Why can't natural gas and liquefied gas nozzles be mixed

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In daily life, many people do not know the essential difference between natural gas and liquefied gas, let alone the key role carried by the 1 tiny parts of the stove nozzle. Accidents of misuse and mixed gas sources occur from time to time, ranging from damage to stove to poisoning or even explosion. This paper will start from the physical and chemical characteristics of the two kinds of gas, in-depth analysis of the design principle of the stove nozzle, revealing why the two are incompatible. Understanding this knowledge is not only related to cooking efficiency, but also an important barrier to protect family safety.

(1)、Difference between natural gas and liquefied gas

To understand the difference between nozzles, we must first understand that natural gas and liquefied petroleum gas are essentially different substances.

1. natural gas

The main ingredient is methane (CH-4 ), which usually comes from oil and gas fields and is transported by pipeline. Its characteristics are:

①. Low pressure: The entry pressure is about 2000 Pa SCA (equivalent to 0.02 atm).

②. Moderate calorific value: about 36 MJ/m3.

③. Low density: lighter than air, will float upward after leakage.

2. liquefied petroleum gas

The main components are propane and butane (C≡HC and C≡HC ), which come from petroleum refining. Its characteristics are very different:

①. High pressure: the pressure in the tank can reach more than 2800 Pa SCA.

②. The calorific value is extremely high: about 108 MJ/m3 (nearly 3 times that of natural gas).

③. Density: heavier than air, after leakage will be deposited in the corner of the ground, not easy to spread.

It is these fundamental physical and chemical differences that determine the throat of the stove, the nozzle, must be tailored.

(2)、Know the nozzle

The nozzle is the last pass before the gas is ejected from the valve into the burner. It is usually a small part made of brass with a carefully calculated tiny hole in the middle. Its central role is twofold:

1. Control gas flow

Like the water outlet of a faucet, it determines how much gas is ejected per unit time.

2. Formation of jet flow

The gas ejected at high speed will bring in air (primary air) and realize premixing in the burner.

Only when the gas is sprayed at the right pressure and speed, and mixed with air in the best ratio (natural gas requires about 10:1 air, liquefied gas requires about 25:1), can it burn an efficient and stable blue flame.

(3)、Four different decisions can not be mixed

1. aperture difference

①. Liquefied gas nozzle

The holes are small, usually between 0.6-0.9mm in diameter. Because of the high pressure of liquefied gas, small holes are needed to limit the flow and prevent it from gushing out.

②. Natural gas nozzle

The holes are large, typically 1.0-1.2mm or more in diameter. Because of the low pressure of natural gas, large holes are needed to increase the flow rate to ensure sufficient gas supply.

2. flow design

The aperture of the nozzle is not arbitrarily determined, but is accurately calculated by the fluid mechanics formula according to the pressure, density and calorific value of the two gases. To achieve the same firepower (like 4.0 kW):

①. Use of liquefied gas

Due to its high calorific value, only a small volume flow is required.

②. Use of natural gas

Due to its low calorific value, it requires about 2.5-3 times the volume flow rate to output the same amount of heat.

Therefore, natural gas nozzles must be designed to pass a greater flow of gas.

3. physical Structure

Although the two are similar in appearance, there may be subtle differences in internal structure:

①. Part of the liquefied gas nozzle has a special flow restriction design at the inlet.

②. The natural gas nozzle may take into account the lower supply pressure and optimize the flow curve.

③. Although the material is mostly brass, there may be slight differences in the treatment of the corrosion of different gases.

4. safety identification

The gas type code is usually clearly marked on the nozzle body or the nameplate of the cooker:

①. "12T" stands for natural gas

②. "20Y" stands for LPG.

This is their inaliable identity card.

(4)、The serious consequences of mixing

1. wrong combination 1: liquefied gas stove connected with natural gas.

①. Phenomenon: weak flame, yellow, erratic.

②. Reason: natural gas pressure is low, and through the hole, the flow is seriously insufficient.

③. Results: cooking efficiency is very low, basically can not use.

2. wrong combination 2: natural gas stove connected with liquefied gas (extremely dangerous!)

The high-pressure liquefied gas is ejected from the large hole, and the flow rate is too large to fully mix the air, which will cause very serious consequences:

①. flame out of control

Low-pressure gas through the large hole, the flow is too large, the ignition moment may deflagration, the flame up tens of centimeters high, can not be adjusted by the knob.

②. Produces deadly carbon monoxide

Excess gas can not be fully mixed with air, resulting in incomplete combustion, resulting in a large amount of odorless, colorless carbon monoxide (CO). In poorly ventilated kitchens,

lethal concentrations can be reached within half an hour.

③. Risk of backfire explosion

The flame may "burn back" through the nozzle to the inside of the gas line, causing an explosion.

④. Quick damage to the stove

Within a few days, the bottom of the pot will be blackened and the internal carbon deposition of the stove will be serious.

Conclusion

The small nozzle on the stove, although inconspicuous, is a precision hub connecting energy and safety. From the low-pressure lightness of natural gas to the high-pressure abundance of liquefied gas, different characteristics determine that they must have exclusive channels. Understanding the scientific principles behind it and respecting the design guidelines for exclusive use of gas is by no means a big deal. It is not only about whether the food in the pot can be fragrant quickly, but also the practical protection of family health and family peace.