Defluorination method of fluorine-containing wastewater, and fluidized bed crystallization separator for defluorination

Abstract

The invention provides a fluidized bed crystallization separator for defluorination. The fluidized bed crystallization separator comprises a cylinder body, a guide cylinder, a screening device, and areturn pipe; a water distribution area, a chemical distribution area, a granulation area and a clear water area are sequentially arranged in the cylinder body from bottom to top; the guide cylinder isarranged in the cylinder body and is designed to be coaxial with the cylinder body; the granulation area is divided into a fluidization area, a separation area and a static settling area; the screening device is arranged in the cylinder body, and between the water distribution area and the medicine distribution area, and comprises a screen and a storage device arranged below the screen; one end of the return pipe is connected with the seed crystal feeding opening, and the other end of the return pipe is connected with the storage device and is used for returning screened particles with smaller sizes to the granulation area for recycling. The invention also provides a fluorine-containing wastewater defluorination method realized by the fluidized bed crystallization separator. The fluidizedbed crystallization separator for defluorination and the fluorine-containing wastewater defluorination method provided by the invention are relatively simple in operation condition, relatively low intreatment cost, good in treatment effect, lower in fluorine ion concentration of effluent, free of sludge dehydration and less in seed crystal dosage.

Description

Technical field [0001] The invention relates to a method for removing fluorine from fluorine-containing wastewater and a fluidized bed crystallization separator for removing fluorine, belonging to the technical field of water treatment. Background technique [0002] Fluorine is one of the essential trace elements for human life. The right amount of fluorine can make bones and teeth firm and reduce the incidence of dental caries. However, long-term drinking of water with a fluoride concentration higher than 1 mg / L will cause dental fluorosis; long-term drinking of water with a fluorine concentration of 3-6 mg / L can cause skeletal fluorosis. According to recent data reports, long-term excessive intake of fluoride can cause carcinogenesis and teratogenic reactions. In recent years, environmental water bodies have been suffering from fluorine pollution. On the one hand, more than 150 kinds of fluorine-containing minerals, including the common minerals fluorite, cryolite and fluoro...

AI Technical Summary

Problems solved by technology

At present, the chemical precipitation method is generally used for defluoridation of wastewater, that is, the reaction of lime and fluoride ions is used to generate CaF2, and at the same time, the pH of wastewater is adjusted to 10~11 to reduce the solubility of CaF2. After crystal precipitation occurs, it is removed by precipitation and filtration. The fluorine process will produce a large amount of water-rich sludge with poor settling properties, difficult solid-liquid separation, difficult sludge reuse, and difficulty in reaching the standard for effluent

In addition, since the sedimentation method involves four independent process steps: coagulation, flocculation, sludge / water separation plus sludge dewatering, especially the sludge / water separation in the settler requires high hydraulic retention time, so the traditional sedimentation process requires The area is very high

Adsorption and ion exchange methods are difficult to use in some occasions due to complex operating conditions, solid waste treatment problems in adsorbents or ion exchangers, high cost, and unsuitability for super large water volume (about 10,000~40,000 cubic meters per day). For example, the promotion and application of mining areas

At present, with the development of membrane filtration technology, membrane treatment technology is used in some mining areas, but the current process has the following shortcomings: high operating cost, low average water production rate, high price of membrane modules, and easy pollution; Some minerals that are beneficial to the human body have been removed, so it is not suitable for long-term drinking water

However, the existing fluidized bed crystallizer crystallization method usually obtains calcium fluoride particles, which are difficult to separate due to the light weight of calcium fluoride precipitates and poor settling properties.

In addition, after crystallization, the conventional crystallizer regularly discharges particles, which contain ungrown particles, resulting in waste of crystal seeds, and more new seeds need to be added

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