A bag filter membrane distillation device and a method for extracting water from a water-containing liquid

Abstract

A bag-type membrane distillation device comprises an evaporation membrane bag for storing an evaporation liquid to be treated, a distillation air chamber for containing the evaporation membrane bag and having an air outlet and an air inlet capable of passing a continuous air flow, and a heater for heating the air flow. The invention also discloses a method for operating the bag-type membrane distillation device, which comprises measuring a temperature difference between the air inlet and the air outlet; and determining that the evaporation treatment of the evaporation liquid in the evaporation membrane bag is completed when the temperature difference is less than a temperature difference threshold. The invention uses the evaporation membrane bag as an evaporation container to facilitate taking and placing and storage and transportation of waste liquid after evaporation; places the evaporation membrane bag in the distillation air chamber having the air outlet and the air inlet capable of passing the continuous air flow to realize output of water vapor and meet the requirements of use in a small closed environment; and sets the heater to improve evaporation efficiency.

Description

Technical Field

[0001] This invention belongs to the field of space station water recycling technology, specifically relating to a bag-type membrane distillation device and a method for extracting water from aqueous liquids. Background Technology

[0002] To reduce the high costs of ground resupply, manned spacecraft similar to space stations are equipped with environmental control and life support systems, often simply referred to as EPSS systems. These systems treat and purify various types of wastewater within the station to achieve a cyclical water supply. Among these, urine treatment and water recovery are the most challenging and crucial aspects in improving the closure of the water cycle.

[0003] Currently, mainstream environmental control and life support systems use steam compression distillation to treat urine, recovering up to 85% of the water content. The residual urine after steam compression distillation is collected and discarded. However, this residual urine contains a large amount of water, and this water loss affects the water circulation closure of the environmental control and life support system. Furthermore, to improve distillation efficiency and product water quality, strong acids and strong oxidants are added to the urine for pretreatment before it enters the compression distillation process. This results in the concentrated residual urine being highly acidic and corrosive (pH 1-2), significantly increasing the risks associated with its storage and transportation.

[0004] Given the limited space and high storage and transportation costs within space stations or spacecraft, further extracting and recovering water from residual urine in environmental control and life support systems within small, sealed devices to reduce the volume of residual urine can improve the closure of the water cycle in existing environmental control and life support systems and mitigate the potential safety risks associated with the storage of residual urine. This is of great significance for the long-term operation of manned spacecraft such as space stations and for manned deep space exploration missions. Summary of the Invention

[0005] The purpose of this invention is to further extract and recover moisture from residual urine in an environmentally controlled life support system in a small, closed device.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A bag-type membrane distillation apparatus includes: an evaporation membrane bag for storing and evaporating an aqueous liquid to be treated; a distillation chamber for housing the evaporation membrane bag and having an air outlet and an air inlet for a continuous air flow; and a heater for heating the air flow.

[0008] Preferably, the evaporation membrane bag is made of a composite membrane that allows water molecules to selectively permeate.

[0009] Preferably, the evaporation membrane bag is made into a closed bag structure with a filling valve by means of hot melt welding or adhesive bonding.

[0010] Preferably, the filling valve is connected to the evaporation membrane bag via a hose.

[0011] Preferably, the composite membrane includes a microporous hydrophobic membrane as the inner layer and an ion exchange membrane composited on the outer side of the microporous hydrophobic membrane and selectively permeable to water molecules.

[0012] Preferably, the microporous hydrophobic membrane is made of PTFE material.

[0013] Preferably, the distillation chamber includes a distillation chamber housing with an air outlet and an air inlet, an air passage adaptive mechanism fixed inside the distillation chamber housing for supporting the evaporation film bag to form an air passage, a power supply assembly fixed to the distillation chamber housing, an inlet temperature sensor installed at the air inlet, an outlet temperature sensor installed at the air outlet, a fan located at the air outlet and fixed to the distillation chamber housing, and a controller fixed to the distillation chamber housing; the controller is electrically connected to the power supply assembly, the inlet temperature sensor, the outlet temperature sensor, and the fan, respectively.

