Internal circulation type three-section reverse osmosis high-salinity wastewater concentration treatment system

Abstract

The invention provides an internal circulation type three-section reverse osmosis high-salinity wastewater concentration treatment system which comprises a water inlet unit and an internal circulation type three-section reverse osmosis unit, and the internal circulation type three-section reverse osmosis unit comprises a first-section reverse osmosis device, a second-section reverse osmosis device and a tail-section reverse osmosis device. The first-section reverse osmosis device comprises a group of reverse osmosis membrane elements, a water producing pump, a produced water discharge pipe and a water producing tank, the secondary-section reverse osmosis device comprises a group of reverse osmosis membrane elements, a circulating pump and a circulating pipe, and the tail-section reverse osmosis device comprises a group of reverse osmosis membrane elements, a concentrated water discharge pipe and an energy recovery device. The concentrated water side of the first-section reverse osmosis device is connected with the water inlet side of the second-section reverse osmosis device, the osmosis side of the first-section reverse osmosis device is connected with the water production tank through a water production discharge pipe, and the concentrated water side of the second-section reverse osmosis device is connected with the water inlet side of the tail-section reverse osmosis device; the permeation side of the secondary-section reverse osmosis device is connected with the water inlet side of the first-section reverse osmosis device through a circulating pipe, the concentrated water side of the tail-section reverse osmosis device is connected with an energy recovery device and a discharge pipe to discharge concentrated liquid, and the permeation side of the tail-section reverse osmosis device is connected with the discharge pipe to discharge high-salinity produced water.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and in particular relates to the design and application of an internal circulation three-stage reverse osmosis high-salt wastewater concentration treatment system. Background Art

[0002] In order to reduce the negative impact of industrial wastewater on the environment, the government has implemented more stringent emission standards, and zero wastewater discharge (ZLD) or near-zero wastewater discharge (MLD) technology has therefore received attention. In the ZLD system, high-salinity wastewater is first concentrated by membrane and thermal methods, and finally the water is completely removed by a crystallization process. However, the high investment and operating costs of thermal concentration limit the widespread application of ZLD technology. Therefore, in order to reduce the cost of ZLD technology, reverse osmosis (RO) technology can be used to achieve high-rate concentration of high-salinity wastewater, thereby reducing the operating burden of thermal concentration. However, in conventional RO operations, in order to avoid excessive pressure from damaging the membrane and components, the operating pressure is subject to certain restrictions (generally not higher than 85 bar), which also restricts the concentration rate of high-salinity wastewater and the pure water recovery rate.

[0003] Therefore, in order to break through the limitation of operating pressure on wastewater concentration rate in traditional RO technology, the multi-stage and multi-segment RO system can be optimized through internal circulation reorganization to reduce the transmembrane osmotic pressure of each RO membrane, so that high-salt wastewater can be enhanced concentrated under normal operating pressure. Summary of the invention

[0004] Aiming at the problem that the existing RO process is limited by the operating pressure, resulting in low high-salinity wastewater concentration rate and pure water recovery rate, the present invention proposes an internal circulation three-stage reverse osmosis high-salinity wastewater concentration treatment system, which reduces the use cost by using waste membranes in the secondary and final stages, and at the same time returns the low-salinity water produced on the osmotic side of the secondary stage to the water inlet side of the first stage to reduce the trans-membrane osmotic pressure difference, thereby improving the high-salinity wastewater concentration rate and pure water recovery rate of the system, and reducing the unit water production energy consumption.

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

[0006] An internal circulation type three-stage reverse osmosis high-salinity wastewater concentration treatment system comprises (1) a water inlet unit: comprising a raw water tank, a raw water pump, a flow meter, and a feed pipe, for feeding raw water to be treated into the system; (2) an internal circulation type three-stage reverse osmosis unit: comprising a three-stage reverse osmosis membrane assembly, a water production pump, a water production discharge pipe, a water production tank, a circulation pump, a circulation pipe, a concentrated water discharge pipe, and an energy recovery device.

