If the steam leakage interface of high pressure cylinder of steam turbine leaks to the steam delivery place of shaft seal cooler, will it affect the load?

(1) The exhaust parameters of the high-pressure cylinder are high. The actual exhaust parameters of the high-pressure cylinder are 4.0 1 MPa/343.4℃, the exhaust pressure and temperature are 0.44 MPa and 26.4℃ higher than the design value respectively, and the efficiency of the high-pressure cylinder is 79.08%, which is 7.64% lower than the design value. (2) The efficiency of the regulating stage is low. The work share of the regulating stage accounts for about 18% of the high-pressure cylinder power, and the efficiency of the regulating stage is lower than the design value by 15.04%, which seriously affects the efficiency of the high-pressure cylinder and the output of the unit. (3) The actual efficiency of the intermediate pressure cylinder is low. The nominal efficiency of the intermediate pressure cylinder is 92.4%, and the actual efficiency is 89.7%, which is 2.5% lower than the design value. (4) The steam leakage rate from the interlayer of HP cylinder to the inlet of HP cylinder 1 stage moving blade is high. The designed steam leakage is 10.37t/h, accounting for 1.39% of the reheat steam flow. The actual steam leakage is 42.60t/h, and the steam leakage rate is 3.77%. (5) The temperature difference between the upper and lower cylinders of HP and IP cylinders is large. The temperature of the cooling steam leaked from the interlayer of HP cylinder of No.3 steam turbine to the IP cylinder is basically the same as the exhaust temperature of HP cylinder, and the steam flow direction does not conform to the design, resulting in two hazards: ① excessive cooling in the high-temperature section of the IP rotor, large temperature difference between the inside and outside of the rotor, increased additional temperature stress at the stress concentration part of the rotor surface structure, increased rotor fatigue life loss and surface cracks at the stress concentration part of the structure; (2) During normal operation, the exhaust steam flows back from the upper half of the high-pressure cylinder, resulting in an increase in the temperature difference between the upper and lower cylinders in the high-temperature section at the front end of the high-pressure inner and outer cylinders, which leads to cylinder deformation, easy fracture or relaxation of the cylinder bolts, serious steam leakage at the joint surface of the cylinder, and easy wear of the radial steam seal on the flow passage of the cylinder, reducing the efficiency of the cylinder. ? (6) The regeneration effect is poor. There is a big difference between the upper ends of this machine 1 and No.2 high-pressure heater. Although the feed water temperature has reached the design value, it has not reached the level it should have under the extraction parameters. The total amount of desuperheating water of boiler superheater and reheater reaches 73t/h, and this part of feed water does not pass through high-pressure heater, which reduces the regenerative effect. The drainage of No.7 low-pressure heater can't normally flow to No.8 low-pressure heater, but directly flows into condenser, which not only increases the heat load of condenser and causes the pressure of condenser to rise, but also increases the extraction capacity of No.8 low-pressure heater, which affects the output and economy of the unit. ?

Measures to improve the thermal system of Unit 3?

2. 1 Main contents of optimization and improvement

2. 1. 1 turbine body part

(1) Adjustment of steam quantity in interlayer of HP and HP cylinders. Main measures: the steam stop ring of the middle and high pressure cylinder is changed to "0" gap, and 1 movable steam seal is added; Cancel the medium pressure cooling steam pipeline. At this position, two Dg 100 pipelines are led out from the upper and lower parts of the high-pressure outer cylinder, and each pipeline is provided with a 1 electric valve to discharge the interlayer steam to the front of the secondary extraction check valve, and the temperature difference between the upper and lower cylinders is controlled by adjusting the electric valve; Two temperature measuring points and 1 pressure measuring point were added to the pipeline. (2) Modification of steam seal of regulating stage. The seal at the top and root of rotor blade was changed from single-tooth embedded seal to double-tooth telescopic seal, and the radial clearance was adjusted from 2.5mm to 1mm to reduce steam leakage. ?

(3) Improvement of the seal of the medium pressure balance piston. Add a flat tooth movable seal on the steam jacket to reduce steam leakage. (4) Low pressure 1 inner cylinder joint surface eliminates steam leakage. Change the inner cylinder 12 bolt into hot tightening to improve the tightening force; Eliminate the deformation of the joint surface of No.5 and No.6 steam extraction ports, and solve the problem of high extraction temperature of No.5 and No.6 steam due to the leakage of the joint surface during operation. ?

(5) Improvement of balance piston seal. The traditional steam seals of middle and high pressure balance piston and end inner shaft seal, including three high pressure exhaust balance rings, five high pressure steam inlet balance rings and two medium pressure steam inlet balance rings, and the 1 * * 12 steam seals at both ends of the middle and high pressure outer cylinder were changed into blade steam seals to reduce steam leakage.

