How Does a Kerosene Cooking Stove Work?

In North America, kerosene is a seldom-used fuel for heating and cooking, but that isn't true in other parts of the world. Japan is a good example. Room heaters that burn kerosene are popular throughout the country, and kerosene, which is called toyu in Japan, is available at gas stations.

Kerosene is similar in composition to diesel fuel, but it's more highly refined and burns cleaner. It's popular as a cooking and heating fuel in many urban areas outside North America, and in rural areas of many countries where there's no electricity, people use kerosene stoves for both cooking and heating. Part of the reason, besides the fact that kerosene is a relatively cheap fuel, is that the stoves themselves are uncomplicated and inexpensive, and you don't have to plug them in.

A kerosene stove doesn't actually burn kerosene, which incidentally isn't flammable enough to ignite on its own. Instead, the stove uses a mechanism to vaporize the kerosene and then burns the vapors. This makes kerosene stoves safer than most other stoves, but not 100 percent safe because kerosene combustion creates pollution and, with prolonged use, a wick-type kerosene stove can generate enough heat to ignite the kerosene reservoir.

Kerosene combustion generates heat, of course, and you can use the heat to warm up a room or cook food. The appliance that cooks food is called a kerosene stove, as opposed to a kerosene heater. Whereas a heater may have a radiative plate or fan to broadcast heat into the space around it, a kerosene cooking stove has a grate or plate upon which you can place a pot or griddle.

Kerosene stoves come in two types: wick and pressure style. The kerosene wick stove working principle is similar to that of a kerosene lamp, which also generates heat but is used mostly to provide light. Both devices employ strands of woven fabric partially immersed in a reservoir of kerosene.

Instead of a wick, a kerosene pressure stove has a pipe that feeds the kerosene through a valve and into an air chamber and a hand pump is used to pressurize the chamber. The kerosene vaporizes inside the chamber, and when you pump the stove, the pressure forces the vapor through an aperture in the burner where it burns.

Just like gasoline and diesel fuel, kerosene comes from crude oil extracted from the earth at various sites around the world. It's produced during the distillation process and is a medium distillate, meaning that many, but not all, impurities are filtered out. It's a combination of paraffin, naphthenes and aromatic hydrocarbons, and since paraffin dominates, many people refer to kerosene as paraffin.

The combustion of kerosene produces carbon monoxide (CO), nitric oxide (NO_x) and sulfur dioxide (SO₂), which are all dangerous gases that can cause respiratory ailments, asthma and cancer, so kerosene stoves require adequate ventilation. Despite this, kerosene is still considered safer than solid fuels, biomass and coal, which is why it's used so extensively in much of the world.

Besides the pollution created by kerosene combustion, wick-type kerosene lamps also contribute black carbon to the atmosphere because of partially burnt wicks. While the pollution from a single stove is probably insignificant, the widespread use of wick-style stoves can create an environmental issue.

If you can understand how a kerosene lamp functions, you can understand the kerosene wick stove working principle. Instead of a single wick, though, a kerosene stove can have as many as 40, usually arranged in a circle. Kerosene soaks through the wicks and vaporizes, and when you light the stove, the vapor is what actually burns.

The wicks are usually made of cotton and are attached to a mechanism that allows the user to raise and lower them by using a knob or lever. Raising the wicks exposes more of it to the atmosphere, releasing more vapor and making the flame hotter and brighter. Because the wicks partially combust, they have to be replaced from time to time, so anyone who owns a wick stove needs a stock of replacement wicks.

Instead of a wick, a pressure stove has a pressurized chamber and a nozzle that releases the vaporized gas into the burner. Before you use a pressure stove, you have to do two things. The first is to pump up the tank to pressurize the gas, and the second is to create enough heat for the vapor to ignite.

Kerosene isn't nearly as flammable as other petroleum distillates, such as gasoline or propane, and you can't ignite the vapor simply by holding a match to it. For this reason, a pressure stove has a small tray in the burner into which you pour denatured alcohol, which is far more flammable. You light the alcohol to preheat the burner, and when the alcohol is almost gone, you pump the tank to pressurize it, and the pressure and high temperature vaporizes the kerosene and forces it through the valve and into the burner where it ignites.

The flame from a pressure stove, and thus the heat from the stove, can be controlled in two ways. You can adjust the control knob, which regulates the aperture size and the amount of gas it emits. You can also pump the tank to increase the gas pressure.

Both wick and pressure stoves can be small and portable, which is suitable for personal cooking, or large and constructed on a fixed base to cook family meals. The pressure stove is superior to the wick stove in many ways:

• It creates more heat. A typical pressure stove can generate up to 9,000 BTUs, while the maximum output of a wick stove is about 7,000 BTUs.
• It's safer. A wick stove gets hotter the longer it burns, and as the fuel reservoir slowly empties, there may be enough vapor to ignite the remaining kerosene and start a fire. This can't happen with a pressure stove.
• It's easier to regulate. A pressure stove has two mechanisms to control heat output, whereas a wick stove has just one.
• It's cleaner. A pressure stove doesn't have a wick to burn and fill the air with particulate matter.
• You don't need replacement wicks. A pressure stove needs nothing other than the parts that come with it, although you may have to clean out the pressure valve from time to time.

Despite its drawbacks, however, a wick stove has one advantage. It's cheaper. It's such a basic device that you can purchase a new one for about $40. Pressure stoves don't cost much more — only about $20 more — but the price differential can be a factor for anyone on a budget.