GAS-FIRED STEAM-INJECTION BOILER FOR OIL FIELD

FIELD

The present disclosure relates to the technical field of steam injection boilers for oil field, in particular to a gas-fired steam-injection boiler for oil field.

BACKGROUND

Existing steam injection boilers for oil field are usually horizontal direct-flow water pipe boilers mainly consisting of a radiation section, a transition section connected to the tail end of the radiation section, and a convection section arranged above the transition section. The inner wall of the radiation section is lined with aluminum-silicate ceramic fibers and provided with a coil pipe arranged in a serpentine form, with a capacious hearth formed in the middle; the convection section is a rectangular structure composed of a plain pipe and a finned pipe; the transition section is a semi-circular flue gas diversion channel connected between the radiation section and the convection section, with an axial dimension of about 1.3 meters, and doesn't has a heat exchange effect.

The gas-fired steam-injection boilers used presently are large in size, mainly reflected in the great axial length of the radiation section and great elevation of the flue gas outlet above the ground, which are adverse for flexible steam injection in heavy oil blocks.

Existing gas-fired boilers are renovated from oil-fired boilers with a heat exchange surface mainly having oil combustion characteristics. The gas-fired boilers can't meet the current requirements for high efficiency and energy saving after modification to natural gas firing, because the heat exchange characteristics and flue gas characteristics are changed.

The mechanism of heat carrying by steam indicates that the higher the steam dryness is, the more the carried heat is and the better the effect of steam injection into heavy oil is. Direct drying operation can't be realized through conventional water treatment in direct-flow gas-fired boilers for oil field, owing to the limitation of the existing process.

Therefore, it is urgent task to develop a novel high-efficiency gas-fired steam-injection boiler for oil field to overcome the above-mentioned drawbacks.

The Patent Publication No. CN101343989B published on Aug. 22, 2012 has disclosed a high-dryness steam injection boiler for oil field and a high-dryness steam production method. The high-dryness steam injection boiler for oil field comprises a radiation section, a convection section and a transition section, and further comprises a boiler body, a feed water pump and a steam separator; a steam superheater is mounted in the boiler body between the convection section and the transition section; the water inlet of the inlet pipe of the convection section is in communication with the water outlet of the feed water pump, and the water outlet of the inlet pipe of the convection section is in communication with the water inlet at the upper end of the convection section; the steam inlet of the outlet pipe of the convection section is in communication with the steam outlet at the lower end of the convection section, and the steam outlet of the outlet pipe of the convection section is in communication with the steam inlet of the radiation section. The high-dryness steam injection boiler has a reasonable and compact structure, is convenient to use and capable of achieving 100% steam dryness, has a certain degree of superheat, and can meet the requirements of the steam injection process for super heavy oil exploitation. Therefore, the disclosure greatly improves the efficiency of steam injection in super heavy oil exploitation, improves heat efficiency, and reduces the energy consumption and the production cost.

The Patent Publication No. CN101551097A published on Oct. 7, 2009 is directed to a steam injection boiler for producing high-dryness super-heated steam, which comprises a heat exchanger, a radiation section, a convection section, a stack, a water displacement steam separator, a superheater, a boiler body, a water supply pipeline, a burner, an electric heater, an oil heater, and a flash tank. The burner is arranged in the front part of the boiler body, the radiation section is arranged in the middle part, the convection section is arranged in the rear part, and the burner is connected with the electric heater and the oil heater respectively through wires and pipes; the heat exchanger is arranged outside the radiation section, the external steam separator is arranged at the outlet of the radiation section, the heat exchanger is connected with a feed water pump through the water supply pipeline, and the steam separator is connected with the superheater and the flash tank respectively through pipes; the superheater is arranged at the lower part of the convection section, and the stack is arranged at the upper part of the convection section; the radiation section and the convection section are connected with the heat exchanger respectively through pipes. The steam injection boiler has a novel structure and a reasonable design, and can operate reliably. It can be utilized to produce high-dryness and high-temperature super-heated steam, thereby improves the effect of a SAGD thermal recovery process for heavy oil.

The Patent Publication No. CN202660522U published on Jan. 9, 2013 is directed to a high-dryness steam injection boiler for oil field, which belongs to the technical field of steam injection boilers for oil field. The high-dryness steam injection boiler comprises double feed water pumps, a heat exchanger, a steam separator and a boiler; the boiler comprises a transition flue, a convection and evaporation section, a secondary convection section, a primary convection section and a flue stack; the transition flue, the convection and evaporation section, the secondary convection section, the primary convection section and the flue stack are fixedly connected together sequentially from bottom to top; a burner in communication with the transition flue is fixedly connected outside the transition flue; the water outlets of the double feed water pumps are fixedly connected with the water inlet at the shell side of the heat exchanger through a first pipeline. The utility model has a reasonable and compact structure, is convenient to use, and utilizes the double feed water pumps, the heat exchanger, the burner, the transition flue, the convection and evaporation section, the secondary convection section, the primary convection section and the flue stack in combination, thus attains the object of improving the volume of steam injected into the well and the dryness of the steam reaching the bottom of the well, and meets the requirements of a SAGD development process.

