CN104791749B - Band pipe laying and evaporation coil direct current couple CFB injection boiler with Natural Circulation - Google Patents

Abstract

The utility model relates to a CFB steam injection boiler with buried pipes and evaporation coils coupled with direct current and natural circulation, which belongs to the technical field of oil field steam injection boilers. In order to solve the problem that the existing natural circulation circulating fluidized bed oilfield steam injection boiler has the problem that the inner wall of the water wall tube is prone to salt scale, which will lead to deterioration of heat transfer and tube burst in the long run. The lower ends of the multiple buried pipes fixed to the front and rear walls of the furnace body are connected to the lower headers of the buried pipes fixed on the outer side of the front and rear walls of the furnace body, and the upper ends of the multiple buried pipes fixed to the front and rear walls of the furnace body are connected to the lower headers fixed to the furnace body. The buried pipes on the outer side of the front and rear walls are connected to the upper header, the outlet of the upper header of the two buried pipes is connected to the lower header, the lower header is connected to one end of the connecting pipe five, and the evaporation coil surrounds the inner circumference of the furnace body The wall is wound from bottom to top to form the water-cooled wall of the furnace. One end of the evaporation coil is connected to the other end of the connecting pipe five, the other end of the evaporation coil is connected to the upper collection header, and the upper collection header is connected to the steam-water separator one in the steam drum. The invention is used for steam injection in oil fields.

Description

CFB Steam Injection Boiler with Buried Tube and Evaporation Coil Coupling Direct Flow and Natural Circulation

technical field

The invention relates to a circulating fluidized bed steam injection boiler, which belongs to the technical field of oil field steam injection boilers.

Background technique

Most of the existing steam injection boilers in oilfields are oil-fired and gas-fired direct-flow steam-injection boilers. In order to save operating costs, some units have developed coal-fired seam-fired direct-flow steam injection boilers. The implementation of the pollutant discharge standard GB13271-2014 has made the layer-fired steam-injection boiler lose the favor of the market. This is because the NOx emission concentration of the layer-fired steam-injection boiler is much higher than the existing emission standard, and the furnace cannot desulfurize, which makes environmental protection investment Even higher than the investment of the boiler itself. So people turn their attention to circulating fluidized bed boilers, because the NOx emission concentration of circulating fluidized bed boilers is lower than the current environmental protection emission standards, and when the limestone is added to the furnace with a Ca/S molar ratio of about 2, the bed temperature is 850~880 The desulfurization efficiency reaches 80~90% at ℃, which has obvious advantages.

However, the existing circulating fluidized bed coal-fired steam injection boiler is a natural circulation boiler, such as a utility model patent with the authorized announcement number CN202709071U and the authorized announcement date being January 30, 2013, which discloses a "circulating fluidized bed Oilfield Steam Injection Boiler", the furnace water-wall tube burst occurred during the operation of the steam injection boiler, because the feed water of the oil field steam injection boiler is only softened water, not demineralized water, and the salt content of the feed water is as high as 2300mg/kg. Using natural circulation, when the blowdown rate is set at 5%, the salt concentration of the furnace water in the drum is 48300mg/kg, that is, the salt concentration of the furnace water entering the water wall tube through the downcomer is 48300mg/kg. The circulation ratio of the natural circulation ultra-high pressure (14~18MPa) boiler is 5~8. Since the oil field steam injection boiler has a small capacity (20~-130t/h) and low height, when the circulation ratio is 5, the outlet of the boiler water wall tube The salt concentration is as high as 60375mg/kg. In this way, the near wall area of the water-cooled wall tube has a higher salt concentration due to the evaporation of the pot water. When the salt concentration exceeds the solubility of the salt, the salt will precipitate on the tube wall and scale. Over time, the salt scale becomes thicker and thicker, which leads to deterioration of heat transfer and tube burst.

Contents of the invention

The purpose of the present invention is to solve the problem that the existing natural circulation circulating fluidized bed oil field steam injection boiler has the problem that the inner wall of the water wall tube is easy to form salt scale, which will lead to the deterioration of heat transfer and the tube burst in the long run, and further provides a buried tube And evaporating coil direct current and natural circulation coupling CFB steam injection boiler. It can burn low-quality fuel with a calorific value between 1500~3000Kcal/kg.

