Purification device and method for coking waste water based on membrane distillation

Abstract

The application discloses a coking waste water purification device and method based on membrane distillation. The membrane of the device comprises a first porous membrane, the first porous membrane has air permeable channels, and the surface of the first porous membrane is coated with a photocatalyst; an intermediate porous membrane, the intermediate porous membrane has air permeable channels; and a second porous membrane, the second porous membrane has air permeable channels, and the surface of the second porous membrane is coated with a hydrophilic coating.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of wastewater treatment in environmental engineering, and in particular, relates to a coking wastewater purification device and method based on membrane distillation. BACKGROUND

[0002] Coking wastewater is a kind of high-toxicity and refractory wastewater in coal chemical industry. It has complex composition, contains a large amount of phenolic substances, ammonia substances, and oil substances such as tar, its pH is usually above 8, and the turbidity is very high, and the water temperature can reach 80℃, so it is very difficult to treat. Using membrane distillation technology can help to separate and recover oil and phenolic substances in coking wastewater, and most of the water can be collected and utilized on the condensation side.

[0003] For the membrane distillation, it is a technology for realizing liquid separation and purification by allowing only water vapor and other volatile components to pass through the membrane pores by means of hydrophobic microporous membranes. When there is a certain temperature difference between the two sides of the membrane, there is a vapor pressure difference between the hot and cold sides. The water vapor on the hot side passes through the membrane pores to the cold side under the action of the vapor pressure difference, and condenses into distillate when encountering cooling water or cold air, thereby realizing the purification and separation of non-volatile substances and ionic components. Membrane distillation technology combines the advantages of evaporation and membrane method, and has wide application prospects in the fields of desalination, concentration, separation, and water treatment.

[0004] As described above, although the non-volatile oil and phenolic substances in coking wastewater can be separated to a certain extent by membrane distillation technology, the part of substances that volatilize due to heating during the membrane distillation process cannot be properly and effectively treated, such as a large amount of volatile organic compounds (VOCs) in the wastewater itself. These volatilized substances will pass through the membrane pores together with water vapor to the cold side during the membrane distillation process, and condense into distillate when encountering cooling water or cold air, resulting in the inability to obtain high-quality condensed water.

[0005] In addition, it is worth mentioning that the tar and other substances contained in the coking wastewater as described above are themselves sticky substances, and these sticky substances can easily cause membrane blockage during the purification treatment of coking wastewater by using membrane distillation technology, interrupting the processing progress and processing rhythm. SUMMARY

[0006] 1. Problem to be solved

[0007] Based on the problem of easy blockage during the treatment of coking wastewater by using the existing membrane distillation technology, the present application provides a coking wastewater purification device and method based on membrane distillation, which can solve the problem and also obtain high-quality condensed water.

[0008] 2. Technical solution

[0009] To solve the above problems, the technical scheme adopted by the present application is as follows:

[0010] The present application provides a coking waste water purification device based on membrane distillation, which comprises a water body purification unit, and the water body purification unit comprises:

[0011] a liquid inlet assembly;

[0012] a heating assembly;

[0013] a tubular membrane assembly;

[0014] and an ultraviolet light assembly and a condensing assembly located on both sides of the tubular membrane assembly;

[0015] wherein the tubular membrane assembly is supplied with liquid through the liquid inlet assembly;

[0016] The liquid entering the tubular membrane assembly is heated and vaporized under the action of the heating assembly, and then sequentially passes through the second porous membrane, the intermediate porous membrane and the first porous membrane, and is condensed by the condensing assembly;

[0017] The ultraviolet light assembly provides ultraviolet light for the tubular membrane assembly;

[0018] wherein the tubular membrane assembly comprises a membrane tube, and the membrane constituting the membrane tube comprises:

[0019] a first porous membrane, the first porous membrane having photocatalytic function;

[0020] a second porous membrane, the third porous membrane having a hydrophilic surface.

[0021] According to any embodiment of the first aspect of the present application, the liquid inlet assembly comprises a feed pipe and a water flow controller;

[0022] The feed pipe is in communication with the tubular membrane assembly or a liquid inlet, and the water flow controller is used to control the water flow of the feed pipe.

[0023] According to any embodiment of the first aspect of the present application, the water flow controller comprises a water amount control valve and / or a delivery pump arranged on the feed pipe.

[0024] According to any embodiment of the first aspect of the present application, the water amount control valve is preferably a self-controlled flow control valve.

[0025] According to any embodiment of the fourth aspect of the present application, the delivery pump is a variable frequency water pump.

[0026] According to any embodiment of the first aspect of the present application, the membrane constituting the membrane tube further comprises an intermediate porous membrane located between the first porous membrane and the second porous membrane.

[0027] According to any one of the embodiments of the first aspect of the present application, the first porous membrane comprises a first base membrane selected from at least one of a glass fiber membrane, a polytetrafluoroethylene fiber membrane, a polyvinylidene fluoride fiber membrane;

[0028] The first base membrane is subjected to photocatalyst loading to form the first porous membrane.

