A large capacity subcritical coal-fired CFB type steam injection boiler for oil field

Abstract

The application relates to the field of oilfield steam injection boiler equipment, in particular to a large-capacity subcritical coal-fired CFB type oilfield steam injection boiler. The highest pressure of the boiler can reach a subcritical pressure. The boiler comprises a steel frame, a drum, a furnace water cooling wall and a flue arranged on the steel frame. A superheater, a high-level economizer, an SCR device, a low-level economizer and an air preheater are sequentially arranged on the flue. A softened water pipeline for conveying oilfield sewage is arranged on the steel frame. The softened water pipeline is sequentially connected with the low-level economizer, the high-level economizer and the bottom coil of the furnace water cooling wall. The middle and top coils of the furnace water cooling wall are connected with the drum. A separation assembly for separating brine and steam is arranged in the drum. A steam pipeline is connected between the top of the drum and the superheater. A salt discharge pipeline is connected to the bottom of the drum. Pressure measuring elements for monitoring the pressure change in the coils are arranged on the coils of the furnace water cooling wall. The application has the effect of reducing the equipment investment cost.

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. Summary of the Invention

[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 coal feeding device is located at the bottom of the furnace water-cooled 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 material device is installed between the dust separator and the furnace water-cooled walls to transport the dust separated by the dust separator. At the bottom of the furnace water-cooled wall, a softened water pipe for conveying 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 component 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 through 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. Meanwhile, the coal supplied by the feeding device burns inside the furnace water-cooled wall. The high-temperature flue gas from the combustion is separated by a dust separator and discharged through the flue. The separated dust is returned to the furnace water-cooled wall for secondary combustion by a 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 a separation component. The high-concentration brine at the bottom of the boiler drum flows to the water spray desuperheater through the brine discharge pipe, while the brine is removed... High-temperature, high-pressure steam flows through steam pipes to the superheater for reheating. The high-temperature, high-pressure steam heated by the superheater is then cooled by high-concentration brine sprayed from the water spray desuperheater and transported to the oil well through pipelines. This solves the problem of high-concentration brine and reduces environmental impact. Meanwhile, pressure sensors constantly monitor pressure changes in the coils of the furnace water-cooled wall. When salt accumulation and scaling are severe in the coils of the furnace water-cooled wall, the pressure in the coils will increase even with constant input pressure from the softened water pipes 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 maintenance costs.

[0008] Optionally, the pressure measuring device includes multiple pressure sensors, each disposed on a coil of the furnace water-cooled wall, and the pressure sensors are electrically connected to the control system.

[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 on 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 flowing out of the coil at the top of the water-cooled wall of the furnace is mixed with water under the action of the separator. The steam in the mixture will flow to the inner top of the boiler drum, and the brine in the steam will flow to the inner bottom of the boiler drum. The holes on the drain baffle will isolate the impurities in the brine flowing out of the bottom of the steam-water separator, and the impurities flowing to the inner bottom of the boiler drum will be discharged from the boiler drum through the brine drain pipe, thereby achieving the effect of continuous separation of brine and air.

[0014] 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.

[0015] 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.

[0016] Optionally, the pot drum is placed horizontally, and multiple vertical guide posts are evenly arranged around the inside of the pot drum. A needle plate is slidably mounted on the multiple guide posts. Several vertical pore-removing needles are arranged on the needle plate, and each pore-removing needle corresponds to a hole. The pore-removing needles are used to insert into the holes. A dredging component is provided on the pot drum to drive the needle plate to slide vertically back and forth.

[0017] By adopting the above technical solution, when the high-concentration brine at the bottom of the boiler drum crystallizes in the holes of the drain baffle, the unblocking component will drive the needle plate to slide vertically back and forth. The vertically sliding needle plate will drive the unblocking needle to repeatedly insert and pull out the holes in the drain baffle, thereby unblocking the holes in the drain baffle and reducing the possibility that the holes in the drain baffle will be blocked, causing the boiler drum to malfunction.

