36。72 1。87 12。59 1。01 12435

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

1。66 11。45 34。7 52。7

Table 4Ultimate Analysis of Fired Coal Anthracite

The main operation result and discussion

The operation condition

This research was carried on three 300MWe CFB boilers with different arrangement types。

The operation condition of No。1 boiler

The operation results were from four different boiler loads, they were 95。6 % boiler maximum continuous rate (BMCR), 79。2% BMCR, 63。5% BMCRand54。8%

BMCR, respectively。 The boiler operation parameters are shown in Table 5。

When the boiler operated at 95。6 % BMCR, the bed temperature was 960～983℃, the fluidized velocitywas

5。0 m/s。 The reason why the bed temperature is higher than the design temperature 890℃ is that the fired coal is different from the designed coal。 The ash content ofthe

fired coal is much lower than that of the designed coal, which indicates that the actual heat transfer coefficient is lower than design value。 So the actual bed temperature is rather high during the boiler operation。 The primary air was fed into the furnace below the air grid and the sec- ondary air was fed into the furnace above the air grid when the boiler operated at 95。6 % BMCR。 The air flow ratio of the primary air to the total combustion air was 43

% and the air flow ratio of the secondary air to the total combustion air was 55 %。

The operation condition of No。2 boiler

temperature was 840～850℃, the fluidized velocitywas

combustion air was 33 % and the air flow ratio of the secondary air to the total combustion air was 50 %。

the hot circuit, and the heat balance can be calculated through the formula (1) and the formula (2)。

The operation condition of No。3 boiler

QB (Q

100 q4 q6Q

I I)

(1)

The operation results were from four different boiler loads, they were 94 % BMCR, 85% BMCR, 72%BMCR and50% BMCR, respectively。 The boiler operation pa- rameters are shown in Table 7。

1 j net,ar 100 q k yx fh

QwQ1Qps Qpr

K Q H Δt

(2)

(3)

Whentheboileroperatedat94%BMCR,the bed

temperature was 910～930℃, the fluidized velocitywas

5。2 m/s。 The air flow ratio of the primary air to the total combustion air was 45 % and the air flow ratio of the secondary air to the total combustion air was 50 %。

The heat transfer coefficient of the waterwall

For these three boilers, the absorbed heat of the water wall is obtained by the calculation of thermal balance in

According to the methods mentioned above, the ab- sorbed heat of the waterwall can be calculated。 Mean- while the formula (3) was used to calculate the heat transfer coefficient of the waterwall at different boiler loads, the ultimate results are shown in Figs。 8~10, indi- cating that the heat transfer coefficient of waterwall in- creases gradually with the increase in boiler load。 The main reason is the change of the solid suspension con- centration and the bed temperature with the boiler load。