Delayed coker

Last updated January 25, 2024

A delayed coker is a type of coker whose process consists of heating a residual oil feed to its thermal cracking temperature in a furnace with multiple parallel passes. This cracks the heavy, long chain hydrocarbon molecules of the residual oil into coker gas oil and petroleum coke.^[1]^[2]^[3]

Delayed coking is one of the unit processes used in many oil refineries. The adjacent photograph depicts a delayed coking unit with 4 drums. However, larger units have tandem pairs of drums, some with as many as 8 drums, each of which may have diameters of up to 10 meters and overall heights of up to 43 meters.^[4]

The yield of coke from the delayed coking process ranges from about 18 to 30 percent by weight of the feedstock residual oil, depending on the composition of the feedstock and the operating variables. Many refineries worldwide produce as much as 2,000 to 3,000 tons per day of petroleum coke and some produce even more.^[5]

Schematic flow diagram and description

The flow diagram and description in this section are based on a delayed coking unit with a single pair of coke drums and one feedstock furnace. However, as mentioned above, larger units may have as many as 4 pairs of drums (8 drums in total) as well as a furnace for each pair of coke drums.

A delayed coking unit. A schematic flow diagram of such a unit, where residual oil enters the process at the lower left (see -), proceeds via pumps to the main fractionator (tall column at right), the residue of which, shown in green, is pumped via a furnace into the coke drums (two columns left and center) where the final carbonization takes place, at high temperature and pressure, in the presence of steam. Delayed Coker.png — **A delayed coking unit.** A schematic flow diagram of such a unit, where *residual oil* enters the process at the lower left (see →), proceeds via pumps to the *main fractionator* (tall column at right), the residue of which, shown in green, is pumped via a furnace into the *coke drums* (two columns left and center) where the final carbonization takes place, at high temperature and pressure, in the presence of steam.

Residual oil from the vacuum distillation unit (sometimes including high-boiling oils from other sources within the refinery) is pumped into the bottom of the distillation column called the main fractionator. From there, it is pumped, along with some injected steam, into the fuel-fired furnace and heated to its thermal cracking temperature of about 480 °C. Thermal cracking begins in the pipe between the furnace and the first coke drums, and finishes in the coke drum that is on-stream. The injected steam helps to minimize the deposition of coke within the furnace tubes.

Pumping the incoming residual oil into the bottom of the main fractionator, rather than directly into the furnace, preheats the residual oil by having it contact the hot vapors in the bottom of the fractionator. At the same time, some of the hot vapors condense into a high-boiling liquid which recycles back into the furnace along with the hot residual oil.

As cracking takes place in the drum, gas oil and lighter components are generated in vapor phase and separate from the liquid and solids. The drum effluent is vapor except for any liquid or solids entrainment, and is directed to main fractionator where it is separated into the desired boiling point fractions.

The solid coke is deposited and remains in the coke drum in a porous structure that allows flow through the pores. Depending upon the overall coke drum cycle being used, a coke drum may fill in 16 to 24 hours.

After the first drum is full of the solidified coke, the hot mixture from the furnace is switched to the second drum. While the second drum is filling, the filled first drum is steamed out to reduce the hydrocarbon content of the petroleum coke, and then quenched with water to cool it. The top and bottom heads of the full coke drum are removed, and the solid petroleum coke is then cut from the coke drum with a high pressure water nozzle, where it falls into a pit, pad, or sluiceway for reclamation to storage.

Composition of coke

The table below illustrates the wide range of compositions for raw petroleum coke (referred to as green coke ^[6]) produced in a delayed coker and the corresponding compositions after the green coke has been calcined at 2375 °F (1302 °C):

**Composition Of Coke From A Delayed Coker**
Component	Green coke as produced	Coke calcined at 2375 °F
Fixed carbon, wt %	80 − 95	98.0 − 99.5
Hydrogen, wt %	3.0 − 4.5	0.1
Nitrogen, wt %	0.1 − 0.5
Sulfur, wt %	0.2 − 6.0
Volatile matter, wt %	5 − 15	0.2 − 0.8
Moisture, wt %	0.5 − 10	0.1
Ash, wt %	0.1 − 1.0	0.02 − 0.7
Density, g/cm³	1.2 − 1.6	1.9 − 2.1
Metals, ppm weight:
Aluminum	15 − 100	15 − 100
Boron	0.1 − 15	0.1 − 15
Calcium	25 − 500	25 − 500
Chromium	5 − 50	5 − 50
Cobalt	10 − 60	10 − 60
Iron	50 − 5000	50 − 5000
Manganese	2 − 100	2 − 100
Magnesium	10 − 250	10 − 250
Molybdenum	10 − 20	10 − 20
Nickel	10 − 500	10 − 500
Potassium	20 − 50	20 − 50
Silicon	50 − 600	50 − 600
Sodium	40 − 70	40 − 70
Titanium	2 − 60	2 − 60
Vanadium	5 − 500	5 − 500

