Heating surface arrangement structure of n-shaped secondary boiler with steam parameter of 630-650 degrees

Abstract

The invention relates to the technical field of efficient ultra-supercritical coal-fired power generation, in particular to an arrangement structure for a heating surface of an n-shaped secondary boiler with the steam parameter ranging from 630 degrees to 650 degrees. The primary medium-temperature reheater, the secondary medium-temperature reheater, the primary high-temperature reheater and the secondary high-temperature reheater are symmetrically arranged on the horizontal flue in a left-right crossing manner in the width direction of the hearth; and the coal economizers are arranged in the tail shaft flue in three groups in a series-parallel connection manner. Compared with the prior art, by arranging the multiple stages of heating surfaces and reasonably distributing the enthalpy increase of each stage, the influence of smoke temperature deviation on the use temperature of the boiler heating surface pipe is effectively weakened, and the use amount of high-grade alloy materials is reduced. According to the scheme, a flue gas recirculation fan is not arranged, it is guaranteed that steam parameters of the boiler reach the standard in a wide load range only through the flue gas adjusting baffle, system configuration is simple, and economical efficiency is better.

Description

Technical Field

[0001] The invention relates to the field of high-efficiency ultra-supercritical coal-fired power generation technology, and in particular to a heating surface arrangement structure of a Π-type secondary boiler with a steam parameter of 630° to 650°. Background Art

[0002] The existing coal-fired units generally adopt a thermal cycle based on the recuperation and reheating Rankine cycle. Improving the initial steam parameters is an effective means to improve the power generation efficiency of the unit. After successfully conquering the 620℃ and secondary reheating technology, the overall research and development level and unit operating efficiency of my country's high-parameter units have reached the world's leading level. Further improving the initial steam parameters to 630℃~650℃ and achieving a power generation efficiency of 50% is one of the main directions of development of coal-fired power technology at this stage.

[0003] Compared with 620℃ grade units, the power generation efficiency of 630℃~650℃ units is only increased by 1%~3%. In order to ensure construction benefits, it is necessary to reduce the cost of unit equipment as much as possible under the condition of ensuring safety. Compared with 620℃ boilers, 630℃~650℃ boilers have higher main and reheat steam temperatures, higher pressures, and higher operating temperatures for heating surface tubes, so the use of new materials is inevitable. In order to ensure that boiler steam parameters meet standards and minimize the use of high-grade alloy materials, it is necessary to put forward higher requirements for thermal deviation control of the heating surface, and adjusting the heating surface layout plan is an important means.

[0004] The layout of large-capacity and high-parameter pulverized coal boilers mainly includes Π-type furnace and tower furnace. Π-type furnace is widely used in new units because of its low boiler steel frame and convenient installation and lifting.

[0005] In addition to the combustion system, the core of boiler design lies in the heating surface, which must be matched with the temperature control scheme. For Π-type boilers, there are currently two major mainstream heating surface layout schemes. One is to adopt the "flue gas recirculation + double flue baffle" temperature control scheme, and the heating surface layout method is: the front of the boiler is the furnace, and the furnace outlet is arranged with a partition screen superheater, a rear screen superheater, and a high-temperature superheater in sequence; the horizontal flue is arranged with a primary high-temperature reheater and a secondary high-temperature reheater in sequence; the tail shaft is divided into front and rear double flues, the front flue is arranged with a primary low-temperature reheater and an economizer, and the rear flue is arranged with a secondary low-temperature reheater and an economizer, and the two-stage economizer is connected in parallel. Since the superheater heating surface is all arranged at the furnace outlet and the reheater inlet flue gas temperature is relatively low, this scheme must be used with flue gas recirculation (FGR) to ensure that the reheat steam parameters meet the standards. Due to the reliability deviation of the recirculation fan system, the actual effect of this scheme is not ideal. The other is to adopt the "three flue dampers" temperature control scheme, the heating surface is arranged in the following way: the front of the boiler is the furnace, the furnace outlet is arranged with the rear screen superheater and the high temperature superheater in sequence; the horizontal flue is arranged with the secondary high temperature reheater and the primary high temperature reheater in sequence; the tail shaft is divided into three flues, the front flue is arranged with the primary low temperature reheater and the economizer, the middle flue is arranged with the secondary low temperature reheater and the economizer, and the rear flue is arranged with the low temperature superheater and the economizer. The three-stage economizers are connected in parallel. This scheme relies only on the dampers of the three tail flues to balance the heat absorption between the superheater and the reheater. The inlet flue gas temperature of the boiler high temperature superheater and the primary / secondary high temperature reheater has increased, and the control of the boiler wall temperature deviation is also stricter. Summary of the invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the defects in the prior art, thereby providing a Π-type secondary boiler heating surface arrangement structure with a steam parameter of 630° to 650°.

