Based on the dynamic method

a quaternary system of ammonium polyphosphate (APP)-urea ammonium nitrate (UAN

CO(NH

2

)

2

-NH

4

NO

3

)-potassium chloride (KCl)-H

2

O and its subsystems (APP-[CO(NH

2

)

2

-NH

4

NO

3

]

-H

2

O

KCl-[CO(NH

2

)

2

-NH

4

NO

3

]

-H

2

O and APP-KCl-H

2

O) were systematically investigated at the temperature of 273.2 K. Each ternary phase diagram contains one invariant point and three crystallization regions. The crystallization regions are: (1) (NH

4

)

3

HP

2

O

7

(NH

4

)

4

P

2

O

7

and ((NH

4

)

3

HP

2

O

7

+ (NH

4

)

4

P

2

O

7

) for APP-[CO(NH

2

)

2

-NH

4

NO

3

]

-H

2

O diagram; (2) KCl

KNO

3

and (KCl + KNO

3

) for KCl-[CO(NH

2

)

2

-NH

4

NO

3

]

-H

2

O diagram and (3) (NH

4

)

3

HP

2

O

7

KCl and ((NH

4

)

3

HP

2

O

7

+ KCl) for APP-KCl-H

2

O diagram. The quaternary phase diagram of APP-[CO(NH

2

)

2

-NH

4

NO

3

]

-KCl-H

2

O has no quaternary invariant point but includes four solid phase crystallization regions

i

.

e

.

(NH

4

)

3

HP

2

O

7

(NH

4

)

4

P

2

O

7

KNO

3

and KCl

in which the KNO

3

region occupies the largest area. The maximum total nutrient content (N + P

2

O

5

+ K

2

O) existing as ionic forms in the APP-[CO(NH

2

)

2

-NH

4

NO

3

]

-H

2

O

KCl-[CO(NH

2

)

2

-NH

4

NO

3

]

-H

2

O

APP-KCl-H

2

O and quaternary systems is 44.70%

32.86%

45.56% and 46.23% (mass)

respectively

indicating that the maximum nutrient content can be reached using raw materials of the corresponding systems to prepare liquid fertilizer. In the quaternary system

the content of ascends with the increase of the total nutrient content

while the contents of and CO(NH

2

)

2

-N increase with elevated total N. This work can help optimize the operating parameters for the production

storage and transportation of liquid fertilizers.