Method and plant for the treatment of materials, in particular waste materials and refuse

Abstract

A plant for the treatment of materials, in particular waste materials and refuse, comprises a combustion reactor to which the material to be treated can be supplied. The combustion reactor has an input for a combustion supporter comprising oxygen and an output for the gases that are produced during the combustion of the materials inside the reactor and, in use, is substantially isothermic or quasi-isothermic at high or very high temperature, and without substantial oxygen deficit, in all of its parts. A portion of the combustion gases is recirculated and mixed with the combustion supporter to bring about a high degree of opacification thereof, which is increased by increasing the total pressure of the combustion chamber. The substances which cannot be gasified inside the reactor are immediately fused. The parameters of the gases at the output from the reactor are constantly measured by sensors with response-time characteristics of about 2 seconds.

Claims

1. Method for the treatment of materials, in particular waste materials and refuse, comprising: supplying the material to be treated and a combustion supporter to an oxidation chamber or a combustion reactor, wherein the combustion supporter consists essentially of oxygen and recycled gases; and discharging gases produced during the oxidation or combustion of the material from the oxidation chamber or combustion reactor, wherein the material to be treated and the products resulting from the oxidation or combustion are subjected to conditions of isothermy or quasi-isothermy at high or very high temperature, without oxygen deficit, in any part of the chamber or reactor, such that cold zones are eliminated, wherein the oxidation chamber or combustion reactor is operated at a pressure from greater than atmospheric pressure to 600 kPa and includes a single combustion chamber, wherein water is injected into the recycled gases to raise the concentration of water in the recycled gases to higher than 30% by volume, wherein at the mouth of the reactor the produced combustion fumes show a TOC content less than 1 ppm and an ash content lower than 10 mg/Nm.sup.3, wherein an incombustible slag produced inside the reactor is collected on a base of the reactor, wherein the reactor base is inclined towards an output duct, wherein the slag is maintained as a liquid by heating the output duct, wherein the slag is delivered to a collecting tank, wherein the oxidation chamber or combustion reactor is operated at a temperature of 1300K to 2130K, wherein the gases output from the reactor are mixed with a portion of the gas output from a boiler, and wherein the portion of the gas output from the boiler which is not mixed with the gases output from the reactor is mixed with the oxygen supplied at the input of the reactor and producing a combustion-supporting mixture which is opaque to infra-red.

2. Method for the treatment of materials according to claim 1, further comprising the supply of a combustion supporter comprising oxygen mixed with gases resulting from the combustion, with water, or with a combination of gases and water, to bring about opacification of the combustion supporter and to ensure almost instantaneous heating of the combustion supporter that is supplied into the reactor.

3. Method for the treatment of materials according to claim 2, wherein the recycled gases resulting from combustion are supplied at flow-rate and/or temperature so as to minimize the overall volume of gas in the reactor for a gas residence time in the reactor and to ensure the removal of a reaction heat from the reactor.

4. Method for the treatment of materials according to claim 2, wherein the mixing of the oxygen with the recycled combustion gases takes place with a concentration of more than 10% by volume and preferably more than 60% by volume.

5. Method for the treatment of materials according to claim 2, wherein the recycled gases which ensure the thermal balance of a plant that is operated continuously by removing the excess reaction heat owing to an appreciable enthalpy difference between the input and the output of the reactor are recycled at a minimum temperature that is compatible with normal cooling means.

6. Method for the treatment of materials according to claim 2, wherein the recycled gases which ensure the thermal balance are constituted wholly or partially by steam.

7. Method for the treatment of materials according to claim 1, wherein, in the reactor, the high rate of heating of the combustible material reduces to negligible value a fraction of dust that is entrained out of the reactor with the burnt gases.

8. Method for the treatment of materials according to claim 1, wherein the fused slag is cooled and solidified into beads so as to ensure that toxic heavy metals contained in the incombustible slag are rendered completely inert.

9. Method for the treatment of materials according to claim 1, further comprising a MIMO (multiple input/multiple output) control and optimization procedure which is focused on the parameters at the output of the reactor and in particular on measurement of gas composition at the output of the reactor.

