A large-capacity subcritical coal-fired CFB type oilfield steam injection boiler

Abstract

This application relates to the field of oilfield steam injection boiler equipment, and in particular to a large-capacity subcritical coal-fired CFB type oilfield steam injection boiler. This boiler can reach subcritical pressure. It includes a steel frame, on which a boiler drum, furnace water-cooled walls, and a flue are mounted. A superheater, an upper economizer, an SCR device, a lower economizer, and an air preheater are sequentially arranged on the flue. A softened water pipeline for conveying oilfield wastewater is installed on the steel frame. This softened water pipeline sequentially connects to the lower economizer, the upper economizer, and the bottom coil of the furnace water-cooled wall. The middle and top coils of the furnace water-cooled wall are connected to the boiler drum. A separation component for separating brine and steam is installed inside the boiler drum. A steam pipeline connects the top of the boiler drum to the superheater, and a brine discharge pipe connects to the bottom of the boiler drum. Pressure measuring devices for monitoring pressure changes within the coils are installed on the furnace water-cooled wall coils. This application has the effect of reducing equipment investment costs.

Description

Technical Field

[0001] This application relates to the field of oilfield steam injection boiler equipment, and in particular to a large-capacity subcritical coal-fired CFB type oilfield steam injection boiler. Background Technology

[0002] Oilfield steam injection boilers are a type of boiler equipment widely used in oilfield extraction. They are used to inject high-pressure, high-temperature steam into oil wells to heat crude oil in the oil layer, thereby reducing the viscosity of heavy oil, increasing its fluidity, and thus significantly improving the recovery rate of heavy oil.

[0003] Oilfield steam injection boilers are divided into two types based on fuel: natural gas and coal. Due to the high input cost and poor economic efficiency of natural gas, it has been gradually phased out. Among the coal-fired boilers, there are ordinary coal-fired CFB boilers and small once-through CFB boilers.

[0004] For ordinary coal-fired CFB boilers, the requirements for boiler water quality are very high during use. The boiler feedwater must meet the water quality standards of power plant boilers. However, given the actual conditions of oilfield operating areas, oilfield areas can only provide pre-treated oilfield wastewater (oilfield softened water). This requires the installation of complex water treatment equipment, which has very high equipment investment and operating costs. Moreover, once the water quality changes, the boiler may experience a tube rupture accident in a short period of time. Furthermore, many oilfield mining areas do not have the conditions to provide tap water or river surface water and groundwater. For small-scale DC CFB boilers, although they can directly use oilfield wastewater (oilfield softened water), severe salt and scale buildup occurs on the heating surfaces inside the boiler (inside the wastewater conveying pipes). Prolonged operation can also easily lead to tube rupture accidents. The traditional solution is to disassemble and clean the boiler periodically. However, the maintenance time is usually long. Therefore, periodic cleaning is prone to problems such as excessive salt and scale buildup or even tube rupture on the heating surfaces inside the boiler (inside the wastewater conveying pipes) due to fluctuations in the salt content of the oilfield wastewater, or insufficient salt and scale buildup, which wastes a lot of production time and has shortcomings. Utility Model Content

[0005] In order to improve the problems existing in the use of coal-fired CFB boilers, this application provides a large-capacity subcritical coal-fired CFB type oilfield steam injection boiler.

