Ammonium nitrate technology. Ammonium nitrate production technology

Production ammonium nitrate consists of neutralization of nitric acid with ammonia gas and crystallization of the product. Ammonia should not contain more than 1% moisture, and the presence of oil is not allowed. Nitric acid is taken at a concentration of more than 45% HNO 3; the content of nitrogen oxides in it should not exceed 0.1%. To obtain ammonium nitrate, waste from ammonia production can also be used - for example, ammonia water and tank and purge gases removed from liquid ammonia storage facilities and obtained by purging ammonia synthesis systems. Composition of tank gases: 45-70% NH 3, 55-30% H 2 + N 2 (with traces of methane and argon); composition of purge gases: 7.5-9% NH 3, 92.5-91% H 2 + N 2 (with traces of methane and argon). In addition, distillation gases from urea production are also used to produce ammonium nitrate; their approximate composition is: 55-57% NH 3, 18-24% CO 2, 15-20% H 2 O.

The thermal effect of the reaction NH 3(g) +HNO 3(l) NH 4 NO 3 is 35.46 kcal/(g mol). In the production of ammonium nitrate, 45-58% acid is usually used. In this case, the thermal effect of the neutralization reaction is correspondingly reduced by the amount of heat of dilution of nitric acid with water and by the amount of dissolution of ammonium nitrate.

With rational use of neutralization heat, concentrated solutions and even melted ammonium nitrate can be obtained by evaporating water.

In accordance with this, there are schemes for producing an ammonium nitrate solution with its subsequent evaporation (the so-called multi-stage process) and for producing melt (a single-stage or non-evaporation process). To select a rational neutralization scheme, it is necessary to compare four fundamentally different schemes for producing ammonium nitrate using neutralization heat:

1) installations operating at atmospheric pressure (excess pressure of juice steam 0.15-0.2 at);

2) installations with a vacuum evaporator;

3) installations operating under pressure, with a single use of the heat of juice steam;

4) installations operating under pressure, with double use of the heat of juice steam (production of concentrated melt).

In industrial practice, they are widely used as the most efficient installations operating at atmospheric pressure, using neutralization heat and partially installations with a vacuum evaporator.

Technical requirements for finished products

According to the current GOST 2-85 in Russia, granulated ammonium nitrate is produced in two grades: A - the highest quality category and B - the highest quality category (highest grade) and the first quality category (first grade). The quality indicators of industrially produced ammonium nitrate are presented in Table 1.

Table 1

ammonium nitrate GOST 2-85
appearance	Granular product without foreign mechanical impurities
Total mass fraction nitrite and ammonium nitrogen in terms of:
for NH4NO3 in dry matter, % not less		not standardized
for nitrogen in dry matter, %, not less
Mass fraction of water, %, no more
pH of 10% aqueous solution, not less
Mass fraction of substances insoluble in a 10% solution of nitric acid, %, no more		not standardized
Granulometric composition:
Mass fraction of granules
from 1 to 3 mm, %, not less		not standardized
from 1 to 4 mm, %, not less
from 2 to 4 mm, %, not less
less than 1 mm,%
more than 6 mm, %
Statistical strength of granules n / granule (kg / granule), not less
Friability, %, not less
Conditioning additive	magnesium nitrate

Enterprises producing ammonium nitrate must guarantee the consumer that the quality indicators of the product provided for by GOST 2-85 will be maintained for 6 months if the consumer complies with the storage conditions established by the standard.

Application of ammonium nitrate

Ammonium nitrate is one of the types of mineral fertilizers without which modern agriculture is almost unthinkable. Belonging to the family of nitrogen fertilizers, versatility of application, the possibility of industrial volumes of production and supply, proven production technology - these are the advantages that maintain the unshakable position of ammonium nitrate in the fertilizer market.

Nitrogen is absolutely necessary for plants. Chlorophyll, which harnesses solar energy and produces building material for living cells, contains nitrogen. Externally, ammonium nitrate is granules white. The granular substance is highly soluble in water and contains 34.4% nitrogen. It is applied as a top dressing for all types of agricultural crops, in all types of soils and to prepare the soil for sowing. In industry, ammonium nitrate is used as a raw material for the production of explosives and further use in the chemical, mining and construction industries.

There is a problem associated with the high hygroscopicity of ammonium nitrate. The granules lose their hardness and spread when air humidity increases. However, modern technological developments make it possible to take this nuance into account and eradicate it at the production stage.

One of the advantages of ammonium nitrate is traditionally considered to be that the soil completely absorbs the ammonia part due to the rapid solubility of the fertilizer. At the same time, ammonium nitrate has a longer action compared to nitrate. Fractional application of ammonium nitrate can reduce the loss of nitrate nitrogen from leaching. It is successfully used in the production of fertilizer mixtures as the most optimal nitrogen component. Currently, the chemical market is experiencing a steady increase in demand for ammonium nitrate both as a fertilizer and as an industrial chemical raw material. This is also due to the support provided by the state to the agricultural industry and the development of domestic industry in general.

Basic method

In industrial production, anhydrous ammonia and concentrated nitric acid are used:

The reaction proceeds rapidly with the release of a large amount of heat. Carrying out such a process in artisanal conditions is extremely dangerous (although ammonium nitrate can be easily obtained under conditions of large dilution with water). After a solution is formed, usually with a concentration of 83%, excess water is evaporated to a melt, in which the ammonium nitrate content is 95-99.5%, depending on the grade of the finished product. For use as a fertilizer, the melt is granulated in sprayers, dried, cooled and coated with compounds to prevent caking. The color of the granules varies from white to colorless. Ammonium nitrate for use in chemistry is usually dehydrated, since it is very hygroscopic and the percentage of water in it (a(H2O)) is almost impossible to obtain.

