US 3841239 A
A method and apparatus for thermally refuse (pyrolysis is the process of chemically decomposing an organic substance by heating it in an oxygen deficient atmosphere) containing a random mixture of organic and inorganic materials. The apparatus includes an upright cylindrical furnace, a refuse chute having at the uppermost part of the furnace doors which are constructed so as to be always able to shut off the outside atmosphere, combustible gas outlet located in the middle of the furnace, a heat molten material bath located at the lowermost part of the furnace, a means for directly heating the heat molten material in the tank, exhaust openings formed respectively in the middle and lower parts of the tank. Materials chiefly composed of metallic oxides are kept molten in the molten material bath shut off from the outside atmosphere, the combustible gas byproduct of the pyrolyzed organic materials in the refuse dropped into the bath is taken outside the bath and the silicious byproduct and metallic byproduct of the pyrolyzed inorganic materials in the refuse are taken outside the bath respectively from above and below the molten material.
Description (OCR text may contain errors)
United States Patent 1 Nakamura et al.
14 1 Oct. 15, 1974 METHOD AND APPARATUS FOR THERMALLY DECOMPOSING REFUSE  lnventors: Takezo Nakamura, Amagasaki;
-Yuki0 lwasaki, Takarazuka, both of Japan  Assignee: Shinmeiwa Kogyo Kabushiki Kaisha, Toyko, Japan  Filed: June 15, 1973 [21'] Appl. No.: 370,467
 Foreign Application Priority Data June 17, 1972 Japan 47 60579 Sept. 7, 1972 Japan 47-87872 Nov. 15, 1972 Japan 47-114416 Mar. 29, 1973 Japan 48-36542 52 I vs. c1, 110/8 c, 110/8E, 110/17  Int. Cl. F23g 7/00  Field of Search, 110/8 R, 8 E, 18 R, 18 E, 110/11, 17
 References Cited UNITED STATES PATENTS 1,184,351 5/1916 Kidwell 110 17 3,592,151 711971 Webber 3,744,438 7/1973 Southwick 110/18 Primary Examiner-Kenneth W. Sprague Attorney, Agent, or Firm-Holman & Stern 5 7 7 ABSTRACT A method and apparatus for thermally refuse (pyrolysis is the process of chemically decomposing an organic substance by heating it in an oxygen deficient atmosphere) containing a random mixture of organic and inorganic materials. The apparatus includes an upright cylindrical furnace, a refuse chute having at the uppermost part of the furnace doors which are constructed so as to be always able to shut off the outside atmosphere, combustible gas outlet located in the middle of the furnace, a heat molten material bath located at the lowermost part of the furnace, a means for directly heating the heat molten material in the.
tank, exhaust openings formed respectively in the middle and lower parts of the tank. Materials chiefly composed of metallic oxides are kept molten in the molten material bath shut off from the outside atmosphere, the combustible gas byproduct of the pyrolyzed organic materials in the refuse dropped into the bath is taken outside the bath and the silicious byproduct and metallic byproduct of the pyrolyzed inorganic materials in the refuse are taken outside the bath respectively from above and below the molten material.
' 9 Claims, 5 Drawing Figures PAIENTED w 1 974 sum ear 3 Fig.4
PATENTEDBET 1 5:974
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METHOD AND APPARATUS FOR THERMALLY DECOMPOSING REFUSE BACKGROUND OF THE INVENTION-DESCRIPTION OF THE PRIOR ART Various proposals have heretofore been made and carried out as to a method and apparatus for disposing of refuse. Among such proposals are a method and apparatus for incinerating the refuse that have long been practised. According to such method and apparatus, for example, the refuse is merely burnt by hot blast or oil burner. But in resorting to a means of burning little use is made of the gas generated during burning, and the only thing that can be turned into account is noncombustibles and heat, and moreover a means for preventing environmental disruption such as a means for disposing of exhaust gas, a means for collecting duct, etc. is required.
When grates are used in the incinerating means, the grates show a tendency to be plugged and distorted or disintegrated, with the disadvantageous result that immense labor in maintenance and repair of the grates as well as extended periods of dowmtime during the repair and maintenance is required. The prior art that has obviated the drawkbacks of the kind described is US. Pat.
