Ammonium Sulfate
Ammonium Sulfate
Ammonium Sulfate Fertilizer
Fertilizers are categorized in three main groups:
- Macro Nutrients (N, P, K)
Urea, Ammonium Sulfate, Ammonium Nitrate, Potassium Sulfate, Calcium Nitrate, Potassium Nitrate, Sodium Nitrate, Mono/Di Ammonium Phosphate (MAP & DAP), Single/Triple Superphosphates (SSP & TSP), Potassium Chloride, Mono potassium phosphate, urea phosphate etc.
- Micro Nutrients
Ca, S, Mg, B, Fe, Zn, Mn, Cu, Ni and etc. Chemical Compounds
- Other Nutrients
Humic Acid, Amino Acid and etc.
Ammonium sulfate ([NH4]2SO4) is generally used as an agricultural fertilizer and is one of the first nitrogenous fertilizers in agricultural industries that has found wide application. More than 75% of ammonium sulfate produced worldwide is used as agricultural fertilizer. The high solubility of this fertilizer is one of its features that has facilitated the use of this material in agriculture.
Desirable physical properties, chemical stability, and effectiveness of ammonium sulfate in the growth of plants are among the characteristics of this material. The following table shows ammonium sulfate’s most important physical and chemical properties.
Commercial ammonium sulfate is generally white in color, but its color can vary from white to yellow and gray. The color change of ammonium sulfate is due to the presence of some impurities in its composition.
Ammonium sulfate, which is obtained as a byproduct of various processes, does not have free acid. Other grades of this product can have up to 0.15% free acid (sulfuric acid), but in general, the amount of free acid should not exceed 0.03% by weight. The presence of large amounts of free acid in this product may cause lumps or hard cakes in the transportation process. This problem is sometimes controlled by neutralizing the free acid with ammonia. According to the production process, ammonium sulfate is marketed in two types of granules and crystals.
Ammonium sulfate is generally used in cases where there is a need for nitrogen and sulfur supplements. These compounds provide the necessary materials for the growth of plants. Ammonium sulfate is a very rich source of sulfur to supply the materials required for the growth of many agricultural products, but due to having 21% nitrogen, other fertilizers may be used along with it. Due to the presence of nitrogenous agent in the composition of ammonium sulfate, this substance is widely used for the erosion and flooded soils for rice production, gardens and greenhouses. A solution containing dissolved ammonium sulfate is usually added to herbicide sprays to increase the effectiveness of these substances. After adding ammonium sulfate to the soil, ammonium sulfate dissolves into its components. If this substance remains on the soil surface, ammonia is prone to gas loss in alkaline conditions. In this situation, it is necessary to introduce the solution into the soil or use it before irrigation or possible rainfall.
Many agricultural products can use both ammonia and nitrate forms of nitrogen for growth. In warm soils, microbes quickly convert ammonia into nitrates. During this microbial reaction, H+ ions are released and soil acidity increases. Ammonium sulfate has an acidifying effect on the soil, and this effect is mainly due to the nitrification process and has nothing to do with the presence of sulfate, because sulfate has only a small effect on pH. Among other uses of ammonium sulfate, it can be mentioned adding it to bread as a dough softener. Also, this material is used as one of the components of fire retardant materials in fire extinguishers. It also has other applications in chemical, wood, paper and pharmaceutical industries.
Ammonium sulfate is generally used in cases where there is a need for nitrogen and sulfur supplements. These compounds provide the necessary materials for the growth of plants. Ammonium sulfate is a very rich source of sulfur to supply the materials required for the growth of many agricultural products, but due to having 21% nitrogen, other fertilizers may be used along with it. Due to the presence of nitrogenous agent in the composition of ammonium sulfate, this substance is widely used for the erosion and flooded soils for rice production, gardens and greenhouses. A solution containing dissolved ammonium sulfate is usually added to herbicide sprays to increase the effectiveness of these substances. After adding ammonium sulfate to the soil, ammonium sulfate dissolves into its components. If this substance remains on the soil surface, ammonia is prone to gas loss in alkaline conditions. In this situation, it is necessary to introduce the solution into the soil or use it before irrigation or possible rainfall.
