WO2013060991A1 - Method for making profitable use of industrial fumes containing acidic gases, to improve the energy performance of a boiler - Google Patents

Abstract

The invention relates to a method for making profitable use of industrial fumes (1), involving steps consisting in: -incinerating (10) waste (100) in a furnace (110) at an incineration temperature of between 600°C and 1100°C, producing industrial fumes (1) comprising acidic gases and dust, - performing a post‑combustion (20) of the fumes (1) in a post‑combustion zone (120) at a post‑combustion temperature, if the incineration temperature is below a threshold temperature, and - introducing (30) the fumes (1) into a boiler (150). It is essentially characterized in that it further comprises, upstream of the introduction into the boiler (150), steps consisting in: treating (40) the fumes (1) by injecting reagents (141) that at least partially neutralize the acidic gases, and - performing a catalytic filtration (50) of the treated fumes using a catalytic filter (131).

Description

 PROCESS FOR THE VALORIZATION OF INDUSTRIAL SMOKE COMPRISING ACIDIC GASES FOR THE IMPROVEMENT OF

 ENERGY PERFORMANCE OF A BOILER.

The present invention relates to the treatment of industrial fumes.

More specifically, the invention relates, according to a first of its objects, to an industrial fume recovery process comprising acid gases, comprising the steps of:

 - incinerating waste in an oven at an incineration temperature between 600 ° C and 1100 ° C, producing industrial fumes including acid gases and dust,

 - post-combustion of fumes in a post-combustion zone, at a post-combustion temperature, if the incineration temperature is lower than a threshold temperature, and

 - introduce the fumes into a boiler.

Such a process is known to those skilled in the art. However, the fumes at the inlet of the boiler are heavily loaded with pollutants, which in particular causes heat exchangers in the boiler at the same time:

 - corrosion due to acid gases and certain dusts, especially as the temperature is high, and

fouling due to some dust. Boilers used today in incineration typically operate at 450 ° C, 40 bar, and with a yield of about 22%. Thus, the production of energy by the boilers in the operating conditions current is limited because of the pressure losses due to fouling and corrosion that can pierce boiler piping. The present invention aims to overcome these disadvantages by providing a solution to reduce corrosion and fouling; which also makes it possible to substantially increase the energy performance of the boilers.

With this objective in view, the method according to the invention, moreover, in accordance with the preamble cited above, is essentially characterized in that it further comprises, upstream of the introduction into the boiler, steps consisting of:

 - treat the fumes by injecting at least partially neutralizing the acidic acid reactants between 600 ° C and 1100 ° C, and

 - Perform a catalytic filtration of fumes treated with a catalytic filter.

Preferably,

 if the incineration temperature is lower than the threshold temperature, the fumes do not undergo heating between the post-combustion step and the step of introducing said fumes into the boiler, and

 if the incineration temperature is higher than the threshold temperature, the fumes do not undergo heating between the incineration step and the step of introducing said fumes into the boiler.

In one embodiment, there is provided a step of creating a filter cake on the surface of the filter catalytic and a cyclic step of at least partial declogging of the filter.

In one embodiment, the step of treating the fumes consists of injecting limestone or lime as at least partially neutralizing the acidic acid at a temperature of between 600 ° C. and 1100 ° C. By 1100 ° C is meant the maximum temperature or sintering temperature of the reagent, that is to say the one at which it begins to sinter. By sintering is meant the passage from a powder compact to a coherent material under the action of heat.

In one embodiment, the filtration is performed by a catalytic metal filter at a temperature above 600 ° C.

According to another of its objects, the invention relates to an industrial smoke recovery system, capable of implementing the method according to the invention, and comprising

an oven for incinerating waste at an incineration temperature between 600 ° C and 1100 ° C, and producing industrial fumes including acid gases and dusts, and

 a boiler in which the fumes are introduced.