From the viewpoint of effective use of resources on earth, active and intense studies have recently been continued as to the development of the technique of recycling and reusing the components of refuse of various kinds. One of the methods in response thereto of recycling of refuse by pyrolysis is to shut off the refuse from the outside atmosphere and heat the same from outside, but for reasons of art it is technically difficultto provide a pyrolysis temperature of higher than about 900C, with the result that an organic material is pyro- 7 lyzedbutan inorganic materi al i pot decomposed.
SUMMARY OF THE INVENTION This invention relates to a method and apparatus for pyrolysis of refuse, and more particularly to a method and apparatus for charging refuse into a specified mol-' ten slag tank in the state of the outside atmosphere being shut off and for pyrolysis of the refuse without causing a combustion stage.
A primary object of this invention is to make effective use of refuse by droping the refuse into a hightemperature molten slag bath regardless of the kind of refuse and pyrolyzing the refuse at high temperatures in such a manner that the organic matter in the refuse is effectively used in the form of gasified byproduct and the inorganic matter is melted and tapped off singly or together with the molten slag and used repeatedly.
Another object of this invention is to pyrolyze refuse 65 without sorting or crushing the refuse.
Still another object of the invention is to pyrolyze refuse within a shorter period of time than was conventionally needed by a marked improvement in heat efficiency.
A further object of the invention is to increase the calorific value of gas generated in conjunction with the pyrolysis of the refuse and to make effective use of the calorific value.
Still further object of the invention is to prevent the formation of clinkers by high temperatures produced in the bath.
Yet further object of the invention is to cover the energy necessary for the operation of the furnace by the heat quantity of the gas generated.
Yet another object of the invention is to continuously pyrolyze refuse by producing superhigh temperature nonoxygen atmosphere of the order of 1,600C by a direct charge slag bath type pyrolysis apparatus.
According to the invention, a magmalike material (which is a metallic oxide and under which are ineluded SiO A1 0 CaO, MgO, FeO, Fe O TiO etc. etc., and slag, wasteglass and the like belong also in this category) is initially dropped into the bottom of a closed bath and is melted and softened by an electrical or chemical means.
Melting and decomposition temperature of the magma-like material is considerably high, but when the temperature is raised above 1,000C, the material becomes softened. And at normal temperature the mate-' rial is a nonconductor, but when it is in a molten state, the material becomes a conductor of electricity as is seen in electro-slag welding and direct charge melting of glass. Accordingly, when the magmalike material was softened tosuch a degree as to permit the same to be energized with a current, the material is energized by direct contact of electrodes therewith, to thereby expedite melting and use the molten material as a source of heat generation.
According to the invention, preliminaries such as sorting, crushing, etc., of refuse are not at all necessary, and not only solid refuse but also liquid refuse and refuse to be liquefied by heating, such as for example waste oil, waste plastics, can be disposed of.
According to the invention, as soon as municipal refuse is collected and transported, it can immediately by charged into a closed decomposition bath and disposed of at high temperatures, and hence an offensive odor is completely decomposed. Accordingly, the apparatus of the invention has little or no need of equipment for the prevention of environmental disruption caused by air, waste water and soil pollution that have been problems to the conventional refuse furnaces. Chloric acid originating from polyvinyl chloride, sulphurous acid gas from a rubber vulcaninzing agent, hydrogen sulfide, etc. are neutralized with a large amount of ammonium produced from protein of scraps of food and melamine resins into nonpoisonous salts such as NH Cl, (NH SO (NH S, etc., and hence there is no fear of environmental pollution by waste water either.
