Liquefied gas propane production. How to liquefy gases? Production and use of liquefied gas

public joint-stock company Gazprom is a global energy company engaged in exploration and production natural gas, gas condensate and oil, their transportation, storage, processing and sale, as well as the production of electricity in Russia and abroad.

PJSC Gazprom, its subsidiaries and organizations form a vertically integrated company (hereinafter referred to as the Company), in which PJSC Gazprom is the parent company, which determines overall strategy development.

PJSC Gazprom's strategy is to become a leader among global energy companies. This implies a responsible attitude towards preserving a favorable environment for present and future generations.

The environmental policy of PJSC Gazprom is based on the Constitution Russian Federation, federal laws and other regulatory legal acts of the Russian Federation, international legal documents in the field of environmental protection and rational use natural resources.

The Environmental Policy is a document expressing the official position of PJSC Gazprom regarding the Company's role and its obligations in maintaining a favorable environment in the regions where the Company operates.

The environmental policy is the basis for setting medium-term corporate environmental goals and is subject to consideration when developing programs for the Company's long-term development.

The environmental policy is brought to the attention of every employee of the Company and should become a guideline for all partners of the Company without exception.

The environmental policy is subject to revision, adjustment and improvement in case of changes in development priorities and conditions of the Company's activities in accordance with the procedures established in PJSC Gazprom's environmental management system.

Commitments of the Company

PJSC Gazprom declares its commitment to the principles of sustainable development, which means a balanced and socially acceptable combination of economic growth and preservation of a favorable environment for future generations.

Based on this, the Company assumes the following obligations, which it will fulfill and require their fulfillment from its partners, contractors and counterparties:

1. Guarantee compliance with environmental standards and requirements established by the legislation of the Russian Federation, international legal acts in the field of environmental protection and the legislation of the countries of presence.
2. Ensure the reduction of the negative impact on the environment, resource conservation, take all possible measures to preserve the climate, biodiversity and compensate for possible damage environment.
3. Carry out preventive actions to prevent negative impacts on the environment, which means priority of preventive measures to prevent negative impacts over measures to eliminate the consequences of such impacts.
4. Guarantee compliance with the norms and requirements for ensuring environmental safety during the development of hydrocarbon deposits in continental shelf and in the Arctic zone of the Russian Federation.
5. Improve the energy efficiency of production processes, take measures to reduce greenhouse gas emissions.
6. Provide at all stages of implementation investment projects minimization of the risks of negative impact on the environment, including on natural objects with increased vulnerability and objects, the protection and preservation of which is of particular importance.
7. Take into account the interests and rights of indigenous peoples to lead a traditional way of life and preserve their original habitat.
8. Ensure the involvement of the Company's employees in activities to reduce environmental risks, continuous improvement of the environmental management system, indicators in the field of environmental protection.
9. To increase the competence and awareness of the role of the Company's employees in solving issues related to environmental protection.
10. Ensure wide availability of environmental information related to the Company's activities in the field of environmental protection and decisions made in this area.

Mechanisms for fulfilling the obligations of the Environmental Policy

The main mechanisms for fulfilling the obligations of this Environmental Policy are:

• maintenance and improvement corporate system environmental management based on the requirements of international ISO standard 14001;
• setting measurable corporate environmental goals aimed at reducing the negative impact on the environment and providing the necessary resources for measures to achieve them;
• mandatory consideration of environmental aspects and risk assessment when planning activities, developing and implementing investment projects;
• conducting industrial environmental control and monitoring, conducting impact assessment economic activity Companies on the environment;
• implementation of gasification programs settlements Russia;
• integrated development the market for the use of natural gas as a gas motor fuel in the Russian Federation and abroad;
• participation of the Company in global environmental programs and projects aimed at achieving sustainable development of the regions of presence;
• stimulation scientific research and implementation innovative projects aimed at improving energy efficiency, the use of renewable energy sources and non-traditional energy resources;
• application of the best available technologies at various stages production activities including procurement of technologies, materials and equipment;
• high environmental risk insurance;
• organizing the study, understanding and practical application by each employee of the Company of applicable legislative and other requirements related to the environmental aspects of activities in the regions of presence;
• system improvement environmental education employees of the Company;
• involvement of all employees of the Company in activities related to the environmental management system;
• interaction with organizations and persons interested in improving the environmental safety of the Company;
• communication of the obligations of the Environmental Policy to the attention of all persons working for the Company or on its behalf, including subcontractors working at the Company's facilities.

Public Joint Stock Company Moscow United Energy Company (PJSC MIPC) is the largest heat and power company in Russia. Its main task is to reliably provide the city of Moscow with heating and hot water supply. The activities of PJSC MIPC include the production, transportation, distribution and sale of thermal energy, as well as the generation of electrical energy.

More than 95% of the population of the capital, as well as hundreds of enterprises and organizations use the services of PJSC MOEK daily. Realizing your high social role and a place in creating a comfortable urban environment, PJSC MOEK not only aims at uninterrupted and high-quality supply of heat to consumers, but also strives to do this taking into account environmental values, following international principles of sustainable development.

