DEF /Diesel Exhaust Fluid is simply a urea solution that comprises 32.5%urea and 67.5% deionized water.
It is used in the SCR-selective catalytic reduction process to reduce the Nox in the Diesel engine .Because nox is a poisonous gas which will harm human health, environment and many more.
Nox is the oxides of nitrogen which forms when the combustion chamber temperature rises above 2200°F.Thus heat reduction can be a problem solver but it will affect the engine output.There came the importance of SCR and def which helps to reduce the emission of nox without compromising much on the engine efficiency.
There is a Diesel oxy cat to reduce carbon monoxide and DPF to reduce particulate matter-soot before the SCR system.Def is injected into the exhaust upstream of SCR cat.Because of heat in the exhaust the Urea hydrolyze into ammonia.The ammonia produced is then reacts with the nox and convert the gas into nitrogen and water vapour.
2NH3+NO+NO2= 2N2+ 3H2O.
Many types/grades of urea are used for many kinds of purposes,like agricultural grade, industrial grade and automobile grade.The last one is the purest urea form with traces of biuret and NH3,free of aldehydes,sulphur, chloride , nitrate etc.This urea is mixed with deionized water that is low in organic and inorganic contaminants.A genuine/standard def is produced in accordance with ISO 22241 .ISO 22241 standard means that the solution meets certain fixed parameters like freezing point of -11°C,basicity of min9 to max10ph ,alkalinity as NH3 is .3%,urea content of 32.5%,biuret of .3%, .5 mg/kg of phosphate, calcium,iron, aluminium, magnesium, sodium,pottasium, and .2mg/kg of nickel,zinc,copper and chromium, Density at 20°C must be min 1.087 and a maximum of 1.093g , viscosity of 1.4mPa.S and aldehyde of 5mg.Urea solution that meets these parameters/ISO 22241 standard only can be named as DEF.
Thus any brand of genuine def that meets these parameters can be used for diesel vehicle.Brand name only doesn't play any role.What matter is the right composition only.
24 окт 2023
