阅读说明：本技术 尾部烟道内置的回形循环流化床锅炉及其驱动发电系统 (Circle-shaped circulating fluidized bed boiler with built-in tail flue and driving power generation system thereof ) 是由 钟文琪 刘雪娇 邵应娟 崔颖 于 2019-09-11 设计创作，主要内容包括：本发明公开了一种烟道内置回形循环流化床锅炉及其驱动的发电系统,该锅炉包括回形炉膛、置于锅炉回形内腔的尾部烟道和关于炉膛中心对称布置的分离器。回形炉膛内环和外环均布有冷壁,按照功能特性分为第一区域冷壁与第二区域冷壁。尾部烟道中沿烟气流动方向依次布置烟气混合室、低温再热器、上级空气预热器、烟气冷却器以及下级空气预热器。本发明的有益效果为,现锅炉结构紧凑一体化,减少约1/3的锅炉岛占用空间,同时中心对称布置的分离器及烟气混合室使烟气对称汇集,有效增加分离器负荷均匀；根据炉膛内部气固流动状态和热量分布将炉膛宽、深方向的边壁区及四角区域分割为不同功能的加热区,减少能量损失,实现灵活调节。(The invention discloses a circulating fluidized bed boiler with a built-in flue and a power generation system driven by the boiler. The inner ring and the outer ring of the square-shaped hearth are uniformly provided with cold walls and are divided into a first area cold wall and a second area cold wall according to functional characteristics. And a flue gas mixing chamber, a low-temperature reheater, a superior air preheater, a flue gas cooler and a subordinate air preheater are sequentially arranged in the tail flue along the flow direction of flue gas. The invention has the advantages that the existing boiler has compact and integrated structure, the occupied space of a boiler island of about 1/3 is reduced, meanwhile, the separators and the flue gas mixing chambers which are arranged in a centrosymmetric way enable flue gas to be collected symmetrically, and the load uniformity of the separators is effectively increased; according to the gas-solid flow state and heat distribution in the hearth, the wall area and the four corner areas in the width and depth directions of the hearth are divided into heating areas with different functions, so that the energy loss is reduced, and flexible adjustment is realized.)

1. The utility model provides a built-in shape of returning circulating fluidized bed boiler of afterbody flue, includes the shape of returning boiler main part (1) that is enclosed by furnace inner wall, outer wall, wherein, be equipped with inner ring cold wall (2) and outer loop cold wall (3), its characterized in that on the wall of furnace inner wall and outer wall respectively: a tail flue (14) is arranged in a closed space which is formed by enclosing the inner wall of the hearth, and a heat exchange device is arranged in the tail flue (14).

2. The circulating fluidized bed boiler with a built-in back flue according to claim 1, wherein: the inner ring cold wall (2) and the outer ring cold wall (3) are respectively divided into a first area cold wall and a second area cold wall; the first area cold wall comprises an inner ring first area cold wall (201) and an outer ring first area cold wall (301), wherein the inner ring first area cold wall and the outer ring first area cold wall are arranged on the periphery of the boiler main body and used for carrying out primary high-temperature heating on the circulating working medium; the second area cold wall comprises an inner ring second area cold wall (202) and an outer ring second area cold wall (302) which are arranged at four corners of the boiler main body and carry out high-temperature reheating on the wall surface.

3. The circulating fluidized bed boiler with a built-in back flue according to claim 1, wherein: according to the flowing direction of the hearth flue gas, the heat exchange device in the tail flue (14) comprises a low-temperature reheater (15), a superior air preheater (16), a flue gas cooler (17) and a subordinate air preheater (18) which are arranged in sequence.

4. The circulating fluidized bed boiler with a built-in back flue according to claim 1, wherein: the boiler also comprises separators (6) which are arranged outside the boiler main body (1) and are symmetrically arranged, wherein the inlets of the separators (6) are connected with the side wall of the upper part of the boiler main body (1) through pipelines, and the outlets are communicated with the inlet of the tail flue (14) through pipelines.

5. The circulating fluidized bed boiler with a built-in back flue according to claim 4, wherein: and a heating surface is arranged on the inner surface of the separator (6) and serves as an upper working medium preheater (7).

6. The circulating fluidized bed boiler with a built-in back flue according to claim 4, wherein: the outlet of the separator (6) is collected into a flue gas mixing chamber (12) through a pipeline, and the flue gas mixing chamber (12) is communicated with the inlet of a tail flue (14).

7. The circulating fluidized bed boiler with a built-in back flue of claim 6, wherein: a guide plate is arranged in the communicating part of the flue gas mixing chamber (12) and the outlet pipeline of the separator.

8. The circulating fluidized bed boiler with a built-in back flue of claim 6, wherein: a smoke expansion area (13) is arranged between the smoke mixing chamber (12) and the inlet of the tail flue (14), the smoke expansion area (13) is of an expansion structure with a narrow upper part and a wide lower part, and the shape of an outlet is consistent with that of the inlet of the tail flue.