This Environmental Policy is a document that demonstrates to all interested parties the obligations of PJSC MIPC and its management regarding the preservation and improvement of the environment. Since PJSC MIPC is a subsidiary of LLC Gazprom Energoholding, a member of the Gazprom Group, PJSC MIPC Environmental Policy is based on the Environmental Policy of PJSC Gazprom and develops its obligations in relation to its activities.

The environmental policy of PJSC MIPC applies to the entire PJSC staff MOEK, as well as for the personnel contractors performing works and services for PJSC MIPC, and is mandatory for accounting when accepting management decisions.

Obligations of PJSC MIPC

1. Comply with the norms and requirements in the field of environmental protection applicable to the activities of PJSC MIPC, established by the legislation of the Russian Federation and the city of Moscow.

2.Prevent environmental pollution by improving design, optimizing production processes and using the best available technologies.

3. Strive to reduce the negative impact on the environment by increasing the energy efficiency of production processes at all stages.

4. Constantly improve the environmental management system at PJSC MIPC to ensure its effectiveness.

Promising areas of activity of PJSC MIPC in the field of environmental protection and rational use of natural resources

The obligations of PJSC MIPC serve as the basis for determining promising directions activities in the field of environmental protection and rational use of natural resources.

Such activities of PJSC MIPC are:

- increasing the efficiency of the use of non-renewable natural resources and energy sources;

- minimization of negative technogenic impact on the natural and urban environment.

Actions of PJSC MIPC on the implementation of the Environmental Policy

To implement this Environmental Policy, PJSC MIPC will systematically perform the following actions:

- implement and maintain an environmental management system that meets international standards;

- consistently involve PJSC MIPC personnel in activities to reduce environmental risks and improve production environmental performance;

- introduce new technologies and methods of work that help reduce air pollution, noise pollution, land pollution, production waste generation

- provide professional and environmental education for employees of PJSC MIPC;

- ensure the availability of environmental information on the economic activities of PJSC MIPC for interested parties, the validity and transparency of decisions made that affect the implementation of the Environmental Policy.

This Environmental Policy of PJSC MIPC is a priority and is brought to the attention of every employee of PJSC MIPC.

Liquefied hydrocarbon gases (LHG) are produced from associated petroleum gas. These are pure gases or special mixtures that can be used for home heating, as automotive fuel, and also for the production of petrochemical products.

NGL to HFC

Liquefied hydrocarbon gases are obtained from the wide fraction of light hydrocarbons (NGL), which, in turn, is separated from associated petroleum gas (APG).

Separation of NGL into its constituent components - individual hydrocarbons - takes place at gas fractionation units (GFU). The separation process is similar to the separation of APG. However, in this case, the separation should be more careful. From NGLs in the process of gas fractionation, various products can be obtained. It can be propane or butane, as well as a propane-butane mixture (it is called SPBT, or a technical propane-butane mixture). SPBT is the most common type of liquefied gases - it is in this form that this product is supplied to the population, industrial enterprises and exported. Thus, out of 2.034 million tons of LPG sold by Gazprom Gazenergoset in 2012, propane-butane mixture accounted for 41%, butane - a third of deliveries, propane - about 15%.

Also, by separating NGL, technical butane and technical propane, automobile propane (PA) or a mixture of PBA (propane-butane automobile) are obtained.

There are other components that are isolated by processing NGLs. These are isobutane and isobutylene, pentane, isopentane.

How are liquefied petroleum gases used?

Liquefied hydrocarbon gases can be used in a variety of ways. Probably, everyone is familiar with bright red propane cylinders since Soviet times. They are used for cooking on household stoves or for heating in country houses.

Also, liquefied gas can be used in lighters - either propane or butane is usually pumped there.

Liquefied hydrocarbon gases are also used for heating industrial enterprises and residential buildings in those regions where natural gas has not yet reached through pipelines. LPG in these cases is stored in gas holders - special containers, which can be both ground and underground.

In terms of efficiency, propane-butane ranks second after the main natural gas. At the same time, the use of LPG is more environmentally friendly compared to, for example, diesel fuel or oil.

Gas in motors and packages

Propane, butane and their mixtures, along with natural gas (methane), are used as an alternative fuel for refueling cars.
The use of natural gas motor fuel is currently very relevant, because every year the domestic vehicle fleet, consisting of more than 34 million units Vehicle, along with exhaust gases, 14 million tons of harmful substances are emitted. And this is 40% of the total industrial emissions into the atmosphere. Exhaust gases from gas-powered engines are several times less harmful.

The exhaust of gas engines contains 2–3 times less carbon monoxide (CO) and 1.2 times less nitrogen oxide. At the same time, compared to gasoline, the cost of LPG is approximately 30–50% lower.

The gas motor fuel market is actively developing. At present, there are more than 3,000 gas stations and more than 1 million LPG vehicles in our country.