Since the bath is operated at superhigh temperatures, there is no possibility of clinkers being produced, and deterious material, such as polychlorinated biphenyl, which is considered difficult to decompose, is completely decomposed into a harmless material, and a nitrogen oxide attendant upon high-temperature incineration is not produced because of pyrolysis in a nonoxygen atmosphere. A greater part of nitrogen oxide is nitrogen monoxide, and temperature and concentration of oxygen have much to do with the production of nitrogen monoxide, but even at high temperatures the amount of nitrogen monoxide produced is small when combustion is effected at an air ratio of less than one. According to the system of the invention, there IS no oxygen existing in the bath except that brought in to- 4 In this manner the raw material components of the meltable material 6 are all metallic oxides, which are insulators at normal temperature but which become conductors of electricity because, as well known, the oscillation of molecules and ions given by the high temgether with the refuse charged into the furnace, and perature of the plasma are 5 disperses electron waves hence what little oxygen exists in the bath is low in cont thereby reduce resistance. Accordingly, after the centration, and because oxygen reacts with hydrocarmeltable material 6 has been melted, are 5 is produced bon and hydrogen sooner than with nitrogen, no n obetween the track 2 and the molten material 6 in the gen monoxide is allowed to be produced. In addition, same manner as it wa in FIG 1, Thus, the molten masince the effects of nitrogen in the molecule of refuse terial 6 is increased in temperature, but about 2,000C become smaller in proportion to an increase in temperis the maximum temperature the material 6 will attain ature, n0 nitrogen oxide is p o u ed o, because, in the light of the fire resistance of the walls of the furuhllke the System in whlch heallhg lakes Place Outside nace tank 1 and of the melting temperature of the rethe bath, a heat Source iS provide inside the furnace i5 fuse. After the furnace has been brought into this state, of the invention, there is little or no difficulty in point fuse is dro ped downwardly through the chute 7. The of technical engineering when a furnace is increased in refuse dr pp d i inst ntly melted, General town refuse size. is made up of some percentage of inorganic matters These and other objects, advantages and features of and a greater percentage of organic matters, the inorlhe lhvehlloh Wlll become more PP from a COII- 2 ganic matters being iron and aluminum in large quantisideration of the following description taken in coni d b i f n l d at h hi h temperature d junction with the accompanying dra g wherein pr scribed above and mixed into the molten material 6. On ferl'ed embodiments are lllusll'aled y y of p the other hand, the organic matters are varied in kind D l m but small in the number of components and they are BRlEF DESCRlPTlON OF THE DRAWlNG carbon, hydrogen, oxygen, nitrogen, sulfur, phospho- Ih thedrawings; rus, halogens and a small amount of metallic elements FIG. I is a diagrammatic sectional view showing the as lmpul'ltles- Accordlhglyv also h the P 'g principle of this invention; matters, metals are melted and mixed likewise into the FIG. 2 is a block diagram of a reclaiming system assomalel'lal Olher Components are mostly g ciated with a bath of this invention; ifledand tapped off through an outlet 8 to a known pro- FIG. 3 is another diagrammatic sectional view showducllon (El/lee as shown m ing the principle of the invention; The device 10 is adapted to separate the gas thus col- FIG. 4 is a front elevation, partly in section, of an emleqed and Produce the a capable 9 bemg bodiment of the invention; and utilized, and a gas normally impossible of practical use FIG, 5 is a front elevation, partly in section, of a mods collected as by dust collector l1 and exhausted outified embodiment of the invention 6 side in such a manner as to prevent environmental polr t "mlution. Also, since the molten material 6 18 increased In DESCRIPTION OF THE PREFERRED volume, it is flowed out through an outlet 9, colled by EMBODIMENTS a solid producing device 12 and collected as a solid consisting chiefly of a magma-like material. The solid Referrlhg how to the drawlhgs and Particularly to matter thus obtained may be used for reclamation, enthere is Show" a furnace lahk 1 Constructed of gineering and building works. The heat resulting from refractory material in which is beforehand received a h production f the Solid matter i last i part, but can meltable material 6 having inexpensive metals such as be utilized f the most pal-L For example, the power iron mixed thereinto and consisting