2025-11-22

New choice for clean energy: liquefied petroleum gas

Liquefied petroleum gas, or LPG for short, is a volatile light hydrocarbon produced during the petroleum refining process, with its main components being propane and butane. With the development of the petrochemical industry, liquefied petroleum gas, as a basic chemical raw material and a new type of fuel, has received increasing attention from people.

I. Source and Composition

Liquefied petroleum gas is a core by-product in the petroleum refining process, mainly derived from the catalytic cracking and thermal cracking processes of crude oil. The components of catalytic cracking gas include: hydrogen (5-6%), methane (10%), ethane (3-5%), ethylene (3-16%), propylene (6-11%), propane (16-20%), butene (5-6%), butane (42% - 46%), and hydrocarbons containing more than five carbon atoms (5-12%), etc. The percentage of propane to butane exceeds 60%. If it is lower than this ratio, it cannot be called liquefied petroleum gas.

These hydrocarbons are all easy to liquefy. When they are compressed to only 1/250 to 1/33 of their original volume, and then separated and refined, LPG products are obtained. Stored in high-pressure resistant steel tanks, when in use, open the valve of the liquefied gas tank, and flammable hydrocarbon gases will enter the burner through the pipeline. When ignited, it forms a pale blue flame and generates a large amount of heat during the combustion process. And the firepower can be adjusted as needed. It is both convenient and hygienic to use.

Ii. Main Processing Techniques

The processing technology of LPG is centered around three major goals: quality improvement, refinement and transformation, with the core being to enhance product quality, stability and added value.

1. Mainstream processes:

⑴ Traditional cracking processes (catalytic cracking/thermal cracking)

Principle: Under the influence of high temperatures (450-550℃) and catalysts (such as aluminum silicate, molecular sieves), crude oil undergoes reactions like C-C bond breakage and isomerization, generating light hydrocarbons.

Characteristics: It is the main source of LPG, but the product contains unstable hydrocarbons (such as alkenes) and impurities (sulfides, nitrides), which require subsequent refining treatment.

⑵ Saturated hydrogenation process (Core technology for LPG quality improvement)

It is widely used in LPG production, aiming to improve product stability and safety.

Process:

Heat the crude oil to an appropriate temperature (200-300℃);

It enters the hydrogenation reactor together with hydrogen and, under high pressure (> 10MPa) and low temperature conditions, unstable hydrocarbons (such as alkenes) react with hydrogen to form stable alkanes (propane, butane).

At the same time, it removes impurities such as sulfides and nitrides (converting them into easily treatable substances like H₂S and NH₃).

Advantages

Enhancing the density, anti-explosion performance and low-temperature liquefaction capacity of LPG enables liquefaction at lower temperatures/pressures, thereby reducing the operating costs of liquefaction equipment.

Reduce corrosiveness and toxicity, and minimize damage to equipment and pipelines;

Improve combustion performance, enhance energy utilization efficiency and reduce fuel consumption.

⑶ Methanol-to-low-carbon LPG technology (MTO, Key to low-carbon Transformation)

Principle: Using methanol as the raw material, under the action of catalysts with high specific surface area and acidic sites (such as molecular sieves), dehydration, polymerization and isomerization reactions occur to generate the main components of LPG such as propane and butane.

Features

The raw material sources are extensive and non-petroleum resources can be utilized.

The process is simple, energy consumption is low, and it does not rely on water, which conforms to the concept of low-carbon development.

It has achieved industrial application, and many large-scale facilities around the world have been put into operation, such as China's "coal-to-methanol - methanol-to-LPG" industrial chain.

⑷ Deep processing technology (high value-added conversion)

Objective: To transform LPG into high-end chemical products and enhance the added value of the industrial chain.

Main processes and products:

Alkylation: Using isobutane and olefins (propylene/butene) as raw materials, isooctane (a component of high-octane gasoline) is produced, which can be used as an additive for automotive fuel.

