Oilfield produced water multiphase flow photocatalysis hydrogen-heat co-production system and use method

Abstract

The invention discloses an oilfield produced water multiphase flow photocatalysis hydrogen-heat co-production system and a use method, and belongs to the technical field of oilfield produced water utilization. The system comprises an oilfield produced water delivery device, a water outlet of the oilfield produced water delivery device is connected with water inlets of a plurality of groups of optical fluid reactors, water outlets of the plurality of groups of optical fluid reactors are connected with a water inlet of a heat exchange system, and a water outlet of the heat exchange system is connected with the oilfield produced water delivery device; gas outlets of the plurality of groups of optical fluid reactors are connected with a hydrogen treatment system; the interior of the optical fluid reactor is divided into an upper half part and a lower half part, the upper half part of the optical fluid reactor is a space for allowing the dynamic multiphase flow to pass through, a gas gap is formed in the upper half part, a photocatalyst and a carbonaceous organic matter are stored in the upper half part, and a full-dielectric reflecting film is laid on the lower half part of the optical fluid reactor; and the light absorption amount of the catalyst is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield produced water utilization, and specifically relates to an oilfield produced water multiphase flow photocatalytic hydrogen-heat cogeneration system and a use method. Background Art

[0002] Solar direct photocatalytic decomposition of water to produce hydrogen is becoming a new and effective way to utilize solar energy, and has attracted great attention from academic and industrial circles around the world. After years of research, the quantum efficiency of chemical catalytic decomposition of water to produce hydrogen in the ultraviolet region has exceeded 50%, and the quantum efficiency of decomposition of water to produce hydrogen in the visible light region has reached 2.5%, and the industrialization goal of 5-10% is not far away.

[0003] A large amount of produced water is generated during the development of oil and gas fields. The annual production of produced water is about 1 billion cubic meters, of which the gas field produced water of Changqing Oilfield is about 2.47 million cubic meters per year. There is a problem that some waste liquids in oil field produced water urgently need to be utilized as resources. The produced water of oil and gas fields has the characteristics of high mineralization and complex water quality. The existing technology usually uses green chemical technology electrocatalytic oxidation to decompose the produced water of oil and gas fields into harmless H2O and CO2, but its manufacturing cost is high and it cannot recover the heat in the produced water. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art such as high cost, complex structure and inability to recover heat in produced water, the purpose of the present invention is to provide an oilfield produced water multiphase flow photocatalytic hydrogen and heat cogeneration system and a method of use, which directly utilizes solar energy to photocatalytically produce hydrogen, and can recover the heat in the produced water for crude oil heating while photocatalytically producing hydrogen from oilfield produced water, thereby realizing hydrogen and heat cogeneration.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides an oilfield produced water multiphase flow photocatalytic hydrogen and heat cogeneration system, comprising an oilfield produced water conveying device, wherein the water outlet of the oilfield produced water conveying device is connected to the water inlet of a plurality of groups of photofluid reactors, the water outlets of the plurality of groups of photofluid reactors are all connected to the water inlet of a heat exchange system, the water outlet of the heat exchange system is connected to the oilfield produced water conveying device; the gas outlets of the plurality of groups of photofluid reactors are all connected to a hydrogen treatment system;

[0007] The interior of the photofluid reactor is divided into an upper half and a lower half. The upper half of the photofluid reactor is used to accommodate the passage of dynamic multiphase flow. A gas gap is opened in the upper half, and photocatalysts and carbon-containing organic matter are stored. The lower half of the photofluid reactor is paved with a full dielectric reflective film for focusing reflection and increasing the light absorption of the catalyst.

[0008] In the specific implementation process, the oilfield produced water delivery device includes a high-level normal pressure buffer tank and a water outlet pipeline;

[0009] The first water inlet of the high-level atmospheric pressure buffer tank is connected to the outlet of the oilfield production and output water pipeline, and the second water inlet of the high-level atmospheric pressure buffer tank is connected to the outlet of the heat exchange system; the water outlet of the high-level atmospheric pressure buffer tank is connected to the water inlet of the outlet pipeline, and the water outlet of the outlet pipeline is connected to the water inlet of several groups of photofluid reactors.

