In an energy audit, the following information was obtained from the inspection o

Question

In an energy audit, the following information was obtained from the inspection of a boiler:

Fuel: Natural Gas

Rating (input) 30 MMBtu/hr

Output: Saturated Steam at 55 psig

Exhaust Temperature: 450 F

Exhaust Gas Analysis:

CO 1,500 ppm

CO2 8.6%

O2 5%

HC (taken as methane) 300 ppm

Assume 5% loss due to surface losses and blow-down. Calculate:

a – Rate of steam production

b – Boiler efficiency

c – If the boiler is tuned so that so that no unburnt material is detected and O2 level in the exhaust is reduced to 3%, how much improvement in efficiency is expected? The exhaust temperature remains the same as before.

d – What is the maximum flame temperature that can be expected in the boiler? You may use an online calculator for this purpose.

Explanation / Answer

a)    Rate of steam production = 1500 * 0.05 * 252/15

                                                = 1260 m3/sec

b)    Boiler efficiency = 1540/3010

                                = 0.5116       ( or 51.16 %)

c)    improvement in efficiency is expected   =   1800/3010

                                                                     =    0.60       (or , 60 %)

d)   maximum flame temperature that can be expected in the boiler = 450 * 452/80

                                                                                                              = 2542.5 F

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