[0014] Preferably, the airway adaptive mechanism includes: a lower support net for supporting the evaporation film bag and fixing it to the distillation chamber housing; a sliding component fixed inside the distillation chamber housing; an upper support net fixed by the sliding component and forming an evaporation film bag placement space and an evaporation airway with the lower support net; and the upper support net having flexible windproof curtains at both ends of the air outlet and air inlet for sealing the outer space of the evaporation airway.

[0015] Preferably, both the lower support mesh and the upper support mesh are mesh structures.

[0016] Preferably, the flexible windproof curtain adopts an accordion-style folding structure.

[0017] Preferably, the air outlet is connected to a condenser via a pipe to collect and recover moisture evaporated from the evaporation membrane bag.

[0018] Based on the same inventive concept, the present invention also provides a method for extracting water from an aqueous liquid, which uses the aforementioned bag-type membrane distillation apparatus and includes the following steps:

[0019] Add the water-containing liquid to be treated to the evaporation membrane bag in the distillation chamber;

[0020] The heater is turned on to heat the airflow passing through the distillation chamber to promote the evaporation of the water-containing liquid;

[0021] Measure the temperature difference between the air inlet and the air outlet;

[0022] When the temperature difference is less than the temperature difference threshold, the evaporation process of the water-containing liquid in the evaporation membrane bag is considered to be complete.

[0023] Preferably, the temperature of the airflow at the air inlet is 30±2℃.

[0024] Preferably, the temperature difference threshold is 3°C.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. A bag-type membrane distillation apparatus, comprising: an evaporation membrane bag for storing and evaporating an aqueous liquid to be treated; a distillation chamber for housing the evaporation membrane bag and having an air outlet and an air inlet allowing a continuous airflow; and a heater for heating the airflow. This invention facilitates the handling and storage of waste liquid after evaporation by using an evaporation membrane bag as the evaporation container; it achieves water vapor output and meets the spatial environment requirements for evaporation in a small, closed device by placing the evaporation membrane bag in a distillation chamber with an air outlet and an air inlet allowing a continuous airflow; and it improves evaporation efficiency by incorporating a heater. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the principle of a bag-type membrane distillation device according to the present invention;

[0028] Figure 2 This is a three-dimensional assembly drawing of a bag-type membrane distillation device according to the present invention;

[0029] The components are as follows: 1-Power supply assembly; 2-Pipe heater; 3-Inlet temperature sensor; 4-Distillation chamber; 4.1-Lower support net; 4.2-Upper support net; 4.3-Sliding assembly; 4.4-Flexible windproof curtain; 5-Evaporation film bag; 5.1-Composite membrane; 5.2 Filling valve; 6-Outlet gas temperature sensor; 7-Fan; 8-Controller. Detailed Implementation

[0030] Example 1

[0031] This invention addresses the unique application requirements of manned spacecraft such as space stations, which face limited space and high storage and transportation costs. Specifically, it targets the high-salt, high-solids-concentration, and highly acidic / oxidizing residual urine from environmental control and life support systems. By combining a microporous hydrophobic membrane with a water-selectively permeable ion-exchange membrane to form a membrane bag structure, the invention achieves urine residue retention and water extraction. Furthermore, it develops corresponding distillation apparatus and operating methods, achieved through the following pathways:

[0032] A bag-type membrane distillation apparatus for evaporating and extracting water from an aqueous liquid includes: an evaporation membrane bag for storing the aqueous liquid being evaporated, a distillation chamber for housing the evaporation membrane bag and having an air outlet and an air inlet for a continuous airflow, and a heater for heating the airflow.

[0033] The specific implementation structure is as follows: Figure 1 or Figure 2 The diagram shows a bag-type membrane distillation device, comprising a power supply assembly 1, a pipe heater 2, an inlet temperature sensor 3, a distillation chamber 4, an evaporation membrane bag 5, an outlet temperature sensor 6, a fan 7, and a controller 8. The power supply assembly 1, pipe heater 2, and inlet temperature sensor 3 are integrated and installed at the inlet. A continuous airflow passes sequentially through the power supply assembly 1, pipe heater 2, and inlet temperature sensor 3 before entering the distillation chamber 4. The evaporation membrane bag 5 is placed in the distillation chamber 4. Air sweeps across the outer surface of the evaporation membrane bag 5 along the airflow direction, exits the distillation chamber 4, and then passes through the outlet temperature sensor 6 before being discharged into the environment via the fan 7 or fed into a condenser through a pipe to extract moisture from the airflow. The fan 7 provides the purging gas power for the distillation device, forming a continuous airflow to carry away the moisture evaporated from the evaporation membrane bag 5.

