Hydrocracking Processes

Question 1

What is the requirement for the feed of the HCK ?

Answer 1

The feed needs to not contain metal (catalyst poison)

Question 2

What are the products of the HCK ?

Answer 2

• Gas
• Light gasoline
• Heavy gasoline
• Kerosene
• Gas oil

Question 3

What is the consumption of H2 in a HCK ?

Answer 3

2 to 3 wt%

Question 4

What are the operating conditions in the HCK ?

Answer 4

• T : 350-400°C
• P : 160-180 bar
• H2 : 2-3 wt%
• space velocity < 1t of catalyst per t/h

Question 5

What are the two catalysts in the HCK ?

Answer 5

1. Ni-Mo on alumina (desulfuration, denitrogenation, hydrogenation)
2. Ni-Mo on acidic zeolite (hydrocracking)

Question 6

What is done to control the exothermicity of the HCK reaction ?

Answer 6

Quench with cold H2

Question 7

How are the products separated after the second reactor of the HCK ?

Answer 7

• HP separator (170 bar) to recover H2
• LP separator (20 bar) to recover gas + H2S
• Fractionation column

Question 8

What are the two reactors in a HCK ?

Answer 8

1. Hydrotreatment reactor

2. Conversion reactor

Question 9

What are the two functions of the catalyst in a HCK ?

Answer 9

• acidic function provided by the amorphous or crystalline alumina support
• hydrogenation property provided by metal

Question 10

How can unconverted oil from HCK can be used ?

Answer 10

• low sulfur for heqvy fuel blend
• recycled to HCK
• other cracking unit (FCC, thermal or steam cracking)
• base oil for lube

Question 11

What can be said about Gas and LPG produced in the HCK ?

Answer 11

• high iso/normal C4 ratio

- small fuel gas production

Question 12

What can be said about the light naphtha produced in the HCK ?

Answer 12

• high iso/normal C5 and C6 ratio

- higher octane than direct naphtha (75-85)

Question 13

What can be said about the heavy naphtha produced in the HCK ?

Answer 13

• low sulfur

- very paraffinic -> medium quality for gasoline base

Question 14

What can be said about the kerosene produced in the HCK ?

Answer 14

Good quality but low sulfur that is not required for jet fuel

Question 15

What can be said about the diesel produced in the HCK ?

Answer 15

• Good cetane number (a lot of paraffins and few aromatics)

- low sulfur

Question 16

What are the ways to produce H2 ?

Answer 16

• Reforming unit
• Steam Methane Reforming
• Partial Oxidation

Question 17

What are the reactants in the SMR ?

Answer 17

• Light and cheap HC (usually methane)

- Steam (oxydant)

Question 18

What are the chemicals reaction occuring in the SMR ?

Answer 18

• Steam reforming : CH4 + H2O ->

Question 19

What are the operating conditions in the SMR ?

Answer 19

1. 800°C, 25 bar, Ni catalyst

2. 340°C, 20 bar

Question 20

How is H2 purifyed after the SMR or POX ?

Answer 20

Pressure Swing Adsorption (molecular sieves)

Question 21

What are the reactants for POX ?

Answer 21

• Heavy HC (residues, asphalt)
• pure O2
• steam

Question 22

What are the reactions in a POX ?

Answer 22

1. Partial oxydation : HC + O2 -> CO + H2

2. Conversion of CO : CO + H2O -> CO2+H2

Question 23

What are the operating conditions in a POX ?

Answer 23

1. 1300-1450°C, 70 bar

2. 68 bar