History

Petroleum coke was first made in the 1860s in the early oil refineries in Pennsylvania which boiled oil in small, iron distillation stills to recover kerosene, a much needed lamp oil. The stills were heated by wood or coal fires built underneath them, which over-heated and coked the oil near the bottom. After the distillation was completed, the still was allowed to cool and workmen could then dig out the coke and tar.^[7]

In 1913, William Merriam Burton, working as a chemist for the Standard Oil of Indiana refinery at Whiting, Indiana, was granted a patent^[8] for the Burton thermal cracking process that he had developed. He was later to become the president of Standard Oil of Indiana before he retired.
In 1929, based on the Burton thermal cracking process, Standard Oil of Indiana built the first delayed coker. It required very arduous manual decoking.^[7]
In the late 1930s, Shell oil developed hydraulic decoking using high-pressure water at their refinery in Wood River, Illinois. That made it possible, by having two coke drums, for delayed decoking to become a semi-continuous process.^[7]
From 1955 onwards, the growth in the use of delayed coking increased.
As of 2002, there were 130 petroleum refineries worldwide producing 172,000 tons per day of petroleum coke.^[9] Included in those worldwide data, about 59 coking units were operating in the United States and producing 114,000 tons per day of coke.^[9]

Uses of petroleum coke

The product coke from a delayed coker has many commercial uses and applications.^[7]^[10]^[11] The largest use is as a fuel.

The uses for green coke are:

As fuel for space heaters, large industrial steam generators, fluidized bed combustions, Integrated Gasification Combined Cycle (IGCC) units and cement kilns
In silicon carbide foundries
For producing blast furnace coke

The uses for calcined coke are:

As anodes in the production of aluminium
In the production of titanium dioxide
As a carbon raiser in cast iron and steel making
Producing graphite electrodes and other graphite products such as graphite brushes used in electrical equipment
In carbon structural materials

Other processes for producing petroleum coke

There are other petroleum refining processes for producing petroleum coke, namely the Fluid Coking and Flexicoking processes^[12]^[13] both of which were developed and are licensed by ExxonMobil Research and Engineering. The first commercial unit went into operation in 1955. Forty-three years later, as of 1998, there were 18 of these units operating worldwide^[14] of which 6 were in the United States.

There are other similar coking processes, but they do not produce petroleum coke. For example, the Lurgi-VZK Flash Coker which produces coke by the pyrolysis of biomass.^[15]

Related Research Articles

An oil refinery or petroleum refinery is an industrial process plant where petroleum is transformed and refined into useful products such as gasoline (petrol), diesel fuel, asphalt base, fuel oils, heating oil, kerosene, liquefied petroleum gas and petroleum naphtha. Petrochemical feedstock like ethylene and propylene can also be produced directly by cracking crude oil without the need of using refined products of crude oil such as naphtha. The crude oil feedstock has typically been processed by an oil production plant. There is usually an oil depot at or near an oil refinery for the storage of incoming crude oil feedstock as well as bulk liquid products. In 2020, the total capacity of global refineries for crude oil was about 101.2 million barrels per day.

<span class="mw-page-title-main">Cracking (chemistry)</span> Process whereby complex organic molecules are broken down into simpler molecules

In petrochemistry, petroleum geology and organic chemistry, cracking is the process whereby complex organic molecules such as kerogens or long-chain hydrocarbons are broken down into simpler molecules such as light hydrocarbons, by the breaking of carbon-carbon bonds in the precursors. The rate of cracking and the end products are strongly dependent on the temperature and presence of catalysts. Cracking is the breakdown of large hydrocarbons into smaller, more useful alkanes and alkenes. Simply put, hydrocarbon cracking is the process of breaking a long chain hydrocarbon into short ones. This process requires high temperatures.

Vacuum distillation or Distillation under reduced pressure is a type of distillation performed under reduced pressure, which allows the purification of compounds not readily distilled at ambient pressures or simply to save time or energy. This technique separates compounds based on differences in their boiling points. This technique is used when the boiling point of the desired compound is difficult to achieve or will cause the compound to decompose. Reduced pressures decrease the boiling point of compounds. The reduction in boiling point can be calculated using a temperature-pressure nomograph using the Clausius–Clapeyron relation.

