Foreground system:
Petroleum refineries are complex plants. The combination and sequence of a large number of processes is usually very specific to the characteristics of the crude oil and the products to be produced. Additional influencing factors are the market demand for the type of products, the available crude oil quality and certain requirements set by authorities the configuration and complexity of a refinery.
Simple hydro-skimming refineries can process only a few crude oil qualities and produce few high-quality products. Complex refineries with many conversion plants can process different crude oil types.
Petroleum refinery activities start with the reception of crude oil. After desalting, the crude oil is feeded to the distilling column of the atmospheric distillation (fractionation of the crude oil by separation according to density/ boiling/ condensation areas). The light ends (gases) go up to the head of the column and are employed to the liquid gas system to recover methane and ethane for use as refinery fuel and LPG (propane and butane) as saleable products. This light product separation is done in almost every refinery. These gases can also be used in a steam-reforming process to produce hydrogen, which is needed for the desulphurisation processes, the hydro cracking and to a lesser extent for the isomerisation unit. The straight-run naphtha of the atmospheric distillation, which is taken in the upper trays of the column are spitted and fed to three different processes. The light naphtha fraction is introduced to the chemical sweeten process. Some sweeted naphtha is directly blended in the gasoline pool, the main fraction is sent to the isomerisation unit where the aliphatic paraffins are converted into iso-paraffins with a high octane value. Often there is a de-isopentaniser (distillation) downstream to increase the gain of iso-components. These iso-paraffins are very valuable components for the gasoline production with high RON content. After desulphurisation the heavy naphtha fractions are sent to the reformer for catalytic transformation from aliphatic paraffins to iso-paraffins and from cyclo-paraffins to aromatic compounds, with a reduction of the net calorific value. The specific feature of this process is the production of hydrogen (the only hydrogen producer besides additional plants, like steam-reforming). The outputs of the isomerisation (often including a de-isopentaniser) and catalytic reforming go to the gasoline blending system and premium or regular gasoline follow as products. Kerosene is directly obtained from the atmospheric distillation and is separately treated from the rest of the middle distillates fraction. The main part of the middle distillates produced in the atmospheric distillation is employed into the hydrofiner (for desulphurisation). The desulphurised product is fed to the middle distillate blender. The residue from the atmospheric distillation is, mainly, introduced to the vacuum distillation. Here there is a distillation in light vacuum gas oil, vacuum gas oil (wax distillate) and vacuum residue. A part of the atmospheric residue is fed into the visbreaker (mild thermal cracking). Small amounts are introduced directly into the heating oil blending system and the asphalt-blowing process. The light gas oil, as a product of the vacuum distillation, goes to the hydrofiner, is desulphurised, and employed to the middle distillate blender. Some of the vacuum distillate, which has been taken from the middle trays of the vacuum distillation, is introduced to the base oil production of lubricants and waxes. Most of it is fed either to a catalytic cracker (first desulphurised) or a hydrocracker, where the feeds are converted into shorter chains by molecule restructuring. The products are gases, gasoline, middle distillates and heavy cycle gas oils (components of the heavy fuel oil). The gases of the catalytic cracking are treated in an alkylation and polymerisation unit to manufacture additional valuable gasoline components. These processes are used to combine small petroleum molecules into larger ones. Butylene of the catalytic cracker is further used to produce Methyl-Tertiary- Butyl- Ether (MTBE), a product used as octane booster. Sometimes, external purchased bio-ethanol is used instead. The naphtha of the FCC has to be treated in a special desulphurisation process to reduce the high sulphur content. The vacuum residues go into the coking process, which produces gases, gasoline, middle distillates and heating oil. A further product is petroleum coke, which is then purified. The vacuum residue, like some of the atmospheric residue, is also used as feed for the visbreaking, which also produces gases, naphtha, middle distillates and heating oil. The extracted hydrogen sulphides of all desulphurisation processes are fed to a sulphur recovery unit (claus plant) to recover elemental sulphur. The energy generation (heat, steam and electricity) requires a large amount of fuels. The fuel burned in refineries power plants and incinerators may be refinery gas, heating oil (residual oil), petrol coke and sometimes middle distillates and LPG. Beside purchased natural gas and electricity is employed.
All important material and energy flows (input- output) are shown in the following graph system boundary of the refinery model.
Furthermore a simplified flow chart is shown below. The arrangement of these processes varies among refineries, and few, if any, employ all of these processes.
The data set describes a mass-weighted average refinery for the respective country / region.
The data set considers the whole supply chain from crude oil exploration / well installation, production, transport to refining operation. If indicated in the process name, some fuels have certain shares of bio-components. The supply of these bio-components (bio-ethanol and bio-diesel) is modelled according to the national / regional situation).
Background system:
Electricity: Electricity is modelled according to the individual country-specific situations. The country-specific modelling is achieved on multiple levels. Firstly, individual energy carrier specific power plants and plants for renewable energy sources are modelled according to the current national electricity grid mix. Modelling the electricity consumption mix includes transmission / distribution losses and the own use by energy producers (own consumption of power plants and "other" own consumption e.g. due to pumped storage hydro power etc.), as well as imported electricity. Secondly, the national emission and efficiency standards of the power plants are modelled as well as the share of electricity plants and combined heat and power plants (CHP). Thirdly, the country-specific energy carrier supply (share of imports and / or domestic supply) including the country-specific energy carrier properties (e.g. element and energy content) are accounted for. Fourthly, the exploration, mining/production, processing and transport processes of the energy carrier supply chains are modelled according to the specific situation of each electricity producing country. The different production and processing techniques (emissions and efficiencies) in the different energy producing countries are considered, e.g. different crude oil production technologies or different flaring rates at the oil platforms.
Thermal energy, process steam: The thermal energy and process steam supply is modelled according to the individual country-specific situation with regard to emission standards and considered energy carriers. The thermal energy and process steam are produced at heat plants. Efficiencies for thermal energy production are by definition 100% in relation to the corresponding energy carrier input. For process steam the efficiency ranges from 85%, 90% to 95%. The energy carriers used for the generation of thermal energy and process steam are modelled according to the specific import situation (see electricity above).
Transports: All relevant and known transport processes are included. Ocean-going and inland ship transport as well as rail, truck and pipeline transport of bulk commodities are considered.
Energy carriers: The energy carriers are modelled according to the specific supply situation (see electricity above).
Refinery products: Diesel fuel, gasoline, technical gases, fuel oils, lubricants and residues such as bitumen are modelled with a parameterised country-specific refinery model. The refinery model represents the current national standard in refining techniques (e.g. emission level, internal energy consumption, etc.) as well as the individual country-specific product output spectrum, which can be quite different from country to country. The supply of crude oil is modelled, again, according to the country-specific situation with the respective properties of the resources.