[0029] According to any one of the embodiments of the first aspect of the present application, the first base membrane has a thickness of 0.5-2mm and a pore size of 1-300um.

[0030] According to any one of the embodiments of the first aspect of the present application, the first base membrane has a thickness of 1-2mm and a pore size of 10-300um.

[0031] According to any one of the embodiments of the first aspect of the present application, the first porous membrane has a surface with a photocatalyst coating.

[0032] According to any one of the embodiments of the first aspect of the present application, the second porous membrane comprises a second base membrane selected from at least one of a polypropylene fiber membrane, a polyester fiber membrane;

[0033] The second base membrane is subjected to hydrophilic treatment to form the second porous membrane.

[0034] According to any one of the embodiments of the first aspect of the present application, the second base membrane has a thickness of 0.1-2mm and a pore size of 1-300um.

[0035] According to any one of the embodiments of the first aspect of the present application, the second base membrane has a thickness of 1-2mm and a pore size of 10-300um.

[0036] According to any one of the embodiments of the first aspect of the present application, the second porous membrane has a surface with a hydrophilic coating.

[0037] According to any one of the embodiments of the first aspect of the present application, the hydrophilic coating is independently selected from at least one of a calcium chloride coating, a sodium carboxymethyl cellulose coating, a chitosan coating.

[0038] According to any one of the embodiments of the first aspect of the present application, the intermediate porous membrane is selected from at least one of a polyethylene membrane, a polytetrafluoroethylene membrane, a polyvinylidene fluoride membrane, a polyester membrane.

[0039] According to any one of the embodiments of the first aspect of the present application, the intermediate porous membrane has a thickness of 0.1-1mm and a pore size of 0.05-0.25um.

[0040] According to any embodiment of the first aspect of the present application, the tubular membrane assembly comprises a plurality of membrane tubes;

[0041] The membrane tubes are connected in parallel and / or in series.

[0042] According to any embodiment of the first aspect of the present application, the tubular membrane assembly comprises a plurality of membrane tubes connected in series.

[0043] Between two membrane tubes connected in series, a liquid inlet is provided.

[0044] According to any embodiment of the first aspect of the present application, the membrane tube satisfies the length-diameter ratio shown in formula (1):

[0045]

[0046] In the formula:

[0047] L represents the length of the membrane tube, cm;

[0048] D represents the diameter of the membrane tube, cm;

[0049] T represents the design evaporation temperature of the tubular membrane assembly, ℃;

[0050] C represents the COD of the liquid inlet, mg / L;

[0051] Z represents the suspended solids concentration of the liquid inlet, mg / L;

[0052] k1 represents an empirical coefficient, which is selected from 0.5 to 10;

[0053] ε1 represents an adjustment amount, which is determined by test and selected from -5 to 5.

[0054] According to any embodiment of the first aspect of the present application, the liquid inlet assembly comprises a feed pipe and a delivery pump.

[0055] The delivery pump is in communication with the tubular membrane assembly or the liquid inlet through the feed pipe.

[0056] According to any embodiment of the fourth aspect of the present application, a water amount control valve is provided on the feed pipe, which is preferably a self-controlled flow control valve.

[0057] According to any embodiment of the fourth aspect of the present application, the delivery pump is a variable frequency water pump.

[0058] According to any embodiment of the first aspect of the present application, the device further comprises:

[0059] a liquid storage unit in communication with the water body purification unit and used for containing the liquid to be treated;

[0060] and a preheating unit for heating the liquid to be treated.

[0061] The second aspect of the present invention provides a method for purifying lignite wastewater using a lignite wastewater purification device provided by any embodiment of the first aspect of the present invention. During the purification process, pulsed water inflow to the tubular membrane assembly is achieved through a water inlet assembly.

[0062] According to any embodiment of the second aspect of the present invention, the pulsed water inlet follows the rule shown in the following formula (2):

[0063]

[0064] Where:

[0065] t represents the interval between peak flow and trough flow (h);

[0066] Q represents valley flow (m 3 / h);

[0067] C represents the COD content in the wastewater to be treated (g / L);

[0068] S represents the membrane area through which the wastewater to be treated passes (m 2 );

[0069] k0 represents the empirical coefficient, which ranges from 1 to 3;

[0070] ε0 represents the adjustment amount, which ranges from -1 to 1.

[0071] According to any embodiment of the second aspect of the present invention, operation is started in the valley flow state, the flow state is adjusted to the peak flow at interval t, and the duration of operation in the peak flow state is 0.1 to 1 times of t time, wherein the flow size during the peak flow operation is 1.5-3 times the flow size during the valley flow operation. DETAILED DESCRIPTION

[0072] The present disclosure may be more readily understood by reference to the following description in conjunction with the examples, all of which constitute a part of this disclosure. It should be understood that the present disclosure is not limited to the specific products, methods, conditions, or parameters described and / or illustrated herein. Further, the terms used herein are intended only to describe specific embodiments by way of example and are not intended to be limiting unless otherwise indicated.

