The Importance of Coal Testing
Here at KG Smith & Son, we only supply high quality coal that has been deemed suitable for the purposes we’re selling it for, so you can rest easy knowing our coal won’t be doing damage to you, your environment or your boiler and flue. That’s because the coal we supply is all smokeless, meaning you can use it anywhere in the UK, in any type of fire or suitable stove.
And that is just one of the reasons we’re the UK’s leading independent coal supplier.
What you may not be aware of, however, is that there are a number of varieties of coal, some of which are suitable for use for domestic heating, but many of which are not. For instance, we recently discussed the new coal mine being opened in Cumbria, which will only be producing coking coal that is suitable for use in the steelmaking industry.
Whatever the coal in question is to be used for, testing samples to ascertain quality is essential. This month, we’re taking a look at the different types of coal we get out of the ground, and why it matters that we have the right sort for the job in hand.
What is coal and what are the four types of coal?
Coal is combustible sedimentary rock that is mostly made of carbon. Originally dead plant matter, it decayed into peat before being converted into coal as a result of being deeply buried and subject to intense heat for millions of years.
Coal comes in four types. Lignite and subbituminous are ‘low ranked’ coal (i.e. those with the least carbon and most moisture) and are used primarily for electricity generation. Bituminous coal and anthracite (‘high ranked’ coal with higher levels of carbon and lower levels of moisture) are used for thermal (i.e. heating) and metallurgical (e.g. steelmaking) purposes – that includes the smokeless coals and anthracite we sell at KG Smith & Son.
When coal is being tested, one of the main aims is to determine its ‘rank’ and therefore its suitability for the range of potential purposes. For instance, too much moisture would make it unusable in many boilers because of the damage the emissions would likely cause.
However, analysing the coal will also determine its emissions when burned and what their likely effects would be on the environment and our health.
What sort of tests are carried out?
There are two main types of testing carried out on coal:
Proximate Analysis – this determines levels of moisture, volatile matter (gases and vapours discharged while the coal is being heated without oxygen), fixed carbon (i.e. non-volatile) and ash. It is the combination of these results that will determine the ‘rank’ of the coal in question.
Ultimate Analysis – this establishes the weight percent of carbon in a sample, as well as its other elements, which are mainly hydrogen, sulphur, oxygen and nitrogen. This information helps to work out how much air would be needed for combustion, together with the volume and composition of combustion gases.
Other tests include establishing the calorific value of the coal (how much heat it gives out) and, in the case of coking coal, its strength and resistance to degradation.
Together, these tests provide the data that will ensure the right coal is being used in the right applications.