Methods and apparatus for the thermal treatment of mixed urban wastes

Abstract

The invention concerns a device for the thermal transformation of waste, in particular mixed urban waste. It comprises conveyor means, housed in an enclosed space, for discharging waste into a furnace having inductively heated zones of successively higher temperatures. Gases and oils produced by pyrolysis are removed at stages of the process.

We claim: 
     
         1 . A process for the thermal transformation of waste, in particular urban waste, in particular organic waste, vegetable waste, synthetic materials or the like, in which the said waste is fed into at least one confined site, in the absence of oxygen, with a view to treating it in order to obtain transformed products, in which a substantial reduction in its humidity is carried out before and during its penetration into the said confined site, and in which a gradual rise in temperature is carried out, in zones of predetermined temperatures, and in that this is done in the course of the continuous movement of the said waste, to their vertical settling by gravity in said confined site, through said zones of predetermined temperatures, characterized in that said gradual rise in temperature of said waste is carried out, in zones of predetermined temperatures, by independent electrical induction heating means disposed specifically in each of said zones of predetermined temperatures and in that said transformed products are evacuated at outlets of said confined site, after the thermal transformation of said waste according to the treatment temperatures, in gaseous, liquid or solid form. 
     
     
         2 . The process according to  claim 1 , characterized in that the said increase in temperature of the said waste is carried out by heating heat-transferring elements which are in direct contact with the said waste to be heat-treated and which transmit at least part of their heat thereto. 
     
     
         3 . Process according to  claim 1 , characterized in that the temperature of the waste to be treated is first raised to a dehydration value, which is between 100 and 250° C., then raised to a roasting value between the dehydration value and 450° C., and then raised to a pyrolysis value between roasting value and 900° C. 
     
     
         4 . Process according to  claim 3 , characterized in that products from the processing of the waste are collected in the form of combustible gases which are substantially free of CO 2 , in the form of combustible oils, and in the form of solid particles. 
     
     
         5 . A device for the thermal transformation of waste comprising one or more of household waste, agricultural waste, and synthetic materials, comprising transport means for bringing said waste into at least one confined site, in the absence of oxygen, with a view to thermally treating it in order to obtain transformed products, the device comprising drying means for effecting a substantial reduction in their humidity before and during their penetration into said confined site, heating means for effecting a gradual rise in temperature, in zones of predetermined temperatures, and compacting means for effecting during the continuous movement of said waste, to their vertical settling by gravity in said confined site, through said zones of predetermined temperatures, characterized in that said means for heating said waste comprises at least one electrical induction heating means, specific to each predetermined temperatures, said induction heating means being independent and, disposed specifically in each of said zones of predetermined temperatures, and in that the device comprises evacuation means arranged to evacuate said transformed products at selective outlets of said confined site, after the thermal transformation of said waste. 
     
     
         6 . The device according to  claim 5 , characterized in that it comprises at least one furnace, which contains said confined space into which the waste to be transformed is poured, wherein the furnace comprises a tower partly of cylindrical shape, and a central core, positioned symmetrically inside the tower, induction heating means positioned, at least partially, in a first cylindrical space delimited along an outer wall of said tower and said confined space, through which said waste passes during its transformation. 
     
     
         7 . The device according to  claim 5 , characterized in that the predetermined temperature zones are delimited by horizontal sectors positioned from top to bottom, in the direction of movement of the waste during its transformation, each of which zone comprises induction heating means capable of generating a temperature which increases with respect to the previous zone. 
     
     
         8 . The device according to  claim 5 , characterized in that the wall of the central core is a magnetizable material. 
     
     
         9 . The device according to  claim 5 , characterized in that the outer wall of said tower is made of a non-magnetic material. 
     
     
         10 . The device according to  claim 5 , characterized in that the outer wall of said tower is a magnetizable material. 
     
     
         11 . The device according to  claim 5 , characterized in that the induction heating means are positioned at least partly in the annular space between the outer wall of the tower and the inner wall of said tower, and in that complementary induction heating means are housed in said central core. 
     
     
         12 . The device according to  claim 5 , characterized in that the furnace is constructed according to the principle of nestable sectors, each of the components of which corresponds to a predetermined temperature zone and in that the components of each individual part of the furnace are composed of a central sector comprising a central core element, a wall element of the furnace and a set of electric coils arranged to constitute the heating means corresponding to the predetermined temperature zone concerned. 
     
