Distillation operations have been branded as high energy users. An estimate 3% of the total energy used in the United States in 1976 was for distillation. Energy conservation is indicated. This manual is addressed to the small or medium sized chemical or refining company. It is structured to guide these people on how to analyze and reduce energy requirements. The criteria of no reduction or increased profitability of the process are stressed in analyzing any energy saving proposals.
Information for writing the sections came from technical articles, design and operating experience, and seminars on energy conservation.
This manual is divided into seven sections. The contents of
the sections are discussed in the following paragraphs.
Before any energy conservation steps can be logically taken, a
knowledge of energy usage of the existing facility must be known.
Section 2 of this manual describes a procedure for reviewing the
original plant design, auditing the energy usage as presently
operated, and collecting plant data if required for the audit.
After the distillation process is analyzed for energy usage, the first step is to study energy saving improvements needing minimal capital investments and quickly implementable. Section 3 covers this, giving ideas on changing the operating procedure and scheduling shutdowns to maximize profits and minimize energy usage.
Capital investments to save energy are generally longer term projects. These projects include the optimization of heat recovery and revisions of the column. Capital intensive and complex systems using vapor recompression or heat pumps are possible energy savers. These are covered in Section 4 along with heat losses and column control.
For distillation processes, the energy used per pound of product is a simple ratio for evaluating the performance of the program to reduce energy usage. Similarly, an economic guideline is helpful in requesting management to make decisions concerning capital investments. In Section 5, the concept of investment equivalence to save a unit of energy is developed for use as an economic guideline. The economic interpretations of several energy savings proposals are discussed. Potential conflicts in placing a cost value on various steam pressures by accountants compared to its value from a thermo-dynamic or energy level viewpoint are discussed.
The appendices include reprints of technical articles pertinent
to distillation columns, a general energy savings checklist, a
process energy checklist, and the results of a sample work problem
on vapor recommendation.