High salinity mine water zero emission system and method thereof

Abstract

The application discloses a kind of high salinity mine water zero discharge system and method thereof, system includes: first pressure exchange unit, reverse osmosis desalination concentration unit, first heat energy exchange unit, second pressure exchange unit, second heat energy exchange unit, pressure delayed osmosis unit and bipolar membrane electrodialysis unit, the renewable energy driving is used in the application, by introducing pressure delayed osmosis and double cycle geothermal power generation into conventional high salinity mine water zero discharge system, renewable energy energy supply is realized;In addition, by introducing bipolar membrane electrodialysis unit, the efficient use of inorganic salt and water resources is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and in particular to a high-mineralization mine water zero-discharge system and method thereof. Background Art

[0002] Highly mineralized mine water typically contains salinity exceeding 1000 mg / L. Direct discharge would adversely impact the surrounding environment of the mining area. Furthermore, national requirements are becoming increasingly stringent: if mine water must be discharged after full utilization, its quality must meet or exceed the corresponding surface water environmental quality values ​​specified in the receiving water body's environmental functional zoning, and its salinity must not exceed 1000 mg / L. Therefore, zero discharge of highly mineralized mine water is imperative. However, a zero discharge system inevitably involves a salt concentration stage, where the concentrate concentration may reach 100,000 mg / L or even higher. From an energy perspective, such a high-salinity concentrate contains three times the salinity energy of seawater. Effectively utilizing this energy could significantly reduce energy consumption in the salt concentration stage. Furthermore, high temperatures enhance the efficiency and utilization of this energy. Furthermore, western mining areas are rich in geothermal resources. If these resources are effectively combined, utilizing geothermal tail heat and salinity energy as renewable energy sources simultaneously, zero discharge of highly mineralized mine water could be achieved, moving towards a low-carbon economy.

[0003] Conventional mine water zero-discharge resource utilization systems include pretreatment units, nanofiltration salt separation units, reverse osmosis concentration units, high-pressure concentration units (disc-tube reverse osmosis, etc.), evaporation units, etc., which achieve zero wastewater discharge while realizing resource utilization of by-product salts such as sodium chloride. However, the energy supply still relies on the traditional power process model, does not make significant use of renewable energy processes, and inevitably has the problem of high concentration energy consumption. Although the subsequent evaporation and crystallization of concentrated brine can achieve zero waste liquid discharge, the recovered miscellaneous salts have low economic value and are hazardous solid waste, and true green production has not yet been achieved. Summary of the Invention

[0004] In view of this, the main purpose of the present invention is to provide a high-mineralization mine water zero-discharge system and method thereof, which are driven by renewable energy and realize the energy supply of renewable energy by introducing pressure delayed osmosis and dual-circulation geothermal power generation into the conventional high-mineralization mine water zero-discharge system; in addition, by introducing bipolar membrane electrodialysis, efficient utilization of inorganic salts and water resources is achieved.

[0005] To achieve the above-mentioned purpose, the present invention adopts the following technical solution: a high-mineralization mine water zero discharge system, comprising:

[0006] The first pressure exchange unit is used for the entry of the mine raw water to be treated to increase the hydraulic pressure and obtain pressurized mine raw water;

[0007] Reverse osmosis desalination and concentration unit, used for the pressurized mine raw water to enter to achieve high concentration, to obtain RO produced water and high-pressure RO concentrated liquid;

[0008] The first heat exchange unit is used for the RO produced water and high-temperature geothermal steam from the outside to enter and exchange heat energy, thereby obtaining high-temperature steam and low-temperature geothermal produced water;

[0009] The second pressure exchange unit is used for high-pressure RO concentrate to enter to achieve pressure exchange and obtain reduced-pressure RO concentrate;

[0010] The second heat exchange unit is used for the low-temperature geothermal water and low-temperature sewage from the outside to enter and exchange heat energy, thereby obtaining sewage with elevated temperature and geothermal water at normal temperature;

[0011] A pressure delayed osmosis unit is used for the temperature-elevated sewage and the decompressed RO concentrate to enter to realize the conversion of salt production into mechanical energy, thereby obtaining a diluted RO concentrate and concentrated sewage. The diluted RO concentrate enters the first pressure exchange unit and is decompressed to obtain a normal-pressure RO concentrate.