[0006] This application provides a large-capacity subcritical coal-fired CFB-type oilfield steam injection boiler with the following technical solution: A large-capacity subcritical coal-fired CFB-type oilfield steam injection boiler includes a steel frame on which a boiler drum, furnace water-cooled walls, and a flue are mounted. The furnace water-cooled walls are equipped with air distribution plates and a secondary air device. A superheater, an upper economizer, an SCR device, a lower economizer, and an air preheater are sequentially arranged on the flue. A feeding device is installed on the furnace water-cooled walls to supply coal to the bottom of the walls. An expansion joint is installed between the top outlet of the furnace water-cooled walls and the flue. A dust separator is installed between the flue and the expansion joint to separate dust and air from the flue gas. A return device is installed between the dust separator and the furnace water-cooled walls to remove the dust. The flue gas separated by the separator is transported to the bottom of the furnace water-cooled wall. A softened water pipe for transporting oilfield wastewater is installed on the steel frame. The softened water pipe is sequentially connected to the lower economizer, the upper economizer, and the bottom coil of the furnace water-cooled wall. The top coil of the furnace water-cooled wall is connected to the boiler drum. A separation assembly for separating brine and steam is installed inside the boiler drum. A steam pipe connects the top of the boiler drum to the superheater. A brine discharge pipe connects to the bottom of the boiler drum. A water spray desuperheater is installed on the main steam outlet pipe of the superheater. The brine discharge pipe is connected to the water spray desuperheater. The water spray desuperheater is connected to the oil well via a pipe. A pressure measuring device for monitoring pressure changes inside the coil is installed on the coil of the furnace water-cooled wall.

[0007] By adopting the above technical solution, oilfield wastewater flows sequentially through the lower and upper economizers via softened water pipes, and then flows into the boiler drum through the bottom and top coils of the furnace water-cooled wall. The coal supplied by the feeding device burns inside the furnace water-cooled wall. The high-temperature flue gas is separated by a dust separator and discharged through the flue. The separated dust returns to the furnace water-cooled wall for secondary combustion under the action of the return material device. The heat from the high-temperature air after dust removal is absorbed by the oilfield wastewater flowing through the lower and upper economizers. The high-temperature, high-pressure steam flowing into the boiler drum is separated into brine and steam by the separation components. The high-concentration brine at the bottom of the boiler drum flows to the water spray desuperheater through the brine discharge pipe. High-temperature, high-pressure steam flows through steam pipes to the superheater for reheating. The high-temperature, high-pressure steam heated by the superheater carries the high-concentration brine sprayed by the water spray desuperheater through the pipeline to the oil well, thus solving the problem of high-concentration brine discharge and reducing environmental impact. At the same time, pressure sensors constantly monitor the pressure changes in the coils of the furnace water-cooled wall. When salt accumulation and scaling in the coils of the furnace water-cooled wall become severe, the pressure in the coils will increase even with constant input pressure from the softened water pipeline and constant output pressure from the boiler drum. When the pressure fed by the pressure sensors exceeds the designed safe pressure, precise maintenance of the equipment can be performed, greatly reducing equipment maintenance costs.

[0008] Optionally, the pressure measuring device includes a monitoring plate disposed on the furnace water-cooled wall, the monitoring plate being provided with a plurality of pressure sensors electrically connected to the control system, and the sensing ends of the plurality of pressure sensors being located inside the coils of the furnace water-cooled wall.

[0009] By adopting the above technical solution, multiple pressure sensors can feed back the pressure changes of the coils at different locations on the furnace water-cooled wall to the control system. The control system can indirectly monitor the salt accumulation and scaling in the coils of the furnace water-cooled wall by analyzing the information fed back by multiple pressure sensors. This makes it easier for workers to accurately control the maintenance time of the furnace water-cooled wall and greatly reduces the maintenance cost.

[0010] Optionally, the furnace water-cooled wall includes a bottom water-cooled wall, a middle water-cooled wall, and an upper water-cooled wall. Disassembly plates are provided between the middle water-cooled wall and the bottom water-cooled wall, and between the middle water-cooled wall and the upper water-cooled wall. Disassembly straight pipes are connected between the coils on the middle water-cooled wall and the coils on the bottom water-cooled wall, and between the coils on the middle water-cooled wall and the coils on the upper water-cooled wall.

