阅读说明：本技术 一种页岩气压返液锂离子资源化处理工艺 (Shale air pressure liquid returning lithium ion recycling treatment process ) 是由 金艳 宋兴福 李丽 张建海 狄磊 黄伙 李峰 陈胤晖 徐曙华 张航 祁嘉炜 于 2020-12-26 设计创作，主要内容包括：一种页岩气压裂返排液中锂资源化处理工艺,包括锂回收、除硬、膜浓缩、生化处理及蒸发结晶五个步骤；首先,页岩气压返液通过依次连接的锂吸附塔、锂脱附装置、富锂收集罐、碳酸锂反应罐和离心分离装置实现锂回收；离心分离装置实现固液分离,分离出的固体为碳酸锂产品,溶液则与锂吸附塔产水混合进入除硬,除硬后进入膜浓缩；膜浓缩产出的浓水进入蒸发结晶得到结晶盐,淡水进入生化处理,达标后排放。本发明可实现页岩气压返液中锂资源的回收；锂回收工艺置于除硬之前可避免锂离子与除硬药剂反应造成损失；解决了锂回收过程中产生的高盐洗脱废液处理问题；膜脱盐浓缩耦合生化处理系统实现压返液中氯化钠的回收及产水达标排放。(A process for recycling lithium in shale gas fracturing flowback fluid comprises five steps of lithium recovery, hardness removal, membrane concentration, biochemical treatment and evaporative crystallization; firstly, shale gas pressure liquid return realizes lithium recovery through a lithium adsorption tower, a lithium desorption device, a lithium-rich collection tank, a lithium carbonate reaction tank and a centrifugal separation device which are connected in sequence; the centrifugal separation device realizes solid-liquid separation, the separated solid is a lithium carbonate product, the solution is mixed with water produced by the lithium adsorption tower to remove hardness, and the solution enters a membrane for concentration after the hardness is removed; concentrated water produced by membrane concentration enters evaporation and crystallization to obtain crystal salt, and fresh water enters biochemical treatment and is discharged after reaching the standard. The invention can realize the recovery of lithium resources in the shale gas pressure return liquid; the lithium recovery process is arranged before the hardness removal, so that the loss caused by the reaction of lithium ions and the hardness removal agent can be avoided; the problem of treatment of high-salt elution waste liquid generated in the lithium recovery process is solved; the membrane desalination concentration coupling biochemical treatment system realizes the recovery of sodium chloride in the pressure return liquid and the standard discharge of produced water.)

1. A shale air pressure liquid returning lithium ion recycling treatment process is characterized by comprising the following steps:

(1) and (3) lithium recovery: recovering lithium ions in the shale gas pressure return liquid;

(2) and (3) hardness removal: adding a softening agent into the shale air pressure return liquid after lithium recovery in the step (1) to remove hardness, suspended matters and organic matters in high-salinity water;

(3) and (3) membrane concentration: carrying out membrane concentration treatment on the shale air pressure return liquid subjected to hardness removal in the step (2) to obtain concentrated water and fresh water;

(4) biochemical treatment: performing biochemical treatment on the fresh water obtained in the step (3), degrading organic matters and ammonia nitrogen, and discharging the produced water up to the standard;

(5) evaporation and crystallization: evaporating and crystallizing the concentrated water obtained in the step (3) to obtain crystalline salt;

wherein the content of the first and second substances,

in the step (1), shale air pressure liquid return realizes lithium recovery through a lithium adsorption tower, a lithium desorption device, a lithium-rich collection tank, a lithium carbonate reaction tank and a centrifugal separation device which are connected in sequence; and the solid obtained after the centrifugal separation device realizes solid-liquid separation is a lithium carbonate product, and the obtained solution is mixed with the water produced by the lithium adsorption tower and then enters the next treatment step.

2. The shale air pressure liquid returning lithium ion recycling treatment process according to claim 1, characterized in that: in the step (1), the adsorbent in the lithium adsorption tower is an ion sieve type adsorbent.

3. The shale air pressure liquid returning lithium ion recycling treatment process according to claim 1, characterized in that: in the step (1), the flow rate in the lithium adsorption tower is 5-15 BV/H.

