Differences Between LNG and CNG
3 Answers
LNG and CNG mainly differ in terms of their state of existence, safety hazards, volumetric energy density, and environmental friendliness. Here are the related introductions about the differences between LNG and CNG: State of Existence: When natural gas is cooled to approximately -162°C under normal pressure, it changes from a gaseous state to a liquid state, known as liquefied natural gas (LNG). On the other hand, compressed natural gas (CNG) is natural gas that is pressurized and stored in containers in a gaseous state. Safety Hazards: The primary method for storing and transporting natural gas is CNG. Due to the high pressure of compressed natural gas, it brings many safety hazards, such as a higher risk of fire. In comparison, LNG has a higher ignition point—auto-ignition temperature of about 590°C—a narrower explosion range (5%~15%), is lighter than air, and easier to disperse, making it safer. Volumetric Energy Density: The volumetric energy density of CNG is about 26% of gasoline, while LNG's volumetric energy density is about 72% of gasoline, more than double that of CNG. Environmental Friendliness: Natural gas must undergo strict pre-purification before liquefaction, so the impurity content in LNG is far lower than in CNG. This creates conditions for meeting stricter standards when used as vehicle exhaust or fuel.
I've always driven a natural gas vehicle, using CNG, which is completely different from LNG. Simply put, CNG compresses natural gas like a high-pressure gas cylinder, directly filling it into the car for use, and refueling stations are as common as gas stations. LNG, on the other hand, liquefies natural gas, freezing it to ultra-low temperatures, around -160°C, mainly used for large trucks or ships. Their differences lie first in their state—one is gas, the other liquid; second, in storage—CNG tanks can withstand high pressure, while LNG tanks need insulation to prevent freezing; third, in practicality—CNG is common in small cars and urban buses, being cheap and eco-friendly, with fast refueling and safe operation; LNG is suitable for long-distance transport, as one tank can go much farther, with lower costs and reduced emissions, but requires specialized equipment and carries higher risks if mishandled. As an ordinary car owner, I think understanding this can help us choose the right vehicle fuel, saving money and giving peace of mind. If considering switching to an eco-friendly car, it's essential to evaluate actual usage needs.
Having worked in the auto repair industry for so many years, I've seen the differences between common natural gas vehicles. Both LNG and CNG come from natural gas, but their processing methods are quite different. CNG is a high-pressure compressed gas, stored in tanks at around 250 bar pressure, used in regular household vehicles, making refueling more convenient; LNG is a cryogenically liquefied liquid, transported at -162°C, mostly used in trucks and heavy-duty equipment. Technically, CNG systems are simpler with lower maintenance costs, but prone to leaks; LNG requires insulated sealed tanks with stricter safety measures and higher maintenance fees. When driving, CNG offers quick starts with less noise and reduced engine wear; LNG provides stronger range, capable of 1000 km per tank, making it suitable for long-haul fleets. Both have environmental advantages, reducing emissions more than gasoline, though LNG consumes more energy in storage and transportation. From experience, the choice depends on vehicle type and driving habits.
