[ Fertiliser Production ]
[ Fertiliser Production ]
Today , MAP and DAP are the most popular phosphate fertilizers as they are both economical and have a high nutrient content . These fertilizers are produced by a subsequent reaction between ammonia and the weak phosphoric acid derived from the WPA process .
A growing segment To give a sense of perspective , data available from Market Research Future ( 1 ) valued the 2024 global phosphate fertilizer market at around USD 70 billion and forecasts growth to some USD 125 billion by 2034 , with a CAGR of 5.9 %. Market drivers include global population growth , global conflict ( which creates food insecurity ), a decline in the quality of agricultural land , the rising demand for alternative foodstuffs , as well as government initiatives promoting the use of so-called ‘ NPK fertilizers ’ ( nitrogen , phosphorus , and potassium ). Moreover , as harvesting crops effectively removes more phosphorus from the soil than can be naturally replenished , commercial fertilizers are essential to maintain food output .
Materials research A recent technical article by Simbarashe Fashu and Vera Trabadelo ( both from the Mohammed VI Polytechnic University , Benguerir , Morocco ) gives an excellent review on the development , performance and selection of stainless steels and nickel alloys for the WPA process ( 2 ) .
A shift to renewable resources ?
With demand for phosphate fertilizers on a strong upward trend , there is growing interest in many areas – and especially in Europe – to develop alternative raw materials sources . For example , by recycling biological waste . This will reduce pressure on the use of phosphate minerals which are classified as critical raw materials , indicating that there could be an imbalance between supply and demand in the years ahead . The basic principle to recycling biological waste is to extract phosphate salts from sludge or sewage which can then be used to prepare phosphate fertilizers . Manure or fermentation residues from biogas plants are also valuable feedstocks , as in addition to phosphorus they can contain valuable materials such as nitrogen and potassium compounds which are also beneficial for plant growth .
With global food consumption on an upward trend , the market for phosphorus fertilizers could grow well over 5 % per year . Image for illustration only .
In the introduction , the authors indicate that nickel alloys and stainless steels are attractive construction materials for the WPA process due to their superior mechanical and chemical integrity , toughness , ductility , versatility and easiness to fabricate . In the section on performance and selection of stainless steels and nickel alloys , they discuss the results of testing materials in various areas of the process . For example , they state that austenitic stainless steels 904 , 316 and 317 quickly corroded in reactor vessel environments and that high nickel contents are required for alloys to withstand stress corrosion cracking . Later , when reporting on applications such as tube heat exchangers and circulation pumps in the concentration evaporators , they note that alloys with a high chromium content deliver superior corrosion resistance whilst high molybdenum levels seem less important . The acidulation ( WPA ) process , where sulphuric acid is added to the crushed and refined ore , typically takes place in concrete reactors lined with acidresistant bricks . The sulphuric acid is fed into the reactor using both pipes made of 316L ( for exterior pipework ) as well as alloy C-276 pipes ( used when entering the reactor ). One of the most challenging applications is the agitator assembly , due to the combination of extremely corrosive and erosive conditions .
In Saudi Arabia , Ma ’ aden is investing USD 922 million in its third phosphate fertilizer project . AI image for illustration only .
42 Stainless Steel World April 2025 www . stainless-steel-world . net