Zero-discharge treatment method for salt-containing mine well water for in-situ descaling of external cooler

Abstract

The invention relates to the technical field of salt-containing mine water treatment, and discloses a salt-containing mine water zero discharge treatment method for external cooler in-situ descaling, which comprises the following steps: S1, carrying out suspended matter removal and membrane concentration on salt-containing mine water, and sequentially carrying out evaporative crystallization to separate anhydrous Na2SO4, freezing crystallization to separate mirabilite, evaporative crystallization to separate NaCl and drying to obtain carnallite; collecting steam condensate water formed after heat exchange of the steam condensate water used in the evaporative crystallization and steam condensate water evaporated in the drying process; s2, when scale is formed in a cold exchange pipe of the external cooler used in the freezing crystallization process in the step S1, the scale is removed by adopting the following method: refrigerating fluid in the external cooler is subjected to heat exchange by adopting the steam condensate water collected in the step S1, and then flows back into a refrigerating fluid pipeline of the external cooler; and / or live steam is introduced into the cold exchange pipe. According to the method, in-situ descaling can be achieved under the condition that the external cooler is not disassembled, the labor cost can be reduced, and the salt separation crystallization treatment efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of salt mine water treatment, and in particular to a zero-discharge treatment method for salt mine water with in-situ descaling of an external cooler. Background Art

[0002] Saline mine water refers to mine water with a salt content of more than 1000 mg / L. It is produced along with coal mining and is characterized by large production volume, high salt content, and complex composition. At present, for this type of mine water, the main methods of pretreatment, membrane concentration, and salt separation and crystallization are used to achieve zero-emission treatment, that is, to remove suspended matter in the mine water through a pretreatment process, to remove salt in the mine water through a membrane concentration process, to obtain product water, and finally to perform salt separation and crystallization on the highly concentrated brine produced by the membrane concentration process, to turn the salt in the concentrated brine into solids, and to realize the resource utilization of the salt in the concentrated brine.

[0003] In the process of zero-discharge treatment of saline mine water, frozen crystallization is a key link in salt separation and crystallization. It further extracts the sodium sulfate component in the mother liquor, converts it into mirabilite, and dissolves it to form a sodium sulfate solution, which is returned to the sodium sulfate evaporation and crystallization system for further evaporation and concentration. This can not only increase the crystallization yield of sodium sulfate, but also effectively reduce the amount of impure salts. However, in the actual operation process, due to the rapid crystallization during the frozen crystallization process, scaling is easily generated, which will lead to the failure to timely detect the blockage of the external cooler exchange pipe, causing the frozen crystallization system to be paralyzed, increasing the difficulty of cleaning, and increasing the impure salt rate and the operation and processing costs.

[0004] In the past, when the freezing crystallization system encountered the problem of blockage of the cooling tube of the external cooler, the system could only be forced to suspend operation and remove the scale by disassembly, soaking, etc., which would inevitably shorten the service life of the freezing crystallization system. Considering the occurrence of such situations, some coal mines have set up two external coolers in the freezing crystallization system that can meet the processing load. When one external cooler is blocked, it is switched to another external cooler. Although the freezing crystallization system can be maintained in operation, the first external cooler is disassembled and the scale on the surface of the cooling tube is removed by soaking, which greatly increases the labor cost. Summary of the invention

[0005] In order to solve the above technical problems, namely, the existing zero-discharge treatment system for saline mine water is heavy, and the external cooler used for freezing crystallization cannot be descaled in situ, and must be disassembled for descaling, which increases labor costs, the present invention provides a zero-discharge treatment method for saline mine water with in-situ descaling of the external cooler. The method of the present invention can achieve in-situ descaling without disassembling the external cooler, which can reduce labor costs and improve the efficiency of salt separation crystallization treatment.

[0006] The specific technical scheme of the present invention is: A zero-discharge treatment method for saline mine water with in-situ descaling of an external cooler, comprising the following steps: S1: After removing suspended solids and membrane concentrating the salt-containing mine water, evaporation and crystallization are performed in sequence to separate anhydrous Na2SO4, freezing and crystallization are performed to separate sodium sulfate, evaporation and crystallization are performed to separate NaCl, and drying is performed to obtain miscellaneous salts; steam condensed water formed after heat exchange with steam condensed water used in the evaporation and crystallization, and steam condensed water evaporated in the drying process are collected; S2: When scaling forms inside the cooling tube of the external cooler used in the freezing crystallization process of S1, the following scheme A and / or scheme B shall be used for descaling: Solution A: The refrigerant in the external cooler is heat exchanged with the steam condensate collected in S1 and then flows back into the refrigerant pipeline of the external cooler; Option B: Introduce raw steam into the cooling pipes.

[0007] The present invention adopts a step-by-step crystallization method in the process of zero-discharge treatment of saline mine water. Anhydrous Na2SO4 is first separated by evaporative crystallization, then mirabilite is separated by freezing crystallization, and then NaCl is separated by evaporative crystallization, and finally the impure salt is obtained by drying. This method fully considers the water quality characteristics of the saline mine water, can realize salt separation crystallization, and recover most of the sodium sulfate and sodium chloride and a small amount of impurities therein.

[0008] In the zero-discharge treatment system for salt-containing mine water, the scaling components in the cooling tube of the external cooler are relatively complex, including calcium, magnesium, bicarbonate, silicon and other substances. The present invention designs Scheme A and Scheme B for these specific scaling components. In Scheme A, the heat in the steam condensed water generated during the salt separation crystallization (including evaporative crystallization to separate anhydrous Na2SO4, evaporative crystallization to separate NaCl, and drying to obtain miscellaneous salts) is used to heat the refrigerant (the working fluid circulating in it when the external cooler is working normally), and the heated refrigerant is refluxed into the external cooler to exchange heat with the mother liquor of scaling attached to the inner wall of the cooling tube, which can eliminate the scaling and recycle the heat in the steam condensed water. In Scheme B, by passing raw steam into the cooling tube, the scaling attached to the inner wall of the cooling tube is directly heated, which can also achieve the purpose of eliminating scaling. Through the above-mentioned method, in-situ descaling can be achieved without disassembling the external cooler, so that the freezing crystallization unit can operate stably. This descaling method is conducive to reducing labor costs and improving the efficiency of salt separation crystallization treatment.

[0009] Preferably, in step S2, scheme A is first used for descaling, and then scheme B is used for descaling; the ratio of the duration of descaling by scheme A to that of descaling by scheme B is 1:1-2.