[0073] It should also be understood that certain features of the disclosure, which are, for clarity, described in the context of separate embodiments, can also be provided in combination in a single embodiment. That is, unless explicitly stated to the contrary, each separate or unique embodiment is considered an embodiment independent of the other embodiments, and all combinations of embodiments are considered to be incorporated into another embodiment. Conversely, various features of the disclosure, which are, for brevity, described in the context of a single embodiment, can also be provided separately or in any subcombination. Finally, while the specific embodiments can be described as a series of steps or as a series of structures, each of the steps and the structures can be considered independent embodiments.

[0074] Unless otherwise stated, it is to be understood that each individual element in a list and every combination of individual elements in that list will be interpreted as a different embodiment. For example, a list of embodiments recited as“A, B, or C” should be interpreted as including the embodiments“A,”“B,”“C,”“A or B,”“A or C,”“B or C,” or“A, B, or C.”

[0075] In the disclosure, the singular forms“a,”“an,” and“the” include their

[0076] Terms including ordinal numbers such as“first” and“second” can be used to explain various components or fluids, but the components, fluids are not limited by the terms. Thus, the terms are used only to distinguish the component / fluid from another component / fluid without departing from the teaching of the disclosure.

[0077] When describing items by using conjunctive terms such as“… and / or …” and the like, the description should be understood to include any one of the associated listed items and all combinations of one or more of them.

[0078] In general, the use of the term“about” indicates an approximation that can vary depending on the desired characteristics obtained by the disclosed subject matter and will be interpreted based on functionality in a context-dependent manner. Thus, a person of ordinary skill in the art will be able to interpret a degree of difference on a case-by-case basis. In some cases, the number of significant digits used in expressing a particular value can be representative of the degree of precision to which the term“about” allows for variation. In other cases, a range of values in a series of values can be used to determine the range of variation allowed by the term“about.” Further, all ranges in the disclosure are inclusive and combinable, and the mention of a value recited in a range includes each value within that range.

[0079] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the meaning and scope of the terms used herein should be clear; and any and all combinations of one or more relevant listed items are intended to be included.

[0080] The following examples are not intended to be specific conditions, according to the conventional conditions or manufacturer recommended conditions. The reagents or instruments used are not specified by the manufacturer, are conventional products that can be obtained by commercial purchase.

[0081] The following embodiments are further described in conjunction with specific examples, but the examples do not make any form of limitation to the present application. Unless otherwise specified, the reagents, methods and equipment used in the present application are conventional reagents, methods and equipment in the art. The essential features and significant effects of the present application can be embodied in the examples described below, which are part of the examples of the present application, but not all examples, therefore, they do not make any limitation to the present application, and those skilled in the art can make some non-essential improvements and adjustments according to the content of the present application, which are within the scope of protection of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0082] Figure 1 The structure diagram of the combined membrane provided for embodiment 1 of the present application is shown in the figure;

[0083] Figure 2 The structure diagram of the membrane tube provided for embodiment 1 of the present application is shown in the figure;

[0084] Figure 3 The structure diagram of the tubular membrane module provided for embodiment 1 of the present application is shown in the figure;

[0085] Figure 4-1 The structure diagram of the water body purification unit provided for embodiment 1 of the present application is shown in the figure;

[0086] Figure 4-2 The structure diagram of the water body purification unit provided for embodiment 1 of the present application is shown in the figure;

[0087] Figure 5 The structure diagram of the water body purification device provided for embodiment 1 of the present application is shown in the figure;

[0088] As Figure 6 The raw semi-coke wastewater described in embodiment 2 of the present application;

[0089] As Figure 7 The concentrated liquid after evaporation of the semi-coke wastewater described in embodiment 2 of the present application;

[0090] As Figure 8 The evaporation condensate after treatment of embodiment 2 of the present application;

[0091] Figure: 1000, water purification unit; 1100, tubular membrane module; 1110, membrane tube; 1111, first porous membrane; 1112, intermediate porous membrane; 1113, second porous membrane; 1120, pipeline; 1121, liquid inlet; 1200, liquid inlet assembly; 1210, feed pipe; 1220, delivery pump;

[0092] 1400, ultraviolet irradiation assembly; 1500, condensation assembly; 1600, chamber;

[0093] 2000, liquid storage unit; 2100, liquid storage tank; 2200, input port; 2300, output port; 2400, suspended matter discharge port;

[0094] 3000, pre-heating unit.

