Showing posts with label Raw Material. Show all posts
Showing posts with label Raw Material. Show all posts

February 22, 2010

Improvement in the Quality of Indian China Clay after Various Treatments

In our earlier post [Beneficiation of China Clays] we have discussed regarding the different processes employed for the beneficiation of china clays. The various treatments of beneficiation help to enhance the required chemical constituents through: (a) elimination of the mineral and other impurities, and (b) concentration by achieving required particle size and thus, improve other physical and optical properties for the china clay.     

The following table shows the improvements in the quality of china clay after various treatments:
Constituents %
Feed
Method of Beneficiation
Wet Screening (Product <50 µ)
Hydrocycloning
High Intensity Magnetic Separation (HIMS)
<50 µ
<20 µ
<20 µ
After HIMS
SiO2
82.5
54.9
54.9
46.4
46.4
46.8
TiO2
0.10
0.32
0.32
0.22
0.22
0.10
Al2O3
10.7
30.6
30.6
37.5
37.5
38.0
Fe2O3
0.47
1.21
1.21
1.10
1.10
0.81
CaO
0.03
0.11
0.11
0.12
0.12
0.12
MgO
0.15
0.37
0.37
0.25
0.25
0.25
K2O
2.35
2.51
2.51
1.89
1.89
1.37
Na2O
0.12
0.29
0.29
0.13
0.13
0.10
LOI
2.95
9.69
9.69
12.29
12.29
12.44
% <2µ
--
39
39
50
50
52
Yield %
--
25
--
75
--
90

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February 9, 2010

Characteristics of China Clay Required for Ceramic and Other Industries

China clay is used as an important raw material for a number of industries. The most important is the ceramic industry where it is used for the manufacture of earthware, fine china, tiles etc. and also in other industries such as paper, textile, rubber, pharmaceutical, leather, paint, plastics, petroleum, cosmetic etc. Use of China Clay as Raw Material in the Production of Refractory Insulation Bricks has been discussed in a separate post.

India has extensive deposits of all varieties of china clays most of which after mining and processing, get consumed by the various domestic industries while around 20% - 30% of its total annual production are exported to other countries. The chemical compositions, other properties, uses, and occurrences of Indian china clays have been discussed in detail in a separate article [Read]. 
As we know that the specific requirements of china clays for different industries are different. Here in this article we present the important characteristics [see the Table below] of china clay required for ceramic industry (IS: 2840 - 1993) -

Characteristics
Requirements
Type - I (unwashed)
Type - II (washed)
Grade 1
Grade 2
Grade 3
Grit content / Fineness               (+45 micron IS sieve, max%)
2
3
4
1
Particle size distribution (%)
(a) Coarser than 25 micron (max)
(b) Coarser than 10 micron (max)
(c) Finer than 2 micron (max)

3
10
70

6
12
65

9
15
45

1
5
75
Plasticity (by hand feel)
Very
Good
Fair
Very good
Water of plasticity (max %)
30
32
34
28
Attenberg Number (min)
18
15
12
20
Al2O3 % (min)
28
25
20
28
Fe2O3 % (max)
1.5
2.0
2.0
1.5
TiO2 % (max)
1.5
2.0
2.0
1.5
(Fe2O3 + TiO2) % (max)
2.75
3.5
3.75
2.5
LOI % (max) [dried at 110OC]
10.5
9.5
9.0
11.0
Shrinkage, linear % (max)          [dried at 110OC]
6
7
8
6
Water absorption % (max)        [after firing at 1350OC]
3
5
9
2
Colour after firing at 1350OC
Creamish white
Pale to dull cream
Light gray
White pale cream without specks
MOR (MPa) [at 110OC] (min)
3.5
3.0
2.5
4.0
        
