Method for treating high-calcium coalbed methane produced water and recycling lithium and strontium resources

Abstract

The invention relates to the technical field of sewage treatment and resource utilization, in particular to a method for treating high-calcium coalbed methane produced water and recycling lithium and strontium resources, which comprises the following steps: respectively adding sodium sulfate, hydrogen peroxide, a demulsifier and a flocculant into coalbed methane produced water, respectively reacting, and removing solid impurities through solid-liquid separation after the reaction is finished; effluent is subjected to nanofiltration A treatment, and nanofiltration A produced water and nanofiltration A concentrated water are treated respectively; a treatment method of nanofiltration A produced water comprises the steps of electrolytic oxidation A, high-pressure reverse osmosis and adsorption and desorption; the treatment method of the concentrated water of the nanofiltration A comprises the following steps: carrying out thermogravimetric precipitation, electrolytic oxidation B, resin adsorption and nanofiltration B, respectively carrying out evaporative crystallization on the produced water of the nanofiltration B and the concentrated water of the nanofiltration B to respectively obtain NaCl and strontium chloride, and discharging or recycling condensed water. According to the treatment process method disclosed by the invention, up-to-standard discharge or reuse of the produced water is realized, and byproducts such as calcium, strontium and lithium are separated from the water.

Description

Technical Field

[0001] The invention relates to a method for treating high-calcium coalbed methane produced water and recovering lithium and strontium resources, belonging to the technical field of sewage treatment and resource utilization. Background Art

[0002] Coalbed methane produced water mainly refers to groundwater discharged through drainage equipment. The composition of coalbed methane produced water produced during the production stage is complex, mainly containing high concentrations of calcium, sodium, chlorine, organic matter, ammonia nitrogen, suspended solids, petroleum, etc., and also contains barium, strontium, lithium, etc. It is high-calcium and high-salt produced water, and the total dissolved solids (TDS) can generally be as high as 40,000 mg / L or more, which is difficult to handle and has high operating costs. The water quality data of a typical high-calcium and high-salt coalbed methane produced water are shown in the following table:

[0003] index content Suspended matter (mg / L) 80-500 Turbidity (NTU) 200-1000 Chroma 50-150 Petroleum (mg / L) 50-500 COD(mg / L) 1000-3000 Ammonia nitrogen (mg / L) 100-500 Barium (mg / L) 100-1000 Calcium (mg / L) 10,000-50,000 Magnesium (mg / L) 50-150 Strontium (mg / L) 5-30,000 Lithium (mg / L) 30-150 TDS(mg / L) 40,000-120,000

[0004] At present, the produced water of coalbed methane is mainly treated by the process of "flotation oil removal + coagulation sedimentation + oxidation + evaporation". The treated effluent is discharged or reused in compliance with the standards. However, the treatment effect of the flotation process is not ideal, especially when the emulsified oil content is high, the petroleum content of the effluent is generally difficult to reach below 5 mg / L, which affects the operation of the back-end system; after adding flocculants in the coagulation sedimentation process, the suspended matter is still difficult to precipitate completely, and the suspended matter and turbidity of the effluent are both high, causing frequent fouling of the back-end system. The oxidation process generally adopts Fenton oxidation, ozone catalytic oxidation, electrochemical oxidation, etc., but due to the high salt content of coalbed methane produced water, no matter which catalytic oxidation method is used, the hydroxyl radicals in the treatment process are easily annihilated and consumed by chloride ions, making the oxidation efficiency extremely low. The COD removal rate is generally only about 30%, and the oxidation treatment cost is high; the solids obtained by evaporation treatment are generally miscellaneous salts, which become hazardous wastes, and the cost of hazardous waste treatment is generally as high as 3000-5000 yuan / ton, resulting in the overall operating cost of produced water as high as 200 yuan / m 3 Therefore, the development of efficient and low-cost technology for the treatment of coalbed methane produced water to meet standards and resource utilization has broad application prospects. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a method for treating high-calcium coalbed methane produced water and recovering lithium and strontium resources, thereby achieving standard discharge or reuse of water, and separating by-products such as calcium, strontium, and lithium from the water. The by-products can be utilized as resources, reducing or avoiding the generation of hazardous waste. The economic benefits brought by the by-products can offset a portion of the wastewater treatment costs, ultimately reducing the treatment costs.

[0006] The technical solution of the present invention to solve the above technical problems is as follows: a method for treating high-calcium coalbed methane produced water and recovering lithium and strontium resources, the method comprising:

[0007] S1, three-phase baffled reaction: sodium sulfate, hydrogen peroxide, demulsifier and flocculant are added to the coalbed methane produced water to react respectively. After the reaction is completed, solid impurities are removed by solid-liquid separation operation;

[0008] S2, nanofiltration A treatment: the effluent from step S1 is subjected to nanofiltration A treatment, and the nanofiltration A produced water and nanofiltration A concentrated water are treated separately;

[0009] S2', the treatment method of the water produced by nanofiltration A is:

[0010] S2'-1, electrolytic oxidation A: electrolytic oxidation A treatment is performed on the nanofiltration A produced water to remove ammonia nitrogen and residual COD in the nanofiltration A produced water;

[0011] S2'-2, high pressure reverse osmosis: the water treated by electrolytic oxidation A is subjected to high pressure reverse osmosis treatment, the high pressure reverse osmosis produced water is discharged or reused, and the high pressure reverse osmosis concentrated water is subsequently treated;

[0012] S2'-3, adsorption and analysis: lithium in water is adsorbed by a lithium adsorbent, and then the lithium adsorbent after lithium adsorption is analyzed by hydrochloric acid to obtain a lithium-rich liquid, and the lithium-rich liquid is concentrated and refined to obtain lithium carbonate; the effluent from the adsorption and analysis is evaporated and crystallized to obtain NaCl, and the condensed water is discharged or reused;

[0013] S2”, the treatment method of nanofiltration A concentrated water is:

[0014] S2"-1, thermal gravity precipitation: adding sodium hydroxide to the concentrated water of nanofiltration A to carry out precipitation reaction, and obtaining calcium hydroxide product by solid-liquid separation;

[0015] S2"-2, electrolytic oxidation B: The effluent after thermogravimetric precipitation is subjected to electrolytic oxidation B to remove TOC and ammonia nitrogen in the water;

[0016] S2"-3, resin adsorption: the water treated by electrolytic oxidation B is treated by resin adsorption to reduce the total organic carbon TOC in the water;

[0017] S2"-4, Nanofiltration B: The effluent after resin adsorption is separated from the strontium and sodium in the water by nanofiltration B, and then the produced water and concentrated water are evaporated and crystallized to obtain NaCl and strontium chloride respectively, and the condensed water is discharged or reused.

