FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
COMPLETE SPECIFICATION (See section 10; rule 13)
1. Title of the invention: Manufacturing of Water Soluble
Urea Phosphate (17:44:00)
2. Applicants
a. Name : Shri BJ Joshi and Shri K AChaudhary
b. Nationality : Indian
c. Address : IFFCO Kandla, Distt. Kutch, Gujarat (India)
The following specification describes the invention (in case the specification is provisional)
Not Applicable as specification is complete
The following specification particularly describes the invention and the manner in which it is to be performed (in case the specification is complete):
Urea phosphate is an organic compound composed of carbon, hydrogen, nitrogen, oxygen and phosphorus. Its formula is CO(NH2)2.H3P04. It is a dry, white crystalline material and contains 17% nitrogen (N) and 44% P205. Urea phosphate is acidic & highly soluble in water. The complex chemistry in manufacturing arises due to the quality of phosphoric acid and this offers distinct advantage of optimizing the various process parameters for increasing yield, quality and efficiency in the process. IFFCO has carried out various experiments and developed a process suitable for industrial production and based on the inferences of the experiment, a 50 MTPD plant has been successfully designed and is in operation at IFFCO - Kandla, Gujarat.
The specifications of the product is provided in the following table:

Sr. No.
Composition (% wt / wt) Urea Phosphate
1. Total P2O5 (minimum) 44.0
2. Total Nitrogen as N (minimum) 17.0
3. Sulphate as So4 (maximum) 0.3
4. Fluorine as F % (maximum) 0.1
5. Iron as Fe2O3 % (maximum) 0.2
6. Aluminum as AI2O3 (maximum) 0.1
7. Magnesium as MgO (maximum) 0.05
8. Calcium as CaO % (maximum) 0.01
9. Moisture % (maximum) 0.5
10. Bulk Density (gm/cc) 0.8 to 1.0
The particle size distribution is provided in the following table :

s.no particle size microns Percentage by weight
1 less than 100 0 to2
2 100 to 200 30 to 40
3 200 to 400 40 to 50
4 400 to 600 10 to 20
5 600 to 800 5 to 10
6 800 to 900 0to5
Presented below is the approach to innovative process for obtaining the product:
I) PROCESS DESCRIPTION FOR MANUFACTURE OF UREA PHOSPHATE FERTILISER
The manufacture of water soluble Urea Phosphate is carried out in which:
(i) The reaction is a batch process and two reactors are alternately taken for
batch reaction, (ii) The process of crystallization is also a batch process with retention time of
2 hours (iii) Centrifuging and drying is a continuous process.

REACTION VESSEL
Phosphoric acid of 50 - 54% P2O5 concentration is taken into the reaction vessel. The phosphoric acid feed into the reaction vessel is metered by using a magnetic flow meter in the reactor inlet line. At the beginning of making the batchy phosphoric acid in reactor is heated to 70 - 75 °C by steam coils which are installed along the circumference of the reactor. The coils are specifically designed to ensure that the entire phosphoric acid temperature rises to 70 - 75 °C. This temperature helps in fast dissolution of urea with better Urea Phosphate crystal quality (larger crystal size) and increase in the final yield.
Urea is fed into the reactor at fixed weighed quantity which is determined on the basis of quality of phosphoric acid. The urea should be pure and free from foreign impurities for efficient operation of centrifuge.
An agitator is provided for increasing the contact of urea particles with phosphoric acid in the reaction vessel which helps in obtaining super saturated slurry. The following reaction takes place between phosphoric acid and urea:
H3PO4 + NH2CONH2 NH2CONH2.H3PO4
(Phosphoric acid) (Urea) (Urea Phosphate)
Crystalline urea phosphate is an adduct of urea and phosphoric acid. The slurry consists of crystalline urea phosphate embedded in the liquor. For enhancing final yield & crystal size, the slurry is cooled by circulating cooling water in the coils to lower down the temperature up to 45-50°C. Mother liquor obtained after centrifuging operation is recycled to the reactor in 1:1 ratio of phosphoric acid. This helps in lowering the slurry temperature and fluidity. The specific gravity and Percentage solids of the slurry is 1.42 - 1.45 and 70 - 75% respectively.
. Phosphoric acid, concentration and impurities affect the reaction efficiency and yield. Higher P205 concentration and I ower impurities in the acid lead to higher reaction efficiency and yield as well as better crystal nuclei growth is obtained.
CRYSTALLISER
The solution from the reaction vessel is pumped to a draft tube type crystallizer. The feed enters the crystallizer at about 45 - 50 °C and slurry is cooled by adiabat'tc

