The reason for the high acetylene flame temperature, how much is the acetylene flame temperature

The flame formed by the mixed combustion of acetylene and oxygen is called an oxygen-acetylene flame. The oxygen-acetylene flame has a very high temperature (about 3200 °C) and is heated intensively, so it is the main flame used in gas welding. The combustion process of acetylene (C2H2) in oxygen (O2) can be divided into two stages, firstly, acetylene is decomposed into carbon (C) and hydrogen (H2) under the action of heating, and then carbon reacts with oxygen in the mixture to form carbon monoxide (CO) to form the first stage of combustion; The subsequent combustion in the second stage is an oak grinding based on oxygen in the air, in which the oxygen beam reacts with oxygen to form carbon dioxide (CO2) and water (H2O), respectively

The above reaction releases a free source of heat, i.e., the process of burning acetylene in oxygen is an exothermic process. According to the different proportions of oxygen and acetylene, the oxygen-acetylene flame can be divided into three types: neutral flame, carbonization flame and oxidation flame, the core of the neutral flame is composed of oxygen and acetylene, the temperature is low (800 1200), and the internal flame is mainly composed of the incomplete combustion products of acetylene, that is, the carbon and hydrogen from the flame core and the carbon monoxide and hydrogen gas, the products of oxygen combustion. The internal flame is located in the front of the flame core 2 4mm part, the combustion is the most intense, the temperature is the highest, up to 3100 3150

When gas welding, this temperature zone is generally used for welding, so it is called the welding zone. The outer flame is located on the outside of the inner flame, and the color of the outer flame changes from lilac to orange-yellow from the inside out. In the outer flame, the carbon monoxide and hydrogen produced by the combustion of the inner flame are fully combusted with the oxygen in the air, that is, the second stage of combustion is carried out.

The products of the outer flame combustion are carbon dioxide and water. The outer flame temperature is 1200 2500Since carbon dioxide (CO2) and water (H2O) decompose easily at high temperatures, the outer flame is oxidizing.

The carbonization flame is a gas flame formed by the combustion of a mixture when the ratio of the volume of oxygen to acetylene (O2 C2H2) is less, because acetylene has a surplus, so the combustion is incomplete. The maximum temperature is 2700 3000The oxidation flame is a gas flame formed by the combustion of the mixture when the ratio of the volume of oxygen to acetylene (O2 C2H2) is greater, and there is excess oxygen in the oxidation flame, and the maximum temperature of the oxidation flame can reach about 3100 3400.

The neutral flame, carbonization flame and oxidation flame described above are suitable for welding different materials due to their different properties. The gas flame formed by the combustion of mixed gas with different volume ratios of oxygen and acetylene (02 C2H2) has a great influence on the welding quality.

Pure acetylene burns in the air with a flame temperature of 2100 degrees. Burns in oxygen, flame height up to 3600 degrees.

Acetylene is the simplest alkyne, also known as calcium carbide gas. Structural formula H-C C-H, structural simple formula CH, simplest formula (also known as experimental formula) CH, molecular formula.

C2H2, acetylene center C atom is hybridized with SP. Electronic formula h:c c:h acetylene molecular weight.

Gas specific gravity. The flame temperature is 3150, and the calorific value is 12800

kcal m3, the rate of combustion in oxygen.

The chemical properties are very active, and can cause addition, oxidation, polymerization and metal substitution reactions.

A flame formed by the mixed combustion of acetylene and oxygen. By adjusting the oxygen valve and acetylene valve, the mixing ratio of oxygen and acetylene can be changed to obtain three different flames: neutral, oxidizing and carbonizing.

1.Neutral flame oxygen and acetylene are fully combusted, there is no excess of oxygen and acetylene, and the internal flame has a certain reduction. Maximum temperature 3050 3150 . It is mainly used for welding low carbon steel, low alloy steel, high chromium steel, stainless steel, copper, tin bronze, aluminum and its alloys, etc.

2.Oxidation flame Excess oxygen flame is oxidizing, and the weld is prone to porosity and brittleness when welding steel parts. Maximum temperature 3100 3300 . It is mainly used for welding brass, manganese brass, galvanized iron sheet, etc.

3.Carbonization flame acetylene is excessive, there is free carbon and too much hydrogen in the flame, and the hydrogen content of the weld will be increased during welding, and there is carburizing phenomenon in welding low carbon steel. Maximum temperature 2700 3000 .

It is mainly used for welding or welding repair of high-carbon steel, high-speed steel, cemented carbide, aluminum, bronze and cast iron.

The thermochemical equations for ethylene and acetylene combustion are:

2c2h2(g)+5o2(g)=4co2(g)+2h2o(l)；△h=-2600 kj•mol-1

c2h4(g)+3o2(g)=2co2(g)+2h2o(l)；△h=-1411 kj•mol-1

The heat of combustion is ethylene acetylene, but the flame is high when the flame is heated and the acetylene is burned. Acetylene burns in air or oxygen, and its flame temperature can be as high as 3200 °C. Although the heat of combustion of acetylene is slightly lower than that of ethane and ethylene, it has the least oxygen consumption during complete combustion, the water content in the product is relatively low, and the heat loss required for water evaporation is less, so acetylene can obtain a higher temperature when burning.

The high carbon content is more fully combusted, so the outer flame is high.

The acetylene flame temperature formed by the combustion of acetylene in pure oxygen can be as high as 3000, but the combustion heat of acetylene is lower than that of ethylene and ethane. CH2 = CH2 (gas) + 3O2 (gas) 2CO2 (gas) + 2H2O (liquid) + 1411kJ

The temperature of the alkyne flame is particularly high due to the small heat capacity of the products produced by the combustion of acetylene. As a result of the combustion of acetylene, ethylene, and ethane in the same amount of substance, the amount of oxygen required for the complete combustion of acetylene is the smallest, and the amount of substance required to produce water is also the smallest. Therefore, during combustion, the temperature of acetylene flame is the highest because the temperature of the reaction is consumed to increase the temperature of oxygen and vaporize the water.

The absolute value of the enthalpy of combustion is large.

Let's compare the chemical formulas of the three first, ethane C2H6, ethylene C2H4, acetylene.

C2H2 From the chemical formula we can see that acetylene has the largest carbon-to-hydrogen ratio, and the cavity collapses so that the amount of other substances is burned and carbon dioxide is released.

As much, but acetylene emits the least amount of H2O, and in junior high school physics, it is said that the specific heat capacity of H2O.

The largest, and the water is heated and gasified to absorb heat, and acetylene produces the least water, so the heat absorbed by gasification is the least, and then the heat released by acetylene combustion is the most, the temperature is the highest, Wu Duanyuan is commonly known as oxyylene flame.