The technical schemes, technical problem to be solved, and beneficial effects disclosed above are different from those in the present disclosure, or the technical field or application scenarios are different from those in the present disclosure. None of the technical documents disclosed above provides a technical enlightenment for more technical features, technical problems to be solved, and beneficial effects in the present disclosure.

SUMMARY

In view of the above-mentioned drawbacks in the prior art, the object of the present disclosure is to provide a gas-fired steam-injection boiler for oil field, in which the radiation section of the boiler is further designed into sections, so that the risk of over-temperature of the pipes incurred by regional change of temperature regions is eliminated and any region where scaling or over-temperature occurs can be monitored conveniently; and a third pipe section and the convection section are designed into a combined form, so as to reduce the thermal shock of the flue gas to the plain pipe of the high-dryness section and effectively improve the steam dryness as well. With a flue gas condenser, the flue gas temperature is further decreased, the latent heat of vaporization of the steam in the flue gas is adsorbed and a condensate is formed, thus the boiler efficiency is improved to 96% or above. The ratio of heat exchange between the radiation section and the convection section is optimized to 5:5 by optimizing the heating surface and the flue structure, so that the heat exchange is more in line with the exothermic character of natural gas flames.

To attain the object described above, the present disclosure employs the following technical scheme: A gas-fired steam-injection boiler for oil field, which comprises a radiation section, a convection section, and a condensation section that are arranged in the flue gas flow direction, wherein the convection section is provided with a plain pipe of the convection section and a finned pipe of the convection section; a third pipe section is disposed between the plain pipe of the convection section and the finned pipe of the convection section, wherein the third pipe section is provided with a plain pipe for evaporation and a finned pipe for evaporation, and the flue gas flows through the radiation section, the plain pipe of the convection section, the plain pipe for evaporation, the finned pipe for evaporation, the finned pipe of the convection section, and a heat exchange plain pipe of the condensation section.

Optionally, the radiation section comprises a high-temperature radiation section and a low-temperature radiation section, and provided with a plain pipe of the high-temperature radiation section in the high-temperature radiation section and a plain pipe of the low-temperature radiation section in the low-temperature radiation section, and a heat exchange medium flows through the plain pipe of the high-temperature radiation section and the plain pipe of the low-temperature radiation section sequentially.

Optionally, the gas-fired steam-injection boiler for oil field further comprises a water tank, the feed water from which flows through the heat exchange plain pipe of the condensation section, a deaerator, the plain pipe of the convection section, the finned pipe of the convection section, the finned pipe for evaporation, the plain pipe for evaporation, and a steam injection pipe connected to a steam outlet of the boiler sequentially.

Optionally, a softener is arranged in the connecting water path between the water tank and the heat exchange plain pipe of the condensation section.

Optionally, a plunger pump is arranged in the connecting water path between the deaerator and the plain pipe of the convection section.

Optionally, the condensation section is provided with a condensation baffle, which is disposed below the heat exchange plain pipe of the condensation section and above the plain pipe of the convection section, and is provided with a water collection tank that has a drain port in an edge, the drain port is connected to a recovery tank through a pipe, and the recovery tank is connected to a water tank via a condensate recovery pump.

Optionally, the water path connected between the plain pipe of the convection section and the plain pipe for evaporation runs through the radiation section.

Optionally, the high-temperature radiation section employs a horizontal serpentine water-cooled wall, with a cylindrical hearth formed in the middle; and the low-temperature radiation section employs a horizontal serpentine water-cooled wall, with a cylindrical hearth formed in the middle.

Optionally, heat exchange by radiation and convection at 5:5 ratio is employed.

In another aspect, the present application employs the following scheme:

A gas-fired steam-injection boiler for oil field, comprising a flue having a radiation section and a convection section that are arranged in a flue gas flow direction, and a water supply pipeline comprising a first pipe section, a second pipe section, and a third pipe section,

- wherein in the flue gas flow direction, the first pipe section is located upstream the convection section, the second pipe section is located downstream the convection section, and the third pipe section is arranged between the first pipe section and the second pipe section; and
- wherein in a water flow direction of the water supply pipeline, the second pipe section, the first pipe section and the third pipe section are arranged sequentially.

Optionally, the first pipe section is a plain pipe of the convection section, and the second pipe section is a finned pipe of the convection section.

Optionally, the third pipe section comprises a plain pipe for evaporation and a finned pipe for evaporation that are arranged in the water flow direction of the water supply pipeline, and the plain pipe for evaporation and the finned pipe for evaporation are arranged sequentially in the flue gas flow direction of the convection section.

Optionally the third pipe section is arranged in a region at 800-900° C. in the convection section.

Optionally, the radiation section extends horizontally, an opening is provided in an upper part of a downstream end of the radiation section, and the convection section is in communication with the upper part of the downstream end of the radiation section and extends upward vertically.

Optionally, the flue comprises a condensation section extending upward vertically from an upper end of the convection section.

Optionally, the water supply pipeline comprises a heat exchange plain pipe of the condensation section arranged in the condensation section, which is located upstream the second pipe section in the water flow direction of the water supply pipeline.