cooling. Feed is flashed under vacuum to reduce the temperature and by flashing of water, temperature is lowered to 25-30 °C. Water evaporation takes place in the specially designed crystallizer under the vacuum. Vacuum is created in the crystallizer using steam jet booster/ejectors. Vacuum of 700 - 720 mm Hg is maintained in the crystallizer. Due to lowering of the temperature, slurry will become super saturated and crystallization takes place. Draft Tube Type arrangement is provided with Propeller type Agitator at bottom of Crystallizer in order to increase the crystal size and dissolve fines generated during crystallization. The slurry is transferred to clarifier from crystalliser.
CENTRIFUGAL SEPARATION
Concentrated slurry from clarifier is pumped to continuous pusher type centrifuge. The urea phosphate crystals containing 3 to 4% moisture separated out and fed to dryer for drying operation. The urea phosphate separated is free from the major impurities in phosphoric acid.
The mother liquor generated, containing all the impurities of phosphoric acid is collected into the mother liquor tank which is reused in the process or may be used in manufacturing process for suitable grades of phosphatic fertilisers.
DRYING
Urea Phosphate crystals obtained from the centrifuge contains around 3 to 4% moisture. The urea phosphate crystals are passed through a Rotary dryer. Clean hot air is generated by heating air with steam. Drying is carried out at temperature of 70 to 80°C. The hot air is fed concurrent to the product through special air distribution arrangement that maximizes the contact of hot air with the product.
Different types of flight arrangements and low speed of dryer help in optimizing the retention time for drying as a result of which dry urea phosphate crystals containing less than 0.5 % moisture is obtained at the dryer outlet. Dry crystalline Urea Phosphate from the Rotary dryer is packed in pouches.

FINE DUST RECOVERY
Fine crystals during the drying action flow out along with the hot air. These fine crystals are recovered in the cyclone and further scrubbing is done with water in counter current venturi. The air free from dust particles are vent through stack. The water discharged from venturi is collected and used in phosphatic fertilizer plant. This has made the process environment friendly.
II) LABORATORY EXPERIMENTS
The following experimental examples have helped in developing the process for production of urea phosphate:
Raw materials used for the experiments
1.0 Phosphoric acids of various concentrations received at IFFCO - Kandla plant.
2.0 Urea prills
3.0 Mother liquor (separated during centrifuging of Urea Phosphate slurry)
Specifications
1.0 Phosphoric acid

Sr. No. Composition Content as Phosphoric Acid
1. Total P205 (%wt./wt.) 50 to 54
2. Sulphate as S04 (%wt./wt.) 1 to 4
3. Fluorine as F (%wt./wt.) Less than 1 %
4. Iron as Fe203 (%wt./wt.) Less than 2 %
5. Aluminum as Al203 (%wt/wt.) Less than 2 %
6. Magnesium as MgO (%wt./wt) Less than 1 %
7. Calcium as CaO (%wt./wt.) Less than 0.5 %
8. Specific Gravity at 30°C (%wt./wt.) 1.60 to 1.67
2.0 Urea prills (46% N)
3.0 Mother liquor
It is a saturated solution of urea phosphate separated While centrifuging the slurry.
Typical analysis of the mother liquor (at 30 °C).