Finally, liquefied hydrocarbon gases are the raw material for petrochemical industry. For the production of LPG products, they are subjected to a complex process that takes place at very high temperatures- pyrolysis. The result is olefins - ethylene and propylene, which are then, as a result of the polymerization process, converted into polymers or plastics - polyethylene, polypropylene and other types of products. That is, the plastic bags we use in daily life, disposable tableware, containers and packaging of many products are made from liquefied gases.

Technologies for oil and gas production, as well as their transportation, are constantly being improved. And one of brightest examples This is liquefied natural gas (LNG), namely the technology of large-scale liquefaction of gas and the transportation of LNG by sea over long distances. LNG is a real revolution in the gas market, changing the image of modern energy, proof that the raw materials industry is capable of generating modern high-tech solutions. LNG opens up new markets for "blue" fuel, involves more and more countries in the gas business, helping to solve the puzzle of global energy security. The term "gas pause", meaning the active consumption of gas and its possible transformation into the number one fuel, is not an empty phrase.

Technology industrial production liquefied natural gas is not much time. The first LNG export plant was put into operation in1964 But since then, the process has been constantly improved, and today, for example, designs are already being prepared for the world's first mobile floating gas liquefaction plants located on large-capacity ships.

Liquefied natural gas pulls several industrial sectors along the chain. These are shipbuilding, transport engineering and chemistry. Liquefied natural gas even shapes the aesthetics of today's highly industrialized society. Anyone who has seen a gas liquefaction plant can be convinced of this.

Russia, with the world's largest gas reserves, has long been out of the liquefaction and LNG business. But this unfortunate gap has been filled. In 2009, the first gas liquefaction plant on Sakhalin, the Sakhalin-2 project, was put into operation. It is very important that advanced technologies in the field of gas liquefaction are implemented in Russia. For example, the Sakhalin plant is based on modern technology liquefaction with a double mixed reagent, developed specifically for this project. Since LNG production is carried out at over low temperatures, climate conditions can benefit by making LNG production cheaper and more efficient production process.

On the other hand, Russia has no other choice than LNG. Integration processes are developing in the world, competitors' LNG is already coming to the traditional export markets of Russian gas, that is, to Europe, displacing Gazprom, and Qatar and Australia are building up their positions in the Asia-Pacific region, jeopardizing Russia's plans to export to these markets.

The old giant fields are in the stage of declining production, the new fund left "stars" in the form of Bovanenkovskoye and Kharasaveyskoye fields. Next, the country needs to go to the shelf and master new technologies. And it so happened that LNG plants are considered the basis for monetization of gas reserves of precisely such fields - close to the coast, but remote from the consumer.

The Russian phrase "liquefied natural gas" corresponds to the English Liquified Natural Gas (LNG). It is important to distinguish LNG from the group of liquefied hydrocarbon gases(LPG), which includes liquefied propane-butane (SPB) or liquefied petroleum gas (LPG). But it is easy to distinguish them from each other and understand the “family” of liquefied hydrocarbon gases. Actually, the main difference is what kind of gas is liquefied. If a we are talking about the liquefaction of natural gas, which primarily consists of methane, then the term liquefied natural gas - or abbreviated LNG - is used. Methane is the simplest hydrocarbon, it contains one carbon atom and has the chemical formula CH4. In the case of a propane-butane mixture, we are talking about liquefied propane-butane. As a rule, it is extracted from associated petroleum gas (APG) or during oil refining as the lightest fraction. LPG is used primarily as a raw material in petrochemistry for the production of plastics, as an energy resource for gasification of settlements or in vehicles.

LNG is not separate product, although there are opportunities to use LNG directly. This is practically the same methane that is supplied through pipelines. But this is a fundamentally different way of delivering natural gas to the consumer. In liquefied form, methane can be transported by sea over long distances, which contributes to the creation of a global gas market, allowing the gas producer to diversify sales, and the buyer to expand the geography of gas purchases. The LNG producer has great freedom in the geography of supplies. After all, to create an infrastructure for shipping over long distances is more profitable than pulling a gas pipeline for thousands of kilometers. It is no coincidence that LNG is also called a "flexible pipe", showing its main advantage over the traditional method of gas delivery: a conventional pipeline extremely rigidly connects fields with a specific region of consumption.

After delivery to the destination, the LNG turns into a gaseous state again - at the regasification plant, its temperature is brought to ambient temperature, after which the gas becomes suitable for transportation through conventional pipeline networks.

LNG is a clear, colorless, non-toxic liquid that forms at -160C. After delivery to its destination, the LNG turns back into a gaseous state: in the regasification plant, it is brought to ambient temperature, after which the gas becomes suitable for transportation through conventional pipeline networks.

The main advantage of liquefied gas over its pipeline counterpart is that it occupies 618–620 times less volume during storage and transportation, which significantly reduces costs. After all, natural gas has a lower thermal density compared to oil, and therefore, for transporting volumes of gas and oil with the same calorific value(that is, the amount of heat released during the combustion of fuel) in the first case, large volumes are required. This is where the idea of ​​liquefying gas came from in order to provide it with a gain in volume.