(6) Increase temperature measuring points. In order to effectively monitor the parts of the cylinder prone to large temperature difference, the upper cylinder temperature measuring point on the high-pressure inner cylinder adjusting section is added to form a pair of upper and lower cylinder temperature monitoring points with the original lower cylinder measuring point in this section, and a pair of upper and lower wall temperature measuring points are added in the high-temperature section in front of the high-pressure outer cylinder.

(7) Replacement of high pressure ring. The width of the joint surface is appropriately widened, the bolts are rearranged and the diameter is thickened to reduce the steam leakage of the joint surface. In addition, it also includes adjusting the radial gap of high and medium pressure flow reasonably; Replace1~1class gland with a gap of 0.70mm；; ; The tip of the high-pressure retaining ring is scraped to 0.70 mm; With1~1/movable gland; Replace damaged gland blocks, springs and related parts. ?

2. 1.2 hydrophobic system part?

(1) Cancel the high-pressure cylinder exhaust ventilation valve used to start the medium-pressure cylinder. Cancel the main steam supply of steam source pipeline of small steam turbine. ?

(2) the main valve, tone steam leakage to the front of the medium pressure main steam. ?

(3) The secondary extraction is connected to the exhaust non-return valve of the high pressure cylinder. ?

(4) Cancel the steam source pipeline of the auxiliary main steam pipe of the fourth stage extraction steam supply, and change the electric door of the fourth stage extraction steam to the deaerator inlet from fully open and fully closed to inching control. ?

(5) Cancel the condensate collecting box and add 1 multistage water seal for shaft drainage and discharge it into the condenser. ?

(6) Replace the shaft seal heater and the inlet of the shaft seal steam return pipe of the small machine. Shaft seal overflow increased 1 to No.7 low-pressure heater. After the condensate throttle hole at the inlet of the original shaft seal heater, it will be cooled to the steam supply pipeline of the main shaft seal and then connected to the shaft throttle hole. ? (7) Improve the auxiliary steam drain system, cancel the auxiliary steam drain tank, and drain the original water into the condenser. ?

(8) Cancel the start-up circulating pump and system of deaerator, and increase the heating steam source at the bottom of deaerator water tank. ?

(9) Rearrange the normal drain pipes of No.7 to No.8 low-pressure heaters to reduce the system resistance, and replace and rearrange the installation direction of valves to realize normal drain. ?

(10) Technical transformation was carried out on the condensate pump to reduce the lift and power consumption of the condensate pump. ?

(1 1) The left and right drainage before and after the main steam tee was changed from the original drainage flash tank to the emergency drainage flash tank of the high-pressure heater. In order to prevent the valve core from melting due to the leakage of the trap, a manual stop valve was installed behind the high temperature and high pressure hydrophobic pneumatic valve. Under normal working conditions, the manual cut-off valve should be fully closed.

(12) For the pipeline or equipment in hot standby state during operation, the pipeline before the entrance of steam equipment shall be heated. The warm pipe adopts combined automatic trap, and the trap adopts DFS inverted floating cup automatic trap. 2.2 the implementation of thermal system improvement

The performance improvement of No.3 steam turbine body and drainage system in Shi Heng Power Plant is provided by Guodian Thermal Power Research Institute with improvement scheme and technical services; The outsourcing project of ontology system and auxiliary equipment transformation is undertaken and completed by Shanghai Steam Turbine Works. The improvement of drainage system shall be undertaken by the power plant according to the specific scheme; The traditional shaft seal and end inner shaft seal of high and medium pressure balance piston were transformed from Harbin Bladen shaft seal technology application Co., Ltd. to Bladen shaft seal?

Effect of 3 3 units after improvement

In order to measure the technical performance of steam turbine units and evaluate the transformation effect of steam turbine units, the National Electric Power Thermal Research Institute, Shandong Electric Power Science Experimental Research Institute and Shi Heng Power Plant conducted thermal tests on the technical performance of steam turbine units before and after transformation. The test shall be carried out in accordance with the relevant provisions of ASME PTC 6- 1996, and the test results are shown in table 1. ?