     
         13 . A device for the gasification by thermal treatment of mixed waste, in particular municipal waste containing synthetic materials or the like, organic waste, vegetable waste or the like, characterized in that the gasification device comprises at least one transit tank into which said mixed waste is supplied, and at least one gasification furnace which communicates with said at least one transit tank, wherein said at least one transit tank has heating means for at least partially dehumidifying the mixed waste, wherein said at least one mixed waste gasification furnace comprises heating means for at least partially converting said mixed waste into combustible gases and wherein said at least one transit tank and said at least one mixed waste gasification furnace are connected to each other by a central duct which at least partially surrounds, a first sealed space through which air flows from an opening of the gasification furnace and which communicates with a second annular space containing electric induction heating elements arranged to raise the temperature of the gasification furnace and the mixed waste to cause said gasification of said mixed waste. 
     
     
         14 . The device for gasification of mixed waste according to  claim 13 , characterized in that said first sealed space contains heating elements for heating the mixed waste contained therein to a temperature sufficient to remove moisture and cause partial dehumidification of said mixed waste. 
     
     
         15 . The device for the gasification of mixed waste according to  claim 14 , characterized in that the heating elements are induction heating means which are distributed in sectors to define temperature zones of the mixed waste to be heat-treated. 
     
     
         16 . Device for gasification of mixed waste according to  claim 13 , characterized in that the central part of said at least one furnace for gasification of said mixed waste comprises an opening arranged to evacuate water and in that said opening is connected to a mouth which opens into said at least one transit tank for discharging said liquids onto said mixed waste. 
     
     
         17 . The device for gasification of mixed waste according to  claim 13 , characterized in that said central part of said at least one furnace for gasification of said mixed waste comprises an opening arranged to evacuate air and in that said opening is connected to said first sealed space, peripheral to the lower part of said at least one tank. 
     
     
         18 . The device for gasification of said mixed waste according to  claim 13 , characterized in that said central part of said at least one furnace for gasification of said mixed waste comprises an opening arranged to evacuate gas obtained by the pyrolysis of said mixed waste by thermal treatment, and in that said opening is connected to a cogeneration device. 
     
     
         19 . The device for gasification of said mixed waste according to  claim 13 , characterized in that said central part of said at least one furnace for gasification of said mixed waste comprises an opening arranged to transport gas obtained by the pyrolysis of said mixed waste by thermal treatment and in that said opening corresponds to a torch for supplying heat to a heat-transfer fluid. 
     
     
         20 . The device for gasifying said mixed waste according to  claim 13 , characterised in that said arrangement comprises a plurality of tanks for storing mixed waste and a single gasification furnace, said single gasification furnace being connected point-wise to all of said tanks of said plurality of tanks, by means of at least one central conduit and in that said at least one central conduit comprises connection valves for selectively unblocking the connection of each of said storage tanks for waste mixed with said gasification furnace. 
     
     
         21 . The device for gasification of said mixed waste according to  claim 13 , characterized in that said arrangement comprises a plurality of gasification furnaces and a single mixed waste storage tank, said single mixed waste storage tank being connected point-wise to all of said gasification furnaces of said plurality of furnaces, through at least one central conduit and in that said at least one central conduit has connection valves for selectively unblocking the connection of each of said storage tank for waste mixed with said plurality of said gasification furnaces. 
     
     
         22 . The device for gasifying said mixed waste according to  claim 13 , characterized in that said device comprises a plurality of gasification furnaces and a plurality of mixed waste storage tanks, each of said mixed waste storage tanks of said plurality of mixed waste storage tanks being point-connected to each of said gasification furnaces of said plurality of furnaces, through at least one central conduit and in that said at least one central conduit has connection valves for selectively unblocking the connection of each of said waste storage tank mixed with said plurality of said gasification furnaces. 
     
     
         23 . A process for the gasification, by thermal treatment, of mixed waste comprising household waste, characterized in that said mixed waste is brought into at least one transit tank which communicates with at least one gasification furnace, in that said mixed waste is heated in said at least one tank to dehumidify it at least partially, in that said mixed waste is transferred into said at least one gasification furnace which comprises heating means for at least partially converting it into combustible gases, by means of a central duct which at least partially surrounds a first sealed space in which air flows from a mouth of the gasification furnace and which communicates with a second annular space containing electric induction heating elements arranged to raise the temperature of the gasification furnace and the mixed waste to cause said gasification of said mixed waste, characterized in that said mixed waste is heated sequentially in sectors by induction heating means which are arranged to bring the mass of mixed waste to be heat treated to temperatures between 400 and 1000° C.