Destruction efficiency, incineration

The different technologies can be used separately or combined, such as gas adsorption followed by incineration. Depending on the system used and the organic compound content in the gas stream being treated, the resulting destruction efficiencies normally range between 90% and 99%. 

The key to efficient destruction of liquid hazardous wastes lies in minimizing unevaporated droplets and unrcacted vapors. Just as for the rotary kiln, temperature, residence time, and turbulence may be optimized to increase destruction efficiencies. Typical combustion chamber residence time and temperature ranges arc 0.5-2 s and 1300-3000°F. Liquid injection incinerators vary in dimensions and have feed rates up to 1500 gal/h of organic wastes and 4000 gal/h of aqueous waste. 

Factors that influence the destruction efficiency in incineration include... 

General Electric Company, under an EPA permit, incinerated nearly 6,000 L (1,500 gal.) of 20% liquid DDT formulations in a liquid injection incinerator near Pittsfield, Massachusetts, in September 1974 (4). The facility utilized a vortex combustor of the type normally used for disposal of oils and solvents. Operating temperatures ranged from 870 to 980°C with retention times of 3 to 4 s and 120 to 160% excess air. Overall destruction efficiency exceeded 99.99%. Concentrations of DDT, DDE, and DDD in the stack gas and scrubber water were below analytical detection limits. 

In a similar study, Versar, Inc., in 1974-1975, demonstrated for EPA that DDT and 2,4,5-T formulations were destroyed in a municipal sewage sludge incinerator in Palo Alto, California (5). The pesticides were added to sludge (which contained 20% by weight of solids) to form a mixture that was 2 to 5% by weight in pesticides. Destruction efficiencies ranged from 99.95 to 99.99% for an average hearth temperature from 600 to 690°C and an afterburner temperature from 650 to 660°C. 

In 1974 Midwest Research Institute operated a pilot-scale multiple chamber incinerator to evaluate for EPA the operational variables for pesticide incineration (8). The system included a. pilot-scale incinerator, a three-stage scrubber system, and a scrubber water treatment system. Nine pesticides (aldrin, atrazine, captan, DDT, malathion, mirex, picloram, toxaphene, and zineb) in 15 liquid and solid formulations were studied. Destruction efficiencies generally exceeded 99.99% over a range of temperatures and retention times ( 950 to 1100°C, 1.2 to 6 s, and 80 to 160% excess air). This study also documented the generation of measurable quantities of cyanide in the incinerator off-gas during the incineration of organonitrogen pesticides. 

TRW Systems, Inc., conducted a laboratory-scale incineration study for the U.S. Army from 1973 to 1975 (9). Eleven individual pesticide formulations and three mixed pesticide formulations containing six different active ingredients (chlordane, 2,4-D, DDT, dieldrin, lindane, and 2,4,5-T) were incinerated in a liquid injection incinerator. The experimental apparatus consisted of a fuel atomizer, combustion chamber, afterburner, quench chamber, and scrubber unit. Destruction efficiencies exceeded 99.99% for a minimum 0.4-s residence time at temperatures above 1000°C with 45 to 60% excess air. 

In 1981 the Los Alamos National Laboratory investigated for EPA the thermal destruction of wooden boxes treated with penta-chlorophenol (PCP). The incineration system consisted of a dual-chamber, controlled-air incinerator, a spray quench column, a venturi scrubber, and a packed-column acid gas absorber (11). Destruction efficiencies for PCP exceeded 99.99% for combustion chamber temperatures above 980°C, 20% excess air, and a retention time greater than 2.5 s. For these conditions, TCDD and... 

Waste streams resulting from the inadvertent production of hexachlorobutadiene as a by product of certain chlorinated hydrocarbons typically contain 33-80% hexachlorobutadiene. These wastes are disposed of by various methods. Over the last decade, disposal practices have shifted from landfilling to incineration. Incineration, which is considered the preferred method of disposal, reportedly achieves greater than 99.9% destruction efficiency (EPA 1982d). In 1982, approximately 68% of an estimated 27 million pounds of hexachlorobutadiene wastes were disposed of by incineration, 32% by deep well injection, and less than 0.2% by hazardous waste landfill operations (EPA1982d). 

Operational Considerations. The performance of catalytic incinerators (28) is affected by catalyst inlet temperature, space velocity, superficial gas velocity (at the catalyst inlet), bed geometry, species present and concentration, mixture composition, and waste contaminants. Catalyst inlet temperatures strongly affect destruction efficiency. Mixture compositions, air-to-gas (fuel) ratio, space velocity, and inlet concentration all show maiginal or statistically insignificant effects (30). 

The SCWO process is able to achieve destruction efficiencies for organic waste comparable with those attained by incineration technology, without the requirement of expensive dewatering equipment. The key to a successful SCWO process is a design that integrates various unit operations. Important design considerations include ... 

The relative ease or difficulty of incineration has been estimated on the basis of the heat of combustion, thermal decomposition kinetics, susceptibility to radical attack, autoignition temperature, correlations of other properties, and destruction efficiency measurements made in laboratory combustion tests. Laboratory studies have indicated that no single ranking procedure is appropriate for all incinerator conditions. In fact, a compound that can be incinerated easily in one system may be the most difficult to remove from another incinerator due to differences in the complex coupling of chemistry and fluid mechanics between the two systems. 