[0010] Based on the analysis of the causes of scaling in the external cooler in the zero-discharge treatment system for saline mine water, the scaling contains water-soluble scaling components (mainly soluble inorganic salts, such as sodium sulfate and sodium carbonate) and hard scaling components (mainly insoluble inorganic salts of calcium, magnesium and silicon). For water-soluble scaling components, Scheme A or Scheme B can achieve better descaling. However, for hard scaling components, the effect is not good when Scheme A or Scheme B is used alone. The present invention first performs scheme A, using the refrigerant that has been heated by heat exchange with steam condensate to heat the scale in the cooling tube, so that the scale layer is partially dissolved or peeled off. Since the heated refrigerant heats the cooling tube outside the cooling tube, it is beneficial for the side of the scaling layer close to the tube wall to be better heated and then partially dissolved or peeled off, thereby generating more gaps that penetrate the scaling layer in the scaling layer, which is beneficial for the subsequent raw steam to fully contact the scaling layer and improve the effect of the raw steam; then scheme B is performed, and raw steam is introduced into the cooling tube to contact the scale in the cooling tube, which can provide water and external force to further dissolve and peel off the remaining hard scale components. In the above manner, scheme A and scheme B are used in combination in a specific order, which can improve the descaling effect (especially the descaling effect when the scaling layer is thick), and effectively remove water-soluble scale components and hard scale components.

[0011] Preferably, in step S2, when the liquid pressure at the outlet of the cooling tube increases by 50-400% compared with normal operation, the flow rate decreases by 35% or more and the flow rate is not 0, the hardness increases by 40-125%, and the signal detected at 0.40-0.45ms under 50-100kHz ultrasound in the cooling tube shows a deformed irregular wavelength, or when the flow rate at the outlet of the cooling tube is 0, scheme A and / or scheme B is used for descaling.

[0012] The descaling method of the present invention can be used for descaling in two situations: scaling occurs in the cooling tube but does not cause complete blockage in the cooling tube, and scaling causes complete blockage of the cooling tube. "Scaling causes complete blockage of the cooling tube" means that when operating according to step S1, the flow rate at the outlet of the cooling tube is 0.

[0013] The judgment standard of "scaling occurs in the cooling tube but does not cause complete blockage in the cooling tube" in the present invention is that when operating according to step S1, "the liquid pressure at the outlet of the cooling tube is increased by 50-400% compared with the normal operation, the flow rate is reduced by 35% or more and is not 0, the hardness is increased by 40-125%, and the signal at 0.40-0.45ms detected under 50-100kHz ultrasound in the cooling tube shows a deformed irregular wavelength". Among them, the liquid pressure, flow rate and hardness can be monitored in real time by an online pressure gauge, flow meter and hardness meter installed at the outlet of the cooling tube, and the ultrasonic signal can be monitored in real time by an ultrasonic meter installed in the cooling tube. The scaling of the cooling tube can be judged in time by the change of the feedback signal to avoid paralysis of the cooling crystallization unit due to blockage of the cooling tube.

[0014] Liquid pressure, flow, hardness and ultrasonic signal are four factors that play important roles in the scaling process of the external cooler, and they interact and influence each other. Therefore, when judging "scaling occurs in the cooling tube but does not cause complete blockage in the cooling tube", taking them as a whole and considering these factors comprehensively can make the judgment of scaling in the cooling tube more accurate. Specifically: (1) Liquid pressure and flow: Liquid pressure and flow rate are key factors that determine the water flow velocity and flow state in the cooling tube, and directly affect the subsequent formation and deposition rate of the scale layer. Specifically: a higher water flow velocity can reduce the deposition of the scale layer on the inner wall of the cooling tube, because the water flow will wash away part of the scale layer. However, too high a water flow velocity may also cause impurities and ions in the water to deposit on the inner wall of the cooling tube more quickly, forming a harder scale layer; different flow states (such as laminar flow and turbulent flow) will affect the distribution and morphology of the scale layer. For example, the turbulent state can more effectively wash the scale layer, while the laminar state may cause the scale layer to accumulate in a specific area.

[0015] (2) Hardness: Hardness is an indicator of the content of metal ions such as calcium and magnesium in water. These ions easily form a scale layer on the inner wall of the crystallizer, which has a negative impact on the normal operation of the external cooler. Therefore, the change in hardness can reflect the content of metal ions entering the water from the scale layer.

[0016] (3) Ultrasonic signal: Ultrasonic measurement reflects the thickness, density and hardness of the scale layer through the propagation speed and attenuation of ultrasonic waves in the medium.

[0017] (4) Mutual influence among various factors: The four factors of liquid pressure, flow, hardness and ultrasonic signal affect each other during the operation of the external cooler. For example, changes in flow will affect the propagation speed and attenuation of ultrasonic waves, and changes in hardness will affect the formation and deposition rate of scale.

[0018] Preferably, step S1 specifically includes: S1.1: After removing suspended solids and concentrating the salty mine water through membrane, concentrated brine is obtained; S1.2: After the concentrated brine is heat exchanged with steam condensation, it is heated for crystallization and concentration, and the resulting slurry is thickened, centrifuged and dried to obtain anhydrous Na2SO4; the steam condensate formed after the steam condensation heat exchange is collected; the liquid separated during the thickening and centrifugation process is collected and recorded as mother liquor A; S1.3: The mother liquor A is passed into the cooling pipe of the external cooler for freezing, crystallization and concentration. The obtained slurry is thickened and centrifuged to obtain mirabilite. The liquid separated during the thickening and centrifugation process is collected and recorded as mother liquor B. S1.4: After the mother liquor B is subjected to heat exchange with steam condensation, it is heated for crystallization and concentrated, and the resulting slurry is thickened, centrifuged and dried to obtain NaCl; the steam condensate formed after the steam condensation heat exchange is collected; the liquid separated during the thickening and centrifugation process is collected and recorded as mother liquor C; S1.5: Dry the mother liquor C to obtain impure salts, and collect the steam condensed water.

[0019] Preferably, in step S1.3: the obtained sodium sulfate is dissolved in the concentrated brine after heat exchange in S1.2, and then heated for crystallization and concentration. The obtained slurry is thickened, centrifuged and dried to obtain anhydrous Na2SO4.

[0020] Preferably, after collecting mother liquor A, mother liquor A is first heat exchanged with cooling water and then heat exchanged with mother liquor B. The mother liquor A after heat exchange is subjected to step S1.3, and the mother liquor B after heat exchange is subjected to step S1.4.

[0021] Preferably, in step S1.2: the temperature of the steam condensed water is 105-143°C, and the absolute pressure is 120-400 kPa; the temperature of heating crystallization and concentration is 100-110°C; the mass concentrations of sodium chloride and sodium sulfate in the mother liquor A are 18.0-25.9% and 4.0-11.0%, respectively.

[0022] Preferably, in step S1.3: the temperature of the freezing crystallization and concentration is -5 to 0°C; the mass concentrations of sodium chloride and sodium sulfate in the mother liquor B are 20.0 to 25.6% and 0.5 to 1.2%, respectively.

[0023] Preferably, in step S1.4: the temperature of the steam condensed water is 105-143°C, and the absolute pressure is 120-400 kPa; the temperature of heating crystallization and concentration is 100-110°C; the mass concentration of sodium chloride in the mother liquor C is 25.9%-28.2%, and the mass concentration of sodium sulfate is 0.0%-4.5%.

[0024] Preferably, in step S1.5: air heated by steam is used as a heat source to dry the mother liquor C.

[0025] Preferably, in step S2: in scheme A, the temperature of the refrigerant after heat exchange is 40-60°C.