In the present invention, the bottom of the circulating fluidized bed furnace is a combination of a high-speed bed and a low-speed bed with buried pipes. The water-cooled wall of the upper furnace is composed of a direct-flow evaporation coil coiled from bottom to top along the inner walls around the furnace. Evaporation heating surface), using natural circulation.

Realize above-mentioned purpose, technical scheme of the present invention is:

Direct flow and natural circulation coupling CFB steam injection boiler with buried pipe and evaporator coil, including furnace body, connecting pipe 1, coal inlet, economizer water outlet main pipe, low-velocity bed air chamber, primary air duct, secondary air duct, and secondary air duct Secondary air pipe, cyclone separator, downcomer, steam connecting pipe, connecting pipe four, superheater, evaporator, economizer, secondary air air preheater, primary air air preheater, return valve, high-speed bed Air chamber, sewage outlet, steam drum, tail flue, slag discharge pipe, low-speed bed air distribution plate, high-speed bed air distribution plate, two connecting pipes 2 and 2 connecting pipes 3; the furnace body is circulating fluidized The steam drum is provided with a steam-water separator 1 and a steam-water separator 2, the bottom of the steam drum is provided with a sewage outlet, the bottom of the furnace body is provided with a high-speed bed air chamber, and the bottom of the furnace body There is a low-speed bed air chamber on both sides of the high-speed bed air chamber, the upper part of the high-speed bed air chamber is provided with a high-speed bed air distribution plate, and each of the low-speed bed air chambers is equipped with a low-speed bed air chamber. The air distribution plate, the upper end of the slag discharge pipe passes through the high-speed bed air chamber and is installed on the high-speed bed air distribution plate. The secondary air pipe is arranged above the mouth, the furnace outlet of the furnace body is connected with the cyclone separator, the bottom of the cyclone separator is connected with the lower part of the furnace body through the return valve, and the outlet of the cyclone separator is connected with the tail flue. The superheater, evaporator, economizer, secondary air air preheater and primary air air preheater are arranged in sequence from top to bottom in the tail flue, and the primary air air preheater communicates with the The high-speed bed air chamber is connected, and the secondary air air preheater is respectively communicated with the two low-speed bed air chambers and the secondary air pipe through the secondary air duct; One end of the water outlet is lower than the end of the steam-water mixture outlet of the evaporator; the economizer is connected to one end of the economizer outlet main pipe, and the other end of the economizer outlet water main pipe is connected to one end of the two connecting pipes. And evaporating coil direct current and natural circulation coupling CFB steam injection boiler also includes lower collecting header, upper collecting header, at least one evaporating coil, two buried pipe lower headers, multiple buried pipes, two buried pipe upper A header, at least one connecting pipe five and a plurality of partitions;