[0010] In a specific implementation process, a first quick-open cleaning port is provided at the front end of the photofluid reactor, and a second quick-open cleaning port is provided at the rear end of the photofluid reactor.

[0011] In a specific implementation process, a filter screen is arranged after the gas gap and before the second quick-open cleaning port of the photofluid reactor.

[0012] In a specific implementation process, the hydrogen processing system includes a hydrogen pipeline and an oxygen content sensor, a hydrogen-oxygen separator, a moisture sensor and a dryer which are sequentially arranged on the hydrogen pipeline.

[0013] In a specific implementation process, the gas outlet of the photofluid reactor is opened in the upper half of the photofluid reactor.

[0014] In a specific implementation process, the gas inlet of the hydrogen pipeline is connected to the gas outlet of the upper half of the optical fluid reactor, and the gas outlet of the hydrogen pipeline is connected to the hydrogen storage device.

[0015] In the specific implementation process, the heat exchange system includes a low-level atmospheric pressure buffer tank, a pump and a heat exchanger;

[0016] The water outlet of the low-level normal pressure buffer tank is connected to the water inlet of the heat exchanger, and the water outlet of the heat exchanger is connected to the oilfield produced water delivery device through the heat exchanger outlet pipe; the pump is arranged on the pipeline between the low-level normal pressure buffer tank and the heat exchanger.

[0017] In a specific implementation process, the internal flow state of the photofluid reactor adopts a non-full flow state, and the shape of the photofluid reactor is an elliptical pipe.

[0018] The present invention provides a method for using the oilfield produced water multiphase flow photocatalytic hydrogen and heat cogeneration system based on any one of the above, comprising the following steps:

[0019] S1: The produced water from the oil field is buffered by the produced water delivery device of the oil field and then enters several groups of photofluid reactors. Sunlight irradiates the photofluid reactor, and the all-dielectric reflective film in the photofluid reactor gathers and reflects the light to the photocatalyst. The photocatalyst undergoes redox reaction with carbon-containing organic matter and produced water from the oil field. The generated oxygen reacts with the carbon-containing organic matter and is consumed, and the generated hydrogen enters the hydrogen storage device through the hydrogen treatment system;

[0020] S2: The residual oilfield produced water in the photofluid reactor enters the heat exchange system for heat exchange for crude oil heating, and is then recycled to the oilfield produced water delivery device for cyclic use.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention provides a multiphase photocatalytic hydrogen and heat cogeneration system for oilfield produced water, and constructs a dynamic balance mechanism of oxidation and reduction in the hydrogen production process. When the oilfield produced water containing an appropriate amount of carbon-containing organic matter enters the photofluid reactor, the flow state in the reactor adopts a non-full flow state, and the upper part is a solid photocatalyst, carbon-containing organic matter and water to form a dynamic multiphase flow accommodation space. In the process of reducing hydrogen under light, oxygen and carbon-containing organic matter in the produced water are oxidized and consumed, and the dynamic balance is achieved, thereby improving the stability and safety of the production process. The photofluid reactor only discharges hydrogen, and there is no need for secondary separation of hydrogen and oxygen, thereby improving the hydrogen production efficiency, recovering the waste heat of the photofluid reactor, and realizing hydrogen and heat cogeneration. Compared with the electrolysis of water, the operation cost of directly using solar energy photocatalytic hydrogen production from oil and gas field produced water can be as low as 20% of the prior art.

[0023] The present invention further adopts an elliptical tube to increase the illumination area, and a fully dielectric reflective film is laid on the lower half of the elliptical tube for focusing reflection to increase the light absorption of the catalyst. The lower part of the fluid reactor does not need to be provided with a conventional metal focusing groove, thereby reducing the manufacturing cost. The hot fluid in the fluid reactor can be used for heating crude oil after heat exchange in a heat exchanger while producing hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the oilfield produced water multiphase flow photocatalytic hydrogen and heat cogeneration system of the present invention;

