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Understanding the fertilizer that set the stage for ammonium phosphates #TSP #Phosphates #Phosphoric #Fertilizers Triple Superphosphate (TSP) marked a major step forward after Single Superphosphate, made possible by the advent of phosphoric acid production. By the mid-20th century, it became the leading high-phosphorus fertilizer before ammonium phosphates took over. This article looks at Run of Pile TSP (ROP TSP) —its process, product characteristics, and role in modern fertilizer production. Agropolychim TSP Picture Example Introduction Run of Pile TSP (ROP TSP) – was the first major advancement that followed the production of Single Superphosphate. Its development became possible once phosphoric acid units started operating. The production process is relatively straightforward: ground phosphate rock is reacted with phosphoric acid. By the 1950s and 1960s, TSP had become the dominant high-phosphorus fertilizer, benefiting from the scaling up of phosphoric acid plants. This era marked its golden age, just before the industry shifted toward ammonium phosphates (DAP and MAP), which gradually took over the market. Two different processes Within the industry, two distinct processes are used to produce TSP: Run of Pile TSP (ROP TSP) – the subject of this presentation. The final product is a powder containing significant levels of free acidity and moisture. The “curing” process is carried out in this powdered form. Once cured, the ROP TSP can be fed to a granulation unit, where it can be used as the sole feedstock or incorporated into the production of NP and NPK fertilizers. Slurry TSP (GTSP) – this will be the focus of another presentation. In this process, phosphate rock and phosphoric acid are reacted together in a heated tank and sprayed into a granulator as a slurry. The final curing occurs in the granular form, making this process capable of producing only granular TSP on an economically viable scale. Product Specifications In international trade, the accepted product specification for granular TSP is: 46% available P₂O₅, typically defined as P₂O₅ soluble in Neutral Ammonium Citrate (NAC) . Moisture content: around 2%. Unlike granular TSP, Run of Pile TSP (ROP TSP) has very limited international trade. Most of it is consumed internally within the same industrial complex where it is produced. The product quality of ROP TSP is highly dependent on: The raw materials used, The final destination/application, And the economic considerations of the plant. When ROP TSP is intended for ammoniated granular fertilizers (NP/NPK), it is common practice to manufacture it with a higher level of free acidity. This has two main advantages: Improves conversion efficiency, Facilitates ammoniation and granulation. Phosphoric Acid Phosphoric acid is the key raw material in the manufacture of run-of-pile Triple Superphosphate (TSP). Its composition and level of impurities directly determine both the chemical and physical quality of the final product, as well as the efficiency of P₂O₅ solubilization from the phosphate rock. The critical parameters influencing phosphoric acid behavior in the TSP process include: Concentration: defined by water-soluble P₂O₅ and H⁺ content. Temperature: governs the kinetics of dissolution and reaction. Viscosity: affected by soluble impurities and suspended solids. These factors, together with the balance between primary P₂O₅ (from the acid) and secondary P₂O₅ (from the rock), determine the performance of the reaction system. Phosphate Rock The type of phosphate rock plays a decisive role in selecting the appropriate process for Triple Superphosphate (TSP) production. Rocks with lower reactivity, such as igneous phosphates, are better suited for the Run-of-Pile (ROP) TSP route, where longer reaction times are tolerated. The GTSP process works efficiently with high-reactivity sedimentary rocks such as those from Florida and Morocco. However, when the feedstock is switched to igneous phosphate rock, the process efficiency drops. Reaction between Rock Phosphate & Phosphoric Acid In Run-of-Pile (ROP) TSP production, the reaction proceeds through three distinct physical phases: fluid, plastic, and solid . Fluid phase: This is the initial and most critical stage. The reaction mass must be discharged into the den before this phase is complete. Controlling its duration is essential—the fluid state should last as long as possible within the operational limits of the mixer and den. At the end of the den, the product should already have transitioned into a solid phase. Plastic phase: The material becomes more viscous and begins to solidify as the reaction progresses, with liquid absorption by solids playing a dominant role. Solid phase: The final state, where the reaction mass consolidates into the desired product structure. On a microscopic level, as phosphoric acid contacts phosphate rock, it forms a thin liquid film of reaction solution around the rock particles. The acid must then diffuse through this layer to continue reacting with the unconverted rock beneath. This interplay between reaction kinetics and physical absorption is fundamental to controlling the efficiency and quality of ROP TSP production. An important parameter is the H⁺ concentration of the acid, since it is the hydrogen that play a key role to the attack on phosphate rock. The difference between the total P₂O₅ content of the acid and its effective acidity can be quite significant. Temperature is another key factor influencing the reaction between phosphate rock and phosphoric acid. Conclusion For more detailed insights into Run of Pile TSP—its production, applications, and optimization—feel free to reach out to us. In our upcoming articles, we will explore the next steps in greater depth, covering process parameters, operating conditions, and equipment design to provide a complete technical perspective on TSP production.

