RU2656772C1 - Method of air abandonment of steam boiler of steam power plant - Google Patents

Abstract

FIELD: power engineering; heat exchange.

SUBSTANCE: invention relates to heat engineering. Method includes the creation of two abandonment circuits: circuit of the boiler part of the high-pressure steam-water path with the primary superheater and the intermediate superheater circuit. "Dry" shutdown of the boiler with emptying at a pressure in the water part of the first of these circuits above the atmospheric one, preliminary removal of residual moisture from both of these circuits by creating a vacuum in them with pumping of atmospheric air through both circuits, final drying of the said circuits by venting them with a gaseous agent after cooling the metal of the said circuits to ambient temperature. Permissible residual relative humidity in the boiler abandonment circuits is assumed equal to 80 %. As the specified gaseous agent, atmospheric air is withdrawn from the upper part of the boiler house. During final ventilation drying of the said circuits, the absolute humidity of the ventilation air is determined at the inlet and outlet of each of the said circuits, and the completion of the process of final drying of the circuits is carried out after the equalization of these parameters.

EFFECT: technical result consists in the possibility of using undried atmospheric air as a gaseous agent in ventilating circuits and increasing the reliability of the determination of the moment when it is possible to complete the process of transferring the boiler to the long-term abandonment regime.

1 cl, 2 dwg

Description

Technical field

The invention relates to the field of power engineering and can be used for preservation of steam boilers of steam power plants when the boiler is stopped for various periods of time for repair or a long reserve.

State of the art

A known method of preserving a steam boiler of a steam power plant adopted as a prototype of the patented invention, comprising the creation of two preservation circuits: a circuit of the boiler part of the high-pressure steam and water duct with a primary superheater, and an intermediate superheater circuit, “dry” shutdown of the boiler with emptying at a pressure above the atmospheric water part of the first from these circuits, preliminary removal of residual moisture from both of these circuits by creating a vacuum in them with pumping through both atmospheric air circuits, which completes the drying of these circuits by venting them with a gaseous agent after cooling the metal of these circuits to ambient temperature (RD 153-34.1-30-502-00 "Guidelines for organizing the conservation of heating equipment with air." http: // snipov.net/database/c_4294966483_doc_4294817665.html [1]).

According to [1], dried atmospheric air is used as a gaseous agent for the final ventilation drying of these circuits. To produce such air, the selected source atmospheric air is passed through a dehumidifier operating on the principle of sorption or freezing of moisture in the air, which makes it possible to bring the moisture content in the air to be drained to a level that ensures relative humidity of 40-60% at the outlet of each of the circuits . The disadvantage [1] is, on the one hand, the need to use a dehumidifier of atmospheric air, which requires significant energy costs to remove moisture in the air. On the other hand, the method [1], despite the deep drying of the ventilation air, does not reliably prevent atmospheric corrosion of the metal of the preserved circuits due to the possible premature completion of the ventilation process, the duration of which is controlled only by the readings of the moisture meter at the outlet of the corresponding circuit.

Disclosure of invention

The objective of the invention is to increase the reliability of preservation of the boiler from the point of view of preventing parking corrosion of the metal of its steam-water path while reducing the cost of conservation, and the technical results are the possibility of increasing the permissible level of relative humidity of the gaseous agent in the circuits of the steam-water path of the boiler at the final stage of putting the boiler into preservation mode and during a period of prolonged maintenance of it in this mode, the use of a cheap gaseous agent with accurately small (without the need for additional drying) relative humidity, increasing the reliability of establishing the moment of the possibility of completing the process of transferring the boiler to the long-term preservation mode, as well as the moments of the necessary correction of the degree of humidity of the gaseous agent in mothballed circuits.