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February 8, 2010

Beneficiation of China Clay

Major Impurities in China Clay are quartz, mica, feldspar and iron oxide minerals. China clay is an important raw material for many industries like rubber, textile, paper, pharmaceutical, cosmetic, paint, and refractory besides ceramic industry. For any value-added application, the run-of-mines (ROM) clay is to be processed to remove or reduce the ancillary mineral impurities associated with the same. Beneficiation helps to achieve required particle size and size distribution and also to attain other physical and optical properties for the clay. [Refer to the article Improvement in the Quality of Indian China Clay after Various Treatments]. The different processes generally employed for beneficiation of china clays are:
1. Size separation through levigation technique;
Refractory Lining | Installation: China clay lump image2. Hydrocycloning by wet route;
3. Magnetic separation by high intensity magnetic separator (HIMS);
4. Froth flotation;
5. Deflocculation;
6. Chemical treatments like Acid Leaching and Bleaching.
7. Drying
8. Micronizing
9. Air-classification and Surface treatment.
Refractory Lining | Installation: China clay after beneficiation image
The ‘Levigation’ process by which the washing is done, involves passing the clay slurry through a series of troughs or channels with different slopes. This process aids in the settling of grit and other heavy mineral while floating of light fractions like mica. Settling of finest quality takes place in the final tank. This beneficiated clay is then dried and marketed to different industries as per the required specification and grading. 
‘Micronizing’ includes Test for physical properties like Bulk density, Oil absorption, Whiteness, and Particle - size distribution analysis etc. Sometimes, Surface Treatment is also done for testing of hydrophobicity, oil absorption and uniformity of coating.   
Mining and beneficiating activities often occur in a single location. De-colorization of clay is also attempted for certain clays which are coloured due to the presence of iron and titanium oxides. This is important since colour after firing is an important characteristic criterion of the china clay which is required for Ceramic Industry and some times in refractory industry too. 
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January 16, 2010

Refractory Properties of Fireclay Deposits Found Around Bihar, Bengal and Jharkhand in India


