Research progress of preparing ammonia technologies by urea in gas denitrification

The flue gas of coal-fired and gas-fired power station after combustion must be processed by denitrification technology,the denitrification reducing agents are ammonia and urea.Because liquid ammonia is restricted by safety,region and other factors and has been listed as a major hazard source,domestic units are facing a large number of problems in the transformation of liquid ammonia.Urea decomposition ammonia production is becoming more and more popular.Direct injection of urea is too strict on temperature requirements,resulting in extremely low urea utilization rate,sometimes less than 50%,and increases operating costs.The pyrolysis of urea direct injection technology operates at a high temperature with extremely high energy consumption.After the introduction of gas-gas heat exchange technology,the problem of forced shutdown and low utilization rate of urea caused by blockage at the end of pyrolysis furnace is still unsolvable.Ordinary urea hydrolysis technology has low energy consumption and high utilization rate,but the reaction speed is slow and the response time is long,which can't meet the needs of ammonia supply in the unit's fast variable load,limiting the flexibility of the unit operation and the depth of peak shaving.Although late ordinary hydrolysis technology by increasing the reactor volume to increase the ammonia buffer capacity,reaction temperature and reaction speed,the needs of the scene can be basically met,but the size of the reactor is increased,and the temperature rise is easy to aggravate the corrosion and further reduces the utilization rate of urea.Urea direct injection technology,urea pyrolysis ammonia production technology and hydrolysis technology of urea all have certain shortcomings. The newly developed low-energy urea catalytic hydrolysis ammonia production technology greatly improves the response speed,lowers running temperature and reduce the corrosion.The urea utilization rate can reach more than 99%,reduces the volume and energy consumption,reduces the running cost.It has been applied in the main domestic power generation groups.