System and method for efficiently removing iron from make-up water of offshore heavy oil thermal recovery boiler

Abstract

The invention discloses a system and a method for efficiently removing iron from make-up water of an offshore heavy oil thermal recovery boiler. The structure of the system is as follows: an electrochemical reactor, a compact cyclone air floater, a heat exchanger, an inorganic ultrafiltration membrane, a primary reverse osmosis membrane, an ion exchanger membrane and a thermal deaerator are connected in sequence; and the compact cyclone air floater is also connected with a bypass inlet for inputting seawater / geothermal water. The method comprises the following steps: seawater / geothermal water is introduced into an electrochemical reactor in the system and is treated by a compact cyclone air floater, a heat exchanger, an inorganic ultrafiltration membrane, a primary reverse osmosis membrane, an ion exchanger and a thermal deaerator in sequence, and produced water meets the water inlet requirement of an offshore thermal recovery boiler. The method comprises the following steps: oxidizing ferrous ions in water into iron ions through an electrochemical reactor, and then adjusting the pH value to convert the iron ions into ferric hydroxide; according to the present invention, the electrochemical oxidation is performed on the incoming water, the generated strong oxidizing free radicals can demulsify the dissolved oil in the water, and then the oil is removed in the cyclone air flotation so as to reduce the pollution of the oil to the rear end membrane;

Description

Technical Field

[0001] The invention relates to a system and method for efficiently removing iron from feed water of offshore heavy oil thermal recovery boiler, belonging to the field of seawater desalination. Background Art

[0002] Offshore heavy oil reserves are abundant, and the development of offshore heavy oil fields is of great significance for increasing reserves and production. In order to effectively promote the goal of increasing offshore heavy oil thermal production by 3 million tons by 2025, how to reasonably and efficiently develop heavy oil reservoirs through thermal recovery has received widespread attention from petroleum science and technology workers (Quan Dengjiang. Bohai Oilfield Heavy Oil Thermal Recovery Technology [J]. Chemical Management, 2014 (23): 141.). In actual development, compared with onshore oil fields, due to factors such as geological reservoir characteristics, platform space and operating costs, offshore heavy oil thermal recovery is more difficult than onshore oil fields. At the same time, the water quality of thermal recovery boiler feed water is required to meet the GB / T 12145 "Water and Steam Quality for Thermal Power Generators and Steam Power Equipment" standard, which puts higher requirements on seawater desalination technology with complex water quality (Jiang Weidong, et al. Research and Application of Optimization Methods for Offshore Heavy Oil Thermal Recovery Boiler Feed Water System).

[0003] In view of the special situation of offshore platforms, taking into account factors such as low cost, energy saving, stability, high efficiency, and convenient operation, it is most appropriate to use reverse osmosis membrane method to desalinate the seawater and produce fresh water as feed water for thermal recovery steam injection boilers. However, the reverse osmosis membrane and the water quality requirements are very high. If the pretreatment process before entering the reverse osmosis membrane cannot ensure the stability of the produced water quality, the service life of the reverse osmosis membrane will be reduced, and the membrane material will be frequently replaced, resulting in a large increase in operating costs. In more serious cases, it will cause the entire desalination system to be paralyzed.

[0004] There are four options for the water supply of offshore thermal boilers: fresh water, seawater, production water, and geothermal water. Fresh water can meet the water quality requirements of thermal boilers after simple treatment. However, there is a shortage of fresh water at sea, and it needs to be transported from land, which is expensive and increases the cost of thermal recovery; the purification process of oilfield production water is relatively difficult. Geothermal water and seawater are currently the more feasible water source options for offshore thermal recovery. The higher temperature of geothermal water can reduce the heating load, and the mineralization of geothermal water in most oil fields is lower than that of seawater, which is slightly easier to handle, but the water contains gas and oil, and also contains a large amount of ferrous ions. Ferrous ions will be oxidized to ferrous ions in the pipeline, and ferrous ions will oxidize the surface of organic membranes, causing irreversible damage. The advantage of seawater is that the source is stable and easy to obtain. However, the water quality of offshore seawater is poor, the mineralization is high, and the corrosiveness is strong, which will cause corrosion of steel pipelines and increase the total iron content in the water.