The other ends of the two connecting pipes are respectively connected with a lower header of buried pipes, and the lower headers of the two buried pipes are respectively fixed under the outer side of the front and rear walls of the furnace body, and the multiple buried pipes are arranged in the furnace In the low-velocity bed in the body, and multiple buried pipes are respectively fixed on the front wall and rear wall of the furnace body, and the lower ends of the multiple buried pipes fixed to the front wall of the furnace body are all connected to the buried pipes fixed on the outer side of the front wall of the furnace body The lower header is connected, and the lower ends of the multiple buried pipes fixed on the rear wall of the furnace body are connected with the lower header of the buried pipes fixed on the outer side of the rear wall of the furnace body, and the upper ends of the multiple buried pipes fixed on the front wall of the furnace body are all connected. It communicates with the upper header of the buried pipe fixed on the outer side of the front wall of the furnace body, and the upper ends of the multiple buried pipes fixed on the rear wall of the furnace body are all connected with the upper header of the buried pipe fixed on the outer side of the rear wall of the furnace body. The lower header of the buried pipe and the upper header of each buried pipe are respectively fixed with a plurality of partitions vertically arranged at intervals, and the plurality of partitions in the upper header of the buried pipe and the lower header of the buried pipe on the same side are respectively Dislocation setting, the water outlet of the upper header of the two buried pipes is connected to one end of a connecting pipe 3, the other ends of the two connecting pipes 3 are connected to the lower collecting header, and the lower collecting header is connected to at least one connecting pipe 5 The other end of the connecting pipe five is connected with one end of the evaporating coil, the number of connecting pipe five is the same as that of the evaporating coil, and at least one evaporating coil is wound around the inner peripheral side wall of the furnace body from bottom to top It constitutes the water wall of the furnace, and the other ends of all the evaporating coils are connected with the upper collection box, and the upper collection box is connected with the steam-water separator in the steam drum through the connecting pipe one; the steam-water mixture entering the steam drum passes through the steam-water separator one The steam-water separation is carried out, the separated water enters the water space of the steam drum, and the steam separated by the steam-water separator enters the steam space of the steam drum, and the water space of the steam drum communicates with the water inlet of the evaporator through the downcomer, and the The steam-water mixture outlet communicates with the steam-water separator 2 through the connecting pipe 4; the steam separated by the steam-water separator 2 enters the steam space of the steam drum, and the steam space of the steam drum communicates with the superheater through the steam connecting pipe.

The beneficial effect of the present invention relative to prior art is:

1. Since the buried pipes and evaporating coils in the furnace adopt direct current, the buried pipes and evaporating coils will never burst again. This is because when the salt concentration of the feed water is 2300mg/kg, when the gas content rate of the outlet mass of the furnace water wall is 90%, the salt concentration in the furnace water is 23000mg/kg, while the actual operating once-through steam injection boiler feed water salt concentration The highest is 7000mg/kg. When the mass gas content in the furnace water wall at the furnace outlet is 80%, the operation is normal, and there has never been a tube explosion. At this time, the salt concentration of the furnace water is 35000mg/kg (7000/0.2 mg/kg = 35000 mg/kg), it can be proved that it is safe and reliable to use direct current for the buried pipe in the furnace and the water wall of the furnace.

2. The evaporator located at the tail is arranged in a temperature zone lower than 550°C. The pipe material of the evaporator is 12Cr1MoVG. Since the wall temperature of this material is allowed to be 580°C, even if the inside of the evaporator pipe is partially blocked by salt scale, it will not There will be no tube explosion, which completely solves the problem of tube explosion on the heating surface and ensures the safe and stable operation of the boiler.

3. The surface of the evaporating coil facing the fire side is covered with a layer of 60~80mm refractory and wear-resistant material, and the problem of pipe burst due to wear and tear of the evaporating coil can be completely eliminated.

Description of drawings

Fig. 1 is the overall structure front view of the present invention;

Figure 2 is a schematic diagram of water inflow and outflow of buried pipes;

Fig. 3 is the K direction view of Fig. 2;

Fig. 4 is a schematic diagram of the water supply circulation path;

FIG. 5 is a partially enlarged view of A in FIG. 1 .

In the figure, furnace body 1, connecting pipe 1 2, evaporation coil 3, connecting pipe 2 4, coal inlet 5, connecting pipe 3 6, economizer water outlet main pipe 7, buried pipe lower header 8, buried pipe 9, Buried pipe upper header 10, low-velocity bed air chamber 11, primary air duct 12, secondary air duct 13, secondary air duct 14, cyclone separator 15, descending pipe 16, steam connecting pipe 17, connecting pipe 4 18, overheating device 19, evaporator 20, economizer 21, secondary air air preheater 22, primary air air preheater 23, return valve 24, high-speed bed air chamber 25, lower collection box 26, sewage outlet 27, Steam-water separator 1 28a, steam-water separator 2 28b, steam drum 29, tail flue 30, slag discharge pipe 31, connecting pipe 5 32, vertical partition 33, refractory and wear-resistant material 34, upper collection box 35, low speed Bed cloth wind plate 36 and high-speed bed cloth wind plate 37.