[0018] Optionally, the unblocking component includes an outer tube communicating with the bottom of the boiler drum, one end of the salt discharge pipe being sleeved on the bottom end of the outer tube, a vertically slidable upright rod coaxial with the outer tube being mounted on the drain baffle, a hollow float being mounted on the top of the upright rod, and a limiting cone being mounted on the bottom of the upright rod, the diameter of which gradually decreases along the direction from the upright rod to the float, the conical surface of which abuts against the end edge of the outer tube, a mounting plate being mounted on the upright rod on the side of the drain baffle facing away from the float, and the inner side of the end of the boiler drum along the axis of the boiler drum... The line is rotatably equipped with an arc rod, the center of which is located on the axis of the boiler drum. The arc rod is symmetrically arranged about the axis of the upright. A connecting rod is hinged between the mounting plate and the arc rod. A support block is provided at the end of the arc rod away from the connecting rod and below the needle plate. The support block is used to abut against the lower surface of the needle plate. A side flow port is opened on the drain baffle. A vertical guide post is provided on the needle plate. The guide post slides through the drain baffle. A sealing plate is provided on the guide post on the side of the drain baffle facing away from the needle plate. The sealing plate is used to block the side flow port.

[0019] By adopting the above technical solution, when the valve on the salt discharge pipe is closed, the brine in the salt discharge pipe cannot be discharged. Under the action of gravity, the needle plate separates the perforated needle from the drain baffle. The sealing plate blocks the side outlet on the drain baffle. The float, under the buoyancy of the liquid in the boiler drum, drives the upright to rise. The upright, through the connecting rod, drives the arc rod to rotate and descend. The conical surface of the limiting cone abuts against the edge of the outer tube, at which point the outer tube is blocked. When the valve on the salt discharge pipe is opened, the pressure in the salt discharge pipe decreases, and the high pressure in the boiler drum causes the limiting cone to disengage from the edge of the outer tube. The high-concentration brine at the bottom of the boiler drum flows from the outer pipe to the brine discharge pipe, causing the liquid level inside the boiler drum to drop. At the same time, the brine flowing out of the outer pipe impacts the limiting cone, causing the upright to descend. The descending upright pushes the arc rod to rotate via the connecting rod. The arc rod drives the support block to rise and push the needle plate. The needle plate drives the guide column and the pore-clearing needle to rise synchronously. The guide column drives the sealing plate to open the side outlet, and the pore-clearing needle rises to clear the holes on the drain baffle. The crystals cleared from the holes flow from the side outlet on the drain baffle to the outer pipe, thereby reducing the possibility of the holes on the drain baffle being blocked again.

[0020] Optionally, multiple arc rods are evenly arranged along the axial direction of the pot drum. Multiple scrapers are provided together among the multiple arc rods on the side of the connecting rod facing away from the axis of the upright rod. The multiple scrapers are evenly arranged on the arc rods circumferentially along the axis of the pot drum. The connecting rod is connected to one of the arc rods, and the scraper is attached to the inner wall of the pot drum.

[0021] By adopting the above technical solution, the scraper on the arc rod will scrape off the crystallized salt on the bottom wall of the boiler drum during the sliding process, thereby achieving the function of automatically cleaning the bottom side wall of the boiler drum, which helps to reduce the frequency of worker maintenance.