Optionally, the water supply pipeline is provided with a deaerator and a pressure pump between the heat exchange plain pipe of the condensation section and the second pipe section, and is provided with a water tank and a softener upstream the heat exchange plain pipe of the condensation section.

Optionally, the gas-fired steam-injection boiler further comprises a condensation baffle at a lower part of the condensation section, and a water collection tank arranged below the condensation baffle and connected to a recovery tank through a pipeline.

Optionally, the cross-sectional area of flow at a joint between a lower port of the condensation section and an upper port of the convection section is greater than that of the upper port of the condensation section, and a flue gas stack is provided at the upper port of the condensation section.

Optionally, the water supply pipeline comprises a radiation pipe section in the radiation section, and the second pipe section, the first pipe section, the radiation pipe section and the third pipe section are arranged sequentially in the water flow direction of the water supply pipeline.

Optionally, the radiation section comprises a high-temperature radiation section and a low-temperature radiation section that are arranged in the flue gas flow direction, and the radiation sections include a plain pipe of the high-temperature radiation section in the high-temperature radiation section and a plain pipe of the low-temperature radiation section in the low-temperature radiation section, and the plain pipe of the high-temperature radiation section and the plain pipe of the low-temperature radiation section are arranged sequentially in the water flow direction of the water supply pipeline.

Compared with the prior art, the present disclosure attains the following beneficial effects:

- 1. The third pipe section and the convection section are designed into a combined form, so as to reduce the thermal shock of the flue gas to the third pipe section and effectively improve the steam dryness as well.
- 2. With a flue gas condenser, the flue gas temperature is further decreased, the latent heat of vaporization of the steam in the flue gas is adsorbed and a condensate is formed, thus the boiler efficiency is improved to 96% or above.
- 3. The ratio of heat exchange between the radiation section and the convection section is optimized to 5:5 by optimizing the heating surface and the flue structure, so that the heat exchange is more in line with the exothermic character of natural gas flames.
- 4. The quality of the feed water is improved by utilizing feed water preheating and flue gas condensation in combination.
- 5. The radiation section is arranged into regions, thus pipes made of different materials can be employed according to the flame temperature, thereby the risk of over-temperature of the pipes incurred by regional change of the flame temperature of the low-nitrogen burner can be eliminated; uniform heat exchange in the water-cooled walls can be controlled more easily; the entire steam region in the high-temperature and low-temperature pipes is shifted backward, and any region where scaling or over-temperature occurs can be monitored more conveniently.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural diagram of the gas-fired steam-injection boiler for oil field in an embodiment of the present disclosure;

FIG. 2 is a schematic structural diagram of the gas-fired steam-injection boiler for oil field in another embodiment of the present disclosure.

Reference Numbers: 1—radiation section, 2—convection section, 3—third pipe section, 5—condensation baffle, 4—condensation section, 6—recovery tank, 7—condensate recovery pump, 8—water tank, 9—softener, 10—deaerator, 11—plunger pump, 16—high-temperature radiation section, 17—low-temperature radiation section, 18—plain pipe of the high-temperature radiation section, 19—plain pipe of the low-temperature radiation section, 21—plain pipe of the convection section, 31—plain pipe for evaporation, 32—finned pipe for evaporation, 22—finned pipe of the convection section, 41—heat exchange plain pipe of the condensation section.

EMBODIMENTS

Hereunder the technical scheme in the embodiments of the present disclosure will be detailed clearly and completely with reference to the accompanying drawings of the embodiments. Obviously, the embodiments described herein are only some embodiments of the present disclosure, but not all possible embodiments of the present disclosure. Those having ordinary skills in the art can obtain other embodiments on the basis of the embodiments described herein without expending any creative labor; however, all such embodiments shall be deemed as falling in the scope of protection of the present disclosure.

Embodiment 1

Please see FIGS. 1-2. The present disclosure provides a technical scheme:

A gas-fired steam-injection boiler for oil field, comprising a radiation section 1, a convection section 2, and a condensation section 4, wherein the convection section is provided with a plain pipe 21 of the convection section and a finned pipe 22 of the convection section, a third pipe section 3 is disposed between the plain pipe of the convection section and the finned pipe of the convection section, wherein the third pipe section is provided with a plain pipe for evaporation 31 and a finned pipe for evaporation 32, and the flue gas flows through the radiation section, the plain pipe 21 of the convection section, the plain pipe for evaporation 31, the finned pipe for evaporation 32, the finned pipe 22 of the convection section, and a heat exchange plain pipe 41 of the condensation section.

Furthermore, the gas-fired steam-injection boiler for oil field further comprises a water tank 8, the feed water from which flows through the heat exchange plain pipe of the condensation section, a deaerator 10, the plain pipe of the convection section, the finned pipe of the convection section, the finned pipe for evaporation, the plain pipe for evaporation, and a steam injection pipe connected to a steam outlet of the boiler sequentially. The dryness of the medium in the steam injection pipe connected to the steam outlet of the boiler is 90%.

Furthermore, a softener 9 is arranged in the connecting water path between the water tank and the heat exchange plain pipe of the condensation section.

