Any addiction is a difficult test not only for the health and psyche of the patient himself, but also for his relatives. Alcoholism in our country is not considered a universal evil, unlike drug addiction, and this is fundamentally wrong. Alcoholism destroys the lives and families of patients just as much as other diseases. You can only be cured if you have the determination and desire to start a new life. Chemicals such as disulfiram and calcium urea citrate, known in our country as Tempozil, can help you get on the path to a sober life.
Tempozil
Tempozil is a drug that causes aversion to alcohol. The drug has been quite widely known since the middle of the last century and was already used as maintenance therapy in the treatment of alcoholism in the USSR and abroad. Actually, Tempozil, as well as other coding methods, does not have any therapeutic effect, but nevertheless, for patients who decide to quit the addiction, this medicine helps them withstand a long pause, abstaining from drinking during this time.
The essence of the method
Tempozil belongs to the so-called aversion therapy, that is, a number of drugs that make it impossible to drink alcohol due to severe physical consequences for the body. Its active ingredient, calcium urea citrate, acts on enzymes that process ethanol. As a result of this effect, alcohol does not break down in the body into safe products, but freely “walks” through the organs, simultaneously poisoning the entire body. Considering the fact that ethanol is a powerful toxic substance, it is easy to imagine how a person who drinks a little alcohol after administering Tempozil will feel.
In cases where the patient, while under the influence of the drug, does not drink alcohol, his life and health are not in danger - the drug Tempozil is absolutely non-toxic and safe. Its sensitizing effect manifests itself only after products containing ethyl alcohol enter the body: fever appears, a rush of blood to the face and head, a strong heartbeat begins, cold sweat appears, and a person can easily lose consciousness.
This condition is very life-threatening and very unpleasant for the patient himself. Having experienced such sensations at least once, the patient is afraid to take alcohol-containing drinks again. This is what Tempozil's action is based on.
Treatment
Tempozil is available in the form of tablets and injections. The drug is administered intravenously or prescribed orally, but only under the supervision of the attending narcologist. Such strictness is due to the fact that the medicine has many contraindications and, when prescribing Tempozil as a sensitizing therapy, the doctor must be sure of the patient’s full health and the absence of alcohol intoxication in the patient at the time of injection.
After administering the drug in the required dosage, according to the instructions for use, the patient is given an alcohol test. The patient is offered alcohol in an amount of 20-40 ml. so that he can experience all the delights of drinking alcohol while being under the blocking influence of Tempozil. After such a provocation, patients are afraid to drink alcohol.
In fact, not a single drug administered intravenously can circulate in the patient’s blood for a long time. This is how Tempozil works. Its sensitizing effect lasts a short amount of time - no more than three days, so the patient must continue to maintain himself in a sober state either with the help of tablets that are used for no more than a week, or with the help of other means of aversion therapy.
Tablets can be prescribed to patients outside the clinic, but under the mandatory supervision of a narcologist, since patients’ failure to comply with the schedule for taking tablets and the dosage prescribed by the doctor can lead to a persistent decrease in the effect of the tablets and, consequently, to a possible relapse of the disease.
Efficacy of the drug
Tempozil can be used as aversion therapy only after. Only then, if the patient has a strong desire to lead a sober, healthy lifestyle, will the medicine show its effectiveness. The remedy itself does not have a very long-lasting effect, although the effect appears almost instantly - within an hour after administering the dose or taking the tablets.
Tempozil can be used as an auxiliary therapy only with a set of measures in the treatment of alcohol dependence, so independent use and, especially, treatment without the knowledge of the patient with this medicine does not make sense. Moreover, self-medication can be dangerous to the health and life of the patient, since the medicine has a number of contraindications.
Contraindications
An absolute contraindication to taking Tempozil is the patient's pregnancy. In addition, intolerance to the components of the drug may make it impossible to use it as a sensitizing agent. Tempozil is also not prescribed to patients with heart pathologies.
It is strictly forbidden to take Tempozil for diseases such as:
- bronchial asthma;
- severe hypertension;
- pulmonary tuberculosis;
- liver diseases;
- kidney pathologies;
- emphysema;
- blood diseases;
- mental illness;
- malignant neoplasms;
- glaucoma;
- nerve inflammation;
- state of alcoholic intoxication.
Relative contraindications to the use of the drug are:
- age over 60 years;
- ulcerative lesions of the stomach in the acute stage;
- organic lesions of brain tissue;
- hypertension;
- minor endocrine disturbances.
In the presence of such diseases, a decision on the advisability of using Tempozil can only be made by a narcologist. Otherwise, you may experience serious side effects.