The solution of this problem by achieving the indicated technical results is ensured by the fact that when implementing the method of preserving a steam boiler of a steam power plant, which includes the creation of two preservation circuits: the circuit of the boiler part of the high-pressure steam and water duct with a primary superheater and the intermediate superheater circuit, “dry” shutdown of the boiler with emptying when pressure above the atmospheric water part of the first of these circuits, preliminary removal of the remainder from both of these circuits full-time moisture by creating a vacuum in them with pumping through both circuits of atmospheric air, completing the drying of these circuits by venting them with a gaseous agent after cooling the metal of these circuits to ambient temperature,

according to the patented invention

the permissible value of the residual relative humidity in the boiler preservation circuits is taken to be 80%, atmospheric air is taken from the upper part of the boiler room as the gaseous agent for the final ventilation drying of these circuits, and the value of the absolute humidity of ventilation air at the inlet and outlet of each is determined during the final ventilation drying of these circuits from these circuits, and the completion of the process of the final drying of the circuits is carried out after the alignment of these values .

The causal relationship between the totality of the essential features of the patented invention and the achieved technical results is as follows. As studies have shown with prolonged exposure of carbon steel samples in atmospheric air with a relative humidity in the range of 40 ÷ 80%, the rate of uniform corrosion of these samples does not exceed 0.01 g / (m ² ⋅ h), which practically does not affect the regulatory period service of all elements of the boiler’s steam-water path.

Based on the results of these studies, the adoption of the permissible value of the residual relative humidity in the boiler preservation circuits equal to 80% can accordingly reduce the requirements for the degree of humidity of the gaseous agent used for final ventilation, the choice of the specified atmospheric air circuits from the upper part of the boiler as the gaseous agent for final ventilation drying premises allows you to get a cheap gaseous agent with a relatively small relative humidity, not requiring energy-intensive additional drying for ventilation of the boiler steam-water circuit circuits during its preservation, determination of the absolute humidity of ventilation air at the inlet and outlet of each of these circuits with the completion of the process of final drying of the circuits after aligning these values improves the reliability of establishing the moment of completion the process of transferring the boiler to the long-term preservation mode, as well as the moments of the necessary correction of the degree of humidity gaseous agent in canned circuits.

Brief Description of the Drawings

In FIG. 1 shows a flow chart of the implementation of the patented method of preservation of the boiler with dry air; in FIG. 2 - I-d diagram with the designation of points that determine the absolute humidity of the ventilation air in the places of measuring its relative humidity in a specific example of the method.

Legend

HEU - ventilation dehumidifier;

GP - the main steam line;

GPZ - main steam valve;

PC - steam boiler;

PP - primary superheater;

PPP - an intermediate superheater;

PSU - steam power installation;

CVP - high pressure cylinder;

CSD - medium pressure cylinder

The list of positions of the figures of the drawing

10 - PC; 11 - PP; 12 - IFR; 20 and 30 contours of conservation, respectively, with PP and PPP; 21 - drainage line; 22 - gate valve; 23 and 31 - inlet pipes on the ventilation lines of both circuits, respectively; 24 and 32 - outlet pipes on the ventilation lines of both circuits, respectively; 25, 26, 33, 34 - measuring instruments; 40 - section of the main steam line to the main valve; 41 - the main gate valve; 42 - line connecting 40 with the atmosphere; 421 - gate valve 42; 50 - section of the feed pump; 51 - shutoff valve on the feed pipe; 60 - section of the "cold" thread of the steam pipe of the intermediate overheating from the turbine CVP; 61 - gate valve on line 60; 70 - section of the "hot" thread of the steam pipe of the intermediate overheating to the turbine central cylinder; 71 - gate valve on line 70; 80 - HEU; 81 and 82 - lines designed for the parallel supply of ventilation air through the inlet nozzles, respectively, in both of these circuits; 811 and 821 - locking valves installed respectively on lines 81 and 82; 90 - dust removal filter; 100 and 200 - steam ejectors on both circuits; 300 and 400 steam lines connected to the pressure pipes of the respective ejectors; shutoff valves 310 and 410 on lines 300 and 400, respectively; 320 and 420 - pipelines for dumping the vapor-air mixture and air into the atmosphere on lines 300 and 400, respectively; 500 and 600 - drainage lines from the circuits of the suction vapor-air mixture through the outlet pipes 24 and 32, respectively; 510 and 610 - gate valves on lines 500 and 600.

