High performance nitrate-based fertilizers

NITRATE PRODUCTS

High performance nitrate-based fertilizers

The delivery of nitrogen in nitrate form can deliver superior yields and quality in arable, fruit and vegetable crops. Because of this, production and consumption of the principal nitrate fertilizers – ammonium nitrate (AN), calcium ammonium nitrate (CAN), urea ammonium nitrate (UAN), potassium nitrate (NOP) and calcium nitrate (CN) – continue to grow.

SQM solar evaporation ponds in the Salar de Atacama, Chile. Potassium nitrate is produced by combining potassium chloride from the Salar de Atacama brines with caliche-derived sodium nitrate.

PHOTO: SQM

Nitrate fertilizers have a deserved reputation as efficient sources of agricultural nitrogen. Indeed, their superior performance over urea – in terms of yield and quality – has been demonstrated in numerous agronomic trials for fruit, vegetables and arable crops.

Nitrates also have a much lower environmental impact relative to urea-based fertilizers. This is due to their ability to avoid volatilisation losses. Their production can also have a lower carbon footprint.

In the EU, for example, ammonium nitrate production is associated with average carbon emissions of 1.112 kg CO2 e/t versus 1.611 kg CO2 e/t for urea. Furthermore, urea will release an additional 0.733 CO2 e/t of captured emissions when applied in agriculture.

Supplying nitrogen in nitrate form has the following advantages:

• Nitrate can be readily absorbed by plants via efficient direct uptake from soil
• Nitrogen is supplied in a non-volatile nitrate form with no need for incorporation into the soil
• Avoids the soil acidification associated with the nitrification of ammonium fertilizers
• Higher nitrogen use efficiency improves yields and prevents unwanted nitrogen losses to the environment
• Avoids root damage and toxicity associated with high ammonium concentrations
• Generally highly soluble in water and easily dissolved and therefore ideal for fertigation and foliar application
• Compatible in tank mixes with most other fertilizers and agrochemicals
• Ability to combat excess chloride in soils and irrigation water
• Promotes the uptake of other valuable plant nutrients (K, Ca, Mg)

Nitrates – soluble, readily available, less volatile

Ammonium nitrate is a popular nitrogen fertilizer in North America, Europe and Russia. Notably, it supplies nitrogen in both ammonium and nitrate form. Its extremely high solubility (1,900 g/L) also makes it ideal for fertigation and foliar spraying.

The nitrate component of AN is readily available for plant uptake. Once dissolved, it moves easily from the soil solution into the roots. Its ammonium content, meanwhile, is either partly taken up by roots or gradually converted to nitrate by soil microorganisms.

AN is more stable than urea, being less prone to volatilisation, and overall nitrogen uptake is also generally quicker.

These characteristics make AN well-suited to countries and regions in northern latitudes with shorter growing seasons, such as Canada, parts of Europe and Russia. The fact that AN releases 90 percent less ammonia to the atmosphere than urea means it is finding favour in the EU where reducing ammonia emissions has become a priority.

Fig. 1: Top five exporting countries (left) and import destinations (right) for ammonium nitrate. Total world trade was 9.4 million tonnes in 2019

Fig. 2: Top five exporting countries (left) and import destinations (right) for calcium ammonium nitrate (CAN). Total world trade was 9.5 million tonnes in 2019

Ammonium nitrate use does have downsides. Urea’s ability to deliver nitrogen in more concentrated form – with 42 percent N content versus 33-34% for AN – makes it the preferred nitrogen fertilizer in India, China and South America. A number of countries have also imposed outright bans on the sale of straight AN following a series of terror-related and factory and warehouse explosions (Nitrogen+Syngas 367, p18; Fertilizer International 491, p15). Even when the sale of AN is permitted, its use is often highly circumscribed due to major safety concerns. Soil-applied AN can also be prone to leaching.

Tried and tested manufacturing route

AN is produced industrially from the acid-base reaction between ammonia and nitric acid:

HNO3 + NH3 Æ NH4 NO3

Because AN is synthesised from ammonia, as is nitric acid, production plants are typically co-located with ammonia and nitric acid production.

The AN generated via this manufacturing route is firstly obtained as a weak solution in water. Solid AN is then typically produced by concentrating this solution to a strength of 95-99 percent at high temperature (c. 150°C) in an evaporator or concentrator. This ‘melt’ is then passed to a prill tower to generate solid AN prills.