[0018] Furthermore, in step S1, the dosage of sodium sulfate is 80-800 mg / L, and the reaction time is 5-10 min; the mass concentration of hydrogen peroxide is 27.5%, the dosage is 1-3 g / L, and the reaction time after adding hydrogen peroxide is 1-10 min;

[0019] The amount of the demulsifier added is 5-50 mg / L, and the reaction time after the demulsifier is added is 10-30 min;

[0020] The added amount of the flocculant is 1-10 mg / L, and the reaction time after the flocculant is added is 1-10 min.

[0021] Furthermore, in step S2, the operating pressure of the nanofiltration A is 10-90 bar, and one or more stages may be used to ensure that the calcium ion content of the water produced by the nanofiltration A is within 100 mg / L.

[0022] Furthermore, the current density during the electrolytic oxidation A in step S2'-1 and the electrolytic oxidation B in step S2"-2 is 200-600 A / m 2 , the voltage is 3-6V, and the oxygen evolution potential of the anode material is 2-3V;

[0023] Furthermore, after the electrolytic oxidation A treatment, a reducing agent is first added to the effluent to reduce the ORP to below 150 mV, and then the high-pressure reverse osmosis treatment is performed. The operating pressure of the high-pressure reverse osmosis is 40-90 bar. The concentrated water Li + The content is above 150-500mg / L.

[0024] Further, in step S2"-1, the concentration of sodium hydroxide added is the same as that of Ca in the nanofiltration A concentrated water. 2+ The mass concentration ratio is (1-2): 1; the reaction temperature is 60°C-100°C, and the stirring reaction time is 0.5-2h.

[0025] Furthermore, hydrochloric acid is first added to the effluent after thermal gravity precipitation to adjust the pH to 6-8, and then electrolytic oxidation B is performed to remove TOC and ammonia nitrogen in the water.

[0026] Furthermore, a reducing agent is first added to the effluent of the electrolytic oxidation B to reduce the ORP from 800-1200mV to below 150mV, and then resin adsorption is performed; the resin adsorption is a 1-3-stage adsorption series operation;

[0027] During the resin adsorption process of step S2"-3, the resin filtration rate is 0.5-2BV / h and the residence time is 0.5-2h.

[0028] Furthermore, during the operation of the nanofiltration B in step S2"-4, the operating pressure is 20-60 bar, and the pH of the nanofiltration B influent is 6-8.

[0029] Furthermore, NaCl products are obtained by MVR evaporation and crystallization, and SrCl is obtained by multi-effect evaporation and crystallization. 2 product.

[0030] The beneficial effects of the present invention are:

[0031] (1) The present invention not only achieves the discharge or reuse of water in compliance with the standards through the coordination of various process steps, but also separates by-products such as calcium, strontium, and lithium from the water. The by-products can be utilized as resources, reducing or avoiding the generation of hazardous waste. The economic benefits brought by the by-products can offset a part of the wastewater treatment costs, which is equivalent to reducing the treatment costs.

[0032] (2) Conventional high-calcium and high-salt produced water is generally subjected to flotation oil removal and coagulation sedimentation processes respectively, which has a complex process flow, occupies a large area, and has poor effects in removing oil and suspended solids. Indicators such as suspended solids and turbidity in the effluent are relatively high. The present invention designs a three-phase baffled reactor that integrates coagulation sedimentation and flotation. Sodium sulfate, hydrogen peroxide, demulsifier and flocculant are added to high-calcium and high-salt produced water for baffled reaction, which prolongs the reaction path and the residence time of each reaction zone, avoids short-circuiting, allows the chemical agents to react fully, and promotes the structure and polarity of stable macromolecular substances in the water body to change and quickly precipitate. In one reactor, the three-phase substances of water, gas and solid (oil, suspended solids, macromolecules, colloids, etc.) are effectively separated, and the treatment effect can be improved without the need for additional flotation tanks, sedimentation tanks, etc. The reactor has a high degree of integration and occupies a small area.

[0033] (3) The present invention adopts nanofiltration A to separate high concentrations of calcium in the produced water, replacing the conventional double-alkali hardness removal technology, avoiding the problems of high operating costs and large amounts of sludge due to the addition of a large amount of chemical agents; at the same time, according to the water quality conditions, nanofiltration A can be set to multiple levels. When the calcium content of the effluent from the first-level nanofiltration A does not meet the effluent requirements, two levels, three levels, etc. can be set until the effluent water quality meets the design requirements. It can be seen that the system can not only ensure the effluent effect, but also has strong adaptability and flexibility.

