Anti-caking agent general intro: how does it solve npk compound fertilizer clumping problem?

Introduction: why we use anti-caking agent to prevent fertilizer caking?

Clumping of fertilizers is caused by a variety of factors. Therefore, in fertilizer production, efforts should be made to weaken the influence of these factors. For example, by improving equipment level, optimizing process conditions, improving storage environment and other measures to improve particle strength and particle uniformity, reduce moisture content and packaging temperature, etc., these are all active anti-caking measures. However, a more effective anti-caking measure is to anti-caking the fertilizer. Currently commonly used anti-caking agents include inert powders, inorganic salts, surfactants and non-surfactants, etc.

The history of compound fertilizer anti-caking agent technology

• Since the 1970s, a series of compound fertilizer outer packaging technologies have appeared, mainly including dusting powder, coating, etc. At first, lubricating materials such as talcum powder were sprayed on the surface of compound fertilizer.
• In the former Soviet Union, Вовкотруб used a mixed powder of highly dispersed silica and ammonium carbonate to coat the particles, but the effect was poor;
• French Navascus invented the use of melts of oils and waxes to process compound fertilizers. However, the material has a small thermoplastic range, making the product particles low in strength and easy to pulverize.
• Japan’s Iwasaki Enji uses aldehydes as anti-caking agents, but the volatilization of low-boiling point aldehydes and engine oil diluents produces pungent odors and is toxic;
• In the late 1980s, Germany’s Blouin and Gullett et al. studied calcium lignosulfonate and similar substances to treat fertilizers to improve their anti-caking and breakage resistance, which overcomes the shortcomings of using aldehydes. However, the fertilizer turns brown, making it difficult for farmers to accept it. .
• Finland’s Alnas combines aminodicarboxylates formed from cationic amines dissolved in ether and anionic carboxylic acids dissolved in methanol, and then dissolves them into mineral oil to wrap the compound fertilizer. Although the anti-caking effect is good, the cost is high. , it is inconvenient to produce and use, and it is unsafe to use a large amount of solvents, so it is difficult to apply in practice;
• Japan’s Kurata Atsushi directly uses amide compounds as the main component of anti-caking agents, but they are expensive.

What are the 2 types of npk fertilizer anti-caking agents?

Fertilizer anti0caking agent can be divided into 2 categories according to the method of addition: internal anti-caking agent and external anti-caking agent. 

• The external anti-caking agent is mainly wrapped on the surface of fertilizer particles to form a protective film to prevent moisture absorption;
• The internal anti-caking agent is mainly used in the production process of fertilizers to improve hygroscopicity, increase the strength, roundness or change of fertilizer particles. Crystal form.

What are the 2 types of internal anti-caking agent?

internal anti-caking agent: Inorganic salt

• Certain small amounts of additives can well improve the crystallization habits of solution crystallizing substances (crystal habit improvers). Such as magnesium nitrate, dithionate, cadmium salt, etc., each of which is used in different fertilizers, can cause the fertilizer salt to form long, fibrous and flexible crystals, which are very brittle when dry, thus reducing the tendency of agglomeration.
• If 0.3% magnesium nitrate is added, the phase change temperature of ammonium nitrate can be reduced from 32 ℃ to 22 ℃. Magnesium nitrate has hydratability (an inorganic salt that can be partially or completely hydrated, turning free water in the material into crystal water, inhibiting Due to the dissolution and capillary adsorption of chemical fertilizers caused by moisture, it is especially suitable for crystallized fertilizers (ammonium sulfate, etc.). It plays the role of crystal (phase) stabilizer and desiccant.
• Adding certain inorganic salts to fertilizers to promote the formation of complex salts can improve the hygroscopicity of fertilizers. For example, at 30°C, the hygroscopic point of pure ammonium nitrate is 59.4%; but after adding ammonium sulfate, NHNO·(NH)SO double salt is formed, and its hygroscopic point increases to 62.3%.
• A small amount of water-soluble iron salt can also be added. It imitates the use of wet phosphoric acid to make ammonium phosphate fertilizers. The iron and aluminum phosphate impurities contained in the phosphoric acid itself form water-insoluble crystals. Its network structure is like an amorphous gel, which hardens the product and inhibits the interaction between fertilizers.
• Since inorganic salt raw materials are cheap and easy to obtain, they have similar properties to many chemical fertilizers, there are few problems when adding them, and most of them are harmless to crops and soil, so many manufacturers are using them.

