Bunsen Burner – Principle, Parts, Types, Operation, Functions

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In an ordinary Bunsen burner flame the unburned gas is confined by the burner tube and by the combustion wave which rests on the tube rim in the shape of a cone.

Bunsen burners are generally used to rapidly heat high-boiling liquids with low flammability (such as water). Safety note: It is important to know that they can reach temperatures of approximately approximately 1500^oC, and can easily ignite most organic compounds. If an apparatus is improperly set up, or if there is a small gap that allows organic vapors to escape from an apparatus, these vapors can ignite with a burner. Therefore, it is generally recommended to use other heat sources to warm flammable organic liquids (for example in distillation or reflux). Bunsen burners should never be used with highly flammable solvents such as diethyl ether.

However, burners do have their place in the organic lab. Burners are often used in steam distillation as the vapors are generally not flammable. In this context, a wire mesh set atop a ring clamp is often used under the flask to dissipate the heat and avoid overheating one area. Burners are also used in the Beilsten test for halogens, with Thiele tubes in melting and boiling point determinations, and for softening pipettes to create capillary TLC spotters. They may also be used in sublimations.

What is a Bunsen Burner?

• Robert Bunsen invented the Bunsen burner, which is a type of ambient air gas burner used in laboratories. It has a single open gas flame and is used to heat, sterilise, and burn things.

• The most interesting thing about the Bunsen burner is that the part of the flame just above the tip of the main flame that gets the hottest gets to about 1500 °C or 2700 °F. It has this kind of high temperature and needs less space, so it is also called a “micro incineration plant.” Because it is a physical method, it is also a part of sterilisation.

• Natural gas, which is mostly methane, or a liquefied petroleum gas like propane, butane, or a mix of the two, can be used. The adiabatic flame temperature of the chosen fuel mixture affects the temperature of the combustion.

• Using a simple gas-powered burner is probably the easiest way to make a relatively clean environment on the lab bench.

• This common piece of machinery burns a steady stream of an ignitable gas, usually natural gas (methane). Its design is based on one made by the German chemist Robert Wilhelm Bunsen almost 150 years ago.

• In aseptic technique, the open flame is used to make a cone of hot air above and around the lab bench. This kills organisms on dust particles that are in the air.

• Because the flame from a Bunsen burner heats things up very quickly, it is also a great way to sterilise inoculating loops, warm the necks of glass bottles, or start the alcohol on culture spreaders.

• The gas burner is made up of a vertical metal tube through which a narrow jet of natural gas is sent. The air comes in through holes near the stand.

• The mixture of gas and air burns above the top hole. The metal collar can be turned to cover or partially cover the air holes. This lets you control how much air gets in and how hot and round the flame gets.

Principle of Bunsen burner

• At the bottom of the barrel of a Bunsen burner, there are usually spiky fittings that help connect the rubber tube that brings gas to the burner.

• From the bottom of the burner, the gas goes through the rubber tube and up the barrel.

• The bunsen burner works because it can use the venturi effect to mix gases with oxygen before the mixture is set on fire.

• The venturi effect says that when a fluid flows through a hole or pipe that is narrowed, its speed goes up. This makes the pressure drop.

• In the same way, gas moving through a bunsen burner’s chimney has less pressure than the steady air around it.

• With the help of the venturi effect, this difference in pressure pulls air into the air hole as the gas flows through it. So, the flame at the top of the barrel comes from gas and oxygen mixing together.

• So, the strength and colour of the flame are directly related to the amount of air supplied, which can be controlled by the collar (adjustable valve).

• With the valve closed, only a small amount of air (oxygen) gets through, and a low-temperature, smoky yellow flame is made.

• When the valve is open, enough air comes in, and the roaring flame gets hot enough to be almost colourless.

Fuel Sources for Bunsen Burner

A Bunsen burner has two main sources of fuel;

1. Natural gas (mostly methane)

• Natural gas, which is also called fossil gas or just “gas,” is a mixture of gaseous hydrocarbons that occurs naturally. It is mostly made up of methane and smaller amounts of other higher alkanes.

• Trace gases like carbon dioxide, nitrogen, hydrogen sulphide, and helium are often also present in small amounts.

• Natural gas is colourless and has no smell, so odorizers like mercaptan, which smells like sulphur or rotten eggs, are often added to make it safer and easier to find leaks.