Side effects
When Tempozil is taken correctly, patients usually do not experience any side effects. However, long-term use of tablets can lead to exacerbation of the patient’s pre-existing diseases - gastritis, cardiovascular diseases, thrombophlebitis. In a number of cases, uncontrolled use of pills led to an acute mental disorder such as alcoholic delirium.
Most often, nitrogen fertilizers are used in the spring: during this period they are applied to the soil during its cultivation. This is done before the onset of July, since when nitrogen fertilizers are added after this period, the plants’ resistance to frost will decrease, and the fruit or vegetable crop will not tolerate storage well. For vegetable crops, these additives can be applied until July inclusive. Nitrogen fertilizers promote plant growth and development, but only in moderation. An excess of such additives can cause excessive vegetation to the detriment of the formation and development of fruits.
- Urea (otherwise called urea) - this product contains about 45 percent nitrogen;
- Ammonium nitrate (otherwise called ammonium nitrate) - the percentage of nitrogen in the composition varies from 34 to 35.6 percent;
- Ammonium sulfate (otherwise known as ammonium sulfate) - the proportion of nitrogen is about 21 percent;
- Sodium nitrate (otherwise known as sodium nitrate) - contains 16 percent nitrogen;
- Calcium nitrate (otherwise known as calcium nitrate) - the proportion of nitrogen contained is 24 percent.
Of all the fertilizers described above, the most famous is urea. It can be used everywhere: for feeding house plants, garden plants, greenhouse plants or garden plants. Urea is a very effective remedy that is inexpensive. You can purchase this fertilizer at any specialized store.
Use of urea for agricultural crops Properties of urea
Urea is a chemical compound that is organic in structure, but at the same time belongs to the category of mineral nitrogen-containing fertilizers.
How to improve productivity?We are constantly receiving letters in which amateur gardeners are worried that due to the cold summer this year there will be a poor harvest of potatoes, tomatoes, cucumbers, and other vegetables. Last year we published TIPS on this matter. But unfortunately, many did not listen, but some still applied. Here is a report from our reader, we would like to recommend plant growth biostimulants that will help increase the yield by up to 50-70%.
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Externally, urea looks like crystals that have neither color nor odor. The final product is produced in round granular form in light shades.
Urea contains about 46 percent nitrogen - the highest concentration of nitrogen among similar fertilizers.
Urea is highly soluble in an aqueous environment, and this property increases with increasing temperature. Urea enters into a hydrolytic reaction with water molecules, which proceeds with the release of ammonia and carbon dioxide.
These fertilizers are used when feeding plants both by root and foliar methods. In addition, urea is very effective in controlling pests and protects vegetation from diseases.
The correct way to feed plants with urea
Fertilizing potatoes with urea This fertilizer can be used to feed vegetable, berry, fruit or ornamental crops. Urea contains ammonia nitrogen, which, compared to inorganic nitrogen-containing salts, is better absorbed by plant organisms, is more intensively used in their life processes, and therefore its use seems more effective.
After adding urea granules to the ground, they should be immediately embedded into the soil to a depth of three to four centimeters. In soil layers in which high bioactivity is observed, this fertilizer turns into ammonium carbonate in a few days (usually two or three), and it, in turn, easily decomposes to ammonia, i.e. a portion of the nitrogen evaporates. That is why the surface addition of urea will be ineffective if the granules are not embedded in the soil layer.
Use of urea for plant nutrition
If you use urea to improve soil fertility for vegetable or berry crops, then the granules should be dug up along with the soil before planting in an amount of 5 to 10 grams per cubic meter of land. However, it should be remembered that when ammonia is formed, young shoots may be damaged. To avoid this, this fertilizer is applied to the soil one to two weeks before sowing. Also, the negative effects of ammonia gas can be almost completely neutralized if potassium additives are used, which will only increase the effectiveness of fertilizers.
You can also feed perennial flowers with urea during their growth. To do this, you need to use 20 to 30 grams of fertilizer per 10 liters of water. One liter for one adult plant.
In addition, urea is used to feed fruit and ornamental trees 1-2 times a season. Fertilizer is applied over an area of land on which the shadow of the crown falls. If organic substances are also used as fertilizer, then the amount of urea is reduced by one and a half to two times. To feed an adult apple tree you need about 200 grams of fertilizer, for plums - about 120, for currants - about 35 grams. When feeding vegetable crops, you need from 5 to 20 grams of urea per cubic meter of land, cucumbers and peas - from 5 to 8 grams.