[0025] Among them: 1-high-level normal-pressure buffer tank; 2-water outlet pipeline; 3-photofluid reactor; 4-hydrogen pipeline; 5-oxygen content sensor; 6-hydrogen-oxygen separator; 7-water sensor; 8-dryer; 9-low-level normal-pressure buffer tank; 10-pump; 11-heat exchanger; 12-heat exchanger water outlet pipe; 13-first quick-open cleaning port; 14-photocatalyst; 15-carbon-containing organic matter; 16-all-dielectric reflective film; 17-gas gap; 18-filter; 19-second quick-open cleaning port. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0027] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0028] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0029] See also Figure 1 , the present invention provides an oilfield produced water multiphase flow photocatalytic hydrogen heat cogeneration system, including an oilfield produced water delivery device, a photofluid reactor 3, a heat exchange system, and a hydrogen treatment system;

[0030] The water outlet of the oilfield produced water conveying device is connected to the water inlet of several groups of photofluid reactors 3, the water outlets of several groups of photofluid reactors 3 are all connected to the water inlet of the heat exchange system, and the water outlet of the heat exchange system is connected to the oilfield produced water conveying device; the gas outlets of several groups of photofluid reactors 3 are all connected to the hydrogen treatment system; the gas outlet of the photofluid reactor 3 is opened in the upper half of the photofluid reactor 3; the interior of the photofluid reactor 3 is divided into an upper half and a lower half, the upper half of the photofluid reactor 3 is to accommodate the dynamic multiphase flow passing space, the photocatalyst 14 and the carbon-containing organic matter 15 are arranged in the upper half, and the gas gap 17 is opened in the upper half; the all-dielectric reflective film 16 is laid on the lower half of the photofluid reactor 3, which is used for focusing reflection and increasing the catalyst light absorption. The produced water from the oil and gas fields is directly used to produce hydrogen by solar photocatalysis at a low cost. The temperature of the fluid reactor is stabilized while producing hydrogen. The excess heat in the water is exchanged and used to heat the crude oil, realizing the co-production of hydrogen and heat. The heat in the produced water is recovered to reduce the manufacturing cost. The photofluid reactor 3 only discharges hydrogen, and there is no need for secondary separation of hydrogen and oxygen.

[0031] A first quick-open cleaning port 13 and a second quick-open cleaning port 19 are respectively provided at the front and rear ends of the photofluid reactor 3, and a filter screen 18 is provided after the gas gap 17 and before the second quick-open cleaning port 19. When dirt is generated at the bottom of the photofluid reactor 3, the first quick-open cleaning port 13 and the second quick-open cleaning port 19 are opened for cleaning. The internal flow state of the photofluid reactor 3 adopts a non-full flow state. The shape of the photofluid reactor 3 is an elliptical pipe with low manufacturing cost, which increases the illumination area and improves the hydrogen production efficiency. Specifically, the photofluid reactor 3 is manufactured using an elliptical tube to increase the illumination area. A full dielectric reflective film 16 is laid on the lower half of the elliptical tube for focusing reflection to increase the light absorption of the catalyst. The lower part of the photofluid reactor 3 does not need to be provided with a conventional metal focusing groove, thereby reducing the manufacturing cost.

[0032] Among them, the oilfield produced water delivery device consists of a high-level normal pressure buffer tank 1 and a water outlet pipeline 2; the first water inlet of the high-level normal pressure buffer tank 1 is connected to the water outlet of the oilfield produced water pipeline, the water outlet of the high-level normal pressure buffer tank 1 is connected to the water inlet of the water outlet pipeline 2, and the water outlet of the water outlet pipeline 2 is connected to the water inlets of several groups of photofluid reactors 3. Specifically, several parallel branches are opened on the water outlet pipeline 2, and water is delivered to the photofluid reactor 3 through the branches; the second water inlet of the high-level normal pressure buffer tank 1 is connected to the water outlet of the heat exchange system.

[0033] The hydrogen processing system includes a hydrogen pipeline 4, an oxygen content sensor 5, a hydrogen-oxygen separator 6, a moisture sensor 7, and a dryer 8; the air inlet of the hydrogen pipeline 4 is connected to the air outlet of the upper half of the optical fluid reactor 3, and the air outlet of the hydrogen pipeline 4 is connected to the hydrogen storage device. The oxygen content sensor 5, the hydrogen-oxygen separator 6, the moisture sensor 7, and the dryer 8 are sequentially arranged on the hydrogen pipeline 4. The oxygen content sensor 5 provides oxygen content monitoring, and the dryer 8 provides moisture monitoring to ensure the smooth collection of hydrogen. The hydrogen-oxygen separator 6 further improves the purity of hydrogen.

