Urea is the first synthetic organic substance, which widely exists in nature. For example, fresh human excrement contains 0.4% urea. Urea production accounts for about 40% of the total nitrogen fertilizer production in China at present, and it is one of the main nitrogen fertilizer varieties after ammonium bicarbonate. Urea as a nitrogen fertilizer began in the early 20th century. Since 1950s, urea has developed rapidly all over the world because of its high nitrogen content (45% ~ 46%), wide application and continuous improvement of industrial technology. China started to build a medium-sized urea plant in 1960s. From 1986 to 1992, China's urea output is above 9 million tons. At present, it accounts for 40% of the total nitrogen fertilizer output.
The molecular formula of urea is CO(NH2)2. Because human urine contains it, it is named urea. Urea contains N)46%% nitrogen (N), which is the highest among solid nitrogen fertilizers. Urea is synthesized directly from liquid ammonia and carbon dioxide at high temperature and high pressure in industry. The chemical reaction is as follows.
2NH3+CO2 → NH2coonh4 → Co (NH2) 2+N2O urea is easily soluble in water, and 105g can be dissolved in 100 ml water at 20℃, and the aqueous solution is neutral. There are two kinds of urea products. Crystallized urea is a white needle-like or prismatic crystal with strong hygroscopicity. Granular urea is translucent, with a particle size of 1 ~ 2 mm, smooth in appearance and obviously improved in hygroscopicity. At 20℃, the critical moisture absorption point is 80% of the relative humidity, but at 30℃, it drops to 72.5%. Therefore, urea should be avoided to be stored in the open air in humid climate in midsummer. At present, hydrophobic substances such as paraffin wax are added in urea production, which greatly reduces the hygroscopicity.
Urea is a kind of physiological neutral fertilizer, which will not leave any harmful substances in the soil and will not have adverse effects after long-term application. However, when the granulation temperature is too high, a small amount of biuret, also known as biuret, will be produced, which will inhibit crops. China stipulates that the biuret content of urea for fertilizer should be less than 0.5%. When the biuret content exceeds 1%, it cannot be used as seed fertilizer, seedling fertilizer and foliar fertilizer, and the urea content in other application periods should not be too high or too concentrated.
Urea is an organic nitrogen fertilizer, which can only be absorbed and utilized by crops after being hydrolyzed into ammonium carbonate or ammonium bicarbonate by urease in soil. Therefore, urea should be applied 4 ~ 8 days before the fertilizer requirement period of crops.
Uses: Urea is suitable for base fertilizer and topdressing, and sometimes used as seed fertilizer. Urea is a molecule before transformation and cannot be absorbed by soil, so it should be prevented from losing with water. Ammonia formed after conversion is also volatile, so urea should also be covered with soil.
CO(NH2)2, also known as urea. Diacylamide equivalent to carbonic acid. It occupies a considerable proportion in the final product of protein decomposition. In the case of ordinary diet, 25-30 grams can be excreted from urine every day, which is close to 87% of the total nitrogen in urine. Generally speaking, amphibians, cartilaginous fishes and mammals all have the same tendency. In these organisms, urea is formed in the ornithine cycle, so animals that excrete urea have the necessary complete enzyme system. Without these enzymes, animals will excrete uric acid (birds) or ammonia (bony fish). There are many urease in the seeds of kidney bean and soybean plants, which can hydrolyze urea into carbon dioxide and ammonia. Urea is also an important fertilizer.
The appearance of urea is white crystal or powder. It is the product of protein metabolism in animals and is usually used as nitrogen fertilizer for plants.
Urea is a nitrogen-containing metabolite secreted by mammals. It is synthesized in the liver and the process is called urea cycle.
Alias: carbonyl diamine, carboxamide, urea
Molecular formula: CO(NH2)2, named after urea in human urine. Urea contains N)46%% nitrogen (N), which is the highest among solid nitrogen fertilizers.
Production method: urea is directly synthesized from ammonia and carbon dioxide at high temperature and high pressure. The chemical reaction is as follows.
