The technical transformation of multi-channel water jet extractor products in steam turbines is explained, the reasons and necessity of the technical transformation of multi-channel water jet extractors of 4 steam turbines in a factory are analyzed, and the technical treatment methods and methods of how to improve the safe, economical and reliable operation of the original high-efficiency and energy-saving multi-channel water jet extractors of 4 steam turbines are described, which provides methods and references for dealing with the same type of equipment.
A plant has two 300MW pure condensing steam turbines, steam turbine units, and the water jet aerator used to maintain the vacuum operation of the steam turbine is a high-efficiency and energy-saving improved multi-channel water jet aerator, and the working fluid used is the circulating water from the water tower (but it is affected by the summer temperature), and the effect is ideal, which provides a reliable guarantee for the safe and economical operation of the unit of a plant. The following describes the technical content of this high-efficiency and energy-saving multi-channel water jet extractor retrofit.
Technical parameters (before upgrading).
Name: High-efficiency and energy-saving multi-channel water jet aerator.
Model: DC6 32 0Type 35.
Channels: 6 channels.
Pumping capacity: 32kg h
Rated working water pressure: 035MPa (Allowable Range: 0.)33～0.39mpa）
Water jet pump model: SH 19A
Motor power: 75kw
Current: 139A
Speed: 1480 rpm.
Technical parameters (after technical transformation).
Name: High-efficiency and energy-saving improved multi-channel water jet aerator.
Model: DC4 (27 30) 0Type 35.
Channels: 4 channels.
Pumping capacity: 27 30kg h
Rated working water pressure: 035MPa (Allowable Range: 0.)33～0.39mpa）
Water jet pump model: SH 19A
Motor power: 75kw
Current: 98 102A (the current is the reduced working current after the transformation).
Speed: 1480 rpm.
1. Introduction to the structure and working principle of multi-channel water jet pump.
This kind of water jet aerator is a replacement product of the original long-diameter nozzle water ejector in recent years, and the power consumption of the long-diameter nozzle single-channel aspirator is reduced by 30 45 under the condition of the same air pumping volume, and the vacuum degree of the steam turbine is better than that of the single-channel water jet aerator 1 2. Its main technical points:
The original single-channel water column outer circle encapsulation mode was changed to a multi-channel water column outer circle enveloping mode, which increased the area of the outer circle of the water column in contact with air, that is, increased the amount of air enveloping; This is also the case for the rest of the quick utilization.
The working water pressure is increased, which increases the air pumping capacity and discharges the air carried by the water column smoothly.
Due to the increased operating water pressure, the vacuum value of the turbine is provided.
Due to the increased working water pressure and reduced jet flow, the power consumption of the jet pump unit is reduced and energy is saved.
2. The cause of the upgrade of the multi-channel water jet pump.
A factory in the main jet aerator of the steam turbine (its suction air capacity of 25kg h, for the long-diameter nozzle single-channel jet aerator, supporting the jet pump motor power of 95kw) next to the purchase and installation of a high-efficiency and energy-saving multi-channel water jet aerator (its suction air capacity of 32kg h, supporting the jet pump motor power of 75kw), to replace the main jet aerator, its purpose is for the vacuum value of the steam turbine and reduce power consumption. Another reason is that the original two 95kw vertical water jet pump sets often have large vibration and aging equipment, and they want to replace the original vertical water jet pump with a double-suction horizontal circulating water pump to improve the safety and reliability of the equipment.
At that time, the understanding of the working principle of the multi-channel water jet pump, the water pressure and the installation technical requirements for the transformation of the water jet pump nozzle was insufficient, as well as the limitations of the production site (the drainage outlet pipe of the multi-channel water jet pump was connected with the outlet pipe of the main water jet pump, and the water injection was discharged into the circulating ditch outside the machine room through two elbows and a pipeline more than ten meters long after the diffuser pipe of the air pump, that is, the drainage port was pierced into the circulating water at a depth of 2 meters), so that the air carried by the water in the drainage pipe could not be discharged. After several failed attempts, it has been left idle.
Yu proposed technical measures to improve the two sets of equipment. There are three main ways:
Using the principle of relatively small air resistance, the multi-channel water jet aerator is moved to the outdoors and directly placed in the upper part of the circulating water ditch, and the drainage pipe mouth of the water jet aerator is directly inserted into the water to a depth of 350 500mm, so as to facilitate the air discharge, and the air extraction pipe of the condenser is connected to the outside.
