(2)hydrocracking technology

8/10/2019 (2)Hydrocracking Technology

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HYDROCRACKING 12

Hydro-crackingProcesses

Hydro-Cracking processes

CHAPTER 02


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HYDROCRACKING 13

CHAPTER

02 Hydro-crackingProcesses

Recent Advances in Hydro-cracking:Hydrocracking is a versatile catalytic refining process that upgrades petroleum feedstocks

by adding hydrogen, removing impurities and cracking to a desired boiling range.Hydrocracking requires the conversion of a variety of types of molecules and ischaracteri ed by the fact that the products are of significantly lo!er molecular !eightthan the feed. Hydrocracking feeds can range from heavy vacuum gas oils and coker gasoils to atmospheric gas oils."roducts usually range from heavy diesel to light naphtha. Hydrocrackers are designedfor and run at a variety of conditions depending on many factors such as type of feed,desired cycle length, e#pected product slate but in general they !ill operate at the

follo!ing range of conditions$ %H&' - (.)-2.( hr-1, H2 circulation - ),(((-1(,((( &C*+)(-1, (( /03 03 , H2"" 1,)((- 2,((( "isa 1(3-13 bars and & 4 temperatures

ranging bet!een 5 ) and 2) * 3) -3 ) C . Hydrocracking is particularly !ell suited togenerating products that meet or e#ceed all of the present tough environmentalregulations.

Brief History:

6he large scale industrial development of hydrogenation in 7urope, "articularly in

8ermany, !as due entirely to military considerations. 8ermany used hydrogenatione#tensively during 9orld 9ar :: to produce 8asoline$ 3.) million tons !ere produced in1;


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HYDROCRACKING 1et aircraft in the late1;)(s increased the demand for diesel fuel and >et fuel. 6he fle#ibility of the ne!lydeveloped hydro cracking processes made possible the production of such fuels fromheavier feed stocks.

Flow c!e"es:

'arious licensors have slightly different names for their hydrocracking units flo! schemes, but ingeneral, they can be grouped into ma>or t!o categories$ single stage and t!o stages. 6able belo!sho!s the general evolution of flo!s schemes, generally driven by improvements in catalysts.

ingle tage #nce-T!ro$g! Hydrocracking:

*igure belo! sho!s a schematic of a single stage, once through hydrocracking unit,!hich is the simplest configuration for a hydrocracker. :t is a variation of the single stagehydrocracking !ith recycle configuration . 6he feed mi#es !ith hydrogen and goes to thereactor. 6he effluent goes to fractionation, !ith the unconverted material being taken outof the unit as unconverted material. 6his type of unit is the lo!est cost hydrocrackingunit, can process heavy, high boiling feed stocks and produces high value unconvertedmaterial !hich becomes feed stock for *CC units, ethylene plants or lube oil units. :ngeneral, the conversion of the feed stock to products is 5(- ( vol?, but can range as high as;( vol?.



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HYDROCRACKING 1)

ingle tage wit! Recycle Hydrocracking:

6he most !idely found hydrocracking unit is the single stage !ith recycle in !hich theunconverted feed is sent back to the reactor section for further conversion. *igure belo!depicts this type unit. :t is the most cost-effective design for 1((? or near 1((?conversion and is especially used to ma#imi e diesel product.

Two tage Recycle Hydrocracking

6he t!o stage hydrocracking process configuration is also !idely used, especially for large throughput units. :n t!o stage units, the hydrotreating and some cracking takes

place in the first stage. 6he effluent from the first stage is separated and fractionated, !ith



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HYDROCRACKING 15

the unconverted oil going to the second stage. 6he unconverted oil from the second stagereaction section goes back hydrocracker is sho!n in *igure


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HYDROCRACKING 1

C!aracteristics of Petrole$" Prod$cts

Hydrocracking

"urpose$ process gas oil to break carbon-carbon bonds of largecarbon bonds of large aromatic compounds @ remove contaminants.

Hydrogenation addition of hydrogen Cracking carbon-carbon scission of aromatic bonds

6ypically creates distillate range products, not gasoline range products.

&' Hydrocracking Tec!nologies



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HYDROCRACKING 1;

*as #il Hydrocracker Prod$cts Hydrocracking primarily to make distillates.

o :n B& hydrocracking normally a speciali ed operation used to optimi ecatalytic cracker operation

o :n B& cat cracking preferred to make gasoline from heavier fractions Hydrocracking capacity is only about ? of the crude distillation

Capacityo /ot all refineries have hydrocrackers

:ntent is to minimi e the production of heavy fuel oilo %ight ends are appro#imately )? of the feed.o 0iddle distillates kerosene, >et fuel, diesel, heating oil still contain

uncracked polynuclear aromatics =ll liquid fractions are lo! in sulfur @ olefins

Hydrocracking C!e"istryCracking reactions Hydrogenation

Reactions,so"eri ationReactions

CondensationReactions

&aturated paraffins crackedto form lo!er molecular

!eight olefins @ paraffins&ide chains cracked off smallring aromatics &4= @cycloparaffins naphthenes

&ide chains cracked off resins@ asphaltenes leavingthermally stable polynuclear aromatics "/=s+ut condensationdehydrogenation alsooccurs if not limited byHydrogenation

7#othermic giving off heatHydrogen inserted tosaturate ne!ly formedmolecule from aromaticcrackinglefins are saturated to formlight hydrocarbons,especially butane

=romatic rings hydrogenatedto cycloparaffinsnaphthenesCarbon-carbon bondscleaved to open aromatic @cycloparaffins naphthenesringsHeteroatoms form hydrogensulfide, ammonia, !ater,hydrogen chloride

:someri ation provides branching of alkyl groups of paraffins and opening ofnaphthenic rings

&uppressed byhydrogen



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HYDROCRACKING 2(

Hydrogen Cons$"%tion

Carbon bonds !ith heteroatom broken @ saturatedo Creates light ends

Heavier distillates make more light ends from breaking more comple#molecules

o &ulfur converted to hydrogen sulfideo /itrogen converted to ammoniao #ygen converted to !ater o rganic chlorides converted to hydrogen chloride

&aturation of carbon-carbon bondso lefins saturated to form light hydrocarbons.

Consumption stoichiometric one hydrogen molecule added foreach

double bondo =romatic rings hydrogenated to cycloparaffins naphthenes .

&evere operation hydrogen consumption strong function ofcomple#ityof the aromatics

:someri ation reactions generally not present 0etals deposited directly on the catalysts

o 7#cess metals reduce catalyst activity @ promote dehydrogenationproduces coke @ hydrogen

Have cracking of carbon-carbon bonds

o &evere operation hydrogen consumption strong function of comple#ityof the aromatics

Hydrogen lost in mi#ture !ith productso 7quilibrium !ith light gases

&ignificant may double amount required for sulfur removalo =bsorbed in liquid products

Bsually small compared to hydrogen used for sulfur removalo %ost !ith purge gas



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HYDROCRACKING 21

ingle tage Hydrocracking



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(2)hydrocracking technology

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