Foliar feeding of plants with urea
The use of urea will be effective if there are signs of nitrogen deficiency in plants. This fertilizer has significant advantages over other nitrogen-containing products: it burns leaves less. To carry out foliar feeding, it is necessary to prepare an aqueous solution in which urea will be present in an amount of 50 grams per 10 liters. In a solution for indoor plants, this indicator remains approximately the same. Foliar feeding is best done in the morning or evening.
First feeding of strawberries with urea
Use of urea: main rules
- In order to avoid the loss of nitrogen valuable for plants, urea must be added to the soil layer at least three to four centimeters;
- To prevent the negative impact of urea on plants, it is better to use them together with potassium-containing fertilizers;
- But at the same time, urea can be mixed with other additives only during the sowing period. Urea cannot be mixed with some substances (lime, chalk, superphosphate);
- Urea does not burn the foliage of plants when compared with ammonium nitrate, therefore the use of this fertilizer is preferable for feeding;
- This nitrogen fertilizer must be stored in a dry place, since urea absorbs moisture well.
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Urea is a white crystalline substance that is soluble in water and other polar liquids. It got its name precisely because it was first isolated from human urine (around 1770) by a certain French chemist named Ruel.
And almost 50 years later, the German chemist Wöhler managed to obtain a substance (of organic origin) similar in properties to urea by evaporating an inorganic compound dissolved in water. It was an alloy of calcium urea - that is, an alloy of zinc with coal and calcium. Actually, it was with the discovery of urea that the science of organic chemistry began its development. Therefore, the second name of urea is urea.
1 Urea production
The demand for urea production is closely related to the breadth of the range of uses of urea in life. For example, every year the global demand for the synthesis of urea for industrial use reaches hundreds of tons.
The main by-product in the synthesis of urea is ammonia. There are three grades of urea according to GOST:
- grade A – for industry;
- grade B – for crop production;
- for retail trade.
Grade A (two grades) of urea solutions is actively used in the production of fat solvents for dishes and equipment, in the oil industry for the purification of fuel and oil, and for environmental protection at refineries. In addition, there are also 3 grades of grade B urea. The grade is determined by the percentage of the mass fraction of ammonia, which comes in two types: polished and crystalline.
2 What is urea used for?
Urea as a substance is included in the blood of warm-blooded mammals and some species of fish as the final product of protein synthesis. It can form many complexes with various chemical elements, resulting in various modifications, some of which are familiar to us:
- dry hydrogen peroxide – hydropyrite;
- carbamide peroxide – for teeth whitening;
- the synthesis of carbamide triclosans produces bactericidal preparations for the production of antibacterial and antifungal hygiene products (soaps, shampoos);
- used in dentistry for fillings;
- urea pharmaceutical resins – for the production of fiberboard;
- diuretics - drugs for dehydration of the body (for various types of edema);
- food additive E927b.
Considering all these properties, urea can be used for bleaching dark hair, spraying trees in gardening, as a fertilizer, in pharmacology, for the manufacture of drugs against edema and various tumors, in the furniture industry, and even for the production of certain food products.
The demand for urea in agriculture is also extremely wide. Tilling the garden in the spring, spraying the trees in the fall—the application of urea is as indispensable for agriculture as the usual ammonium nitrate and copper sulfate.
2.1 How to properly use and apply urea?
Urea contains substances that have to be actively used in spring and autumn almost everywhere:
- cereals;
- corn;
- sunflower;
- trees;
- bushes;
- vegetables;
- fruit and berry crops;
- ornamental crops.
Urea has the highest nitrogen content as a percentage of other fertilizers. Applying the composition diluted in the required proportions, depending on the purposes, into the soil or spraying it in spring and autumn is the norm for farming. In addition, the introduction of urea into the soil makes it possible to increase the moisture capacity of soil covers. The only thing is that it needs to be sealed immediately, otherwise it can evaporate.
For example, treating beds with urea is necessary in order to form a high-quality ovary. The solution used here is 1 tablespoon of urea per bucket of water. Irrigation density is approximately two liters of solution per square meter of bed with normal planting density. It is not difficult. And it can be done both in autumn and spring, depending on the spring or winter type of garlic.
Another thing is how to apply and dilute urea for cucumbers. The first feeding is root feeding. You need to dilute 1 tbsp. spoon per 10 liters of water and add a phosphate preparation. Foliar feeding at the flowering stage can be combined with - against powdery mildew.
In this case, the cucumber leaf does not suffer at all - unlike ammonium nitrate, urea does not burn the surface of the plant and does not leave stains. Naturally, if they were produced according to the rules, and not in sunny weather.
The third feeding can be done either root (50 g/10 liters of water) or foliar (1 tbsp/10 liters of water). This works for cucumbers as a flowering activator. The fourth feeding for cucumbers is carried out to rejuvenate the leaves during the fruiting period at the rate of (15g/10 liters of water).