10. Method for the treatment of materials according to claim 9, wherein the measurements of the gas composition are implemented with characteristic response times of about 2 seconds.

11. Method for the treatment of materials according to claim 5, wherein the minimum temperature is above the dew point of the recycled gases.

12. Method for the treatment of materials according to claim 1, wherein oxygen is substituted with technical oxygen.

13. Method for the treatment of materials according to claim 1, wherein the solid fuel is introduced into the combustor reactor by using recycled gas under pressure withdrawn from the output line of the reactor.

14. Method for the treatment of materials according to claim 1, wherein the oxidation chamber or combustion reactor is operated at a temperature of 1773K to 2130K.

15. Method for the treatment of materials according to claim 1, wherein the oxidation chamber or combustion reactor is operated at a temperature of 1900K to 2130K.

16. An apparatus for the treatment of materials operating in accordance with the method according to claim 1.

17. An apparatus for the treatment of materials, in particular waste materials and refuse, comprising: an oxidation chamber or a combustion reactor to which the material to be treated can be supplied comprising: an input for a combustion supporter consisting essentially of oxygen and recycled gases; and an output for the gases produced during the oxidation or combustion of the above-mentioned material inside the chamber or reactor, wherein the oxidation chamber or combustion reactor is isothermic or quasi-isothermic operated at a temperature of 1300 K to 2130 K, without oxygen deficit, in all of its parts, such that cold zones are eliminated, wherein the oxidation chamber or combustion reactor is operated at a pressure from greater than atmospheric pressure to 600 kPa, wherein water is injected into the recycled gases to raise the concentration of water in the recycled gases to higher than 30% by volume, wherein at the mouth of the reactor the produced combustion fumes show a TOC content less than 1 ppm and an ash content lower than 10 mq/Nm.sup.3,wherein the gases output from the reactor are mixed with a portion of the gas output from a boiler, and wherein the portion of the gas output from the boiler which is not mixed with the gases output from the reactor is mixed with the oxygen supplied at the input of the reactor and producing a combustion-supporting mixture which is opaque to infra-red.

18. An apparatus for the treatment of materials according to claim 17, wherein the walls of the reactor comprise a ceramic lining material which participates in the isothermy or quasi-isothermy of the reactor.

19. An apparatus for the treatment of materials according to claim 17, further comprising a plurality of feeders for supplying materials to the reactor, selected from solid materials in pieces, granular materials, liquid or sludgy materials, and/or gaseous materials.

20. An apparatus for the treatment of materials according to claim 19, further comprising at least one propulsion chamber for the pressurized and discontinuous supply of solid materials in pieces into the reactor, said propulsion chamber comprising a duct for the supply of gas under pressure, withdrawn from the output line.

21. An apparatus for the treatment of materials according to claim 17, wherein the reactor comprises a base portion communicating with and inclined towards a heated duct for collecting fluid slag.

22. An apparatus for the treatment of materials according to claim 21, wherein the collecting duct communicates with a container for collecting the fluid slag which is cooled rapidly in a water bath with the formation of solid beads so as to form a dilute water slurry.

23. An apparatus for the treatment of materials according to claim 21, wherein the collecting duct comprises heating means for keeping the slag fluid.

24. An apparatus for the treatment of materials according to claim 17, further comprising sensor means for measuring output parameters of the reactor, a control and management system receiving the signals of the sensor means in order substantially to improve the number of effective predictions for intervention in the operating conditions of the plant and to control fluctuations due to the non-homogeneity of the materials that are supplied into the reactor.

