Natural gas refers to all gases naturally present in nature, including gases formed by various natural processes in the atmosphere , hydrosphere , and lithosphere (including oil field gas , gas field gas, mud volcanic gas , coal bed methane, and biogenic gas, etc.).
The definition of "natural gas" that has been commonly used for a long time is a narrow definition from the perspective of energy , which refers to a mixture of hydrocarbons and non-hydrocarbon gases naturally stored in the formation . In petroleum geology , it usually refers to oil field gas and gas field gas. Its composition is dominated by hydrocarbons and contains non-hydrocarbon gases.
On May 6, 2020, PetroChina Southwest Oil & Gas Field Company disclosed that the company has recently discovered a new zone rich in natural gas, with an estimated potential resource volume exceeding one trillion cubic meters .
source
Natural gas is stored in underground porous rock formations , including oil field gas, gas field gas, coal bed methane, mud volcanic gas and biogenic gas, etc., and a small amount is also derived from coal seams. It is a high-quality fuel and chemical raw material.
The main purpose of natural gas is as fuel, which can be used to produce carbon black , chemicals and liquefied petroleum gas. Propane and butane produced from natural gas are important raw materials for modern industry. Natural gas is mainly composed of a mixture of gaseous low-molecular hydrocarbons and non-hydrocarbon gases.
It is mainly composed of methane (85%) and a small amount of ethane (9%), propane (3%), nitrogen (2%) and butane (1%). Mainly used as fuel, but also used to produce raw materials for chemicals such as acetaldehyde, acetylene, ammonia, carbon black, ethanol, formaldehyde, hydrocarbon fuels, hydrogenated oil, methanol, nitric acid, synthesis gas and vinyl chloride. Natural gas is compressed into liquid for storage and transportation. Coal miners, nitric acid manufacturers, power plant workers, organic chemical synthesis workers, gas users, petroleum refiners, etc. have the opportunity to come into contact with this product. It enters the human body mainly through the respiratory tract. It is a simple suffocating gas . When the concentration is high, the replacement of air causes hypoxia, resulting in shortness of breath and loss of consciousness; in severe cases, hypoxemia may suffocate and die. High-pressure natural gas can cause frostbite. Incomplete combustion can produce carbon monoxide .
Physical and chemical properties
Natural gas is a general term for mixed gas mainly composed of hydrocarbons in underground rock reservoirs . It has a specific gravity of about 0.65, which is lighter than air, and has the characteristics of colorless, odorless, and non-toxic.
The main components of natural gas are alkanes , of which methane accounts for the vast majority, and a small amount of ethane , propane and butane . In addition, there are generally hydrogen sulfide , carbon dioxide , nitrogen and water vapor, a small amount of carbon monoxide and trace amounts of rare gases such as helium and argon . Before the natural gas is sent to the end user, in order to help leak detection, mercaptan, tetrahydrothiophene, etc. are used to add odor to the natural gas.
Natural gas is insoluble in water , with a density of 0.7174kg/Nm 3 , a relative density (water) of 0.45 (liquefied), an ignition point (℃) of 650, and an explosion limit (V%) of 5-15. Under standard conditions , methane to butane exists as a gas, and above pentane is liquid. Methane is the shortest and lightest hydrocarbon molecule.
Organic sulfur compounds and hydrogen sulfide (H₂S) are common impurities and must be removed in advance in most cases where natural gas is used. Natural gas with a lot of sulfur impurities is described as "sour (sour)" in English technical terms.
The calorific value of combustion per cubic meter of natural gas is 8,000 to 8,500 kcal. The calorific value of combustion per kilogram of liquefied gas is 11,000 kcal. The specific gravity of gaseous liquefied gas is 0.55. Per cubic LPG combustion heat value of 25,200 kcal. Each bottle of liquefied gas weighs 14.5 kg, with a total combustion calorific value of 159,500 kcal , which is equivalent to the combustion calorific value of 20 cubic meters of natural gas.
