Crushing strength depends upon Vacuum condition, free ammonia present in molten urea prill size distribution.

 The above practical’s done at constant prills size, and variation in temperature & moisture.

The following sieve analysis is used for above practical’s, for strength average Crushing strength is used for different particle size with its percentage.
-2.8+1(normal Size)
96.32 %
+2.8(Oversize)
2.26%
-1+0.85(undersized)
0.96%
And -0.85
0.46%

Crushing strength depends upon Vacuum condition, free ammonia present in molten urea prill size distribution.The crushing strength of fertilizer particles differs greatly depending on the chemical composition. Mechanical resistance is the ability of the fertilizer to resist the stresses imposed upon them in the handling chain. The mechanical resistance depends on surface structure and particle strength. Dust and fines normally arise during handling from
Water absorption
• Poor surface structure and particle strength
• Low mechanical resistance
• Mechanical stresses in the handling chain
• Wear and tear from equipment (scrapers, screw feeders, grain trimmers etc) See also how to prevent dust formation.
Crushing strength is the minimum pressure needed to crush individual particles. Determining the crushing strength, or hardness, will help determine handling and storage requirements of a chosen granular product.
generally the crushing strength in our unit about 700 gm to 1.2 Kg per prill. The crushing strength of Granule Urea is about 1.3 to 3.2 kg per granual.
The crushing strength widely depends upon moisture & Prills Temp
• MAXIMUM STRENGTH 930 Gram/prill at 0.1777% Moisture.
• Below 0.12% Moisture strength reduced 698 gram/prill.
• Above 0.3% moisture strength=640 g/prill.
• At 40 deg C Maximum strength 850 g/prill
• Below 34 deg C the strength reduced 640 g/p.
• Above 66 deg C the strength reduced 640 g/p.
• OBSERVE THE ABOVE RESULT PRILLS STRENGTH IS MAXIMUM AT TEMPERATURE 40 degC & MOISTURE 0.1777%
For More detail Please read following links.

https://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=7&t=1012&p=5352&hilit=crushing#p5348

https://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=7&t=712&p=3699&hilit=crushing#p3699

https://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=7&t=629&p=3189&hilit=crushing#p3189

Regards,
Prem Baboo

PHYSICAL & CHEMICAL PROPERTIES OF UREA
Physical Appearance
Urea appears to be a white. It is normally translucent and comes in the form of a liquid or solid (pellets).
Odour
The smell of urea is almost non-existent. If a sample of urea is not odorless, it will have a slight ammonia scent.
Density
The density of this mineral is 1.33 g/cm3. Density is the ratio between the mass and volume.
Specific Gravity
The specific gravity of urea is 1.34 at room temperature: 68 degrees Fahrenheit or 20 degrees Celsius. This makes the mineral heavier than water.
Solubility
Urea is soluble in water. Its solubility ratio is 119 grams per 100 grams water at a temperature of 77 degrees Fahrenheit or 25 degrees Celsius.
Molecular Weight
The molecular weight, or molar mass, of urea is measured at 60.06 grams. This measurement indicates the mass of one mole of urea.
Decomposition
Urea decomposes at 270.8 degrees Fahrenheit (132.47 degrees Celsius); it decomposes into ammonia and carbon dioxide. If burned, it emits small amounts of nitrogen oxides
Properties & Definitions
Molecular Formula : CH4N2O
Molecular Weight : 60.06
Melting Point : 132.47 deg C
Boiling Point : decomposition** State
Crystal prismatic or powder
Flamable Limit : Non-flammable
Density : 1323 kg/m3 at 20-24 deg C
Vapour Pressure : 80 Pa (0.6 mmHg) at 20C
CAL*** Octanol/Water Partition : Coefficient -1.59 at 20-25 C
experimental Water Solubility : 1080 g/L at 20C Solubility in other :
Solvents 10 g/L in 95% alcohol, 167 g/L in methanol, 500 g/L in glycerol
Colour : Colourless to white
Taste Cooling, saline Odour : Almost odourless
Additives : Urea-formaldehyde binder can be used in some prilling processes.
Impurities : Biuret 0.3 – 2 wt%;
cyanates. Analysis of technical urea gave the followings: water (as moisture) 0.4 wt%;
free ammonia 0.4 wt%;
Fe 2+ < 0.02 wt%.
Degree of purity -98-99 wt%.
General Comments: *On further heating decomposes to biuret, NH3 and cyanuric acid. On standing or on heating decomposes to NH3 and CO2.
** Urea decomposes before boiling.***VP of saturated water solution=2kPa at 20C. Hypochlorites can react with urea to form the explosive compound, nitrogen trichloride.
Reacts violently with gallium perchlorate.
Tripple point- at 6535 atm-102.3 deg C
Heat of solution in water—57.8 cal/gm
Specific Heat at 25 deg C-0.460 cal/gm
Crystal Form- Tetragonal-Selando headral
Nitrogen Contents-46.6 %
Bulk Density 672.56 kg/m3
Critical relative Humidity-72 at 30 deg C
Angle of repose 23 Deg,(according to prills size varies from 23 degree to 28 degree)
Voscocity-2.58 CP
CAS No. 57-13-6
refractive index – n20/D 1.40

The Normal value of Chromium ,Nickel & Iron in Urea Product are
Iron-˂0.1 ppm
Nickel-˂0.02 ppm
Chromium˂0.03 ppm
If the value increase this the indication of corrosion , the passivation air must be increased in CO2 as well as stripper. Subjected to inerts analysis in MP vents (it must be far from explosive triangle range.). and also increase N/C ratio . The temperature of the reactor top reduce 1 degree and also stripper bottom reduce by 1 degree Cent.If there is no decreasing tends then shut down should be taken and check HP/MP vessels and others equipments.

Regards,Regards,
Prem Baboo