Fuels widely used in human societies today, hydrocarbons such as coal and oil or their derivatives, are fossil fuels. They are plant remains that have accumulated before humans were born, and even dinosaurs did not appear. Large numbers of plants can only produce small amounts of fossil fuels. For example, 1 gallon (about 3.79 liters) of oil requires 90 tons of plants to conceive, which is equivalent to 40 acres (about 161,900 square meters) of wheat (including the whole wheat with seeds, roots, and stems combined). "Natural gas" is also one of the gaseous fossil fuels composed mainly of methane.
The ancients had long discovered natural gas
Humans have a long history of using natural gas. Two thousand years ago, in the Han Dynasty, there was a record of "fire wells" in China's Sichuan Basin. Many literati wrote poems and listed the peculiar landscape of Huojing as the "four famous places" in Sichuan. The Western Jin Dynasty literary scholar Zuo Si (250-305 AD) conceived 10 years and wrote the famous "Three Capital Fu", and in his "Shu Du Fu", he has a wonderful description of the magnificent scenery of natural gas erupting from the well and burning:
The fire well sinks in the fountain, and the high flames fly in the sky.
Wang Xizhi, a great calligrapher of the Eastern Jin Dynasty who lived in Jiangnan, also wrote a letter to a friend thousands of miles away in Sichuan to inquire about the situation of the fire well: "Is there a fire well in the salt well?" See it under your feet, not for the sake of hearing it. It can be seen that the "fire well" in Sichuan was already famous at that time.
<h1 class="pgc-h-arrow-right" > Huojing Town, Qionglai City, Chengdu, Sichuan Province. Source/Screenshot of the documentary "Chinese Image Fangzhi"</h1>
There is a saying that "relying on the mountain to eat the mountain, relying on the water to draft water". The ancient people of Sichuan, who lived in the "land of fire wells", gradually used lighting natural gas to boil salt. With the development of the fire well boiling salt industry, drilling technology has also been continuously improved. In the 30th year of the Qianlong Dynasty (1765), the old Shuangsheng well was drilled in the artesian well gas field, with a depth of 530 meters and a daily gas output of 160 cubic meters. Even the Qianlong Emperor, who was far away in Beijing, knew about the existence of the "fire well" in Sichuan and wrote a "fire well poem" specifically. Of course, Ai Xin Jue Luo Hongli is the champion of poetry writing in Chinese history, and a poem is not unusual at all. Importantly, however, the emperor himself certified the use of natural gas ("boiled salt can also be used").
Ground fire. Source/Fragment of the documentary "Chinese Image Fang Zhi"
Worldwide, natural gas is often the "companion" of oil. After the rise of the modern oil industry, people did not look at natural gas for a long time.
The reason is simple, compared with liquid oil, gaseous natural gas is both difficult to collect, and has the risk of fire and even explosion, which seems to be a "waste gas" that does more harm than good. As a result, in the process of extracting oil, the natural gas that is extracted together is often burned in the oil field in vain. According to a 1935 report by the Federal Trade Commission to Congress, between 1919 and 1930, the United States wasted 20 percent more natural gas than was consumed, wasting 437.5 billion cubic feet of natural gas, compared with 352 billion cubic feet of natural gas consumption in the United States.
When natural gas was "abandoned", gas took the lead on the stage of history.
Why gas?
The coal is heated under air-isolated conditions (for example, in a coke oven), as the temperature rises, the organic matter in the coal gradually decomposes, in which the volatile products are gaseously escaped, leaving a solid substance - coke, this processing method is called coal distillation (referred to as coking). After coking, the gaseous product can be obtained is gas, also known as coke oven gas. In 1812, Britain, which took the lead in completing the Industrial Revolution, built the world's first coking gas plant in London, and the gas produced was originally mainly used for lighting, so it was called "light gas" for a long time.
