What is the approximate annual boiler fuel cost to produce 100,000 lb/hr of steam all year?

A. US$1 million
B. US$3 million
C. US$5 million
D. US$7 million

Much more detailed information is needed to perform this calculation accurately, but a rough estimate can be obtained by making appropriate assumptions such as the boiler efficiency (80 percent) and the cost of natural gas (US$5.00/million British thermal units [mmBtu]) while recognizing that approximately 1000 Btu of energy is required to boil a pound of water to make saturated steam. Using these assumptions, the annual energy cost would be approximately US$5.475 million:

(8760 hr/yr) x (100,000 lb/hr) x (1000 Btu/lb) x (US$5.00/mmBtu) / (0.80)

The above expression yields US$4.475 million per year, which is close to Answer C.

Additional complicating factors

The assumptions are different for each plant location and will change over time.

David W. Spitzer is a regular contributor to Flow Control magazine and a principal in Spitzer and Boyes LLC, which offers engineering, seminars, strategic, marketing consulting, distribution consulting and expert witness services for manufacturing and automation companies. Spitzer and Boyes is also the publisher of the Industrial Automation INSIDER. He has more than 40 years of experience and has written more than 10 books and 350 articles about flow measurement, instrumentation and process control.

Spitzer may be reached at 845-623-1830 or via spitzerandboyes.com. Click on the “Products” tab to find his Consumer Guides to various flow and level measurement technologies.