[0034] The heat exchange system includes a low-level atmospheric pressure buffer tank 9, a pump 10, a heat exchanger 11, and a heat exchanger outlet pipe 12; the water inlet of the low-level atmospheric pressure buffer tank 9 is connected to the water outlet of the photofluid reactor 3, the water outlet of the low-level atmospheric pressure buffer tank 9 is connected to the water inlet of the heat exchanger 11, and the water outlet of the heat exchanger 11 is connected to the oilfield produced water delivery device through the heat exchanger outlet pipe 12; the pump 10 is arranged on the pipeline between the low-level atmospheric pressure buffer tank 9 and the heat exchanger 11.

[0035] The photocatalyst 14 is preferably one of Cu-SA / TiO2 photocatalyst, cadmium telluride CdTe / V-In2S3 photocatalyst, methylammonium lead iodide perovskite (MAPbI3) photocatalyst or Au@UiOS@ZIS photocatalyst. According to the optimal operating temperature of the catalyst used, the hot fluid in the photofluid reactor 3 is used for crude oil heating after heat exchange through the heat exchanger 11 while hydrogen is produced.

[0036] There are 15 carbon-containing organic matters in the produced water of oil fields, mainly hydrocarbon organic matters. Hydrocarbon is the abbreviation of hydrocarbons, and its main part is alkane. Alkanes are named according to the carbon atoms and numbers contained in the molecule. For those with less than 10 carbon atoms, they are represented by A, B, C, D, E, H, H, O, N, and Decane from 1 to 10. For those with more than 11 carbon atoms, they are represented by numbers. At normal temperature and pressure, C1-C4 alkanes are gaseous and exist in natural gas; C5-C16 alkanes are liquid and are the main components of petroleum; alkanes above C16 are solid.

[0037] Another aspect of the present invention provides a method for using an oilfield produced water multiphase flow photocatalytic hydrogen and heat cogeneration system, the specific steps of which are as follows:

[0038] The produced water from the oil field is buffered by the produced water conveying device of the oil field and then enters a plurality of groups of photofluid reactors 3. Sunlight irradiates the photofluid reactor 3. The all-dielectric reflective film 16 in the photofluid reactor 3 gathers and reflects the light to the photocatalyst 14. The photocatalyst 14 undergoes an oxidation-reduction reaction with the carbon-containing organic matter 15 and the produced water from the oil field. The generated oxygen reacts with the carbon-containing organic matter 15 and is consumed. The generated hydrogen enters the hydrogen storage device through the hydrogen treatment system.

[0039] The residual oilfield produced water in the photofluid reactor 3 enters the heat exchange system for heat exchange for heating crude oil, and is then recycled to the oilfield produced water delivery device for cyclic use.

[0040] In the specific implementation process, the usage is as follows:

[0041] The produced water from the oil field is buffered by the high-level normal-pressure buffer tank 1 and the outlet pipeline 2 in the produced water delivery device of the oil field, and then enters into several groups of photofluid reactors 3 through several branches. Sunlight irradiates the photofluid reactor 3, and the all-dielectric reflective film 16 in the photofluid reactor 3 gathers and reflects the light to the photocatalyst 14. The photocatalyst 14 undergoes oxidation-reduction reaction with the carbon-containing organic matter 15 and the produced water from the oil field. The generated oxygen reacts with the carbon-containing organic matter 15 and is consumed. The generated hydrogen passes through the hydrogen pipeline 4, the oxygen content sensor 5, the hydrogen-oxygen separator 6, The hydrogen treatment system composed of a moisture sensor 7 and a dryer 8 enters the hydrogen storage device; a dynamic balance mechanism of oxidation and reduction is constructed in the hydrogen production process. When oilfield produced water containing an appropriate amount of carbon-containing organic matter enters the photofluid reactor 3, the flow state in the reactor adopts a non-full flow, and the top is a gas space. A solid photocatalyst 14, carbon-containing organic matter 15 and oilfield produced water are arranged inside to form a dynamic multiphase flow. After illumination, in the process of reducing hydrogen, oxygen and carbon-containing organic matter 15 in the produced water are oxidized and consumed, and a dynamic balance is achieved, thereby improving the stability and safety of the production process.