9. The circulating fluidized bed boiler with a built-in back flue according to claim 1, wherein: the bottom of the hearth is provided with an air distribution plate, the surface of the air distribution plate is provided with a cooling heating surface, and the heating surface is used as a lower working medium preheater (5).

10. A power generation system, characterized in that the power generation system is driven by the loop-shaped circulating fluidized bed boiler arranged in the tail flue of any one of claims 1 to 9 to generate power.

Technical Field

The invention relates to a circulating fluidized bed boiler and a driving power generation system thereof, in particular to a clip-shaped circulating fluidized bed boiler with a built-in tail flue and a driving power generation system thereof.

Background

In the amplification process of the circulating fluidized bed coal-fired boiler, the proportion of the heating surface of the high-temperature region is increased because the acceleration of the heating area of the boiler hearth is smaller than the increasing speed of the heat release capacity of the hearth, and the heating surface is difficult to arrange, so that the method is a general challenge in the large-scale fluidized bed coal-fired boiler. Simply increasing the heating surface in the furnace can cause the heating screen in the furnace to be arranged too much and too densely, which causes serious unevenness of combustion power field and heat transfer in the furnace and brings problems of boiler efficiency and safety; and the volume of the hearth and the whole boiler island is too large by simply increasing the volume capacity of the hearth, so that the construction and maintenance cost is increased. Meanwhile, along with the increase of the volume capacity of the boiler and the increase of the heating surface in the boiler, the uneven distribution of the heat load in the coal-fired boiler along the width and depth directions of the hearth is aggravated, and the problem is also the important problem that the safety, the working medium quality and the unit efficiency of the boiler are seriously influenced. On the other hand, a large circulating fluidized bed boiler needs to adopt a parallel arrangement structure of a plurality of cyclone separators, and generally faces the difficult problems of gas-solid flow, temperature and heat flow density in the boiler caused by uneven cyclone load.

In chinese patent nos. CN201510217373.9 and CN201110031308.9, the shape of the boiler furnace is designed to be a square shape to increase the heating surface, as shown in fig. 1(a), but these designs have the following problems: (1) the tail flues are all located on one side outside the hearth main body, and the flue gas at the outlets of the cyclone separators is firstly collected to one or two upper flues in sequence and then flows to the tail flues. Although various flue divergent designs are adopted, the upper flue structure which is converged in sequence fundamentally causes different dynamic states at the outlets of the cyclone separators (particularly the cyclone separators which are positioned at the same side of the furnace body), thereby causing uneven load of the cyclone separators. Especially under the condition of variable working conditions, the unevenness is more serious; (2) the increased heating surface can cause the uneven distribution of heat load in the coal-fired boiler along the width and depth direction of the hearth to be aggravated. In order to solve the problems of overlarge integral volume of the boiler, uneven load of a separator, uneven heat load in the boiler and the like, the invention provides a boiler device with a tail flue arranged in an inner annular space of a square-shaped circulating fluidized bed and a coal-fired power generation system driven by the boiler device.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a compact type zigzag fluidized bed boiler with a built-in flue, wherein the heat absorption area ratio of a working medium high-temperature area is large, the space of a boiler island is greatly saved, and a plurality of separators work in parallel and uniformly; it is a second object of the present invention to provide a power cycle power plant driven by the boiler.

The technical scheme is as follows: the invention relates to a zigzag circulating fluidized bed boiler with a built-in tail flue, which comprises a zigzag boiler main body enclosed by a hearth inner wall and an outer wall, wherein an inner ring cold wall and an outer ring cold wall are respectively arranged on the wall surfaces of the hearth inner wall and the outer wall, and the zigzag circulating fluidized bed boiler is characterized in that: a tail flue is arranged in a closed space formed by the inner wall of the hearth, and a heat exchange device is arranged in the tail flue.

Preferably, the distance C between the inner ring and the outer ring of the hearth₁W is W/3, and W is the minimum dimension of the section of the inner ring of the hearth; space C between hearth inner ring and tail flue₂1.5 m. Size C of the four corner region-₃＝1.2C₁。

The vertical heights of the inner ring cold wall and the outer ring cold wall are the same, and the inner ring cold wall and the outer ring cold wall are both of a vertical ascending type. The outlet of the inner ring cold wall and the outlet of the outer ring cold wall are connected with the inlet of the primary heating header, and the outlet of the screen type high-temperature reheater is connected with the inlet of the reheating header. A large number of secondary tuyeres are distributed on the bevel slope surface of the outer ring furnace wall.

The inner ring cold wall and the outer ring cold wall are divided into a first area cold wall and a second area cold wall; the first area cold wall comprises an inner ring first area cold wall and an outer ring first area cold wall which are arranged on the periphery of the boiler main body and used for carrying out primary high-temperature heating on the circulating working medium, and the working medium vertically and parallelly rises from the bottom in the first area cold wall; the second area cold wall comprises an inner ring second area cold wall and an outer ring second area cold wall which are arranged at four corners of the boiler main body and used for reheating the wall surface at a high temperature, the inlet of the second area cold wall is connected with the outlet of the low-temperature reheater, and the outlet of the second area cold wall is connected with the inlet of the reheating working medium header.