2. liquefied petroleum gas (propane, butane, or a mixture of the two)

• Liquefied petroleum gas, or LPG or LP gas, is a type of fuel gas that is made up of a mixture of hydrocarbon gases, like propane and butane, that can catch fire.

• LPG can be bought and sold in mixes that are mostly propane (C3H8), mostly butane (C4H10), or, most often, both propane and butane.

• *Make sure you choose the right burner for the fuel you will be using. It is dangerous to use a burner for one type of fuel with another type of fuel.

Parts of Bunsen burner

• Base Gas inlet: The gas enters the Bunsen burner through a tube that sticks out from below the air hole. This is where the gas and oxygen mix. Needle valve to change the flow of gas

• Rotary barrel for air adjustment: The flames come out of the barrel, which is the tallest part of the Bunsen burner. Don’t touch the barrel because it can get very hot while it’s being used and can stay hot for a long time after.

• Air hole: The air hole is a small hole above the barrel’s gas inlet that can be covered. It lets air into the Bunsen burner where it mixes with the gas. By turning the collar, you can cover all or part of the air hole.

• Collar: The collar is a metal tube that can be moved to cover or show the air hole. This controls how much oxygen can get into the Bunsen burner and, by extension, how much oxygen can mix with the gas. If you let more oxygen into the Bunsen burner, the flame will get hotter. Always turn on the Bunsen burner with the collar covering all of the air holes.

• Gas valve or Gas regulator: It helps to keep the flow of gas in check.

• Gas intake or Rubber tubing: The Bunsen burner is connected to the gas source on your lab bench by a short piece of tubing that is connected to the gas inlet.

• Base: It is a wide, heavy piece with different shapes that holds up the Bunsen burner. It’s attached to a tube on the side called the gas tube.

Types of Bunsen burners

Three varieties of Bunsen burners exist:

1. Meker Fisher Burner

• The diameter of the barrel is greater than that of the bunsen burner. Due to the bigger dimensions, air and gas are more thoroughly mixed.

• A grid covers the top of the barrel and divides the flame into tiny flames.

• The gas supply can be regulated via a gas valve situated beneath the chimney or barrel.

• The lower portion of the tube contains more apertures with a bigger total cross-section, admitting more air and allowing for better air and gas mixing.

• Its surface is covered by a wire grid.

• The grid divides the flame into an array of smaller flames with a common exterior envelope and prevents flashback to the bottom of the tube, which is a problem at high air-to-fuel ratios and limits the maximum air intake rate in a typical Bunsen burner.

• If used appropriately, flame temperatures of up to 1,100–1,200 °C (2,000–2,200 °F) are possible.

• In addition, the flame burns quietly, unlike Bunsen or Teclu burners.

2. Teclu Burner

• This burner is more effective than the bunsen burner at producing heat.

• It has a longer barrel tube than other burners.

• Excellent mixing of air and gas occurs. This leads in an increase in the flame’s combustion power.

• The lower portion of its tube is conical, and below its base is a spherical nut for adjusting the gas supply.

• Similar to the open slots of a Bunsen burner, the distance between the nut and the tube’s end controls the airflow.

• The Teclu burner mixes air and fuel more effectively and can produce higher flame temperatures than the Bunsen burner.

3. Tirrill Burner

• The base of the burner is equipped with a needle valve that regulates gas intake directly from the Burner, rather than the gas source.

• Maximum flame temperature can reach 1560 degrees Celsius.

Operation Technique of Bunsen burners

• Put the Bunsen burner away from any shelves, equipment, or lights that hang from the ceiling.

• Take away all papers, books, things that can catch fire, and extra chemicals from the area.

• Wear safety glasses and a lab coat. If your hair is long, you should tie it back.

• Link the rubber hose to a gas tap.

• If the surface can’t handle the heat, put a heat mat under the Bunsen burner.

• Turn the collar around to cover the air hole.

• Hold a lit match about 3 cm from the top of the barrel.

• Turn the gas tap so that it says “on.”

• Put out the flame by putting out the match.

• Leave the flame in “safety mode” until you need to heat something.

During Use

• Never leave a burner that is on without watching it. Even if a draught, like one from a hood, puts out the flame, the gas will still be on. This could cause a bomb to go off.

• Never heat something in a test tube, beaker, or other container with the opening facing you or someone else close to the burner. A hot plate can be used instead of a Bunsen burner in some experiments.