internal anti-caking agent: organic matter

Dyes and related compounds are recognized crystallization habit improvers. However, harmful substances in dyes are difficult to remove and are harmful to crops and soil. The effect of using only internal anti-caking agents is limited. Usually the increase in moisture absorption point is difficult to exceed 3%, and is restricted by factors such as cost, so its application is limited.

What are the 5 types of external anti-caking agent?

External anti-caking agent: inert powder

Some inert substances that are insoluble in water and do not interact chemically with fertilizers, such as clay, diatomaceous earth, zeolite, etc., are characterized by very fine particles, low density, strong adhesion, and the ability to mechanically isolate and absorb moisture on the surface of the particles. , to prevent the formation of junctions between grains. This method has lower cost, but the dosage is large and the dust content of the fertilizer increases.

External anti-caking agent: Non-surfactant (also known as waterproofing agent)

Coating with this kind of hydrophobic organic matter can not only isolate the particles from each other, but also isolate the particles from the surrounding water vapor. Such as paraffin, heavy oil, Vaseline, etc. This method works better when the ambient temperature is not too high. Higher temperatures will destroy the hydrophobic layer and cause agglomeration.

External anti-caking agent: Surfactant

• Anti-caking agents are very selective for fertilizer types. Anionic surfactants such as sulfonates and non-ionic surfactants such as polyethylene are not effective in anti-caking ammonium nitrate, while fatty amines containing long carbon chains are not effective. It has a strong anti-caking effect on ammonium nitrate, especially the mixture of industrial amines with an average chain length of (17.5 ±1.5) carbon atoms, which also shows excellent protective effects on granular fertilizers. The key to preventing caking is to reduce the hygroscopicity of the product. Highly hygroscopic
• The crystals all have high surface energy. When it absorbs water, the surface energy decreases. When treating fertilizers with surfactants, their special amphiphilic structure allows them to be oriented and arranged to form a hydrophobic film on the surface of the particles, which reduces the interfacial tension and contact angle between solid and liquid, and improves the crystallization habit of the fertilizer (interference within the crystal) Intermolecular forces change the crystal form, weaken the crystallization strength and binding force), and reduce the surface energy of the crystal, thus greatly reducing the hygroscopicity of the product.
• In order to overcome the localized and limited effects of a single type of surfactant, two or more surfactants are often used to form a compound modifier. Due to the synergistic effect between different surfactants, their own surface activity is increased and they can be more easily adsorbed on the particle surface to form a dense hydrophobic thin layer.

What are the 3 types of external&internal anti-caking agent?

Studies have shown that simply using surfactants as anti-caking agents does not have a strong mechanical isolation effect and cannot prevent the formation of junctions between grains for a long time. In order to improve performance, compounding is often performed.