[0007] A 630°~650° Π-type secondary boiler heating surface arrangement structure, comprising a water-cooled wall, an economizer, a primary low-temperature reheater, a secondary low-temperature reheater, a low-temperature superheater, a platen superheater, a high-temperature superheater, a primary medium-temperature superheater, a secondary medium-temperature reheater, a primary high-temperature reheater and a secondary high-temperature reheater;

[0008] The water-cooled wall is provided with a water-cooled wall spiral section and a water-cooled wall vertical section along the height direction;

[0009] The platen superheater and high-temperature superheater are arranged at the furnace outlet, the primary medium-temperature reheater and secondary medium-temperature reheater, the primary high-temperature reheater and secondary high-temperature reheater are arranged in a horizontal flue in a cross-symmetrical manner along the width direction of the furnace; three flues are arranged in the vertical shaft at the rear of the boiler, and the three flues are respectively recorded as the front flue, the middle flue and the rear flue; the primary low-temperature reheater, the secondary low-temperature reheater and the low-temperature superheater are respectively arranged in the front flue, the middle flue and the rear flue;

[0010] The steam parameter 630°~650° Π-type secondary boiler heating surface layout structure also includes a primary reheater intermediate header and a secondary reheater intermediate header. Both the primary reheater intermediate header and the secondary reheater intermediate header are annular headers, which overlap in the width direction but are not overlapped in the height direction. The primary reheater intermediate header is connected to the primary medium-temperature reheater and the primary high-temperature reheater, and the secondary reheater intermediate header is connected to the secondary medium-temperature reheater and the secondary high-temperature reheater.

[0011] Further, the economizer includes a secondary economizer and a primary economizer;

[0012] The first-stage economizer includes the first-stage economizer group, the second-stage economizer group and the third-stage economizer group;

[0013] The secondary economizer is arranged in the lower flue of denitrification, and the first group of economizers, the first-stage second group of economizers and the first-stage third group of economizers are arranged in three stages in three flues of the boiler tail shaft in series or in parallel.

[0014] Furthermore, the first group of economizers of the first stage are arranged in the front flue, the second group of economizers of the first stage are arranged in the middle flue, and the third group of economizers of the first stage are arranged in the rear flue.

[0015] Furthermore, the first group of economizers at the first stage and the second group of economizers at the first stage are connected in parallel, and the whole after parallel connection is connected in series with the third group of economizers at the first stage.

[0016] Further, the device also includes a smoke regulating baffle;

[0017] The smoke regulating baffles include a primary smoke regulating baffle, a secondary smoke regulating baffle and a low-pass smoke regulating baffle;

[0018] The first flue gas regulating baffle, the secondary flue gas regulating baffle and the low flue gas regulating baffle are respectively arranged at the outlets of the front flue, the middle flue and the rear flue.

[0019] Furthermore, the first-side flue gas regulating baffles, the secondary flue gas regulating baffles and the low-side flue gas regulating baffles are arranged in no less than 6 groups along the width direction of the furnace.

[0020] Furthermore, the screen-type superheater has multiple small screens evenly distributed along the width of the furnace, each of which is formed by bending 18-28 stainless steel tubes. The outer 4 to 6 circles of tubes and the inlet section of the innermost circle of tubes of each small screen are made of TP310HCbN, the bottom U-shaped bend section is made of S31035, and the outlet section is made of S31035; the inlet section and the bottom U-shaped bend section of the remaining tubes are made of S30432, and the outlet section is made of S31035; the tube screen outlet header still uses mature 9Cr martensitic heat-resistant steel.