The implementation of the invention

The technological scheme (Fig. 1) for preservation of a steam boiler (PC) 10 with a primary superheater (PP) 11 and an intermediate superheater (PPP) 12 of a steam power plant (PSU) not shown in the drawing includes two independent preservation circuits: circuit 20 of the steam-water boiler section PSU high pressure path and PPP 12 preservation circuit 30. The circuit 20 includes the steam-water duct elements of PC 10 (not shown in the drawing, a water economizer, screen pipes, for a boiler with natural circulation a separation drum and PP 11), as well as a section 40 of the main steam line (GP) to the main steam valve (GPP) 41 and a section 50 of the supply pipe to the shutter valve 51. To drain moisture from the circuit 20, a drainage line 21 with a shutter valve 22 is connected to its lower part. To allow moisture to be removed from the PP 11, an ejection method of the boiler section 40 GP connects the line 42 with the open free end on which the shutter valve 421 is installed. The circuit 30, in addition to the BCP 12, also includes the section 60 adjacent to the boiler to the shutter valve 61 of the “cold” string of the intermediate steam pipeline overheating from a high pressure cylinder (CVP) of the turbine (not shown) and the valve portion 70 to 71 of "hot" yarn reheat steam pipe to the pressure medium cylinder (MPC) of the turbine (not shown). In the upper part of the boiler room (not shown) there is a ventilation dehumidifier (HEU) 80 with an upstream filter 90 that removes dedusted air, intended for parallel supply of ventilation air through inlet pipes 23 and 31, respectively, to both of these circuits along lines 81 and 82 with steam shutoff valves 811 and 821, respectively. Steam ejectors 100 and 200 are provided for sucking moisture from both circuits. Steam lines are connected to the pressure pipes of these ejectors, respectively 300 and 400 with shut-off valves 310 and 410 and with pipelines for discharging the vapor-air mixture and air into the atmosphere 320 and 420 connected to the indicated steam lines, and lines to 500 and 600, respectively, for draining the vapor-air mixture through the outlet pipes respectively to the suction nozzles 24 and 32. These lines are equipped with shut-off valves 510 and 610, respectively. For measuring the temperature and relative humidity of ventilation air at the inlet and outlet sections of both circuits, limited by shut-off valves respectively 811 and 821, 510 and 610, standard measuring means of the power plant are used, respectively 25 and 26, 33 and 34.

The method of preservation of the steam boiler steam power installation according to the patented invention is carried out with the following sequence of operations.

After stopping the CCP, the shutoff valves 41, 51, 61, 71 are closed, connecting the high-pressure steam and water duct and the IFR to PC 10. The ejector 200 is turned on to suck out moisture in the vapor state and create a vacuum in the PPP circuit 12 with pumping atmospheric air of arbitrary humidity through it. In this case, air is taken from the upper part of the boiler room through HEU 80 with open valves 821 and 610, followed by its discharge into the atmosphere via line 420.

Then, without shutting off the ejector 200, the boiler is “stopped” dry by emptying the circuit 20 of the boiler part of the high-pressure steam and water duct at atmospheric pressure by opening the shutter valve 22 on drain line 21 and valve 421 on line 42 with the atmosphere of the boiler section of the main steam pipeline subsequent closure of the gate valve 22 after the drain. The pressure above atmospheric pressure is maintained due to the evaporation of the residual moisture after drainage of the circuit 30 by the heat accumulated by the slowly cooling metal, insulation and lining of the boiler.

An ejector 100 is turned on to suck out moisture in the vapor state and create a vacuum in the circuit 20 of the high-pressure steam-water path with the pumping of atmospheric air of arbitrary humidity through it. For pumping this circuit, outside atmospheric air (usually on the roof of the boiler room) is taken along line 42 with the shut-off valve 421 open.

Then, without shutting off the ejectors, close the shut-off valve 421 on line 42 and turn on the HEU 80 ventilation dehumidifier to more completely remove residual moisture in the vapor state from both of these circuits by filling the stored volumes with atmospheric air with a relative humidity allowed by the conditions of conservation released into the atmosphere with using these ejectors. After cooling the metal to ambient temperature and drying the indicated circuits with ventilation air at the inlet and outlet of this air from the indicated circuits, measure the value of relative humidity and air temperature using instruments 25, 26, 33, 34 with the determination of the corresponding absolute humidity values according to the id diagram (Fig. . 2). The drainage process is considered complete after leveling the absolute humidity values of the ventilation air at the inlet and outlet of these circuits.

