Thermal diagram of T-178/210-130 power unit

Brief description of boiler structures

The boiler unit has a U-shaped arrangement and consists of a furnace chamber, which is an ascending gas duct, a downhole convective shaft and a horizontal gas duct connecting the furnace with the convective shaft.

In the furnace chamber there are evaporative screens, and in its upper part, in addition, there is a two-stage screen superheater. Two stages of high-pressure convective superheater are installed in horizontal gas duct.

Outlet and inlet stages of low-pressure superheater and water economizer are located in convective shaft (in series along gas flow).

The ceiling of the furnace chamber, horizontal gas duct and rotary ka-measure are shielded by pipes of the high-pressure superheater of the 1st and 11th stages.

Fresh Steam Piping

The main steam pipelines are made two-line DN = 250 with connection to two stop valves of the turbine HPC (HPC SC). Main steam valves (GPV) are installed on steam pipelines before HPC SC.

Main steam lines shall have no lifting sections except for the section immediately before the GPP. The latter shall have a visible lift in such a way as to exclude the possibility of moisture ingress into the CS housings at the stage of preliminary heating of steam pipelines. Before lifting the steam pipelines, Dou50 drains are connected. Considering that the turbine start-up from all initial thermal states is performed by control valves with fully open GPVs, the main purpose of the GPV bypasses is to equalize the pressures before and after the GPV before their opening at the stage of preliminary heating of the turbine steam inlet parts. Therefore, it is recommended to perform bypasses of GPP of reduced diameter (Dn = 20).

From the lower point of each bypass pipe from HPC SC to control valves (RC), drain Dn = 20 and from each pair of bypass pipes immediately before the RC drain Dn = 50 are provided.

Drains upstream the RCP are connected to the RBNT high pressure drains expander, steam and water from which are discharged to the lower points tank (LBT). Drains of turbine HPC bypass pipes are connected to RDT and discharged to turbine condenser.

Intermediate steam superheating pipelines

Steam pipelines of cold (PPX) and hot (PPG) steam overheating in typical diagrams are provided with two-strand, respectively, Dn = 400 and Dn = 600.

Disconnecting engines are not installed on the steam pipelines of PPX and PPG. During hydraulic pressure testing, the boiler blankings are installed in the flange connectors of PPH and the stop valves of the turbine DSC are closed.

Safety valves of the steam overheating system are installed on the PCC jumper. Drains of PPX and PPG, medium pressure bypass pipes are connected to the RDT high pressure drain expander. Diameter of drains of bypass pipes of DSC is accepted: for lines from each internal point Dn = 20, and for lines from upper points of each pair - Dn = 50. Drains from PPG are accepted as Dn = 50.

Condensation unit

Condensation plant of turbines consists of condenser group, air removal device, condensation pumps, start-up ejectors, circulation pumps and water filters (or ECS).

The condenser group consists of two surface two-way capacitors with a total cooling surface of 9000 m2.

The condenser housing is all-welded with end and intermediate tube boards welded into it. Water chambers form an integral part with the body and are closed by removable covers. Both bodies of condenser-group are connected by equalizing branch pipe.

In order to maintain high-quality rolling of tubes during operation, lens compensators are provided on condenser housings to ensure compliance of tube boards relative to the housing.

To compensate for thermal expansions, the capacitor housing is installed on spring supports designed to perceive the capacitor's own weight and compensate for thermal expansions.

Each condenser has a separate supply and discharge of cooling water, which makes it possible to disconnect one of them by water when the turbine operates with a reduced load.

The load reduction at this time is determined by the temperature in the exhaust part of the cylinder, which should not exceed 60OS.

Each condenser has a built-in PND1 section, sections of heaters consist of brass tubes littered in pipe boards.

Each condenser is provided with a special device for receiving steam in the amount of 300 t/h at a pressure of 6 ata and a temperature of 200OS during unit starts and load discharges. There is also a device for adding condensate in an amount of up to 30 t/h at a pressure of 4-5 ata and a temperature of 40OS.

For detection of turbine condenser clogging there are compartments located at end pipe boards. To increase the hydraulic density of the condenser, it is allowed to apply sealing coatings on the pipe boards on the side of cooling water.

The hydraulic resistance of each condenser at clean tubes and cooling water flow rate of 12500 m3/h is 3.3 mW. The maximum allowable working pressure inside the water space is 1 kg/cm2.

The level in the condensate collector is maintained by a regulator with a nominal value of 200 mm below the capacitor housing.

The air removal device consists of two main three-stage ejectors and one start-up ejector (to quickly raise the vacuum in the condenser to 500600 mmHg during turbine starts).

One main ejector is constantly in operation, the second is standby. Power source of ejectors is steam from deaerator 7 ata. The steam flow rate per main ejector is 700 khh.

The heat of the working steam of the ejectors is used to heat the main condensate.

Both main steam and condensate ejectors are connected in parallel.

Drain of working steam condensate of ejector is made cascade along stages.

Condensate is discharged from the first stage through a special pipeline through a hydraulic seal to a condenser. From the second to the first, from the third stage to the second or to the funnel and further to the BNT.

