Nitric Acid – Provided with High-efficiency, Low-consumption, and Intelligent Industrial Solution
Nitric acid (HNO₃) is an important strong inorganic acid, known as the mother of industry, and is widely used in chemical, fertilizer, pharmaceutical, explosives, metallurgy, and electronics industries. Tianli has deep expertise in nitric acid production, building complete standardized nitric acid production units. We adopt mature and advanced end-to-end processes, covering ammonia oxidation, NOx conversion, nitric acid absorption, and finished product refining. Leveraging our comprehensive technological advantages, we provide customers with efficient, low-consumption, environmentally friendly, and intelligent nitric acid production solutions, helping them to achieve large-scale, green production.
I. Properties of Core Materials
The core materials for nitric acid production plants are ammonia, air, and nitric acid.
(1) Ammonia (NH₃)
It is a colorless gas with pungent odor, relative molecular mass of 17.03, density of 0.771 g/L (standard conditions), melting point of -77.7℃ and boiling point of -33.5℃, it is easily soluble in water with flammable and explosive features. It is the core raw material for the production of nitric acid.
(2) Air
It provides the oxygen required for the reaction, which is then compressed and purified before use.
(3) Nitric acid (HNO₃)
It is colorless and transparent liquid (industrial grade is slightly yellow due to the presence of nitrogen oxides), with relative molecular mass of 63.01, density of 1.50 g/cm³, melting point of -42℃, and boiling point of 83℃. It is highly corrosive and oxidizing, easily volatile, and decomposes easily when exposed to light or high temperatures.
Our production facilities can flexibly produce nitric acid products of different specifications: dilute nitric acid (45%~68%) and concentrated nitric acid (≥98%), suitable for the needs of various fields such as fertilizers, chemicals, pharmaceuticals, and electronics. During the production process, reaction temperature, pressure, and material ratios must be strictly controlled to ensure production safety and product quality.
II. Introduction to Core Technologies (Detailed Process)
Nitric acid production adopts a closed-loop process of ammonia oxidation → NOx conversion → nitric acid absorption → finished product purification, relying on advanced production equipment to achieve precise linkage of each link and full control.
1. Raw material pretreatment
The raw ammonia gas is purified and dried to remove impurities and moisture (moisture content ≤0.05%) to avoid affecting the catalytic reaction efficiency. Filtered air is compressed and dried to remove dust, oil mist, and other impurities, ensuring stable oxygen concentration. The pretreated ammonia gas and air are mixed in the precise ratio (ammonia-air volume ratio 1:10~1:12) and then fed into the ammonia oxidation reactor.
2. Ammonia oxidation reaction
The mixed gas enters ammonia oxidation reactor loaded with a platinum-rhodium alloy mesh catalyst. Under conditions of 800–920℃ (800–850℃ for the atmospheric pressure method and 880–920℃ for the medium pressure method) and 0.3–1.0 MPa, ammonia is oxidized by oxygen to produce nitric oxide (NO). The main reaction equation is as follows:
4NH₃ + 5O₂ → 4NO + 6H₂O
The catalytic efficiency reaches 95%~98%. A large amount of heat is released during the reaction, and the waste heat is recovered through a waste heat boiler to generate high-pressure steam for subsequent processes or power generation, realizing the cascade utilization of energy.
3. NOx Conversion
The NO gas produced by ammonia oxidation (temperature reduced to approximately 150-200℃) enters the oxidation tower. Under **pressure conditions of 0.3-1.0 MPa**, NO reacts with excess oxygen to gradually convert into nitrogen dioxide (NO₂).
The main reaction equation is:
2NO + O₂ ⇌ 2NO₂
The reaction is a reversible exothermic reaction, and pressurization favors the forward reaction. The overall system conversion rate (including NO recycling and conversion within the absorber) can reach over 95%. The converted NOx mixture (mainly containing NO₂ and a small amount of NO) is then fed into the absorber.
4. Nitric acid absorption
NOx mixed gas enters the packed absorber and comes into countercurrent contact with the demineralized water sprayed from the top of the tower, where an absorption reaction occurs to produce nitric acid. The overall reaction equation is:
3NO₂ + H₂O → 2HNO₃ + NO
The generated NO is insoluble in water and rises with the exhaust gas, where it is re-oxidized with supplemental oxygen before returning to the absorption tower for recycling, thus ensuring full utilization of the raw materials. By precisely controlling the absorption temperature (20~40℃), operating pressure (0.3~1.0MPa), and gas-liquid ratio, 45%~68% dilute nitric acid can be flexibly produced. For higher concentration products, distillation and concentration section can be configured to produce ≥98% concentrated nitric acid.
5. Finished product refining and exhaust gas treatment
The generated dilute nitric acid is cooled and filtered to remove trace amounts of suspended solids and nitrogen oxides, ensuring the product is clear and transparent. The exhaust gas (containing a small amount of NOx) from the absorption tower is treated with selective catalytic reduction (SCR) technology—using ammonia as reducing agent and dedicated denitrification catalyst—to reduce NOx to nitrogen and water, ensuring that the NOx emission concentration in the exhaust gas is lower than the national environmental protection standard (≤200mg/m³), achieving clean production.
III. Core Technical Advantages
1. Technical advantages
l Utilizing mature ammonia oxidation + pressurized absorption core process, the ammonia conversion rate reaches 95%~98%, the NOx absorption rate reaches 95%~98%, and the raw material utilization rate is high.
l Platinum-rhodium alloy catalysts exhibit stable activity and long service life (up to 3-5 years).
l The production unit features modular design, compact structure, and convenient operation and maintenance, enabling continuous and large-scale production.
l By adjusting the absorption parameters, the output of 45%~68% dilute nitric acid or ≥98% concentrated nitric acid can be flexibly switched to meet the needs of multiple industries.
2. Energy efficiency advantages
l Equipped with high-efficiency waste heat recovery system, it recovers the high-temperature waste heat (approximately 1000°C) generated by the ammonia oxidation reaction to produce steam, which drives the compressor or generates electricity, significantly reducing external energy consumption.
l The optimized process flow reduces overall energy consumption by more than 20% compared to traditional equipment, significantly lowering production costs for enterprises.
3. Environmental advantages
l The entire production process is closed-loop and equipped with a high-efficiency denitrification device, ensuring that the NOx emission concentration in the exhaust gas is ≤200mg/m³, far below the industry standard.
l The small amount of condensate generated during production is neutralized and treated before being recycled, achieving near-zero emissions.
l Waste platinum-rhodium catalysts are recycled and regenerated by professional manufacturers, resulting in no secondary pollution and aligning with the concept of green and low-carbon development.
4. Product Advantages
l It can flexibly produce dilute nitric acid (45%~68%) and concentrated nitric acid (≥98%), suitable for the needs of fertilizers, chemicals, pharmaceuticals, explosives, electronics and other fields.
l By precisely controlling the process parameters at each stage, the finished nitric acid has high purity and stable concentration, appearing as a colorless or slightly yellow clear liquid with no abnormal odor or visible sediment. The product quality far exceeds industry standards.
5. Control Advantage
l Equipped with fully automatic DCS/PLC intelligent control system, it monitors key parameters such as reaction temperature, pressure, material ratio, NOx concentration, and liquid level in the tower in real time.
l Equipped with automatic alarm, interlock protection, and emergency stop functions, it can be operated remotely, reducing manual intervention.
l Precise control throughout the entire process ensures stable operation of production facilities and consistent product quality.