The system according to the invention is essentially characterized in that it further comprises upstream of the boiler:

 a device for injecting reagents at least partially neutralizing the acid gases, and

a catalytic filter for fumes. The catalytic filter makes it possible to prolong the neutralization reaction of organic pollutants and to filter the dust. In addition, the catalytic filter is used to at least partially oxidize persistent organic pollutants, hereinafter called "carbonaceous imbrulés".

 Preferably, the neutralizing reagents, injected in solid or liquid form, comprise products based on at least one of the following elements:

 alkali, alkaline earth, calcium oxide, hydrated lime, limestone, calcium, calcium carboxylic salts, clays, reducing organic compounds, aluminosilicates.

Preferably, the neutralizing reagents injected in solid form have a small particle size.

A small particle size makes it possible to increase the surface of contact of the reagent with the fumes and thus to increase the effectiveness of the reagent.

Advantageously, the injected reagent is limestone or lime.

In one embodiment, the catalytic filter comprises a porous metallic filter bag. In another embodiment, the porous filter bag comprises a ceramic material (for example cordierite, hoelite, or silicon carbide), or a composite material (for example fiberglass, or carbon fiber).

Preferably, the filter bag is doped with metal catalysts in post-sintering by grafting of transition metal. Preferably, the catalytic filter comprises a metallic material from an austenitic, ferritic, quasi-crystalline or intermetallic alloy. Advantageously, the material used for the construction of the filtering surface is FeCrAl.

Preferably, the filter bag has at least one of the following characteristics:

 a pore diameter of between 1 and 10 micrometers;

 a porosity of filter materials greater than 60%,

a specific surface greater than 1 m ² / g,

 a thickness of the order of 1 to 10 millimeters, and

a diameter of 50 to 200 millimeters.

In one embodiment, the filter bag comprises metal fibers having an apparent diameter of 0.1 to 100 micrometers and a length of 5 to 50 millimeters.

The high temperature resistant filter increases the residence time of the neutralizing reagents. It thus promotes the neutralization reactions of the acidic gases HC1 and SO2, and nitrogen oxides, in particular on the filter cake formed on the filter bags. It makes it possible to catalyze the reactions of hyper-oxidation (CO 2 conversion) of unburnt carbonaceous, potentially precursors of formation reactions of PCDD / F and PAH. It thus very significantly reduces the risk of reforming PCDD / F by Novo synthesis.

In one embodiment, the system further comprises an afterburner zone into which fumes from the furnace are introduced to post-burn to a post-combustion temperature above the incineration temperature if the incineration temperature is below a threshold temperature. The system comprises means for regulating the temperature of at least one oven. Thanks to the invention the flue gas temperature can only be regulated by the regulation of the oven temperature or the post ^¬ combustion zone.

Advantageously, the flue gas temperature is almost constant between the outlet of the post-combustion zone and the inlet of the boiler. That is, it is not necessary to heat and / or cool the fumes between the post-combustion zone and the boiler. It can be provided to regulate only the temperature of the oven.

Advantageously, the temperature of the fumes at the outlet of the furnace or of the post-combustion zone, in the catalytic filter, and at the inlet of the boiler is between 600 ° C. and 1100 ° C.

The higher temperature of the fumes at the inlet of the boiler allows a greater electrical efficiency thereof, because the presence of so-called "clean" fumes thanks to the catalytic filtration coupled with the treatment makes it possible to increase the vapor conditions (Temperature and Pressure ). In addition, the heat exchangers have a better performance and an improved life.

In one embodiment, the catalytic filter is disposed in an intermediate zone, and the system further comprises at least one of the following: a pipe for directly introducing the fumes from the furnace into the post-combustion zone;

 a pipe for introducing the fumes directly from the post-combustion zone into the intermediate zone; and a pipe for introducing the fumes directly from the intermediate zone into the boiler.

Thanks to the invention, the energy efficiency of a UVEOM installation is improved.

