Incinerators liquid-injection

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... 

Liquid injection incinerators. This t3q)e of incinerator has a cylindrical refractory-lined combustion chamber mounted verti-... 

Liquid Injection. Liquid injection units are the most common type of incinerator today for the destmction of Hquid hazardous wastes such as solvents. Atomizers break the Hquid into fine droplets (100—150 microns) which allows the residence time to be extremely short (0.5—2.5 s). The viscosity of the waste is very important the waste must be both pumpable and capable of being atomized into fine droplets. Both gases and Hquids can be incinerated in Hquid injection units. Gases include organic streams from process vents and those from other thermal processes in the latter case, the Hquid injection incinerator operates as an afterburner. Aqueous wastes containing less than 75% water can be incinerated in Hquid injection units. 

Applicability/Limitations Liquid injection incineration can be applied to all pumpable organic wastes including wastes with high moisture content. Care must be taken in matching waste (especially viscosity and solids content) to specific nozzle design. Particle size is a relevant consideration so that the wastes do not clog the nozzle. Emission control systems will probably be required for wastes with ash content above 0.5 percent (particulate control) or for halogenated wastes (acid gas scrubbers). 

Residuals Produced Liquid injection incinerators produce ash which may require application of a post treatment technology prior to disposal. The byproducts from the emission control devices may also require further treatment prior to disposal. 

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... 

Liquid injection incinerators are currently the most commonly used type of incinerator for hazardous waste disposal. A wide variety of units are marketed today, mainly horizontally and vertically fired types a less common unit is the tangentially fired vortex combustor. 

As the name implies, the liquid injection incinerator is confined to hazardous liquids, slurries, and sludges with a viscosity value of 10,000 SUS (Saybold universal seconds) or less. This limitation reflects the requirement that a liquid waste be converted to a gas before combustion. This change is brought about in the combustion chamber and is generally expedited by increasing the waste surface area through atomiziition. An ideal droplet size is... 

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. 

Because acrylonitrile is listed as a hazardous substance, disposal of waste acrylonitrile is controlled by number of federal regulations (see Chapter 7). Rotary kiln, fluidized bed and liquid injection incineration are acceptable methods of acrylonitrile disposal (HSDB 1988). Underground injection is another disposal method. The most recent quantitative information on amount of acrylonitrile disposed in waste sites is for 1987. Emissions were 0.9 metric tons in surface water, 152 metric tons disposed through Publicly Owned Treatment Works (POTW), 92 metric tons disposed of on land 1,912 metric tons by underground injection (TR11988). Because acrylonitrile is relatively volatile and is also readily soluble in water, release to the environment from waste sites is of concern. 

Di-ft-octylphthalate, including waste containing di-n-octylphthalate, is classified as a hazardous waste product by EPA. Generators of waste containing this contaminant must conform to EPA regulations for treatment, storage, and disposal (see Chapter 7). Rotary kiln or fluidized bed incineration methods are acceptable disposal methods for these wastes. Liquid injection incineration may also be used (HSDB 1995). 

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. 

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. 

One incinerator that has been evaluated rather extensively and for which test results have been reported is the liquid chemical waste incinerator facility owned by the Metropolitan Sewer District (MSD) of Greater Cincinnati, Ohio (1 ). The MSD facility uses a rotary kiln and liquid injection cyclone furnace to incinerate a wide variety of liquid industrial chemical wastes. The total design heat release rate is 120 million kJ/h (114 million Btu/h). Tests conducted over a wide temperature range ( 900°C to 1300°C) for six Appendix VIII chemicals (carbon tetrachloride, chloroform, hexachlorobenzene, hexachlorocyclo-pentadiene, and hexachloroethane) have shown DREs equal to or very near 99.99%. 

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).

Thermal Treatment Melhods Advanced Liquid Injection Incineration Cyclm Cyclone Incinerator Rotary Kilns... 

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). 

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