Potash

Potash ( ) is a name for mined and manufactured salts that contain potassium in water-soluble form.Potash , USGS 2008 Minerals Yearbook

The term potash derives from pot ash, either plant ashes or wood ashes that were soaked in water in a pot, which was the primary means of manufacturing potash before the Industrial Era. The majority of production during this period was in forested areas like Europe, Russia and North America. Some potash is derived from mines into evaporite deposits -- deposits of salts from ancient seas that are deposited in sedimentary layers.

In 2021, the worldwide production of potash exceeded 71.9 million tonnes (~45.4 million tonnes K2O equivalent), and Canada is the largest producer of potash, the majority of which is used as fertilizer; other major producers include Russia and Belarus. As the third most important nutrient for agricultural plants, control of production can lead to risks, such as market manipulation and disruptions by geopolitics.

Terminology The old method of making potassium carbonate () was either by collecting or by producing wood ash (the occupation of the ash burner), chemically leaching the ashes and then evaporating the resulting solution in large iron pots, which yielded a white residue called "pot ash"; approximately 10% by weight of common wood ash can be recovered as potash.

The word potassium derives from potash. Potassium was first derived in 1807 by electrolysis of caustic potash (potassium hydroxide).

The term potash later identified minerals that contained potassium salts and the artificial commercial product derived from the salts. The table identifies eight (8) potassium compounds with the term potash in their traditional names:

Common name Chemical name (Formula)Potash fertilizer To the early 20th century: potassium carbonate (K2CO3); from the late-19th century: one or more compounds of potassium chloride (KCl), potassium sulfate (K2SO4), or potassium nitrate (KNO3). Does not contain potassium oxide (K2O), which plants do not take up; Reprinted from Agri-Briefs, of the Agronomists of the Potash & Phosphate Institute, Winter 2001–2002, No.7 the amount of potassium is reported as K2O equivalent (i.e. if in K2O form), however, to allow direct comparison between different fertilizers using different types of potash.Caustic potash or potash lye potassium hydroxide (KOH) or potassium carbonate (K2CO3)Chlorate of potash potassium chlorate (KClO3)Muriate of potash (MOP) potassium chloride (KCl:NaCl = 95:5 or higher)Nitrate of potash or saltpeterpotassium nitrate (KNO3)Sulfate of potash (SOP) potassium sulfate (K2SO4) potassium permanganate (KMnO4)

History

Origin of potash ore Most of the world reserves of potassium (K) were deposited as sea water in ancient inland oceans. After the water evaporated, the potassium salts crystallized into beds of potash ore. These are the locations where potash is being mined today. The deposits are a naturally occurring mixture of potassium chloride (KCl; mineral name sylvite) and sodium chloride (NaCl; mineral name halite), more commonly known as table salt. Over time, as the surface of the earth changed, these deposits were covered by thousands of feet of earth.Robert C. Fite Origin and occurrence of commercial potash deposits , Academy of Sciences for 1951, p. 123

Bronze Age Potash (especially potassium carbonate) has been used in bleaching textiles, making glass, ceramic, and making soap, since the Bronze Age. Potash was principally obtained by leaching the ashes of wood burned for heating and cooking.

14th–17th century

Potash mining Beginning in the 14th century potash was mined in Ethiopia. One of the world's largest deposits, 140 to 150 million tons, is located in the Dallol area of the Afar Region.Ethiopia Mining . Photius.com. Retrieved on 2013-06-21.

Wood-derived potash Potash was one of the most important industrial chemicals. It was refined from the ashes of broadleaved trees and produced primarily in the forested areas of Europe, Russia, and North America. Although methods for producing artificial alkalis were invented in the late 18th century, these did not become economical until the late 19th century and so the dependence on organic sources of potash remained.

Potash became an important international trade commodity in Europe from at least the early 14th century. It is estimated that European imports of potash required 6 or more million cubic metres each year from the early 17th century. Between 1420 and 1620, the primary exporting cities for wood-derived potash were Gdańsk, Königsberg and Riga. In the late 15th century, London was the lead importer due to its position as the centre of soft soap making while the Dutch dominated as suppliers and consumers in the 16th century.Paul Warde, 'Trees, Trade and Textiles: Potash Imports and Ecological Dependency in British Industry, c. 1550–1770', Past & Present, 240, 1, 2018, 47–82 From the 1640s, geopolitical disruptions (i.e. Russo-Polish War (1654–1667)) meant that the centres of export moved from the Baltic to Arkhangelsk, Russia. In 1700, Russian ash was dominant though Gdańsk remained notable for the quality of its potash.

18th century

Kelp ash On the Orkney islands, kelp ash provided potash and soda ash, production starting "possibly as early as 1719" and lasting for a century. The products were "eagerly sought after by the glass and soap industries of the time."