[0011] By adopting the above technical solution, when equipment needs to be moved, workers can disassemble the entire furnace water-cooled wall into three parts—the bottom water-cooled wall, the middle water-cooled wall, and the upper water-cooled wall—by cutting the disassembly plates and disassembly straight pipes. This facilitates subsequent transfer and transportation. Furthermore, the bottom water-cooled wall, the middle water-cooled wall, and the upper water-cooled wall can be reassembled into a whole by welding the disassembly plates and disassembly straight pipes, thus solving the current problem of inconvenient transportation of large furnace water-cooled walls.

[0012] Optionally, the separation assembly includes a steam-water separator disposed inside the boiler drum, a coil at the top of the furnace water-cooled wall connected to the inlet end of the steam-water separator, the steam outlet end of the steam-water separator located above the liquid level inside the boiler drum, a liquid level sensor electrically connected to the control system disposed on the boiler drum, a sludge discharge baffle disposed at the bottom of the boiler drum, the sludge discharge baffle having several holes, a liquid drain valve at the bottom of the steam-water separator located below the sludge discharge baffle, and the connection point between the salt discharge pipe and the boiler drum located below the sludge discharge baffle.

[0013] By adopting the above technical solution, the high-temperature and high-pressure steam-water mixture flowing out of the coil at the top of the furnace water-cooled wall is separated by a separator. The steam in the mixture flows to the top of the boiler drum, while the brine in the steam flows to the bottom of the boiler drum. The holes on the drain baffle isolate the impurities in the brine flowing out from the bottom of the steam-water separator, and the impurities flowing to the bottom of the boiler drum are discharged through the brine drain pipe, thereby achieving the effect of continuous separation of brine and air.

[0014] Optionally, the boiler drum is provided with a central drain pipe, the top liquid inlet of the central drain pipe is lower than the top steam outlet of the steam-water separator, and the central drain pipe is provided with a drain valve electrically connected to the control system.

[0015] By adopting the above technical solution, when the liquid level sensor in the boiler drum is triggered, the control system starts the drain valve. The high-concentration brine in the boiler drum can be quickly discharged to the external collection box through the central drain pipe and drain valve. This reduces the possibility of saturated steam in the boiler carrying a large amount of saturated water into the superheater, causing damage due to salt accumulation and scaling in the superheater. At the same time, the liquid level in the boiler drum can be regulated through the central drain pipe, thereby controlling the dryness value of the main steam at the boiler outlet, so that the steam can meet the steam requirements of oilfield mines.

[0016] Optionally, a filter screen is provided inside the boiler drum, and the filter screen is located below the connection between the steam pipe and the boiler drum.

[0017] By adopting the above technical solution, the filter screen will further filter the salt-containing steam floating in the boiler drum, thereby further reducing the salt content of the steam flowing to the superheater and reducing the possibility of damage to the superheater by the salt-containing steam.

[0018] Optionally, the filter screen is arranged in multiple layers inside the boiler drum.

[0019] By adopting the above technical solutions, the salt content of the steam flowing into the steam pipeline can be further reduced, which is beneficial to extending the service life of the superheater.

[0020] Optionally, a maintenance ladder may be provided on the steel frame.

[0021] By adopting the above technical solutions, the overall equipment can be easily inspected and maintained.

[0022] In summary, this application includes at least one of the following beneficial technical effects: 1. During the flow of oilfield wastewater through the coils in the furnace water-cooled wall, pressure sensors constantly provide feedback on the pressure changes within the coils. When salt accumulation and scaling are severe in the coils, the pressure inside the coils will increase even with constant input pressure from the softened water pipeline and constant output pressure from the boiler drum. When the pressure fed back by the pressure sensors exceeds the designed safe pressure, precise equipment maintenance can be performed, greatly reducing equipment maintenance costs. 2. Multiple pressure sensors can feed back the pressure changes of the coils at different locations on the furnace water-cooled wall to the control system. The control system can indirectly monitor the salt accumulation and scaling in the coils of the furnace water-cooled wall by analyzing the information fed back by multiple pressure sensors. This makes it easier for workers to accurately control the maintenance time of the furnace water-cooled wall and greatly reduces the maintenance cost. 3. When the liquid level in the boiler drum triggers the level sensor, the control system activates the drain valve. The high-concentration brine in the boiler drum can be quickly discharged to the external collection box through the central drain pipe and drain valve. This reduces the possibility of saturated steam carrying a large amount of saturated water into the superheater, causing damage due to salt accumulation and scaling. At the same time, the liquid level in the boiler drum can be regulated through the central drain pipe, thereby controlling the dryness value of the main steam at the boiler outlet, so that the steam can meet the steam requirements of oilfield mines. Attached Figure Description