In addition, all types of such fertilizing can be done using liquid fertilizer in the form of a universal urea-ammonium mixture Kas. At different stages of plant development and for different needs, appropriate solutions of this mixture can be made for intended use.
This mixture is used not only for fertilizing, but also for spraying fruit trees. The spring period of agricultural work and the final chords of soil preparation in the fall - the Cas mixture is universal.
For example, in the spring it will not only help to completely eliminate insects and larvae on the branches, but will also slow down the development of buds, which can be very useful in early spring when there are very strong temperature changes. They will almost bloom when they are completely safe.
As for ornamental plants and fruit and berry plantings, they can be fed no more than twice per season.
Separately, I would like to clarify the difference between urea and carbamide peroxide. Because when it was mentioned above about the properties of urea to whiten teeth, in the form of hydrogen peroxide. It’s just that hydrogen peroxide is initially included in the composition of carbamide peroxide, but it also contains residues of unrefined urea, so the concentration is much higher.
But, after 20 minutes, carbamide peroxide simply turns into hydrogen peroxide. Due to this long-lasting effect, it is often used for use in whitening strips and long-lasting professional toothpastes.
2.2 Popularity of urea among farmers (video)
Urea (urea) is a substance of endogenous origin, synthesized in the body of vertebrates. The scope of its application is very wide. Urea is used in medicine, cosmetology and, of course, in gardening. Feeding plants with this fertilizer must be done according to certain rules.
Urea (urea): composition
In horticulture, urea is the highest concentration nitrogen fertilizer (up to 46%). It is produced in the form of a yellowish or white crystalline powder. Urea is odorless and dissolves well in water. Some disadvantage of urea is its hygroscopicity. It absorbs moisture very quickly, so it has to be stored in sealed bags.
Urea is produced industrially from carbon dioxide and ammonia. Nitrogen is included in its composition in an easily digestible amide form.
Main characteristics and application
Urea (urea) is the safest nitrogenous fertilizer to date. If the dosage and application technology are followed, it does not burn the leaves and roots of plants. The chemical formula of urea is as follows: (NH 2) 2CO.
The use of urea allows you to accelerate the development of garden crops and significantly increase productivity. This effect is primarily due to the fact that nitrogen is directly related to the construction of biomolecules. This substance is included in all the most important acids and proteins.
It is especially advisable to use urea in cases where plants show signs of nitrogen deficiency: they grow very slowly, have thin and weak shoots, pale leaves, weak and underdeveloped flower buds.
Urea is also used as a remedy for garden and vegetable pests. It helps very well against aphids, apple blossom beetles, weevils, and copperheads. In addition, it is used in the fight against diseases such as monilial burn, scab and purple spot.
What you should know
Very often, urea is used if the owners do not have the opportunity to use organic fertilizers for the garden. It has approximately the same effect. Of course, this substance is chemical and in terms of ecology is inferior to manure. However, unlike organic matter, urea is a much more balanced fertilizer and makes it possible to fertilize in strictly measured doses.
Urea should be used as a fertilizer taking into account the fact that when it gets into the soil it very quickly changes under the influence of soil bacteria. The transformation process is accompanied by the release of ammonium carbonate. This substance promotes the rapid penetration of nitrogen into plant tissues. However, in air, ammonium carbonate decomposes very quickly. Therefore, urea should be embedded deep enough into the soil. For the same reason, urea acts most effectively on plants in protected soil - in greenhouses and greenhouses.
Urea is a universal fertilizer. It can be used on absolutely any soil. However, it should be taken into account that different cultures need different amounts of it.
Also, a gardener who decides to feed plants with urea should take into account the fact that it quite acidifies the soil. If the soil in the garden has a low pH, chalk, dolomite flour or limestone should be used together with urea in a 1:1 ratio.
Do not use urea on soils with low urease content. In this case, it is advisable to purchase organic fertilizers for the garden.
Dosages for plants
Below in the table you can see the required amount of urea for certain types of plants.
Compliance with dosages is a fairly important condition for the effectiveness of using a fertilizer such as urea. Urea, the use of which under no circumstances causes any particular harm to plants, in high concentrations, however, can inhibit flowering and fruit development. If the dose is exceeded, as in the case of organic matter, the crops begin to rapidly develop green mass due to fruiting.
Dosages for foliar feeding
In this case, for garden crops, a solution is usually used at a concentration of 9-15 g per 10 liters of water. When treating shrubs and fruit trees, a more concentrated product is usually used.
It is easy to measure the required amount of urea even in the absence of a dispenser. A tablespoon contains 10 g, a matchbox contains 13 g, and a glass contains 130 g.