The chief raw material for the manufacture of fireclay bricks is fireclay itself. In India there are some very good deposits of fireclay spread over many parts of the country mainly Bihar, Bengal, Jharkhand, Andhra Pradesh (AP), Gujarat, Rajasthan and Tamilnadu. Fire clays from Raniganj, Jharia and Rajhara coalfields are very important. The fireclays found in these areas are of all type: Plastic, Semi-plastic, and Non-plastic fireclays. In general, the fire clays from both these coal fields occur within Barakars. Important deposits are found around Suri (Patelnagar or PMI), Birbhum, Raniganj, Barakar, Kulti, Kumardhubi, Mugma, Purulia, Garphalbari-Dahibari region, Damagoria, Ramgarh, Ranchi, Sahjora, Lohardaga, Balumath (near Ranchi, Latehar), Pathardih, Dhanbad, Bankura (Manipur - Beldanga), Rampurhat, Churulia, Radhaballabhpur, Chaibasa, Rajhara and Daltonganj.
Being a refractory technologist, I (the author of this Blog) had been to most of these fireclay mines of the above-mentioned areas and evaluated their samples in refractory labs and also used some of them in the production of refractory bricks and monolithics. Below are the data showing some important refractory and other properties of these fireclays (raw / non-calcined):
Bankura Plastic Clay
(1) Briquette Test at 1400OC / 2hrs:
Total Shrinkage % = 9 - 11
AP % = 24 - 25
BD = 2.20
Characteristics =   Buff, minor crizzling
(2) Chemical Properties:
LOI % - 10  
Al2O3% (min) - 33.0
Fe2O3% (max) - 2.5
TiO2% (max) - 2.5
Na2O% (max) - 0.72
K2O% (max) - 0.44
(3) Refractoriness:
PCE (OC) = 30 - 31
Rampurhat Plastic Clay
(1) Briquette Test at 1330OC / 2hrs:
Total Shrinkage % = 13 - 14
Characteristics =   Buff, crizzling.
(2) Chemical Properties:
LOI % - 12  
Al2O3% (min) - 33.0
Fe2O3% (max) - 4.0
TiO2% (max) - 4.16
Na2O% (max) - 0.70
K2O% (max) - 0.13
(3) Refractoriness:
PCE (OC) = 32½  
Sahjora Plastic Clay (Pink type)
(1) Briquette Test at 1400OC / 2hrs:
Total Shrinkage % = 8 - 10
AP % = 22 - 24
BD = 2.15
Characteristics =   Yellowish, Off-white.
(2) Chemical Properties:
LOI % - 10  
Al2O3% (min) - 25.0
Fe2O3% (max) - 2.5
TiO2% (max) - 1.70
Na2O% (max) - 0.82
K2O% (max) - 1.25
(3) Refractoriness:
PCE (OC) = 28 - 30
Sahjora Plastic Clay (White type, Grade - B)
(1) Briquette Test at 1400OC / 2hrs:
Total Shrinkage % = 8 - 10
AP % = 18 - 20
BD = 2.25
Characteristics =   Deep buff. Shining lusture.
(2) Chemical Properties:
LOI % - 10  
Al2O3% (min) - 28.0
Fe2O3% (max) - 3.0
TiO2% (max) - 2.0
Na2O% (max) - 0.82
K2O% (max) - 1.25
(3) Refractoriness:
PCE (OC) = 28 - 30
Suri Semi-Plastic Clay (Patelnagar)
(1) Briquette Test at 1400OC / 2hrs:
Total Shrinkage % = 13 - 15
AP % = 25 - 27
BD = 2.10
Characteristics =   White, crizzling.
(2) Chemical Properties:
LOI % - 13 - 14  
Al2O3% (min) - 37.0
Fe2O3% (max) - 2.5
TiO2% (max) - 2.5
Na2O% (max) - 0.63
K2O% (max) - 0.08
(3) Refractoriness:
PCE (OC) = 33+
Purulia Stone
(1) Briquette Test at 1400OC / 2hrs:
Total Shrinkage % = Very less (around 1%)
AP % = 7 - 8
Characteristics =   White, no crizzling (a type of hard fireclay or clay-stone).
(2) Chemical Properties:
LOI % - 1 - 3  
Al2O3% - 30 to 31
Fe2O3% (max) - 1.0
(3) Refractoriness:
PCE (OC) = 31
Balumath (near Latehar, Ranchi) Non-Plastic Clay (Black type)
(1) Briquette Test at 1400OC / 2hrs:
Total Shrinkage % = 18 - 20
AP % = 18 - 20
BD = 2.2
Characteristics =   Cream or Off-white.
(2) Chemical Properties:
LOI % - 10 - 11  
Al2O3% (min) - 30.0
Fe2O3% (max) - 1.3
TiO2% (max) - 1.8
(CaO + MgO)% - 0.5
Na2O% (max) - 0.72
K2O% (max) - 0.82
(3) Refractoriness:
PCE (OC) = Close to 32.
Balumath (near Latehar, Ranchi) Non-Plastic Clay (White/Gray type)
(1) Briquette Test at 1400OC / 2hrs:
Total Shrinkage % = 4 - 6
AP % = 22 - 24
BD = 2.2
Characteristics =   White.
(2) Chemical Properties:
LOI % - 10 - 11  
Al2O3% (min) - 30.0
Fe2O3% (max) - 1.3
TiO2% (max) - 2.0
(CaO + MgO)% - 0.5
(Na2O + K2O)% (max) - 1.0
(3) Refractoriness:
PCE (OC) = 31½.
Balumath (near Latehar, Ranchi) Non-Plastic Clay (Brown type)
(1) Briquette Test at 1400OC / 2hrs:
Total Shrinkage % = 8 - 9
AP % = 22
BD = 2.2
Characteristics =   Milky White.
(2) Chemical Properties:
LOI % - 10 - 11  
Al2O3% (min) - 31.5
Fe2O3% (max) - 1.2
TiO2% (max) - 2.0
(CaO + MgO)% - 0.5
(Na2O + K2O)% (max) - 1.0
(3) Refractoriness:
PCE (OC) = 32. 
(To be continued)