RU2170387C1 - Method of preservation of boilers with gas - Google Patents

Abstract

FIELD: preservation of boilers after shutting down with reduction of pressure to atmospheric values. SUBSTANCE: proposed method can be used for preservation of drum, straight-through and hot-water boilers. Method comes to draining water from boiler and filling the boiler with gas, for instance, with subsequently maintaining gauge pressure inside boiler. Prior to filling boiler with gas, it is filled up with deaerated water to capacity and then gas is delivered to force water out of boiler through drains in boiler through drains in boiler bottom points. EFFECT: improved reliability and efficiency of preservation of standby boilers. 1 dwg

Description

 The invention relates to the field of power engineering, in particular to methods for preserving boilers after shutdown with a decrease in pressure to atmospheric, and can be used for preserving drum, direct-flow and hot water boilers.

There is a method of preserving a steam boiler, which consists in the fact that after stopping, filling the boiler with gas (nitrogen) is carried out at an excess pressure in the heating surfaces of 2-5 kg / cm ² while draining the water in the drum in order to prevent air from entering the boiler, which activates corrosion . The preservation scheme provides for the supply of nitrogen to two points: to the outlet collectors of the superheater and to the drum through air vents, while the nitrogen flow rate should provide a slight excess pressure in the boiler [1].

 The disadvantage of this technical solution is the inability to use it for preservation of boilers with pressure reduction after stopping to atmospheric and draining water from the boiler, for example, after an emergency stop and subsequent repair on heating surfaces or after maintenance or overhaul, when the boiler is completely freed from water when inside his air.

 If the boiler was completely filled with atmospheric air, then replacing it with nitrogen by feeding the latter into the air in all sections of the boiler’s steam-water path is almost impossible, because the specific gravity of air and nitrogen differs slightly. In all elements where there was air with a humidity of over 40%, oxygen corrosion will occur.

In addition to a slight difference in specific gravities, a uniform distribution of nitrogen and air displacement is impossible for the following reasons:
- the nitrogen supply circuit only through the exhaust manifolds of the superheater and drum does not provide hydraulic conditions for uniform distribution of gas throughout the boiler tube system;
- Some elements of the boiler have non-draining areas, which does not allow filling them with nitrogen.

 Thus, the known method of conservation can only be used immediately after the boiler has been operating under load, while overpressure is maintained.

 The technical problem to which the invention is directed is to increase the reliability and efficiency of preservation of boilers put into reserve by completely filling the steam-water duct with preservative gas under all shutdown modes.

 To solve the problem according to the known method of preserving the boiler, which consists in emptying the boiler from water and filling it with gas, for example, nitrogen, followed by maintaining its excess pressure inside the pipe system of the boiler; after the boiler is emptied of water in the event of, for example, an emergency stop with damage to the pipes of the heating surfaces, it is filled with deaerated water before gas is supplied, and gas is supplied through all boiler air vents while water is displaced from the boiler through the drains of its lower points.

 The proposed method of preservation of the boiler is illustrated by the diagram shown in the drawing.

 The preservation scheme of a boiler containing a drum 1 with air vents 2, a superheater 3 with air vents 4, a condenser 5 with air vents 6, an output collector of a superheater 7, an external cyclone 8 with air vents 9, screens of the boiler circulation panels 10, economizer 11, drainage of the lower points of the boiler 12, air vents of the outlet chamber of the superheater 13, includes a line for supplying nitrogen with a valve 14, a line for venting air from vents with a valve 15, a line for venting and supplying water with a valve 16.

 Implemented the proposed method (for example, a steam drum boiler) as follows.

 After the boiler stops, it is completely freed from water by opening all the lower points of the boiler. At the same time, in the individual elements of the boiler there remains a steam-air mixture containing oxygen, which causes corrosion. In order to completely displace the vapor-air mixture, all elements of the boiler: drum 1, superheater 3, condenser 5, outlet header of the superheater 7, remote cyclone 8, screens of the circulation panels 10, economizer 11, are filled with completely deaerated water. Filling is carried out through the drains of the lower points and the boiler 12.

 The full filling of the boiler is controlled by valve 15 on a common line of air vents specially performed on the boiler. After the boiler is completely filled, valve 15 is closed and nitrogen is supplied by opening valve 144 and then through air vents 9, 2, 6, 4, 13.

 Simultaneously with the supply of nitrogen to the boiler, the drains of the lower points of all elements of the boiler are opened. Water is displaced and all elements of the boiler are filled with nitrogen. The nitrogen pressure in the boiler is regulated on the supply line 14 and, if necessary, by the valve 16 on the discharge line from the lower points of the boiler.

 After the water is completely displaced and the boiler is filled with nitrogen, the excess nitrogen pressure necessary for preservation of the boiler is set (for example, 25-100 mm of water. Art.).

 The presence of a certain amount of deaerated in individual non-drained boiler elements does not lead to a negative effect on the boiler metal, which is confirmed by studies of recent years by NPO CKTI.

 Thus, the proposed method of preserving the boiler can significantly increase the reliability of preservation due to the complete release of the boiler from the air by filling it with deaerated water and then filling it with nitrogen through all the upper points of the boiler (air vents) while simultaneously displacing water from the boiler through the drainage of its lower points.

Literature
1. Guidelines for the conservation of heat and power equipment RD 34.20.591-97.- M .: ORGRES, 1997, section 2.8, p. 21-22 (prototype).

Claims (1)

 A method of preserving the boiler with gas after shutdown, which consists in emptying the boiler from water and filling it with gas, for example, nitrogen supplied through all air vents, followed by maintaining excessive pressure inside the boiler pipe system, characterized in that the boiler is freed from water, in which the pressure after shutdown decreased to atmospheric, before puffing, the gas is completely filled with deaerated water, after which gas is supplied while water is displaced from the boiler through the drains of its lower points.