Dust and moisture control agents

FERTILIZER COATINGS

Dust and moisture control agents

The quality of finished fertilizers can be maintained during transport, handling and storage by protecting the surfaces of granules and prills with coating agents. We survey the range of anti-caking, water repellent and anti-dusting additives currently on the market.

Preventing degradation, preserving value

Granular fertilizers can be protected through the addition of anti-caking and dust control agents (Fertilizer International 492, p28; Fertilizer International 477, p28; Fertilizer International 464, p32; Fertilizer International 453, p26). These agents are usually applied as surface coatings and help prevent dust formation and caking by reducing water absorption under humid conditions. They include both synthetic and natural compounds. These need to be harmless to soil, plants and humans. Coating chemicals generally function by:

• Controlling dust formation
• Minimising caking and particle bridging
• Enhancing powder flow
• Reducing moisture absorption
• Enhancing appearance
• Regulating nutrient release.

They are often combined with a pigment to introduce colour.

The caking of fertilizers, if not prevented, can be a major headache during storage, transport and field application. It can destroy the value of fertilizers, halt loading and unloading, damage handling equipment and be a safety hazard.

Urea, urea-based NPKs, ammonium nitrate, calcium nitrate and other NPK fertilizers are more hygroscopic – due to their lower critical relative humidity (CRH) – and therefore often benefit the most from the addition of anti-caking agents (Figure 1). In comparison, the need for anti-caking treatment in other types of fertilizers, such as phosphates and ammonium sulphate, can be lower if they are less hygroscopic.

Selected products and producers

Arkema-ArrMaz has been a leading provider of coatings and process control chemicals to the fertilizer industry since the late 1960s. The new company was formed when Florida-based ArrMaz was acquired by French-headquartered Arkema Group in 2019.

Some of the world’s major fertilizer producers treat tens of million tonnes of fertilizers every year with the company’s DUSTROL® and Fluidiram® range of anti-caking and dust control agents. These tailor-made agents are generally suitable for all solid fertilizers including granules, prills and powders. They reduce airborne dust and minimise product losses and can be applied to a variety of fertilizers. These include diammonium phosphate (DAP), monoammonium phosphate (MAP), ammonium nitrate (AN) and NPKs.

Treatment with Arkema-ArrMaz coatings:

• Reduces caking of prills or granules
• Provides dust control for ease of handling and storage
• Benefits flow properties, colour, appearance and product marketability
• Improves workplace safety and compliance with environmental, health and safety (EHS) regulations
• Promotes better environmental stewardship.

Fig. 1: Critical relative humidity (CRH) of various fertilizers at 25°C

DUSTROL coatings supress dust by forming a barrier around granular products and also adsorb dust after it is generated.

The Fluidiram product range successfully keeps fertilizers free-flowing by preventing caking, dusting and moisture uptake, and is available globally.

Arkema-ArrMaz also offers sustainable fertilizer coatings (see accompanying article on page 24). These fully bio-renewable and biodegradable products deliver comparable dust, moisture and caking control performance to traditional coatings. Coating products offered include REACH-compliant, organic (OMRI listed) and water-soluble types.

Arkema-ArrMaz’s expertise is not limited to coating products alone. The company also offers its customers safe, effective and easy-to-operate systems for applying coatings to fertilizers. Coating equipment can be designed, engineered, constructed and installed as part of a comprehensive service package.

Sustainable solutions to dust and caking in fertilizers

NAQ Global is well known for its advanced and innovative fertilizer additives sourced from crop-based materials. Prakash Mathur and Anmol Mathur explain the company’s commitment to sustainability.

Fig. 2: Hard cake of uncoated ammonium nitrate phosphate (ANP) fertilizer (left) with a magnified image (right) showing salt bridge formation and particle deformation.

Problematic dust formation and caking

Chemical fertilizers are the engine of agriculture. Yet storing and handling these materials in bulk can be highly problematic due to dust formation and caking (Figure 2). In the fertilizer industry, the occurrence of these problems can cause unnecessary waste and incur major costs on a vast scale. Fertilizer degradation is also associated with a number of safety, environmental, and health hazards. Phosphate fertilizers, for example, whether they are in powder, crystalline, or granular form, tend to either cake or break into dust.

The resulting fertilizer dust is easily transported by air, creating numerous difficulties. These include:

• Environmental compliance breaches
• Worker safety hazards – and associated productivity declines
• High maintenance and repair costs for handling and warehousing equipment.

Caking/agglomeration is another significant concern during the production, handling and application of solid fertilizers. Granular products – due to the physical and chemical nature of freshly-manufactured fertilizers – tend to coalesce to form difficult-to-separate cakes. These cakes are troublesome because they eventually tend to break-up and create more dust the longer they are stored.

Conventional coatings have downsides

These problems are commonly addressed by applying protective synthetic coatings to granular fertilizers. These are typically composed of furnace oil, petroleum wax, asphalt, and other fossil-fuel derived materials. These products can potentially be harmful to soil fertility and plant growth, cause heavy metal contamination, and increase carbon footprint.