A visbreaker is a processing unit in an oil refinery whose purpose is to reduce the quantity of residual oil produced in the distillation of crude oil and to increase the yield of more valuable middle distillates by the refinery. A visbreaker thermally cracks large hydrocarbon molecules in the oil by heating in a furnace to reduce its viscosity and to produce small quantities of light hydrocarbons.. The process name of "visbreaker" refers to the fact that the process reduces the viscosity of the residual oil. The process is non-catalytic.

<span class="mw-page-title-main">Catalytic reforming</span> Chemical process used in oil refining

Catalytic reforming is a chemical process used to convert petroleum refinery naphthas distilled from crude oil into high-octane liquid products called reformates, which are premium blending stocks for high-octane gasoline. The process converts low-octane linear hydrocarbons (paraffins) into branched alkanes (isoparaffins) and cyclic naphthenes, which are then partially dehydrogenated to produce high-octane aromatic hydrocarbons. The dehydrogenation also produces significant amounts of byproduct hydrogen gas, which is fed into other refinery processes such as hydrocracking. A side reaction is hydrogenolysis, which produces light hydrocarbons of lower value, such as methane, ethane, propane and butanes.

Petroleum coke, abbreviated coke, pet coke or petcoke, is a final carbon-rich solid material that derives from oil refining, and is one type of the group of fuels referred to as cokes. Petcoke is the coke that, in particular, derives from a final cracking process—a thermo-based chemical engineering process that splits long chain hydrocarbons of petroleum into shorter chains—that takes place in units termed coker units. Stated succinctly, coke is the "carbonization product of high-boiling hydrocarbon fractions obtained in petroleum processing ". Petcoke is also produced in the production of synthetic crude oil (syncrude) from bitumen extracted from Canada's tar sands and from Venezuela's Orinoco oil sands.

Coking is the heating of coal in the absence of oxygen to a temperature above 600 °C to drive off the volatile components of the raw coal, leaving a hard, strong, porous material of high carbon content called coke. Coke consists almost entirely of carbon. The porosity gives it a high surface area, which makes it burn faster. When a kilogram of coke is burned it releases more heat than a kilogram of the original coal.

Continuous distillation, a form of distillation, is an ongoing separation in which a mixture is continuously fed into the process and separated fractions are removed continuously as output streams. Distillation is the separation or partial separation of a liquid feed mixture into components or fractions by selective boiling and condensation. The process produces at least two output fractions. These fractions include at least one volatile distillate fraction, which has boiled and been separately captured as a vapor condensed to a liquid, and practically always a bottoms fraction, which is the least volatile residue that has not been separately captured as a condensed vapor.

<span class="mw-page-title-main">Fluid catalytic cracking</span> Petroleum conversion process

Fluid Catalytic Cracking (FCC) is the conversion process used in petroleum refineries to convert the high-boiling point, high-molecular weight hydrocarbon fractions of petroleum into gasoline, alkene gases, and other petroleum products. The cracking of petroleum hydrocarbons was originally done by thermal cracking, now virtually replaced by catalytic cracking, which yields greater volumes of high octane rating gasoline; and produces by-product gases, with more carbon-carbon double bonds, that are of greater economic value than the gases produced by thermal cracking.

Pyrolysis oil, sometimes also known as bio-crude or bio-oil, is a synthetic fuel with limited industrial application and under investigation as substitute for petroleum. It is obtained by heating dried biomass without oxygen in a reactor at a temperature of about 500 °C (900 °F) with subsequent cooling, separation from the aqueous phase and other processes. Pyrolysis oil is a kind of tar and normally contains levels of oxygen too high to be considered a pure hydrocarbon. This high oxygen content results in non-volatility, corrosiveness, partial miscibility with fossil fuels, thermal instability, and a tendency to polymerize when exposed to air. As such, it is distinctly different from petroleum products. Removing oxygen from bio-oil or nitrogen from algal bio-oil is known as upgrading.

A crude oil assay is the chemical evaluation of crude oil feedstocks by petroleum testing laboratories. Each crude oil type has unique molecular and chemical characteristics. No two crude oil types are identical and there are crucial differences in crude oil quality. The results of crude oil assay testing provide extensive detailed hydrocarbon analysis data for refiners, oil traders and producers. Assay data help refineries determine if a crude oil feedstock is compatible for a particular petroleum refinery or if the crude oil could cause yield, quality, production, environmental and other problems.

