CN104743586A

CN104743586A - Joint production method of alkali leaching of aluminium in Bayer red mud and aluminium oxide decomposed mother liquid evaporation for salt elimination

Info

Publication number: CN104743586A
Application number: CN201310741424.9A
Authority: CN
Inventors: 张亦飞; 郭涛; 曹绍涛; 张懿
Original assignee: Institute of Process Engineering of CAS
Current assignee: Institute of Process Engineering of CAS
Priority date: 2013-12-27
Filing date: 2013-12-27
Publication date: 2015-07-01
Anticipated expiration: 2033-12-27
Also published as: CN104743586B

Abstract

The invention relates to a joint production method of alkali leaching of aluminium in Bayer red mud and aluminium oxide evaporation for reinforcing salt elimination. The method comprises the following steps: dissolution of aluminium in Bayer red mud in a high alkaline solution, alkali extraction of Al-extracted red mud, red mud digested liquor and evaporation discharged material blending, sedimentation and salting-out, evaporation of a feed liquid after salting-out, deep crystallization of evaporation mother liquor for Al extraction, and circulation dissolution of Bayer red mud for crystallization mother liquor. According to the method, the alkaline solution is a NaOH solution or a KOH solution, and recovery rates of aluminium oxide and sodium oxide in red mud are both above 82%. By the above method, energy consumption of the evaporation process can be remarkably reduced.

Description

The combine production method of the leaching of aluminium alkali and the salt discharge of alumina decomposition mother liquid evaporation in a kind of Bayer process red mud

Technical field

The present invention relates to field of aluminum oxide production, particularly Bayer process red mud comprehensive utilization and alumina evaporation operation are saved energy and reduce the cost field.

Background technology

Have Bayer process, sintering process and integrated process three kinds for industrial alumina-producing method, wherein more than 90% is adopt Bayer process to produce.China's bauxite resource more than 98% is diaspore, and the leaching temperature of bayer process is usually at 240 ~ 260 DEG C, and stripping liquid concentration is 240 ~ 300g/L Na ₂o.Because ore grade is different, often produce 1 ton of aluminum oxide and be about output 0.6t ~ 1.5t red mud, nearly 300,000,000 tons of domestic red mud accumulation volume of cargo in storage.Within 2011, China's aluminum oxide output reaches 3417.6 ten thousand tons, and outer row's red mud is more than 5,000 ten thousand tons, and within 2012, China's aluminum oxide output increases by 10.3% than last year, and outer row's red mud also increases by a year-on-year basis.The main processing ways of red mud is stored up red mud dump for building a dam and is caused alkalization of soils, and serious environmental problem is brought in polluted underground water source, becomes the thorny problem of China's aluminum i ndustry Sustainable development.Domestic and international researchist does a lot of work to red mud comprehensive utilization, achieves some application in fields such as cement adding material and road-making materials, but is limited to economic dispatch factor and fails to realize large-scale application, and red mud comprehensive utilization ratio is about 4%.

Evaporization process is operation very important in alumina producing Bayer process technique, and its task is the water yield in balance aluminium oxide production process and despumation salt.According to the tenth aluminum oxide technology information fair statistic data, evaporation energy consumption accounts for 20% ~ 25% of alumina producing energy consumption, and the steam consumption accounts for 48% ~ 52% of total steam consumption, and cost accounts for 10% ~ 12% of production cost.The evaporation unit of China's alumina technology exists that steam consumption is high, cycle efficiency is low, easy fouling, evaporative water capacity do not reach many drawbacks such as design load, makes evaporation become the weak link of China's alumina producing.Current evaporation technology is many evaporates enrichment in falling-film evaporator, enters pump feed evaporator evaporation again and analyse salt in solution before the precipitation of impurity salt.Pump feed evaporator speed of circulation is high, efficiency is high, can adapt to have the evaporation under solid precipitation condition preferably, but its internal circulating load is large, and power consumption is high, hot face energy consumption about 0.3 ~ 1.8kw/m ².

Patent CN101538058B, CN101607725B provide the method that two kinds are reclaimed aluminum oxide and sodium oxide from red mud; Patent CN103030160A discloses a kind of method reclaiming aluminum oxide and sodium oxide fast from Bayer process red mud, can realize the degree of depth crystallization of aluminium silicon high efficiency separation and sodium aluminate solution.The flow process of above patent is high to sodium aluminate crystallization process entails, and crystalline mother solution could realize the recycle of medium after pervaporation.

Summary of the invention

The present invention is in conjunction with the Bayer process red mud treatment technology of patent CN103030160A, target is utilized as with the recycle to extinction of the degree of depth crystallization of sodium aluminate and material, Bound moisture chemical method red mud dissolution fluid alkali concn is high, molecular ratio advantages of higher, combine existing Bayer process evaporation technology, realize the quick precipitation of impurity salt in mother liquid evaporation, analyse the solution after salt and again enter vaporizer enrichment.Because salt is separated out when entering vaporizer, the efficiency of vaporizer can increase substantially, and the mother liquid evaporation after enrichment carries out the crystallization of the sodium aluminate degree of depth, and crystalline mother solution can meet the stripping of Bayer process red mud.

