Method And Apparatus For Thermally Decomposing Refuse

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.

Description

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 U.S. Pat. No. 3,592,151.

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 900.degree.C, with the result that an organic material is pyrolyzed but an inorganic material is not decomposed. From the above reason stages of sorting and crushing the refuse were required. Another method is the one in which part of the refuse is burnt by use of burners under supply of air or oxygen and pyrolysis is effected through direct contact of the refuse with the combustion gas produced by the burning, but from the viewpoint of utilization of resources, this method also is, like former's method of burning, no better than the utilization of waste heat and residues.

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 molten 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 high-temperature 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 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 1,600.degree.C 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 included SiO.sub.2, Al.sub.2 O.sub.3, CaO, MgO, FeO, Fe.sub.2 O.sub.3, TiO.sub.2, etc. etc., and slag, waste glass 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 1,000.degree.C, the material becomes softened. And at normal temperature the material 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 to such 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.sub.4 Cl, (NH).sub.4 SO.sub.4, (NH.sub.4).sub.2 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 together with the refuse charged into the furnace, and hence what little oxygen exists in the bath is low in concentration, and because oxygen reacts with hydrocarbon and hydrogen sooner than with nitrogen, no nitrogen monoxide is allowed to be produced. In addition, since the effects of nitrogen in the molecule of refuse become smaller in proportion to an increase in temperature, no nitrogen oxide is produced. Also, because, unlike the system in which heating takes place outside the bath, a heat source is provided inside the furnace of the invention, there is little or no difficulty in point of technical engineering when a furnace is increased in size.

These and other objects, advantages and features of the invention will become more apparent from a consideration of the following description taken in conjunction with the accompanying drawings wherein preferred embodiments are illustrated by way of example.

BRIEF DESCRIPTION OF THE DRAWING

In the drawings:

FIG. 1 is a diagrammatic sectional view showing the principle of this invention;

FIG. 2 is a block diagram of a reclaiming system associated with a bath of this invention;

FIG. 3 is another diagrammatic sectional view showing the principle of the invention;

FIG. 4 is a front elevation, partly in section, of an embodiment of the invention; and

FIG. 5 is a front elevation, partly in section, of a modified embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings and particularly to FIG. 1, there is shown a furnace tank 1 constructed of refractory material in which is beforehand received a meltable material 6 having inexpensive metals such as iron mixed thereinto and consisting of rock and slag as its chief component. A plasma arc torch 2, plasma arc electrode 3 and power source 4 for plasma arc, as shown, are located as a heat source for heating. At the top of the furnace tank 1 are formed a refuse chute 7 and a gas outlet 8 and on the side of the tank 1 is formed a molten material outlet 9. Voltage is impressed by power source 4 between the torch 2 and the electrode 3 to start a plasma arc 5 by a known method. The arc 5 is generated between the torch 2 and electrode 3 before the meltable material 6 is molten. The following examples may be applied as the raw material composition of the meltable material 6.

Composition (percent by weight):

Example: SiO.sub.2 MnO CaO MgO Al.sub.2 O.sub.3 CaF.sub.2 FeO S P TiO.sub.2 (A) 35% 24 5 6 13 16 1.5 0.15 0.15 -- (B) 41% 12 20 -- 5 4 -- -- -- 18

Example: SiO.sub.2 Na.sub.2 O K.sub.2 O CaO MgO Al.sub.2 O.sub.3 B.sub.2 O.sub.3 ZnO Fe.sub.2 O.sub.3 (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.sub.2 Al.sub.2 O.sub.3 Fe.sub.2 O.sub.3 FeO MgO CaO Na.sub.2 O TiO.sub.2 P.sub.2 O.sub.5 (E) 73% 15 5 6 1 (F) 60% 15 3 3.5 4 5 1

