Khamizov icsoba2014

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SCIENTIFIC GROUNDS AND PROSPECTS FOR

CLOSED–CIRCUIT PROCESSING OF ALUMINA-

CONTAINING RAW MATERIALS WITH THE USE

OF SALT-ACID METHOD

«NEWCHEM TECHNOLOGY»LLC

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Ruslan Kh. Khamizov,

Natalya S. Vlasovskikh,

Lilya P. Moroshkina

Sultan Kh. Khamizov

Scientific and Technological Company

“NewChem Technology” LLC.

Chasovaya str.,28, Moscow, Russia

Tel. +7(499)137-76-25, Fax. +7(495)939-70-77,

E-mail: [email protected],` [email protected]


mailto:[email protected]

mailto:[email protected]

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1. Acid methods for treatment of low grade bauxite and alumino-

silicates. Analysis of disadvantages.

2. Separation of acids from salts (Acid retardation) with the use of

NewChem process for acid recycling.

3. Closed–circuit processing of alumina-containing raw materials with

the use of salt and salt-acid methods.

OUTLINE


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1. ACID METHODS FOR TREATMENT OF LOW

GRADE BAUXITE AND ALUMINO-SILICATES.

ANALYSIS OF DISADVANTAGES.


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Main advantage

Silica is separated at the very first stages of the process without

additional inputs of its binding reagents

Disadvantage of acid methods

a) supplementary processing and additional steps are needed

for iron removal;

b) difficulties arise in the creation of closed reagent-free or low-

reagent-intake processes.

c) as a rule, these processes are characterized by high energy

consumption;

d) typically, hard-filterable mixes are formed at acid digestion

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Difficulties in reagent saving and high energy

consumption

Thermo-hydrolysis of compounds containing acid residues and aluminum

(as well as iron) is the main approach to “save” and recycle acids in

technological circuits.

1. High-temperature treatment of nitrates or sulfates leads to the emission

of SO2 or NO2 from which the acids should be recovered

2. Thermo-hydrolysis requires high energy.

CLAY

DIGESTION SEPARATION SEPARATION

HCl

H2O

SiO2 Fe2O3

CRYSTALLIZATION CALCINATION

Al2O3

Principle of Hydrochloric Acid Process with Thermo-Hydrolysis of AlCl3.6H2O

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2. SEPARATION OF ACIDS FROM SALTS (ACID

RETARDATION) WITH THE USE OF NEWCHEM

PROCESS FOR ACID RECYCLING.


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Hatch M. J. and Dillon J. A, US Patent No. 3067007, Dec. 4, 1962 ;

Hatch M. J. and Dillon J. A, US Patent No. 3099529, July 30, 1963;

Hatch M. J. and Dillon J. A., Industrial and Engineering Chemistry : Process

Design and Development, 2 (4), 253, October 1963.

ACID RETARDATION PROCESS

At the treatment anionic resin with concentrated mixed solutions of acids and their

metal salts, the acids can be retained by the resins at the conditions of anion

equilibrium between phases.

R-SO4

NiSO4+H2SO4

NiSO4

1-st phase

UPSTROKE R-SO4

H2O

H2SO4

2-nd phase

DOWNSTROKE

V

C

NiSO4 H2SO4 H2O

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Recoflo unit (Eco-Tec Inc.)

More than 400 industrial units operate in the world. Fields of application:

acid treatment in different industries, treatment of liquid concentrates after

acid leaching in hydro-metallurgy

Special requirement to the units is their loading with highly compressed

sorption bed to exclude (reduce) the inter-particle space (porosity) which

allows good separation.

Diameter – 274 cm

Height - 122 cm

Bead sizes – 80-120 US

mesh (175-125 microns)

Now, 250 -270 US mesh

(65-75 microns)

Pressure – more than 435

psi or 30 bars (1 psi = 6.9

kPa)

Cycle time – 15 -30 min,

dependently on the process

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Modern research has revealed the mechanism of AR – process which consists in

the possibility of separation of acids and salts by any nano-porous medium due

to the large difference between the sizes of their ion pairs in concentrated

solutions.