According to the flowing direction of the hearth flue gas, the heat exchange device in the tail flue comprises a low-temperature reheater, a superior air preheater, a flue gas cooler and a subordinate air preheater which are sequentially arranged.

The screen type high-temperature reheaters are arranged on the upper portion of the inner wall of the hearth in an embedded mode, the screen type high-temperature reheaters are symmetrically arranged on the upper portion of the inner ring furnace wall and are arranged in the depth direction of the hearth, and the height of a single screen of each screen type high-temperature reheater is lower than the height of an inlet flue of the separator. The inlet of the screen type high-temperature reheater is connected with the outlet of the low-temperature reheater, and the outlet of the screen type high-temperature reheater is connected with the inlet of the reheating header.

The low-temperature reheater is arranged in a bilaterally symmetrical double-flow way, namely, double-inlet and double-outlet.

The heating pipe wall of the flue gas cooler is also arranged in a double-flow way, the pipe wall is longitudinally divided into odd and even pipe rows, and the odd and even pipe groups are arranged in a staggered and staggered manner.

The air preheater adopts a pipe type, smoke in the pipe and air outside the pipe. The air preheater is divided into two stages, the upper stage air preheater is a single return stroke, and the lower stage air preheater is a three return stroke. The outlet of the lower air preheater is connected with the inlet of the upper air preheater, and the outlet of the upper air preheater is connected with the primary/secondary air inlet. The cold air is in double-in and double-out in the upper air preheater and the lower air preheater.

The outer side of the boiler main body is provided with symmetrically arranged separators, the inlets of the separators are connected with the side wall of the upper part of the boiler main body through pipelines, and the outlets of the separators are communicated with the inlet of the tail flue through a pipeline.

Preferably, the separator is a cyclone separator.

And a heating surface is arranged on the inner surface of the separator and serves as an upper working medium preheater.

The bottom of the separator is connected with a return pipe, the bottom of the return pipe is divided into two paths, one path is directly connected with a return inlet at the bottom of the hearth through a return feeder, the other path is connected with an external high-temperature reheater or an external ash storage box through an ash content control valve, and then the other path is connected to a dense-phase area at the bottom of the hearth through an outlet of the external reheater or the ash storage box.

Furthermore, the structures and types of the four separators on the left wall and the right wall of the hearth, the material returning devices connected with the separators and the external heat exchange devices are completely consistent, and the external heat exchangers are external high-temperature reheaters; two separation devices on the same side are in mirror symmetry, and the centers of dust-containing flue gas inlets of the two separators are located at two quartering points in the depth direction of the outer wall. The center of the dust-containing smoke inlet of the two sets of separators on the front wall and the rear wall of the hearth is positioned in the center of the width direction of the outer wall of the hearth, the connected external devices are ash storage boxes, the structures of the two external ash storage boxes are completely consistent, and heat-insulating materials are laid on the inner wall of each ash storage box.

The outlet of the separator is collected to a flue gas mixing chamber through a pipeline, and the flue gas mixing chamber is communicated with the inlet of the tail flue. Preferably, the flue gas mixing chamber is in a regular N-edge shape, and the number of edges of the flue gas mixing chamber is equal to that of the separators. The flue gas outlet at the upper part of the separator is connected with the flue gas mixing chamber at each vertex angle of the regular polygon flue gas mixing chamber through a pipeline. The distance a between the opposite sides of the flue gas mixing chamber is equal to the minimum size of the cross section of the square-shaped hearth main body. The diameter D of the circular outlet at the bottom of the flue gas mixing chamber is equal to the minimum size on the cross section of the tail flue.

And a guide plate is arranged in the communicating part of the flue gas mixing chamber and the outlet pipeline of the separator.

The baffles are located on the quarter lines of the respective top corners, i.e. the angle α is 45 ° (N-2)/N. Distance l between one end of guide plate and vertex angle₁R is the diameter of the positive N deformed circumcircle; distance l between the other end of the connecting line and the vertex angle₁＝R/3。

A smoke expansion area is arranged between the smoke mixing chamber and the inlet of the tail flue, the smoke expansion area is of an expansion structure with a narrow upper part and a wide lower part, and the shape of an outlet is consistent with that of the inlet of the tail flue.

And an air distribution plate is arranged at the bottom of the hearth, a cooling heating surface is arranged on the surface of the air distribution plate, and the heating surface is used as a lower working medium preheater.

The power generation system is driven by the clip-shaped circulating fluidized bed boiler arranged in the tail flue to generate power.

