Mercury incinerator

The most popiilar dry scrubbing systems for incinerators have involved the spray drying of hme slurries, followed by dry coUection in electrostatic precipitators or fabric filters. Moller and Christiansen [Air Poll. Cout. Assoc. 84-9.5 (1984)] published data on early European technology. Moller et al. [U.S. Patent no. 4,889,698 (1989)] describe the newer extension of that technology to include both spray-dryer absorption and dry scrubbing with powdered, activated carbon injection. They claim greatly improved removal of mercury, dioxins, and NOx. 

In catalytic incineration, there are limitations concerning the effluent streams to be treated. Waste gases with organic compound contents higher than 20% of LET (lower explosion limit) are not suitable, as the heat content released in the oxidation process increases the catalyst bed temperature above 650 °C. This is normally the maximum permissible temperature to which a catalyst bed can be continuously exposed. The problem is solved by dilution-, this method increases the furnace volume and hence the investment and operation costs. Concentrations between 2% and 20% of LET are optimal, The catalytic incinerator is not recommended without prefiltration for waste gases containing particulate matter or liquids which cannot be vaporized. The waste gas must not contain catalyst poisons, such as phosphorus, arsenic, antimony, lead, zinc, mercury, tin, sulfur, or iron oxide.(see Table 1.3.111... 

Laijava K, Laitinen T, Vahhnan T, Artmann S, Siemens V, Broekaert JAC, Klockow D. 1992. Measurements and control of mercury species in flue gases from liquid waste incineration. Int J Anal Chem 149 73-85. 

Reductions in U.S. mercuiy emissions from medical and municipal waste incinerators and other industrial sectors have already occurred. Additional emission reductions from some coal-fired power plants have also already begun as co-benefits from technologies used to control SO2 and NO emissions. These mercury emissions from power plants are, however, expected to be reduced further over the next few decades. Meanwhile, changes in mercuiy emissions in other parts of the world may also affect some U.S. ecosystems. 

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. 

The wastewater generated in the membrane cell and other process wastewaters in the cell are generally treated by neutralization.28 Other pollutants similar to those in mercury and diaphragm cells are treated in the same process stated above. Ion exchange and xanthate precipitation methods can be applied in this process to remove the metal pollutants, while incineration can be applied to eliminate some of the hydrocarbons. The use of modified diaphragms that resist corrosion and degradation will help in reducing the amount of lead, asbestos, and chlorinated hydrocarbon in the wastewater stream from the chlor-alkali industry.28... 

On April 19, 1996, U.S. EPA published a proposed rule, called the MACT rule, under the joint authority of the RCRA and the CAA, to upgrade the emission standards for HWCs. Specifically, this rule will affect incinerators, cement kilns, and lightweight aggregate kilns. It proposes emission standards for dioxins, furans, mercury, cadmium, lead, PM, hydrochloric acid, chlorine,... 

The combustors affected by this rule detoxify or recover energy from hazardous waste and include incinerators, cement kilns, lightweight aggregate kilns, boilers and process heaters, and hydrochloric acid production furnaces. U.S. EPA estimates that 145 facilities operate 265 devices that burn hazardous waste. These technology-based standards reduce emissions of hazardous pollutants, including lead, mercury, arsenic, dioxin and furans, and HC1 and chlorine gas. In addition, emissions of PM are also reduced. 

Handling and processing of stripped components containing particularly hazardous substances Batteries and accumulators are classified as hazardous wastes even if they are recycled. Mercury is classified as a hazardous waste and can be recovered in special plants. Condensers containing PCBs must be incinerated in a hazardous waste incineration plant. 

Because many batteries contain toxic constituents such as mercury and cadmium, they pose a potential threat to human health and the environment when improperly disposed. Although batteries generally make up only a tiny portion of MSW, <1%, they account for a disproportionate amount of the toxic heavy metals in MSW. For example, the U.S. EPA has reported that, as of 1995, nickel-cadmium batteries accounted for 75% of the cadmium found in MSW. When MSW is incinerated or disposed of in landfills, under certain improper management scenarios, these toxics can be released into the environment. 

Again, the waste treatment scenario with incineration has by far to the highest score for human toxicity. The scores for the other scenarios are more or less the same. The incineration of EoL PVC will lead to toxic emissions of metals (arsenic, lead, chromium, see Table 5) causing human health effects. However, the most important contribution to the human health effect is caused by the emission of mercury in the upchain processes of the production of mercury and sodium hydroxide. Sodium hydroxide is an auxiliary material in the waste incineration process. Mercury... 

In the results the emissions of mercury appear to have a very substantial contribution for the human toxicity impact score. These emissions are caused by the coproduction of chlorine and sodium hydroxide by electrolysis using a mercury cell. However, this technique is phased out. Therefore, the process descriptions in the Ecoinvent database do not represent up to date technology. In the Ecoinvent database the process for PVC production, in which chlorine is used as one of the compounds, is an aggregated processes based on, seemingly outdated, data from PlasticsEurope. These outdated data also influence the impacts related to waste treatment by incineration because sodium hydroxide is necessary for the waste incineration process. 

Debatox A rotary kiln system for recycling consumer battery materials developed by Sulzer Chemtech. The system first shreds the batteries and then incinerates them. Carbon, plastics, and paper are burnt. Dioxins are destroyed in an afterburner, and mercury is condensed in a scrubber. The residual solids, containing zinc, manganese, and iron, can be recycled by standard smelters. 

Sulfur- and nitrogen-containing compounds will produce their corresponding oxides and should not be incinerated without considering their effects on air quality. Halogenated hydrocarbons not only may affect air quality but also may corrode the incinerator. Also, organo-metallic compounds containing cadmium, mercury, and so on, are not recommended for incineration because of the potential for air and solid waste contamination. 

Critics of waste incineration argue that these plants often create more environmental problems than they solve. They point out, for example, that incinerators are a major source of dioxin, mercury, and halogenated hydrocarbon release into the atmosphere. In addition, incinerators are very expensive to build and to maintain, and they provide fewer jobs to members of the surrounding community than other methods of solid waste disposal. Also, companies have a dismal record of siting incinerators in disadvantaged communities, where residents suffer the worst consequences of incinerator use. Finally, waste-to-energy incinerators are of little value in tropical and subtropical countries, where the cost of plants and the availability of additional energy sources make them impractical. 

The NORIT Porta-Powdered Activated Carbon (Porta-PAC) dry injection system pneumatically conveys an adjustable amount of powdered activated carbon (PAC) from bulk bags into the flue gas streams of incinerators for mercury and dioxin emission reductions. PAC is metered using a volumetric feeder into a pneumatic eductor where moving air transfers the carbon to the injection point. A series of interlocks control the operation of the unit and allow local or remote operation and monitoring of the unit. This technology is commercially available. All information is from the vendor and has not been independently verified. 

Approximately two-thirds of atmospheric mercury comes from human activities, including coal burning, waste incineration, and Cl2 production by the chlor-alkali process (Problem 17-7). 

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