Economic and Reliability Analysis of Generator Set Variable Frequency Primary Fan

Datang Zhangjia Power Generation Plant (Zhangjiakou 075131, Hebei Province) Wang Haibin has a comprehensive experimental study to help users understand the frequency conversion performance of this fan and the problems in operation, and also analyze the investment return period of the inverter fan for the future. The power plant chooses the wind turbine to provide data basis.

Rate; speed.

26: B. Implementing “separate plant network and bidding online” puts higher requirements on the reliability and economy of power plant operation. From the economic point of view, the boiler side fan is the largest power consumption in the unit, and the power consumption accounts for about 30% of the total unit consumption. One of the main fans is the main auxiliary machine of the boiler, and it is also the main target of energy saving work. From the perspective of reliability, the boiler auxiliary machine failure caused the unit to reduce the load, and the boiler fire extinguishing and even forced shutdown occurred frequently, which seriously affected the reliability of the unit's power generation. Considering the reliability and economy of boiler auxiliary machines from these two aspects, it is of great significance for power generation enterprises and power grids to find and solve problems. To this end, Zhangjiakou Power Plant has adopted frequency conversion technology in the design of primary fans of Units 7 and 8 for the problems of low efficiency and high power consumption of some auxiliary machines. Surgery. During the installation and commissioning process, a number of cold and hot performance tests were carried out for the primary fan. After the production was completed, the economical comparison of the primary and secondary units of the No. 7 and No. 8 units was carried out in combination with the power plant test. Through the analysis of test data, the reliability and economy of the frequency conversion primary fan are discussed and studied.

1 Equipment overview and design parameters 1.1 Main equipment introduction The boilers of No.7 and No.8 units of Zhangjiakou Power Plant are domestic subcritical coal-fired steam drum boilers with a power output of 1025t/h. 6 sets of medium-speed coal mill direct-blowing pulverizing system and three Separate the warehouse and turn the air preheater. The primary air system is two double-suction centrifugal cold primary fan main pipe systems produced by Shanghai Blower Factory. The fan type is 2248AZ/977, the fan adjustment mode is the inlet baffle adjustment + speed adjustment, the blade is the rear curved plate shape, and the motor is rated. The power is 1 800kW, the rated speed is 1480r/mm. The designed full-pressure efficiency of the fan (ECR working condition): (1) The inlet baffle is adjusted by 62.2%; (2) The frequency converter is adjusted by 84.8%. The frequency conversion matched with the primary fan The device is six...! ! - The second generation AB-PowerFlex7000 inverter from Bradley Rockwell Automation. The sealed air system is a mother pipe system composed of two centrifugal sealed fans, and the inlet medium of the sealed fan is taken from the pressure cold air at the outlet of the primary fan.

The design parameters of primary fan are shown in Table 1. The operating parameters are shown in Table 2. Table 1 Primary fan design parameters Project parameters or description Fan type centrifugal type, double suction double support type fan inlet and outlet angle inlet 45°, outlet 135° (each Furnace left and right rotation 1) adjustment mode import baffle adjustment (full range) + speed adjustment (35% BMCR above conditions) blade type rear curved plate type blade outer diameter / mm motor model motor nameplate output / kW motor current / A motor Speed ​​/ (r 480 / 丨 489 (fan design / motor nameplate value) moment of inertia / (kg fan maximum torque / (N impeller circumferential speed / (m 2 main test content 2.1 fan cold test fan cold test mainly used to test The throttling and regulating characteristics under separate operating conditions, including some test conditions for different output forces of the fan at different speeds, and the parallel running test of the fan.

2.2 Fan hot state test The hot state test of the fan is carried out under the stable working condition of the boiler unit. The change of the fan output is mainly by adjusting the fan speed. When the fan current is allowed, the opening degree of the inlet baffle is generally 100%. The range of fan output change may be changed by boiler load. Table 2 Primary fan operation parameter Item Design condition Volume flow rate / (m3 mass flow / (kg.s -. Fan total pressure rise / Pa fan static pressure rise / Pa inlet pressure / Pa The inlet temperature / C inlet density / (kg full pressure efficiency (inlet baffle adjustment) /% full pressure efficiency (inverter regulation) /% fan shaft power / kW range to determine the adjustment characteristics of the fan in the working system The unit consumption of the fan is M. After the end of one working condition test, the boiler evaporation amount is changed and the next working condition test is performed.

2.3 Comparison of economical efficiency of wind turbines: Under different stable load conditions, compare the unit power consumption of primary fans of units 7 and 8. In order to ensure the comparability of the data in this test, the test is carried out under the same load, while maintaining the same pulverizing system and the outlet air pressure of the primary fan, adjusting the preheater gap at the automatic position, and setting the same gap setting value.