[0023] Figure 1 This is a structural schematic diagram of an embodiment of this application.

[0024] Figure 2 yes Figure 1 Sectional view along the middle AA.

[0025] Figure 3 This is a cross-sectional view used in the embodiments of this application to illustrate the positional relationship between the steam-water separator, the drain baffle, and the central drain pipe.

[0026] Figure 4 This is a cross-sectional view used in the embodiments of this application to illustrate the positional relationship between the disassembly plate, the disassembly straight pipe, and the pressure sensor.

[0027] Explanation of reference numerals in the attached drawings: 1. Steel frame; 2. Boiler drum; 3. Furnace water-cooled wall; 31. Bottom water-cooled wall; 32. Middle water-cooled wall; 33. Upper water-cooled wall; 34. Disassembly plate; 35. Disassembly straight pipe; 4. Flue; 5. Air distribution plate; 6. Secondary air device; 7. Superheater; 8. Upper economizer; 9. SCR equipment; 10. Lower economizer; 11. Air preheater; 12. Feeding device; 13. Expansion joint; 14. Dust separator; 15. Return material device. 16. Softened water pipe; 17. Separation component; 171. Steam-water separator; 172. Liquid level sensor; 173. Sewage discharge baffle; 174. Hole; 18. Steam pipe; 19. Brine discharge pipe; 20. Water spray desuperheater; 21. Pressure measuring component; 211. Monitoring board; 212. Pressure sensor; 22. Central sewage discharge pipe; 23. Drain valve; 24. Filter screen; 25. Maintenance ladder; 26. Ignition device; 27. Slag discharge pipe; 28. Water-cooled air chamber. Detailed Implementation

[0028] The following is in conjunction with the appendix Figures 1-4 This application will be described in further detail.

[0029] This application discloses a large-capacity subcritical coal-fired CFB type oilfield steam injection boiler.

[0030] Reference Figure 1 and Figure 2 A large-capacity subcritical coal-fired CFB type oilfield steam injection boiler includes a steel frame 1, which is assembled from several sheet steel pieces. The steel frame 1 is bolted with an inspection ladder 25, a boiler drum 2, a furnace water-cooled wall 3, and a flue 4. The bottom of the furnace water-cooled wall 3 is equipped with an air distribution plate 5, a secondary air device 6, an ignition device 26, and a slag discharge pipe 27. The connection between the ignition device 26 and the bottom of the furnace water-cooled wall 3 forms a water-cooled air chamber 28. The coils on the furnace water-cooled wall 3 are arranged in a spiral shape.

[0031] Reference Figure 1 The flue 4 is arranged from top to bottom as follows: superheater 7, upper economizer 8, SCR equipment 9, lower economizer 10 and air preheater 11. The upper economizer 8 and the lower economizer 10 are arranged in multiple sets on the steel frame 1. The bottom of the furnace water-cooled wall 3 is provided with a feeding device 12 for conveying coal. An expansion joint 13 is welded between the top outlet of the furnace water-cooled wall 3 and the flue 4.

[0032] Reference Figure 1 A dust separator 14 for separating dust and air in flue gas is bolted between flue 4 and expansion joint 13. A return material device 15 is arranged between the bottom of dust separator 14 and furnace water-cooled wall 3. The return material device 15 is used to transport the dust separated at the bottom of dust separator 14 to the bottom of furnace water-cooled wall 3.