Calculate the heat consumption rate of steam turbine unit according to the test results, and modify the parameters according to the data provided by the manufacturer. The coal consumption rate of power generation is calculated according to the boiler efficiency of 92% and the pipeline efficiency of 99%. Based on the 5-valve fully open (5VWO) evaluation condition, the effects before and after improvement are compared under the same initial and final parameters. The comprehensive effects are as follows: the heat consumption rate before transformation is 8 533.85 kJ/kWh, and that after transformation is? 8 200.4 kJ/kWh, and the heat consumption rate decreased by 333.45 kJ/kWh；; ; The coal consumption rate of power generation was 3 19.7g/kWh before transformation, 307.2 g/kWh after transformation, and the coal consumption rate of power generation was reduced to 3.9 12.5g/kWh, with remarkable economic and social benefits. Table 1 Comparison of Thermal Test Results before and after Improvement (5WO Assessment Condition) Item Active Power of Generator /MW302.72302.87 Unknown Leakage/T h-14.92/.17 Unknown Leakage Rate/%0.4557 kJ before Improvement. 8533.858200.4 High pressure cylinder efficiency /%79T h- 142.9620.78 coal consumption rate of power generation/g (kwh)-1319.7307.243 Technical analysis after improvement.

4. 1 regulating stage efficiency?

Under rated design conditions, the in-cylinder power of domestic and imported 300 MW steam turbines is 89.5 MW, accounting for 29% of the total power. The pressure difference of the regulating stage is 4.28 MPa, the efficiency is about 7 1%, and the internal power is 18.6 MW, accounting for 20.8% of the power of the high pressure cylinder. In actual operation, the efficiency of regulating stage is 45% ~ 60%, and the low efficiency of regulating stage affects the power (2 ~ 4) MW. After improvement, the efficiency of the regulating stage is 69. 17% at 5VWO, which is close to the design value and higher than that before improvement by 1 1.7%. The deviation between the regulating stage temperature and the design value is reduced from 1 1.35℃ to 7.9℃. This shows that the steam leakage is greatly reduced and the efficiency of the regulating stage is obviously improved after the improvement of the steam seal of the regulating stage. 4.2 High pressure cylinder efficiency

Under the rated design conditions, the efficiency of the high pressure cylinder of this type of steam turbine is about 87%. The actual operation of the unit is generally about 80%, the exhaust temperature of the high pressure cylinder is high, and the reheat desuperheating water quantity is large. ?

In the test before improvement, because there is no designed steam temperature measuring point on the exhaust pipe of the high pressure cylinder, the exhaust temperature of the high pressure cylinder can only be measured through the water inlet prevention point on the horizontal pipe. Because the depth of the measuring point inserted into the pipeline is too shallow, the measured temperature is low, and the efficiency of calculating the high pressure cylinder is high. In order to compare the changes of exhaust temperature and efficiency of high pressure cylinder before and after improvement, the test is still measured at the same position after improvement. The results show that the actual exhaust temperature of high-pressure cylinder decreases 13.4℃ on average, and the desuperheating water of reheater decreases 10t/h on average. The efficiency of high-pressure cylinder is 84%, which is actually improved by 4.8%. ? In view of the imperfect design of exhaust temperature measuring point of high pressure cylinder, which can not truly reflect the real level of exhaust temperature of high pressure cylinder, a new steam temperature measuring point was installed on the exhaust riser of high pressure cylinder during overhaul. The measurement results show that the water inlet prevention temperature measuring point is about 2.5℃ lower than the newly added measuring point. The efficiency of high pressure cylinder is 82.4%. ?

According to the structural characteristics of the high-pressure cylinder of the unit, the exhaust temperature of the newly installed high-pressure cylinder truly reflects the state of the high-pressure cylinder, which can be used as an important basis for the state maintenance of the unit in the future. Table 2 shows the changes of exhaust temperature and efficiency of high pressure cylinder. Table 2 Changes of exhaust temperature and efficiency of high-pressure cylinder Project name: Design value before improvement and rated working condition after improvement 5WO15WO25WO15WO2 main steam pressure/MPa16.7016.4816.62916.52.

The steam turbine is of high and medium pressure cylinder structure. The high and medium pressure cylinders are separated by the steam seal of the steam inlet balance plate of the medium pressure cylinder, and the balance plate has two sets of steam seals. The mixed steam leaked into the interlayer between the high-pressure inner cylinder and the outer cylinder from the shaft seal of the rear balance plate of the high-pressure inner cylinder regulating stage and six steam guide pipes, and part of it passed through the steam seal of the steam inlet balance plate of the middle-pressure cylinder and leaked to the rear of the first-stage stator blade of the middle-pressure cylinder. Under rated working conditions, the designed steam leakage is 10.4t/h, which is 1.4% of the reheat steam flow. Similar unit tests show that the steam leakage rate of this part is 4% ~ 6%. This part of the steam is mixed with the steam at the outlet of the first stage of the medium-pressure stator blades, which reduces the temperature and enthalpy of the steam entering the medium-pressure stage group and affects the economy of the unit. Because the temperature of mixed steam cannot be measured, the efficiency of intermediate pressure cylinder is calculated with the measured parameters in front of the intermediate pressure main steam valve as the initial parameters, which leads to the illusion of high efficiency of intermediate pressure cylinder. The greater the steam leakage, the higher the efficiency of the measured intermediate pressure cylinder. This is also the reason why the efficiency of the intermediate pressure cylinder is low after overhaul, but it is improved with the increase of running time. Therefore, we define the efficiency of the intermediate pressure cylinder measured by experiments as the nominal efficiency of the intermediate pressure cylinder. ?