[0022] In summary, this application includes at least one of the following beneficial technical effects: 1. The pressure measuring device constantly reflects the pressure changes in the coils of the furnace water-cooled wall. When the salt accumulation and scaling in the coils of the furnace water-cooled wall are severe, the pressure in the coils of the furnace water-cooled wall will increase if the input pressure of the softened water pipe and the output pressure in the boiler drum remain unchanged. When the pressure fed back by the pressure measuring device exceeds the designed safe pressure, the equipment can be accurately maintained, which greatly reduces the cost of equipment maintenance. 2. When equipment needs to be moved, workers can cut the disassembly plates and disassembly pipes to 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. This facilitates subsequent transfer and transportation. At the same time, 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 pipes, which solves the current problem of inconvenient transportation of large furnace water-cooled walls. 3. When the valve on the salt discharge pipe is opened, the pressure inside the salt discharge pipe decreases. The high pressure inside the boiler drum causes the limiting cone to disengage from the edge of the outer pipe. The high-concentration brine at the bottom of the boiler drum flows from the outer pipe to the salt discharge pipe, causing the liquid level inside the boiler drum to drop. At the same time, the brine flowing out of the outer pipe impacts the limiting cone, causing the upright to descend. The descending upright pushes the arc rod to rotate through the connecting rod. The arc rod drives the support block to rise and push the needle plate. The needle plate drives the guide column and the pore-clearing needle to rise synchronously. The guide column drives the sealing plate to open the side outlet. The pore-clearing needle rises to clear the holes on the sewage discharge baffle. The crystals cleared from the holes will flow from the side outlet on the sewage discharge baffle to the outer pipe, thereby reducing the possibility of the holes on the sewage discharge baffle being blocked again. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of this application.

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

[0025] Figure 3 This is a cross-sectional view in Embodiment 1 of this application used to illustrate the positional relationship between the disassembly plate, the disassembly straight pipe, and the pressure sensor.

[0026] Figure 4 This is a cross-sectional view in Embodiment 1 of this application used to illustrate the positional relationship between the steam-water separator, the drain baffle, and the filter screen.

[0027] Figure 5 This is a cross-sectional view in Embodiment 2 of this application used to illustrate the positional relationship between the float, the upright, and the outer tube.

[0028] Figure 6 This is a cross-sectional view in Embodiment 2 of this application used to illustrate the positional relationship between the scraper, the arc rod, and the needle plate.

[0029] 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 assembly; 171. Steam-water separator; 172. Liquid level sensor; 173. Sewage discharge baffle; 17 4. Hole; 18. Steam pipe; 19. Salt discharge pipe; 20. Water spray desuperheater; 21. Pressure sensor; 22. Filter screen; 23. Guide column; 24. Needle plate; 25. Hole-clearing needle; 26. Unblocking component; 2601. Outer pipe; 2602. Vertical pole; 2603. Float ball; 2604. Limiting cone; 2605. Mounting plate; 2606. Arc rod; 2607. Connecting rod; 2608. Support block; 2609. Side outlet; 2610. Guide column; 2611. Sealing plate; 27. Scraper; 28. Limiting block; 29. ​​Ignition device; 40. Slag discharge pipe; 41. Water-cooled air chamber; 42. Central sewage pipe. Detailed Implementation

[0030] The following is in conjunction with the appendix Figures 1-6 This application will be described in further detail.

[0031] Example 1 This application discloses a large-capacity subcritical coal-fired CFB type oilfield steam injection boiler.

[0032] Reference Figure 1 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. A boiler drum 2, a furnace water-cooled wall 3, and a flue 4 are bolted onto the steel frame 1. An air distribution plate 5, a secondary air device 6, an ignition device 29, and a slag discharge pipe 40 are installed at the bottom of the furnace water-cooled wall 3. The connection between the ignition device 29 and the bottom of the furnace water-cooled wall 3 forms a water-cooled air chamber 41. The coils on the furnace water-cooled wall 3 are arranged in a spiral shape.

[0033] 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.

[0034] Reference Figure 1A 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.

[0035] 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.

[0036] Reference Figure 1 , Figure 3 and Figure 4 A steam pipe 18 connects the top of the boiler drum 2 to the superheater 7, and a brine discharge pipe 19 connects to the bottom of the boiler drum 2. A pipe valve (not shown in the figure) electrically connected to the control system is connected to the brine discharge pipe 19. 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 and then transported to the oil well through the brine flowing out of the brine discharge pipe 19. Pressure measuring devices for monitoring pressure changes inside the coil are arranged on the coil of the furnace water-cooled wall 3.

[0037] Reference Figure 3 The pressure measuring device includes multiple pressure sensors 21 that are bolted to the outside of the furnace water-cooled wall 3. The pressure sensors 21 can be high-temperature and high-pressure resistant pressure sensors 21 in the prior art. The sensing end of the pressure sensor 21 extends into the coil on the furnace water-cooled wall 3. The pressure sensor 21 is electrically connected to the control system. The pressure sensor 21 can also be replaced by a high-temperature and high-pressure resistant pressure gauge in the prior art.

