Environmental issues and the need to reduce costs while remaining competitively viable impact process industries, manufacturers, hospitals, schools, commercial buildings, and government institutions. Energy conservation is key for building owners to remain successful in today's economic environment.
Industrial Boilers
About 160,000 boilers are in the U.S. industrial sector. Approximately 90,000 to 100,000 of those boilers are more than 20 years old, average 350 to 400 hp, and produce steam at pressures exceeding 15 psig.
A 400-hp high-pressure steam boiler operating at 100 psig consumes 17,851,733 Btuh when operating at 75-percent fuel-to-steam efficiency. This equals 179 therms of natural gas per hour. If this boiler operates for 5,000 hr annually at $1 per therm, it will cost $895,000 to operate per year. This boiler-operating cost can be associated with the manufacturing of a product, which then must be sold. If the costs to create the product are reduced and the price maintained, the margin of cash flow increases.
Energy should be tracked as closely as any other operating expense. Unfortunately, many businesses consider boiler energy as a cost of doing business, raising prices to cover energy escalation without any price/value offset. Although some operational expenses can be reduced, boilers have certain inefficiencies that cannot be eliminated because of physics and boiler-system thermodynamics. For example, convection and radiation losses in the previously mentioned boiler can account for efficiency reductions of 1 to 2 percent. Some combustion inefficiencies that ensure safety cannot be eliminated, amounting to non-recoverable energy losses of 3 percent. That leaves up to 10 to 11 percent of efficiency that can be recovered (approximately $98,450 per year).
Thus far, this article has focused on a process-steam boiler's potential savings, while omitting total steam-boiler systems and process equipment. However, 20 to 30 percent of savings in the form of trapped condensate return, flash-steam recovery, blowdown heat recovery, vent condensing, etc., is potentially available in these areas. This article's examination of hot-water heating systems will provide a short discussion on the importance of evaluating an entire system when considering possible system inefficiencies and potential energy-cost savings.
Commercial Boilers
About 240,000 commercially sized hot-water boilers are in the United States. Approximately 154,000 of them are more than 20 years old. Many are operating at efficiencies of 60 to 70 percent because of poor design, inadequate control, piping/pumping and radiation deficiencies, excessive cycling, etc.
Often, condensing boilers with efficiencies of 90 to 95 percent can help solve such issues. However, in many cases, non-condensing boilers are replaced at a significant expense, when the cost of the condensing unit and the old boiler's removal are considered. Unless a condensing boiler and its system are understood and configured properly, outcomes can be far less than expected, with high capital expenditures and protracted to nonexistent returns on investment (ROI).
Retrofit or Replacement
Boiler retrofits and replacements involve specific criteria that must be evaluated before a decision is made. These criteria impact several areas of a steam or hot-water-heating facility, such as operations (present and long-term needs, operating hours, downtime impact, load criticality, etc.), the physical plant (mechanical floor area, access, power, piping systems, processes, operating personnel, etc.), and budget constraints (available capital expenditures).