CN-116751988-B - Lithium extraction method for evaporation mother liquor of water produced in high COD and high boron-containing gas field

CN116751988BCN 116751988 BCN116751988 BCN 116751988BCN-116751988-B

Abstract

The invention discloses a lithium extraction method for evaporation mother liquor of water produced in a high-COD and high-boron-content gas field, which solves the technical problem of resource utilization of evaporation concentration mother liquor of high-COD, high-boron-content and high-sulfate and carbonate. The method comprises the steps of impurity removal and solubilization, solid-liquid separation and cleaning, filtrate concentration, centrifugal desalting and cleaning, crude extraction of lithium carbonate, high-temperature carbonization of organic matters, acid dissolution and boron removal, deep hardness removal, extraction of lithium carbonate and carbonization and purification of lithium carbonate. The invention realizes the recycling utilization of lithium and boron in the evaporation and concentration mother liquor of the produced water of the gas field, and obviously reduces the disposal cost of the evaporation mother liquor.

Inventors

LIU YUCHENG
ZHANG TAO
YANG KUAN
WANG GUANJUN
HUANG FUYOU
ZHAO LIMING

Assignees

成都兴澳晶元科技有限公司

Dates

Publication Date: 20260512
Application Date: 20230523

Claims (5)

1. The lithium extraction method of the evaporation mother liquor of the produced water of the high COD and high boron-containing gas field is characterized by comprising the following steps of: S1, removing impurities and solubilizing, namely slowly adding a calcium hydroxide solution into a stirring reaction tank filled with an evaporation mother solution, fully stirring and reacting, removing most sulfate radicals and carbonate radicals in water, dissolving lithium resources in the water in a lithium ion form, and simultaneously raising the pH value of the mother solution to be more than 12 to thoroughly precipitate magnesium ions in the water; S2, solid-liquid separation and cleaning, namely performing solid-liquid separation on the mixed solution after the reaction in the step S1 is fully stirred by using a filter press, and enabling the obtained filtrate to enter a next concentration process; S3, concentrating the filtrate, namely evaporating and concentrating the filtrate obtained in the step S2 by using a refrigerant heat pump low-temperature evaporator, so that the lithium content in the filtrate is increased to be more than 20000mg/L, discharging the obtained condensed water up to the standard, and cooling and crystallizing the concentrated solution in a thickener; s4, centrifugal desalting and cleaning, namely realizing brine separation of lower salt slurry by using a centrifugal machine 1, enabling filtrate obtained by separation to enter a reaction kettle 1, enabling salt slag to enter a cleaning pool, cleaning salt slag obtained by centrifugation by using clear water, and enabling cleaning liquid to return to a refrigerant heat pump low-temperature evaporator for concentration; S5, coarse extraction of lithium carbonate, namely heating filtrate to 90 ℃ in a reaction kettle 1, slowly adding saturated sodium carbonate solution under the stirring condition, conveying the solution to a centrifugal machine 2 while the solution is hot for rapid solid-liquid separation, drying the crushed lithium carbonate filter cake under the condition of 105 ℃ for 2 hours, collecting filtrate separately, adding a reagent for full reaction, and returning to the step S1; s6, carbonizing organic matters at a high temperature, namely loading the lithium carbonate filter cake dried in the step S5 into a high temperature resistant container, putting the container into a high temperature furnace for reaction, burning for 15-60 minutes at 500-650 ℃, taking out and cooling after the organic matters are fully carbonized, and exhausting generated flue gas after alkali liquor absorption and active carbon filtration; S7, acid dissolving to remove boron, namely transferring the lithium carbonate burnt and cooled in the step S6 into a reaction tank 2 with a forced exhaust device, adding a proper amount of hydrochloric acid or sulfuric acid solution to thoroughly dissolve the lithium carbonate, and then filtering by using a filter press to obtain the lithium carbonate Cooling the filtrate to 4 ℃ in a refrigerated cabinet for 2-3 hours, then rapidly filtering, collecting the obtained clear liquid into a reaction tank 3, uniformly collecting filter residues, washing the filter residues with saturated boric acid liquid, and then dehydrating, drying and packaging to obtain boric acid byproducts; S8, deeply removing hardness, namely collecting the clear liquid obtained in the step S7 into a reaction tank 3, sampling and detecting the content of calcium ions and magnesium ions in the clear liquid, adjusting the pH value to be more than 12 by using sodium hydroxide, adding sodium carbonate solution according to the content of the calcium ions, fully reacting, filtering, and allowing filtrate to enter a reaction kettle 2; s9, extracting lithium carbonate, namely heating filtrate to 90 ℃ in a reaction kettle 2, slowly adding saturated sodium carbonate under the stirring condition, conveying the mixture to a centrifugal machine 3 while the mixture is hot for rapid solid-liquid separation, crushing and drying a lithium carbonate filter cake, collecting filtrate separately, adding a reagent for full reaction, and returning to the step S1; And S10, carbonizing and purifying lithium carbonate, namely adding the dried lithium carbonate in the step S9 into a cleaning and dissolving tank with an emptying device, adding pure water for cleaning, continuously introducing high-purity carbon dioxide under normal temperature conditions for aeration, completely dissolving the lithium carbonate, then rapidly filtering, feeding filtrate into a reaction kettle 3, heating to 90 ℃ to separate out a lithium carbonate product, rapidly performing solid-liquid separation while hot by using a centrifugal machine, drying filter residues into a filter cake, collecting and crushing and drying the filter cake, and grinding, screening and bagging the dried lithium carbonate to obtain an industrial grade lithium carbonate product.
2. The method for extracting lithium from the evaporation mother liquor of water produced in a high COD and high boron-containing gas field according to claim 1, wherein in the step S5, the addition amount of the saturated sodium carbonate solution is 1.2 times of the lithium content, the temperature is 90 ℃, and the reaction time is 23 hours.
3. The method for extracting lithium from the evaporation mother liquor of water from a high COD and high boron-containing gas field of claim 1, wherein in said step S9, the crushed lithium carbonate filter cake is dried for 2 hours at 105 ℃.
4. The method for extracting lithium from the evaporation mother liquor of water produced in a high COD and high boron-containing gas field of claim 1, wherein in the step S10, the mass ratio of lithium carbonate to pure water is 1:20, and the cleaning water is recycled for a plurality of times.
5. The method for extracting lithium from the evaporation mother liquor of the produced water of the high-COD and high-boron-containing gas field, which is disclosed in claim 1, is characterized in that the filtrate obtained in the steps S5 and S9 is collected independently, a proper amount of calcium hydroxide or calcium chloride is added for full reaction, and then the filtrate is returned to the step S1, and the filtrate is recycled for a plurality of times.