[0005] The main methods of traditional water iron removal are: aeration, contact oxidation, chemical oxidation, ozone oxidation, etc. Aeration equipment occupies a large area, and the iron removal efficiency is low, which is not suitable for use on compact offshore platforms; contact oxidation is a method that combines aeration with manganese sand. Its problem is that it takes a long time to generate a hydrated iron hydroxide oxide film on the manganese sand particles in the early stage, the iron removal efficiency is unstable, and the filter material needs to be replaced frequently; the main agent used in the chemical oxidation method is sodium hypochlorite, but adding a large amount of sodium hypochlorite will lead to an increase in the concentration of chloride ions, causing serious corrosion of equipment and pipelines; ozone oxidation consumes a lot of electricity, has high operating costs, and high-concentration ozone is a toxic gas, which is very harmful to on-site workers.

[0006] The above traditional iron removal methods have a long treatment process and a large equipment footprint. Moreover, the use of the above methods will further increase the pretreatment process of membrane desalination, which is not suitable for application on offshore platforms with limited load and space. Therefore, how to efficiently remove iron and other pollutants, reduce operating costs, and reduce the footprint has become an important problem that needs to be solved in the current offshore heavy oil thermal recovery platform water iron removal. Summary of the invention

[0007] The invention aims to provide a method and system for efficiently removing iron from feed water of offshore heavy oil thermal recovery boilers. The method adopts an electrochemical oxidation and compact cyclone flotation coupling process to remove iron, suspended matter and oil. Ferrous ions in water are oxidized into ferric ions by an electrochemical reactor, and then the pH value is adjusted to convert the ferric ions into ferric hydroxide. Since ferric hydroxide has a strong flocculation effect, suspended matter in water can be flocculated together in cyclone flotation to achieve the effect of removing suspended matter. The incoming water is electrochemically oxidized to generate strong oxidizing free radicals, which can demulsify dissolved oil in water, and then oil is removed in cyclone flotation to reduce oil pollution to the rear-end membrane.

[0008] The invention provides a system for efficiently removing iron from feed water of offshore heavy oil thermal recovery boilers, comprising an electrochemical reactor, a compact cyclone air flotation device, a heat exchanger, an inorganic ultrafiltration membrane, a primary reverse osmosis membrane, an ion exchanger and a thermal deaerator connected in sequence.

[0009] Preferably, the compact cyclone air flotation device is also connected to a bypass inlet for inputting seawater / geothermal water, so that when the water treatment system operates normally, the seawater / geothermal water directly enters the compact cyclone air flotation device through the electrochemical reactor.

[0010] Preferably, the compact cyclone flotation device is also connected to a bypass outlet, which is connected to the electrochemical reactor. When the oil content in seawater / geothermal water exceeds the standard, it enters the electrochemical reactor and the compact cyclone flotation device for cyclic treatment. Only when the water production index reaches the requirement can it enter the next treatment unit. If it does not meet the requirement, it will continue to circulate.

[0011] Preferably, the ion exchanger is also connected to a bypass outlet, which is connected to the electrochemical reactor. After normal operation, the water produced by the ion exchanger enters the electrochemical reactor to prevent electrode scaling, because after being treated by the electrochemical reactor, the water contains strong oxidizing substances, and after mixing with seawater / geothermal water, the calcium and magnesium content of the water produced after the ion exchanger is low. Using this water for electrochemical oxidation can reduce the risk of electrode scaling and extend the cleaning cycle and service life of the electrode.

[0012] Preferably, the electrochemical reactor is a tubular electrochemical reactor, the shell of which is made of 2205 stainless steel and the electrode material is titanium dioxide.

[0013] Preferably, the shell material of the compact cyclone air flotation device is 2205 stainless steel, and the internal material is 2205 stainless steel.

