Chemical and Material Engineering DepartmentChemical and Material Engineering DepartmentThe Engineering Interdisciplinary Clinic (EIC) at Cal Poly Pomona provides an opportunity for Science, Engineering, and Business majors to work in a real project posed by an industrial client. Currently, each client commits to $33,000 for each EIC project that an EIC team undertakes for them. Each EIC team consists of 6-8 students under the supervision of a faculty advisor or coach who is selected because of their relevant experience and their ability to work well with students. Each EIC team also works with a representative (a liaison) from the client to facilitate communication between the team and the industry.
The EIC program at Cal Poly Pomona is founded in 1990 by Dr. C. L. Caenepeel, a faculty in the Chemical and Materials Engineering department. Many other universities have a similar program. The goal of the EIC is to provide students with internship opportunities that have become very important for anyone seeking employment that requires previous experience. This is specially important for a chemical engineer because of the diversify of the field. A good internship has three characteristics. First it is a caption experience that occurs late in ones academic experience after a student has had a good foundation in both the basic curriculum and major courses. Second it offers an interdisciplinary environment where students with different backgrounds and training interact. Lastly, the internship should include mentoring and training by experienced faculty and client liaisons. The EIC has been built on a foundation of these three characteristics.
EIC teaches project oriented teamwork and helps students develop an understanding of professional practice. Student participants become acquainted with the important of the constraints of time and money. They are involved in their project from the beginning planning phase, through project plan implementation, with continuous client communication, and finally completion of the project and final report. Each student in a team is also required to give an oral presentation to the client and general audience. There is a process of combined faculty and peer performance reviews of student participants. The goal of the reviews is to identify individual strengths and recommended areas of improvement.
A classical role of the chemical engineer is the design of chemical plants. In a design process an engineer will need to make a large number of calculations which are readily adaptable to computer solution. In recent years, effective programs have been developed on main frames and personal computers which allow users to make the calculations needed and report the results. This approach is generally referred to as computer-aided design. As new technology are introduced or better understood, subroutines will be developed to add to the existing computer program to simulate the new unit operations. Most of these unit operations are used to conduct the physical steps of preparing the reactants, separating and purifying the products[1].
Cyclones are commonly used for the recovery of dust particles from air and process gases. Due to the increasing number of emissions regulations, the fractional recovery of dust particle or the efficiency of cyclones is a major concern. A cyclone can be considered as a continuously working centrifuge without any moving parts. A conventional cyclone consists of a cylindrical body joined to a cone. A dust-bearing gas stream is injected tangentially at the circumference of the upper part of the cylinder, thereby causing the rotation of the gas contained in the cyclone. The rotation imparts a centrifugal force to the particles, usually on the order of several hundred g's of acceleration. This force drives them to the cylinder wall. The particles slide along the wall to the apex of the cone while the spiraling gas stream turns around and exits from the cylindrical tube at the opposite end. The flows through the tube and apex are usually referred to as overflow and underflow respectively. The cylindrical tube, fixed in the center of the top and projecting some distance to the cyclone, is called the vortex-finder or exit duct [2]. Since the gravity force is negligible in the operation of a cyclone, it is usual but not essential to build cyclones with the apex pointing downwards and the overflow might just as well be directed sideways or downwards.
The flow in a cyclone is complicated and highly turbulent so that a complete theory of cyclone design and performance has not been developed. The normal practice up to now has been to collect systematic information on cyclone flow, separation efficiencies, and pressure losses and then correlate these data. Some of these correlation's are based on the critical particle diameter which is defined as the theoretically smallest completely collectable particle diameter.
A cyclone is capable of removing different sizes of dust particles with high efficiency. It is recommended for separation of solid particles with diameters between 5 and 200 micron. For particles less than 5 mm the collection efficiency is low unless very small units and flow rates are used. For particles higher than 200 micron the cyclone will be subject to excessive abrasion [2]. A cyclone can be designed to minimize the amount of solids in the exiting gas stream. The amount of particles that remain is dependent on the inlet conditions and the dimensions of the cyclone. The following is a discussion of some cyclone design factors which have an effect on the efficiency of the cyclone.
