Proximate analysis
Select Parameter for Expert Details
1
Enter Weight Readings (W1–W5)
W1
Empty crucible weight
g
W2
Crucible + sample (initial)
g
W3
After moisture (107°C)
g
W4
After volatile (900°C)
g
W5
After ash (750°C)
g
2
Auto-Calculated Parameters
Moisture
8.50%
Volatile
28.00%
Ash
12.00%
Fixed C
51.50%
3
Formulas & Working
Moisture
M = (W2 − W3)/(W2 − W1) × 100
| Sample weight (W2 − W1) | 1.0000 g |
| Moisture loss (W2 − W3) | 0.0850 g |
| Moisture % | 8.50% |
Volatile Matter
VM = (W3 − W4)/(W2 − W1)×100 − M
| Volatile loss (W3 − W4) | 0.2800 g |
| Moisture % (subtract) | 8.50% |
| Volatile Matter % | 28.00% |
Ash
A = (W5 − W1)/(W2 − W1) × 100
| Ash residue (W5 − W1) | 0.1200 g |
| Sample weight (W2 − W1) | 1.0000 g |
| Ash % | 12.00% |
Fixed Carbon
FC = 100 − (M + A + VM)
| Moisture + Ash + Volatile | 48.50% |
| 100 − Sum | 51.50% |
| Fixed Carbon % | 51.50% |
All values auto-update in real time
Fixed Carbon — Quality Guide
Fixed Carbon (FC) indicates the solid combustible residue left after volatile matter is driven off. Higher FC = better quality coal.
Best Quality Range
> 70%
Anthracite / Premium Coal. High heat value, low smoke. Best for metallurgical & industrial use.
★★★★★ Excellent
Good Quality Range
55% – 70%
Bituminous Coal. Standard thermal coal. Good balance of heat output & burn time.
★★★★ Good
Moderate Range
40% – 55%
Sub-bituminous / Lignite. Lower heat value, higher moisture. Used in power plants.
★★★ Moderate
Poor Range
< 40%
Low-grade Lignite / Peat. High moisture & ash. Low calorific value, high smoke.
★★ Poor
Fixed Carbon Quality Spectrum
Higher is Better
0%40%55%70%100%
Higher FC = Higher Calorific Value. More fixed carbon means more heat energy per kg of coal.
Relationship with Volatile Matter: High FC + Low VM = slow burning, high heat (Anthracite). High VM + Low FC = fast burning, low heat.
Moisture & Ash Impact: High moisture or ash reduces FC%. Ideal coal has low M, low A, and high FC.
Industrial Use: FC > 70% → Metallurgy & Coke. FC 55–70% → Thermal Power. FC < 40% → Low-grade heating only.
Standard Reference: IS 1350 / ASTM D3172 define FC as 100 − (M + A + VM). No direct heating is done.
Typical Values: Anthracite: 85–95% · Bituminous: 50–70% · Lignite: 25–35% · Peat: 10–25%.
Best Quality Fixed Carbon: Above 70% · Ideal Coal: Low Moisture + Low Ash + High FC
All Parameters — Complete Definitions
Standard definitions of each proximate analysis parameter as per IS 1350 / ASTM standards.
Moisture (M)
Volatile at 107°C
Moisture is the amount of water present in coal. It is determined by heating the sample at 107°C ± 2°C for 60 minutes in a drying oven until constant weight. Moisture is expressed as a percentage of the original sample weight.
107°C
60 min
Drying Oven
Ash (A)
Incombustible residue
Ash is the inorganic, incombustible residue left after complete combustion of coal. It is determined by burning the sample at 750°C ± 10°C in a muffle furnace until constant weight. Ash reduces the calorific value of coal.
750°C
2–4 hours
Muffle Furnace
Volatile Matter (VM)
Gases & vapours at 900°C
Volatile Matter is the combustible gases and vapours released when coal is heated in the absence of air. It is determined by heating the sample in a covered crucible at 900°C ± 10°C for exactly 7 minutes. VM affects ignition and combustion behaviour.
900°C
7 min
Muffle Furnace
Fixed Carbon (FC)
Solid combustible residue
Fixed Carbon is the solid, combustible residue remaining after moisture, volatile matter, and ash have been removed. It is calculated by difference — not measured directly. Higher FC indicates better quality coal with higher calorific value.
Calculated
Calorific Value
Quality Indicator
All four parameters together define the Proximate Analysis of coal. Proximate = M + A + VM + FC = 100%