♻️ Can phosphogypsum become a valuable resource? As the global demand for phosphate-based fertilizers continues to rise, so does the production of phosphogypsum—a byproduct of phosphate rock processing. Traditionally viewed as industrial waste and stockpiled in massive quantities, phosphogypsum has long posed environmental and logistical challenges. But times are changing. With growing interest in circular economy principles and sustainable industrial practices, researchers and innovators are exploring new ways to repurpose this material. In this post, we’ll dive into the emerging opportunities for recycling phosphogypsum, from construction and agriculture to rare earth recovery, and examine how turning waste into value could redefine an entire industry's environmental footprint. 📥Download the full report to explore in-depth insights and innovative solutions for phosphogypsum recycling. #Phosphogypsum #Recycling #Report #IFA #Mohamed #Lembaid #Engiphos #Phosphoric

Article from World Fertilizer Magazine Edition May/June 2025 We’d love to hear your thoughts—feel free to share your questions, insights, or experiences in the comments below! #screens #rhewum #npk #fertilizers #vibrating #screening #lembaid #engiphos

In this article, we’ll explore the DAP production process, focusing on its chemistry, the importance of mole ratio, and the raw materials involved. Introduction Diammonium Phosphate (DAP) is produced from phosphoric acid neutralized with ammonia. The resulting solid is granulated and shipped either in bulk or in bags. DAP is one the biggest commodity phosphate fertilizer being traded on the world market. DAP is a concentrated phosphate fertilizer with an additional content of nitrogen. DAP popularity is mainly due to the very high nutrient content which minimizes the transport cost per kg of nutrient. Chemistry In most parts of the world, phosphate is commonly measured as phosphorus pentoxide, or P2O5, although P2O5 is not actually an occurring chemical species in fertilizer. The international recognized chemical quality of DAP is 18-46-00, 18% nitrogen, 46% P2O5, and no Potash. The main reactions of the DAP process can be expressed in two chemical equations : Reaction 1 : NH 3 + H3PO 4 = NH 4 H 2 PO 4 Reaction 2 : NH 3 + NH 4 H 2 PO 4 = (NH 4 ) 2 HPO 4 Phosphoric acid used for the fertilizer production contains generally some sulphuric acid. The most important side reaction of sulphuric acid with ammonia is : Reaction 3 : 2NH 3 + H 2 SO 4 = (NH 4 ) 2 SO 4 Sulphuric acid being a stronger acid than phosphoric acid, reaction 3 will go to completion before the ammonia will react with phosphoric acid. All reactions 1,2,3 are exothermic. Normally, in DAP granulation processes, reaction 2 is not taken to completion, and therefore fertilizer grade DAP (18-46-00) consists of a mixture of MAP and DAP. N:P mole ratio The degree to which the reactions are completed is expressed as N:P mole ratio: A ratio of 1:1 corresponds to Mono Ammonium Phosphate (MAP) A ratio of 2:1 corresponds to Di Ammonium Phosphate (DAP) The design ratio required to achieve the 18-46-00 product analysis is a function of the phosphoric acid purity and will normally be between 1.8:1 and 1.9:1 The ratio is strictly referring to the relationship between ammonia and P2O5 in the ammonium phosphate, any ammonia associated with sulphuric acid is excluded. Mole ratio versus DAP content pH as function of mole ratio Solubility of ammonium phosphate as a function of mole ratio The production process for DAP is designed to overcome the challenges presented by the solubility, or lack of solubility of ammonium phosphate. At mole ratio of 1:1 (MAP) and above 1.8:1 (DAP), it is practically insoluble, whereas it is quite soluble below N:P mole ration 0.4 and around N:P mole ratio 1.4-1.5:1 DAP cannot be easily pumped without using a large proportion of water. The control of water content and the N:P mole ratio is therefore major objective