Isomerization: Using n-butane as the raw material, isobutane is generated, which can be used as the alkylation raw material (to improve the quality of the raw material).

Aromatization: Using low-carbon hydrocarbons (propane/butane) as raw materials, aromatics (benzene, toluene) are generated, which can be used for plastics (polyethylene, polypropylene) and rubber.

Oxidative dehydrogenation: Using propane/butane as raw materials, propylene/butene is produced, which can be used as olefin raw materials for the synthesis of fibers and plastics.

2. Key technical links

The core competitiveness of LPG processing lies in technological optimization. The following are the key links:

⑴ Catalyst design and optimization

Hydrogenation process: Non-precious metal or bimetallic catalysts (such as Fe, Co, Ni combined with Mo, W) are adopted to enhance hydrogenation activity and stability and reduce costs.

MTO process: Molecular sieve catalysts with high specific surface area and abundant acidic sites are key, affecting reaction efficiency and product selectivity.

Thermal cracking process: New zeolite molecular sieve catalysts (such as Y-type molecular sieves) can enhance cracking efficiency and reduce energy consumption.

⑵ Refining process (Impurity removal)

Molecular sieve adsorption refining: By taking advantage of the porous structure and selective adsorption characteristics of molecular sieves, impurities such as sulfides, nitrogen compounds, and heavy metal ions in LPG are removed to enhance purity. The process operation is simple and the energy consumption is low, making it the mainstream refining method in industry.

Tail gas recycling treatment: The tail gas (such as H₂S, CO₂) generated during pyrolysis/hydrogenation is purified and recycled to reduce waste emissions and achieve resource recycling.

⑶ Intelligent control and monitoring

Real-time online monitoring: Through devices such as temperature and pressure sensors, internal parameters of the reactor, such as reaction temperature, pressure, and hydrogen-oil ratio, are obtained in real time.

Machine learning optimization: Establishing mathematical models and machine learning algorithms, such as neural networks; Optimize process parameters such as space velocity and reaction time to enhance production efficiency and stability.

The processing technology of liquefied petroleum gas is developing towards improving quality and efficiency, being low-carbon and environmentally friendly, and having high added value. By improving product stability through hydrogenation processes, achieving low-carbon transformation through MTO technology, and enhancing added value through deep processing techniques, LPG has been upgraded from a traditional by-product to a clean fuel and high-end chemical raw material, meeting the constantly changing market demands and environmental regulations. With the further optimization of technologies, such as catalyst regeneration technology and digital twin monitoring, the LPG processing technology will become more efficient and sustainable.

Iii. Main Features

1. Volatile: It is in a gaseous state at normal temperature and pressure. Liquefied petroleum gas in a liquid phase immediately volatilizes into a gas upon pressure relief. After vaporization, its volume expands by 250 to 300 times and spreads rapidly. That is to say, 1 liter of liquefied petroleum gas can volatilize into more than 250 liters of gas.

2. High relative density: Liquefied petroleum gas is heavier than air, with a relative density 1.5 to 2 times that of air. It is prone to stagnation and accumulation in low-lying areas of the ground and is not easily blown away by the wind in a short time. When mixed with air, it can form explosive substances and will explode upon encountering a fire source.

3. Toxicity: Liquefied petroleum gas is colorless and transparent, with a special hydrocarbon odor. When its concentration in the air is below 1%, it poses no threat to human health. However, prolonged exposure to highly concentrated liquefied petroleum gas can cause people to lose consciousness, vomit, and in severe cases, it can lead to suffocation or even death.

4. High latent heat of evaporation: When liquefied petroleum gas changes from liquid to gas, it absorbs a lot of heat. Once the liquefied gas tank or pipeline valve leaks, if the liquefied gas is sprayed and splashes onto a person, the rapid heat absorption can cause frostbite.

5. Low corrosiveness: Liquefied petroleum gas has a low sulfur content and is generally non-corrosive, but it can soften rubber.

Iv. Fuel Advantages

Compared with other fuels, LPG has the following unique advantages.