4. The shale air pressure liquid returning lithium ion recycling treatment process according to claim 1, characterized in that: in the step (1), the temperature of the lithium desorption device is controlled to be 40-80 ℃, and 0.5-2.5mol/L hydrochloric acid is used as an eluent to desorb lithium ions into the eluent.

5. The shale air pressure liquid returning lithium ion recycling treatment process according to claim 1, characterized in that: in the step (1), the pH value of the lithium-rich collection tank is adjusted to be 6.5-7.5.

6. The shale air pressure liquid returning lithium ion recycling treatment process according to claim 1, characterized in that: in the step (1), a precipitator is added into the lithium carbonate reaction tank, wherein the precipitator is a sodium carbonate solution, and the addition amount of the precipitator is 1.2-1.5 times of the theoretical amount.

7. The shale air pressure liquid returning lithium ion recycling treatment process according to claim 1, characterized in that: in the step (2), the softening agent is one or more of sodium carbonate, sodium sulfate or sodium hydroxide.

8. The shale air pressure liquid returning lithium ion recycling treatment process according to claim 1, characterized in that: in the step (3), an electrodialysis method, a reverse osmosis method or a nanofiltration method is selected to realize the concentration and recovery of sodium chloride.

9. The shale air pressure liquid returning lithium ion recycling treatment process according to claim 1, characterized in that: in the step (3), the salt content of the produced fresh water is controlled to be 1-5%, and the salt content of the concentrated water is controlled to be 18-20%.

Technical Field

The invention relates to a recycling treatment process for high-salinity wastewater, in particular to a recycling treatment process for shale air pressure liquid returning lithium ions.

Background

The shale gas field can generate a large amount of flowback water at different stages of fracturing in the process of exploitation, the conventional disposal method is deep well injection, and due to the limitation of the existing laws and regulations, the limited reinjection capacity and other factors, other flowback water disposal schemes have to be found. Therefore, the shale gas produced water treatment scheme which is stable in operation, good in treatment effect and good in economic benefit has great practical significance.

The shale gas produced water is characterized by high salinity (TDS), high Total Suspended Solids (TSS) and high organic matter (COD), and the total dissolved solid content of partial areas can reach 300000 mg/L. The organic matter in the flowback fluid is complex in composition, high in content and poor in biodegradability, and the water quality index fluctuation range of different regions is large.

For salt-containing wastewater, the common treatment modes are nanofiltration, reverse osmosis and electrodialysis. The conventional reverse osmosis is suitable for low salt content, the produced water has low salt content, the salt content in the treatment cannot exceed 5 percent, and the recovery rate is not high; the electrodialysis is suitable for the salt content higher than 3 percent and the concentrated water has large concentration, but the investment and the operation cost are higher. In addition, the membrane treatment method has the inevitable problem of membrane pollution, and an efficient pretreatment process is needed for de-hardening.

Shale gas produced water is usually rich in various useful elements such as Br, I, Li and the like, and is a national shortage substance. Because the components in the shale gas produced water are complex, the fluctuation of various ionic components and concentrations is large, and the difficulty of resource recovery is large, wherein the content of Li is different from 50-300mg/L, the shale gas produced water is suitable for comprehensive utilization or single exploitation, but the existing shale gas produced water treatment process does not involve enrichment and lithium extraction, and the realization of lithium resources in the shale gas pressure return liquid has high industrial value.

Therefore, in order to overcome the defects in the prior art, a shale air pressure liquid-returning lithium ion recycling treatment process needs to be designed to solve the problems.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention aims to provide a shale air pressure liquid-returning lithium ion recycling treatment process.

