Gases - Miscellaneous

Question 1

Describe what are Aldehydes

Answer 1

A particular group of organic compounds of carbon, hydrogen & oxygen. Small amounts of aldehydes are found in the exhausts gases of diesel engines. Aldehydes can cause irritation to the eyes & throat.
Aldehydes are generated when using polyurethane (PUR). There are exposure limits listed in Schedule 6 of the Coal Mining Safety & Health Regulation 2001.

Question 2

Describe what are Oxides of Nitrogen (NOx)

Answer 2

Term applied to mixtures of nitrogen & oxygen
compounds found in mines. Mainly nitrogen dioxide (NO2) & nitrogen peroxide (N2O2) with nitric oxide (NO). Found in working places immediately after shot firing. A small amount is found in diesel
exhaust. There are exposure limits limits listed in Schedule 6 of the Coal Mining Safety & Health
Regulation 2001.

Question 3

Describe what is Water Gas?

Answer 3

Water gas is a combustible mixture of gases. The composition is variable, however, a typical
composition of undiluted water gas would be 45% of each carbon monoxide & hydrogen with small amounts of carbon dioxide, methane, nitrogen &
oxygen. The explosive limits for water gas are
approximately 6 – 70%.
The water gas reaction & the potential for an
explosion is often identified as a risk when fighting coal fires with water. There is no empirical evidence for this occurring due to the condition of superheated steam that must be at pressure, being required for the reaction. Addition of water to red hot coal can produce a sudden & massive increase in volume as the water is converted to steam. This is often
mistaken for the water gas reaction.

Question 4

Describe what is Illawarra Gas/Bottom Gas?

Answer 4

Found in the Illawarra or Southern Coalfields & has been found in some Bowen Basin mines. It is a
mixture of CH4 & CO2, ranging down from pure CO2 The concentration of CO2 needs to be greater than 46% & CH4 less than 54%. This will result in the
relative density of the seam gas being greater than 1. In areas of low ventilation & with the gas being
heavier than air, it will migrate along the floor in
poorly ventilated areas.