Condenser water replenishment renovation

1、 Purpose:
Based on the thermal theory of "equivalent enthalpy drop method", the chemical makeup water of the original deaerator is supplemented into the condenser using the "mechanical rotary jet atomization nozzle" designed and manufactured by Huaneng Company.
2、 Feasibility analysis of water replenishment system renovation:
Taking the BII-25-3 high-temperature and high-pressure heating unit of a certain power plant as an example, the feasibility analysis of the equivalent enthalpy drop method for renovation is carried out:
The machine is equipped with two high-pressure heaters and three low-pressure heaters. The water replenishment system is a "deaerator type" water replenishment system. Chemical softened water is replenished to the low-pressure deaerator, which is then fed into the high-pressure deaerator by a relay pump. The inlet and outlet water for both low-pressure and high-pressure deaeration are operated through a main control system.
Under normal operating conditions, with a heating load of 40-70T/H and 0.8~1.3Mpa.
We conducted research and investigation, focusing on the rated and design parameters of the unit, and made corrections based on actual parameters. We applied the equivalent enthalpy drop method for analysis.

1. Feasibility analysis results of heat recovery:

For this unit, for every 1% increase in vacuum degree, 750 tons of coal can be saved in six months.
2. Through the analysis of "equivalent enthalpy drop", we know that the advantages of changing the makeup water from "deaerator type" to "condenser type" are as follows:
(1) The economic efficiency of heat recovery is significantly improved, and the comprehensive conversion of coal consumption can be reduced by 1-3g/KW. Chemical makeup water is added from the condenser, flows through the shaft seal cooler, and reaches the deaerator after the low-pressure heater. This process increases the amount of low-grade extraction steam and reduces the amount of high-grade extraction steam, increasing the work of this part of steam in the turbine. At the same time, it reduces the deviation of the heat absorption process of the makeup water, improves the heat exchange efficiency, and significantly improves the heat recovery effect. Deviation in the heat absorption process improves heat exchange efficiency and significantly enhances the heat recovery effect.
(2) The condenser performs vacuum deoxygenation on chemical makeup water, improving the deoxygenation capacity of the entire reheating system.
(3) Enhanced heat exchange, reduced exhaust steam temperature, improved unit vacuum, and had a significant effect when the makeup water temperature was lower than the exhaust steam temperature, which was both economical and beneficial for the unit to load (the conventional temperature of power plant makeup water is between 20-38 ℃).

3、 Determination of renovation plan and related parameters for the number of water replenishment systems:
In order to achieve better economic benefits, the following should be noted when formulating renovation plans:
1. When the amount of water added to the condenser is too large, the condenser water pump cannot extract the water from the condenser in a timely manner, which will lead to full water and affect the safe operation of the unit. Therefore, the amount of water added to the condenser cannot exceed the difference between the output of the condensate pump and the amount of condensate. To solve the above problems, another small condensate pump can also be installed.
2. The main water pump, shaft seal cooler, and low-pressure heater all have a rated flow rate. When the amount of water passing through exceeds their rated flow rate, the outlet water temperature decreases due to insufficient heating capacity, which weakens the heat recovery effect. Therefore, the amount of water added to the condenser cannot exceed the difference between the rated flow rate of the main water pump, shaft seal cooler, and low-pressure heater and the amount of water in the condenser.
Secondly, due to the limitation of deoxygenation capacity, the deoxygenation capacity of the determined unit and condenser water replenishment device is determined. If the amount of supplementary water is too large, it will not be able to reduce the oxygen content in the supplementary water below the required value, resulting in excessive oxygen content in the condensed water and corrosion of the condensed water pipeline.
Furthermore, during operation, the amount of supplementary water should be matched with the load carried by the unit.
3. Introduction to measures and related methods for improving the water replenishment system:
(1) As long as the make-up water is added to the condenser, good heat recovery efficiency can be obtained
(2) In order to achieve the goal of effectively absorbing exhaust heat in the condenser and improving the vacuum of the steam turbine, the method and position of adding water to the condenser must meet the requirements of thermal deoxygenation, so the method of adding water is crucial.
Huaneng Company has determined through evidence collection and analysis that the replenishment state of water should be atomized from the throat, preferably forming an "atomization zone". Through selection, the company's technical personnel independently designed and manufactured a "mechanical rotary jet atomizing nozzle".
The use of this nozzle enhances the heat exchange between the supplementary water and the exhaust steam, making it easy for the supplementary water to reach saturation, creating conditions for gas to overflow and diffuse from water droplets, while preventing the phenomenon of supplementary water flowing along the inner wall of the condenser.
In summary, the pipeline layout and position of the "water replenishment device" inside the condenser should be determined based on the size of the condenser throat, and then the optimal position of the nozzle should be determined. After determining the above two items, set the spray angle of the nozzle to a constant. At the same time, consideration should be given to preventing nozzle loosening and supporting the "water replenishment device" in the condenser.

4、 Ordering Notice:
1. Provide surplus capacity for condensate pumps;
2. Provide drawings of the condenser throat. 

 

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