LNG?
Liquefied natural gas (LNG) is natural gas that has been cooled to a liquid state, at about -260°Fahrenheit, for shipping and storage. The volume of natural gas in its liquid state is about 600 times smaller than its volume in its gaseous state. This process, which was developed in the 19th century, makes it possible to transport natural gas to places pipelines do not reach and to use natural gas as a transportation fuel.
For large-volume ocean transport, LNG is loaded onto double-hulled ships, which are used for both safety and insulating purposes. Once the ship arrives at the receiving port, LNG is off-loaded into well-insulated storage tanks, and later regasified for entrance into a pipeline distribution network.
LNG can also be shipped in smaller quantities, usually over shorter ocean distances. There is a growing trade in small-scale LNG shipments, which are most commonly made using the same containers used on trucks and in international trade, specially outfitted with cryogenic tanks. Other small-scale LNG activities include “peak-shaver” liquefaction and storage facilities, which can hold gas compactly for when it is needed in local markets in the U.S. during times of peak demand. LNG is also sometimes imported or exported by truck from this kind of facility.
LNG increases markets for natural gas
Where natural gas pipelines are not feasible or do not exist, liquefying natural gas is a way to move natural gas from producing regions to markets, such as to and from the United States and countries in Asia or Europe. LNG is shipped in special ocean-going ships (tankers) between export terminals, where natural gas is liquefied, and import terminals, where LNG is returned to its gaseous state (regasified). At an import terminal, it can be injected into pipelines for transmission to distribution companies, industrial consumers, and power plants.
Most LNG is transported by large ships/tankers called LNG carriersthat are equipped with onboard, super-cooled cryogenic tanks. LNG is also transported in relatively small volumes on ships using International Organization for Standardization (ISO)-compliant containers and on trucks.
LNG can be used as a fuel for ships, trucks, and buses with specially designed fuel tanks. Some power plants store LNG and use it to generate electricity when electricity demand is high and their natural gas demand exceeds pipeline delivery capacity.
The United States imports and exports LNG
In recent years, the United States has become a net exporter of LNG, largely because of increasing U.S. natural gas production, declining imports of LNG, and expansion of LNG export terminal capacity.
The United States imported very small amounts of LNG until 1995, and then LNG imports generally increased each year until peaking in 2007 at about 771 billion cubic feet (Bcf). Increases in U.S. natural gas production and expansion of natural gas pipelines have reduced the need to import natural gas. LNG imports declined in most years since 2007.
In 2017, the United States imported about 78 Bcf of LNG—the lowest amount since 1997—from three countries:
Trinidad and Tobago–70 Bcf
Nigeria–6 Bcf
Canada–2 Bcf
Most of U.S. LNG imports are into the Everett regasification terminal near Boston, Massachusetts. Massachusetts, Connecticut, Maine, New Hampshire, Vermont, and Rhode Island may have significant pipeline constraints when heating demand increases substantially during periods of very cold weather. LNG imports help to meet natural gas demand in New England because the region currently has limited pipeline interconnections with the Northeast and U.S. producing regions.
In 2017, the U.S. exported about 708 Bcf of LNG to 28 countries, more than in any previous year. The top five destination countries and their shares of total U.S. LNG exports in 2017 were
Mexico–20%
South Korea–18%
China–15%
Japan–8%
Jordan–5%

In 2017, nearly all U.S. LNG exports were transported on LNG carriers. Less than 1 Bcf was exported to Barbados and the Bahamas on small tankers equipped with ISO containers. Less than 1 Bcf of LNG was exported by truck to Canada and Mexico.
Sometimes the U.S. re-exports natural gas that it originally imported when natural gas prices are favorable to do so. About 0.4 Bcf of LNG was re-exported to Mexico in 2017.
U.S. LNG exports are expected to increase in coming years as new U.S. LNG export capacity comes online.
Petroleum coke, abbreviated 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 crackingprocess—a thermo-based chemical engineering process that splits long chain hydrocarbons of petroleum into shorter chains—that takes place in units termed coker units. (Other types of coke are derived from coal.) Stated succinctly, coke is the “carbonization product of high-boiling hydrocarbon fractions obtained in petroleum processing (heavy residues).” Petcoke is also produced in the production of synthetic crude oil (syncrude) from bitumen extracted from Canada’s oil sands and from Venezuela’s Orinoco oil sands.
In petroleum coker units, residual oils from other distillation processes used in petroleum refining are treated at a high temperature and pressure leaving the petcoke after driving off gases and volatiles, and separating off remaining light and heavy oils. These processes are termed “coking processes”, and most typically employ chemical engineering plant operations for the specific process of delayed coking.
This coke can either be fuel grade (high in sulfur and metals) or anode grade (low in sulfur and metals). The raw coke directly out of the coker is often referred to as green coke. In this context, “green” means unprocessed. The further processing of green coke by calcining in a rotary kiln removes residual volatile hydrocarbons from the coke. The calcined petroleum coke can be further processed in an anode baking oven to produce anode coke of the desired shape and physical properties. The anodes are mainly used in the aluminium and steel industry.
Petcoke is over 90% carbon and emits 5% to 10% more carbon dioxide (CO2) than coal on a per-unit-of-energy basis when it is burned. As petcoke has a higher energy content, petcoke emits between 30 and 80 percent more CO2 than coal per unit of weight. The difference between coal and coke in CO2 production per unit of energy produced depends upon the moisture in the coal, which increases the CO2 per unit of energy – heat of combustion) and on the volatile hydrocarbons in coal and coke, which decrease the CO2 per unit of energy.

There are at least four basic types of petroleum coke, namely, needle coke, honeycomb coke, sponge coke and shot coke. Different types of petroleum coke have different microstructures due to differences in operating variables and nature of feedstock. Significant differences are also to be observed in the properties of the different types of coke, particularly ash and volatile matter contents.
Needle coke, also called acicular coke, is a highly crystalline petroleum coke used in the production of electrodes for the steel and aluminium industries and is particularly valuable because the electrodes must be replaced regularly. Needle coke is produced exclusively from either FCC decant oil or coal tar pitch.
Honeycomb coke is an intermediate coke, with ellipsoidal pores that are uniformly distributed. Compared to needle coke, honeycomb coke has a lower coefficient of thermal expansion and a lower electrical conductivity.
Fuel-grade coke is classified as either sponge coke or shot coke morphology. While oil refiners have been producing coke for over 100 years, the mechanisms that cause sponge coke or shot coke to form are not well understood and cannot be accurately predicted. In general, lower temperatures and higher pressures promote sponge coke formation. Additionally, the amount of heptane insolubles present and the fraction of light components in the coker feed contribute.
While its high heat and low ash content make it a decent fuel for power generation in coal-fired boilers, petroleum coke is high in sulfur and low in volatile content, and this poses environmental (and technical) problems with its combustion. Its gross calorific value (HHV) is nearly 8000 Kcal/kg which is twice the value of average coal used in electricity generation. A common choice of sulfur recovering unit for burning petroleum coke is the SNOX Flue gas desulfurisation technology, which is based on the well-known WSA Process. Fluidized bed combustion is commonly used to burn petroleum coke. Gasification is increasingly used with this feedstock (often using gasifiers placed in the refineries themselves).
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 industry. The green coke must have sufficiently low metal content to be used as anode material. Green coke with this low metal content is called anode-grade coke. When green coke has excessive metal content, it is not calcined and is used as fuel-grade coke in furnaces.