Cold reheat steam enters the first stage reheater in the front pass of the convection pass before the economizer。 The final reheater stage is in the furnace as platen type。 Reheat steam temperature is controlled by the flue gas damper at the end of the convection pass。

Fig。 5Steam-water System of No。1 Boiler

No。2 boiler: Fig。6 shows steam-water system of No。2 boiler。 The steam outflow from drum is further heated in the superheater stageⅠlocated in the two EHEs nearthe

front of furnace, then it flows to medium temperature superheaterⅠ(MTSⅠ)andmediumtemperaturesuper-

heaterⅡ(MTSⅡ) located in the two EHEs near the back of furnace, The final superheater is the first heating sur- face in the back pass of the convection pass。 Cold reheat steam is heated by the first stage reheater in the front pass of the convection pass and the final reheater stage is inthe EHEs。 The first stageattemperator is located be-

tween LTSand ITSⅠ, the second stage attemperatoris

localed between ITSⅠand ITSⅡ, and the final stage attemperator is localed between ITSⅡ and HTS。

Fig。 6Steam-water System of No。2 Boiler

No。3 boiler: Fig。7 shows steam-water system of No。3 boiler。 Its steam-water circuits is very similar to No。1, the main difference is that the saturated steam from drum firstly flows to steam-cooled separator before it feeds the steam to the enclosure of the convection pass。 The ar- rangement of the heating surface of the convection pass and platen heating surface is the same to that of No。1 and the reheat steam circuit is the same to that of No。1。

Fig。 7Steam-water System of No。3 Boiler

Table 1Boilers Main Parameters

SH flow t/h SH pressure MPa SH temp。 ℃ RH inlet pressure MPa RH inlet temp。 ℃

1065 17。4 541 4。02 334

RH flow t/h RH outlet pressure MPa RH outlet temp。 ℃ Feed water temp。 ℃ SH pressure MPa

874 3。82 541 280 18。7

Boilers main parameters and fired coal

The main parameters of the boilers are shown in Table 1(the main parameters of three types of boiler are almost the same)。 The ultimate analysis of fired coal is given in Table 2, Table 3 and Table 4, which are gangue, lignite and anthracite, respectively。

Table 2Ultimate Analysis of Fired Coal Gangue

Carbon Car % Hydrogen Har % Oxygen Oar % Nitrogen Nar % Heat value Qnet。 kJ/kg

40。63 2。57 7。08 0。61 15210

Sulfur Sar % Ash Aar % Moisture War % Volatile Vdaf %

0。23 35。08 13。8 39。86

Table 3Ultimate Analysis of Fired Coal Lignite

Carbon Car % Hydrogen Har %