LNG can be stored at atmospheric pressure, its boiling point is -163ºС, it is non-toxic, odorless and colorless. Liquefied natural gas is not corrosive to structural materials. The high environmental properties of LNG are explained by the absence of sulfur in liquefied gas. If sulfur is present in natural gas, it is removed before the liquefaction procedure. Interestingly, the beginning of the era of liquefied gas in Japan is precisely due to the fact that Japanese companies decided to use LNG as a fuel in order to reduce air pollution.

The LNG produced at modern plants consists mainly of methane - about 95%, and the remaining 5% is ethane, propane, butane and nitrogen. Depending on the manufacturer, the molar content of methane can vary from 87 (Algerian plants) to 99.5% (Kenai plant, Alaska). lower heat combustion is 33,494 kJ/cu m or 50,116 kJ/kg. To produce LNG, natural gas is first purified from water, sulfur dioxide, carbon monoxide and other components. After all, they will freeze at low temperatures, which will lead to the breakdown of expensive equipment.

Of all hydrocarbon energy sources, liquefied gas is the cleanest - for example, when it is used to produce electricity, CO2 emissions into the atmosphere are half that of coal. In addition, LNG combustion products contain less carbon monoxide and nitrogen oxide than natural gas - this is due to better purification during combustion. There is also no sulfur in liquefied gas, which is also the most important positive factor in assessing the environmental properties of LNG.

The complete chain of production and consumption of LNG includes the following stages

gas production;

its transportation to the liquefaction plant;

the procedure for liquefying gas, transferring it from a gaseous state to a liquid state; pumping it into storage tanks on tankers and further transportation;

regasification at onshore terminals, that is, the conversion of LNG into a gaseous state;

delivery to the consumer and its use.

As is known, at present and in the medium term, natural gas remains a vital component in meeting global energy needs due to its advantages over other types of fossil fuels and due to the ever-growing demand for it.

Currently most of gas is delivered to consumers via main pipelines in gaseous form.

At the same time, in some cases, for hard-to-reach remote fields, transport of liquefied natural gas (LNG) is more preferable than traditional pipeline transport. Calculations have shown that LNG transportation by tankers, taking into account the construction of liquefaction and regasification facilities, turns out to be economically viable at distances of 2,500 km (although the example of the Sakhalin LNG plant proves the relevance of exceptions). In addition, the LNG industry is today a leader in the globalization of the gas industry and has gone far beyond the boundaries of individual regions, which was not the case in the early 1990s.

As the demand for LNG grows, technical support competitive LNG projects in today's environment is a challenge. An important feature of LNG plants is that most cost items are dictated by specific parameters: the quality of the produced raw gas, natural and climatic conditions, topography, volumes of offshore operations, infrastructure availability, economic and political conditions.

Of particular interest in this regard are gas treatment and liquefaction technologies, which are already used today at modern LNG plants and which can be classified according to various criteria. But it is especially important that they are located in comfortable southern or more severe northern latitudes.

Based on this, it is possible to analyze the differences between these two groups, take into account the features and shortcomings of each, apply the experience of construction and operation in the implementation of new LNG projects in Russia, in particular in Arctic conditions. But even taking into account the existing experience, the promising development of the Arctic territories, where up to 25% of undiscovered hydrocarbon reserves are located, can be ensured in the future by innovations that increase efficiency and competitiveness.

History of LNG production

Experiments to liquefy natural gas began in the late 19th century. But it was only in 1941 that a commercial LNG plant was built in Cleveland (USA, Ohio). The fact that LNG can be transported by ship over long distances has been demonstrated by the example of transportation LNG tanker"Methane Pioneer" in 1959

The first export baseload LNG plant was the Camel project in Arzev (Algeria), which was launched in 1964. The first plant to produce LNG in northern conditions in 1969 was the US plant in Alaska. Most of the developments in the technologies of gas preparation for liquefaction and its liquefaction were carried out earlier and are currently being done by groups of scientists working on a regular basis. commercial enterprises. Main contributors international business LNG and plant start-up dates by years are presented in Table. one.

At the beginning of 2014, there were 32 LNG plants in operation in 19 countries; 11 LNG plants in five countries are under construction; 16 more LNG plants are being planned in eight countries. In Russia, in addition to the LNG plant on about. Sakhalin, there is a project to build a Baltic LNG plant in the Leningrad Region, and an LNG plant is planned in Yamal with the involvement of foreign partners. There are proposals for the construction of LNG facilities for the development of the Shtokman and Yuzhno-Tambeyskoye fields and for the implementation of the Sakhalin-1 and Sakhalin-3 projects.

A large number of Russian organizations were involved in projects related to liquefied gas: Gazprom VNIIGAZ LLC, Moscow Gas Processing Plant, Sosnogorsk and Orenburg Gas Processing Plants, JSC " Machine building plant"Arsenal", OJSC "NPO Geliymash", OJSC "Cryogenmash", OJSC "Uralkriomash", OJSC "Giprogaztsentr" and others.