[0095] Example 1

[0096] The present example provides a purification device for treating semi-coke wastewater, as shown in the figure, the water purification device comprises a liquid storage unit 2000, a pre-heating unit 3000 and a water purification unit 1000. Figure 5

[0097] The liquid storage unit 2000 is used for storing liquid to be treated, and based on this, the liquid storage unit 2000 comprises a liquid storage tank 2100, which is provided with a liquid input port 2200, a liquid output port 2300 and a suspended matter discharge port 2400; the output port 2300 of the liquid storage tank 2100 is in communication with the delivery pump 1220 of the water purification unit 1000 through a pipeline;

[0098] The pre-heating unit 3000 is used for heating the liquid in the liquid storage unit 2000.

[0099] The water purification unit 1000, as shown in the figure, comprises a chamber 1600 capable of forming a closed state, a liquid inlet assembly 1200, a heating assembly, a tubular membrane module 1100 located in the chamber, and an ultraviolet irradiation assembly 1400 and a condensation assembly 1500 located on both sides of the tubular membrane module 1100. Figure 4-2

[0100] ​​The liquid inlet assembly 1200 comprises a feed pipe 1210 and a delivery pump 1220, which is communicated with the other end (also called idle end) of the first membrane tube, the other end (also called idle end) of the sixth membrane tube of the tubular membrane assembly and all the liquid inlets 1121 on the pipeline 1120 through the feed pipe 1210; in addition, the feed pipe 1210 can be provided with a water quantity control valve. In the embodiment, the delivery pump 1220 is a variable frequency water pump, and the water quantity control valve provided on the feed pipe 1210 is a self-control type flow control valve.

[0101] The heating assembly can be arranged outside the membrane tube 1110 of the tubular membrane assembly 1100 and close to the accessory of the membrane tube 1110, or arranged in the membrane tube 1110. In the embodiment, the heating assembly is arranged in each membrane tube 1110. The heating assembly can be any existing heater.

[0102] As shown in Figure 4-1 The ultraviolet light irradiation assembly 1400 is arranged on the inner wall of the chamber and can provide ultraviolet light irradiation for the first porous membrane 1111 of the membrane tube 1110. Therefore, the ultraviolet light irradiation assembly 1400 can be a plurality of ultraviolet lamps arranged on the inner wall of the chamber. In the embodiment, the ultraviolet light irradiation assembly 1400 is an ultraviolet lamp.

[0103] The condensing assembly 1500 can be any existing design in the prior art. In the embodiment, the condensing assembly 1500 used is a glass steel grid plate.

[0104] Therefore, under the action of the delivery pump 1220, the liquid to be treated enters each membrane tube 1110 of the tubular membrane assembly 1100 through the feed pipe 1210. At the same time, the heating assembly arranged in the membrane tube 1110 heats the liquid, and then the liquid is evaporated in the form of vapor under the action of the heating assembly, sequentially passes through the second porous membrane 1113, the intermediate porous membrane 1112 and the first porous membrane 1111, and finally is condensed by the condensing assembly 1500. At the same time, the ultraviolet light irradiation assembly 1400 provides ultraviolet light irradiation.

[0105] As shown in Figure 3 The tubular membrane assembly 1100 comprises a plurality of membrane tubes 1100. The number of the membrane tubes 1100 can be flexibly adjusted as required. In the embodiment, the number of the membrane tubes 1100 is six.

[0106] The membrane tube 1100 satisfies the length-diameter ratio shown in formula (1):

[0107]

[0108] In the formula:

[0109] L represents the length of the membrane tube, cm;

[0110] D represents the diameter of the membrane tube, cm;

[0111] T represents the temperature of the liquid evaporated by the design of the tubular membrane module, ℃;

[0112] C represents the COD of the inlet liquid, mg / L;

[0113] Z represents the concentration of suspended solids in the inlet liquid, mg / L;

[0114] k1 represents an empirical coefficient, which is selected from 0.5 to 10;

[0115] ε1 represents an adjustment amount, which is determined by experiments and is selected from -5 to 5.

[0116] In addition, taking the number of the membrane tubes as 6 for further structural description, one end of the first membrane tube is communicated with one end of the second membrane tube through the pipeline 1120, the other end of the second membrane tube is communicated with one end of the third membrane tube through the pipeline 1120, the other end of the third membrane tube is communicated with one end of the fourth membrane tube through the pipeline 1120, the other end of the fourth membrane tube is communicated with one end of the fifth membrane tube through the pipeline 1120, the other end of the fifth membrane tube is communicated with one end of the sixth membrane tube through the pipeline 1120, and the liquid inlet 1121 is arranged on each pipeline 1120. Based on the above, the tubular membrane module 1100 can be liquid from the other end (also known as the idle end) of the first membrane tube, and then sequentially flow into the second, third, fourth, fifth, and sixth membrane tubes, at this time, all the liquid inlets 1121 on the pipeline 1120 are in a closed state, and the other end (also known as the idle end) of the sixth membrane tube is also in a closed state; or the tubular membrane module 1100 can be liquid from the other end of the sixth membrane tube, and then sequentially flow into the fifth, fourth, third, second, and first membrane tubes, at this time, all the liquid inlets 1121 on the pipeline 1120 are in a closed state, and the other end of the first membrane tube is also in a closed state; or the tubular membrane module 1100 can be liquid from any one of the liquid inlets 1121 on the pipeline 1120, at this time, other liquid inlets 1121 on the pipeline 1120 are in a closed state, and the other end of the first membrane tube and the other end of the sixth membrane tube are also in a closed state; or the tubular membrane module 1100 can be liquid from any several liquid inlets 1121 on the pipeline 1120 at the same time, at this time, other liquid inlets 1121 on the pipeline 1120 are in a closed state, and the other end of the first membrane tube and the other end of the sixth membrane tube are also in a closed state.