Lengthen the straight section of the inlet standpipe in front of the nozzle chamber of the jet aerator to 15 meters, try to ensure that the water entering the front of the nozzle chamber of the jet aerator is laminar, and ensure the verticality of the nozzle jet flow, and try not to deflect the angle.
The height of the multi-channel jet aerator from the water surface of the circulating ditch is increased, and the height of the falling water is increased to increase its ability to absorb air and the effect of residual velocity utilization. After the installation of the multi-channel water jet extractor according to the above three technical measures, it was put into operation and achieved a success, saving 300,000 kWh of electricity per year.
5. The steam turbine vacuum suddenly changed from 0086MPa reduced to 0066MPa, the exhaust temperature is increased from 45 to 67, and the load of the unit is reduced from 270MW to 220MW. After finding and analyzing the cause of the abnormal operation of the multi-channel water jet pump. Due to the high temperature of the circulating water during this period, it reached 37 38. According to the working principle of multi-channel water jet pump, when the working water temperature is high to a certain extent, the vaporization phenomenon will occur in its mixing chamber, and the pump will not work for a short time, and when the vacuum drops to a certain value, it will start to work again, during which the vacuum will drop sharply, and affect the vacuum and load output of the unit. Through comparison, it was found that the phenomenon did not occur at that time in the 4 steam turbines, what is the reason? Due to the limited space, the inlet pipe and outlet pipe section of the 5 steam turbine multi-channel water jet extractor are longer than those of the 4 steam turbine. Therefore, although the multi-channel water jet aerator and water jet pump model of the two engines are the same, the working pressure of the nozzle chamber of the water jet aerator of the 5 steam turbine is lower than that of the 4 steam turbine. In addition, the opening of the extraction valve of the shaft seal heater is relatively large, which is also the reason for the abnormal operation of the multi-channel water jet extractor (i.e., increasing the load of the water jet pump). At that time, the low frequency of the power grid caused the low outlet pressure of the jet pump, which was also one of the reasons for the abnormal operation of the jet pump. The above factors are the main reasons for this vacuum reduction.
3. Handling method.
After research and testing, it was found that the suction capacity of these two multi-channel (6-channel) water jet aerators used in a factory was excessive (i.e., 32kg h of suction air, that is, less than 667 pa minutes when the steam turbine tightness test was qualified, and the actual amount of non-condensable air produced was 236 25kg h), just because the working water pressure of the jet pump does not reach the design pressure value of its multi-channel jet aerator (0.33～0.39MPa), the actual pressure is only 0316mpa。
Using Bernoulli's principle and equations in fluid mechanics, the critical point (i.e., the optimal working point) of the vacuum value of the multi-channel water jet aerator under each working water pressure is obtained by blocking 1, 2 and 3 channels (i.e., blocking the nozzle, the main channel and the residual velocity utilization channel at the same time). The test data of various states are shown in the annex.
4. Processing technical scheme.
At the same time, the nozzles, main channels and residual velocity utilization channels of two channels of the multi-channel water jet aerator are blocked; Because its working fluid uses circulating water, there are more sundries in the water, and a filter screen device is installed between the water jet pump and the water jet pump; In order to prevent the drain pipe mouth of the water jet aerator from exposing the circulating water surface, the water surface water level monitoring ruler of the circulating water ditch is installed; The injection pump is operated as a mother pipe, and the backup is used as each other, simplifying the system and increasing the economy and reliability.
After changing the 6 channels to 4 channels, the motor current of the jet pump was reduced from 139A to 98 102A, which further improved the efficiency of the equipment and achieved remarkable energy saving and consumption reduction.
Increasing the working water pressure of the water jet pumper is to increase the water pressure value of the working circulating water of the water jet pumper, and there is a margin of saturation pressure of the corresponding water when the vaporization occurs after the temperature of the circulating water rises due to the increase in the temperature of the circulating water of the pumper, so as to avoid the possibility of vaporization of the water jet pump due to the increase in the temperature of the circulating water in summer.
The 5 steam turbine multi-channel water jet extractor also took advantage of the opportunity of minor repairs to carry out the same modification. The two water jet aerators have not been vaporized since they were in operation.