[0034] The evaporation membrane bag 5 is made of a composite membrane 5.1 that allows water molecules to selectively permeate.

[0035] The evaporation membrane bag 5 is formed by hot-melt welding or adhesive bonding to create a closed bag structure with a filling valve for the composite membrane 5.1.

[0036] The filling valve 5.2 is connected to the evaporation film bag 5 via a hose.

[0037] The composite membrane 5.1 includes a microporous hydrophobic membrane as the inner layer and an ion exchange membrane composited on the outer side of the microporous hydrophobic membrane, which allows water molecules to selectively permeate.

[0038] The microporous hydrophobic membrane is made of PTFE material.

[0039] The heater is a pipe heater 8 that is connected to the air inlet.

[0040] The distillation chamber 4 includes a distillation chamber housing with an air outlet and an air inlet, an air passage adaptive mechanism fixed inside the distillation chamber housing for supporting the evaporation membrane bag 5 to form an air passage, a power supply assembly 1 fixed to the distillation chamber housing, an air inlet temperature sensor 3 installed at the air inlet, an air outlet temperature sensor 6 installed at the air outlet, a fan 7 located at the air outlet and fixed to the distillation chamber housing, and a controller 8 fixed to the distillation chamber housing; the controller 8 is electrically connected to the power supply assembly 1, the air inlet temperature sensor 3, the air outlet temperature sensor 6, and the fan 7 respectively.

[0041] The adaptive airway mechanism includes: a lower support net 4.1 for supporting the evaporation film bag 5 and fixing it to the distillation chamber shell; a sliding assembly 4.3 fixed inside the distillation chamber shell; an upper support net 4.2 fixed by the sliding assembly 4.3 and forming an evaporation film bag 5 placement space and evaporation airway with the lower support net 4.1; and the upper support net 4.2 having flexible windproof curtains 4.4 at both the air outlet and air inlet ends for sealing the outer space of the evaporation airway.

[0042] Both the lower support net 4.1 and the upper support net 4.2 are mesh structures.

[0043] The distillation chamber shell, lower support net 4.1, sliding assembly 4.3, and lower support net 4.2 are all made of stainless steel.

[0044] The flexible windproof curtain 4.4 adopts an accordion-style folding structure.

[0045] The distillation chamber 4 includes the following structure: a lower support net 4.1, an upper support net 4.2, a sliding component 4.3, and a flexible windproof curtain 4.4. The upper support net 4.2, the sliding component 4.3, and the flexible windproof curtain 4.4 are connected together, and the connecting assembly of the three can slide freely up and down. Both the upper support net 4.2 and the lower support net 4.1 are mesh structures. The evaporation membrane bag 5 is placed on the lower support net 4.1. At the same time, the upper support net 4.2, under the action of its own gravity and the sliding component 4.3 (in a microgravity environment) or under the operation of an automatic control mechanism (in a zero-gravity environment), is tightly attached to the upper part of the evaporation membrane bag 5, ensuring that there are relatively fixed airflow channels on both the upper and lower sides of the membrane bag under different filling states of the evaporation membrane bag 5 (full filling, half filling, or no filling, etc.), thus ensuring the stability of the flow field inside the distillation chamber 4 during the distillation process.

[0046] The evaporation membrane bag 5 is made of two layers of membrane materials bonded together. The inner membrane is a hydrophobic membrane material made of PTFE, and the outer membrane is an ion exchange membrane that allows water molecules to pass through selectively. The two membranes work together to ensure the quality and purity of the water vapor gas that passes through the distillation. The two membranes are made into a bag structure by hot-melt welding or adhesive bonding, and a filling valve 5.2 and pipeline are provided.