Description

Lithium extraction method for evaporation mother liquor of water produced in high COD and high boron-containing gas field Technical Field The invention relates to the technical field of resource utilization of evaporation and concentration mother liquor of formation produced water of a gas field, in particular to a lithium extraction method of evaporation mother liquor of produced water of a gas field with high COD and high boron content. Background In the production process of natural gas wells, partial wells can be accompanied with produced water, the produced water usually has the characteristics of high salt content and high COD (chemical oxygen demand), partial produced water contains boron, the produced water can not be directly discharged, corresponding desalting, COD (chemical oxygen demand) removal and ammonia nitrogen removal treatments are needed, and the main treatment mode at present is to perform pretreatment for removing hard matters and suspended matters, membrane concentration, evaporation crystallization of concentrated water and condensate water post-treatment. Most of the water in the evaporation process is converted into condensed water to be discharged, but a small amount of concentrated mother liquor remains, and the condensed mother liquor is usually recycled into the stratum or disposed as dangerous waste, so that the treatment difficulty and the treatment cost are high. The concentrated mother liquor is usually saturated sodium chloride brine, various soluble substances in the water are extremely high in enrichment degree, the appearance is in a reddish brown semitransparent state, and the concentrated mother liquor of a part of treatment stations is found to have lithium content up to 2000-4000mg/L which is far higher than the lithium-rich standard of 80mg/L of salt lake brine and can be recycled through large-scale water quality screening, but at the same time, the COD (chemical oxygen demand) of part of the concentrated mother liquor is found to be up to 50000-100000mg/L, the boron content is found to be up to 20000-40000mg/L, the sulfate concentration is found to be up to 30000-50000mg/L, the carbonate content is also high to be up to about 20000mg/L, the lithium extraction process difficulty is far higher than that of the salt lake brine, and no relevant similar concentrated mother liquor lithium extraction process route or case report exists at home and abroad. Disclosure of Invention The invention aims to provide a lithium extraction method for evaporation mother liquor of water produced in a high COD and high boron-containing gas field, so as to solve the technical problem of resource utilization of evaporation concentration mother liquor of high COD, high boron-containing, high sulfate and carbonate. In order to achieve the above purpose, the present invention provides the following technical solutions: the invention provides a lithium extraction method of a high COD and high boron-containing gas field produced water evaporation mother liquor, which is characterized by comprising the following steps: S1, removing impurities and solubilizing, namely slowly adding a calcium hydroxide solution into a stirring reaction tank filled with a concentrated mother solution, fully stirring and reacting, removing most sulfate radical and carbonate radical in water, dissolving lithium resources in the water in a lithium ion form, and simultaneously raising the pH value of the mother solution to be more than 12 to thoroughly precipitate magnesium ions in the water; S2, solid-liquid separation and cleaning, namely performing solid-liquid separation on the mixed solution after the reaction in the step S1 is fully stirred by using a filter press, and enabling the obtained filtrate to enter a next concentration process; S3, concentrating the filtrate, namely evaporating and concentrating the filtrate obtained in the step S2 by using a refrigerant heat pump low-temperature evaporator, so that the lithium content in the filtrate is increased to be more than 20000mg/L, discharging the obtained condensed water up to the standard, and cooling and crystallizing the concentrated solution in a thickener; s4, centrifugal desalting and cleaning, namely realizing brine separation of lower salt slurry by using a centrifugal machine 1, enabling filtrate obtained by separation to enter a reaction kettle 1, enabling salt slag to enter a cleaning pool, cleaning salt slag obtained by centrifugation by using clear water, and enabling cleaning liquid to return to a refrigerant heat pump low-temperature evaporator for concentration; S5, coarse extraction of lithium carbonate, namely heating the mother liquor to 90 ℃ in a reaction kettle 1, slowly adding saturated sodium carbonate solution under the stirring condition, conveying the solution to a centrifugal machine 2 while the solution is hot for rapid solid-liquid separation, drying the crushed lithium carbonate filter cake under the condition of 105 ℃ for 2 h