The power generation system driven by the flue built-in zigzag fluidized bed boiler is a system of 'single reheating + two-stage compression + intermediate cooling', and comprises the boiler heating surface, a high-pressure turbine, a low-pressure turbine, a high-temperature heat regenerator, a low-temperature heat regenerator, an auxiliary compressor, a main compressor and an intermediate cooler. The high-pressure turbine inlet is connected with the outlet of a primary heating header of the boiler, the high-pressure turbine outlet is connected with the inlet of a low-temperature reheater of the boiler, the low-pressure turbine inlet is connected with the outlet of the reheating header, and the outlet is connected with the inlet of the hot side of the high-temperature reheater. And the hot side inlet of the low-temperature heat regenerator is connected with the hot side outlet of the high-temperature heat regenerator, and the hot side outlet of the low-temperature heat regenerator is connected with the inlet of the intercooler and the inlet of the auxiliary compressor. And a cold side inlet of the low-temperature heat regenerator is connected with an outlet of the main compressor, and a cold side outlet of the low-temperature heat regenerator is connected with an outlet of the auxiliary compressor, a cold side inlet of the high-temperature heat regenerator and an inlet of the boiler flue gas cooler. And the outlet of the cold side of the high-temperature heat regenerator is connected with the outlet of an upper working medium preheater at an air cooling position and the inlet of a cold wall header. Preferably, the flow distribution ratio of the working medium flowing into the inner and outer ring cold walls of the hearth (D)₁:D₂) The perimeter (L) of the inner and outer ring walls after the removal of the four corners₁And L₂) It is decided that,

d is the total working medium flow. The primary flow dividing coefficient is the ratio of the flow of the working medium flowing into the boiler flue gas cooler to the total flow of the working medium, and the secondary flow dividing coefficient is the ratio of the flow of the working medium flowing into the intercooler 25 to the total flow of the working medium, preferably, the primary flow dividing coefficient is 0.02-0.05, and the secondary flow dividing coefficient is 0.5-0.75.

Has the advantages that: compared with the prior art, the invention has the following remarkable advantages:

(1) the tail flue is arranged in the square-shaped inner cavity, so that on one hand, the idle space of the square-shaped inner cavity can be fully utilized, the compact integration of the boiler is realized, and the occupied space of a boiler island of 1/3 is reduced; on the other hand, the design that the inner ring of the hearth and the tail flue are mutually wrapped can improve the heat insulation performance of the clip-shaped hearth and the tail flue and reduce the heat insulation material consumption of the outer wall of the inner ring and the outer wall of the tail flue.

(2) The separators are completely and centrosymmetrically arranged, so that the separated flue gas is symmetrically collected to the flue, the structural and flow direction symmetry can effectively improve the uniformity of the working load of each separator, and the uniformity and stability of a combustion power field and heat transfer in the furnace are facilitated; the problem of traditional separator arrange side by side along the furnace degree of depth, export flue gas collects in the top flue and then leads to the afterbody flue of arranging furnace one side in order, and each separator top export flue structure of homonymy is different, and the serious inequality of on-the-way separator work load that brings along the on-the-way constantly change in top export flue gas flow field is effectively improved.

(3) The method is characterized in that the wall area and the four corner areas in the width and depth directions of the hearth are divided into heating areas with different functions according to the gas-solid flow state and heat distribution in the hearth, the square-shaped wall area with uniform flow and high heat load is used as a main gas heating area of a working medium, and when the heat absorption capacity meets the requirement of primary heating of the working medium, the problems of energy loss, regulation and control and safety when the working mediums with different temperatures are mixed, which are caused by the fact that the heat absorption capacity of the working medium in the tube is generally low and the temperature is seriously uneven, are avoided; the cold wall of the square-rectangular-shaped region with relatively low heat load is arranged into a high-temperature reheater, the working medium in the high-temperature reheater is parallel to the screen-type high-temperature reheater arranged in the high-heat load region and the high-temperature reheater arranged on the external heating surface, the screen-type high-temperature reheating positioned in the high-temperature region of the hearth can effectively make up for insufficient heat absorption caused by low heat flux density at the four corners of the square-shaped hearth, and the external heat exchange can effectively adjust the temperature of the working medium, so that the high-efficiency and low.

(4) The top of the separator is provided with a regular polygon flue gas mixing chamber, so that the symmetry and uniformity of a flow field at the top of the separator are further ensured; the flue gas guide plate is arranged in the mixing chamber, so that on one hand, flue gas entering the mixing chamber is fully diffused along the guide plate to form better mixing, and the uniformity of a flue gas power field and a temperature field entering the tail flue is ensured; meanwhile, the guide plate can also reduce the reverse influence of the mixing chamber flue gas field on the separator. The bottom of the flue gas mixing chamber is provided with a flue gas expansion area, which is also beneficial to improving the uniformity of a flue gas dynamic field and a temperature field entering the tail flue.

