Compound Fertilizer Granulation Method
Compound Fertilizer Granulation Methods & Process
1. Dry Granulation and Wet Granulation
In general, compound fertilizer granulation technologies can be classified into two types: wet granulation and dry granulation. The difference between dry granulation and wet granulation is whether they use liquid solution. Dry granulation method is without using a liquid solution such as water or binder, while wet granulation does.
Dry Granulation
Dry granulation traditionally means the extrusion granulation technology because of no water or binder needing to be added during the compound fertilizer manufacturing process. In extrusion granulation, raw materials are aggregated under high pressure as primary powder, which will be squeezed between rollers to produce fertilizer granules. All finished fertilizer granules are free of drying or cooling, and can be packaged directly, so dry granulation method is widely for small and middle fertilizer plants with low investment. The fertilizer granules produced by dry granulation method are always with flat shape.
shape of compound fertilizer granules produced by extrusion granulator
Extrusion Granulation Technology
Double roller extrusion granulator is the most popular equipment in extrusion granulation technology. It adopts special extrusion sheet design, and uses screw, piston, rollers and rotary knives to press wet powder and extrude granules from holes.
uses of specially designed extrusion sheet.
Advantages of extrusion granulation technology
1.This extrusion granulation do not need dry and cool process.
2.The fertilizer granulation rate is high and the final fertilizer granules are rough, but with a high solidity.
3.This granulation technology can be used to produce compound fertilizer with low concentration.
Wet Granulation
Compared with dry method, wet granulation produces granular fertilizer with a higher moisture so the finished products need to be dried, cooled and solidified. In wet granulation process, the first 3 most commonly-used fertilizer granulators are rotary drum granulator, disc pan granulation machine, spray granulation machine and tower spray granulation equipment.
Rotary drum granulation technology
Rotary drum granulator is a key equipment in fertilizer industries to produce both high and low-density compound fertilizer. The theory of rotary drum granulation process is that all raw materials roll and solidify in the drum so that the raw materials could be fully react with each other. By means of rotary movement, material particles are granulated into compound fertilizer balls under pressing force.
Features of rotary drum fertilizer granulation method
1. It is widely used in large-scale compound fertilizer production plant.
2. The high steam temperature in the drum dries fertilizer granules, and improves the solidity.
3. Rotary drum granulators can be used to produce many kinds of compound fertilizer such as DAP(Di-ammonium phosphate), MAP (mono-ammonium phosphate), Ammonium Sulfate, TSP(Triple super phosphate), SSP(single super phosphate) and Urea etc.
Disc pan granulation technology
The theory of disc pan granulation is that all mixed raw materials roll in a slope disc pan, with the addition of binder and water to make different sizes of fertilizer granules.
Advantages of disc pan granulation:
1.Cheaper then rotary drum granulator or other compound fertilizer equipment, cost 30% less, with production capacity from 1-4 t/h.
2.Wild application in many fields, such as fertilizer, pharmacy, feeds, coal, metallurgy etc.
3.High granulation rat
Spray Granulation Technology
Spray granulation technology is widely used to produce urea with high N content more than 20%. The liquid urea is sprayed by high pressure pump into designed compound fertilizer granulation equipment, and then under the high temperature and screening process to produce granular urea.
This fertilizer spray granulation technology requires less for fertilizer formula, and granulates good shape of urea, but it costs more in terms of producing low N content urea.
Tower Granulation Technology
Tower granulation technology is a typical wet granulation method. It’s raw materials are all liquid solution. The theory of this tower granulation is that all melting materials mixed in a certain ratio are sprayed from a high point and become granules during falling. It is mainly to produce high concentration of NPK fertilizer such as NPK 21-21-21 and NPK 20-20-20. Besides, tower granulation technology costs more once the fertilizer plants change their fertilizer formula because of it’s high production capacity and limitations for raw materials. The fertilizer granules are always smooth and round, with low water content, so it no need drying process.
2. Compound Fertilizers Granulation Process
Here we introduce the granulation processes of 4 basic compound fertilizers – NPK, SSP(single super phosphate), DAP(Di-ammonium phosphate), and SOP(single super phosphate).