[0033] Reference Figure 1 and Figure 2 A softened water pipe 16 for transporting oilfield wastewater is bolted to the steel frame 1. The softened water pipe 16 is connected in sequence to the lower economizer 10, the upper economizer 8 and the bottom coil of the furnace water-cooled wall 3. The middle and top coils of the furnace water-cooled wall 3 are connected to the boiler drum 2.

[0034] Reference Figure 1 , Figure 2 and Figure 3 A steam pipe 18 connects the top of the boiler drum 2 to the superheater 7, and a brine discharge pipe 19 connects the bottom of the boiler drum 2. A water spray desuperheater 20 is connected to the main steam outlet pipe of the superheater 7. The brine discharge pipe 19 is connected to the water spray desuperheater 20. The superheated steam flowing out of the superheater 7 is desuperheated inside the water spray desuperheater 20 by the brine flowing out of the brine discharge pipe 19 and then transported to the oil well through the pipe. Pressure measuring devices 21 for monitoring pressure changes inside the coil are arranged on the coil of the furnace water-cooled wall 3.

[0035] Reference Figure 4The pressure measuring component 21 includes a monitoring plate 211 welded to the furnace water-cooled wall 3. Multiple pressure sensors 212, all electrically connected to the control system, are bolted to the monitoring plate 211. The sensing ends of the multiple pressure sensors 212 are all located inside the coil of the furnace water-cooled wall 3. The pressure sensors 212 can be existing high-temperature and high-pressure resistant pressure sensors 212. The pressure sensors 212 are electrically connected to the control system. The pressure sensors 212 can also be replaced by existing high-temperature and high-pressure resistant pressure gauges.

[0036] The feeding device 12 feeds coal to the bottom of the furnace water-cooled wall 3, the ignition device 26 ignites the coal, the air distribution plate 5 and the secondary air device 6 supply air into the furnace water-cooled wall 3, the flue gas from the coal combustion in the furnace water-cooled wall 3 flows to the dust separator 14 through the expansion joint 13, the dust separator 14 separates the dust in the flue gas, and the return material device 15 transports the separated dust back into the furnace water-cooled wall 3 for secondary combustion.

[0037] After being separated by the dust separator 14, the air flows to the flue 4, from the top to the bottom. During this process, the SCR device 9 treats the exhaust gas to render it harmless. Meanwhile, the oilfield wastewater is pumped into the softened water pipe 16 by a high-pressure pump. The oilfield wastewater in the softened water pipe 16 absorbs heat from the exhaust gas as it flows through the lower economizer 10 and the upper economizer 8.

[0038] The heat is then absorbed by the bottom coil of the furnace water-cooled wall 3 through the layers of spiral coils inside the furnace water-cooled wall 3, and then flows into the boiler drum 2 through the top coil of the furnace water-cooled wall 3. During this process, the pressure sensor 212 constantly feeds back the pressure changes on multiple coils.

[0039] Reference Figure 1 and Figure 4 The furnace water-cooled wall 3 includes a bottom water-cooled wall 31, a middle water-cooled wall 32, and an upper water-cooled wall 33. Disassembly plates 34 are welded between the middle water-cooled wall 32 and the bottom water-cooled wall 31, and between the middle water-cooled wall 32 and the upper water-cooled wall 33. Disassembly straight pipes 35 connect the coils on the middle water-cooled wall 32 and the coils on the bottom water-cooled wall 31, and between the coils on the middle water-cooled wall 32 and the coils on the upper water-cooled wall 33.

[0040] Reference Figure 3 The boiler drum 2 is equipped with a separation assembly 17 for separating brine and steam. The separation assembly 17 includes a steam-water separator 171 welded inside the boiler drum 2. The coil on the furnace water-cooled wall 3 is connected to the inlet end of the steam-water separator 171. The steam outlet end of the steam-water separator 171 is located above the liquid level inside the boiler drum 2. A liquid level sensor 172 electrically connected to the control system is bolted onto the boiler drum 2.

