Furnaces – Refuse incinerator – Rotary drum
Reexamination Certificate
2002-06-11
2004-03-02
Lazarus, Ira S. (Department: 3749)
Furnaces
Refuse incinerator
Rotary drum
C110S226000, C110S227000, C110S228000, C110S234000, C110S246000, C110S259000, C432S106000, C202S216000
Reexamination Certificate
active
06698365
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for thermal treatment wherein material to be treated is dehydrated (or dried) and thermally decomposed in a substantially oxygen-free state using mainly superheated steam. Here, the material to which the present apparatus is applicable is viscous and/or solid material excluding liquid and gaseous matter, for example, waste comprising one or more of garbage generated in general households, plants, restaurants or the like, used paper diapers, waste plastics easy to generate dioxin during combustion and other plastics, livestock excrement or human wastes, and sludge residue generated in sewage disposal plants. Further, the apparatus for thermal treatment according to the present invention can be applied to dehydration or thermal decomposition of materials or products comprising various kinds of organic and inorganic materials used at plants or the like.
Conventionally, for disposing of waste generated such as in plants and households, an incineration method has been adopted in view of a merit that a large quantity of waste can be treated at a relatively low cost. Moreover, various kinds of methods, such as an incineration method having a reaction zone where dioxin can be decomposed, a hydrothermal reaction method, a plasma reaction method and so forth have been proposed for disposing of waste containing toxic constituents to human bodies and an environment, such as CFC, PCB and trichloroethylene or the like, or waste plastics containing a chlorine element, since dioxin will generate by the simple incineration disposal. Further, for dehydrating materials and products at plants, dehydration using hot wind comprising air, nitrogen gas, or the like has been performed.
However, the above-mentioned conventional incineration method for disposing of waste has the following drawbacks. Since heat capacity generated during the incineration varies with calorie contained in the waste to be treated, it is difficult to control a furnace temperature. That is, in case of disposing of material containing much water or with a low calorie by the incineration, it is necessary to heat by a supplemental burner. On the other hand, in case of disposing of flammable material such as lumbers or papers by the incineration, the material burns by itself (namely, spontaneous combustion) without necessity of heating by the supplemental burner. However, it is necessary to control a charge of the material to be treated lest a temperature of a furnace should become too high. Further, when such waste with a high heat capacity is included as part of the waste to be treated, there is a problem such that the furnace temperature becomes high partially.
There is another treatment method in which the waste is first put into an oxygen-free furnace to be carbonized, and gas generated therefrom is subjected to a secondary combustion in another furnace. However, since it is difficult to heat the waste while stirring in the oxygen-free furnace, it takes much time to treat the waste, and further, when the waste contains chloride, it is necessary to install an apparatus additionally to treat generated dioxin.
Alternatively, to detoxify dioxin, CFC, PCB and trichloroethylene, the hydrothermal reaction method is extremely effective. However, since conditions of decomposition are high-temperature and high-pressure, such as the temperature is in a range of 300 to 450° C. and the pressure is in a range of 100 to 250 kg/cm
2
, a vessel used in a decomposition apparatus needs to be resistant to high-temperature and high-pressure. Consequently, construction, maintenance and running costs of the apparatus are high and also, it is difficult to perform a continuous treatment. Therefore, the hydrothermal reaction method is not suitable for disposing of the above-mentioned waste. Furthermore, the plasma reaction method wherein the above-mentioned toxic substances are introduced into high temperature plasma for decomposition has a drawback that an apparatus and treatment costs are extremely high.
Next, in the dehydration of the material to be treated using air or nitrogen, a heat exchanger is necessary for raising the temperature of air or nitrogen to a high temperature. However, since heat capacities of air and nitrogen are small, a large heat exchanger is indispensable for treating a large amount of the material, thus when a treatment temperature exceeds 500° C., the dehydration is not performed generally in the present situation.
BRIEF SUMMARY OF THE INVENTION
The present invention is achieved in view of the above situation, and aims to provide an apparatus for thermal treatment using high temperature superheated steam performing dehydration (drying) and thermal decomposition of material (including waste), whereby a whole apparatus can be built relatively small and moreover, a treatment time can be shortened.
An apparatus for thermal treatment using superheated steam according to the present invention for attaining the above object comprises: a first rotary kiln having a first nozzle pipe therein for spouting a first high temperature gas, a first charge portion of material to be treated on one side thereof and a first discharge portion of the material dehydrated with the first high temperature gas on the other side thereof, the first high temperature gas comprising one or both of high temperature superheated steam and high temperature combustion exhaust gas; a second rotary kiln having a second nozzle pipe therein for spouting a second high temperature gas, a second charge portion of the material dehydrated by the first rotary kiln on one side thereof and a second discharge portion of the material carbonized with the second high temperature gas on the other side thereof respectively, the second high temperature gas comprising mainly high temperature superheated steam with a temperature higher than a temperature of the first high temperature gas; and a mechanism for discharging treated material provided to the second discharge portion of the second rotary kiln for discharging the carbonized material outside after lowering a temperature of the material in an oxygen-free state so that spontaneous combustion of the carbonized material may not occur in an atmosphere.
Thereby, the material can be thermally treated in two-steps at the first and second rotary kilns separately, i.e., dehydration and partial carbonization of the material can be carried out in the first rotary kiln, and perfect carbonization of the dehydrated and partially carbonized material can be carried out in the second rotary kiln. Further, if superheated steam is used as a heat source in the first and second rotary kilns, when the steam temperature is lowered, the superheated steam turns into water. Thereby, treatment of exhaust gas becomes easy. Accordingly, by using the two rotary kilns with different roles to treat the material, the thermal treatment can be carried out more evenly compared to a case where the thermal treatment of the material is carried out in only one rotary kiln, and further, efficient treatment becomes possible by properly dispersing heat energy into the two rotary kilns. Moreover, since the mechanism for discharging treated material is provided by which the material from the second rotary kiln is discharged outside after the temperature is lowered in an oxygen-free state so that the treated material may not burn by itself in an atmosphere, spontaneous combustion of the thermally treated material can be prevented when the material is discharged in the atmosphere. Further, it is preferable that the material to be treated is fractured to 2 cm or smaller (still preferably, 0.5-1.5 cm or so), and further to be granular. However, the present invention is not limited to a size and form of the material to be treated.
Additionally, in the apparatus for thermal treatment using superheated steam according to the present invention, it is preferable that the first rotary kiln is disposed above the second rotary kiln, the first discharge portion of the first rotary kiln having a chute for dis
Armstrong Westerman & Hattori, LLP.
Lazarus Ira S.
Rinehart K. B
S.T.M. Co., Ltd.
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