Low pollution: LPG is a hydrocarbon composed of carbon three and carbon four, which can be completely burned without generating dust. When applied in modern cities, it can significantly reduce the pollution caused by the use of coal and firewood as fuel in the past.

High calorific value: The calorific value of LPG of the same weight is twice that of coal, and the calorific value of liquid is 45,185 to 45,980 kJ/kg.

Easy to transport: LPG is a gas at normal temperature and pressure. Under certain pressure or when frozen to a certain temperature, it can be liquefied into a liquid and transported on land and water by train (or truck) tank trucks or LPG ships.

Stable pressure: The pressure in front of the LPG pipeline user's stove remains constant, making it convenient for users to operate.

Simple storage and flexible supply: Compared with the production, storage and supply of urban gas, the storage equipment for LPG is relatively simple. LPG is stored in LPG storage tanks at gas stations, and can also be filled in gas cylinders for users' use. It can also be supplied through pipelines at gas distribution stations and supply networks. Even small bottles of butane gas can be used as fuel for hot pot on the dining table, which is very convenient to use.

V. Product Application and Advantages

Liquefied petroleum gas is mainly used as a raw material for petrochemicals, for the cracking of hydrocarbons to produce ethylene or the steam conversion to produce syngas. It can be used as fuel for industrial, civil and internal combustion engines, as well as a chemical raw material. It is also used for cutting metals, baking agricultural products and roasting in industrial kilns, etc., and has significant economic and environmental advantages:

1. Civil fuel: Liquefied petroleum gas has significant advantages as a civil fuel, such as ease of use and environmental protection. Liquefied petroleum gas is used as fuel due to its advantages such as complete combustion, high calorific value (45.22-50.23MJ/kg), odorlessness, non-toxicity, no smoke or dust, no carbon residue, and low pollution. As a clean fuel, it is widely used in home cooking and commercial catering, entering People's Daily lives.

2. Chemical raw materials: In the field of chemical production, liquefied petroleum gas can be used as a raw material for petrochemicals. After separation, it can obtain ethylene, propylene, butene, butadiene, etc. Deep-processed products (such as propylene, isooctane) are used in the production of plastics, synthetic rubber, synthetic fibers, as well as in the production of pharmaceuticals, explosives, dyes and other products.

(1) Non-ferrous metal smelting

In the smelting of non-ferrous metals, fuel is required to have stable thermal quality, be a non-combustible furnace product, and be pollution-free. Liquefied petroleum gas all meet these conditions. After being heated and vaporized, liquefied petroleum gas can be conveniently introduced into the smelting furnace for combustion, reducing the harm of impurities such as sulfur and phosphorus.

(2) Kiln roasting

In China, various industrial kilns and heating furnaces have long been dominated by coal burning, which not only leads to energy waste but also the smoke they emit seriously pollutes the environment. To optimize the energy structure, establish a world-class clean, safe and efficient energy supply system, and set up a promotion mechanism for energy technology development. Many industrial kilns and heating furnaces have switched to using liquefied petroleum gas as fuel, such as using liquefied petroleum gas to fire porcelain and make tiles. Baking and rolling thin plates with liquefied petroleum gas not only reduces air pollution but also significantly improves the firing quality of the products.

⑶ Automobile fuel

At present, approximately 70% of urban air pollution sources come from vehicle exhaust emissions. To address this issue, since the end of the 20th century, major and medium-sized cities in China have successively built gas filling stations for automobiles, using liquefied petroleum gas to replace gasoline as the fuel for vehicles. This change in fuel variety has greatly purified the air quality of cities and is also another major development direction for the utilization of liquefied petroleum gas.

3. Low-carbon advantage: The application of low-carbon processes such as MTO has made LPG an important alternative to traditional fossil fuels, meeting global environmental protection requirements.

