FR2736278A1 - Neutralising acidic waste incineration gas - by contacting with fine particles of regenerated salt from cleaning saline product contaminated with organic matter - Google Patents

Abstract

The process for treating sulphur- and/or chlorine-contg. waste incineration off-gas involves contacting the gas (6), in a reactor (10), with fine particles (16) of a regenerated salt (14) produced by a pollution redn. unit which treats a saline product (11) contaminated with organic matter. Also claimed is an installation for carrying out the above process, comprising a waste incinerator (2), a reactor (10) and a pollution redn. unit pref. contg. a fluidised bed (12).

Description

PROCESS AND PLANT FOR TREATING SMOKE
OF WASTE INCINERATION WITH RECYCLING OF SALT
REGENERATED FROM THE TREATMENT OF A POLLUTED SALINE PRODUCT
BY ORGANIC MATERIALS.

 The invention relates to the field of waste treatment. It relates in particular to a process for treating the fumes produced by an incineration of waste, as well as an installation for the implementation of said process.

 The waste targeted by the present invention is of very diverse origin and nature. In the broad sense, these are materials rejected or left as residues of a process or an operation, and which have no immediate value. The waste is generally unstable at the physico-chemical level and contains toxic molecules which can present dangers for the environment.

 Also, their landfill often requires prior treatment.

 Different methods of waste treatment are known. Among these methods, the so-called incineration methods propose bringing the waste to a temperature of the order of 1000 OC. At this temperature, said waste undergoes physicochemical transformation and forms bottom ash and incineration fumes composed essentially of incineration gas and fly ash. The incineration fumes, possibly freed from fly ash, are then treated in a reactor into which reactive materials such as lime or pure salts are introduced, which will fix and stabilize the toxic and / or dangerous molecules.

They are then discharged into the atmosphere, the transformed reactive materials being landfilled, for example after solidification.

 However, these incineration processes are expensive. Indeed, they require, on the one hand, the acquisition of reactive materials which are not waste and which, therefore, have a price. They lead, on the other hand, to a landfill of said materials, which constitutes, for an industrialist in the field of waste treatment, a major drawback given that the rates for landfill are proportional to the volume and / or the weight of the waste.

 Furthermore, the French patent application filed on June 19, 1995 and registered under number 95.07276 describes a process in a fluidized bed treatment of waste consisting of saline products polluted by organic matter, intended to regenerate mineral salts substantially free of organic matter .

 The object of the present invention is to propose a process for treating incineration fumes, which overcomes the aforementioned drawbacks, and which in particular makes it possible to ensure physicochemical fixation and stabilization of certain compounds, in particular acids, of said fumes, without requiring reactive materials which are not waste.

 This object, as well as others which will appear subsequently, is achieved by a process according to which the fumes or incineration gases are brought into contact, in a reactor, with a reagent comprising saline particles resulting from the treatment. of a saline product polluted by organic matter.

Also, the first object of the invention is a process for the treatment of sulfur and / or chlorinated waste incineration fumes, according to which
- said waste is incinerated in an incineration oven
- recovering the acid fumes produced by said incineration and comprising incineration gases and fly ash
- the incineration gases are introduced into a reactor
and, characterized in that
- One puts in contact, in said reactor, said incineration gases and particles of small particle size of a regenerated salt, said regenerated salt being obtained from the treatment, in a depollution unit, of a saline product polluted by materials organic.

In addition, the second object of the invention is an installation for treating smoke from the incineration of sulfur and / or chlorinated waste, comprising
- an incineration oven for said waste;
- a reactor and, characterized in that it further comprises
- a depollution unit for a saline product polluted by organic matter.

 The description which follows, and which does not include any limiting character, will allow a better understanding of the way in which the invention can be implemented.

It should be read in conjunction with the accompanying drawings, in which
- Figure 1 shows, schematically, the succession of steps of a method according to the invention, as well as an installation for the implementation of said method.

 According to the invention, waste incineration fumes are treated.

 This waste, referenced 1 in FIG. 1, is in particular industrial waste or household waste, in a solid, liquid or pasty form, which contains chlorine compounds, sulfur compounds, as well as other toxic compounds, that is - to say dangerous for the environment.

 To this end, said waste 1 is introduced into an incineration oven 2. This oven 2 is a rotary oven or a rack oven. It is brought to a temperature between about 900 and 1100 OC, for example of the order of 1000 OC.

 At this temperature, the waste 1 is oxidized and most of the toxic compounds which it contains decompose. For example, sulfur compounds oxidize to sulfur dioxide S02 and chlorine compounds decompose into HCl. At the outlet of the oven 2, clinkers 3 are then obtained, on the one hand, and, on the other hand, acid incineration fumes 4 comprising HCl and SO2 gases.

 The bottom ash 3 is separated by gravity from the incineration fumes 4 in a post-combustion chamber 5 placed immediately at the outlet of the incineration oven 2. In this chamber 5, the temperature is close to 1000 ° C. Also, the oxidation and decomposition reactions, which took place in oven 2, continue.

 The incineration fumes 4 are composed of a mixture of incineration gases 6 and fly ash 7.

 The incineration gas mixture 4 is an acid mixture comprising 10 to 15% by weight of o2, 10 to 15% by weight of carbonaceous gases CO and C02, 20% by weight of H 2 O in gaseous form, nitrogen N2, up to approximately 10 g / m3 of hydrochloric acid HCl in gaseous form, 5 to 7 g / m3 approximately of sulfur gases such as S02 and, in less quantity, S03, a few nanograms of dioxins and heavy metals in variable proportion.