[0034] (4) Generally speaking, during the oxidation process of high-chlorine wastewater, the Cl - The hydroxyl radicals produced in the oxidation process will compete for the hydroxyl radicals, and the oxidation efficiency is low. In the present invention, nanofiltration A is used to separate and remove calcium chloride in the water, so that the salt content of the water produced by nanofiltration A is greatly reduced. At this time, electrolytic oxidation A is used to greatly improve the oxidation efficiency, effectively avoiding the influence of high salt on the oxidation efficiency, and the residual organic matter in the water can be oxidized more thoroughly. COD can be reduced to below 30 mg / L, and ammonia nitrogen can be reduced to below 1 mg / L, which can ensure the quality of the back-end NaCl salt. NaCl meets the requirements of the best industrial dry salt in "Industrial Salt" (GBT5462-2015); in addition, due to the thermal gravity precipitation of salt and Cl in the water - The content is also very high. Electrolytic oxidation B can effectively remove ammonia nitrogen, but it is difficult to completely treat organic matter. Therefore, after electrolytic oxidation B, resin adsorption is used to deeply remove the residual organic matter in the water to ensure the back-end SrCl 2 The quality of salt, strontium chloride meets the first-class requirements in "Industrial Strontium Chloride" (HGT4501-2013).

[0035] (5) The calcium and strontium contents in the concentrated water of nanofiltration A are very high, and the salt produced by direct evaporation is hazardous waste. The present invention utilizes the basic principle that the solubility of calcium hydroxide gradually decreases with increasing temperature, while the solubility of strontium hydroxide gradually increases with increasing temperature, and performs thermal precipitation separation to finally obtain calcium hydroxide as a by-product. The calcium hydroxide meets the requirements of first-class products in "Industrial Calcium Hydroxide" (HG4120-2009), can be utilized as a resource, avoids the formation of a large amount of mixture of calcium chloride and strontium chloride to generate hazardous waste, and reduces the cost of hazardous waste treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a flow chart of the process for resource treatment of high-calcium and high-salt coalbed methane produced water according to the present invention;

[0037] Figure 2 This is the equipment process diagram of the high-calcium and high-salt coalbed methane produced water resource treatment process of the present invention;

[0038] Figure 3 It is the front view of the three-phase baffled reactor;

[0039] Figure 4 It is the right view of the three-phase baffled reactor;

[0040] Figure 5 is an internal top view of a three-phase baffled reactor;

[0041] In the figure, 1, sodium sulfate reaction zone; 2, hydrogen peroxide reaction zone; 3, demulsification zone; 4, slag collection zone; 5, flocculation zone; 6, water collection zone; 7, ejector. DETAILED DESCRIPTION

[0042] The specific implementation of the present invention is described in detail below. The present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used are only for describing specific embodiments and are not intended to limit the present invention.

[0044] like Figure 1-2 As shown, a method for treating high-calcium coalbed methane produced water and recovering lithium and strontium resources is as follows:

[0045] S1. Three-phase baffle reaction: Sodium sulfate can be added to form barium sulfate precipitation with barium ions in water to remove barium in water. At the same time, the dosage of sodium sulfate is controlled to 80-800 mg / L to ensure that sulfate radicals react fully with less residue and avoid the formation of calcium sulfate precipitation. Then, hydrogen peroxide (concentration of 27.5%) is added at 1-3 g / L to react for 10-30 minutes, and then demulsifier (polyoxyethylene polyoxypropylene polyether) is added at 5-50 mg / L to react for 10-30 minutes, and PAM is added at 1-10 mg / L to react for 1-10 minutes. in, mainly using hydrogen peroxide and demulsifier to reduce the surface tension of oil droplets in water, reduce the strength of the interface film, the absolute value of Zeta potential is reduced from 30-50mV to below 5-10mV, the attraction between particles gradually becomes greater than the repulsion, the oil and colloid particles in the water lose stability and condense, and then form a large number of alum flowers through bridging, part of the alum flowers settle to the bottom sludge bucket to form mud residue, and the other part floats to the scum tank and is discharged through the scraper, thereby completing the separation and removal of impurities such as oil, suspended matter, turbidity, chromaticity, colloid, etc. in the wastewater;

[0046] S2, nanofiltration A: The effluent of step S1 is treated with nanofiltration A. The number of nanofiltration A levels is determined to be 1-3 according to the calcium ion content and effluent requirements. Each nanofiltration A membrane can be selected from one or more brands such as DuPont, Veolia, Hyde Energy, and Times Vonton. The nanofiltration A membrane model is one or more combinations to ensure that the calcium ion content in the final nanofiltration A effluent is within 100 mg / L, the operating pressure during the operation of nanofiltration A is 10-90 bar, the final concentrated water TDS is between 130,000 and 160,000 mg / L, the final produced water TDS is between 3,000 and 50,000 mg / L, and the total recovery rate is 60-90%. Nanofiltration A produced water and nanofiltration A concentrated water are treated separately.

[0047] S2', the treatment method of the water produced by nanofiltration A is:

[0048] S2'-1, Electrolytic oxidation A: Electrolytic oxidation A mainly removes ammonia nitrogen and residual COD in water to ensure the purity of lithium and NaCl products at the back end. The COD of electrolytic oxidation A outlet water is ≤30mg / L, and ammonia nitrogen is ≤1mg / L. The current density of the electrolytic oxidation process is 200-600A / m 2 , voltage 3-6V, pH=5-8.5, oxygen evolution potential of anode material 2-3V.

[0049] S2'-2, high pressure reverse osmosis: before high pressure reverse osmosis concentration, it is necessary to add a reducing agent, such as hydrogen peroxide, to reduce the ORP from 800-1200mV to below 150mV, control the operating pressure at 40-90bar, and concentrate Li + The content reaches above 150-500 mg / L, and the TDS reaches above 70,000 mg / L.

[0050] S2'-3, adsorption and analysis: lithium in water is adsorbed by lithium adsorbent, which is titanium or manganese adsorbent, with an adsorption capacity of more than 10 mg / g and a lithium recovery rate of more than 90%. The lithium adsorbent after lithium adsorption is analyzed by hydrochloric acid to obtain lithium-rich liquid, in which the lithium content reaches more than 500 mg / L. The lithium-rich liquid can be directly sold as a lithium raw material, or it can be further concentrated and refined to obtain lithium carbonate, thereby realizing resource utilization. The effluent from the adsorption and analysis is evaporated and crystallized to obtain NaCl industrial salt, and the condensed water is discharged or reused.