Haber method

at pressure, high temperature and catalyst

According to the Haber method, ammonia is synthesized from nitrogen and hydrogen, part of which is oxidized to nitric acid and reacts with ammonia, resulting in the formation of ammonium nitrate:

Nitrophosphate method

This method is also known as the Odd method, named after the Norwegian city in which the process was developed. It is used directly to produce nitrogen and nitrogen-phosphorus fertilizers from widely available natural raw materials. In this case, the following processes occur:

• 1. Natural calcium phosphate (apatite) is dissolved in nitric acid:
• 2. The resulting mixture is cooled to 0 °C, while calcium nitrate crystallizes in the form of tetrahydrate - Ca(NO3)2·4H2O, and it is separated from phosphoric acid.

The resulting calcium nitrate and unremoved phosphoric acid are treated with ammonia, and as a result ammonium nitrate is obtained:

To obtain practically non-caking ammonium nitrate, a number of technological methods are used. An effective remedy To reduce the rate of moisture absorption by hygroscopic salts is their granulation. The total surface of homogeneous granules is less than the surface of the same amount of fine-crystalline salt, so granular fertilizers absorb moisture from the air more slowly. Sometimes ammonium nitrate is fused with less hygroscopic salts, such as ammonium sulfate.

The technological process for the production of ammonium nitrate consists of the following main stages: neutralization of nitric acid with ammonia gas, evaporation of ammonium nitrate, crystallization and granulation of the melt, cooling, classification and dusting of the finished product (Fig. 4.1.).

Figure 4.1 Schematic diagram ammonium nitrate production

Currently, in connection with the development of production of 18 - 60% nitric acid, the bulk of ammonium nitrate is produced at AS-67, AS-72, AS-72M units, with a capacity of 1360 and 1171 tons/day with evaporation in one stage (Fig. 4.2. ) , as well as in installations of the non-evaporation method (Fig. 4.4.).

Figure 4.2 Technological diagram of AS-72M production: 1 - ammonia heater; 2 - acid heater; 3 - ITN apparatus; 4 - pre-neutralizer; 1 - evaporator; 6 - water seal-neutralizer; 7 - melt collection; 8 - pressure tank; 9 - vibroacoustic granulator; 10 - granulation tower; 11 - conveyor; 12 - pellet cooler “KS”; 13 - air heater; 14 - washing scrubber

Gaseous ammonia from heater 1, heated by juice steam condensate, heated to 120 - 160°C, and nitric acid from heater 2, heated by juice steam, at a temperature of 80 - 90°C, enter the heat pump apparatus (using the heat of neutralization) 3. To reduce ammonia losses together The reaction with steam is carried out in excess of acid. The ammonium nitrate solution from the ITN apparatus is neutralized in the after-neutralizer 4 with ammonia, into which the conditioning additive magnesium nitrate is simultaneously added and is sent for evaporation to the evaporator 1. From it, the ammonium nitrate melt formed through the water seal-after-neutralizer 6 and the melt collector 7 is sent to the pressure tank 8 and from it, using vibroacoustic granulators 9, enters the granulation tower 10. It is sucked into the lower part of the tower atmospheric air, and air is supplied from the granule cooling apparatus “KS” 12. The resulting ammonium nitrate granules from the bottom of the tower enter the conveyor 11 and into the fluidized bed apparatus 12 for cooling the granules, into which dry air is supplied through the heater 13. From apparatus 12 the finished product is sent to packaging. Air from the top of tower 10 enters scrubbers 14, irrigated with a 20% ammonium nitrate solution, where ammonium nitrate dust is washed off and released into the atmosphere. In the same scrubbers, the gases leaving the evaporator and neutralizer are purified from unreacted ammonia and nitric acid. The ITN apparatus, granulation tower and combined evaporator are the main devices in the AS-72M technological scheme.

The ITN apparatus (Fig. 4.3.) has a total height of 10 m and consists of two parts: the lower reaction and the upper separation. In the reaction part there is a perforated glass into which nitric acid and ammonia are supplied. Moreover, due to the good heat transfer of the reaction mass to the walls of the glass, the neutralization reaction proceeds at a temperature lower than the boiling point of the acid. The resulting ammonium nitrate solution boils and water evaporates from it. Due to the lifting force of the steam, the vapor-liquid emulsion is ejected from the top of the glass and passes through the annular gap between the body and the glass, continuing to evaporate. Then it enters the upper separation part, where the solution, passing a series of plates, is washed from ammonia with a solution of ammonium nitrate and juice steam condensate. The residence time of the reagents in the reaction zone does not exceed one second, due to which thermal decomposition of acid and ammonium nitrate does not occur. By using the heat of neutralization in the apparatus, most of the water evaporates and a 90% solution of ammonium nitrate is formed.

The 16 m high combination evaporator consists of two parts. In the lower shell-and-tube part with a diameter of 3 m, evaporation of the solution occurs, passing through tubes heated first by superheated steam heated to 180°C by air. The upper part of the apparatus serves to clean the steam-air mixture leaving the apparatus and partially evaporate the ammonium nitrate solution entering the apparatus. Ammonium nitrate melt with a concentration of 99.7% with a temperature of about 180°C comes out of the evaporator.

The granulation tower has a rectangular cross-section of 11x8 m2 and a height of about 61 m. Outside air and air from the granule cooler enter the tower through an opening in the lower part. The ammonium nitrate melt entering the upper part of the tower is dispersed using three vibroacoustic granulators, in which the stream of melt turns into droplets. When drops fall from a height of about 10 m, they harden and turn into granules. Crystallization of melt with a moisture content of 0.2% begins at 167 °C and ends at 140 °C. The volume of air supplied to the tower is 300 - 100 m3/hour, depending on the time of year. In AS-72M units, a magnesium additive against product caking (magnesium nitrate) is used. Therefore, the operation of processing surfactant granules, provided for in schemes AC - 67 and AC - 72, is not required. The fundamental differences in the technological scheme for the production of ammonium nitrate using the non-evaporation method (Fig. 4.) are: the use of more concentrated nitric acid; carrying out the neutralization process at elevated (0.4 MPa) pressure; rapid contact of heated components. Under these conditions, at the neutralization stage, a vapor-liquid emulsion is formed, after separation of which a melt with a concentration of 98.1% is obtained, which makes it possible to eliminate a separate stage of evaporation of the solution.