Furthermore, a plunger pump 11 is arranged in the connecting water path between the deaerator and the plain pipe of the convection section. The medium temperature in the water path is 60° C.

Furthermore, the condensation section is provided with a condensation baffle, which is disposed below the heat exchange plain pipe of the condensation section and above the plain pipe of the convection section and is provided with a water collection tank that has a drain port in an edge, the drain port is connected to a recovery tank 6 through a pipe, and the recovery tank is connected to a water tank via a condensate recovery pump 7.

Furthermore, the water path connected between the plain pipe of the convection section and the plain pipe for evaporation runs through the radiation section.

Furthermore, the radiation section employs a horizontal serpentine water-cooled wall, with a cylindrical hearth formed in the middle.

Furthermore, heat exchange by radiation and convection at 5:5 ratio is employed.

It can be seen from FIG. 1 that the embodiment of the present disclosure is as follows: the novel high-efficiency gas steam injection boiler for oil field comprises a radiation section, a convection section, and a condensation section; wherein the flue gas flows through the radiation section, the plain pipe of the convection section, the plain pipe for evaporation, the finned pipe for evaporation, the finned pipe of the convection section, and the plain pipe of the condensation section sequentially. The third pipe section is mounted between the plain pipe of the convection section and the finned pipe of the convection section and arranged in the axial direction of the radiation section. The condensation section is right above the convection section.

The core idea of the embodiment of the present disclosure is as follows: with a flue gas condenser, the flue gas temperature can be further decreased, the latent heat of vaporization of the steam in the flue gas is adsorbed and a condensate is formed, thus the boiler efficiency is improved to 96% or above; the ratio of heat exchange between the radiation section and the convection section is optimized to 5:5 by optimizing the heating surface and the flue structure, so that the heat exchange is more in line with the exothermic character of natural gas flames; the quality of the feed water is improved by utilizing feed water preheating and flue gas condensation in combination. Besides, the entire boiler is shortened by 2-3 meters, and the weight of the steam injection boiler is reduced, thus the steam injection boiler can be transported more easily.

In the present disclosure, with a flue gas condenser, the flue gas temperature is further decreased, the latent heat of vaporization of the steam in the flue gas is adsorbed and a condensate is formed, thus the boiler efficiency is improved to 96% or above. Besides, the dynamic resistance of flue gas flow is decreased owing to the volume shrinkage of the flue gas after flue gas condensation.

In the present disclosure, the quality of the feed water is improved by utilizing feed water preheating and flue gas condensation in combination. Besides, the entire boiler is shortened by 2-3 meters, and the weight of the steam injection boiler is reduced, thus the steam injection boiler can be transported more easily.

The core features of the present disclosure lie in several aspects, i.e., heat exchange ratio balance design, flue gas condensation and waste heat recovery design, and flue gas preheating and feed water deaeration design.

In the heat exchange ratio balance design, the heat exchange ratio between the convection section and the radiation section is readjusted according to the characteristics of short combustion flames and low radiant heat of the gas-fired steam-injection boiler, and the radiation section, the plain pipe of the convection section, the plain pipe for evaporation, the finned pipe for evaporation, the finned pipe of the convection section, and the plain pipe of the condensation section are arranged sequentially in the flue gas flow direction for the arrangement of heat exchange surfaces. A 5:5 heat exchange ratio of radiation to convection is used for the high-efficiency and high-dryness gas-fired boiler, instead of a 6:4 heat absorption ratio of radiation to convection for conventional boilers. The ratio is more suitable for the combustion characteristics of a gas-fired boiler, and the entire heat exchange process at the flue gas side is more reasonable and efficient.

In the flue gas condensation and waste heat recovery design, a heat exchange plain pipe of the condensation section is added at the tail part of the condensation section, the temperature of the flue gas flowing through the shell side is decreased to 55° C. or a lower temperature, so that 90% steam in the flue gas forms condensate, the latent heat of the flue gas is recovered, and the thermal efficiency of the boiler is higher than 96%.

In the flue gas preheating and feed water deaeration design, the water from the outlet of the softener is led to the pipe side of the flue gas condensation and heat exchange region, thus the feed water temperature is increased by about 20° C. after heat exchange with the flue gas; the partial pressure of oxygen entering the vacuum deaerator is changed to improve the feed water deaeration effect for the boiler, so that the feed water can't meet the requirements of operation without dosing. The steam generated from feed water is recirculated, and the feed water is subjected to heating, deaeration, steam formation and reheating, thus a layout of high-dryness steam process is generated.

Embodiment 2

Please see FIGS. 1-2. The present disclosure provides a technical scheme:

A gas-fired steam-injection boiler for oil field, comprising a radiation section 1, a convection section 2, and a condensation section 4, wherein the convection section is provided with a plain pipe 22 of the convection section and a finned pipe 21 of the convection section, a third pipe section 3 is disposed between the plain pipe of the convection section and the finned pipe of the convection section, wherein the third pipe section is provided with a plain pipe for evaporation 31 and a finned pipe for evaporation 32, and the flue gas flows through the radiation section, the plain pipe of the convection section, the plain pipe for evaporation, the finned pipe for evaporation, the finned pipe of the convection section, and a heat exchange plain pipe 41 of the condensation section.