[0012] The bipolar membrane electrodialysis unit is used for the atmospheric pressure RO concentrate to enter for electrodialysis to obtain acid, alkali and low-salt feed solutions.

[0013] The system according to the present invention further comprises a steam power generation unit for receiving the high-temperature steam to realize conversion of thermal energy into electrical energy.

[0014] According to the system of the present invention, the normal-temperature geothermal water obtained by the second heat energy exchange unit enters the first heat energy exchange unit for heat energy exchange.

[0015] According to the system of the present invention, the low-temperature sewage is municipal sewage or domestic sewage from a factory.

[0016] Another aspect of the present invention provides a method for zero discharge of high-mineralization mine water, comprising the following steps:

[0017] Inputting the mine raw water to be treated into the first pressure exchange unit to increase the hydraulic pressure and obtain pressurized mine raw water;

[0018] The pressurized mine raw water is input into a reverse osmosis desalination and concentration unit to achieve high concentration, thereby obtaining RO produced water and high-pressure RO concentrated liquid;

[0019] The RO produced water and high-temperature geothermal steam from the outside are input into a first heat exchange unit for heat exchange to obtain high-temperature steam and low-temperature geothermal produced water;

[0020] The high-pressure RO concentrate is input into the second pressure exchange unit to achieve pressure exchange and obtain a reduced-pressure RO concentrate;

[0021] The low-temperature geothermal water and low-temperature sewage from outside are input into the second heat energy exchange unit and heat energy is exchanged to obtain temperature-increased sewage and normal-temperature geothermal water;

[0022] The temperature-increased sewage and the RO concentrated solution after pressure reduction are input into the pressure delayed osmosis unit to realize the conversion of salt energy into mechanical energy, and the diluted RO concentrated solution and concentrated sewage are obtained, the diluted RO concentrated solution is input into the first pressure exchange unit to release pressure and obtain normal-pressure RO concentrated solution;

[0023] The normal-pressure RO concentrated solution is input into the bipolar membrane electrodialysis unit to perform electrodialysis, and acid, alkali and low-salt feed liquid are obtained.

[0024] According to the method, the acid and alkali are applied to the pretreatment section of the reverse osmosis desalination and concentration unit, and / or the low-salt feed liquid is introduced into the low-pressure section reverse osmosis membrane assembly of the reverse osmosis desalination and concentration unit to perform deep desalination, and water is produced as water for the steam power generation unit.

[0025] According to the method, the high-temperature steam is input into the steam power generation unit to realize the conversion of heat energy into electric energy.

[0026] According to the method, the normal-temperature geothermal water obtained by the second heat energy exchange unit is input into the first heat energy exchange unit to perform heat energy exchange.

[0027] According to the method, the salt content in the high-pressure RO concentrated solution is greater than or equal to 10wt%.

[0028] According to the method, the pressure of the RO concentrated solution after pressure reduction is 40-50bar.

[0029] Compared with the prior art, the method has the following beneficial effects:

[0030] The present invention uses a pressure-delayed osmosis unit as a salt production capacity extraction module and a dual-circulation geothermal power generation module (i.e., a first heat exchange unit, a second heat exchange unit, and a steam power generation unit) as a geothermal energy extraction module, and uses a bipolar membrane electrodialysis unit to concentrate mine water for acid and alkali production, thereby realizing resource disposal of miscellaneous salts. Among them, the pressure-delayed osmosis unit can convert the salt production capacity contained in the high-salinity concentrated liquid in the reverse osmosis desalination concentration unit into efficiently usable mechanical energy, greatly reducing the energy input of the reverse osmosis desalination concentration unit. Second, the low-quality tail heat (<100°C) remaining after the thermoelectric conversion can enter the pressure-delayed osmosis unit to improve the salt production capacity extraction efficiency, thereby realizing the enhanced effect of thermal energy on the conversion of salt production capacity into mechanical energy. Third, the diluted atmospheric pressure RO concentrate enters the bipolar membrane electrodialysis unit. Due to the decrease in salt content, the energy consumption of water production in the desalination chamber of the bipolar membrane electrodialysis unit decreases, and it can enter the reverse osmosis membrane assembly in the reverse osmosis desalination and concentration unit without entering the pretreatment section to produce pure water. At the same time, the produced acid and alkali can be used in the pretreatment section of the reverse osmosis desalination and concentration unit, realizing the effective circulation of materials while reducing salt.

[0031] In summary, the system and method of the present invention can utilize renewable energy supply to significantly reduce energy consumption and carbon dioxide emissions; can produce acid and alkali products for process pretreatment to achieve green recycling of materials; can effectively reduce the output of by-product salt and reduce the company's processing costs for miscellaneous salts. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic structural diagram of a high-mineralization mine water zero discharge system according to an example of the present invention.

[0033] The figures are marked as follows: 1-high-temperature geothermal steam; 2-low-temperature geothermal water; 3-normal-temperature geothermal water; 4-low-temperature municipal sewage or domestic sewage from factory areas; 5-high-temperature municipal sewage or domestic sewage from factory areas; 6-RO produced water; 7-high-temperature steam; 8-concentrated municipal sewage or domestic sewage from factory areas; 9-diluted RO concentrate; 10-depressurized RO concentrate; 11-high-pressure RO concentrate; 12-pressurized mine raw water; 13-mine raw water; 14-normal-pressure RO concentrate; 15-bipolar membrane electrodialysis product.

[0034] A-first heat energy exchange unit, B-second heat energy exchange unit; C-steam power generation unit; D-reverse osmosis desalination concentration unit; E-second pressure exchange unit, G-first pressure exchange unit; F-pressure delayed osmosis unit; H-bipolar membrane electrodialysis unit. DETAILED DESCRIPTION

[0035] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, but are not to be construed as limiting the present invention.

[0036] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] Unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," and "fixed" should be interpreted broadly. For example, they may refer to fixed or removable connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on specific circumstances.

[0038] The main idea of ​​the present invention is to provide a high-mineralization mine water zero discharge system, including:

[0039] The first pressure exchange unit is used for the entry of the mine raw water to be treated to increase the hydraulic pressure and obtain pressurized mine raw water;

[0040] Reverse osmosis desalination and concentration unit, used for the pressurized mine raw water to enter to achieve high concentration, to obtain RO produced water and high-pressure RO concentrated liquid;

[0041] The first heat exchange unit is used for the RO produced water and high-temperature geothermal steam from the outside to enter and exchange heat energy, thereby obtaining high-temperature steam and low-temperature geothermal produced water;

[0042] The second pressure exchange unit is used for high-pressure RO concentrate to enter to achieve pressure exchange and obtain reduced-pressure RO concentrate;

[0043] The second heat exchange unit is used for the low-temperature geothermal water and low-temperature sewage from the outside to enter and exchange heat energy, thereby obtaining sewage with elevated temperature and geothermal water at normal temperature;

[0044] A pressure delayed osmosis unit for the temperature-boosted wastewater and the pressure-reduced RO concentrate to enter to realize the conversion of salt energy to mechanical energy, to obtain a diluted RO concentrate and a concentrated wastewater, the diluted RO concentrate entering a first pressure exchange unit to release pressure to obtain an atmospheric pressure RO concentrate;

[0045] A bipolar membrane electrodialysis unit for the atmospheric pressure RO concentrate to enter to perform electrodialysis to obtain an acid, a base and a low-salt feed liquid.