Figure 4.4 Technological diagram of the non-evaporation method: 1 - nitric acid heater; 2 - ammonia heater; 3 - reactor (neutralizer); 4 - emulsion separator; 1 - drum crystallizer; 6 - knife; 7 - drum drying

Heated in heaters 1 and 2, heated by steam coming out of the separator, emulsions 4, nitric acid and ammonia enter neutralizer 3, where as a result of the reaction an emulsion is formed from an aqueous solution of ammonium nitrate and water vapor. The emulsion is separated in separator 4 and the ammonium nitrate melt is fed into a drum crystallizer 1, in which ammonium nitrate crystallizes on the surface of a metal drum, cooled from the inside with water.

A layer of solid ammonium nitrate, about 1 mm thick, formed on the surface of the drum is cut off with a knife 6 and in the form of flakes is supplied for drying in a drum dryer 7. A similar product in the form of flakes is used for technical purposes.

The cooled product is sent to a warehouse, and then for shipment in bulk or for packaging in bags. Treatment with a dispersant is carried out in a hollow apparatus with a centrally located nozzle spraying an annular vertical flow of granules, or in a rotating drum. The quality of processing of the granular product in all used devices satisfies the requirements of GOST 2-85.

Granulated ammonium nitrate is stored in a warehouse in piles up to 11 m high. Before shipping to the consumer, the nitrate from the warehouse is served for sieving. The non-standard product is dissolved, the solution is returned for distillation. The standard product is treated with an NF dispersant and shipped to consumers.

Tanks for sulfuric and phosphoric acids and pumping equipment for their dosing are arranged in a separate unit. The central control point, electrical substation, laboratory, service and household premises are located in a separate building.

Nitrate is packaged in bags with a polyethylene liner weighing 50 kg, as well as specialized containers - big bags, weighing 500-800 kg. Transportation is carried out both in prepared containers and in bulk. Travel by various types of transport is possible, but air transport is excluded due to the increased fire danger.

Ammonium nitrate is one of the most common fertilizers.

Ammonium nitrate (otherwise known as ammonium nitrate) is produced in factories from nitric acid and ammonia by chemical interaction of these compounds.

The production process consists of the following stages:

1. Neutralization of nitric acid with ammonia gas.
2. Evaporation of ammonium nitrate solution.
3. Crystallization of ammonium nitrate.
4. Drying salt.

The figure shows a simplified form technological scheme production of ammonium nitrate. How does this process take place?

The feedstock - gaseous ammonia and nitric acid (aqueous solution) - enters the neutralizer. Here, as a result of the chemical interaction of both substances, a violent reaction occurs with the release of a large amount of heat. In this case, part of the water evaporates, and the resulting water vapor (so-called sap vapor) is discharged outside through the trap.

The incompletely evaporated ammonium nitrate solution flows from the neutralizer to the next apparatus - the final neutralizer. In it, after adding an aqueous solution of ammonia, the process of neutralization of nitric acid ends.

From the pre-neutralizer, the ammonium nitrate solution is pumped into an evaporator - a continuously operating vacuum apparatus. The solution in such devices is evaporated at reduced pressure, in this case at a pressure of 160-200 mm Hg. Art. Heat for evaporation is transferred to the solution through the walls of tubes heated by steam.

Evaporation is carried out until the concentration of the solution reaches 98%. After this, the solution goes for crystallization.

According to one method, crystallization of ammonium nitrate occurs on the surface of a drum, which is cooled from the inside. The drum rotates, and a crust of crystallizing ammonium nitrate up to 2 mm thick is formed on its surface. The crust is cut off with a knife and sent through a chute for drying.

Ammonium nitrate is dried with hot air in rotating drying drums at a temperature of 120°. After drying, the finished product is sent for packaging. Ammonium nitrate contains 34-35% nitrogen. To reduce caking, various additives are added to its composition during production.

Ammonium nitrate is produced by factories in granular form and in the form of flakes. Flake saltpeter strongly absorbs moisture from the air, so during storage it spreads and loses its friability. Granulated ammonium nitrate has the form of grains (granules).

Granulation of ammonium nitrate is mostly carried out in towers (see figure). The evaporated solution of ammonium nitrate - melt - is sprayed using a centrifuge mounted in the ceiling of the tower.

The melt flows in a continuous stream into the rotating perforated drum of the centrifuge. Passing through the holes of the drum, the spray turns into balls of the appropriate diameter and hardens as it falls down.

Granulated ammonium nitrate has good physical properties, does not cake during storage, disperses well in the field and slowly absorbs moisture from the air.

Ammonium sulfate - (otherwise - ammonium sulfate) contains 21% nitrogen. Most of the ammonium sulfate is produced by the coke industry.

In the coming years, the production of the most concentrated nitrogen fertilizer - urea, or urea, which contains 46% nitrogen, will receive great development.

Urea is obtained from high pressure synthesis from ammonia and carbon dioxide. It is used not only as fertilizer, but also for feeding livestock (supplements protein nutrition) and as an intermediate for the production of plastics.

Liquid nitrogen fertilizers - liquid ammonia, ammonia and ammonia water - are also of great importance.