NAQ Global, having looked into the negative aspects of synthetic chemical additives for fertilizers, identified a market need for biodegradable, environment-friendly coating products. This led to the creation of the company’s highly efficient and costeffective Green Technology product line for the fertilizer industry.

At NAQ Global, innovation was – and remains – the key to addressing this challenge. The need to nourish the world in a safe, responsible and sustainable way is central part of the company’s purpose and way of doing business. We believe that sustainability and agricultural development go together hand-in-hand and can thrive simultaneously. We are therefore committed to finding innovative solutions that, as well as being economically viable for fertilizer producers and farmers, still protect our planet.

Biodegradable, environment-friendly coating agents

The company’s commitment to sustainability led it to delve deeper and look at the potential for developing advanced and innovative additive technologies derived from crop-based source materials. The most esoteric but promising of these involved the catalysis of a waste by-product from the vegetable oil industry. We subsequently incorporated this as an important functional constituent in our dust control and moisture control agents.

NAQ Global’s innovative moisture control agents are easy to apply, biodegradable and environment-friendly. Crucially, they provide long-lasting caking control in fertilizers by effectively preventing the formation of salt bridges between granules.

For dust and caking control under standard conditions, our analyses indicate that NAQ Global’s new generation of anti-dusting and anti-caking agents are much more efficient, compared to other common phosphate fertilizer coating products on the market. These advanced coating solutions – because of the unique adhesive properties of the vegetable fats they contain – offer long-term anti-caking and anti-dusting protection.

Going further…

But we did not stop there. Our commitment to sustainability drove us further onwards – to look for even more innovative ways to drastically reduce our environmental footprint. Today, NAQ Global offers a complete range of eco-friendly products for the entire fertilizer supply chain. From mining, to phosphoric acid production, to granulation, and, finally, to retailing and distribution, NAQ Global’s comprehensive Green Technology range is able to optimise product performance, improve process efficiency, and help produce superior quality products.

While dust and caking in fertilizers have been significant long-term challenges for the industry, advanced and environmentally-friendly solutions that address both these problems are now available – doing so both efficiently and cost-effectively. The pioneering use of vegetable oils and by-products for fertilizer additives is just one example of how our industry can harness innovation to deliver on its mission to provide farmers with affordable, safe and sustainable crop nutrient products.

Netherlands-based speciality chemicals company Holland Novochem has been a leading global supplier of anti-caking, moisture repellents and de-dusting agents to the fertilizer industry since the early 1990s. It currently serves customers in more than 90 countries through four branch offices located across Eastern and Western Europe.

The company is well-known for its extensive range of Novo-branded fertilizer additives. These low-toxicity, environmentally-friendly products successfully address many of the problems associated with the production, storage and transportation of fertilizers (see accompanying article on page 26). The Novo product range includes:

• NovoFlow anti-caking and moisture repellent coatings: these provide protection against caking and moisture uptake. They are suitable for all major types of fertilizers. Formulations are custom-made – according to the specific needs of fertilizer producers – to reduce caking and/or moisture.
• NovoDust anti-dust coatings: these substantially reduce dust generation during the handling and storage of fertilizers. This is becoming increasingly important due to the introduction of ever more stringent environmental and safety regulations – and the general requirement for cleaner workplaces.
•  NovoTec granulation additive: this granulation enhancer can optimise the production process and/or improve the quality of fertilizer granules for a variety of fertilizer grades, especially AN, CAN and NPKs.

The CHEMISIL range of additives offered by Spanish firm Chemipol are designed to prevent fertilizer caking during manufacture and storage. They are based on two main formulations. CHEMISIL NS is a soluble sulphonated coating agent designed to prevent caking in bagged fertilizers stored under load on pallets. The anti-caking agent CHEMISIL AG, in contrast, is a highly-absorbent form of silica dioxide used to prevent agglomeration during the manufacture of powdered fertilizers.

China’s biggest fertilizer additive producer Forbon Technology manufactures four anti-caking agents for urea, phosphates and compound fertilizers under the Hisoft brand name. These oil-based and powder-form coating agents are designed to solve fertilizer quality problems such as caking, dust generation and weak granule strength.

India’s Neelam Aqua & Speciality Chem Ltd markets the NEELCOAT range of anti-caking agents for granular NPK, ammonium phosphate (DAP/MAP), and calcium ammonium nitrate fertilizers. The company’s NEELCOAT DS products combine anti-caking behaviour with dust suppressant properties. They are derived from plant extracts and are fully biodegradable. Neelam Aqua also offers three URECOAT anti-caking formulations for urea, the first designed for prills, the second incorporating neem oil and the third including an urease inhibitor.

Fertibon Products manufactures a wide range of fertilizer additives, including anti-caking agents and colourants, at its production site in Maharashtra, India. These are non-toxic and also designed to protect conveyor belt systems as they are inert when in contact with rubber.

Kao Global Chemicals sells paste and powder anti-caking agents for a wide range of fertilizers (AN, CAN, DAP and NPKs) under the SK FERT marque. It also offers the liquid anionic surfactant product URE-SOFT A-10, a low-toxicity anti-caking agent designed especially for urea and ammonium sulphate.