2NH3+CO2 → NH2coonh4 → Co (NH2) 2+N2O urea is easily soluble in water, and 105g can be dissolved in 100 ml water at 20℃, and the aqueous solution is neutral. There are two kinds of urea products. Crystallized urea is a white needle-like or prismatic crystal with strong hygroscopicity. Granular urea is translucent, with a particle size of 1 ~ 2 mm, smooth in appearance and obviously improved in hygroscopicity. At 20℃, the critical moisture absorption point is 80% of the relative humidity, but at 30℃, it drops to 72.5%. Therefore, urea should be avoided to be stored in the open air in humid climate in midsummer. At present, hydrophobic substances such as paraffin wax are added in urea production, which greatly reduces the hygroscopicity.
Urea is a kind of physiological neutral fertilizer, which will not leave any harmful substances in the soil and will not have adverse effects after long-term application. However, when the granulation temperature is too high, a small amount of biuret, also known as biuret, will be produced, which will inhibit crops. China stipulates that the biuret content of urea for fertilizer should be less than 0.5%. When the biuret content exceeds 1%, it cannot be used as seed fertilizer, seedling fertilizer and foliar fertilizer, and the urea content in other application periods should not be too high or too concentrated.
Urea is an organic nitrogen fertilizer, which can only be absorbed and utilized by crops after being hydrolyzed into ammonium carbonate or ammonium bicarbonate by urease in soil. Therefore, urea should be applied 4 ~ 8 days before the fertilizer requirement period of crops.
Uses: Urea is suitable for base fertilizer and topdressing, and sometimes used as seed fertilizer. Urea is a molecule before transformation and cannot be absorbed by soil, so it should be prevented from losing with water. Ammonia formed after conversion is also volatile, so urea should also be covered with soil.
Use of urea:
Urea is a commonly used quick-acting nitrogen fertilizer, and it has many other uses besides topdressing.
1. Adjust the flower amount In order to overcome the situation that the apple is big and small in the same year, spraying 0.5% urea aqueous solution on the leaves for two times in 5-6 weeks after flowering (the critical period of apple flower bud differentiation, the growth of new shoots is slow or stopped, and the nitrogen content of leaves decreases) can increase the nitrogen content of leaves, accelerate the growth of new shoots, inhibit flower bud differentiation, and make the flower amount suitable for the new year.
Secondly, the flower organs of peach trees are sensitive to urea, but slow to water. Therefore, the experiment of thinning flowers and fruits of peach and nectarine with urea was carried out abroad. The results show that peach and nectarine need a large concentration (7.4%) to show good results, and the most suitable concentration is 8%- 12%, after spraying 1-. However, under different land conditions, the responses of different periods and varieties need to be further tested.
Third, rice seed production In the hybrid rice seed production technology, in order to improve the outcrossing rate of parents and increase the seed production of hybrid rice or sterile lines, red toxin is generally sprayed on the female parent to reduce the neck entanglement of the female parent or make it completely extracted; Or spray parents to adjust growth and synchronize flowering. Because gibberellin is expensive, the cost of seed production with it is high. People use urea instead of gibberellin for experiments, and use 1.5%-2% urea at booting stage and heading stage, which has similar breeding effect with gibberellin and will not increase plant height.
4.4:/kloc-0: 400 parts of urea, washing powder and clear water can control pests, such as aphids, red spiders and cabbage worms on fruit trees, vegetables and cotton, and the insecticidal effect can reach over 90%.
5. Urea iron fertilizer Urea forms chelated iron with Fe2+ in the form of complex. This organic iron fertilizer has low cost and good effect on preventing iron deficiency chlorosis. In addition, adding 0.3% urea when spraying 0.3% ferrous sulfate on leaves is better than spraying 0.3% ferrous sulfate alone.