[0117] As shown in the drawing, the film tube 1110 is in a tubular shape, and the film constituting the tubular film tube 1110 is a composite film, as shown in the drawing, which includes a first porous film 1111, an intermediate porous film 1112, and a second porous film 1113, which are stacked in sequence. Figure 2 Figure 1 The first porous film 1111 has a gas permeation channel and a photocatalytic function, and therefore, the first porous film 1111 can be selected from existing porous films as a first base film, one of the functions of which is to have a gas permeation channel for water vapor to pass through, and the other of which is to be able to load a photocatalyst. Based on this, the first base film can be at least one of, for example, a glass fiber film, a polytetrafluoroethylene fiber film, and a polyvinylidene fluoride fiber film, and is required to have a thickness of 0.5-2 mm and a pore size of 1-300 um. Then, a material having a photocatalytic function (such as forming a photocatalyst coating on the first base film) is loaded on the first base film to form the first porous film 1111, wherein the loading of the material having a photocatalytic function on the first base film can be achieved in any existing technology, such as by dipping and spraying, or by using a photocatalytic coating.

[0118] Further, the main role of the material having a photocatalytic function is to be able to timely degrade volatile organic compounds (VOCs) passing through the first porous film 1111 under the cooperation of ultraviolet light, or to simultaneously form adsorption and degradation, based on which the catalyst can be, for example, metal oxide photocatalytic materials (such as TiO2, Fe2O3, WO3, ZnO, Cu2O, SnO2, etc., among which TiO2 is favored by people due to its stable chemical properties, high catalytic activity, low price, non-toxicity, and non-pollution), metal sulfide photocatalytic materials (such as CdS, ZnS, and MoS2, etc.), Bi-based photocatalytic materials (such as bismuth oxyhalide BiOX (X = Cl, Br, I), BiVO4, Bi2WO6, Bi2MoO6, etc.).

[0119] Further, the main role of the material having a photocatalytic function is to be able to timely degrade volatile organic compounds (VOCs) passing through the first porous film 1111 under the cooperation of ultraviolet light, or to simultaneously form adsorption and degradation, based on which the catalyst can be, for example, metal oxide photocatalytic materials (such as TiO2, Fe2O3, WO3, ZnO, Cu2O, SnO2, etc., among which TiO2 is favored by people due to its stable chemical properties, high catalytic activity, low price, non-toxicity, and non-pollution), metal sulfide photocatalytic materials (such as CdS, ZnS, and MoS2, etc.), Bi-based photocatalytic materials (such as bismuth oxyhalide BiOX (X = Cl, Br, I), BiVO4, Bi2WO6, Bi2MoO6, etc.).

[0120] ​In this embodiment, the first porous membrane 1111 uses a glass fiber membrane as the first base membrane, the thickness of the first base membrane is 0.1 mm, the pore size is 10 um, and TiO2 photocatalyst is loaded on the first base membrane by immersion (see the article Y.S. You et al., "Photocatalytic oxidation of toluene over TiO2 catalysts supported on glass fiber", Korea J. Chem. Eng. 1861. 924-929 (2001)) using a 5 wt% TiO2 solution.

[0121] The intermediate porous membrane 1112 has a gas permeable channel, which mainly functions as a separation functional layer, and can effectively intercept oil and phenolic substances in the waste water of blue carbon, and therefore, the surface of the intermediate porous membrane 1112 is expected to exhibit hydrophobic and oleophobic properties; on this basis, it is further expected that the intermediate porous membrane 1112 has the properties of high temperature resistance, acid and alkali resistance, and chemical corrosion resistance, and based on this, the intermediate porous membrane 1112 can be at least one of, for example, a polyethylene membrane, a polytetrafluoroethylene membrane, a polyvinylidene fluoride membrane, and a polyester membrane, and is required to have a thickness of 0.1-1 mm and a pore size of 0.05-0.25 um.

[0122] In this embodiment, the intermediate porous membrane 1112 uses a polytetrafluoroethylene membrane, which has a thickness of 0.1 mm and a pore size of 0.05 um.

