The HiTAC technology (High Temperature Air Combustion) is a reliable, industry proven combustion method allowing emissions reduction, combustion process improvement, thermal field flattening and heat transfer increase in high temperature energy intensive applications.

HiTAC combustion principle

The main feature of the HiTAC combustion technology is propagation of combustion process to large volume (usually almost total furnace volume) and carrying out the combustion process with low oxygen concentration. Therefore, the HiTAC is often referred to as “volumetric combustion” or “flameless combustion”.

This, together with a high temperature of the combustion process, leads to very uniform temperature and heat flux, prevents enormous temperature peaks, and reduces NO_x emission.

NO_x creation reduction

Nitrogen Oxides commonly abbreviated as NO_x are a family of reactive chemical compounds responsible for a range of undesirable environmental effects and having an impact on human health. The NO_x creation in industrial combustion processes is unwelcome and efforts are taken to minimize it. The main mechanism of the NO_x generation in high temperature combustion processes is so-called “thermal NO_x formation”, where nitrogen oxide compounds are formed through high temperature oxidation of the diatomic nitrogen found in combustion air. Since the temperature peaks (“hotspots”) are formed within flame feathers, which are significantly hotter than furnace temperature, conventional burners are unable to significantly reduce the NO_x emissions, but it is perfectly realized by the HiTAC combustion.

High velocity air and fuel injection results in intense mixing

HiTAC combustion technology principle requires fuel and preheated combustion air to be injected at high velocities directly into combustion chamber. Injection points alignment is a crucial factor, burner throat and fuel nozzles are located in a custom made burner tile.

Through injection velocity and injection points placement intense mixing of combustion chamber contents takes place creating a specific, low oxygen combustion environment.

HiTAC combustion technology at work

B: F: A: H: BA: BH: (*):

Burnt Gas Fuel Air Highly-preheated Air Mixture of B and A Mixture of B and H Combustion

Such low oxygen environment in the combustion chamber promotes flame expansion. The HiTAC flame is a “diluted”, low luminosity voluminous flame filling the combustion space evenly, therefore the HiTAC is often referred to as “volumetric combustion”. Because conventional concentrated flame is not observed, the combustion method is sometimes also referred to as “flameless”.

Comparison of combustion processes in respect to temperature level and oxygen concentration

Flat temperature distribution

Oxygen deficient environment causes the expanded flame to engulf combustion chamber space and air/fuel mixture combusts less aggressively in what is referred to as “mild combustion process” assuring flat temperature field over the combustion space, higher and uniform heat release and unprecedented combustion process stability. An additional effect is higher refractory lining durability in the furnace and burners resulting in lower maintenance costs, longer maintenance periods and more predictable refractory wear progress.

Practical advantages

Flat temperature distribution in combustion chamber

High injection velocities, intensive mixing and volumetric combustion create a flat thermal field inside the chamber without local hotspots.

Higher and more uniform thermal flux

Uniform thermal field throughout the furnace is connected with uniform energy release throughout combustion space. This ensures more even, uniform and higher heat flux to the material heated.

Longer refractory lifetime

Flat temperature distribution profile and lower zone temperatures minimize thermal stress and thermal load on combustion chamber and burner refractory lining. Refractory deterioration process is slower and milder. As an effect maintenance stops are required less frequently and become more predictable.

Reduced fuel demand

Overall lower zone temperatures and heat release with higher heat flux to heated material allows lower fuel consumption compared to conventional burners.

Higher product quality

Uniform temperature profile is the result of uniform energy distribution in combustion chamber’s volume. In such conditions high heat flux into the heated material.

Reduced costs of operation

All of the above aspects – flat temperature distribution, higher heat flux, lower temperatures, longer refractory lifetime, reduced fuel demand and higher final product quality influences lower total cost of operation and ownership of the whole installation.

Uniform furnace atmosphere composition

Intensive internal mixing and expanded voluminous flame eliminate oxidizing and reducing spots inside combustion chamber.

Broad fuel compatibility

HiTAC technology is compatible with hydrogen, hydrocarbon and biomass fuel types. Additionally the technology is compatible with various post-process and waste/off gases. The most common are gaseous fuels, but liquid, solid and pulverized are also found in various HiTAC installations.

HiTAC is perfectly suited for demanding fuel types that contain large quantities of solid particles and high moisture content. It works well also with the fuels characterized by low and variable Lower Heating Value (LHV). With all of the above excellent combustion process stability and quality, fuel efficiency and clean emissions are provided by the HiTAC technology.

Multi-fuel capability

The HiTAC technology enables versatile fuel arrangement within a heating system and within a single burner. While a typical HiTAC compatible burner operates a single type of gaseous fuel, variants are available that include a range of gaseous, liquid, solid and pulverized fuels.

Ultra low NO_x emission

The HiTAC combustion technology is a simple way of achieving clean emissions in standard and difficult heavy industry conditions. Numerous applications have proved that clean emission technology is ready at hand, easy to apply and operate, cost-effective both at implementing stage as well as further in maintenance.