waste incineration

To convert the waste components into benign or useful materials, one of suitable solutions is using the thermal processing methods. These kinds of methods are implemented by elevating the temperature in designed equipment. Both pyrolysis and incineration are included in the thermal processing measures. However, the process occurred when the temperature increased in these two processes is totally different. Incineration requires the presence of substantial quantities of oxygen in the process, while pyrolysis requires the absence of oxygen.

Table 1. Calculation of volume reduction by various solid waste disposal systems 

	Original Volume as Fractions	Reduction Factor	Final Landfill Volume as Fraction as Original Volume
Sanitary Landfill
Combustible Waste          Bulky and Noncombustible Waste          Total Waste	0.8 0.2 1.0	0.166 0.5	0.133 0.100 0.233
Sanitary Landfill with Shredding and Resource Recovery
Total Waste	1.0	(0.1252)	(0.125)
Conventional Incineration
Combustible Waste          Bulky and Noncombustible Waste          Total Waste	0.8 0.2 1.0	0.0145 0.5	0.012 0.100 0.112
Incineration with Shredding and Resource Recovery
Total Waste	1.0	(0.0082)	(0008)
Pyrolysis Processes with/without Resource Recovery
Total Waste	1.0	(0.004-0.03)	(0.004-0.03)

In the past, incineration was popular in where the landfill capacity is insufficient. In practice, incineration converts the waste into flue gas, and heat with adequate quantities of air. A well-designed incinerator can significantly reduces both the weight and volume of the waste and produce residue that can be used as a fill material in construction business. As shown in the table 1, the pyrolysis process is the most efficient method to reduce the volume of the waste. Incineration shows less performance than pyrolysis, but still have a high efficiency on size reduction of waste.

In theory, the combustion gases should be comprised by carbon dioxide, water, nitrogen and oxygen entirely. All of these gases are normal constituents in the air. However, other constituents usually exist in the flue gas as well, including carbon monoxide and some other hazard gases. These gases are mostly generated due to the inefficient combustion. Thus, air pollution control equipment is necessary in the incineration plant. Then, gases discharged to the atmosphere can be treated to reach governmental standards for emission of chemical constituents as well as particulates. Moreover, the residue after the process should low heating values.

Before initiate the incineration process, it is important to consider several factors firstly. Air supply is always the most crucial factor in incineration design. Only fully circulating surplus airflow can introduce complete combustion and minimize the generation of pollution and hazard like carbon monoxide. The second factor is that different incinerator has different requirements to the refuse. Therefore, refuse preparation is sometimes necessary for some kinds of incinerators. After the incineration process is finished, the gas cleaning process is important to deal with the flue gases. Removing the pollutants like dioxin, furans and other emissions in the gases is compulsory for industries according to relevant legislation codes. Otherwise, these pollutants can cause harmful impacts on local and regional environment. Finally, the residue from the grate usually contains metal and it should be separated from the residue and be stored. Remaining ash may be used as an aggregate replacement or be disposed to landfill.