[0123] The second porous membrane 1113 has a gas permeable channel and a hydrophilic surface, and therefore, the second porous membrane 1113 can select an existing porous membrane as the second base membrane, one of the functions of the second base membrane is to have a gas permeable channel for water vapor to pass through, and the second function is to support, and based on this, the second base membrane can be at least one of, for example, a polypropylene fiber membrane and a polyester fiber membrane, and is required to have a thickness of 0.1-2 mm and a pore size of 1-300 um. The second base membrane is then subjected to hydrophilic modification to form the second porous membrane 1113 having a gas permeable channel and a hydrophilic surface, and the hydrophilic modification can be achieved by any existing technology, such as by immersion, coating and spraying, or by using a hydrophilic coating to achieve the surface modification.

[0124] Further, the main purpose of the hydrophilic treatment is to reduce oil adhesion, improve pollution resistance, and prolong the service life of the second porous membrane 1113, and based on this, the hydrophilic material can be, for example, calcium chloride, carboxymethyl cellulose sodium, and chitosan.

[0125] In the embodiment, the second porous membrane 1113 uses a polypropylene fiber membrane as a second base film, with a thickness of 1 mm and a pore size of 1 um. The second base film is subjected to hydrophilic modification treatment by immersing it in a 5wt% calcium chloride solution for 5h (see article Ch Li et al., "Effect of Calcium Chloride on the Surface Properties of Kevlar Fiber", J. APPL. POLYM. SCI. 2015, DOI: 10.1002 / APP.41358): the polypropylene fiber membrane is coated with a calcium chloride solution to load calcium chloride and produce hydrophilicity. Embodiment 2

[0127] In this embodiment, the water purification device provided in Embodiment 1 is used to treat coking waste water.

[0128] The coking waste water has a water volume of 0.2m 3 / h, and is pretreated by the liquid storage unit 2000 to remove floating oil, and is heated to 70℃ by the preheating unit 3000. The water quality indicators are as shown in Table 1:

[0129] Table 1:

[0130]

[0131]

[0132] Based on this, in the embodiment, the diameter D of the membrane tube 1100 is 15 cm, and the evaporation temperature T is designed to be 90℃. The length L is calculated by the length-diameter ratio formula (1):

[0133]

[0134] In the formula, C represents the COD of the inlet liquid, which is 40000 mg / L;

[0135] Z represents the concentration of suspended solids (SS) of the inlet liquid, which is 300 mg / L;

[0136] k1 represents an empirical coefficient, and the value is 1.1;

[0137] ε1 represents an adjustment amount, and the value is -4;

[0138] Based on the above, the length L is calculated to be 207.3 cm, and L is taken as 210 cm.

[0139] It should be noted that the control of the inlet liquid of the water purification device:

[0140] (1) the temperature of the semi-coke wastewater to be treated is controlled at 65-75℃, and the oil content in the liquid is not more than 3000 mg / L;

[0141] (2) the liquid inlet mode of the original liquid is pulse type, and the water flow is divided into peak flow and valley flow, which changes periodically. The change period is related to water quality, and is determined by formula (2). This is an improvement for the properties of semi-coke wastewater containing tar and other viscous substances. The purpose is twofold, one is to prevent the membrane group from being polluted by tar or other easily adhering substances by pulse flow flushing, and the other is to prevent continuous large flow from exceeding the membrane treatment capacity, resulting in increased energy consumption.

[0142]

[0143] In the formula:

[0144] t represents the interval time (h) of peak flow and valley flow;

[0145] Q represents the valley flow (m 3 / h);

[0146] C represents the COD content (g / L) in the wastewater to be treated;

[0147] S represents the membrane area (m 2 ) passed by the wastewater to be treated;

[0148] k0 represents an empirical coefficient, which is valued between 1 and 3;

[0149] ε0 represents an adjustment amount, which is valued between -1 and 1.

[0150] Start running in valley flow state, adjust flow state at interval time t, and the duration of peak flow state is 0.1-1 times of t time, wherein the flow size during peak flow operation is 1.5-3 times of the flow size during valley flow operation.

[0151] The water inlet point (i.e. liquid inlet 1121) is switchable. The flow at the liquid inlet 1121 is higher than that at the liquid outlet, and the switching of the liquid inlet 1121 can flush the previous low-flow point to avoid accumulation of viscous substances in the dead zone. The switching period is affected by the operating parameters, and is generally switched after 50-200 peak-valley flow pulses, which is determined by experiments.

[0152] In the specific embodiment, the water inlet peak-valley flow switching time t is designed and calculated by formula (2):

[0153]

[0154] The peak and valley flow rates are switched every 1 minute. According to the test and experience, the peak flow duration is 1.0 times t; and the flow size during the peak flow operation is 3 times the flow size during the valley flow operation.