[0046] Preferably, a steam power generation unit is further included for the high-temperature steam to enter to realize the conversion of heat energy to electric energy.

[0047] Preferably, the normal-temperature geothermal water obtained by the second heat energy exchange unit enters the first heat energy exchange unit to perform heat energy exchange.

[0048] The specific structure and working parameters of each unit are described in detail as follows:

[0049] The first heat energy exchange unit and the second heat energy exchange unit: mainly realize the efficient conversion of heat energy between two fluids, complete the heat transfer between the two fluids. By setting multiple heat energy exchange units, the gradient and staged utilization of heat energy are realized. For example, a heat exchanger can be used.

[0050] The first pressure exchange unit and the second pressure exchange unit: mainly realize the efficient conversion of hydraulic pressure between two fluids, complete the recovery of pressure energy. By setting multiple pressure exchange units, the gradient and staged utilization of pressure energy are realized. For example, a PX pressure exchange device can be used.

[0051] The reverse osmosis desalination and concentration unit: realizes the high-fold concentration of high-mineralization well water, the salt content of the concentrated water can reach more than 10wt% and extremely high operating pressure, and then enters the second pressure exchange unit; the produced water has low salt content and enters the first heat energy exchange unit. It should be noted that this unit includes: a pretreatment section including but not limited to flocculation, sedimentation, softening, ultrafiltration, etc., a multi-stage reverse osmosis membrane assembly (low-pressure section and high-pressure section), a high-pressure pump, a booster pump, a pressure exchange device, etc. High-pressure and disc tube reverse osmosis and other capacitive deionization or electrodeionization process devices can be used, and the specific reverse osmosis desalination system structure in the prior art can be referred to.

[0052] Pressure-delayed osmosis unit; mainly realizes the recovery of salinity difference energy. The low-salt solution is a common unconventional low-salt water body such as municipal sewage (such as the sewage with elevated temperature as mentioned above), and the high-salt solution is RO concentrate (such as the RO concentrate after decompression as mentioned above). Pressure-delayed osmosis mainly uses the osmotic pressure difference of the solution on both sides of the semipermeable membrane to realize the spontaneous permeation of water from the low-salt side to the high-salt side, resulting in an increase in the volume of the drawn liquid. At the same time, due to the application of a certain hydraulic pressure on the drawn liquid side, the conversion of salinity difference energy into mechanical energy can be realized. The unit includes a pressure-delayed membrane assembly, a feed liquid delivery pump, a booster pump, etc. For details, please refer to the pressure-delayed osmosis system structure in the prior art.

[0053] The bipolar membrane electrodialysis unit can recycle highly mineralized mine water. The resulting mixed acid and alkali solutions can be used in the pretreatment stage of the reverse osmosis desalination and concentration unit. Furthermore, the high-salinity RO concentrate with high osmotic pressure is recovered through salinity gradient energy, reducing salinity and significantly reducing the salt content in the desalination chamber of the bipolar membrane electrodialysis unit. The feed in this chamber can then be fed into the low-pressure reverse osmosis membrane assembly of the reverse osmosis desalination and concentration unit to produce high-purity water as a steam source. This unit includes a bipolar membrane dialysis stack, a DC power supply, and a feed pump. For details, please refer to the existing bipolar membrane electrodialysis device structure.

[0054] Steam power generation unit: Through steam turbines and other equipment, it realizes the conversion of thermal energy into electrical energy and achieves the effective utilization of renewable energy.

[0055] The treatment process of the high-mineralization mine water zero-discharge system of the present invention is described below with reference to embodiments.

[0056] use Figure 1 In the system shown, the mine raw water undergoes the following treatment processes:

[0057] 1) The raw mine water 13 (salt content 10,000 wt%) to be treated is fed into the first pressure exchange unit G to achieve a first increase in the hydraulic pressure of the raw water, producing pressurized raw mine water 12 (with the hydraulic pressure increased to approximately 40 bar). The water is then subjected to a secondary pressurization by the booster pump in the pressure delayed osmosis unit F to meet the operating pressure of the reverse osmosis desalination and concentration unit D (approximately 80 bar).