of rock and slag as generated by driving a generator 13 can be utilized f lls Chlef compohehl- A Plasma are torch Plasma arc the aforestated heat source for heating. The molten electrode 3 and POWer Source 4 Plasma arc, as material 6 naturally sets up a convection current but shown, are located as a heat source for heating. At the may electromagneticany be brought i f ed i top of the furnace tank 1 are formed a refuse chute 7 lation as b hi h frequency heating. and a gas Ohllel 8 and Oh the Slde of the tank 1 is In the embodiment described above, for example the formed a molten malel'lal Outlet vollage l5 lmpl'essed heat source for heating need not be limited to a plasma y Power Source 4 between the torch 2 and the elec are along but may be replaced by various known heat tl'Ode 3 to start a plasma are 5 a known method. The ources uch as for example an ordinary are Joule are 5 is generated between the t0rC 2 and electrode 3 heat resulting from an electric current directly through before the meltable material6is molten. The following the material 6, high frequency heating and the like, examples may be applied as the raw material composiwhich can heat the material 6 to high temperatures. tion of the meltable material 6. Shown in FIG. 3is an embodiment in which a vitre- COmPOShiOH (P by g ous meltable material is chiefly used and in which the Example: sio, MnO CaO MgO Ai,o car, FeO s i TIC), (A) 35% 24 5 6 l3 16 1.5 0.15 015 a 41% i2 20 5 4 l8 ExzimifiQ no, N3 0 ll x 0 CaO 'ngo xijo'," 6361""216" F6 0,; (C) 71.6% 15 10.7 2.02 0.48 0.14 (D) 67.5% 6.77 3.64 6.82 0.1 6.53 7.93 0.7 0.08
Example: sio, Ano F56. FeO M o E56 Nine Tio v.6 A i m (E) 73% I5 5 6 I (F) 60% i5 3 3.5 4 5 l embodiment is illustrated in greater detail than the one in FIG. 1. The furnace tank used is the same in structure as that in FIG. 1. The furnace tank 1 is provided with a chute 7 and an exhaust outlet 8 each having a cover. The numerals 2 and 3 designate electrodes inserted into a meltable material 6; a power source 4 giving a potential difference to the electrodes 2 and 3; and 5 designates an initial heating element made up of a plasma jet torch. The raw material of the meltable material consists chiefly of a vitreous substance. Scraps of ordinary glass are used for reasons of economy. In addition, a substance such as soda water glass, potash water glass, which have fluidity at normal temperature; and a vitreous substances such as soda-lime silica glass, neutral glass, boric silica glass, Pyrex glass and so on may all be used.
The raw material of the meltable material 6 is heated by a plasma jet torch 5 in the furnace 'tank 1 and is given fluidity. As well known, vitreous substance, when it is non-fluid, is a nonconductor of electricity but becomes a good conductor, when it is molten into a fluid matter. Accordingly, when a potential difference is given by a power source 4 to the electrodes 2 and 3, the molten material 6 is energized with a current and heated by Joule heat to high temperatures. Then, when the refuse to be pyrolyzed is dropped through a chute 7, the refuse is pyrolyzed by the high-temperature molten material 6. In this case, the covers of chute 7 and exhaust outlet 8 are closed so as to pyrolyze and pyrolyze the refuse in the state of the inside of the bath being shut off from the air.
An experiment effected by the inventor showed that 500 kg of scraps of ordinary glass was used as the meltable material 6, was melted at temperatures in the range of about 500 to 700C to cover a surface area of l m and a depth of cm in the bath, and electrodes 2 and 3 were inserted into the molten material so as to make a flow of electricity as uniform as possible, and
' a potential difference of 200v was given and a current high temperature is not always necessary for the pyrolysis of the refuse, and the highest temperature needed is about l,800C, and hence it is advisable to control power source 4 by use of a thermostat and to thereby maintain the temperature of the material 6 at a high temperature of a substantially constant degree. However, the refuse dropped sinks deeper into the molten material 6 and becomes better in conduction efficiency of heat in proportion as the material 6 is increased in fluidity.
Pyrolysis of refuse by use of the molten material described above showed that about 250 kg of refuse could be pyrolyzed per hour. The pyrolyzed organic matters are chiefly hydrogen, carbon monoxide, methane, ethylene, etc., and are exhausted in gas from the furnace, while the inorganic matters are mostly iron, aluminum and are mixed together with the residues of the organic matters into the molten material 6. Nitrogen oxide was scarcely produced, which showed that prevention of environmental disruption is possible.
