Field of the invention

The present invention relates to a method and a system for thermal disposal of waste, particularly waste that is regarded as special or dangerous, with no distinction based on waste type.

Background art

Incineration plants for disposal of waste regarded as special or dangerous have been known and operated for a long time.

Each of these prior art plants is designed and constructed for disposal of a restricted and special class of waste, i.e. each plant is designed and constructed with particular technical features, for incinerating particular types of waste but not others.

A waste disposal plant is typically composed of a series of waste treatment sections, namely a section for amassing and possibly preparing waste to obtain sizes compatible with the plant features, a section for burning waste that comes from the waste amassing and preparing section, a section for collecting the fumes generated by waste burning, possibly a section for recovering thermal energy from combustion, a section for treating and filtering combustion fumes before final reintroduction thereof into the outside environment.

In the field of burning, an after-burning apparatus is also provided for combustion fumes to comply with the standards in force.

Waste may be generally divided into two main types, i.e. organic waste and inorganic waste.

Organic waste includes all waste that is composed of materials that can be molecularly or bacteriologically transformed either spontaneously or chemically, whereas inorganic waste includes all waste that are not exposed to spontaneous molecular and bacteriological changes.

Proper operation of a waste disposal plant requires the amassing section to have a sufficient waste storage capacity for continuous supply of incinerators that have a continuous operation. One method for treating leachate or waste water in a closed system and by using the potential heat of waste gas from an incinerator is known from EP 076976.

According to this patent, leachate from industrial waste, and/or waste water containing toxic components, which is used in industrial waste processing steps, is treated in a closed system by pooling, in an equalizing tank, one or more of the treated leachates with an apparatus for removing toxic components, which prevents discharge of heavy metals contained and their ashes.

A solid waste disposal system is known from US 4,308,809.

According to this patent, the system includes a building enclosure having an interior storage area for accumulating combustible refuse, and an incinerator for thermally oxidizing the refuse.

The incinerator includes a combustion chamber which is maintained at a reduced pressure level relative to the pressure of the surrounding atmosphere This sub-atmospheric pressure state produces a positive flow of air into the chamber as it is loaded during combustion virtually without risk of injury to personnel or damage to surrounding combustible material

A further waste reducing and recycling plant is known from DE 4,407,600.

According to this patent, the plant has one or more working modules for separately processing collected waste fractions and at least one cooling unit for cooling selected waste fractions.

The working modules have arrangements for crushing and/or reducing the volume of individual waste fractions.

This prior art suffers from certain drawbacks.

A first drawback is that storage of perishable waste, typically organic waste causes generation of foul smells with time, which smells spread to the surrounding environment through air streams and wind, and may reach long distances from the storage area, thereby creating discomfort in the people who live in the areas affected by these smells. Another drawback is that prior art disposal plants, as mentioned above, are designed and constructed for disposal of particular waste, and an adequate number of plants have to be built for disposal of every type of waste, i.e. one for each waste class.

This requires large investments, adequate selective waste collection as well as the availability of areas suitable for disposal plants which are often strongly opposed by the people that live nearby, who are afraid of being exposed to health damages and discomfort due to waste accumulation and disposal.

Therefore, the difficulty of finding suitable areas increases with the number of plants to be built.

Yet another drawback is that each waste class has to be carried to its disposal plant, thereby requiring adequate means of transport, arrangements for safe transport, disinfection systems for disinfecting the means of transport after use.

Disclosure of the invention

One object of the invention is to improve the state of the art. Another object of the invention is to provide a system for thermal disposal of waste that eliminates any occurrence of foul smell deriving from storage of waste awaiting disposal.

A further object of the invention is to provide a system for thermal disposal of waste that alone is capable of incinerating waste of any type, while requiring simple and limited adjustments of burning members to be adapted to each waste mixture to be incinerated.

Yet another object of the invention is to set up a method for disposal of waste that allows disposal of any type of waste, and prevents the creation of miasmas that pollute the surrounding environment to large distances.

In one aspect the invention relates to a method for thermal disposal of waste as defined in claim 1.

In a further aspect the invention relates to a system for thermal disposal of waste as defined in claim 4.

Therefore the invention affords disposal of any kind of waste in a single disposal system, while preventing the creation of undesired miasmas and having a fully automatic disposal cycle.

Brief description of the drawings

Further features and advantages of the invention will be more apparent from the detailed description of one preferred but non-exclusive embodiment of a system for thermal disposal of waste according to the present invention, which is described as a non-limiting example with the help of the annexed drawings, in which:

FIG. 1 is a general schematic view of a system for thermal disposal of waste of the invention;

FIG. 2 is a schematic enlarged view of a magazine for low- temperature storage of perishable organic waste;

FIG. 3 is a broken schematic enlarged view of one end of a waste burning kiln, having multiple waste receiving inlets, each inlet being designed for one particular waste type;

FIG. 4 is a very schematic front view of a loading end of a waste burning kiln as is used in the thermal disposal system of Fig. 1.