[0021] Furthermore, the high-temperature superheater has multiple groups of heating surfaces evenly distributed along the width direction of the furnace, and each group of heating surfaces is formed by bending 18-28 stainless steel pipes. The material of the inlet section of the outer 4 to 6 circles of pipes and the innermost circle of pipes of each group of heating surfaces is TP310HCbN, and the material of the bottom U-shaped bend section and the outlet section is S31035; the material of the inlet section of the remaining pipes is S30432, and the material of the bottom U-shaped bend section and the outlet section is S31035; the tube panel outlet header is made of new martensitic heat-resistant steel.

[0022] Furthermore, the material of the vertical section of the boiler water-cooled wall is SA213-T91, and the superheat degree of the working fluid at the boiler separator outlet is 130°C to 150°C.

[0023] The technical solution of the present invention has the following advantages:

[0024] 1. The technical solution of the present invention does not have a flue gas recirculation fan, and only relies on the flue gas regulating damper to adjust the distribution of heat between superheated steam and reheated steam, ensuring that the steam parameters of the boiler meet the standards within a wider load range, the system configuration is simpler, and the equipment reliability is higher.

[0025] 2. The technical solution of the present invention reasonably distributes the enthalpy increase of each level of heating surface, effectively weakens the influence of smoke temperature deviation on the use temperature of boiler heating surface tubes, and reduces the use of high-grade alloy materials.

[0026] 3. The technical solution of the present invention limits the economizer outlet section to the rear flue through a series-parallel arrangement, reduces the impact of flue gas temperature deviation on the vaporization of the working fluid at the economizer outlet, and eliminates operational risks. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 A schematic diagram of the heating surface arrangement structure of a Π-type secondary boiler with a steam parameter of 630° to 650° according to the present invention;

[0029] Figure 2 This is a simplified diagram of the layout of the primary reheater intermediate header and the secondary reheater intermediate header.

[0030] Description of reference numerals:

[0031] 1- water supply pipe; 2- second-stage economizer; 3- first-stage economizer group 1;

[0032] 4-second group of economizers at the first level; 5-third group of economizers at the first level; 6-economizer outlet pipe;

[0033] 7- primary low-temperature reheater; 8- secondary low-temperature reheater; 9- low-temperature superheater;

[0034] 10-platen superheater; 11-high temperature superheater; 12-primary medium temperature reheater;

[0035] 13-secondary medium temperature reheater; 14-primary high temperature reheater; 15-secondary high temperature reheater;

[0036] 16-main steam pipeline; 17-primary reheat hot section steam pipeline;

[0037] 18- Secondary reheat hot section steam pipe; 19- First-side flue gas regulating damper;

[0038] 20- Secondary flue gas regulating damper; 21- Low-pass side flue gas regulating damper;

[0039] 22-water-cooled wall spiral section; 23-water-cooled wall vertical section; 24-wall superheater;

[0040] 25-Intermediate header of primary reheater; 26-Intermediate header of secondary reheater. DETAILED DESCRIPTION

[0041] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0043] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0045] See also Figure 1 and Figure 2 The present invention provides a 630°~650° Π-type secondary boiler heating surface arrangement structure, comprising a water-cooled wall, an economizer, a primary low-temperature reheater 7, a secondary low-temperature reheater 8, a low-temperature superheater 9, a platen superheater 10, a high-temperature superheater 11, a primary medium-temperature superheater 12, a secondary medium-temperature reheater 13, a primary high-temperature reheater 14, a secondary high-temperature reheater 15 and a wall-wrapped superheater 24;

[0046] The water-cooled wall is provided with a water-cooled wall spiral section 22 and a water-cooled wall vertical section 23 along the height direction; the water-cooled wall spiral section 22 and the water-cooled wall vertical section 23 are transitioned in the form of a two-stage mixed header to reduce the carryover deviation. After flowing out of the water-cooled wall, the working fluid enters each superheater in turn. In order to reduce the heat absorption of the boiler screen area and reduce the use of high-temperature grade materials, the boiler water-cooled wall outlet adopts a higher superheat (130°~150°), and the corresponding water-cooled wall vertical section 23 is made of SA213-T91.

