Generator stator cooling circulating water alkali-adding device
Pure water, with its high heat capacity, good non-conductivity and easy to obtain characteristics is widely used in large capacity generators, as the cooling medium of generators. The copper stator coil of the turbogenerator is cooled by hollow wire through water, which is the most traditional method used for a long time. In the power plant, the cooling water of the generator comes from the debrine or condensate water of the power plant. The cooling water can achieve a low conductivity, but its PH value can only barely reach about 7, most of the time less than 7, so that the generator stator copper hollow wire is always in the weak acid corrosion rate high area, has a certain degree of erosion to the system. With the gradual increase of the single generator capacity, especially at more than 600MW, due to the increase of the stator coil voltage to the ground and the increase of the coil current density, we gradually found that the stator coil waterway copper hollow wire scaling phenomenon is becoming more and more frequent, the corrosion of the cooling water on the copper wire is also more and more apparent, especially the water quality control is not good, This phenomenon is even more pronounced.
The water quality control of the fixed cold water system of the generator in the thermal power plant is related to the operation safety of the unit. Corrosion will produce precipitation to block the hollow rod of the generator and affect the normal operation of the generator, which is a common phenomenon in many domestic power plants. Once the hollow conductor of the stator coil of the generator is blocked due to corrosion, it is necessary to stop the machine for dredging, which also causes great economic losses.
At present, the vast majority of generators in China use copper hollow wire for water cooling, in the face of a large number of generator sets, how to find a solution to the cooling water on the copper wire corrosion method, not only can improve the operation efficiency of the generator, but also can save social wealth, help the development of the national economy.
Through inquiring information, I learned that large foreign generator companies increase the addition of NaOH in cooling water to control the PH value of water, so as to control the corrosion of cooling water on copper wire. However, in a closed water system, oxygen plasma will be dissolved in the water, the content of Cu+ will rise, and the conductivity of the cooling water will be affected.
Although before this, various methods have been used to control the PH value of cooling water in China, but each has its own shortcomings. On this basis, our company proposed the ultra-purification micro treatment technology of cooling water with conductivity control. In this technology, NaOH is added to control the PH value of cooling water in the large generator water system with copper wire as cooling pipe. Thus, the corrosion of copper wire by cooling water is controlled.
Basic principle: By querying the data, it is found that there is a corresponding relationship between conductivity and PH value, that is, we can control the PH value of cooling water by controlling the conductivity. At the same time, in order to prevent the influence of Cu+ on the PH value of cooling water, we add sodium hydroxide solution to the cooling water at the outlet of the ion exchanger, and the PH value of the cooling water is only affected by the concentration of sodium hydroxide solution. Therefore, it is convenient to control the injection rate of the alkali injection pump through the numerical change of the mixed liquid conductivity.
The most effective measure to solve the copper wire corrosion caused by cooling water quality is to inject dilute NaOH solution into the stator cooling water system and precisely control it according to the system requirements. The reliability and feasibility of similar technology have been fully confirmed by practical operation.