[0007] Furthermore, the three-stage reverse osmosis unit includes: (1) a first-stage reverse osmosis device: including a group of reverse osmosis membrane elements, a water production pump, a water production discharge pipe, and a water production tank. Its main function is to preliminarily concentrate the pretreated water and recover the product water (pure water) to the water production tank through the water production discharge pipe; (2) a second-stage reverse osmosis device: including a group of reverse osmosis membrane elements, a circulation pump, and a circulation pipe. Its main function is to further concentrate the first-stage reverse osmosis concentrate and return the low-salinity water produced on the secondary osmosis side to the first-stage water inlet side; (3) a final-stage reverse osmosis device: including a group of reverse osmosis membrane elements, a concentrated water external discharge pipe, and an energy recovery device. Its main function is to deeply concentrate the second-stage reverse osmosis concentrate and discharge the concentrate and the high-salinity water produced on the osmosis side through the external discharge pipe, and recover the remaining energy.

[0008] Furthermore, the concentrated water side of the first-stage reverse osmosis device is connected to the water inlet side of the second-stage reverse osmosis device, and the osmosis side of the first-stage reverse osmosis device is connected to the water production tank through a water production discharge pipe to realize water production collection; the concentrated water side of the second-stage reverse osmosis device is connected to the water inlet side of the last-stage reverse osmosis device, and the osmosis side of the second-stage reverse osmosis device is connected to the water inlet side of the first-stage reverse osmosis device through a circulation pipe to reflux low-salinity produced water; the concentrated water side of the last-stage reverse osmosis device is connected to an energy recovery device to recover residual energy, and is connected to an external discharge pipe to discharge the concentrated liquid, and the osmosis side of the last-stage reverse osmosis device is connected to an external discharge pipe to discharge high-salinity produced water.

[0009] Furthermore, the first-stage reverse osmosis device adopts a conventional reverse osmosis membrane with a salt retention rate of >99.5%; the second-stage reverse osmosis device adopts a waste reverse osmosis membrane with a salt retention rate of 60%-80%; the final-stage reverse osmosis device adopts a waste reverse osmosis membrane with a salt retention rate of 0%-60%.

[0010] Furthermore, the operating pressure applied by the high-pressure pump in the system is 60-80 bar.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] (1) Compared with the traditional reverse osmosis membrane concentration system, the present invention adopts conventional reverse osmosis membrane components in the first stage, and waste reverse osmosis membrane components in the second stage and the last stage, which effectively reduces the investment cost of the system.

[0013] (2) Under the condition that waste reverse osmosis membrane components are used in both the secondary and final stages, compared with a three-stage reverse osmosis membrane concentration treatment system without internal circulation, the present invention not only improves the pure water recovery rate under the same operating pressure conditions, but also reduces the osmotic pressure difference between the feed side and the permeate side of the reverse osmosis membrane, thereby reducing the unit water production energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be described in more detail below based on embodiments and with reference to the accompanying drawings. It should be noted that the accompanying drawings are only one embodiment of the present invention, and those skilled in the art can obtain other accompanying drawings without creative work.

[0015] Figure 1 It is a schematic diagram of the internal circulation three-stage reverse osmosis high-salt wastewater concentration treatment system of the present invention.

[0016] Among them, 1. the first section reverse osmosis membrane assembly; 2. the second section reverse osmosis membrane assembly; 3. the final section reverse osmosis membrane assembly; 4. the high-pressure pump; 5. the produced water (pure water) tank; 6. the energy recovery device.

[0017] Figure 2 This is a schematic diagram of a non-circulating three-stage reverse osmosis high-salt wastewater concentration treatment system.

[0018] Among them, 1. the first section reverse osmosis membrane assembly; 2. the second section reverse osmosis membrane assembly; 3. the final section reverse osmosis membrane assembly; 4. the high-pressure pump; 5. the produced water (pure water) tank; 6. the energy recovery device. DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with the accompanying drawings. This will allow the present invention to fully understand how to use technical means to solve technical problems and achieve technical effects and implement them accordingly. It should be noted that as long as there is no conflict, the various technical features mentioned in each embodiment can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions within the scope of the claims.

[0020] The present invention provides an internal circulation three-stage reverse osmosis high-salt wastewater concentration treatment system, which can improve the high-salt wastewater concentration rate and pure water recovery rate, and reduce the unit water production energy consumption.