Ammonium sulfate, like other ammonia fertilizers, is acidic in nature, and based on studies, when it is added to the soil, there is an increase in the concentration of dissolved hydrogen ions in the soil. When soil acidity increases, many beneficial processes are initiated in the soil. Acidification of the soil due to the addition of ammonium sulfate can be controlled by using lime or other alkaline substances. Studies have shown that continuous application of ammonium sulfate without adding lime leads to the production of substances in the soil that are toxic to plants. If ammonium sulfate is added to the soil in wet environments, free acid is produced and reacts with calcium and magnesium compounds in the soil. In the absence of these compounds, the produced acid reacts with iron, aluminum and manganese compounds, which may cause the creation of toxic compounds in the long term. If the neutralization of the acidic condition of the soil is done efficiently by adding ammonium sulfate, toxic compounds will not be created. Also, if ammonium sulfate is combined with chlorinated fertilizers, it may create toxic compounds in the soil. The chart below shows the status of global demand for ammonium sulfate by its applications.
Ammonium Sulfate
The figure below shows the price changes of various ammonium sulfates in the world in 2021 and 2022.
Capro: Ammonium sulfate produced as a byproduct of the caprolactam manufacturing process
Granular: Ammonium sulfate produced synthetically
Changes in the price of ammonium sulfate in different regions of the world in the past year (dollars per ton)
Global trends show that the demand for two grades of spherical granule and coarse crystal of ammonium sulfate is higher than other types of this fertilizer, and spherical granule has the first place in demand in the world. The figure below shows this issue, and the next figure shows the changes in the import of ammonium sulfate in Brazil based on the form of the product.
Internationally, it is predicted that the three regions of Southeast Asia, China, Central and South America will account for about 46% of the total consumption of nitrogenous fertilizers, including ammonium sulfate, in the world. The forecast of reputable international institutions shows that the market size of ammonium sulfate in the world will reach about 4 billion dollars by 2027. Currently, more than 75% of the ammonium sulfate market is in the field of agricultural fertilizer, which forecasts show that in the coming years, other markets for this product will increase, such as food, wood and paper, textile, pharmaceutical, etc.
Among the most important producers of ammonium sulfate in the world, China, Belgium, the Netherlands, South Korea, and the United States can be mentioned. China is the largest exporter of ammonium sulfate in the world and nearly 50% of the world’s exports of this product are related to China (about 7 million tons). Among other countries in the world, Brazil, Indonesia, Vietnam, the United States of America, and Malaysia are the largest importers of ammonium sulfate, of which 50% of the total 13 million tons of ammonium sulfate imported in the world belong to these countries. According to the latest statistics of 2021, the total production of ammonium sulfate in the world is about 30 million tons.
Ammonium Sulfate Production Methods
About 90% of ammonium sulfate is produced by three main methods: (1) as a byproduct of caprolactam production ([(CH2)5COHN]), (2) synthetic method, and (3) as a byproduct of gas or coke production from coal. In some cases, ammonium sulfate is also a byproduct of nickel or methyl methacrylate production. Ammonium sulfate is obtained as a byproduct of caprolactam oxidation process. Synthetic ammonium sulfate is also produced by combining ammonia and sulfuric acid in a reactor. Also, ammonium sulfate is produced as a byproduct of gas or coke production through the reaction between ammonia recovered from the exhaust gases of the coke production process with sulfuric acid. Figure 3 shows a diagram of different processes of ammonium sulfate production in different ways.
After the formation of ammonium sulfate solution, the production method is similar in almost all processes. Ammonium sulfate crystals are produced by swirling an ammonium sulfate solution in a water evaporator. In this process, the solution is concentrated. Ammonium sulfate crystals are separated from the solution by centrifugation process. In the case where ammonium sulfate is a byproduct of the caprolactam production process, the product is first transferred into a sedimentation tank to reduce the amount of the liquid phase in the centrifugation process and the saturated solution is returned in the process. The crystals, which contain 1 to 2.5% by weight of moisture after the centrifugation process, are introduced into a fluidized bed or rotary dryer.