• When heating liquids that can catch fire, you must use a hot plate or a heating mantle.

After Use

• If a Bunsen burner was used to heat something, it is likely to be very hot. Do not touch equipment with your bare hands unless the air around it feels cool.

• Use crucible tongs or thermal gloves if you need to handle something hot. If you put something hot on paper, it could catch fire. Let the machine cool down where it is, with the burner removed or turned off.

• Turn off the gas when you’re done.

• Wait until the burner is cool to touch it. Make sure the main gas valve is turned off before you leave the lab.

Uses of Bunsen Burner

• Sterilization of the loop for giving shots

• Sterilization of straight wire used for stabbing

• Sterilization of the parts of the forceps that touched the specimens

• With the help of a tripod and a safety flame, something that heats up stands there.

• Used to remove water from complexes.

• Salts are dried with this.

• Used to start a fire

• Used to figure out what kind of water has crystallised.

• Used to see if a compound can catch fire.

• Used to clean and sterilise.

• Used to warm up.

• Used to measure moisture.

• Used to find the flash point of a solvent.

• Classical calorimetry is used to figure out the melting point.

• The Thiele tube method is used to find the boiling point.

Advantages of Bunsen Burner

• The highest temperature it can get to is 1500 degrees Celsius.

• It can be used anywhere that gas is available, such as coal gas, natural gas, etc.

• The burner comes in different sizes, so we can choose the one that works best for us.

• It’s easy to deal with.

• Simple to set up and use.

• Cost-effective

• We can not only heat with it, but also use it to blow simple glass.

Limitations of Bunsen Burner

• Fire is always a possibility.

• It’s not easy to keep the temperature at the level you want.

Safety Rules for Bunsen Burner

As you are aware, the temperature of this burner is extremely high, at 1500 °C or 2700 °F; consequently, we must adhere to safety regulations to prevent any accidents.

• When using this burner, you should always wear safety glasses and a lab coat.

• If your hair is long, you should always pull it back.

• Always light it with the collar covering the hole that lets air in.

• Before turning on the gas tap, you should always light a match or lighter and hold it above the barrel of the Bunsen burner.

• Never turn on a gas faucet without a Bunsen burner attached and a lit match above the barrel.

• Put out the match as soon as you light it.

• Leave it on the yellow safety flame even when you aren’t cooking.

• When you want to heat something, you should always leave it on the blue heating flame.

• Don’t put your hand near a fire.

• Turning off the gas valve is the only way to put out a Bunsen flame.

• Never try to put out a Bunsen flame by blowing on it.

• If the flame goes out by accident, turn off the gas right away.

• If there’s a fire, turn off the gas tap right away.

 

What is Flame?

• A fuel and an oxidizer undergo a chemical reaction to produce flame (or oxidant).

• In certain circumstances, the fuel and oxidant may be included within the same chemical molecule, as is the case with certain propellants and explosives.

• Combustion refers to the chemical reaction between the fuel and oxidant, which is accompanied by the release of heat and, typically, the emission of visible light.

• In the case of a premixed hydrocarbon flame burning in air, the light emitted is often blue if the mixture is fuel-rich, and it indicates the location of the flame and, in particular, the position of the flame front due to its greater intensity.

• However, if the mixture entering the flame is rich in fuel, a yellow soot-producing flame known as a bright flame is formed.

• Depending on the fuel-air ratio, flames are capable of reaching temperatures as low as 1300K. The majority of flames occur from highly exothermic reactions that produce flame temperatures of about 2200K.

• Certain flames, termed “cool” flames, can be maintained below this temperature, although only partial combustion occurs.

• Typical flames originate from the burning with air of a gaseous fuel, such as natural gas, commercial and industrial liquid fuels, sometimes referred to as fuel oils, which are burned as a spray, or by crushed coal particles suspended in air, as in a power plant boiler.

• Depending on the manner in which the fuel and oxidant are mixed in a burner and their respective flow rates, many types of flames can result.

• When fuel gas and air are mixed before to entering the burner, premixed gas flames can result; when they mix after leaving the burner, diffusion flames are produced. In the event that the gas flow rate is relatively low, the incoming gaseous flow of fuel and air is laminar, as is the flame.

• When gas fluxes are strong, they may be turbulent. As seen in Table 1, flames can be laminar premixed, laminar diffusion, turbulent premixed, or turbulent diffusion.