[0051] S2”, the treatment method of nanofiltration A concentrated water is:

[0052] S2"-1, thermal gravity precipitation: by adding sodium hydroxide, the amount of sodium hydroxide added is the same as the Ca 2+ The mass concentration ratio is (1-2): 1, the heating temperature is 60℃-100℃, the reaction is stirred for 0.5-2h, and calcium hydroxide solid is precipitated from the bottom of the reactor. Calcium hydroxide (slaked lime) is recovered. At this time, strontium hydroxide will not precipitate. The reason is that with the increase of temperature, the solubility of strontium hydroxide increases, while calcium hydroxide decreases with the increase of temperature. At 60-100℃, the solubility of calcium hydroxide is only 0.076-0.121g / 100g, while the solubility of strontium hydroxide is 8.42-91.2g / 100g. There is a significant difference between the two. Moreover, under alkaline conditions, ammonia in water exists in the form of weak alkaline ammonia water, which can inhibit the precipitation of strontium hydroxide and ensure the maximum precipitation of calcium hydroxide (slaked lime) to obtain solid calcium hydroxide with higher purity. The clear liquid after separation is cooled to below 40℃. At this time, Ca 2+ The content is below 50 mg / L, and other main substances are strontium, sodium and chlorine.

[0053] S2"-2, electrolytic oxidation B: After thermal gravimetric precipitation, the effluent is adjusted to pH 6-8 by adding hydrochloric acid, and TOC and ammonia nitrogen in the water are removed by electrolytic oxidation B. The current density during electrolytic oxidation B is 200-600A / m 2 , voltage 3-6V, oxygen evolution potential of anode material 2-3V, after electrolytic oxidation B treatment, ammonia nitrogen is reduced to below 1mg / L, but because it is a high chloride wastewater system, electrolytic oxidation B is not efficient in degrading organic matter, and the organic matter removal rate is only about 20-30%.

[0054] S2"-3, resin adsorption: before resin adsorption, a reducing agent (hydrogen peroxide) needs to be added to reduce the ORP from 800-1200mV to below 150mV, and then enter the resin adsorption system. The resin adsorption system determines the 1-3 stages in series operation according to the TOC concentration of the effluent, and each stage of resin can use the same or different types of resins. The resin filtration rate is 0.5-2BV / h, the residence time is 0.5-2h, the inlet TOC = 50-150mg / L, and the outlet TOC ≤ 20mg / L. The regenerated liquid after resin adsorption can be regenerated by any one of methanol, ethanol, and sodium hydroxide, and the regenerated resin can be reused repeatedly. The resin model used in the embodiment of the present invention is one or more of LS-109D, LSV-16, and SD300.

[0055] S2"-4, Nanofiltration B: The effluent after resin adsorption is separated from the strontium and sodium in the water by nanofiltration B, and then the produced water and concentrated water are evaporated and crystallized to obtain NaCl and strontium chloride respectively, so as to realize the resource recovery of strontium chloride, and the condensed water is discharged or reused, so as to realize resource utilization, avoiding the direct evaporation and crystallization of calcium strontium mixed liquid in the conventional treatment process to obtain hazardous waste, thereby generating huge hazardous waste disposal costs. The operating pressure of nanofiltration B process is 20-60bar, the pH of nanofiltration B inlet water is 6-8, and the concentrated water SrCl 2 The content reaches more than 140,000 mg / L, and the NaCl content of produced water is more than 70,000 mg / L.

[0056] Since NaCl has a lower boiling point, SrCl 2 The boiling point is relatively high. In order to save energy and obtain salt products, the produced water after adsorption and analysis of lithium is treated by MVR evaporation and crystallization to obtain NaCl products, and the concentrated water of nanofiltration B is treated by multi-effect evaporation and crystallization to obtain strontium chloride products.

[0057] Specifically, the equipment process flow of the high-calcium and high-salt coalbed methane produced water resource treatment process is as follows: Figure 2 As shown. Among them, the structure of the three-phase baffled reactor is as follows Figure 3-Figure 5 As shown, the three-phase baffled reactor includes a sodium sulfate reaction zone 1, a hydrogen peroxide reaction zone 2, a demulsification zone 3, a slag collection zone 4, a flocculation zone 5, and a water collection zone 6. The sodium sulfate reaction zone 1 and the hydrogen peroxide reaction zone 2 are both provided with an ejector 7. The high-calcium and high-salt coalbed methane produced water reacts with sodium sulfate in the sodium sulfate reaction zone 1, then enters the hydrogen peroxide reaction zone 2, reacts with hydrogen peroxide in the hydrogen peroxide reaction zone 2; reacts with a demulsifier in the demulsification zone 3; reacts with PAM in the flocculation zone 5, and finally enters the subsequent nanofiltration A process through the water collection zone 6.

[0058] Example 1

[0059] A method for treating high-calcium coalbed methane produced water and recovering lithium and strontium resources, the method comprising:

[0060] S1. Three-phase baffle reaction: by adding 800 mg / L of sodium sulfate solution (mass concentration 10%), reacting for 10 minutes, then adding 2 g / L of hydrogen peroxide (27.5%) and reacting for 20 minutes, then adding 25 mg / L of demulsifier (polyoxyethylene polyoxypropylene polyether) and reacting for 20 minutes, and PAM at 5 mg / L and reacting for 5 minutes, a large amount of alum flocs are generated in the system, part of which settles to the bottom sludge bucket to form sludge, and the other part floats to the scum tank and is discharged through a scraper, thereby completing the separation and removal of impurities such as oil, suspended matter, turbidity, chromaticity, colloid, etc. in the wastewater;

[0061] S2, Nanofiltration A: The effluent from step S1 is treated with 3-stage nanofiltration A. The operating pressure of the nanofiltration A process is 60 bar. The calcium ion content of the final nanofiltration A effluent is within 100 mg / L, the concentrated water TDS is between 130,000-160,000 mg / L, and the produced water TDS is between 3,000-50,000 mg / L. The produced water from nanofiltration A and the concentrated water from nanofiltration A are treated separately.