The starting ejector is powered by steam from the same line as the main ejectors. The steam flow rate is 1100 kg/h. Exhaust from the starting ejector is carried out into the atmosphere.

To pump out condensate from the condenser and supply it to the deaerator through ejector coolers, seal coolers and low-pressure heaters, three condensate pumps are provided, driven by AC motors. At full load of the turbine, two pumps operate, the third-standby.

Cooling water for condensers, oil coolers is supplied by circulation pumps. The total cooling water flow to the turbine plant is 25,000 m3/h.

To clean cooling water supplied to the unit oil coolers and generator gas coolers from mechanical impurities, self-washing rotary filters with contamination removal pipeline are installed in pressure circulating water ducts.

To remove air from the upper points of the drain circulation arguments when filling the circulation system with water, a starting ejector of the circulation system is installed.

Ejector is fed from deaerator 7 ata or from ICS at steam flow rate of 1100 kg/h.

To break the vacuum, a gate valve is used on the suction pipeline from the condenser.

Low Pressure Condensate Duct and IPA

The low pressure condensate path is designed to preheat the main condensate to a temperature of 156OS with steam withdrawn from the intermediate stages of the turbines, and consists of four low pressure heaters. The plant also provides for the use of heat of the working steam of the main ejectors and steam sucked from labyrinth seals (PS50).

PND-1 is built into the capacitor, PND2,3,4 are installed in a separate group. Each of the LP heaters, except for PND1, is equipped with a control valve for removal of heating steam condensate from the heater, controlled by an electronic level controller.

Heating steam condensate from PND1 is directed through siphon to condenser. Heating steam condensate from heaters No. 4,3,2 is drained cascade. From preheater No. 2, condensate is pumped out by a drain pump with a capacity of about 80 m3/h with a pressure gauge of 160 mmwater. to the main condensate line downstream of PND2. Two drain pumps are installed, one of which is standby. Heater No. 3 is equipped with a horizontal type remote drain cooler. The drainage is cooled by passing the heating steam LPD-2 through the cooler.

For steam suction from the extreme chambers of the labyrinth seals of the turbine, a special vacuum cooler is installed, equipped with an ejector that maintains a pressure of 0.950.97 ata in the cooler. Working steam of ejector of vacuum cooler is steam from deaerator 7 ata. The main condensate of the turbine is supplied to the cooler to use the heat of the medium being sucked, as well as the heat of the working steam of the ejector. The cooler is turned on after PND1. Steam suction from intermediate chambers of labyrinth seals of the turbine is performed in the regenerative heating diagram of the main condensate after MND1.

All heaters are equipped with water and instrumentation.

Deaeration unit

The deaerator of the unit (DB) is an installation located at an elevation of 21 m in the deaerator deck of the main body, consisting of a horizontal but lying tank-accumulator with a de-aeration head installed on it in the upper part, and also includes a network of pipelines with valves.

Deaeration column DSP-800:

- D - deaerator;

- C - mixing type;

- U - high pressure, with a capacity of 800 t/h, is a vertical cylinder with a height of 4 m and a diameter of 2432 mm. The wall thickness in the cylindrical part is 12 mm, in the upper spherical part - 16 mm.

In the upper part of the column there is a mixing distribution device, which includes the following connectors:

- main condensate;

- standby condensate;

- evaporator distillate;

- output of turbine low point tank pumps.

Below the tiers there are jet trays with holes through which water flows cascading downwards.

Heating steam collectors are located under lower plate:

- 2nd and 3rd turbine selections;

- suction from the turbine control and stop valves rods;

- standby steam from auxiliary manifold of the unit.

Washing the jets flowing from the trays, the heating steam is mainly condensed, and its smaller part along with the gases is removed through the exhaust pipe located in the uppermost part of the head on:

- PS50 ejector;

- to atmosphere during unit start-up.

Upstream of exhaust pipe:

- operating temperature - 164OS;

- column capacity - 17 m3.

The battery tank is a horizontal cylinder oriented along the main body of the station.

Length - 13.5 m

Diameter - 3437 mm

Wall thickness in cylindrical part - 12 mm

Wall thickness in the end part - 20 mm

Tank capacity - 100 m3.

End parts of tank have spherical shape to exclude voltage concentrators.

Middle part of tank rests on fixed support.

With extreme parts on both sides, the tank rests on movable roller supports, which contribute to thermal movements of the tank cylinder.

Tanks installed on the units are divided into three compartments by bubbling devices having blind partitions at a height of up to half a meter from the tank bottom. 3.3. Pipelines and valves are connected to the deaerator in the following order:

Steam-gas mixture exhaust pipeline (80 mm) leaves the center of spherical column at the top. It is then divided into two lines:

- the line (50 mm), with the electrified SZ3 gate installed on it, crashes into an exhaust pipe of the safety valve in the atmosphere;

- line (80 mm) with check valve and valve installed on it goes to PS50 ejector, connecting to the line coming from auxiliary manifold (MV) of the unit, which allows to supply steam to PS50 both from MV manifold and from DB exhaust.