[0026] Preferably, in step S2: in scheme B, the temperature of the raw steam introduced into the cooling pipe is 105-143° C., and the absolute pressure is 120-400 kPa.

[0027] Compared with the prior art, the present invention has the following advantages: (1) The present invention utilizes the steam condensate recovered during the salt separation crystallization process to heat the refrigerant in the external cooler, or introduces live steam into the cooling pipe of the external cooler, thereby achieving in-situ descaling of the external cooler without disassembling the external cooler, which is beneficial to reducing labor costs and improving the efficiency of the salt separation crystallization process.

[0028] (2) In the present invention, the scale in the cooling tube is heated by first using the refrigerant liquid that has been heated by heat exchange with steam condensate, and then raw steam is introduced into the cooling tube. This can improve the descaling effect (especially the descaling effect when the scaling layer is thick) and effectively remove water-soluble scale components and hard scale components.

[0029] (3) The present invention adopts a method of monitoring the liquid pressure, flow rate, hardness at the inlet and outlet ends of the cooling tube, as well as the ultrasonic signal inside the cooling tube. It can timely judge the scaling condition in the cooling tube according to the change of the feedback signal, and can effectively avoid the paralysis of the cooling crystallization unit caused by the blockage of the cooling tube. Moreover, by comprehensively considering these factors, the scaling condition in the cooling tube can be judged more accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The present invention is a flow chart of the zero-discharge treatment process of saline mine water.

[0031] Figure 2 It is a schematic diagram of the zero-discharge treatment system for saline mine water of the present invention (the external cooler descaling unit is not shown).

[0032] Figure 3 It is a schematic diagram of the descaling unit of the external cooler in the present invention.

[0033] The accompanying drawings are marked as: concentrated brine tank 1, heat exchanger I 2, steam condensate tank I 3, heater I 4, separator I 5, thickener I 6, centrifuge I 7, mother liquor A tank 8, heat exchanger II 9, heat exchanger III 10, external cooler 11, freezing crystallizer 12, thickener II 13, centrifuge II 14, mother liquor B tank 15, preheating mother liquor B tank 16, heat exchanger IV 17, steam condensate tank II 18, heater II 19, separator II 20, thickener III 21, centrifuge III 22, mother liquor C tank 23, dryer 24, dissolver 25, pressure gauge 26, flow meter 27, hardness tester 28, ultrasonic meter 29, heat exchanger V 30, electric steam boiler 31, and temperature and pressure reduction device 32. DETAILED DESCRIPTION

[0034] The present invention will be further described below in conjunction with the embodiments.

[0035] Overall embodiment A zero-discharge treatment method for saline mine water with in-situ descaling of an external cooler, comprising the following steps: S1: After removing suspended solids and membrane concentrating the salt-containing mine water, evaporation and crystallization are performed in sequence to separate anhydrous Na2SO4, freezing and crystallization are performed to separate sodium sulfate, evaporation and crystallization are performed to separate NaCl, and drying is performed to obtain miscellaneous salts; steam condensed water formed after heat exchange with steam condensed water used in the evaporation and crystallization, and steam condensed water evaporated in the drying process are collected; S2: When scaling forms inside the cooling tube of the external cooler used in the freezing crystallization process of S1, the following scheme A and / or scheme B shall be used for descaling: Solution A: The refrigerant in the external cooler is heat exchanged with the steam condensate collected in S1 and then flows back into the refrigerant pipeline of the external cooler; Option B: Introduce raw steam into the cooling pipes.

[0036] In some specific embodiments, in step S2, when the liquid pressure at the outlet of the cooling tube increases by 50-400% compared with normal operation, the flow rate decreases by 35% or more and the flow rate is not 0, the hardness increases by 40-125%, and the signal at 0.40-0.45ms detected under 50-100kHz ultrasound in the cooling tube shows a deformed irregular wavelength, or when the flow rate at the outlet of the cooling tube is 0, scheme A and / or scheme B is used for descaling.

[0037] In some specific implementations, in step S2, scheme A is first used for descaling, and then scheme B is used for descaling; the ratio of the duration of descaling by scheme A to that of descaling by scheme B is 1:1-2.

[0038] In some specific embodiments, in step S2: in scheme A, the temperature of the refrigerant after heat exchange is 40-60°C.

[0039] In some specific embodiments, in step S2: in scheme B, the temperature of the raw steam introduced into the cooling tube is 105-143° C., and the absolute pressure is 120-400 kPa.

[0040] In some specific implementations, step S1 specifically includes: S1.1: After removing suspended solids and concentrating the salty mine water through membrane, concentrated brine is obtained; S1.2: After the concentrated brine is heat exchanged with steam condensation, it is heated for crystallization and concentration, and the resulting slurry is thickened, centrifuged and dried to obtain anhydrous Na2SO4; the steam condensate formed after the steam condensation heat exchange is collected; the liquid separated during the thickening and centrifugation process is collected and recorded as mother liquor A; S1.3: The mother liquor A is passed into the cooling pipe of the external cooler for freezing, crystallization and concentration. The obtained slurry is thickened and centrifuged to obtain mirabilite. The liquid separated during the thickening and centrifugation process is collected and recorded as mother liquor B. S1.4: After the mother liquor B is subjected to heat exchange with steam condensation, it is heated for crystallization and concentrated, and the resulting slurry is thickened, centrifuged and dried to obtain NaCl; the steam condensate formed after the steam condensation heat exchange is collected; the liquid separated during the thickening and centrifugation process is collected and recorded as mother liquor C; S1.5: Dry the mother liquor C to obtain impure salts, and collect the steam condensed water.

[0041] As a specific implementation, in step S1.3: dissolving the obtained sodium sulfate with the concentrated brine after heat exchange in S1.2, heating for crystallization and concentration, thickening the obtained slurry, centrifuging and drying to obtain anhydrous Na2SO4.

[0042] As a specific implementation, after collecting mother liquor A, mother liquor A is first heat exchanged with cooling water, and then heat exchanged with mother liquor B. The mother liquor A after heat exchange is subjected to step S1.3, and the mother liquor B after heat exchange is subjected to step S1.4.

[0043] As a specific implementation, in step S1.2: the temperature of the steam condensed water is 105-143°C, and the absolute pressure is 120-400 kPa; the temperature of heating crystallization and concentration is 100-110°C; the mass concentrations of sodium chloride and sodium sulfate in the mother liquor A are 18.0-25.9% and 4.0-11.0%, respectively.

[0044] As a specific implementation, in step S1.3: the temperature of the freezing crystallization and concentration is -5 to 0°C; the mass concentrations of sodium chloride and sodium sulfate in the mother liquor B are 20.0 to 25.6% and 0.5 to 1.2%, respectively.

[0045] As a specific implementation, in step S1.4: the temperature of the steam condensed water is 105-143°C, and the absolute pressure is 120-400 kPa; the temperature of heating crystallization and concentration is 100-110°C; the mass concentration of sodium chloride in the mother liquor C is 25.9%-28.2%, and the mass concentration of sodium sulfate is 0.0%-4.5%.

