Refining Model Answers

7/28/2019 Refining Model Answers

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Refining Model Answers (Note: these are not from the Facilitator, they are just proposed answers, so be guided! :)

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1. 10 Common Reactions & ExamplesReaction Examplei. Hydrogenation Benzene to Cyclohexaneii. Dehydrogenation Isopropanol to Acetone and Hydrogeniii.

Oxidation Ethane + oxygen to Ethylene oxide

iv. Reduction Acetaldehyde reduced to Ethanol & Hydrogenv. Halogenation Chlorination of Methanevi. Alkylation Benzene + Octane to give Octyl Benzenevii. De-alkylation Toluene to Benzeneviii. Esterification Ethanol + Ethanoic Acid to give Ester & waterix. Hydrolysis Ester + Water to give Ethanol & Ethanoic Acidx. Polymerization n(ethylene) to give polyethelene

2. Typical Petrochemical Plant Equipment Crystallizers Settling tanks Cyclones Evaporators Filters Tubular reactors Leaching plant Continuous Stirred Tank Reactors (CSTR)

3. Primary Feedstocks to Petrochemical PlantsFeedstock SourceSynthesis Gas (CO & H2) Steam-Reformed natural Gas or Liquid HC

Olefins Treated refinery gases from FCC fractionator

Aromatics Refinery liquids e.g. reformates (BTX)

4. List 5 6 other compounds produced during BTX productionEthylbenzene; Styrene; Nitrobenzene, Phenols, Chlorobenzene; Cyclohexane

5. Describe the process of recovering valuable HCs from Vacuum Residue The process is Propane De-asphalting Unit (PDU), which dissolves Vacuum/Short residue (Feedstock from HVDU) by

counter-current washing with liquid propane in a Rotating Disc Contactor.

Major outlines of the process are as listed below:

RDC Conditions: Temperature 70750C at the top, 39400C at the bottom; Pressure 32 bars at the base SolventLiquid propane


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Vacuum Resid Feed (heavier component with SG 0.98) enters from the top Liquid Propane (Lighter component with SG 0.47) enters from close to the bottom Liquid propane dissolves the oil De-asphalted oil (DAO) leaves the tower top (10% wt Oil, 90% Propane) Propane-Asphalt (PA) leaves the tower base (77% wt Asphalt, 23% Propane) Both product streams go through independent evaporation and stripping for propane recovery Recovered propane vapour from both recovery sections is compressed, cooled and recycled to the RDC

6. List the equipment used to remove wax from Waxy Raffinates & their usesEquipment UsesDouble-pipe Heat Exchanger Chills the charge mix

Chiller To drop the temperature to the filtration temperature

Heater Heats waxy raffinates to 25oC to ensure that the wax dissolves completely

Rotary Vacuum Filter Separates crystallized wax from the oil in the form of a thin cake using inert gas,

usually Nitrogen.

Stripper Used to strip off all final traces of solvent from the oil

Evaporator Used for the dewaxed oil recovery

Propane-Asphalt

(77% wt Asphalt, 23% Propane)

DAO

(10% wt Oil, 90% wt Propane)

Liquid Propane (solvent)

Vacuum Resid (from HVDU)

RDC


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7. How do you recover Waxy Distillates?Waxy distillates from HVDU and DAO from PDU, which together are rich in polyaromatics known to impact

negatively on the oxidation stability and viscosity index of oil, are recovered in Furfural Extraction Unit, where these

feedstock is passed through a counter-current liquid-liquid extraction process using Furfural as solvent in a

Rotating Disc Contactor.


Furfural, the solvent, selectively dissolves the aromatics. Furfural (heavier component) enters from the top of RDC Waxy distillates (Lighter components) enter from the bottom Operation is batch-wise, as each feed is processed separately Top product stream: 15-20% wt Furfural, 80-85% Waxy Raffinate Bottom product stream: 80-90% wt Furfural, 10-20% wt Extract Both product streams go through independent solvent recovery and steam stripping to remove all the Furfural Recovered Furfural from both recovery sections is condensed, dried and recycled to the RDC

8. Describe Furnace Process Production of Carbon BlackCarbon Black can be defined as elemental carbon made under conditions permitting control of its particle size, degree of

particle agglomerization and surface chemistry. It mainly contains elemental carbon, ash, volatile hydrocarbons, and

oxygen compounds.

There are 3 types of Processes for Carbon Black Production viz:

1. The Channel Process (Channel black)2. The Thermal Process (Thermal black)3. The Furnace Process (Furnace black)

The Furnace Process Production Process

Extract

(80-90% wt Furfural, 10-20% wt Extract)

Waxy Raffinate

(15-20% wt Furfural, 80-85% Waxy Raffinate)

Feed (Waxy

Furfural (solvent)

RDC


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This is a controlled incomplete combustion /thermal decomposition of feed in the presence of air and fuel gas

(mainly propane) and pyrolysis of the remainder. The exothermic oxidation furnishes the energy for the

endothermic pyrolysis.

