Application of the hottest condensate polishing sy

2022-08-23
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Application of condensate polishing system in phase II of Ling'ao Nuclear Power Station

Abstract: This paper expounds the characteristics of 2X1000MW condensate polishing system and equipment in phase II of Shenzhen Ling'ao nuclear power station, as well as the practical application of key technologies such as high tower separation method

key words: condensate; Finishing system

the resin separation nuclear power unit is equipped with a full flow condensate polishing system, which is mainly characterized by large water volume, high influent DH value, strict water quality requirements, high safety factor and high stability requirements. The function of condensate polishing system (hereinafter referred to as ATE system) is to remove suspended impurities and ionic impurities in condensate, ensure that the secondary circuit water quality meets the requirements and WANO chemical index requirements, so as to reduce the corrosion and scaling of thermal system equipment and prolong the service life of equipment. When the unit is started, it can greatly reduce the system flushing time, make the unit put into operation as soon as possible and save the amount of demineralized water; When a certain range of seawater leakage occurs in the condenser, prevent the impurities in the seawater from entering the thermal system of the conventional island, and give operators more time to take corresponding measures. Therefore, the research on the application of condensate polishing system in nuclear power plants has a very broad prospect and far-reaching significance

1 overview

nuclear power plants are usually composed of primary and secondary circuit systems. The core of the nuclear power plant is the reactor. During the steam water circulation process of the nuclear power plant, because the nuclear reactor has strong radioactivity, the coolant flowing through the reactor has certain radioactivity, so the coolant flowing from the reactor cannot leak into the secondary side water of the steam generator, otherwise it will cause radioactive pollution to the secondary circuit system. The key to prevent the coolant in the reactor from leaking into the secondary side water of the steam generator is to control the feedwater quality, so as to prevent the tubesheet of the steam generator from being damaged by intergranular corrosion or stress corrosion, and the steam generator pipes are not easy to replace. Therefore, the requirements for the Feedwater Quality of the steam generator are higher than those of the conventional high parameter thermal power units

2 main process flow

the condensate polishing system adopts the medium pressure side flow polishing system, as shown in Figure 1, that is, the condensate polishing is achieved by setting the full flow condensate polishing system at the side flow position of the main condensate system. Considering that 5% - 10% of the net condensate returns to the main condensate pipe and enters the population main pipe of the fine treatment unit with the untreated condensate, the bypass isolation valve is no longer set on the main condensate circuit

the condensate polishing process system consists of two parts, one is the condensate polishing part, and the other is the external regeneration part of condensate polishing. Advantages of the device: in order to install the non horizontal working piston on the first main engine and ensure the safety of the system, there will be friction between the working cylinder and the working piston, and no valve is set on the bypass. In this way, when the condensate polishing system fails, the water will automatically pass through the valveless bypass, and failure to stabilize the scrap market will lead to accidents caused by water loss of the system; On the other hand, due to the design of the condensate lift pump, when the condensate lift pump is started, the operation resistance of the fine treatment system will be overcome, so that the condensate will be sent out after being treated by the bed, and the operation safety of the system will be maximized

3 parameters and water quality standards of condensate polishing system

see table 1-3 for parameters and water quality standards of condensate polishing system

4 characteristics of condensate polishing system equipment

local resistance of solids to invasion of external objects

4.1 main equipment parameters (single unit)

see Table 4 for main equipment parameters of condensate polishing system

4.2 structural characteristics of the equipment

the front cation bed is a welded 16MnR carbon steel cylindrical container, lined with silicon free natural rubber, and the equipment diameter is 3200. Because the DH value of condensate is as high as 9.7, the designed cation bed height is 1.3m (which is rare in domestic technology), and the same structure as the high-speed mixed bed is adopted; The resin trapper is a 16MnR carbon steel cylindrical container, lined with silicon free natural rubber, and the equipment diameter is 800. It adopts a side in and side out structure, which can save space. In order to fill the overflow area of the filter element gap, the single column tensile testing machine has only one column to meet the requirements of the maximum condensate flow, six DN125 small-diameter reinforced filter elements are directly welded on the perforated plate, which not only reduces the equipment diameter, reduces the equipment height, but also increases the strength of the filter element, making the filter element device portable and convenient for disassembly and installation. The mixed bed is the last barrier of the treatment device. In order to achieve the most effective desalination function, we determine the mixed bed as a 3200 equipment diameter, welded 16MnR carbon steel cylindrical container, lined with silicon free natural rubber, rather than a spherical tank that is easy to manufacture, low-cost and mature technology, which is also a rare choice in China. The inner wall of the equipment is lined with rubber, which is composed of two-stage water distribution inlet device, resin inlet device and water outlet device

mixed bed resin separation tower is the key equipment of high tower separation method. The welded carbon steel cylindrical vessel of the mixed bed resin separation tower is composed of 1800 cylinders at the lower part and 1800/2600 conical cylinder sections at the upper part. It is lined with silicon free natural rubber. The water inlet device is a T-shaped branch pipe type with a winding gap of 0.30mm, which is convenient for the discharge of impurities. The water outlet device is a dished orifice plus a small resistance double flow 316L stainless steel water cap, which ensures the need for large flow during flushing and is conducive to the rapid discharge of impurities. The internal devices of this equipment distribute water evenly and collect water evenly, which can avoid excessive flow velocity and eccentric flow locally

working principle of the separation tower: the cation and anion exchange resins that fail after operation in the high-speed mixed bed are sent to the separation tower through the inlet of the failed resin of the separation tower for backwashing and layering. The uniform columnar water flow enters the separation tower through the water distribution device at the bottom of the separation tower. Because the specific gravity and particle size of the cation resin are larger than that of the anion resin, the sedimentation speed of the cation resin and the anion resin is different during backwashing. By slowly reducing the backwashing water flow, Make the cation resin slowly settle in the lower part of the equipment, while the anion resin slowly settle in the upper part of the separation tower. The middle part near the anion resin delivery port is the mixing transition area of cation and anion resin, and the upper part of the resin delivery port is completely anion resin, which can ensure that all the anion resin sent from the delivery port is anion resin. The anion resin is sent out from the anion resin outlet on the side wall of the separation tower through the flushing water, and the cation resin is sent out from the cation resin outlet on the bottom of the separation tower. After the resin transportation is completed, the amount of mixed fat left in the separation tower is controlled by the mobile photoelectric level meter installed on the side wall of the separation tower. When the resin is transported to the photoelectric level meter, the signal sent by the level meter is sent to the operation control room, so that the program control can automatically judge that the resin has been transported completely, so that the whole separation process ends

5 Conclusion

since the completion of Qinshan nuclear power station in December 1991, China has built four nuclear power stations, Qinshan, Daya Bay, Shenzhen Lingao and Lianyungang Tianwan, with a total installed capacity of 9million kW. The state plans to build at least 30 nuclear power units in the next 15 years. By 2010, the installed capacity of nuclear power in operation will reach 12million kW; by 2020, the installed capacity of nuclear power in operation will reach 40million kW, accounting for 4% of the total installed capacity, and the installed capacity of nuclear power under construction will reach 18million kW. Therefore, the research on the application of condensate polishing system in nuclear power plants has a very broad prospect and far-reaching significance. This system is now in the construction and implementation stage. It is believed that it has forward-looking reference significance in the field of condensate polishing in nuclear power plants.

References:

[1] Wang Hua. Condensate polishing in nuclear power plants Water purification technology, 2002, (4) ->

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