# Calorific value (PCI / PCS) of gases, fuels and combustibles

## Calorific value of the main gases and liquid or solid fuels: PCI and PCS.

### gross calorific value: PCS

Definition: the calorific value greater than constant volume of a fuel represents the quantity of heat released by the combustion of the unit of mass of the fuel:

• in oxygen saturated with water vapor,
• the reacting products and the products formed being at the same temperature,
• in the same enclosure,
• the water formed being liquid.

This test is the subject of standard NF M 07-030, and uses a container called a calorimetric bomb.

The definition of calorific value at constant volume does not correspond to industrial combustion taking place at constant pressure, in an open forum, but in fact the difference is small and generally neglected.

The PCS is “useful” when condensing the combustion water (condensing boiler for example).

### lower heating value: PCI

Most of the time the smoke leaves the exchange surfaces at a temperature above the dew point. Water is therefore emitted in the form of vapor.

The PCI is calculated by deducting, by convention, from the PCS, the heat of condensation (2511 kJ / kg) from the water formed during combustion and possibly from the water contained in the fuel.

If the fuel does not produce water, then the PCS = PCI.

### calorific mixtures

The precise analysis of a gas or a liquid makes it possible to calculate its calorific value starting from the calorific power of its constituents using the relation:

#### PCm = sum (xi * PCi)

with:

• PCm: calorific value of the mixture
• PCi: calorific value of the constituents
• xi: mass fraction of each constituent

### Calorific units

Calorific value is expressed in:

• kcal / kg
• kJ / kg
• kWh / kg (= 861 kcal / kg)
• TEP / tonne (= 10000 thermies / tonne) (TEP: Tonne Petrol Equivalent)

The other units (head unit) are as follows:

• milithermy / kg (= kcal / kg) (desused)
• therm / tonne (= kcal / kg) (desused)
• BTU / pound (= 0,5554 kcal / kg) (Anglo-Saxon)

For gas: not expressed per kg but Nm3.

### calorific gas

PCI / PCS kcal / Nm3

• Hydrogen: 2570 / 3050
• Carbon monoxide: 3025/3025 (PCI = PCS as there is no water formation)
• hydrogen sulfide: 5760 / 6200
• Methane: 8575 / 9535
• Ethane: 15400/16865
• Propane: 22380 / 24360
• Butane: 29585 / 32075
• Ethylene: 14210/15155
• Propylene: 20960 / 22400
• Acetylene: 13505 / 13975

### calorific value of liquid fuels. PCI / PCS in kcal / kg

• Hexane 10780 / 11630
• Octane: 10705 / 11535
• Benzene: 9700 / 10105
• Styrene: 9780 / 10190
• Heavy oil: 9550
• Heating oil: 10030 (= 11.7 kWh / kg or 9.9 kWh / L density 0.85)

### calorific value of commercial fuels

Gaseous fuels:

• poor natural gas: 9.2 kWh / Nm3
• rich natural gas: 10.1 kWh / Nm3
• Butane: 12.7 kWh / kg or kWh 30.5 / 3 Nm7.4 or kWh / L (liquid) to 15 ° C
• Propane: 12.8 kWh / kg or kWh 23.7 / 3 Nm6.6 or kWh / L (liquid) to 15 ° C

(Boiling point: butane 0 ° C, propane -42 ° C)

Liquid fuels:

• heating oil: 9.9 kWh / L
• Light Oil: 10.1 kWh / L
• 10.5 average fuel kWh / L
• Heavy oil: 10.6 kWh / L
• Oil extra heavy: 10.7 kWh / L

Solid fuels:

• Coal: 8.1 kWh / kg
• Coke: 7.9 kWh / kg
• Anthracite 10 / 20: 8.7 kWh / kg

calorific various in kCal / kg

• Wood (30% humidity): 2800
• Dry wood: 4350 or 5 kWh / kg

2 kg of dry wood therefore produces approximately the equivalent of 1 L of petroleum

### CO2 emissions

The problem posed by the emission of greenhouse gases by industry makes it necessary to consider fuels from the angle of the CO2 emission generated by their use.

The table below shows the CO2 emission of different fuels per unit of calorific value.

Unit: Tons CO2 PET on the PCI

• Hydrogen: 0
• Natural gas: 2,37
• GPL: 2,67
• Heavy oil: 3,24
• Heating oil: 3,12
• Dry wood: 3,78

### Conversion factors in PET

Coefficients of conversion to TEP (Tonne Oil Equivalent) of various energy sources:

• Coal-Briquettes: 1T = 0,619 toe
• Lignite coal poor: 1T = 0,405 toe
• Coke: 1T = 0,667
• Petroleum coke: 1T = 0,762 toe
• Butane Propane: 1T = 1,095
• Heavy fuel oil (FOL): 1T = 0,952
• heating oil (FOD): 1T 1200L = = 1 toe
• Electricity: 1000kwh = 0,222
• Species: 1T 1320L = = 1 toe
• Super Fuel: 1T 1275L = = 1 toe
• Diesel: 1T 1200L = = 1 toe

## 1 comment on “Calorific value (PCI / PCS) of gases, fuels and combustibles”

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