The entire LNG system includes elements of production, processing, pumping, liquefaction, storage, loading, transportation and unloading, regasification. LNG projects require a sufficient amount of time, money and effort at the design stage, with economic evaluation, construction and commercial implementation. It usually takes more than 10 years from design to implementation. Therefore, it is common practice to enter into 20-year contracts. The gas reserves in the field should be sufficient for 20–25 years in order for it to be considered as a source of light hydrocarbons for LNG. The determining factors are the nature of the gas, the available pressure in the reservoir, the association of both free and dissolved gas with crude oil, transport factors, including the distance to the seaport.

The LNG industry has made great leaps over the years. If the totality of all innovations during this time is conditionally taken as 100%, then 15% is process improvement, 15% is equipment improvement, and 70% is heat and power integration. At the same time, capital costs decreased by 30%, and there was also a decrease in the cost of transporting gas through pipelines. There is a clear trend towards increasing the volume of production lines. Since 1964, the capacity of a single production line has increased 20 times. At the same time, according to the current state of the economy and technology, gas resources, which are considered difficult to access, are estimated at 127.5 trillion. m3. So actual problem It consists in transporting compressed fuel over long distances and across large bodies of water.

Table 1

Commissioning of LNG plants in the world

The country	Year	Company	The country	Year	Companies
Algiers, city of Arzu, city of Skikda	1964/1972	Sonatrach/Saipem-Chiyoda	Egypt, SEGAS Damietta		Union Fenosa, Eni, EGAS, EGPC
USA, Kenai	1969	ConocoPhillips, Marathon	Egypt, Idku (Egyptian LNG)	2005	BG, Petronas, EGAS/EGPC
Libya, Marsael Brega	1971	Exxon Sirte Oil	Australia, Darwin	2006	Kenai LNG, Conoco Phillips, Santos, Inpex, Eni, TEPCO
Brunei, Lumut	1972	Shell	Eq. Guinea, oh Bioko	2007	Marathon, GE Petrol
UAE	1977	BP, Total, ADNOC	Norway, about Melkoya, Snowit	2007	Statoil, Petoro, Total
Indonesia, Bontang, about. Borneo	1977	Pertamina, Total	Indonesia, Irian Jaya, Tangu	2009	BP, CNOOC, INPEX, LNG Japan, JX Nippon Oil &Energy, KG Berau”, “Talisman
Indonesia, Arun, sowing. Sumatra	1978	Pertamina, Mobil LNG Indonesia, JILCO	Russia, Sakhalin	2009	Gasprom, Shell
Malaysia, Satu	1983	Petronas, Shell	Katargaz 2	2009	Qatar Petroleum, ExxonMobil
Australia, Northwest	1989	Woodside, Shell, BHP, BP, Chevron, Mitsubishi/Mitsui	Yemen, Balhaf	2009	Total, Hunt Oil, Yemen Gas, Kogas, Hyundai, SK Corp, GASSP
Malaysia, Dua	1995	Petronas, Shell	Qatar, Rasgaz 2	2009	Qatar Petroleum, ExxonMobil
Katargaz 1	1997	Qatar Petroleum, ExxonMobil	Qatar, Rasgaz 3	2009	Qatar Petroleum, ExxonMobil
Trinidad and Tobago	1999	BP, BG, Repsol, Tractebel	Norway, Risavika	2009	Scangass (Lyse)
Nigeria	1999	NNPC, Shell, Total, Eni	Peru	2010	Hunt Oil, Repsol, SK Corp, Marubeni
Qatar, Rasgaz	1999	Qatar Petroleum, Exxon Mobil	Katargaz3,4	2010	ConocoPhillips, Qatar Petroleum, Shell
Oman/Oman Qalhat	2000/06	PDO, Shell, Fenosa, Itochu, Osaka gas, Total, Korea LNG, Partex, Itochu	Australia, Pluto	2012	Woodside
Malaysia, Tiga	2003	Petronas, Shell, JX Nippon, Diamond Gas	Angola	2013	Chevron, Sonangol, BP, Eni, Total

With the uneven distribution of natural gas resources in the world, the task of selling these resources through pipelines may turn out to be impossible or economically unattractive. For markets more than 1,500 miles (over 2,500 km) away, the LNG option has proven to be quite economical. Largely for this reason, from 2005 to 2018, the volume of global LNG supplies should double.

LNG markets were mainly located in areas with high industrial growth. Some contracts were fixed prices; this changed in 1991 when the cost of LNG began to be tied to oil and petroleum products. The share of trading in the spot market increased from 4% in 1990 to 18% by 2012.

In the value chain LNG liquefaction natural gas is the part requiring the largest investments and operating costs. Many liquefaction processes differ only in refrigeration cycles. Single mixed refrigerant processes are suitable for production lines of 1 to 3 Mtpa. Technological processes with volumes from 3 to 10 million tons per year are based on the use of two successive refrigeration cycles that minimize the pressure drop in the natural gas circuit. The use of the third refrigeration cycle made it possible to bypass such "bottlenecks" in technological process, as the diameter of the cryogenic heat exchanger and the volume of the refrigeration compressor for the propane cycle. Studies of various liquefaction processes show that each is not much more efficient than the others. Rather, every technology has competitive advantages under certain conditions. It is unlikely that large changes in capital costs due to small process improvements can be expected, since the process itself is based on the invariable laws of thermodynamics. As a result, the LNG industry remains highly capital intensive.