The integration of the reagent injection device and a filter makes it possible to obtain an integrated smoke treatment system that simultaneously makes it possible to:

 dust off the fumes at high temperature (for example 700 ° C - 900 ° C), between the furnace and the boiler,

 treat the acid gases at the same place, using them at the same temperatures, and

 treat the precursors for dioxin reformation upstream of the boiler (at a temperature above 450 ° C).

Thanks to these characteristics, it is possible to simultaneously reduce the fouling and corrosion of boilers and increase the life of the exchangers. This also reduces investment and operating costs by reducing maintenance costs.

Other characteristics and advantages of the present invention will emerge more clearly on reading the following description given by way of illustrative and nonlimiting example and with reference to the appended figures in which:

FIG. 1 illustrates an embodiment of the system according to the invention, FIG. 2 illustrates an embodiment of the injection of reagents according to the invention, and

 FIG. 3 illustrates an embodiment of the method according to the invention.

An industrial fume recovery system 1 is illustrated in FIG.

Waste 100 is introduced into a furnace 110 for an incineration step 10. The incineration of the waste produces fumes 1 which contain acid gases (SO 2, HCl) and dust.

The waste can be of any kind: garbage, sludge, grease, ordinary or dangerous industrial waste (from pharmacy, petrochemical, building, or Public Works); they may be organic and / or inorganic, in solid and / or liquid form (including pasty), and may for example be derived from energy recovery units of household waste (UVEOM).

The incineration temperature of the furnace 110 is between 600 ° C and 1100 ° C. It is adapted to the nature of the waste. For the sake of brevity, only domestic waste or sludge, whose incineration temperature is typically between 650 ° C. and 1100 ° C., will be mentioned here only.

If the incineration temperature is higher than a threshold temperature (for example 850 ° C), the temperature is sufficient to burn all or part of the organic compounds including dioxins, and it is not necessary to carry out a post- combustion. For example, the case hazardous waste for which the incineration temperature can reach about 1100 ° C.

If the incineration temperature is lower than a threshold temperature (for example 850 ° C), there may still be a level of organic compounds including unacceptable dioxins (see for example the European Directive 2000/76 / EC). There is then provided an afterburner step of heating the fumes to a post-combustion temperature for a predetermined time. For example for a post combustion ^¬ UVEOM is provided a temperature of post combustion ^¬ equal to 850 ° C for 2 seconds.

The implementation of a post-combustion stage depends on the type of waste and the incineration temperature.

In one embodiment, there is provided a post ^¬ combustion in a secondary combustion zone 120, which may be useful for example to household garbage or sludge.

The post-combustion zone 120 may be a zone of the furnace 110, which is the case in most current incinerators, or a separate chamber of the furnace 110 and into which the fumes are introduced.

The post-combustion temperature is higher than the incineration temperature. It is greater than or equal to the threshold temperature. Preferably, it is greater than 800 ° C and less than the sintering temperature of the reagents 141 described below, in this case 900 ° C to 1100 ° C. With or without post-combustion, there is provided a device 140 for injecting 40 reagents 141. The injection of reagents can be done:

 in the oven 110,

 at the interface between the furnace outlet and the inlet of the afterburner zone / chamber,

 - in the afterburner zone / chamber,

 at the interface between the exit of the zone / post-combustion chamber and the inlet of the boiler, or

- as shown in Figure 1 and Figure 2, in an area or an intermediate chamber 130, located between the inlet of the boiler 150 and the outlet of zone / post combustion chamber ^¬ 120 (when present) or the output of the oven 110 (when there is no afterburner zone).

Those skilled in the art will readily understand that the zone or intermediate chamber 130 may be confused with the post-combustion chamber or zone 120, itself integrated in a part of the furnace 110.

The injection of reagents 141 is preferably carried out at the outlet of the zone / post-combustion chamber 120 so as not to risk sintering the reagents, for example of the calcareous type.

