General terms and conditions of sale


Solid fuels

MK Systemy Kominowe offers chimneys for all solid fuels.


Fuels can be divided based on their state into:

  • solid fuels
  • liquid fuels
  • gaseous fuels

Hard coal – a sedimentary rock of plant origin, containing 75-97 % carbon, formed mainly in the Carboniferous (Palaeozoic era) from the remains of plants that have undergone carbonification in the absence of oxygen. It is black in colour, matte-gloss, leaves black traces.

Hard coal is widely used as a fuel. Its calorific value ranges from 16.7 to 29.3 MJ/kg and is strongly dependant of its composition (soot, sulphur and moisture content). The calorific value of pure carbon is approx. 33.2 MJ/kg. Coal is a non-renewable energy source.

Lignite – a version of coal that is a few million years younger than hard coal. When buying lignite you must be aware that it has a calorific value equal to that of wood (which can be bought cheaper) and that it leaves significant amounts of ash after burning.

Wood – counted among renewable energy sources, even though the process of renewal takes more than half a century. It is low in energy, but inexpensive. Wood in logs is used for burning in fireplaces. Wood-fired central heating boilers are not very popular because of the need to segregate wood species that can be used in the stove (the wood of coniferous trees, due to its high resin content, can only be used in stoves made of special acid-resistant alloys). Acacia, oak, beech and birch are best for heating. Spruce, fir, willow and poplar are the worst. If you decide to heat your home with wood, it is important that it be dry – it will be twice as efficient as wet wood.

Pellets and briquettes – these products deserve special attention in the group of eco-friendly fuels. They are inexpensive, like wood, while their calorific value is similar to that of coal. Pellets and briquettes consist of biomass – sawdust, wood waste, charcoal, wood chips, peat, etc. compacted under positive pressure. They are formed without the use of any adhesives or chemical additives.
They burn producing a limited amount of ash which can be used as a fertilizer, and because of the purity of the fuel, pollution does not accumulate in the boiler.

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