[0046] As a specific implementation, in step S1.5: air heated by steam is used as a heat source to dry the mother liquor C. Specific embodiments The present invention is described below by specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. Without departing from the spirit and scope of the inventive concept, changes and advantages that can be thought of by those skilled in the art are included in the present invention, and the attached claims and any equivalents thereof are the protection scope of the present invention.

[0048] Unless otherwise defined, all technical terms and scientific terms used in the present invention have the same meanings as those commonly understood by ordinary technicians in the field to which the present disclosure belongs. Unless otherwise specified, the raw materials and equipment used in the present invention are conventional raw materials and equipment in the field and can be obtained from conventional commercial channels; unless otherwise specified, the methods used in the present invention are conventional methods in the field.

[0049] Example 1 This embodiment provides a zero-discharge treatment method for salt-containing mine water with in-situ descaling of an external cooler, and the process is as follows: Figure 1 As shown, the system used is as Figure 2 and Figure 3 As shown, the specific process is as follows: (1) Preprocessing unit (in Figure 2 Not shown): After the suspended matter in the salty mine water is removed, membrane concentration is performed to obtain concentrated brine, which is stored in a concentrated brine tank 1 .

[0050] (2) Sodium sulfate evaporation crystallization unit: The concentrated brine is passed into the heat exchanger 12 to exchange heat with the steam condensate; the steam condensate forms steam condensate after heat exchange and is stored in the steam condensate tank 13; the concentrated brine after heat exchange is passed into the heater 14, and after circulating heating, crystallization and concentration in the heater 14 and the separator 15, the crystal slurry is discharged. The crystal slurry is thickened by the thickener 16 and centrifuged by the centrifuge 17, and then dried to obtain anhydrous sodium sulfate; the liquid separated in the thickener 16 and the centrifuge 17 is collected, recorded as mother liquor A, and stored in the mother liquor A tank 8.

[0051] In the above process: the temperature of the concentrated brine entering the heat exchanger I2 is 20°C, and the mass flow rate is 16.0 t / h; the temperature of the steam condensate entering the heat exchanger I2 is 116°C, and the absolute pressure is 180 kPa; the temperature of the feed liquid for circulating heating, crystallization and concentration in the heater I4 and the separator I5 is 108°C; in the sodium sulfate evaporation and crystallization unit, 13.35 t / h of steam condensate, 1.05 t / h of mother liquor A, and 1.67 t / h of anhydrous sodium sulfate are obtained; the mass concentration of sodium chloride in the mother liquor A is 20.00%, and the mass concentration of sodium sulfate is 6.9%.

[0052] (3) Glauber's Salt Freezing Crystallization Unit: The mother liquor A is passed into the heat exchanger II 9, and after heat exchange with the circulating cooling water, it is passed into the heat exchanger III 10 to exchange heat with the mother liquor B to achieve precooling of the mother liquor A. The precooled mother liquor A is passed into the cooling pipe of the external cooler 11, and after circulating freezing crystallization and concentration in the external cooler 11 and the freezing crystallizer 12, the crystal slurry is discharged. After the crystal slurry is thickened by the thickener II 13 and centrifuged by the centrifuge II 14, Glauber's salt is obtained; the liquid separated in the thickener II 13 and the centrifuge II 14 is collected and recorded as mother liquor B, and stored in the mother liquor B tank 15. The Glauber's salt is passed into the dissolver 25, and a part of the concentrated brine preheated by the heat exchanger I 2 is used for dissolution, and then passed into the heater I 4, and merged with the other part of the concentrated brine preheated by the heat exchanger I 2.

[0053] In the above process: the temperature of the circulating frozen crystallization and concentrated liquid in the external cooler 11 and the frozen crystallizer 12 is 0°C; in the thenardite frozen crystallization unit, 0.16t / h of thenardite and 0.90t / h of mother liquor B are obtained; the mass concentration of sodium chloride in the mother liquor B is 23.5%, and the mass concentration of sodium sulfate is 1.10%.

[0054] (4) Sodium chloride evaporation crystallization unit: The mother liquor B is passed into the heat exchanger III 10, and after heat exchange with the mother liquor A, a preheated mother liquor B is obtained, which is stored in the preheated mother liquor B tank 16. The preheated mother liquor B is passed into the heat exchanger IV 17, and heat exchange is performed with the steam condensate; the steam condensate forms steam condensate after heat exchange, which is stored in the steam condensate tank II 18; the preheated mother liquor B after heat exchange is passed into the heater II 19, and after cyclic heating, crystallization and concentration in the heater II 19 and the separator II 20, the crystal slurry is discharged. The crystal slurry is thickened by the thickener III 21 and centrifuged by the centrifuge III 22, and then dried to obtain sodium chloride; the liquid separated in the thickener III 21 and the centrifuge III 22 is collected, recorded as mother liquor C, and stored in the mother liquor C tank 23.

[0055] In the above process: the temperature of the steam condensate entering the heat exchanger IV 17 is 116°C and the absolute pressure is 180 kPa; the temperature of the feed liquid for circulating heating, crystallization and concentration in the heater II 19 and the separator II 20 is 110°C; in the sodium chloride evaporation crystallization unit, 0.50 t / h of steam condensate, 0.23 t / h of mother liquor C and 0.15 t / h of sodium chloride (meeting the standard for refined industrial salt) are obtained; the mass concentration of sodium chloride in the mother liquor C is 25.9%, and the mass concentration of sodium sulfate is 4.2%.

[0056] (5) Mother liquor drying unit: The mother liquor C is lifted to the dryer 24, and the steam-heated air is used as a heat source to evaporate and dehumidify the moisture in the mother liquor, thereby achieving the purpose of drying and obtaining impurities; the steam condensed water evaporated during the drying process is collected.

[0057] In the mother liquor drying unit, 0.05t / h of impurities and 0.15t / h of steam condensate are obtained.

[0058] (6) Descaling unit: During the operation of the system, the pressure gauge 26, flow meter 27 and hardness meter 28 installed at the inlet and outlet of the cooling pipe of the external cooler 11, as well as the ultrasonic meter 29 installed in the cooling pipe, are used for real-time monitoring. When the system is operating normally, the pressure value detected at the outlet is 41kPa and the flow rate is 403m 3 / h, hardness is 350mg / L, and the ultrasonic signal frequency is 60kHz. The signal at 0.45ms has a regular wavelength. When the pressure value detected at the outlet is 77kPa and the flow rate is 259m 3 / h, hardness of 497mg / L, ultrasonic signal frequency of 60kHz, when the signal at 0.45ms shows a deformed irregular wavelength, it is judged that scaling occurs.

[0059] After determining that scaling occurs, the steam condensed water collected in the sodium sulfate evaporation crystallization unit in step (2), the sodium chloride evaporation crystallization unit in step (4) and the mother liquor drying unit in step (5) is introduced into the heat exchanger V30 to exchange heat with the refrigerant in the external cooler 11, wherein: the temperature of the steam condensed water collected in the sodium sulfate evaporation crystallization unit in step (2) is 116°C, and the flow rate is 13.35m 3 / h; Step (4) The temperature of the steam condensed water collected in the sodium chloride evaporation crystallization unit is 108°C and the flow rate is 0.5m 3 / h. The temperature of the refrigerant after heat exchange is 50°C, and it is returned to the refrigerant pipeline of the external cooler 11 to exchange heat with the scale mother liquid attached to the inner wall of the cooling pipe. The steam condensate after heat exchange in the heat exchanger V 30 is collected in the product water pool and reused as product water.

