Combustion and Incineration Process
Principles of Combustion
The combustion and incineration process or thermal oxidation, pyrolysis, or thermal destruction, typically conjures up a negative connotation due to environmental concerns about airborne pollution waste produced from incinerators. In fact, incineration can be an effective method of pollution control and is currently one of the few ways to effectively dispose of certain types of industrial, chemical, and biological waste.
Incineration simply means "to burn to ashes through a combustion process." An incinerator provides the optimal, controlled environment for the combustion process to take place. In an ideal setting, combustion combines hydrocarbons (fuel) and oxygen, and yields carbon dioxide, water vapor, and heat.
In reality, perfect combustion cannot be attained and non-organic elements, carbon, and gases will remain behind. A correctly designed incinerator system will minimize the by-products of incomplete combustion, otherwise known as Products of Incomplete Combustion (PICs), through use of a completed combustion system.
There are three control variables in the combustion process, otherwise known as the 3 Ts of combustion, used to create the optimal conditions for combustion.
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The 3 "Ts" of Combustion
The time that the solid waste spends in the incinerator system is directly proportional to the waste type, form, composition, heat release rate, and burning rate of the waste. The goal of the primary chamber is to consume the present hydrocarbons and drive off the remainder. The time that is needed for complete combustion of the solids determines in a large way how the primary chamber of the incinerator is designed.
The gaseous retention time is relative to the size of the secondary chamber, where gaseous by-products of combustion from the primary chamber are combusted again.
A function of heat balance, temperature is a critical component of the secondary chamber. As an environmental cautionary device, the minimum temperature of the secondary chamber furnace outlet is required to be 1,800°F (982°C). This temperature is required to ensure biological pathogen destruction of medical and municipal waste.
In reference to the combustion process, turbulence refers to the mixing of combustion reactants, and two processes are utilized to ensure complete combustion.
Mechanical turbulence refers to the mixing of air with the actual waste solids in the primary chamber. This is accomplished by a hydraulic charging ram that simultaneously pushes the waste into the primary chamber while removing the previous charge. Additional mechanical turbulence is provided by the internal ash stoking transfer ram, which pushes the waste toward the ash discharge port.
Aerodynamic turbulence is accomplished by mixing combustion air with combustible gases and is achieved through design applications throughout the combustion system.
Combustion and Incineration Process Application
Incinerators using the controlled combustion and incineration process can be utilized by industrial, commercial, and medical facilities. They can effectively destroy biologically hazardous waste and reduce solid waste volume by up to
The solid waste is pyrolyzed in the primary chamber, the remaining by-products are then further oxidized in the secondary chamber. Finally, the remaining waste is removed by a wet scrubber system, ensuring that the emissions produced meet acceptable standards.
The two primary regulatory bodies for incinerator systems are the US-EPA and EU directive 2000/76/EC . The performance guidelines proposed by these bodies are the basis for regulation by the applicable government agency. Each state has their own regulations for operation of a incinerator and guidelines may differ by location. Questions about the combustion and incineration process? Our GEI Works Product Specialists will be happy to support you.
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