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10. APPENDIX 1. FUEL CONSUMPTION CALCULATION
Figure 16
Generic boiler efficiency chart with determined working point
We assume that we have to calculate natural gas fuel consumption for the production of 2500 kg/h of
saturated steam, working pressure is
9 bar
, the steam generator is a UNI-MATIC UM 300, without air
preheater. Feeding water temperature is 70 °C.
In accordance with heat balance equation
Q = M steam * (hg-he)/3600
, where:
Q = heat needed to achieve saturated steam production with the above indicated characteristics (watt);
M steam = steam production, t/h;
hg = enthalpy of saturated steam at the above indicated temperature and pressure;
he = enthalpy of feeding water at the above indicated water temperature;
Values regarding enthalpy are taken from Appendix 2.
As calorific power of natural gas is
8500 kcal/Nm
3
, we determine hg - enthalpy of saturated steam
under 9 bar gauge pressure and he - enthalpy under 70 °C feed water temperature.
Q= (2500/3600)*(663,9-69,1) = 413 kcal/s or 1731 kW,
According to Table 1 heat power of UNI-MATIC UM 300 steam generator is 2100 kW, which is 100%
boiler’s steam production load.
Actual load of the boiler = (1731/2100)*100%=82%,
In accordance with actual modifications of the steam generator (without air preheater) and graphics
regarding coefficient of performance (COP) of the boiler UNI-MATIC UM crossed with the load, under
different working pressures (Figure 16), we determine that COP (under 9 bar, 82% actual load) is 89,4%.
Determined the COP of the boiler, we consider Qp= (413/89,4%)*100= 462 kcal/s. Therefore we calculate
natural gas fuel consumption with the relation 462/8500=
0,054 Nm3/s
or
196 Nm3/h
.
