A combined convection section for oilfield steam injection boilers

Abstract

This invention belongs to the petrochemical field and discloses a combined convection section suitable for oilfield steam injection boilers. It integrates an air preheater, a preheating zone, a convection heat exchange zone, and a high-pressure section. The steam injection boiler includes a burner and a radiant section. The air preheater is connected to the burner via piping. The preheating zone, convection heat exchange zone, and high-pressure section are integrated into a single housing, forming three independent areas. The high-pressure section is located near the radiant section, while the lower part of the other side is designated as the convection heat exchange zone, and the upper part as the heat exchange zone. Alternatively, the preheating zone, convection heat exchange zone, and high-pressure section can be arranged sequentially from top to bottom. Other supporting equipment and facilities within the steam injection station remain unchanged. This invention utilizes a redesigned heat exchange structure to reduce the exhaust gas temperature of the steam injection boiler, improve its thermal efficiency, and achieve energy conservation and emission reduction.

Description

Technical Field

[0001] This invention belongs to the field of petrochemicals and is mainly applied to the scenario of improving the thermal efficiency of steam injection boilers in oil fields. Specifically, it relates to a combined convection section suitable for steam injection boilers in oil fields. Background Technology

[0002] In oilfield development, especially heavy oil extraction, steam injection boilers play a crucial role. Also known as wet steam generators, steam injection boilers are specialized equipment for extracting heavy crude oil. They utilize the generated high-temperature, high-pressure wet steam injected into the oil well to heat the crude oil in the reservoir, reducing its viscosity and increasing its fluidity, thus significantly improving the recovery rate. The convection section, as a vital component of the steam injection boiler, directly impacts the boiler's thermal efficiency and overall operational performance.

[0003] The convection section, located in the boiler's tail flue, primarily functions to heat boiler feedwater using the waste heat from the flue gas. Traditional convection section designs often employ finned tubes or bare tubes as the convection heating surface. However, when using liquid fuels or fuels with high ash content, such as residual oil, emulsified oil, or extra-heavy oil, ash easily accumulates on the finned tubes, forming ash deposits. Ash accumulation not only degrades the heat transfer performance between the flue gas and the working fluid but also prevents the working fluid from effectively absorbing the heat from the high-temperature flue gas, leading to increased exhaust gas temperature, increased heat loss, and reduced thermal efficiency.

[0004] Natural gas accounts for 88.8% of the total energy consumption in the Liaohe Oilfield production system, mainly used for steam injection in heavy oil thermal recovery. This is a key energy-consuming sector, and reducing natural gas consumption is of great significance to the Liaohe Oilfield. Most of the oilfield company's steam injection boilers have been in use for over 20 years, resulting in corrosion of the boiler convection sections and high flue gas temperatures, with an average flue gas temperature of approximately 145℃ and some exceeding 170℃.

[0005] To address these issues, the industry has undertaken various attempts and improvements. For example, a patent proposes a design for the convection section of an oilfield fuel-fired gas-fired steam injection boiler. This design, employing a vertical structure and a multi-pass convection tube bundle composed of bare tubes, mitigates ash accumulation in the convection section and improves heat transfer capacity and thermal efficiency. However, with continuous technological advancements and evolving oilfield development needs, higher demands are being placed on the design of the convection section. The invention patent "Condensing Gas-fired Oilfield Steam Injection Boiler" (CN103104905A) improves the thermal efficiency of steam injection boilers through tail-end convection section efficiency enhancement technology. However, this process is not suitable for older boilers, requiring a significant increase in heat exchange area in the convection section to achieve improved thermal efficiency. Furthermore, it does not address the air required for combustion. Therefore, this invention develops a novel combined convection section with multiple heat exchange methods to enhance thermal efficiency. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention designs a combined convection section for oilfield steam injection boilers. On the one hand, it optimizes the combustion of the boiler body and improves combustion efficiency; on the other hand, it modifies the convection section of existing steam injection boilers, thereby improving the thermal efficiency of the steam injection boilers, reducing gas consumption, and achieving energy conservation and emission reduction.

[0007] This invention provides a combined convection section suitable for oilfield steam injection boilers, which integrates an air preheater, a preheating zone, a convection heat exchange zone, and a high-dry section. The steam injection boiler includes a burner and a radiant section. The air preheater is connected to the burner via piping. The preheating zone, the convection heat exchange zone, and the high-dry section are integrated into a single equipment shell, forming three independent areas. The high-dry section is located on the side closest to the radiant section, while the lower part of the other side is set as the convection heat exchange zone, and the upper part is set as the heat exchange zone. Alternatively, the preheating zone, the convection heat exchange zone, and the high-dry section can be arranged sequentially from top to bottom. Other supporting equipment and facilities within the steam injection station remain unchanged.

[0008] Optionally, the air preheater is connected to a blower.

[0009] Furthermore, the combined convection section has a horizontal, box-type, single-flue structure.

[0010] Furthermore, a radiation section is provided between the convective heat transfer zone and the high-pressure section.

