According to the proposal in the present paper, these requirements are covered by a three-tier computer-based knowledge supply comprising databases, simulation programs and hypertexts. Software details of a typical simulation program for continuous vacuum filtration on belt filters are presented. In addition, a hypertext-based electronic handbook on equipment scale-up and design is described. This handbook represents an easy-to-use reference manual for empirical knowledge in the expert group. The above-mentioned tools enhance work quality and efficiency in the expert group; knowledge is preserved and easily accessible. The tools allow rapid training of newcomers. In a crossfunctional team effort, the solid-liquid separation expert can provide rapidly well-founded informations.

Analysis of chaos in fluidization using electrical capacitance tomography

Fluidized beds display a degree of structure which it is vital to understand in any design and scale-up of equipment. This paper is on the employment of chaos theory to describe this structure. The measuring technique of electrical capacitance tomography is used to determine the local porosity of a gas - solids fluidized bed and to monitor its fluctuation with time. These raw data are translated into invariants characteristic of the structure mentioned, such as the Kolmogorov entropy. Initial measurements have shown a strong variation in these chaotic invariants with bed position and operational parameters. First results are compared with earlier data from pressure measurements.

Design and Economic Analysis for Continuous Countercurrent Processing of Milk Fat with Supercritical Carbon Dioxide

Fractionation of anhydrous milk fat using supercritical CO2 provides various fractions of different physicochemical and functional properties that should enhance its utilization. Based on a mass transfer study of a pilot plant setup of a continuous countercurrent fractionation of anhydrous milk fat by supercritical CO2, economic analysis of manufacturing plants was improved. Equipment was sized for six commercial-scale plant capacities, ranging from 800 to 10,000 tonnes/yr of anhydrous milk fat. Analysis considers capital investment, annual manufacturing expenses, revenues, sales, and payback time. The equipment scale-up index was .53, which is the usual literature value. For a plant processing 10,000 tonnes/yr of anhydrous milk fat, conversion cost is $.15/kg over a base price of $1.98/kg. Such a plant would have a capital investment of $4.4million and annual manufacturing costs of $21.1million. Example selling prices are calculated assuming a desired rate of return of 20% or a payback period of 5 yr, which further adds $.11/kg to the base price and conversion cost, yielding annual sales of $22.2million. The economics of the process are attractive, even though further optimization of operating conditions has not yet been performed, primarily because of the continuous nature of the process, the heat regeneration systems designed, and the large plant capacities considered. Thus, the notion that supercritical processing is expensive may be valid only for batch or semi-continuous systems rather than for continuous large-scale systems such as those studied herein.

Ranking dimensionless groups in fluidized-bed reactor scale-up

The “principle of similarity” is a cornerstone of equipment scale-up in the chemical process industry. This principle involves setting up the relationships existing between different scales of processing equipment. Such relationships are usually instituted by determining the so-called dimensionless groups (ie, size-independent parameters) characterizing the process phenomena. These dimensionless groups must be maintained invariant during the conversion of experimental-scale information to the commercial scale. For a complex phenomenon such as fluidization, employing the principle of similarity requires that a large number of dimensionless groups be held constant during scale-up. This is almost impossible in practice. Thus, when scaling up such systems, it is necessary to engage a ranking and trade-off strategy in deciding precisely which dimensionless groups must be maintained constant. Although extremely qualitative, the knowledge underlying the ranking and trade-off strategy for fluidized-bed reactors is a valuable component of design expertise in the chemical process industry. Consequently, emphasis must be placed on the tasks of extracting, embodying, and articulating this knowledge in designing economically viable large-scale process systems. The present work is motivated by the need to hardness qualitative design knowledge in fluidized-bed reactor scale-up. On the basis of the available domain knowledge, several scale-up rules are formulated; these rules relate specific process conditions to the importance of maintaining a particular dimensionless group invariant in scale-up. A nonadditive evaluative strategy relying on a nine-point linguistic scale is employed in ranking each dimensionless group according to the particular situation at hand. Two of the key features of this strategy are its ability to operate in the presence of incomplete information and its relative insensitivity to judgmental differences. These properties are especially appropriate in real-world scale-up and design.

An expression of energy spectrum function for wide wavenumber ranges.

Assuming that the turbulent flow field consists of eddy-groups and that each of them has respective average frequency, a formula for the one-dimensional energy spectrum function (ESF) for wide wavenumber ranges is proposed by using the information entropy from the standpoint of statistical mechanics. The newly proposed formula appears to be a satisfactory approximation of past practical distributions of ESF even if the distribution has more than one order of wavenumber range to which the Kolmogoroff spectrum law can be applied. In addition, the relationship between micro and macro scale, the displacement of fluid particle, the turbulent eddy diffusivity and the points to be noted for scale-up of equipment are discussed on the basis of the newly proposed expression of the one-dimensional ESF.