Similar to RCRA, once the trial plan has been approved, a trial burn will be conducted and the results reported to the regional administrator or the director, National Program Chemical Division, for approval. At TOCDF, trial burns were conducted in accordance with RCRA and TSCA protocols for certain M55 rockets. The acceptance criteria for the RCRA trial burn of the liquid incinerators, the deactivation furnace system (DFS), and the metal parts furnace were met. A second test of the DFS destruction efficiency for PCBs showed that emissions levels meet TSCA criteria (NRC, 1999). 

CO, are toxic. To include the effects of pollution control at this early design stage, it is assumed that unreacted raw material, byproducts, and unrecovered product exiting the reactor are incinerated to C02 with 99% destruction efficiency with the remaining 1% released to the environment. The recovery of MA in the separation system is assumed to be 99%, with the remaining 1% going to pollution control. 

Thermal incineration uses a flame to oxidize EtO to carbon dioxide and water at high temperature (typically 760-982°C or 1400-1800°F). A residence time of 0.3 sec-0.5 sec is enough to achieve a high EtO destruction efficiency. 

Many of the benefits associated with OEC relate to increasing the partial pressure of 02 in the incinerator. The combustion process becomes more reactive (see Figure 2.15) which tends to increase the destruction efficiency of any hydrocarbons in the system. This lowers the pollutant emissions. 

Over the past several decades of SCWO work ranging from research to commercial applicahons and from lab to full-scale in size, a long list of feeds has been shown to be effectively destroyed by this technology (I able 7). The variety of compounds treated is considerable, ranging from simple hydrocarbons to complex mulh-substituted mixed wastes. Under normal SCWO operating conditions, nearly all of these compounds have been destroyed to at least 99 percent destruction efficiency (and typically much higher for the vast majority of cases) without the noxious byproducts typically produced by other waste destruction technologies such as air incineration. 

Mustard Mustard is immediately destroyed at temperatures above 500°C to S02, HQ, C02 and water vapor. The contractor operated a commercial, transportable 7 MM Btu/hr incinerator which could readily achieve an organic destruction efficiency of 99.9999% and which was used to destroy frozen bulk mustard introduced as solid waste and to thermally treat agent-contaminated metal scrap. The incinerator incorporated a two-stage combustion process, e.g., a rotary kiln (900°C, 1.5 tonnes/hr capacity) and a down-fired secondary combustion chamber (1200°C, 2.5s residence time), backed by a venturi wet flue gas scrubber. System components were erected on a prepared concrete foundation and housed in a prefabricated building to provide shelter for the equipment and operators. Natural gas from a nearby well provided a fuel source. 

Required Tests Before an incinerator can be used to treat a large volume of hazardous waste, it must pass a trial bum demonstrating that it can achieve a 99.99% organic destruction efficiency. If the soil at the site does not contain enough contamination to demonstrate the 99.99% destruction and removal efficiency, explosives might have to be shipped to the site to spike the feed soil for the trial bum. 

During the last decade, various remedial actions were carried out on dioxin-contaminated wastes in the United States and Europe. Historically, building rubble from industrial accidents was used as fill or disposed in the ocean. In 1977, about 2.2 million gallons of Agent Orange and similar herbicide formulations was incinerated on the ship Vulcanus in the Pacific (1). This solution was simplified by the ability to transfer the waste to the ship at a remote location in the Pacific and by the large quantity of liquid waste, which made the incineration on ship economically possible. The destruction efficiency of this at-sea-incineration was about 99.9% according to the limits of analytical detection at that time. 

The Portable Unit has successfully demonstrated its capability for thermal treatment of hazardous wastes at the source of the material. This type of on-site treatment would eliminate the need of transportation of hazardous materials to a distant site of stationary treatment equipment. The Portable Unit also has demonstrated that it can be moved to a site and be ready to treat material very quickly, a capability which will be very important in operation of full scale equipment. The on-site treatment of the Times Beach dioxin contaminated soil resulted in no dioxin detected in any of the incinerator effluent streams. The product of the testing activity was soil with no detectable level of dioxin. Dioxin contaminated soil thermally treated in this manner will yield soil which can be disposed as non-hazardous material. The decontamination was performed without exceeding RCRA requirements for particulate emissions and with dioxin destruction efficiencies surpassing the required percentage. The overall conclusion was that the infrared incinerator can very effectively remove dioxin from contaminated... 

In an evaluation of the destruction of VOCs by catalytic incineration, Tichenor and Palazzolo reported that, over the Pt/Pd catalysts used in that investigation, "The destruction efficiency for the chlorinated hydrocarbons was quite low. In addition, tests conducted after the chlorinated hydrocarbon burns showed that the catalyst had been partially deactivated." In contrast, of the 8 multicomponent mixtures and 16 single component VOCs covered by the investigation, all the compound classes except chlorinated hydrocarbons could be destroyed at 98% to 99% efficiencies at sufficiently low space velocities/high temperatures. 

Plasma arc Good destruction efficiency, robust, promising test results on simulated neutralent Large vapor stream requiring treatment may not be perceived as true alternative to incineration Promising candidate if acceptable to public interest groups... 

There are two types of incinerators used predominantly for incineration of hazardous waste. The first type is the rotary kiln, which operates at temperatures of approximately 2300 "F. More hazardous wastes are burned in this type of kiln than any other and it is the one for which most tests on destruction efficiencies have been done. A second type is the cement kiln, which is now being used more often. The temperature of the cement kiln reaches 3000 "F. The hazardous waste is blended with the fuel and used in the making of cement. By modifying the fuel blend, it is possible to obtain efficient destruction, even for chlorinated solvents. 

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