Source/Network
In 1865, a group of foreign investors raised funds to establish the "Great British Fire House" (later renamed "Shanghai British Merchant Gas Company") in Shanghai, and built the earliest gas plant in Shanghai on the south bank of the Suzhou River and west of Middle Xizang Road, which was the first public utility in Shanghai and China, and Shanghai became the first city in Asia to use gas. On November 1, 1865, the gas plant began to supply gas, and the gas street lamp that shanghainese had never seen before replaced the original kerosene lamp and shone brightly on the road. For a time, the citizens of Shanghai, who did not know the details, could not figure out where the source of the fire was, and simply called it "self-propelled fire". The gaslight flickered on the shanghai beach for more than half a century before it was eventually replaced by a safer tungsten filament bulb. In 1935, all gas lamps in the public concession were removed, and the era of gas lamp lighting in Shanghai came to an end.
Exterior view of the British Fire House. Source/Network
By this time, people had discovered another use of gas beyond lighting – cooking and heating. In Chinese urban life at that time, coal was still the main energy source. Two or three pieces of honeycomb coal, a few matches for ignition, a fan for making a fire... The day often begins with the smoke of carrying a briquette (or briquette) stove to make a fire. It's hard for today's young people to imagine that piles of honeycomb coal were crammed into narrow alleys and alleys, and the smell of soot would fill everywhere during the peak cooking season. Coal contains impurities such as sulfur and nitrogen, and will produce a large amount of soot during combustion, which is really painful. In addition, residues such as ash residue from coal combustion were a major source of municipal waste at that time.
Honeycomb coal stacked at the entrance of the Beijing courtyard. Photography/Image TC, Source/Figureworm Creative
In contrast, gas that does not produce dregs after combustion is much more convenient and has a high combustion efficiency. It is said that it takes only seven minutes to boil a copper pot of water on the gas stove and twenty-eight minutes to boil it on the briquette stove. Therefore, in the early 20th century, Shanghai began to introduce Western stoves for burning gas, but this was a luxury that only rich people could use at that time. To lay the pipe and install a gas stove, two gold bars are needed, and the price of one cubic meter of gas is equivalent to 5 catties of rice. At that time, Shanghai's lanes were divided into "old-style lanes" and "new-style lanes", and the criterion between the two was whether there was gas or not.
As a result, until 1949, the penetration rate of gas stoves in Shanghai was only 1.9%. There are only nine cities in the country that supply gas, including Shanghai, Dalian, Fushun, Anshan, Shenyang, Dandong, Changchun, Jinzhou and Harbin. Even the capital, Beijing, did not combine the construction of the "Ten Major Buildings" such as the Great Hall of the People until 1959 to start the supply of city gas with the Coking Plant of Shijingshan Iron and Steel Company and the Beijing Coking Plant as the gas source. In November 1959, the first coke oven of Beijing Coking Chemical Plant was officially put into operation, with an annual output of 450,000 tons of coke and a daily supply of 200,000 cubic meters of gas to the city. After renovation and expansion, the plant has gradually formed a scale of 1.8 million tons of coke production per year and 800,000 cubic meters of coke oven gas per day. From 1987 to 1989, the plant successively built two coke ovens and 20 gas generators, making the annual gas supply reach 1.3 million cubic meters, and the highest annual gas supply reached 1.44 million cubic meters, accounting for 67% of the total gas source of the city, becoming the main gas source plant of artificial gas in Beijing.
Old photos of kitchens in Shanghai with gas stoves. Photography / Lu Jie, Source / Xinmin Evening News
However, the real popularization of gas in China's big city households has been after the 1990s. In Shanghai, for example, in the late 1980s, there were still 1 million briquette stoves, and half of urban households did not have access to gas. To this end, Zhu Rongji, then mayor of Shanghai, once said a sentence: We must not carry the backward way of life left over from the previous century to the next century. In 1990, Shanghai decided to raise funds for gas construction in the form of bonds. During the "Eighth Five-Year Plan" period since 1990, more than 1.1 million household users have been developed in five years, and the penetration rate of gas users has exceeded 80%, which can be regarded as the basic realization of Shanghai's "coal gasification".
