1. Crude Oil

2. Refining is Boiling Oil
A large part of refining involves separating the different fractions of crude oil and other intermediate streams. While water boils at a single temperature, crude oil boils over a wide range of temperatures. By controlling the temperature using very tall distillation columns, different fractions of the crude oil can be separated.
At the top of the column, fuel gas and liquefied petroleum gas (or LPG) is produced. A little lower down the column, gasoline (or, more precisely, one of the blending stocks for gasoline called naphtha) is withdrawn. Still lower down the column, jet fuel and diesel fuel are produced.

3. At the very bottom of the column, asphalt is the "bottom of the barrel". Asphalt can either be sold to make roads and roofing materials, or it can be thermally cracked in a coker, where under high temperatures, the asphalt breaks down into a synthetic crude oil, producing the same products as crude oil as well as petroleum coke. Similar columns are found at all the cokers.
Between asphalt and diesel fuel is a substance called gas oil. In some refineries, this stream can be further processed into lubricating oil. However, the crude oil that FHR processes doesn't make very good lubricating oil, so like asphalt it is catalytically cracked into another synthetic crude oil. Again, similar columns are found in the catalytic cracking unit.

5. Another significant portion of refining is converting individual molecules into different sizes and shapes. There are three main conversion processes in the refinery:
Cracking
Combining
Reforming
Cracking takes place in two units: the cokers and the fluid catalytic cracking units (or FCCUs). In the coker, asphalt is heated to 900 to 1000º F in large drums. The asphalt is allowed to cook for 16 to 24 hours. While cooking, the asphalt turns into a synthetic crude oil which is separated into the different fractions. What remains is a black solid, similar in appearance to coal, called petroleum coke. Petroleum coke is used the same way that coal is, primarily to produce electricity in coal fired power plants. Gasoil, a fraction of crude oil between asphalt and diesel fuel, is cracked in the FCCU. Gasoil is contacted by very hot (> 1300º F), very small (like flour) particles of catalyst, which cracks it into a synthetic crude oil which is again separated into different fractions. In the process, some of the gasoil turns into coke, which attaches to the catalyst particles. This coke must be burned off in the FCCU regenerator, which also reheats the catalyst for another ride around the unit.

6. Eventually, some of the catalyst wears down and is too small to be captured by the internal capture mechanisms, and escapes from the regenerator. An electrostatic precipitator (like a 14 story electronic dust cleaner on your furnace at home) removes most of these fine pieces of catalyst before they escape into the air.
Combining takes place in three units: the alkylation (or Alky) unit, the dimersol and the polymerization (or Polly) unit. In all three of these units, small LPG molecules are combined into larger, gasoline molecules. FHR uses sulfuric acid, nickel and phosphoric acid to combine different combinations of LPG into gasoline.
Reforming takes place in three units as well: the platformer, the powerformer and the isomerization (or isom) unit. Reforming changes the shapes of molecules so that they have more desirable characteristics. For example, the gasoline which comes directly from the separation of crude oil has too low an octane rating to be used directly in automobiles. By reforming this gasoline with the help of a platinum catalyst, the octane can be raised significantly. FHR uses platinum and other rare metals to rearrange gasoline molecules to improve their octane and other properties.

7. Making clean products out of dirty raw materials
FHR processes a type of crude oil known as "heavy, sour" crude oil - heavy, because it contains more asphalt than most crudes, and sour because it contains a lot of sulfur. In order to meet state and federal standards for clean burning transportation fuels, FHR must treat the oil to remove sulfur and other contaminants.
The treating process starts with the desalters. Crude oil contains a small percentage of salt water (which is present in the rock formations from which it is pumped) and a small amount of solids, which must be removed so that they do not plug up or corrode the processing equipment. The water and solids do not form separate layers, but are mixed in with the oil in an emulsion. To break the emulsion, chemicals are added to the crude oil, and the oil passes through an electrically charged grid, which separates the oil from the water and solids. The oil is washed with additional water to be sure all the salt and solids are removed, and the water, salts and solids are sent to the wastewater treatment plant where oil and solids are recovered. The oil and solids are returned to the process to make more products.