Instructions for use
Using urea, you can carry out both regular and foliar feeding of plants. In spring it is introduced into the soil in advance. The fact is that when urea is granulated, a special substance is formed - boiret, which can inhibit the growth of young plants. Therefore, fertilizing with urea is carried out approximately two weeks before planting seeds or seedlings. At the same time, it is embedded in the ground in such a way that a layer of soil remains between it and the roots of young plants. In any case, the depth of urea should not be less than 3-4 cm.
Foliar feeding of plants with urea is carried out in the morning or evening hours. Spraying of fruit trees and shrubs is carried out directly in the tree trunk area.
Urea: price
The cost of urea depends on many factors. In some regions it may be more, in others it may be less. Also, the price very much depends on seasonality. In the midst of dacha work, urea, of course, will be more expensive.
This fertilizer is usually sold in sealed plastic bags or bags. Packaging can be very different. In addition, the cost of fertilizer depends on the supplier. In general, you can buy both expensive and cheap urea. The price for this feeding is a minimum of 16 rubles/kg, a maximum of 40 rubles/kg. Of course, it’s worth looking for cheaper fertilizer. It is best to purchase it in a large container in winter.
Urea for spraying against pests
Thus, urea (urea) is usually used only to protect fruit trees and shrubs. The treatment is carried out twice during the warm period - in early spring, before buds open, and in autumn.
In this case, special kits are used. Urea for spraying against pests is sold not in bags or packages, as usual, but in boxes. One package is designed for 10 liters of water. The kit includes 700 g of urea and 50 g of copper sulfate. Of course, if you wish, you can purchase these components separately and mix them in the same proportions.
Many summer residents prefer urea even to the very popular and well-known Bordeaux mixture. The thing is that urea not only helps to destroy harmful insects and fungi, but also feeds trees and shrubs at the same time. In addition, spraying with urea helps delay flowering. This is useful in the sense that in early spring frosts very often occur in central Russia. With later flowering, therefore, a better harvest can be obtained.
How to spray
Before treating against pests or infections, trees and shrubs should be carefully prepared. Frozen or damaged branches must be removed, the trunks whitened, and the trunk circles dug up. Spray on a sunny day. In hot weather, the procedure should be carried out in the morning or evening.
The first treatment is carried out before buds open, the second - during the flowering period, the third - after fruit set. If it rains immediately after spraying, the operation should be repeated. The treatment is carried out using a special sprayer. During the procedure, be sure to wear protective glasses and gloves.
As you can see, carbamide (urea) fertilizer is very useful and also easy to use. Spraying or root feeding with its use is quite simple. The main thing is to follow the dosage and timing. This will allow you to get maximum effect with minimal investment.
In Russia, two grades of urea are produced - A and B. Grade A urea is intended for industrial use in the production of plastics, resins, and adhesives. Urea grade B is used in agriculture as a mineral nitrogen fertilizer and as a feed additive in livestock farming.
Product properties and technical specifications
Urea is colorless crystals, easily soluble in water, alcohol, liquid ammonia, and sulfur dioxide. Melting point 132.7°C, density 1.33.103 kg/m3.
Under normal conditions, urea is fire- and explosion-proof and non-toxic.
Urea is packaged in valve paper and polymer bags in accordance with regulatory and technical documentation. Bulk in hopper-type railway cars, mineral carriers, as well as in specialized metal containers. For retail sales, the product is packaged in plastic bags weighing no more than 3 kg. Store in closed dry warehouses. Containers with urea and transport packages may be stored in open areas.
They are transported packaged and in bulk by all types of covered transport, except air.
Urea is produced in two grades: A - for use in the chemical industry and livestock farming, and B - for use in agriculture.
The table below briefly presents the technical requirements for urea in accordance with GOST 2081-92.
Technical characteristics of urea (according to GOST 2081-92)
Specifications | Grade A | Brand B | ||
| I grade | higher variety | I grade | II grade | |
| Appearance | White and lightly colored granules | |||
| Mass fraction: | ||||
| Nitrogen in terms of dry matter, %, not less | 46,2 | 46,2 | 46,2 | 46,2 |
| Biuret, %, no more | 1,4 | 1,4 | 1,4 | 1,4 |
| Water, %, no more | ||||
| drying method | 0,3 | 0,3 | 0,3 | 0,3 |
| Fisher method | 0,6 | 0,5 | 0,5 | 0,6 |
| Free ammonia,%, not less | 0, 03 | |||
| Granulometric composition, mass fraction of granules size, %: | ||||
| from 1 to 4 mm, not less | 94 | 94 | 94 | |
| from 2 to 4 mm, not less | 70 | 50 | ||
| less than 1 mm, no more | 3 | 5 | 5 | |
| residue on the sieve 6 mm, no more | absent | |||
| Friability, %, not less | 100 | 100 | 100 | |
| Static strength of granules, kgf/granule, not less | 0,7 | 0,5 | 0,3 | |
| Condensing additive: Urea-formaldehyde resin, % | 0,2-0,5 | |||
Areas of application of urea
Urea is a highly reactive compound and forms complexes with many compounds, such as hydrogen peroxide, which are used as a convenient and safe form of “dry” hydrogen peroxide. The ability of urea to form inclusion complexes with alkanes is used for dewaxing oil.