[0021] like Figure 1 As shown, the system mainly includes: (1) water inlet system: including raw water pump 4, etc., whose main function is to deliver the raw water to be treated into the system; (2) first-stage reverse osmosis device: including first-stage reverse osmosis membrane assembly 1, water production discharge pipe, etc., whose main function is to preliminarily concentrate the pretreated water, and at the same time recover the product water (pure water) to the water production tank 5 through the water production discharge pipe; (3) secondary reverse osmosis device: including secondary reverse osmosis membrane assembly 2, circulation pump 4, etc., whose main function is to further concentrate the first-stage reverse osmosis concentrated liquid, and at the same time return the low-salinity water production on the secondary osmosis side to the first-stage water inlet side; (4) final reverse osmosis device: including final reverse osmosis membrane assembly 3, external discharge pipe, energy recovery device 6, etc., whose main function is to deeply concentrate the secondary reverse osmosis concentrated liquid, and at the same time discharge the concentrated liquid and the high-salinity water production on the osmosis side through the external discharge pipe, and recover the remaining energy.

[0022] The pipeline connection relationship of the system is as follows: the concentrated water side of the first-stage reverse osmosis membrane assembly 1 is connected to the water inlet side of the second-stage reverse osmosis membrane assembly 2, and the osmosis side of the first-stage reverse osmosis membrane assembly 1 is connected to the water production tank 5 through a water production discharge pipe to realize water production collection; the concentrated water side of the second-stage reverse osmosis membrane assembly 2 is connected to the water inlet side of the last-stage reverse osmosis membrane assembly 3, and the osmosis side of the second-stage reverse osmosis membrane assembly 2 is connected to the water inlet side of the first-stage reverse osmosis membrane assembly 1 through a circulation pipe to reflux low-salinity produced water; the concentrated water side of the last-stage reverse osmosis membrane assembly 3 is connected to an energy recovery device 6 for residual energy recovery, and is connected to an external discharge pipe to discharge the concentrated liquid, and the osmosis side of the last-stage reverse osmosis membrane assembly 3 is connected to an external discharge pipe to discharge high-salinity produced water.

[0023] The beneficial effects of the present invention are demonstrated through several specific embodiments below.

[0024] Embodiment 1:

[0025] like Figure 1 As shown, in this embodiment, the treated high-salinity wastewater inlet concentration is 37500 mg / L, the required concentrate end concentration is 100000 mg / L, and the maximum operating pressure is 60 bar. When the minimum unit water production energy consumption is achieved by adopting the technical solution of the present invention, the corresponding secondary salt retention rate is 72%, the final salt retention rate is 57%, the pure water recovery rate is 53.0%, and the unit water production energy consumption is 2.59 kWh / m 3 Under the same conditions, using Figure 2 In the comparative example shown in the figure, when the minimum unit water production energy consumption is achieved, the corresponding second-stage salt retention rate is also 72%, and the final-stage salt retention rate is also 57%. At this time, the pure water recovery rate is 41.8%, and the unit water production energy consumption is 2.77 kWh / m 3 Therefore, under the condition that waste reverse osmosis membrane elements are used in both the secondary and final stages, the present invention improves the pure water recovery rate by 26.8% and reduces the unit water production energy consumption by 6.5% compared with the three-stage reverse osmosis membrane concentration system without internal circulation.

[0026] Embodiment 2:

[0027] In this embodiment, the high-salinity wastewater inlet concentration is 50000 mg / L, the required concentrate end concentration is 150000 mg / L, and the maximum operating pressure is 80 bar. When the minimum unit water production energy consumption is achieved by adopting the technical solution of the present invention, the corresponding secondary salt retention rate is 63%, the final salt retention rate is 45%, the pure water recovery rate is 57.5%, and the unit water production energy consumption is 3.80 kWh / m 3 Under the same conditions, using Figure 2In the comparative example shown in the figure, when the minimum unit water production energy consumption is achieved, the corresponding second-stage salt retention rate is also 63%, and the final-stage salt retention rate is also 45%. At this time, the pure water recovery rate is 41.8%, and the unit water production energy consumption is 4.10 kWh / m 3 Therefore, under the condition that waste reverse osmosis membrane elements are used in both the secondary and final stages, the present invention improves the pure water recovery rate by 37.6% and reduces the unit water production energy consumption by 7.3% compared with the three-stage reverse osmosis membrane concentration system without internal circulation.