detailed description

Specific implementation mode 1: As shown in Figures 1 to 5, a CFB steam injection boiler with buried pipes and evaporation coils coupled with direct current and natural circulation includes a furnace body 1, a connecting pipe 1, a coal inlet 5, and an economizer water outlet Main pipe 7, low-speed bed air chamber 11, primary air duct 12, secondary air duct 13, secondary air duct 14, cyclone separator 15, downcomer 16, steam connecting pipe 17, connecting pipe 4 18, superheater 19, evaporation 20, economizer 21, secondary air air preheater 22, primary air air preheater 23, return valve 24, high-speed bed air chamber 25, sewage outlet 27, steam drum 29, tail flue 30, exhaust Slag pipe 31, low-speed bed air distribution plate 36, high-speed bed air distribution plate 37, two connecting pipes two 4 and two connecting pipes three 6; the furnace body 1 is a circulating fluidized bed, and the steam drum 29 Steam-water separator one 28a and steam-water separator two 28b are arranged inside, the bottom of the steam drum 29 is provided with a sewage outlet 27, the bottom of the furnace body 1 is provided with a high-speed bed air chamber 25, and the bottom of the furnace body 1 A low-speed bed air chamber 11 is provided on both sides of the high-speed bed air chamber 25 (that is, the bottom of the furnace body 1 is provided with a high-speed bed and a low-speed bed combination), and the upper part of the high-speed bed air chamber 25 is provided with a high-speed bed air distribution chamber. plate 37, each of the low-speed bed air chambers 11 is provided with a low-speed bed air distribution plate 36, and the upper end of the slag discharge pipe 31 passes through the high-speed bed air chamber 25 and is installed on the high-speed bed air distribution plate 37 (This structure and operating parameters have been disclosed in the invention patent "A Low-rate Circulating Fluidized Bed Hot Water Boiler Burning Inferior Fuel and Its Combustion Method" with the publication number CN 102901212B and the publication date of March 11, 2015 ), the lower part of the side wall of the furnace body 1 is located above the high-speed bed air chamber 25 and the coal inlet 5 is arranged, and the secondary air pipe 14 is arranged on the furnace body 1 above the coal inlet 5, and the furnace outlet of the furnace body 1 and the cyclone separator 15 The bottom of the cyclone separator 15 communicates with the lower part of the furnace body 1 through the return valve 24, and the outlet of the cyclone separator 15 communicates with the tail flue 30, and the tail flue 30 is arranged in sequence from top to bottom. 19, evaporator 20, economizer 21, secondary air air preheater 22 and primary air air preheater 23, the primary air air preheater 23 passes through the primary air duct 12 and the high-speed bed The air chamber 25 communicates, and the secondary air air preheater 22 communicates with the two low-speed bed air chambers 11 and the secondary air pipe 14 respectively through the secondary air channel 13; the evaporator 20 is arranged obliquely, and evaporates One end of the water inlet of the evaporator 20 is lower than the steam-water mixture outlet end of the evaporator 20; the economizer 21 communicates with one end of the economizer water outlet pipe 7, and the other end of the economizer water outlet pipe 7 is connected to two connecting pipes 24 One end is connected, and the CFB steam injection boiler with buried pipe and evaporating coil coupled with direct current and natural circulation also includes a lower collecting header 26, an upper collecting header 35, at least one evaporating coil 3, and two buried pipes lower collecting Box 8, multiple buried pipes 9, two buried pipe upper headers 10, at least one connecting pipe 5 32 and multiple partitions 33;