in the design and operation of an ammonium phosphate reactor. Solubility of ammonium phosphate as a function of mole ratio Raw materials - Phosphoric acid The phosphoric acid for DAP production must have a P2O5 content of at least 40% P2O5, although 50% is preferable to avoid a liquid effluent from the scrubbers. Some integrated phosphoric acid - DAP plants use a mix of 28% acid and 54%. Wet process phosphoric acid contains a number of impurities which have an impact on the chemistry of the process and the product quality. Iron, Aluminium and Magnesium react to produce metal ammonium phosphate salts, such as MgNH4PO4, AlNH4HPO4F2, FeNH4(HPO4)2. Some phosphate component of these complexes are water insoluble but remain citrate soluble, and therefore can be counted as available P2O5. Some other metal phosphates are however citrate insoluble and are "lost" as salable P2O5. The reactions from which these metal phosphates are formed are generally slow, and the formation can be limited by minimizing the residence time in the reactor. There are other unfavorable effects of a high content of impurities in the phosphoric acid. For example, high magnesium content in the phosphoric acid tends to make the DAP reactor slurry very viscous, and difficult to handle. Raw materials - Ammonia Ammonia can be supplied to the DAP process in gaseous or liquid form. In a Tank Reactor process, the gaseous ammonia is generally used. The cooling duty of evaporating ammonia can then be used to condition the air to the final product cooler. In a Pipe Reactor process, liquid ammonia is generally used. Raw materials - Filler If the phosphoric acid contains little impurities, the nutrient content in the product may be come too high. In that case, a filler material can be added to dilute the product to the correct grade. Conclusion If you have any questions about the DAP production process, raw materials, or related challenges, feel free to reach out—we’re always happy to discuss and exchange ideas! #Phosphate #DAP #Diammonium #Fertilizer #Engiphos #Lembaid #mole #ratio

#GTSP #TSP #Fertilizers #Acidulation #Granulation #Den Reactor I am writing this article to share my thoughts about how to select the most appropriate process for GTSP fertilizer production. There are two principle processes for production of Granular Triple Superphosphate (GTSP), there are normally called the Den Route and Slurry Route. Each process has its particular advantages and disadvantages, and the process finally chosen is determined mostly by local circumstances. The Den route description In the Den Process (also named as run of pile TSP route), finely ground phosphate rock is reacted with about 50% P2O5 phosphoric acid, in a special piece of equipment known as Den (A Den is an elaborate enclosed conveyor). The material flowing from the Den is a solid of wide size range in which reaction between acid and rock is about 80% complete. The material is conveyed to a maturation building, where it remains for about 10 days after which reaction is about 95% completed. At this stage, TSP is suitable for feeding to a low recycle granulation plant where it is formed into granules with size range generally between 1.5-4.0 mm. The final chemical quality is good with water and citrate P2O5 contents maximized (within the limits of rock and acid quality) and free acidity minimized. The main features of the granulation of powder TSP (produced in the Den reactor) is the very low recycle ratio of about 2:1 in the granulation loop, whilst achieving good physical quality and minimizing utility consumptions. The granulation unit can also be designed to produce other granular NPK fertilizers from the same equipment. Advantages of the Den Route : Low capital cost for the granulation section because of the low process recycle ratio. Low operating cost because utility consumptions per ton of product are minimized. The Den equipment can be used alternatively and independently