Prills of different density can be generated by varying the concentration of the ammonium nitrate melt. High-density (1.69) fertilizer-grade AN or (FGAN) prills are formed from a 99.5-99.8 percent AN melt. Low-density (1.29) ‘technical’ or ‘industrial’ grade AN (TAN/IGAN) prills, in contrast, are formed from a 95-97.5 percent AN melt. These prills are suitable for manufacturing explosives, being more porous and so able to absorb oil more easily.

Ammonium nitrate is also the starting point for other popular nitrate fertilizers (Nitrogen+Syngas 367, p18). Calcium ammonium nitrate (CAN), for example, is produced by mixing the AN melt with calcium carbonate (limestone). While urea ammonium nitrate (UAN) is produced by mixing non-concentrated AN solution, obtained directly from the reactor, with dissolved urea.

UAN solutions are generally offered in three different concentrations: 28 percent, 30 percent or 32 percent nitrogen content, respectively. The most popular form – 32 percent N – consists of a solution of 45 percent ammonium nitrate and 35 percent urea diluted with 20 percent water. UAN solutions are adjusted to neutral pH (7) using ammonia and nitric acid.

Production rises to meet growing demand

Global AN production reached 49.1 million tonnes in 2019, versus world production of 15.9 million tonnes for CAN and 25.6 million tonnes for UAN. Nitrate production globally continues to grow, particularly for UAN solutions. World output for AN and CAN grew by 19 percent and 17 percent, respectively, over the decade to 2019 – broadly similar to the urea growth rate – while global UAN output leapt upwards by around 70 percent over the same period.

The top five exporting countries and import destinations for AN and CAN currently are shown in Figures 1 and 2, respectively.

Major UAN producing countries include the US, Russia, Canada, Trinidad and Belarus. Around one-third of world UAN production was traded internationally in 2019.Countries in Europe and the Americas are the main import destinations (Figure 3).

Among the main regional producers of fertilizer-grade AN and its derivatives are:

• Norway’s Yara International, the world’s largest NPK and nitrates producer, which produced 6.5 million tonnes of nitrates and 960,000 tonnes of UAN in 2020.
• CF industries which produced 6.8 million tonnes of UAN in 2020 from its Donaldsonville, Port Neal, Verdigris, Woodward and Yazoo City sites in the US and Courtright site in Canada. The company also produced 2.2 million tonnes of AN in 2020 from Yazoo City in the US and its Ince and Billingham UK sites.
• Uralchem – which has three million t/a of AN production capacity – alongside other major nitrate producers Acron, EuroChem and SDS Azot in Russia.
• Egypt’s Abu Qir Fertilizers which operates a 792,000 t/a capacity AN plant and a 280,500 t/a capacity UAN unit.

Primary AN production has been growing on average at 4-5 percent p.a. over the last two decades, rising (on a nutrient basis) to around 21 million tonnes N in 2019 (Nitrogen+Syngas 367, p18). Of this total:

• 34 percent was manufactured as straight fertilizer-grade AN (FGAN)
• 29 percent as technical and industrial grade AN (TAN/IGAN) for commercial explosives
• 19 percent as calcium ammonium nitrate (CAN)
• 17 percent as urea ammonium nitrate (UAN) solutions.

A small proportion of output also goes into the manufacture of ammonium sulphate nitrate and other derivatives. CAN and AN are also used as sources of nitrogen in NPK blends.

Fig. 3: Top five UAN import destinations for urea ammonium nitrate (UAN)

Concentrated demand

The ammonium nitrate market was valued at $17.0 billion in 2019 – with the agricultural segment worth $11.9 billion (70%). Demand for AN is relatively concentrated with the top five consuming countries – the US, Russia, China, Ukraine and Australia – accounting for more than half of world demand (Figure 4).

Each regional market has a distinctly different pattern of use (Nitrogen+Syngas 367, p18). In Europe, for example, restrictions on the sale of straight AN – due to its potential for misuse – has created a sizeable market for CAN. Consequently, EU countries together with Turkey are now responsible for more than half of global CAN consumption (Figure 5).

In the US, meanwhile, a preference for liquid fertilizers – when combined with tight regulations on the storage, transport and direct application of ammonia – has led to a rapid increase in demand for UAN solutions. As a result, the North American nitrates market is heavily skewed towards UAN.

Consumption of AN and its derivates has risen steeply in Russia and neighbouring countries – with Russian consumption of AN having more than tripled since 2000. CAN and UAN, in contrast, are not generally as favoured by the region’s farmers.