Furthermore, the gas-fired steam-injection boiler for oil field further comprises a water tank 8, the feed water from which flows through the heat exchange plain pipe of the condensation section, a deaerator 10, the plain pipe of the convection section, the finned pipe of the convection section, the finned pipe for evaporation, the plain pipe for evaporation, and a steam injection pipe connected to a steam outlet of the boiler sequentially. The water temperature at the outlet of the water tank is 25° C. normal temperature. The dryness of the medium in the steam injection pipe connected to the steam outlet of the boiler is 90%.

Furthermore, a softener 9 is arranged in the connecting water path between the water tank and the heat exchange plain pipe of the condensation section.

Furthermore, a plunger pump 11 is arranged in the connecting water path between the deaerator and the plain pipe of the convection section. The medium temperature in the water path is 60° C.

Embodiment 3

Please see FIGS. 1-2. The present disclosure provides a technical scheme:

A gas-fired steam-injection boiler for oil field, comprising a radiation section 1, a convection section 2, and a condensation section 4, wherein the convection section is provided with a plain pipe of 21 the convection section and a finned pipe 22 of the convection section, a third pipe section 3 is disposed between the plain pipe of the convection section and the finned pipe of the convection section, wherein the third pipe section is provided with a plain pipe for evaporation 31 and a finned pipe for evaporation 32, and the flue gas flows through the radiation section, the plain pipe of the convection section, the plain pipe for evaporation, the finned pipe for evaporation, the finned pipe of the convection section, and a heat exchange plain pipe 41 of the condensation section.

Furthermore, the gas-fired steam-injection boiler for oil field further comprises a water tank 8, the feed water from which flows through the heat exchange plain pipe of the condensation section, a deaerator 10, the plain pipe of the convection section, the finned pipe of the convection section, the finned pipe for evaporation, the plain pipe for evaporation, and a steam injection pipe connected to a steam outlet of the boiler sequentially. The water temperature at the outlet of the water tank is 25° C. normal temperature. The dryness of the medium in the steam injection pipe connected to the steam outlet of the boiler is 90%.

Embodiment 4

Please see FIG. 2. The present disclosure provides a technical scheme:

A gas-fired steam-injection boiler for oil field, comprising a flue having a radiation section 1 and a convection section 2 that are arranged in a flue gas flow direction, and a water supply pipeline comprising a first pipe section, a second pipe section, and a third pipe section,

- wherein in the flue gas flow direction, the first pipe section is located upstream the convection section 2, the second pipe section is located downstream the convection section 2, and the third pipe section is arranged between the first pipe section and the second pipe section; and
- wherein in a water flow direction of the water supply pipeline, the second pipe section, the first pipe section and the third pipe section 3 are arranged sequentially.

In the third pipe section (or may be referred to as an evaporation section), most of the liquid water is transformed into steam, and the steam accounts for a high ratio (e.g., higher than 80%) and has high dryness; the third pipe section in this scheme is the last part of the water supply pipeline that exchanges heat with the flue, so that high-dryness steam is formed therein for use.

The water (and the steam generated gradually) in the water supply pipeline flows through the second pipe section, the first pipe section and the third pipe section sequentially, while the flue gas flows through the first pipe section, the third pipe section and the second pipe section, so as to perform heat exchange.

Since the formation of steam in the water supply pipeline mainly occurs in the third pipe section and the third pipe section is arranged in the convection section 2 where the temperature is somewhat lower than that in the radiation section 1, excessive shock of flue gas at a higher temperature to the pipeline can be avoided when compared with the scheme in which the third pipe section is arranged in the radiation section, so that the third pipe section is protected better.

Of course, other pipelines may be included, besides the first pipe section, the third pipe section and the second pipe section, as further detailed below.

The first pipe section is a plain pipe 21 of the convection section, and the second pipe section is a finned pipe 22 of the convection section. That is to say, the flue gas exchanges heat with the plain pipe 21 of the convection section first, and then exchanges heat with the finned pipe 22 of the convection section.

The third pipe section comprises a plain pipe for evaporation 31 and a finned pipe for evaporation 32 that are arranged in the water flow direction of the water supply pipeline, and the plain pipe for evaporation 31 and the finned pipe for evaporation 32 are arranged sequentially in the flue gas flow direction of the convection section 2. The feed water flows through the plain pipe for evaporation 31 and the finned pipe for evaporation 32 sequentially, and the flue gas exchanges heat with the plain pipe for evaporation 31 and the finned pipe for evaporation 32 sequentially. For the third pipe section, the flue gas at a higher temperature exchanges heat with the fluid (water and steam) at a lower temperature in the plain pipe first, and then the flue gas at a lower temperature exchanges heat with the fluid (water and steam) at a higher temperature in the finned pipe, so that the third pipe section is protected better.

The radiation section 1 extends horizontally, an opening is provided in an upper part of a downstream end of the radiation section 1, and the convection section 2 is in communication with the upper part of the downstream end of the radiation section 1 and extends upward vertically. In addition, the flue comprises a condensation section 4 extending upward vertically from an upper end of the convection section 2.