• As the flow velocity increases, there is a shift from laminar to turbulent flame. In addition, they can be classified as either stationary flames or propagating (moving) flames, with the former being the most common type of flame used in home or industrial burners and the latter being associated with explosions.

The most studied flame is the laminar premixed flame with a gaseous fuel and oxidant, often air, because it is the simplest flame and shares properties with many other systems.

Typical is the Bunsen burner flame, which is commonly utilised in gas fireplaces, gas ranges, and central heating equipment.

The flame of a Bunsen burner is depicted in Figure, however for research purposes, a special burner producing uniform flow is employed to produce a flat flame, as depicted in Figure.

However, the Bunsen burner demonstrates both the premixed flame and the diffusion flame theory.

The inner core of a premixed flame is the reaction zone, but the flame is fuel-rich, so the products of incomplete combustion burn as a diffusion flame with the surrounding air in the outer core.

The ratio of fuel to air determines the precise nature of the flame. If there is an abundance of fuel, it is considered rich, and the flame will be yellow and bright.

If there is an abundance of air (or oxygen), it is termed lean. It would be dubbed stoichiometric if it contained the ideal proportions of fuel and air.

Overall, the combustion products would be represented by the stoichiometric equation, which for methane (the most abundant component of natural gas) is:

CH4 + 2O2 → 2CO2 + 2H2O -ΔHc

where –ΔHc is the heat generated by burning, also known as the heat of combustion or calorific value (cv).

Stoichiometric refers to a scenario in which no fuel or oxidant is left over after complete combustion.

The zone of incomplete combustion in the flame depicted in Figure indicates only partial burning of the fuel, which produces carbon monoxide and hydrogen, which then combust with the secondary air to produce carbon dioxide and water.

This two-stage combustion can be represented, for example, by the processes for methane, by

CH4 → {CO,H2} → CO2, H2O

In general, all hydrocarbon flames, whether rich or lean, pass through this stage, where CO and H2 are formed in the first main reaction zone, and the second stage combustion of the CO and H2 initially formed is characterised by the emission of blue light; this blue emission being a defining characteristic of the combustion of all carbon (and hydrocarbon) containing fuels.

This phenomenon is referred to as afterburning and is more prominent in flames with a modest excess of fuel.

The burning velocity, flame temperature, and flammability limit of a premixed flame of a specific fuel-air mixture are determined by the pressure, temperature, and, of course, mixture ratio.

Premixed fuel air mixtures have a distinctive burning velocity, which allows flames to be stabilised on a burner, as depicted in Figures, if the flow rate of the gas mixture is equal to the laminar burning velocity.

The burning velocity is simply defined for a flat, laminar flame as shown in Figure, i.e., the approach velocity gives the burning velocity (relative to the unburned gas, Su), which is often expressed in metres per second.

The laminar flame for a conical flame is depicted in Figure. In the case of laminar diffusion flames, the fuel and oxidant only meet at the burner mouth (i.e., they are not pre-mixed) and combine by diffusion processes as the flame burns, as seen in Figure 1. In this instance, the fuel gas and oxidant gas streams are slotted, resulting in a flat flame. However, similar axisymmetric flames can be produced by using concentric tubes, with the fuel typically entering through the inner tube.

The proportion of the fuel-oxidant mixes that will support a stable flame is the flammability limit. There are two types of restrictions on the spread of a laminar flame.

The flammability limit is connected with the chemically reactive capacity of the combination to sustain a flame.

The second factor is gas flow impacts. The stoichiometric ratio for methane, where the lower and upper flammability limits are 5 and 14 mol%, is 9.47 mol%.

The limitations for n-heptane are 1 and 6 mol%, respectively, with a stoichiometric ratio of 1.87 mol%.

Combustion of liquid fuels or powdered coal (or pulverised fuel, both abbreviated as pf) is used extensively in industrial burners, particularly for big boilers used to generate steam for power generation.

Industrial flames are typically turbulent in nature and, for convenience and safety reasons, involve diffusion flames in which the fuel and air are injected separately for safety reasons and the lengthening of the diffusion flame after the burner exit occurs with an increase in gas flow velocity

There is a transition from laminar to turbulent diffusion combustion with increasing flow velocity, although some diffusion mixing does occur (turbulent diffusion).

The flames of liquid fuels can range from blue, premixed-like flames to highly brilliant coal-like flames, according to Williams (1990).