[0060] After the refrigerant after heat exchange is continuously introduced into the refrigerant pipeline of the external cooler 11 for 40 minutes, the descaling unit is stopped. According to steps (1) to (5) of this embodiment, the zero discharge treatment of salt mine water is restarted. The pressure value detected at the outlet of the cooling pipe is 40 kPa, and the flow rate is 397 m 3 / h, hardness is 354mg / L, and when the ultrasonic signal frequency is 60kHz, the signal at 0.45ms has a regular wavelength, which is close to the normal operation before scaling, indicating that the scaling in the cooling tube has been effectively removed.

[0061] Example 2 This embodiment provides a zero-discharge treatment method for salt-containing mine water with in-situ descaling of an external cooler, and the process is as follows: Figure 1 As shown, the system used is as Figure 2 and Figure 3 As shown, the specific process is as follows: (1) Preprocessing unit (in Figure 2 Not shown): After the suspended matter in the salty mine water is removed, membrane concentration is performed to obtain concentrated brine, which is stored in a concentrated brine tank 1 .

[0062] (2) Sodium sulfate evaporation crystallization unit: The concentrated brine is passed into the heat exchanger 12 to exchange heat with the steam condensate; the steam condensate forms steam condensate after heat exchange and is stored in the steam condensate tank 13; the concentrated brine after heat exchange is passed into the heater 14, and after circulating heating, crystallization and concentration in the heater 14 and the separator 15, the crystal slurry is discharged. The crystal slurry is thickened by the thickener 16 and centrifuged by the centrifuge 17, and then dried to obtain anhydrous sodium sulfate; the liquid separated in the thickener 16 and the centrifuge 17 is collected, recorded as mother liquor A, and stored in the mother liquor A tank 8.

[0063] In the above process: the temperature of the concentrated brine entering the heat exchanger I2 is 20°C, and the mass flow rate is 10.0 t / h; the temperature of the steam condensate entering the heat exchanger I2 is 113°C, and the absolute pressure is 160 kPa; the temperature of the feed liquid for circulating heating, crystallization and concentration in the heater I4 and the separator I5 is 107°C; in the sodium sulfate evaporation crystallization unit, 8.34 t / h of steam condensate, 0.66 t / h of mother liquor A, and 1.04 t / h of anhydrous sodium sulfate are obtained; the mass concentration of sodium chloride in the mother liquor A is 23.5%, and the mass concentration of sodium sulfate is 5.6%.

[0064] (3) Glauber's Salt Freezing Crystallization Unit: The mother liquor A is passed into the heat exchanger II 9, and after heat exchange with the circulating cooling water, it is passed into the heat exchanger III 10 to exchange heat with the mother liquor B to achieve precooling of the mother liquor A. The precooled mother liquor A is passed into the cooling pipe of the external cooler 11, and after circulating freezing crystallization and concentration in the external cooler 11 and the freezing crystallizer 12, the crystal slurry is discharged. After the crystal slurry is thickened by the thickener II 13 and centrifuged by the centrifuge II 14, Glauber's salt is obtained; the liquid separated in the thickener II 13 and the centrifuge II 14 is collected and recorded as mother liquor B, and stored in the mother liquor B tank 15. The Glauber's salt is passed into the dissolver 25, and a part of the concentrated brine preheated by the heat exchanger I 2 is used for dissolution, and then passed into the heater I 4, and merged with the other part of the concentrated brine preheated by the heat exchanger I 2.

[0065] In the above process: the temperature of the circulating frozen crystallization and concentrated liquid in the external cooler 11 and the frozen crystallizer 12 is 0°C; in the thenardite frozen crystallization unit, 0.10 t / h of thenardite and 0.56 t / h of mother liquor B are obtained; the mass concentration of sodium chloride in the mother liquor B is 25.0%, and the mass concentration of sodium sulfate is 1.1%.

[0066] (4) Sodium chloride evaporation crystallization unit: The mother liquor B is passed into the heat exchanger III 10, and after heat exchange with the mother liquor A, a preheated mother liquor B is obtained, which is stored in the preheated mother liquor B tank 16. The preheated mother liquor B is passed into the heat exchanger IV 17, and heat exchange is performed with the steam condensate; the steam condensate forms steam condensate after heat exchange, which is stored in the steam condensate tank II 18; the preheated mother liquor B after heat exchange is passed into the heater II 19, and after cyclic heating, crystallization and concentration in the heater II 19 and the separator II 20, the crystal slurry is discharged. The crystal slurry is thickened by the thickener III 21 and centrifuged by the centrifuge III 22, and then dried to obtain sodium chloride; the liquid separated in the thickener III 21 and the centrifuge III 22 is collected, recorded as mother liquor C, and stored in the mother liquor C tank 23.

[0067] In the above process: the temperature of the steam condensate entering the heat exchanger IV 17 is 113° C. and the absolute pressure is 160 kPa; the temperature of the feed liquid for circulating heating, crystallization and concentration in the heater II 19 and the separator II 20 is 108° C.; in the sodium chloride evaporation crystallization unit, 0.31 t / h of steam condensate, 0.15 t / h of mother liquor C, and 0.10 t / h of sodium chloride (meeting the standard for refined industrial salt) are obtained; the mass concentration of sodium chloride in the mother liquor C is 27.5%, and the mass concentration of sodium sulfate is 2.2%.

[0068] (5) Mother liquor drying unit: The mother liquor C is lifted to the dryer 24, and the steam-heated air is used as a heat source to evaporate and dehumidify the moisture in the mother liquor, thereby achieving the purpose of drying and obtaining impurities; the steam condensed water evaporated during the drying process is collected.

[0069] In the mother liquor drying unit, 0.06t / h of impurities and 0.09t / h of steam condensate are obtained.

[0070] (6) Descaling unit: During the operation of the system, the pressure gauge 26, flow meter 27 and hardness meter 28 installed at the inlet and outlet of the cooling pipe of the external cooler 11, as well as the ultrasonic meter 29 installed in the cooling pipe, are used for real-time monitoring. When the system is operating normally, the pressure value detected at the outlet is 45kPa and the flow rate is 492m 3 / h, hardness is 400mg / L, and the ultrasonic signal frequency is 60kHz. The signal at 0.45ms has a regular wavelength. When the pressure value detected at the outlet is 106kPa and the flow rate is 230m 3 / h, hardness of 893 mg / L, and ultrasonic signal frequency of 60 kHz. When the signal at 0.45 ms showed a deformed irregular wavelength, scaling was determined to have occurred.