The water supply pipeline comprises a heat exchange plain pipe 41 of the condensation section arranged in the condensation section 4, which is located upstream the second pipe section in the water flow direction of the water supply pipeline. The feed water may exchange heat with the flue gas in the condensation section 4 in the heat exchange plain pipe 41 of the condensation section first, so that the feed water is preheated preliminarily.

In addition, the water supply pipeline is provided with a deaerator 10 and a pressure pump 11 between the heat exchange plain pipe 41 of the condensation section and the second pipe section, and is provided with a water tank 8 and a softener 9 upstream the heat exchange plain pipe 41 of the condensation section. The water tank 8 can store the feed water, and the softener 9 is configured to soften the feed water; after the feed water is preheated, the oxygen in the feed water is removed by means of a deaerator, and flow power is provided by means of a pressure pump 11.

Furthermore, the gas-fired steam-injection boiler for oil field further comprises a condensation baffle 5 at a lower part of the condensation section 4 and a water collection tank located below the condensation baffle 5 and connected to a recovery tank 6 through a pipeline. The condensation baffle 5 can change the direction of the flue gas and drive the flue gas to wash the pipeline, and absorb the latent heat of the steam in the flue gas to further decrease the flue gas temperature and form condensate, so that the boiler efficiency is improved to 96% or above; besides, the dynamic resistance of flue gas flow is decreased owing to the volume shrinkage of the flue gas after the steam in the flue gas is condensed. The condensate is recovered by means of the water collection tank, so that the cost is decreased further. The recovery tank 6 is in communication with the water tank 8, and the water is conveyed into the water tank 8 for further use.

The cross-sectional area of flow at a joint between a lower port of the condensation section 4 and an upper port of the convection section 2 is greater than that of the upper port of the condensation section 4, and a flue gas stack is provided at the upper port of the condensation section 4. The flue gas stack part may serve as a thermal stack effect region 15 for the flue gas.

Furthermore, the water supply pipeline comprises a radiation pipe section in the radiation section 1, and the second pipe section, the first pipe section, the radiation pipe section and the third pipe section 3 are arranged sequentially in the water flow direction of the water supply pipeline. The feed water flows through the first pipe section, the radiation pipe section and the third pipe section sequentially; wherein the feed water exchanges heat with the flue gas in the radiation section in the radiation pipe section to absorb the heat greatly.

Furthermore, the radiation section 1 comprises a high-temperature radiation section 16 and a low-temperature radiation section 17 that are arranged in the flue gas flow direction, and the radiation sections include a plain pipe 18 of the high-temperature radiation section in the high-temperature radiation section 16 and a plain pipe 19 of the low-temperature radiation section in the low-temperature radiation section 17, and the plain pipe 18 of the high-temperature radiation section and the plain pipe 19 of the low-temperature radiation section are arranged sequentially in the water flow direction of the water supply pipeline. As shown in FIG. 2, a high-temperature radiation section 16 is located upstream an low-temperature radiation section 17, and the flue gas temperature in the high-temperature radiation section 16 is at a higher temperature; the feed water flows through the high-temperature radiation section 16 first, and then flows through the low-temperate radiation section 17; especially, according to tests and calculations, essentially no steam is formed from the feed water in the plain pipe 18 of the high-temperature radiation section; instead, the formation of steam begins in the plain pipe 19 of the low-temperature radiation section. In the structure, the low-temperature radiation section 17 has lower requirements for the material than the high-temperature radiation section 17, and may use pipe fittings at a lower cost.

Pipes corresponding to the radiation section 1, the convection section 2, and the condensation section 4 respectively are provided in the hearth of the flue and exposed to the flue gas environment, so as to exchange heat with the flue gas therein.

Embodiment 5

Please see FIG. 2. The present disclosure provides a technical scheme:

A gas-fired steam-injection boiler for oil field, comprising a radiation section 1, a convection section 2, and a condensation section 4 that are arranged in the flue gas flow direction, wherein the convection section 2 is provided with a plain pipe 21 of the convection section and a finned pipe 22 of the convection section, a third pipe section 3 is disposed between the plain pipe of the convection section and the finned pipe of the convection section, wherein the third pipe section 3 is provided with a plain pipe for evaporation 31 and a finned pipe for evaporation 32, and the flue gas flows through the radiation section, the plain pipe of the convection section, the plain pipe for evaporation, the finned pipe for evaporation, the finned pipe of the convection section, and a heat exchange plain pipe 41 of the condensation section.

In addition, the radiation section 1 comprises a high-temperature radiation section 16 and a low-temperature radiation section 17, and provided with a plain pipe 18 of the high-temperature radiation section in the high-temperature radiation section 16 and a plain pipe 19 of the low-temperature radiation section in the low-temperature radiation section 17, and a heat exchange medium flows through the plain pipe 18 of the high-temperature radiation section and the plain pipe 19 of the low-temperature radiation section sequentially.

