Ecotube® technology was introduced and patented in 1992 by the Swedish company ECOMB AB to optimize combustion process and reduce toxic compounds emissions (including NO_x and CO) from low and medium power boilers.
This technology is based on the use of special perforated pipes called Ecotube® introduced automatically at an adjustable depth into the combustion chamber of the boiler through one of the side walls of the boiler. Ecotube® pipes are equipped with three or four rows of air-dispensing nozzle to enable injection of several technological media like: air, exhaust gas, urea or ammonia water at a very high speed into the combustion chamber in a selected direction. 

Ecotube® pipe

Each nozzle is controlled separately to achieve optimal efficiency of NO_x reduction under different operating conditions of the boiler. The use of Ecotube® pipes allow to connect the primary method (air stratification) and secondary method (SNCR) of nitrogen oxides (NO_x) reduction created during combustion of various gas and solid fuel types in boilers.
The use of air stratification creates two combustion zones with different proportions of oxygen inside the boiler:

• reducing (λ<1) in the lower part of the combustion chamber of the boiler,
• oxidizing (λ>1) in the upper part of the combustion chamber.

In the first zone less NO_x is formed because the formed NO_x are reduced by reacting with organic compounds, mainly CO in the reduced excess air. In the second zone the nitrogen oxides are reduced by the two-stage combustion process called reburning and additionally by injecting the reactant (ammonia or urea) in SNCR method. 

Boiler with Ecotube® pipes

In other words, by using the additional air injection trought Ecotube® the ultimate air-supply system is attained helps to achieved low NO_x emission below the limits resulting from IED (Industrial Emission Directive) and the BAT (Best Available Techniques) conclusions. Thus, by obtaining a greater turbulence in the combustion chamber and better mixing of air and fuel the combustion process optimization is achieved. The larger degree of mixing of air and fuel provides to complete oxidation of the fuel and thus very low emissions of CO. It also reduces the share of oxygen in the exhaust gas, and thereby improves the efficiency of the boiler, which leads to reduced fuel consumption and thus lower emission of CO₂, dust and lower operating costs. This technology is applicable in all types of boilers burning different fuels solid, liquid and gas.