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The Story Of Polyethylene Garbage Bags

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1997 Annual Conference


Milwaukee, Wisconsin

Publication Date

June 15, 1997

Start Date

June 15, 1997

End Date

June 18, 1997



Page Count


Page Numbers

2.428.1 - 2.428.13



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Paper Authors

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Bruce A. Finlayson

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NOTE: The first page of text has been automatically extracted and included below in lieu of an abstract

Session 3513

The story of polyethylene garbage bags

Bruce A. Finlayson University of Washington

Overview. The story of polyethylene garbage bags has been used as a structure around which to organize a course on numerical methods applied to chemical engineering problems. Starting with natural gas, a series of problems is posed that must be solved if one is to eventually end up with a garbage bag.

The course begins with a theme, written about some aspect of polyethylene: raw materials, production methods, uses, business trends, recycling, etc. These themes are then put on the course Web-site so that they can be read by all the class. It is also necessary to use many differ- ent computer tools (e-mail, anonymous ftp servers, local area networks) to accommodate the diverse needs of the students, some of whom have their own computers and different software. Most problems are solved using Microsoft EXCEL™ or Mathworks MATLAB™. After the standard problems are solved, the students prepare multimedia displays illustrating the math- ematical problems a chemical engineer runs into in order to convert natural gas into garbage bags. Two displays are done: one for a technical audience (a prospective sophomore chemical engineer) and one for a general audience (middle school or high school students). Even the patent literature is used in lectures to display the role of innovation. Safety aspects in polyethyl- ene plants can be addressed by using films prepared by SACHE (Safety and Chemical Engineer- ing Education).

Course Objectives. The goal of the course is to learn to apply mathematical and numerical methods to chemical engineering problems. This goal involves learning to use existing software like EXCEL and MATLAB, learning some rudimentary programming in MATLAB, and espe- cially learning to check your results numerically, since there are often no known analytical solutions for comparison. The instructor’s task is to achieve those goals within a structure imposed by a case study. In this course the structure was provided by a series of problems arising when modeling processes to obtain natural gas, separate the ethane, react it to ethylene, polymerize it to polyethylene, and extrude it to make polyethylene garbage bags. This provides the story line of the course. The sequence of problems is: sets of algebraic equations, ordinary differential equations as initial value problems, ordinary differential equations as boundary value

Finlayson, B. A. (1997, June), The Story Of Polyethylene Garbage Bags Paper presented at 1997 Annual Conference, Milwaukee, Wisconsin. 10.18260/1-2--6795

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