Petroleum coke (often abbreviated pet coke or petcoke) is a carbonaceous stable delivered from oil refinery coker units or different cracking processes. Coking processes that can be employed for making petcoke embody contact coking, fluid coking, flexicoking and delayed coking. Other coke has traditionally been delivered from coal.
This coke can both be gas grade (high in sulfur and metals) or anode grade (low in sulfur and metals). The raw coke straight out of the coker is often referred to as inexperienced coke On this context, “green” means unprocessed. The further processing of green coke by calcining in a rotary kiln removes residual unstable hydrocarbons from Natural Gas Refining Equipment the coke. The calcined petroleum coke might be additional processed in an anode baking oven in order to supply anode coke of the desired shape and physical properties. The anodes are primarily used in the aluminium and steel business.
Petcoke is over 90 percent carbon and emits 5 to 10 % more carbon dioxide (CO2) than coal on a per-unit-of-vitality basis when it is burned. As petcoke has a better vitality content material, petcoke emits between 30 and 80 percent extra CO2 than coal per unit of refinery petroleum weight. The distinction between coal and coke in CO2 production per unit energy produced relies upon upon the moisture within the coal (will increase the CO2 per unit vitality – heat of combustion) and unstable hydrocarbon in coal and coke (lower the CO2 per unit energy).
Sorts of petroleum coke
There are at the very least 4 fundamental forms of petroleum coke, specifically, needle coke, honeycomb coke, sponge coke and shot coke. Different types of petroleum coke have different microstructures on account of differences in operating variables and nature of feedstock. Vital differences are additionally to be observed within the properties of the several types of coke, notably ash and volatile matter contents.
Needle coke, additionally referred to as acicular coke, is a extremely crystalline petroleum coke used in the manufacturing of electrodes for the steel and aluminium industries and is particularly beneficial as a result of the electrodes have to be replaced usually. Needle coke is produced exclusively from either FCC decant oil or coal tar pitch.
Honeycomb coke is an intermediate coke, with ellipsoidal pores which are uniformly distributed. In comparison with needle coke, honeycomb coke has a decrease coefficient of thermal enlargement and a lower electrical conductivity.
Gas grade coke
Gas grade coke is classified as both sponge coke or shot coke morphology. While oil refiners have been producing coke for effectively over one hundred years, the mechanisms that trigger sponge coke or shot coke to kind will not be properly understood and can’t be precisely predicted. Normally, decrease temperatures and higher pressures promote sponge coke formation. Additionally, the quantity of heptane insolubles current, and fraction of mild elements within the coker feed contribute.
Whereas its excessive heat and low ash content make it a good gasoline for energy era in coal fired boilers, petroleum coke is excessive in sulfur and low in risky content material, and this poses environmental (and technical) issues with its combustion. To satisfy present North American emissions requirements, some type of sulfur seize is required, a standard choice of sulfur recovering unit for burning petroleum coke is the SNOX Flue gasoline desulfurisation technology, which is based on the nicely-recognized WSA Process. Fluidized bed combustion is usually used to burn petroleum coke. Gasification is increasingly used with this feedstock (typically using gasifiers positioned in the refineries themselves).
Calcined petroleum coke
Calcined petroleum coke (CPC) is the product from calcining petroleum coke. This coke is the product of the coker unit in a crude oil refinery. The calcined petroleum coke is used to make anodes for the aluminium, steel and titanium smelting trade. The green coke must have sufficiently low metals content material so as to be used as anode material. Inexperienced coke with this low metals content material is referred to as anode grade coke. The inexperienced coke with too excessive metals content will not be calcined and is used for burning. This green coke is called fuel grade coke.
Desulfurization of petcoke
A high sulfur content in petcoke reduces its market worth and should prevent its use as gasoline on account of restrictions on sulfur oxides emissions for environmental reasons. Methods have thus been proposed to cut back or eliminate the sulfur content of petcoke. Most of them involve the desorption of the inorganic sulfur present in the pores or floor of the coke, and the partition and removal of the natural sulfur hooked up to the aromatic carbon skeleton.
Potential petcoke desulfurization methods might be categorized as follows:
- Solvent extraction
- Chemical remedy
- Thermal desulfurization
- Desulfurization in an oxidizing environment
- Desulfurization in an environment of sulfur-bearing gasoline
- Desulfurization in an environment of hydrocarbon gases
As of 2011 there was no industrial course of accessible to desulfurize petcoke.
Storage, disposal, and sale
Practically pure carbon, petcoke is a potent source of carbon dioxide if burned.
Petroleum coke could also be stored in a pile close to an oil refinery pending sale. One example, as of 2013, was the big stockpile owned by Koch Carbon close to the Detroit River which was produced by a Marathon Petroleum refinery in Detroit which started refining bitumen from the oil sands of Alberta in November 2012. Massive stockpiles of petcoke also existed in Canada as of 2013. China and Mexico were markets for petcoke exported from California to be used as fuel. As of 2013 the EPA was declining permits to make use of petcoke as gasoline in the United States[quotation wanted] but markets existed in India and Latin America the place it was used to gas cement manufacture. As of 2013 Oxbow Corporation, owned by William I. Koch, was a major supplier in petcoke, promoting 11 million tons annually.
Petroleum coke is sometimes a supply of effective dust, which might get by way of the filtering strategy of the human airway and lodge in the lungs. As soon as these small mud particles lodge within the lungs they could cause severe well being problems.
Petroleum coke can comprise vanadium, a toxic steel, in ample quantities to poison individuals. Vanadium was discovered in the mud, collected in occupied dwellings near the petroleum coke stored subsequent to the Detroit River. Vanadium is toxic in tiny portions, 0.Eight micrograms per cubic meter of air, in line with the EPA.