It is possible that LNG production in 30 years will be different from what exists today. Significant experience has been accumulated abroad in the design, manufacture and operation of vehicles and ships powered by LNG. Thanks to the solution of a number of technical problems, a decrease in investment activity on coastal complexes LNG, due to the difficulty of finding available gas, floating LNG projects are attracting increasing attention from all participants in the LNG industry. Technical innovation and integration of efforts can ensure the continued success of such projects; this requires the solution of a complex of multifaceted tasks - economic, technical and environmental.

However, already today, as in recent years, the LNG industry deservedly occupies an important place in the energy market and, most likely, will retain this position in the foreseeable future.

Gas preparation for liquefaction

The gas treatment process in high degree depends on the properties of the raw gas, as well as on the ingress of heavy hydrocarbons through the raw gas. In order to make gas liquefaction possible, the gas is first treated. When it enters the plant, the initial separation of the fractions usually occurs and the condensate is separated.

Since most of the impurities (water, CO2, H2S, Hg, N2, He, COS carbonyl sulfide, RSH mercaptans, etc.) freeze at LNG temperatures or adversely affect the quality of the product that meets the required product specification, these components are also separated. The heavier hydrocarbons are then separated to prevent them from freezing during the liquefaction process.

In table. Table 2 presents a summary of the hydrocarbon feedstock used at all plants under consideration.

Table 2

Gas compositions at northern and southern plants

	Component	Raw gas at southern LNG plants				Raw gas at northern LNG plants
		UAE (average flow)	Oman (average flow)	Qatar	Iran (m. South Pars)	Kenai, USA		Melkoya, Norway (average)	Sakhalin, Russia
						dry gas	Wet gas
1	C1, %	68,7	87,1	82,8	82,8–97,4	99,7	83,5	There is	There is
2	C2, %	12,0	7,1	5,2	8,4–11,5	0,07	1,4	Same	Same
3	C3, %	6,5	2,2	2,0		0,06	2,2	«	«
4	C4, %	2,6	1,3	1,1			2,2	«	«
5	C5, %	0,7	0,8	0,6			1,2	«	«
6	C6+, %	0,3	0,5	2,6			8,6	«	«
7	H2S, %	2,9	0	0,5	0,5–1,21	0,01	Not		«
8	CO2, %	6,1	1	1,8	1,8–2,53	0,07	0,4	5–8%	0,7
9	N2, %	0,1	0,1	3,3	3,3–4,56	0,1	0,5	0,8–3,6%	<0,5
10	hg		There is	There is	There is			There is	There is
11	He			There is
12	cos, ppm				3
13	rsh, ppm				232
14	H2O	There is	There is	There is	There is	There is	There is	There is	There is

It is clear that the hydrocarbon mixtures of each of the seven plants are suitable for LNG production, since the majority of them are light compounds of methane and ethane. The gas stream entering each of the considered LNG plants contains water, nitrogen, carbon dioxide. At the same time, the nitrogen content varies within 0.1–4.5%, CO2 - from 0.07 to 8%. Wet gas content ranges from 1% at the UAE LNG plant to 5-11% at Iran and Alaska LNG plants.

In addition, mercury, helium, mercaptans, and other sulfur impurities are present in the gas composition of a number of plants. The problem of hydrogen sulfide recovery has to be solved at every plant, except for the LNG plant in Oman. Mercury is present in the gas

Sakhalin, Norway, Iran, Qatar and Oman. The presence of helium is confirmed only at the Katargaz2 project. The presence of RSH, COS is confirmed in the gas of Iran's LNG project.

The composition and volume of gas affect not only the amount of LNG produced, but also the volume and variety of by-products, as shown in Table 1. 3. It becomes clear that, first of all, the composition of the gas affects the choice and use of equipment for gas processing, and hence the entire process of gas preparation and the final product yield.

Table 3

By-products in the gas composition of the considered LNG plants

by-product	UAE	Oman	Qatar	Iran	Melkoya, Norway
CIS	Not	Not	Yes	Not	Yes
Condensate	Yes	Yes	Yes	Yes	Yes
Sulfur	Yes	Not	Yes	Yes	Not
Ethane	Not	Not	Not	Not	Yes
Propane	Yes	Not	Not	Yes	Yes
Butane	Yes	Not	Not	Yes	Not
Naphtha	Not	Not	Yes	Not	Not
Kerosene	Not	Not	Yes	Not	Not
gasoil	Not	Not	Yes	Not	Not
Helium			Yes

To remove acid gases, LNG plants use the Hi-Pure process, a combination of a K2CO3 solvent process to remove most of the CO2 and a DEA (diethanolamine) amine solvent process to remove the remainder of CO2 and H2S (Figure 1) .