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 temperature of the plasma arc 5 disperses electron waves to thereby reduce resistance. Accordingly, after the meltable material 6 has been melted, arc 5 is produced between the track 2 and the molten material 6 in the same manner as it was in FIG. 1. Thus, the molten material 6 is increased in temperature, but about 2,000.degree.C is the maximum temperature the material 6 will attain in the light of the fire resistance of the walls of the furnace tank 1 and of the melting temperature of the refuse. After the furnace has been brought into this state, refuse is dropped downwardly through the chute 7. The refuse dropped is instantly melted. General town refuse is made up of some percentage of inorganic matters and a greater percentage of organic matters, the inorganic matters being iron and aluminum in large quantities and being fully melted at the high temperature described above and mixed into the molten material 6. On the other hand, the organic matters are varied in kind but small in the number of components and they are carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorus, halogens and a small amount of metallic elements as impurities. Accordingly, also in the case of organic matters, metals are melted and mixed likewise into the molten material 6. Other components are mostly gasified and tapped off through an outlet 8 to a known production device 10 as shown in FIG. 2.

The device 10 is adapted to separate the gas thus collected and produce the same into a gas capable of being utilized, and a gas normally impossible of practical use is collected as by dust collector 11 and exhausted outside in such a manner as to prevent environmental pollution. Also, since the molten material 6 is increased in volume, it is flowed out through an outlet 9, colled by a solid producing device 12 and collected as a solid consisting chiefly of a magma-like material. The solid matter thus obtained may be used for reclamation, engineering and building works. The heat resulting from the production of the solid matter is last in part, but can be utilized for the most part. For example, the power generated by driving a generator 13 can be utilized for the aforestated heat source for heating. The molten material 6 naturally sets up a convection current but may electromagnetically be brought into forced circulation as by high frequency heating.

In the embodiment described above, for example the heat source for heating need not be limited to a plasma arc along but may be replaced by various known heat sources, such as for example an ordinary arc, Joule heat resulting from an electric current directly through the material 6, high frequency heating and the like, which can heat the material 6 to high temperatures.

Shown in FIG. 3 is an embodiment in which a vitreous meltable material is chiefly used and in which the 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.degree. to 700.degree.C to cover a surface area of 1 m.sup.2 and a depth of 20 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 of 325A flowed. Namely, the material 6 was heated by a current of 65 kw, and the maximum temperature reached was on the order of 2,000.degree.C. However, such a high temperature is not always necessary for the pyrolysis of the refuse, and the highest temperature needed is about 1,800.degree.C, 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 upright cylindrical construction. At the top of 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 100.degree. to 200.degree.C. The numeral 21d designates a jacket portion of the outer periphery of the preheating chamber 21c; 21e an outlet communicating with the preheating chamber 21c; 21g an intermediate portion of the furnace body 21, the temperature inside of which furnace body reaches about 500.degree.C; 21h an outlet communicating with the intermediate portion 21 g; and 21i designates a molten material both in the lowermost part of the furnace body and a discharge outlet 21j 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 21i. The numeral 22 designates 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 21i 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 21g 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 21i and which is adapted to measure the temperature inside the furnace tank 21i by a sensor 32 when necessary and to maintain such temperature substantially constant in the range of about 1,600.degree. to 1,800.degree.C 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 21i 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 21i are melted by starting a torch 33a. 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 21a through the revolving doors 21b and 21f into 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 21e 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 21i, it is pyrolyzed without being burnt because of the high temperature ranging from 1,600.degree. to 1,800.degree.C 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, 15 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 21c 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 21i 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 21j 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 21i 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 33b 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 21i.

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 40 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 21i of the furnace body. In the intermediate part of the piping 40a is provided a control valve 28a, which is controlled by a sensor 29a 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 23a 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.degree. to 200.degree.C 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 21e 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 21i, and the output is impressed upon a pair of electrodes 33b disposed on the outer periphery of the tank 21i.

In the same manner as in the embodiment in FIG. 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 1,600.degree.C 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 21i, 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.degree. to 200.degree.C. 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.degree. to 200.degree.C within the preheating chamber 21c 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.degree. to 1,800.degree.C 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 .times. 0.45 .times. 0.98 .times. 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 invention as defined by the appended claims.

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.

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 material and 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, and control means being electrically connected to the previously mentioned electric heating means for the meltable molten bath of material.