Report submission at Hindustan Petroleum Corporation Limited , Vizag

Why do oil refineries exist ?

• crude oil is very poor fuel.1. Wide boiling range-cannot burn cleanly or efficiently.2. Wide variation in composition and quality.3. Contains many impurities. (e.g. S,N,Metal)

• Refining1. The process used to convert crude oil into usable and

marketable products .

There are four main HC types produced in the refinary.

1. Paraffins (straight chain) e.g. c-c-c-c-c N-pentane paraffin good for diesel cetane.

2. Olefins (unsturated) e.g. c=c-c-c-c- Isopentane Olefins are reactive component.

3. Naphthenes (saturated ring) e.g. cyclopentane.

4. Aromatics e.g. Benzene Aromatics are good for gasoline octane.

• Refineries aim to maximise production of valuable lighter hydrocarbons.

• Crude also contain many contaminants .1. Sulphur compound2. Nitrogen compound 3. Oxygen compound 4. Salt 5. Water6. Drilling fluids 7. Metal compound

These have to be removed or reduced in refining.

Crude oil is mixture of various size of HC

Refining objective

• While meeting environmental and safety regulation

1. Make saleable product.2. Meet certain market demands. 3. Maximise product.

Primary refining step distillation

• Physical separation1. Separation of crude oil is achieved by the compounds

differing volatility.2. Crude oil is split into a number of cuts depending on boiling

point.3. Separation take place with a crude distillation unit (CDU) or

topping unit.4. Furthur separation of CDU residue in a vaccum distillation

unit (VDU).

Crude distillation unit

1. Represent the foundation of refining.2. Configuration can be simple or complex.3. Some flexibility in feedstock quality according to unit design.4. Can run in dedicated or block mode.5. Segregation is based on feedstock sweet , sour , lube oil ,

asphalt.6. Crude may be blended to achieve optimum operation.7. Involves only physical separation.8. Can significantly impact refineries economics.9. Can compensate for seasonal demand variation by varying

cut points .

Vaccum distillation unit (VDU)

1. Heavier fraction require high temperature . 2. Thermal cracking might occur .3. Results in loss of product and equipment fouling .4. Hence under vaccum boiling point decreases in

pressure. 5. 25-40 mm absolute pressure.6. Effective pressure upto 10 mm by addition of steam to

furnance Inlet and to bottom of the tower.7. Pressure is maintain by steam ejectors and barometric

condensers or vaccum pmps and surface condensers .

Need for addition of steam to furnace inlet

1. the tube velocity 2. Minimise coke formation3. Decreases the total hydrocarbon partial pressure4. Furnace outlet temp. are of the order of 388-454 C

Operating conditions

1. Dry • when no steam is added…. Gives highest Temperature.2. Wet • When steam is added to furnace inlet and to the

bottom of vaccum tower… Gives lowest temp.3. Damp • When steam is added to furnace inlet only… Gives

intermediate temperature

Catalytic reforming

• Main purpose

1. Convert low octane heavy nephtha from <60 RON to > 100 RON for gasoline.

2. Produce aromatics (benzene , toluene , xylene) for chemicals.3. Feed is heavy straight run ex. CDU or hydrocracker naphtha

which has an alternative value as petrochemical feedstock.4. Rearrange paraffins and nephtha to isoparaffins and

aromatics.5. High temp. medium or low pressure plus fixed bed or

circulating alumina/ nobel metal catayst

Catalyst reforming

1. Produce large amount of hydrogen for furthur use in refinery .

2. Feed has to be pre-treated to remove catalyst poison , sulphur & nitrogen .

3. Catalyst need to regenerated periodically and unit shutdown.

4. Run length depend upon severity of operation and feed quality .

5. Benzene and aromatics can be problem in gasoline blend.

Hydro treating

Why hydrotreat ?• Ans :- Gasoline need to be low sulphur , low

nephthenes and aromatics for diesel production.

• Hydrotreating reduce this compound and these require hydrogen come from catalytic reformer or hydrogen unit.

Fluid catalytic cracking (FCC)

• Main purpose :- Produce high volume gasoline component typical 92 RON / 82 RON .

• Feed is heavy vaccum gas oil , coker gas oils or residue.