After turning off the HEU, the valves 811 and 821, 510 and 610 are closed.

Using measuring instruments 25, 26, 33, 34, the relative humidity of the air inside the canned circuits is continuously monitored and, if it is increased to the maximum permissible value of 80%, periodic ventilation of the conserved circuits is performed. Carrying out such control with adjusting the state of air in mothballed circuits is also possible in automatic mode using standard means of automation of the power plant equipment.

An example implementation of the method.

A preservation of the steam boiler with natural circulation was carried out, which included an intermediate steam overheating system in front of the steam turbine central cylinder. Previously, two preservation circuits were created in the boiler: a high pressure circuit and an intermediate steam overheating circuit, limited by the corresponding shut-off valves and equipped with all the necessary means for preservation, as described above. All the above technological operations were carried out sequentially to transfer the boiler to the long-term preservation mode. In this case, the operation on the ejector suction from the contours of residual moisture in the vapor state was carried out for four hours. For ventilation drying circuits using HEU 80 with an upstream dedusting filter 90, air was taken from the upper part of the boiler room at a temperature (tx) of 30 ° C and a relative humidity (ϕ1) of 40%, which were controlled using measuring instruments 25 and 33, installed at the entrances to these circuits. The absolute humidity (d) of air with these parameters was determined by the I-d diagram (Fig. 2) and amounted to 11.0 g / kg (point A of the diagram). In the same way, the absolute humidity at the exit from the indicated circuits was periodically monitored using instruments 26 and 34. In particular, for a high pressure circuit immediately after switching on the HEU, this value at a temperature (tin) of 25 ° C and a relative humidity (ϕ1) of 80% was 16 , 0 g / kg (point B of the diagram). After 5 hours of operation of the HEU, the absolute humidity (d) of the ventilation medium at the inlet and outlet of the high pressure circuit was equalized (at the inlet and outlet of 11 g / kg) with the output parameters of the state of the specified medium at a temperature (tin.) Of 25 ° С, relative humidity (ϕ1 ) 50% (point B of the diagram). The specific removal rate of residual moisture (Δd) is 0.0 g / kg. On this, the process of transferring the boiler to the long-term preservation mode was completed. The mode of prolonged preservation of the boiler lasted three months. During this period, the absolute humidity of the vapor-air medium was monitored every two weeks at the output sections of the preserved circuits. In the third test, correction of the state of the vapor-air medium in the high pressure circuit was required by additional ventilation purging for one hour. A check of the state of the metal of the indicated circuits after completion of the preservation of the boiler did not reveal that the corrosion rate exceeded the normalized values.

Industrial applicability

The method of preservation of the steam boiler of the steam power plant by air according to the patented invention meets the condition of "industrial applicability". The essence of the technical solution is disclosed in the formula, description and figures of the drawing is sufficiently clear for understanding and industrial implementation by relevant specialists in the field of heat power engineering.

Claims (9)

A method of preserving a steam boiler of a steam power plant, including: the creation of two preservation circuits: the circuit of the boiler part of the high-pressure steam-water duct with a primary superheater and the intermediate superheater circuit; “Dry” shutdown of the boiler with emptying at a pressure above the atmospheric water part of the first of these circuits; preliminary removal of residual moisture from both of these circuits by creating a vacuum in them with pumping through both circuits of atmospheric air; final drying of these circuits by ventilation with a gaseous agent after cooling of the metal of these circuits to ambient temperature, characterized in that the permissible value of the residual relative humidity in the boiler conservation circuits is taken equal to 80%; as a gaseous agent for the final ventilation drying of these circuits, atmospheric air is taken from the upper part of the boiler room; during the final ventilation drying of these circuits, the absolute humidity of the ventilation air at the inlet and outlet of each of these circuits is determined, and the final drying of the circuits is completed after these values are aligned.

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