The inlet guide vane adjustment is to adjust the performance curve of the fan by adjusting the angle of the inlet guide vane to make the airflow entering the inlet of the fan impeller to adapt to the different working conditions of the unit. The centrifugal fan generally adopts the positive winding adjustment mode. It can be known from the theoretical indenter formula * that the flu is positive and the pressure head is lowered. That is to say, when the guide vane installation angle is adjusted to 90* (the vane is fully open), the impeller inlet airflow is not rotated Ulu = 0), and the fan output is the largest; when the vane installation angle is small, the impeller inlet airflow is positively convoluted. -lu>0>, the fan output is reduced.

During the adjustment of the inlet guide vane, the characteristics of the pipe network matched with the fan have also changed. At this time, the smaller the guide vane is closed, the greater the throttling loss, and the lower the operating efficiency of the fan. Large units must participate in the peaking of the power grid. Therefore, the boiler side fans often operate in a low load state, which deviates from the high efficiency area of ​​the fan design. In addition, the fan considers a certain margin during the selection process, resulting in a larger deviation. . This inefficient operation of the fan is uneconomical.

From the aerodynamic theory, it is most reasonable to change the adjustment method of the fan speed. When the fan is running, the working efficiency of the fan can still maintain a high level with the decrease of the rotational speed. At this time, the power of the fan is significantly reduced by the decrease of the flow M and the pressure. When the speed of the fan changes, the relationship between the flow rate of the fan, the total pressure, the power corpse and the rotational speed follows the formula of the F formula: from the above relationship, the power reduction is the largest, which is reduced to the third. In theory, this also shows that the variable speed adjustment mode has significant energy saving effect. Compared with the relationship between the full-pressure and the flow in the above-mentioned variable speed process, the change of the fan characteristic curve coincides with the change of the pipe network resistance characteristic curve during the variable speed adjustment process. This adjustment process is also the most A reasonable one. At the same time, the use of variable speed adjustment can effectively reduce the wear of the impeller, extend the service life of the impeller, reduce the noise of the fan, thereby reducing the failure rate of the fan and the motor, improving the reliability of the operation of the r fan, and reducing the maintenance cost of the fan. The variable speed adjustment provides favorable conditions for the automatic adjustment of the fan, especially for the frequency conversion speed regulation, the adjustment range is larger, the adjustment process is more stable and smooth, and the adjustment quality is excellent, so that the combustion stability of the boiler is achieved during the adjustment process. Positive action, which improves the reliability of the entire unit. In addition, the use of frequency converter adjustment can achieve soft start, with little impact on the motor and the grid.

The starting speed of the fan is 180r/min and the starting current is 28A. The impact on the grid is small at startup.

When the fan starts, the noise is reduced, the inlet baffle is fully open, the inlet throttling loss is reduced, and the on-site working environment is significantly improved.

1 Test results Table 3 1030r/min speed fan test results Item Test number Ding inlet baffle opening degree Inverter opening degree x/% primary fan current / / A fan static pressure rise / Jsf / Pa fan inlet flow Qi / (m3 fan Mass flow Mi / (kg motor input power Pf: / kW fan inlet section wind speed wi / (ms - fan outlet section wind speed w / (ms-1) medium average density. V (kg.m3) fan shaft power corpse sI> AW fan effective power PeAW fan equipment efficiency, E /% fan full pressure efficiency f /% Table 4 1J75r / min speed fan test results test number of shell H H into U baffle opening 3> /% inverter opening W primary fan Current / / A fan full pi / Pa fan static pressure rise / M / Pa fan inlet flow MQiAn motor input power corpse F: / kW fan inlet section wind speed wi / (m fan outlet section wind speed. S-4 medium average density pi. 2/(kg fan shaft power eight h/kW fan effective power / VkW fan equipment efficiency / fan full pressure efficiency TF /% table 5 1319r / min speed fan test results test number; shellfish inlet baffle opening y /% 'Inverter opening degree 1%% primary fan current / / A fan full Pi / Pa fan static pressure rise M / Pa fan inlet flow Q" (m3 fan mass flow MM1 / (kg motor input power PeAW fan inlet section wind speed Wl / (ms - 1) fan out U section wind speed W2 / (nS-1) medium average density - 3) fan shaft power Pth / kW fan effective power Pe / kW fan Equipment efficiency 咋 /% fan full pressure efficiency 7, .f /% table 61389r / min speed fan test results project test number 1-4 inlet baffle opening jy /% inverter opening fan current / / A fan full pressure Autai / Pa fan static pressure rise Af / Pa fan inlet flow *S-1) fan mass flow MJ (kg motor input power Z / kW fan into 14 section wind speed wi / (m fan outlet section wind speed * s" medium average density pi.s /tkg.m-3) Fan shaft power corpse sh/kW fan effective power / VkW fan equipment efficiency 胙 /% fan full pressure efficiency table 7 maintains 11kPa or more wind pressure condition fan test results item test number D into U-baffle open Degree.y/% inverter sweat x/% - secondary fan current / / A fan static pressure rise / * / Pa fan into turbulence * Sl) motor input power corpse E / kW fan into U section wind speed / (m fan Export section wind speed *sM medium average density! K (kg f4 machine shaft power hh / kW fan effective power P "kW K machine full pressure efficiency 7uf /% table 81 first fan Hot working condition fan test result item 臼 test number n n baffle opening % inverter degree. W times fan current / / A Ml machine full pressure fan static pressure rise hf / Pa fan quality child flow A / i motor input power //kW K machine into U section wind speed wi/(m*s-1) fan outlet section wind speed / medium f average density Sichuan. :; / (kg) 4 shaft power / \hZkW fan effective power / VkW pneumatic equipment efficiency /% fan full pressure efficiency table 92 primary fan hot state wind turbine test results test number inlet baffle opening V% Inverter degree i/% primary fan current / / A fan full pressure office mal / Pa fan static pressure rise psf / Pa fan import flow Qi / (m3 * s-1) fan mass flow A / i / (kg * s - 1) Motor input power corpse E/kW fan inlet section wind speed *s-0 fan outlet section wind speed u2 / (m * s -) medium average density Pu / Ckg * m-3) fan shaft power / WkW fan effective power h / kW fan equipment efficiency / fan full pressure efficiency, t, F /% item table 10 7 and 8 units primary fan power consumption and unit unit consumption comparison data table project parameters working conditions 1 working conditions 2 working conditions 3 working conditions 4 units Load / MW main steam flow Sichuan *h-1) No. 7 unit No. 1 primary fan parameters......