Liquid ammonia is produced from gaseous ammonia by liquefaction under high pressure. It contains 82% nitrogen. Ammonia compounds are solutions of ammonium nitrate, calcium nitrate or urea in liquid ammonia with a small addition of water. They contain up to 37% nitrogen. Ammonia water is an aqueous solution of ammonia. It contains 20% nitrogen. In terms of their effect on the crop, liquid nitrogen fertilizers are not inferior to solid ones. And their production is much cheaper than solid ones, since the operations of evaporating the solution, drying and granulating are eliminated. Of the three types of liquid nitrogen fertilizer, ammonia water is the most widely used. Of course, the application of liquid fertilizers to the soil, as well as their storage and transportation, require special machines and equipment.

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Introduction

The most important type of mineral fertilizers are nitrogen fertilizers: ammonium nitrate, urea, ammonium sulfate, aqueous solutions of ammonia, etc. Nitrogen belongs exclusively to important role in the life of plants: it is part of chlorophyll, which is an acceptor of solar energy, and protein necessary for the construction of a living cell. Plants can only consume fixed nitrogen - in the form of nitrates, ammonium salts or amides. Relatively small amounts of fixed nitrogen are formed from atmospheric nitrogen due to the activity of soil microorganisms. However, modern intensive agriculture can no longer exist without additional application of nitrogen fertilizers to the soil, obtained as a result of the industrial fixation of atmospheric nitrogen.

Nitrogen fertilizers differ from each other in their nitrogen content, in the form of nitrogen compounds (nitrate, ammonium, amide), phase state (solid and liquid), and there are also physiologically acidic and physiologically alkaline fertilizers.

Production of ammonium nitrate

Ammonium nitrate, or ammonium nitrate, NH4NO3 - a white crystalline substance containing 35% nitrogen in ammonium and nitrate forms , both forms of nitrogen are easily absorbed by plants. Granulated ammonium nitrate is used on a large scale before sowing and for all types of fertilizing. On a smaller scale, it is used to produce explosives.

Ammonium nitrate is highly soluble in water and has high hygroscopicity (the ability to absorb moisture from the air). This is the reason that fertilizer granules spread out, lose their crystalline shape, caking of fertilizers occurs - bulk material turns into a solid monolithic mass.

Ammonium nitrate is produced in three types:

A and B - used in industry; used in explosive mixtures (ammonites, ammonials)

B is the effective and most common nitrogen fertilizer, containing about 33-34% nitrogen; has physiological acidity.

Feedstock

The starting materials in the production of ammonium nitrate are ammonia and nitric acid.

Nitric acid . Pure nitric acid HNO

-colorless liquid with density 1.51 g/cm at - 42 C it solidifies into a transparent crystalline mass. In the air, it “smoke”, like concentrated hydrochloric acid, since its vapors form small droplets of fog with the moisture in the air. Nitric acid is not durable. Even under the influence of light, it gradually decomposes:

The higher the temperature and the more concentrated the acid, the faster the decomposition. Nitrogen dioxide released dissolves in acid and gives it a brown color.

Nitric acid is one of the most powerful acids; in dilute solutions it completely disintegrates into ions

i- Nitric acid is one of the most important nitrogen compounds: in large quantities It is used in the production of nitrogen fertilizers, explosives and organic dyes, serves as an oxidizing agent in many chemical processes, and is used in the production of sulfuric acid. nitrous method, used for the production of cellulose varnishes, film .

Industrial production of nitric acid . Modern industrial methods for producing nitric acid are based on the catalytic oxidation of ammonia with atmospheric oxygen. When describing the properties of ammonia, it was indicated that it burns in oxygen, and the reaction products are water and free nitrogen. But in the presence of catalysts, the oxidation of ammonia with oxygen can proceed differently. If a mixture of ammonia and air is passed over a catalyst, then at 750 °C and a certain composition of the mixture, almost complete conversion occurs

Formed

easily transforms into, which with water in the presence of atmospheric oxygen gives nitric acid.

Platinum-based alloys are used as catalysts for the oxidation of ammonia.

The nitric acid obtained by the oxidation of ammonia has a concentration not exceeding 60%. If necessary, it is concentrated,

The industry produces diluted nitric acid with a concentration of 55, 47 and 45%, and concentrated nitric acid - 98 and 97%. Concentrated acid is transported in aluminum tanks, diluted - in acid-resistant steel tanks.

Ammonia synthesis

Ammonia is a key product of various nitrogen-containing substances used in industry and agriculture. D. N. Pryanishnikov called ammonia “alpha and omega” in the metabolism of nitrogenous substances in plants.

The diagram shows the main applications of ammonia. The composition of ammonia was established by C. Berthollet in 1784. Ammonia NH3 is a base, a moderately strong reducing agent and an effective complexing agent with respect to cations with vacant bonding orbitals.

Physico-chemical basis of the process . The synthesis of ammonia from elements is carried out according to the reaction equation

N2+ЗН2 =2NНз; ∆H<0

The reaction is reversible, exothermic, characterized by a large negative enthalpy effect (∆H = -91.96 kJ/mol) and at high temperatures becomes even more exothermic (∆H = -112.86 kJ/mol). According to Le Chatelier's principle, when heated, the equilibrium shifts to the left, towards a decrease in the yield of ammonia. The change in entropy in this case is also negative and does not favor the reaction. With a negative ∆S value, an increase in temperature reduces the probability of a reaction occurring,

The reaction of ammonia synthesis proceeds with a decrease in volume. According to the reaction equation, 4 moles of initial gaseous reactants form 2 moles of gaseous product. Based on Le Chatelier's principle, we can conclude that, under equilibrium conditions, the ammonia content in the mixture will be greater at high pressure than at low pressure.

Characteristics of the target product

Physico-chemical properties Ammonium nitrate (ammonium nitrate) NH4NO3 has a molecular weight of 80.043; the pure product is a colorless crystalline substance containing 60% oxygen, 5% hydrogen and 35% nitrogen (17.5% each in ammonia and nitrate forms). The technical product contains at least 34.0% nitrogen.

