Search results for "Chemical engineering"
showing 10 items of 5892 documents
Control of the Biodegradation of Mixed Wastes in a Continuous Bioreactor by a Type-2 Fuzzy Logic Controller
2009
Abstract Type-2 fuzzy logic control is proposed for nonlinear processes characterized by bifurcations. A control simulation study was conducted for a bioreactor with cell recycle containing phenol and glucose as carbon and energy sources in which a pure culture of Pseudomonas putida is carried out. The model developed by Ajbar [Ajbar, A. (2001). Stability analysis of the biodegradation of mixed wastes in a continuous bioreactor with cell recycle. Water Research, 35 (5), 1201–1208] was used for the simulations. The particular dynamics of the bioreactor, characterized by two saddle-node bifurcations, makes its control difficult, since it may become unstable also for small variations of some p…
Oscillation dynamics of free vortex surface in uncovered unbaffled stirred vessels
2016
Abstract The main feature of unbaffled stirred tanks is the highly swirling liquid motion, which leads to the formation of a central vortex on the liquid free surface, when the vessel is operated without top-cover (Uncovered Unbaffled Stirred Tanks, UUST). One of the main drawbacks of such vessels, that limits their industrial applicability, is the possible onset of low-frequency sloshing of the free surface. In this work, original data on oscillation dynamics in UUST are presented. In particular, data focus on the oscillation amplitude as well as on their frequency. Data were obtained by means of a novel experimental technique based on digital image analysis. The effect of impeller geometr…
A phenomenological model for the quantitative interpretation of partial suspension conditions in stirred vessels
2000
Publisher Summary Many important chemical engineering operations involve the suspension of solid particles in a liquid phase inside stirred tanks. Relevant examples include adsorption, crystallization, dissolution, leaching, precipitation, ion exchange and catalytic multiphase processes. This chapter describes a phenomenological model for the quantitative determination of the suspended solids mass fraction in stirred tanks operated at partial suspension conditions. Experimental data on fractional suspension, obtained by the “Pressure Gauge Technique” in vessels stirred by a downward-pumping pitched-blade-turbine, are presented. Furthermore, model predicted trends are compared with experimen…
Clean recovery of antioxidant compounds from plant foods, by-products and algae assisted by ultrasounds processing. Modeling approaches to optimize p…
2015
Ultrasound treatment is an alternative affordable, effective and reproducible method for the improved recovery of bioactive compounds from various processing streams. The objective of this review is to discuss the impact of ultrasound-assisted extraction on the recovery of polyphenols, carotenoids and chlorophylls from vegetal and algae matters. Optimization strategies will need to focus on appropriate equipment design and configuration of ultrasonic components, and extrinsic and intrinsic control parameters including ultrasonic power, temperature and extraction time to maximize the yield and biological activity of the extract. Modeling strategies to characterize and optimize ultrasound pro…
Performance evaluation of CHCP hybrid seawater desalination plants
2007
There are many ways to improve efficiency and reduce fresh water cost in desalination plants, like the integration of two or more desalination systems into a hybrid mechanical/thermal lay-out. Most common results that could be achieved by hybrid systems are savings in pretreatments, overall cost reduction and significant primary energy savings, especially when cogeneration unit are concerned. In this paper a small size (2000 m 3 /day) thermal desalination system (MEE) is coupled with a single-stage seawater reverse osmosis (SWRO) system; the system is fed by a natural gas (NG) reciprocate engine, where heat is recovered both from exhaust gases and from the cooling jacket water circuit. Tech…
A critical assessment of desalination operations in Sicily
2005
In this paper a brief history of desalination plants in Sicily is presented together with an in-depth description of processes and operating data, relevant to the plants actually operating on the island. 5 multi stage flash (MSF) units and one reverse osmosis (RO) plant are operating in Gela (total nominal production of about 80,000 m 3 /d), thus providing drinking water for more than 300,000 people living in the southern coast of the island. A thermal vapour compression multiple effect distillation (TVC-MED) plant (36,000 m 3 /d) is operating in Trapani and a small mechanical vapour compression (MVC) unit (5000 m 3 /d) is located in Porto Empedocle. In the oldest MSF units in Gela, several…
Energy saving with MSF-RO series desalination plants
2003
Two major techniques are commercially used in different parts of the world: distillation and membrane processes. The dominant distillation process is multi-stage flash (MSF), and the main membrane process is reverse osmosis (RO). Although cost factors vary by site, the total cost of producing potable water from seawater with the RO process is today usually less than thermal desalting processes and the economic advantages of RO vs. evaporation process, such as MSF, are responsible for the rapid increase in use of seawater RO. In many countries both RO and MSF processes are operating. Reduction in product water cost could be achieved when a hybrid MSF-RO system is used, instead of a parallel …
Cost modelling for wastewater treatment processes
2011
Abstract The aim of this paper is to provide a methodology for a better understanding of the cost structure of wastewater treatment processes. This methodology may be useful in the planning of new facilities. The existing models in the literature are focused on the influence of the capacity of plant, expressed as inhabitants or flow rate, on the cost of treatment. We propose a new approach for the operating cost function that includes the most representative variables in the process. The idea is that the modelling of treatment costs enables us to understand the key role of the economies of scale in this context; and also the influence of other variables such as contaminants removed, or the …
Analysis of the bubbling behaviour of 2D gas solid fluidized beds
2008
Abstract In the field of gas–solid fluidization, bubbles, and all features regarding them, have a very great importance, as they significantly affect the process performance. Numerous experimental studies on bubbles, and their formation, evolution, and properties, have been performed in the past. These investigations appear particularly difficult, due to the nature of these systems, since the gas phase is distributed in both the bubble and the emulsion phase. Several experimental approaches have been developed to tackle this study. Among these, the Digital Image Analysis Technique purposely developed in Part I of the present work, based on the use of a video camera for monitoring the phenom…
Particle distribution in dilute solid liquid unbaffled tanks via a novel laser sheet and image analysis based technique
2013
The availability of experimental information on particle distribution inside stirred tanks is a topic of great importance for many industrial applications such as catalysis and polymerization. The measurement of solid particle distribution is not simple and the development of suitable measuring techniques is still an open problem in chemical engineering research. In this work, a non-intrusive optical technique for measuring particle concentration fields in solid–liquid systems is discussed. The “Laser Sheet Image Analysis” (LSIA) technique described here makes use of a laser sheet, a digital camera for image acquisition and a suitable procedure for post-processing. It is able to provide sol…