The other ends of the two connecting pipes 2 and 4 are respectively connected with a lower header 8 of buried pipes. Tube 9 is arranged in the low-velocity bed in body of furnace 1, and many buried pipes 9 are respectively fixed on the front wall and back wall of body of furnace 1, and the lower ends of many buried pipes 9 fixed with the front wall of body of furnace 1 are all connected with The buried tube lower header 8 fixed on the outer side of the front wall of the furnace body 1 communicates with the lower end of the multiple buried tubes 9 fixed on the rear wall of the furnace body 1 and the buried tube lower header fixed on the outer side of the rear wall of the furnace body 1 8 connected, the upper ends of the multiple buried pipes 9 fixed on the front wall of the furnace body 1 are connected with the buried pipe upper header 10 fixed on the outer side of the front wall of the furnace body 1, and the multiple buried pipes fixed on the rear wall of the furnace body 1 The upper ends of 9 are all communicated with the buried pipe upper header 10 fixed on the outer side of the rear wall of the furnace body 1, and each buried pipe lower header 8 and each buried pipe upper header 10 are respectively fixed with vertically arranged multiple headers at intervals. A partition 33, and multiple partitions 33 in the upper header 10 of the buried pipe and the lower header 8 of the buried pipe on the same side are respectively misplaced (the function is to ensure that the mass flow rate of the water in the buried pipe 9 is greater than 1000kg/m ² .s), the water outlets of the upper header 10 of the two buried pipes are connected with one end of a connecting pipe 36, and the other ends of the two connecting pipes 36 are connected with the lower collecting header 26, and the lower collecting header 26 is connected with the One end of at least one connecting pipe five 32 is connected, and the other end of the connecting pipe five 32 is connected with one end of the evaporation coil 3, the number of connecting pipe five 32 is the same as that of the evaporation coil 3, and at least one evaporation coil 3 The inner peripheral side wall surrounding the furnace body 1 is wound from bottom to top to form a furnace water wall. The other ends of all the evaporation coils 3 communicate with the upper collection box 35, and the upper collection box 35 is connected to the steam drum 29 through the connecting pipe 1. The steam-water separator-28a is connected; the steam-water mixture entering the steam drum 29 is separated from the steam-water through the steam-water separator-28a, and the separated water enters the water space of the steam drum 29, and the steam separated by the steam-water separator-28a enters the steam drum The steam space of 29, the water space of steam drum 29 is communicated with the water inlet of evaporator 20 by downcomer 16, and the steam-water mixture outlet of evaporator 20 is communicated with described steam-water separator 2 28b through connecting pipe 4 18; The steam separated by device two 28b enters the steam space of the steam drum 29, and the steam space of the steam drum 29 communicates with the superheater 19 through the steam connecting pipe 17.

Specific embodiment two: as shown in Figure 1, the direct current and natural circulation coupling CFB steam injection boiler with buried pipe and evaporation coil described in specific embodiment one, the angle between the evaporator 20 and the horizontal plane is α , α=5~10°.

Specific embodiment three: as shown in Figure 1, the direct current and natural circulation coupling CFB steam injection boiler with buried pipe and evaporating coil described in specific embodiment 1, the number of the evaporating coil 3 is 1, and the evaporating coil The outer pipe diameter (diameter) of the tube 3 is Φ51 mm to Φ108 mm.

Embodiment 4: As shown in Figure 1, the CFB steam injection boiler with buried pipes and evaporator coils coupled with direct current and natural circulation described in Embodiment 1, the number of the evaporator coils 3 is 2 to 6, 2~6 evaporating coils 3 surround the inner peripheral side wall of the furnace body 1 and are synchronously wound from bottom to top to form a furnace water wall. The capacity needs to be between 7 and 130t/h.

Specific embodiment five: as shown in Figure 1, the direct current and natural circulation coupled CFB steam injection boiler with buried pipe and evaporating coil described in specific embodiment 1, 2, 3 or 4, the evaporating coil 3 faces the furnace The outer surface of the body 1 on the fire side is covered with a layer of 60-80 mm thick refractory and wear-resistant material 34, in order to prevent the evaporation coil 3 from being worn.

The working process is: as shown in Figures 1 to 5, the primary air is preheated by the primary air preheater 23 and sent into the high-speed bed air chamber 25 of the furnace body 1 through the primary air duct 12, and then enters the furnace body 1. The furnace participates in the combustion; the secondary air is preheated by the secondary air air preheater 22 and sent to the low-velocity bed air chamber 11 and the secondary air pipe 14 of the furnace body 1 respectively through the secondary air channel 13 to realize staged combustion.