25. Method for the treatment of materials according to claim 17, wherein oxygen is substituted with technical oxygen.

26. Method for the treatment of materials, in particular waste materials and refuse, comprising: supplying the material to be treated and a combustion supporter to an oxidation chamber or a combustion reactor, wherein the combustion supporter consists essentially of oxygen and water; and discharging gases produced during the oxidation or combustion of the material from the oxidation chamber or combustion reactor, wherein the material to be treated and the products resulting from the oxidation or combustion are subjected to conditions of isothermy or quasi-isothermy operated at a temperature of 1300 K to 2130 K, without oxygen deficit, in any part of the chamber or reactor, such that cold zones are eliminated, wherein the oxidation chamber or combustion reactor is operated at a pressure from greater than atmospheric pressure to 600 kPa and includes a single combustion chamber, wherein at the mouth of the reactor the produced combustion fumes show a TOC content less than 1 ppm and an ash content lower than 10 mg/Nm.sup.3, wherein an incombustible slag produced inside the reactor is collected on a base of the reactor, wherein the reactor base is inclined towards an output duct, wherein the slag is maintained as a liquid by heating the output duct, wherein the slag is delivered to a collecting tank, wherein the oxidation chamber or combustion reactor is operated at a temperature of 1300K to 2130K, wherein the gases output from the reactor are mixed with a portion of the gas output from a boiler, and wherein the portion of the gas output from the boiler which is not mixed with the gases output from the reactor is mixed with the oxygen supplied at the input of the reactor and producing a combustion-supporting mixture which is opaque to infra-red.

Description

(1) Further characteristics and advantages will become clear from the following detailed description of a preferred embodiment which is given by way of non-limiting example with reference to appended FIG. 1 which shows an illustrative layout of the reactor and of the basic reaction circuit of a plant formed in accordance with the present invention.

(2) With reference now to FIG. 1, a plant for the treatment of materials comprises an oxidation reactor or chamber 10 with at least one input opening 11 through which the material to be treated is supplied. In particular, the plant of the present invention can treat solid materials in coarse pieces, loaded by means of a feeder 12 by means of a propulsion chamber 13, as well as granular materials loaded by means of a feeder 14, and liquids comprising in general terms, both mixtures of water and suspended and sedimented solids and viscous pitches or sludges of various densities and compositions, which are loaded into the reactor by means of a feeder 15. Gaseous materials can also be loaded into the reactor 10 by means of a loader generally indicated 16.

(3) The reactor 10 also comprises an input 17 to which oxygen coming from a duct 18 is supplied, mixed with a proportion of recirculated fumes coming from a duct 19 in accordance with procedures which will become clearer from the following portion of this description. A predetermined flow of steam may also be admitted to the duct 19 in a variable ratio according to the material treated. The flow-rate of oxygen is regulated automatically on the basis of the preset excess in the stream 25 output from the reactor 10, within predefined ranges, on the basis of the quantity and quality of material supplied to the reactor which, preferably but in non-limiting manner, is admitted to the reactor in small and frequent loads.

(4) The reactor 10 comprises a shell, preferably made of metal and lined with a ceramic coating, and cooled externally by cooling water coming from a feeder 20. The incombustible slag which is produced inside the reactor collects on its base 21 which is inclined towards an output duct 22 which, preferably but in non-limiting manner, comprises a tube made of a material with a high melting point (e.g. molybdenum, tantalum, or tungsten, treated to resist oxidation, or silicon carbide), which is heated to keep the slag liquid, and is disposed in the vicinity of a closure end 23 of the reactor 10. The liquid slag is cooled rapidly (quenched) in a water bath with the formation of solid beads so as to form a very dilute sludge in water which is then sent continuously from a collecting tank 24 for subsequent filtration and disposal by known means, for example, by means of a filter (not shown).

(5) A output duct 25 is provided on the closure end 23 of the reactor 10 and supplies the gas that is generated inside the reactor 10 towards means for recovering energy by the exchange of heat of the gases output from the reactor by known systems, which means will be identified below for simplicity of description by the term boiler which should be understood in its broadest sense. Such a boiler 26, which is preferably but in non-limiting manner of the type with smoke tubes, generates and superheats steam from supply water coming from a duct 27. The superheated steam leaves the boiler 26 through a duct 35 and is sent for generally known uses, for example, for the supply of a turbine or the like.

