Chemical equation of nitric acid: 4NH3+5O2=4NO+6H2O (Pt catalyzed, ignition) 2NO+O2=2NO2 3NO2+H2O=2HNO3+NO

Nitric acid is one of the six major inorganic acids, and is also an important chemical raw material. Nitric acid (English name), is a strong oxidizing, corrosive monomer inorganic strong acid, is one of the six strong inorganic acids, but also an important chemical raw materials, the chemical formula for HNO3, molecular weight of 63.01, and its aqueous solution is commonly known as nitric acid water or ammonia nitrogen water. In industry, it can be used to make fertilizers, pesticides, explosives, dyes and so on.

In organic chemistry, the mixture of concentrated nitric acid and concentrated sulfuric acid is an important nitrification reagent. The hazard symbols to which it belongs are O (Oxidizing agent) and C (Corrosive corrosive). The acid anhydride of nitric acid is nitrogen pentoxide (N2O5).

Since 1980, the development of China's domestic nitric acid industry began to accelerate, and the total output grew at a rate of 10% to 15% per year. Especially in the late 1990s, China's nitric acid industry entered a period of booming development, with the total output growing at an annual rate of 15% to 20%.

But in this period, China's nitric acid production technology was still relatively backward, and the early atmospheric pressure method and comprehensive process units were mostly obsolete production lines, and the high-pressure method units all relied on imported second-hand equipment from abroad. Soon after, Shanxi Chemical Fertilizer Plant (now Sky Ridge Group) introduced China's first double-pressurized nitric acid plant from abroad, and from then on, China's nitric acid industry began to move towards the international advanced ranks.

In 1999, Xi'an Shaangu Power Co., Ltd. successfully developed China's first set of "four-in-one" unit and applied it to Yunnan Yunfeng Chemical Industry Company, which accelerated the pace of China's nitric acid double-pressurized process of domestic equipment to the international advanced level. Yunnan Yunfeng Chemical Industry Company, as the first nitric acid producer to use the localized "four-in-one" unit, has strengthened the confidence of China's domestic nitric acid producers to choose domestic equipment.