Correct storage method
1. Urea has the highest nitrogen content among solid nitrogen fertilizers, and its physical and chemical properties are relatively stable. After application, it has no effect on soil properties. It can be applied to any soil and crops, and can be used as an external fertilization. At the same time, urea is also an important raw material for resin, plastics, explosives, medicine, food and other industries.
2. Urea can also partially replace protein feed. For example, adding urea to the green feed of dairy cows can partially replace the protein feed, but the amount of urea should not exceed 3% of the green feed or 1% of the total feed, otherwise the burden on the kidneys of livestock will be too heavy, which will easily lead to diseases. Bean cake contains urease, so don't mix it with urea.
1. If urea is improperly stored, it is easy to absorb moisture and agglomerate, which will affect the original quality of urea and bring certain economic losses to farmers, which requires farmers to store urea correctly. Before use, the urea packaging bag must be kept intact, handled carefully during transportation to prevent rain, and stored in a dry, well-ventilated place with a temperature below 20 degrees.
2, if it is a large number of storage, the following should be padded with about 20 cm of wood square, and there should be a gap of more than 50 cm between the upper part and the roof to facilitate ventilation and moisture dissipation, and there should be an aisle between the stacks. So as to facilitate inspection and ventilation. If the opened urea is not used up, the bag mouth must be sealed in time for next year's use.
Raw materials for production: natural gas, coal and petroleum are the three major raw materials for the production of chemical fertilizers, which are usually called gas head, coal head and oil head. In recent years, due to the price increase of oil and coal far exceeding that of natural gas, they are ranked as gas head, coal head and oil head according to cost advantage. For example, the gross profit margin of gas head enterprise Yuntianhua is 58%, and that of coal head enterprise Luhua Hengsheng is 20%.
Market situation of urea, nitrogen fertilizer and chemical fertilizer
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urea
Drug name: urea
Drug alias: nh2conh2
English name: urea
Drug description: injection: 30g per bottle (100 ml); 60 grams (250 ml).
Main ingredients: none.
Features: Not yet.
Indications: Same function as sorbitol. However, about 50% of this product is reabsorbed from renal tubules after glomerular filtration, and its hypertonic solution is used for brain edema, cerebral hernia, glaucoma and so on. Dehydration is fast and strong (15 ~ 30 minutes), but the duration is short (about 3 ~ 4 hours). After taking the medicine, brain volume often increases and intracranial pressure rebounds, so other dehydration drugs must be added 3 ~ 4 hours after injecting this medicine. Its ointment or cream can soften skin and prevent chapped hands and feet.
Usage and dosage: intravenous injection or rapid intravenous drip: 0.5 ~ 1g/kg each time, and complete the drip within 20 ~ 30 minutes. /kloc-It can be repeated after 0/2 hours. Generally, 1 ~ 3 days can be used.
Adverse reactions: None.
Note: (1) This product is unstable in nature. Injection must be dissolved in 10% glucose solution before use, and must be used up within 24 hours to prevent ammonia from being released after decomposition and causing toxicity. The use time cannot exceed 24 hours. (2) If the drug is stored for too long or the temperature of the liquid medicine is too low, it will cause flushing, mental excitement, dryness and anxiety after injection. (3) The leakage of liquid medicine from blood vessels can cause local swelling and blistering, and 0.25% procaine should be used for local sealing and hot compress. Or wet compress with Ruyi gold powder or 50% magnesium sulfate. (4) It can increase non-protein nitrogen in blood, so it is forbidden for patients with renal insufficiency, severe shock and obvious dehydration, active intracranial hemorrhage and excessive nitrogen accumulation in blood.
CASNo.: 57- 13-6
Chinese name urea; Urea; Carbonamide; Carbonyl diamine
English name urea
Relative molecular weight or atomic weight 60.06
Density 1.335
Melting point (℃) 132.7
Viscosity MPa s (20℃) 2.33 (140℃)
Refractive index 1.484
Character; Role; letter
White, odorless needle-like or prismatic crystals. Industrial products contain impurities, sometimes reddish.
