PTRT 1301 Overview of Petroleum Industry Part 4

PTRT 1301 Overview of Petroleum Industry Part 4. 2 – Refining and Processing Oil and Gas Technology Program

Refining • Removes anything from the crude that is not hydrocarbon • Breaks down the crude into various hydrocarbon components – Paraffins – Olefins – Naphthenes – aromatics • Blends various hydrocarbon into other products with more desirable properties Oil and Gas Technology Program

Oil and Gas Technology Program

Paraffins • Main component of natural gas and a major fraction of crude oil • Straight-chain hydrocarbons (Fig 7. 3 A) – Simplest is methane – CH 4 – Propane and butane plus many others – All end in “ane” • With more than 4 carbon atoms more than one arrangement of atoms is possible (isomers) – Normal butane (n-butane) – straight chain – Iso-butane (i-butane) – branched chain • Isomers have different properties Oil and Gas Technology Program

Olefins • Straight-chains but with carbon double bonds (Fig 7. 3 B) • One double bond – end in “ylene” or “ene” – Ethylene – Propylene • Two double-bonds – end in “adiene” – butadiene Oil and Gas Technology Program

Oil and Gas Technology Program

Naphthenes Rings rather than chains (Fig 7. 3 C) Cycloparaffins All single bonds – stable Cyclohexane often occurs in natural gasoline • Chemical properties similar to paraffins • • Oil and Gas Technology Program

Aromatics • Contain a ring with 6 carbon atoms in it • Alternating double and single bonds in the ring • Known as benzene rings • BTX’s – Benzene – Toluene – Xylene • Regulatory issues - BTEX’s (same compounds) Oil and Gas Technology Program

Oil and Gas Technology Program

Refining Crude Oil and Gas Technology Program

Oil and Gas Technology Program

Refinery products • Petroleum Gas • Naphtha • Gasoline • Kerosene • Gas Oil or Diesel Distillate • Lubricating Oil • Heavy Gas or Fuel Oil • Residuum Oil and Gas Technology Program

Oil and Gas Technology Program

Oil and Gas Technology Program

Oil and Gas Technology Program

Oil and Gas Technology Program

Oil and Gas Technology Program

Oil and Gas Technology Program

Oil and Gas Technology Program

Oil and Gas Technology Program

Fractional Distillation • Separating crude oil into different fractions (MW) using distillation • Process called fractionation (distillation) • Output products are called distillates • Process similar to tea kettle – Different hydrocarbons have different boiling temperatures – Condense at different heights in the column • Two types – atmospheric and vacuum Oil and Gas Technology Program

Atmospheric Distillation (Fig 7. 7) • Vapors condense at differing heights in the column • Drawn off from the trays to collection tanks • Distillates useful as is or blended together to make other products Oil and Gas Technology Program

Oil and Gas Technology Program

Vacuum Distillation • High temperatures needed to boil heavy hydrocarbons instead decompose them • Vacuum distillation allows these compounds to boil at lower temperature • Gases and liquids recovered from this process act the same as those recovered using atmospheric distillation Oil and Gas Technology Program

Cracking • Even heavier hydrocarbons must be broken into smaller molecules in order to be used • “cracking” breaks these molecules chemically instead of physically – Catalytic– Thermal– Hydro. Oil and Gas Technology Program

Catalytic Cracking • Catalyst is a chemical which speeds up a chemical reaction without itself being changed or used up in the process • “fluidized” bed of powder • Output – Gasoline – Light oils – Cracked gas oils – Cycle oils – Coke (must be removed from the catalyst) Oil and Gas Technology Program

Thermal Cracking • Use heat to break down the bottoms • Light hydrocarbons released used for gasoline and distillate fuels • Two types – Viscosity breaking (mild) • High pressure • Immediate quenching prevents coke formation – Coking (severe) • Cracked products vaporize • Coke broken up with high-pressure water jets Oil and Gas Technology Program