FIG. 4 shows an embodiment of an apparatus provided by this invention. A furnace body generally indicated at 21 is made of refractory material and is of an 6 upright cylindrical construction. At the topof the furnace body 21 is mounted a refuse hopper 21a and below the hopper is provided an air shielding type revolving door 21b adapted to prevent the air from entering the inside of the furnace body 21. Below the revolving door 21b of the furnace body 21 is disposed another revolving door 21f of the same air shielding type. A space in the form of a preheating chamber 21c between the revolving doors 21b and 21f is naturally subjected to heat of to 200C. The numeral 21d designates a jacket portion of the outer periphery of the preheating chamber 21c; 21e an outlet communicating with the preheating chamber 210; 21g an intermediate portion of the furnace body 21, the temperature inside of which furnace body reaches about 500C; 21h an outlet communicating with the intermediate portion 21 g; and 2li designates a molten material both in the lowermost part of the furnace body and a discharge outlet 21 j having a door is provided at the same height as the tank and another discharge outlet 21k, having a door, is formed at the bottom of the tank 2li. The numeral 22 desigriates a cooler, which is adapted to cool the gas from the aforestated outlet 21e with water or the like and to collect the cooled gas from the outlet 22a. The numeral 23 indicates a heat exchanger, and the air heated by the exchanger 23 is fed by a controlling blower 24, for example, to the molten material tank 2li or used for other purposes; 25 a control valve interposed in the intermediate portion of the piping between the outlet 21h communicating with the intermediate portion 21g of the furnace and the heat exchanger 23, said valve 25 being controlled by a sensor 26 that measures a flow rate in the intermediate portion of the aforestated piping; 27 a known scrubber; 27a an outlet of the scrubber, and a control valve 28 is interposed in the intermediate portion of the piping between the aforestated outlet 21h and the inlet of the scrubber 27; 29 a sensor that is designed to detect a pressure difference between the inside of the intermediate portion 213 of the furnace body and the atmospheric pressure and is adapted to control the valve 28 to maintain the pressure difference constant; 30 a hot air blowing-in pipe which is constructed so as to blow hot air from the heat exchanger 23 into the furnace tank 2li and which is adapted to measure the temperature inside the furnace tank 211 by a sensor 32 when necessary and to maintain such temperature substantially constant in the range of about l,600 to 1,800C by means of a control valve 31 interposed in the piping between the heat exchanger 23 and the pipe 30. General reference character 33 designates a means for directly heating the material inside the bath 33a a plasma torch; and 33b designates two electrodes in said means 33. The material of the electrodes is a high-temperature resisting material such as graphite and is designed to be automatically extended forwardly in succession in proportion to the wear of the material.
The numeral 34 designates a gas bleeding pipe extending from above the opening of the blowing-in pipe 30 inside the tank 2li to the inlet of the scrubber 27; 35 a valve for the bleeding pipe 34; and 36 designates a molten material.
Now, a description will be made of operation of the invention. Substances, as a raw material for a meltable material consisting chiefly of the aforestated metallic oxides are dropped through the chute 21a while the revolving doors 21b and 21f are turned. The substances collected in the tank 211' are melted by starting a torch 3311. They come to acquire electric conductivity by resistance being reduced in their molten state, and accordingly, if continuity is established across two electrodes 33b while the substances being melted, electric potential is impressed across the electrodes from a power source (not shown) to thereby melt the substances completely into a molten bath of material 36.