[0014] Preferably, the heat exchanger is a fully welded plate heat exchanger, the panel material is Q345R, the heat exchange plate material is TA1, the thickness is not less than 1mm, and the heat exchange area design margin is 20-30%;

[0015] The inorganic ultrafiltration membrane is a multi-channel ceramic-based inorganic ultrafiltration membrane, the surface material of the membrane is zirconium oxide, the average pore size is 10-50nm, the porosity is 30-50%, and the pure water flux is 500-800m 3 ·m -2 ·h -1 ;

[0016] The thermal deaerator is an atmospheric built-in deaerator, the tank body is made of titanium, the internal parts are made of 316L, the operating temperature is 104-106°C, and the dissolved oxygen content of the produced water is 10-25μg / L.

[0017] When using the system of the present invention to efficiently remove iron from feed water of offshore heavy oil thermal recovery boiler, the following steps can be followed:

[0018] The seawater / geothermal water is introduced into the electrochemical reactor in the system, and is sequentially treated by the compact cyclone air flotation device, the heat exchanger, the inorganic ultrafiltration membrane, the primary reverse osmosis membrane, the ion exchanger and the thermal deaerator, so that the produced water meets the inlet water requirements of the offshore thermal recovery boiler;

[0019] After the seawater / geothermal water passes through the electrochemical reactor and enters the compact cyclone flotation, the pH value is adjusted to 8-10.

[0020] Preferably, seawater / geothermal water is directly introduced into the compact cyclone air flotation device;

[0021] When the system is running stably, part of the water produced by the ion exchanger enters the electrochemical reactor, and then is mixed with seawater / geothermal water in the compact cyclone flotation device. After subsequent treatment, the produced water meets the water inlet index of the thermal recovery boiler.

[0022] When the oil content of seawater / geothermal water is ≥10mg / L, the incoming water is circulated between the electrochemical reactor and the compact cyclone flotation until the oil content of the produced water is ≤0.1mg / L and enters the next treatment unit.

[0023] Preferably, the current density of the electrochemical reactor is 10 to 500 A / m 2 , voltage is 4~20V;

[0024] The hydraulic retention time of the compact cyclone air flotation device is 1 to 3 minutes;

[0025] The water production rate of the inorganic ultrafiltration membrane is 85-95%;

[0026] The water production rate of the primary reverse osmosis membrane is 35-50%, and the desalination rate is 97-99.5%;

[0027] The de-hardening rate of the ion exchanger is 99-99.9%.

[0028] The present invention realizes the principle of iron removal in the feed water system of thermal recovery boiler of offshore heavy oil field: by electrochemically oxidizing the incoming water, a large number of strongly oxidizing hydroxyl radicals are generated, ferrous ions in the water are oxidized into ferric ions, and the ferric ions are converted into ferric hydroxide colloids by adjusting the pH value; since the ferric hydroxide colloid has a strong flocculation effect, the suspended matter in the water can be adsorbed and removed; if the oil content of the incoming water is too high, the incoming water can be circulated between the electrochemical reactor and the cyclone flotation to demulsify and remove the oil pollution in the water; after the overall water treatment process runs stably, the water produced by the oxidation part of the ion exchanger is mixed with the seawater in the cyclone flotation, and since the water produced by the ion exchanger has been de-hardened, the electrode structure phenomenon of the electrochemical reactor can be reduced and the service life of the electrode can be extended. In addition, after the incoming water is electrochemically oxidized, a large number of fine bubbles will be generated in the water, so the subsequent compact cyclone flotation does not need to add an additional aeration device, and the flotation separation effect is good.

[0029] The present invention has the following beneficial technical effects:

[0030] 1. The electrochemical oxidation method for iron removal has the characteristics of low energy consumption and high efficiency. The ferrous ion content of the raw water is 60-150 mg / L, and it is completely oxidized into ferric ions. The energy consumption per ton of water is 0.5-0.8 kW·h, and the oxidation rate exceeds 99.5%;

[0031] 2. The ferric hydroxide generated by oxidation can be used as a natural flocculant. Only a small amount of flocculant or no flocculant is needed to completely remove the suspended solids in the water. This saves a lot of reagents and reduces the pollution to the equipment and environment.

