Question

The steam requirements of a manufacturing facility are being met by a boiler whose rated heat input is 5.5 × 106 Btu/h. The combustion efficiency of the boiler is measured to be 0.7 by a hand-held flue gas analyzer. After tuning up the boiler, the combustion efficiency rises to 0.8. The boiler operates 5200 h a year intermittently. Taking the unit cost of energy to be $23/106 Btu, determine the annual energy and cost savings as a result of tuning up the boiler.

Answer 1

Solution:

Given Information,

Heat input is ( $Q_{in}$ ) = 5.5 × $10^{6}$ Btu/h

Combustion efficiency of the boiler ($n_{furnance}$) = 0.7

Combustion efficiency after turn up ($n_{furnance,now}$) = 0.8

Operation Hour (t) = 5200h

Unit cost (c) = $\frac{23 dollar}{10^{6}Btu }$

Calculate heat output from the boiler  $Q_{out}$ = $Q_{in}$ x $n_{furnance}$

                                                                      = 5.5 x $10^{6}$ x 0.7

                                                                      = 3.85 x $10^{6}$ Btu/h

Calculate the heat input to the boiler after the tune-up

$(Q_{in} ){new}$ = $Q_{out}$ / $(n_{furnance} ){new}$

               = 3.85 x $10^{6}$ / 0.8

               = 4.8125  x $10^{6}$ Btu/h

Calculate the saved energy after the tune-up

$(Q_{in} ){saved}$ = $Q_{in}$ - $(Q_{in} ){new}$

                 = 5.5 x $10^{6}$ - 4.8125  x $10^{6}$ Btu/h

                 = 0.6875  x $10^{6}$ Btu/h

Calculate the annual energy saving ( $E_{Saving}$ )

$E_{Saving}$ = $(Q_{in} ){saved}$ x t

           = ( 0.6875  x $10^{6}$ Btu/h ) ( 5200 hr/yr)

           = 3575 x $10^{6}$ Btu/h

Calculate the annual cost saving

Annual cost saving = $E_{Annual saving}$ x Unit cost

                                = 3575 x $10^{6}$ Btu/h x $\frac{23 dollar}{10^{6}Btu }$

                                = 82225