Thus, the injection of reagents 141 is made at incineration temperature or post combustion temperature. In all cases, the injection of reagents is carried out upstream of the boiler. The reagents 141 are injected in solid or liquid form. It is not necessary to preheat them before they are injected.

The reagents 141 are capable of neutralizing the SO 2 / HCl or even NO 2 acid gases at reaction temperatures above 600 ° C., or even above 650 ° C., and below the sintering temperature of the reagents 141, in this case 1100 ° C.

The reagents 141 may comprise products based on alkalis (Li, Na, K, Rb, Cs, etc.), alkaline earth metals (Be, Mg, Ca, Sr, Ba, etc.). calcium oxide, hydrated lime (Ca (OH) 2), limestone, calcium carboxylic salts (acetate, formate, propionate), clays and / or reducing organic compounds of adsorbents recovered by processes Calcium water treatment.

The solid reagents 141 preferably have a small particle size, that is to say 10-100 micrometers of equivalent diameter.

It is intended to inject a set of at least one reagent. Preferably only one solid reagent is injected, in powder form. In one embodiment, the injected reagent is limestone. The CaC03 limestone is decarbonated in CaO lime which then reacts with the acidic gases HC1, SO2 through well-known chlorination and sulfation reactions. It is possible to inject lime directly. Organic compounds from carboxylic salts or ammonium salts ((NH4) 2SO4 in particular) react with NOX nitrogen oxides to reduce them to N2. Even after reaction with neutralizing reagents acid gases, fumes 1 always include dusts, aerosols of neutralizing reagents 141, and halogenated or non-halogenated carbon unburnt.

There is then provided a filtering step 50 of the fumes 1, between the zone / post-combustion chamber 120 and the inlet of the boiler 150, by a filter.

Advantageously, the filtration of the fumes and the neutralization of the acid gases by the injection of reagents take place almost simultaneously (at the transit time near) and at the same place (in the zone / intermediate chamber 130), therefore at close or identical temperatures. , which allows in particular a saving of space and a simplification of the stages of treatment of the fumes.

Advantageously, a single acid gas neutralization step by the injection of reactants upstream of the boiler can be implemented, that is to say that it is not mandatory to implement a second step of neutralization of acid gases by the injection of reagents downstream of the boiler. The filter may be disposed at the outlet of the post-combustion zone / chamber, possibly inside the oven.

When the zone / intermediate chamber 130 exists, the filter may be disposed outside this zone / intermediate chamber 130:

upstream, that is to say between the exit of the post-combustion zone 120 and the zone / intermediate chamber downstream, that is to say at the outlet of the zone / intermediate chamber 130.

 The filter may also be disposed within the zone / intermediate chamber 130.

Preferably, the filter is disposed downstream of the reagent injection device 141, which allows a synergy between the filter and the injected reagents by creating a filter cake, as described later.

The filter is a catalytic filter 131 that can be effective at temperatures between 600 ° C and 1100 ° C, and in particular between 650 ° C and 900 ° C. In this case the filter comprises porous catalytic metal filter sleeves.

The filter simultaneously exhibits catalytic properties for the reduction of persistent organic pollutants (POPs), and dust filtration properties, at filtration temperatures of 600 ° C-1100 ° C, which allows the increase in environmental performance of UVEOM.

The metallic materials are, for example, austenitic, ferritic, quasi-crystalline or intermetallic alloys. In particular, the steel grades can be NiCrFe, CrNiSi, CrNi, NiCrFeAl, FeCrAlY, FeCrAl, AlCuFe, AlCoNi, AlMoNi, Ni ₃ Al, Fe ₃ Al, Al ₁₂ W and Al ₁₂ Mo. For FeCrAl-type alloys and NiCrFeAl Al contents above 4% are preferred for producing an alumina anticorrosion pre-coating. Anglicism "pre-coating" is a layer of protection against corrosion. This layer of alumina contributes to the corrosion protection and forms a support for the filter cake. It ensures better mechanical and chemical resistance of the filter sleeve against the chemical attack of the pollutants contained in the fumes. Less than 0.5% boron additions can be made to improve corrosion performance as well as the thermal ductility of the alloys.