[0032] 3. Electrochemical oxidation of seawater / well water produces strong oxidizing free radicals, which can demulsify the dissolved oil in the water, and then remove the oil in the cyclone flotation to reduce the pollution of the oil to the rear-end membrane;

[0033] 4. After the incoming water is electrochemically oxidized, a large number of fine bubbles will be generated in the water, so the subsequent compact cyclone flotation does not require additional aeration devices, and the flotation separation effect is good.

[0034] 5. The overall equipment occupies a small area, has a high degree of automation and low operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The present invention is a schematic structural diagram of a high-efficiency iron removal system for feed water of offshore heavy oil thermal recovery boiler. DETAILED DESCRIPTION

[0036] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0037] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0038] like Figure 1 As shown, the system for efficient iron removal of offshore heavy oil thermal recovery boiler feed water provided by the present invention comprises an electrochemical reactor 1, a compact cyclone flotation device 2, a heat exchanger 3, an inorganic ultrafiltration membrane 4, a primary reverse osmosis membrane 5, an ion exchanger membrane 6 and a thermal deaerator 7 which are connected in sequence.

[0039] like Figure 1 As shown, the compact cyclone flotation device 2 is also connected to a bypass inlet for inputting seawater / geothermal water. The compact cyclone flotation device 2 is also connected to a bypass outlet, which is connected to the electrochemical reactor 1. When the oil content in the seawater / geothermal water exceeds the standard, it enters the electrochemical reactor 1 and the compact cyclone flotation device 2 for circulation treatment. The water production index reaches the requirements before entering the next treatment unit. If it does not meet the requirements, it will continue to circulate between the two. The ion exchanger 6 is also connected to a bypass outlet, which is connected to the electrochemical reactor 1. After normal operation, the water produced by the ion exchanger enters the electrochemical reactor 1 to prevent electrode scaling, because after being treated by the electrochemical reactor 1, the water contains strong oxidizing substances, and after mixing with seawater / geothermal water, the water produced after the ion exchanger has a lower content of calcium and magnesium. The use of this water for electrochemical oxidation can reduce the risk of electrode scaling and extend the cleaning cycle and service life of the electrode.

[0040] In the system of the present invention, the electrochemical reactor 1 is a tubular electrochemical reactor, the shell of which is made of 2205 stainless steel and the electrode material is titanium dioxide.

[0041] In the system of the present invention, the shell material of the compact cyclone air flotation device 2 is 2205 stainless steel, and the internal material is 2205 stainless steel.

[0042] In the system of the present invention, the heat exchanger 3 is a fully welded plate heat exchanger, the panel material is Q345R, the heat exchange plate material is TA1, the thickness is not less than 1mm, and the heat exchange area design margin is 20-30%;

[0043] In the system of the present invention, the inorganic ultrafiltration membrane 4 is a multi-channel ceramic-based inorganic ultrafiltration membrane, the surface material of the membrane is zirconium oxide, the average pore size is 10-50nm, the porosity is 30-50%, and the pure water flux is 500-800m 3 ·m -2 ·h -1 ;

[0044] In the system of the present invention, the thermal deaerator 7 is an atmospheric built-in deaerator, the tank body is made of titanium, the internal material is 316L, the operating temperature is 104-106°C, and the dissolved oxygen content of the produced water is 10-25 μg / L.

[0045] When the system of the present invention is used for removing iron from feed water of thermal recovery boiler in offshore heavy oil fields, the following steps are followed:

[0046] The seawater / geothermal water is introduced into the electrochemical reactor 1 in the system, and is processed in sequence by the compact cyclone flotation device 1, the heat exchanger 3, the inorganic ultrafiltration membrane 4, the primary reverse osmosis membrane 5, the ion exchanger 6 and the thermal deaerator 7, and the produced water meets the inlet water requirements of the offshore thermal recovery boiler;

[0047] The seawater / geothermal water passes through the electrochemical reactor 1 and enters the compact cyclone flotation device 2, where the pH value is adjusted to 8-10.

