# 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 at 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 fumes leave the exchange surfaces at a temperature above the dew point. The 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) of the water formed during combustion and possibly of 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 from the calorific value 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

The 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
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### 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
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calorific various in kCal / kg

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

2 kg of dry wood therefore produces about the equivalent of 1 L of oil

### 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 emissions generated by their use.

The table below reports the CO2 emissions 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

Conversion coefficients in TOE (Ton 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

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#### 4 comments on “Calorific value (PCI / PCS) of gases, fuels and fuels”

1. LOUIS BERTHIER says:

hello .. my annual consumption is 10000KW / year average over 6 years of super BP fuel oil, ie 700 to 970 euros a year depending on the price of fuel oil for a house of 110 M2. hoping with the research of the engineers of the valley of energy to have an organic fuel oil therefore close to the gas energy in rejection. Happy reading. tchao.

2. jluu says:

It would be necessary to define the unit Nm3

1. They are from NORMO M3 (in my time it was still taught ...) ... That is to say this:

The Nm3 is a unit of measurement of quantity of gas which corresponds to the content of a volume of one cubic meter, for a gas found in normal conditions of temperature and pressure (0 ° C or 15 ° C or more rarely 20 ° C according to the standards and 1 atm, i.e. 101 Pa).

3. Louis L'Esperance says:

In BTU, put in order of best performance to worst performance:

Propane
Heating oil
dry wood
Electricity

Goods.