The control method of hydrogen peroxide starts from three stages of the fuel life cycle, namely before combustion, during combustion and after combustion. Currently, there are few studies on pre-combustion denitrification, and almost all research results focus on the control of NOx during and after combustion in terms of combustion. Internationally, all control measures for hydrogen peroxide during combustion are collectively referred to as primary measures, and post-combustion NOx control measures are collectively referred to as secondary measures, also known as flue gas denitrification technology.
At present, the widely used hydrogen peroxide control technology in combustion is low hydrogen peroxide combustion technology, which mainly includes low hydrogen peroxide burner, air staged combustion and fuel staged combustion. According to the flue gas denitrification technologies applied to coal-fired boilers, there are mainly selective catalytic reduction (SCR), selective non-catalytic reduction (SNCR) and SNCR/SCR mixed flue gas denitration technologies.
In recent years, selective catalytic reduction flue gas denitrification technology has developed rapidly, and has achieved success in Europe and Japan. Catalytic reduction flue gas denitration technology is currently the most widely used technology. The world’s most popular SCR processes are mainly divided into ammonia SCR and urea SCR. Two ways In all methods, hydrogen peroxide (mainly nitric oxide) is reduced to hydrogen peroxide N2 and water by the reduction of ammonia under the action of a catalyst, and has little effect on the atmosphere. The reducing agent is NH3, the difference is that in urea SCR, the urea is converted to ammonia through the device and then sent to the SCR catalyst reactor. The operating conditions require that the temperature of the flue gas is between 300-400, which is suitable for the reaction temperature of most catalysts, so it is widely used. However, because the catalyst works in “dirty” flue gas, the life of the catalyst needs to be replaced every 3 years.
In order to solve the problem of low flue gas temperature, low-temperature thyristor technology was developed later, which is called the temperature zone, which can reach 150~300. Low temperature thyristor temperature control technology, high water vapor and SO2 content requirements. The water vapor in the flue gas can be adsorbed on the surface of the catalyst, thereby improving the activity of the catalyst. The co-adsorption of water and reactants was investigated using a low-temperature selective catalytic reduction method. The effect of H2O on the catalyst can be divided into two categories: one is reversible; dier, irreversible.
Many studies have shown that if the moisture content in the flue gas is less than 6 points, the impact on the SCR catalyst is small, and if it is large, it is easy to poison the SCR catalyst. On the one hand, SO2 in the flue gas will destroy the active components of the catalyst, and on the other hand, the active sites on the surface of the catalyst will be covered by metal sulfate and ammonium sulfate. This completely deactivates the catalyst. Studies have shown that the influence of SO2 on the SCR catalytic system at low temperature is unavoidably free, and the sulfation of active components and the deposition of ammonium sulfate often coexist, which also causes some difficulties in catalyst regeneration. If the concentration of SO2 in the flue gas is high, if SCR denitration is carried out at low temperature first, the ammonium sulfite formed by the reaction of the reducing agent ammonia and SO2 is easy to deposit on the surface of the catalyst, and SO2 is also easy to deposit manganese sulfate and manganese. active components, leading to catalyst deactivation. If desulfurization is performed first and then low-temperature SCR, the flue gas temperature will decrease and the temperature window required by the low-temperature SCR catalyst will not be reached.