Coking Technology

Petroleum cokePetroleum coke (often abbeviated Pet coke) is a carbonaceous solid derived from oil refinery coker unit [delayed coker unit]

Petroleum cokePetcoke has a higher energy content than coal and emits between 30~80% more CO2 than coal per unit of weightThe coke can be either be :[1] Fuel grade (high in sulfur and metal) called as green coke[2] Anode grade (low in sulfur and metal) called as calcined cokeFuel grade (green) cokeThe raw coke directly out of the delayed coker is referred as green coke. In this context, green means unprocessedThis coke is used in fuel application for power generation such as utility boiler and cement kilnsDue to high content of sulfur and metal that can be harmfull for enviroment, then to meet current tighther enviromental regulation, some form of sulfur capture process is required which is known as SNOX process

Anode grade (calcined) cokeThe further processing of green coke by calcining in a rotary kiln to removes residual volatile matter and also metal from the cokeThis coke is used to make anodes for aluminium, steel and titanium smelting industry

Crude oil refinery in glance

Thermal crackingAs the term implies, thermal cracking reaction are those that occur when the temperature is raised to a point at which bonds that hold a molecule together are broken. This breaking of bonds result predominantly in an increase in smaller molecules. However, breaking of bonds also leads to free radical formation that can also result in subsequent polymerization or condensation reactions. These reactions form larger, more condensed molecules. As applied to the refining industry, thermal cracking is used to produce smaller molecules from larger one. As such, it is an endothermic reaction when considered on an overall basis; however, some of the condensation reactions that eventually lead to coke are exothermic.

Thermal cracking process designed to handle heavy residues with high asphaltene, resin, metal and sulfur contents. These residue can not fed to catalytic cracking unit because their impurities can deactivate and poison the catalyst

Thermal crackingIn thermal cracking generally 2 [two] types of reactions take place :[1] Primary reaction by decomposition of larger molecules to smaller one[2] Secondary reaction by which active product from primary cracking reaction further crack or react to form other molecule or polymerize to generate heavy product (coke)

Thermal crackingVarious thermal cracking processes :[1] Visbreaking : it is a thermal cracking process producing gas, distillates and visbroken residue (471~493oC at 50~200 psig)[2] Delayed cooking : continuous thermal cracking which generates coke and produces various distillates in fractionator from vacuum residue. Coke drum temperature remains around 482~516oC at 90 psig[3] Fluid coking : continuous coking process where residue is sprayed on to fluidized bed of hot coke particles. Here cracking takes place at much higher temperature than delayed coking (up to 565oC)[4] Flexi coking : continuous coking process like fluid coking which includes gasification section of coke produced in fluid coking operationAmong the above, Delayed Coking is most popularGoal for delayed coker operation is to maximize the yield of distillates and minimize of coke (as byproduct). The main products of delayed coking is off gas (from which LPG is recovered), naphta, light coker gas oil (LCGO) and heavy coker gas oil (HCGO)Most typical of delayed coking feedstock is vacuum residue (+530oC)

Delayed coking

Delayed cokingSome of well known process licencors of Delayed Coker Unit are as under :[1] Foster Wheeler[2] KBR[3] Lummus Technology[4] Conoco Philips[5] Exxon Mobil, etc

Delayed coking licenced by Foster Wheeler/UOP

Delayed coking licenced by Foster Wheeler/UOPOperating condition : typical ranges are [1] Heater outlet temperature : 900~950oF[2] Coke drum pressure : 15~100 psig[3] Recycle ratio, equivalent fresh feed : 0~1Note : (1) Increasing coking temperature decrease coke production, increase liquid yield and gas oil end point(2) Increasing pressure and/or recycle ratio increase coke production decrease liquid yield and gas oil end pointEconomic :Investment (basis 65,000~100,000 bpd)2Q 2005 US Gulf : 6,700~13,600 US$/barrelUtilities, typical per bbl feed[1] Fuel : 120,000 BTU[2] Electricity : 3 kWh[3] Steam : 35 lb[4] Cooling water : 36 gallonCurrenly, 52 delayed coker installed worlwide with total capacity over 2,5 million bpsd

Delayed coking licenced by kbrExperiences, KBR has provided process technology for more than 15 cokers.

Delayed coking licenced by lummus technology

Delayed coking licenced by lummus technologyOperating condition : typical ranges are [1] Heater outlet temperature : 900~950oF[2] Coke drum pressure : 15~90 psig[3] Recycle ratio, equivalent fresh feed : 0~100% vol/vol feedEconomic :Investment (basis 20,000 bpd)2008 US Gulf Coast : 8,000 US$/barrelUtilities, typical per bbl feed[1] Fuel : 123,000 BTU[2] Electricity : 3.6 kWh[3] Steam : 1 lb[4] Cooling water : 58 gallon[5] Boiler feed water : 38 lb[6] Condensate : 24 lbCurrenly, 60 delayed coker installed worlwide

Delayed coking conoco philips

Delayed coking conoco philipsOperating condition : typical ranges are [1] Heater outlet temperature : 920~945oF[2] Coke drum pressure : 15~25 psig[3] Recycle ratio, equivalent fresh feed : 15~20% vol/vol feedEconomic :Investment (basis 60,000 bpd)Year 2000 : 3,000 US$/barrelUtilities, typical per bbl feed[1] Power : 13,940 BHP[2] Fuel : 361 x 106 BTU/hr[3] 600# Steam : 13,400 lb/hr[4] 475# Steam : 52,000 lb/hr[5] 150# Steam : 7,350 lb/hr[6] Condensate : 25 gallon/minute[7] Boiler feed water : 140 gallon/minute

flexicoking exxon mobil research & engineeringFluidized bed coking with integrated steam gasification technology to covert heavy HC to lighter liquid product, clean fuel gas with minimum coke

Cyclic process of delayed coking

Snox processThe SNOX process is a process which removes sulfur dioxide, nitrogen dioxide and particulates from flue gases. The sulfur is recovered as concentrated sulfuric acid and the nitrogen oxides are reduced to free nitrogen The SNOX process developed by Haldor Topsoe has been specifically designed for power and steam generation plants to remove sulfur and nitrogen oxides from combustion of heavy residuals, petroleum coke, sour gas or other waste products from refineries The SNOX process includes the following steps:[1] Dust removal [2] Catalytic reduction of NOx by adding NH3 to the gas upstream the SCR DeNOx reactor [3] Catalytic oxidation of SO2 to SO3 in the oxidation reactor [4] Cooling of the gas to about 100 C whereby the H2SO4 condenses and can be withdrawn as concentrated sulfuric acid product

Snox process

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Coking Technology