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Mass-transfer Operations ^HOT^



Some common examples of mass transfer processes are the evaporation of water from a pond to the atmosphere, the purification of blood in the kidneys and liver, and the distillation of alcohol. In industrial processes, mass transfer operations include separation of chemical components in distillation columns, absorbers such as scrubbers or stripping, adsorbers such as activated carbon beds, and liquid-liquid extraction. Mass transfer is often coupled to additional transport processes, for instance in industrial cooling towers. These towers couple heat transfer to mass transfer by allowing hot water to flow in contact with air. The water is cooled by expelling some of its content in the form of water vapour.




Mass-transfer operations



CBE 340 - Mass Transfer and Separation Processes3 Credit Hours Stagewise operation. Application of analytical, graphical, and computer methods to design of stagewise separatory operations. Differential operations application of analytical and computer methods to the design of diffusive processes. Applications include gas absorption, stripping, binary distillation, and extraction. (RE) Prerequisite(s): 201, 240, and 250.Registration Restriction(s): 2.3 GPA.


This Subject is divided in two main parts: mass transport processes and unit operations. The 1st part consists of the fundamentals of mass transport in gases, liquids and solids, including the mass transport models for molecular diffusion, convective mass transfer coefficient, interphase mass transfer, Fick's law and models for mass transfer coefficients. The 2nd part contains the application of mass transfer mechanisms in separation processes, such as absorption and stripping, liquid-liquid extraction, membrane separation, adsorption, drying, crystallisation and distillation. McCabe-Thiele method will be introduced for the design and calculation of equipment dimensions.


For each of the numerous examples he uses to demonstrate mass-transfer applications, he sets forth the problem, provides the necessary data, explains the underlying physical laws, presents relevant experimental references, and indicates the mathematical path to the solution. The text includes too many examples of this approach to generalize, but each instance is impressive in its relevance and practicality.


Mass-transfer operations is not an everyday subject. Even today, it remains largely the province of the chemical engineer. But in this reviewer's opinion, the subject should be a required course in every physical-science curriculum today because it is basic to almost all separation processes. Mass transfer is related to the tendency toward equilibrium that derives from concentration gradients. It involves the transfer of material, or mass, from one homogeneous phase to another. Any arrangement that includes several components in unequal concentrations exhibits mass transfer toward equilibrium (i.e., from the concentrate to the dilute).


The text's breadth of focus is astonishing. It deals with interphase mass transfer and the relevant theories, the material balances, the equilibria, and equilibrium-stage operations. It treats diffusion, diffusion coefficients, and diffusion in solids and liquids. Other subjects covered include the distillation of multicomponents, batch distillations, packed and trayed towers, Fenske's equation, and optimum-reflux ratios. Among many other activities discussed in similar detail are humidification operations, mass transfer in membranes, and sorption processes.


Today's students are lucky to have textbooks such as Benítez's for their instruction. Mass-transfer operations were little organized as a discipline in the 1930s and '40s. Scientists formerly used distillation and liquid-extraction techniques, prepared ultrapure water, and purified drugs with membrane processes without sufficient instruction in mass-transfer operations. Only recently has industry realized the importance of the hydrogen bond, understood the reflux ratio in distillations, and appreciated the centrality of surface physics.


Rather than learning by trial and error, today's students have the means to learn the factors and interactions involved in mass-transfer processes, thus gaining confidence and skill. Understanding is the indispensible basis of practice, and Benítez supplies that understanding up front.


The reactor lay-out of a biological gas treatment system is generally relatively simple, but the process of biological gas treatment involves a series of complex physical, chemical, and biological processes. Many of these fundamental processes in biological gas treatment systems like mass transfer still require research (Popat and Deshusses 2010). As a result, biological gas treatment systems are often built and operated without knowledge of the rate-limiting steps in the system (often resulting in scale-up problems) and design and operations are mainly based on empirical experience.


