| Energy in the form of heat is obtained when fuel | | | | much excess air is no good because the heat |
| is burnt in air. The release of this heat energy can | | | | generated will be lost through the exhaust |
| be slow or can be very rapid. | | | | trunking. |
| When fuel oil is sprayed as a fine mist in the boiler | | | | Boilers are able to achieve a good combustion. |
| burners, it is able to burn at a relatively slow rate. | | | | Oxygen content percentage of up to 5% or |
| When fuel is sprayed into the cylinders of diesel | | | | lower can be achieved. |
| engines, the fuel burns in such a rapid rate that | | | | Internal combustion engines have a lot of excess |
| explosions occur. Fortunately, these explosions are | | | | air because mixing of the combustible mixture is a |
| protected from persons as these engines are | | | | challenge for them. Furthermore, the combustion |
| called internal combustion engines. | | | | is meant to provide the power to drive the |
| Whatever type of combustion, it is a chemical | | | | pistons. |
| reaction between carbon, hydrogen, sulphur and | | | | The burning of sulphur in the fuel is a problem for |
| oxygen. | | | | combustion equipment. This is because the |
| C + O2 = CO2 | | | | byproducts of combustion will create sulphur |
| 2CO + O2 = 2CO | | | | dioxide and sulphur trioxide. These will react with |
| 2H2 + O2 = 2H2O | | | | the water, also a byproduct of combustion of |
| S + O2 = SO2 | | | | Hydrogen to form sulphuric acid and sulphurous |
| 2S + 3O2 = 2SO3 | | | | acid. |
| Air consists of 77% Nitrogen and 23% Oxygen | | | | SO3 + H2O = H2SO4 |
| by mass. For a particular design of combustion air, | | | | SO2 + H2O = H2SO3 |
| the theoritical oxygen multiplied by 100/23 will give | | | | 2H2SO3 + O2 = H2SO4 |
| the theoritical air required. | | | | However, the effects of corrosion, called low |
| How do you measure a good combustion. The | | | | temperature corrosion can be avoided by keeping |
| percentage of Oxygen or Carbon Dioxide will tell | | | | the temperature above the dewpoint. That |
| us whether the combustion is good or not good. | | | | means to keep the exhaust temperature high so |
| The lower the Oxygen content in the exhaust | | | | that water droplets will not form on the exhaust |
| gas, the better the combustion. It means that the | | | | ducts. |
| Oxygen has been fully utilized for burning. It also | | | | Folks, get hot! |
| means that the fuel air ratio is set properly. Too | | | | Until next time... |