(5) An external reheater is arranged at the lower part of the separator in the depth direction of the rectangular furnace, and the reheating temperature can be effectively adjusted by adjusting the amount of circulating ash entering the external reheater; meanwhile, in the width direction of the hearth, the ash storage hopper is arranged at the lower part of the separator, and the bed temperature in the width direction of the hearth is changed by controlling the circulating ash amount passing through the ash storage hopper, so that the main air temperature is adjusted without influencing the working states of other heat exchangers. The design scheme that the external reheater is arranged in the depth direction and the main air adjusting ash storage hopper is arranged in the width direction according to the structural characteristics of the rectangular hearth is favorable for realizing independent and flexible adjustment of the main air temperature and the reheating temperature.

(6) After flowing out of the low-temperature reheater 10, the working medium is divided into three branches, and the three branches uniformly flow into the four-corner high-temperature reheater, the screen-type high-temperature reheater 4 and the external high-temperature reheater 10 respectively. The working medium flow division is beneficial to reducing the reheating pressure drop of the working medium.

(7) The air preheater is arranged by adopting a single-return-stroke upper-level air preheater 11 and a three-return-stroke lower-level air preheater 13, so that on one hand, the heat exchange area of the air preheater is greatly increased, the flue gas waste heat utilization capacity of a tail flue is improved, and the exhaust gas temperature is reduced; on the other hand, the design of the multi-return air preheater can reduce the temperature difference between the single-return flue gas side and the air side, reduce the thermal deformation of the air preheater caused by the large temperature difference, prolong the service life of the air preheater and improve the upper limit of the temperature of the hot air at the outlet of the air preheater.

Drawings

FIG. 1(a) is a schematic perspective view of a prior art serpentine boiler;

FIG. 1(b) is a schematic perspective view of the boiler structure of the present invention;

FIG. 2 is a schematic structural view of the present invention;

FIG. 3 is a block diagram of the present invention for partitioning the wall area and distributing the function of the boiler;

FIG. 4 is a schematic top view of a boiler in an embodiment of the invention;

FIG. 5 is a block diagram of a top flue gas mixing chamber of a boiler in an embodiment of the present invention;

FIG. 6 is a schematic illustration of a power generation system of the present invention;

FIG. 7(a) is the flue gas flow at the outlet of 6 separators in the example;

FIG. 7(b) shows the state of highly uniform particle motion in the separator in the example.

Detailed Description

The technical scheme of the invention is further explained by combining the attached drawings.

As shown in fig. 1(a), the inventor has found that the arrangement of the back pass 27 of the circulating fluidized bed boiler of the prior art at one side of the boiler main body 26 is one of the causes of asymmetry of the separator outlet pass structure. Almost all circulating fluidized bed all adopt the afterbody flue to all lie in furnace main part one side at present, and a plurality of separator export flue gas collects one or two upper portion flues in order, and the rethread is toward the afterbody flue. The fluidized bed boiler system with the design has larger overall occupied area, and meanwhile, the flue structure which is collected in sequence fundamentally determines the difference of the dynamic states of the outlets of the separators, thereby causing the uneven working state of the separators. The invention provides a boiler structure, wherein tail flues are positioned in an annular chamber in the middle of an annular hearth, separators arranged around the hearth are symmetrical about the center of the hearth, and outlet flues of the separators are synchronously and symmetrically converged to a flue gas mixing chamber at the top of the hearth, as shown in figure 1 (b).

The boiler can solve the problems of large flow of working medium, large pressure drop, high exhaust gas temperature, difficult arrangement of the working medium heating surface in a high-temperature area, serious uneven load of a separator, insufficient penetrating power of secondary air and the like in the large-scale process of the CFB boiler, and can greatly reduce the occupied space of a boiler island, simplify the arrangement of furnace pipelines, homogenize a flow field, reduce the abrasion of the heating surface and reduce the heat preservation cost. The symmetry of the top flue effectively ensures the uniformity of the dynamic state of the outlet, and eliminates the influence of the nonuniformity of the tail flue on the separation working state. As shown in fig. 7, fig. 7(a) shows the simulated statistics of the gas flow distribution at the outlets of 6 separators after the flue structure is arranged in a centrosymmetric manner, and the results show that the gas-phase flow field of the separators in the structure is highly uniform; the simulation results of fig. 7(b) show a highly uniform particle motion state within the separator after both the separator and the flue structure have been arranged centrosymmetrically.