[0042] The residual oilfield produced water in the photofluid reactor 3 enters the heat exchange system consisting of a low-level atmospheric pressure buffer tank 9, a pump 10, a heat exchanger 11 and a heat exchanger outlet pipe 12 for heat exchange for crude oil heating, and is then recovered to the high-level atmospheric pressure buffer tank 1 in the oilfield produced water delivery device for recycling.

[0043] Example

[0044] The outlet of the produced water from the oil field is connected to the first water inlet of the high-position normal-pressure buffer tank 1, and the second water inlet of the high-position normal-pressure buffer tank 1 is connected to the outlet of the heat exchanger 11 in the heat exchange system; the outlet of the high-position normal-pressure buffer tank 1 is connected to the water inlet of the outlet pipeline 2, and the outlet of the outlet pipeline 2 is connected to the water inlet of several groups of photofluid reactors 3. The photofluid reactor 3 is composed of a first quick-open cleaning port 13, a photocatalyst 14, carbon-containing organic matter 15, a full dielectric reflective film 16, a gas gap 17, a filter screen 18, and a second quick-open cleaning port 19, which are arranged in sequence. An air outlet is provided in the upper half, which is connected to the air inlet of the hydrogen pipeline 4 in the hydrogen processing system. The hydrogen processing system also includes an oxygen content sensor 5, a hydrogen-oxygen separator 6, a moisture sensor 7 and a dryer 8 which are sequentially arranged on the hydrogen pipeline 4. The air outlet of the hydrogen pipeline 4 is connected to the hydrogen storage device; the water inlet of the low-level atmospheric pressure buffer tank 9 in the heat exchange system is connected to the water outlet of the photofluid reactor 3, the water outlet of the heat exchanger 11 is connected to the second water inlet of the high-level atmospheric pressure buffer tank 1 through the heat exchanger outlet pipe 12, and the pump 10 is arranged on the pipeline between the low-level atmospheric pressure buffer tank 9 and the heat exchanger 11.

[0045] After the produced water from the oil field is buffered by the high-position atmospheric pressure buffer tank 1, it flows by gravity through the outlet pipeline 2 into the photofluid reactor 3. At this time, sunlight irradiates the photofluid reactor 3, and the all-dielectric reflective film 16 concentrates and reflects the light to the photocatalyst 14. The photocatalyst 14 undergoes an oxidation-reduction reaction with water and carbon-containing organic matter 15. The generated oxygen reacts with the carbon-containing organic matter 15 and is consumed. The generated hydrogen enters the gas gap 17 and is collected through the hydrogen pipeline 4 to the hydrogen-oxygen separator 6 and the dryer 8, and finally enters the hydrogen storage link; the heated fluid in the photofluid reactor 3 is filtered by the filter 18, enters the low-position atmospheric pressure buffer tank 9, and is pressurized to enter the heat exchanger 11 for heat exchange, which is used for crude oil heating. The cold fluid after heat exchange is recovered to the high-position atmospheric pressure buffer tank 1 through the heat exchanger outlet pipe 12 for recycling.

[0046] The operating cost of directly using solar energy to photocatalytically produce hydrogen from produced water in oil and gas fields can be as low as 20% compared with the electrolysis of water to produce hydrogen. A low-manufacturing-cost photofluid reactor 3 has also been developed to increase the illumination area, improve the hydrogen production efficiency, recover the waste heat of the photofluid reactor, and realize the cogeneration of hydrogen and heat.

[0047] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. An oilfield produced water multiphase flow photocatalytic hydrogen and heat cogeneration system, characterized in that: It comprises an oilfield produced water conveying device, the water outlet of the oilfield produced water conveying device is connected to the water inlet of a plurality of groups of optical fluid reactors (3), the water outlets of the plurality of groups of optical fluid reactors (3) are all connected to the water inlet of a heat exchange system, the water outlet of the heat exchange system is connected to the oilfield produced water conveying device; the gas outlets of the plurality of groups of optical fluid reactors (3) are all connected to a hydrogen treatment system; The interior of the photofluid reactor (3) is divided into an upper half and a lower half. The upper half of the photofluid reactor (3) is a space for accommodating dynamic multiphase flow. A gas gap (17) is provided in the upper half, and a photocatalyst (14) and carbon-containing organic matter (15) are stored. The lower half of the photofluid reactor (3) is paved with a full dielectric reflection film (16) for focusing reflection and increasing the amount of light absorbed by the catalyst.