[0062] S2', the treatment method of the water produced by nanofiltration A is:

[0063] S2'-1. Electrolytic oxidation mainly removes ammonia nitrogen and residual COD in water to ensure the purity of lithium and NaCl products at the back end. COD of electrolytic oxidation effluent is ≤30mg / L, ammonia nitrogen is ≤1mg / L. The current density of electrolytic oxidation process is 600A / m 2 , voltage 4V, pH=5-8.5, oxygen evolution potential of anode material 3V.

[0064] S2'-2, High-pressure reverse osmosis: Before high-pressure reverse osmosis concentration, a reducing agent (hydrogen peroxide) needs to be added to reduce the ORP from 800-1200mV to below 150mV, and the operating pressure is controlled at 60bar. + The content reaches above 150-500 mg / L, and the TDS reaches above 70,000 mg / L.

[0065] S2'-3, adsorption and analysis: lithium in water is adsorbed by lithium adsorbent, which is titanium adsorbent (adsorbent model G-100). The lithium adsorbent after lithium adsorption is analyzed by hydrochloric acid to obtain lithium-rich liquid, which can be further concentrated and refined to obtain lithium carbonate. The effluent from adsorption and analysis is evaporated and crystallized to obtain NaCl, and the condensed water is discharged or reused.

[0066] S2”, the treatment method of nanofiltration A concentrated water is:

[0067] S2"-1, thermal gravity precipitation: by adding sodium hydroxide, the amount of sodium hydroxide added is the same as the Ca2+ The mass concentration ratio is 2:1, the heating temperature is reached to 80°C, the reaction is stirred for 1 hour, calcium hydroxide solid is precipitated from the bottom of the reactor, and calcium hydroxide (slaked lime) is recovered; the supernatant mainly contains Sr, sodium, chlorine, and a small amount of residual calcium, and the supernatant is cooled to below 40°C.

[0068] S2"-2, electrolytic oxidation B: The effluent after thermal gravity precipitation is adjusted to pH 6-8 by adding hydrochloric acid, and TOC and ammonia nitrogen in the water are removed by electrolytic oxidation B, ammonia nitrogen is reduced to less than 1mg / L, TOC is reduced to less than 300mg / L, and the current density of the electrolytic oxidation process is 500A / m 2 , voltage 4V, oxygen evolution potential of anode material 3V.

[0069] S2"-3, Resin adsorption: Before resin adsorption, a reducing agent (hydrogen peroxide) needs to be added to reduce the ORP from 800-1200mV to below 150mV, and then enter the resin adsorption system. The resin adsorption system is a three-stage series operation. The first-stage resin, second-stage resin and third-stage resin are: LS-109D, LSV-16, SD300. The resin filtration rate is 1BV / h, the residence time is 1h, the inlet TOC is 50-150mg / L, and the outlet TOC is ≤20mg / L. The regenerated liquid after resin adsorption is regenerated by one of methanol, ethanol and sodium hydroxide, and the regenerated resin can be reused repeatedly.

[0070] S2"-4, Nanofiltration B: The effluent after resin adsorption is separated from the strontium and sodium in the water by nanofiltration B, and then the produced water and concentrated water are evaporated and crystallized to obtain NaCl and strontium chloride respectively, so as to realize the resource recovery of crude product strontium chloride, and the condensed water is discharged or reused. The whole process is resource-based, avoiding the direct evaporation and crystallization of calcium-strontium mixed solution to obtain hazardous waste in the conventional treatment process, and the cost of hazardous waste disposal is huge. The operating pressure of nanofiltration B process is 40bar, the pH of nanofiltration B inlet water is 6-8, and the concentrated water SrCl 2 The content reaches more than 140,000 mg / L, and the NaCl content of produced water is more than 70,000 mg / L.

[0071] Among them, NaCl products are obtained by MVR evaporation and crystallization, and SrCl is obtained by multi-effect evaporation and crystallization. 2 product.

[0072] Example 2

[0073] A method for treating high-calcium coalbed methane produced water and recovering lithium and strontium resources, the method comprising:

[0074] S1, three-phase baffle reaction:

[0075] By adding 100 mg / L of sodium sulfate solution (mass concentration 10%), reacting for 10 minutes, then adding 1 g / L of hydrogen peroxide (27.5%) and reacting for 30 minutes, and then adding 50 mg / L of demulsifier (polyoxyethylene polyoxypropylene polyether) and reacting for 10 minutes, and PAM at 10 mg / L and reacting for 1 minute, a large amount of alum flocs are generated in the system, part of which settles to the bottom sludge bucket to form sludge, and the other part floats to the scum tank and is discharged through a scraper, thereby completing the separation and removal of impurities such as oil, suspended matter, turbidity, chromaticity, colloid, etc. in the wastewater;

[0076] S2, Nanofiltration A: The effluent from step S1 is treated with 3-stage nanofiltration A. The operating pressure of the nanofiltration A process is 90 bar. The calcium ion content of the final nanofiltration A effluent is within 100 mg / L, the concentrated water TDS is between 130,000-160,000 mg / L, and the produced water TDS is between 3,000-50,000 mg / L. The produced water from nanofiltration A and the concentrated water from nanofiltration A are treated separately.

[0077] S2', the treatment method of the water produced by nanofiltration A is:

[0078] S2'-1. Electrolytic oxidation mainly removes ammonia nitrogen and residual COD in water to ensure the purity of lithium and NaCl products at the back end. COD of electrolytic oxidation effluent is ≤30mg / L, ammonia nitrogen is ≤1mg / L. Current density of electrolytic oxidation process is 200A / m 2 , voltage 3V, pH=5-8.5, oxygen evolution potential of anode material 2V.