[0038] The feeding device 12 feeds coal to the bottom of the furnace water-cooled wall 3, the ignition device 29 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.

[0039] 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.

[0040] 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 21 constantly feeds back the pressure changes on multiple coils.

[0041] 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.

[0042] Reference Figure 4 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 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 to the boiler drum 2.

[0043] Reference Figure 4 A 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 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.

[0044] Reference Figure 4 A filter screen 22 is welded to the top of the boiler drum 2. The filter screen 22 is located below the connection between the steam pipe 18 and the boiler drum 2. A middle drain pipe 42 is connected to the boiler drum 2. The top of the middle drain pipe 42 is lower than the top of the steam-water separator 171. A level valve (not shown in the figure) that is electrically connected to the control system is connected to the middle drain pipe 42.

[0045] The central drain pipe 42 can discharge the brine in the boiler drum 2. Through the cooperation of the liquid level sensor 172 and the central drain pipe 42, 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 operation, 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.

[0046] 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 22 filters the steam flowing to the steam pipe 18 again, and the filtered steam flows to the superheater 7 through the steam pipe 18.

[0047] 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 and the high-temperature and high-pressure steam discharged from the superheater 7 are injected into the oil well together. Under the condition that the pressure of the oilfield sewage input into the softened water pipe 16 remains unchanged and the discharge pressure inside the boiler drum 2 remains unchanged.

[0048] When the salt and scale buildup in the coils of the furnace water-cooled wall 3 is severe, the pressure inside the coils of the furnace water-cooled wall 3 will increase. Moreover, the heating and salt and scale buildup conditions of each coil are not the same, so the pressure values ​​fed back by the pressure sensor 21 at different locations will be different.

[0049] The control system can accurately detect the salt accumulation and scaling inside the coil by analyzing the pressure values ​​fed back by multiple pressure sensors 21. When the pressure fed back by the pressure sensor 21 exceeds the designed safe pressure, the control system can promptly remind the workers to perform maintenance.

[0050] The implementation principle of Example 1 is as follows: the feeding device 12 delivers coal to the bottom of the furnace water-cooled wall 3, the ignition device 29 ignites the coal, the air distribution plate 5 and the secondary air device 6 deliver 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 delivers the separated dust back into the furnace water-cooled wall 3 for secondary combustion.

[0051] 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.

[0052] 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 21 constantly feeds back the pressure changes on multiple coils.

[0053] The central drain pipe 42 can discharge the brine in the boiler drum 2. Through the cooperation of the liquid level sensor 172 and the central drain pipe 42, 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 operation, 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.

[0054] 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 22 filters the steam flowing to the steam pipe 18 again, and the filtered steam flows to the superheater 7 through the steam pipe 18.

[0055] 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 and the high-temperature and high-pressure steam discharged from the superheater 7 are injected into the oil well together. Under the condition that the pressure of the oilfield sewage input into the softened water pipe 16 remains unchanged and the discharge pressure inside the boiler drum 2 remains unchanged.

[0056] When the salt and scale buildup in the coils of the furnace water-cooled wall 3 is severe, the pressure inside the coils of the furnace water-cooled wall 3 will increase. Moreover, the heating and salt and scale buildup conditions of each coil are not the same, so the pressure values ​​fed back by the pressure sensor 21 at different locations will be different.

[0057] The control system can accurately detect the salt accumulation and scaling inside the coil by analyzing the pressure values ​​fed back by multiple pressure sensors 21. When the pressure fed back by the pressure sensor 21 exceeds the designed safe pressure, the control system can promptly remind the workers to perform maintenance.