[0048] When the system is running stably, part of the water produced by the ion exchanger 6 enters the electrochemical reactor 1, and then mixes with seawater / geothermal water in the compact cyclone flotation device 2. After subsequent treatment, the produced water meets the thermal recovery boiler water inlet index.

[0049] When the oil content of seawater / geothermal water is ≥10 mg / L, the incoming water is circulated between the electrochemical reactor 1 and the compact cyclone flotation device 2 until the oil content of the produced water is ≤0.1 mg / L and enters the next treatment unit.

[0050] In the above method, the current density of the electrochemical reactor is 10 to 500 A / m 2, voltage is 4~20V; the hydraulic retention time of the compact cyclone flotation device is 1~3min; the water production rate of the inorganic ultrafiltration membrane is 85~95%; the water production rate of the primary reverse osmosis membrane is 35~50%, and the desalination rate is 97~99.5%; the hardness removal rate of the ion exchanger is 99~99.9%.

[0051] use Figure 1 The system shown is used for deironing feed water of thermal recovery boilers in offshore heavy oil fields:

[0052] Embodiment 1:

[0053] The total hardness of seawater is 54.9 mmol / L, active silicate is 0.646 mg / L, conductivity is 47.4 mS / cm, turbidity is 53 NTU, suspended matter is 103 mg / L, total dissolved solids is 31.46 g / L, dissolved oxygen is 8.51 mg / L, and total iron is 100 mg / L.

[0054] The treatment was carried out according to the above method, wherein the current density in the electrochemical reactor was 100A / m 2 , voltage is 10V; compact cyclone flotation residence time is 2min, and the pH of water in the flotation device is adjusted to 9.0.

[0055] The turbidity of inorganic ultrafiltration water is 0.15NTU, the suspended solids content is 0.76mg / L, the total iron content is 0.12mg / L, and the SDI is 15 is 2.67; the dissolved oxygen content of the system water is 20μg / L, TDS is 950mg / L, and the hardness is 0.08mg / L.

[0056] Embodiment 2:

[0057] The total hardness of seawater is 54.9 mmol / L, active silicate is 0.646 mg / L, conductivity is 47.4 mS / cm, turbidity is 53 NTU, suspended matter is 103 mg / L, total dissolved solids is 31.46 g / L, dissolved oxygen is 8.51 mg / L, and total iron is 100 mg / L.

[0058] The treatment was carried out according to the above method, wherein the current density in the electrochemical reactor was 200A / m 2 , voltage is 20V; compact cyclone flotation residence time is 1.5min, and the pH of water in flotation is adjusted to 9.5.

[0059] The turbidity of inorganic ultrafiltration water is 0.11NTU, the suspended solids content is 0.81mg / L, the total iron content is 0.08mg / L, and the SDI is 15 is 2.32; the dissolved oxygen content of the system water is 22μg / L, TDS is 940mg / L, and the hardness is 0.07mg / L.

[0060] Embodiment 3:

[0061] The total hardness of seawater is 54.9 mmol / L, active silicate is 0.646 mg / L, conductivity is 47.4 mS / cm, turbidity is 53 NTU, suspended matter is 103 mg / L, total dissolved solids is 31.46 g / L, dissolved oxygen is 8.51 mg / L, and total iron is 100 mg / L.

[0062] The treatment was carried out according to the above method, wherein the current density in the electrochemical reactor was 50A / m 2 , voltage is 10V; compact cyclone flotation residence time is 2.5min, and the pH of water in flotation is adjusted to 9.2.

[0063] The turbidity of inorganic ultrafiltration water is 0.17NTU, the suspended solids content is 0.86mg / L, the total iron content is 0.19mg / L, and the SDI is 15 is 2.74; the dissolved oxygen content of the system water is 23μg / L, TDS is 960mg / L, and the hardness is 0.08mg / L.

[0064] Embodiment 4:

[0065] The geothermal water TDS is 10249 mg / L, suspended solids are 16 mg / L, total iron is 150 mg / L, oil content is 4.21 mg / L, and COD value is 126 mg / L.