In a typical cyclone separator, the gas-dust mixture enters the top cylindrical section of the cyclone through a tangential opening. As particles must reach the wall of the cyclone before they can be recovered from the gas stream, it is best if the inlet shape is rectangular instead of circular. A circular inlet would have only one point tangential to the wall, but a rectangular inlet should have at least a quarter of the perimeter tangent. When a rectangular inlet is used, it is recommended that the height of the inlet duct be greater than the width, to increase the tangential inlet surface. In order to reduce erosion and the migratory loss of particles it is best to place the inlet duct flush with the cyclone roof. For best efficiency the penetration of the outlet duct should be 1 to 1.2 times the height of the inlet duct to prevent the inlet particles from going directly out of the cyclone with the exiting gas stream. Increasing the penetration of the outlet duct beyond 1.2 is not economically feasible as the entire length of the cyclone would also have to be increased [2]. The contraction of the outlet gas stream represents a pressure loss which should be minimized by maximizing the area of the outlet gas duct. The main areas of pressure loss in a cyclone are due to the contraction of the inlet and outlet ducts. If the ratio of outlet area to inlet area is less than one, an increased pressure drop is experienced and the cyclone must be lengthened to avoid dust reentrainment in the spiraling gas stream [2].
The main goal of the project was to create a computer model of a cyclone separator unit operation. This model allows the user to either design a new cyclone or rate the performance of an existing cyclone. The model has been developed to run in both rating and design mode. There are many calculation option available to the user. Additional options, such as series cyclones and dipleg sizing, have been incorporated into the model to increase the usefulness of the simulation. The coding of the program is in FORTRAN 77.
- Rating mode: The model will predict the fractional recovery of dust particles and the power requirements given the dimensions of the cyclone, the physical properties of the gas, and the volumetric flow rate.
- Design mode: The model will predict the cyclone dimensions and power requirements given the fractional recovery of dust particles, the physical properties of the gas, and the volumetric flow rate.
Another major goal of the project is to evaluate the performance of the computer model. This was done using literature examples and industrial cyclone data. The literature examples were used to produce performance curves on graphs. These were compared to the graphs found in literature to verify trends. Industry data was used to determine the best methods. Although it gave some indication of the best methods, the amount of data was insufficient to draw firm conclusion about the calculation methods.
The computer model for the cyclone separators was completed in the academic
year 1994-95 for Simulation Sciences which is a leading company in process
simulator designed for the gas processing, oil refining, petrochemical,
chemicals, and synthetic fuels industries. The Faculty Advisor for the 1994-95
EIC/Simulation Sciences (SIMSCI) team was Thuan Nguyen, Professor of Chemical
and Materials Engineering. The Project Engineers were Mechanical Engineers
Mateus Andrade, Kenny Lau and Triet Nguyen, and Chemical Engineers David
Eaton-Messer, David Jones, Corrie Kernan (Project Manager), Giai Pham, and
Jeff Waller. The Technical Liaison was Simulation Sciences' Software Engineer,
Bruce Cathcart (Cal Poly Pomona Chemical Engineering graduate, class of
1976)
The wiped film evaporator WFE has become well-established in the chemical
process, food, pharmaceutical, and oil refining industries as a devolatilizer
where substances of lower boiling points are removed from a liquid stream
of much higher boiling point. WFE has been most economically applied to
materials with particular difficult processing characteristics, such as
heat sensitivity, high viscosity, high boiling contaminated mixtures [3].
The typical construction of a consits of a vertical cylindrical shell, surrounded
by a heating jacket, forms the heat treatment zone. Above the heat treatment
zone there is an outlet to let the vapors escape. At the bottom end there
is a conical outlet for the product solution. A set of wiper blades is mounted
on the shaft which rotates with a fixed angular velocity. The blades lay
out a thin film on the wall of the cylindrical shell. The film formed on
the wall of the evaporator is usually thicker than the clearance between
the wiper blades and the wall. As the blade moves, a fillet of liquid or
"bow wave" is created on its front edge. The thin-film process
is however limited by viscosity. As the viscosity of the fluid increases
the hold-up in the device causes an increase in the film thickness and consequently
the power required to turn the blades increases considerably. WFE's can
operate at liquid viscosities between 1 and 100,000 poise [5], viscosity
of liquid water is about 0.01 poise. For polymer melt with very high viscosity,
polymer machine and vented extruder will be used.