[0011] Furthermore, one end of the combined convection section is connected to a plunger pump, and the other end is connected to an exhaust expansion container and a sampler.

[0012] A steam injection boiler with a combined convection section also includes a high-temperature resistant viewing window, a maintenance platform, a maintenance door, and a condensate outlet.

[0013] Utilizing the modified convection section structure for energy conservation and emission reduction, softened wastewater is pressurized by a raw water heating pump and a plunger pump, and then sequentially enters the preheating zone, convection heat exchange zone, radiation zone, and high-temperature zone. Once the temperature meets the standard, it enters the subsequent steam injection pipeline; otherwise, it is discharged from the emission expansion tank. The exhaust gas generated by combustion sequentially passes through the radiation zone, high-temperature zone, convection heat exchange zone, and preheating zone before reaching the air preheater.

[0014] Specifically, the wastewater softening process includes the following steps:

[0015] 1) The oilfield steam injection softening water is connected to the softening water tank with an average flow rate of 10-19.5t / h and a water temperature of 40-90℃.

[0016] 2) The softened water in the softened water tank is pressurized and metered by the water supply booster pump, and then sent to the preheating zone in the newly made convection section structure after being pressurized by the plunger pump 1, where the temperature is heated to 50-80℃.

[0017] 3) The softened water continues to flow through the convective heat exchange zone, where it is heated to 200-240℃ and turns into saturated steam.

[0018] 4) The fluid continues to enter the boiler radiant section for heating, increasing its dryness, and the fluid flowing out of the radiant section is heated to 330-350℃.

[0019] 5) Finally, it enters the high-dryness section, where the temperature and dryness are further increased, reaching the design temperature of 353℃ and the dryness of 75%.

[0020] 6) Steam enters the steam pipeline network and is transported to the steam injection wellhead.

[0021] Compared with the prior art, the advantages of the present invention are mainly as follows:

[0022] This invention provides a combined convection section suitable for steam injection boilers in Liaohe Oilfield. By utilizing a redesigned heat exchange structure, the flue gas temperature of the steam injection boiler is reduced, the thermal efficiency of the steam injection boiler is improved, and energy conservation and emission reduction are achieved.

[0023] This technological achievement replaces existing convection sections and other equipment, directly improving the thermal efficiency of existing steam injection boilers to 95%; it also reduces the flue gas temperature of steam injection boilers. This device has the following main advantages:

[0024] 1) Heating the combustion air optimizes the combustion process;

[0025] 2) The original infrastructure (fixed workshop) was preserved as much as possible, resulting in lower renovation costs;

[0026] 3) Make full use of the waste heat of flue gas to improve boiler thermal efficiency and reduce boiler steam consumption per ton. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the modified condensing section of the steam injection boiler;

[0028] Figure 2 This is a field application illustration of the furnace condenser convection section.

[0029] The components include: 1. plunger pump; 2. air preheater; 3. blower; 4. preheating zone; 5. convection heat exchange zone; 6. discharge expansion tank; 7. high-pressure section; 8. radiation section; 9. sampler; 10. condensate outlet; and 11. burner. Detailed Implementation

[0030] The present invention will now be described in detail through specific embodiments.

[0031] Example 1

[0032] like Figure 1As shown, this invention provides a combined convection section suitable for oilfield steam injection boilers. The original convection section is removed and redesigned, utilizing the redesigned structure to maximize the reduction of boiler exhaust gas temperature and improve thermal efficiency. This device is a novel convection section structure, a horizontal, box-type, and single-flue structure, housing an air preheater 2, a preheating zone 4, a convection heat exchange zone 5, and a high-pressure section 7. Other supporting equipment and facilities within the steam injection station remain unchanged. The energy-saving and emission-reduction process using the modified convection section structure is as follows:

[0033] 1) The oilfield steam injection softening water is connected to the softening water tank with an average flow rate of 18t / h and a water temperature of 40-90℃.

[0034] 2) The softened water in the softened water tank is pressurized and metered by the water supply booster pump, and then sent to the preheating zone 4 in the newly made convection section structure after being pressurized by the plunger pump 1, where the temperature is heated to 77℃.

[0035] 3) The softened water continues to flow through the convective heat exchange zone 5, where it is heated to 240°C and becomes saturated steam.

[0036] 4) The fluid continues to enter the boiler radiant section 8 for heating, increasing its dryness, and the temperature of the fluid flowing out of the radiant section 8 is heated to 350℃.

[0037] 5) Finally, it enters the high-dryness section 7, where the temperature and dryness are further increased, reaching the design temperature of 353℃ and the dryness of 75%.

[0038] 6) Steam enters the steam pipeline network and is transported to the steam injection wellhead.

[0039] Example 2

[0040] Based on the structure of Example 1, a blower 3 is added. The working principle and process of each part of the system are as follows:

[0041] 1) Air preheater 2: After the blower 3 draws in indoor air, it goes through the air duct to the end air preheater 2 at the tail flue for heating. After the temperature is increased, it returns to the burner to mix and burn with the fuel, thereby improving combustion efficiency.