The above alloys have catalytic properties of oxidation reactions by the very presence of active compounds such as Ni, Cr, Co, Cu, Mo, Pt, Pd, V or W.

However, these catalytic properties can be enhanced by catalytic doping porous metal filter bags by catalysts. In the present case, catalytic doping of the fibers made by post-sintering by grafting of transition metals, for example noble metals (Pt, Pd, Rh, Mo, W, V) or non-metals (Cr, Cu, Ni), is provided. ), according to known techniques, for example the washcoating (anglicism of the skilled person in the field sol-gel) or the sol-gel impregnation followed by pre-oxidizing treatments or even sintering the fibers at temperatures of 400 ° C at 1000 ° C.

Heavy metals, mainly in the gas phase, are partly captured by preferred gas-particle conversions at the filter surface. Also, the filter has in its internal matrix catalytic sites favoring the hyper-oxidation reactions of unburned carbonaceous chlorinated or not, thus limiting any risk of reforming persistent organic pollutants such as dioxins, especially polychlorinated dibenzodioxins and dibenzofurans (PCDD / PCDF) and polycyclic aromatic hydrocarbons (PAHs).

The filter sleeve can be prepared by weaving followed by sintering. Preferably it is sintered from filler of metal fibers having an apparent diameter of 0.1 to 100 micrometers and a length of 5 to 50 millimeters. Sintering from metal powder having a particle size of between 0.1 and 10 microns is also possible. Two sintering modes can be provided: cold isostatic or hot rolled.

The pore diameter of the filter sleeve is preferably between 1 and 10 micrometers. Preferably, the filtering materials have a porosity greater than 60% (preferably between 70% and 90%), a specific surface area greater than 10 m 2 / g (preferentially 10 and 50 m 2 / g, a thickness in the range of 1 to 10 millimeters (preferably 4 to 5 mm) and a diameter ranging from 50 to 200 millimeters (preferably from 90 to 120 mm). Preferably, the filtration rate is high, ie from 2 to 4 cm / s for a pressure drop of the filter of the order of 150 to 220 mm CE.

Preferably, the chemical composition of the filter is adapted to the operating conditions, that is to say to the nature of the waste, which involves the incineration temperature and the nature of the pollutants, dusts and acid gases. During the filtration of the fumes 1, the unfiltered particles and dust agglutinate on the surface of the filter, which creates a filter cake 132, which participates for a certain time in the filtration itself. Beyond a certain thickness of the filter cake, or a "critical" pressure drop (that is to say greater than a threshold value), the pores are clogged and a declogging step is expected at less partial filter 131. For example, it is possible to provide a threshold value of 200mm Water column, that is 200mmCE. This value may vary depending on the operating conditions.

The filter cake once formed remains on the surface of the filter, despite the unclogging. Only the upper part goes, but a part glued to the filter remains. This remaining layer also participates in the performance of the filter. The sleeves can be unclogged by gas pulses comprising a neutral gas (for example compressed air or nitrogen) against the current and in line (with or without isolation of sleeves compartments). For example, the unclogging pressures are of the order of 2 to 5 bar, and the duration of the puices comprised between 20 and 80 milliseconds. The declogging process is cyclical. Preferably, a declogging instruction of the filter is set to the loss of charge values mentioned above.

On the filter cake 132, the neutralization reactions of the acid gases can continue with the residue of the reagents 141 not previously reacted via the increase of the contact time. It is thus possible to achieve a high degree of use of the reagents 141.