[0047] The controller 8 controls the power supply to the pipe heater 2 and the fan 7, collects temperature data at the inlet and outlet, and automatically determines and stops the operation of the device based on the temperature difference between the inlet and outlet.

[0048] The technical features of this invention include:

[0049] (1) The flexible bag membrane structure is both a distiller and a urine residue storage device. The process is simple, the supporting equipment is few, the equipment weight is small, and it meets the requirements of lightweight.

[0050] (2) The flexible membrane bag is for single use only. Any remaining residue remains inside the membrane bag and is carried away from the manned spacecraft without any subsequent processing burden.

[0051] (3) The weight of the membrane bag accounts for less than 5% of the weight of the recovered water, resulting in high recycling efficiency;

[0052] (4) The combination of hydrophobic membrane and ion exchange membrane effectively controls the overflow of pollutants and results in good quality recycled water.

[0053] (5) It adopts atmospheric pressure and low temperature distillation, which has low energy consumption.

[0054] This invention can be widely applied to fields such as liquid concentration and industrial waste treatment.

[0055] The device frame and outer enclosure are made of stainless steel, and the entire device is airtight. A sealed door is located on the front of the device for placing and removing membrane bags. The overall dimensions are 775mm (length) × 391mm (width) × 343mm (height), and the membrane bag dimensions are 580mm × 360mm. A 10m... 3 A fan with a flow rate of / h is equipped with a heater with a power of 30W.

[0056] The main structure of the distillation chamber 4 includes a lower support net 4.1, an upper support net 4.2, a sliding component 4.3, and a flexible windproof curtain 4.4. The upper support net 4.2, the sliding component 4.3, and the flexible windproof curtain 4.4 are connected together, and the connecting assembly of the three can slide freely up and down. Both the upper support net 4.2 and the lower support net 4.1 are mesh structures. The evaporation membrane bag 5 is placed on the lower support net 4.1. At the same time, the upper support net 4.2, under the action of its own gravity and that of the sliding component 4.3, is tightly attached to the upper part of the evaporation membrane bag 5, ensuring that there are relatively fixed airflow channels on both the upper and lower sides of the membrane bag 5 under different filling states (full filling, half filling, or no filling, etc.), thus ensuring the stability of the flow field inside the distillation chamber 4 during the distillation process.

[0057] The evaporation membrane bag 5 is composed of two layers of membrane material bonded together. The inner membrane is a hydrophobic PTFE membrane material, and the outer membrane is an ion exchange membrane that allows selective permeation of water molecules. The two membranes are bonded together using hot-melt welding and adhesive bonding to form a bag-like structure, and a filling valve 5.2 and pipeline are provided. The evaporation membrane bag 5 is completely sealed, and the filling valve 5.2 and pipeline are the only inlet and outlet of the evaporation membrane bag 5.

[0058] The controller 8 completes the power supply and distribution to the pipeline heater 2 and the fan 7, completes the acquisition of air inlet and outlet temperature data, the inlet temperature is 30±2℃, the lower limit of the temperature difference between the inlet and outlet is set to 3℃, and automatically judges and stops the operation of the device based on the size of the temperature difference between the inlet and outlet.

[0059] The operation method of the bag-type membrane distillation device of the present invention is as follows: First, place a new evaporation membrane bag 5 in the distillation chamber 4, add 11L of urine residue through the filling valve 5.2 until the bag is full, close the filling valve 5.2, disconnect the external pipeline connection, close the device sealing door, start the device in automatic operation mode, turn on the fan 7 and the pipeline heater 2, and start collecting the inlet and outlet temperatures and temperature difference values. As the distillation process proceeds, the inlet and outlet temperature difference gradually decreases. When it is less than 3°C, the device automatically stops operating. Open the distillation chamber 4, take out the evaporation membrane bag 5, and put the remaining concentrate or residue after distillation, together with the evaporation membrane bag 5, into the waste storage device to complete the processing of this batch and start the processing of the next batch.

[0060] The urine residue treated by this invention has a solids content of approximately 12.2%, a pH of 1.38, and a conductivity of 71 mS / cm. It can recover 89% of the water content within 6 days. The recovered condensate is of good quality, with an average conductivity of 97.6 μS / cm, an average TOC of 23 mg / L, and an average ammonia nitrogen of 2.2 mg / L. After simple purification, it meets drinking water standards.

