Material balance of Diesel production plant. Calculation of Make up hydrogen requirement.

1. Chapter 3: Material balance
A mass balance, also called a material balance, is an application of conservation of mass
to the analysis of physical systems. By accounting for material entering and leaving a
system, mass flows can be identified which might have been unknown, or difficult to
measure without this technique. Mass balances are used widely in engineering and
environmental analyses. Material balances are fundamental to the control of processing,
particularly in the control of yields of the products. When any changes occur in the process,
the material balances need to be determined again.
Basis: 5000 kg/hr. of Vacuum Gas Oil (VGO) is fed to the unit [16].
Feed streams (wt. %) Product streams (wt. %)
VGO 100.00 FG 1.83
Hydrogen 2.25 LPG 4.83
Light Naphtha 12.83
Heavy Naphtha 3.33
ATF / Kerosene 39.78
Diesel 39.63
Total 102.25 Total 102.25
Reactor – 1
Stream Component
Flow
rate
2 VGO 5000.00 kg/hr.
H2 Required (wt. %) 2.25
H2 Excess (wt. %) 12.88
1 H2 644.00 kg/hr.
Conversion 60%
VGO Converted 3000.00 kg/hr.
VGO unconverted 2000.00 kg/hr.
H2 Converted 67.5 kg/hr.
H2 unconverted 576.5 kg/hr.
Product Mixture 3067.5 kg/hr.
H2/VGO (molar ratio) 21.81

2. Make up Hydrogen Required = H2 Converted
= 67.5 Kg /hr.
H2 Converted = (VGO feed) * 2.25 / 100
= 5000 * 2.25 / 100
= 67.5 Kg/hr.
Product Mixture = VGO converted + H2 Converted
= 3000 + 67.5 = 3067.5 Kg/hr.
Separator – 1
Stream Component
Flow
rate
3 Product 5644.00 kg/hr.
4 H2 576.00 kg/hr.
5 VGO + Product Mixture 5067.50 Kg/hr.
Reactor – 2
Stream Component
Flow
rate
13 VGO 2000.00 kg/hr.
H2 required (wt. %) 2.25
H2 Excess (wt. %) 15.40
14 H2 308.00 kg/hr.
Conversion 100%
VGO Converted 2000.00 kg/hr.
VGO unconverted 0.00 kg/hr.
H2 Converted 45.00 kg/hr.
H2 unconverted 263.00 kg/hr.
Product Mixture 2045.00 kg/hr.
H2/VGO (molar ratio) 26.08
Make up Hydrogen Required = H2 Converted
= 45.00 Kg /hr.
H2 Converted = (VGO feed) * 2.25 / 100

3. = 2000 * 2.25 / 100
= 45.00 Kg/hr.
Product Mixture = VGO converted + H2 Converted
= 2000 + 45 = 2045.00 Kg/hr.
Separator – 2
Stream Component
Flow
rate
15 Product 2308.00 kg/hr.
16 H2 263.00 kg/hr.
17 Product mixture 2045.00 Kg/hr.
Fractionator
Stream Component
Flow
rate
6 Feed 7112.5 kg/hr.
7 FG 91.67 kg/hr.
8 LPG 241.67 kg/hr.
9 Light naphtha 641.67 kg/hr.
10 Heavy naphtha 166.67 kg/hr.
11 ATF/ kerosene 1989.17 kg/hr.
12 Diesel 1981.67 kg/hr.
13 VGO unconverted 2000.00 kg/hr.
Total 7112.5 kg/hr.
Total Product Mixture = Product Mixture (Reactor 1 + Reactor 2)
= 3067.5 + 2045
= 5112.5 Kg/hr.
Diesel flow rate = (Total product mixture) * 39.63 / 102.25
= 5112.5 * 39.6 / 102.25
= 1981.67 Kg/hr.