1. Inert-surfactant composite type: It combines mechanical isolation and reduction of surface tension to achieve better results.
2. Polymer-surfactant composite type: It solubilizes polymers in concentrated solutions of surfactants to form complexes. Some polymers have anti-caking effects, mainly by increasing particle strength and absorbing condensed water to prevent recrystallization. The composite anti-caking agent has significant synergistic effect.Once the fertilizer treated with polymer surfactant is dried, clusters of aggregated crystals will be formed. The unit volume is several times that of the blank sample or fertilizer with only surfactant added. Fertilizer with only a single water-soluble polymer cannot be dried. Produces the same large volume of crystals. Even if the relative humidity of the air is greater than the critical relative humidity of the fertilizer, it is not easy to agglomerate, and its dosage is small and the effect is good. Representative polymers are polyvinyl acetate, polyacrylamide, etc.; representative surfactants are sodium dodecyl benzene sulfonate, alkyl (aryl) polyoxyethylene ether, etc. The above external anti-caking agents can also be added internally, but when the inert powder is added to the molten material, it is easy to suspend, but it can promote the formation of fine-grained particles with greater density and strength, delaying the release of fertilizers.
3. Comprehensive anti-caking agent: including surfactant, inorganic salt, polymer (or inert matter) compound, etc. When studying the anti-caking effect of various additives, it was found that a single additive has certain anti-caking properties, but has little effect when the humidity is high; surfactants (such as octadecylamine) and polymer compounds (such as polyacrylamide) Used separately with composite inorganic additives, the ammonium nitrate can maintain a certain anti-caking effect under higher humidity; and if the above three are used together, the ammonium nitrate can maintain a certain anti-caking effect under higher humidity (65% ~ 80 %) to maintain good anti-caking properties, in which inorganic salt additives play an important role. Therefore, comprehensive anti-caking agents are currently the focus of applied research.

What are the 5 types of new anti-caking agent technologies

Polymer surfactant compound type

The British patent dissolves water-soluble vinyl polymers in concentrated anionic surfactant solutions, and uses this compound solution to treat fertilizers. Compared with traditional anionic and cationic surfactants, it has a better anti-caking effect. Among them, the water-soluble vinyl polymers are polyvinyl acetate, urea-formaldehyde resin, polyvinyl alcohol, etc.
Using the traditional wrapping method (coating products with oil and inert coating agents), the caking time of high-nitrogen compound fertilizers is extended from the original 7 to 10 days without wrapping to about 20 days. After technical improvements, the surfactant sodium dodecyl sulfonate was added to 20% phosphoric acid solution, and then a polymer active organic compound was added, and wrapped particles were added to the mixer, commonly known as “egg shelling”, and stored in the south. No clumping for 3 months.

Environmentally friendly anti-caking agent

• At present, traditional anti-caking agents will cause pollution to farmland, fisheries and water conservancy after application. When exporting fertilizers, foreign investors are clearly required to add non-toxic and harmless anti-caking agents. Tongli has developed a new high-concentration sulfur-based compound fertilizer anti-caking agent. The selected raw materials are mainly inorganic minerals (talcum powder is used as filler). Three of the other four surfactants are food grade (including sodium stearate). , calcium stearate, anionic and cationic surfactants).
• The other is a food additive (also a polymer emulsifier with high water absorption and water retention), which is mixed and ground into a powder of less than 40 μm, rolled through a cooling roller, and evenly attached to the surface of the particles. It has no pollution to the soil and the fertilizer does not freeze for 3 months. piece. Tongli pickles, neutralizes, filters and removes impurities from three kinds of plants, and centrifuges them, then reacts with four different surfactants under the action of a catalyst to produce a light green, thick liquid. This product does not require mechanical oil as a carrier.

Tongli Internal additives

• Traditional outer wrapping technology requires the use of mineral oil and melting and atomizing equipment. The coated oil film greatly reduces the water solubility of fertilizers; and the compound oil can easily block pipelines and nozzles during pipeline flow and spraying. Tongli designed to add powdery loosening agent during the production process and form moisture-proof and anti-caking particles with a uniform mixed crystal structure through spray granulation.
• Based on the physical properties and crystal structure of the main components of compound fertilizer, it is composed of additives such as anti-sticking agents, crystal control agents, lubricants, anti-powdering agents, moisture-proof agents and flame retardants. It has complementary properties and low cost. Compound fertilizer has good water solubility.
• Among them, the most critical anti-sticking agent is an amide-type cationic surfactant with mobility, and the crystal control agent uses a planar anionic surfactant containing polar groups -COOH, -SOH, -SOH, and -POH. Tongli designed a flaky anti-caking agent, which can be used as an outer wrapping agent and as an internal additive before granulation.
• It has good thermal compatibility with compound fertilizer components, the raw materials are cheap and easy to obtain, and it is easy to process without using solvents during processing. At 90°C, the amines and carboxylic acids in its composition can generate amide compounds, which can form an association effect with ammonium ions or related ionic groups, thereby making the compound fertilizer resistant to powdering and agglomeration. The compound fertilizer processed with the above two patented technologies can be stored for 6 months with a looseness of more than 90%.

