【3D Process Flow】Summary Post--Analysis of Nitric Acid Production Process

Thread Content

【3D Process Flow】Summary Post – Useful for understanding the process flow: https://bbs.hcbbs.com/thread-5711616-1-1.html ---------------------------------------------------------- I. Core Chemical Reactions The synthesis of nitric acid is a multi-step exothermic reaction process: 1. Ammonia oxidation reaction: 4NH3 + 5O2 —— 4NO + 6H2O + Q 2. Nitric oxide oxidation: 2NO + O2—— 2NO2 + Q 3. Nitrogen dioxide absorption: 3NO2 + H2O——2HNO3 + NO + Q II. Analysis of the Process Unit Flow 1. Preparation of ammonia-air mixture Liquid ammonia vaporizes in an ammonia evaporator; after impurities are removed using an ammonia filter, it enters the ammonia-air mixer. The air is pressurized by a compressor and divided into primary air (going to the mixer) and secondary air (going to the bleaching tower). 2. Oxidation of ammonia and heat recovery: The mixture reacts on the platinum mesh in the ammonia oxidation furnace, releasing a large amount of heat instantly, which raises the gas temperature to about 860°C. Subsequently, the high-temperature gas flows through the waste heat boiler and superheater to recover heat and generate steam. 3. Oxidation and absorption of nitric oxide: The nitric oxide gas is cooled in a economizer, and then enters a low-pressure reaction water condenser where its temperature is reduced to around 40°C. At this point, water molecules condense and react with nitrogen dioxide to produce about 34% dilute nitric acid. After being pressurized by a compressor, the gas comes into counter-current contact with process water in an absorption tower to produce dilute nitric acid with a concentration of 60%. 4. Exhaust gas treatment: The exhaust gas emitted from the top of the absorption tower still contains NOx; it must enter an ammonia conversion and reduction reactor, where it reacts with ammonia in the presence of a catalyst to be converted into N2 and H2O, thereby meeting environmental emission standards. The purified exhaust gas enters the expander to recover about 60% of the work. 5. Ammonia absorption (auxiliary system): During the commissioning phase of the plant, excess ammonia is converted into dilute ammonia water using an ammonia absorption tower for reuse, thereby preventing pollution caused by the direct release of ammonia into the atmosphere.