of the granulation plant to produce other intermediates such as SSP. Production flexibility : the powder TSP can be used directly for GTSP production or as a raw material for granular NPK fertilizers. Low design recycle ratio for the granulation section resulting in small equipment and easier/low maintenance cost. Large capacities in a single line are possible. Removal of fluorine gases from process air streams is simple because it is contained in a single air stream. In general, the Den route is favored where phosphoric acid is imported (normally 54% P2O5) and/or where client requires superphosphates as an intermediate in NPK production in addition to straight GTSP production. The Slurry route description In the slurry process, finely ground phosphate rock is reacted with about 42% P2O5 acid in series (normally two) of stirred tank reactors. The reaction system is operated at chemical equilibrium (P2O5-CaO-H2O) with the rock about 70% reacted at temperature of about 100°C and water content about 20%. Reaction is completed in the granulation section. Under these conditions the resulting reaction slurry is pumpable and is fed directly to the granulator. The high water content in the TSP slurry requires that the granulation plant is designed with a recycle ration of about 8:1. The high recycle ratio results in a large plant in terms of equipment sizes for a relatively low production rate. The product chemical quality is comparable with that obtained from the Den route, and is determined by rock and acid quality. Product size is 90-95% in the range of 2.0-4.0 mm. Advantages of the Slurry Route : Fully integrated process in which rock and acid are fed at one end, and final product flow from the other end. Phosphoric acid can be used directly from the hemihydrate process (if rock is fed in dry conditions). Therefore neither an evaporation nor steam for evaporation is required. Lower phosphoric acid concentration required (42% compared to 50%). Thus even with a dihydrate acid plant, steam savings are possible. An intermediate maturation building is not required. No intermediate solid handling. Plant plot size is small. Lower labor cost. In general, the Slurry process is more appropriate where production takes place in a fully integrated factory with sulphuric and phosphoric acid production at the same site, and client required only GTSP as a final product. Do we need to test the phosphate rock before selecting the best process ? Unless the phosphate source has been already used to produce TSP, laboratory tests are beneficial to understand how the phosphate rock will react in Den route or Slurry route. The tests are used to evaluate the rock phosphate performances in both Den route or Slurry route. The purpose of the tests are : Specify raw materials characteristics, phosphate granulometry, phosphoric acid concentration and temperature. Predict phosphoric acid and rock phosphate consumptions, to meet the final product quality. Predict final product chemical quality (Total P2O5, soluble P2O5, citrate P2O5, free acidity). Determine phosphate rock reactivity index. It is to be noted that some phosphates with low reactivity index may not be suitable for Slurry route. Low rock quality will tend to consume more acid, to meet the final product compositions requirements, and will also provide a final product with high free acidity. Acid quality has also an impact on the reaction conversion. Acid with low impurities will have positive effect on the final product chemical quality. Conclusion From the above statements, we can conclude that every project can be unique. Final decision has to be taken, based on local circumstances, lab tests results, production flexibility requirements and a CAPEX/OPEX/profitability exercise. Do you have any additional comments ? If you enjoyed this article, please share it with your friends and colleagues. Please let us know your thoughts in the comments section. Thank you !

