Method for removing sodium oxalate from sodium aluminate solution through lime causticization

A technology of sodium oxalate and sodium aluminate, which is applied in the field of metallurgy, can solve the problems of large amount of lime addition, difficulty in sedimentation and separation, and large loss of alumina, so as to reduce the amount of lime addition, increase the causticization rate, and suppress back-causticization Effect

Active Publication Date: 2013-10-09
SHANDONG NANSHAN ALUMINUM +1
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Problems solved by technology

As a result, the impact on alumina production is relatively large: ①The amount of lime added is large, and the loss of alumina is large; ②The solid content of causticizing slurry is high (calcium oxalate monohydrate, calcium aluminate hydrate and calcium carbonate), and sedimentation and separation are difficult; ③Oxalic acid Calcium is easy to undergo reverse causticization reaction in a relatively concentrated sodium aluminate solution, resulting in the conversion of the generated calcium oxalate to sodium oxalate and calcium aluminate hydrate during the red mud washing process, and the sodium oxalate returns to the solution again and loses alumina again

Method used

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  • Method for removing sodium oxalate from sodium aluminate solution through lime causticization

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0015] Dilute the aluminum hydroxide fine seed lotion with red mud washing water, and control the composition of the diluted solution to: Na 2 O T 15g / L, Na 2 O k 15g / L, Al 2 O 3 8.2g / L, Na 2 C 2 O 4 10g / L, according to CaO / Na 2 C 2 O 4 With a molecular ratio of 1, add lime with a particle size of less than 0.9mm, control the stirring speed to 900rpm, and react at 50°C for 1h. The slurry obtained by the reaction is sedimented and separated to obtain a sodium aluminate solution after sodium oxalate. The removal rate of sodium oxalate in sodium aluminate solution is 80.45%, and the sodium aluminate solution after sodium oxalate removal 2 C 2 O 4 The concentration is 0.95g / L. Put the underflow obtained after sedimentation and separation in Na 2 O k 10g / L, Al 2 O 3 11g / L, stirring for 2h at 95℃, decausticizing rate of calcium oxalate is 2.1%, Na in solution 2 C 2 O 4 The concentration is 0.13g / L.

Embodiment 2

[0017] Dilute the aluminum hydroxide fine seed lotion with red mud washing water, and control the composition of the diluted solution to: Na 2 O T 10g / L, Na 2 O k 8g / L, Al 2 O 3 4.1g / L, Na 2 C 2 O 4 8g / L, according to CaO / Na 2 C 2 O 4 The molecular ratio is 0.6 and fresh lime milk is added. The solid particle size in the lime milk is less than 0.9mm. The stirring speed is controlled to 900 rpm, and the reaction is performed at 30°C for 1 hour. The slurry obtained from the reaction was separated by sedimentation to obtain an overflow of the sodium aluminate solution after sodium oxalate, and the solid content in the overflow was 0.1 g / L. The removal rate of sodium oxalate in sodium aluminate solution is 60.78%, and the sodium aluminate solution after sodium oxalate removal 2 C 2 O 4 The concentration is 3.92g / L. Put the underflow obtained after solid-liquid separation in Na 2 O k 3g / L, Al 2 O 3 3.2g / L, stirring at 95℃ for 2h, the decausticizing rate of calcium oxalate is 0....

Embodiment 3

[0019] Dilute the aluminum hydroxide fine seed lotion with red mud washing water, and control the composition of the diluted solution to: Na 2 O T 25g / L Na 2 O k 20g / L, Al 2 O 3 11.1 / L, Na 2 C 2 O 4 15g / L, according to CaO / Na 2 C 2 O 4 With a molecular ratio of 2, add lime with a particle size of less than 0.15mm, control the stirring speed to 1000rpm, and react at 70°C for 10min. The slurry obtained by the reaction is sedimented and separated to obtain a sodium aluminate solution after sodium oxalate. The removal rate of sodium oxalate in sodium aluminate solution is 90.34%, and the sodium aluminate solution after sodium oxalate removal 2 C 2 O 4 The concentration is 1.45g / L. Place the wet cake obtained after solid-liquid separation in Na 2 O k 3g / L, Al 2 O 3 3.2g / L, stirring at 95℃ for 2h, the decausticizing rate of calcium oxalate is 0.24%, Na in solution 2 C 2 O 4 The concentration is 0.10g / L.

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Abstract

The invention discloses a process for removing sodium oxalate from a sodium aluminate solution through lime causticization. The process comprises the following steps of: (1) adding a fine aluminum hydroxide crystal seed cleansing solution into part of red mud wash water, adding a lime additive into a diluted cleansing solution (sodium aluminate solution) containing sodium oxalate according to a molecular ratio of CaO to Na2C2O4 of 0.6-2.0, and reacting for 10-90 minutes at 30-70 DEG C under an enhanced mass transfer condition; (2) performing solid-liquid separation on slurry after reaction to obtain the sodium aluminate solution without the sodium oxalate and an underflow containing calcium oxalate; and (3) adding the sodium aluminate solution without the sodium oxalate into a last tank for red mud washing or a penultimate washing tank for red mud washing, and adding the underflow into the last tank for red mud washing or discharging the underflow along with red mud. According to the process, the sodium oxalate in the sodium aluminate solution can be economically and efficiently removed through lime causticization, the lime addition can be significantly reduced, the causticization rate of the sodium oxalate is improved, the reverse causticization of the calcium oxalate is effectively inhibited, and the alkali consumption is reduced.

Description

Technical field [0001] The invention belongs to the technical field of metallurgy, and particularly relates to a method for causticizing sodium oxalate with lime in a sodium aluminate solution. Background technique [0002] With the rapid development of my country’s alumina industry, the Bayer process, which has a simple process and low cost, has been widely used in my country, whether it is using imported gibbsite-type bauxite as a raw material to produce alumina, or using my country’s monohydrate The diaspore-type bauxite is used as a raw material to produce alumina, and the organic matter in the bauxite will partially enter the sodium aluminate solution during the dissolution process, and complex decomposition reactions occur. During the circulation of the sodium aluminate solution, short-chain organics such as sodium oxalate will accumulate rapidly, causing the concentration of sodium oxalate in the solution to rise rapidly, which significantly affects alumina production, whic...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01F7/47C01F7/14
Inventor 皮溅清赵瑜刘桂华王永林
Owner SHANDONG NANSHAN ALUMINUM
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