Can you meet the steam challenge? It could lower costs considerably

Do you still think steam is an uncontrollable fixed cost of production?

By Russ Kratowicz

Following on the heels of the Green Lights Program, the Motor Challenge, and the Compressed Air Challenge, the aim of this latest program coming out of Washington is retrofitting, maintaining, and operating steam systems more efficiently and profitable. The goals for the Steam Challenge, a voluntary program, are:

  • a 20 percent increase in efficiency within the next 12 years;
  • increased market penetration of energy-efficient industrial steam systems;
  • helping industry adopt the systems approach in the design, purchase, installation, and management of boilers, distribution systems, and steam applications.

The program, unveiled last April 30, is a public-private initiative sponsored by the U.S. Department of Energy's Office of Industrial Technologies. The program is being developed in partnership with the Alliance to Save Energy, a national nonprofit organization and over 50 other leading industrial corporations. American industry will benefit by successful measures it takes in reducing the energy consumed in generating and using steam. According to the program description, the Steam Challenge is dedicated to:

  • improving industrial competitiveness through enhanced productivity and lower production costs;
  • providing steam plant operators with the tools and technical assistance they need to improve the efficiency of their steam plants; and
  • promoting greater awareness of the energy and environmental benefits of efficient steam systems through improved technology and operation.

Background

The Department of Energy claims that in 1995, U.S. manufacturers used 9.34 quadrillion BTUs for the 54,000 large boilers that produce steam for process use, driving mechanical equipment, and generating electricity. The fuel being burned for these purposes releases 196 million metric tons of carbon dioxide each year--forty percent of industrial CO² emissions and 13 percent of overall U.S. emissions of the gas. Finally, The DOE estimates that the demand for steam will increase by 20 percent in five major industries by 2015 (compared to 1990 levels). Current domestic manufacturing energy costs are about $21 billion per year. If successful, the Steam Challenge will result in savings of $4.2 billion annually.

The DOE says that the average efficiency of a boiler fired by natural gas is about 78 percent. If fired by oil, the efficiency is about 81 percent and, if coal-fired, the efficiency is about 83 percent. Attempts to improve these efficiencies can be stymied by lack of information about natural limits and technology that make savings possible. Therefore, the Steam Challenge program is planning several actions to educate industry:

  • supporting five showcase steam systems;
  • qualifying plant staff in best technology practices;
  • communicating the benefits of energy efficiency;
  • supporting plant improvements that integrate efficiency programs; and
  • develop software and information for industry.

Boilers burn fuel to generate heat that, in turn, boils water to make steam. The fraction of the heat released by the fuel that actually generates useful steam determines the thermal efficiency of a boiler. Unfortunately, it is impossible to make a boiler 100 percent efficient.

There are unavoidable heat losses--in the network of steam pipes, in steam traps, in equipment that uses the steam, radiant losses from the boiler to the surroundings in the boiler room, and up the stack.

Even if the entire steam system could be perfectly insulated to avoid heat release to the plant environment, this last type of loss--stack loss--remains unavoidable. Corrosion in the stack is the reason. Water vapor is one of the gaseous products formed when fuel burns.

The exhaust going up the boiler stack, therefore, contains more water vapor than was contained in the air feeding the combustion process. The higher humidity in the stack gas has a higher propensity to condense to liquid water inside the exhaust ductwork. It does not take much of a temperature drop to initiate condensation.

When the water vapor condenses, it attracts and dissolves other products of combustion, like sulfur compounds. Then, the condensed water turns to sulfuric acid. The point is that there exists a stack temperature below which corrosion occurs. Therefore, to prevent corrosion, the temperature of the stack gas must remain above some natural limit--its dew point--to avoid formation of corrosive materials.

In general, adding insulation is a good idea to prevent extraneous loss of heat, BTUs, and the dollars the fuel equivalent represents. However, if one expects a payback to the insulation project, then more is definitely not better. We need to deal with the concept of economic insulation thickness if a payback is to exist. The object is to insulate to the extent that the net present value of the energy saved over the life of the insulation is equal to the current cost of the insulation. Over-insulating costs too much relative to the expected value of the increased energy savings. Under-insulating does not save enough energy to justify the cost.

Future activities

There are several future activities planned for the Steam Challenge. One is the support of five showcase demonstrations for motors, steam, and compressed air. Another future activity is reaching out to plant operators and managers through training that qualifies operators in best practices for steam systems. Since this program is voluntary, the bureaucrats will not shut down your steam system if your operators elect not to get involved. However, your bottom line may not be as crisp as it could be. The only way to find out is to get the training. It certainly won't hurt you to learn more. According to the Alliance to Save Energy, the Steam Challenge and the National Institute for the Uniform Licensing of Power Engineers are exploring the idea of creating an examination to certify steam operators for steam-system efficiency.

Speaking of learning, another planned future activity is supporting the development of unbiased tools and information that does not exist today. The idea is that the Steam Challenge organization will partner with trade and technical associations to develop this material.

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