Why excess air is required for the complete combustion of fuel?

In order to ensure complete combustion, combustion chambers are fired with excess air. Excess air increases the amount of oxygen and nitrogen entering the flame increasing the probability that oxygen will find and react with the fuel.

How much excess air does complete combustion have?

Research has shown that 15\% excess air is the optimal amount of excess air to introduce into the boiler combustion process.

What is the purpose of excess air?

The excess air results in oxygen that isn’t consumed during combustion, and this oxygen absorbs otherwise usable heat and carries it out of the stack. The chemically ideal amount of air entering a furnace is just enough for all the oxygen in the air to be consumed.

Which fuel requires more amount of excess air for combustion?

Therefore, in practice more air than ideal must be supplied to burn all fuel completely. The amount of air more than the theoretical requirement is referred to as excess air….Stable and efficient combustion requires correct mixture of fuels and oxygen.

What is meant by excess air in combustion?

Excess air means that amount of air supplied in addition to the theoretical quantity necessary for complete combustion of all fuel or combustible waste material present.

What happens when too much excess air is supplied to the furnace in the process of combustion of coal *?

What happens when too much excess air is supplied to the furnace in the process of combustion of coal? If the excess air is supplied above this amount, there is a loss of heat in the furnace. In such cases, the supply of air to the hearth is cut short or the rate of fuel supply is increased.

How much air is needed for the complete combustion of diesel fuel?

∴ Oxygen required from air for the complete combustion of fuel will be (2.66C + 8H + S – O) which can be written as 2.66C + 8 (H – O/8) + S, the term in the bracket being known as the available hydrogen.

Which of the following fuel needs maximum amount of excess air for complete combustion Mcq?

Explanation: artificial solid fuels need excess amount of air for complete combustion because they have low calorific value compared to liquid fuels and the rate of combustion of solid fuels cannot be easily controlled. they have tendency to form clinkers at high temperatures.

How does the fuel air mix affect combustion?

The effect of air-fuel ratio was more visible on the initial stage of the combustion at lower speeds while it is visible on the rapid burning stage at higher speeds. Moreover, the combustion duration was increased with an increase in engine speed.

What is definition of excess air?

Why is an excess of oxygen used in combustion reactions?

Combustion involves complete oxidation reaction where biomass reacts with excess oxygen at high temperature (700–1400°C) to generate heat in the form of steam and other gaseous by-products such as carbon dioxide (CO2) and water (H2O). NOx and SOx are also emitted from the process.

How does excess air affect the vent gas CO2 percentage?

Excess air is added to insure complete combustion. This reduces the CO2 percentage by adding more air than is used in the combustion process. Excess air reduces the flame temp, thus lowering combustion efficiency. However, some excess air is necessary for complete combustion.

How does excess air affect the efficiency of combustion?

Excess air increase the amount of oxygen to the combustion and the combustion of fuel. when fuel and oxygen from the air are in perfect balance – the combustion is said to be stoichiometric. The combustion efficiency increases with increased excess air – until the heat loss in the excess air is larger than the heat provided by more efficient

How much excess air is needed to achieve maximum fuel efficiency?

Excess air to achieve highest possible efficiency for some common fuels: 5 – 10\% for natural gas. 5 – 20\% for fuel oil. 15 – 60\% for coal.

Why is the combustion of fuel stoichiometric?

To ensure complete combustion of the fuel used combustion chambers are supplied with excess air. Excess air increase the amount of oxygen to the combustion and the combustion of fuel. when fuel and oxygen from the air are in perfect balance – the combustion is said to be stoichiometric

What are the requirements for complete combustion of a fuel?

In all requirements for complete combustion of a fuel is to make sure that the products of combustion, provide a oxidising atmosphere and that the products are CO2 Carbon-dioxide and H2O Water vapour.and that any impurities in fuel or air are also combusted.