Sr. No. Composition Content as L
Mother liquor
1. Total P205 (%wt./wt.) 25.31
2. Total Nitrogen as N (%wt./wt.) 9.21
3. Sulphate as S04 (%wt./wt.) 6.89
4. Fluorine as F (%wt./wt.) 1.15
5. Iron as Fe203 (%wt./wt.) 2.95
6. Aluminum as Al203 (%wt./wt.) 1.86
7. Magnesium as MgO (%wt./wt.) 0.50
8. Calcium as CaO (%wt./wt.) 0.26
9. Specific Gravity at 30°C (%wt./wt.) 1.39
Example 1:
Objective: To study effect of crystallisation temperature on Urea Phosphate yield
300 g of wet process Phosphoric acid, and 130 g prilled Urea (46% N) were allowed to react at 30°C (ambient temperature) in reaction beaker. On continuous agitation, urea dissolves in the acid with rise in temperature 60 to 65°C due to exothermic reaction. After the reaction ceases, 50 ml of mother liquor added in the reaction vessel to maintain fluidity in the slurry. Different set of the experiment were made and final cooling of slurry done at various temperatures to study the yield of urea phosphate obtained. The slurry was cooled for 2 hours and centrifuged to separate urea phosphate crystals.
The experiment results of Urea phosphate yield with variation in cooling temperatures are as below:

Crystallisation Temperature
(°C> 5 10 15 20 25 30 35 40
Yield (grams) 302 292 274 252 225 206 180 163


Conclusion:
It was found that urea phosphate yield increases with decrease in crystallization temperature. With experimental results, at 40°C, the yield is 163 grams and at 5°C, yield is 302 grams. Hence, by reducing the temperature by 35°C, the yield increases by 139 grams (85% increment of yield.).
Example 2:
Objective : To study effect of crystallisation time on Urea Phosphate yield
300 g of wet process Phosphoric acid, and 130 g prilled Urea (46% N) were allowed to react at 30°C (ambient temperature) in reaction beaker. On continuous agitation, urea dissolves in the acid with rise in temperature 60 to 65°C due to exothermic reaction. After the reaction ceases, 50 ml of mother liquor added in the reaction vessel to maintain fluidity in the slurry. Final slurry is cooled to a temperature of 25 °C and centrifuged to separate urea phosphate crystals. The yield (urea phosphate crystals) determined for different sets at different retention time given for

crystillsation is in the below tables.

Crystallization Time (hours) 1 2 3 4
Yield (grams) 180 225 230 225

Conclusion:
It was found that high yield was obtained with crystallization retention time of 2 to 3
hours.
Example 3:
Objective: To study effect of crystallisation temperature on Urea Phosphate crystal size
The experiment was carried out at different crystallization temperature for the growth
of urea phosphate crystals. 300 g of wet process Phosphoric acid, and 130 g prilled Urea (46% N) were allowed to react at 30°C (ambient temperature) in reaction beaker. On continuous agitation, urea dissolves in the acid with rise in temperature 60 to 65°C due to exothermic reaction. After the reaction ceases, 50 ml of mother liquor added in the reaction vessel to maintain fluidity in the slurry. Final slurry was cooled and centrifuged to separate urea phosphate crystals.

The experiment was carried out for different sets to observe the variation of crystal size with temperature as shown below:

Crystal size (microns) 500 600 700 700 725
Crystallisation
0
Temperature ( C) 5 10 15 20 25