[0071] After determining that scaling has occurred, the electric steam boiler 31 generates fresh steam at a temperature of 133°C. After being processed by the temperature reduction and pressure reduction device 32, the steam temperature is changed to 113°C, and the absolute pressure is changed to 160 kPa. It is then passed into the cooling tube of the external cooler 11 to heat the scaling adhered to the inner wall of the cooling tube.

[0072] After the raw steam is continuously introduced into the cooling pipe of the external cooler 11 for 40 minutes, the descaling unit is stopped. According to steps (1) to (5) of this embodiment, the zero discharge treatment of the salt mine water is restarted. The pressure value detected at the outlet of the cooling pipe is 48 kPa, and the flow rate is 488 m 3 / h, hardness is 401mg / L, and when the ultrasonic signal frequency is 60kHz, the signal at 0.45ms has a regular wavelength, which is close to the normal operation before scaling, indicating that the scaling in the cooling tube has been effectively removed.

[0073] Example 3 This embodiment provides a zero-discharge treatment method for salt-containing mine water with in-situ descaling of an external cooler, and the process is as follows: Figure 1 As shown, the system used is as Figure 2 and Figure 3 As shown, the specific process is as follows: (1) Pretreatment unit → sodium sulfate evaporation crystallization unit → mirabilite freezing crystallization unit → sodium chloride evaporation crystallization unit → mother liquor drying unit: The operation was carried out in the same manner as in Example 1, and the setting of the equipment operating parameters was the same as in Example 1.

[0074] (2) Descaling unit: During the operation of the system, the pressure gauge 26, flow meter 27 and hardness meter 28 installed at the inlet and outlet of the cooling pipe of the external cooler 11, as well as the ultrasonic meter 29 installed in the cooling pipe, are used for real-time monitoring. When the system is operating normally, the pressure value detected at the outlet is 42kPa and the flow rate is 409m 3 / h, hardness is 346mg / L, and the ultrasonic signal frequency is 60kHz. The signal at 0.45ms has a regular wavelength. When the pressure value detected at the outlet is 183kPa and the flow rate is 102m 3 / h, hardness of 778 mg / L, and ultrasonic signal frequency of 60 kHz. When the signal at 0.45 ms shows a deformed irregular wavelength, scaling is determined to have occurred.

[0075] After determining that scaling occurs, the steam condensed water collected in the sodium sulfate evaporation crystallization unit, the sodium chloride evaporation crystallization unit and the mother liquor drying unit is passed into the heat exchanger V30 to exchange heat with the refrigerant in the external cooler 11, wherein: the steam condensed water collected in the sodium sulfate evaporation crystallization unit has a temperature of 118°C and a flow rate of 13.84m 3 / h; the temperature of the steam condensed water collected in the sodium chloride evaporation crystallization unit is 109°C and the flow rate is 0.5m 3 / h. The temperature of the refrigerant after heat exchange is 51°C, and it is returned to the refrigerant pipeline of the external cooler 11 to exchange heat with the scale mother liquid attached to the inner wall of the cooling pipe. The steam condensate after heat exchange in the heat exchanger V30 is collected in the product water pool and reused as product water.

[0076] After continuously introducing the heat exchanged refrigerant into the refrigerant pipeline of the external cooler 11 for 20 minutes, the introduction is stopped. The temperature of the fresh steam generated by the electric steam boiler 31 is 140°C. After being processed by the temperature reduction and pressure reduction device 32, the temperature of the fresh steam changes to 118°C and the absolute pressure changes to 165kPa. It is introduced into the cooling pipe of the external cooler 11 to heat the scale attached to the inner wall of the cooling pipe.

[0077] After the raw steam is continuously introduced into the cooling pipe of the external cooler 11 for 20 minutes, the descaling unit is stopped. According to step (1) of this embodiment, the zero discharge treatment of the salt mine water is restarted. The pressure value detected at the outlet of the cooling pipe is 40 kPa, and the flow rate is 405 m 3 / h, hardness is 349mg / L, and when the ultrasonic signal frequency is 60kHz, the signal at 0.45ms has a regular wavelength, which is close to the normal operation before scaling, indicating that the scaling in the cooling tube has been effectively removed.

[0078] Example 4 The difference between this embodiment and embodiment 3 is that: during descaling, only the steam condensate descaling method is used, and the time for passing the refrigerant after heat exchange is extended. Specifically, this embodiment provides a zero-discharge treatment method for salt-containing mine water with in-situ descaling of an external cooler, and its process is as follows: Figure 1 As shown, the system used is as Figure 2 and Figure 3 As shown, the specific process is as follows: (1) Pretreatment unit → sodium sulfate evaporation crystallization unit → mirabilite freezing crystallization unit → sodium chloride evaporation crystallization unit → mother liquor drying unit: The operation was carried out in the same manner as in Example 1, and the setting of the equipment operating parameters was the same as in Example 1.

[0079] (2) Descaling unit: During the operation of the system, the pressure gauge 26, flow meter 27 and hardness meter 28 installed at the inlet and outlet of the cooling pipe of the external cooler 11, as well as the ultrasonic meter 29 installed in the cooling pipe, are used for real-time monitoring. When the system is operating normally, the pressure value detected at the outlet is 41kPa and the flow rate is 404m 3 / h, hardness is 350mg / L, and the ultrasonic signal frequency is 60kHz. The signal at 0.45ms has a regular wavelength. When the pressure value detected at the outlet is 171kPa and the flow rate is 120m 3 / h, hardness of 783 mg / L, and ultrasonic signal frequency of 60 kHz. When the signal at 0.45 ms shows a deformed irregular wavelength, scaling is determined to have occurred.

[0080] After determining that scaling occurs, the steam condensed water collected in the sodium sulfate evaporation crystallization unit, the sodium chloride evaporation crystallization unit and the mother liquor drying unit is passed into the heat exchanger V30 to exchange heat with the refrigerant in the external cooler 11, wherein: the steam condensed water collected in the sodium sulfate evaporation crystallization unit has a temperature of 118°C and a flow rate of 12.70 m 3 / h; the temperature of the steam condensed water collected in the sodium chloride evaporation crystallization unit is 120℃, and the flow rate is 0.5m 3 / h. The temperature of the refrigerant after heat exchange is 50°C, and it is returned to the refrigerant pipeline of the external cooler 11 to exchange heat with the scale mother liquid attached to the inner wall of the cooling pipe. The steam condensate after heat exchange in the heat exchanger V 30 is collected in the product water pool and reused as product water.

[0081] After the refrigerant after heat exchange is continuously introduced into the refrigerant pipeline of the external cooler 11 for 40 minutes, the descaling unit is stopped. According to step (1) of this embodiment, the zero discharge treatment of salt mine water is restarted. The pressure value detected at the outlet of the cooling pipe is 66 kPa, and the flow rate is 317 m 3 / h, hardness is 455mg / L, and when the ultrasonic signal frequency is 60kHz, the signal at 0.45ms shows a deformed irregular wavelength.