Students develop a broad understanding of the molecular interactions that determine fluid properties; an in-depth knowledge of the modern methods used to predict thermodynamics; and knowledge of the applicability and the limitations of the various predictive methods. Topics covered in this unit include the fundamentals of statistical mechanics, calculation of molecular properties, intermolecular potentials and their use in thermodynamic, corresponding states, virial and cubic equations of state, multiparameter equations of state, limitations of EOS methods, and activity coefficient models. Students will develop a deeper understanding of advanced topics of mass transfer operations built upon those learned in the heat and mass transfer unit.


In recirculating aquaculture operations, the daily nitrogen budget of a production system is typically known and allows to make specific predictions about nutrient removal requirements based on acceptable concentration of nitrate and other nutrients in the system [34, 41]. Our trials with salt water gradients revealed a predicted mass transfer rate from the membrane cartridge into the reactor chamber of 0.5 kg/24 h/reactor, assuming optimal operating conditions as they were determined in this study. While this value is based on the small 60-L prototype reactor and a 50% membrane surface capacity, it allows to make certain predictions about the scalability and application of our new reactor technology. Specifically, the use of dimensionless parameters, Rn for fluid dynamics and Sherwood number for mass transfer, allows us to extrapolate the reactor properties beyond the dimensions of the current prototype. This is a crucial aspect of our study, as scalability can frequently be a difficult aspect of photobioreactor design [47].


The objective of this course is to present the principles of mass transfer and their application to separation and purification processes. The course develops rate expressions for mass transfer in multiphase, multicomponent systems based on diffusion and convective processes. Starting with Fick's law and macroscopic balances the course moves to the design of large scale separation processes including equilibrium stage and continuous separations for the separation and purification of chemical compounds. Specific separation operations analyzed include distillation, absorption, extraction, membrane units, adsorption. The course also introduces the use of modern software tools in the design of such processes.


Transportation of people and goods in many parts of the world depend almost completely on petroleum fuels, such as gasoline, jet fuel, diesel fuel, and marine fuel. Apart from the fuels, materials that are necessary for operating the combustion engines of cars, trucks, planes, and trains also come from petroleum. These materials include lubricating oils (motor oils), greases, tires on the wheels of the vehicles, and asphalt to pave the roads for smooth rides in transportation vehicles. All petroleum fuels and many materials are produced by processing of crude oil in petroleum refineries. Petroleum refineries also supply feedstock to the petrochemicals and chemical industry for producing all consumer goods from rubber and plastics (polymers) to cosmetics and medicine. This course explains how physical processes and chemical reactions that take place in separate petroleum refinery units are integrated to convert crude oil into desired fuels and materials. Refinery processes are divided into four types that include separation, conversion, finishing, and support. The overall objective of petroleum refining is to convert crude oil into fuels and materials that comply with commercial specifications and environmental regulations. All refining processes and refinery operations are also subjected to the applicable environmental regulations. A historical evolution of process concepts is introduced to demonstrate how the refining efficiency has increased with significant reduction of pollutant emissions from individual refinery processes. The principal objectives of this course are to enable students to: 1. explain the market drivers for the refining industry (ABET student outcome 2). 2. indicate what crude oils consist of and how crude oils are characterized based on their physical properties (ABET 1, 2); 3. express the objectives of petroleum refining and classify the processes used in petroleum refining (ABET 1, 2, 7); 4. demonstrate how a petroleum refinery works and sketch a flow diagram that integrates all refining processes and the resulting refinery products (ABET 2); 5. examine how each refinery process works and how physical and chemical principles are applied to achieve the objectives of each refinery process (ABET 1, 2, 7); 6. assess implications of changing crude oil feedstocks on refinery configuration and propose strategies to resolve conflicts with degrading crude oil quality and increasingly stringent environmental regulations on petroleum fuels (ABET outcome 4, 7); 7. discuss different sources of natural gas and explain how natural gas is processed at well sites and in processing plants with application of selected refinery processes and other physical operations (ABET 1, 2). 041b061a72


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