Waste, amount incineration

Table 2.3. Temporal trend of the number of incinerators (unit n) and waste amounts incinerated (unit 103 ton yr 1)...

One notes that the heavily populated areas of the country also have the highest number of WTE facilities as well as the highest intake of municipal waste into incinerators. This is also due to the lack of open space for landfills compared to the midwest and western states. The amount of waste combusted in the northeastern states is 20.7 percent of the total generated compared to 8.44 per-... 

Hazardous waste burning incinerators, cement kilns, and LWAKs do not follow a tiered approach to regulate the release of toxic metals into the atmosphere. The MACT rule finalized numerical emission standards for three categories of metals mercury, low-volatile metals (arsenic, beryllium, and chromium), and semivolatile metals (lead and cadmium). Units must meet emission standards for the amount of metals emitted. For example, a new cement kiln must meet an emission limit of 120pg/m3 of mercury, 54pg/m3 of low-volatile metals, and 180 pg/m3 of semivolatile metals. 

Fig. 2.4. Annual trend of number of all the incinerators in operation (bar plots from Kim et al., 2002d) and waste amounts treated by each method (symbol-line plots from KMOE NIER, 1997, 1998, 1999, 2000, 2001, 2002, 2003) in Korea.

As with most chemical transformations the waste generated are many folds greater than the amount of material produced. Our waste treatment philosophy is to eliminate, reduce, recycle, or treat in that order of preferences. Eliminate, reduce, and recycle are basic process alternatives that are routinely part of the process strategy and are the most cost effective choices. Waste treatment is usually the last alternative and the most expensive option and is necessary in order for a chemical company to maintain its obligations to the environment and community. However, it also offers the most and diverse methods that could be tailored to a specific waste problem. Examples of methods to treat waste are incineration, wet air oxidation, chemolysis, ozonolysis, chlorinolysis, UV treatment, activated carbon, biotreatment, and supercritical oxidation. 

The amounts of wastes produced from a 1000 MWe power station per year are of the order of 5000 m LLW and 500 m MLW. Liquid wastes may be reduced in volume by purification or concentration, combustible solid wastes by incineration. The general tendency is to transform larger volumes of LLM into smaller volumes of MLW. The latter are enclosed in blocks of concrete or mixed with bitumen and loaded into steel drums. 

Type of waste Amount generated (miUion tons/yr) Number of incineration facilities Amount of waste combusted (million tons/yr)... 

The environmental considerations for the biotechnological process are also important. A comparison of the waste stream (Fig. 2) from the bio-process with that from the Lonza chemical synthesis [5] showed that the amount of waste water, total organic carbon (TOC), salts, and waste for incineration were all considerably lower for the bio-process [6],... 

Every hour, up to 6.2 t of waste are incinerated. The combustion of one ton of waste yields, on average, 16 000 MJ. The carbon dioxide emission amounts to only half of the hourly emission rate of a commercial airplane. 

The composition of the exhaust depends on the type and composition of the fuel and on combustion conditions. The main components are O2 (0-15%), CO2 (3-12%), H2O (6-18%) and N2. Typical ranges of air pollutants from the combustion of natural gas, oil and coal are shown in Table I. In addition to NOx, commonly encountered pollutants include carbon monoxide (CO), hydrocarbons or Volatile Organic Compounds (VOCs), sulfur oxides (SOx) and particulates. Municipal Solid Waste (MSW) incinerator or waste-to-energy plant exhausts may also contain acid gases (e.g., HCl, HF), dioxins, furans and trace amounts of toxic metals such as mercury, cadmium and lead. 

In an industrial atmosphere all types of contamination by sulfur in the form of sulfur dioxide or hydrogen sulfide are important. The burning of fossil fuels generates a large amount of sulfur dioxide, which is converted to sulfuric and sulfurous acids in the presence of moisture. Combustion of these fossil fuels and hazardous waste products should produce only carbon dioxide, water vapor, and inert gas as combustion products. This is seldom the case. Depending on the impurities contained in the fossil fuel, the chemical composition of the hazardous waste materials incinerated, and the combustion conditions encountered, a multitude of other compounds may be formed. 

Temperature. The temperature for combustion processes must be balanced between the minimum temperature required to combust the original contaminants and any intermediate by-products completely and the maximum temperature at which the ash becomes molten. Typical operating temperatures for thermal processes are incineration (750—1650°C), catalytic incineration (315—550°C), pyrolysis (475—815°C), and wet air oxidation (150—260°C at 10,350 kPa) (15). Pyrolysis is thermal decomposition in the absence of oxygen or with less than the stoichiometric amount of oxygen required. Because exhaust gases from pyrolytic operations are somewhat "dirty" with particulate matter and organics, pyrolysis is not often used for hazardous wastes. 

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