Simple Guide To Oil & Gas Refinary Part 2 - Conversion
Distillation separates the crude oil into unfinished products.However,the products do not
naturally exist in crude in the same proportions as the product mix that consumers demand.
The biggest difference is that there is too little gasoline and too much heavy oil naturally
occurring in crude oil.That is why conversion processes are so important.Their primary purpose is to convert low valued heavy oil into high valued gasoline.
All products in the refinery are based on the same building blocks,carbon and hydrogen chains,which are called hydrocarbons.The longer the carbon chain,the heavier the product will be.Converting heavier hydrocarbons to lighter hydrocarbons can be ompared to cutting a link on a steel chain to make two smaller chains.This is the function of the Fluidized Catalytic Crackers (FCCs), Cokers and Hydrocrackers .In addition to reaking chains,there are times when we want to change the form of the chain or put chains together.This is where the Catalytic Reformer and Alkylation are necessary.Specialized catalysts are of critical importance in most of these processes.
The FCC is usually the key conversion unit.It uses a catalyst (a material that helps
make a chemical reaction go faster,occur at a lower temperature,or control which reactions occur)to convert gas oil into a mix of Liquified Petroleum Gas (LPG),gasoline and diesel.
The FCC catalyst promotes the reaction that breaks the heavier chains in the right place to make as much gasoline as possible.However,even with the catalyst,the reactions require a lot of heat;therefore the FCC reactor operates at about 1,000 degrees Fahrenheit.
The heaviest material in the refinery is Vacuum Tower Bottoms (VTB)or “resid.” If allowed to cool to room temperature,it would become a solid.Some resid is actually sold into the paving asphalt market as a blend component.Resid is too heavy and has too many contaminants to process in the FCC.The Delayed Coker is used to convert this heavy material into more valuable products.The delayed coker uses high temperature to break the hydrocarbon chains.Delayed coking reactions are less selective than FCC reactions.Delayed coking also produces a relatively low valued petroleum coke as a by-product.
In some refineries,the FCCs and Delayed Cokers are supplemented by Hydrocracking.
Similar to the FCC,the Hydrocracker uses high temperature and a catalyst to get the desired reactions.In Hydrocracking,the catalyst stays in one place and the gas oil passes over the catalyst,whereas in the FCC the catalyst is much finer and moves together with the gas oil.
The catalyst compositions differ.In Hydrocracking,the reactions take place at high temperatures in the presence of high concentrations of hydrogen.The Hydrocracker produces products with low sulfur levels.The light liquid product can be sent directly to Catalytic Reforming and the other liquid products can be blended directly into jet fuel and diesel.
The conversion processes that have been discussed up to this point have focused
on reducing the length of some hydrocarbon chains.However,there are other hydro carbon chains that are too short.Butane is produced as a byproduct of other conversion
units.The Alkylation Unit (Alky)takes two butanes and combines them into a longer chain
using a catalyst.
The last conversion process is Catalytic Reforming .The purpose of the reformer is
to increase the octane number of gasoline blend components and to generate hydrogen for use in the refinery hydrotreaters.The same length carbon chains can have very different octane numbers based on the shape of the chain.Straight chains,or paraffins,have a relatively low octane number,while rings,or aromatics,have high octane numbers.At high temperatures and in the presence of hydrogen,the catalyst will “reform ” paraffins into aromatics,thus the name catalytic reforming.Some of the aromatics produced are sent to petrochemical manufacturers,where they are converted to plastics and fabrics.
of
crude oil makes.
Product Gallons per Barrel
Gasoline 19.4
Distillate Fuel Oil 9.7
(Includes both home
heating oil and diesel fuel)
Kerosene-Type Jet Fuels 4.3
Coke 2.0
Residual Fuel Oil 1.9
(Heavy oils used as fuels
in industry, marine
transportation, and for
electric power generation)
Liquefied Refinery Gases 1.9
Still Gas 1.8
Asphalt and Road Oil 1.4
Petrochemical Feedstocks 1.1
Lubricants 0.5
Kerosene 0.2
Other 0.4
Source: API
naturally exist in crude in the same proportions as the product mix that consumers demand.
