Nitrogen oxides are between the most widely spread pollutants; the most effective technique to mitigate them is the selective catalytic reduction (SCR).
Using the SOLVAir® bicarbonate solution allows to avoid the re-heating of flue gases, leading to a great savings in energy consumption, CO2 emission and costs.
NOx is formed during any high temperature combustion process where both oxygen and nitrogen are present. These oxides are formed as heat from combustion drives endothermic reactions between nitrogen and oxygen.
Natural gas-fired combustion processes generate NOx as atmospheric nitrogen reacts with oxygen. Coal- and oil-fired combustion processes, wastes and biomass combustion generate NOx also as a result of the oxidation of the nitrogen content in the fuel.
NOx is the primary cause of ground level ozone. It contributes to acid rain and particulate formation. Its geographical impact can be extensive as it is easily moved via prevailing winds.
The SOLVAir® Solution: dry sorbent injection of sodium bicarbonate for flue gas cleaning
When used as a dry sorbent injected upstream from a sodium bicarbonate BICAR® supplied by SOLVAir® readily react with acid gases. In special cases some mitigation of NOx occurs in conjunction with the removal of SO2. Tests have shown NOx reduction of 10-20%.
NOx reduction is often accomplished by installation of a Selective Catalytic Reduction (SCR) system. The SCR uses ammonia and a catalyst to convert the NOx to N2. The SCR needs to operate at quite high temperature in order to avoid the condensation and the deposit on the catalyst layer of ammonium (bi)sulfate.
When the catalyst system is installed at the end of the treatment chain, like in the waste to energy plants, using sodium bicarbonate BICAR® allows enhancing the energy recovery.
First of all, the sodium bicarbonate has the highest reactivity toward SO2 that allows a very low level of remaining pollutant, and minimizes the risk of formation and thereby condensation of ammonium (bi)sulfate.
On the other hand, the extended operating temperature range of BICAR® permits to avoid any injection of water and the subsequent cooling of the flue gases which are required with other treatment options.
The sum of these facts allows the use of the catalytic device at the same temperature as the bag filter, saving the energy needed to re-heat the gases and avoid related CO2 emission. Additionally, another step of energy recovery of the heat of the clean gases can be installed.
The SOLVAir® bicarbonate solution is also compatible with non catalytic DENOX systems (SNCR).