LNG plants in Iran, Norway, Qatar, Oman and Sakhalin use an amine acid gas treatment system MDEA (methyldiethanolamine) with an activator (“aMDEA”).

This process has a number of advantages over physical processes and other amine processes: better absorption and selectivity, lower vapor pressure, better operating temperature, energy consumption, etc.

Gas liquefaction

By most estimates and observations, the gas liquefaction module accounts for 45% of the capital costs of the entire LNG plant, representing 25–35% of the total project costs and up to 50% of subsequent operating costs. The liquefaction technology is based on the refrigeration cycle, when the refrigerant transfers heat from low temperature to high temperature through successive expansion and contraction. The production volume of a process line is mainly determined by the liquefaction process, the refrigerant used, the largest available combination of compressor and drive that cycles, and heat exchangers that cool the natural gas.

The basic principles of gas refrigeration and liquefaction are to fit the cooling-heating curves of the gas and refrigerant as closely as possible.

The implementation of this principle leads to a more efficient thermodynamic process, requiring less cost per unit of LNG produced, and this applies to all liquefaction processes.

The main parts of a gas liquefaction plant are the compressors that circulate the refrigerants, the compressor drives and the heat exchangers used to cool and liquefy the gas and exchange heat between the refrigerants. Many liquefaction processes differ only in refrigeration cycles.

Table 4

Summary data table for LNG plants

Component	northern factories			Southern LNG Plants
	kenai	Sakhalin	Snowit	Iran	Katargaz	UAE	Oman
Number of participants in LNG production
Number of LNG buyers		³5	³2			³1	³3
Duration of LNG purchase contracts, years
Number of LNG tanks	3	2	2	3	5	3	2
Tank capacity, thousand m3	36	100	125	140	145	80	120
Tank farm capacity, thousand m3
Number of tankers	2	3	4	–	14	5	–
Tanker capacity, thousand m3	87,5	145	145	–	210…270	88…125	–
Number of production lines	1	2	1	2	2	3	3
Volume of the 1st line, million tons/year	1,57	4,8	4,3	5,4	7,8	2,3-3,0	3,3
Total volume, million tons/year	1,57	9,6	4,3	10,8	15,6	7,6	10
Gas reserves, billion m3	170…238	397…566	190…317	51000	25400	–	–
Start of operation of the plant	1969	2009	2007	–	2008	1977	2000

Component	northern factories			Southern LNG Plants
	kenai	Sakhalin	Snowit	Iran	Katargaz	UAE	Oman
Plant area, km2	0,202	4,9	1	–	–	–	1,4
Used liquefaction technology	Optimized Cascade	DMR	MFC	MFC	AP-X	"C3/MR"	"C3/MR"
Number of refrigeration cycles	3	2	3	3	3	2	2
Composition of the 1st refrigerant. pre-cooling	Propane	Ethane, propane	Methane, ethane, propane, nitrogen	Methane, ethane, propane, nitrogen	Propane	Propane	Propane
Composition of the 2nd refrigerant	Ethylene	Methane, ethane, propane, nitrogen	Methane, ethane, propane, nitrogen	Methane, ethane, propane, nitrogen	Mixed	7% nitrogen, 38% methane, 41% ethane, 14% propane	Mixed
Composition of the 3rd refrigerant	Methane	–	Methane, ethane, propane, nitrogen	Methane, ethane, propane, nitrogen	Nitrogen	–	–
Additional cooling	Water, air	Air	Sea water	Sea water, water, air	Water, air		Sea water, air
Maximum productivity of the 1st production line for this liquefaction technology, million tons/year	7,2	8	8…13	8…13	8…10		5

In table. 4 shows comparative characteristics of liquefaction processes for all analyzed plants. The “C3/MR” liquefaction technology scheme (Fig. 2), which is used at LNG plants in Oman and the UAE, is also the most common in the world today.

A review and comparison of all of the current northern LNG plants and LNG plants in the Middle East leads to the following conclusion: there are differences between them in design, choice of gas liquefaction technologies and operation.

This means that climate and location will influence current and future Arctic LNG projects.

Production volumes and the choice of technology are not least determined by factors such as environmental conditions. On the example of the Norwegian and Sakhalin LNG plants, it is shown that it is more productive to produce LNG in the northern territories. The analysis did not reveal any reasons that could prevent the use of the gas liquefaction technologies under consideration at plants in the climatic conditions of the south and north, with the exception of the new DMR technology, which was developed specifically for the conditions of Sakhalin.

However, the choice of technology for a particular region affects the efficiency and energy consumption of LNG production, since these parameters of the liquefaction process are determined by whether the plant is operated in the cold. It is also important to note that all northern projects required a new technological solution for the liquefaction process each time, while in the Middle East the use of standard technologies is common.

The number of project participants in the southern plants ranges from 3 to 9, which is 1.5 times more than in the northern LNG projects, where the number of producers ranges from 2 to 6.

It can be assumed that such a difference is determined not only by the policies of states and national companies, but also by the specifics of the location of the northern industries, where the reliability and confidence of strong and large market players are necessary. It is unlikely that the availability of investments plays a decisive role here, since there are always many potential market players for LNG projects.

