Yunnan Yunfeng Chemical Industry Company is a large phosphatic and compound fertilizer manufacturer. Now it owns fixed assets 1.7 billion, more than 5,000 employees (of which more than 1,200 professional and technical personnel). The company is located in the southern suburbs of Xuanwei City, Yunnan Province. It covers an area of 2.5 square kilometers; the company has its dedicated 7 kilometers railway, more than 250 vehicles, and the transport capacity is 1.7 million tons per year (China Chemical Fertilizer Information). The company links with Guiyang-Kunming railway, as well as railway network of China. The location of the company, Xuanwei City, is one of the national key coal storage cities. The Xuanwei City is 100 kilometers away from Guizhou Liupanshui District, which is the base of coke production (China Chemical Fertilizer Information). And the Xuanwei City is 200 kilometers away from reserves of high-quality phosphate rock in Yunnan Dianchi Lake. The location of the company created an advantage for company to produce and sell nitrogenous fertilizer, phosphate and compound fertilizer (China Chemical Fertilizer Information).
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The spirit of the company is unity, enterprising, realistic and civilized. The management aim of the company is to seek survival by quality, seek development by reputation, regard vast consumers as sustenance and pay attention to the interests of dealers and franchisee (China Chemical Fertilizer Information).
Besides the main product ---- Phosphoric acid (H3PO4) and phosphatic and compound fertilizer, the company also produce large amount of nitric acid. Now let us look at the process of making nitric acid in detail.
Part II. Starting Materials of Making Nitric Acid
In the process of making nitric acid, the raw materials are quite simple, just ammonia (NH3) and oxygen (O2).
Part III. The Manufacturing Process of Making Nitric Acid
Nitric acid industry is closely related to ammonia industry. The catalytic oxidation of ammonia is the main way to get nitric acid in industrial production system. The method is widely used because of its low cost, high productivity and low power consumption. The raw materials for first step are ammonia (NH3) and oxygen (O2). Usually oxygen is obtained by purifying the air. The equipment for the step is oxidizing furnace. The catalyst is platinum rhodium (Pt-Rh) alloy mesh and the condition for reaction is high temperature of 800°C (A Five-star). The chemical equation is as following:
4NH3 (g) +5O2 (g) ==== 4NO (g) + 6H2O (g) ------- (proceeded in oxidizing furnace)
The products of the reaction are nitrogen oxide (NO) and water vapor, while a large number of heat is released.
Now let us come to the second step. The products of first step ----nitrogen oxide (NO) and water become raw materials of the second step. The equipment needed is cooling condenser. After cooling nitrogen oxide (NO) in the cooling condenser, nitrogen oxide (NO) reacts with oxygen in the air and produces nitrogen dioxide. What need we pay attention is that the oxygen must be plentiful (A Five-star).
2NO (g) + O2 (g) == 2NO2 (g) ------- (proceeded in cooling condenser)
In the absorption tower, the nitrogen dioxide is absorbed by water and produces nitric acid. In order to make nitrogen dioxide absorbed by water completely, and get as much as possible into nitric acid, we often add some air into the absorption process (A Five-star). In the process, nitrogen dioxide undergoes cyclic oxidation absorption (Baidu). The chemical equations are as following.
3NO2 (g)+ H2O (l) == 2HNO3 (aq) + NO (g) ------ (proceeded in the absorption tower)
------ Cyclic oxidation absorption of nitrogen dioxide
4NO2 (g) + O2 (g) + 2H2O (l) == 4HNO3 (aq) ------ (proceeded in absorption tower)
4NO (g) + 3O2 (g) + 2H2O (l) == 4HNO3 (aq) ------ (proceeded in absorption tower)
There are a small amount of nitrogen oxide (NO) and nitrogen dioxide in the exhaust. Emitting them into the atmosphere will cause pollution, so the generated NO should be recycled. We often use alkali liquor to absorb nitrogen oxide (NO) and nitrogen dioxide (NO2).
NO + NO2 + 2NaOH == 2NaNO2 + H2O ------ (proceeded in alkali liquor absorption tower)
2NO2 + 2NaOH == NaNO3 + NaNO2 + H2O ------ (proceeded in alkali liquor absorption tower)
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In the whole process, we know that nitrogen oxide (NO) is recycled. So in theory, 1 mol NH3 ~ 1 mol HNO3. That means we could use 1 mol NH3 to produce 1 mol HNO3 (High-School Students Online).
The nitric acid outflow from the bottom of the tower is only 50% consistency and it can not be directly used in military, dye and other industry. The dilute nitric acid must be made into more than 98% concentrated nitric acid. The main approach of concentration is to mix dilute nitric acid with concentrated sulfuric acid (H2SO4) or magnesium nitrate Mg(NO3)2 , then distill at low temperature and obtain concentrated nitric acid (Sina).
Part IV. The Product
From the whole process, we know that the final product is nitric acid (HNO3).
A Suggestion Part ---- Physical and Chemical Properties of Substances in the Whole Process
Ammonia is highly soluble in water, colorless toxic gas with pungent odor. Its melting point is -77.7°C and boiling point is -33.5°C. Ammonia is relatively stable, and it is often used as a refrigerant and making ammonium salt and nitrogenous fertilizer. When ammonia is absorbed in water, the ammonia molecules and water molecules bond together through hydrogen bonding to form a ammonia monohydrate (NH3 • H2O). Small part of ammonia monohydratea can be ionized into ammonium ions (NH4+) and hydroxide ions (OH--), so ammonia water is weak alkaline, and it can make phenolphthalein solution turn red (Baidu).
