Compact dual cyclone combustor

Details Compact dual cyclone combustor Compact dual cyclone combustor

2001-01-09

2003-08-05

Lazarus, Ira S. (Department: 3749)

Furnaces

Process

Incinerating refuse

C110S347000, C110S213000, C110S214000, C110S244000, C110S248000, C110S295000

Reexamination Certificate

active

06601526

ABSTRACT:

This invention pertains to a combustor designed to provide a non-toxic method of completely combusting organic or inorganic materials by using a dual cyclone to recirculate particulate matter.
The disposal of waste vegetation (i.e., trees, brush, yard waste, etc.) and other organic materials is a major concern of municipal, commercial, and private sectors. Various techniques are currently used to dispose of such waste. The most common technique has been burying waste in landfill sites. However, landfill sites are becoming scarce and cost-prohibitive due to rapidly expanding urban areas. See U.S. Pat. No. 5,415,113.
One alternative to landfills is incineration. An incinerator is a device that uses high temperature combustion to produce relatively complete oxidation of the waste material. The efficiency of combustion can be increased by maximizing mixing. Mixing has important effects on heat and mass transfer and on chemical reactions. See S. Zabrodsky,
Hydrodynamics and Heat Transfer in Fluidized Beds
, (M.I.T. Press, Cambridge, 1966). Incineration (combustion) is one of the most widely used treatments of hazardous waste, offering the following advantages: (1) volume reduction, (2) detoxification, (3) environmental impact mitigation, (4) regulatory compliance, and (5) energy recovery. See W. Niessen,
Combustion and Incineration Processes
, (Marcel Dekker, Inc., New York, 1978). Additionally, incineration of waste vegetation produces an ash residue high in natural nutrients that are beneficial to plant growth. When the ash is mixed with compost and varying amounts of soil, a range of products including high-grade potting soil and top soil can be produced.
As compared to other waste treatment methods, incineration achieves the highest overall destruction and control for the broadest range of waste streams. Therefore, incineration is gradually replacing the disposal of wastes in landfills. See C. Lee et al., “Incinerability Ranking Systems for RCRA Hazardous Constituents,”
Hazardous Waste and Hazardous Materials
, vol. 7, no. 4, pp. 385-415 (1990). The environmental hazards of burning trash in barrels or other types of open burning are not present with proper incineration. Unlike backyard open fires, which burn in the range of 200-300° C., resulting in incomplete combustion, municipal waste incinerators burn at temperatures over 1000° C. and add enough oxygen to achieve essentially complete combustion. Many dangerous compounds can be completely eliminated at these high temperatures, while eliminating smoke and odor. See Lee et al., 1990.
The primary objective of waste combustion is to destroy the organic and pathogenic constituents in the waste streams, leaving behind an inert residue with minimum carbon content. To be a successful waste management option, combustion must accomplish this goal in a cost-effective and fuel-efficient manner, without creating significant risks from emissions. See R. Seeker, “Waste Combustion,” Twenty-third Symposium on Combustion/The Combustion Institute, pp. 867-885 (1990).
The simplest definition of combustible waste is material that has primarily an organic content and that can be oxidized by combustion. Three features of the waste generally determine the combustion characteristics and type of equipment that is suitable. These include the average physical and chemical characteristics of the waste, any special constituents in the waste streams, and the variability of the waste properties.
Several parameters have been found to increase combustion efficiency, including high temperature and excitation of particles by acoustic vibrations. See Seeker, 1990; I. Glassman, “Combustion,” Academic Press, 2
nd
ed., pp. 386-409 (1987); and J. Willis et al., “Acoustic Alteration in a Dump Combustor Arising From Halon Addition,” Combustion and Science and Technology, vol. 94, pp. 469-481 (1993). Another important factor in efficient combustion is recirculation of incompletely burned particles. One way to increase recirculation is to use a cyclone separator. Cyclone separation occurs when air and waste enter tangentially at the top of the tube and descend with a generally circular motion described by an outer vortex. During the downward descent, the heavier material travels along the periphery of the tube and is thus separated from the lighter “clean air.” See S. Henderson et al.,
Agricultural Process Engineering
, (John Wiley and Sons, Inc., New York, 1955).
Combustion is a complicated process. A complete analytical description of a combustion system requires consideration of the following factors, among others: (1) chemical reaction kinetics and thermodynamics under nonisothermal, heterogeneous, and nonsteady conditions; (2) fluid mechanics in nonisothermal, heterogeneous, reacting mixtures, with heat release that can involve laminar, transition, turbulent, plug, recirculating, and swirling flows within geometrically complex enclosures; and (3) heat transfer by conduction, convection, and radiation between gases, liquids, and solids with high heat release rates and (with boiler systems) high withdrawal rates.
One important physical parameter in waste incinerator design and operation is the character of the waste feed. Waste materials can include a wide spectrum of physical forms, e.g., pumpable liquids, sludge, slurries, tarry semi-solids, contaminated soils, solid refuse (paper, plastic), and bulky solids. The physical characteristics largely dictate the method used to introduce the waste into the device and the combustion chamber configuration employed. See Seeker, 1990.
Another key parameter that dictates the design and operation of combustion systems for a particular form of waste is the presence of any special constituents that can influence system operation or performance, e.g., lead to pollution formation, retard the flame, form fine salt particles, or cause corrosion.
When combusting organic materials such as wood, several factors must be considered, including the “global” molecular formula, the low heat value in the dry-ash-free state, and the heat of formation. The “global” molecular formula of wood is about C
6
H
9
O
4
. In the dry-ash-free state, the heat value ranges between 4200 and 4500 kcal/kg, depending on the wood species. A standard heat of formation for wood is −188 kcal/mol at 25° C. Wood that has been naturally dried in ambient air stabilizes its moisture content at about 20 percent. As wood is heated, it first gives off primarily water vapor. When temperatures reach about 275° C. or above, fuel gases are produced that spontaneously burn in air between 450 and 650° C., a process called pyrolysis. After pyrolysis, the residual carbon remaining (probably due to an insufficient amount of oxygen) represents about 15 to 30 weight percent of the initial wood. The rate of the thermal degradation, as well as the nature and quantities of the various products, depend on the temperature. The overall kinetics depend on the size of the wood particles. See A. Beenackers,
Advanced Gasification
, (Kluwer Academic, Massachusetts, 1986).
Stoichiometric combustion of typical wood is described by the following reaction:
C
6
H
9
O
4
+6.25O
2
→6CO
2
+4.5H
2
O
Temperature, one of the most important parameters in combustion processes, is difficult to measure and control. Temperature variability inside an incinerator is caused by many factors, including wall radiation, flow velocity, and oxidation reactions on wall surfaces.
The presence of sound waves in a dump combustion chamber has been shown to increase the rate at which particles decompose. The acoustic vibrations cause a higher rate of mixing of particles and oxygen, producing a reduced combustion time. See J. Willis et al., “Destruction of Liquid and Gaseous Waste Surrogates in an Acoustically Excited Dump Combustor,” Combustion and Flame, vol. 99, pp. 280-287 (1994).
It has also been determined that resonant acoustic conditions in dump combustors can materially increase the rate of heat release, resulting in high volumetric heat release rates, i.e., high power in a compact device

Affiliated with

Also associated with

Rating

Compact dual cyclone combustor does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Compact dual cyclone combustor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Compact dual cyclone combustor will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3077810