Conclusion:
It was found that by increasing the crystallization temp, up to 25°C, Urea Phosphate crystal size increases and beyond 25°C,increase in crystal size is negligible. Hence, at 25°C crystallization temperature is an optimum temperature for a better crystal size with quality yield.
Example 4:
Objective : To study the effect of pre-heating of phosphoric acid of different concentrations on urea phosphate crystallisation:
Example 4.1 : Study made with phosphoric acid temperature at 30 °C.
The experiment was carried out for P2O5 concentration varying from 50% to
54% at 30°C. Three phosphoric acid samples each of quantity 1kg of different P205

concentration acid were taken in a reaction vessel at 30°C. Different quantity of area was added to each phosphoric acid sample. The reaction was allowed to take place at 30°C for one hour with constant stirring. The resultant product was cooled to 25°C and centrifuged to separate Urea phosphate crystals. The inference drawn are as under:

Phosphoric acid % P2O5 urea
temperature 50 52 54 added (in grams)
N.C. N.C. P.C. 500
30 °C P.C. C C 450
C C c 400
N.C.: No crystallization P.C. : Poor crystallization C : Good crystallization
Conclusion:
It was found that crystallization did not take place when urea addition was high with lower P2O5 concentration phosphoric acid as higher urea content cools down reaction temperature on dissolution with water content in acids. It is concluded that with lower P2O5 concentration phosphoric acid, urea addition has to be lowered than the theoretical ratio for achieving crystallization.
Example (4.2): Study made with phosphoric acid temperature at 50 °C.
The experiment was carried out for P2O5 concentration varying from 50% to 54% at 50°C. Three phosphoric acid samples each of quantity 1kg of different P2O5 concentration were taken in a reaction vessel at 50°C. Different quantity of urea was added to each phosphoric acid sample. The reaction was allowed to take place at 50°C for one hour with constant stirring. The resultant product was cooled to 25°C and centrifuged to separate Urea phosphate crystals. The inferences drawn are as under:

Phosphoric acid temperature % P2O5 urea

50 52 54 added (in grams)
50 °C P.C. c C 500

c c c 450

c c c 400
P.C.: Poor crystallization C : Good crystallization
Conclusion:
It was found that preheating of Phosphoric acid favours crystallisation.
Example(4.3): Study made with phosphoric acid temperature at 70 °C.
The experiment was carried out for P2O5 concentration varying from 50 % to 54% at 70°C. Three phosphoric acid samples each of quantity 1kg of different P205 concentration were taken in a reaction vessel. Different quantity of urea was added to each phosphoric acid sample. The reaction was allowed to take place at 70°C for one hour with constant stirring. The resultant product was cooled to 25°C and centrifuged to separate Urea phosphate crystals. The inferences drawn are as under:

Phosphoric acid temperature % P2O5 urea
added (in
grams)

50 52 54

70 °C C c C 500

c c C 450
c c C 400
Conclusion:
It was found that excellent crystallization took place with different P2O5 concentration
when phosphoric acid temperature was increased to 70°C.

We claim:
1. A process for producing solid urea phosphate from phosphoric acid and urea with different concentrations of phosphoric acid by suitable variations in process of manufacturing as concluded in the above cited examples.
2. A process of manufacturing urea phosphate in which steam and cooling water coils are installed along the circumference of reactor for heating phosphoric acid to 70 - 75°C before addition of urea to the reactor for reduction in reaction time and lowering down of temperature of slurry to 45 - 50°C respectively. This improves crystal growth and helps in better size separation during centrifuging operation. This special feature has helped in use of lower concentration of phosphoric acid up to 50 % P205
3. A process of manufacturing urea phosphate in which rotary dryer has been designed with suitable types of flights, proper retention time and hot air feeding arrangement to obtain moisture content consistently less than 0.5%.
4. A process of manufacturing urea phosphate in which reducing the crystallization temperature, crystals of more than 500 microns are consistently obtained. The specially designed bottom agitator has helped this process by giving uniform temperature of cooling the slurry mass in the crystalliser.
5. Mother liquor which is mainly saturated solution of the urea phosphate containing impurities of wet process phosphoric acid is used in the DAP/ NPK plant.
6. The process is able to recover the dust particulate matter by using high efficiency cyclone and venturi scrubber making it environment friendly.