Vi. Transportation and Storage

1. Pipeline transportation

The liquefied petroleum gas pipeline supply system consists of gasification stations and pipelines. The gasification station is equipped with gas storage tanks, vaporizers and pressure regulators, etc. It is produced by the city gas company by mixing liquefied petroleum gas with air, liquefied petroleum gas with coal gas or liquefied petroleum gas with air discharged from fertilizer plants, etc. The liquefied petroleum gas continuously enters the vaporizer from the gas storage tank, is vaporized, and then the pressure is reduced and sent to users through pipelines. To prevent liquefied petroleum gas from re-liquefying in the pipeline, it is necessary to accurately determine the outlet pressure of the pressure regulator.

At present, many cities have realized this form of supply.

2. Bottled supply

Bottled supply refers to the distribution of liquefied petroleum gas from storage and distribution stations to individual households through a sealed steel cylinder, serving as the gas source for household stoves. It originated in the early 1960s and has now spread to rural areas and towns.

Liquefied petroleum gas cylinders are thin-walled pressure vessels, and their specifications vary from country to country. The capacities of cylinders used in households include 10, 12, 15, 20 kilograms, etc. The capacity of gas cylinders used by public buildings and small industrial users includes 45, 50 kilograms, etc. Special filling machines are used in liquefied petroleum gas storage and distribution stations to fill liquefied petroleum gas into steel cylinders, which are then supplied to users through supply stations or directly sold to them.

When in use, gaseous liquefied petroleum gas is reduced in pressure through a pressure reducer and then sent to the gas appliance. The liquid liquefied petroleum gas inside the cylinder absorbs heat from the environment and continuously vaporizes naturally. When the user's consumption is large and natural gasification cannot meet the usage requirements, forced gasification can be adopted for gas supply. Forced gasification is the continuous gasification of liquefied petroleum gas in a dedicated gasification device by using an external heat source.

3. Allocate the supply of tank trucks

When choosing tanker trucks for transportation, the operating cost is high and the transportation volume is not large. However, it is highly flexible and easier to dispatch, so it is usually applied in small and medium-sized liquefied petroleum gas stations. If it is a large or medium-sized liquefied petroleum gas supply base, it can be used as an auxiliary transportation tool. When transporting in this way, the filling should be in appropriate quantities and over-pressure or over-quantity transportation is not allowed. All kinds of traffic conditions within the range of vehicle transportation should be taken into account, such as traffic regulations, the slope of the road surface and the load limit of Bridges, etc.

4. Precautions for Storage and Transportation

Flammable compressed gases should be stored in a cool, dry and well-ventilated warehouse, and the warehouse temperature should not exceed 30℃. Keep away from fire and heat sources, avoid direct sunlight, and store separately from oxygen, compressed air, halogens (fluorine, chlorine, bromine), oxidants, etc. The lighting, ventilation and other facilities in the storage room should be explosion-proof, and the switches should be located outside the warehouse. When stored in tanks, fire prevention and explosion prevention technical measures should be in place. The storage area should be equipped with emergency handling equipment for leakage. The use of mechanical equipment and tools that can easily produce sparks is prohibited. Handle with care during transportation to prevent damage to the cylinders and accessories.

Vii. Safe Use

Although liquefied petroleum gas is convenient to use, it also has potential safety hazards. In case of a gas leak in the pipeline or if the valve is not closed tightly, liquefied petroleum gas will spread into the room. When the content reaches the explosive limit (1.7% to 10%), an explosion will occur upon encountering a spark or electric spark. To remind people to detect in time whether liquefied gas is leaking, processing plants often mix a small amount of mercaptans or sulfides with a foul smell into the liquefied gas. Once there is a liquefied gas leak, smell the odor immediately so that emergency measures can be taken.

1. Usage environment: When using liquefied petroleum gas, ensure good ventilation in the gas usage area. Users are not allowed to use other fuels. It is prohibited to store natural gas and liquefied gas cylinders, coal stoves, environmental protection oil stoves and other gas and fire sources in the same room or use them in the same room.