Next, the refuse to be pyrolyzed is dropped from the chute 2111 through the revolving doors 21b and 2lfinto the furnace body. While the refuse dropped is being downwardly moved through the inside of the furnace body, it is preheated in the preheating chamber 21c heated by the heat of said bath of material 36 and is thus deprived of its moisture. The moisture thus separated from the refuse passes through the outlet 2le to the cooler 22, where the moisture is tapped off in the form of water through the outlet 22a. The time during which the refuse is subjected to said preheating continues for approximately 10 odd minutes. When the refuse is dropped into the intermediate portion 21g of the furnace body and onto the tank 211', it is pyrolyzed without being burnt because of the high temperature ranging from l,600 to I,800C of the molten material 36 and because of the inside of the furnace body 21 being shut off from the air. The time necessary for pyrolysis is about 45 to 90 minutes per ton of refuse. Particularly, organic matters are pyrolyzed into a gas, which consists generally of 50 percent hydrogen, 20 percent carbon monoxide, percent methane, 5 percent ethylene and the like. This combustible gas passes for the most part through the outlet 21h and valve 28 to the scrubber 27 where it is freed of unnecessary material and tapped off through the outlet 27a and used for other purposes. Another part of the gas is led to the heat exchanger 23 through the outlet 21h and valve 25 and, after it has heated the air forcedly supplied by blower 24, the gas is transferred to a jacket portion 21d and preheats the preheating chamber 210 and is then processed in the scrubber 27. In the meantime, a valve 28 is controlled by a sensor 29 to keep the inner pressure of the furnace body 21 constant, and a valve 25 is controlled by a sensor 26 to control a flow rate of gas in order to control the temperatures of the preheating chamber 21 c and heat exhanger 23.
The inorganic substances in the refuse are pyrolyzed by the high temperature inside the tank 2li and separated roughly into a silicious matter and a metallic matter and are reduced in bulk, and because the silicious matter becomes less in specific gravity than the molten material 36, it floats, and because the metallic matter is higher in specific gravity, it sinks, the silicious matter is removed through the outlet 2lj at suitable time and the metallic matter is removed through the outlet 21k, and both are used for their respective purposes.
Also, in the meantime, hot air from the blower 24 and heat exchanger 23 is blown into the tank 2li by the the blowing-in pipe 30 and mixed and burnt together with the combustible gas in this part to thereby maintain the temperature of the molten heat source 36 economically constant. Also, in this case, a valve 31 may be controlled by a sensor 32 to maintain said constant temperature, but when there is a possibility of making it impossible to maintain the constant temperature by control of the valve 31 alone because the refuse is not uniform in quality, all that is necessary is to establish continuity across the electrodes 3312 by operation of the sensor 32. The gas resulting from the combustible gas having been burnt by blowing in hot air through the blowing-in pipe 30 is exhausted out of the furnace body 21 through a pipe 34 by opening the valve 35 at suitable time. As described above, one embodiment of the invention has been described and illustrated, and it should be understood that the meltable material may be melted as by using a plasma torch alone as a heating means 33 or by burning powdered aluminum or iron inside the tank 2li.
FIG. 5 shows an embodiment of the invention in which the heat quantity of the gas obtained by pyrolysis is used as a heat source for the meltable material in the bath. The furnace body in this embodiment is of the same structure as that in the embodiment in FIG. 4, and like parts of the furnace body are designated by like reference characters and explanation of such parts is omitted. In FIG. 5, the numeral designates a combustion tower connected by piping 40a to an outlet 21h formed in the intermediate portion 21g corresponding to the upper part of the tank 2li of the furnace body. In the intermediate part of the piping 40a is provided a control valve 28a, which is controlled by a sensor 290 adapted to detect a difference between the inner pressure of the intermediate portion 21g of the furnace body and atmospheric pressure in the manner that the pressure difference therebetween can be kept definite. To the combustion tower 40 is also connected an outlet pipe 23:: of the heat exchanger 23, and a control valve 41 is provided between the outlet pipe 23a and the combustion tower 40.
The control valve 41 includes a sensor 42 adapted to detect the velocity of flow inside the piping 40a between the outlet 21h and the combustion tower 40 and to operate the valve 41 to thereby provide the velocity of flow of a specified ratio to said velocity of flow. A control valve 25 interposed in the intermediate portion between the outlet 21h and the heat exchanger 23 is equipped with a sensor adapted to detect the temperature inside the preheating chamber 21c and to thereby operate the valve 25 for making the temperature constant (about 100 to 200C in the embodiment illustrated).,The numeral 43 designates a boiler, into the lower part of which hot air by flames ignited in the combustion tower 40 is introduced through a pipe 40b. The steam generated is tapped off through a steam outlet 43a. The numeral 44 designates a steam generator, for example, a turbine, which is driven by steam fed through the outlet 43a and exhaust steam is condensed by a steam condenser 45; 46 a feed water preheater which preheates the water supplied to the boiler 43 by hot air from the outlet 2le in the upper part of the furnace body; and 47 designates a known scrubber designed to dispose of the exhaust from the boiler 43, and the exhaust disposed of by the scrubber 47 is let out by exhaust blower 48 through a chimney 49. The power of generator 50 driven by the aforestated steam prime mover 44 is supplied to a power source controlling device 51, the output of which is controlled by a signal from a temperature sensor 52 in the molten slag tank 2li, and the output is impressed upon a pair of electrodes 33b disposed on the outer periphery of the tank 2li.