Working fluid side: After the feed water is heated by the economizer 21, it passes through the economizer outlet water main pipe 7, enters the two connecting pipes 24 respectively, and enters the multiple buried pipes 9 through the lower header 8 of the two buried pipes, and then passes through the A plurality of buried pipes 9 enter the upper header 10 of the two buried pipes, and then enter the lower collecting header 26 through two connecting pipes 3 6, and then lead into the evaporation coil 3 through the connecting pipe 5 32, because the evaporation coil 3 is all communicated with the upper collection header box 35, then enters the steam drum 29 through the upper collection header box 35 and the connecting pipe-2, and separates the steam and water through the steam-water separator-28a (the steam-water separator-28a is a cyclone separator, which separates The efficiency reaches 99.9%), the separated steam enters the steam space of the steam drum 29, the separated water enters the water space of the steam drum 29, the separated water enters the evaporator 20 through the downcomer 16, and the steam water produced by the evaporator 20 The mixture is introduced into the steam-water separator 2 28b in the steam drum 29 through the connecting pipe 3 18 to realize steam-water separation, and the separated steam enters the steam space of the steam drum 29 . The steam generated by the water-cooled wall of the furnace and the evaporator 20 is combined and enters the superheater 19 through the steam connection pipe 17 to be heated to a set temperature, and then injects steam downhole.

The CFB is referred to as a circulating fluidized bed.

Claims (5)

