During the operation of the generator, there is energy consumption. These energies become heat energy. If no cooling measures are taken, the temperature of the rotor, stator and other components will rise, resulting in aging of the insulation winding, output drop, and even burning of the motor. .
Regardless of the capacity of the generator, the stator windings are generally cooled by water, some of the rotor windings are cooled by water, and some are cooled by air. Water cooling is to make the winding copper coil hollow. During operation, high-purity water passes through the inside of the copper tube to bring out heat. The cooling water from the generator returns to the water tank, which is then pumped out through the cooler to cool, and then enters the generator. Inside, recycle.
Since the generator cooling water is used as a cooling medium in a high-voltage electric field, the water quality is high. Compared with ordinary cooling water, in addition to meeting the requirements of non-corrosion and non-fouling, it must also have good electrical insulation properties.
At present, the circulating water technology of power plants has become increasingly mature. The generator cooling water is generally not required to be sterilized or scale inhibited because of its small amount of water, high purity of water, and small tendency to scale. Therefore, it did not attract enough attention, and some factories even relaxed the control standards. However, if the water quality of the generator cooling water does not meet the requirements, long-term operation will have serious consequences.
According to statistics, nearly half of the accidents caused by generators in recent years are related to cooling water. Therefore, its processing technology is very demanding, and pay attention to some problems.
1 generator cooling water quality in the power plant, the generator cooling water supplement water is condensed or demineralized, its water quality is pure. Therefore, what needs to be controlled is the running water quality, and the indicators related to it have conductivity, pH value, and Cu2+ content.
1.1 Conductivity Conductivity reflects the amount of ions in the water. When the conductivity is too large, it will cause a large leakage current, which will cause the insulation water conduit to age, causing the generator to flash between phases and even destroy the equipment. As the capacity of the unit increases, the requirements for electrical conductivity are also increasing.
1.2 pH control The purpose of controlling the pH value of the internal cooling water is to prevent the corrosion of the copper wire. From the potential-pH balance diagram analysis, the stable pH range of copper is between 7 and 10, and the pH value of the industrial equipment is controlled at 7.6~ 9 is more suitable. In pure water, copper corrosion is generally uniform corrosion, and the probability of damage caused by corrosion perforation is small, but the corrosion product is blocked by the generator magnetic field in the system, and is deposited inside the hollow wire, which reduces the flow area and even causes blockage. The cooling effect is deteriorated, causing the temperature of the wire rod to rise, which affects the normal operation of the unit.
1.3 Status of internal cold water quality control In order to ensure that the generator has sufficient electrical insulation performance and small copper corrosion, the national and industry have established corresponding standards (see Table 1). The generator manufacturer puts forward higher requirements for water quality standards. For units with unit capacity of 200MW and above, the actual control conductivity is generally required to be no more than 2 2 within the cold water treatment method and precautions along with the ultra high pressure. The commissioning of the unit and the water quality requirements are also increasing. Some traditional methods of treatment are no longer sufficient and require constant exploration and innovation.
2.1 Condensed water as supplementary water for internal cooling water 2.1.1 Method: In the thermal power plant, adding trace ammonia to the feed water to adjust the pH value to achieve the purpose of anti-corrosion, the volatility of ammonia makes the condensed water pH: 2002 Table 1 The internal cold water quality standard of the generator Standard code standard name pH value remarks (82) Hydropower word No. 24 generator operation regulations Thermal power generator sets and steam power equipment water without corrosion inhibitor steam quality standards Add corrosion inhibitors Hydropower plant water vapor quality supervision guidelines are not slowed down Corrosion inhibitor addition agent corrosion power plant water vapor quality standard without corrosion inhibitor added corrosion inhibitor value of about 8.6, conductivity is 3. 0pS / cm. Inward cold water supplement condensate is equivalent to adding trace amounts of cold water Ammonia, in order to increase the pH value for anti-corrosion purposes.
This can be applied to control the internal cold water conductivity less than 5 groups, generally adopting continuous filling of condensed water and continuously draining or recovering. Because the condensate has a high pH value and a small oxygen content, it can be added to the internal cold water system to prevent C2 corrosion and prevent oxygen corrosion, and there is no need to worry about the dissolution of 2 and C2 in the recovery system.
The problem with this method is that if the backwater is completely drained, the demineralized water of about 10 tons or more will be lost every day, and the waste is large. If it is recycled to the condenser, the corrosion product copper of the hollow copper wire is brought into the boiler feed water system, causing copper scale in the thermal system.
