Comprehensive utilization method of ionic membrane electrolytic saline solution waste liquid

Abstract

The invention relates to a comprehensive utilization method of an ionic membrane electrolytic saline solution waste liquid, which comprises the step of sending dechlorinated dilute brine coming out of an electrolytic tank to a membrane process denitration device for denitration. The comprehensive utilization method is characterized by comprising the following steps of: pre-adjusting the pH value of a system to 3-8 by using a saline solution pH value automatic control device, exchanging the heat till the temperature of the system is 25-50 DEG C, removing free chlorine till the content of chlorine is less than or equal to 3 ppm, sending into a primary membrane separation system for primary membrane separation and controlling the primary membrane separation pressure to be not higher than 3.0MPa; and then sending into a secondary membrane separation system for secondary membrane separation, controlling the secondary membrane separation pressure to be not higher than 3.5 MPa, separating to obtain desulfurized brine and concentrated nitrate water, sending the dissolved desulfurized brine to an ionic membrane electrolytic saline solution device for reutilization and sending the concentrated nitrate water to a thermal method denitration device to prepare thenardite. The invention has the beneficial effects that as the two stages of membrane separation systems are adopted, the pressure is more stable, the membrane service life is long, and the separation effect is good; the content of sodium sulfate in the separated concentrated nitrate water can reach above 90 g / l, and the content of sodium sulfate in the desulfurized brine can reach below 3 g / l.

Description

technical field [0001] The invention belongs to the field of salt water electrolysis, and in particular relates to a comprehensive utilization method of ion membrane electrolysis salt water waste liquid. Background technique [0002] Ion membrane electrolysis brine waste (light brine) can still be recycled in the ion membrane electrolysis process after further treatment. However, ion membrane electrolysis of brine waste liquid needs to be dechlorinated first with sodium sulfite, and sulfate radicals will be brought into the system after dechlorination with sodium sulfite. The existing ion membrane electrolysis process has strict requirements on the content of sulfate radicals, so it must Separation of sulfate. The traditional separation method of sulfate is to add barium chloride to generate barium sulfate precipitate, and then remove the barium sulfate precipitate. This not only consumes a large amount of barium chloride, but also because barium sulfate is a toxic substan...

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Problems solved by technology

However, in actual operation, since the flow rate and PH value of light brine change, when the flow rate or PH value of light brine changes suddenly, the operator must slowly adjust the flow rate of hydrochloric acid to control the PH value within the acceptable range, and the consumption It takes a long time and the operation is difficult. In addition, because the chemical reaction after acid addition takes time, there is a measurement lag error in the online pH meter, which further leads to errors in the regulation of the pH value of the light brine.

[0004] In addition, the current membrane denitrification system generally adopts a high-pressure one-stage membrane separation process, which has high energy consumption and short membrane life.

In addition, the concentrated nitrate water produced by the membrane denitrification process is not used, which is a serious waste

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