W9- Downstream Processes

Question 1

Overall stages of refining

Answer 1

Pre-treatment, separation, conversion, treatment

Question 2

Desalting (Pre-treatment)

Answer 2

Hot water for extraction agent and electrostatic potential difference (electrostatic separator).
Remove salt, water, sediments, and suspended solids

Question 3

Problem if salts not removed from crude oil

Answer 3

fouling and corrosion in pipes downstream

Question 4

O&G Separation

Answer 4

Split crude oil feeds into HC cuts, with light HC vaporising and rising up and heavier drawn at bottom

Question 5

Fractional Distillation (ADU) (Separation)

Answer 5

Straight-run cuts from different boiling fractions separated: light & heavy naphtha, kerosene, atmospheric gas oil and residue.

Fractionator collects separate crude cuts as they condense on tray at Temp below BP.

Question 6

Fractionator internals (Separation)

Answer 6

Bubble caps (prevent condensate flowing down, allow vapour flow up)
Downcomers (ensure vapour/liquid flow separately)
Income/outcoming weirs (prevent waves on each tray)
Valve trays (collect condensed liquid)

Question 7

Vacuum Distillation (VDU) (Separation)

Answer 7

Separates high BP material from ADU residue & avoids too high temp in separating the residue.

Higher temps would result in thermal cracking

Question 8

Conversion & types

Answer 8

Increase yield of high-value HC products.

Cracking, catalytic reforming, isomerization, oligomerization (alkylation & polymerisation).

Question 9

Steam Cracking (Conversion)

Answer 9

Steam used to produce unsaturated HCs from alkanes

Products: ethylene, alkenes/alkynes.

Question 10

Hydrocracking (Conversion)

Answer 10

Cracks lighter waxes in crude with H2 to produce high-demand lighter oil fractions.
Wax is hydrotreated before cracked & S removal to ensure sweet (low S).

Products: Naphtha, diesel oil, gas oils.

Question 11

Fluid Catalytic Cracking (FCC) (Conversion)

Answer 11

High temp and zeolite-based catalyst to crack heavy gas oils & wax (ADU residue and vacuum gas oil) into lighter fractions and components for blending.
Feedstock is pre-heated and vaporizes in contact with a hot catalyst.

Products: Naphtha, gas oils, fuel oil

Question 12

Coking (severe thermal cracking) (Conversion)

Answer 12

Thermal cracking (heavy wax upgrade to lighter cuts)
Converts VDU residue to lighter valuable distillate products, off-gas and petroleum coke.

Heavy product remains as solid coke- periodically removed.

Products: Naphtha, gas oil, coke

Question 13

Catalytic Reforming (Conversion)

Answer 13

Improve naphtha quality by enhancing aromatic content - increase of ON.

(Aromatics=high ON, paraffins = low ON)

Question 14

Isomerization (Conversion)

Answer 14

Chemical transformation of molecule to other form, with same molecular formula (normally branched).

Increase ON as branched molecules = high ON

Question 15

Oligomerisation (Alkylation & Polymerisation) (Conversion)

Answer 15

Combine light gaseous HCs to increase MW and ON.

Question 16

Hydrotreating (Treatment)

Answer 16

Removes harmful components (s-N2-O2-metals) from HCs using H2 over a metal catalyst.

Question 17

What happens if S left/burnt?

Answer 17

Toxic gas oxides yield corrosive acids that destroy catalysts, equipment etc.

Question 18

Hydrosulpherisation (Treatment)

Answer 18

Catalytic HC vapour hydrogenation/S removal.

Question 19

Amine Gas Treater (Treatment)

Answer 19

Gas sweetening to remove CO2/H2S from gases via aqueous amine solutions (absorption column).

Question 20

Claus Sulfur Units (Treatment)

Answer 20

Sulfur recovery from previously captured H2S in amine gas treater.
H2S converted into sulfuric acid/S to be sold as feedstock for fertilisers, medicine etc.

Question 21

Ethylene & Olefins Production & source

Answer 21

Steam cracking process using light HCs (Mainly Naphtha, else ethane, propane, butane).

Steam transports HC feedstock into heaters and cracked -> ethylene, H2, other olefins

Question 22

Ethylene derivatives

Answer 22

Plastics: polymerisation with catalyst for ethylene into PE;
Intermediates, reactive/flammable feed (converted for stability first)