When heated to 150-160°C, urea decomposes to form biurethane, ammonia, carbon dioxide and other products. In aqueous solution it hydrolyzes to CO2 and NH3, which determines its use as a mineral fertilizer. When interacting with acids, it forms salts. Alkylation produces alkylureas, interaction with alcohols produces urethanes, and acylation produces ureides (N-acylureas). The latter reaction is widely used in the synthesis of heterocyclic compounds, for example, pyrimidines. Urea easily condenses with formaldehyde, which makes it widely used in the production of resins.
The chemical properties of urea determine its widespread use in the chemical industry in the synthesis of urea-aldehyde (primarily urea-formaldehyde) resins, which are widely used as adhesives, in the production of fiberboards (DFB) and furniture production. Urea derivatives are effective herbicides.
Part of the urea produced is used to produce melamine. A significantly smaller share is used for the needs of the pharmaceutical industry.
By its nature, urea is a mineral fertilizer that is used on all types of soils for any crops. This form of fertilizer provides a significant increase in crop yield. It is produced in this quality in caking-resistant granular form. Compared to other nitrogen fertilizers, urea contains the largest amount of nitrogen (46.2%), which mainly determines the economic feasibility of its use as a fertilizer for many crops on any soil.
The rumen of ruminants contains microorganisms that can use urea for protein biosynthesis, so it is added to feed as a protein substitute.
In medical practice, pure urea is used as a dehydration agent to prevent and reduce cerebral edema.
Interesting areas of application of urea are associated with its use for purifying emissions from thermal power plants and waste incineration plants, where the products of thermal decomposition of urea are used as a nitrogen oxide reducer. Moreover, urea can be used both in solid form and in the form of an aqueous solution. Today, this technology is already being implemented at waste incineration plants.
Another promising area for using urea is the production of the AdBlue product - a 32.5% urea solution used to treat exhaust gases from diesel engines. The use of this solution makes it possible to achieve compliance of the composition of exhaust emissions with Euro-4 and Euro-5 standards. In this case, the use of prilled urea is more preferable due to its physical properties.
PRODUCTION TECHNOLOGY
Development of domestic urea production
Urea was discovered by Ruel in 1773 and identified by Prout in 1818. Particular importance to urea in the history of organic chemistry was given by the fact that its synthesis by Wöhler in 1828 was the first synthesis of an organic compound from an inorganic one: Wöhler obtained it by heating ammonium cyanate obtained in situ reaction of potassium cyanate with ammonium sulfate.
All industrial methods for producing urea are based on its formation by the reaction of ammonia with carbon dioxide at temperatures of about 200°C and pressures of about 200 atm. and higher, therefore, in most cases, urea production is combined with ammonia production.
The first industrial installations for the production of urea abroad appeared in the 1920s on the basis of work carried out by chemists in Germany, the USA and France at the beginning of the 20th century. These installations operated according to the so-called open scheme: the urea melt was throttled to atmospheric pressure, at this pressure the unreacted gases were separated and the ammonia contained in them was used to produce ammonium salts, and then the urea solution was evaporated and urea was obtained in crystalline form. This method was extremely uneconomical.
Therefore, in the 1930-40s, research work was intensified in different countries, which was aimed at creating more economical methods for producing urea.
In the USSR, the beginning of industrial production of urea dates back to 1935, when the first unit with a capacity of 240 kg per day was launched at the Chernorechensky Chemical Plant (Dzerzhinsk).