As shown in FIG. 2, in the radiation section 1, the flue gas flows through the high-temperature radiation section 16 and the low-temperature radiation section 17 sequentially, i.e., the flue gas reaches the plain pipe 18 of the high-temperature radiation section and the plain pipe 19 of the low-temperature radiation section sequentially; the heat exchange medium (e.g., the water in the water tank described below) flows through the plain pipe 18 of the high-temperature radiation section and the plain pipe 19 of the low-temperature radiation section sequentially to absorb the heat energy in the radiation section 1; accordingly, according to the time of heat absorption, the temperature of the heat transfer medium in the plain pipe 18 of the high-temperature radiation section is lower than that of the heat transfer medium in the plain pipe 19 of the low-temperature radiation section; in the case that the heat transfer medium is water, the plain pipe 18 of the high-temperature radiation section may be positioned in the radiation section 1 in a way that the temperature of the water therein is lower than or equal to the critical temperature for vaporization, and no steam occurs in the plain pipe 18 of the high-temperature radiation section, and the plain pipe 19 of the low-temperature radiation section may be positioned in a way that the water therein absorbs heat further to form steam, which is to say, the plain pipe in which the formation of steam begins is located at a downstream position of the radiation section 1.

The arrangement of the high-temperature radiation section 16 and the low-temperature radiation section 17, i.e., the selection of the regions for the plain pipe 18 of the high-temperature radiation section and the plain pipe 19 of the low-temperature radiation section, should be based on the heat absorption and evaporation condition of the water. The plain pipe 18 of the high-temperature radiation section and the plain pipe 19 of the low-temperature radiation section are arranged in appropriate regions according to the specific boiler structure and relevant calculations, so that the water entering the plain pipe 18 of the high-temperature radiation section will not be evaporated and form steam (lower than the critical temperature of evaporation), while steam is formed only in the plain pipe 19 of the low-temperature radiation section. In short, the division of the high-temperature radiation section 16 and the low-temperature radiation section 17 is based on the state of the water flowing through the plain pipe 18 of the high-temperature radiation section and the plain pipe 19 of the low-temperature radiation section (whether steam is formed or not).

Please see FIG. 2, which illustrates the arrangement of the plain pipe 18 of the high-temperature radiation section and the plain pipe 19 of the low-temperature radiation section, for the purpose of explaining that the heat exchange medium adsorbs heat in the high-temperature radiation section 16 first, then enters the low-temperature radiation section 17 and adsorbs heat there, but doesn't flow to-and-fro between the high-temperature radiation section 16 and the low-temperature radiation section 17.

Furthermore, the gas-fired steam-injection boiler for oil field further comprises a water tank 8, the feed water from which flows through the heat exchange plain pipe of the condensation section, a deaerator 10, the plain pipe of the convection section, the finned pipe of the convection section, the finned pipe of the high-dryness section, the plain pipe of the high-dryness section, and a steam injection pipe connected to a steam outlet of the boiler sequentially. The water temperature at the outlet of the water tank is 25° C. normal temperature. The dryness of the medium in the steam injection pipe connected to the steam outlet of the boiler is 90%.

Furthermore, a softener 9 is arranged in the connecting water path between the water tank and the heat exchange plain pipe of the condensation section.

Furthermore, a plunger pump 11 is arranged in the connecting water path between the deaerator and the plain pipe of the convection section. The medium temperature in the water path is 60° C.

Furthermore, the water path connected between the plain pipe of the convection section and the plain pipe for evaporation runs through the radiation section. That is to say, the water path runs through the plain pipe 18 of the high-temperature radiation section and the plain pipe 19 of the low-temperature radiation section sequentially.

Furthermore, the high-temperature radiation section 16 employs a horizontal serpentine water-cooled wall, with a cylindrical hearth formed in the middle; the low-temperature radiation section 17 employs a horizontal serpentine water-cooled wall, with a cylindrical hearth formed in the middle; the outlet of the condensation section is connected with a tail stack, in which a flue gas thermal pressure stack effect region is formed in the flue, so as to form a negative pressure section environment, wherein the flue gas entering the tail stack is at 56° C.

Furthermore, heat exchange by radiation and convection at 5:5 ratio is employed.

It can be seen from FIG. 2 that the embodiment of the present disclosure is as follows: the novel high-efficiency gas-fired steam-injection boiler for oil field comprises a radiation section, a convection section, and a condensation section, wherein the radiation section comprises a high-temperature radiation section 16 and a low-temperature radiation section 17 that are arranged in the flue gas flow direction, the radiation section is provided with a plain pipe 18 of the high-temperature radiation section arranged in the high-temperature radiation section 16 and a plain pipe 19 of the low-temperature radiation section arranged in the low-temperature radiation section 17; wherein the flue gas flows through the plain pipe 18 of the high-temperature radiation section, the plain pipe 19 of the low-temperature radiation section, the plain pipe of the convection section, the plain pipe for evaporation, the finned pipe for evaporation, the finned pipe of the convection section, and the plain pipe of the condensation section sequentially. The third pipe section is mounted between the plain pipe of the convection section and the finned pipe of the convection section and arranged in the axial direction of the radiation section. The condensation section is right above the flue gas effect region.