[0047] In order to reduce the enthalpy increase of the heating surface of each level of reheater in the invention, the present invention divides the primary reheater and the secondary reheater into three-level arrangements, and the primary medium-temperature reheater 12 and the secondary medium-temperature reheater 13, the primary high-temperature reheater 14 and the secondary high-temperature reheater 15 are arranged symmetrically in a left-right cross direction along the width direction of the furnace. In order to reduce the steam carryover deviation, the present invention sets a primary reheater intermediate header 25 and a secondary reheater intermediate header 26. The primary reheater intermediate header 25 and the secondary reheater intermediate header 26 are both annular headers. At the same time, in terms of the arrangement mode, the two overlap in the width direction and do not overlap in the height direction to realize the left-right crossover of the intermediate steam and eliminate the steam carryover deviation. The primary reheater intermediate header 25 is connected to the primary medium-temperature reheater 12 and the primary high-temperature reheater 14, and the secondary reheater intermediate header 26 is connected to the secondary medium-temperature reheater 13 and the secondary high-temperature reheater 15.

[0048] The vertical shaft at the rear of the boiler is divided into three flues by a wall-wrapped tube panel, and the three flues are respectively recorded as a front flue, a middle flue and a rear flue; the panel superheater 10 and the high-temperature superheater 11 are arranged at the furnace outlet, the primary medium-temperature reheater 12 and the secondary medium-temperature reheater 13 and the primary high-temperature reheater 14 and the secondary high-temperature reheater 15 are arranged in a horizontal flue in a cross-symmetrical manner along the width direction of the furnace, and the primary low-temperature reheater 7, the secondary low-temperature reheater 8 and the low-temperature superheater 9 are respectively arranged in the front flue, the middle flue and the rear flue;

[0049] The economizer is arranged in three or four stages in the flue at the tail of the boiler, and the wall-wrapped superheater 24 is arranged on the inner wall of the flue;

[0050] The economizer includes a secondary economizer 2 and a primary economizer;

[0051] The first-stage economizer includes the first-stage economizer group 3, the second-stage economizer group 4 and the third-stage economizer group 5; wherein the second-stage economizer 2 adopts an H-shaped fin tube and is arranged in the lower flue of denitrification; the first-stage economizer group 3 is arranged in the front flue, the second-stage economizer group 4 is arranged in the middle flue, and the third-stage economizer group 5 is arranged in the rear flue. The first-stage economizer group 3 and the second-stage economizer group 4 are connected in parallel, and the two have the same inlet and the same outlet, and the outlet is connected in series with the third-stage economizer group 5; according to this arrangement, the working fluid flow share of the first-stage economizer group 3 and the second-stage economizer group 4 is 50% each, and the working fluid flow share of the third-stage economizer group 5 is 100%. The design here concentrates the vaporization deviations scattered in the three flues in the rear flue, and the working fluid vaporization risk is relatively small.

[0052] The water passes through the water supply pipe 1 and the secondary economizer 2, and then enters the first economizer group 3 and the second economizer group 4 of the first stage, and then enters the third economizer group 5, and then flows out through the economizer outlet pipe 6 and enters the water-cooled wall spiral section 22 and then passes through the water-cooled wall vertical section 23 in sequence to heat the water into steam, and the impurities in the steam are removed by the built-in separator of the water-cooled wall. The steam is then further heated by the wall superheater 24, the low-temperature superheater 9, the platen superheater 10, and the high-temperature superheater 11, and then enters the turbine ultra-high pressure cylinder, the primary low-temperature reheater 7, the primary medium-temperature reheater 12, the primary high-temperature reheater 14, the primary reheating hot section steam pipe 17, the turbine high-pressure cylinder, the secondary low-temperature reheater 8, the secondary medium-temperature reheater 13, the secondary high-temperature reheater 15, the secondary reheating hot section steam pipe 18, the turbine medium-pressure cylinder and the low-pressure cylinder through the main steam pipe 16.