By the 1950s, there were two industrial installations for the production of urea in the USSR at the Novomoskovsk and Lisichansk chemical plants with a total capacity of about 20 thousand tons per year, created on the basis of the pre-war work of the State Internal Affairs Directorate, Leningrad, and operating on an open circuit. Research work in the field of improving urea production technology was carried out in parallel in several directions; schemes for the synthesis of urea with gas, partial and liquid recycling were developed. At this time, the Research and Design Institute of Urea (NIIK) was created, which designed and tested in 1958-59 in Stalinogorsk (Novomoskovsk) on a pilot industrial scale two processes - the process of two-stage distillation of urea melt with condensation and recycling of excess ammonia and the process of separating distillation gases by selective absorption of carbon dioxide in a solution of monoethanolamine. At the same time, together with ChKhZ, a process for continuous evaporation of urea solution and its crystallization in screw-type devices was developed and tested. These works served as the basis for the projects of the first, considered at that time large-tonnage, urea units with a capacity of 35 thousand tons per year with partial ammonia recycling (Novomoskovsk, Salavat, Angarsk, Grodno, Kemerovo) and full gas recycling (Shchekino).
Abroad during this period, the company Stamicarbon (Netherlands) developed and in 1959 brought to industrial implementation a process for the production of urea with complete recycling of unreacted substances in the form of an aqueous solution of ammonium carbon salts - the so-called complete liquid recycling - with the production of a granular product by spraying the urea melt in a hollow tower towards the upward flow of air.
Later, this granulation method was called “prilling”. Simultaneously with the construction in the USSR of the mentioned units with a capacity of 35 thousand tons per year, several sets of equipment were purchased abroad for units with a capacity of 90 thousand tons per year, operating using the technology of full liquid recycling from Stamicarbon. The workshops were put into operation in the period 1963-1965. at the Shchekino and Severodonetsk chemical plants, the Chirchik electrochemical plant and the Salavat petrochemical plant (workshop No. 24-1).
Based on the experience of developing these units, in the 1960-70s, projects were completed for more than 25 urea production units with a capacity of 90 thousand tons per year using full liquid recycling technology, including a project for re-equipping a workshop with gas recycling in Shchekino. Shops with two units were launched at the Novomoskovsk, Nevinnomyssk, Novgorod chemical plants, at the Salavat Petrochemical Plant (workshop No. 24-P), the Vakhsh Nitrogen Fertilizer Plant, the Kuibyshevazot Production Association, the Grodno Azot Production Association, the Ionavsky ZAU, the Kirovkan and Rustavi Chemical Plants. factories, as well as at the Angarsknefteorgsintez Production Association, the Chernorechensk Production Association Korund, in the city of Kokhtla-Jarve, etc. In total for this project for 1966-1972. 32 urea production units were put into operation.
By the end of 1972, the capacity of urea plants in the USSR exceeded 5 million tons per year - more than 30% of the world's total.
In the 1970s, by government decision, sets of equipment for units for the production of urea with a capacity of 330 and 450 thousand tons per year were purchased using technologies from all leading foreign companies.
Currently, the urea production industry is based on a scheme with full liquid recycling from TES (Japan), JSC NIIK, as well as on stripping process schemes from Stamicarbon, Snamproggetti (Italy) and Tecnimont (Italy).
Urea production enterprises are located in seven countries of the former USSR (Russia, Ukraine, Belarus, Uzbekistan, Lithuania, Estonia, Tajikistan). These plants employ five main methods of urea production: full liquid recycle AK-70 (31 plants), Stamicarbon CO2 stripping process (13 plants), Snamproggetti ammonia stripping process (3 plants), Tecnimont (3 plants) and TEC (1 installation). Regarding the technologies used, the capacities are distributed as follows:
Urea production technologies at enterprises of the former USSR
Source: "Chemistry and Business"
As can be seen from the diagram, liquid recycling technology is one of the most common in the territory of the former USSR (31%). For Russia this is even higher - 36%. In addition, three countries of the former USSR have only this type of urea production.
Despite the fact that the installations were built a long time ago, they are quite competitive. The measures taken at most enterprises to reconstruct production facilities increase capacity and reduce energy costs. This will be discussed in more detail when considering urea production technologies at Russian enterprises.
OVERVIEW OF MODERN TECHNOLOGIES
Characteristics of Russian production
Stripper for urea production using the Stamicarbon process
As mentioned earlier, in Russia, urea production is carried out using the technologies of Stamicarbon, Snamprogetti, Tecnimont, NIIK, GIAP. Initially, the development of urea production in the USSR was carried out by GIAP (until the 50s). After the creation of the Urea Research Institute, the institute began to play an important role in the creation and reconstruction of urea production. Russian enterprises subsequently began to widely use the technologies of the above-mentioned Western companies. The most common technology at the moment is the Stamicarbon process. Kemerovo and Berezniki OJSC Azot use Tecnimont technology. The initial technology at Mineral Fertilizers OJSC is TEC. A number of units (in particular, 1 of the 3 units of NAC Azot) uses Snamprogetti technology. More details about the production of urea at enterprises will be discussed in the next part of the subsection.
