3 replies to this topic

[engr muzzi]

I m working on calculation of diesel consumption for a fire tube boiler. This steam is dry saturated steam and is produced at a pressure of 9 bars and 170 C. The boiler gives its steam to two different lines. A reducer is installed in one of the line that is coming to main production area which reduces the pressure to 4.5 bar. The whole production plant use this steam at 4.5 bar. Now hw to calclate the deisel consumption of the boiler for this main production, when the boiler is producing steam at 9 bar and not at 4.5 bar.

[Andree]

Q_9.0 = Q_4.5 + (H_9.0 - H_4.5)/(Hv*efficiency)

where:
Q_9.0 - consumption of diesel when 9bar steam is produced
Q_4.5 - consumption of diesel when 4.5bar steam is produced
H_9.0 - enthalpy of 9 bar steam
H_4.5 - enthalpy of 4.5bar steam
Hv - heating value of diesel fuel
efficiency - efficiency of boiler (note: above formula is valid if efficiency is constant regardless of steam parameters produced, which does not have to be true)

[latexman]

Throttling from a high pressure to a lower pressure is considered isenthalpic (no change in enthalpy), therefore it has no effect on the boiler duty. H_9.0 = H_4.5 (the 4.5 bar steam will be somewhat superheated after the reducing station) and therefore Q_9.0 = Q_4.5.

[engr muzzi]

Thnx Andree for ur prompt response.
can i have a source of the formula u just described??/