Basic physical and chemical properties of ammonium nitrate :

Ammonium nitrate, depending on temperature, exists in five crystalline modifications that are thermodynamically stable at atmospheric pressure (table). Each modification exists only in a certain temperature range, and the transition (polymorphic) from one modification to another is accompanied by changes in the crystal structure, release (or absorption) of heat, as well as an abrupt change in specific volume, heat capacity, entropy, etc. Polymorphic transitions are reversible - enantiotropic.

Table. Crystal modifications of ammonium nitrate

The NH4NO3-H2O system (Fig. 11-2) refers to systems with simple eutectics. The eutectic point corresponds to a concentration of 42.4% MH4MO3 and a temperature of -16.9 °C. The left branch of the diagram—the water liquidus line—corresponds to the conditions for the release of ice in the HH4MO3--H20 system. The right branch of the liquidus curve is the solubility curve of MH4MO3 in water. This curve has three breaking points corresponding to the temperatures of modification transitions NH4NO3 1 = 11 (125.8 ° C), II = III (84.2 ° C) and 111 = IV (32.2 ° C). Melting (crystallization) temperature anhydrous ammonium nitrate is 169.6 ° C. It decreases with increasing moisture content of salt.

Dependence of crystallization temperature of NH4NO3 (Tcrystal, "C) on moisture content (X,%) up to 1.5% is described by the equation:

tcrist == 169.6-13, 2x (11.6)

Dependence of the crystallization temperature of ammonium nitrate with the addition of ammonium sulfate on moisture content (X,%) up to 1.5% and ammonium sulfate (U, %) up to 3.0% is expressed by the equation:

tcrist = 169.6- 13.2X+2, OU. (11.7).

Ammonium nitrate dissolves in water and absorbs heat. Below are the values ​​of the heats of dissolution (Q dist) of ammonium nitrate of various concentrations in water at 25 ° C:

C(NH4NO3) % mass 59,69 47.05 38,84 30,76 22,85 15,09 2,17

Qsolute kJ/kg. -202.8 -225.82 -240.45 -256.13 -271.29 -287.49 -320.95

Ammonium nitrate is highly soluble in water, ethyl and methyl alcohols, pyridine, acetone, and liquid ammonia.

Federal Agency for Education

CALCULATION AND EXPLANATORY NOTE

For course work on general chemical technology on the topic:

“Production of ammonium nitrate. Calculation of a neutralizer with a productivity of G=10 t/hour NH 4 NO 3

Completed:
student gr. ХН-091
Artemenko A.A.
Checked:
Ushakov A.G.

Kemerovo 2012

Introduction 4
1.Feasibility study of the chosen method 7
2.Flow diagram for the production of ammonium nitrate 12
3. Calculation of material and heat balances of neutralization
nitric acid with ammonia 17
3.1.Material balance 17
3.2. Heat balance 20
4. Selection of contact device sizes 21
Conclusion 22
References 23

Introduction

Mineral fertilizers are widely used both in agriculture and in various fields of industry. Unlike the world market, it is the industrial consumption of nitrogen fertilizers that is the main one in the domestic market.
The most important type of mineral fertilizers are nitrogen fertilizers: ammonium nitrate, urea, ammonium sulfate, aqueous solutions of ammonia.
Ammonium nitrate, or ammonium nitrate, NH 4 NO 3 is a white crystalline substance containing 35% nitrogen in ammonium and nitrate forms, both forms are easily absorbed by plants.
The main consumers of ammonium nitrate are the following industries:
- agriculture;
- production of complex mineral fertilizers;
- mining complex (own production of explosives);
- coal industry (own production of explosives);
- production of explosives;
- construction industry;
Ammonium nitrate has potential, or physiological acidity. This acidity occurs in the soil, on the one hand, as a result of faster consumption of ions (NH 4 +) by plants and, accordingly, the accumulation of acid residue (NO 3 ions) in the soil and, on the other hand, as a result of the oxidation of ammonia into nitric acid by nitrifying soil microorganisms . With long-term use of ammonium nitrate, the potential acidity of this fertilizer can lead to changes in the chemical composition of the soil, which in some cases causes a decrease in yield

Agricultural crops.
Granulated ammonium nitrate is used on a large scale before sowing and for all types of fertilizing. On a smaller scale, it is used to produce explosives. Ammonium nitrate is highly soluble in water and has high hygroscopicity (the ability to absorb moisture from the air). This is due to the fact that the fertilizer granules spread out, lose their crystalline shape, caking of the fertilizer occurs - the bulk material turns into
solid monolithic mass. Ammonium nitrate has a number of advantages over other nitrogen fertilizers, since it contains 34% nitrogen and in this ratio is second only to urea.
In addition, ammonium nitrate contains both ammonium and nitrate forms of nitrogen, which are used by plants during different periods of growth, which positively increases the yield of almost all agricultural crops.
Industries using ammonium nitrate as a raw material for the production of explosives are the second largest segment of its consumption in the domestic market after agriculture. Ammonia-
saltpeter explosives are a large group of explosives.
They are usually classified as low-power high explosives (in TNT equivalent, 25% weaker than TNT). However, this is not entirely true. In terms of brisance, ammonium nitrate explosives are usually low in

They are inferior to TNT, but in terms of high explosiveness they exceed TNT, some of them quite significantly. Ammonium nitrate explosives are used to a greater extent in the national economy and to a lesser extent in military affairs. The reason for this use is the significantly lower cost of ammonium nitrate explosives and their significantly lower reliability in use. First of all, this is due to the high hygroscopicity of ammonia explosives, therefore, when humidified by more than 3%, such explosives completely lose their ability to explode. They are susceptible to caking, i.e. lose their flowability during storage, which is why they completely

Or they partially lose their explosive ability.
The most important reasons for caking are:
1. Increased moisture content in the finished product;
2.Heterogeneity and low mechanical strength of saltpeter particles;
3.Change in crystalline modifications of ammonium nitrate.
Ammonium nitrate is a strong oxidizing agent. It reacts violently with solutions of some substances, even to the point of explosion (sodium nitrite). It is insensitive to shocks, friction, impacts, and remains stable when hit by sparks of varying intensity. It is capable of exploding only under the influence of a strong detonator or during thermal decomposition. Saltpeter is not a flammable product. Combustion is supported only by nitric oxide. Thus, one of the conditions for the production of ammonium nitrate is the purity of its initial solutions and the finished product.

