Application scope of burner: it can be used in any situation where liquid and gas fuel are used as energy and its heat energy is directly used. Such as all kinds of boiler, heating furnace, baking furnace, spraying furnace, direct fired air conditioner and so on.

Basic requirements of burner: safe operation, energy saving and environmental protection.

The three elements of combustion process are fuel, oxidant and ignition source. This refers to the process that industrial combustion produces a large amount of energy for industrial heating in order to oxidize hydrocarbon fuel rapidly. Generally, atmospheric air is the oxidant of fuel (O2 accounts for about 21% of the volume). In some applications, the oxidant content is less than 21% O2 (such as gas turbine with flue gas recycling) or more than 21% O2 (such as oxygen enriched combustion).

Six parts involved in industrial combustion process: 1. Burner, 2. Load (materials, water, etc.), 3. Furnace (boiler, dryer, etc.), 4. Waste heat recovery device (air preheater, etc.), 5. Control system (combustion and load control), 6. Air pollution control system (dust removal, etc.)

Burner classification: 1. Complete premixed burner, 2. Diffusion burner, 3. Partial premixed burner

Classification of gas: gas can be divided into natural gas, artificial gas, liquefied petroleum gas and biogas.

Based on Huabai number and combustion potential: (national standard classification of urban gas)

Artificial gas: 5R, 6R, 7R; natural gas: 4T, 6T, 10t, 12t; LPG: 19y, 22y, 20Y

Natural gas

About 25% of the world's energy is natural gas. Natural gas can be generally divided into four types: gas field produced from gas wells or pure natural gas; oil gas produced along with oil, also known as oil associated gas; condensate gas field containing light oil fraction; coal mine gas extracted from underground coal seams. Generally, the methane content is not less than 90%, and the calorific value is 34300-36000kj / Nm3. The relative density is 0.55, the ratio of hydrocarbon is the smallest, no sulfur, and the greenhouse gas is the least. It is the transition of human being to use hydrogen fuel.

Artificial gas

The relative density is 0.45. The main components of artificial gas are h2-50 ~ 60%, co-15 ~ 20%, ch4-10 ~ 15%, and the rest are inert gases (N2, CO2, etc.). The calorific value of solid fuel gas is generally about 16700 kJ / Nm3. Each ton of coal can produce 300-400 Nm3 of gas. The calorific value of solid fuel gasification gas is about 15100 kJ / Nm3.

Oil to gas can be divided into heavy oil and light oil to gas. Heavy oil gas can be divided into two types: regenerative pyrolysis gas and regenerative catalytic pyrolysis gas. The calorific value of the regenerative pyrolysis gas is about 41900 kJ / Nm3. The gas production per ton of heavy oil is 500-550m3. The calorific value of regenerative catalytic cracking gas is about 17600-20900 kJ / Nm3. The gas production per ton of heavy oil is about 1200-1300nm3. The calorific value of blast furnace gas is about 3500 kJ / Nm3.

Liquefied petroleum gas (LPG)

The main components of LPG are propane (C3H8), propylene (C3H6), butane (C4H10) and butene (C4H8), which are also known as C3 and C4, that is, they are only expressed by the number of carbon atoms (c) of hydrocarbon. These hydrocarbons are gaseous under normal temperature and pressure. When the pressure increases or the temperature decreases, they are easy to change into liquid. From gas to liquid, its volume is reduced about 250 times. The calorific value of Gaseous LPG is about 92100-121400 kJ / Nm3. The calorific value of LPG is about 45200-46100kj / kg.

methane

Biogas is a kind of mixed gas, which contains 60% - 70% methane, 30% - 35% carbon dioxide, and a small amount of carbon monoxide, hydrogen, ammonia, hydrogen sulfide, oxygen and nitrogen. As a high-quality gas fuel, biogas can be used not only for cooking and lighting, but also for power generation, chicken hatching, silkworm rearing, drying, grain and fruit storage, carbon dioxide fertilization and other production fields. The relative density is 1.9, which has the advantage of convenient storage and transportation.

Gas property and burner form

The nature of the gas determines the form of the burner. For the burner, the main influencing factor is the combustion speed of the gas (the scientific name is flame propagation speed).

The combustion speed is determined by the nature of gas firstly. For pure gas, hydrogen combustion speed is the fastest, while methane combustion speed is the slowest. Therefore, combustion speed: artificial gas > liquefied petroleum gas > Natural Gas > biogas. The combustion speed is related to the mixture concentration of gas and air, which is in the inverted U-shape relationship. It is the fastest when it is close to the stoichiometric ratio. The reason why the full premixed burner is easy to backfire is that before combustion, the gas and air have been mixed well at the concentration close to the stoichiometric ratio. The combustion speed is also related to the initial temperature. The higher the temperature is, the faster the combustion speed is. Therefore, the burner with preheating air is easy to backfire.

Because there is a large amount of inert gas CO2 in the gas, the burning speed of biogas is the slowest, and its ignition and combustion are relatively difficult, so some special measures need to be taken to achieve the ideal combustion. For example, the main technical problem of natural gas burners is how to prevent the desquamation. For the gas with fast combustion speed, the problem of preventing the burner head from being burnt by tempering should be solved.

The first burner

In the early days, few equipment could be considered as burners. The industrial furnace is simply equipped with several air and gas openings (see Figure). The gas and air flow are properly mixed in the furnace. Although this method is simple and has obvious security risks, it can work well, especially in high temperature furnaces. In fact, this concept still appears in some regenerative glass furnaces and open hearth steelmaking furnaces.

Injection burner: it has the ability to automatically adjust the proportion of gas and air.

Fan mixed burner