Methane combustion equation
Complete combustion : CH 4 +2O 2 === CO 2 + 2H 2 O (reaction condition is ignition)
Methane + oxygen → carbon dioxide + water vapor
Incomplete combustion : 2 CH 4 +3 O 2 =2 CO +4 H 2 O
Methane + oxygen → carbon monoxide + water vapor
unit of measurement
Kilowatt hour (kw·h) or Joule (J)
Gas station sales unit: CNG yuan/cubic meter (yuan/m³), LNG **yuan/kg
Composition classification
1. Natural gas can be divided into free state , dissolved state , adsorbed state and solid hydrate according to the phase state existing underground . Only the free natural gas can be developed and utilized after being accumulated to form a natural gas reservoir.
2. Natural gas can be divided into associated gas and non-associated gas according to the form of existence and generation .
Associated gas: oil field gas produced at the same time as crude oil along with the symbiosis of crude oil . Associated gas is usually the volatile part of crude oil , which exists in the form of gas above the oil-bearing layer. It is present in all formations with crude oil, but the ratio of oil to gas is different. Even the sources of oil and natural gas in the same oil field are not necessarily the same. They are collected in the same rock reservoir by different ways and through different processes.
Non-associated gas: a pure gas fields and natural gas condensate gas two kinds of fields, in the formation are in the gaseous present. After the natural gas in the condensate gas field flows out of the wellhead from the formation, as the pressure drops and the temperature rises, it separates into two phases of gas and liquid . The gas phase is condensate gas field natural gas, and the liquid phase is condensate liquid, called condensate oil . If it is non-associated gas, it has nothing to do with liquid accumulation and may be produced from plant matter. The world's natural gas production is mainly gas field gas and oil field gas . The mining of coalbed methane has now been paid more and more attention.
3. According to the state of natural gas reserves, it is further divided into three types: structural natural gas, water-soluble natural gas, and coal mine natural gas. Structural natural gas can be divided into wet natural gas produced with crude oil and dry natural gas without liquid components.
4. Natural gas can be divided into biogenic gas, oil-type gas and coal-type gas according to its genesis . Inorganic gas, especially non-hydrocarbon gas, is highly valued.
5. According to the occurrence of natural gas underground, it can be divided into oil field gas, gas field gas, condensate gas, water-soluble gas, coal bed gas, and solid gas hydrate .
Basic Features
Natural gas is one of the safer fuels. It does not contain carbon monoxide and is lighter than air. Once it leaks, it will immediately diffuse upwards and is not easy to accumulate to form explosive gases. It is relatively safer than other combustibles.
Using natural gas as an energy source can reduce the consumption of coal and oil, thereby greatly improving environmental pollution; natural gas, as a clean energy source, can reduce sulfur dioxide and dust emissions by nearly 100%, and reduce carbon dioxide emissions by 60% and nitrogen oxides emissions 50%, and help to reduce the formation of acid rain, slow down the global greenhouse effect , and fundamentally improve the environmental quality.
Natural gas, as a vehicle fuel, has the advantages of high unit calorific value, low exhaust pollution, reliable supply, and low price. It has become the development direction of clean fuel for vehicles in the world, and natural gas vehicles have become the fastest growing and most used new fuel. Energy vehicles.
However, for the greenhouse effect , natural gas, like coal and oil, produces carbon dioxide . Therefore, natural gas cannot be regarded as a new energy source. Its advantages are:
Green
Natural gas is a clean and environmentally friendly high-quality energy source, which contains almost no sulfur, dust and other harmful substances. It produces less carbon dioxide when burned than other fossil fuels, resulting in a lower greenhouse effect, and thus can fundamentally improve the quality of the environment.
Economical
Compared with artificial gas , natural gas has the same calorific value year-on-year, and natural gas is clean and clean, which can prolong the service life of stoves and help users reduce maintenance costs. Natural gas is clean gas with stable supply and can improve air quality. Therefore, it can provide new impetus for the economic development of the region, drive economic prosperity and improve the environment.
Safe and reliable
Natural gas is non-toxic, easy to emit, and its specific gravity is lighter than air, and it is not easy to accumulate into explosive gas. It is a safer gas.
