SG1025/17.4 M847 type boiler at a factory for manufacturing subcritical boiler plant in Shanghai, a reheat, natural circulation, solid-state slag furnace, boiler of ∏ type is decorated, USES the balanced ventilation, tangential firing, with four reservoir type in low speed ball mill coal pulverizing system. Design coal for zhengzhou area lean coal. 50% rated load sliding pressure boiler design superheated steam temperature of 540, under the condition of reheat steam temperature 515 ℃.
The primary and secondary air of the main burner are arranged counterclockwise. 719 /? 686. Three times the wind clockwise direction layout, with one, two times the wind direction of the main axis back 10 degrees. SOFA burner is arranged in a clockwise direction, 6 degrees backward from the main axis in the direction of first and second wind. Three times wind and SOFA wind together play the role of anti - cyclone.
Both the primary and secondary air vents and the SOFA burner vents are equipped with automatic vertical swing devices. First, the secondary air nozzle can swing up and down plus or minus 30 degrees, the swinging mechanism is divided into upper and lower groups. SOFA air nozzle can also swing from left to right in manual mode, plus or minus 15 degrees.
2.Analysis of steam temperature problem and its causes in 150MW low load condition of unit 21
The main steam temperature and reheat steam temperature of a single set of pulverized powder are low after the modification of the boiler low nitrogen burner. Through the study found that when in 150 mw if put two bearing powder system, such as A, C or B and C pulverizing system steam temperature can reach 536 ℃ ~ 538 ℃, and the screen is not overtemperature, superheater with warm water. When single bearing powder system, superheated steam temperature when a minimum of 504 ℃ or so, low reheat steam temperature of 495 ℃ or so, but the superheater level of desuperheating water flow to nearly 40 t/h, front panel also often overtemperature.
The reasons for the low reheat steam temperature of the single set pulverized powder system are as follows:
(1) when the operation of two grinding, the corners of the burner to three times the wind two relative was put into operation, the methods of three wind field despun function is relatively uniform, furnace exit deviation is small, smoke flow in the bottom of the screen overtemperature is better.
(2) when cast waybill grinding machine, three times in the corners of the burner can only put a diagonal wind to form effective despun flow field, moreover diagonal three times the wind of the gas-solid two phase flow rate may be uneven and could lead to disorder, the flow field in the furnace exit deviation of smoke flow in increasing, lead to the bottom of the screen overtemperature, superheater reduction with warm water, screen after smoking temperature is reduced, limits the superheated steam temperature and reheat steam temperature increase.
(3) compared with the two mills, the coal powder concentration in the embers area in the single mill is lower than that in the two mills, and the flue gas temperature at the bottom of the screen is lower.
3. Governance scheme and effect
In order to solve the problem of low main and reheat steam temperature of low-load single set pulverized powder system, the following measures are proposed:
(1) to increase the air flow in the furnace can increase the smoke flow.
(2) adjust the left and right Angle of SOFA wind, and the middle and lower SOFA wind has been adjusted to be consistent with primary and secondary wind, both of which are arranged counterclockwise. The upper SOFA wind is opposite to primary and secondary wind. Cooperate with the main burner despun secondary air and other secondary air ratio of air to control the furnace exit flue gas temperature and smoke deviation, control panel metal temperature without deviation on both sides to minimize desuperheating water flow to improve the steam temperature.
(3) when the temperature of the above foundation is still low, the swing Angle of the main burner is adjusted upwards; Properly start part D layer burner; Reduce the recirculation rate of the mill and increase the air volume three times. The steam temperature can be increased by increasing the speed of layer C and layer D feeder as much as possible, and decreasing the speed of layer A or layer B feeder.