2.Flow diagram for the production of ammonium nitrate

The ammonium nitrate production process consists of the following main stages:
1. Neutralization of nitric acid with ammonia gas;
2. Evaporation of ammonium nitrate solutions to a melt state;
3. Crystallization of salt from melt;
4. Drying or cooling salt;
5.Packaging.
To obtain almost non-caking ammonium nitrate, a number of technological methods are used. The process of producing ammonium nitrate is based on a heterogeneous reaction between gaseous ammonia and a solution of nitric acid:
NH 3 + HNO 3 = NH 4 NO 3 (2)
?H = -144.9 kJ
The thermal effect of the reaction during the interaction of 100% starting substances is 35.46 kcal/mol.

The chemical reaction occurs at high speed; in an industrial reactor it is limited by the dissolution of gas in liquid. To reduce diffusion inhibition, stirring the reagents is of great importance. Intensive conditions for carrying out the process can be ensured to a large extent when developing the design of the apparatus. Reaction (1) is carried out in a continuously operating ITN apparatus (use of neutralization heat) (Fig. 2.1).

Fig.2.1. ITN apparatus

The reactor is a vertical cylindrical apparatus consisting of reaction and separation zones. In the reaction zone there is a glass 1, in the lower part of which there are holes for circulation of the solution. Somewhat above the holes inside the glass there is a bubbler 2 for supplying ammonia gas, above it there is a bubbler 3 for supplying nitric acid. The reaction vapor-liquid mixture exits from the top of the reaction glass; part of the solution is removed from the ITN apparatus and enters the final neutralizer, and the rest (circulation) goes down again. The juice steam released from the vapor-liquid mixture is washed on cap plates 6 from splashes of ammonium nitrate solution and nitric acid vapor with a 20% solution of nitrate, and then with juice steam condensate.
The heat of reaction (1) is used to partially evaporate water from the reaction mixture (hence the name of the apparatus - ITN). The difference in temperatures in different parts of the apparatus leads to more intense circulation of the reaction mixture.

The technological process for the production of ammonium nitrate includes, in addition to the stages of neutralization of nitric acid with ammonia, also the stages of evaporation of the nitrate solution, granulation of the melt, cooling of the granules, treatment of the granules with surfactants, packaging, storage and loading of nitrate, purification of gas emissions and wastewater.
Figure 2.2 shows a diagram of a modern large-scale unit for the production of ammonium nitrate AS-72 with a capacity of 1360 tons/day. The initial 58-60% nitric acid is heated in heater 1 to 70-80? C with juice steam from the apparatus of ITN 3 and supplied for neutralization. Before apparatus 3, phosphoric and sulfuric acids are added to nitric acid in such quantities that the finished product contains 0.3-0.5% P 2 O 5 and 0.05-0.2% ammonium sulfate.
The unit contains two ITN devices operating in parallel. In addition to nitric acid, ammonia gas is supplied to them, after
heated in heater 2 by steam condensate to 120-130? C. The amounts of supplied nitric acid and ammonia are regulated so that at the exit from the ITN apparatus the solution has a slight excess of acid (2-5 g/l), ensuring complete absorption of ammonia.

Fig.2.2 Diagram of the ammonium nitrate unit AS-72
In the lower part of the apparatus, a neutralization reaction occurs at a temperature of 155-170? C; this produces a concentrated solution containing 91-92% NH 4 NO 3 . In the upper part of the apparatus, water vapor (so-called juice vapor) is washed away from splashes of ammonium nitrate and nitric acid vapor. Part of the heat from the juice steam is used to heat the nitric acid. The juice steam is then sent for purification and released into the atmosphere. The ammonium nitrate solution leaving the neutralizer has a slightly acidic or slightly alkaline reaction.
The acidic solution of ammonium nitrate is sent to the neutralizer 4; where ammonia is supplied, necessary to react with the remaining nitric acid. Then the solution is fed into the evaporator 5. The resulting melt, containing 99.7-99.8% nitrate, passes through a filter 21 at 175? C and is fed by a centrifugal submersible pump 20 into a pressure tank 6, and then into a rectangular metal granulation tower 16.
In the upper part of the tower there are granulators 7 and 8, into the lower part of which air is supplied, cooling the drops of nitrate falling from above. When drops of nitrate fall from a height of 50-55 m and air flows around them, fertilizer granules are formed. Granule temperature at

The exit from the tower is 90-110?C; hot granules are cooled in a fluidized bed apparatus 15. This is a rectangular apparatus having three sections and equipped with a grid with holes. Fans supply air under the grille; in this case, a fluidized layer of nitrate granules is created, arriving via a conveyor from the granulation tower. After cooling, the air enters the granulation tower.
Ammonium nitrate granules are fed by conveyor 14 for treatment with surfactants into a rotating drum 11. Then the finished fertilizer is sent by conveyor 12 to packaging.
The air leaving the granulation tower is contaminated with particles of ammonium nitrate, and the juice steam from the neutralizer and the steam-air mixture from the evaporator contain unreacted ammonia and

Nitric acid, as well as particles of entrained ammonium nitrate. For these
There are six streams in the upper tower of the granulation tower
parallel operating washing scrubbers of the plate type 10, irrigated with a 20-30% solution of ammonium nitrate, which is supplied by pump 18 from the collection 17. Part of this solution is discharged to the ITN neutralizer for washing juice steam, and then mixed with ammonium nitrate, and, therefore, used to produce products. The purified air is sucked out of the granulation tower by fan 9 and released into the atmosphere.