[0079] S2'-2, high pressure reverse osmosis: before high pressure reverse osmosis concentration, it is necessary to add a reducing agent (hydrogen peroxide) to reduce the ORP from 800-1200mV to below 150mV, control the operating pressure at 40bar, and concentrate Li + The content reaches above 150-500 mg / L, and the TDS reaches above 70,000 mg / L.

[0080] S2'-3, adsorption and analysis: lithium in water is adsorbed by lithium adsorbent, which is titanium adsorbent (adsorbent model G-100). The lithium adsorbent after lithium adsorption is analyzed by hydrochloric acid to obtain lithium-rich liquid, which can be further concentrated and refined to obtain lithium carbonate. The effluent from adsorption and analysis is evaporated and crystallized to obtain NaCl, and the condensed water is discharged or reused.

[0081] S2”, the treatment method of nanofiltration A concentrated water is:

[0082] S2"-1, thermal gravity precipitation: by adding sodium hydroxide, the amount of sodium hydroxide added is the same as the Ca 2+The mass concentration ratio is 1.5:1, the temperature is heated to 60°C, the reaction is stirred for 2 hours, calcium hydroxide solid is precipitated from the bottom of the reactor, and calcium hydroxide (slaked lime) is recovered; the supernatant mainly contains Sr, sodium, chlorine, and a small amount of residual calcium, and the supernatant is cooled to below 40°C.

[0083] S2"-2, electrolytic oxidation B: The effluent after thermogravimetric precipitation is adjusted to pH 6-8 by adding hydrochloric acid, and TOC and ammonia nitrogen in the water are removed by electrolytic oxidation B, ammonia nitrogen is reduced to below 1 mg / L, TOC is reduced to 300 mg / L, and the current density of the electrolytic oxidation process is 200A / m 2 , voltage 3V, oxygen evolution potential of anode material 2V.

[0084] S2"-3, Resin adsorption: Before resin adsorption, a reducing agent (hydrogen peroxide) needs to be added to reduce the ORP from 800-1200mV to below 150mV, and then enter the resin adsorption system. The resin adsorption system is a three-stage series operation. The first-stage resin, second-stage resin and third-stage resin are: LS-109D, LSV-16, SD300, the resin filtration rate is 2BV / h, the residence time is 0.5h, the inlet TOC is 50-150mg / L, and the outlet TOC is ≤20mg / L. The regeneration liquid after resin adsorption is regenerated by one of methanol, ethanol and sodium hydroxide, and the regenerated resin can be reused repeatedly.

[0085] S2"-4, Nanofiltration B: The effluent after resin adsorption is separated from the strontium and sodium in the water by nanofiltration B, and then the produced water and concentrated water are evaporated and crystallized to obtain NaCl and strontium chloride respectively, so as to realize the resource recovery of crude product strontium chloride, and the condensed water is discharged or reused. The whole process is resource-based, avoiding the direct evaporation and crystallization of calcium-strontium mixed solution to obtain hazardous waste in the conventional treatment process, and the cost of hazardous waste disposal is huge. The operating pressure of nanofiltration B process is 20bar, the pH of nanofiltration B inlet water is 6-8, and the concentrated water SrCl 2 The content reaches more than 140,000 mg / L, and the NaCl content of produced water is more than 70,000 mg / L.

[0086] Among them, NaCl products are obtained by MVR evaporation and crystallization, and SrCl is obtained by multi-effect evaporation and crystallization. 2 product.

[0087] Through experiments, it is found that after the treatment process of the present invention is used in Example 1 and Example 2, the effluent water quality meets the requirements of "Open circulating cooling water system make-up water" in "Water Quality for Industrial Water Use in Urban Wastewater Recycling" (GBT 19923-2005), and can achieve standard discharge or reuse; the obtained lithium-rich liquid can be sold as a lithium raw material or further refined to obtain lithium products; the obtained by-product NaCl meets the requirements of "Industrial Salt"

[0088] (GBT5462-2015) The requirements for the best quality industrial dry salt; the strontium chloride obtained meets the requirements of "Industrial Strontium Chloride"

[0089] The calcium hydroxide obtained meets the first-class requirements of "Industrial Calcium Hydroxide" (HG4120-2009) after centrifugal drying, and can fully realize the resource utilization of by-products and reduce the cost of hazardous waste treatment.

[0090] Comparative Example 1

[0091] The same method as in Example 1 is used to treat high-calcium coalbed methane produced water and recover lithium and strontium resources, except that: in step S1 of this comparative example 1, no three-phase baffled reactor treatment is performed, but conventional flotation oil removal and coagulation sedimentation are used for pretreatment, and the subsequent treatment process is the same as in Example 1. The pretreatment operation of this comparative example is: adding a demulsifier (polyoxyethylene polyoxypropylene polyether) to the flotation reactor to perform a demulsification reactor, removing emulsified oil and suspended matter by flotation, and then the effluent enters the coagulation sedimentation reactor, and PAC and PAM are added respectively for stirring reaction, and the muddy water after the reaction is mixed and enters the sedimentation tank for muddy water separation. The water quality data before and after pretreatment are as follows:

[0092] Table 1 Water quality data before and after pretreatment

[0093]

[0094] From the comparison of the data of Example 1 and Comparative Example 1, it can be seen that if the three-phase baffled reactor of the present invention is not used for treatment, the water quality indicators such as suspended solids, turbidity, oil, etc. in the effluent are relatively high, which is easy to cause serious fouling problems in the nanofiltration A system at the back end, and the barium is not removed, which will cause the barium content in the calcium hydroxide and strontium chloride products extracted at the back end to exceed the standard, thereby affecting the quality of the two products.