North America By the 18th century, higher quality American potash was increasingly exported to Britain. In the late 18th and early 19th centuries, potash production provided settlers in North America badly needed cash and credit as they cleared wooded land for crops. To make full use of their land, settlers needed to dispose of excess wood. The easiest way to accomplish this was to burn any wood not needed for fuel or construction. Ashes from hardwood trees could then be used to make lye, which could either be used to make soap or boiled down to produce valuable potash. Hardwood could generate ashes at the rate of 60 to 100 bushels per acre (500 to 900 m3/km2). In 1790, the sale of ashes could generate $3.25 to $6.25 per acre ($800 to $1,500/km2) in rural New York State – nearly the same rate as hiring a laborer to clear the same area. Potash making became a major industry in British North America. Great Britain was always the most important market. The American potash industry followed the woodsman's ax across the country.

The first US patent The first US patent of any kind was issued in 1790 to Samuel Hopkins for an improvement "in the making of Pot ash and Pearl ash by a new Apparatus and Process".Patent X1: the making of Pot ash and Pearl ash by a new Apparatus and Process (1790). en.wikisource.org Pearl ash was a purer quality made by calcination of potash in a reverberatory furnace or kiln. Potash pits were once used in England to produce potash that was used in making soap for the preparation of wool for yarn production.

19th century After about 1820, New York replaced New England as the most important source; by 1840 the center was in Ohio. Potash production was always a by-product industry, following from the need to clear land for agriculture.

Canada From 1767, potash from wood ashes was exported from Canada. By 1811, 70% of the total 19.6 million lbs of potash imports to Britain came from Canada. Exports of potash and pearl ash reached 43,958 barrels in 1865. There were 519 asheries in operation in 1871.

20th century industrialization

The wood-ash industry declined in the late 19th century when large-scale production of potash from mineral salts was established in Germany. In the early 20th century, the potash industry was dominated by a cartel in which Germany had the dominant role. WWI saw a brief resurgence of American asheries, with their product typically consisting of 66% hydroxide, 17% carbonate, 16% sulfate and other impurities. Later in the century, the cartel ended as new potash producers emerged in the USSR and Canada.

In 1943, potash was discovered in Saskatchewan, Canada, during oil drilling. Active exploration began in 1951. In 1958, the Potash Company of America became the first potash producer in Canada with the commissioning of an underground potash mine at Patience Lake. As numerous potash producers in Canada developed, the Saskatchewan government became increasingly involved in the industry, leading to the creation of Canpotex in the 1970s.

In 1964 the Canadian company Kalium Chemicals established the first potash mine using the solution process. The discovery was made during oil reserve exploration. The mine was developed near Regina, Saskatchewan. The mine reached depths greater than 1500 meters. It is now the Mosaic Corporation's Belle Plaine unit.

The USSR's potash production had largely been for domestic use and use in the Council for Mutual Economic Assistance countries. After the dissolution of the USSR, Russian and Belarusian potash producers entered into direct competition with producers elsewhere in the world for the first time.

In the beginning of the 20th century, potash deposits were found in the Dallol Depression in the Musely and Crescent localities near the Ethiopean-Eritrean border. The estimated reserves in Musely and Crescent are 173 and 12 million tonnes respectively. The latter is particularly suitable for surface mining. It was explored in the 1960s but the works stopped due to flooding in 1967. Attempts to continue mining in the 1990s were halted by the Eritrean–Ethiopian War and have not resumed as of 2009.

Mining

Shaft mining and strip mining All commercial potash deposits come originally from evaporite deposits and are often buried deep below the earth's surface. Potash ores are typically rich in potassium chloride (KCl), sodium chloride (NaCl) and other salts and clays, and are typically obtained by conventional shaft mining with the extracted ore ground into a powder. Most potash mines today are deep shaft mines as much as 4,400 feet (1,400 m) underground. Others are mined as strip mines, having been laid down in horizontal layers as sedimentary rock. In above-ground processing plants, the KCl is separated from the mixture to produce a high-analysis potassium fertilizer. Other potassium salts can be separated by various procedures, resulting in potassium sulfate and potassium-magnesium sulfate. Saskatchewan is the world’s largest producer of potash.

Dissolution mining and evaporation methods Other methods include dissolution mining and evaporation methods from brines. In the evaporation method, hot water is injected into the potash, which is dissolved and then pumped to the surface where it is concentrated by solar induced evaporation. Amine reagents are then added to either the mined or evaporated solutions. The amine coats the KCl but not NaCl. Air bubbles cling to the amine + KCl and float it to the surface while the NaCl and clay sink to the bottom. The surface is skimmed for the amine + KCl, which is then dried and packaged for use as a K rich fertilizer—KCl dissolves readily in water and is available quickly for plant nutrition.Potassium Fertilizer Production and Technology . International Plant Nutrition Institute.

Recovery of potassium fertilizer salts from sea water has been studied in India.Recovery of Potassium Fertiliser Salts from Sea Bittern . Tifac.org.in. Retrieved on 2013-06-21. During extraction of salt from seawater by evaporation, potassium salts get concentrated in bittern, an effluent from the salt industry.

Production