As shown in FIG. 2, the flue-embedded square-wave fluidized bed boiler mainly comprises a square-wave hearth, a separator, an external heater/ash storage box and a tail flue. Cold walls are uniformly distributed on the wall surfaces of the inner ring and the outer ring of the furnace wall of the square hearth, first cold wall areas including 201 and 301 are arranged on the cold walls along the square side wall areas, and cold walls in four corner areas are arranged on the wall surfaces of the high- temperature reheaters 202 and 302. The screen type high-temperature reheaters 4 are symmetrically arranged on the left side wall surface and the right side wall surface of the inner ring furnace wall, the lower working medium preheaters 5 are arranged at the air distribution plates, the separators 6 are symmetrically arranged relative to the hearth respectively, and the separators are preferably cyclone separators. The working medium heating surface in the separator is a superior working medium preheater 7, an external high-temperature reheater 10 is arranged at the feed back section of four groups of separators on the left wall and the right wall of the hearth, and the high-temperature ash share entering the external high-temperature reheater 10 is adjusted through an ash control valve 9. An external ash storage box 11 is arranged at the feed back section of the two-component separator on the front wall and the rear wall of the hearth, and the flow of high-temperature ash flowing into the hearth from the external ash storage box 11 is adjusted through an ash amount control valve. The tail flue is arranged in the square-shaped inner cavity of the boiler, and a flue gas mixing chamber 12, a flue gas expansion area 13, a low-temperature reheater 15, a superior air preheater 16, a flue gas cooler 17 and a subordinate air preheater 18 are sequentially arranged in the tail flue along the flow direction of flue gas.

As shown in figure 3, the inner ring cold wall 2 and the outer ring cold wall 3 are respectively divided into two parts according to the gas-solid flow and heat distribution state in the hearth, the first part is a cold wall 2-1 arranged along the inner ring side wall area and a cold wall 3-1 of the outer ring area corresponding to the inner ring side wall area by separating the hearth space, and the second part is cold walls 2-2 and 3-2 of the four corner areas of the annular hearth. The cold walls 2-1 and 3-1 function as primary high temperature carbon dioxide working medium heaters, and the working medium vertically rises from the bottom in parallel. The cold walls 2-2 and 3-2 in the four corner areas are wall surface high-temperature reheaters, the inlets of the cold walls are connected with the outlets of the low-temperature reheaters 15, and the outlets of the cold walls are connected with the inlets of the reheated working medium header tanks. Preferably, the distance C between the inner ring and the outer ring of the hearth₁W is W/3, and W is the minimum dimension of the section of the inner ring of the hearth; space C between hearth inner ring and tail flue₂1.5 m. Size C of the four corner region-₃＝1.2C₁。

As shown in fig. 4, the six groups of separators are arranged in a completely central symmetrical manner. Further, the structures and types of the four separators on the left wall and the right wall of the hearth, the material returning devices connected with the separators and the external heat exchange devices are completely consistent, and the external heat exchangers are external high-temperature reheaters 10; two separation devices on the same side are in mirror symmetry, and the centers of dust-containing flue gas inlets of the two separators are located at two quartering points in the depth direction of the outer wall. The center of the dust-containing smoke inlet of the two sets of separators on the front wall and the rear wall of the hearth is positioned at the center of the width direction of the outer wall of the hearth, the connected external device is an ash storage box 11, the structures of the two external ash storage boxes are completely consistent, and heat insulating materials are laid on the inner wall of the ash storage box. Preferably, the flue gas mixing chamber 12 is in a regular N-sided shape, and the number of sides is equal to the number of separators. The flue gas outlet at the upper part of the separator is connected with the flue gas mixing chamber at each vertex angle of the regular polygon flue gas mixing chamber through a pipeline. The distance a between the two sides of the flue gas mixing chamber is equal to the minimum size of the cross section of the annular hearth body. The diameter D of the circular outlet at the bottom of the flue gas mixing chamber is equal to the smallest dimension in the cross-section of the back pass 14. The flue gas entrance of each apex angle region in flue gas mixing chamber 12 respectively sets up 3 guide plates, and the guide plate is located the quartering line of each apex angle, and angle alpha is 45 (N-2)/N promptly. One end of three guide plates is connected into a straight line and has a distance l from the vertex angle₁R is the diameter of the positive N deformed circumcircle; distance l between the other end of the connecting line and the vertex angle₁R/3. The flue gas outlet at the upper part of the separator 6 is connected with the flue gas mixing chamber at each vertex angle of the regular polygon flue gas mixing chamber 12 through a pipeline, so as to further ensure the symmetry and uniformity of the top flow field of the separator. The flue gas guide plate is arranged in the mixing chamber, so that on one hand, flue gas entering the mixing chamber is fully diffused along the guide plate to form better mixing, and the uniformity of a flue gas power field and a temperature field entering the tail flue is ensured; meanwhile, the guide plate can also reduce the reverse influence of the flue gas flow field of the mixing chamber on the separator. The bottom of the flue gas mixing chamber is provided with a flue gas expansion area, which is also beneficial to improving the uniformity of a flue gas dynamic field and a temperature field entering the tail flue.