Improve life
As families use safe and reliable natural gas, they will greatly improve the home environment and improve the quality of life .
Calculation of natural gas oxygen consumption: 1 cubic meter of natural gas ( purity is calculated as 100%) requires about 2.0 cubic meters of oxygen for complete combustion , and about 10 cubic meters of air.
Cause of formation
The causes of natural gas are diverse. The formation of natural gas runs through diagenesis, deep formation, post-formation and metamorphism. Various types of organic matter can form natural gas. Form organic matter mainly generates gaseous hydrocarbons.
Biogenesis
In the early stage of diagenesis (stage), in the shallow biochemical zone, the natural gas formed by the colony fermentation and synthesis of sedimentary organic matter by microorganisms is called biogenic gas . It is sometimes mixed with gas formed by early low-temperature degradation. Biogenic gas appears in shallow, new-age and low-evolved rock formations, mainly containing methane gas. The prerequisites for the formation of biogenic gas are richer organic matter and a strong reducing environment .
The organic parent material that is most conducive to gas generation is the herbaceous humus type-saprophytic humus type. These organic matter are mostly distributed in the delta and marsh lakeside belts with abundant supply of terrestrial materials . Usually, the sand and mudstone series containing terrestrial organic matter are the most beneficial. The reason why it is difficult to form a large amount of biogenic gas in the sulfuric acid rock is because sulfuric acid has obvious resistance to methanogens . H2 preferentially reduces sulfate to sulfide ions to form metal sulfide or hydrogen sulfide, so carbon dioxide cannot be converted into methane by hydrogen. .
The growth of methanogens requires a suitable geochemical environment, first of all, strong enough reducing conditions, generally Eh<-300mV (that is, the oxygen and SO42 in the formation water are all reduced in turn, before they multiply); secondly, the pH The value requirements should be close to neutral, generally 6.0-8.0, and the best value is 7.2-7.6; furthermore, the growth temperature of methanogens is 0-75°C, and the best value is 37-42°C. Without these external conditions, the methane bacteria cannot multiply in large numbers, and thus cannot form a large amount of methane gas.
Organic origin
Oil type gas
Sedimentary organic matter, especially sapropel organic matter , is formed with petroleum during the thermal degradation of natural gas, or natural gas formed by thermal cracking of organic matter and early-formed liquid petroleum in the post-formation stage is called oil-type gas, including Moisture gas (oil-associated gas), condensate gas and cracked gas .
Like the gradual formation of oil through pyrolysis of organic matter, the formation of natural gas also has obvious vertical zoning. In the uppermost part of the profile (diagenesis stage), it is biogenic gas . In the late stage of deep formation , it is low molecular weight gaseous hydrocarbons (C2～C4), that is, moisture, and condensate gas formed by reverse evaporation of light liquid hydrocarbons due to high temperature and high pressure . In the lower part of the profile, due to the rise in temperature, the generated petroleum is cracked into small molecules of light hydrocarbons to methane, and organic matter also further generates gas. The methane-based petroleum cracked gas is the final product of the gas generation sequence. This stage is usually called dry gas. bring.
From petroleum-associated gas→condensate gas→dry gas, the methane content gradually increases, so the drying coefficient increases.
Coal-type gas
Natural gas generated by thermal evolution of coal- measure organic matter (including the dispersed organic matter in coal seams and coal-measure strata ) is called coal-type gas.
In coal mining, a large amount of gas gushes frequently . For example, a gas outburst in a well in Hechuan District, Chongqing has discharged gas as high as 1.4 million cubic meters. This shows that coal strata can indeed generate natural gas.
Coal-based gas is a multi-component mixed gas, in which the hydrocarbon gas is mainly methane, and the content of heavy hydrocarbon gas is small. It is generally dry gas, but it may also contain moisture or even condensate gas. Sometimes it can contain more Hg steam and N2.
