What are the basic conditions for complete combustion? What are the basic conditions for combustion

There are four conditions for complete combustion of fuel:

1) Air conditions: When the fuel is burned, the appropriate amount of air must be supplied according to the different stages of combustion. If the amount of air is too small, the combustion is not complete, and the amount of air is too large, it will cause the furnace temperature to drop and the exhaust smoke to increase.

2) Temperature conditions: only when the ignition temperature is reached, it can be burned by oxidation. The temperature is higher than the ignition temperature, and the rate of heat release during the combustion process is higher than the rate of heat dissipation to the surroundings in order for the combustion process to continue.

The ignition temperature refers to the minimum temperature that a combustible substance must reach to start burning in the presence of oxygen.

3) Time conditions: The residence time of the fuel in the combustion chamber is another basic factor affecting the completeness of combustion, and the residence time of the fuel in the high temperature zone should exceed the time required for fuel combustion. At the required combustion reaction rate, the residence time will be determined by the size and shape of the combustion chamber.

The higher the temperature, the faster the reaction.

4) Mixing conditions of combustion with air. The full mixing of fuel and oxygen in the air is the basic condition for effective combustion, and the degree of mixing is determined by the degree of turbulence of the air. For the combustion of vapors, turbulence can accelerate the evaporation of liquid fuels; For the combustion of solid fuels, turbulence can destroy the laminar boundary layer formed by combustion products on the surface of fuel particles, thereby improving the oxygen utilization rate of surface reactions and accelerating the combustion process.

Behind the Mpemba phenomenon, a cup of cold water and a cup of hot water are placed in the freezer compartment of the refrigerator at the same time, which glass of water freezes first? "Of course the cold water froze first! "I believe that many people will not hesitate to do this.

Unfortunately, this answer is wrong. The mistake was discovered by Mpemba, a junior high school student at Magamba Middle School in Tanzania, Africa. One day in 1963, Mpemba found that the hot milk he kept in the freezer of his refrigerator froze before the cold milk of his classmates.

This puzzled him, so he immediately ran to the teacher and asked for advice. The teacher said easily, "You must be mistaken, Mpamba."

Unconvinced, Mpemba tried again, but the hot milk froze before the cold milk. One day, Dr. Osborn, Head of the Department of Physics at the University of Dar es Salaam, visited Mpemba's school. Mpemba mustered up the courage to ask the doctor his question.

Dr. Osborn said, "I can't ask you questions right away, but I promise to do this experiment myself as soon as I get back to Dar es Salaam." As a result, the doctor's experiment was exactly what Mpemba said.

As a result, this phenomenon is known as the "Mpemba phenomenon". For more than 40 years, the "Mpemba phenomenon" has been recognized as truth to this day. It doesn't end there.

In 2004, Yu Shunxi, a girl from Xiangming Middle School in Shanghai, questioned this phenomenon. Under the guidance of Huang Zengxin, a famous science and technology teacher, Yu Shunxi and two other female students began to study the Mpemba phenomenon. They use sugar, water, milk, starch, ice cream and other ingredients to collect.

There are three basic conditions that must be met for combustion:

1. Combustibles: Regardless of solids, liquids and gases, any substances that can react violently with oxygen or other oxidants in the air are generally combustibles.

2. Combustibles: Any substance that can help and support combustion is called combustible. Generally refers to oxygen and oxidants, mainly referring to oxygen in the air.

3. Fire source: Any energy source that can cause the combustion of combustible substances is called an ignition source.

Combustibles, oxidizers, and ignition sources are known as the combustion triad, and combustion occurs when these three elements are present and interact with each other. Combustion is a kind of exothermic and luminescent chemical reaction, and its reaction process is extremely complex, the chain reaction of free radicals is the essence of the combustion reaction, and light and heat are the physical phenomena that occur during combustion.

The four sufficient conditions for combustion are combustibles, combustibles (oxygen), temperature and reaching the ignition point.

1.Oxidizing agent:

Substances that can help and support the combustion of combustibles, that is, substances that can oxidize with combustibles are called oxidants. The oxidizing agent in the combustion process is mainly oxygen, which includes free oxygen or oxygen in compounds.

2.Combustibles:

Any substance that can react with oxygen or other oxidants in the air is called combustible. According to its physical state, it is divided into three categories: gaseous combustibles, liquid combustibles and solid combustibles.

3.Temperature (ignition source):

The ignition source is the energy supplied to the combustible material for the combustion reaction with the oxidant**. The common one is thermal energy, and there are other thermal energy that transforms into chemical energy, electrical energy, mechanical energy, etc.