Concentrated salt-acid mixes are formed at acid digestion of alumina-containing

raw materials. In principle, the Acid Retardation process can be used for further

processing of them to recycle acid as the reagent

At acid removal from aluminum- and iron – containing solutions, hydrolysis can

take place and suspends can be formed

The existing standard AR - units loaded with highly compressed beds of sorption

materials can not be applied because they can not operate with suspensions

Another approach is required

How to use the AR-process

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Soft sponge

Sorbent bead

Organic liquid

Solution to be treated

Effluent

NewChem

method

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NewChem

method

Ultra-thin film of

solution under treatment

Fluid draining at

contact points

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Photograph of bench-scale pilot plant for separation of ionic mixtures in column

with organic phase. Loading: strong base anionic resin AV-17, sulfate form; bed

volume: 3150 ml, swollen in water and filled with decanol.

Organic phases and equipment

Dodecane

Decanol

Nonanoic acid

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Composition of initial solution of acid leaching

H2O - 67.00%

Al(NO3)3 - 16.01%*

HNO3 - 7.28%

NaNO3 - 5.91%

KNO3 - 2.10%

Fe(NO3) - 1.25%*

SiO2 - 0.005%

Three problems related to the residual nitric acid (7.28% versus 25.72% of the sum of

other nitrates):

1) at neutralization, up to 30% of acid consumed in the technological process is uselessly

discharged (lost);

2) over-expenditure of alkali – around 30%

3) removal of iron is difficult (partial precipitation is impossible)

It is advisable to try to perform “soft” hydrolysis of Fe(NO3) at Acid Retardation

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Treatment of the acid solution of nepheline leaching

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Break-through concentration

curves of HNO3 (1, 1`) and

dissolved Al (2) in one of the

repetitive separation cycles of

the acid process. 3 –

concentration of Fe in effluent

samples before the precipitation

of iron hydroxide . Laboratory

column loadings: 90 ml of

granulated strong base anionic

resin AV-17 of gel type in NO3-

form. Organic phase - decanol.

Flow rate: 2 BV h-1.

Two effects:

1.All the residual acid is separated and can be recycled into the digestion process

2.Due to “soft” hydrolysis, nitrate bonded with Fe is transformed into HNO3 and recycled

3[R-NO3…H2O] + Fe(NO3)3 = Fe(OH)3↓ + 3[R-NO3

…HNO3]

3[R-NO3…HNO3] + 3H2O = 3[R-NO3…H2O] + 3HNO3

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3. Closed–circuit processing of alumina-containing

raw materials with the use of salt and salt-acid

methods


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The Buchner (“Aloton”) process.

Ammonium hydro-sulfate (bisulfate) process was invented by Max Buchner in Hanover-Kleefeld

in 1921, piloted in Germany in the 1920s and in USA (Oregon) in 1944. Now this is included in the

List of Named Processes in Chemical Technology as the “Aloton” or “Buchner” process.

Circular process comprising the steps of thermal decomposition of ammonium sulfate into

ammonia and ammonium bisulfate, dissolving the latter to treat the aluminum-containing

feedstock in an autoclave, filtration of solution of alum and precipitating aluminum hydroxide with

ammonia, isolation of ammonium sulfate from the mother liquor to return it to the head of circuit.

The process was not commercialized, and it can be assumed that in those days, in the case of

good access to high quality raw bauxite materials, the Buchner process could not withstand

competition with the Bayer one

CLAY

DIGESTION SEPARATION EXTRACTION

H2O

H2SiO3 Fe-COMPAUND

PRECIPITATION SEPARATION

Al(OH)3

(NH4)2SO4 NH4HSO4 NH3

EVAPORATION

(NH4)2SO4-SOLUTION

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Disadvantages of the Buchner process.

