FR2565843A1 - Process and device for neutralising acidic components present in fumes originating from incinerators - Google Patents

Abstract

The device comprises an injector 7 situated in the wall of a postcombustion chamber 2 arranged at the exit of the incinerator 1 and comprising a vertical refractory pipe 5. Basic compounds can be blown in through the injector 7 into the fumes at the exit of the incinerator 1. Application to incineration plants, especially for household waste.

Description

 The present invention relates to a process for neutralizing acid elements contained in fumes from incinerators, in particular household waste, and a device for implementing this process.

 The fumes or gases resulting from the combustion, in particular of household waste contain elements which must be eliminated before their rejection in the atmosphere, either because these elements have a certain market value, or, more often, in order to satisfy the environmental protection legislation. Thus the discharged fumes must not contain, for example, large particles, lead particles or acid elements such as in particular chloride ions.

 One of the great difficulties at present is to neutralize the acid elements in such fumes.

Various processes, all of which require the use of lime or magnesia, have been developed. Products likely to neutralize acid elements such as chlorides, sulfides, sulfates, are generally added to incinerators: this has the main disadvantage of causing a deposit of calcium chloride or, of magnesium sulfate or sulfide on the walls of incinerators, most often in combination with other incineration residues. Therefore, it is necessary to clean these walls, which represents an easement.

 Other methods make it possible to get rid of this easement if they consist in an insufflation of lime or magnesia in the fumes or gases once cooled. However, the neutralization of the acid elements is difficult to control under these conditions.

 One of the aims of the present invention is therefore to provide a method for neutralizing acid elements contained in fumes from incinerators, in particular household waste, which makes it possible to ensure satisfactory neutralization of these elements.

 Another object of the invention is to provide such a process which is simple, inexpensive and easily controllable.

 These aims, as well as others which will appear subsequently, are achieved by a process for neutralizing acid elements contained in fumes from incinerators, in particular of household waste, which, according to the present invention, consists of insufflation. of a basic compound in the fumes at the very outlet of the incinerator.

 This insufflation is preferably carried out by creating a vortex zone at this outlet.

 Advantageously, the basic compound is lime or magnesium oxide.

 The present invention also relates to a device for implementing this method.

 Preferably, this device for blowing a basic compound consists of an injector located in the wall of a post-combustion chamber disposed at the outlet of the incinerator, and comprising a vertical refractory tube.

 Advantageously, this injector is disposed at the inlet of the fumes from the incinerator in the afterburner chamber.

 Preferably, the injector is directed substantially perpendicular to this refractory tube.

The description which follows and which is in no way limiting, should be read with reference to the appended figures, among which
- Figure 1 schematically shows an installation for incinerating waste
- Figure 2 is a top view of an incinerator and its post-combustion chamber with partial cutaway at this level; and
- Figure 3 is a vertical section at this cutaway.

 An installation for incinerating waste such as household waste includes an incinerator (î) to which is attached an after-combustion chamber <2) connected to a boiler <3) provided with a chimney <4). This type of installation makes it possible to recover the heat released during incineration in order to heat, thanks to the boiler (3), a heat transfer fluid.

 In the post-combustion chamber (2), immerse a refractory tube (5) connecting the latter to the boiler (3). At the bottom of this chamber is located a receptacle (6) in which a significant proportion of the particles is collected. solids contained in the fumes from the incinerator 1.

 This refractory tube is which is therefore vertical, has a circular cross section.

 By the very mounting of this refractory tube (5) in the post-combustion chamber <2), a cyclone is created which makes it possible to separate the solid particles entrained by the fumes coming from the incinerator 1.

 According to the process of the present invention, a basic compound is injected into this post-combustion chamber which can for example be lime (CaO), magnesium oxide (MgO). In particular to neutralize chlorine elements, lime is used, and magnesium oxide for sulfur elements. This insufflation is preferably carried out perpendicular to the refractory tube <5) which generates a vortex zone this allows optimal dispersion of the basic compound in the flue gases.

 According to a preferred embodiment of the invention, the basic compounds are blown at the outlet of the incinerator (1), that is to say at the inlet of the fumes into the post-combustion chamber (2).

 The device for implementing this method comprises an injector (7) located in the wall (8) of the post-combustion chamber (2), as shown in FIGS. 2 and 3, preferably at the inlet smoke in this room. This injector (7) is preferably directed substantially perpendicular to the refractory tube (5) in order to create a zone with high turbulence and thereby allow optimal dispersion of the basic compounds in the flue gases.

 This injector (7) is connected to a reservoir containing the basic compound to be injected.

 As has been said, the intimate mixture between the acid elements and the basic compounds which have to neutralize them is favored not only by the turbulence generated by the insufflation of the basic compounds, but also by the cyclonic movement inside of the post-combustion chamber (2) caused by the very structure of the latter.

 Such a device therefore makes it possible to treat these gases or fumes originating from incineration, in particular household waste, at high temperature (800 to 1000 ° C.) before they pass through the heat recovery boiler, and this thanks to the post- cyclonic combustion which takes place in the post-combustion chamber (2). An advantage of this device is to effectively protect the wall of the heat recovery boiler against premature corrosion since the hot gases or fumes which penetrate therein have been previously, at the level of the post-combustion chamber, rid of harmful elements

Claims (6)

 1. Method for neutralizing acid elements contained in fumes from incinerators, in particular for household waste, characterized in that a basic compound is blown into said fumes at the outlet of said incinerator (1).  2. Method according to claim 1, characterized in that said insufflation is carried out by creating a vortex zone at the level of said outlet.  3. Method according to claim 1 or 2, characterized in that said basic compound is lime or magnesium oxide.  4. Device for implementing the method according to any one of claims 1 to 3, characterized in that it is constituted by an injector (7) located in the wall (8) of an after-combustion chamber (2) disposed at the outlet of said incinerator (1) and comprising an axial vertical refractory tube (5).  5. Device according to claim 4, characterized in that said injector (7) is disposed at the inlet of the fumes from said incinerator (1) in said post-combustion chamber (2).  6. Device according to claims 4 and 5, charac terized in that said injector (7) is directed substantially perpendicular to said refractory tube (5).