[0041] Reference Figure 3A drain baffle 173 is welded to the bottom of the boiler drum 2. Several holes 174 are vertically opened on the drain baffle 173. The holes 174 are evenly distributed on the drain baffle 173. The drain valve 23 at the bottom of the steam-water separator 171 is located below the drain baffle 173. The connection between the salt discharge pipe 19 and the boiler drum 2 is located below the drain baffle 173.

[0042] Reference Figure 3 The top of the boiler drum 2 is welded with multiple layers of filter screens 24, which are stacked vertically. The filter screens 24 are located below the connection between the steam pipe 18 and the boiler drum 2. The boiler drum 2 is connected to a middle drain pipe 22. The top liquid inlet of the middle drain pipe 22 is lower than the top steam outlet of the steam-water separator 171. The middle drain pipe 22 is connected to a drain valve 23 that is electrically connected to the control system.

[0043] The central drain pipe 22 can discharge brine from the boiler drum 2. Through the cooperation of the liquid level sensor 172 and the central drain pipe 22, the liquid level in the boiler drum 2 can be effectively controlled to always be at a safe height. This reduces the possibility that the water level in the steam-water separator 171 is difficult to control under load, causing saturated steam to carry a large amount of saturated water into the superheater 7, thus ensuring the safety of the superheater 7. At the same time, it is convenient to adjust the dryness value of the main steam at the outlet of the boiler drum 2 in a timely manner to meet the steam requirements of the oilfield well.

[0044] The high-temperature and high-pressure steam-water mixture flowing into the boiler drum 2 is separated by a steam-water separator 171. The steam in the mixture flows to the top of the boiler drum 2, while the brine in the steam flows to the bottom of the boiler drum 2. The filter screen 24 filters the steam flowing to the steam pipe 18 again, and the filtered steam flows to the superheater 7 through the steam pipe 18.

[0045] The holes 174 on the drain baffle 173 will isolate the impurities in the brine flowing out from the bottom of the steam-water separator 171. The impurities flowing to the bottom of the boiler drum 2 will flow to the water spray desuperheater 20 through the salt discharge pipe 19. The high-temperature brine sprayed by the water spray desuperheater 20 will cool the high-temperature and high-pressure steam discharged from the superheater 7 and then be injected into the oil well through the pipeline.

[0046] When the pressure of the oilfield sewage entering the softened water pipe 16 remains constant and the pressure of the boiler drum 2 remains constant, the pressure inside the coil of the furnace water-cooled wall 3 will increase when the salt and scale buildup inside the coil is severe. Moreover, the heating and salt and scale buildup conditions of each coil will not be the same, so the pressure values ​​fed back by the pressure sensor 212 at different locations will be different.

[0047] The control system can accurately detect the accumulation of salt and scale in the coil by analyzing the pressure values ​​fed back by multiple pressure sensors 212. When the pressure fed back by the pressure sensor 212 exceeds the designed safe pressure, the control system can promptly remind the workers to perform maintenance.

[0048] The implementation principle of a large-capacity subcritical coal-fired CFB type oilfield steam injection boiler in this application embodiment is as follows: the feeding device 12 conveys coal to the bottom of the furnace water-cooled wall 3, the ignition device 26 ignites the coal, the air distribution plate 5 and the secondary air device 6 convey air into the furnace water-cooled wall 3, the flue gas from the coal combustion in the furnace water-cooled wall 3 flows to the dust separator 14 through the expansion joint 13, the dust separator 14 separates the dust in the flue gas, and the return material device 15 conveys the separated dust back into the furnace water-cooled wall 3 for secondary combustion.

