System for spent lye treatment and treatment method thereof

Abstract

The invention provides a system for spent lye treatment and a treatment method thereof. The system comprises recirculated cooling water unit and a wet-type catalytic oxidation unit, a neutralizing tank unit, an electrolytic oxidation unit, an evaporative crystallization unit and a low-temperature evaporative crystallization unit which are successively connected. The recirculated cooling water unitis respectively connected to the wet-type catalytic oxidation unit, the electrolytic oxidation unit, the evaporative crystallization unit and the low-temperature evaporative crystallization unit. Thesystem has obvious COD removal effect. COD of evaporative crystallization water can be controlled to be less than 100 mg/L. normal and continuous operation of the evaporative crystallization unit isguaranteed, and purity of sodium sulfate salt is also guaranteed. By almost completely converting wastewater into high-quality reuse water and high-quality sodium sulfate salt, the system has a certain economic benefit. According to the system, waste heat generated by oxidation reaction and neutralization reaction is fully recovered and is used as supplementary heat of the evaporative crystallization unit and the low-temperature evaporative crystallization unit. Thus, self-balancing of heat in the whole system can be realized, and operational consumption is greatly reduced.

Description

technical field [0001] The invention relates to the technical field of wastewater treatment, in particular to a system for treating waste lye and a treatment method thereof. Background technique [0002] In the process of petrochemical production, sodium hydroxide solution is often used to absorb hydrogen sulfide, alkali-washed oil and cracking gas, resulting in waste lye containing a large amount of pollutants. The wastewater is characterized by high COD of tens of thousands to hundreds of thousands of milligrams per liter, high concentrations of sulfides, phenols, petroleum and other toxic and harmful substances, strong alkalinity, and pH above 12. [0003] The treatment methods of waste lye mainly include neutralization method, wet air oxidation method, incineration method and so on. The neutralization method is to use inorganic acid to neutralize the waste alkali, and the acid gas (CO2, H2S, etc.) produced is sent to the torch for combustion, and the neutralized waste a...

AI Technical Summary

Problems solved by technology

[0004] For waste lye, the most mainstream treatment process is "wet air oxidation + neutralization + evaporation concentration", which has the following problems: 1. The removal rate of COD by wet air oxidation is limited, resulting in evaporation after neutralization The COD of the concentration system is too high, which seriously affects the operation of the evaporator; 2. Due to the limited removal effect of the system on COD, the organic content of the sodium sulfate salt produced is too high, which has no recovery value as a hazardous disposal; 3. Energy recovery The system is not perfect, a lot of reaction heat is wasted, resulting in high operating costs

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