Resource recovery and zero discharge process for treating rare-earth wet-method smelting wastewater

Abstract

The invention discloses a resource recovery and zero discharge process for treating rare-earth wet-method smelting wastewater, which comprises the following steps: (1) carrying out segregated collection on wastewater; (2) pretreatment: recovering kerosene and P507 from wastewater by floatation oil removal, and precipitating by adding alkali to remove heavy metals and oxalate radicals; (3) recovering NH4Cl in high-concentration ammonia nitrogen wastewater by triple-effect evaporation, concentration and crystallization; (4) denitrifying medium / low-concentration ammonia nitrogen wastewater by ammonia stripping / absorption; (5) carrying out reverse osmosis desalination advanced treatment on the wastewater; and (6) recovering CaCl2 by evaporating, concentrating and crystallizing the reverse osmosis concentrated water. The invention can produce certain economic benefits by recovering kerosene, P507 and industrial-grade NH4Cl products in the wastewater, and the wastewater can achieve the water quality standard for reuse water, thereby realizing zero discharge of wastewater in rare-earth wet-method smelting enterprises.

Description

technical field [0001] The invention relates to a rare earth wet smelting wastewater resource recovery and wastewater zero-discharge treatment process, which belongs to the technical field of wastewater treatment. Background technique [0002] my country is rich in rare earth resources. The world and China's rare earth resource reserves and basic reserves are 88 million tons (REO, the same below) and 150 million tons, 27 million tons and 89 million tons respectively; China's rare earth resource reserves and basic reserves account for the proportion of the world respectively 30.7% and 59.0%, its resource reserves and basic reserves rank first in the world. The main rare earth resources are Baiyun Obo mixed rare earth mine in Inner Mongolia, Maoniuping in Mianning, Sichuan, bastnaesite in Weishan, Shandong, and ion adsorption rare earth mines in Jiangxi, Guangdong, Guangxi, Hunan, Fujian, Yunnan, and Zhejiang. In 2005, the output of rare earth smelting and separation products ...

AI Technical Summary

Problems solved by technology

The process is easy to operate, but it needs to add a large amount of phosphorus and magnesium chemicals, and the operating cost is high. If the precipitated magnesium ammonium phosphate can be sold as agricultural fertilizer, the operating cost can be reduced and its practicability can be increased.

Magnesium ammonium phosphate precipitation method can avoid problems such as scaling and odor of the stripping tower caused by the stripping method, and the treatment efficiency is not limited by temperature. However, the main problem of this method in the treatment of high ammonia nitrogen wastewater is the high treatment cost. Therefore, looking for Inexpensive and efficient precipitants and developing the value of sediments as fertilizers are the future development direction

[0017] At present, most rare earth smelting enterprises in my country are facing serious environmental pressure due to the limitation of wastewater treatment technology and treatment cost. Only some enterprises only use simple evaporation, concentration and crystallization process to recover ammonium chloride for high-concentration ammonia-nitrogen wastewater. Short, high energy consumption, high operating costs, and because of incomplete pretreatment, the recovered ammonium chloride product has low purity, poor economic benefits, and enterprises are not motivated to operate; on the other hand, for the medium For low-concentration ammonia nitrogen wastewater, most enterprises simply add lime to adjust the pH and then discharge it directly, causing great pollution to the ecological environment

At present, there are no relevant reports that comprehensively consider the recycling of rare earth hydrometallurgy wastewater resources and wastewater zero discharge technology. Due to the complex water quality components of rare earth hydrometallurgy wastewater and the large difference in ammonia nitrogen concentration in different process sections, it is obviously not enough to use a single denitrification method. It can meet the requirements of wastewater treatment, so it is urgent to develop a complete set of technology for rare earth hydrometallurgy wastewater resource recovery and wastewater zero discharge treatment

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