[0095] Comparative Example 2

[0096] The same method as in Example 1 was used to treat high-calcium coalbed methane produced water and recover lithium and strontium resources, except that: during the thermogravimetric precipitation in step S2"-1 of this comparative example 2, the sodium hydroxide in Example 1 was replaced with sodium carbonate, and the main components of the solid obtained by centrifugal drying after thermogravimetric precipitation were as follows:

[0097] Table 2 Solid components obtained by centrifugal drying after thermogravimetric precipitation

[0098] Example The main components of solid Solid properties Example 1 Calcium hydroxide, small amount of other impurities Industrial grade product, recyclable Comparative Example 2 Calcium carbonate, strontium carbonate, other impurities Basically hazardous waste

[0099] From the comparison of the data of Example 1 and Comparative Example 2, it can be seen that if sodium hydroxide is replaced with sodium carbonate during thermogravimetric precipitation, the solid obtained by thermogravimetric precipitation is mainly a mixture of calcium carbonate, strontium carbonate, etc., which is basically hazardous waste and has high processing cost.

[0100] Comparative Example 3

[0101] The same method as in Example 1 was used to treat high-calcium coalbed methane produced water and recover lithium and strontium resources, except that: in step S2"-1 of this comparative example 3, no heating was performed during the thermogravimetric precipitation, and sodium hydroxide was added at room temperature to react. The solid product data obtained by centrifugal drying of the obtained calcium hydroxide was as follows:

[0102] Table 3 Data of solid products obtained by centrifugal drying after thermogravimetric precipitation

[0103]

[0104] From the comparison of the data of Example 1 and Comparative Example 3, it can be seen that: if no heating is performed during the thermal gravity precipitation, and sodium hydroxide is added at room temperature for reaction, the solubility of calcium hydroxide is high, and it is difficult to precipitate solids from it. The amount of solids precipitated is small, and the corresponding recovery rate of calcium hydroxide is greatly reduced. At the same time, even if a small amount of solids is obtained, the impurity content is high, especially the strontium content is high, which may cause the solid to become hazardous waste, increasing the treatment cost.

[0105] Comparative Example 4

[0106] The same method as in Example 1 was used to treat high-calcium coalbed methane produced water and recover lithium and strontium resources, except that: in this comparative example 4, the resin adsorption operation of step S2"-3 was not performed, but the nanofiltration B operation was directly performed after the electrolytic oxidation B treatment. The specific result data are shown in Table 4 below.

[0107] Table 4 Experimental results of Example 1 and Comparative Example 4

[0108]

[0109]

[0110] From the comparison of the data of Example 1 and Comparative Example 4, it can be seen that if there is no resin adsorption operation, and the nanofiltration B operation is directly performed after the electrolytic oxidation B treatment, the COD, TOC, and ammonia nitrogen contents of the organic matter in the final nanofiltration B product water and concentrated water are relatively high, which will directly affect the quality of the sodium chloride salt and strontium chloride salt extracted at the back end, resulting in both salts failing to meet the requirements of qualified products, as well as the water quality of the evaporated condensed water.

[0111] Comparative Example 5

[0112] The same method as in Example 1 was used to treat high-calcium coalbed methane produced water and recover lithium and strontium resources, except that: in this comparative example 5, the electrolytic oxidation A operation was replaced with a conventional ozone catalytic oxidation operation, and the specific operation method of ozone catalytic oxidation in this comparative example 5 was to add a solid catalyst filler (carbon-based catalyst, the catalyst model was OC-4) into the oxidation tower, pass wastewater, and simultaneously pass ozone gas for reaction, and the other process operations were the same as in Example 1. The specific treatment result data are shown in Table 5 below.

[0113] Table 5 Experimental results of Example 1 and Comparative Example 5

[0114]

[0115]

[0116] From the data comparison of Example 1 and Comparative Example 5, it can be seen that if the electrolytic oxidation B operation is replaced with a conventional ozone oxidation operation, the COD and ammonia nitrogen in the oxidized effluent are relatively high, affecting the quality of the lithium-rich liquid and sodium chloride products, as well as the water quality of the evaporated condensate.

[0117] Comparative Example 6

[0118] The same method as in Example 1 was used to treat high-calcium coalbed methane produced water and recover lithium and strontium resources, except that: in this comparative example 6, the electrolytic oxidation B operation was replaced with a conventional Fenton oxidation operation, and the Fenton oxidation process conditions in this comparative example 6 were to add hydrochloric acid to the wastewater, adjust the pH to 3-5, and then add ferrous chloride and hydrogen peroxide in sequence, and stir the reaction, and the other process operations were the same as in Example 1. The specific results are shown in Table 6 below.

[0119] Table 6 Experimental results of Example 1 and Comparative Example 6

[0120]

[0121] From the data comparison of Example 1 and Comparative Example 6, it can be seen that if the electrolytic oxidation B operation is replaced with a conventional Fenton oxidation operation, the TOC removal efficiency is low and the ammonia nitrogen is not removed, which not only affects the water quality of the multi-effect evaporation condensate, but also easily affects the quality of the strontium chloride product obtained by the multi-effect evaporation crystallization.

[0122] Comparative Example 7

[0123] The same method as in Example 1 was used to treat high-calcium coalbed methane produced water and recover lithium and strontium resources, except that: in step S1 of this comparative example 7, no sodium sulfate was added to the three-phase baffled reactor, and hydrogen peroxide, demulsifier, and PAM were directly added for treatment. The other process operations were the same as in Example 1, and the content data of the solid obtained by pretreatment of water quality and thermal gravity precipitation and centrifugal drying were shown in Table 7 below.

[0124] Table 7 Pretreatment water quality and the content of solids obtained by centrifugal drying after thermal gravity precipitation

[0125]

[0126] From the comparison of the data of Example 1 and Comparative Example 7, it can be seen that if sodium sulfate is not added to the three-phase baffled reactor, the final calcium hydroxide and strontium chloride will contain barium, which will affect the quality of the two products and even become hazardous waste, increasing the processing cost.

