Fixed-hearth incinerator

The tests were conducted with the knowledge of the importance of post-combustion, low-temperature reactions, and represented an advance on the 1987 GCP study. The results of the trials on cement kilns, lightweight aggregate kilns, hazardous waste incinerators, liquid injection incinerators, fluidized bed incinerators, fixed hearth incinerators and hazardous waste boilers were summarized as follows 6... 

Five separate destruction technologies were tested for the destruction of waste HMX and PBX high explosives (HE). Since incineration is the baseline technology, a series of tests was conducted at a commercial two-stage, fixed-hearth incinerator. Destruction by molten salt injection was tested at LLNL. The last three destruction techniques are based on a base hydrolysis (BH) explosive pretreatment to produce a nonexplosive solution for further treatment. Three secondary treatments for BH were tested, including hydrothermal, biodegradation, and thermal decomposition. BH and hydrothermal techniques were tested at Los Alamos National Laboratory (LANL), and LLNL tested biological and thermal decomposition. 

The purpose of the testing was to determine the feasibility for disposal of PBXs with HMX explosive and Viton-A binder in a full-scale, dualchamber, fixed-hearth incinerator. A test combustor, or small-scale incinerator, was used for this purpose. A total of 125 lb of LX-04 and LX-10 explosives were combusted in the testing. 

Cost estimates were developed for four disposal techniques fixed hearth incineration, fludized bed oxidation, molten salt oxidation, and base hydrolysis/supercrital water oxidation. The estimates must be considered... 

Fixed hearth incinerators, which are used extensively for medical waste incineration, are less commonly nsed to incinerate hazardous wastes. There are several units employed at commercial sites as well as plant sites for haz-ardons waste destmction. Fixed hearths can handle bnlk solids and liquids, however, this design does not have the versatility of a rotary kiln. 

In many fixed-hearth incinerators, known as controlled-air or starved-air incinerators, 70-80% of the stoichiometric air required is provided in the PCC thus, the PCC is operated in a reducing, substoichiometric or starved air mode. In this situation, the feed is pyrolyzed and partially combusted. In some cases, steam is injected into the PCC. 

Fixed-hearth incinerators with single or multiple hearths upon which combustion of liquid or solid wastes oeeurs... 

The Subpart O standards apply to units that treat or destroy hazardous waste and which meet the definition of an incinerator. An incinerator is any enclosed device that uses controlled flame combustion and does not meet the criteria for classification as a boiler, sludge dryer, carbon regeneration unit, or industrial furnace. Typical incinerators1 2 3 include rotary kilns, liquid injectors, fixed hearth units, and fluidized bed incinerators (Table 23.1). The definition of an incinerator also includes units that meet the definition of an infrared incinerator or plasma arc incinerator. An infrared incinerator is any enclosed device that uses electric-powered resistance as a source of heat and which is not listed as an industrial furnace. A plasma arc incinerator is any enclosed device that uses a high-intensity electrical discharge as a source of heat and which is not listed as an industrial furnace. 

Once an undesirable material is created, the most widely used approach to exhaust emission control is the application of add-on control devices (6). For organic vapors, these devices can be one of two types, combustion or capture. Applicable combustion devices include thermal incinerators (qv), ie, rotary kilns, liquid injection combusters, fixed hearths, and fluidized-bed combustors catalytic oxidization devices flares or boilers/process heaters. Primary applicable capture devices include condensers, adsorbers, and absorbers, although such techniques as precipitation and membrane filtration are finding increased application. A comparison of the primary control alternatives is shown in Table 1 (see also Absorption Adsorption Membrane technology). 

In multiple-chamber incinerators, automatic ash removal systems usually feature mechanical grates or stokers. In rotary kiln systems, ash removal is accomphshed via the kiln rotation. However, automatic, continuous ash removal has historically been diflicult to achieve in controlled air systems which have conventionally featured stationary, or fixed, hearths. 

Incineration rotating hearth with single, fixed plough. Combustion air enters tangentially and exits the top. 

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