Incinerating hazardous waste materials

The use of PMDI as a binder for foimdry cores, rubber waste products, and solid rocket fuel are also known. Isocyanate-terminated prepolymers, often prepared from TDI or MDI with polyether polyols are also used as binders for composite products that require elastomeric properties. Athletic surfaces are sometimes prepared from groimd rubber tire scrap bonded with isocyanate-based prepolymers. Similarly, flexible polyurethane foam scrap is bonded with isocyanate prepolymers to form rebonded foam usefiil as carpet imderlay. Solidification of incineration ashes with PMDI-based binder systems is another waste disposal application. In this manner hazardous waste materials imdergo chemical fixation and detoxification. 

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. 

The treatment of waste is the third element of the hierarchy and should be utilized only in the absence of feasible source reduction or recychng opportunities. Waste treatment involves the use of chemical, biological, or physical processes to reduce or eliminate waste material. The incineration of wastes is included in this categoiy and is considered preferable to other treatment methods (i.e., chemical, biological, and physical) because incineration can permanently destroy the hazardous components in waste materials (Ref. 4). It can also be employed to reduce the volume of waste to be treated. 

Schofield, W.R. Lutzman, John Patterson, Gene W. Use of Chemical Additives to Reduce The Impact of Slag Formation in Hazardous Waste Incineration. Hazardous Materials Control Journal, USA, 1992. 

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. 

Incinerators are used to bum hazardous waste primarily for waste destruction/treatment purposes however, some energy or material recovery can occur. When performed properly, incineration destroys the toxic organic constituents in hazardous waste and reduces the volume of the waste.3 Since metals will not combust, incineration is not an effective method for treating metalbearing hazardous wastes. 

In addition to the aforementioned issues regarding the incineration process, other concerns of relevance to public health need to be addressed. For example, hazardous waste to be fed to the incinerator and process effluents resulting from the incinerator should be stored in a manner that does not allow for uncontrolled environmental releases of potentially harmful substances. Dry, dusty materials should be enclosed or otherwise stored to prevent windborne transport of contaminated particulates. Wastes containing volatile organic compounds should be stored under conditions that safely collect and remove gases released from the wastes. 

Approved Methods of Waste Disposal Decontamination of waste or excess material shall be accomplished according to procedures outlined above and can be destroyed by incineration in EPA approved incinerators according to appropriate provisions of federal, state, and local Resource Conservation Act (RCRA) regulations. Note Some decontamination solutions are hazardous waste according to RCRA regulations and must be disposed of according to these regulations. 

However, various countries use different definitions of chemical waste and there are often several inconsistencies in the definitions. Usually, the definiUon involves qualification of whether or not the material is hazardous. For example, in some counties, a hazardous waste is any material that is especially hazardous to human health, air, or water, or which is explosive, flammable, or may cause disease. Poisonous waste is material that is poisonous, noxious, or polluting and whose presence on the land is liable to give rise to an environmental hazard. But in more general terms (in any country), hazardous waste is waste material that is unsuitable for treatment or disposal in municipal treatment systems, incinerators, or landfills and which therefore requires special treatment. 

The plasma energy recycle and conversion (PERC) process is an indirectly heated ex situ thermal recycling and conversion technology. According to the vendor, it treats hazardous waste, mixed radioactive waste, medical waste, municipal solid waste, radioactive waste, environmental restoration wastes, and incinerator ash in gaseous, hquid, slurry, or solid form. The technology uses an induction-coupled plasma (ICP) torch as its heat source coupled to a reaction chamber system to destroy hazardous materials. 

Contract disposal agencies offer their services to relieve the chemical industry of unwanted materials however, the cost of such disposal (primarily incineration) is high. The manufacturer should ascertain that the disposal agency employees are adequately aware of chemical hazards and can responsibly handle and dispose of the waste materials (see Wastes, industrial). 

The need to design inherently safer plants has been expanded to encompass designing evironmentally acceptable plants. Environmentally acceptable plants generate minimum quantities of potentially hazardous wastes either as potential emissions to the environment or as materials requiring disposal. Wastes are recycled and reused where possible. If this is not possible, they may be treated to reduce or eliminate the hazard or destroyed through incineration. Disposal in a secure landfill is the final option. 

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