[0127] The above embodiments and comparative examples all used the same batch of coal seam produced water, that is, the water quality of the coal seam produced water used was the same.

[0128] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0129] For those skilled in the art, several modifications and improvements may be made without departing from the concept of the present invention, all of which belong to the protection scope of the present invention. The protection scope of the present invention shall be based on the attached claims.

Claims

1. A method for treating high-calcium coalbed methane produced water and recovering lithium and strontium resources, characterized in that: The method is: S1, three-phase baffled reaction: sodium sulfate, hydrogen peroxide, demulsifier and flocculant are added to the coalbed methane produced water in sequence to carry out baffled reaction respectively. After the reaction is completed, solid impurities are removed by solid-liquid separation operation; S2, nanofiltration A treatment: the effluent from step S1 is subjected to nanofiltration A treatment, and the nanofiltration A produced water and nanofiltration A concentrated water are treated separately; S2', the treatment method of the water produced by nanofiltration A is: S2'-1, electrolytic oxidation A: electrolytic oxidation A treatment is performed on the nanofiltration A produced water to remove ammonia nitrogen and residual COD in the nanofiltration A produced water; S2'-2, high pressure reverse osmosis treatment: the effluent after electrolytic oxidation A treatment is subjected to high pressure reverse osmosis treatment, the high pressure reverse osmosis produced water is discharged or reused, and the high pressure reverse osmosis concentrated water is subjected to subsequent treatment; S2'-3, adsorption and analysis: lithium in water is adsorbed by a lithium adsorbent, and then the lithium adsorbent after lithium adsorption is analyzed by hydrochloric acid to obtain a lithium-rich liquid, which can be sold as a lithium raw material; The effluent from adsorption and decomposition is evaporated and crystallized to obtain NaCl, and the condensed water is discharged or reused; S2”, the treatment method of nanofiltration A concentrated water is: S2"-1, thermal gravity precipitation: adding sodium hydroxide to the concentrated water of nanofiltration A to carry out precipitation reaction, and obtaining calcium hydroxide product by solid-liquid separation; S2"-2, electrolytic oxidation B: The effluent after thermogravimetric precipitation is electrolytically oxidized B to remove total organic carbon TOC and ammonia nitrogen in the water; S2"-3, resin adsorption: the water treated by electrolytic oxidation B is treated by resin adsorption to reduce the total organic carbon TOC in the water; S2"-4, Nanofiltration B treatment: The effluent after resin adsorption is separated from the strontium and sodium in the water by nanofiltration B, and then the produced water and concentrated water are evaporated and crystallized to obtain NaCl and strontium chloride respectively, and the condensed water is discharged or reused.

2. The method for treating high-calcium coalbed methane produced water and recovering lithium and strontium resources according to claim 1, characterized in that: In step S1, the dosage of sodium sulfate is 80-800 mg / L, and the reaction time is 5-10 min; the mass concentration of hydrogen peroxide is 27.5%, the dosage is 1-3 g / L, and the reaction time after adding hydrogen peroxide is 1-10 min. The amount of the demulsifier added is 5-50 mg / L, and the reaction time after the demulsifier is added is 10-30 min; The added amount of the flocculant is 1-10 mg / L, and the reaction time after the flocculant is added is 1-10 min.

3. The method for treating high-calcium coalbed methane produced water and recovering lithium and strontium resources according to claim 1, characterized in that: In step S2, the operating pressure of the nanofiltration A is 10-90 bar, and the recovery rate is 60-90%; the nanofiltration A can be one-stage or multi-stage to ensure that the calcium ion content of the produced water is within 100 mg / L.

4. The method for treating high-calcium coalbed methane produced water and recovering lithium and strontium resources according to claim 1, characterized in that: The current density during the electrolytic oxidation A in step S2'-1 and the electrolytic oxidation B in step S2"-2 is 200-600A / m 2 , the voltage is 3-6V, and the oxygen evolution potential of the anode material is 2-3V.

5. The method for treating high-calcium coalbed methane produced water and recovering lithium and strontium resources according to claim 1, characterized in that: After the electrolytic oxidation A treatment, a reducing agent is first added to the effluent to reduce the ORP to below 150 mV, and then the high-pressure reverse osmosis treatment is performed. The operating pressure of the high-pressure reverse osmosis is 40-90 bar.

6. The method for treating high-calcium coalbed methane produced water and recovering lithium and strontium resources according to claim 1, characterized in that: In step S2"-1, the concentration of sodium hydroxide added is the same as that of Ca in the nanofiltration A concentrated water. 2+ The mass concentration ratio is (1-2): 1; the reaction temperature is 60°C-100°C, and the stirring reaction time is 0.5-2h.

7. The method for treating high-calcium coalbed methane produced water and recovering lithium and strontium resources according to claim 1, characterized in that: The effluent after thermal gravity precipitation is first adjusted to pH 6-8 by adding hydrochloric acid, and then electrolytic oxidation B is used to remove TOC and ammonia nitrogen in the water.

8. The method for treating high-calcium coalbed methane produced water and recovering lithium and strontium resources according to claim 1, characterized in that: A reducing agent is first added to the effluent of the electrolytic oxidation B to reduce the ORP to below 150 mV, and then resin adsorption is performed; the resin adsorption is a 1-3-stage adsorption operation in series; During the resin adsorption process of step S2"-3, the resin filtration rate is 0.5-2BV / h and the residence time is 0.5-2h.

9. The method for treating high-calcium coalbed methane produced water and recovering lithium and strontium resources according to claim 1, characterized in that: During the operation of nanofiltration B in step S2"-4, the operating pressure is 20-60 bar, and the pH of the nanofiltration B influent is 6-8.

10. The method for treating high-calcium coalbed methane produced water and recovering lithium and strontium resources according to claim 1, characterized in that: The NaCl product is obtained by MVR evaporation and crystallization, and the SrCl2 product is obtained by multi-effect evaporation and crystallization.

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