Coal-type gas can also form super large gas fields. Since 1960s, super large coal-type gas fields have been discovered in the K2, Eastern Netherlands Basin, and P in the southern North Sea Basin in northern West Siberia. The proven reserves of these three gas areas are 22 trillion cubic meters, accounting for Weak 1/3 of the world's total proven natural gas reserves. According to statistics (MT Harbuti, 1970), of the 26 large gas fields discovered in the world, 16 are coal-type gas fields, accounting for 60% of the total and 72.2% of reserves. It can be seen that coal-type gas is combustible in the world. It occupies an important position in the composition of natural gas resources.
Coal to form a coal-type gas: Coal can be divided into peat and coalification two stages. In the previous stage, plant remains and fragments accumulated in swamps , lakes or shallow seas were biochemically formed into peat, the precursor of coal; as the basin subsides , the burial deepens and the temperature and pressure increase, and it enters the coalification stage from the peatification stage in coalification peat through microbial enzyme action solutions, compacting, dewatering becomes lignite ; buried gradually deepened when the lignite has been formed under the factors of temperature, pressure and time, by flame coal → gas coal → fat coal → coking → lean coal → lean coal → no bituminous sequence conversion.
The actual measurement shows that the volatile content of coal decreases significantly with the increase of coalification. From lignite→bituminous coal→anthracite, the volatile content decreases from about 50% to 5%. These volatiles mainly escape in the form of gaseous products such as CH 4 , CO 2 , H 2 O, N 2 , and NH 3 , which are the basis for the formation of coal-type gas and are the main volatile products precipitated during coalification .
1. Port of total volatile products in coalification;
2．CO2
3．H2O
4．CH4
5．NH3
6．H2S
From the perspective of the formation of coal-type gas, attention should be paid to the four more obvious changes in coal-forming materials during the process of coalification (called coalification jump in coal petrology):
The first jump occurred at the beginning of long flame coal, with carbon content Cr=75-80%, volatile matter Vr=43%, Ro=0.6%;
The second jump occurred in the fat coal stage, Cr=87%, Vr=29%, Ro=1.3%;
In the third transition, the bituminous coal → anthracite stage, Cr=91%, Vr=8%, Ro=2.5%;
The fourth jump occurred in the stage of anthracite → metamorphic anthracite, Cr=93.5%, Vr=4%, Ro=3.7%, and the degree of aromatic fused ring condensation is greatly improved.
Among the four jumps, the most obvious changes in coal quality are the first and second jumps. The coalification jump is not only manifested as a qualitative change of coal, but each jump is correspondingly a peak of gas (methane) formation.
The formation and yield of coal-type gas are not only related to coal rank, but also related to the coal rock composition. Humic coal can be divided into three microscopic components of vitrinite group, lipid group and inert group under the microscope. Among the humic coals in most coal fields in China, the vitrinite group has the highest content of each component, accounting for about 50% to 80%, and the inert group accounts for 10% to 20% (the higher is 30% to 50%). The group content is the lowest, generally not more than 5%.
In coal formation, the contribution of each microscopic component to gas formation is different. Changqing Oilfield and the Institute of Geochemistry of the Chinese Academy of Sciences (1984) successfully separated and purified the organic microscopic components of coal , carried out simulation experiments on the thermal evolution of the organic microscopic components of low-rank coal , and discussed different microscopic groups. Partial hydrocarbon generation and hydrocarbon generation mechanism. It is found that the final hydrocarbon generation efficiency ratio of the three microscopic components is about the lipid group : vitrinite group : inert group=3:1:0.71, and the gas production capacity ratio is about 3.3:1:0.8, indicating that the inert group also has a certain The ability to be angry.
Inorganic origin
All the elements on the earth without exception have undergone a process similar to nuclear fusion on the sun. When carbon is formed from some lighter elements in a certain period of time after nuclear fusion, it reacts with hydrogen in the original atmosphere to produce methane. .
Deep earth magmatic , metamorphic and combustible gas distribution space, and a gas generated by the decomposition of rock inorganic salts, inorganic origin belong gas or non-biological causes of gas. It is dry gas, mainly methane, sometimes containing CO2, N2, He, H2S, Hg steam, etc., or even one of them, forming a non-hydrocarbon gas reservoir of industrial significance.