Utilize the method, the technique of hydro chemical method process Bayer process red mud can be connected with existing bayer process preferably, reduce facility investment, the carbonate content in Bayer process circulating mother liquor can be reduced simultaneously, reduce evaporization process energy consumption.Described process for combination producing, comprises the following steps:

1) by Bayer process red mud, alkali lye, lime mixing, carry out stripping after allotment, obtain stripping slurries.In stripping slurries liquid phase, the massfraction of alkali lye is 30 ~ 80%, and the mass ratio of alkali and butt red mud is 2:1 ~ 10:1, CaO and SiO in stripping slurries solid phase ₂mass ratio be 1:1 ~ 3.8:1;

2) stripping slurries after filtration, obtains dissolution fluid and red mud, and red mud is outer row after de-sodium;

3) decomposition nut liquid is after evaporator enrichment, obtains evaporating discharging.The severe alkali concn of evaporation discharging is 200-300g/L, and molecular ratio is 2.8-3.2;

4) by step 2) the evaporation discharging that obtains of the dissolution fluid and the step 3) that obtain mixes, and the impurity such as sodium carbonate, sodium sulfate salt rapid crystallization is separated out, and mixed serum, through sedimentation, obtains overflow and underflow, and underflow goes causticization operation;

5) overflow devaporation device evaporation concentration step 4) obtained, obtains mother liquid evaporation;

6) mother liquid evaporation that step 5) obtains is cooled to 30 ~ 90 DEG C, crystallization carried out solid-liquor separation after 3 ~ 10 hours, obtained aluminate hydrates sodium crystal filter residue and crystalline mother solution;

7) crystalline mother solution that obtains of step 6), after mending alkali allotment and be qualified, carries out the hydro chemical method circulation stripping of Bayer process red mud.The aluminate hydrates sodium crystal filter residue that step 6) obtains, after dissolving desiliconization, obtains decomposing front liquid, through decomposition process, obtains aluminum hydroxide precipitation, and after washing, calcining, obtains alumina product, decomposition nut liquid devaporation device evaporation concentration;

Accompanying drawing explanation

Fig. 1 is the process flow sheet of combine production method embodiment of the present invention.

Embodiment

Using the Bayer process red mud of Henan alumina producer as raw material, red mud composition, evaporation discharging composition are as described in table 1, table 2:

Table 1 red mud composition

Table 2 evaporates discharging composition

Embodiment 1:

(1) Henan alumina producer Bayer process red mud is mixed with concentrated sodium hydroxide, be deployed into that liquid phase NaOH massfraction is 45%, the mass ratio of liquid phase NaOH and butt red mud is the slip of 4:1, add lime and make CaO and SiO in solid phase ₂mass ratio be 1.4:1, slip is carried out stripping in autoclave, and leaching temperature is 230 DEG C, and dissolution time is 1h, the stripping slurries containing sodium aluminate and red mud slag obtained;

(2) filtered by stripping slurries, filtrate lightens with evaporation three expects that 4:3 mixes by volume, obtains mixed serum, and filter after 80 DEG C of standing 1h, the severe alkali concn of mixing filtrate is 409.9g/L, and molecular ratio is 6.52.Filter cake removes de-sodium, outer row's red mud Al ₂o ₃, Na ₂o is down to 4.77%, 1.20% respectively;

(3) mixing filtrate being carried out evaporation concentration to severe alkali concn in self-control vaporizer is 485g/L, separates out in evaporative process without salt.Mother liquid evaporation is crystallization 4h at 60 DEG C, and crystalline mother solution molecular ratio is 27.8.

Embodiment 2:

(1) mixed by the crystalline mother solution that Henan alumina producer Bayer process red mud and example 1 obtain, the mass ratio being deployed into liquid phase NaOH and butt red mud is the slip of 5:1, adds lime and makes CaO and SiO in solid phase ₂mass ratio be 1.2:1, slip is carried out stripping in autoclave, and leaching temperature is 230 DEG C, and dissolution time is 1h, the stripping slurries containing sodium aluminate and red mud slag obtained;

(2) stripping slurries are filtered, filtrate and evaporation force to imitate discharging by volume 1:1 mix, obtain mixed serum, filter after 80 DEG C of standing 1h, mixing the severe alkali concn of filtrate is 428.6g/L, and molecular ratio is 5.91.Filter cake removes de-sodium, outer row's red mud Al ₂o ₃, Na ₂o is down to 5.14%, 1.61% respectively;

(3) mixing filtrate being carried out evaporation concentration to severe alkali concn in self-control vaporizer is 530.9g/L, separates out in evaporative process without salt.Mother liquid evaporation is crystallization 4h at 60 DEG C, and crystalline mother solution molecular ratio is 31.9.

