CAUSE AND EFFECT OF CHEMICAL REACTION

"BURNING"

A. What is Burning Reaction?

             The combustion reaction occurs when the substance reacts quickly with oxygen (O₂). For example, in Figure above, the charcoal is joined with oxygen. Combination reactions commonly called combustion reactions, and burning substances are commonly referred to as fuels. The products of a perfect combustion reaction include carbon dioxide (CO₂) and water vapor (H₂O). The reaction usually emits heat and light as well. The general equations for the perfect combustion reaction are: Fuel + O₂→ CO₂ + H₂O

Theoretically, combustion can be interpreted as a chain chemical reaction between oxygen and combustible elements. The combustion process is used in various human needs. Energy conversion engineering utilizes the combustion process for power generation, motor vehicles, and other needs. To get the maximum benefit from the combustion process, it needs a perfect combustion process. The conditions for perfect combustion are: 1. Quantity of air (oxygen) supplied to sufficient fuel. 2. Oxygen and fuel are completely mixed. 3. The air-fuel mixture is maintained above its ignition temperature. 4. The volume of the furnace is large enough to allow sufficient time for the air-fuel mixture to completely burn.

            Under ideal conditions, combustion processes can occur when the amount of fuel and air in a given proportion, based on chemical principles (stoichiometric). But the fact is, the mixture of fuel with air in the furnace (combustion chamber) is impossible to achieve perfect conditions. For that we need excess water supplied to the combustion process to ensure the perfect combustion. The amount of excess water depends on the fuel used in the combustion process.   

            The combustion reaction of the fuel, may occur if the following chemical conditions are achieved:

 > There is a perfect combination of two or more reactants based on stoichiometric ratios.

 > The mass of the reactant element must be equal to the mass of the reaction (mass conservation law Chemical compounds are formed from combinations of elements with a fixed mass relationship. 

> Formation of compounds that produce heat (exothermic reactions) or those that require heat (an endothermic reaction), based on the free energy change of the reaction.

·         Hydrocarbon Burning

               The burning fuel in the combustion reaction contains a compound called hydrocarbons. Hydrocarbons are compounds containing only carbon (C) and hydrogen (H). The charcoal depicted in the above Figures consists of hydrocarbons. So examples of fossil fuels such as natural gas.Natural gas is a common fuel used in home furnaces and gas stoves. The main component of natural gas is a hydrocarbon called methane (CH4). You can see the methane flame in Figure below. Reaction Methane burning is represented by the equation. There are two types of burning:
1. Perfect Burning                
         Burning methane is a perfect combustion reaction, because the result is carbon dioxide and water.In perfect combustion, the burning reactant with oxygen produces several products. When a hyrocarbon burns with oxygen, then the main reaction will produce carbon dioxide and water. When an element is burned, the resulting product is usually also an oxide. Carbon burns produce carbon dioxide, sulfur is burned to produce sulfur dioxide, and iron is burned to produce iron (III) oxide. Nitrogen is not considered a combustible component if oxygen is used as an oxidizing agent, but small amounts of NOx nitrogen oxide will normally be formed.The amount of air required for complete combustion is called theoretical air. However, in practice the amount of 2-3 times the amount of theoretical air is used.
 2. Incomplete combustion               
             Incomplete combustion is generated when there is not enough oxygen to completely burn the fuel into carbon dioxide and water.In many fuels, such as diesel, coal, and wood, pyrolysis appears before combustion. In incomplete combustion, pyrolysis products do not burn and contaminate fumes with harmful particles, for example the oxidation of some ethanol produces harmful acetaldehyde, as well as the oxidation of some carbon that produces toxic carbon monoxide.Combustion quality can be enhanced by the design of combustion devices, such as oil burners and internal combustion engines. Further improvements include post-combustion catalytic tools (such as catalytic converters). Some of these tools are usually required by many cars / vehicles in different countries to meet their country's environmental regulations regarding emissions stasis.The degree of combustion can be measured and analyzed by the test equipment. HVAC contractors and engineers use a combustion analyzer to test the burner's efficiency during the combustion process.
 B. Because of the combustion in the chemical reaction
               Carbon monoxide gas comes from the unsightly fuel in a motor vehicle. Gas discharges from motor vehicles containing 10,000 to 40,000 ppm CO. It is colorless and odorless, therefore, not immediately known. The gas continues to poison, causing pain in the eyes, respiratory tract, and lungs. When entering the blood by breathing, CO is pregnant with hemoglobin in the blood to form COHb (carboxyhemoglobin) with the reaction as follows: COHbOCO + Hb O2Hb. As we know, this hemoglobin should be oxygen to O2Hb (oxyhemoglobin) and bring oxygen Required to the cells with the body as follows: O2 + Hb The bonding of CO with Hb is stronger than O2 with Hb so it is an important function of Hb to carry oxygen to the body, resulting in the body lacking oxygen causing headaches and respiratory disturbances and even death. A. Source: motor vehicle, industrial process, B. Harmful health: 9 ppm (10 mg / m3) more than 8 hours, 35 ppm (40 mg / m3) more than 1 hour, no more than one season (for second)
C. Hydrocarbon combustion effect
               Carbon dioxide comes from the complete combustion of hydrocarbons in it including petroleum and natural gas. Actually carbon dioxide gas is not harmful to humans. However, rising levels of CO2 in the air have resulted in rising temperatures on the Earth's surface. This phenomenon is called the green house effect (green house effect). The greenhouse effect is an event in nature where sunlight can penetrate the glass roof, but the reflected infrared light can not penetrate it. The inexplicable sunlight remains trapped inside the greenhouse and causes the temperature inside the greenhouse to rise. As it is also carbon dioxide in the air, it can be passed through ultraviolet rays and visible light, but withstand the infrared rays reflected from the earth. As a result the earth's surface temperature rises if the levels of CO2 in the air rise. The rise in global temperatures can melt the ice caps at the poles. The next consequence is the rise in sea level so it can flood coastal cities around the world.
A. Source: all sources of combustion;
B. Endanger health at> 5000 ppm for more than 2 - 8 hours,
C. Level in the atmosphere increased from 280 ppm (before the industrial age) to> 350 ppm          (1990s).
D. Acceleration rate occurs.
E. Although desired CO2 is a greenhouse gas. Together with other greenhouse gases such as methane, CO2 absorbs infrared radiation that reflects the earth, thereby increasing the energy deposited on the earth by the sun and increasing atmospheric temperature.
F.Therefore, CO2 emissions became a global issue, especially after Kyoto Protocol 1997.