[0155] In the embodiment, the liquid inlet 1121 is switched between only two modes:

[0156] (1) liquid is introduced from the other end (also referred to as the idle end) of the first membrane tube, and then sequentially flows into the second, third, fourth, fifth, and sixth membrane tubes, at this time all the liquid inlets 1121 on the pipeline 1120 are in a closed state, and the other end (also referred to as the idle end) of the sixth membrane tube is also in a closed state, and after the end, the concentrated liquid is discharged from the other end (also referred to as the idle end) of the sixth membrane tube;

[0157] (2) the tubular membrane module 1100 is introduced from the liquid inlet 1121 on the pipeline 1120 between the third membrane tube and the fourth membrane tube, at this time all the liquid inlets 1121 on the pipeline 1120 are in a closed state, and the other end of the first membrane tube and the other end of the sixth membrane tube are also in a closed state, and after the end, the concentrated liquid is discharged from the other end (also referred to as the idle end) of the first membrane tube and the sixth membrane tube.

[0158] According to the test results, the switching time of the liquid inlet 1121 is 100 times t, i.e. 100 minutes, and the switching is performed once between the above-mentioned (1) and (2).

[0159] The device is designed to evaporate 20L per hour, and the COD of the condensed water is below 60mg / L. The long-term operation observation equipment can achieve this efficiency, and can be observed for a long time. The basic information is shown in Table 2:

[0160] Table 2:

[0161] Days Daily average condensate COD (mg / L) Daily average condensate production (L) 1 51 475 2 56 478 3 53 476 4 55 477 5 49 474 6 58 479 7 52 475

[0162] According to Table 2, the daily average water production fluctuates within 1.1%, and there is no obvious attenuation, indicating that the membrane module is not obviously blocked. The COD of the condensed water is stable and reaches below 60mg / L, indicating that the treatment effect is good.

[0163] As shown in Figure 6 , it is the raw semi-coke wastewater before treatment as described in Table 1, as shown in Figure 7 , it is the concentrated liquid after evaporation, and as shown in Figure 8 , it is the evaporated condensed water. Embodiment 3

[0165] In this embodiment, the water purification device provided in Embodiment 1 is used to treat semi-coke wastewater.

[0166] The amount of said semi-coke wastewater is 5m 3 The water quality indexes of the sample after the pretreatment and standing to remove floating oil by the liquid storage unit 2000 and heating to 70 DEG C by the pre-heating unit 3000 are shown in Table 3:

[0167] Table 3:

[0168] Serial number Project name Index 1 Oil (mg / L) 3000 2 Total phenol (mg / L) 9000 3 Volatile phenol (mg / L) 5500 4 Total nitrogen (mg / L) 3000 5 Ammonia nitrogen (mg / L) 2000 6 CODcr(mg / L) 50000 7 SS (mg / L) 500 8 Dissolved solids (mg / L) 5000 9 pH value 8.5～8.9 10 Colority 300 times

[0169] Therefore, in the embodiment, the diameter D of the membrane tube 1100 is 35 cm, the designed evaporation temperature T is 100 DEG C, and the length L is calculated by the length-diameter ratio formula (1):

[0170]

[0171] The calculated length L is 457 cm, and L is taken as 460 cm.

[0172] According to the situation, the designed water inlet peak-valley flow switching time t is calculated by formula (2):

[0173]

[0174] The peak-valley flow is switched once every 3 min. According to the test and experience, the peak flow duration is taken as 0.5 times of t, and the flow size during the peak flow operation is 1.5 times of the flow size during the valley flow operation.

[0175] In the embodiment, the liquid inlet 1121 switching is only between the following four:

[0176] (1) liquid inlet from the other end (also called idle end) of the first membrane tube, and then sequentially flow into the second, third, fourth, fifth and sixth membrane tubes, at this time all the liquid inlets 1121 on the pipeline 1120 are in a closed state, the other end (also called idle end) of the sixth membrane tube is also in a closed state, and after the end, the concentrated liquid is discharged from the other end (also called idle end) of the sixth membrane tube;

[0177] (2) liquid inlet from the other end (also called idle end) of the sixth membrane tube, and then sequentially flow into the fifth, fourth, third, second and first membrane tubes, at this time all the liquid inlets 1121 on the pipeline 1120 are in a closed state, the other end (also called idle end) of the first membrane tube is also in a closed state, and after the end, the concentrated liquid is discharged from the other end (also called idle end) of the first membrane tube;

[0178] (3) the tubular membrane module 1100 takes in liquid from the liquid inlet 1121 on the pipeline 1120 between the third membrane tube and the fourth membrane tube, at this time, other liquid inlets 1121 on the pipeline 1120 are in a closed state, and the other end of the first membrane tube and the other end of the sixth membrane tube are also in a closed state, and after the end, the concentrated liquid is discharged from the other end of the first membrane tube and the other end of the sixth membrane tube (also known as the idle end).

[0179] (4) the tubular membrane module 1100 takes in liquid from the other end of the first membrane tube and the other end of the sixth membrane tube at the same time, and after the end, the concentrated liquid is discharged from the liquid inlet 1121 on the pipeline 1120 between the third membrane tube and the fourth membrane tube, and other liquid inlets 1121 on the pipeline 1120 are in a closed state.