[0066] The treatment was carried out according to the above method, wherein the current density in the electrochemical reactor was 300A / m 2 , voltage is 10V; compact cyclone flotation residence time is 5min, and the pH of water in flotation is adjusted to 9.3.

[0067] The turbidity of inorganic ultrafiltration water is 0.19NTU, the suspended solids content is 0.65mg / L, the total iron content is 0.09mg / L, and the SDI is 15 The dissolved oxygen content of the system water is 19μg / L, the TDS is 850mg / L, and the hardness is 0.05mg / L.

[0068] Comparative Example 1

[0069] The following system is used for deironing of feed water for thermal recovery boilers in offshore heavy oil fields:

[0070] and Figure 1 The system shown is different in that it does not include the electrochemical reactor 1 and the compact cyclone flotation device 2, but only includes a heat exchanger 3, an inorganic ultrafiltration membrane 4, a primary reverse osmosis membrane 5, an ion exchange membrane 6 and a thermal deaerator 7 connected in sequence.

[0071] The total hardness of seawater is 54.9 mmol / L, active silicate is 0.646 mg / L, conductivity is 47.4 mS / cm, turbidity is 53 NTU, suspended matter is 103 mg / L, total dissolved solids is 31.46 g / L, dissolved oxygen is 8.51 mg / L, and total iron is 100 mg / L.

[0072] The turbidity of inorganic ultrafiltration water is 0.23NTU, the suspended solids content is 0.90mg / L, the total iron content is 95.6mg / L, and the SDI is 15 The total iron content of the inorganic ultrafiltration water cannot meet the water inlet requirements of the reverse osmosis membrane.

[0073] Comparative Example 2: The following system is used to remove iron from feed water of thermal recovery boilers in offshore heavy oil fields:

[0074] and Figure 1 The system shown is different in that it does not include a compact cyclone flotation device 2, but only includes an electrochemical reactor 1, a heat exchanger 3, an inorganic ultrafiltration membrane 4, a primary reverse osmosis membrane 5, an ion exchanger membrane 6 and a thermal deaerator 7 connected in sequence.

[0075] The total hardness of seawater is 54.9 mmol / L, active silicate is 0.646 mg / L, conductivity is 47.4 mS / cm, turbidity is 53 NTU, suspended matter is 103 mg / L, total dissolved solids is 31.46 g / L, dissolved oxygen is 8.51 mg / L, and total iron is 100 mg / L.

[0076] The turbidity of inorganic ultrafiltration water is 0.24NTU, the suspended solids content is 0.91mg / L, the total iron content is 88.2mg / L, and the SDI is 15 The dissolved oxygen content of the system water is 18μg / L, the TDS is 836mg / L, and the hardness is 0.08mg / L. The electrochemical reactor oxidizes ferrous ions into ferric ions, but without flotation treatment, the ferric ions cannot be precipitated and removed.

[0077] Comparative Example 3: The following system is used to remove iron from feed water of thermal recovery boiler in offshore heavy oil fields:

[0078] and Figure 1 The system shown is different in that it does not include an electrochemical reactor 1, but only includes a compact cyclone flotation device 2, a heat exchanger 3, an inorganic ultrafiltration membrane 4, a primary reverse osmosis membrane 5, an ion exchanger membrane 6 and a thermal deaerator 7 connected in sequence.

[0079] The total hardness of seawater is 54.9 mmol / L, active silicate is 0.646 mg / L, conductivity is 47.4 mS / cm, turbidity is 53 NTU, suspended matter is 103 mg / L, total dissolved solids is 31.46 g / L, dissolved oxygen is 8.51 mg / L, and total iron is 100 mg / L.

[0080] The turbidity of inorganic ultrafiltration water is 0.24NTU, the suspended solids content is 0.84mg / L, the total iron content is 56.7mg / L, and the SDI is 15 The dissolved oxygen content of the system water is 17μg / L, TDS is 912mg / L, and hardness is 0.09mg / L. The electrochemical reactor is not suitable for oxidizing ferrous ions. After flotation treatment, a large amount of ferrous ions still remain in the solution.