Embodiment 3:

(1) mixed by the crystalline mother solution that Henan alumina producer Bayer process red mud and example 2 obtain, the mass ratio being deployed into liquid phase NaOH and butt red mud is the slip of 4:1, adds lime and makes CaO and SiO in solid phase ₂mass ratio be 1.4:1, slip is carried out stripping in autoclave, and leaching temperature is 230 DEG C, and dissolution time is 1h, the stripping slurries containing sodium aluminate and red mud slag obtained;

(2) filtered by stripping slurries, filtrate lightens with evaporation three expects that 1:1 mixes by volume, obtains mixed serum, and filter after 80 DEG C of standing 1h, the severe alkali concn of mixing filtrate is 390.2g/L, and molecular ratio is 6.46.Filter cake removes de-sodium, outer row's red mud Al ₂o ₃, Na ₂o is down to 5.25%, 1.53% respectively;

(3) mixing filtrate being carried out evaporation concentration to severe alkali concn in self-control vaporizer is 472.4g/L, separates out in evaporative process without salt.Mother liquid evaporation is crystallization 3h at 60 DEG C, and crystalline mother solution molecular ratio is 27.1.

Embodiment 4:

(1) mixed by the crystalline mother solution that Henan alumina producer Bayer process red mud and example 2 obtain, the mass ratio being deployed into liquid phase NaOH and butt red mud is the slip of 5:1, adds lime and makes CaO and SiO in solid phase ₂mass ratio be 1.16:1, slip is carried out stripping in autoclave, and leaching temperature is 230 DEG C, and dissolution time is 1h, the stripping slurries containing sodium aluminate and red mud slag obtained;

(2) stripping slurries are filtered, filtrate and evaporation force to imitate discharging by volume 3:4 mix, obtain mixed serum, filter after 80 DEG C of standing 1h, mixing the severe alkali concn of filtrate is 414g/L, and molecular ratio is 5.29.Filter cake removes de-sodium, outer row's red mud Al ₂o ₃, Na ₂o is down to 4.74%, 1.33% respectively;

(3) mixing filtrate being carried out evaporation concentration to severe alkali concn in self-control vaporizer is 497g/L, separates out in evaporative process without salt.Mother liquid evaporation is crystallization 3h at 60 DEG C, and crystalline mother solution molecular ratio is 28.3.

Claims

1. aquation method process Bayer process red mud and an alumina decomposition mother liquid evaporation salt discharge combine production method, is characterized in that, comprise the steps:

1) by bauxite at concentrations by weight be 30% ~ 80% alkaline solution in carry out stripping, the mass ratio of alkaline solution and butt red mud is 2:1 ~ 10:1, CaO and SiO in stripping slurries solid phase ₂mass ratio be 1:1 ~ 3.8:1;

2) the stripping slurries that step 1) obtains obtain dissolution fluid and red mud after filtration;

3) evaporating discharging severe alkali concn is 200-320g/L, with step 2) dissolution fluid that obtains mixes, and the severe alkali concn of mixed solution is 320-450g/L, and molecular ratio is 2.8 ~ 9, carries out sedimentation and analyses salt, obtain overflow and underflow;

4) overflowing liquid that step 3) obtains concentrates through evaporator evaporation, and the severe alkali concn of the mother liquid evaporation obtained is 450-580g/L, and molecular ratio is 2.8 ~ 9;

5) temperature of mother liquid evaporation degree of depth crystallization is 30 ~ 90 DEG C, and crystallization time is 3 ~ 10 hours, and crystalline mother solution molecular ratio is 22 ~ 30;

6) crystal filter residue water step 5) obtained or sig water dissolve, and then decompose after desiliconization, decompose the rear roasting of aluminium hydroxide washing obtained, obtain alumina product.

2. by aquation method process Bayer process red mud according to claim 1 and alumina decomposition mother liquid evaporation salt discharge combine production method, it is characterized in that, aquation method process Bayer process red mud dissolution fluid mixes with the feed liquid of evaporization process by the method, utilize the feature that aquation method red mud dissolution fluid alkali concn is high, make the evaporation feed liquid close to sodium carbonate saturation point separate out the impurity such as sodium carbonate, sodium sulfate salt fast.

3. by aquation method process Bayer process red mud according to claim 1 and alumina decomposition mother liquid evaporation salt discharge combine production method, it is characterized in that, vaporizer is mainly used to concentrated alkali lye, the impurity such as sodium carbonate, sodium sulfate salt is not separated out in vaporizer, effectively prevent the fouling of hot face, thus significantly improve vaporization efficiency.