At the same level, pipelines cut into the top of the column:

- main condensate (250 mm) with a reverse valve installed on it. On the approach to the head, this pipeline is divided into two hoses (200 mm) and enters the head with a distribution of water flow. Disconnecting gate valve on main condensate pipeline VK30 is located at elev. 7.5 m near PVD6. At the level

14 m along row "B" flow washer is installed on OK pipe;

- standby condensate (200 mm) crashes into OK line in row "B" at elev. 10, there is also a shutoff gate valve;

- ISV distillate (100 mm). Disconnecting valves at elevation O in row "B," check valve near CPD column;

- output of low point tank pumps (BNT) (80 mm), disconnecting valves are located in the basement of the turbine hall along row "B."

The following pipelines cut into the lower part of the column:

- heating steam (159 mm) with a direct pressure control valve with MEO installed on it. This steam line combines 3 steam sources:

a) 2nd turbine extraction (pressure 26 ati, temperature 325OS) taken from the jumper between cold lines of steam overheating after HPC. PO2D latch.

b) The 3rd turbine bleed (pressure 12.13 atm, temperature 543OS) is taken after the 15th stage of DSD. DPC gate valve;

c) jumper from MV manifold of the unit (pressure 13 ati, temper-tour 300OS). PSND gate valve is installed near deaerator. Latches of PO2D and PO3D are on otm.7.5 near the right lock valve of the turbine.

All these gate valves on the steam supply lines to the deaerator are electrified, their control keys are located on the control panel No. -3 of the MCS.

- steam suction from the turbine stop and control valves rods (150 mm).

Disconnecting gate valve at elev. 9 m along row "B." If you read from the permanent end face of the GRES, the pipes crash into the accumulator tank from above in the following order:

-Invent of continuous boiler blowdown expander (RNPK, 159 mm). Gate valve and check valve are installed along Medium.

- Steam supply from DB to turbine seal. (159 mm). In the course of steam, a check valve and an electrified PTMS gate valve are installed.

- Steam supply to turbine ejectors. (100 mm). Check valve and gate valve are installed along steam flow.

The pipeline for drainage of heating steam of HPH group 200 mm is connected to the deaerator in the same way. After the fork, it crashes into the tank on both sides of the column with two 159 mm sleeves.

Disconnecting valves are located at the elevation of 3.0 m, near the HPH group. KD5D gate valve is installed on drain line from PVD5. KD6D gate valve is installed on drain line from PVD6. Both gate valves are electrified. Check valve is installed on common line.

At the very end of the upper part of the tank there are pulse and main safety valves of the deaerator. Direct action impulse valves. Main parts:

- valve body;

- plate tightly lying on the valve seat;

- rod;

- a post on which one end of the lever is hinged;

- lever with load;

- lever with rod are in contact through hinge system providing free movement of rod.

The direct action valves are opened by the force generated by the steam pressure and applied directly to the seal tray. While the pressure in the de-aerator is lower than permissible, the tray is pressed against the seat, since the load from the side is greater than the increase from the differential pressure on the tray. The difference in these forces, perceived by the sealing surfaces of the trays and the seat, ensures the tightness of the valve. With increasing pressure, the force acting on the tray from below increases and, when the pressure exceeds the limit, this force, overcoming the load force, opens the valve and steam passes to the main valve.

Main indirect valves with loading servomotor. Main parts:

- valve body;

- the disc, unlike the pulse valve, is pressed from the bottom up;

- rod connecting the plate and the servomotor piston;

- rod connecting servomotor piston with spring;

- auxiliary spring;

- servomotor housing.

In normal condition, the spring, being in some compressed state, resting with its lower end against the valve body, and with its upper end against the tension nut, tends to lift the upper rod upwards. The upper rod through the servomotor piston raises the rod and through it the plate. Thus, the plate is tightly fitted to the seat by spring and steam. When the pulse valve operates and passes steam into the upper chamber of the servomotor, pressure rises above the piston, creating a much greater force than the spring, and the piston, compressing the spring, rushes down, with the help of a rod lowers the plate. Steam from the deaerator rushes through the pipeline into the atmosphere above the roof of the building.

The pulse valve shall be operated at 6.9 kg/cm2. The valve is adjusted by moving the load on the lever. The closer the weight is to the free end of the lever, the higher the pressure required to actuate the valve. After adjustment, the load must be securely fixed and sealed.

To prevent water accumulation in exhaust pipelines, 22 mm drain pipes are removed from the inner part. Drain pipes must be installed on the funnel, and drain to BNT.

Emergency drain pipe with AS-DB electrified gate valve is removed from the middle part of the tank by height. Diameter 200 mm. The upper end of the pipe starts 350 mm below the upper generatrix of the tank. Therefore, if the emergency drain gate valve is opened even for a long time, then a significant decrease in the level will not occur, but it should be remembered that opening the NPP-DB for a long time can lead to a decrease in steam pressure in the DB through the NPP.

From the lower part of the tank there are two 600 mm pipes, which are then combined into one, which goes to the suction of feed electric pumps (FEP) of the units.

In order to ensure pre-start deaeration, a DN = 150 bridge is provided between the suction pipelines of the LDPE and the drain pumps of the IPA.

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