Current / A outlet primary air pressure / kPa input power 4W unit load / MW main steam flow 八 1 7 unit No. 2 primary fan parameters.

Current / A outlet primary air pressure / kPa input power / kW Unit 7 primary fan consumption total power / kW Unit 7 primary fan unit consumption AkW unit load / MW main steam flow fi / (t total fuel volume / (t 8 Unit No. 1 primary fan parameter current / A fan speed / (r outlet... secondary air E / kPa input power, / kW unit load / MW main steam flow eight 1 total fuel amount At.h No. 8 unit No. 2 primary fan parameter current /A fan speed / (r outlet primary air l / kPa input power / kW 8 unit primary fan consumption total power / kW 8 unit primary fan unit consumption AkW 7 and 8 unit primary fan consumption total power difference / kW 7 The difference between the unit consumption of the primary unit of the No. 8 unit AkW efficiency and the specific transmission power C1) Under the cold condition, the test data and the plotted curve are basically consistent with the data provided by the manufacturer, and the fan is under the adjustment of the inverter. The total pressure efficiency is relatively high, even at low loads, it is basically above 70%.

From the analysis of the graph, the fan maintains the outlet wind pressure kPa (this is also the area where the unit is frequently operated). The fan efficiency is higher at different speeds, above 80.85%, which means that the variable speed adjustment can ensure the fan maintenance. The range of high efficiency operation is increased.

Above the speed) is the area required for the operation of the unit. The W machine has an optimal running air volume at different speeds. Due to the large adjustment range of the variable speed and smooth adjustment, the speed is adjusted during normal operation, and the fan meets the operation requirements of the unit. At the same time, basically the best way to run.

1 The relationship between the air volume and efficiency of the U-speed and the transmission power is maintained at 1310r/mm. The relationship between the efficiency of the wind domain and the transmission power 囝2 maintains the relationship between the wind M and the efficiency and transmission work under the condition of 1030r/mm. The total pressure efficiency of the fan is above 80% (this includes conditions at low load), which means that the fan operates more efficiently in the actual operation of the plant and is stable. As (3) analyzed, the fan maintains 1389 rpm. When the relationship between the wind M and the efficiency and the transmission work is maintained at 70% of the rated speed, the inverter has good regulation and is active in the combustion stability of the boiler. effect. If the coal type does not change much, the fan can fully meet the unit operation requirements below 1 300"mm, which makes the fan operation reliability improve, the noise is reduced, and the maintenance period can be extended accordingly, thus saving one heat mode. The relationship between the load of the primary fan unit and the fan speed, the outlet wind pressure, and the fan efficiency. The unit load/MW thermal state No. 2 primary fan unit load and the fan speed, outlet wind pressure, fan efficiency relationship curve maintenance costs.