Hydrocracking Cracking in the presence of hydrogen Hydrogenated the hydrocarbons Also reacts with contaminants Some of the hydrogen comes from the reforming process • Remaining comes from steam methane reforming that extracts hydrogen from steam and methane • • Oil and Gas Technology Program

Rearranging Hydrocarbon Molecules • Build new molecules to produce high quality gasoline, jet fuels, petrochemicals • Alkylation • Isomerization • Reforming • Solvent extraction • treating Oil and Gas Technology Program

Alkylation • Olefins are combined chemically with isobutane to form larger branched-chain molecules (isoparaffins) that make highoctane gasoline • Alkylates (liquid gasoline components) • Light hydrocarbon gases are stored under pressure • Isobutane is recycled Oil and Gas Technology Program

Isomerization • Chemical process converts paraffins (straight chains) into isoparaffins (branched chains) • Branched chains have higher octane properties than straight chain equivalents Catalytic Reforming • Uses a combination of heat, pressure, and a catalyst • Usually a multi-step process with hydrogen to prevent coke formation Oil and Gas Technology Program

Typical Gas Processing • Check for acid gases and poisonous gas - CO 2, H 2 S, . . . – Remove H 2 S - typically by scrubber with an amine type agent – Remove excess CO 2 – generally by scrubber agent or membrane separation • Remove Water - generally by molecular sieve or glycol • Remove Oil and Condensate, if it is ‘associated dissolved natural gas’ – generally by separation in field • Remove Nitrogen (N 2), if greater than pipeline specification • Remove Helium (He), if present • Remove NGLs • Deliver gas to sales pipeline • Deliver recovered NGLs to pipeline as either raw makeup for further fractionation to purity products or as purity products, if fractionation is on site Oil and Gas Technology Program

Gas Processing • Gas processing serves two purposes: – Gas Conditioning: Removal of impurities and other substances necessary to make the gas quality merchantable for sale (meets gas pipeline residue specification). – Value Enhancement: NGLs usually have greater value as a marketable liquid than as a Btu equivalent in the raw natural gas • Domestically, 70 -80% of all natural gas must be processed Oil and Gas Technology Program

Oil and Gas Technology Program

Oil and Gas Technology Program

Oil and Gas Technology Program

Typical Composition of Natural Gas Molecule Molecular Formula Percentage Methane CH 4 70 -90% Ethane C 2 H 6 0 -20% Propane C 3 H 8 0 -8% Butane C 4 H 10 0 -8% Carbon Dioxide CO 2 0 -8% Oxygen O 2 0 -0. 2% Nitrogen N 2 0 -5% Hydrogen Sulphide H 2 S 0 -5% Rare Gases A, He, Ne, Xe trace Oil and Gas Technology Program

Sources of Natural Gas Oil and Gas Technology Program

Recovering NGL Mixtures • Four processes – Straight Refrigeration • Heat exchanger with refrigerant (Freon or propane) – Cryogenic Recovery • Combination of very low temperature and high pressures to recover most of the ethane plus all of the propane and heavier hydrocarbons • Defined by temperatures below -150 ⁰F • Special materials and treatment critical to use – Oil Absorption – Dry-bed Adsorption (see dehydration) Oil and Gas Technology Program

Cryogenic Recovery • Expander processing – Inlet Gas Treatment • Dry • Clean • Must be cooled – Inlet separator upstream of expander • NGL’s condense and drop out • Methane and remaining hydrocarbon vapor pass to the expander • Further cooling in expander forces remaining NGL’s to separate • Demethanizer maximizes NGL recovery • Cascade Refrigeration – Two-stage refrigeration for recovery of NGL’s – Three-stage refrigeration for LNG production Oil and Gas Technology Program

