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

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) =
`(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
`(23 dollar)/(10^(6)Btu )`

= 82225