[0058] Example 2 Reference Figure 5 and Figure 6 The difference between this embodiment and embodiment 1 is that: the pot cylinder 2 is placed horizontally, and multiple vertical guide posts 23 are evenly welded around the inside of the pot cylinder 2. A needle plate 24 is slidably sleeved on the multiple guide posts 23. A number of vertical sparse needles 25 are welded on the upper surface of the needle plate 24. The sparse needles 25 correspond one-to-one with the holes 174 and are used to insert into the holes 174.

[0059] Reference Figure 5 and Figure 6The boiler drum 2 is provided with a dredging component 26 that drives the needle plate 24 to slide vertically back and forth. The dredging component 26 includes an outer tube 2601 connected to the bottom of the boiler drum 2, a salt discharge pipe 19 that is away from the water spray desuperheater 20 is sleeved and welded to the bottom end of the outer tube 2601, and a vertical rod 2602 that is coaxial with the outer tube 2601 is vertically slidably arranged on the sewage baffle 173.

[0060] Reference Figure 5 and Figure 6 The top of the upright 2602 is welded with a hollow float 2603. The bottom of the upright 2602 is integrally formed with a limiting cone 2604. The diameter of the limiting cone 2604 gradually decreases along the direction from the upright 2602 to the float 2603. The conical surface of the limiting cone 2604 is used to abut against the inner edge of the bottom end of the outer tube 2601. An installation plate 2605 is welded to the upright 2602 on the side of the sewage baffle 173 facing away from the float 2603.

[0061] Reference Figure 5 and Figure 6 An arc rod 2606 is rotatably connected to the inner side of the end of the boiler drum 2 and along the axis of the boiler drum 2. A limiting block 28 for sliding through the arc rod 2606 is welded on the inner wall of the boiler drum 2. The limiting block 28 is arranged at both ends of the arc rod 2606 in the length direction, and the arc center of the arc rod 2606 is located on the axis of the boiler drum 2.

[0062] Reference Figure 5 and Figure 6 The arc rod 2606 at the same end of the boiler drum 2 is arranged symmetrically about the axis of the upright rod 2602. The mounting plate 2605 and the arc rod 2606 are hinged together by a connecting rod 2607. The end of the arc rod 2606 away from the connecting rod 2607 and located below the needle plate 24 is welded with a support block 2608. The support block 2608 is used to abut against the lower surface of the needle plate 24.

[0063] Reference Figure 5 and Figure 6 Side outlets 2609 are provided on both sides of the sewage baffle 173. Vertical guide posts 2610 are welded on the needle plate 24. The guide posts 2610 slide through the sewage baffle 173. A sealing plate 2611 is welded on the guide post 2610 on the side of the sewage baffle 173 facing away from the needle plate 24. The sealing plate 2611 is used to block the side outlets 2609.

[0064] Reference Figure 5 and Figure 6 Multiple arc rods 2606 are evenly arranged along the axial direction of the boiler drum 2. Multiple scraper rods 27 are welded together between the multiple arc rods 2606 on the side of the connecting rod 2607 facing away from the axis of the upright rod 2602. The multiple scraper rods 27 are evenly arranged on the arc rods 2606 along the circumferential direction of the axis of the boiler drum 2. The connecting rod 2607 is connected to one of the arc rods 2606. The scraper rods 27 are attached to the inner side wall of the boiler drum 2.

[0065] When the valve on the salt discharge pipe 19 is closed, the brine in the salt discharge pipe 19 cannot be discharged, and the liquid in the boiler drum 2 continues to increase. Under the buoyancy of the liquid in the boiler drum 2, the float ball 2603 drives the upright rod 2602 to rise. The upright rod 2602 drives the arc rod 2606 to rotate and descend through the connecting rod 2607. The support block 2608 moves away from the needle plate 24, and the conical surface of the limiting cone 2604 will abut against the edge of the outer tube 2601. At this time, the outer tube 2601 is blocked.

[0066] Under the influence of gravity, the needle plate 24 causes the perforated needle 25 to separate from the drain baffle 173. At this time, the sealing plate 2611 will block the side outlet 2609 on the drain baffle 173 until the liquid level sensor 172 is triggered. At this time, when the pipeline valve on the salt drain pipe 19 is opened, the pressure in the salt drain pipe 19 decreases, and the liquid in the salt drain pipe 19 is discharged. The high pressure in the boiler drum 2 causes the limiting cone 2604 to disengage from the edge of the outer tube 2601.

