The boiler of Example 8.1 uses 1,500,000 L of fuel oil per year. An instrumentation kit is purchased at a cost of $20,000 and is used to adjust the boiler operation so its excess of O2 is only 3 percent. Determine the payback of the instrumentation if the cost of fuel oil is $0.20/L.

Question

The boiler of Example 8.1 uses 1,500,000 L of fuel oil per year. An instrumentation kit is purchased at a cost of $20,000 and is used to adjust the boiler operation so its excess of [latex]O_{2}[/latex] is only 3 percent. Determine the payback of the instrumentation if the cost of fuel oil is $0.20/L.

Accepted Answer

From Example 8.1, the existing boiler has excess [latex]O_{2}[/latex] of 6 percent and an overall boiler thermal efficiency of about 78 percent (i.e., [latex]η_{std}[/latex] = 0.78 ).

After the boiler tune-up, the excess [latex]O_{2}[/latex]is 3 percent. Using the monograph of Figure 8.1, the new boiler efficiency can be determined from the flue gas temperature (343°C or 650°F) and the excess [latex]O_{2}[/latex](3 percent). It is found to be [latex]η_{eff}[/latex] = 84% = 0.84 . Using Eq. (8.4), the fuel savings can be calculated:

[latex]ΔFU=\frac {η_{eff}-η_{std}}{η_{eff}}.FU_{std}[/latex] (8.4)

[latex]ΔFU=\frac {0.84-0.78}{0.84}, 1,500,000=107,104L/yr[/latex]

Therefore, the simple payback period for the instrumentation is:

[latex]SBP=\frac{\$20,000}{107,104L/yr *\$0.20/L}=1.0 year[/latex]

Question 8.2: The boiler of Example 8.1 uses 1,500,000 L of fuel oil per y...

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