The biggest difference is that there is too little gasoline and too much heavy oil naturally
occurring in crude oil.That is why conversion processes are so important.Their primary purpose is to convert low valued heavy oil into high valued gasoline.
All products in the refinery are based on the same building blocks,carbon and hydrogen chains,which are called hydrocarbons.The longer the carbon chain,the heavier the product will be.Converting heavier hydrocarbons to lighter hydrocarbons can be ompared to cutting a link on a steel chain to make two smaller chains.This is the function of the Fluidized Catalytic Crackers (FCCs), Cokers and Hydrocrackers .In addition to reaking chains,there are times when we want to change the form of the chain or put chains together.This is where the Catalytic Reformer and Alkylation are necessary.Specialized catalysts are of critical importance in most of these processes.
The FCC is usually the key conversion unit.It uses a catalyst (a material that helps
make a chemical reaction go faster,occur at a lower temperature,or control which reactions occur)to convert gas oil into a mix of Liquified Petroleum Gas (LPG),gasoline and diesel.
The FCC catalyst promotes the reaction that breaks the heavier chains in the right place to make as much gasoline as possible.However,even with the catalyst,the reactions require a lot of heat;therefore the FCC reactor operates at about 1,000 degrees Fahrenheit.
The heaviest material in the refinery is Vacuum Tower Bottoms (VTB)or “resid.” If allowed to cool to room temperature,it would become a solid.Some resid is actually sold into the paving asphalt market as a blend component.Resid is too heavy and has too many contaminants to process in the FCC.The Delayed Coker is used to convert this heavy material into more valuable products.The delayed coker uses high temperature to break the hydrocarbon chains.Delayed coking reactions are less selective than FCC reactions.Delayed coking also produces a relatively low valued petroleum coke as a by-product.
In some refineries,the FCCs and Delayed Cokers are supplemented by Hydrocracking.
Similar to the FCC,the Hydrocracker uses high temperature and a catalyst to get the desired reactions.In Hydrocracking,the catalyst stays in one place and the gas oil passes over the catalyst,whereas in the FCC the catalyst is much finer and moves together with the gas oil.
The catalyst compositions differ.In Hydrocracking,the reactions take place at high temperatures in the presence of high concentrations of hydrogen.The Hydrocracker produces products with low sulfur levels.The light liquid product can be sent directly to Catalytic Reforming and the other liquid products can be blended directly into jet fuel and diesel.
The conversion processes that have been discussed up to this point have focused
on reducing the length of some hydrocarbon chains.However,there are other hydro carbon chains that are too short.Butane is produced as a byproduct of other conversion
units.The Alkylation Unit (Alky)takes two butanes and combines them into a longer chain
using a catalyst.
The last conversion process is Catalytic Reforming .The purpose of the reformer is
to increase the octane number of gasoline blend components and to generate hydrogen for use in the refinery hydrotreaters.The same length carbon chains can have very different octane numbers based on the shape of the chain.Straight chains,or paraffins,have a relatively low octane number,while rings,or aromatics,have high octane numbers.At high temperatures and in the presence of hydrogen,the catalyst will “reform ” paraffins into aromatics,thus the name catalytic reforming.Some of the aromatics produced are sent to petrochemical manufacturers,where they are converted to plastics and fabrics.
of
crude oil makes.
Product Gallons per Barrel
Gasoline 19.4
Distillate Fuel Oil 9.7
(Includes both home
heating oil and diesel fuel)
Kerosene-Type Jet Fuels 4.3
Coke 2.0
Residual Fuel Oil 1.9
(Heavy oils used as fuels
in industry, marine
transportation, and for
electric power generation)
Liquefied Refinery Gases 1.9
Still Gas 1.8
Asphalt and Road Oil 1.4
Petrochemical Feedstocks 1.1
Lubricants 0.5
Kerosene 0.2
Other 0.4
Source: API
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