Fossil-fuel-fired once-through steam generator

A once-through steam generator, comprising:

• a combustion chamber for combusting a fossil fuel, said combustion chamber having an end face;
• a horizontal gas flue communicating with said combustion chamber on a heating-gas side thereof, said horizontal gas flue having an inlet region;
• a vertical gas flue communicating with said combustion chamber via said horizontal gas flue;
• a plurality of burners disposed on said end face to combust the fossil fuel in said combustion chamber at a level of said horizontal gas flue;
• said combustion chamber having a length defined by a distance from said end face to said inlet region of said horizontal gas flue, and said length is at least equal to a burn-out length of the fuel during full-load operation of the once-through steam generator;
• and
• said length of said combustion chamber being selected in dependence on a boiler maximum continuous rating (BMCR) value (W) of said combustion chamber, a burn-out time (tA) of the fuel, and an outlet temperature (TBRK) of a working medium from said combustion chamber approximately according to the following:
• L(W, tA)=(C1+C2·W)·tA
• L(W, TBRK)=(C3·TBRK+C4)W+C5(TBRK)2+C6·TBRK+C7
• where
• C1=8 m/s
• C2=0.0057 m/kg
• C3=−1.905·10−4 (m·s)/(kg° C.)
• C4=0.2857 (s·m)/kg
• C5=3·10−4 m/(° C.)2
• C6=−0.8421 m/° C.
• C7=603.4125 m;
• wherein, for a BMCR value of said combustion chamber, the respectively larger value of said length of said combustion chamber applies.