Liter coal stove. Photography / Dong Zhiwen 954, source / Figureworm Creative
To popularize gas, pipes and gas stoves are small things. The big question is where the gas comes from. For example, in order to "eliminate" 1 million briquette furnaces, Shanghai has specially launched the second phase of the Pudong gas plant, which is a national key project, and also expanded the Wusong gas plant. For a long time, limited by production capacity, the supply of gas is far from meeting the needs of people's lives. Since construction is a time-consuming process, it is urgent for the people to bid farewell to the requirements of the briquette stove. Thus, in that period of history, there is a memory of "liquefied gas (LPG)" or "cylinder".
What's in the liquefied gas tank?
It is actually an abbreviation of "liquefied petroleum gas". LPG is a mixture of propane and butane, usually accompanied by small amounts of propylene and butene. It is a gas produced while refining crude oil or volatilized from the extraction of oil or natural gas. This combustible gas can be liquefied at room temperature, under conditions of 6 atmospheres (volume compressed to 1/250 of the gaseous state), so it can be loaded into a pressure cylinder. Usually LPG is only 85% of the capacity, which leaves room for gas expansion as the cylinder is heated.
Compared with the gas at that time, liquefied gas had a significant advantage. Gas relies on pipelines to develop users, and where the gas pipeline passes to, where can gas be used. In contrast, liquefied petroleum gas is mainly supplied by liquefied gas cylinders, which can be taken home after being filled with gas at the liquefied gas supply station, which is much more convenient.
The picture of sending a liquefied gas tank in the film and television drama. Source/Clip from the TV series "Mother's Uncle"
In the spring of 1964, Premier Zhou Enlai instructed the State Science and Technology Commission to vigorously develop the comprehensive utilization of oil and gas resources in China. In accordance with this directive, and the State Science and Technology Commission issued by the State Science and Technology Commission, Beijing will develop a part of the LPG users and build a LPG filling station to determine the feasibility of LPG as a civilian fuel experimental project. On November 30, 1965, Beijing built a filling station in the western suburbs using liquefied petroleum gas from Jinzhou Petroleum Plant No. 6 as a gas source, and supplied liquefied petroleum gas to 4,882 households. This is the first bottling station in China to supply civil liquefied petroleum gas.
At first, the capacity of liquefied gas limited its popularity. For example, Hangzhou, as the capital city of Tangtang Province, did not know what liquefied gas was until 1973. In the autumn of that year, then-French President Pompidou visited Hangzhou. In order to receive the needs, the relevant departments of Zhejiang Province and Hangzhou City urgently purchased liquefied gas cookers in Nanjing, Jiangsu Province, and then transferred liquefied petroleum gas from Shanghai. For the first time, the blue flame rose on the shore of West Lake. After entering the 1980s, with the development of China's petrochemical industry, large and medium-sized cities gradually began to use liquefied gas as a gas source or auxiliary gas source, and liquefied gas finally entered the household as a high-quality fuel. For example, by the end of 1980, Beijing's liquefied petroleum gas residents reached 702,000 households, helping the city's urban residents to increase the rate of cooking gasification to 62.5%. For safety reasons, the local transportation departments at that time stipulated that buses, subways, and taxis were not allowed to carry liquefied steel cylinders. Therefore, many urban residents will install a hook on the back of their bicycles to hang liquefied gas cylinders, and pedal their bicycles to change liquefied gas cylinders once a month. It also became a memory of an era.
Liquefied gas cylinders. Photography / Alexander, Source / Figureworm Creative
Intriguingly, artificial gas and liquefied gas competed with each other, and no one laughed to the end. In September 1997, the first natural gas pipeline in the Shaanxi-Gansu-Ningxia Basin entered Beijing (the gas consumption in that year was 180 million cubic meters), ushering in the era of the great development of natural gas in contemporary China. In 1999, some residents of Shanghai also first used natural gas directly from the Pinghu gas field in the East China Sea to replace gas, opening a new page in the history of Shanghai gas.
