Incinerators hearth

Hearth incinerators. This type of incinerator is designed primarily to incinerate solid waste. Solids are moved through the combustion chamber mechanically using a rake. 

Mu/tihearth Furnace. Multihearth furnaces are most often used for incineration of municipal and industrial sludges, and for generation and reactivation of char. The main components of the multihearth are a refractory-lined shell, a central rotating shaft, a series of soHd flat hearths, a series of rabble arms having teeth for each hearth, an afterburner (possibly above the top hearth), an exhaust blower, fuel burners, an ash removal system, and a feed system. 

A more simplified description is a unit that combusts materials in the presence of oxygen at temperatures normally ranging from 800 to 1650°C. A typical configuration of an incinerator is shown in Figure 9. Typical types of incineration units that are discussed herein are catalytic oxidation, fluidized beds, hquid injection, multiple hearth furnaces, and rotary kiln. Thermal desorption is also discussed. However, an overview of the main factors affecting incinerator performance is presented first, below. 

Air Supply. Oxygen in excess of stoichiometric requirements for complete combustion is needed because incineration processes are not 100% efficient and excess air is needed to absorb a portion of the combustion heat to control the operating temperature. In general, units that have higher degrees of turbulence such as Hquid injection incinerators require less excess air (20 to 60%) while units with less mixing such as hearth incinerators require... 

Incineration can be accompHshed ia multiple-hearth furnaces, ia which the sludge passes vertically through a series of hearths. In a fluidized-bed sludge, particles are fed iato a bed of sand fluidized by upwardly moving air. 

Incineration Incineration has been used to reduce the volume of sludge after dewatering. The organic fractions in sludges lend themselves to incineration if the sludge does not have an excessive water content. Multiple-hearth and flmd-bed incinerators have been extensively used for sludge combustion. 

A multiple-hearth incinerator consists of several hearths in a vertical cyhndrical furnace. The dewatered sludge is added to the top hearth and is slowly pushed through the incinerator, dropping by gravity to the next lower layer until it finally reaches the bottom layer. The top layer is used for diying the sludge with the hot gases from the... 

There are four basic types of incinerators used in wastewater treatment plants. They are the multiple hearth incinerator, the fluid bed incinerator, the electric furnace, and the cyclonic furnace. Each system has it s own distinct method of incineration and while one may be more cost efficient, another may have more of an environmental impact. 

The basic configuration and features of the multiple hearth incinerator are illustrated in Figure 23. This incinerator is the most prevalent incinerator technology for the disposal of sewage sludge in the U.S. due to it s low ash discharge. Sludge cake enters the furnace at the top. The interior of the furnace is composed of a series of circular refractory hearths, which are stacked one on top... 

Solid wastes arc disposed of by two basic methods. The first is by some type of dumping or landfill procedure the second is by incinerating (burning) the waste. This section focuses on incinerators, namely the rotary kiln, liquid injection, fuidized-bed, and multiple-hearth dc ices, which are the four types... 

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. 

The multiple-hearth incinerator (Fig. 16-6) can accept sludges containing between 60 and 75% water. The operating costs run between 0.50 and 5.00 per ton of dry solids, with total costs between 8 and 14 per ton. Design information is given in reference 62. When the sludges contain more water, fluidized-bed incinerators are sometimes used. Their operating costs run between 11 and 21 per ton of dry solids and capital costs are 15/ton.6 See reference 63 for more details. All incinerators must have the proper air-pollution abatement devices attached. 

Figure 16-6 Multiple-hearth incinerator. The wet solids enter at the top of the incinerator onto the top hearth. A rake-like device plows the sludge across the top to drop holes where they descend to the hearth below. The agitation of the sludge exposes the maximum amount of surface to the hot gases, which promotes drying.

Moving body viscometers, 21 737-739 Moving-hearth incinerators, 13 177 MOX fuel, 19 686 Moxifloxacin, 21 224, 228, 231 Moxifloxacin, 3 25, 29 Mozley multigravity separators (MGS),... 

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. 

Multiple effects evaporation-steam and/or oil, multiple hearth and rotary kiln incineration, and other special thermal oxidation systems. 

Figure 14 Incineration system flow diagram. Waste is incinerated in the presence of air and supplemental fuel the incinerator can be multiple hearth, fluidized bed, liquid injection, rotary kiln, or other types caustic or lime scrubbers are used to remove gaseous pollutants from exhaust gases (from Ref. 11).

A similar technology called Oxygen-Enhanced Sludge Incineration was involved in a 5-month study conducted by Praxair and the New York State Energy Research and Development Authority (NYSERDA). This study was carried out at Monroe County s Erank E. Van Fare Sewage Treatment Plant in Rochester, New York. One of the facility s two 11-hearth furnaces was converted for use with oxygen for the test. The total cost of this study was 400,000 (D229170, p. 1). 

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). 

The incinerator configuration used by Firestone at these two plants appears best suited to a tire manufacturing operation with capability to use the process steam. Each of the incinerators has the capacity to handle approximately 500,000 tires per year. No additional tire-burning incinerators using the pulsed hearth design have been built since these two plants were constructed. 

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... 

Multiple-chamber incinerators, rotary kilns, and multiple-hearth furnaces are most widely used in industrial waste disposal. 

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