#Phosphate #Rock #Fertilizers #Acidulation #Testing #Phosphoric #Acid #SSP #TSP #MAP #DAP I am writing this article to share my thoughts about the general methodology to be followed during a typical phosphate rock assessment. The tests are carried out in a laboratory scale. This can be followed by a pilot plant investigations if necessary. The result of the rock assessment gives process engineers valuable input to evaluate the potential manufacture of phosphoric acid and fertilizers. Phosphoric Acid Pilot Plant Why do we need Laboratory Investigation ? Laboratory scale tests are carried out to provide preliminary but valuable representative indications of how a phosphate rock is likely to behave in full scale phosphoric acid process. This is particularly useful as a screening exercise when an indication of their relative performances is required. Laboratory scale test also allow the most promising starting conditions to be identified for any pilot plant investigations that may follow. The tests are performed continuously to evaluate the performance and reaction conditions in the dihydrate (DH) and hemihydrate (HH) processes. The conversion of hemihydrate to dihydrate can also be carried to assess the potential use of a rock in the hemidihydrate process (HDH). But first, let's make a chemical and physical analysis of our phosphate Samples of rock are first analyzed to determine a basis for the subsequent testing. The analysis includes generally a chemical determination of the components P2O5, CaO, SO3, F, SiO2, Na2O, K2O, MgO, Al2O3, Fe2O3, CO2, H2O, Organic Carbon, Chlorides, Cadmium, and others minor elements if necessary. A full assessment of the rock particle size distribution is also performed. Now, here is a general list of the test works to be performed 1. Foam Tests Foam tests are carried out to assess the foaming characteristics of the rock when used for full-scale manufacture of phosphoric acid, which govern the need of any antifoam-addition. The rock is treated with acid under carefully controlled standard conditions of agitation in a calibrated reaction vessel. The height of foam produced and its persistence is measured at predetermined times after the addition of the acid. If required, different anti-foam agents can be tested. 2. Crystallization Tests The crystallization tests are carried out in a continuous laboratory scale unit using a standard phosphoric acid composition for the initial start-up. To increase the representativeness of the test work, the reactors should be chosen to simulate the actual full scale flowsheet as close as possible. The duration of each trials depends on the type of process being studied, but in all cases should be chosen to be sufficient to allow chemical equilibrium to be achieved. In the initial test, the sulfate level and P2O5 levels in the liquid phase of the slurry are fixed. The fineness of the rock is also fixed by the requirements developed for each particular laboratory technique. It is sometimes necessary to examine the effect of different sulfate levels and different P2O5 levels. As the test progress, samples of calcium sulfate crystals can be taken from the reaction vessel for microscopic examination and photography (see pictures below). Their specific surface area can also be determined. By monitoring any changes in the crystal structure, a confirmation is obtained that equilibrium has been reached. Toward the end of the test, samples from the reaction vessel are filtered in a standard procedure that involves washing. This gives an indication of the filterability and the washing characteristics of the calcium sulfate. At the end of the test, the product acid and calcium sulfate are analyzed for the major components and the more important minor components. The results of the acid analysis allow a preliminary assessment of its corrosive properties also. The crystallization test should leave sufficient acid of representative quality, which can be used to perform other tests if necessary (test for example to produce ammonium phosphate) Here is some examples of calcium sulfate crystals pictures, the shape and form will depend on whether it is HH or DH, but also on the rock phosphate source : SEM Photo of Calcium Sulfate Crystals ( x 150 ) SEM Photo of Calcium Sulfate Crystals ( x 750 ) SEM Photo of Calcium Sulfate Crystals ( x 150 ) SEM Photo of Calcium Sulfate Crystals ( x 750 ) 3. Corrosion Tests Corrosion tests may be carried out on product acid. Materials of construction in common use in phosphoric acid production are tested and corrosion rates are compared with those found in full scale plants with other rocks. 4. Acid Concentration Depending on the concentration of the product phosphoric acid and the required concentration of the phosphoric acid fed to downstream production, acid concentration may be required. This acid is concentrated by vacuum evaporation. The concentrated acid is analyzed for the major components and the more important impurities. The fluorine balance is also examined. 5. Acid physical properties The density, viscosity and vapor pressure of the product acid can be measured. 6. Post Precipitation Tests If appropriate, the post precipitation characteristics are assessed for both the weak and strong acids. The post precipitated material is examined for quantity and composition. 