Incineration dioxin wastes

The misconception that vinyl gives off dioxin when it is incinerated is misleading. A study conducted by ASME in 1995 (162) found that the presence, or absence, of chlorine-containing wastes in incinerators had no effect on the levels of dioxin produced. Rather, it was found that incinerator operating conditions (primarily temperature) were the key to controlling dioxin formation. More recentiy, German officials examined the issue of incinerating vinyl waste and decided there was no cause for concern (180). 

Municipal and industrial incinerators Pathological incinerators Industrial waste Odors, hydrocarbons, HCl, dioxins, furans Particulates, smoke, and combustion contaminants Proper charging, acid gas scrubber, baghouse Modified fuel feed, auxiliary fuel and dryer systems, cyclones, scrubbers... 

Dioxins are some of the most toxic chemicals known to science. Dioxins are unwanted by products of a wide range of manufacturing processes including smelting, chlorine bleaching of paper pulp, and the manufacturing of some herbicides and pesticides. In terms of dioxin release into the environment, waste incinerators (solid waste and hospital waste) are often the worst culprits, due to incomplete burning [115]. One of the most toxic chemical in the class is 2,3,7,8-tetrachlorodibenzo-/ /Y/-dioxin (TCDD) and probably the most toxic compound ever synthesized by man. 

The incineration of waste containing PVC has been a source of much discussion and comment, particularly related to the dioxin and HC1 emissions (66,106, 282, 341). PVC was also targeted in the EU incineration directive (297). 

At present, municipal incinerators, hazardous waste incinerators, and metal smelters discharge from 1-100 ng/Nm of PCDD, about 1-100 g/year per facility. The possibility of PCDD in exhaust emissions from cars has been raised recently, and the U.S. Environmental Protection Agency (EPA) has examined a range of other possible dioxin sources. 

At that time, the design of the mobile incinerator and existing regulatory concepts prevented incineration of dioxin wastes above 1 ppm. However, redesign and operation of the incinerator in 1985 proved these concerns invalid (17). 

Current Cleanup Options for Dioxin Wastes. Governmental regulations and dioxin s negative image currently prevent off-site disposal or treatment of dioxin-contaminated wastes. In response to a need to destroy dioxin wastes, a number of novel process adaptations have been proposed and tested. These processes include incineration, physical-chemical, and biological processes. In addition, on-site containment, storage, and monitoring remain economic alternatives. 

Incineration of dioxin wastes is the most versatile destruction process of those presently available. The mobile incinerator treated a combination of soil, sludge, and solvents... 

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. 

Waste PVC materials, at the end of their useful life, can continue to cause problems. They are likely to be powerful sources of POP if their waste is incinerated, and dioxins can be produced easily by unregulated burning. The environmental group Greenpeace has advocated the global phase-out of PVC with the claim that dioxins are produced as by-products during the manufacture of PVC, as well as from the incineration of waste PVC in domestic garbage. 

There has been considerable concern throughout Europe about the incineration of wastes, yet in Japan about 70% of all MSW is incinerated, and plans are that this should increase to 90% by the year 2000 [33]. Incinerators that are poorly operated may run at temperatures too low to burn potentially hazardous intermediates of the combustion process such as the products from pyrolysis which are believed to be the precursors in the combustion processes [34]. Of particular concern has been the discovery of extremely toxic materials such as dioxins (chlorinated dibenzo-/ -dioxins and benzofuran dioxins), in the flue gases of some incinerators. Such is the level of concern that many European countries have increased the legislative and environmental controls on incinerator operators, and some are moving to ban the incineration of plastics [35], and particularly PVC. In incinerators where the temperature is below about 1400 K, dehydrochlorination of PVC occurs, accompanied by the formation of polyenes. The polyenes can then cyclise and be oxidised, and then be attacked by chlorine-containing species to produce dioxins, the most toxic of which is 2,3,7,8-tetra-chlorodibenzo-/7-dioxin (TCDD), the material at the centre of the disaster at Sveso, Northern Italy, in 1979. More than 70 dioxins are known to exist (Figure 13.11). 

Incineration of waste plastics and polymers, though still widely practiced in many countries, is presently not favoured due to the potential for toxic off-gases such as dioxins from the use of mixed polymer feedstocks, which include halogenated polymers such as poly(vinyl chloride). If this issue can be resolved, incineration and fuel value recovery from waste plastics becomes very attractive and probably the best disposal option. 

R. G. Barton, W. O. Clark, W. S. Lanier, and W. R. Seeker, "Dioxin Emissions During Waste Incineration," presented at Spring Meeting Western States Section of the Combustion Institute, Salt Lake City, Utah, 1988. 

Optimized modern dry scrubbing systems for incinerator gas cleaning are much more effective (and expensive) than their counterparts used so far for utility boiler flue gas cleaning. Brinckman and Maresca [ASME Med. Waste Symp. (1992)] describe the use of dry hydrated lime or sodium bicarbonate injection followed by membrane filtration as preferred treatment technology for control of acid gas and particulate matter emissions from modular medical waste incinerators, which have especially high dioxin emissions. 

Chemical Volume Reduction Incineration has been the method commonly used to reduce the volume of wastes chemically. One of the most attractive features of the incineration process is that it can be used to reduce the original volume of combustible sohd wastes by 80 to 90 percent. The technology of incineration has advanced since 1960 with many mass burn facihties now have two or more combustors with capacities of 1000 tons per day of refuse per unit. However, regiila-tions of metal and dioxin emissions have resulted in higher costs and operating complexity. 

Thermal processes are typically used for highly toxic waste or highly concentrated organic wastes. If the waste contains PCB, dioxins, or other toxic substances, incineration should be chosen in order to assure destruction. If the wastes contain greater than 1000 parts per million of halogens (chlorinated materials), it would probably be desirable to select incineration of these wastes, after consideration of other options. In any case, a material may be incinerated or used as a fuel if the heat content is greater than 8500 BTUs per pound or, if between 2500 and 8500, it may be incinerated with auxiliary fuel. The waste components of concern are halogens, alkali metals and heavy metals. 

Dioxin (2,3,7,8-TCDD) zero 0.00000003 Reproductive difficulties increased risk of cancer Emissions from waste incineration and other combustion discharge from chemical factories... 

Baird is the 20-acre site of a former chemical mixing and batching company. Poor waste disposal practices resulted in the contamination of groundwater, soil, the municipal water supply, and a brook adjacent to the site. Over one hundred contaminants, including chlorinated and nonchlorinated volatile organics, heavy metals, pesticides, herbicides, and dioxins, had been identified in site soil and groundwater. Remediation activities included soil excavation and incineration, and groundwater treatment (the audit focused on the soil excavation and incineration... 

In cleaning up the site, dioxin-contaminated waste from the reaction ve.ssel were pac ked i ri turty-oric barrels that went astray in May 1983. They were eventually found in 1985 in the luirdicrn french town of Anguilcourt-le-Sart at an abattoir. Their contents were burned in t d i liigh-temperature incinerator. 

Mere destruction of the original hazardous material is not, however, an adequate measure of the performance of an incinerator. Products of incomplete combustion can be as toxic as, or even more toxic than, the materials from which they evolve. Indeed, highly mutagenic PAHs are readily generated along with soot in fuel-rich regions of most hydrocarbon flames. Formation of dioxins in the combustion of chlorinated hydrocarbons has also been reported. We need to understand the entire sequence of reactions involved in incineration in order to assess the effectiveness and risks of hazardous waste incineration. 

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