• High temperature , low pressure plus circulating zeolitic catalyst.

• “Carbon out” process.• Medium to high investment cost.

Catalytic cracking product quality

• Propylene , butylene – unsaturated contains sulphur require treating then to chemical feedstock or alkylation.

• Catalytic cracker gasoline – good octane (90-92) unsaturates.

• Cataytic cracker cycle oil low octane no. , high density , high sulphur light to gas oil blending heavy to fuel oil blending.

• Catalytic slurry-heavy residue, cotains catayst fines.

Fluid catalytic cracking

• Coke formed on catalyst is source of heat for reaction.• Products olefinic and aromatic I. fuel gas II. Olefinic LPGIII. Gasoline IV. Gas oil component V. Light fuel component • Operating versality I. Can also run in middle distillate.II. ‘over cracking’ to produce light olefins.

• Level of carbon is feed limits operation unless excess can be removed.

• Paraffinic feeds are most easily cracked .• reliable long run operation.• Aromtic problem in gasoline blend.

alkylation

• Main purpose to produce high octane gasoline component.

• Combines light olefins (C3/C4 from the cataytic cracker) with isobutane from the CDU or reformer to produce a branched chain paraffins.

• Alkylate productI. High octane number (RON=94.5 ; MON=92.5)II. No aromatic , so good for reformulate gasoline.

Isomerisation

• Main purpose :- To increase octane of light naphtha from 75 RON to 85-90 RON.

• High MON product , 2 number lower then RON. • C5/C6 normal paraffin changed to isoparaffin also changed nC4 – iC4 for downstream reaction • Low temp. and medium pr. Plus fixed bed catalyst

Isomerisation Schemes

• Feed has to be treated to remove catalyst poison • sulphur • nitrogen • oxygen compound

• Need recycle to achieve high octane.• No aromatic in product

Hydrocracking

• Main purpose 1. High volume, high quality Diesel and jet kerosene Diesel cetane 55 plus Kerosene smoke point 25mm plus2. Can be designed for Gasoline component Low octane but good reformer bed

• Feed is light to heavy vaccum gas oil , FCC cycle oils , coke gas oils which would be normally used as fuel oil diluents.

• High temp. , very high pressure plus catalyst is fixed bed .

• Often need hydrogen unit.• Highly investment cost.

Main advantages of Hydrocracking over catalyst cracking are:-

• Flexibility of operation and product selectivity. • Maximum yield either Naphtha or diesel.• Less gas.• Virtually no fuel oil.• Essentially no coke.

• Clean & high quality product.• Sweet light naphtha can be blended directly to gasoline• Very low sulphur and nitrogen heavy naphtha for catalyst reforming.

• Environmentally clean unit.• No flue gas containing CO2 or solids produced.• Ammonia and hydrogen sulphide produced easily recovered

Visbreaking

• Main purpose :- 1. Reduce the viscosity of residue and therefore avoid

downgrading diluents (gas oil , kerosene) to fuel oil.2. Simple process , mild thermal cracking.3. Cheap , popular in areas when there is still a high fuel

oil market.4. Best for heavy residue.5. Stability of residue can be a problem some 5%

conversion to gas , naphtha and gas oils .

Coking

• Main purpose to reduce fuel oil make in refinery.• Feed is residue ex. VDU which has a value below that of fuel oil.• Low quality distillate products need further treatment.• High temperature and low pressure.• “Carbon out” process.• Low investment cost but can be labour intensive and

environmentally messy.• Most Coker produce high sulphur coke which can have a

disposal cost to refinery.• Can produce high grade coke if feed is low in Sulphur• Coke make is linked to the amount of carbon in the feed.

Types of Coker

• These type of coking unit:-1. Delayed Coker2. Fluid Coker3. Flexi Coker • Delayed coking produce a solid coke.• Fluid coking:- a smaller yield of granular coke .• Flexi coking a low quality gas.

Thank you

• Submitted by:-• Vishesh bhadariya (B.Tech 3rd yr Petroleum Engg.)• Dhruv vijay singh hada(B.Tech 3rd yr Petroleum

Engg.)• College:- University college of engineering ,

Rajasthan Technical University , Kota , Rajasthan.• Date :- 12/08/2013