7. Single Superphosphate (SSP) Tests Samples of SSP are prepared in the laboratory from the phosphate rock and sulfuric acid. The effects of different acid to rock ratios are determined by a series of tests in which other parameters such acid temperature and rock size are maintained constant. The solidification time is noted in each of these tests and the physical conditions of SSP is examined after a given period. The rate of maturing is monitored by analysis to determine free acidity, water soluble P2O5 and total P2O5 at specific time intervals. When samples of SSP have matured for 14 days they are analyzed for water soluble P2O5, total P2O5, acid P2O5 and citrate soluble P2O5. The results of these tests help process engineers to select the optimum acid to rock ratio which will give information on raw material consumptions. Further samples are prepared at the optimum acid to rock ratio using ground rock to different degrees of grinding. These samples are analyzed after maturation. Selected samples are investigated for maturing rate. The results of these tests help process engineers to select the optimum degree of rock grinding. 8. Triple Superphosphate (TSP) Tests Samples of TSP are prepared in the laboratory from the phosphate rock and phosphoric acid produced from the rock. The effects of different acid to rock ratios are determined by a series of tests in which other parameters such as acid temperature and rock size are maintained constant. The solidification time is noted in each of these tests and the physical conditions of TSP is examined after a given period. The rate of maturing is monitored by analysis to determine free acidity, water soluble P2O5 and total P2O5 at specific time intervals. When samples of TSP have matured for 14 days they are analyzed for water soluble P2O5, total P2O5, acid P2O5 and citrate soluble P2O5. The results of these tests help process engineers to select the optimum acid to rock ratio which will give information on raw material consumptions. Further samples are prepared at the optimum acid to rock ratio using ground rock to different degrees of grinding. These samples are analyzed after maturation. Selected samples are investigated for maturing rate. The results of these tests help process engineers to select the optimum degree of rock grinding. 9. Ammonium Phosphates (MAP/DAP) Tests Samples of concentrated product acid are ammoniated to approximately pH 4 to produce MAP and approximately pH 7 to produce DAP. These products are then analyzed for ammoniacal nitrogen, water soluble P2O5, citrate soluble P2O5 and total P2O5 and the more important impurities. The results are used to predict the expected nutrient grade and further chemical composition of product in full scale industrial production of MAP and DAP. Test work gives also information on the expected consumptions of ammonia and phosphoric acid per ton of end product. A comparison can be made with ammonium phosphates produced from other rocks to assess whether international standards relating to composition are being met. Conclusion Phosphate rock assessment is an important step especially when it comes to a new phosphate source. The results help engineers to provide a full assessment of the economic viability of the phosphate rock for commercial scale phosphoric acid production and fertilizers production. The optimum process route can also be selected. Do you have any additional comments ? If you enjoyed this article, please share it with your friends and colleagues. Please let us know your thoughts in the comments section. Thank you !

#Fertilizers #Properties #Caking #Moisture #Humidity #Flowability I am writing this article to share with you a general description of the physical properties of fertilizers. Physical properties of fertilizers are important in processing, handling, transportation, bagging, storage, and application. Several laboratory methods are available to perform physical quality evaluations of commercial and experimental fertilizer products and raw materials. Hygroscopicity Hygroscopicity is the degree to which a material will absorb moisture from atmosphere. Hygroscopicity of fertilizers is important when considering conditions under which a bulk pile can be stored, and material flowability during handling and field application. Fertilizers materials vary in their ability to withstand physical deterioration when exposed to humid atmosphere Critical Relative Humidity Critical relative humidity (CRH) is that humidity of the atmosphere above which a material will absorb a significant amount of moisture and below which it will not. For each fertilizer compound or mixture, there is a maximum relative humidity to which the fertilizer can be exposed without absorbing moisture from the air. Determining this value is important when controlled humidity storage areas are being designed for a material. the value is of interested also as an indication of the degree of protection that is likely to be required during handling. In the case of mixtures, the blended materials can have an intolerably low CRH, much lower than the CRH of each component alone. Flowability flowability is the ability of a material to remain flowable under humid conditions. flowability is important when considering the movement of material in conveyor systems and fertilizers applicators. Chemical Compatibility in Blends Chemical