[0180] According to the test results, the switching time of the liquid inlet 1121 is 100 times t, that is, 300 min switching once, and the above (1), (2), (3), (4) four modes are switched.

[0181] The device is designed to evaporate 200L per hour, and the COD of the condensed water is below 70mg / L. Long-term operation observation equipment can achieve this efficiency, and can be observed for long-term maintenance. The basic information is shown in Table 4:

[0182] Table 4:

[0183] Days Daily average condensate COD (mg / L) Daily average condensate production (L) 1 56 4777 2 66 4786 3 63 4796 4 65 4787 5 59 4784 6 58 4792 7 62 4795

[0184] According to Table 4, the average daily water production fluctuates within 1%, and there is no obvious attenuation, indicating that the membrane module is not obviously blocked. The COD of the condensed water is stable and reaches below 70mg / L, indicating that the treatment effect is good.

[0185] The above only describes the preferred embodiments of the present application, and it should be noted that for ordinary skilled persons in the technical field, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should be considered as the protection range of the present application.

Claims

1. A semi-coal wastewater purification device based on membrane distillation, characterized in that: The device includes a water purification unit, and the water purification unit includes: Liquid inlet assembly; Heating components; Tubular membrane modules; and an ultraviolet illumination component and a condensation component located on both sides of the tubular membrane component; Wherein, the tubular membrane module is fed with liquid through the liquid inlet module; The liquid entering the tubular membrane module is heated and vaporized under the action of the heating component, and passes through the second porous membrane, the middle porous membrane and the first porous membrane in sequence, and is condensed by the condensation component; The ultraviolet illumination component provides ultraviolet illumination for the tubular membrane assembly; Wherein, the tubular membrane module includes a membrane tube, and the membrane constituting the membrane tube includes: a first porous membrane, wherein the first porous membrane comprises a first base membrane, and the first base membrane is loaded with a photocatalyst to form the first porous membrane; a second porous membrane, wherein the second porous membrane comprises a second base membrane, the second base membrane being selected from at least one of a polypropylene fiber membrane and a polyester fiber membrane, and the second base membrane is subjected to a hydrophilic treatment to form the second porous membrane; The membranes constituting the membrane tube further include: an intermediate porous membrane located between the first porous membrane and the second porous membrane; The membrane tube satisfies the aspect ratio shown in formula (1): （1） Where: L represents the length of the membrane tube, cm; D represents the membrane tube diameter, cm; T represents the designed evaporation liquid temperature of the tubular membrane module, °C; C represents the COD of the influent, mg / L; Z represents the suspended solids concentration of the influent, mg / L; k1 represents the empirical coefficient, which ranges from 0.5 to 10; ε1 represents the adjustment amount, which is determined by experiments and takes a value between -5 and 5.

2. The semi-coke wastewater purification device based on membrane distillation according to claim 1, characterized in that: The liquid inlet assembly includes a feed pipe and a water inlet flow controller; The feed pipe is communicated with the tubular membrane assembly or the liquid inlet, and the water inlet flow controller is used to control the water inlet flow of the feed pipe.

3. The semi-coke wastewater purification device based on membrane distillation according to claim 2, characterized in that, The thickness of the first base film is 0.5-2 mm, and the pore size is 1-300 um.

4. The semi-coke wastewater purification device based on membrane distillation according to claim 2, characterized in that: The thickness of the second base film is 0.1-2 mm, and the pore size is 1-300 um.

5. The semi-coke wastewater purification device based on membrane distillation according to claim 2, characterized in that: The thickness of the intermediate porous membrane is 0.1-1 mm, and the pore size is 0.05-0.25 μm.

6. The semi-coke wastewater purification device based on membrane distillation according to any one of claims 1 to 5, characterized in that: The tubular membrane module includes a number of membrane tubes; The membrane tubes are connected in parallel and / or in series.

7. The semi-carbon wastewater purification device based on membrane distillation according to claim 6, characterized in that The device further comprises: A liquid storage unit connected to the water purification unit through a water inlet assembly and used to receive the liquid to be treated, and a preheating unit for heating the liquid to be treated.

8. A method for purifying blue carbon wastewater, characterized in that: A method for purifying blue carbon wastewater using the purification device according to any one of claims 1 to 7; During the purification process, pulsed water inflow to the tubular membrane assembly is achieved through the water inlet assembly.

9. The method for purifying blue carbon wastewater according to claim 8, wherein The pulsed water inlet follows the rule shown in the following formula (2): （2） Where: t represents the interval between peak flow and valley flow (h); Q represents the valley flow (m 3 / h); C represents the COD content in the wastewater to be treated (g / L); S represents the membrane area through which the wastewater to be treated passes (m 2 ); k0 represents the empirical coefficient, which ranges from 1 to 3; ε0 represents the adjustment amount, which ranges from -1 to 1.

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