[0049] After being separated by the dust separator 14, the air flows to the flue 4, from the top to the bottom. During this process, the SCR device 9 treats the exhaust gas to render it harmless. Meanwhile, the oilfield wastewater is pumped into the softened water pipe 16 by a high-pressure pump. The oilfield wastewater in the softened water pipe 16 absorbs heat from the exhaust gas as it flows through the lower economizer 10 and the upper economizer 8.

[0050] The heat is then absorbed by the bottom coil of the furnace water-cooled wall 3 through the layers of spiral coils inside the furnace water-cooled wall 3, and then flows into the boiler drum 2 through the top coil of the furnace water-cooled wall 3. During this process, the pressure sensor 212 constantly feeds back the pressure changes on multiple coils.

[0051] The central drain pipe 22 can discharge brine from the boiler drum 2. Through the cooperation of the liquid level sensor 172 and the central drain pipe 22, the liquid level in the boiler drum 2 can be effectively controlled to always be at a safe height. This reduces the possibility that the water level in the steam-water separator 171 is difficult to control under load, causing saturated steam to carry a large amount of saturated water into the superheater 7, thus ensuring the safety of the superheater 7. At the same time, it is convenient to adjust the dryness value of the main steam at the outlet of the boiler drum 2 in a timely manner to meet the steam requirements of the oilfield well.

[0052] The high-temperature and high-pressure steam-water mixture flowing into the boiler drum 2 is separated by a steam-water separator 171. The steam in the mixture flows to the top of the boiler drum 2, while the brine in the steam flows to the bottom of the boiler drum 2. The filter screen 24 filters the steam flowing to the steam pipe 18 again, and the filtered steam flows to the superheater 7 through the steam pipe 18.

[0053] The holes 174 on the drain baffle 173 will isolate the impurities in the brine flowing out from the bottom of the steam-water separator 171. The impurities flowing to the bottom of the boiler drum 2 will flow to the water spray desuperheater 20 through the salt discharge pipe 19. The high-temperature brine sprayed by the water spray desuperheater 20 will cool the high-temperature and high-pressure steam discharged from the superheater 7 and then be injected into the oil well through the pipeline.

[0054] When the pressure of the oilfield sewage entering the softened water pipe 16 remains constant and the pressure of the boiler drum 2 remains constant, the pressure inside the coil of the furnace water-cooled wall 3 will increase when the salt and scale buildup inside the coil is severe. Moreover, the heating and salt and scale buildup conditions of each coil will not be the same, so the pressure values ​​fed back by the pressure sensor 212 at different locations will be different.

[0055] The control system can accurately detect the accumulation of salt and scale in the coil by analyzing the pressure values ​​fed back by multiple pressure sensors 212. When the pressure fed back by the pressure sensor 212 exceeds the designed safe pressure, the control system can promptly remind the workers to perform maintenance.

[0056] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A large-capacity subcritical coal-fired CFB type oilfield steam injection boiler, comprising a steel frame (1), wherein a boiler drum (2), a furnace water-cooled wall (3), and a flue (4) are arranged on the steel frame (1), wherein an air distribution plate (5) and a secondary air device (6) are arranged on the furnace water-cooled wall (3), wherein a superheater (7), an upper economizer (8), an SCR device (9), a lower economizer (10), and an air preheater (11) are arranged sequentially on the flue (4), wherein a feeding device (12) is arranged on the furnace water-cooled wall (3), and the feeding device (12) is used to feed the furnace water-cooled wall (3) Coal is conveyed to the bottom of the furnace water-cooled wall (3). An expansion joint (13) is provided between the top outlet of the furnace water-cooled wall (3) and the flue (4). A dust separator (14) is provided between the flue (4) and the expansion joint (13). The dust separator (14) is used to separate dust and air in the flue gas. A return material device (15) is provided between the dust separator (14) and the furnace water-cooled wall (3). The return material device (15) is used to transport the dust separated by the dust separator (14) to the bottom of the furnace water-cooled wall (3). The feature is that: The steel frame (1) is equipped with a softened water pipe (16) for transporting oilfield wastewater. The softened water pipe (16) is sequentially connected to the lower economizer (10), the upper economizer (8), and the bottom coil of the furnace water-cooled wall (3). The top coil of the furnace water-cooled wall (3) is connected to the boiler drum (2). The boiler drum (2) is equipped with a separation component (17) for separating brine and steam. The top of the boiler drum (2) is connected to the bottom coil of the furnace water-cooled wall (3). A steam pipe (18) is connected between the superheaters (7), and a salt discharge pipe (19) is connected to the bottom of the boiler drum (2). A water spray desuperheater (20) is installed on the main steam outlet pipe of the superheater (7). The salt discharge pipe (19) is connected to the water spray desuperheater (20). The water spray desuperheater (20) is connected to the oil well through a pipe. A pressure measuring device (21) for monitoring the pressure change inside the coil is installed on the coil of the furnace water-cooled wall (3).