All considered LNG plants were built for relatively large fields with gas reserves of at least 170 billion m3. There were no dependences of northern and southern projects on gas reserves, but it is obvious that the southern regions have great opportunities for the implementation of single small LNG projects with lower annual production volumes - up to 3 million tons per year.

An argument in favor of this statement is the LNG plant in Kenai (USA), where relatively small production volumes of 1.57 million tons / year and the expected depletion of reserves raise the question of the expediency of continuing the project after 40 years of successful operation.

Duplication of critical equipment such as refrigeration compressors is not common and occurs only at the oldest LNG plant in Kenai. The use of redundant equipment can be not only an outdated technological solution, but also partially justified (if there is only one technological line in northern conditions to increase reliability). One way or another, but the development of 1992 by Phillips provides for the installation of single turbochargers. Phillips' dual safety liquefaction technology may be a viable option for small, isolated gas fields.

In terms of such parameters as contract terms, sales markets, hydrocarbon reserves in the fields, the size of the tanker fleet and tank farms, the use of mixed refrigerants and the number of refrigeration cycles, there were no large discrepancies between the southern and northern plants. The monotony of sales markets (Japan, Korea, Taiwan, Europe) - regardless of the launch time and location of LNG plants - shows the profitability of LNG imports by tankers through large water areas for developed countries in the absence or shortage of energy resources.

The use of liquefied gas technologies with mixed refrigerants is more preferable than the use of technologies with homogeneous liquids, regardless of the region of the plant, since the condensation curve more closely matches the cooling curve of natural gas, increasing the efficiency of the cooling process, and the composition of the refrigerant can be varied with changing gas composition. The main advantage of homogeneous refrigerants is ease of use, but in terms of the combination of advantages they are inferior to mixed refrigerants.

There is no direct dependence of the number of refrigeration cycles on the location of plants in southern or northern latitudes. Most modern gas liquefaction technologies involve the use of three cycles, since the process of condensing natural gas is more perfect. Regardless of the location of the plant, the terms for which long-term contracts for the supply of LNG are concluded have increased from 15 to 20…30 years.

The number of LNG producers and buyers – participants in commodity-production relations – has also increased recently.

The cost of transporting LNG is reduced due to the introduction of large tankers. At the same time, for the transportation of LNG from northern plants, it is necessary to use special reinforced tankers suitable for use in difficult ice conditions. This is evidenced by the following fact: in July and December 1993, the 71,500 m3 Kenai LNG tankers were replaced by 87,500 m3 tankers named Polar Eagle and Arctic Sun. They were 15% shorter than the original tankers and carried 23% more LNG. This was partly due to the requirements of the Japanese side for the use of larger and new tankers, and partly due to an increase in the throughput of the plant. Like their predecessors, these tankers have been designed for difficult weather conditions and low temperatures. Free-standing prismatic containers were placed on them; tankers have ice reinforcement of the hull, propeller, shafts and drive mechanisms.

It is also worth considering the complexity of climatic, ice, wave, wind conditions when loading tankers at the northern LNG plants. Under arctic conditions, improving the efficiency of the primary refrigeration cycle will most likely require the replacement of propane with a refrigerant with a lower boiling point. It can be ethane, ethylene or a multi-component mixed refrigerant. The ability of LNG plants to benefit from the theoretically higher efficiency of gas liquefaction at cold temperatures depends on the design temperatures of Arctic plants and their design operating strategies. If the average annual temperature is considered in projects as a fixed design temperature, then the losses due to temperatures higher than the average temperature (by a factor of 1.8%/°C) can significantly outweigh the benefits of efficient condensing at temperatures below average. This may be due to the fact that LNG production volumes will change in order to achieve and meet production quotas. Conversely, capturing the project by volume and inflating design temperatures (above average ambient temperatures) to achieve required volumes can lead to higher overall efficiency but also higher capital costs.

If the decision is made to operate the plant at varying volumes depending on the ambient temperature, then the properties of the raw gas and the transport logistics of the LNG will have to be adjusted to such variations.

This is not always possible. For example, colder environmental conditions can cause ship delays when the plant can produce the maximum amount of product. Therefore, it will be necessary to balance the economic advantages of large process lines, the optimal configuration of the design from an operational point of view, and the complexities of construction and the challenges of operating a plant in remote locations under changing environmental conditions.

Thus, on the basis of what has been said, the following conclusions can be drawn.

The set of units, their technological parameters and the range of associated products depend on the properties and volumes of the gas used. The analysis did not reveal a significant dependence on the location of the LNG plant of such factors as the sequence of location of process units, the choice of gas treatment technologies and their operation.

Any process is suitable for specific gas properties and specific application conditions, and the most practical and efficient to use of the processes considered are the activator-activated MDEA chemical purification process and the Sulfinol-D physical process.

Significant differences in the choice and operation of liquefaction technology between northern and southern LNG plants have been identified. Climate and location of plants are factors that affect existing and will be a factor influencing future Arctic LNG projects.

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