Detailed description of a preferred embodiment

Referring to the above figures, numeral 1 generally designates a system for thermal disposal of waste, hereinafter briefly referred to as system 1 , which comprises a series of sections for carrying out specific steps of the disposal cycle, which have been indicatively outlined in Fig. 1 by broken lines.

The system 1 comprises a section 2 for receiving waste and amassing it in a warehousing 10, a section 3 for burning waste, a section 4 for decontaminating the smokes created by the burning section 3, and a section 5 for recovering energy from heat generated in the burning section 3.

Referring to the figures, it can be noted that, in addition to the warehousing 10, the section 2 comprises a waste shredder 11 and a pair of elevators 12 that lift the received waste loaded in container carts 13, preferably having wheels and adequately shaped to contain various kinds of waste, and dump them into the inlet of the shredder 11.

Superimposed warehousing surfaces 14 are placed in the warehousing 10, with the container carts 13 arranged thereon, to be lifted and lowered by means of further elevators 15; an automatic handling system, not shown because it is irrelevant for the invention, moves the carts in the warehousing 10, namely from the elevator 15 to the inlet 10A and from one outlet 10B thereof to the elevators 15.

A weighing apparatus 17 is provided at one inlet 10A of the warehousing 10 to weigh the container carts 13 before access thereof to the warehousing 10.

As is shown in the figures, an auger 18 and a sewage collecting pipe 19 are provided on the bottom of the shredder, to transfer the waste awaiting disposal into the burning section 3.

In this section, the solid or semi-solid part of the waste is collected by a handling unit that can comprise, without limitation, continuously- operating lifts 20 that discharge it into a hopper 21 that feeds an incinerating kiln 22, e.g. a rotary incinerating kiln.

The liquid part is collected in a tank 23, which is also connected with the continuously-operating lifts 20, and is transferred therefrom into a tank 24 designed to collect meat treatment blood.

The liquid part is drawn from the tank 23 by a pump 25 and conveyed by another pump 26 to a spray nozzle 70 that is mounted to one loading end of the incinerating kiln 22, designated by numeral 62.

As is shown in the figures, the incinerating kiln 22 is typically equipped with a hydraulic loader 28 that introduces waste awaiting disposal into a primary combustion chamber 22A of the incinerating kiln 22.

The hopper 21 also directly receives the special waste that cannot pass through the shredder 11 and that, like the waste stored in the warehousing 10, is loaded into container carts 13, which are lifted and dumped into the hopper 21 by further elevators 29, also provided in the burning section 3.

The incinerating kiln 22 also has a secondary combustion chamber 22B also known as after-burning chamber, in which smokes created by combustion in the incinerating kiln 22 are thermally treated to decompose the harmful toxic substances contained therein due to waste combustion.

A discharge opening 32 is placed at the bottom 31 of the secondary combustion chamber 22B, through which the ashes generated in the incinerating kiln 22 are discharged and transferred into a collection container 33 through a transfer pipe 34.

The burner 27 also receives high calorific value liquid waste, such as solvents accumulated in the tanks 37 and fuel from a feed line 38.

The secondary combustion chamber 22B is equipped with an emergency chimney 39 for quick ejection of the smokes created during combustion, and is connected by a pipe section 40 with a steam generator 41 , which is part of the heat energy recovery section 5.

This steam generator 41 has at least one outlet pipe 42 for conveying steam to a known apparatus used for generating energy for industrial use or else, and is connected with a downstream economizer 43 that pre-heats the water that flows into the boiler, thereby producing steam by heat exchange with the smokes.

The smokes created by burning and incineration are conveyed through an outlet pipe 44 to the decontamination section 4.

A Venturi profile is placed in the outlet pipe 44, and has an opening for connection with a pipe 45 that extends from containing and metering devices 46 and 47, in which smoke treatment materials, namely activated carbons and sodium bicarbonate respectively, are loaded.

Both the steam generator 41 and the economizer 43 are equipped with corresponding ash discharging pipes 48 and 49 which have discharge ports opening into conveyors 50 and are designed to convey ashes to a container 51. Smokes flow from the outlet pipe 44 into a reactor 52 in which smokes are held in contact with the treatment materials for the time required by the standards in force and are carried therefrom through a pipe 53 into a filtering unit 54, which may also be reached by a compressed air pipe for cleaning the filtering elements.