In the case where ammonium sulfate is a byproduct of gas or coke production, rotating vacuum filters are used instead of centrifuges and dryers. A crystalline product layer remains on the filter and is removed as product. The crystals produced usually have a wide distribution of particle sizes. The exhaust gases of the process pass through a wet scrubber. This process controls the output of the process and recovers waste. Crystalline ammonium sulfate is granulated after drying and the final product is produced.
Fine particles of ammonium sulfate are one of the most important substances that may enter the environment during the process. The drying step produces the largest amount of fine ammonium sulfate particles that may enter the air. The amount of fine particles entering the air depends on the flow rate of hot gases and the particle size distribution of the product. Depending on the type of dryer used in the process, the hot gas flow rate will be different. Generally, the hot gas flow rate in fluidized bed dryers is higher than in rotary dryers.
Therefore, the rate of entry of fine particles into the air is higher in processes with fluid bed dryers. In some industrial units, bag filters are used to control the entry of fine particles into the air, but at the same time, wet scrubbers such as venturi and centrifugal scrubbers perform better. In wet scrubbers, the solid particles taken in this step can be returned to the process.
Different methods are used to produce ammonium sulfate. The selection of the production method is generally done according to the raw materials available. The main methods of producing ammonium sulfate are:
1) The reaction between ammonia and sulfuric acid in a saturated evaporation chamber under vacuum or atmospheric pressure and separating the produced crystals by centrifugation or filtration.
2) Using ammonia released in coke production processes and reacting it with sulfuric acid and separating the produced crystals by centrifugation or filtration.
3) reacting ammonium carbonate with calcium sulfate, separating calcium carbonate by filtration, evaporation and crystallization of ammonium sulfate from the solution by centrifugation.
4) Evaporation of liquid side products containing ammonium sulfate and separating the produced solid material by the following methods: crystallization and centrifugation, granulation and drying.
5) Direct reaction of gaseous ammonia with sulfuric acid in the reactor to produce amorphous and dry products.
6) Simultaneous production of ammonium sulfate and other ammonium salts in the granulation process to produce phosphate, nitrate and nitro phosphate fertilizers containing ammonium sulfate.
7) Other miscellaneous methods such as recovery of ammonium sulfate from SO2 from flowing gas or sulfuric acid vapor.
ScinnoTech recommended method:
Pipe reactor-granulator technology is used to produce ammonium sulfate granules, and Oslo Crystallizer technology is used to produce crystalline ammonium sulfate.
In the pipe reactor-granulator method, liquid ammonia and sulfuric acid are stored in special tanks and enter the pipe reactor (Pipe Reactor) in specific proportions through the piping system and pumps installed in the line along with the ammonium sulfate solution in the process circulation. The length of the reaction tube is between 10-15 meters and part of the main reaction between sulfuric acid and ammonia to form ammonium sulfate is done in this reactor. The slurry produced in this reactor enters the reactive granulator (Granulator) and at this stage, a specific ratio of ammonia and water is added to complete the reaction and control the product conditions.
The granules produced in this stage enter the Rotary Cooler one or more times and after cooling, they are transferred to the sand through an elevator bucket (or conveyor belt). Coarse and fine particles are separated in the sieve and coarse particles enter the mill. Particles with the desired size of 3-6 mm are entered into the packaging unit as a granule product, and part of the fine particles are returned to the granulator by the conveyor belt so that the reaction bed is ready.
Venturi-scrubber systems are used in this process. The scrubber receives exhaust gases along with suspended particles from the granulator with the help of a sucker. Also, the dust produced in the cooling process is also sucked in the rotary cooler and finally recovered in the process, and its entry into the environment and product waste are prevented. By adding a solvent and crystallizer system to the production line, it is also possible to produce crystal ammonium sulfate.