Waste utilization anti-caking agent

• Tongli engineers use waste animal and vegetable fats as raw materials, add liquid alkali to partially hydrolyze them into fatty acid sodium (or potassium), and then add animal and vegetable fats to generate anti-caking agents through emulsification reactions. It has the dual effects of non-polar substances and surfactants to prevent caking.
• Hydrolyzed lignin, a waste material from the hydrolysis industry in the former Soviet Union, is used to treat the particle surface; for high-concentration compound fertilizers, acrylic acid production waste containing ammonium sulfate is matched with monoethanolamine-purified distillation still residue to treat the particle surface;
• Russia uses sapropel at the bottom of lakes and seas, and uses the remaining sediment after separating biologically active substances as a particle surface modifier. Certain crop or food residues, such as peanut shells, lignin, etc., are dried and crushed and then added to the fertilizer to prevent agglomeration by inhibiting the interaction between particles or absorbing moisture in the fertilizer.

Slow release anti-caking agent

• Combining anti-caking and slow release to develop coated fertilizers will be the development direction of fertilizers. The high-efficiency anti-caking compound long-acting agent developed by Tongli Ecology is made from a mixture of thiourea, dicyandiamide, diatomaceous earth (with water-soluble anti-caking agent) or amine tablets (with oil-soluble anti-caking agent), which can improve The comprehensive utilization rate of nitrogen, phosphorus and potassium is 17% to 25%, and the fertilizer efficiency period is extended to 110 to 120 days.
• Tongli uses molten urea liquid as the carrier, uses paraffin and a mixture of anionic surfactant alkyl benzene sulfonate and cationic surfactant alkyl amine salt as a compound fertilizer anti-caking agent, and adds hydroquinone and hydroquinone that inhibit the hydrolysis of urea. Dicyandiamide, which has an inhibitory effect on the oxidation of ammonium ions in the soil, is used as a nitrogen sustained-release agent. The mixed liquid is coated with the particles through a spraying device to obtain a high-nitrogen and high-concentration compound fertilizer with good nutrient slow-release and anti-caking properties. Vitamin utilization rate increased by 13%.
• In recent years, Tongli has designed a coating agent with both anti-caking and sustained-release properties, which is composed of surfactants (Span-60 and Tween-80), paraffin, gelatin, and release factor aqueous solutions. A company in Henan produces zeolite powder. The special porous network structure of zeolite allows it to absorb part of nitrogen, phosphorus, potassium, etc. (it has a strong exchange and adsorption effect on NH) in the early stage of fertilization. In the later stage, the concentration of active ingredients in the soil decreases. When separated, the fertilizer effect can be made even and prolonged, and the utilization rate of fertilizer can be improved.

Conclusion:

In this article we introduce how to use anti-caking agent to prevent the finished compound fertilizer from clumping. And we also introduced the history of fertilizer anti-caking agent’s development. What is external and internal anti-caking agent. And tongli in recent years is alos developing new anti-caking technilogy like slo release anti-caking agent. All these effort is bacause fertilizer clumping is a problem often encountered in fertilizer production and storage, and we want to solve it. Also if you go to our website our youtube channel, there we have a video of how anti-caking agent is applied to the fertilizer, the small DCS system that controls the anti-caking powder and coating oil, so feel free to check it out.