[0082] Example 5 The difference between this embodiment and embodiment 3 is that: during descaling, only the method of descaling with live steam is used, and the time of introducing live steam is prolonged. Specifically, this embodiment provides a zero-discharge treatment method for salt-containing mine water with in-situ descaling of an external cooler, and its process is as follows: Figure 1 As shown, the system used is as Figure 2 and Figure 3 As shown, the specific process is as follows: (1) Pretreatment unit → sodium sulfate evaporation crystallization unit → mirabilite freezing crystallization unit → sodium chloride evaporation crystallization unit → mother liquor drying unit: The operation was carried out in the same manner as in Example 1, and the setting of the equipment operating parameters was the same as in Example 1.

[0083] (2) Descaling unit: During the operation of the system, the pressure gauge 26, flow meter 27 and hardness meter 28 installed at the inlet and outlet of the cooling pipe of the external cooler 11, as well as the ultrasonic meter 29 installed in the cooling pipe, are used for real-time monitoring. When the system is operating normally, the pressure value detected at the outlet is 39kPa and the flow rate is 400m 3 / h, hardness is 343mg / L, and the ultrasonic signal frequency is 60kHz. The signal at 0.45ms has a regular wavelength. When the pressure value detected at the outlet is 165kPa and the flow rate is 113m 3 / h, hardness of 769 mg / L, and ultrasonic signal frequency of 60 kHz. When the signal at 0.45 ms showed a deformed irregular wavelength, scaling was determined to have occurred.

[0084] After determining that scaling has occurred, the electric steam boiler 31 generates fresh steam at a temperature of 140°C. After being processed by the temperature reduction and pressure reduction device 32, the steam temperature is changed to 119°C and the absolute pressure is changed to 165 kPa. The steam is then passed into the cooling tube of the external cooler 11 to heat the scaling attached to the inner wall of the cooling tube.

[0085] After the raw steam was continuously introduced into the cooling pipe of the external cooler 11 for 40 minutes, the descaling unit was stopped. According to step (1) of this embodiment, the zero discharge treatment of the salt mine water was restarted. The pressure value detected at the outlet of the cooling pipe was 52 kPa and the flow rate was 331 m 3 / h, hardness is 417mg / L, and when the ultrasonic signal frequency is 60kHz, the signal at 0.45ms shows a deformed irregular wavelength.

[0086] Example 6 The difference between this embodiment and embodiment 3 is that: during descaling, the method for descaling steam condensate water and the method for descaling live steam are performed simultaneously. Specifically, this embodiment provides a zero-discharge treatment method for salt-containing mine water with in-situ descaling of an external cooler, and the process is as follows: Figure 1 As shown, the system used is as Figure 2 and Figure 3 As shown, the specific process is as follows: (1) Pretreatment unit → sodium sulfate evaporation crystallization unit → mirabilite freezing crystallization unit → sodium chloride evaporation crystallization unit → mother liquor drying unit: The operation was carried out in the same manner as in Example 1, and the setting of the equipment operating parameters was the same as in Example 1.

[0087] (2) Descaling unit: During the operation of the system, the pressure gauge 26, flow meter 27 and hardness meter 28 installed at the inlet and outlet of the cooling pipe of the external cooler 11, as well as the ultrasonic meter 29 installed in the cooling pipe, are used for real-time monitoring. When the system is operating normally, the pressure value detected at the outlet is 37kPa and the flow rate is 410m 3 / h, hardness is 344mg / L, and the ultrasonic signal frequency is 60kHz. The signal at 0.45ms has a regular wavelength. When the pressure value detected at the outlet is 158kPa and the flow rate is 112m 3 / h, hardness of 763 mg / L, and ultrasonic signal frequency of 60 kHz. When the signal at 0.45 ms shows a deformed irregular wavelength, scaling is determined to have occurred.

[0088] After determining that scaling occurs, the steam condensed water collected in the sodium sulfate evaporation crystallization unit, the sodium chloride evaporation crystallization unit and the mother liquor drying unit is passed into the heat exchanger V30 to exchange heat with the refrigerant in the external cooler 11, wherein: the steam condensed water collected in the sodium sulfate evaporation crystallization unit has a temperature of 115°C and a flow rate of 14.25m 3 / h; the temperature of the steam condensed water collected in the sodium chloride evaporation crystallization unit is 108℃, and the flow rate is 0.5m 3 / h. The temperature of the refrigerant after heat exchange is 50°C, and it is returned to the refrigerant pipeline of the external cooler 11 to exchange heat with the scale mother liquid attached to the inner wall of the cooling pipe. The steam condensate after heat exchange in the heat exchanger V 30 is collected in the product water pool and reused as product water.

[0089] While the refrigerant after heat exchange is introduced into the refrigerant pipeline of the external cooler 11, live steam is introduced into the cooling pipe. The specific process of generating and introducing live steam is as follows: the electric steam boiler 31 generates fresh live steam with a temperature of 138°C. After being treated by the temperature reduction and pressure reduction device 32, the live steam temperature is changed to 118°C and the absolute pressure is changed to 165kPa. It is then introduced into the cooling pipe of the external cooler 11 to heat the scale attached to the inner wall of the cooling pipe.

[0090] After continuously introducing the heat exchanged refrigerant into the refrigerant pipeline of the external cooler 11, and continuously introducing the raw steam into the cooling pipe of the external cooler 11 for 20 minutes, the descaling unit was stopped. According to step (1) of this embodiment, the zero discharge treatment of salt mine water was restarted. The pressure value detected at the outlet of the cooling pipe was 46 kPa, and the flow rate was 359 m 3 / h, hardness is 394mg / L, and when the ultrasonic signal frequency is 60kHz, the signal at 0.45ms shows a deformed irregular wavelength.

[0091] In Examples 3 to 6, before descaling, the scaling layer is relatively thick (the pressure, flow rate, and hardness vary more than during normal operation). Compared with Example 3, the descaling effect of Examples 4 to 6 is better, indicating that the present invention combines the method of descaling with steam condensate and the method of descaling with live steam in a specific order to improve the descaling effect. The reason is speculated to be: first, the method of descaling with steam condensate is used to heat the scaling in the cooling tube by using the refrigerant after heat exchange with steam condensate, so that the scaling layer is partially dissolved or peeled off. Since the heated refrigerant heats the cooling tube outside the cooling tube, it is beneficial for the side of the scaling layer close to the tube wall to be better heated and then partially dissolved or peeled off, thereby generating more gaps in the scaling layer that penetrate the scaling layer, which is beneficial for the subsequent live steam to fully contact the scaling layer and improve the effect of the live steam; then the method of descaling with live steam is used to pass live steam into the cooling tube to contact the scaling in the cooling tube, which can provide water and external force to further dissolve and peel off the remaining hard scale components.

[0092] Example 7 This embodiment provides a zero-discharge treatment method for salt-containing mine water with in-situ descaling of an external cooler, and the process is as follows: Figure 1 As shown, the system used is as Figure 2 and Figure 3 As shown, the specific process is as follows: (1) Pretreatment unit → sodium sulfate evaporation crystallization unit → mirabilite freezing crystallization unit → sodium chloride evaporation crystallization unit → mother liquor drying unit: The operation was carried out in the same manner as in Example 1, and the setting of the equipment operating parameters was the same as in Example 1.