(6) Before entering the boiler 26, the gas output from the reactor 10 through the duct 25 is mixed with the moderator recycling gas supplied through a duct 28. The moderator recycling gas represents a portion of the gas output from the boiler 26 through a duct 29, optionally further cooled by a conventional system (not shown) and repressurized by means of a blower 30. The portion of moderator recycling gas which is not sent to the duct 28 to be mixed with the gases output from the reactor 10 is sent towards a duct 31 on which a regulation system 32 acts, admitting a regulated quantity of gas into the duct 19 in order to mix it, as described above, with the oxygen supplied to the input of the reactor 10 through the duct 18. The function of the stream which passes through the duct 31 is also to ensure the thermal balance of the reactor by means of an appreciable input/output heat difference to prevent the skin temperature of the coating exceeding the limits permitted for special refractory materials (about 2130K). The regulator 32 is therefore modulated on the basis of the temperature sensor at the output from the reactor 10 in the stream passing through the duct 25.

(7) The recirculation gases which ensure the thermal balance of plant operate continuously by removing excess reaction heat owing to the appreciable heat difference between the input and the output of the reactor and are recycled at the minimum temperature that is compatible with normal cooling means and preferably just above the dew point.

(8) The portion of gas output from the boiler 26 which is not recycled towards the duct 29 is expanded by an expansion valve 33 and subsequently sent to a smoke line 34 of generally known type. A portion of this output gas is preferably withdrawn through a duct 36 and used to pressurize the propulsion chamber 13 for the periodic admission of the solid material into the reactor 10.

(9) The various components of the above-described plant are preferably mounted on one or more slides for easy transportation and mounting of the plant in the place of use.

(10) The method for the treatment of the materials which is implemented by the plant described above is controlled as a whole by an electronic processor which ensures that the combustion gases remain inside the reactor 10 for a predetermined minimum period of time, preferably but in non-limiting manner of about 2 seconds, at a predetermined minimum guaranteed uniform temperature, preferably but in non-limiting manner of about 1500 C.

(11) In particular, the combustion supporter which is supplied into the reactor 10 and which comprises a proportionally predetermined mixture of oxygen (gas transparent to IR) and moderator recycling gas, is immediately irradiated because it is highly opaque to infra-red. This behaviour is ensured by the absence, or low concentration in the case of the use of enriched air, of nitrogen (a gas which is transparent to IR) in the combustion-supporter mixture and by the predominant presence, instead, of carbon dioxide and of water (markedly of the latter) of which the moderator recycling gas is constituted. At the high reactor-skin working temperatures, the water and the carbon dioxide which are admitted in the combustion-supporter mixture, together with the oxygen, preferably but in non-limiting manner when the process is running under pressure, themselves become optimal absorbers of infra-red energy. On the other hand, the recycled gas and the fumes that are generated behave as efficient emitters of infra-red energy which, also by virtue of the working pressures of the reactor 10 which are preferably but in non-limiting manner between 0.5 and 6 bar, thus enable a uniform temperature to be maintained inside the reactor 10.

(12) The control system arranges for the implementation of a balancing regulation, which uses a determination that is not upset by the weight of the material supplied, by means of a measurement in the loading systems in a position upstream of the propulsion chambers. The control system intervenes instantaneously to keep the temperature and the time spent by the gases inside the reactor 10 above predetermined minimum thresholds and, in the second place, on the flow-rate of the oxygen and on the flow-rate of the refuse, that is, on the loading frequency thereof, to ensure a good quality of the gases output from the reactor 10. A MIMO (multiple input/multiple output) code, on the other hand, uses a broader range of operating data and, in particular, measurements of the composition of the gases at the output of the reactor, which are performed with characteristic response times of about, but in non-limiting manner, 2 seconds, and calculates strategies for optimizing operation for a satisfactory productivity of the material-treatment method and for the reduction of unitary and running costs.

(13) Naturally, the principle of the invention remaining the same, the forms of embodiment and details of construction may vary from those described and illustrated, without thereby departing form the scope of the present invention.