[0067] The high-concentration brine at the bottom of the boiler drum 2 will quickly flow from the outer pipe 2601 to the salt discharge pipe 19, causing the liquid level in the boiler drum 2 to drop rapidly. At the same time, the brine flowing out from the outer pipe 2601 will impact the limiting cone 2604 and drop, thereby causing the upright rod 2602 to drop rapidly. The dropping upright rod 2602 pushes the arc rod 2606 to rotate through the connecting rod 2607. The arc rod 2606 drives the scraper 27 to scrape off the crystallized salt on the bottom wall of the boiler drum 2. The support block 2608 on the arc rod 2606 rises rapidly and pushes the needle plate 24.

[0068] The needle plate 24 drives the guide column 2610 and the pore-clearing needle 25 to rise synchronously. The guide column 2610 will drive the sealing plate 2611 to open the side outlet 2609. The pore-clearing needle 25 rises to clear the hole 174 on the sewage baffle 173. The crystals cleaned in the hole 174 will flow from the side outlet 2609 on the sewage baffle 173 to the bottom of the sewage baffle 173 along with the brine above the sewage baffle 173. The crystallized salt will be discharged to the outer pipe 2601 along with the high concentration of brine at the bottom of the boiler drum 2.

[0069] The implementation principle of Example 2 is as follows: When the pipe valve on the salt discharge pipe 19 is closed, the brine in the salt discharge pipe 19 cannot be discharged, and the liquid in the boiler drum 2 continues to increase. Under the buoyancy of the liquid in the boiler drum 2, the float ball 2603 drives the upright rod 2602 to rise. The upright rod 2602 drives the arc rod 2606 to rotate and descend through the connecting rod 2607. The support block 2608 moves away from the needle plate 24, and the conical surface of the limiting cone 2604 will abut against the edge of the outer tube 2601. At this time, the outer tube 2601 is blocked.

[0070] Under the influence of gravity, the needle plate 24 causes the perforated needle 25 to separate from the drain baffle 173. At this time, the sealing plate 2611 will block the side outlet 2609 on the drain baffle 173 until the liquid level sensor 172 is triggered. At this time, when the pipeline valve on the salt drain pipe 19 is opened, the pressure in the salt drain pipe 19 decreases, and the liquid in the salt drain pipe 19 is discharged. The high pressure in the boiler drum 2 causes the limiting cone 2604 to disengage from the edge of the outer tube 2601.

[0071] The high-concentration brine at the bottom of the boiler drum 2 will quickly flow from the outer pipe 2601 to the salt discharge pipe 19, causing the liquid level in the boiler drum 2 to drop rapidly. At the same time, the brine flowing out from the outer pipe 2601 will impact the limiting cone 2604 and drop, thereby causing the upright rod 2602 to drop rapidly. The dropping upright rod 2602 pushes the arc rod 2606 to rotate through the connecting rod 2607. The arc rod 2606 drives the scraper 27 to scrape off the crystallized salt on the bottom wall of the boiler drum 2. The support block 2608 on the arc rod 2606 rises rapidly and pushes the needle plate 24.

[0072] The needle plate 24 drives the guide column 2610 and the pore-clearing needle 25 to rise synchronously. The guide column 2610 will drive the sealing plate 2611 to open the side outlet 2609. The pore-clearing needle 25 rises to clear the hole 174 on the sewage baffle 173. The crystals cleaned in the hole 174 will flow from the side outlet 2609 on the sewage baffle 173 to the bottom of the sewage baffle 173 along with the brine above the sewage baffle 173. The crystallized salt will be discharged to the outer pipe 2601 along with the high concentration of brine at the bottom of the boiler drum 2.