4.4 About the use effect of Bladen gland.

Aiming at the common problems of imported 300MW steam turbine, according to the particularity of steam turbine structure, blade sealing technology is adopted as one of the important technical improvement measures to make up for the deficiency of steam turbine structure design. Compared with the traditional seal, the Bladen seal in the United States has two obvious characteristics: ① the clearance between the seal teeth and the rotor can be adjusted, which is the largest when the unit is started and the smallest during normal operation; ② Steam leakage is reduced. According to the test and actual operation effect analysis of the improved unit, the steam seal works normally and achieves the expected effect. Taking 5VWO working condition as an example, the following effects are directly related to the adoption of Bladen gland seal technology in the United States. ?

Compared with the test results of (1) unit before and after improvement, the efficiency of the improved high-pressure cylinder has increased by 3.2% on average. ? (2) In order to determine the improvement effect and its influence on the efficiency of the intermediate pressure cylinder, the steam leakage test of the inlet steam balance plate of the intermediate pressure cylinder before and after improvement was carried out under the condition of 5VWO. The steam leakage rate of the steam inlet balance plate decreased from 5. 16% to 2.60%, and the steam leakage rate decreased from 42.96 t/h to 20.78 t/h, which decreased by 5 1.6%. ? (3) The problems of large temperature difference between high and medium pressure cylinders and rapid internal efficiency decline have been improved. ?

(Under the working condition of 5WO, the exhaust temperature of HP cylinder is reduced by 65438 03.4℃ on average, and the desuperheating water of reheater is reduced by 65438 00t/h on average. ? (5) Under the same working conditions and parameters, the main steam flow decreases, while the regulating stage pressure increases, indicating that the steam entering the high-pressure cylinder to do work increases, and the steam leakage of the front axle of the high-pressure cylinder decreases. ?

Based on the above analysis and calculation, the direct effect of Bladen sealing can reduce the coal consumption rate of power generation by about 3 g/kWh. 4.5 Technical transformation of condensate pump

The energy-saving and consumption-reducing technical transformation was carried out for the condensate pump of 3 A unit. The last stage impeller, the positioning key for fixing the last stage impeller and the guide shell of the last stage impeller were removed, and a nipple with flanges on both sides was installed here. After accurate calculation, after the improvement of the condensate pump with the same flow rate, the lift is reduced by about 40 m, the shaft power is reduced by about 100 kW, and the pump efficiency is basically unchanged. The output of condensate pump can completely meet the operation requirements of the unit. The shaft power and motor power of condensate pump are greatly reduced, and the annual auxiliary power is saved by 960,000 kWh. The removed last stage impeller and guide shell can be used as spare parts; After removing the last stage impeller and guide shell, materials are saved, maintenance costs are reduced and spare parts inventory is reduced; At the same time, the investment is small, the effect is quick, the labor cost is low, and the energy saving effect is remarkable. ?

4.6 Temperature difference between HP and IP cylinders

Due to the particularity of the structure of high-pressure cylinder and high-pressure cylinder, the arrangement and connection mode of drain pipes, the problem of large negative temperature difference between the upper and lower cylinders of high-pressure cylinder is common in normal operation of this type of steam turbine. According to the measurement of the same type of unit, the maximum negative temperature difference can reach 70℃-80℃, and the temperature difference of about 70℃ is easy to appear in the middle of the intermediate pressure cylinder during the start-up and stop of the unit. The large temperature difference between high and medium pressure cylinders during normal operation and start-stop of steam turbine is one of the main problems of the unit, and it is also the main reason for cylinder deformation, static and dynamic rubbing, seal wear, fracture or relaxation of inner cylinder bolts, steam leakage at the joint surface, low efficiency of high pressure cylinder and rapid decrease of speed. Especially in the cross-section design of the high-pressure cylinder with the largest temperature difference, there is no cylinder wall temperature measuring point, so the operator can't know the degree of cylinder temperature difference. ?

In view of the existing problems, the steam flow rate in the interlayer of high-pressure cylinder was improved, and the wall temperature measuring point was added in the section with the largest temperature difference of high-pressure cylinder, which changed the hydrophobicity of medium-pressure cylinder and significantly reduced the temperature difference of cylinder. See Table 3 for the temperature difference data of HP and HP cylinders after overhaul of the test measurement unit (at this time, the power of the unit is 302MW).