Unit 7 and 8 unit consumption comparison curve 4.2 Economic analysis and evaluation of the inverter fan operation C1) Since the models of the primary fans of the 7th and 8th units are the same, only the 7th machine is not equipped with the frequency conversion, so the 7 and 8 are passed. Unit comparison is convincing. Both of them are input into C2 according to the input power, and the data from the table 10 and the 9-curve are analyzed. As the load increases, the power consumption of the fan increases. Comparison of 2 units: Under the two working conditions of 150MW and 200MW, the power of the primary fan of No. 7 is 2.0 and 1.693 times of No. 8 machine; under the condition of 250MW and 300MW, the power of No. 7 primary fan is 8 1. 388 and 1.481 times of the number of machines, if the effect of the load ratio is not considered, only the arithmetic average is used, then the average power of the primary fan of the No. 7 machine is 892.75 kW more than that of the No. 8 machine, and the average power of the primary fan consumed by the No. 7 machine is 1. 64 times of the 8th machine. It can be seen that the energy saving effect of the primary fan frequency conversion of Unit 8 is very significant.

Unit load/m Unit 7 and No. 8 unit primary fan power consumption comparison curve (3) With the increase of load, the fan unit consumption shows a downward trend. 2 units are compared, 150MW, 200MW, 250MW, 300MW under four working conditions. The fan consumption is 1855, 1.566, 1.346 and 1.39 times of the No. 8 machine. According to the arithmetic average of different loads, the single fan of the No. 7 machine has more than the No. 8 machine (15. 9+11.1+7+5.5)/4= 9.875 kW * h / t (coal). It can be seen that the energy saving effect of the No. 8 unit variable frequency primary fan is quite obvious.

(4) Analyze the economy from the reliability of variable speed regulation. When the low speed of the fan is started to lower than the rated speed, the failure rate of the fan can be reduced, the operating cycle and service life of the fan can be extended, and the maintenance cost and the number of times can be reduced. Improve the economics of fan operation.

5 Conclusions Through the experimental research on the variable frequency primary fan of Zhangjiakou Power Plant. Based on the above analysis, the following conclusions can be drawn: U) Under the regulation of frequency conversion, the reliability of starting and running is increased, the noise during operation is reduced, the operating conditions are stable, and the operating efficiency is still good.

(2) The economy and energy saving effect of the fan operation through variable speed adjustment are significantly improved. Especially in the case of low load conditions of the unit.

3.4 Renovation of the original blasting system of the pulverizing system The blasting door of the No. 17 pulverizing system was tested in the No. 1 furnace overhaul period in 2002. The original explosion-proof door for the coal casing body explosion-proof door and the coal mill separator was installed. It was unable to open the seat in the explosion of the second coal feeder and the secondary coal inlet box explosion. It is a milling system. A huge hidden danger of safe operation. The PLD explosion-proof door series is made by Shanxi Electric Power Design Institute based on American technology. If the effect is good, it will be widely promoted. The explosion-proof door design uses light high-temperature resistant materials, which can realize the functions of adjustable starting pressure, explosion pilot opening, automatic quick reset, prevention of secondary deflagration and automatic state monitoring. A total of 8 explosion-proof doors are installed in the No. 7 milling system: 2 inlets for the primary air chamber, 2 for the top of the separator, 1 for the distributor inlet manifold, and 1 for the lower part of the coal-filled tube locker. station. Judging from the explosion of the previous milling system, the most serious damage is the coal feeder, which is related to the accumulation of a large amount of combustible gas in the falling coal pipe. Therefore, the focus of the explosion-proof door of the powder-making system is sufficient to supply the coal casing body and the primary air inlet box of the coal mill.

3.5 Plan to cancel the air locker or change the better performance of the air locker The current flap type air locker can no longer adapt to the safe operation of Shenhua coal's milling system. This program is under investigation.

3.6 Strengthening the maintenance of the milling system (1) Ensure that the charcoal and flammable products are not left after repair, the inner wall of the ML powder tube is smooth, the coal-breaking signal of the coal feeder is normal, the gas locker is turned over the mountain, the damper flap is flexible, and the fire is fired. The steam can be put into normal operation to prevent the explosion of the milling system under the condition of coal breakage. ) Strengthen the maintenance and repair of fuel absorbers and coal crushers, and eliminate flammable and explosive materials and three pieces into the mill.

(Acceptance period): Chuan 2 (mi) m (on page 21) (3) When the fan is adjusted in variable speed, the automatic adjustment performance is stable, smooth, and the quality is excellent, which provides r for the automatic input of the unit. It is more suitable for the high automation requirements of modern units.

As the peak-to-valley difference of the power grid is widened, the task M of the large-scale unit participating in the peak-shaving is increased, which increases the time for the large-unit operation of low-load operation. Under the characteristics of such a power grid, the variable frequency speed control technology provides a safe and economical operation mode for the main auxiliary equipment of the power plant. At present, the use of variable frequency speed control technology in the external power plant is relatively extensive. Long-term operation practice shows that the frequency conversion speed regulation has considerable economic benefits and good reliability. It is recommended that power plants with conditional conditions consider the use of variable frequency speed control technology.

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