8. Once the crude oil has been separated into its various fractions, it must be treated to remove the sulfur. FHR uses hydrogen and a molybdenum-cobalt catalyst to remove sulfur from gasoline, jet fuel and diesel fuel, and to pre-treat the gas oil before it is cracked. The sulfur combines with the hydrogen to form hydrogen sulfide, a very smelly, toxic chemical. FHR uses an amine scrubber to remove the hydrogen sulfide from the hydrogen and fuel gas, and recovers it as elemental sulfur in three sulfur recovery units. Sulfur is sold as a by-product or converted to sulfuric acid, which FHR uses as a catalyst in other processes.
Some streams, like LPG and some light gasoline streams, are treated with caustic soda to remove the sulfur, and then washed with water to neutralize the oil and remove the caustic soda and sulfur.

9. Petroleum hydrocarbon structures
Petroleum consists of three main hydrocarbon groups:
Paraffins
These consist of straight or branched carbon rings saturated with hydrogen atoms, the simplest of which is methane (CH4) the main ingredient of natural gas. Others in this group include ethane (C2H6), and propane (C3H8).

10. Naphthenes
Naphthenes consist of carbon rings, sometimes with side chains, saturated with hydrogen atoms. Naphthenes are chemically stable, they occur naturally in crude oil and have properties similar to paraffins.
Aromatics
aromatic hydrocarbons are compounds that contain a ring of six carbon atoms with alternating double and single bonds and six attached hydrogen atoms. This type of structure is known as a benzene ring. They occur naturally in crude oil, and can also be created by the refining process.

11. Paraffins
Naphthenes
Aromatics

12. The refining process
Every refinery begins with the separation of crude oil into different fractions by distillation. The fractions are further treated to convert them into mixtures of more useful saleable products by various methods such as cracking, reforming, alkylation, polymerisation and isomerisation. These mixtures of new compounds are then separated using methods such as fractionation and solvent extraction. Impurities are removed by various methods, e.g. dehydration, desalting, sulphur removal and hydrotreating.
Refinery processes have developed in response to changing market demands for certain products. With the advent of the internal combustion engine the main task of refineries became the production of petrol. The quantities of petrol available from distillation alone was insufficient to satisfy consumer demand. Refineries began to look for ways to produce more and better quality petrol. Two types of processes have been developed:
breaking down large, heavy hydrocarbon molecules
reshaping or rebuilding hydrocarbon molecules.

14. Cracking
Cracking processes break down heavier hydrocarbon molecules (high boiling point oils) into lighter products such as petrol and diesel. These processes include catalytic cracking, thermal cracking and hydrocracking.
e.g.
A typical reaction:
C16H34 -> C8H18 + C8H16
Catalytic cracking is used to convert heavy hydrocarbon fractions obtained by vacuum distillation into a mixture of more useful products such as petrol and light fuel oil. In this process, the feedstock undergoes a chemical breakdown, under controlled heat ( oC) and pressure, in the presence of a catalyst - a substance which promotes the reaction without itself being chemically changed. Small pellets of silica - alumina or silica - magnesia have proved to be the most effective catalysts.

15. The cracking reaction yields petrol, LPG, unsaturated olefin compounds, cracked gas oils, a liquid residue called cycle oil, light gases and a solid coke residue. Cycle oil is recycled to cause further breakdown and the coke, which forms a layer on the catalyst, is removed by burning. The other products are passed through a fractionator to be separated and separately processed.
Thermal cracking uses heat to break down the residue from vacuum distillation. The lighter elements produced from this process can be made into distillate fuels and petrol. Cracked gases are converted to petrol blending components by alkylation or polymerisation. Naphtha is upgraded to high quality petrol by reforming. Gas oil can be used as diesel fuel or can be converted to petrol by hydrocracking. The heavy residue is converted into residual oil or coke which is used in the manufacture of electrodes, graphite and carbides.