2. Gas cylinder management: Qualified liquefied petroleum gas cylinders provided by legal enterprises should be used. The service life of the cylinders is 8 years, and they should be inspected every 4 years. After 8 years, if they pass the inspection and assessment, they can be used for another 4 years.

3. Appliance selection: Liquefied petroleum gas appliances that have passed inspection should be used, and stoves with flameout protection devices should be adopted. According to national regulations, the scrapping period for liquefied petroleum gas stoves and water heaters is 8 years. For safety reasons, it is essential to replace liquefied petroleum gas appliances that have reached their scrapping period. Do not use the gas cylinder upside down. Do not place any items on the gas cylinder to avoid ignition.

4. Installation Requirements: The installation of liquefied petroleum gas appliances should be entrusted to units with the corresponding installation qualifications, and a separate exhaust flue should be used. The exhaust gas must not be discharged into the public flue. The use of direct exhaust water heaters is strictly prohibited. It is strictly prohibited for water heaters to directly discharge exhaust gas into the room without installing a flue.

5. Daily inspection: Liquefied petroleum gas pressure regulators that meet national standards should be used. Stoves and water heaters should be equipped with dedicated and qualified metal hoses, with a length not exceeding 2 meters. They must not be connected to three-way fittings and must not pass through walls, doors, Windows or ceilings.

5. Fire extinguishing method: Cut off the gas source. If the gas source cannot be cut off immediately, it is not allowed to extinguish the burning gas. Spray water to cool the container. If possible, move the container from the fire scene to an open area. Fire extinguishing agents: mist water, foam, carbon dioxide.

Youdaoplaceholder0 usage instructions:

When using liquefied petroleum gas, no one should be at home to prevent the flame from being blown out by the wind or splashed by soup, which could cause gas leakage. When drunk, tired or in other states, try not to use liquefied petroleum gas when alone at home.

⑵ The flame of liquefied petroleum gas is normally light blue. If it turns red, it indicates incomplete combustion. There is a risk of CO poisoning. Gas professionals should be called in immediately to inspect and adjust the stove.

⑶ How can one know if liquefied petroleum gas has leaked?

Smell - Household liquefied petroleum gas is mixed with deodorants, and when it leaks out, it will have a foul smell.

Visual - The leakage of liquefied petroleum gas can cause the formation of misty white smoke in the air.

Hearing - There will be a "hissing" sound.

Tactile sensation - When the hand approaches the leaked hole, there will be a cool feeling.

When you suspect that there is a leak in the liquefied petroleum gas pipe at home, you can check with soap bubbles.

⑷ If a liquefied petroleum gas leak is detected, please follow the steps below

Quickly open the doors and Windows for ventilation to accelerate the diffusion.

Quickly close the gas valve or the Angle valve of the gas cylinder to cut off the source of leakage as much as possible.

Do not turn on or off any electrical switches. Cut off the source of fire and the main outdoor power supply.

In a safe outdoor location, call the fire rescue number: 119.

Evacuate personnel from the contaminated area of the leakage to the upwind direction quickly and isolate the area, strictly restricting entry and exit.

Do not come into direct contact with the leak. Emergency response personnel wear self-contained positive pressure breathing apparatus and protective clothing.

Cover the sewers and other areas near the leakage point with industrial coatings or adsorbents/absorbents to prevent gas from entering.

Leaking containers should be properly handled, repaired and inspected before reuse.

⑸ What should be done if CO poisoning occurs?

Turn off the liquefied petroleum gas switch.

Open the Windows and doors for ventilation to provide fresh air for the injured person.

Unbind and clear the airway.

Artificial respiration or cardiopulmonary abdominal compression may be performed as needed.

Do not turn on or off any power switches before the unpleasant smell of liquefied petroleum gas dissipates to avoid sparks that could cause a fire.

It can be seen from this that the application scope of liquefied petroleum gas is getting wider and wider, the usage volume is getting larger and larger, and the development is getting faster and faster. Therefore, it is extremely necessary and urgently needed to enhance the publicity and learning of knowledge about liquefied petroleum gas and ensure its safe use

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