The conductivity fluctuates greatly, and the pH value is increased by ammonia, which inevitably increases the conductivity of the water. For example, the amount of ammonia added to the feed water is not strict, and the fluctuation is large, which makes the conductivity difficult to control.
Although the internal cold water replenishing water has the above problems, it is a passive treatment method. However, this method is simple and convenient, and some power plants still use this method.
The demineralized water is used as the supplementary water for the internal cold water to ensure the low conductivity of the internal cold water. The internal cold water can be added with the demineralized water, but the system is not tight enough to make 2, C2, etc. enter the internal cold water, and the internal cold water becomes the slightly acidic water containing oxygen. It is strongly aggressive to hollow copper wires. For example, if a plant fills in the cold water, the conductivity is 1.2! S/cm, but the mass concentration of copper is 380 over standard.
In addition to salt water as supplementary water, in order to prevent copper corrosion, a copper corrosion inhibitor can be added to form a dense protective film on the metal surface, thereby achieving anti-corrosion purposes. Currently, the monomeric copper corrosion inhibitors are generally mercaptobenzothiazole (MBT) and benzotriazole (BTA).
MBT, its corrosion inhibition mechanism is to use the sulfhydryl hydrogen ion in the molecule to dissociate in water, and the negatively charged ruthenium atom and copper form a very strong complex protective film due to electrochemical adsorption.
The use of MBT, due to its poor water solubility, can be dissolved by NaOH, and the supernatant is used after clarification.
Since rubber will adsorb MBT in large quantities, all rubber parts in the system should be replaced with plastic or other parts before MBT treatment.
The inhibition mechanism of BTA is that the lone pair of electrons on the N atom in BTA is connected to copper by a coordination bond to form a protective film.
The use of BTA, BTA solubility is relatively large, can be formulated into a 1% ~ 3H aqueous solution directly added. When adding BTA, a small amount of alkaline agent such as NaOH, ethanol, etc. may be added to the cooling water to increase the pH to 7 or more, and the effect is better.
Although the conductivity of demineralized water is low, the conductivity will generally exceed 2 after adding a corrosion inhibitor! S/cm, if the system is not tight, with the increase of running time, the conductivity gradually increases, even more than 5! S / cm. Therefore, this method is only suitable for conductivity control less than 5! S/cm unit.
At the same time, when the conductivity is increased, in order to prevent current loss, drainage is required to reduce the conductivity, which is usually to drain the trench, and the loss of water and corrosion inhibitor increases.
The pre-film treatment of the internal cold water system requires a conductivity of less than 2! The S/cm unit, which is treated with copper corrosion inhibitor alone, does not meet the requirements. In order to solve this problem, in recent years, a combination of chemical cleaning and MBT pre-filming process has been developed to form a dense and strong protective film on the copper surface in a short period of time.
The specific method is as follows: after the generator is shut down, the internal cold water system is flushed until the conductivity is less than 2/cm. The pH value is 6.5~7.0, and the ammonia water with a mass fraction of 0. ~ 0.25H is added to the system, and the temperature is circulated at normal temperature. Wash the ammonia and drain it. Then pre-filming, adding a certain amount of MBT stock solution at a time, and then maintaining the MBT mass concentration of 40 mg / L, pH value of 9.5, a pre-filming time of about 150 h, and then cleaning the system. After the unit is put into operation, continue to add MBT to the internal cold water, the mass concentration control (down to page 20), when the argon is pretreated with ASBR, the operation is carried out at a medium temperature of 35 N, and the p (MLSS) value in the reactor is 22. 9 g /L, the operation cycle is taken for 24h (in which the water is 7.2h, the reaction is 14. the precipitation is 2.0h, the drainage is 0. 5h). When the influent CODcu concentration is 416v, the removal rate is 30Xv40X, and the effluent SS mass concentration is less than 150mg/L. The filamentous bacteria BMP in the middle of the granules shows that the limit ratio of COD. methanation in coking wastewater during anaerobic treatment is 41. Low concentration coking wastewater with inhibition and toxic effects on organisms will not disintegrate granular sludge in ASBR; the important process conditions for ASBR anaerobic pretreatment coking wastewater are: ratio of water infusion time to reaction time (!//! ), stirring strength, intermittent stirring method. The ratio of the influent time to the reaction time is taken as 0.5, the stirring intensity of the biogas is taken as 300 mL/min, and the intermittent stirring is taken as 100 s/45 min;
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