# Methane number

Methane number of different gases

The methane number (abbreviated MZ ) is a measure of the knock resistance when burning gas mixtures, comparable to the octane number and the cetane number . The MZ indicates the percentage mixing ratio of a reference fuel, consisting of methane and hydrogen . MZ 100 is only methane and knock-proof, MZ 0 is only hydrogen and knock-resistant. In between are the comparison mixtures with which the gas mixture to be tested is compared in a test engine and its MZ is thus determined. An MZ 80 of a gas mixture means that it has the same knock properties as the comparison mixture consisting of 80% methane and 20% hydrogen.

The lower the methane number, the lower the knock resistance, which increases the risk of self-ignition and knocking of the engine. The higher the methane number, the more knock-resistant the gas mixture.

The MZ measuring method requires an air ratio of = 1 in the test engine. ${\ displaystyle \ lambda}$

Composition of individual gases in%
gas CH 4 H 2 C 2 H 6 C 3 H 8 C 4 H 10 CO CO 2 N 2 O 2 H 2 O rest
natural gas 88.5 4.7 1.6 0.2 5
Sewage gas 60 3 32 5
Landfill gas 50 40 9 1
Coke oven gas 31 55 8th 1.2 3.8 1
Wood gas 3 7th 2 17th 15th 56
Biogas 50-75 <1 25-45 1 0.3 2-7 NH 3 , H 2 S

For gas mixtures made up of three components, the methane number can be read from triangular diagrams, e.g. B. for sewage gases, consisting of methane, carbon dioxide and nitrogen .

The methane number can also be determined arithmetically, for which a number of computer programs are available.

Natural gas: MZ> 80; Propane: MZ = 35; Landfill gas: MZ> 100

## Individual evidence

1. Klaus Mollenhauer, Helmut Tschöke: Manual Diesel Engines . Springer, Berlin 2007. ISBN 3540412395 , page 130 .
2. ↑ Printing errors in the original text, MZ between 120 and 150
3. Klaus Mollenhauer, Helmut Tschöke: Manual Diesel Engines . Springer, Berlin 2007. ISBN 3540412395 , page 131 .
4. Examples: Archived copy ( Memento of the original dated March 30, 2005 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. P. 63.