[0081] The present invention adopts electrochemical oxidation to protect the service life of ultrafiltration membrane and reverse osmosis membrane and delay the service life of the membrane. According to experimental research, after introducing electrochemical oxidation + compact cyclone flotation, the subsequent inorganic ultrafiltration operation cycle can be extended by 50%, and the corresponding cleaning time is reduced; the reverse osmosis membrane operation cycle can be extended by 30%, and will not be contaminated by ferrous ions.

Claims

1. A system for efficient iron removal of feed water for offshore heavy oil thermal recovery boilers, comprising an electrochemical reactor, a compact cyclone air flotation device, a heat exchanger, an inorganic ultrafiltration membrane, a primary reverse osmosis membrane, an ion exchanger membrane and a thermal deaerator connected in sequence.

2. The system according to claim 1, characterized in that: The compact cyclone air flotation device is also connected to a bypass inlet for inputting seawater / geothermal water.

3. The system according to claim 1 or 2, characterized in that: The compact cyclone air flotation device is also connected to a bypass outlet, which is connected to the electrochemical reactor.

4. The system according to any one of claims 1 to 3, characterized in that: The ion exchanger is also connected to a bypass outlet, which is connected to the electrochemical reactor.

5. The system according to any one of claims 1 to 4, characterized in that: The electrochemical reactor is a tubular electrochemical reactor, the shell of which is made of 2205 stainless steel and the electrode material is titanium dioxide.

6. The system according to any one of claims 1 to 5, characterized in that: The shell material of the compact cyclone air flotation device is 2205 stainless steel, and the internal material is 2205 stainless steel.

7. The system according to any one of claims 1 to 6, characterized in that: The heat exchanger is a fully welded plate heat exchanger, the panel material is Q345R, the heat exchange plate material is TA1, the thickness is not less than 1mm, and the heat exchange area design margin is 20-30%; The inorganic ultrafiltration membrane is a multi-channel ceramic-based inorganic ultrafiltration membrane, the surface material of the membrane is zirconium oxide, the average pore size is 10-50nm, the porosity is 30-50%, and the pure water flux is 500-800m 3 ·m -2 ·h -1 ; The thermal deaerator is an atmospheric type built-in deaerator, and the tank body is made of titanium.

8. A method for efficiently removing iron from feed water of offshore heavy oil thermal recovery boilers, comprising the following steps: introducing seawater / geothermal water into the electrochemical reactor in the system according to any one of claims 1 to 7, and sequentially treating the water through the compact cyclone air flotation device, the heat exchanger, the inorganic ultrafiltration membrane, the primary reverse osmosis membrane, the ion exchanger and the thermal deaerator, so that the produced water meets the feed water requirements of offshore thermal recovery boilers; After the seawater / geothermal water passes through the electrochemical reactor and enters the compact cyclone flotation, the pH value is adjusted to 8-10.

9. The method according to claim 8, characterized in that: Directly introduce seawater / geothermal water into the compact cyclone air flotation device; When the system is running stably, part of the water produced by the ion exchanger enters the electrochemical reactor, and then is mixed with seawater / geothermal water in the compact cyclone flotation device. After subsequent treatment, the produced water meets the water inlet index of the thermal recovery boiler. When the oil content of seawater / geothermal water is ≥10mg / L, the incoming water is circulated between the electrochemical reactor and the compact cyclone flotation until the oil content of the produced water is ≤0.1mg / L and enters the next treatment unit.

10. The method according to claim 8 or 9, characterized in that: The current density of the electrochemical reactor is 10-500A / m 2 , voltage is 4~20V; The hydraulic retention time of the compact cyclone air flotation device is 1 to 3 minutes; The water production rate of the inorganic ultrafiltration membrane is 85-95%; The water production rate of the primary reverse osmosis membrane is 35-50%, and the desalination rate is 97-99.5%; The de-hardening rate of the ion exchanger is 99-99.9%.

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