Sulfuric acid process titanium dioxide primary washing dilute waste acid membrane integrated recycling zero-discharge treatment method

Abstract

The invention discloses a sulfuric acid process titanium dioxide primary washing dilute waste acid membrane integrated recycling zero-discharge treatment method which comprises the following steps: (1) carrying out solid-liquid separation on titanium dioxide primary washing dilute waste acid to obtain first filtrate; (2) carrying out heat exchange cooling on the first filtrate through a heat exchanger; (3) performing separation and concentration treatment on the cooled first filtrate through a multi-stage nanofiltration membrane system to obtain a first-stage nanofiltration concentrated solution, and treating the first-stage nanofiltration concentrated solution through the multi-stage nanofiltration system to obtain a final nanofiltration membrane purified dilute acid solution; (4) pre-concentrating the final nanofiltration purified dilute acid solution to obtain a pre-concentrated sulfuric acid solution; and (5) evaporating and concentrating the pre-concentrated sulfuric acid solution to obtain a high-concentration sulfuric acid solution which can be directly recycled. According to the invention, a full-physical separation method, namely a membrane integrated treatment process, is adopted, no extra chemical agent is added, and the method is environment-friendly and high in filtering precision.

Description

technical field [0001] The invention relates to a treatment method of sulfuric acid-process titanium dioxide-washing dilute waste acid. Background technique [0002] my country's titanium dioxide production mainly adopts sulfuric acid production process, with a market share of over 90%. The production process of titanium dioxide is mainly iron ore grinding→acidolysis→first washing→bleaching→second washing→salt treatment→calcination→post-treatment. For every 1 ton of titanium dioxide produced, 30-40 tons of titanium dioxide will be produced in the first washing process with a concentration of 4 ~6% dilute waste acid, equivalent to producing 1 ton of titanium dioxide, there will be about 1.5 to 2.0 tons of sulfuric acid remaining in the washed waste acid. In addition, it also contains 1% to 3% ferrous sulfate, 1 to 3g / L metatitanic acid and other small amounts of light and heavy metals. [0003] The more common treatment method for titanium dioxide once-washed dilute waste a...

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Problems solved by technology

[0006] (1) Improper selection of pretreatment methods, such as: the residual insoluble hydrolyzed TiO2 in the waste acid is colloidal fine particles with strong viscosity, and the use of solid-liquid separation equipment such as conventional sand filters and carbon filters is likely to cause serious fouling of the filter layer, or even Compaction, difficult and frequent cleaning; conventional coagulation and sedimentation process, due to the formation of flocculation inclusions, entrained iron ions, etc., cannot recover pure titanium dioxide, and it is difficult to reuse; conventional hollow fiber, roll, flat and other ultrafiltration membranes Components, etc. cannot withstand strong acidic environments, and are generally suitable for operation at pH 2 to 11, and are easily fouled by viscous hydrolyzed TiO2 colloids, which is not practical; if ceramic membranes and TUF tubular membranes are used for large-circulation cross-flow filtration, Although it can control the rapid pollution of the membrane surface caused by pollutant sedimentation and concentration polarization to a certain extent, due to the sticky nature of the hydrolyzed TiO2 colloid, as the colloid concentration increases, it will quickly foul and block the membrane pores, the water production will drop precipitously, and it is difficult to clean and restore It needs to be cleaned with concentrated and strong acid. The requirements for equipment pipelines and membrane materials are very high, and the life of the system and membrane will be greatly reduced.

[0007] (2) The design of the nanofiltration membrane system is unreasonable, the distribution of water production in each section is uneven, and the local concentration polarization is serious, resulting in membrane fouling, frequent cleaning, normal and stable production, high operating pressure of the system, and large energy consumption.

[0008] (3) The choice of pre-concentration method is unreasonable, such as: MVR process, which causes corrosion of the steam compressor and cannot operate normally; such as reverse osmosis process, there are problems such as immature technology of acid-resistant reverse osmosis membrane products

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