China is the largest coal consumer in the world. Nitrogen oxides (NOx) from coal-fired emissions are important precursors of photochemical smog and regional haze. The emission reduction of NOx is crucial in improving the quality of our atmospheric environment. At present the power plant in China adopts the most stringent limits of NOx emissions in the entire world. The best way to meet this standard is the technology of ammonia selective catalytic reduction (NH3-SCR) of NOx. In addition, there are “three high” (high ash, high calcium and high sulfur) characteristic emissions of coal-fired gas in China and a big temperature fluctuation. How to realize high denitrification efficiency in high-dust flue gas under low and medium temperatures and how to regenerate lossless high calcium and high arsenic poisoning catalyst are questions faced by the academic world and the industry circles.
In 2015, Professor Li Junhua from the School of Environment at Tsinghua University led his research team in completing the project “Research and application of key technology in coal-fired fuel gas selective catalytic denitrification”, which won the second prize of technical innovation in National Science and Technology Awards. The project has been conducted for more than 10 years, and this was the year in which they first revealed the mechanism of denitrification under low and medium temperatures. Professor Li’s team made many inventions regarding denitrification catalyst and its key carriers, regenerating waste catalyst and denitrification technics. Through the collaborative innovation of production, study and research, they led the development of denitrification theory and technology. This led to the denitrification industry taking a huge leap forward during this period. Researchers in this project include Professor Li Junhua and Professor Hao Jiming from Tsinghua University; senior engineer Liu Hanqiang from Beijing Guodian Longyuan Environmental Engineering Co., Ltd; senior engineer Wang Dezhi from Jiangsu Longyuan Catalyst Co., Ltd; senior engineer Huang Rui from Chongqing Yuanda Catalyst Manufacturing Co.,Ltd.
Professor Li Junhua’s team proposed the mechanism of the enhancement for composite carriers and refinement for grains, invented the titanium silicon tungsten composite carriers with large specific surface areas, in order to solve the problem of the catalyst abrasion and deactivation from “three high” characteristic emissions of coal-fired fuel gas in China. They put forward the denitrification mechanism of double active centers, invented the rare earth catalysts coupling with transition metals, to overcome the problem of low denitrification efficiency under low and medium temperatures. They proposed the balances of the acid-base property and redox property on the catalyst surface are the key to ensure the activity of the catalyst, invented the neutral complex directional regeneration technology, to avoid the corrosion of equipment, the decrease of strength and the loss of active components led by the traditional strong acid cleaning method. They invented the high precision flow field distribution system, in order to guarantee the full uniform contact of the flue gas and the catalysts, and improve denitrification efficiency. A “Key Carrier - Catalyst - Regeneration Technology - Denitrification Process” technological innovation industrial chain was formed. And the oxide carriers, denitrification catalysts and denitrification projects occupied the first places of the market share in China. This project has implemented the high denitrification efficiency in high-dust fuel gas.
Currently, Chinese Society for Environmental Sciences has appraised the project’s accomplishment and marked as “top level in the world”. The project has authorized with 23 national invention patents- including, 8 patents for utility models and 2 software copyrights. It also participated to compile 2 national standards and 1 international standard, published 1 monograph and 83 SCI theses, which were cited 1365 times. In addition, their accomplishment has been applied in 256 power station boilers, such as China Guodian Co., China Huaneng Group, China Datang Co. and Shenhua Group and exported to the US, Japan and numerous other countries, while achieving remarkable economic and environmental benefits.