NPK Fertilizer Granulation Process
Azeus Fertilizer Machinery manufactures customized NPK fertilizer production line. The capacity varies from 20,000 tons to 100,000 tons per year. The whole lines are equipped with quality compound fertilizer machines.
Taking 50,000 t/y NPK fertilizer production line for example, its granulation process is as follow:
Granulated SSP (single super phosphate) Making Process
Raw materials for SSP production are rock phosphate and sulphuric acid, where rock phosphate is a natural deposit of calcium phosphate containing fluorine and carbonate.
Phosphate Rock + Sulphuric Acid → Single Superphosphate
Critical steps in the SSP granulating process include:
★ Crushing the rock phosphate to the correct size
★ Accurately metering the Phosphate Rock, Sulphuric Acid, and water
★ Blending all the raw materials together thoroughly
★ Time for the reactions to occur
After fully reaction, all the materials should be transferred into the rotary drum granulator and then be screened by rotary drum screen (If the size of SSP granules are not uniform, they needs to be re-crushed and re-granulated again) to produce granulated SSP.
SSP fertilizer granulation process
chemical properties of SSP
Being used as a highly demanded fertilizer to prepare land, the single super phosphate contains 16% p2o5 in water-soluble form and has traditionally been very popular in agriculture. Being as one of the cheapest forms of phosphate, it can supply sulphate and calcium for many crops and pasture needs and helps keep soil in good shape by maintaining soil structure.
Benefits of SSP granules to crops/plants:Being used as a highly demanded fertilizer to prepare land, the single super phosphate contains 16% p2o5 in water-soluble form and has traditionally been very popular in agriculture. Being as one of the cheapest forms of phosphate, it can supply sulphate and calcium for many crops and pasture needs and helps keep soil in good shape by maintaining soil structure.
DAP (Di Ammonium Phosphate) Manufacturing Process
Just like single super phosphate, diammonium phosphate is also a type of fertilizer that is rich in phosphate. The main raw material for DAP production is the phosphate ore form phosphate rock. The N:P ration of 1:1 makes it an effective source of nitrogen and phosphate and thus dissolves quickly in soil to release plant-available phosphate and ammonium.
chemical properties of DAP
DAP granulation method:
The phosphoric acid is made from the reaction between the phosphate rock and sulfuric acid, which is then reacted with ammonia in tanks to form a slurry. This slurry is then processed into rotary drum granulator to produce granular DAP. All DAP granules need to dry in rotary drum dryer to rounds and polishes all granules.
SOP (Sulphate of potash) Granulation Process
SOP fertilizer can supply two essential nutrients k2O(50%) and S(18%). Its nutrient composition is approximately:
Potassium: 41%
Sulfur: 18%
SOP are used in crops that are sensitive to chloride, such as tea, potato, orange, apple and vegetables, or fertilizer burn like tobacco, pineapple or avocado, or where sulfur is deficient. It lowers soil salt index.
The SOP granulation technology is not very difficult. In general, the materials for SOP production are sop powder and other adhesives in a certain ratio.
Process of SOP manufacturing technology
How Do You Make Granular Fertilizer for Optimal Plant Growth?
Chemical fertilizer is a type of fertilizer in the form of dry solid pellets that provide essential nutrients to plants and improve soil properties. It releases nutrients over weeks to months, feeding plants gradually.
Like liquid fertilizers, it contains 3 essential nutrients namely nitrogen (N), phosphorus (P), and potassium (K). The lack of any element will affect the normal growth and development of crops.
NPK elements Effects Element deficiency Nitrogen Promote cell division and growth The plants are short and thin with yellowish-green leaves Phosphorus Promote sugar movement and strengthen roots and blooms The plants are small, low in sugar, and the seed wilt. Potassium Promote photosynthesis and improve the plants' cold, disease, and lodging resistance The plants are withered, soft tissue, and easy to lodge
Therefore, agriculture cannot be developed without fertilizers. Granular fertilizers are essential for increasing crop yields. This blog is a step-by-step guide to Granular Fertilizers Production Process.
Step 1 Mixing of the fertilizer ingredients
Based on the soil analysis, you can identify the specific nutrients required to supplement the soil and determine the nutrient ratios. Once the raw materials are acquired, it is time to create the granular fertilizer blend.