The rare gases He, Ar, etc. , because of their special geochemical behavior, scientists often use them as tracers of geochemical processes. The isotope ratios of He and Ar, 3He/4He and 40Ar/36Ar, are very important means to find out the origin of natural gas. Because the two are increasing along the atmosphere → crust source → crust and mantle source mixing → mantle source, the former increases from 1.39×10 -6→>10-5, the latter from 295.6→>2000. In addition, based on the origin of the Ar isotope radioactivity in the surrounding rocks and gas reservoirs, the formation age of the gas can also be calculated ( Zhu Ming , 1990).
Methane
Inorganic synthesis: CO 2 +H 2 →CH 4 +H 2 O Conditions: high temperature (250℃), iron group elements
Methane in the earth’s primitive atmosphere: absorbed in the mantle and discharged along deep faults, volcanic activity, etc.
Plate subduction zone methane: H, C, CO/CO2 → CH4 produced by the decomposition of oceanic plates under high temperature and pressure dehydration under subduction
CO2
The high CO 2 content of natural gas is the same as the high hydrocarbon content gas, which also has important economic significance . For CO 2 gas reservoirs, the economically valuable natural gas is the natural gas with CO 2 content> 80% (volume concentration), which can be widely used Industry, agriculture, meteorology, medical treatment, catering, environmental protection and other fields. The CO 2 content in the natural gas of Shatouwei Shuishen 9 Well in the Sanshui Basin, Guangdong Province, China is as high as 99.55%, and the daily gas production is 5 million cubic meters, making it a gas reservoir with high economic value.
The CO 2 gas reservoirs discovered in the world are mainly distributed in Meso-Cenozoic volcanic areas, fault active areas, oil and gas enrichment areas and coal field areas. In terms of causes, there are the following:
Inorganic cause:
① The upper mantle magma is rich in CO 2 gas. When the magma rises along the weak crustal zone and the pressure decreases, CO 2 escapes.
② Carbonate rocks can be bake at high temperature or deep-form metamorphism can produce a large amount of CO 2. When groundwater is involved or contains Al, Mg, Fe impurities, a considerable amount of CO 2 can also be generated at 98-200 ℃ . This type of CO 2 characteristic ：CO 2 content>35%, δ13CCO2>-8‰.
③ Carbonate minerals interact with other minerals to generate CO2, such as dolomite and kaolinite .
Further, organic origin are: biochemical effects, thermal chemical reaction, oil was oxidation of coal oxidation
N 2
N 2 is the main component in the atmosphere. According to research, the maximum concentration and fugacity of molecular nitrogen appear in the nitrogen-bearing strata at the edge of the ancient platform, especially in the boundary of the distribution area of the evaporative salt rock. Nitrogen migrates from the water layer to the gas reservoir and is reduced by nitrate . Its precursor is NH 4 + .
N 2 content greater than 15% is a nitrogen- rich reservoir. The main types of formation of N 2 in natural gas are:
①N 2 produced by the decomposition of organic matter : reaches a peak at 100-130°C, and the amount of N 2 produced accounts for 2.0% of the total gas generated, and the content is low; (organic)
②Pyrolysis and degassing of crustal rocks: For example , the amount of gas produced by thermal analysis of diabase , N 2 can be as high as 52%, and this type of N 2 can be enriched;
③ Denitrification of underground brine (nitrate): Nitrate generates N 2 O+N 2 through biochemical action ;
④N 2 from the mantle : For example, iron meteorites contain tens to hundreds of ppm of nitrogen;
⑤ source of atmospheric N 2 : atmospheric N 2 with the deep groundwater circulation transport, mixing up gas is mainly hot springs.
From the perspective of isotopic characteristics, in general, the heaviest nitrogen is concentrated in nitrate rocks, the heavier nitrogen is concentrated in aromatic hydrocarbon compounds, and the lighter nitrogen is concentrated in ammonium salts and amino acids.