17. Reforming
Reforming is a process which uses heat, pressure and a catalyst (usually containing platinum) to bring about chemical reactions which upgrade naphthas into high octane petrol and petrochemical feedstock. The naphthas are hydrocarbon mixtures containing many paraffins and naphthenes. In Australia, this naphtha feedstock comes from the crudes oil distillation or catalytic cracking processes, but overseas it also comes from thermal cracking and hydrocracking processes. Reforming converts a portion of these compounds to isoparaffins and aromatics, which are used to blend higher octane petrol.
paraffins are converted to isoparaffins
paraffins are converted to naphthenes
naphthenes are converted to aromatics
e.g.
Catalyst heptane -> toluene + hydrogen C7H16 -> C7H8 + 4H2
Catalyst cyclohexane -> benzene + hydrogen C6H12 -> C6H6 + 3H2

18. Refineries and the environment
Air, water and land can all be affected by refinery operations. Refineries are well aware of their responsibility to the community and employ a variety of processes to safeguard the environment.
The processes described below are those used by the Shell refinery at Geelong in Victoria, but all refineries employ similar techniques in managing the environmental aspects of refining.

19. Air
Preserving air quality around a refinery involves controlling the following emissions:
sulphur oxides
hydrocarbon vapours
smoke
smells
Sulphur enters the refinery in crude oil feed. Gippsland and most other Australian crude oils have a low sulphur content but other crude's may contain up to 5 per cent sulphur. To deal with this refineries incorporate a sulphur recovery unit which operates on the principles described above.

20. Air
Many of the products used in a refinery produce hydrocarbon vapours. The escape of vapours to atmosphere are prevented by various means. Floating roofs are installed in tanks to prevent evaporation and so that there is no space for vapour to gather in the tanks. Where floating roofs cannot be used, the vapours from the tanks are collected in a vapour recovery system and absorbed back into the product stream. In addition, pumps and valves are routinely checked for vapour emissions and repaired if a leakage is found.
Smoke is formed when the burning mixture contains insufficient oxygen or is not sufficiently mixed. Modern furnace control systems prevent this from happening during normal operation.
Smells are the most difficult emission to control and the easiest to detect. Refinery smells are generally associated with compounds containing sulphur, where even tiny losses are sufficient to cause a noticeable odour.

21. Water
Aqueous effluent's consist of cooling water, surface water and process water.
The majority of the water discharged from the refinery has been used for cooling the various process streams. The cooling water does not actually come into contact with the process material and so has very little contamination. The cooling water passes through large "interceptors" which separate any oil from minute leaks etc., prior to discharge. The cooling water system at Geelong Refinery is a once-through system with no recirculation.
Rainwater falling on the refinery site must be treated before discharge to ensure no oily material washed off process equipment leaves the refinery. This is done first by passing the water through smaller "plant oil catchers", which each treat rainwater from separate areas on the site, and then all the streams pass to large "interceptors" similar to those used for cooling water. The rainwater from the production areas is further treated in a Dissolved Air Flotation (DAF) unit. This unit cleans the water by using a flocculation agent to collect any remaining particles or oil droplets and floating the resulting flock to the surface with millions of tiny air bubbles. At the surface the flock is skimmed off and the clean water discharged.

22. Water
Process water has actually come into contact with the process streams and so can contain significant contamination. This water is treated in the "sour water treater" where the contaminants (mostly ammonia and hydrogen sulphide) are removed and then recovered or destroyed in a downstream plant. The process water, when treated in this way, can be reused in parts of the refinery and discharged through the process area rainwater treatment system and the DAF unit.
Any treated process water that is not reused is discharged as Trade Waste to the sewerage system. This trade waste also includes the effluent from the refinery sewage treatment plant and a portion of treated water from the DAF unit.
As most refineries import and export many feed materials and products by ship, the refinery and harbour authorities are prepared for spillage from the ship or pier. In the event of such a spill, equipment is always on standby at the refinery and it is supported by the facilities of the Australian Marine Oil Spill Centre at Geelong, Victoria.

23. Land
The refinery safeguards the land environment by ensuring the appropriate disposal of all wastes.
Within the refinery, all hydrocarbon wastes are recycled through the refinery slops system. This system consists of a network of collection pipes and a series of dewatering tanks. The recovered hydrocarbon is reprocessed through the distillation units.
Wastes that cannot be reprocessed are either recycled to manufacturers (e.g. some spent catalysts can be reprocessed), disposed of in EPA-approved facilities off-site, or chemically treated on-site to form inert materials which can be disposed to land-fill within the refinery.
Waste movements within the refinery require a "Process liquid, Sludge and Solid waste disposal permit". Wastes that go off-site must have an EPA "Waste Transport Permit".