[0058] 2) The pressurized mine raw water 12 is input into the reverse osmosis desalination and concentration unit D to achieve high concentration of the highly mineralized mine water, thereby obtaining RO product water 6 and high-pressure RO concentrate 11 (the hydraulic pressure is reduced to approximately 78 bar). The salt content of the high-pressure RO concentrate 11 reaches 10 wt% or more, and the RO product water 6 meets the water requirements for steam turbine power generation;

[0059] 3) The RO produced water 6 and high-temperature geothermal steam 1 (>100°C) from the outside are input into the first heat exchange unit A for heat exchange. The high-temperature geothermal steam 1 transfers heat energy to the RO produced water 6, generating high-temperature steam 7 and low-temperature geothermal produced water 2 (<100°C). The high-temperature steam 7 enters the steam power generation unit C to complete heat-to-electricity conversion.

[0060] 4) Due to its extremely high operating pressure, the high-pressure RO concentrate 11 must enter the second pressure exchange unit E to achieve matching of the operating pressure with the optimal operating pressure of the pressure delayed osmosis process (about 40-50 bar), thereby obtaining the decompressed RO concentrate 10;

[0061] 5) The low-temperature geothermal water 2 and low-temperature municipal sewage or factory domestic sewage 4 (low-salt solution) from the outside are input into the second heat exchange unit B for heat exchange. The low-salt solution obtains the heat stored in the geothermal tail heat and its temperature is raised to the maximum tolerable temperature of the pressure delayed osmosis membrane (e.g., the temperature difference between the two sides of the membrane is 35°C); thus, the high-temperature municipal sewage or factory domestic sewage 5 and the normal-temperature geothermal water 3 are obtained;

[0062] 6) The high-temperature municipal sewage or factory domestic sewage 5 and the decompressed RO concentrate 10 are fed into a pressure-delayed osmosis unit F to convert salinity difference energy into mechanical energy (energy consumption per ton of water is reduced by more than 20%), thereby obtaining a diluted RO concentrate 9 and concentrated sewage. After the low-salt feed solution is concentrated (see Figure 8), the water volume is significantly reduced, and a certain residual temperature is still present, which is beneficial for reducing the processing load of subsequent biochemical treatment and improving its treatment efficiency.

[0063] 7) After dilution, the RO concentrate 9 still has an elevated operating pressure and enters the first-stage pressure exchange unit G, where it transfers hydraulic pressure to the mine raw water 13, which releases the pressure to produce the atmospheric pressure RO concentrate 14;

[0064] 8) The atmospheric pressure RO concentrate 14 is input into the bipolar membrane electrodialysis unit H for electrodialysis to obtain acid, alkali and low-salt feed solution 15; wherein the acid and alkali can be used as pH regulators in the pretreatment process, and the low-salt feed solution can be introduced into the low-pressure reverse osmosis membrane assembly in the reverse osmosis desalination concentration unit for deep desalination, and the produced water can be used as water for the steam power generation unit.

[0065] Obviously, the above embodiments of the present invention are merely examples for the purpose of illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not possible to enumerate all embodiments here. Any obvious variations or modifications arising from the technical solutions of the present invention are intended to fall within the spirit and scope of the present invention.