As shown in FIG. 5, the boiler-driven cycle power generation apparatus of the present invention comprises the above boiler heating surface, as well as a high pressure turbine 19, a low pressure turbine 20, a high temperature regenerator 21, a low temperature regenerator 22, an auxiliary compressor 23, a main compressor 24, and an intercooler 25. The inlet of the high-pressure turbine 19 is connected with the outlet of a primary heating header of the boiler, the outlet of the high-pressure turbine 19 is connected with the inlet of a low-temperature reheater 15 of the boiler, the inlet of the low-pressure turbine 20 is connected with the outlet of the reheating header, and the outlet of the low-pressure turbine is connected with the inlet of the hot side of the high-temperature reheater 21. And the hot side inlet of the low-temperature regenerator 22 is connected with the hot side outlet of the high-temperature regenerator 21, and the hot side outlet is connected with the inlet of the intercooler 25 and the inlet of the auxiliary compressor 23. The cold side inlet of the low temperature regenerator 22 is connected to the outlet of the main compressor 24 and the cold side outlet is connected to the outlet of the auxiliary compressor 23, the cold side inlet of the high temperature regenerator 21 and the inlet of the boiler flue gas cooler 17. And a cold side outlet of the high-temperature heat regenerator 21 is connected with a first working medium preheating 6 outlet at an air cooling position and a cold wall header inlet.

Hereinafter, embodiments of a rectangular circulating fluidized bed boiler having a built-in tail flue and a power generation system driven by the boiler will be described.

This example S-CO with 600MW power generation capacity₂For example, a circulating fluidized bed boiler is a square-shaped hearth, the width and the depth of an inner ring boiler wall of the boiler are 15m multiplied by 25m, the distance between an inner ring and an outer ring of the hearth is 5m, and the distance between the inner ring and a tail flue of the hearth is 1.5 m. The inner ring cold wall and the outer ring cold wall are respectively divided into a sidewall area I and a four-corner area II according to the gas-solid flow and the heat distribution state in the hearth, wherein the size of the four-corner area is 6m multiplied by 4. The screen type high-temperature reheaters 4 are symmetrically arranged on the upper portion of the inner ring furnace wall and are arranged in the depth direction of the hearth, and the height of a single screen of the screen type high-temperature reheater 4 is lower than that of an inlet flue of the separator. The inlet of the screen type high-temperature reheater 4 is connected with the outlet of the low-temperature reheater 15, and the outlet is connected with the inlet of the reheating header.

As shown in fig. 4, there are six groups of separators, and the six groups of separators are arranged in a completely central symmetry. Further, the structures and types of the four separators on the left wall and the right wall of the hearth, the material returning devices connected with the separators and the external heat exchange devices are completely consistent, and the external heat exchangers are external high-temperature reheaters 10; two separation devices on the same side are in mirror symmetry, and the centers of dust-containing flue gas inlets of the two separators are located at two quartering points in the depth direction of the outer wall. The center of the dust-containing smoke inlet of the two sets of separators on the front wall and the rear wall of the hearth is positioned at the center of the width direction of the outer wall of the hearth, the connected external device is an ash storage box 11, the structures of the two external ash storage boxes are completely consistent, and heat insulating materials are laid on the inner wall of the ash storage box.

As shown in fig. 5, the flue gas mixing chamber 12 has a regular hexagonal shape. The flue gas outlet at the upper part of the separator is connected with the flue gas mixing chamber at each vertex angle of the regular hexagon flue gas mixing chamber through a pipeline. The distance from the opposite side of the flue gas mixing chamber is 25 m. The diameter of the circular outlet at the bottom of the flue gas mixing chamber is 12 m. The inside regional flue gas entrance at each apex angle of flue gas mixing chamber 12 respectively sets up 3 guide plates, and the guide plate is located the quartering line at each apex angle, and the contained angle is 30 between the guide plate. One end of three guide plates is connected into a straight line and has a distance l from the vertex angle₁1.73m, and the distance l between the other connecting line and the vertex angle₁5.78 m. The bottom outlet of the flue gas mixing chamber is connected with a flue gas expansion area 13, the flue gas expansion area is of an expansion structure with a narrow upper part and a wide lower part, the upper flue gas inlet is circular, and the lower outlet is rectangular and is connected with the inlet of a tail flue 14.