On the technology market for creating new capacities, there are various modifications of the stripping process, differing mainly in the hardware design of the synthesis unit. Foreign companies today offer installations with a capacity mainly from 1000 to 2000 and even 3000 tons/day.
All these technologies are at approximately the same level in terms of the degree of use of raw materials; they differ in different solutions for hardware design, used structural materials, and technological methods that allow minimizing the level of energy consumption. For example, the Stamicarbon company offers a flooded synthesis reactor combined with a high-pressure condenser. In TEC units, the synthesis stages and subsequent stages are combined in heat, which reduces energy consumption. OJSC NIIK, together with the Czech company Hepos, offers the supply of a plant with a capacity of 1200-1500 tons per day, which is based on modernized stripping technology.
Let's take a closer look at the Stamicarbon CO2 stripping process. A simplified process diagram is shown in Fig. 1.1.
Rice. 1.1. Stamicarbon CO2 stripping process
Ammonia and carbon dioxide are converted into urea through ammonium carbamate at a pressure of about 140 bar and a temperature of 180-185°C. The conversion of ammonia reaches 41%, carbon dioxide - 60%. Unreacted ammonia and carbon dioxide enter the stripper, with CO2 acting as a stripping agent. After condensation, CO2 and NH3 are recycled and returned to the synthesis process. The heat of condensation is used to generate steam for the CO2 compressor.
This process can have different hardware design. Below is the Urea 2000plusTM Technology - synthesis with a pool condenser.
Rice. 1.2. Urea 2000plus technology: synthesis with Pool Capacitor
This technology is successfully used in a 2,700 ton/day urea production facility in China (CNOOC), launched in 2004, as well as in a 3,200 ton/day capacity in Qatar (Qafco IV), launched in 2005.
The second embodiment of this process involves the use of a pool reactor. The advantages of synthesis using a pool reactor are:
- in this case, 40% less heat exchange surface is required compared to a vertical film-type condenser,
- the HP capacitor and the reactor are combined in one device,
- the height of the production structure is significantly reduced,
- the length of HP pipelines made of corrosion-resistant steel is significantly reduced,
- reduction in investment,
- ease of operation, stable synthesis insensitive to changes in the NH3/CO2 ratio.
Below is a diagram of this process.
Rice. 1.3. Urea 2000plus technology: synthesis with a flooded reactor
Rice. 1.4. Pool reactor diagram
At the moment, there are also developments of mega-urea plants with a capacity of up to 5000 tons/day. Below is a diagram of the mega plant proposed by Stamicarbon.
Rice. 1.5. Mega-production of urea (Stamicarbon).
A variant of the stripping process proposed by Snamprogetti involves the use of ammonia as a stripping agent. NH3 and CO2 react to form carabide at a pressure of 150 bar and a temperature of 180°C. Unreacted carbamate is decomposed in the stripper by the action of ammonia. A simplified process diagram looks like this:
Rice. 1.6. Snamprogetti NH3 stripping process
The final stage of all technological processes of urea synthesis is the production of commercial urea granules. Let's consider this process in more detail.
There are two main ways to produce granules - prilling and granulation. The prilling method involves cooling urea melt droplets in free fall and crystallizing them in a counter flow of cooling air. The granulation method is reduced to spraying and subsequent repeated layering of urea melt onto “seed” (solid) particles of the substandard product with the formation of spherical granules and subsequent cooling of the latter. To obtain granules of nitrogen fertilizers, including urea, the most common method in world practice is prilling.
At the end of the twentieth century, a product appeared on the urea market, obtained by granulation in a “fluidized” bed and differing in its properties from prilled. Currently, the technology for granulating urea in a “fluidized” bed is offered by Stamicarbon, TEC, Jara and a number of others. The main advantage of granular urea is the higher strength of the granules and, accordingly, less caking during transportation. However, capital costs for the construction of a product granulation plant are on average 1.5-1.8 times higher than for prilling. In addition, the urea granulation plant is also characterized by a larger footprint, the presence of a large amount of retour (up to 50% of output), and relatively high energy and operating costs. However, today the growth rate of granular product capacity exceeds the growth rate of prilled product.
Below are the schemes for prilling and granulation in a fluidized bed using Stamicarbon technology.
Rice. 1.7. Diagram of the prilling process (Stamicarbon)
Rice. 1.8. Scheme of the fluidized bed granulation process (Stamicarbon)
The latter option for producing commercial urea is used in particular at GrodnoAzot (Belarus).
Considering that the competitiveness of urea production largely depends on the efficiency of ammonia production, we will consider modern technologies for the production of this product. Then we will consider in detail the production of ammonia and urea at Russian enterprises.
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