2. The oilfield produced water multiphase flow photocatalytic hydrogen and heat cogeneration system according to claim 1, characterized in that: The oilfield produced water delivery device comprises a high-position normal-pressure buffer tank (1) and a water outlet pipeline (2); The first water inlet of the high-level atmospheric pressure buffer tank (1) is connected to the water outlet of the oilfield production and output water pipeline, and the second water inlet of the high-level atmospheric pressure buffer tank (1) is connected to the water outlet of the heat exchange system; the water outlet of the high-level atmospheric pressure buffer tank (1) is connected to the water inlet of the water outlet pipeline (2), and the water outlet of the water outlet pipeline (2) is connected to the water inlets of several groups of optical fluid reactors (3).

3. The oilfield produced water multiphase flow photocatalytic hydrogen and heat cogeneration system according to claim 1, characterized in that: The front end of the photofluid reactor (3) is provided with a first quick-open cleaning port (13), and the rear end of the photofluid reactor (3) is provided with a second quick-open cleaning port (19).

4. The oilfield produced water multiphase flow photocatalytic hydrogen and heat cogeneration system according to claim 3, characterized in that: A filter screen (18) is provided after the gas gap (17) and before the second quick-open cleaning port (19) of the photofluid reactor (3).

5. The oilfield produced water multiphase flow photocatalytic hydrogen and heat cogeneration system according to claim 1, characterized in that: The hydrogen processing system comprises a hydrogen pipeline (4) and an oxygen content sensor (5), a hydrogen-oxygen separator (6), a moisture sensor (7) and a dryer (8) which are sequentially arranged on the hydrogen pipeline (4).

6. The oilfield produced water multiphase flow photocatalytic hydrogen and heat cogeneration system according to claim 5, characterized in that: The gas outlet of the photofluid reactor (3) is opened in the upper half of the photofluid reactor (3).

7. The oilfield produced water multiphase flow photocatalytic hydrogen and heat cogeneration system according to claim 6, characterized in that: The gas inlet of the hydrogen pipeline (4) is connected to the gas outlet of the upper part of the optical fluid reactor (3), and the gas outlet of the hydrogen pipeline (4) is connected to the hydrogen storage device.

8. The oilfield produced water multiphase flow photocatalytic hydrogen and heat cogeneration system according to claim 1, characterized in that: The heat exchange system comprises a low-level atmospheric pressure buffer tank (9), a pump (10) and a heat exchanger (11); The water outlet of the low-level normal-pressure buffer tank (9) is connected to the water inlet of the heat exchanger (11), and the water outlet of the heat exchanger (11) is connected to the oilfield produced water delivery device via the heat exchanger water outlet pipe (12); the pump (10) is arranged on the pipeline between the low-level normal-pressure buffer tank (9) and the heat exchanger (11).

9. The oilfield produced water multiphase flow photocatalytic hydrogen and heat cogeneration system according to claim 1, characterized in that: The internal flow state of the photofluid reactor (3) adopts a non-full flow state, and the shape of the photofluid reactor (3) is an elliptical pipe.

10. A method for using the oilfield produced water multiphase flow photocatalytic hydrogen and heat cogeneration system according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1: The produced water from the oil field is buffered by the produced water conveying device of the oil field and then enters a plurality of groups of photofluid reactors (3). Sunlight irradiates the photofluid reactor (3). The all-dielectric reflective film (16) in the photofluid reactor (3) gathers and reflects the light to the photocatalyst (14). The photocatalyst (14) reacts with the carbon-containing organic matter (15) and the produced water from the oil field to produce oxygen, which is consumed after reacting with the carbon-containing organic matter (15). The produced hydrogen enters the hydrogen storage device through the hydrogen treatment system. S2: The residual oilfield produced water in the photofluid reactor (3) enters the heat exchange system for heat exchange for heating crude oil, and is then recycled to the oilfield produced water delivery device for cyclic use.

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