The fly ash 7 notably comprises the following compounds: Sio2, CaO, A1203, Fe203, MgO, Na2O,
K20, Mn, C (unburnt), P, S, Cl, Zn, Cd, Mg, Pb, Cu,
Ni, Sn, Cr, and Ba.

 In the example described here, the incineration fumes 4 are introduced into a recovery chamber 8. In this chamber 8, the energy of said fumes 4, stored in the form of heat, is recovered, and the incineration gases 6 are separated from the fly ash 7.

 The incineration gases 4 are then introduced into a boiler 9 where they are rapidly cooled, then into a reactor 10.

 This reactor 10 is connected to a unit for depolluting a saline product polluted by organic matter 11.

 This unit, as well as the saline product 11, which constitutes waste, are described in the aforementioned French application 95.07276 and the content of which is incorporated herein by reference. In accordance with the description of this application, the saline product 11 is treated in a fluidized bed 12 where the polluting organic materials are burned, combustion gases 13 being separated from the combustion residues or regenerated salts 14 by a cyclone 15.

 These regenerated salts 14 comprise, for example CaCO3 and / or Na2CO3. However, they are waste because, although substantially free of polluting organic materials, they still contain a certain amount, the total carbon (CT) of said salts 14 being of the order of 1%.

 According to the invention, in order to recycle the regenerated salt 14, the incineration gases 6 and particles 16 of small particle size of said salt 14 are brought into contact in the reactor 10.

 These particles 16 constitute waste. They have a particle size between approximately 5 and 15 μm.

Also, the regenerated salts 14, which have an average particle size of the order of 50 μm, are ground in a mill 17 before being introduced into the reactor 10 by means of introduction.

 There, the particles 16 are suspended in the gas stream 6 and react, in the reactor 10, in a dry medium, with the incineration gases 6.

This reaction is mainly a neutralization of the sulfur and chlorinated acid gases of the acid incineration gases 6 in accordance with the following reactions

 In addition, the particles 16 have an action on other pollutants such as dioxins.

 In another step of the invention, the particles 16, suspended in the gases 6, are transported to a filter 18 at least. This filter 18 is for example a bag filter or an electrostatic precipitator. It is intended to separate the particles 16 which have reacted from the gases 6.

 However, at the outlet of the filter 18, the gases 6 also comprise hydrochloric acid as well as other pollutants in particular, heavy metals.

 Therefore, an additional treatment of said gases 6 is carried out in a reactor 19, in a humid environment.

 This reactor 19 is composed of different stages.

In a first stage or wet stage saturated with water, the gases 6 are cooled to a temperature of the order of approximately 70 ° C. In a second stage or acid stage, the gases 6 are washed with water. In particular, water captures strong acids such as HCl. Heavy metals in the gaseous state are then, at a pH of the order of 2, ionized and dissolve in water. Finally, in a third so-called basic stage, the pH of which is in fact between 6.8 and 7, weak acids are captured, such as residual SO2 which, in neutral medium, dissolves perfectly well in water.

 At the outlet of the reactor 19, the purified gases 20, that is to say substantially free of acids and heavy metals, are driven by a fan 21 and then discharged into the atmosphere.

 Furthermore, according to the invention, the combustion gases 13 separated from the regenerated salts 14 by the cyclone 15, which consist mainly of C02 and H2O, but which also contain sulfur and chlorine gases, are introduced into the afterburner chamber 5 with a view to undergoing the same treatment as the incineration gases 6. The combustion gases 13 cannot, in fact, be discharged as such into the atmosphere.

 It will be noted that said gases 13 are, at the outlet of cyclone 15, at a temperature between 500 to 6000C and that, therefore, their introduction into chamber 5 does not require a considerable rise in temperature to reach 1000 " vs.

 it follows from the above that, thanks to the invention, the regenerated salt 14 as well as the combustion gases 13 will have been recycled by treating the incineration fumes 4 of the waste 1.

Claims (8)

 1. Process for treating smoke from the incineration of sulfur and / or chlorinated waste (1), according to which  - said waste (1) is incinerated in an incineration oven (2)  - recovering the acid fumes (4) produced by said incineration and comprising said incineration gases and fly ash  - the incineration gases (6) are introduced into a reactor (10)  and, characterized in that  these incineration gases (6) and particles (16) of small particle size of a regenerated salt (14) are brought into contact in said reactor (10), said regenerated salt (14) being obtained from the treatment, in a depollution unit, a saline product polluted by organic matter (11).  2. Method according to claim 1, characterized in that the incineration of the waste is carried out at a temperature between 900 and 1100 OC approximately and that, at this temperature, the incineration fumes comprise up to 10 g / m3 of HCl and / or 5 to 7 g / m3 approximately of sulfur gases such as 502.  3. Method according to one of claims 1 or 2, characterized in that the incineration gases (6) comprise HCl and / or S02, the particles (16) comprise CaCO3 and / or Na2CO3, and that said incineration gases (6) are neutralized by said particles (16) according to the following reactions

 4. Method according to one of claims 1, 2 or 3, characterized in that the particles (16), of particle size between 5 and 15 microns approximately, are obtained by grinding the regenerated salts (14).  5. Method according to one of the preceding claims, characterized in that the saline product (11) polluted with organic materials is treated in a fluidized bed (12).  6. Method according to one of the preceding claims, characterized in that combustion gases (13) from the treatment unit are introduced into their post-combustion chamber (5).  7. Installation for treating incineration smoke (4) of sulfur and / or chlorinated waste (1), comprising  - an incineration oven (2) of said waste (1);  - a reactor (10)  and, characterized in that it further comprises  - a unit for cleaning up a saline product polluted by organic matter (11)  8. Installation according to claim 7, characterized in that the unit for depolluting the saline product (11) comprises a fluidized bed (12).