A coker or coker unit is an oil refinery processing unit that converts the residual oil from the vacuum distillation column into low molecular weight hydrocarbon gases, naphtha, light and heavy gas oils, and petroleum coke. The process thermally cracks the long chain hydrocarbon molecules in the residual oil feed into shorter chain molecules leaving behind the excess carbon in the form of petroleum coke.

A de-asphalter is a unit in a crude oil refinery or bitumen upgrader that separates asphalt from the residuum fraction of crude oil or bitumen. The primary purpose of the separation is to remove contaminants from the feed that would cause rapid deactivation of catalysts in downstream processing units. In doing so, the de-asphalter is the first step in a series of processes that upgrade a low-value feedstock to high-value refined products.

The BPRefinery (Kent) was an oil refinery on the Isle of Grain in Kent. It was commissioned in 1953 and had a maximum processing capacity of 11 million tonnes of crude oil per year. It was decommissioned in August 1982.

Petroleum refining processes are the chemical engineering processes and other facilities used in petroleum refineries to transform crude oil into useful products such as liquefied petroleum gas (LPG), gasoline or petrol, kerosene, jet fuel, diesel oil and fuel oils.

Petroleum naphtha is an intermediate hydrocarbon liquid stream derived from the refining of crude oil with CAS-no 64742-48-9. It is most usually desulfurized and then catalytically reformed, which rearranges or restructures the hydrocarbon molecules in the naphtha as well as breaking some of the molecules into smaller molecules to produce a high-octane component of gasoline.

<span class="mw-page-title-main">Alkylation unit</span>

An alkylation unit (alky) is one of the conversion processes used in petroleum refineries. It is used to convert isobutane and low-molecular-weight alkenes (primarily a mixture of propene and butene) into alkylate, a high octane gasoline component. The process occurs in the presence of an acid such as sulfuric acid (H₂SO₄) or hydrofluoric acid (HF) as catalyst. Depending on the acid used, the unit is called a sulfuric acid alkylation unit (SAAU) or hydrofluoric acid alkylation unit (HFAU). In short, the alky produces a high-quality gasoline blending stock by combining two shorter hydrocarbon molecules into one longer chain gasoline-range molecule by mixing isobutane with a light olefin such as propylene or butylene from the refinery's fluid catalytic cracking unit (FCCU) in the presence of an acid catalyst.

Refining of crude oils essentially consists of primary separation processes and secondary conversion processes. The petroleum refining process is the separation of the different hydrocarbons present in crude oil into useful fractions and the conversion of some of the hydrocarbons into products having higher quality performance.

Barmer Refinery is an upcoming public sector refinery and petrochemical complex in the Pachpadra of Rajasthan, India. It is owned by HPCL Rajasthan Refinery Limited (HRRL), a joint venture between Hindustan Petroleum Corporation Limited and the Government of Rajasthan. This refinery will be connected with Jamnagar Refinery and Bathinda Refinery through Amritsar Jamnagar Expressway.

<span class="mw-page-title-main">Steam cracking</span> Petrochemical process to break down saturated hydrocarbons in smaller molecules

Steam cracking is a petrochemical process in which saturated hydrocarbons are broken down into smaller, often unsaturated, hydrocarbons. It is the principal industrial method for producing the lighter alkenes, including ethene and propene. Steam cracker units are facilities in which a feedstock such as naphtha, liquefied petroleum gas (LPG), ethane, propane or butane is thermally cracked through the use of steam in steam cracking furnaces to produce lighter hydrocarbons. The propane dehydrogenation process may be accomplished through different commercial technologies. The main differences between each of them concerns the catalyst employed, design of the reactor and strategies to achieve higher conversion rates.

