Large capacity circulating fluidized bed boiler with supercritical pressure and higher temperature steam (SCCFB) is an advanced combustion technology with high efficiency an 1 low cost NO_x and SO_2 emission control. Compared with pulverized coal fired (PC) boiler, heat flux from the bed of SCCFB to the vertical membrane wall of the furnace is lower as well as the water flux in the tubes of furnace. In this paper, a complete hydrodynamics of an 800MWe SCCFB boiler with sliding pressure, coupled with heat transfer and suspending material density model, is carried out at 100% B-MCR and 40%. 60%, 78%, 90%, 100% T-MCR load. A series of comparison on different operations, for instance, employing orifices or not at the inlet of combustor tubes, using smooth tubes or rifled tubes, are concerned. The influences of distribute header and collect header to pressure drop calculation are also considered. The result shows that no DNB (Departure from Nucleate Boiling) takes place from 40% to B-MCR load. The maximum mid-fin tube temperature appears in B-MCR load, which is 498.87°C. The temperature difference of fluid, inner tubes, outside tubes and mid-fin tubes, across a combustor wall width increases with increasing height. The maximum temperature deviation at the tube outlet always occurs at 60% T-MCR load. The largest heat flux at horizontal direction is near the furnace corner, and the maximum uneven ratio at horizontal direction is only 1.2. It is an effective method of employing orifices at the inlet of tube to decrease the temperature deviation across the combustor wall wide.
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