The computer model for the wiped film evaporators was completed in the
academic year 1994-95 for Simulation Sciences which is a leading company
in process simulator designed for the gas processing, oil refining, petrochemical,
chemicals, and synthetic fuels industries. The Faculty Advisor for the 1995-96
EIC/Simulation Sciences (SIMSCI) team was Thuan Nguyen. This team was composed
of seven Chemical Engineers (Kristin Kellas, Yanti Prasetio, Joshua Eggleston,
Mark Avila, Sarawut Kaewtathip, Leny Kusnandar and Jeannie Kristein) and
one Computer Scientist (Liang Cheng). The Technical Liaison was Simulation
Sciences' Software Engineer, Bruce Cathcart.
Air Cooled Heat Exchangers have been used for many years to cool and condense fluids in areas where water polution is a concern. An EIC team has undertaken for Simulation Sciences Inc. the development of a program that will aide in the design and performance analysis of these air-coolers. This simulator is based on incremental analysis in which energy and momentum transfer calculations are applied to approximately 1200 increments. The solution of this system results in the temperature and pressure profiles along the tubes in the exchanger. Incremental analysis enables to handle air side and tube side flow maldistribution. In addition, this model can account for tube side condensation and two-phase flow and varioations in thermodynamic and transport properties.
The Faculty Advisor for the 1996-97 EIC/Simulation Sciences (SIMSCI) team was Thuan Nguyen, Professor of Chemical and Materials Engineering. The team was assisted by the technical liaisons from Simulation Sciences Inc, Software Engineers Bruce Cathcart and Amar S. Wanni. The six Chemical Engineering students on the team were Huong Lan Bui, Chung-Ho Chau, Ronald W. Lau, Tin Nguyen, Chritopher Scott Wilson, and Herric Chan (Project Manager).
Liquid-liquid extraction is a unit operation useful in separating liquid mixtures that are impractical to separate by distillation. Such components are often separated by their differences in solubility in relation to a suitably chosen solvent. The process of liquid-liquid extraction involves three main steps: (1) Bring the feed mixture and the solvent into intimate contact, (2) Separate the resulting mixture into two phases and (3) Removal and recovery of the solvent from each phase. The design of the liquid extractor necessitates an initial screening of various solvents. A common design technique for a three component system uses graphical techniques on a triangular diagram to solve the material balances and liquid-liquid equilibrium relations. For a system with more than three components, the graphical method cannot be used. Therefore it is highly desirable to develop efficient and general software algorithm to facilitate the design of liquid-liquid extractors.
The computer algorithm for the liquid extractors was completed in the academic year 1994-95 for Simulation Sciences which is a leading company in process simulator designed for the gas processing, oil refining, petrochemical, chemicals, and synthetic fuels industries. The Faculty Advisor for the 1997-98 EIC/Simulation Sciences (SIMSCI) team was Thuan Nguyen, Professor of Chemical and Materials Engineering. This team was comprised of five Chemical Engineering students: Chi Diep, Dan Williamson (Project Manager), Fahd-Bin-Marghoob, Ngoc Dung Nguyen, and Van Nguyen and three students from the Department of Mathematics, Katherine Skelton, Holly Lam, and James Varner. The technical liaison from Simulation Science Inc. was Dr. Raymond Rooks.
1. Peters, M. L. and Timmerhaus, K. D., Plant Design and Economics for Chemical Engineers, McGraw-Hills, 1991.
2. "Manual on Disposal of Refinery Wastes - Volume on Atmospheric Emissions", American Petroleum Institute, (Publication 931), May 1975, Chap. 11.
3. Biesenberger, J. A., "Thin film evaporator", Devolatilization of Polymers, Macmillan, New York, p. 51-63.
4. Heimgartner, E., Devolatilization of Plastics, VDI-Verlag Gmbh, Dusseldorf, 1980, p. 69-97.
5. McKenna, T. F., " Design model of a wiped film evaporator. Applications
to the devolatilization of polymer melts", Chemical Eng. Sci., 50(3),
1995, p. 453-467.