In order to achieve the above objects and other related objects, the present invention provides the following technical solutions: a shale air pressure liquid returning lithium ion recycling treatment process comprises the following steps:

(1) and (3) lithium recovery: recovering lithium ions in the shale gas pressure return liquid;

(2) and (3) hardness removal: adding a softening agent into the shale air pressure return liquid after lithium recovery in the step (1) to remove hardness, suspended matters and organic matters in high-salinity water;

(3) and (3) membrane concentration: carrying out membrane concentration treatment on the shale air pressure return liquid subjected to hardness removal in the step (2) to obtain concentrated water and fresh water;

(4) biochemical treatment: performing biochemical treatment on the fresh water obtained in the step (3), degrading organic matters and ammonia nitrogen, and discharging the produced water up to the standard;

(5) evaporation and crystallization: evaporating and crystallizing the concentrated water obtained in the step (3) to obtain crystalline salt;

wherein the content of the first and second substances,

in the step (1), shale air pressure liquid return realizes lithium recovery through a lithium adsorption tower, a lithium desorption device, a lithium-rich collection tank, a lithium carbonate reaction tank and a centrifugal separation device which are connected in sequence; and the solid obtained after the centrifugal separation device realizes solid-liquid separation is a lithium carbonate product, and the obtained solution is mixed with the water produced by the lithium adsorption tower and then enters the next treatment step.

The preferable technical scheme is as follows: in the step (1), the adsorbent in the lithium adsorption tower is an ion sieve type adsorbent.

The preferable technical scheme is as follows: in the step (1), the flow rate in the lithium adsorption tower is 5-15 BV/H.

The preferable technical scheme is as follows: in the step (1), the temperature of the lithium desorption device is controlled to be 40-80 ℃, and 0.5-2.5mol/L hydrochloric acid is used as an eluent to desorb lithium ions into the eluent.

The preferable technical scheme is as follows: in the step (1), the pH value of the lithium-rich collection tank is adjusted to be 6.5-7.5.

The preferable technical scheme is as follows: in the step (1), a precipitator is added into the lithium carbonate reaction tank, wherein the precipitator is a sodium carbonate solution, and the addition amount of the precipitator is 1.2-1.5 times of the theoretical amount.

The preferable technical scheme is as follows: in the step (2), the softening agent is one or more of sodium carbonate, sodium sulfate or sodium hydroxide.

The preferable technical scheme is as follows: in the step (3), an electrodialysis method, a reverse osmosis method or a nanofiltration method is selected to realize the concentration and recovery of sodium chloride.

The preferable technical scheme is as follows: in the step (3), the salt content of the produced fresh water is controlled to be 1-5%, and the salt content of the concentrated water is controlled to be 18-20%.

Due to the application of the technical scheme, the invention has the beneficial effects that:

1. the process can realize the recovery of lithium resources in the shale gas pressure return liquid, and the recovery rate of lithium carbonate can reach 80-90%;

2. the process can avoid the loss caused by the reaction of lithium ions and the hardness removing agent by recycling and placing lithium before hardness removal;

3. the process couples lithium recovery with high-salt wastewater treatment, and solves the problem of high-salt elution waste liquid treatment generated in the lithium recovery process;

4. the process membrane desalination concentration coupling biochemical treatment system realizes the recovery of sodium chloride in the pressure return liquid and the standard-reaching discharge of produced water.

Drawings

FIG. 1 is a schematic view of the process of the present invention.

Detailed Description

The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.

As shown in fig. 1, the process for recycling lithium in shale gas fracturing flowback fluid sequentially includes five steps of lithium recovery 1, hardness removal 2, membrane concentration 3, biochemical treatment 4 and evaporative crystallization 5.

When lithium recovery 1 is performed, shale gas pressure return liquid realizes lithium recovery through a lithium adsorption tower 11, a lithium desorption device 12, a lithium-rich collection tank 13, a lithium carbonate reaction tank 14 and a centrifugal separation device 15 which are connected in sequence. The centrifugal separation device 15 realizes solid-liquid separation, solid obtained after the solid-liquid separation is a lithium carbonate product, and the solution obtained after the solid-liquid separation is mixed with water produced by the lithium adsorption tower 11 and enters the hardness removal 2; the shale air pressure return liquid treated by the lithium recovery 1 enters a membrane concentration 3 after hardness removal 2; concentrated water produced by the membrane concentration 3 enters an evaporative crystallization 5 to obtain crystallized salt, fresh water produced by the membrane concentration 3 enters a biochemical treatment 4 to degrade pollutants such as organic matters and ammonia nitrogen, and produced water is discharged up to the standard.