1. A direct current and natural circulation coupled CFB steam injection boiler with buried pipes and evaporating coils, including a furnace body (1), a connecting pipe (2), a coal inlet (5), and an economizer outlet water main pipe (7) , low-velocity bed air chamber (11), primary air duct (12), secondary air duct (13), secondary air pipe (14), cyclone separator (15), downpipe (16), steam connecting pipe (17 ), connecting pipe four (18), superheater (19), evaporator (20), economizer (21), secondary air air preheater (22), primary air air preheater (23), return Material valve (24), high-speed bed air chamber (25), sewage outlet (27), steam drum (29), tail flue (30), slag discharge pipe (31), low-speed bed air distribution plate (36), high-speed Bed cloth air plate (37), two connecting pipes two (4) and two connecting pipes three (6); the furnace body (1) is a circulating fluidized bed, and the steam drum (29) is equipped with There are steam-water separator 1 (28a) and steam-water separator 2 (28b). The bottom of the steam drum (29) is provided with a sewage outlet (27), and the bottom of the furnace body (1) is provided with a high-speed bed air blower. chamber (25), the bottom of the furnace body (1) is located on both sides of the high-speed bed air chamber (25), and a low-speed bed air chamber (11) is provided on each side, and the upper part of the high-speed bed air chamber (25) is provided with a high-speed bed Air distribution plate (37), each low-speed bed air chamber (11) is equipped with a low-speed bed air distribution plate (36), and the upper end of the slag discharge pipe (31) passes through the high-speed bed air The chamber (25) is installed on the high-speed bed air distribution plate (37), the lower part of the side wall of the furnace body (1) is located above the high-speed bed air chamber (25) and the coal inlet (5) is arranged, and the furnace body (1) is located on the feeder The secondary air pipe (14) is arranged above the coal port (5), and the furnace outlet of the furnace body (1) is connected to the cyclone separator (15), and the bottom of the cyclone separator (15) is connected to the The lower part of the furnace body (1) is connected, the outlet of the cyclone separator (15) is connected with the tail flue (30), and the superheater (19), evaporator ( 20), economizer (21), secondary air air preheater (22) and primary air air preheater (23), the primary air air preheater (23) passes through the primary air duct (12) It communicates with the high-speed bed air chamber (25), and the secondary air air preheater (22) is respectively connected to the two low-speed bed air chambers (11) and the secondary air duct through the secondary air duct (13). (14) is connected; the evaporator (20) is installed obliquely, and the water inlet end of the evaporator (20) is lower than the steam-water mixture outlet end of the evaporator (20); the economizer (21) and the economizer One end of the water outlet main pipe (7) of the coal appliance is connected, and the other end of the water outlet main pipe (7) of the economizer is connected with one end of two connecting pipes two (4). The circulating coupling CFB steam injection boiler also includes a lower collecting header (26), an upper collecting header (35), at least one evaporation coil (3), two buried tube lower headers (8), multiple buried pipe (9), two buried pipe upper headers (10), at least one connecting pipe five (32) and a plurality of partitions (33); the other ends of the two connecting pipes two (4) are respectively connected to a The lower headers (8) of the buried pipes are connected, and the two lower headers (8) of the buried pipes are respectively fixed under the outer side of the front and rear walls of the furnace body (1), and the multiple buried pipes (9) are arranged in the furnace body (1) in the low-velocity bed, and multiple buried pipes (9) are respectively fixed on the front wall and rear wall of the furnace body (1), and the multiple buried pipes (9) fixed to the front wall of the furnace body (1) The lower ends of the pipes are all connected to the lower header (8) of buried pipes fixed on the outer side of the front wall of the furnace body (1), and the lower ends of the multiple buried pipes (9) fixed to the rear wall of the furnace body (1) are connected to the The buried pipe lower header (8) on the outer side of the rear wall of the body (1) is connected, and the upper ends of the multiple buried pipes (9) fixed to the front wall of the furnace body (1) are all connected to the outside of the front wall of the furnace body (1). The buried pipe upper header (10) on the side is connected, and the upper ends of the multiple buried pipes (9) fixed to the rear wall of the furnace body (1) are all connected to the buried pipe upper header fixed on the outer side of the rear wall of the furnace body (1). (10) Connected, each buried pipe lower header (8) and each buried pipe upper header (10) are respectively fixed with a plurality of vertical partitions (33) at intervals, and the buried pipes on the same side The multiple partitions (33) in the upper header (10) and the buried pipe lower header (8) are respectively misplaced, and the water outlets of the two buried pipe upper headers (10) are connected to a connecting pipe three (6) The other ends of the two connecting pipes three (6) are connected to the lower collection header box (26), and the lower collection header box (26) is connected to one end of at least one connecting pipe five (32). The other end of the connecting pipe five (32) communicates with one end of the evaporating coil (3), the connecting pipe five (32) has the same number as the evaporating coil (3), and at least one evaporating coil (3) surrounds the furnace body ( 1) The inner peripheral side wall is wound from bottom to top to form the furnace water wall, and the other ends of all the evaporation coils (3) are connected to the upper collection box (35), and the upper collection box (35) passes through the connecting pipe one (2) It is connected with the steam-water separator one (28a) in the steam drum (29); the steam-water mixture entering the steam drum (29) is separated from the steam-water by the steam-water separator one (28a), and the separated water enters the steam drum (29) In the water space, the steam separated by the steam-water separator one (28a) enters the steam space of the steam drum (29), and the water space of the steam drum (29) communicates with the water inlet of the evaporator (20) through the downcomer (16). The steam-water mixture outlet of the evaporator (20) communicates with the steam-water separator two (28b) through the connecting pipe four (18); the steam separated by the steam-water separator two (28b) enters the steam space of the steam drum (29) , the steam space of the steam drum (29) communicates with the superheater (19) through the steam connecting pipe (17). 2. The direct current and natural circulation coupled CFB steam injection boiler with buried pipes and evaporator coils according to claim 1, characterized in that: the angle between the evaporator (20) and the horizontal plane is α, α= 5~10°. 3. The direct current and natural circulation coupled CFB steam injection boiler with buried pipes and evaporating coils according to claim 1, characterized in that: the number of the evaporating coils (3) is 1, and the evaporating coils (3 ) The outer pipe diameter is Φ51mm～Φ108mm. 4. The CFB steam injection boiler with buried pipes and evaporating coils coupled with direct current and natural circulation according to claim 1, characterized in that: the number of evaporating coils (3) is 2~6, 2~6 The root evaporating coil (3) wraps around the inner peripheral side wall of the furnace body (1) synchronously from bottom to top to form a furnace water wall. 5. According to claim 1, 2, 3 or 4, the direct current and natural circulation coupling CFB steam injection boiler with buried pipe and evaporating coil is characterized in that: the evaporating coil (3) faces the furnace body (1 ) is covered with a layer of 60-80mm thick refractory and wear-resistant material (34) on the outer surface of the fire side.