Claims

1. A high-mineralization mine water zero discharge system, characterized by: include: The first pressure exchange unit is used for the entry of the mine raw water to be treated to increase the hydraulic pressure and obtain pressurized mine raw water; Reverse osmosis desalination and concentration unit, used for the pressurized mine raw water to enter to achieve high concentration, to obtain RO produced water and high-pressure RO concentrated liquid; The first heat exchange unit is used for the RO produced water and high-temperature geothermal steam from the outside to enter and exchange heat energy, thereby obtaining high-temperature steam and low-temperature geothermal produced water; The second pressure exchange unit is used for high-pressure RO concentrate to enter to achieve pressure exchange and obtain decompressed RO concentrate; The second heat exchange unit is used for the low-temperature geothermal water and low-temperature sewage from the outside to enter and exchange heat energy, thereby obtaining sewage with elevated temperature and geothermal water at normal temperature; A pressure delayed osmosis unit is used for the temperature-elevated sewage and the decompressed RO concentrate to enter to realize the conversion of salt production into mechanical energy, thereby obtaining a diluted RO concentrate and concentrated sewage. The diluted RO concentrate enters the first pressure exchange unit and is decompressed to obtain a normal-pressure RO concentrate. The bipolar membrane electrodialysis unit is used for the atmospheric pressure RO concentrate to enter for electrodialysis to obtain acid, alkali and low-salt feed solutions.

2. The high-mineralization mine water zero discharge system according to claim 1 is characterized by: It also includes a steam power generation unit, which is used for the high-temperature steam to enter to realize the conversion of thermal energy into electrical energy.

3. The high-mineralization mine water zero discharge system according to claim 1 is characterized by: The room-temperature geothermal water obtained by the second heat energy exchange unit enters the first heat energy exchange unit for heat energy exchange.

4. The high-mineralization mine water zero discharge system according to any one of claims 1 to 3, characterized in that: The low-temperature sewage is municipal sewage or factory domestic sewage.

5. A zero-discharge method for high-mineralization mine water, characterized by: The steps include: Inputting the mine raw water to be treated into the first pressure exchange unit to increase the hydraulic pressure and obtain pressurized mine raw water; The pressurized mine raw water is input into a reverse osmosis desalination and concentration unit to achieve high concentration, thereby obtaining RO produced water and high-pressure RO concentrated liquid; The RO produced water and high-temperature geothermal steam from the outside are input into a first heat exchange unit for heat exchange to obtain high-temperature steam and low-temperature geothermal produced water; The high-pressure RO concentrate is input into the second pressure exchange unit to achieve pressure exchange and obtain a reduced-pressure RO concentrate; The low-temperature geothermal water and low-temperature sewage from the outside are input into a second heat exchange unit for heat exchange, thereby obtaining sewage with elevated temperature and geothermal water at room temperature; The temperature-elevated sewage and the decompressed RO concentrate are input into a pressure-delayed osmosis unit to convert salt production into mechanical energy, thereby obtaining a diluted RO concentrate and concentrated sewage. The diluted RO concentrate enters a first pressure exchange unit, where the pressure is released to obtain a normal-pressure RO concentrate. The atmospheric pressure RO concentrated solution is input into a bipolar membrane electrodialysis unit for electrodialysis to obtain acid, alkali and low-salt feed solutions.

6. The zero-discharge method for high-mineralization mine water according to claim 5, characterized in that: The acid and base are applied to the pretreatment section of the reverse osmosis desalination and concentration unit; and / or, the low-salt feed liquid is introduced into the low-pressure reverse osmosis membrane assembly in the reverse osmosis desalination and concentration unit for deep desalination, and the produced water is used as water for the steam power generation unit.

7. The zero-discharge method for high-mineralization mine water according to claim 5, characterized in that: The high-temperature steam is input into a steam power generation unit to achieve conversion of thermal energy into electrical energy.

8. The zero-discharge method for high-mineralization mine water according to any one of claims 5 to 7, characterized in that: The room-temperature geothermal water obtained by the second heat energy exchange unit enters the first heat energy exchange unit for heat energy exchange.

9. The zero-discharge method for high-mineralization mine water according to claim 5, characterized in that: The salt content in the high-pressure RO concentrated liquid is ≥10 wt %.

10. The zero-discharge method for high-mineralization mine water according to claim 5 or 9, characterized in that: The pressure of the RO concentrate after the decompression is 40-50 bar.

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