[0073] 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), and a feeding device for conveying coal is provided at the bottom of the furnace water-cooled wall (3). The furnace water-cooled wall (3) is provided with an expansion joint (13) between its top outlet and the flue (4). A dust separator (14) for separating dust and air in the flue gas is provided between the flue (4) and the expansion joint (13). 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 steel frame (1) is provided with a softened water pipe (16) for transporting oilfield sewage. 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 top coil of the furnace water-cooled wall (3) is connected to the boiler drum (2). The boiler drum (2) is provided with a separation component (17) for separating brine and steam. The top of the boiler drum (2) is connected to the superheater (7) with a steam pipe (18). The bottom of the boiler drum (2) is connected with a salt discharge pipe (19). A water spray desuperheater (20) is provided 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 for monitoring the pressure change in the coil is provided on the coil of the furnace water-cooled wall (3). The separation component (17) includes a steam-water separator (171) disposed 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 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 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). The pot cylinder (2) is placed horizontally. Multiple vertical guide posts (23) are evenly arranged around the pot cylinder (2). A needle plate (24) is slidably mounted on the multiple guide posts (23). Several vertical pore-removing needles (25) are arranged on the needle plate (24). The pore-removing needles (25) correspond one-to-one with the holes (174). The pore-removing needles (25) are used to insert into the holes (174). A dredging component (26) is provided on the pot cylinder (2) to drive the needle plate (24) to slide vertically back and forth.

2. The large-capacity subcritical coal-fired CFB type oilfield steam injection boiler according to claim 1, characterized in that: The pressure measuring device includes multiple pressure sensors (21) that are all mounted on the coils of the furnace water-cooled wall (3), and the pressure sensors (21) are electrically connected to the control system.

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: A filter screen (22) is provided inside the boiler drum (2), and the filter screen (22) is located below the connection between the steam pipe (18) and the boiler drum (2).

5. A large-capacity subcritical coal-fired CFB type oilfield steam injection boiler according to claim 1, characterized in that: The unblocking component (26) includes an outer tube (2601) connected to the bottom of the inner drum (2), one end of the salt discharge pipe (19) is sleeved on the bottom end of the outer tube (2601), a vertical rod (2602) coaxial with the outer tube (2601) is vertically slidably arranged on the drain baffle (173), the top of the vertical rod (2602) is provided with an internally hollow float ball (2603), and the bottom of the vertical rod (2602) is provided with a limiting cone (2604). The diameter of the limiting cone (2604) gradually decreases along the direction from the upright (2602) to the float (2603). The conical surface of the limiting cone (2604) is used to abut the end edge of the outer tube (2601). An mounting plate (2605) is provided on the upright (2602) on the side of the drain baffle (173) facing away from the float (2603). An arc rod (2605) is provided on the inner side of the end of the boiler drum (2) and rotatably arranged along the axis of the boiler drum (2). 6) The center of the arc of the arc rod (2606) is located on the axis of the pot drum (2). The arc rod (2606) is symmetrically arranged about the axis of the upright rod (2602). A connecting rod (2607) is hinged between the mounting plate (2605) and the arc rod (2606). A support block (2608) is provided at the end of the arc rod (2606) away from the connecting rod (2607) and below the needle plate (24). The support block (2608) is used to abut against the... On the lower surface of the needle plate (24), a side outlet (2609) is provided on the drain baffle (173). A vertical guide post (2610) is provided on the needle plate (24). The guide post (2610) slides through the drain baffle (173). A sealing plate (2611) is provided on the guide post (2610) on the side of the drain baffle (173) facing away from the needle plate (24). The sealing plate (2611) is used to block the side outlet (2609).

6. A large-capacity subcritical coal-fired CFB type oilfield steam injection boiler according to claim 5, characterized in that: Multiple arc rods (2606) are evenly arranged along the axial direction of the pot drum (2). Multiple scraper rods (27) are provided together among the multiple arc rods (2606) on the side of the connecting rod (2607) facing away from the axis of the upright rod (2602). Multiple scraper rods (27) are evenly arranged on the arc rods (2606) circumferentially along the axis of the pot drum (2). The connecting rod (2607) is connected to one of the arc rods (2606). The scraper rods (27) are attached to the inner wall of the pot drum (2).

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