600MWS-CO driven by zigzag fluidized bed boiler with built-in flue₂The working medium flow of the circulating coal-fired power generation system is 15400t/h, and the system process is shown in FIG. 5. Firstly, the working medium at the outlet of the intercooler 25 flows into the main compressor 24 and is compressed from 7.6MPa to 29.93MPa, then flows into the low-temperature heat regenerator 22 and is heated to 226.5 ℃, the pressure is reduced to 29.75MPa, and the working medium at the outlet of the auxiliary compressor 23 are converged at the cold side outlet of the low-temperature heat regenerator 22 and are subjected to primary shunting. First order splitting factor X₁The split working medium flows into the flue gas cooler 17, the middle-level working medium preheating 5 and the first working medium preheating 7 in sequence to be heated, wherein the split working medium is 0.05. The rest working medium flows into the high-temperature heat regenerator 21 to be heated, the temperature is heated to 532 ℃, and the rest working medium is converged with the flow splitting working medium in the cold wall header, and the pressure is 29.57MPa at the moment. The working medium flows into the inner and outer annular side wall cold walls 2-1 and 3-1 from the cold wall header uniformly to be heated to 650 ℃, enters the primary heating header connected with the outlet of the cold wall, the pressure is 29MPa at the moment, and then flows into the high pressure turbine 19 to release heat and do work. The working medium with the temperature/pressure parameter of 563.8 ℃/15.47MPa is discharged from the high-pressure turbine 19 and then flows into the boiler again for re-heatingAnd (4) heating. The working medium is preheated to 564 ℃ before the low-temperature reheater 15, then the working medium is divided into three streams at the outlet of the low-temperature reheater 15, 20% of the working medium uniformly flows into the reheaters 2-2 and 3-2 at the four-corner wall surfaces of the square hearth, 60% of the working medium uniformly flows into two groups of screen-type high-temperature reheaters 3 which are symmetrical about the center of the hearth to be heated, and the rest 20% of the working medium uniformly flows into 4 external high-temperature reheaters 10 to be heated. The three working medium flows are heated to 650 ℃, then mixed in a reheating header, the pressure is 15MPa at the moment, and then the working medium flows into a low-pressure turbine 20 to release heat and do work.

As shown in fig. 6, the working medium discharged from the low-pressure turbine 20 can be regarded as exhaust gas, the temperature/pressure parameter of the exhaust gas is 564 ℃/7.9MPa, then the exhaust gas flows into the high-temperature regenerator 21 as a heat source to release heat, the exhaust gas is discharged from the high-temperature regenerator 21 when the temperature of the exhaust gas is reduced to 237 ℃ (the pressure is 7.8MPa), the exhaust gas enters the low-temperature regenerator 22 to release heat continuously, the exhaust gas is discharged from the low-temperature regenerator 22 when the temperature is reduced to 90 ℃ (the pressure is 7.7MPa), the exhaust gas is converted into a circulating working medium, and secondary flow division is started. Coefficient of secondary split X₂Most of the split working medium flows into the intercooler 25 for further cooling to 32 ℃ (the pressure is 7.6MPa), and then flows into the main compressor 24 for compression and the low-temperature heat regenerator 22 for heating in sequence. And the other part of the split working medium flows into an auxiliary compressor 23 to be compressed, and primary circulation of the coal-fired power generation system is completed.

When the boiler operates under variable working conditions, the bed temperature can be changed, the operation stability of the boiler is reduced, the opening degree of the ash amount control valve 9 can be changed at the moment, the high-temperature ash flow rate of the external ash storage box 11 flowing into the hearth is adjusted, the bed temperature is maintained to be stable, the high-temperature ash share flowing into the external high-temperature reheater 10 is adjusted in a matching mode, the bed temperature of the external heat exchanger is maintained to be stable, and the operation stability of the boiler is improved.

In the embodiment, cold air at a normal temperature of 15-25 ℃ is firstly heated to 300 ℃ by flue gas from an outlet of a flue gas cooler 17 in a lower-stage air preheater 18, then flows into an upper-stage air preheater 16 to be continuously heated to 493 ℃, and is respectively used as primary air and secondary air to be sent into a hearth according to a ratio of 6: 4. S-CO₂Flue gas of a circulating coal-fired fluidized bed rectangular boiler tail flue sequentially flows through a low-temperature reheater 15, an upper-stage air preheater 16, a flue gas cooler 17 and a lower portionAfter the stage air preheater 18, the exhaust gas temperature can be reduced to 129 ℃, which is similar to the exhaust gas temperature of a steam CFB boiler, and the exhaust gas heat loss is reduced to a reasonable range.

In the present invention, the primary flow-dividing coefficient X₁Is one of the key parameters for improving the efficiency of the boiler, and the flow dividing coefficient X₁The increase of the heat recovery efficiency can improve the efficiency of the boiler, but can cause the reduction of the heat quantity recovered by exhaust gas in the heat regenerator, the increase of the heat quantity radiated by circulation, and the reduction of the circulation efficiency. In the case where the system pipe heat dissipation loss and the generator efficiency are assumed to be constant values, the power generation efficiency of the system is determined only by the product of the cycle efficiency and the boiler efficiency, and the larger the product is, the higher the power generation efficiency is. At X₁When the power generation efficiency is 0.02-0.05, the power generation cycle has high boiler efficiency and cycle efficiency, and the power generation efficiency is high at the moment. S-CO₂Setting secondary flow dividing coefficient X in power circulation₂The purpose is to avoid the 'pinch point' problem of the heat regenerator, reduce the terminal temperature difference of the low-temperature heat regenerator 22 and improve the cycle efficiency. Terminal temperature difference of low temperature regenerator 22 is dependent on X₂Is increased and decreased, the terminal temperature difference of the high temperature regenerator 21 is increased and decreased with X₂Is increased when X is increased₂When the temperature is 0.5-0.75, the terminal temperatures of the high-temperature regenerator and the low-temperature regenerator are both low, and the circulation efficiency is high.