2. The large-capacity subcritical coal-fired CFB type oilfield steam injection boiler according to claim 1, characterized in that: The pressure measuring device (21) includes a monitoring plate (211) disposed on the furnace water-cooled wall (3). The monitoring plate (211) is provided with a plurality of pressure sensors (212) that are electrically connected to the control system. The sensing ends of the plurality of pressure sensors (212) are all located inside the coil of the furnace water-cooled wall (3).

3. A large-capacity subcritical coal-fired CFB type oilfield steam injection boiler according to claim 1, characterized in that: The furnace water-cooled wall (3) includes a bottom water-cooled wall (31), a middle water-cooled wall (32), and an upper water-cooled wall (33). Disassembly plates (34) are provided between the middle water-cooled wall (32) and the bottom water-cooled wall (31), and between the middle water-cooled wall (32) and the upper water-cooled wall (33). Disassembly straight pipes (35) are connected between the coils on the middle water-cooled wall (32) and the coils on the bottom water-cooled wall (31), and between the coils on the middle water-cooled wall (32) and the coils on the upper water-cooled wall (33).

4. A large-capacity subcritical coal-fired CFB type oilfield steam injection boiler according to claim 1, characterized in that: The separation component (17) includes a steam-water separator (171) disposed inside the boiler drum (2). The coil at the top of the furnace water-cooled wall (3) is connected to the inlet end of the steam-water separator (171). The steam outlet end of the steam-water separator (171) is located above the liquid level inside the boiler drum (2). A liquid level sensor (172) electrically connected to the control system is disposed on the boiler drum (2). A drain baffle (173) is disposed at the bottom inside the boiler drum (2). Several holes (174) are opened on the drain baffle (173). The drain valve (23) at the bottom of the steam-water separator (171) is located below the drain baffle (173). The connection between the salt discharge pipe (19) and the boiler drum (2) is located below the drain baffle (173).

5. A large-capacity subcritical coal-fired CFB type oilfield steam injection boiler according to claim 4, characterized in that: The boiler drum (2) is provided with a central drain pipe (22), the top liquid inlet of the central drain pipe (22) is lower than the top steam outlet of the steam-water separator (171), and the central drain pipe (22) is provided with a drain valve (23) electrically connected to the control system.

6. A large-capacity subcritical coal-fired CFB type oilfield steam injection boiler according to claim 4, characterized in that: A filter screen (24) is provided inside the boiler drum (2), and the filter screen (24) is located below the connection between the steam pipe (18) and the boiler drum (2).

7. A large-capacity subcritical coal-fired CFB type oilfield steam injection boiler according to claim 6, characterized in that: The filter screen (24) is arranged in multiple layers inside the boiler drum (2).

8. A large-capacity subcritical coal-fired CFB type oilfield steam injection boiler according to claim 1, characterized in that: A maintenance ladder (25) is installed on the steel frame (1).

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