3. Calculation of the material and heat balance of neutralization of nitric acid with ammonia

3.1 Material balance

Initial data
The concentration of the initial nitric acid is 50% HNO 3;
Ammonia concentration 100% NH 3 ;
The concentration of the resulting solution is 70% NH 4 NO 3;
Installation capacity G=10 t/hour
The production of ammonium nitrate is based on the following reaction:

NH 3 + HNO 3 = NH 4 NO 3
M(NH 3)=17g/mol
M(NH 4 NO 3) = 80 g/mol
1. Determine the amount of reacted 100% ammonia:
m(NH 3)=17*10000/80=2125 kg/hour
M(HNO 3) = 63 g/mol
2. Determine the amount of reacted 100% nitric acid:
m(HNO 3)=63*10000/80=7875 kg/hour
Then the amount of reacted 50% nitric acid is:
m(HNO 3) = 7875/0.5 = 15750 kg/hour
Find the total amount of reagents entering the neutralizer:
3. Amount of 70% ammonium nitrate solution:
m(NH 4 NO 3)= 10000/0.7=14285.7 kg/hour
4.Amount of water evaporated during neutralization:
m(H 2 O)= 2125 +15750 – 14285.7=3589.3 kg/hour
NH 3 consumption + HNO 3 consumption = Amount of NH 4 NO 3 + juice steam

2125 +15750 = 14285,7+3589,3
17875kg/hour=17875kg/hour

We summarize the calculation results in the table:

Table 1
Material balance

3.2 Heat balance

Initial data.
The boiling point of ammonium nitrate is 120? C.

The pressure in the neutralizer is 117.68 kPa.
Heat capacities:

At 30?: C НNO3 = 2.763 kJ/(m 3 ·? С);
At 50? C: NH3 = 2.185 kJ/ (m 3 ·? C);
At 123.6?C:C NH4NO3 =2.303 kJ/ (m 3 ·?C);

Solution.
Q arrival =Q consumption
Arrival of warmth:
1. Heat introduced by nitric acid:
Q 1 = 15907.5 * 2.763 * 30 = 1318572 kJ = 1318.572 MJ;
2. Heat supplied by ammonia gas:
Q 2 = 2146.25 * 2.185 * 50 = 234478 kJ = 234.478 MJ;
During the production of ammonium nitrate, heat is released, which can be determined quite accurately graphically. For 50% nitric acid Q=105.09 kJ/mol.
3. During neutralization, the following is released:
Q 3 = (105.09* 1000 * 10000)/80 = 13136250kJ = 13136.25MJ;
Total income:
Q arrival = Q 1 + Q 2 + Q 3 = 1318572+234478 +13136250 = 14689300 kJ.
Heat consumption:
1. The ammonium nitrate solution carries away:
Q 1 " = 14285.7 * 2.303 * t boil;

At a pressure of 117.68 kPa, the temperature of saturated water vapor is 103? C.
The boiling point of water is 100? C.
Temperature depression is equal to:
?t = 120 – 100 = 20 ?С;
Let's determine the boiling point of a 70% ammonium nitrate solution:
t boil = 103 + 20 * 1.03 = 123.6? C;
Q 1 " = 14285.7 * 2.303 * 123.6 = 4066436 kJ = 4066.436 MJ.
2. Heat spent on water evaporation:
Q 2 "= 3589.3 * 2379.9 = 8542175 kJ = 8542.175 MJ.
3. Heat loss:
Q losses =Q incoming. -Q cons. = 14689300-8542175-4066436= 2080689kJ=2080.689MJ.
Total consumption:
Q exp. = Q 1 "+ Q 2 "+ Q losses = 4066436 + 8542175 + 2080689 = 14689300 kJ.

We summarize the calculation results in the table:

Table 2
Heat balance

Coming			Consumption
Article	kJ	%	Article	kJ	%
Q 1	1318572	8,98	Q 1"	4066436	27,7
Q 2	234478	1,62	Q 2"	8542175	58,1
Q 3	13136250	89,4	Q losses	2080689	14,2
Total:	14689300	100,00	Total:	14689300	100,00

1.Feasibility study of the chosen method

The most common methods for producing ammonium nitrate are based on the reaction of neutralizing nitric acid with ammonia.
The chemical interaction of ammonia gas and nitric acid solutions occurs at high speed, but is limited by mass transfer and hydrodynamic conditions. Therefore, the intensity of mixing of reagents is of great importance; which mainly depends on the ratio between the rates of movement of nitric acid and ammonia in the reactor. The closest contact of the reagents is achieved if the linear velocity of ammonia gas exceeds the linear velocity of the nitric acid solution by no more than 15 times.
The neutralization process occurs with the release of heat. In production conditions, nitric acid is used with a concentration of 45-60%. The higher the concentration of nitric acid used, the lower the heat of its dilution and the greater the thermal effect of neutralization of nitric acid solutions with ammonia.
Total amount of heat Q? released as a result of the reaction of neutralization of nitric acid solutions with ammonia gas is determined by the equation:
Q? =Q react. -(q 1 -q 2) (1)
The following fundamentally different schemes for producing ammonium nitrate using neutralization heat are possible:
- installations operating at atmospheric pressure (excess pressure of juice steam 0.15-0.2 at);
- installations with a vacuum evaporator;
- single-use pressure installations
heat of juice steam;

Installations operating under pressure, using double heat from juice steam (producing concentrated melt).
The most widespread in Russia is the neutralization scheme under atmospheric pressure, shown in Figure 3.