[0053] The present invention also includes a smoke regulating baffle;

[0054] The smoke regulating baffles include a first-side smoke regulating baffle 19, a second-side smoke regulating baffle 20 and a low-side smoke regulating baffle 21;

[0055] The flue gas regulating damper 19, the secondary flue gas regulating damper 20 and the low-over-side flue gas regulating damper 21 are respectively arranged at the outlets of the front flue, the middle flue and the rear flue, and each flue gas regulating damper is arranged with 8 sets of actuators along the width direction. By adjusting the opening of each set of regulating dampers through the actuator structure, the distribution of tail flue gas heat between superheated steam and primary / secondary reheated steam can be changed. At the same time, in order to increase the flue gas temperature deviation regulation effect, each set of flue gas regulating dampers is arranged in no less than 6 sets along the width direction of the furnace.

[0056] At the same time, water spray desuperheaters are installed between the low-temperature reheater and the medium-temperature reheater, and between the medium-temperature reheater and the high-temperature reheater.

[0057] In this embodiment, the first-side flue gas regulating baffles 19, the secondary flue gas regulating baffles 20 and the low-side flue gas regulating baffles 21 are arranged in no less than 6 groups along the width direction of the furnace.

[0058] The platen superheater 10 has a plurality of small plates evenly distributed along the width of the furnace, and each small plate is formed by bending 18-28 stainless steel pipes. The outer 6 circles of pipes and the inlet section of the innermost circle of pipes of each small plate are made of TP310HCbN, the bottom U-shaped bend section is made of S31035, and the outlet section is made of S31035; the inlet section and the bottom U-shaped bend section of the remaining pipes are made of S30432, and the outlet section is made of S31035. The enthalpy increase design of the platen superheater 10 is preferably based on the use of mature 9Cr martensitic heat-resistant steel for the outlet header.

[0059] The high-temperature superheater 11 is arranged above the flame deflection angle, and multiple groups of heating surfaces are evenly distributed along the width of the furnace. Each group of heating surfaces is formed by bending 18-28 stainless steel pipes. The outer 4 to 6 circles of tubes and the inlet section of the innermost circle of tubes of each group of heating surfaces are made of TP310HCbN, and the bottom U-shaped bend section and outlet section are made of S31035; the inlet sections of the remaining tubes are made of S30432, and the bottom U-shaped bend section and outlet section are made of S31035; the tube panel outlet header is made of new martensitic heat-resistant steel.

[0060] For the convenience of adjustment, two-stage eight-point water spraying is provided between the low-temperature superheater and the platen superheater 10, and between the platen superheater 10 and the high-temperature superheater. Two-stage four-point water spraying is provided between the low-temperature reheater and the medium-temperature reheater, and between the medium-temperature reheater and the high-temperature reheater.

[0061] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A steam parameter 630°~650° Π-type secondary boiler heating surface arrangement structure, characterized in that: It includes a water-cooled wall, an economizer, a primary low-temperature reheater (7), a secondary low-temperature reheater (8), a low-temperature superheater (9), a platen superheater (10), a high-temperature superheater (11), a primary medium-temperature superheater (12), a secondary medium-temperature reheater (13), a primary high-temperature reheater (14) and a secondary high-temperature reheater (15); The water-cooled wall is provided with a water-cooled wall spiral section (22) and a water-cooled wall vertical section (23) along the height direction; The platen superheater (10) and the high-temperature superheater (11) are arranged at the furnace outlet; the primary medium-temperature reheater (12) and the secondary medium-temperature reheater (13), the primary high-temperature reheater (14) and the secondary high-temperature reheater (15) are arranged in a horizontal flue in a cross-symmetrical manner along the width direction of the furnace; three flues are arranged in the vertical shaft at the rear of the boiler, and the three flues are respectively recorded as the front flue, the middle flue and the rear flue; the primary low-temperature reheater (7), the secondary low-temperature reheater (8) and the low-temperature superheater (9) are respectively arranged in the front flue, the middle flue and the rear flue; The steam parameter 630°~650° Π-type secondary boiler heating surface arrangement structure also includes a primary reheater intermediate header (25) and a secondary reheater intermediate header (26), wherein the primary reheater intermediate header (25) and the secondary reheater intermediate header (26) are both annular headers, which overlap in the width direction but are not overlapped in the height direction. The primary reheater intermediate header (25) is connected to the primary medium-temperature reheater (12) and the primary high-temperature reheater (14), and the secondary reheater intermediate header (26) is connected to the secondary medium-temperature reheater (13) and the secondary high-temperature reheater (15).