H2S
H 2 S gas is found in almost all gas reservoirs around the world. Gas reservoirs with H 2 S content> 1% are H 2 S- rich gas reservoirs, and those with commercial significance must be> 5%.
According to research (Zhabrew et al., 1988), H 2 S enrichment areas of commercial significance are mainly large petroliferous sedimentary basins , and the sedimentary sections of these basins contain thick carbonate-evaporate rock series.
There are two main types of H 2 S generation in nature :
①Biogenesis (organic): including biodegradation and biochemical effects;
②Thermochemical causes (inorganic): thermal degradation, thermochemical reduction, high-temperature synthesis, etc. According to thermodynamic calculations, the required temperature for the reduction of gypsum (CaSO 4 ) to H 2 S by hydrocarbons in the natural environment is as high as 150°C. Therefore, gas reservoirs with high H 2 S content found in nature are all produced in deep carbonate-evaporative salt layers. In the series, and the carbonate rock has good reservoir properties.
National Reserve Ranking
In 2005, the world's total proven natural gas reserves were 179.53 trillion cubic meters.
nation | Reserves | Annual output |
|---|---|---|
Russia | 48.14 million | 6328 |
Iran | 27.50 million | Approximately 896.63 |
Qatar | 257,800 | 378 |
Saudi Arabia | 67,500 | 656.8 |
UAE | 6.06 million | 458 |
U.S | 5.60 million | 5532.77 |
Algeria | 45,200 | 820 |
Norway | 44,600 | 880 |
Venezuela | 41,900 | 284 |
Nigeria | 3.40 million | 223.88 |
Toxic hazard
When the content of natural gas in the air reaches a certain level, it will suffocate people. Natural gas is not as toxic as carbon monoxide , it is essentially harmless to the human body. However, if natural gas is in a high concentration state and the oxygen in the air is insufficient to sustain life, it will still cause death. After all, natural gas cannot be used for human breathing. As a fuel, natural gas can also cause casualties due to explosions.
Although natural gas is lighter than air and easy to radiate, when natural gas accumulates in a closed environment such as a house or tent, when it reaches a certain proportion, it will trigger a powerful explosion. The explosion may flatten a house and even damage neighboring buildings. The lower limit of the explosion limit of methane in air is 5%, and the upper limit is 15%.
The explosion of compressed natural gas to be used in natural gas vehicle engines is basically not available under spontaneous conditions due to the nature of gas volatilization. Therefore, external force is required to maintain the concentration of natural gas between 5% and 15% to trigger the explosion.
Identification method
Natural gas is widely distributed in nature, with many types of genesis and different degrees of thermal evolution, and its geochemical characteristics are also diverse, so it is difficult to identify it with a unified index. Practice shows that it is more reliable to use multiple indicators to make comprehensive judgments than to use a single indicator. In terms of the items involved in the identification of natural gas genesis, there are mainly four items: isotopes, gas components, light hydrocarbons and biomarker compounds . Some of the content of the determination criteria are clear and of absolute significance, and some of the content overlaps in the three types of genes. Only has a certain relative meaning.
Derivative products
Natural gas is an important energy source and is widely used as city gas and industrial fuel; however, natural gas generally refers to a combustible gas rich in hydrocarbons that is stored in the deeper part of the formation, and natural gas that co-exists with petroleum is often called Associated gas for oil fields .
Natural gas fuel is one of the earliest and widely used alternative fuels. It is divided into compressed natural gas (CNG) and liquefied natural gas (LNG). Industrial natural gas can be burned with external mixing burners.
Liquefied gas
liquified natural gas
When natural gas is cooled to about -162°C under normal pressure, it changes from a gaseous state to a liquid state, which is called Liquefied Natural Gas (English Liquefied Natural Gas, LNG for short). The main component of LNG is methane, with a small amount of ethane, propane, and nitrogen. The natural gas is further purified in the liquefaction process. The purity of methane is higher, it contains almost no carbon dioxide and sulfide, and is colorless, odorless, and non-toxic.