compatibility in blends is the ability of two or more materials to remain dry, chemically stable, and free flowing when blended together. Incompatibility is observed by wetting, caking, gas evolution, and/or particle disintegration. compatibility of materials is important in any bulk-blending or NPK granulation system. Physical Compatibility in Blends Physical compatibility in blends is the ability of two or more materials to remain well mixed during handling, storage and application. Segregation of materials in a bulk blend is normally caused by mismatched particle sizes. Caking Tendency Caking is the formation of a coherent mass from individual particles in either bulk or bag storage and is affected by one or more of the following : moisture content, particle size, particle hardness, presence of conditioners, storage temperature, storage time, curing time, material composition. Excessive caking can cause problems in handling and field application. Particle Size Distribution Particle Size of fertilizer products and/or raw materials is defined as the particle diameter ranges of the granules. Particle size affects agronomic response, granulation techniques, storage, handling, and blending properties. Angle of Repose The angle of repose is the angle at the base of the cone of fertilizer obtained by allowing a sample to fall onto horizontal baseplate. it is of interest when considering storage capacity and the design of hoppers, conveyors, and sloped roofs of bulk storage buildings. Bulk Density (Loose Pour) Bulk density (loose) is the mass per unit volume of a material, after it has been poured freely into a container under clearly specific conditions. Bulk density is a measure of the material density, material porosity, and the voids between the particles of the material. Loose pour bulk density is of interest in bag sizing, in calibration of volumetric feeders, and when considering capacity of storage bins and transport vehicles for example. Bulk Density (Tapped) Bulk density (tapped) is the mass per unit volume of a material, poured into a container and then compacted under specific conditions. Bulk density is a measure of the material density, material porosity, and the voids between the particles of the material. Tapped bulk density represents the maximum density to which a material might be reduced by vibration during processing or in transport. Apparent Density Apparent density is the mass per unit volume of a material. Apparent density is a measure of the material density and material porosity and excludes the voids between the particles. The apparent density of individual granules often is of interest in connection with development of new fertilizer processes. For a given product, variations in granule density can result in variations in hardness, moisture holding capacity, and storage properties. True Density True density is the mass per unit volume of a material, excluding voids between particles and all porous space. Crushing Strength Crushing strength is the minimum force required to crush individual particles. crushing strength is of interest in estimating the expected handling and storage properties of a granular material and determining the pressure limits applied during bag and bulk storage. Abrasion Resistance Abrasion resistance is the resistance to the formation of dust and fines as a result of granule-to-granule and granule-to-equipment contact. It is useful in determining material losses, handling, storage, and application properties, and also pollution control equipment requirement. Impact Resistance Impact resistance is the resistance of granules to breakage upon impact against a hard surface. Impact resistance is of interest when material is discharged from an overhead point into a bulk pile, and when bags of material are dropped during handling. Sphericity Sphericity is a measure of particle roundness of granular (or prilled) fertilizers. Coating adherence Coating is a substance added to a fertilizer to maintain good physical quality during storage and handling. Granular fertilizers vary in surface smoothness and other characteristics that affect the adherence of coatings. also, coating agents themselves vary in adherence properties. to study these variations, coating tests and measurement of adherence are carried out by special procedures. Specific Surface Area Specific surface areas of a solid material is the surface are per unit weight and gives an indication of the fineness of a material. It is particularly useful in determining the fineness of phosphogypsum created during phosphoric acid production but can also used for other powders. these data can be used to evaluate reaction efficiencies and filtration rates. Porosity Porosity is a measurement of the pore space within fertilizer granules. External and, for the most part, internal pores can be detected. Pores that have openings to the granule surface are considered external pores, pores that are completely enclosed within a granule are considered internal pores. excessive porosity is often the reason for weak granules. Also, in fertilizer compacting systems, porosity is an indication of the degree of compaction. Do you have any additional comments ? If you enjoyed this article, please share it with your friends and colleagues. Please let us know your thoughts in the comments section. Thank you !