2. The 630°-650° Π-type secondary boiler heating surface arrangement structure according to claim 1 is characterized in that: The economizer comprises a secondary economizer (2) and a primary economizer; The first-stage economizer includes a first-stage economizer group (3), a second-stage economizer group (4) and a third-stage economizer group (5); The secondary economizer (2) is arranged in the lower flue of denitrification, and the first group economizer (3), the first-stage second group economizer (4) and the first-stage third group economizer (5) are arranged in three stages in three flues of the boiler tail shaft in a series or parallel manner.

3. The 630°-650° Π-type secondary boiler heating surface arrangement structure according to claim 2 is characterized in that: The first group of economizers (3) of the first stage are arranged in the front flue, the second group of economizers (4) of the first stage are arranged in the middle flue, and the third group of economizers (5) of the first stage are arranged in the rear flue.

4. The 630°-650° Π-type secondary boiler heating surface arrangement structure according to claim 3 is characterized in that: The first-stage first-group economizer (3) and the second-stage second-group economizer (4) are connected in parallel, and the whole after parallel connection is connected in series with the third-stage economizer (5).

5. The 630°-650° Π-type secondary boiler heating surface arrangement structure according to claim 1 is characterized in that: Also includes a smoke regulating damper; The smoke regulating baffle comprises a secondary smoke regulating baffle (19), a secondary smoke regulating baffle (20) and a low-pass side smoke regulating baffle (21); The first flue gas regulating baffle (19), the second flue gas regulating baffle (20) and the low flue gas regulating baffle (21) are respectively arranged at the outlets of the front flue, the middle flue and the rear flue.

6. The 630°-650° Π-type secondary boiler heating surface arrangement structure according to claim 5 is characterized in that: The first-side flue gas regulating baffles (19), the second-side flue gas regulating baffles (20) and the low-side flue gas regulating baffles (21) are arranged in no less than 6 groups along the width direction of the furnace.

7. The 630°-650° Π-type secondary boiler heating surface arrangement structure according to claim 1 is characterized in that: The platen superheater (10) has a plurality of small plates evenly distributed along the width of the furnace, each small plate being formed by bending 18-28 stainless steel tubes, the outer 4-6 circles of tubes and the inlet section of the innermost circle of tubes of each small plate being made of TP310HCbN, the bottom U-shaped bend section being made of S31035, and the outlet section being made of S31035; the inlet sections and bottom U-shaped bend sections of the remaining tubes are made of S30432, and the outlet sections are made of S31035; the tube plate outlet header is still made of mature 9Cr martensitic heat-resistant steel.

8. The 630°-650° Π-type secondary boiler heating surface arrangement structure according to claim 1 is characterized in that: The high-temperature superheater (11) has multiple groups of heating surfaces evenly distributed along the width direction of the furnace, each group of heating surfaces is formed by bending 18-28 stainless steel pipes, the outer 4-6 circles of pipes and the inlet section of the innermost circle of pipes of each group of heating surfaces are made of TP310HCbN, and the bottom U-shaped bend section and outlet section are made of S31035; the inlet sections of the remaining pipes are made of S30432, and the bottom U-shaped bend section and outlet section are made of S31035; the tube panel outlet header is made of new martensitic heat-resistant steel.

9. The steam parameter 630°~650° Π-type secondary boiler heating surface arrangement structure according to claim 1, characterized in that: The material of the boiler water-cooled wall vertical section (23) is SA213-T91, and the superheat degree of the working medium at the boiler separator outlet is 130°C to 150°C.

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