Liquefied natural gas (LNG) has become a new industry in China and is developing rapidly. In addition to solving transportation and storage problems, liquefied natural gas (LNG) technology is also widely used in peak shaving devices when natural gas is used. Since natural gas is often produced in areas not in industrial or populated areas, transportation and storage problems must be solved. The main component of natural gas is methane, and its critical temperature is 190.58K. It cannot be liquefied by pressure alone at room temperature . The liquefaction and storage technology of natural gas has gradually become a major advanced technology.
Advantages of LNG
Compared with natural gas, LNG has the following advantages:
①Easy to store and transport;
The density of LNG is 625 times that of methane under standard conditions. In other words, 1m³ LNG can be gasified into 625m³ natural gas, which shows the convenience of storage and transportation.
②Good safety;
The main method of storage and transportation of natural gas is compression (CNG). Due to the high pressure of compressed natural gas , it has brought many potential safety hazards.
③Low indirect investment;
The volumetric energy density of compressed natural gas (CNG) is about 26% of gasoline, while the volumetric energy density of liquefied natural gas (LNG) is about 72% of gasoline, which is more than twice that of compressed natural gas (CNG). Therefore, vehicles using LNG have a long range. , Relatively can greatly reduce the number of car filling stations.
④ Peak shaving effect;
As natural gas is used as a fuel for civil gas or power plants , there will inevitably be fluctuations in demand, which requires a peak-shaving effect on the supply.
⑤Environmental protection;
Natural gas must undergo strict pre-purification before liquefaction, so the impurity content in LNG is far lower than CNG, creating a way for automobile exhaust gas or when used as fuel to meet more stringent standards (such as "Euro II" or even "Euro III"). Condition.
liquefied petroleum gas
Liquefied petroleum gas is one of petroleum products. The English name is liquefied petroleum gas, or LPG for short. It is a colorless and volatile gas obtained by pressurizing, cooling, and liquefying refinery gas or natural gas (including oilfield associated gas).
Liquefied petroleum gas ( liquefied petroleum gas for short) is a kind of petroleum tail gas left in the process of refining gasoline, kerosene , diesel, heavy oil and other oil products. It becomes a liquid and is placed in a pressurized container. This is where the name of the liquefied gas is derived. Its main components are ethylene , ethane , propylene, propane and butane, etc., while containing a small amount of pentane, pentene and trace sulfur compound impurities. The composition of liquefied gas obtained from natural gas is basically free of olefins . It is liquid in the cylinder. Once it flows out, it will vaporize into combustible gas about two hundred and fifty times the original volume , and it is very easy to diffuse, and it will burn or explode when it encounters an open flame. Therefore, special attention should be paid to the use of liquefied gas.
Liquefied coalbed methane
China is a major coal producer in the world, and the corresponding reserves of coalbed methane are also very large, and the reserves are basically the same as those of natural gas. Its basic component is methane. In addition to being a cheap chemical raw material, it is mainly used as a fuel. It is not only used as a living fuel for residents, but also used as a fuel for vehicles, ships, airplanes and other transportation vehicles . Due to the high calorific value of coalbed methane , the combustion products have little environmental pollution, and it is considered to be a high-quality clean fuel.
There are several advantages to using coalbed methane after liquefaction:
①Economy;
The investment cost is low and the recovery is fast.
②Safety;
The "gas first, coal second" approach has become the basic way of energy utilization in developed countries. "Gas first, coal later" greatly improves the safety of coal mining.
③Policy;
This method can save energy and achieve thorough utilization of energy, which is in line with the relevant national policies. Conducive to obtaining government support.
CBM liquefaction equipment is basically the same as natural gas liquefaction equipment, except that most CBM contains slightly higher oxygen and nitrogen content than natural gas, so a rectification system needs to be added.
compressed gas
CNG (Compressed Natural Gas, referred to as CNG) is in gaseous and pressurized natural gas stored in the container. In addition to natural gas in oil fields and natural gas fields, compressed natural gas can also be used to artificially produce biogas (the main component is methane).