In the same manner as in the embodiment in H6. 4, the heat source 36 is melted by flames of a plasma arc torch 33a. After it has been melted, voltage from the generator 50 is impressed between the electrodes 33b and 33b to thereby energize the power generation source 36 directly with an electric current and to maintain the source 36 above 1,600C by Joule heat and keep the same molten. However, in this starting time of operation, the prime mover 44 for the generator 50 is not operated, and hence the generator 50 is turned either by another generator (not shown) or by use of other starting power source. When the refuse to be pyrolyzed is transported by a dump turck 38, placed on a conveyor 39 and dropped therefrom into the furnace, it passes through revolving doors 21b and 21f in the same manner as in the embodiment in FIG. 4 and reaches the tank 211', where the refuse is pyrolyzed when contacting the molten slag 36 and most of the refuse is changed into a gas. The chief components of the gas are hydrogen, ethylene, methane, ethane, carbon monoxide and the like. On the other hand, inorganic matters are also ultimately pyrolyzed but for the most part become slag and metallic substances, which, like the molten slag 36, are conductors of electricity at high temperatures and mixed into the molten slag 36 and perform the same function therewith.
The gaseous substance described above goes upward to the intermediate portion 21g and is removed outside through the outlet 21h and a part of the substance becomes a heat source for preheating the air forcedly supplied by blower 24, and on the other hand it preheats the preheating chamber 21c in the jacket portion 21d and passes through the pipe 40c to the combustion tower 40. The other part of the gas passes directly to the combustion tower. While the gas is thus passing through the piping, a valve 25 is controlled by sensor 26 to thereby control the flow rate of the gas in the jacket portion 21d, whereby the temperatures in the preheating chamber 21c is controlled to about 100 to 200C. Also, a valve 28a is controlled by a sensor 29a so as to maintain the pressure inside the intermediate portion 21g below a specified pressure.
The refuse preheated to temperatures of 100 to 200C within the preheating chamber 210 is not pyrolyzed but has its moisture removed in the form of vapor which becomes a heat source of feed water preheater 46. Also, the gas produced by decomposition due to heating of the refuse in the intermediate portion 21g and tank 21i is fed to the combustion tower 40 as described previously. Since the gas that reaches the tower 40 has a high temperature and is combustible, it catches fire through mixture with a suitable amount of air heated in the heat exchanger 23 and attains complete combustion. The flames at this time generates steam in the boiler 43 to thereby drive the prime mover 44, which in turn moves the generator 50. Combustion exhaust from the boiler 43 is processed in the scrubber 47 to prevent secondary pollution, and exhausted by blower 48 from a chimney 49.
Experiments show that the heat quantity required for thermally pyrolysis of municipal refuse at temperatures in the range of 1,600 to 1,800C is on the order of 25 percent of the heat quantity held by the pyrolyzed gas produced by disposal of the municipal refuse. On the other hand, the power generation equipment at present gives an efficiency of 90 percent in boilers, 45 percent in turbines (including condensers), 98 percent in generators. Also, in this invention, the Joule heat provided by direct energization of the molten slag in the furnace bath is a heat source used in the thermal pyrolysis described, and the refuse is ultimately combined directly in the molten slag, and accordingly the furnace of the invention is excellent in efficiency of heating. If the furnace body and piping are sufficiently provided with sufficient heat insulating means, radiation of heat from the walls of furnace and piping is small in amount and the efficiency of heating including the radiation is about 91 percent. Accordingly, the efficiency of available thermal energy obtained from the refuse is as represented by 0.9 X 0.45 X 0.98 X 0.91 0.36 36 percent, and still leaves more than the aforestated 25 percent of heat quantity held by the pyrolyzed gas. Accordingly, the heat quantity required for the pyrolysis of refuse can be compensated more than enough by the heat quantity of gas produced by pyrolysis of the refuse, with the result that the furnace can thermally be operated in perfectly closed cycles.