References

↑ Gary, J.H.; Handwerk, G.E. (1984). Petroleum Refining Technology and Economics (2nd ed.). Marcel Dekker, Inc. ISBN 0-8247-7150-8.
↑ Leffler, W.L. (1985). Petroleum refining for the nontechnical person (2nd ed.). PennWell Books. ISBN 0-87814-280-0.
↑ Petroleum Coke Glossary
↑ "Delayed coking innovations and new design trends" (PDF). Archived from the original (PDF) on 2023-05-30. Retrieved 2012-03-01.
↑ Staff (November 2002). "2002 Refining Processes". Hydrocarbon Processing: 85–147. ISSN 0887-0284.
↑ Petroleum coke on the website of the IUPAC Compendium of Chemical Terminology
1 2 3 4 Tutorial: Delayed Coking Fundamentals Archived 2012-08-13 at the Wayback Machine (written by Paul Ellis and Christopher Paul of the Great Lakes Carbon Corporation)
↑ "United States Patent Number 0149667". Archived from the original on 2020-11-09. Retrieved 2012-03-01.
1 2 Staff (31 December 2002). "2002 Worldwide Refining Survey". Oil and Gas Journal: 68–111. ISSN 0030-1388.
↑ Delayed Coking, An Attractive Alternative (by Franz B. Ehrhardt, Conoco Oil Company at Middle East Oil & Gas Conference in Bahrain)
↑ Petroleum coke utilization for cement kiln firing, by E. Kaplan and N. Nedder, Nesher Israel Cement Enterprises Ltd., presented at the Cement Industry Technical Conference, IEEE-IAS/PCA, in Vancouver, British Columbia, Canada, April–May, 2001
↑ John C. McKetta, ed. (1994). Encyclopedia of Chemical Processing and Design (Volume 48). CRC. ISBN 0-8247-2498-4.
↑ Jean-Francois Le Page; Sami Chatila; Michael Davidson (1992). Resid and Heavy Oil Processing. Editions Technip. ISBN 2-7108-0621-5.
↑ Staff (November 1998). "1998 Refining Processes". Hydrocarbon Processing: 53–112. ISSN 0887-0284.
↑ Lurgi's Biomass-To-Liquid (BTL) Strategy ^{[ permanent dead link ]} Dr. Ludolf Plass, Dr. Armin Günther and Pietro Di Zanno, Biomass-To-Liquid (BTL) Congress, Berlin (Scroll down to pdf page 9 of 21 pdf pages)

External links

Glossary for cokers and related topics

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.

[1] Gary, J.H.; Handwerk, G.E. (1984). Petroleum Refining Technology and Economics (2nd ed.). Marcel Dekker, Inc. ISBN 0-8247-7150-8.

[2] Leffler, W.L. (1985). Petroleum refining for the nontechnical person (2nd ed.). PennWell Books. ISBN 0-87814-280-0.

[3] Petroleum Coke Glossary

[4] "Delayed coking innovations and new design trends" (PDF). Archived from the original (PDF) on 2023-05-30. Retrieved 2012-03-01.

[5] Staff (November 2002). "2002 Refining Processes". Hydrocarbon Processing: 85–147. ISSN 0887-0284.

[6] Petroleum coke on the website of the IUPAC Compendium of Chemical Terminology

[Tutorial-7] 1 2 3 4 Tutorial: Delayed Coking Fundamentals Archived 2012-08-13 at the Wayback Machine (written by Paul Ellis and Christopher Paul of the Great Lakes Carbon Corporation)

[8] "United States Patent Number 0149667". Archived from the original on 2020-11-09. Retrieved 2012-03-01.

[OG-9] 1 2 Staff (31 December 2002). "2002 Worldwide Refining Survey". Oil and Gas Journal: 68–111. ISSN 0030-1388.

[10] Delayed Coking, An Attractive Alternative (by Franz B. Ehrhardt, Conoco Oil Company at Middle East Oil & Gas Conference in Bahrain)

[11] Petroleum coke utilization for cement kiln firing, by E. Kaplan and N. Nedder, Nesher Israel Cement Enterprises Ltd., presented at the Cement Industry Technical Conference, IEEE-IAS/PCA, in Vancouver, British Columbia, Canada, April–May, 2001

[McKetta-12] John C. McKetta, ed. (1994). Encyclopedia of Chemical Processing and Design (Volume 48). CRC. ISBN 0-8247-2498-4.

[Technip-13] Jean-Francois Le Page; Sami Chatila; Michael Davidson (1992). Resid and Heavy Oil Processing. Editions Technip. ISBN 2-7108-0621-5.

[14] Staff (November 1998). "1998 Refining Processes". Hydrocarbon Processing: 53–112. ISSN 0887-0284.

[15] Lurgi's Biomass-To-Liquid (BTL) Strategy ^{[ permanent dead link ]} Dr. Ludolf Plass, Dr. Armin Günther and Pietro Di Zanno, Biomass-To-Liquid (BTL) Congress, Berlin (Scroll down to pdf page 9 of 21 pdf pages)

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]

[10]

[11]

[12]

[13]

[14]

[15]