The rise in Russian domestic consumption has helped alleviate another issue that has plagued global AN trade – the alleged dumping of product at below cost price to increase market share (Nitrogen+Syngas 367, p18). Both the US and EU maintained anti-dumping tariffs on sales of Russian-produced AN for many years, following the breakup of the Soviet Union in the early 1990s. These tariffs were linked to claims of unfairly subsidised Russian natural gas.

In recent years, greater liberalisation of the gas market globally, plus the pickup in Russian AN demand, has helped ease dumping concerns. The US reacted by removing its AN tariffs in 2016, with the EU subsequently moving to reduce its tariffs in 2018. Nevertheless, the EU’s imposition of fresh tariffs on Russian UAN imports in 2019 shows that dumping remains a live issue. Russia was not singled out, however, as these duties were also applied to UAN traded by Trinidad and the US.

Fig. 4: Apparent consumption of AN for the 10 leading consuming countries, 2019

Fig. 5: Apparent consumption of CAN for the ten leading consuming countries, 2019

Potassium nitrate

Potassium nitrate (KNO3 ) is a soluble source of two major and essential plant nutrients. It is typically marketed as a speciality NK (13-0-45) fertilizer for high-value crops that prefer chloride-free potassium and the nitrate form of nitrogen. The fertilizer – also known as NOP (nitrate of potash) – is commonly sold in water-soluble crystalline form for fertigation and foliar use or as prills for soil application.

Potassium nitrate can be manufactured via a primary production process from naturally-occurring brines. It can also be generated using a secondary production route by reacting potassium chloride with an available nitrate source, such as sodium nitrate, nitric acid or ammonium nitrate.

KNO3 offers chloride-free potassium (46.3% K2 O) alongside nitrogen (13.7% N). It is widely used as a water-soluble fertilizer in irrigation systems (fertigation) and as a foliar spray applied to crop leaves. Relatively high productions costs have tended to limit its use to higher-value cash crops.

Irrigation systems generally require nutrient-rich and highly-soluble fertilizers that have a low salinity index and are free of impurities and insoluble substances (Fertilizer International 486, p28). Potassium nitrate meets all of these requirements and has become a popular and market-leading fertigation product. It is also widely applied as a foliar spray to correct crop nutrient deficiencies.

Crystalline potassium nitrate is ideal for fertigation and foliar application, while prills are suitable for split applications to soil (basal and side or top dressing).

Agronomic benefits

Potassium nitrate is marketed on its ability to increase the quality and yield of harvested produce. It is said to promote stronger and healthier crops by increasing plant tolerance to abiotic and biotic stresses. Potassium nitrate offers the following advantages over other forms of potash:

• Improves tolerance to drought, frost, pests and diseases
• Increases water use efficiency
• Enhances organoleptic properties of fruit (colour, sugar content and aroma)
• Promotes the synthesis of lycopene to create a deep red colour in fruit, for example Potassium nitrate producers target high-value segments of the market such as vegetables, fruits and flowers. This target market includes chloride-sensitive crops such as potato, strawberry, beans, cabbage, lettuce, peanut, carrot, onion, blackberry, tobacco, apricot, grapefruit and avocado.

Production and producers

The total value of the world potassium nitrate market – including both agricultural and industrial segments – reached $ 1.51 billion in 2018, and is projected to grow at more than three percent p.a. to reach $1.83 billion by 2024.

Potassium nitrate is a high-value niche product with a two percent share of the global potash market. World production capacity (primary and secondary) is around 1.3 million tonnes K2 O. On a product basis, the size of the global market for agriculture was estimated at 1.8 million tonnes in 2016. Production was forecast to grow at around four percent p.a. out to 2021.

“Potassium nitrate producers target high-value segments of the market such as vegetables, fruits and flowers.”

Leading global producers and products include:

• SQM: Ultrasol K and Ultrasol K plus and Qrop K
• Haifa Group: Multi-K
• Yara International: UNIKA PLUS and KRISTA K/ULTRASOLK PLUS ™
• Kemapco
• Uralchem: Solar Potassium Nitrate
• Kingenta
• Wentong Group
• Migao Corporation.

Prayon also markets Kemapco potassium nitrate as part of its Hortipray product portfolio.