Whether they can be overcome.

1. The method is suitable for processing readily degradable clay materials and

other alumino-silicates, but is poorly applicable to Bauxites.

2. Silica is not completely removed at the digestion stage.

3. Complete reagent recycling is not reachable. Due to loosing of the part of

reagent with the components as Na, K, Ca, Si , the recycled solution become

more and more neutral (and inefficient) from cycle to cycle.

All of these problems can be solved by Salt-Acid method at using ammonium

bisulfate with minor addition of sulfuric acid.

The problem of acid recycling can arise again. But the NewChem

(Acid Retardation) process can be applied

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Salt – Acid process compared to the Buchner one

The degree of leaching for various alumina sources at the use of ammonium bisulfate and

it with small addition of sulfuric acid. (S/L = 1:10, digestion time - 3 hours)

Temperature, 0C

Nepheline

40%

solution of

NH4HSO4

Nepheline

40% NH4HSO4

+ 1% H2SO4

Kaolin

40%

solution of

NH4HSO4

Bauxite

40%

solution of

NH4HSO4

Bauxite

40% NH4HSO4

+ 1% H2SO4

85 48 66 52 18 55

90 72 95 59 44 58

98 85 99 59 48 60

120 98 98 65 60 81

150 92 100 80 62 86

175 96 99 87 65 89

Chemical composition of raw materials (mass %)

Al2O3 Fe2O3 SiO2 TiO2 K2O MgO Na2O P2O5 SO3 CaO SrO MnO H2O

Bauxite 47.7 28.3 8.0 2.8 0.63 0.39 0.23 0.22 0.20 0.17 - 0.04 11.5

Kaolin clay 18.3 2.7 64.2 1.7 2.0 0.89 2.1 0.15 - 0.87 - 1.0 7.0

Nepheline 28.0 2.4 44.0 0.55 7.6 0.45 12.5 0.17 - 1.75 0.11 0.08 1.5

Experiments have been carried out with three types of alumina-containing raw materials from

different deposits of Russia : 1)Timan bauxite of hematite-boehmite type; 2)Kaichak kaolin clay

and 3)Kola nepheline concentrate.

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Flow diagram

for salt-acid

process

For the production of

1 kg of the

metallurgical alumina

in repetitive

technological cycles,

are required:

- 2.63 kg of bauxite;

- 100 g of technical

grade (93%) sulfuric

acid;

- 30 g of ammonium

sulfite;

- 40 g of calcium

hydroxide;

- 1.2 l (kg) of softened

water;

- 7.5 kg of steam.

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Treatment of the solution of bauxite leaching with the mix: NH4HSO4 + H2SO4

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Break-through concentration

curves of H2SO4 (1, 1`) and

dissolved Al (2) in one of the

technological cycles. 3 –

concentration of Fe in effluent

before the precipitation. Pilot

column loadings: anionic resin

AV-17 of gel type in SO4 -form.

Organic phase - decanol.

[R-SO4…H2O] + NH4Fe(SO4)2 + 2Н2О = Fe(OH)3↓ + NH4HSO4 + [R-SO4

…H2SO4]

[R-SO4…H2SO4] + 3Н2О = [R-SO4

…H2O] + 2Н2О + H2SO4

H2SO4 + (NH4)2SO4 = 2 NH4HSO4

NH4Fe(SO4)2 + (NH4)2SO4 + 3Н2О = Fe(OH)3↓ + 3NH4HSO4

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CONCLUSION

Salt-acid method is proposed, experimentally tested and the opportunity

for closed-circuit process for high-silica bauxite and alumino-silicates is

demonstrated.

The NewChem method is introduced and its advantages are shown.

They include returning the residual acid in the process; carrying out

additional purification of work solution from iron; carrying out low-energy

consuming process of soft hydrolysis and additional returning the

corresponding amount of acid in the process.


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Thank you very much for

kind attention

Science

Khamizov icsoba2014