Use a mixer to obtain a homogeneous mixture. The uniform mixing of fertilizers not only refers to the individual mixing of new substances like nitrogen, phosphorus, and potassium, but also includes the mixing of new substances and returned substances.
The granulated fertilizers can be divided into two types according to their composition.
1. Nitrogen fertilizer, phosphorus fertilizer, potash fertilizer, and compound fertilizer (NPK fertilizer)
Common ingredients in this type of granular fertilizer include urea (nitrogen), phosphate rock (phosphorus), potassium chloride (potassium), and various sources of micronutrients like iron, zinc, and manganese.
Raw materials such as urea, ammonium nitrate, ammonium chloride, ammonium sulfate, ammonium phosphate (monoammonium phosphate, diammonium phosphate, coarse whiting, single superphosphate), potassium chloride (potassium sulfate), etc. shall be provided at a certain ratio (according to market demand and soil test results in various regions).
Organic fertilizer granules
This fertilizer has recently become more popular. It is to convert high-moisture organic matter like livestock manure, crop straw, household garbage, and sludge into pellets that are easy to spread on fields, lawns, and gardens.
Note: The organic fertilizer should be fermented for 15-20 days before crushing.
1. Livestock manure: Manures from chicken, pig, cow, sheep, rabbit, etc.
2. Crop straw: Important fertilizer component, containing N, P, K, Ca, S, and other nutrients necessary for crops.
3. Household garbage: Leftovers, rice washing water, discarded fruits and vegetables, expired dairy products, etc.
4. Cake fertilizer raw materials: Cake from rapeseed, cottonseed, bean, sesame, castor, tea seed, etc.
5. Sludge: Unpolluted mud from rivers, ponds, ditches, ports, lakes, etc.
Step 2 Crushing of chemical fertilizer
Roller crushers, hammers crushers, double stage crushers, and compound crushers are all suitable for the crushing of various medium-hard materials in the production of compound fertilizers, organic-inorganic compound fertilizers, and organic fertilizers.
The roller crusher has a large crushing ratio of 4:1. Its output particle size can be as fine as 2 mm, and the output can reach 110 tons per hour. The hammer crushers have a larger production, which can be up to 1,200 tons per hour.
Step 3 Fertilizer granulation
Fertilizer granulation is made by mixing various nutrient salts needed for plant growth, such as ammonium nitrate, ammonium phosphate, and potassium chloride, to form a slurry in a large container known as a granulator.
Granulation can prevent ingredients separation, dust loss during fertilization, and solidification caused by moisture absorption and heavy pressure during storage. It can improve fertilizer performance and prolong fertilizer efficiency.
The granulation equipment commonly used in the fertilizer industry can be divided into disc granulation, drum granulation, and spray granulation. Among them, the disc granulator is the most popular among small and medium-sized plants.
The principle of the disc pan granulator is to roll the mixed material in an inclined disc with water and binder, creating various sizes of fertilizer granules. Get the Latest Price
Disc granulator achieves a productivity of 4-24 tons per hour and boasts these distinct features:
1. Automatic classification according to particle size
2. Hard and uniform product, with an intact particle shape
3. Simple operation and maintenance
4. Eco-friendly, energy-efficient, and durable
5. Affordable and compact. Costs 2/3 of comparable granulators, with a much smaller footprint
Step 4 Drying of the fertilizer
After granulation, the newly formed granules contain excess moisture. Proper drying is essential to prevent granular fertilizer caking and ensure pellet stability during storage.
Dryers have drying and secondary granulation functions. The material increases the solubility of its original moisture to the fertilizer by increasing the temperature. Granular fertilizers have the characteristics of a high granulation rate, uniform size, and low water content.
The dryer is equipped with a guide area, secondary granulation polishing area, 180° pre-drying area, 135° drying area, 135°/120° staggered drying area, 120° drying area, and 120°/90° staggered drying area at the exit. It ensures that the wet and soft particles will not be damaged after granulation, and improve the drying efficiency.