Liquid fuels must be entirely evaporated in order to produce a vapour that burns in the same manner as a gaseous flame. This type of spray combustion is known as “homogenous”

For more volatile fuels, the partially volatilized fuel burns as a spherical flame surrounding each droplet, as depicted in Figure 5. This type of spray combustion is referred to as “heterogeneous.”

The first style of combustion is illustrated by the burning of aviation kerosene in an aircraft gas turbine, where the fuel is largely vaporised following injection as a spray into the combustion chamber; however, some bigger droplets tend to burn heterogeneously and produce smoke.

Spray combustion is the second phase, in which burning occurs heterogeneously. This occurs in industrial furnaces and boilers as well as diesel engines.

Types of flame on a Bunsen burner

Safety Flame

• If the air hole is completely sealed, the flame appears yellow (safety fire).

• This yellow flame is easily visible in a well-lit space and serves to remind others that your Bunsen burner is on.

• Temperatures of roughly 300 degrees Fahrenheit are not utilised to heat experimental materials.

• When the vent of a Bunsen burner is closed, the air required for the combustion reaction only comes from the area around the top of the burner, resulting in incomplete combustion and a candle-like yellow flame.

• When the Bunsen is not in use yet we wish to keep it on.

Medium blue flame

• When the air hole is fully open, the flame is blue (powerful combustion, dangerous).

• This flame from a burner can get as hot as 500 degrees.

• Can be hard to see in a bright room and is caused by a partially open air gap.

• The goal is to slowly heat things.

Roaring blue flame

• (It is the only flame that emits sound) This is the hottest flame, reaching temperatures of up to 1400 degrees Fahrenheit, with the hottest component of the flame located at the tip of the white cone in the centre of the blue flame.

• Increasing airflow to the burner results in a more thorough combustion and a hotter flame. The mixture of gas and air is then ignited above the barrel. The result is a loud, bluish flame with three cones.

• This blue flame represents the maximum burner temperature.

• The goal is to heat things quickly.

Reddish flame

• If the air hole is slightly opened, a crimson flame will result (slightly combustion power).

Purple flame

• Half-opening the air vent produces a purple flame (half combustion power).

What is an Alcohol burner?

• A type of scientific equipment used to produce an open flame is an alcohol burner or spirit lamp. It may be constructed of brass, glass, stainless steel, or aluminium.

• Alcohol burners are chosen over Bunsen burners for some applications due to safety concerns and in laboratories where natural gas is unavailable.

• Their flame is restricted to around 5 centimetres (two inches) in height and has a lower temperature than the Bunsen burner’s gas flame.

• While their flames are not as intense as those produced by other types of burners, they are hot enough to execute certain chemistry experiments, typical microbiology laboratory operations, and flame sterilise other laboratory equipment.

• Standard fuels include denatured alcohol, methanol, and isopropyl alcohol.

• Caps are used as snuffers to extinguish the flame.

References

Jensen, W. B. (2005). The Origin of the Bunsen Burner. Journal of Chemical Education, 82(4), 518. doi:10.1021/ed082p518

Ghosh, R. The Bunsen Burner. Reson 27, 745–751 (2022). https://doi.org/10.1007/s12045-022-1369-3

Russell, C. A. (1999). Bunsen without his burner. Physics Education, 34(5), 321–326. doi:10.1088/0031-9120/34/5/309

Lockermann, G. (1956). The centenary of the Bunsen burner. Journal of Chemical Education, 33(1), 20. doi:10.1021/ed033p20

Zhen, H. S., Leung, C. W., Cheung, C. S., & Huang, Z. H. (2014). Characterization of biogas-hydrogen premixed flames using Bunsen burner. International Journal of Hydrogen Energy, 39(25), 13292–13299. doi:10.1016/j.ijhydene.2014.06.126

Bykowski, T. & Verma, Ashutosh & Brissette, Catherine & Stevenson, B.. (2012). Aseptic techniques..

Mondal, Dr Sumanta. (2020). FIREBOY-Bunsen Burner. 10.13140/RG.2.2.18145.66401.

https://www.lsuhsc.edu/admin/pfm/ehs/docs/bunsen.pdf

https://www.lincolnparkboe.org/userfiles/33/Classes/239/BunsenBurner%20%20PowerPoint.ppt

https://www.quora.com/What-are-advantages-and-disadvantages-of-Bunsen-burners