Artificial gas, which has just made a great contribution to the elimination of briquette furnaces, has suddenly become a substitute for natural gas. On July 15, 2006, the Beijing Coking Plant entered a comprehensive shutdown procedure, and artificial gas has since withdrawn from the historical stage of Beijing's gas supply, and Beijing citizens no longer use artificial gas.
At the end of June of the following year, shanghai also surpassed the number of artificial gas users for the first time. Natural gas has become the first "big household" of gas in Shanghai. On June 27, 2015, Yanfeng Visteon Automotive Trim Systems Co., Ltd., located at No. 540 Moyu Road, Anting Town, Jiading District, was connected to natural gas. This is the last artificial gas user in Shanghai, which means that the artificial gas used for a century and a half bid farewell to Shencheng, and Shanghai has achieved "full natural gas" of urban gas.
Beijing Coking Plant. Photography/Passerby_927, Source/Figureworm Creative
Natural gas counterattack
Why did natural gas, which was not popular at the beginning of the oil age, succeed in counterattacking in the late 20th century?
First, LPG, in terms of heat, is indeed superior to natural gas (50,179 kj/kg (m3)). But it belongs to the "secondary energy" produced in oil refining, not the "primary energy" that nature itself has, such as natural gas. The more processing processing liquefied petroleum gas, the higher the cost. Take 2014, on the eve of Shanghai's farewell to artificial gas, as an example, when the standard energy price of natural gas was 2.27 yuan / kg standard coal, which was almost the same as the 2.11 yuan / kg standard coal of gas. However, the price of liquefied petroleum gas is 4.3 yuan / kg of standard coal, which is twice as much. Coupled with the fact that replacing the liquefied gas cylinder is not as convenient as opening the gas valve switch, the victory of natural gas is really reasonable.
Compared with gas, in terms of "average low calorific value", coal gas is 17354kj/kg (m3), which is not as good as coal (20908kj/kg (m3)), while natural gas is much higher, reaching 35544 kj/kg (m3), which is almost double the heat generated by gas. The intuitive reflection of this in life is that natural gas does not emit black smoke after lighting, blue flames, and strong firepower. However, because natural gas needs to be transported over long distances under a large pressure, and the oxygen required during the combustion of natural gas is more than that required by other gases, artificial gas burning appliances and natural gas combustion appliances cannot be mixed. At first, some residents did not understand this, "My stove eye even drilled cockroaches into it, and the natural gas could not go in?" "Now it seems like just a laugh.
Exploration of the safety of natural gas
Of course, whether it is gas or natural gas, there is also a safety issue. In science, there is a concept of "explosion limit", and the explosion limit of natural gas is 5%-15%. That is to say, the concentration of natural gas in the air is 5%-15%, and it will explode when it is fired. In contrast, the "explosion limit" of coke oven gas is 4.72%-37.54%. The upper limit of the visible is higher, the lower limit is lower, that is, it is more likely to explode.
In 1814, several coal mines in Newcastle, Caldive and other coal mines in the United Kingdom successively had gas explosion accidents caused by the open fire of mine lamps, causing thousands of casualties, and the scene was very tragic. Britain even declared national mourning. The following year, Humphrey Davey made the world's first safety miner's lamp— a thin, transparent glass cover surrounded by a flame and a fine copper wire mesh on the upper part of the lamp. Such miner's lamps are both bright and not afraid of the wind, and also effectively avoid open flame explosions and fires.
David Lights. Source/Network
But the problem is that ordinary people use gas at home every day, and they can't always put a miner's lamp on their heads to prevent explosions. What's more, the gas is colorless and odorless, but it contains deadly carbon monoxide. On September 28, 1902, the French writer Zola was heating himself in his apartment in Paris, but the chimney was blocked, and the gas was poisoned at night, and he suffocated to death.