[0028] In summary, compared with the traditional reverse osmosis membrane concentration system, the present invention uses waste reverse osmosis membrane components in the second and last sections except for the conventional reverse osmosis membrane components in the first section, which effectively reduces the investment cost of the system. In addition, under the condition that waste reverse osmosis membrane components are used in the second and last sections, compared with the three-stage reverse osmosis membrane concentration treatment system without internal circulation, the present invention not only improves the pure water recovery rate under the same operating pressure conditions, but also reduces the osmotic pressure difference between the feed side and the osmosis side of the reverse osmosis membrane, thereby reducing the unit water production energy consumption.

[0029] Although the present invention has been described with reference to the above preferred embodiments, the contents described are only embodiments adopted for facilitating the understanding of the present invention and are not intended to limit the present invention. Any person skilled in the art of the present invention may make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present invention, but the scope of patent protection of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. An internal circulation three-stage reverse osmosis high-salt wastewater concentration treatment system, characterized in that: The following units are included: (1) Water inlet unit: includes a raw water tank, a raw water pump, a flow meter, and a feed pipe, and is used to deliver the raw water to be treated into the system; (2) Internal circulation three-stage reverse osmosis unit: It includes three-stage reverse osmosis membrane components, water production pump, water production discharge pipe, water production tank, circulation pump, circulation pipe, concentrated water discharge pipe, and energy recovery device.

2. The internal circulation three-stage reverse osmosis high-salt wastewater concentration treatment system according to claim 1 is characterized in that: The internal circulation three-stage reverse osmosis unit comprises a first-stage, a second-stage and a final-stage reverse osmosis device: (1) The first reverse osmosis device: It includes a set of reverse osmosis membrane elements, a water production pump, a water production discharge pipe, and a water production tank. Its main function is to initially concentrate the pretreated water and recover the product water (pure water) to the water production tank through the water production discharge pipe; (2) Secondary reverse osmosis device: It includes a set of reverse osmosis membrane elements, circulation pumps, and circulation pipes. Its main function is to further concentrate the concentrated liquid from the first stage of reverse osmosis and to return the low-salinity water produced from the secondary osmosis side to the first stage of water inlet side. (3) Final reverse osmosis device: It includes a set of reverse osmosis membrane elements, a concentrated water discharge pipe, and an energy recovery device. Its main function is to deeply concentrate the secondary reverse osmosis concentrate, discharge the concentrate and high-salinity water produced on the osmosis side through the discharge pipe, and recover the remaining energy.

3. The internal circulation three-stage reverse osmosis high-salt wastewater concentration treatment system according to claim 1 is characterized in that: The internal circulation type three-stage reverse osmosis unit, wherein the concentrated water side of the first-stage reverse osmosis device is connected to the water inlet side of the second-stage reverse osmosis device, and the permeation side of the first-stage reverse osmosis device is connected to the water production tank through a water production discharge pipe to realize water production collection; the concentrated water side of the second-stage reverse osmosis device is connected to the water inlet side of the last-stage reverse osmosis device, and the permeation side of the second-stage reverse osmosis device is connected to the water inlet side of the first-stage reverse osmosis device through a circulation pipe to reflux low-salinity produced water; the concentrated water side of the last-stage reverse osmosis device is connected to an energy recovery device to recover residual energy, and is connected to an external discharge pipe to discharge the concentrated liquid, and the permeation side of the last-stage reverse osmosis device is connected to an external discharge pipe to discharge high-salinity produced water.

4. The first-stage reverse osmosis device according to claim 2, characterized in that: The salt rejection rate of the reverse osmosis membrane in the device is >99.5%.

5. The secondary reverse osmosis device according to claim 2, characterized in that: The salt rejection rate of the reverse osmosis membrane in the device ranges from 60% to 80%.

6. The final reverse osmosis device according to claim 2, characterized in that: The salt rejection rate of the reverse osmosis membrane in the device ranges from 0% to 60%.

7. The internal circulation three-stage reverse osmosis high-salt wastewater concentration treatment system according to claim 1 is characterized in that: The operating pressure applied by the high pressure pump in the system is in the range of 60-80 bar.

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