The water of the dried product is preferably 1.0%-1.5%. The optimal temperature difference between the dryer head and tail is 100℃. The exhaust gas temperature should be controlled at 65-80℃ with a plus or minus deviation of 1°C. Get the Latest Price
Step 5 Cooling and screening of the fertilizer
The dried material is transported to a cooler by a belt conveyor for cooling. The cooling process mainly uses the blower to send the natural air through the pipeline to the cooler to cool the material.
After cooling, the material is screened using a trommel screen for screening. Large crushed particles and unqualified powder are re-granulated, while qualified fertilizer goes to automatic packaging. Get the Latest Price
FAQ about fertilizer (compound fertilizer and organic fertilizer) granulation process
1. What are the requirements for compound fertilizer formula design?
① The viscosity of the material in the formula is the basis of granulation.
When low-concentration fertilizer is produced by using superphosphate as the phosphorus source, the conditioning agent of superphosphate and viscous material should be greater than 50%.
When high-concentration compound fertilizer is produced by using ammonium phosphate as the phosphorus source, the conditioning agent of ammonium phosphate and viscous material should not be less than 40%.
The urea formula depends on the amount of urea. The proportion of viscous materials in high-viscosity urea is generally about 35%.
② The ingredients used in the formula must be conducive to improving the roundness of the particles.
The decomposition and softening temperature of dispersive materials (potassium chloride, ammonium chloride, potassium sulfate, ammonium sulfate, etc.) are relatively high, which can increase the strength of the particles in the dryer and play a key role in improving the roundness of the particles. The sum of dispersible materials in the formula should account for more than 35%.
2. How long does the fertilizer stay in the dryer?
The residence time of materials in the dryer should be generally greater than 22 min. Under the same condition, the longer the dryer barrel, the longer the material residence time and the higher the heat energy utilization ratio.
Dryers
Therefore, lengthening the dryer barrel is very beneficial to make full use of thermal energy. It is an effective way to solve the problem that the setting of granulation and pelletizing area affects the drying function.
3. What is the most suitable drying temperature during organic fertilizer processing?
To avoid the death of effective live bacteria due to excessive temperature during the drying process, the drying temperature of the material should not be higher than 60℃ (generally 50℃).
For this reason, the temperature of the hot air in contact with the material should be different according to the moisture content of the material, generally no more than 130℃, so that the hot air temperature can be controlled in sections to improve the thermal efficiency as well as avoid the death of effective live bacteria.
4. What are the factors that affect the granulation of fertilizer disc granulators?
The main factors influencing the granulation of fertilizer disc granulators are mainly the diameter of the disc, the height of the side of the disc, the inclination of the disc, the rotating speed, and the water addition.
① The ratio of side height and diameter of the disc granulator is generally 0.12-0.17. Its diameter can be calculated from the production intensity obtained from the test or actual production assessment.
② The inclination of the disc granulator is determined according to the natural angle of repose of the wet powder before granulation. For example:
The natural angle of repose of potassium chloride is 36°; dipotassium phosphate is 31°; coarse whiting is 31°-35°.
When the inclination is less than the natural angle of repose of the wet powder, the material will stick to the disc; however, as the inclination increases, the rotation speed increases, the material residence time becomes shorter, and the overflow particle size becomes smaller, so it should be determined according to specific conditions, generally 40°-60°.
③ Increasing the disc rotation speed can increase the granulation rate of fertilizers.
④ As the amount of water added increases, the granulation rate of fertilizer first increases and then decreases. The smaller the particle size of raw materials, the higher the granulation rate.
5. Examples of Granular Fertilizers
a. Nitrogen-based fertilizer: It includes urea, ammonium nitrate, and ammonium sulfate.
b. Phosphorous-based fertilizer: It includes monoammonium phosphate, diammonium phosphate, and triple superphosphate.
c. Potassium-based fertilizer: It includes chloride and potassium sulfate.
d. Compound fertilizer: It contains a combination of nitrogen, phosphorous, and potassium (NPK) in specific ratios that are tailored to the needs of different crops. These fertilizers are often labeled with their NPK ratio, such as 10-10-10 or 20-20-20.
e. Specialty fertilizer: It is formulated for specific crops or soil types and contains additional micronutrients or trace elements. It is targeted to address specific nutrient deficiencies or to improve the overall fertility of the soil. Examples of specialty fertilizers include lime, gypsum, and sulfur.
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