Furthermore, the adsorbent in the lithium adsorption tower 11 is an ion sieve type adsorbent, so that the adsorbent is prevented from adsorbing impurity ions such as calcium, magnesium and the like in the wastewater; the flow rate in the lithium adsorption column 11 was 5-15 BV/H.

Furthermore, the temperature of the lithium desorption device 12 is controlled to be 40-80 ℃, 0.5-2.5mol/L hydrochloric acid is used as an eluent to desorb lithium ions into the eluent, and the desorption rate of the lithium ions can reach 92-95%.

Further, the lithium-rich collection tank 13 is adjusted to have a pH value of 6.5 to 7.5, and can be used as a pretreatment device at the front end of the lithium carbonate reaction tank 14.

Furthermore, a precipitator is required to be added into the lithium carbonate reaction tank 14, the precipitator is a sodium carbonate solution, the addition amount is 1.2-1.5 times of the theoretical amount, and the recovery rate of the lithium carbonate can reach 80% -90%.

Furthermore, softening agents are required to be added in the hardness removal step 2, wherein the softening agents comprise one or more of sodium carbonate, sodium sulfate and sodium hydroxide and are used for removing hardness, suspended matters, organic matters and the like in high-salinity water and preventing scaling of a membrane system;

further, an electrodialysis method, a reverse osmosis method or a nanofiltration method is selected for the membrane concentration 3 to realize the concentration and recovery of sodium chloride, the salt content of the fresh water produced by the membrane concentration 3 is controlled to be 1% -5%, and the salt content of the concentrated water is controlled to be 18% -20%.

Example (b):

(1) the conductivity of certain shale gas fracturing flowback fluid is 69000 us/cm, the total hardness is 6700mg/L, the lithium ion concentration is 75mg/L, the COD is 1150mg/L, and the water amount is 1500 t/day.

(2) The shale gas fracturing flowback liquid is conveyed to a sewage collecting tank through an on-site pipeline, wastewater is pumped into a lithium adsorption tower at the speed of 10BV/H, after adsorption saturation, 1mol/L hydrochloric acid is used as an eluent to desorb lithium ions into the eluent through a lithium desorption device at the temperature of 40-80 ℃, the desorption rate of the lithium ions can reach 92% -95%, and the lithium concentration in the desorption liquid is 600 mg/L; conveying the lithium-rich liquid to a lithium-rich liquid collecting tank through a pipeline, and adjusting the pH value to 6.5-7; and conveying the adjusted lithium-rich liquid to a lithium-rich liquid collecting tank by a pipeline, precipitating lithium by using sodium carbonate as a precipitator, and recovering a lithium carbonate product after centrifugal separation, wherein the recovery rate of lithium carbonate can reach 80%.

(3) Conveying the water produced by the lithium adsorption tower to a hardness removal system by a lifting pump, adding a mixed solution of sodium carbonate and sodium sulfate as a softening agent, coagulating and precipitating by using polyaluminium chloride as a coagulant, wherein the total hardness of the effluent of a sedimentation tank is less than 100mg/L, and reducing the total hardness to below 1mg/L by using hardness removal resin;

(4) the hardness-removing water enters a membrane concentration system, the membrane concentration system adopts an electrodialysis and reverse osmosis coupling mode, concentrated water is concentrated to about 18% through an electrodialysis system, and the salt content of the electrodialysis water is about 1%. The water produced by electrodialysis enters reverse osmosis, the pH value is adjusted to about 6, the conductivity of the water produced by reverse osmosis is 625us/cm, and the water produced by reverse osmosis reaches the sewage discharge standard after being treated by a biochemical system;

(5) and (4) enabling the concentrated water to enter an evaporation crystallization system to obtain crystallized salt.

Therefore, the invention has the following advantages:

the process for recycling lithium in the shale gas fracturing flowback fluid can realize the recovery of lithium resources in the shale gas fracturing flowback fluid; the lithium recovery process is arranged before the hardness removal, so that the loss caused by the reaction of lithium ions and the hardness removal agent can be avoided; the problem of treatment of high-salt elution waste liquid generated in the lithium recovery process is solved; the membrane desalination concentration coupling biochemical treatment system realizes the recovery of sodium chloride in the pressure return liquid and the standard discharge of produced water.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.