[0061] Example 2

[0062] Based on the same inventive concept, the present invention also provides a method for extracting water from an aqueous liquid, using a bag-type membrane distillation apparatus as described in Example 1. The method includes the following steps: adding the aqueous liquid to be treated to the evaporation membrane bag 5 in the distillation chamber 4; turning on the heater to heat the airflow flowing through the distillation chamber to promote the evaporation of the aqueous liquid; measuring the temperature difference between the air inlet and the air outlet; and determining that the evaporation treatment of the aqueous liquid in the evaporation membrane bag 5 is completed when the temperature difference is less than a temperature difference threshold.

[0063] The temperature of the airflow at the air inlet is 30±2℃.

[0064] The temperature difference threshold is 3℃.

[0065] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of the claims of the present invention pending approval.

Claims

1. A bag-type membrane distillation apparatus, characterized in that, The apparatus includes: an evaporation membrane bag for storing and evaporating the aqueous liquid to be treated; a distillation chamber for containing the evaporation membrane bag and having an air outlet and an air inlet capable of allowing a continuous airflow; and a heater for heating the airflow. The evaporation membrane bag is made of a composite membrane that allows water molecules to pass through selectively; The evaporation film bag is made into a closed bag structure with a filling valve by hot-melt welding or adhesive bonding of the composite film; The composite membrane includes a microporous hydrophobic membrane as the inner layer and an ion exchange membrane composited on the outer side of the microporous hydrophobic membrane and selectively permeable to water molecules. The distillation chamber includes a distillation chamber housing with an air outlet and an air inlet, an air passage adaptive mechanism fixed inside the distillation chamber housing for supporting the evaporation film bag to form an air passage, a power supply assembly fixed to the distillation chamber housing, an inlet temperature sensor installed at the air inlet, an outlet temperature sensor installed at the air outlet, a fan located at the air outlet and fixed to the distillation chamber housing, and a controller fixed to the distillation chamber housing; the controller is electrically connected to the power supply assembly, the inlet temperature sensor, the outlet temperature sensor, and the fan, respectively. The adaptive airway mechanism includes: a lower support net for supporting the evaporation film bag and fixing it to the distillation chamber housing; a sliding component fixed inside the distillation chamber housing; an upper support net fixed by the sliding component and forming an evaporation film bag placement space and an evaporation airway with the lower support net; and the upper support net having flexible windproof curtains at both the air outlet and air inlet ends for sealing the outer space of the evaporation airway.

2. The bag-type membrane distillation apparatus as described in claim 1, characterized in that, The filling valve is connected to the evaporation film bag via a hose.

3. The bag-type membrane distillation apparatus as described in claim 1, characterized in that, The microporous hydrophobic membrane is made of PTFE material.

4. The bag-type membrane distillation apparatus as described in claim 1, characterized in that, Both the lower and upper support nets are mesh structures.

5. A bag-type membrane distillation apparatus as described in claim 1, characterized in that, The flexible windproof curtain adopts an accordion-style folding structure.

6. A bag-type membrane distillation apparatus as described in any one of claims 1-5, characterized in that, The air outlet is connected to the condenser via a pipe to collect and recover moisture evaporated from the evaporation membrane bag.

7. A method for extracting water from an aqueous liquid, characterized in that, Using a bag-type membrane distillation apparatus as described in any one of claims 1-5, the method comprises the following steps: Add the water-containing liquid to be treated to the evaporation membrane bag in the distillation chamber; The heater is turned on to heat the airflow passing through the distillation chamber to promote the evaporation of the water-containing liquid; Measure the temperature difference between the air inlet and the air outlet; When the temperature difference is less than the temperature difference threshold, the evaporation process of the water-containing liquid in the evaporation membrane bag is considered to be complete.

8. The method for extracting water from an aqueous liquid as described in claim 7, characterized in that, The temperature of the airflow at the air inlet is 30±2℃.

9. The method for extracting water from an aqueous liquid as described in claim 7, characterized in that, The temperature difference threshold is 3℃.

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