Method for excluding sodium oxalate and carbonate from Bayer process solution by adopting ultra-concentration method

Abstract

The invention discloses a method for excluding sodium oxalate and carbonate from Bayer process solution by adopting an ultra-concentration method. The method comprises the steps of: concentrating the mother liquor of an alumina system, sending liquor in the concentrated mother liquor to an alumina production system, and then send to a first segment causticization tank for causticizing for 2 to 4 hours to obtain seriflux B after solid phase dissolution; cooling the seriflux B to 50 to 70 DEG C and send to a second segment causticization tank for causticizing for 1.5 to 3 hours at 50 to 70 DEG C to obtain seriflux C; sending the seriflux C into a separating and washing machine, sending washed liquid to the alumina production system, and sending residues an alumina red mud washing system. The invention not only has the advantages of good excluding effect, simple process, less investment and low production and operation cost, but also achieves less loss of alumina, and has good use value and economic value.

Description

Technical field: [0001] The invention relates to a method for removing sodium oxalate and carbonate from a Bayer solution by adopting a super-concentration method, and belongs to the technical field of removing oxalate and carbonate from a Bayer solution. technical background: [0002] The source of sodium oxalate in the alumina production process is mainly the carrying of bauxite, followed by auxiliary materials containing organic matter added to meet production needs (such as: flocculants, lubricants, antifoaming agents, etc.). Because sodium oxalate continues to accumulate in the process, when the accumulation reaches a certain concentration, it will bring great harm to the production of alumina. The main harm is: 1. Reduce product quality: the solubility of sodium oxalate in sodium aluminate solution varies with As the temperature decreases, the decomposition in Bayer process production is a cooling process, which creates convenient conditions for the precipitation of so...

AI Technical Summary

Problems solved by technology

Because sodium oxalate continues to accumulate in the process, when the accumulation reaches a certain concentration, it will bring great harm to the production of alumina. The main harm is: 1. Reduce product quality: the solubility of sodium oxalate in sodium aluminate solution varies with As the temperature decreases, the decomposition in Bayer process production is a cooling process, which creates convenient conditions for the precipitation of sodium oxalate crystals, which seriously affects product quality.

2. Sodium oxalate promotes the production of fine aluminum hydroxide crystals, resulting in unqualified product particle size. During the decomposition process, sodium oxalate is precipitated with aluminum hydroxide at the same time, so the product particle size will be further refined during the hydroxide roasting process. Sodium oxalate Co-precipitation with aluminum hydroxide will lead to an increase in the alkali content of aluminum hydroxide crystals

3. Reduce the agglomeration efficiency and crystallization growth rate during the decomposition process, reducing the decomposition output rate and cycle efficiency

4. The solution containing high sodium oxalate will produce a lot of foam during the transportation and storage process, causing the equipment to fail to meet the load operation

5. After the sodium oxalate reaches the saturated concentration, it will be precipitated in the vertical seed filter, the heat exchange surface of the semen heat exchange, the inner wall of the decomposition tank and the heating surface of the evaporator, which will not only reduce the production capacity of the equipment itself, but also lead to The equipment cleaning cycle is shortened, and the equipment operation rate is low; in addition, the heat transfer effect of the evaporator and heat exchange equipment will be reduced

6. There are a large number of atmospheric pressure equipment in the production of alumina. If there is a slight carelessness, the lye or slurry in this equipment will overflow together with the organic foam, which will affect industrial hygiene and environmental protection.

This method has been tried in a factory, and it has been proved that not only the removal of organic matter is poor, but also lime will react with sodium aluminate to form calcium aluminate, resulting in the loss of alumina

5. Ion exchange method: the Bayer method solution is passed through the ion exchange resin to achieve the purpose of eliminating organic matter in the solution. This method not only has the problem of difficult regeneration of the ion exchange resin and high cost, but also the removal of organic matter is also very limited.

Images