[0042] 2) After being pressurized by the raw water heating pump and the plunger pump 1, the softened wastewater enters the preheating zone 4, the convection heat exchange zone 5, the radiation section 8 and the high-temperature section 7 in sequence. After the temperature reaches the standard, it enters the subsequent steam injection pipeline. If the temperature does not reach the standard, it will be discharged from the discharge expansion tank 6.

[0043] 3) The exhaust gas generated by combustion passes sequentially through the radiation section 8, the high-temperature section 7, the convection heat exchange zone 5, the preheating zone 4, and the air preheater 2.

[0044] Example 3

[0045] The device mainly consists of a new convection section, a high-temperature resistant viewing window, a maintenance platform, a maintenance door, and a condensate outlet, etc. The external dimensions of the convection section are approximately (length × width × height): 4533mm × 3060mm × 3989mm, and the total weight is approximately 50t.

[0046] The high-temperature resistant viewing window allows for a clear view of the ash and slag conditions within the condensation section structure, facilitating subsequent handling by operators based on actual conditions.

[0047] The condensate outlet 10 is connected to a flexible hose, which can discharge the condensate from the convection section structure and the chimney to the discharge expansion container 6 using the natural elevation difference, so as to reuse and recycle the condensate, saving energy and reducing water softening consumption.

[0048] There are two access doors. Opening these doors allows for cleaning and maintenance work.

[0049] The tube bundle inside the condenser section has been redesigned, increasing the heat exchange area and improving the thermal efficiency to 95%.

[0050] The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A combined convection section suitable for use in oilfield steam injection boilers, characterized in that, The steam injection boiler includes an air preheater (2), a preheating zone (4), a convection heat exchange zone (5), and a high-pressure section (7). The steam injection boiler includes a burner (11) and a radiant section (8). The air preheater (2) is connected to the burner (11) by pipes. The preheating zone (4), the convection heat exchange zone (5), and the high-pressure section (7) are integrated into a single equipment shell to form three independent areas. The high-pressure section (7) is located on the side close to the radiant section (8), and the lower part of the other side is set as the convection heat exchange zone (5), and the upper part is set as the heat exchange zone (5). Alternatively, the preheating zone (4), the convection heat exchange zone (5), and the high-pressure section (7) can be set from top to bottom. Other supporting equipment and facilities in the steam injection station are not modified.

2. The combined convection section for oilfield steam injection boilers according to claim 1, characterized in that, The air preheater (2) is connected to a blower (3).

3. The combined convection section for oilfield steam injection boilers according to claim 1, characterized in that, The combined convection section is a horizontal, box-type, single-flue structure.

4. The combined convection section for oilfield steam injection boilers according to claim 1, characterized in that, A radiation section (8) is provided between the convection heat transfer zone (5) and the high-pressure section (7).

5. The combined convection section for oilfield steam injection boilers according to claim 1, characterized in that, One end of the combined convection section is connected to a plunger pump (1), and the other end is connected to a discharge expansion container (6) and a sampler (9).

6. A steam injection boiler, characterized in that, It includes a combined convection section as described in any one of claims 1-5.

7. The steam injection boiler according to claim 6, characterized in that, It also includes a high-temperature resistant viewing window, a maintenance platform, a maintenance door, and a condensate outlet (10).

8. An energy-saving and emission-reduction process suitable for the combined convection section of an oilfield steam injection boiler, characterized in that, After being pressurized by the raw water heating pump and the plunger pump (1), the softened wastewater enters the preheating zone (4), the convection heat exchange zone (5), the radiation zone (8) and the high-temperature zone (7) in sequence. After the temperature reaches the standard, it enters the subsequent steam injection pipeline. If the temperature does not reach the standard, it is discharged through the discharge expansion container (6). The exhaust gas generated by combustion passes through the radiation zone (8), the high-temperature zone (7), the convection heat exchange zone (5), and the preheating zone (4) in sequence, and then to the air preheater (2).

9. The energy-saving and emission-reduction process for the combined convection section of an oilfield steam injection boiler according to claim 8, characterized in that, The specific softening wastewater treatment process includes the following steps: 1) The oilfield steam injection softening water is connected to the softening water tank; 2) The softened water in the softened water tank is pressurized by the water supply pressurization pump and metered. After being pressurized by the plunger pump (1), it is sent to the preheating zone (4) and heated to 50-80℃. 3) The softened water continues to flow through the convective heat exchange zone (5), and the temperature is heated to 200-240℃; 4) Softened water continues to enter the boiler radiant section (8) for heating, increasing dryness, and the fluid temperature flowing out of the radiant section (8) is heated to 330-350℃; 5) The softened water finally enters the high dry section (7) to continue to increase the temperature and dryness until the design requirements are met; 6) Steam enters the steam pipeline network and is transported to the steam injection wellhead.

10. The energy-saving and emission-reduction process for the combined convection section of an oilfield steam injection boiler according to claim 9, characterized in that, Step 1) The temperature of the softened water in the softened water tank is 40-90℃.

Images