In order to prevent gas leakage without being detected, people deliberately add trace amounts of mercaptan to the gas, and once the gas leaks, it has a foul smell and will not be unconscious. In contrast, natural gas, whose main component is methane, is not as toxic as carbon monoxide, and it is essentially harmless to the human body. Although natural gas cannot be used for human breathing, it is always much safer than gas.
Of course, no matter how safe it is, it cannot reach 100%, and it is impossible to completely eliminate the case of gas explosion. On January 10, 1985, a major explosion occurred in a luxury apartment in Putney, south London, England, killing eight residents. In June 1999, a gas pipeline in the Town of Bellingham, USA, burst and caught fire, killing two children and an 18-year-old and injuring eight others. Once a gas accident occurs, the conventional practice is to close the relevant valves, cut off the gas supply, and gradually reduce the gas leakage until it stops; at the same time, set up a warning area, strictly prohibit all possible ignition sources from entering, and strictly prevent accidental fires and explosions.
The next step is to analyze the cause of the accident. In the case of the Putney apartment explosion, the final investigation found that the explosion was caused by combustible gases leaking into the building from cracks in the cast iron pipes of the gas main pipe, and cracks were caused by uneven loads on the pipes caused by different settlements. The explosion in the United States was later investigated and found that as early as 1996, there were already 3 distortions in the pipe. In fact, whether it is the Soviet Union, the United States, or Europe, pipeline corrosion ranks among the top two causes of accidents. After the Berlinham accident, the United States specifically revised the Pipeline Safety Improvement Act of 2002 in 2002, stipulating that "the necessary tests in the last 10 years will be used to prevent the occurrence of oil and gas pipeline leakage and rupture accidents and ensure the safety of domestic oil and gas pipelines in the United States." And more problem pipelines will be tested within 5 years. All subsequent pipelines must be inspected every 7 years." Of course, then again, no matter how perfect the safety regulations, they also need to be obeyed...
However, it is necessary to divide gas accidents into three stages of manufacturing, supply and use, and the consumption stage (gas consumption stage) is the most, mainly due to careless use. For example, in the 1984 statistics of gas accidents in Japan, there were 92 cases (a total of 141 cases) in the consumption stage, resulting in 61 deaths (64 people in total). In order to ensure the safety of residential gas, the Japanese government and enterprises have vigorously promoted gas leakage alarms, which are said to be indispensable devices in every home today. At present, the rate of gas leakage and explosion accidents in Japan is much lower than that of other developed countries, and it is naturally related to it.
After the 21st century, "global warming" has become a topic of public attention. "Fossil fuels", including natural gas, emit carbon dioxide during combustion (such as the chemical equation for natural gas combustion: CH4 + 2O2 = = CO2 + 2H2O), which is really difficult to blame for "global warming", so the situation has become increasingly embarrassing.
In recent years, "low carbon" and "decarbonization" have gradually become hot words. In this unfavorable "wind direction", the fate of natural gas and other "fossil fuels" has become very different. For example, Europe is a pioneer in the "decarbonization" of energy, including wind power, solar power and other "zero carbon emission" renewable energy generation has accounted for half of Germany's electricity consumption. In this case, the local dependence on natural gas has not decreased but has increased. A big reason why the Nord Stream-2 pipeline project is making a lot of noise between the United States, Europe and Russia is that after the pipeline is completed, it is expected to transport 55 billion cubic meters of natural gas per year, enough for 26 million households. Since it is such a big bounty, it is no wonder that Europe has been under strong pressure from the United States - it is really reluctant!
"Nord Stream-2" pipeline project. Source/Network
Therefore, although natural gas is also a "fossil fuel", its carbon emissions are much lower than that of coal and oil. In terms of carbon emissions, natural gas is 1.6298 kgCO2/kgce, less than 60% of coal (2.7677CO2/kgce) and much lower than gasoline (1.9904CO2/kgce). Since natural gas is efficient and safe, and its carbon emissions are significantly low, it is foreseeable that it will remain an indispensable source of energy for human society for a long time to come.