[0093] (2) Descaling unit: During the operation of the system, the pressure gauge 26, flow meter 27 and hardness meter 28 installed at the inlet and outlet of the cooling pipe of the external cooler 11, as well as the ultrasonic meter 29 installed in the cooling pipe, are used for real-time monitoring. When the system is operating normally, the pressure value detected at the outlet is 41kPa and the flow rate is 394m 3 / h, hardness is 356mg / L, and the signal at 0.45ms has a regular wavelength when the ultrasonic signal frequency is 60kHz. When the flow rate detected at the outlet is 0, it is judged that the cooling pipe is completely blocked.

[0094] After determining that the cooling pipe is completely blocked, the steam condensed water collected in the sodium sulfate evaporation crystallization unit, the sodium chloride evaporation crystallization unit and the mother liquor drying unit is passed into the heat exchanger V30 to exchange heat with the refrigerant in the external cooler 11, wherein: the steam condensed water collected in the sodium sulfate evaporation crystallization unit has a temperature of 115°C and a flow rate of 14.04m 3 / h; the temperature of the steam condensed water collected in the sodium chloride evaporation crystallization unit is 110℃, and the flow rate is 0.4m 3 / h. The temperature of the refrigerant after heat exchange is 48°C, and it is returned to the refrigerant pipeline of the external cooler 11 to exchange heat with the scale mother liquid attached to the inner wall of the cooling pipe. The steam condensate after heat exchange in the heat exchanger V30 is collected in the product water pool and reused as product water.

[0095] After continuously introducing the heat exchanged refrigerant into the refrigerant pipeline of the external cooler 11 for 20 minutes, the introduction is stopped. The temperature of the fresh steam generated by the electric steam boiler 31 is 150°C. After being processed by the temperature reduction and pressure reduction device 32, the temperature of the fresh steam changes to 124°C and the absolute pressure changes to 203kPa. It is introduced into the cooling pipe of the external cooler 11 to heat the scale attached to the inner wall of the cooling pipe.

[0096] After the raw steam was continuously introduced into the cooling pipe of the external cooler 11 for 40 minutes, the descaling unit was stopped. According to step (1) of this embodiment, the zero discharge treatment of the salt mine water was restarted. The pressure value detected at the outlet of the cooling pipe was 43 kPa and the flow rate was 397 m 3 / h, hardness is 350mg / L, and when the ultrasonic signal frequency is 60kHz, the signal at 0.45ms has a regular wavelength, which is close to the normal operation before scaling, indicating that the scaling in the cooling tube has been effectively removed.

[0097] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A zero-discharge treatment method for saline mine water with in-situ descaling of an external cooler, characterized in that the steps include: S1: After removing suspended solids and membrane concentrating the salt-containing mine water, evaporation and crystallization are performed in sequence to separate anhydrous Na2SO4, freezing and crystallization are performed to separate sodium sulfate, evaporation and crystallization are performed to separate NaCl, and drying is performed to obtain miscellaneous salts; steam condensed water formed after heat exchange with steam condensed water used in the evaporation and crystallization, and steam condensed water evaporated in the drying process are collected; S2: When scaling forms inside the cooling tube of the external cooler used in the freezing crystallization process of S1, the following scheme A and / or scheme B shall be used for descaling: Solution A: The refrigerant in the external cooler is heat exchanged with the steam condensate collected in S1 and then flows back into the refrigerant pipeline of the external cooler; Option B: Introduce raw steam into the cooling pipes.

2. The method according to claim 1, characterized in that In step S2, scheme A is first used for descaling, and then scheme B is used for descaling; the ratio of the duration of descaling by scheme A to that of descaling by scheme B is 1:1-2.

3. The method according to claim 1, characterized in that: In step S2, when the liquid pressure at the outlet of the cooling tube increases by 50-400% compared with normal operation, the flow rate decreases by 35% or more and the flow rate is not 0, the hardness increases by 40-125%, and the signal at 0.40-0.45ms detected under 50-100kHz ultrasound in the cooling tube shows a deformed irregular wavelength, or when the flow rate at the outlet of the cooling tube is 0, scheme A and / or scheme B is used for descaling.

4. The method according to claim 1, characterized in that: Step S1 specifically includes: S1.1: After removing suspended solids and concentrating the salty mine water through membrane, concentrated brine is obtained; S1.2: After the concentrated brine is heat exchanged with steam condensation, it is heated for crystallization and concentration, and the resulting slurry is thickened, centrifuged and dried to obtain anhydrous Na2SO4; the steam condensate formed after the steam condensation heat exchange is collected; the liquid separated during the thickening and centrifugation process is collected and recorded as mother liquor A; S1.3: The mother liquor A is passed into the cooling pipe of the external cooler for freezing, crystallization and concentration. The obtained slurry is thickened and centrifuged to obtain mirabilite. The liquid separated during the thickening and centrifugation process is collected and recorded as mother liquor B. S1.4: After the mother liquor B is subjected to heat exchange with steam condensation, it is heated for crystallization and concentrated, and the resulting slurry is thickened, centrifuged and dried to obtain NaCl; the steam condensate formed after the steam condensation heat exchange is collected; the liquid separated during the thickening and centrifugation process is collected and recorded as mother liquor C; S1.5: Dry the mother liquor C to obtain impure salts, and collect the steam condensed water.

5. The method according to claim 4, characterized in that In step S1.3: the obtained sodium sulfate is dissolved in the concentrated brine after heat exchange in S1.2, and then heated for crystallization and concentration. The obtained slurry is thickened, centrifuged and dried to obtain anhydrous Na2SO4.

6. The method according to claim 4, characterized in that After the mother liquor A is collected, the mother liquor A is first heat exchanged with cooling water, and then heat exchanged with the mother liquor B. The mother liquor A after heat exchange is subjected to step S1.3, and the mother liquor B after heat exchange is subjected to step S1.

4.

7. The method according to claim 4, characterized in that In step S1.2: the temperature of the steam condensed water is 105~143°C, and the absolute pressure is 120~400kPa; the temperature of heating crystallization and concentration is 100~110°C; the mass concentrations of sodium chloride and sodium sulfate in the mother liquor A are 18.0~25.9% and 4.0~11.0%, respectively.

8. The method according to claim 4, characterized in that In step S1.3: the temperature of the freezing crystallization and concentration is -5~0°C; the mass concentrations of sodium chloride and sodium sulfate in the mother liquor B are 20.0~25.6% and 0.5~1.2%, respectively.

9. The method according to claim 4, characterized in that In step S1.4: the temperature of the steam condensed water is 105~143°C, and the absolute pressure is 120~400kPa; the temperature of heating crystallization and concentration is 100~110°C; the mass concentration of sodium chloride in the mother liquor C is 25.9%~28.2%, and the mass concentration of sodium sulfate is 0.0%~4.5%.

10. The method according to claim 1 or 2, characterized in that: In step S2: In scheme A, the temperature of the refrigerant after heat exchange is 40~60℃; In Scheme B, the temperature of the raw steam introduced into the cooling tube is 105~143℃, and the absolute pressure is 120~400kPa.

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