Feed: Natural Gas; Petroleum Distillates; Decanted Oils (DCO) from FCCU and Residue from Thermal processesthat are rich in Aromatics


Air (@1000C) absorbs heat in the air pre-heater and goes into the reactor & gets to the Trxn (1000-12000C)in the reactor

DCO is filtered to remove entrained FCCU catalyst Decanted Oil (@300C) absorbs heated to Tvap (300-4000C) in the oil pre-heater and goes into the reactor,

absorbs Hvap to get heated to oxidation reaction temperature (1000-12000C)

Fuel gas provides auxiliary fuel to the reactor to aid pyrolysis Residence time in the reactor is controlled by quenching with water/steam Agglomerator: Control of particle size and specific surface by controlling the rate of agglomeration Bag Filters: Separation of flue gas from carbon black Cyclones: Complete recovery of products from the flue gas Palletizer: Control of PH of carbon black by water and/or chemical (NaNO3) injection. Products leave as

slurries, for the dryer Dryer: Carbon black from the palletizer is dried, and then sent via a bucket elevator to the screener, passing

through the Magnetic Separator that removes any metallic substance. Screener: Separation into various fractions/sizes for storage.

9. Describe Asphalt in terms of the 2 types, characteristics & how they are measured, 4 processes in ABUSources of Raw Asphalt:

Distillation: HVDU. Air Blowing: ABU Precipitation/Extraction: PDU


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2 Types of Asphalts are:(1.)Cured or Cut-Back Asphalt -(2.) Blown or Solid Grade Asphalt

Cured or Cut-Back Asphalt Blown or Solid Grade AsphaltGenerally produced by blending a petroleum solvent (kero, naphtha

etc) with Asphalt.

Rapid Curing Asphalt: A blend with more volatile solvent, Naphtha,which hardens very quickly.

Medium Curing Asphalt: A blend with less volatile solvent, Kerosene,which hardens less quickly.

Produced by air blowing or, sometimes, by direct

blend of PAS and Vacuum Residue-2.

Air blowing produces changes in asphalt by

chemical reaction thereby improving on the

penetration and softening point specifications.

Therefore, blown asphalt is harder and brittle.

Identifying & Determination of Asphalt characteristicsSoftening Point is determined using Ring and Ball tester and is the temperature at which the ball placed on a ring ofheated asphalt falls through the ring and it varies from 45oC for 80/100 to 58oC for 50/60 grade.

Penetration is a measure of hardness and is the distance a needle under a standard load will penetrate the asphalt in 5seconds at a specified temperature, usually 77oF (25oC), measured in 1/10 mm unit. The expression 50/60 Pen asphalt

refers to an asphalt with a hardness of between 50 and 60.

Flash Point: It Varies from 225oC for 80/100 to greater 250oC for 50/60. Test: soften the asphalt between 75-1000C, stirrigorously to remove air bubbles & water, then fill into a cup, fix the open clip and insert thermometer while stirring

continues, then light the test flame & supply heat to ensure 5-60C/min rise in thermometer reading. Temperature at which

a flash first appears on the surface of the material is the flash point.

10.Schematic PFD for Linear Alkyl Benzene (LAB) plantRaw Materials: kerosene & Reformate.

Five units are involved :

Kero Hydrodesulfurisation Unit (HDS): removes S and N impurities that are poisons to molecular sieves and catalysts indown stream Units.

Molex Unit takes the Treated Kerosene as feed using adsorption/desorption processes on zeolite molecular sieve toseparate normal paraffins (C10 to C14) from the isoparaffins.

The Pacol unit converts the C10C

14normal paraffins to the corresponding linear olefins on Platinium on Alumina

support base catalyst. Linear olefins are the first real raw material for LAB production.

Thermal Hydrodealkylation Unit (THDA) produces mainly Benzene, and some Toluene. HF Alkylation Unit: Linear olefins from the Pacol Unit and Benzene for THDA Unit are reacted together in the presence of

HF acid as the catalyst to produce mainly Linear Alkyl Benzenes (LAB) and Heavy Alkylates as byproducts.


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11.Draw and describe the Wax Hydro-finishing Process Raw material is dewaxed oil; Product is called Base Oil It is a batch process whereby wax is hydrotreated to reduce its aromatic, oxygen, nitrogen, and sulphur

contents, in a fixed bed reactor with Nickel/Molybdenum Catalyst on alumina support in the presence of

high partial pressure hydrogen.

Operating conditions: 250-400 oC and 50-110 kg/cm2. Hydrocracking and Isomerization are minimised to avoid off-spec products The finished products are grades A, B and C white commercial waxes

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