NOx Reduction Technology
Reduction of nitrogen oxides emission: optimization of the combustion process, primary methods, secondary non-catalytic (SNCR) and catalytic (SCR) methods. Since 2007, SBB ENERGY S.A. has been a sole partner of Nalco Mobotec Inc. (NMI) in scope of implementation of ROFA™ and Rotamix™ technologies. In 2012, an acquisition agreement of Nalco Mobotec Polska Sp. z o.o., belonging to NMI, was signed and pursuant to that agreement, SBB ENERGY S.A. acquired the right for the exclusive license to offer flue gas denitrification technology based on ROFA™ and Rotamix™ solutions. The license covers the area of Poland and 22 countries in the Middle-East Europe. To meet increasing requirements, SBB ENERGY S.A. supplements the primary methods and secondary non-catalytic (SNCR) methods with the secondary catalytic technology (SCR).
The fields of activity include nitrogen oxide reduction and adaptation of boilers fired with solid fuels to fire and co-fire biomass. A system of volumetric combustion offers the state-of-the-art solutions in the field of combustion process optimization, becoming a part of widely understood primary measures. By means of secondary air nozzles asymmetrically arranged in the furnace, flue gas is put into a strong rotation. The rotating motion intensifies the mixing process and prevents stratification of the flow. Perfect mixing leads to an even temperature distribution in the furnace chamber. This technology assures optimum firing conditions in the entire volume of the furnace chamber and allows:
- NOx reduction without the use of additional reagents,
- effective optimization of the combustion process,
- CO2 reduction.
Secondary non-catalytic methods
Secondary non-catalytic methods – SNCR (Selective Non-Catalytic Reduction) –the second stage of nitrogen oxide emission reduction, where nitrogen oxides are reduced by means of ammonia derivative chemical compounds. Ammonia reaction with nitrogen oxides is applied, in result of which nitrogen and water is formed. The reaction takes place effectively in a strictly defined temperature range. Optimum use of the reagent in the combustion process is assured by simultaneous application of primary methods that create turbulent mixing of overfire air with flue gas and the reagent introduced into the furnace. The reagent injection in a shield of additional conveying air allows to limit the sorbent consumption compared to conventional SNCR systems. Reduction of NOx>30%, combined with primary measures may reach even >80%. Application of proper nozzles of the SNCR system limits the ammonia slip in flue gas. That allows not to deteriorate quality parameters of fly ash and bottom ash.
The SNCR system fan improves distribution of a reagent (urea or ammonia water) in a furnace and allows a precise control of reactions that occur in the boiler.
This station is responsible for water and urea intake from day tanks, monitoring of concentration values and the transfer of the reagent in proper concentration to the distribution station. Components of the system are pumps responsible for water and urea transfer. A displacement pump with a frequency converter is used to transfer urea, whereas a centrifugal pump equipped with an inverter is used to transfer water. A flow and density of the diluted urea are measured by a multiple-parameter Coriolis mass flowmeter, which is located downstream a static mixer
Urea Transfer and Recirculation Station
A multi-stage centrifugal pump is used for a quick supply of urea to the day tank. This device is also responsible for keeping the urea in a constant motion and at sufficiently high temperature, to avoid its crystallization. A source of heat in the system may be both steam and electric current. The station has a double skid of pumps and heaters.
Day tanks are used for a short-term storage of urea and water for the dilution station. The urea day tank reduces a demand for continuous recirculation of urea. The tanks are separated, to eliminate potential contamination of water by urea.
The station supplies urea of concentration 10-20% to injection devices installed at the boiler. One station serves four injection devices.
Injection devices are responsible for injection of urea solution into the furnace chamber. Their design has been developed based on an extensive experience and testing, which resulted in enhancement of NOx reduction and reduced urea consumption.
Urea Storage Tank
An insulated tank made of glass fibre reinforced plastic is used to store the urea. A size of the tank is determined individually for each system.
Nitrogen oxides reduction technologies with the SCR method:
- Reduction of nitrogen oxides and dioxides in the gaseous phase
- High efficiency of NOx reduction with a small slip of ammonia (NH3)
- Lower reagent consumption compared to non-catalytic methods
- Wide application range with regard to the process, fuel and flue gas temperature
HIGH – DUST
Hybrid technology of flue gas denitrification in power boilers. Why this technology? The hybrid technology of flue gas denitrification in power boilers has the following advantages:
- does not entail high investment costs,
- no need to deeply interfere with the existing infrastructure in the facility,
- does not require additional operating procedures
- the use of SNCR and catalytic baskets allows for the achievement of new emission limits,
- reduces the risk of ABS precipitation,
- reduces the ammonia leakage, making it possible to meet the limits of its emission in the exhaust gas and to maintain the commercial value of combustion by-products.