The bottom of the filtering unit 54 has a discharge opening controlled by a valve 56 which opens into further conveyors 57 that collect the solid parts separated from the smokes and transfer them into a tank 58. The filtering unit 54 has an outlet 59 that connects it to a chimney 60 through which the decontaminated smokes are released into the atmosphere by the action of a blowing unit, such as a fan 61.

A probe, referenced 55, is mounted to the main chimney 60 for continuously monitoring emissions.

Referring to Fig. 3, it can be noted that the kiln 22 comprises a waste inlet end, generally referenced 62 and in which waste inlet ports are provided, for receiving waste according to its state.

In more detail there are: a first inlet 63, through which low-viscosity and low-to-medium calorific value waste is introduced into the combustion chamber 22A of the incinerating kiln 22, a second inlet 66 through which pump-deliverable waste are introduced; a third inlet 64 located next to the burner 27, that can be reached both by an auxiliary fuel feed pipe 38 and by an additional feed pipe 38' for other high calorific value waste, that can act as a fuel for the burner 27.

In short, waste of any type may be introduced in the incinerating kiln 22, as ports are provided for receiving each of such types, each of such ports being hermetically sealed to avoid losses and leakages into the surrounding environment.

The operation of the system for thermal disposal of waste according to the invention is as follows: the solid waste awaiting disposal is carried to the receiving section 2, e.g. by transfer vehicles and is introduced into the shredder 11 , in this section 11 , to be reduced into pieces of predetermined sizes.

The elevators 12 lift the waste containing carts 13 and dump their contents into the shredder 11.

The perishable waste-containing carts, if disposal does not occur within a short time, are stored in the warehousing 10 in which internal temperature is maintained considerably lower than external temperature, to prevent or at least delay deterioration and decomposition of perishable waste.

The warehousing 10 is equipped with conventional devices, which are designed to control internal temperature and maintain it to a low level, i.e. not exceeding 4°C for proper system operation.

As soon as the container carts 13 are stored in the warehousing 10, they are first weighed by the weighing apparatus 17, the latter being connected to an electronic system that is programmed for managing the whole system 1 and receives the detected weight data.

Then, the container carts 13 are arranged on the warehousing surfaces 14 by the elevators 15 in predetermined orders and positions, as is stored in the electronic control system.

Once the waste has been shredded by the shredder 11 , it is collected by the auger 18 disposed at the base thereof and discharged onto the continuously-operating lifts 20 that carry it to the hopper 21 that feeds the incinerating kiln 22 and discharge it therein.

At the same time, the sewage derived from solid waste shredding is collected in the tanks 23 and 24 from which it is pushed toward the incinerating kiln 22 by means of the pumps 25 and 26.

The loading end 62 of the kiln 22 has an inlet port for each type of waste to be incinerated, for simultaneous introduction thereof into the combustion chamber.

Therefore, low calorific value waste is introduced through the first inlet 63, whereas more or less viscous, pump-deliverable fluid waste is simultaneously introduced through the second inlet 66. The hydraulic loader 28 is used to feed the primary combustion chamber 22A with the solid waste from the hopper 21 , the latter receiving such waste from the continuously-operating lifts 20 and the other elevators 29.

Each type of waste to be simultaneously introduced into the incinerating kiln 22 is metered by the electronic system, that manages the thermal disposal plant, for the overall waste mass introduced into the incinerating kiln 22 to have a calorific value that is generally compatible with the total or programmed heat capacity of the kiln 22 and the subsequent heat recovery systems.

After waste combustion, the generated smokes flow into the secondary combustion chamber 22B in which they are thermally treated for decomposition of the harmful toxic substances that can be generated by combustion.

The ashes generated by waste incineration deposit on the bottom of the secondary combustion chamber 22B and are transferred into the container 33 in which they are accumulated.

The smokes that flow out of the secondary combustion chamber 22B are conveyed to the steam generator 41 and the economizer 43.

The generated steam may be collected and used for industrial purposes, e.g. for electricity generation, whereas the smokes flow through the pipe 44, the latter also being in communication with the pipe 45 for feeding and adding activated carbons and sodium bicarbonate to eliminate any polluting components in the residual smokes, which are contained in the containing and metering devices 46 and 47 respectively.

As the smokes flow out of the pipe 44, they are first conveyed into the reactor 52, in which chemical reactions occur to make the smokes inert and then into the filtering unit 54.

After filtration, the smokes are conveyed into the chimney 60, which has a probe 55 mounted thereto for continuous monitoring of emissions, and discharged into the environment in purified and cooled form. The invention was found to fulfill the intended objects.

The invention so conceived is susceptible to a number of changes and variants within the inventive concept.

Furthermore, all the details may be replaced by other technically equivalent parts and in practice, any materials, shapes and sizes may be used as needed, without departure from the scope of the following claims.