Dissolution situation
Soluble in water, ethanol and benzene, almost insoluble in ether and chloroform.
use
Mainly used as fertilizer and supplementary feed for animals. As industrial raw materials, melamine, urea-formaldehyde resin and hydration trap are produced in organic synthesis industry; Used in pharmaceutical industry to produce phenobarbital, caffeine, etc. Used in dye industry to produce brown BR, phthalocyanine blue B, phthalocyanine blue BXBS, etc. Used in the textile industry to make polymers containing urea, softeners for fiber products, etc. Used as a stabilizer in the manufacture of explosives and a dewaxing agent in the refining process of petroleum industry; It is also used for printing and dyeing fabrics, ink pigments, etc. .
Preparation or source
(1) Ammonia reacts with carbon dioxide to produce ammonium carbamate, and then dehydrated to produce urea. Unreacted ammonia and carbon dioxide are absorbed by water to generate ammonium carbamate or ammonium carbonate aqueous solution, which is returned to the synthesis system for recycling. The synthesis pressure is about 19.6 1MPa, the temperature is about 185 ~ 190℃, and about 62% of carbon dioxide is converted into urea.
(2) carbon dioxide stripping: synthesis pressure 13.73MPa, temperature 180 ~ 185℃, conversion rate of 57% ~ 58%, using carbon dioxide as stripping agent to decompose unconverted methylamine into carbon dioxide and evaporate ammonia. The stripping efficiency is 80% ~ 83%, and the gas from the stripping tower is condensed in the high-pressure condenser grass to generate ammonium carbamate solution which is returned to the synthesis tower. The stripping effluent is further decomposed, evaporated and sent to granulation.
(3) Ammonia extraction: synthesis pressure 14.7 1MPa, temperature 185 ~ 190℃, and the conversion rate is about 60%. The unconverted methylamine is decomposed by ammonia in the stripper, and the urine in the stripper undergoes two-stage decomposition to further decompose the participating methylamine. Free ammonia is decanted and recovered in the form of aqueous solution, and excess ammonia is condensed into liquid ammonia and returned to the system.
(4) Isobaric double stripping: synthesis pressure17.65 ~19.61MPa, temperature 185 ~ 190℃, ammonia/carbon dioxide 4 ~ 5, conversion rate 70% ~ 75%. Urine leaving the tower passes through two stripping towers in series, and unconverted ammonium carbamate is stripped and decomposed by ammonia gas and carbon dioxide respectively, and part of excess ammonia is evaporated.
other
When the heating temperature exceeds the melting point, it will decompose.
Used as chemical fertilizer, suitable for all kinds of soil and crops, can be used as base fertilizer and topdressing, preferably topdressing. Attention should be paid to prevent water loss before ammoniation, ammonia volatilization loss after ammoniation, nitrate nitrogen loss formed by nitration, denitrification loss and biuret toxicity. Mix with farm manure such as bean cake, human excrement and urine, compost, etc. Due to the action of microorganisms, urea will soon be ammoniated into ammonium carbonate and lost, so it must be mixed and applied immediately. Potassium chloride, lime nitrogen, calcium superphosphate, calcium chloride and other fertilizers with weak hygroscopicity can be mixed with urea, but they should not be stored for too long after mixing and should be used immediately. Ammonium nitrate, sodium nitrate, ammonium bicarbonate and other fertilizers with strong hygroscopicity cannot be mixed with urea. Neutral or weakly alkaline fertilizers such as ammonium sulfate, potassium sulfate, plant ash, lime and phosphate rock powder fertilizers can be mixed with urea at will.
manufacturer
Sichuan Chemical General Factory; Yunnan Natural Gas Chemical Plant; Cangzhou Chemical Plant; Liaohe Chemical Plant; Daqing Chemical Plant; Hubei Chemical Fertilizer Plant; Guangzhou Petrochemical General Factory; Anqing chemical fertilizer plant; Zhenhai Petrochemical General Factory; Urumqi Petrochemical General Factory; Jihua company fertilizer plant