Expander process Oil and Gas Technology Program

Oil and Gas Technology Program

Cascade Refrigeration Oil and Gas Technology Program

Process Specifics Refrigeration: ( ~ -25° F ) – Uses a circulating propane refrigerant to chill the gas. Process gas stays at same pressure. Lean Oil Absorption ( ~ -30° F ) – Uses a circulating cold oil (kerosene type) to chill gas and absorb heavier molecules. Process gas stays at same pressure. A refrigerant fluid (propane) is used to chill the circulating oil. Joule-Thompson expansion ( ~ -90° F ) – Uses the JT effect by dropping the pressure of the gas to provide cooling through an expansion valve - less efficient than Turboexpander process but much more common because of cost Cryogenic Turbo - Expander process ( ~ -130° F) – Uses thermodynamic properties of gas by dropping the pressure of the gas to provide cooling (Joules-Thompson (JT) effect) and extracts work. Requires recompression ( +/- 300 to 500 psig). Oil and Gas Technology Program

NGL Recovery Plant Type CRYO JT Lean Oil Refrigeration Ethane C 2 60 -96% 45 -60% 25 -45% 1 -5% Propane C 3 90 -98% 85 -95% 80 -95% 20 -40% Iso-Butane IC 4 96 -100% 93 -99% 40 -60% N. Butane NC 4 98 -100% 97 -100% 94 -99% 40 -60% N. Gasoline C 5 + 99 -100% 98 -100% 95 -99% 70 -95% Product Oil and Gas Technology Program

Fractionation • Fractionation occurs in stages by boiling off the hydrocarbons one by one • The process starts with the removal of the lightest of the NGLs from the stream • The fractionators are so named for the particular hydrocarbon that is boiled off • The fractionators are used in the following order: – Deethanizer - separates ethane from the NGL stream – Depropanizer - separates propane from the NGL stream – Debutanizer - boils off the butanes and leaves the pentanes and heavier hydrocarbons in the NGLstream – Butane Splitter or Deisobutanizer - separates the iso and normal butanes from the NGL stream Oil and Gas Technology Program

Fractionation Oil and Gas Technology Program

Oil and Gas Technology Program

Properties of NGL’s Oil and Gas Technology Program

Definitions • NGL: Natural Gas Liquids, ethane, propane, butanes and pentane plus • LPG / LRG: Liquefied Petroleum Gas; refinery gases such as ethane, ethylene, propane, propylene, butanes and butylenes • LNG: Liquefied Natural Gas; methane, ethane and propane (-260 F) • GPM: Gallons of NGLs per MCF A measure of the richness of the gas for processing • BTU: British Thermal Unit - The amount of energy required to raise one pound of water 1°F • Dekatherms: 1 Dth = 1 million Btus = MMBtu • Heating Content: MMBtu/ Mcf - measure of how much heating capability is in a fixed volume of gas • Maximum Btu limit: The maximum heating content limit a gas stream may have on a sales pipeline Oil and Gas Technology Program

Definitions (cont) • Raw Gas: • Casinghead Gas: The unprocessed gas stream entering the plant for processing and conditioning Gas sourced from oil production, rich in NGLs • Associated Gas: Gas sourced from oil production, rich in NGLs • Non-Associated Gas sourced from isolated non-oil bearing production, usually leaner in NGLs than Associated Gas • Lean Gas: Gas containing low levels of NGLs - not good for processing • Rich Gas: Gas containing high levels of NGLs - good for processing • Acid Gas: Gas containing H 2 S, CO 2, COS or other corrosive gases Oil and Gas Technology Program

Definitions (cont) • Sour Gas: Gas containing high levels of H 2 S - corrosive, poisonous gas • Sweet Gas: Gas not containing H 2 S, CO 2 or other corrosive gases • Inert Gases: Gases such as Nitrogen (N 2) and Helium (He) • Wet Gas: Gas containing water (H 2 O) above 7 pounds/MMcf • Dry Gas: Gas containing water (H 2 O) below 7 pounds/ MMcf • Dew Point: The Temperature, at a specific Pressure, that a specific gas composition begins to condense (hydrocarbon fallout) Oil and Gas Technology Program