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Figure 5. Curve for heat load on water wall.

The expected highest position of heat load is generally

in the same height in the middle of each side wall in de-

sign, and the heat load of the four corners is low. Fig-

ure 3 reflects this rule, but Figure 4 does not. The main

reason is that 54 m elevation is at the SOFA wind vents

and the air temperature is only 334℃ in SOFA burner,

but its air volume accounts for 23% of the total air vol-

ume. Thus it will produce a certain cooling to the flue

gas of high temperature in furnace. As a result, it reduces

the heat load in this area.

Figure 5 shows the heat load distribution of water wall

surface on condition 1. The heat load distribution of the

four walls is the same when the flame center does not

deflect. The highest head load appears in the center of

each side wall which agrees with the design intention.

5. Conclusions

The complicated calculation model can reflect the calcu-

lation results of simple model. This strategy is closer to

the actual situation in terms of predicting larger variation

range and furnace area. However, there are some aspects

that can influence the precise calculation. The value and

distribution are reasonable by calculating the

two-dimensional area model of 1000 MW USC tower

boiler.

In the same height, the maximum value of heat load on

water wall surface appears in the central position which

shows radial distribution. Of all the calculation condi-

tions, the most dramatic change of heat load appears in

34 m elevation, and it gives a range from 237 kW/m2 to

501 kW/m2 which is 264 kW/m2 in difference.

USC boilers need to avoid heat transfer deterioration

in large specific heat region. The calculation results of

flue gas temperature show that the highest flue gas tem-

perature and heat load occur in the combustion area. The

phase transition point of working medium should be con-

trolled to be away from these areas under the supercriti-

cal pressure.

Calculation results show that the highest heat load on

water wall surface occurs in 34 m elevation. The maxi-

mum value of heat load on water wall surface is 501

kW/m2 on 970 MW condition. The maximum value of

heat load decreases with the decrease of boiler load. The

value becomes 332 kW/m2 on 507 MW condition.

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