[jadelamlam]

Here is the composition of town gas(from my textbook):
H2 49%
CH4 28.5%
CO2 19.5%
CO 3%
CH4 is used for combustion
How about H2?Why should it be added into town gas?It will cause an explosion if there is a fire.(But it doesn't explode actually)
And what about CO And CO2?Why should they be added?
Thx a lot.

[charco]

(Original post by jadelamlam)
Here is the composition of town gas(from my textbook):
H2 49%
CH4 28.5%
CO2 19.5%
CO 3%
CH4 is used for combustion
How about H2?Why should it be added into town gas?It will cause an explosion if there is a fire.(But it doesn't explode actually)
And what about CO And CO2?Why should they be added?
Thx a lot.

These things are not 'added' to the gas mix, they are produced in the course of making town gas.

The gaseous mixture was a by-product of the destructive distillation of coal to make coke, which was required for the manufacture of iron (amongst other things).

Variations could be made by adding water etc during the process.

[jadelamlam]

In fact we just want to start a fire,then why don't we remove H2,CO2 and CO?
And why H2 does not cause an explosion when it is heated?

[charco]

(Original post by jadelamlam)
In fact we just want to start a fire,then why don't we remove H2,CO2 and CO?
And why H2 does not cause an explosion when it is heated?

Hydrogen gas is not explosive, a mixture of hydrogen and air (or oxygen) is explosive ...

... as is a mixture of methane and air, or carbon monoxide and air, etc...

Purifying the gaeous mixure to individual gases was expensive and unnecessary.

[jadelamlam]

That means H2,CO,CO2 doesn't help combustion?
Besides,I still have a question.
From a pastpaper:
Which statement(s) is/are true?
(1)Town gas is produced from coal.
(2)Town gas contains hydrogen as the major component.
(3)Oxygen is added to enhance the flammability of town gas prior to its delievery to consumers.
(2) and (3) are correct.
That means there is O2 in town gas,why H2 doesn't explode?
Sorry for my foolishness.

[jadelamlam]

That means H2,CO,CO2 are useless for the combustion?
Besides,please see the following question(from my pastpaper in the public exam)

Which statement(s) is/are true?
(1)Town gas is produced from coal.
(2)Town gas contains hydrogen as the major component.
(3)Oxygen is added to enhance the flammability of town gas prior to its delievery to consumers.

(2) and (3) are correct.
That means town gas also contains O2,why H2 does not explode?
Sorry for my foolishness.

[charco]

(Original post by jadelamlam)
That means H2,CO,CO2 doesn't help combustion?
Besides,I still have a question.
From a pastpaper:
Which statement(s) is/are true?
(1)Town gas is produced from coal.
(2)Town gas contains hydrogen as the major component.
(3)Oxygen is added to enhance the flammability of town gas prior to its delievery to consumers.
(2) and (3) are correct.
That means there is O2 in town gas,why H2 doesn't explode?
Sorry for my foolishness.

In order for any gas to "explode" the proportions must be correct. The quantity of oxygen added does not create an explosive mixture.

Take, for example, methane. When it leaks from coal seams it is a flammable gas. However, when the ratio of methane to air reaches 1:9 the mixture is highly explosive and responsible for many deaths in coal mines.

[Joinedup]

CO burns very nicely. The CO in coal gas was quite dangerous cos if a coal gas flame blew out the unburned CO in the coal gas still coming out of the nozzle was a poison hazard to people. Turning on a gas oven was a popular method of suicide before the natural gas switchover. Sylvia Plath being a high profile example of coal gas suicide.
Tbh i doubt they ever deliberately added oxygen prior to it reaching the appliance otherwise there'd have been a lot of pipeline explosions, simple enough to design appliances that mix enough air into whatever sort of mains gas you've got.

[jadelamlam]

thx a lot