Compressed natural gas has the same composition as pipeline natural gas, and the main component is methane (CH4). CNG can be used as vehicle fuel. CNG can be used to make LNG (Liquefied Natural Gas). This kind of CNG-fueled vehicle is called NGV (Natural Gas Vehicle). LPG (Liquefied Petroleum Gas, referred to as LPG) and CNG are often easy to confuse, in fact, they are apparently different.
Fire hazard of CNG compressed natural gas
1. Combustion and explosiveness-combustible gas within the range of explosive concentration can burn or explode when encountering ignition sources.
2. Diffusion-gas diffusivity is affected by the density of the gas itself. The lighter the density than air, the greater the diffusion.
3. Expansibility-Compressed gas expands due to heat, which increases the pressure of the cylinder, which can cause the cylinder to rupture or explode.
The combustion gas sources in people's lives can be roughly divided into three categories: liquefied petroleum gas (Y), artificial gas (R), and natural gas (T).
Artificial gas
Coal gas is made from solid raw materials such as coal or coke through dry distillation or gasification. Its main components are carbon monoxide , methane and hydrogen. Therefore, coal gas is toxic and easy to form explosive mixtures with air , so high attention should be paid when using it.
specific purpose
Industrial fuel
Use natural gas instead of coal for factory heating, production boilers and gas turbine boilers in thermal power plants . Natural gas power generation is an effective way to alleviate energy shortages, reduce the proportion of coal-fired power generation, and reduce environmental pollution . From the perspective of economic benefits, natural gas power generation requires less investment per unit installed capacity, short construction period, lower on-grid power price, and strong Competitiveness.
Natural gas power generation, after processing natural gas, and then installing natural gas generator sets to provide electricity,
Craft production
Such as baking varnish production line, tobacco leaf drying, asphalt heating and heat preservation, etc.
Natural Gas Chemical Industry
Natural gas is the best raw material for manufacturing nitrogen fertilizer, and it has the characteristics of low investment, low cost, and low pollution. The proportion of natural gas in the raw materials for nitrogen fertilizer production is about 80% on average in the world.
City gas business
In particular, domestic fuels include conventional natural gas, and two unconventional natural gas, coalbed methane and shale gas . It is mainly integrated into pipelines after production, and natural gas is used daily. With the improvement of people's living standards and the enhancement of environmental protection awareness, the demand for natural gas in most cities has increased significantly. The economic benefit of natural gas as a civil fuel is also greater than that of industrial fuel.
Compressed Natural Gas Vehicle
Substituting natural gas for automobile oil has the advantages of low price, less pollution and safety. Statistics from the International Natural Gas Vehicle Organization show that the average annual growth rate of natural gas vehicles is 20.8%. There are approximately 12.7 million natural gas vehicles in the world. The total number will reach 70 million in 2020, most of which are compressed natural gas vehicles.
Natural gas is a high-quality, high-efficiency, clean energy. The emissions of carbon dioxide and nitrogen oxides are only about half and one-fifth of those of coal, and the emissions of sulfur dioxide are almost zero. As a kind of clean and efficient fossil energy , natural gas has been paid more and more attention by countries all over the world for its development and utilization. From a global perspective, the amount of natural gas resources is much greater than that of oil, and the development of natural gas has sufficient resource guarantee.
Efficient natural gas
It is a new type of energy-saving and environmentally friendly industrial gas formed after the gas-agent intelligent mixing equipment and natural gas synergist are mixed with natural gas as the basic gas source. The combustion temperature can be increased to 3300°C. It can be used for industrial cutting, welding and breaking. It completely replaces acetylene gas and propane gas, and can be widely used in steel mills, steel structures, and shipbuilding industries. It can be used safely in the cabin. The products on the market include Ruifeng gas and Ruifeng natural gas synergist.
People’s awareness of environmental protection has increased, and the world’s demand for clean energy is rising. Governments have also communicated this trend through legislative procedures. Natural gas was once regarded as one of the cleanest energy sources. Coupled with the 1990 Persian Gulf crisis in the Middle East , Deepen the determination of the United States and major oil-consuming countries to develop alternative energy sources . Therefore, the demand for natural gas will naturally increase before real alternative energy sources are discovered.
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