Chile’s SQM is the world’s largest producer of potassium nitrate (see companion article on page 56). The company is a primary producer with an annual potassium nitrate production capacity of 1.3 million tonnes. It sources nitrates from natural caliche ore and brine deposits in northern Chile.

Caliche is mined from surface deposits in the Atacama desert to derive products such as sodium nitrate and iodine. Underground brines in the Salar de Atacama (Atacama salt flat) are also pumped to the surface and transferred to large solar evaporation ponds to yield economically valuable lithium chloride, potassium chloride, magnesium chloride, boric acid and potassium sulphate.

Nitrates are produced by firstly leaching crushed caliche with water. Sodium nitrate is then obtained from the leached solution by crystallization. Potassium nitrate is subsequently produced by combining potassium chloride from the Salar de Atacama brines with the caliche-derived sodium nitrate. This mixture is purified by crystallisation, refining and drying to yield the final product. This primary production route generates up to 40 percent less greenhouse gas emissions compared to secondary nitrate production of potassium nitrate, according to SQM.

SQM’s production complex at Coya Sur includes four potassium nitrate plants with a total capacity of 1.3 million t/a. Production lines at the site for crystalline product have a combined capacity of 1.2 million t/a, supplemented by a 360,000 t/a prilling plant.

SQM’s agricultural sales volumes for potassium nitrate reached 673,400 tonnes in 2018. The company estimates that this volume accounts for around 56 percent of the global potassium nitrate fertilizer market. The completion of a new potassium nitrate plant at Coya Sur in 2011 increased SQM’s potassium nitrate production capacity by 300,000 tonnes.

SQM’s largest international competitor is Israel’s Haifa Group with a potassium nitrate production capacity of around 300,000 tonnes p.a. The company is thought to have contributed about 13 percent to potassium nitrate fertilizer sales (outside China) during 2018.

Haifa Group is a secondary producer, manufacturing crystalline, prilled and special grades of potassium nitrate from ammonia and nitric acid. These are sold as standalone products and also incorporated into water-soluble NPKs and controlled-release fertilizers. Haifa helped pioneer the use of potassium nitrate in the fertilizer market and its high-quality Multi-K product portfolio remains a market-leading brand.

Jordan’s Kemapco, a fully-owned subsidiary of the Arab Potash Company (APC), is a major primary producer, manufacturing 141,700 tonnes of potassium nitrate in 2018. The company’s made sales worth $106 million that year. Its main markets are Europe, Mediterranean countries and Asia.

Kemapco successfully completed a $19 million expansion project in May 2018. This has raised its annual production capacity by nearly 30 percent, from 135,000 tonnes to 175,000 tonnes. A feasibility study for a second expansion to double Kemapco’s current production is currently underway.

Uralchem is Russia’s only potassium nitrate producer. The product is manufactured at its Azot complex at Berezniki in the Perm region, being partly derived from the site’s 1.38 million tonnes of ammonium nitrate production capacity. The company markets SOLAR potassium nitrate for both greenhouse and open field fertigation of crops such as cereals, vegetables, fruit, and the flower and ornamental sector.

EuroChem recently embarked on a three-year project to build a potassium nitrate plant at its Nevinnomysskiy Azot production site. This will manufacture potassium nitrate from potassium chloride and ammonium nitrate melt, a process which will also generate ammonium chloride (a nitrogen fertilizer that contains at least 24% nitrogen) as a by-product.

China is a key market for potassium nitrate, with annual demand from agriculture estimated at 400,000-420,000 tonnes, although this is largely fulfilled by domestic producers. The country currently imports just 20,000-30,000 tonnes of potassium nitrate annually. China’s tobacco growers and horticultural sector are the main consumers, with an annual requirement of around 130,000 tonnes and 120,000 tonnes, respectively.

The Qinghai Salt Lake Nitrate Industry Stock Co – part of Chinese chemicals conglomerate Wentong Group – is said to have a potassium nitrate production capacity of 400,000 tonnes. It was formed in 2016 from the merger of Qinghai Salt Lake Yuantong Potash Fertilizer Co with Qinghai Wentong Yanqiao Fertilizer Co.

The Migao Corporation operates an 80,000 t/a capacity potassium nitrate production plant in Sichuan and a 400,000 t/a capacity potassium nitrate/NPK plant in Yunnan. The company’s secondary production process is based on combining potassium chloride with ammonium nitrate. SQM constructed a 40,000 t/a potassium nitrate production unit in China as part of a joint venture with Migao dating from 2008. This plant has been operational since 2011.