The core idea of the embodiment of the present disclosure is as follows: the radiation section is divided into an upstream high-temperature radiation section 16 and a downstream low-temperature radiation section 17 in the flue gas flow direction, and the plain pipe 18 of the high-temperature radiation section and the plain pipe 19 of the low-temperature radiation section are in regions at different temperatures respectively, so that the heat exchange in the water-cooled wall can be controlled more easily, the low-temperature regions of the heat exchange fluid in the pipes are arranged centrally in the upstream while the high-temperature regions of the heat exchange fluid are arranged centrally in the downstream, thereby the regions where scaling or over-temperature occurs can be monitored more conveniently, and pipes made of different materials can be used according to the flue gas temperature and flame temperature; with a flue gas condenser, the flue gas temperature can be further decreased, the latent heat of vaporization of the steam in the flue gas is adsorbed and a condensate is formed, thus the boiler efficiency is improved to 100% or above; the ratio of heat exchange between the radiation section and the convection section is optimized to 5:5 by optimizing the heating surface and the flue structure, so that the heat exchange is more in line with the exothermic character of natural gas flames; the quality of the feed water is improved by utilizing feed water preheating and flue gas condensation in combination. Besides, the entire boiler is shortened by 2-3 meters, and the weight of the steam injection boiler is reduced, thus the steam injection boiler can be transported more easily.

In the present disclosure, the third pipe section is arranged between the plain pipe of the convection section and the finned pipe of the convention section, the thermal shock of the flue gas to the plain pipe of the high-dryness section is reduced by the heat absorption of the low temperature water at the side of the plain pipe of the convection section, and the steam dryness is improved effectively. In the present disclosure, with a flue gas condenser, the flue gas temperature is further decreased, the latent heat of vaporization of the steam in the flue gas is adsorbed and a condensate is formed, thus the boiler efficiency is improved to 96% or above. Besides, the dynamic resistance of flue gas flow is decreased owing to the volume shrinkage of the flue gas after flue gas condensation.

In the present disclosure, the ratio of heat exchange between the radiation section and the convection section is optimized to 5:5 by optimizing the heating surface and the flue structure, so that the heat exchange is more in line with the exothermic character of natural gas flames. In addition, the tail flue gas resistance is reduced by three times of pressure reduction in different forms in the flue gas flow process.

The core features of the present disclosure lie in three aspects, i.e., heat exchange ratio balance design, flue gas condensation and waste heat recovery design, and flue gas preheating and feed water deaeration design.

The flue gas temperature at the outlet of the condensation section is higher than the air temperature at the outlet of the stack, and a stack effect region is formed under thermal pressure. A negative pressure section environment is formed in the entire tail flue, so as to reduce the dynamic resistance of flue gas flow.

While all of the above embodiments are described with reference to FIGS. 1-2, those skilled in the art can understand clearly that the parts and components or structural features absent in the embodiments can be removed from the figures simply for clear description of the embodiments, without working out separate drawings. That is obvious to those skilled in the art. Of course, embodiments with more components are only preferred embodiments, while embodiments with fewer components are basic embodiments but can also attain the basic object of the present disclosure. Therefore, all of those embodiments are within the scope of protection of the present disclosure.

All of the parts and components not discussed in detail in the present application and all connection methods of the parts and components in the present application belong to well-known techniques in the art, and will not be further detailed here. For example, the connections may be realized by means of welding or threaded connection, etc.

In the present disclosure, the term “a plurality” means two or more, unless otherwise defined explicitly. The terms “install”, “connected”, “connection” and “fix”, etc. shall be comprehended in their general meanings, for example, a “connection” may be a fixed connection, detachable connection, or integral connection; “connected” may be directly connected or indirect connected via an intermediate medium. Those having ordinary skills in the art may interpret the specific meanings of the terms in the present disclosure in their context.

In the description of the present disclosure, it should be understood that the orientation or position relations indicated by terms “top”, “bottom”, “left”, “right”, “front”, or “back”, etc., are based on the orientation or position relations indicated on the accompanying drawings. They are used only to ease and simplify the description of the present disclosure, instead of indicating or implying that the involved device or unit must have a specific orientation or must be constructed and operated in a specific orientation. Therefore, the use of these terms shall not be deemed as constituting any limitation to the present disclosure.

In the description of the present disclosure, the expressions of reference terms “an embodiment”, “some embodiments”, and “specific embodiment”, etc. mean that the specific features, structures, materials or characteristics described in those embodiments or examples are included in at least one embodiment or example of the present disclosure. In this document, the exemplary expression of the above terms may not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined appropriately in any one or more embodiments or example.

While the present disclosure has been illustrated and described with reference to some preferred embodiments, the present disclosure is not limited to those embodiments. Those skilled in the art should recognize that various variations and modifications can be made, without departing from the spirit and scope of the present disclosure as defined by the accompanying claims. Any modification, equivalent replacement, or improvement made to the embodiments without departing from the spirit and the principle of the present disclosure shall be deemed as falling into the scope of protection of the present disclosure.

GAS-FIRED STEAM-INJECTION BOILER FOR OIL FIELD

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