硝酸生产工艺

Production Principle of Nitric Acid
NO
SIMPLE?
NOT REALLY
Complex Reactions of Ammonia Oxidation
H2O吸收NO2的反
应是一个可逆反 应，受化学平衡限制，
常压生产硝酸浓度不超 过 50 ％，加压生产不超 过 70 ％（参见附图）， 通称为稀硝酸
稀HNO3
H2O 3NO2 2HNO3 NO
25℃时 气相NO 和NO2与 HNO3浓 度的关 系
稀HNO3不可以直接蒸馏得浓硝酸
稀硝酸生产工艺
• 常压法 • 全压法（中压0.4一0.6MPa，高压0.8一1.2MPa） • 综合法（双压法） 4NH3+5O2=4NO+6H2O 2NO+O2=2NO2 3NO2+HO2=2HNO3+NO
与水(来自稀硝酸)和氧反应直接生成98％的浓硝酸。
2N2O4+2H2O+O2
5.0MPa 65～75℃
4HNO3
间接法生产浓硝酸工艺
超 共 沸 酸 法 生 产 浓 硝 酸 工 艺
5 硝酸生产尾气治理
小论文
双压法生产工艺（Dual Pressure Plants）
浓硝酸生产工艺
• 直接法 • 间接法 • 超共沸酸精馏法
直接法浓硝酸生产工艺
• 制NO 氨和空气通过铂网催化剂，在高温下被氧化成一氧化氮并 急冷至40一50℃，使生成的水蒸气经冷凝而除去。
• 制NO2 一氧化氮和空气中的氧反应，生成NO2，残余的未被氧化
从热力学上讲，加压对第 一个反应不利，而对后两 个反应有利 。因此，综合 法应该是最科学的。
全压生产工艺 Single Pressure Plants
NH3的氧化
催化剂为 Pt—Rh 二元或 Pt—Rh—Pd 三元 合金，制成直径为0.04—0.1mm的细丝， 编织成网。反应温度 800 － 900 ℃，接触 时间0.0001－0.0002秒，混合气中NH3含 量10％左右，O2和NH3摩尔比 1.7－2.2之 间。
两 种 氨 氧 化 炉
NO 氧 化
NO氧化成NO2不需要催化剂，甚至不需要专门的反 应器，主要管道有足的停留时间即可（约20秒）
NO的氧化是一个体积减 小的可逆放热反应，加 压、低温有利于平衡向 正向移动。在常压下温 度低于100℃，或5atm下 温度低于200℃时，NO 转化率接近100％。当温 度高于800℃时，NO转 化率几乎是0，即NO2几 乎完全分解为NO及O2。
的NO和98％的浓硝酸再反应，完全氧化成NO2
2NO+O2 NO+2HNO3
40℃
2NO2 3NO2+H2O
• NO2吸收 在低温下用浓硝酸（＞98％）吸收NO2成为发烟硝酸，不能被吸收的惰性
气体(N2等)排出系统另行处理。
NO2+HNO3[w(NNO3) ＞98％]
-10℃
HNO3· NO3(发烟硝酸)
• NO2解吸并冷凝聚合为液态N2O4 加热发烟硝酸，它热分解放出
NO2，然后把这纯的NO2冷凝成为液态N2O4
HNO3· NO2
2NO2
•
加热
HNO3+NO2
N2O4
冷凝聚合
高压釜反应制浓硝酸 将液态N2O4与稀硝酸混合(要求稀硝酸中水分
与液态N2O4成一定比例)送入高压釜，在5.0MPa压力下通人氧气，N2O4
PRODUCTION OF NITRIC ACID
HISTORY OF NITRIC ACID
The oxidation of ammonia over a platinum catalyst to nitrogen oxides, and their absorption in water to form nitric acid was first carried out in 1838 by C. F. Kuhlmann. However, this discovery was not then commercialised as ammonia was too expensive compared with the Chile saltpeter used to manufacture nitric acid in those days. The Birkeland- Eyde process, invented at the beginning of the 20th century, which involves the direct combination of atmospheric oxygen and nitrogen in an electric arc, was also of limited application due to poor energy utilization. The history of the modern nitric acid process really begins in 1901 when W. Ostwald established the ammonia oxidation conditions necessary for high nitrogen oxide yields. The first plants using the Ostwald process were started up in the first decade of the 20th century. Since then many improvements have been made by various workers. Milestones include the use of larger ammonia combustion units employing flat platinum rhodium gauzes instead of Ostwald’s rolled up platinum gauze strip and the recovery of the heat of reaction for steam raising or electricity generation. The development of strong, affordable, corrosion resistant stainless steel material of construction made feasible the absorption of the nitrogen oxides in water under pressure, thus reducing the size and cost of the absorption equipment, while progress in turbomachinery technology led to the adoption of the more energy efficient dual pressure process. From the 1920s onwards, advances in the synthesis of ammonia from hydrogen and atmospheric nitrogen by the Haber-Bosch process have given the Ostwald route to nitric acid an additional boost by lowering its feedstock costs. Nowadays practically all nitric acid is manufactured by this process.