In the embodiments described and illustrated above, combustion tower 40, boiler 43, turbine 44 and generator 50 have been used as a power generating means, but alternatively a gas turbine may be directly turned by use of the pyrolysis gas to thereby operate a generator, and it should be understood that, if MHD (magnetohydrodynamics) generation is put to industrial application, recourse may be had to such type of power generation by which the aforestated surplus in heat balance will further be increased. It should be noted that the embodiments described and illustrated are included merely to aid in the understanding of the invention and that various modifications and replacements with equivalents of the invention may be made without departing from the scope and spirit of the inventionas defined by the appended claims.
What is claimed is:
1. A method of pyrolizing and disposing of refuse comprising the steps of (A) melting a solid material into a molten bath by heating means in the lower part of a furnace closed from the outside atmosphere in which said solid material comprises vitreous matter as a component; (B) providing electrodes in said molten bath and energizing the same with an electrical current to maintain the molten state of the molten material; (C) bringing mixed refuse into contact with said molten bath and pyrolyzing the same; (D) removing a gas produced by pyrolysis of refuse from said furnace; (E) and extracting components of the refuse that have been reduced to a molten material; (F) initially providing a plasma flame to keep said molten material molten; and, next subjecting said molten material to high frequency heating to maintain the molten material molten.
2. A method according to claim 1, including burning part of the gas produced from said refuse inside the furnace to retain the heat of the molten material.
3. A method according to claim 1, including generating an electrical current by the heat quantity of gas produced from said refuse, and impressing current thus generated on the molten material.
4. A method according to claim 1 which includes preheating of all the refuse in closed manner in a preheating chamber shut off from the outside atmosphere in the upper part of the furnace tank. i
5. An apparatus for use in a method of pyrolyzing and disposing of refuse comprising melting a solid material into a molten material by heating means in the lower part of a furnace shut off from the outside atmosphere, said solid material consisting of vitreous matter as its component, providing electrodes in said molten material and energizing the same with an electrical current to maintain the molten state of the molten material; bringing all refuse into contact with said molten materialand pyrolyzing the same; removing a gas produced by pyrolysis of refuse from said furnace; and extracting components of the refuse that have been reduced to a molten material; comprising a tank of refractory walls, a molten material bath of pyrolyzing material in said tank of refractory walls; refuse passage means of refractory material opening into said tank from above the tank; plural door means for shielding the bath from the outside atmosphere disposed in said refuse passage means; a preheating stage between said door means; preheating means for said preheating stage; initial heating means provided above the level of the bath of meltable material in the molten material tank; electric heating means for the meltable material disposed in the lower portion of said bath of molten material in the molten material tank; means for collecting thermally pyrolyzed gas of refuse connected to the refuse passage means above the molten material tank; and means for collecting molten refuse disposed in the molten material bath.
6. An apparatus for pyrolyzing refuse according to claim 5 including a heat exchanger, said preheating means includes a means for supplying a preheating gas. said means extending from the means for collecting pyrolyzed gas of refuse and being connected to said preheating means for the preheating stage through said heat exchanger.
7. An apparatus for pyrolyzing refuse according to claim 6 which includes a combustion tower, means conducting the pyrolized gas from said preheating means to said combustion tower, means for supplying heated air through said heat exchanger to said combustion tower.
8. An apparatus for pyrolyzing refuse according to claim 7 which includes a steam generating means connected to receive the combustion gas of said combustion tower and a generator connected to said steam generating means.
9. An apparatus for pyrolyzing refuse according to claim 8 which includes a power source control means connected to said generator, said control means being electrically connected to the previously mentioned electric heating means for the meltable molten bath of