Light oil

Depending on the country, the term "light oil" describes various mineral oils with low viscosity. Commonly used names include "heating oil", "fuel oil", "kerosene" and "Heizöl EL" and "gasóleo". Light oil is a mixture of various crude oil fractions and is closely related to diesel fuel and kerosene. Together with heavy fuel oil, it is the most important liquid fuel for industrial applications. Light oil has relatively high energy density and can be easily stored and transported. Because it is available in an unpressurized state, it can be transported cheaply by ship, rail or truck. In principle it can be supplied to any location in the world, thus light oil ensures both a free choice of supplier and cost-effective firing if no gas is available.

Other advantages of light oil include clean combustion with a wide control range and the lowest emission level. Unlike heavy oil, this fuel does not need to be preheated and offers the possibility (as a low-sulfur variant) of using calorific value technology. This makes it possible to increase the efficiency of heat generation significantly while reducing emission values. The tank plant required for light oil has both advantages and disadvantages: On the one hand it requires a considerable investment, while on the other hand the storage capacity itself provides excellent independence from the fluctuations in the heat market.

In Germany light oil is standardized as extra light fuel oil (LFO) in trade and according to DIN 51603-1.

Extra light fuel oil is a mixture of different hydrocarbon compounds with a kinematic viscosity of less than 6 mm²/s at 20°C. It is closely related to other light oil distillates such as kerosene and diesel fuel and has a heat value of 42.7 MJ/kg. LFO is lighter than water and has a specific density of about 0.86 kg/l at 15°C.

Depending on the batch, LFO boils at temperatures between 170 - 390°C and has a flashpoint of > 55°C. The ignition limit is in the range between 0.6 and 6.5% by vol.

Because LFO is a class 2 water-polluting substance, compliance with a series of requirements if mandatory for storing or using it. Unlike diesel fuel, there are no season-dependent mixtures for operation and storage at low temperatures. Instead DIN 51603-1 specifies a temperature limit value of -10°C for LFO at which it must still be possible to filter the fuel (depending on the cloud point).

In addition to standardized oil, many manufacturers also offer "premium" variants. These fuels have additives, for example to improve capacity for lubrication, to prevent soot from forming or to mask typical fuel oil odor. The sulfur content in LFO has been lowered in recent years and according to DIN 51603-1, since 2008, must be less than 0.1%.

LFO combusts very cleanly if the combustion system is set optimally and requires about 11 m³ of air for 1 kg of fuel with stoichiometric combustion. The process produces primarily carbon dioxide and water. The dew point of wet flue gas in this case is about 120°C, depending on the sulfur content.

Low-sulfur LFO is also standardized in DIN 51603-1. It is distinguished from the standard variant essentially only by its lower sulfur content of maximum 50 mg/kg (0.005%). Due of the lower sulfur content, the flue gas dew point is significantly lower, around 60°C. Because of the lower capacity for lubrication in principle, the combustion plant must be suitable for this fuel, but calorific value technology can then be used.