Oxygen, colorless and tasteless, is not easy to dissolve in water. Under the pressure of 101kPa, oxygen will turn to blue liquid when the temperature is -183°C and it will turn to light blue snow-like solidin when the temperature is -218°C. The chemical property of oxygen is relatively active. In addition to inert gas, less active metal elements, such as gold, platinum, silver, palladium, most of the elements can react with oxygen, and the reaction is called oxidation; the generated compounds of reaction are called oxides. In addition, almost all organic compounds can be intensely burned in oxygen and produce carbon dioxide and water (Baidu).
Nitrogen Oxide (NO):
Nitrogen oxide is colorless gas. Its melting point is -163.6°C and boiling point is -151°C. It is slightly soluble in water and des not react with water. Main applications of nitrogen oxide are making nitric acid, artificial silk bleach, propylene and stabilizers of dimethyl ether. Under normal temperature, nitrogen oxide is easily oxidized to nitrogen dioxide (NO2). Nitrogen oxide is unstable and quickly turned into nitrogen dioxide (NO2) in the air and produces stimulus. Nitrogen oxide damages to respiratory tract. High concentrations of nitrogen oxide can cause methemoglobinemia. Nitrogen oxide has hazard to the environment, and causes pollution on water, soil and air. Nitrogen oxide is combustion-supporting, toxic and irritant (Baidu).
Pure water is colorless, tasteless, odorless and transparent liquid. The pH value of water is very close to 7.0. Water only begins to decompose above 2000°C. When water reacts with active metal or carbon, it performs oxidbillity and hydrogen is reduced to hydrogen gas. The most active non-metal fluorum can oxidize negative divalent oxygen in water into oxygen gas. Under the circumstance, water performs reducibility. Under the effects of currents, water can be decomposed into hydrogen gas and oxygen gas. Industry often uses this way to produce pure oxygen and pure hydrogen (Baidu).
Nitrogen Dioxide (NO2)
Nitrogen dioxide is brown liquid or gas, which has a pungent odor. Its melting point is -9.3°C and boiling point is 22.4°C. It is soluble in water. It is mainly used for making nitric acid, nitrating agent, oxidant, and catalyst and so on. Nitrogen oxides damage to respiratory tract. Its chronic effects mainly show in neurasthenia and chronic respiratory tract inflammation. Nitrogen dioxide has hazard to the environment, and causes pollution on water, soil and air. Nitrogen dioxide is combustion-supporting, toxic and irritant. Nitrogen dioxide may cause people to faint (Baidu).
Nitric Acid (HNO3)ã€€
Pure nitric acid is a colorless liquid. Concentrated nitric acid and fuming nitric acid was brown due to dissolved nitrogen dioxide. Nitric acid is strong oxidizing and strong corrosive. Nitric acid is unstable and it is easy to decompose when it exposed to light, so nitric acid should be put in dark brown bottles and kept in the shadows. Nitric acid is also forbidden to contact with reducing agent. The catalytic oxidation of ammonia is the main way to get nitric acid in industrial production system. And nitric acid is used to make fertilizer, explosives, and nitrate. In organic chemistry, the mixture solution of concentrated nitric acid and concentrated sulfuric acid is an important nitration reagent (Baidu).
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7. Sodium Hydroxide (NaOH)
Sodium hydroxide is easily soluble in water and releases a lot of heat. Its melting point is 318.4°C and boiling point is 1390°C. Its lethal dose is 40mg/kg. Sodium hydroxide is strong corrosive, and it is often used as a drying agent. However, it can't dry sulfur dioxide (SO2), carbon dioxide (CO2), nitrogen dioxide (NO2) and hydrogen chloride (HCl) and other acid gases. In addition to water, sodium hydroxide is also soluble in ethanol and glycerol; but it is insoluble in ether, acetone and liquid ammonia (Baidu).
Sodium Nitrate (NaNO3)
Sodium nitrate is colorless or white patch yellow diamond crystal. It tastes a little bitter and it is easily becomes deliquescence. It is easily soluble in water and liquid ammonia, slightly soluble in ethanol, glycerol. Sodium nitrate is irritant to the skin and mucous membrane. If a person inhales a large amount of sodium nitrateoral, the patient will undergoes severe abdominal pain, vomiting, bloody stool, shock, convulsions, coma and even death. Sodium nitrate is combustion-supporting, toxic and irritant. Sodium nitrate is a strong oxidizing agent (Baidu).
Sodium nitrite (NaNO2)
Sodium nitrite is thin white or light yellow crystalline, which is odorless, slightly salty and easily becomes deliquescence. It is easily soluble in water and liquid ammonia, slightly soluble in methanol, ethanol, and ethyl ether. Its melting point is 271°C and it will decompose at 320°C. It can absorb oxygen from the air, forming sodium nitrate. Sodium nitrite has both reducibility and oxidability. It is mainly used for the manufacturing of dye and medicine, as well as organic synthesis (Baidu).