Rice. 1.1 Scheme for neutralizing nitric acid under atmospheric pressure:
1 – tank for nitric acid; 2 – ammonia heater; 3 – liquid ammonia separator; 4 – heat pump apparatus; 5 – juice steam washer trap; 6 – vacuum evaporator stage I; 7 – complete neutralizer.
In the 1967-1970s, a technological scheme was developed and a project for a large-capacity AC-67 unit with an average daily capacity of 1400 tons was completed.
A special feature of the AC-67 unit is the placement of all the main technological equipment (from the neutralization stage to the melt production stage) on the granulation tower in a cascade, without intermediate operations of pumping ammonium nitrate solutions. Another feature of the AC-67 unit is that air is not sucked out of the tower, but is pumped into the tower from below under the fluidized bed grate with one powerful fan, i.e. the tower operates under support.
Placing all the main technological equipment on the granulation tower, as noted, simplified the scheme due to the refusal to pump concentrated nitrate solutions. At the same time, this decision led to certain complications in the construction processes and

Unit operation:
- the tower trunk bears a large load, as a result of which it is made of reinforced concrete with an internal lining with acid-resistant bricks, which leads to significant capital costs, increased labor intensity and duration of construction;
- the superstructure with technological equipment is located at a high altitude, therefore it must be completely enclosed, heated and ventilated.
- installation of equipment can begin only after the tower is erected, which lengthens the cycle of construction and installation work;
- the location of equipment at height increases the requirements for the performance of lifting and transport equipment (elevators);
- operation of the tower under pressure complicates the maintenance of the fluidized bed product cooling apparatus built into the tower;

The use of a built-in cooling device leads to an increase in energy consumption for supplying air to the tower.
In order to eliminate the shortcomings of the AC-67 scheme and improve the quality of the product in the AC-72 scheme, the following technical solutions were adopted:
- an increase in the strength of the granules is provided as a result of the influence of three factors: the use of a sulfate-phosphate additive, the production of larger granules, and the regulation of the rate of cooling of the granules, for which a sectioned remote apparatus with a fluidized bed and separate air supply to each section was used;
- equipment is located below on a separate shelf; A pump is used to pump the melt.
The technological scheme for the production of nitrate according to the AS-72 scheme consists of the same stages as according to the AS-67 scheme; An additional step is the pumping of highly concentrated ammonium nitrate melt to the top of the granulation tower.

There are no fundamental differences in the technological process at the stages of neutralization and evaporation in the AC-72 scheme compared to the AC-67. The difference is the heating of nitric acid in two heaters individually for each heat pump apparatus, which made it possible to install automatic flow regulators on the nitric acid supply line for heating. And another characteristic difference is the installation of only one more powerful neutralizer, instead of two.
Increasing requirements for environmental protection have put on the agenda a significant reduction in the emission of aerosol particles of ammonium nitrate and ammonia into the atmosphere. A higher degree of purification of these emissions is the main distinguishing feature of the modernized AS-72M units.

In modern ammonium nitrate production, the specific consumption of raw materials is close to theoretical. Therefore, there is no significant difference in the cost of the product obtained in large-scale units AS-67, AS-72 and AS-72M.
The difference in technical and economic indicators depending on specific schemes lies mainly in the area of ​​energy resource consumption: steam, electricity, recycled water. Steam consumption is determined by the initial concentration of nitric acid, the degree of use of the heat of juice steam obtained at the neutralization stage.
Electricity consumption in ammonium nitrate production is not large in absolute terms. But it can fluctuate depending on the method used to cool the product (directly in the tower during the flight of granules,
in devices with a fluidized bed, in rotating drums), on air purification methods, choice
In industry, the AC-72 unit is mainly used, where, as a result of the use of monodisperse granulators, a uniform granulometric composition is ensured, the content of small granules is reduced, and the air speed across the cross section of the tower is reduced, i.e. more favorable

Conditions for reducing dust entrainment from the tower and reducing the load on the washing scrubber.

List of used literature

1. Calculations of chemical technological processes. Under the general editorship of prof. Mukhlenova I.P. L., “Chemistry”, 1976. –304 p.
2.http://www.xumuk.ru//
3. Klevke. V.A., “Technology of nitrogen fertilizers”, M., Goskhimizdat, 1963.
4. General chemical technology: The most important chemical production / I.P. Mukhlenov. - 4th ed. - M.: Higher school, 1984. - 263 p.
5. Basic processes and apparatus of chemical technology: Design manual. Edited by Yu.I. Dytnersky, 2nd ed., M.: Chemistry, 1991.-496 p.
6. Miniovich M. A. Production of ammonium nitrate. M. “Chemistry”, 1974. – 240 p.

Conclusion

In this course work, we studied the production of ammonium nitrate and the basic process flow diagram, justified the choice of main and auxiliary equipment in the production of ammonium nitrate, and calculated the material and heat balances of the neutralization stage.
We examined the physical and chemical properties of ammonium nitrate. Since ammonium nitrate has properties such as caking and hygroscopicity, it is necessary to take the following measures: to reduce caking, use powdered additives that powder the salt particles. Some of the additives reduce the active surface of particles, others have adsorption properties. Add very small amounts of dyes to caking salts, and cool the ammonium nitrate before packaging. To reduce hygroscopicity, it is necessary to granulate saltpeter. Granules have a smaller specific surface area than fine-crystalline salt, so they moisten more slowly.
Ammonium nitrate is the most important and widespread nitrogen fertilizer used in agriculture. Therefore, it is necessary to comply with the storage conditions of ammonium nitrate and create new technological solutions.

4.Selection of contact device sizes

We determine the volume of the apparatus using the heat of neutralization:

Contact time, hour;

M is the productivity of the apparatus, m 3 /hour.

G=10000 kg/hour=36000000 kg/sec.

Ammonium nitrate = 1725 kg/m 3

M= G/ ? ammonium nitrate

M=36000000 kg/sec: 1725 kg/m 3 =20869.5 m 3 /sec

V= 1 sec·20869.5 m 3 /sec=20869.5 m 3

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