The four conditions of combustion: combustibles, combustibles, ignition sources, and chain reaction free radicals.

Aerobic flammable without clogging.

Complete combustion: refers to the fact that all combustible substances (carbon, hydrogen, sulfur, etc.) contained in the fuel are combined with oxidation to produce only carbon dioxide.

Water vapor and sulfur dioxide.

of combustion. Incomplete combustion: refers to the process of insufficient combustion of flammable items in nature during combustion.

There are two types of incomplete combustion, chemical incomplete combustion and mechanical incomplete combustion, depending on the cause of occurrence. The former refers to the residual carbon monoxide in the combustion products.

Hydrogen, methane. and other combustible substances; The latter refers to the fact that a part of the fuel does not participate in the combustion in the combustion equipment, but appears in the form of coal cores, carbon particles, oil droplets or coke deposits.

Causes of incomplete combustion:

Improper coordination of fuel with air (i.e., excess air coefficient.

Too small or too large), the fuel variety is not suitable for the fuel equipment, the fuel is unevenly distributed on the grate when burning lump coal, the fuel is unevenly distributed on the grate when burning pulverized coal, or the pulverized coal is not mixed well with air (secondary air), the combustion temperature of liquid fuel is often too low or too high due to poor atomization quality, and the time of fuel stay in the combustion equipment is too short.

1) Air conditions: The amount of air suitable for fuel combustion must be ensured during fuel combustion. Insufficient air **, incomplete combustion; If the air volume is too large, the furnace temperature will be lowered and the exhaust heat loss of the boiler will be increased.

2) Temperature conditions: Only when the fuel reaches the ignition temperature can it react with oxygen and burn with it. (3) Time quietly conditions:

The residence time of the fuel in the high-temperature zone should exceed the time required for fuel combustion. At the required combustion reaction rate, the residence time will be determined by the size and shape of the combustion chamber. (4) Mixing conditions of fuel and air

Adequate mixing of fuel and oxygen in the air is an essential condition for effective combustion. The degree of mixing depends on the degree of turbulence of the air. 4.

The heat loss of fuel equipment mainly includes: exhaust gas heat loss, incomplete combustion heat loss and furnace heat dissipation loss.

The three basic conditions for combustion are:

1. Have a certain amount of combustibles.

2. There is a sufficient amount of oxidant in eggplant.

3. Have a certain number of ignition sources.

Combustion can only occur if these three hands and pieces are present at the same time, interacting with each other.

Combustion is an exothermic and luminescent chemical reaction, and its reaction process is extremely complex, the chain binadian reaction of free radicals is the essence of the combustion reaction, and light and heat are the physical phenomena that occur during combustion.

Combustion requires the coexistence of three elements: combustibles such as fuel, combustibles such as oxygen, and temperature to reach the ignition point. The three elements of combustion are called the fire triangle. Combustibles are oxidants in combustion reactions, and oxygen is the most common combustion agent in combustion reactions, but other compounds can also be combustion aids, such as magnesium bands, which can be burned in carbon dioxide, in which case carbon dioxide is the combustion.

The conditions for combustion are: combustibles, oxidants (combustibles), and temperature (ignition source).

There are three combustion conditions, namely combustibles, ignition points and oxygen, all three are indispensable, otherwise the conditions for combustion cannot be reached, so as not to trigger the phenomenon of combustion, of course, in addition to oxygen, there are some chemical gases, which can also become the necessary conditions for the existence of oxygen in the combustion process.

The ignition point is a prerequisite for combustion, because only when there is an ignition point, the object may burn, otherwise, it will not produce combustion for no reason, and oxygen is the catalyst for combustion.

Of course, some special substances, such as magnesium bars, need to be burned in carbon dioxide, and if you want it to burn more fully and violently, you need to increase the amount of carbon dioxide. These three are the necessary conditions for combustion, and basically none of them is missing.

Definition of combustion:

Combustibles undergo a rapid exothermic and luminescent oxidation reaction with oxygen or air and appear in the form of a flame. The combustion of coal, oil and natural gas is the main thermal power of all sectors of the national economy.

In addition to the characteristics of the combustible mixture, the ignition temperature is also related to the temperature and pressure of the surrounding environment, the shape and size of the reaction vessel, and other conditions for external heat dissipation. When the heat released by oxidation exceeds the heat lost by the system, the fuel is known to heat up rapidly and ignite. This ignition, which is closely related to flow and heat transfer, is called thermal ignition, and it is the ignition process that most stool dissipating fuels undergo in combustion equipment.

When the fuel is more active, the pressure in the combustion system is higher, and the heat dissipation is less, the thermal ignition temperature of the fuel will become lower.