When the filter 131 is located in the intermediate zone 130, it is possible simultaneously to obtain the reduction of persistent organic pollutants, the dust filtration and the neutralization of the acid gases, at filtration temperatures of 600 ° C. to 1100 ° C. and in particular between 650 ° C and 900 ° C. In addition, the integration of the filter and the reagent injection device 140 reduces the volume of the entire system.

At the outlet of the boiler 150, a chimney is provided The recirculation devices present in the prior art aim to dilute the fumes and thus lower their temperature. Advantageously, the invention is free of flue gas recirculation device at the outlet of the boiler 150, which simplifies the system and avoids loss of charge and also makes it possible to obtain higher temperatures at the boiler inlet.

Thanks to the invention, since the flue gas filtration and the neutralization of the acid gases take place at the same place and at close or identical temperatures, this makes it possible to obtain flue gas temperatures at the boiler inlet 150 which are high, without however increase the risk of corrosion through neutralization, which increases the efficiency of the boiler.

Claims

 Process for the recovery of industrial fumes (1), comprising the steps of:  - incinerating (10) waste (100) in an oven (110) at an incineration temperature of between 600 ° C and 1100 ° C, producing industrial fumes (1) comprising acid gases and dusts,  - Post-combusting (20) the fumes (1) in an afterburner zone (120), at a post-combustion temperature, if the incineration temperature is below a threshold temperature, and  - introducing (30) the fumes (1) in a boiler (150), characterized in that it further comprises, upstream of the introduction into the boiler (150), the steps of:  - treating (40) the fumes (1) by injecting reagents (141) at least partially neutralizing the acid gases, at incineration or post-combustion temperature between 600 ° C and 1100 ° C, and  - Perform a catalytic filtration (50) of the fumes treated with a catalytic filter (131). The method of claim 1, wherein  if the incineration temperature is lower than the threshold temperature, the fumes (1) do not undergo heating between the post-combustion step (20) and the step of introducing (30) said fumes into the boiler ( 150), and if the incineration temperature is higher than the threshold temperature, the fumes (1) do not undergo heating between the incineration step (10) and the step of introducing (30) said fumes into the boiler (150). ). 3. Method according to claim 1 or 2, comprising a step (60) for creating a filter cake (132) on the surface of the catalytic filter (131) and a cyclic step of at least partial declogging of the filter (131). . 4. The method of claim 1 to 3, wherein the step of treatment (40) fumes (1) comprises injecting limestone or lime as a reagent (141) at least partially neutralizing the acid gas at a temperature between 600 ° C and 1100 ° C. 5. Industrial flue gas recovery system (1), capable of implementing the method according to any one of the preceding claims, and comprising:  - an oven (110) for incinerating waste (100) at an incineration temperature of between 600 ° C and 1100 ° C, and producing industrial fumes (1) comprising acid gases and dusts,  a boiler (150) in which the fumes (1) are introduced, and upstream of the boiler (150):  a device (140) for injecting reagents (141) at least partially neutralizing the acid gases, and a catalytic filter (131) for the fumes (1), characterized in that it further comprises  an intermediate zone or chamber (130) situated between the inlet of the boiler (150) and the outlet of the oven (110),  the catalytic filter (131) being arranged in the zone or intermediate chamber (130),  the reagent injection device (140) being configured so that the injection of reagents (141) can take place o in the oven (110) or in the zone or intermediate chamber (130). 6. System according to claim 5, in which the neutralizing reagents (141), injected in solid or liquid form, comprise products based on at least one of the following elements:  alkali, alkaline earth, calcium oxide, hydrated lime, limestone, calcium, calcium carboxylic salts, clays, reducing organic compounds, aluminosilicates. 7. System according to any one of claims 5 or 6, in which the neutralizing reagents (141) injected in solid form have a small particle size. 8. System according to any one of claims 5 to 7, wherein the catalytic filter (131) comprises:  a porous metallic filtering sleeve comprising a metallic material from an austenitic, ferritic, quasi-crystalline or intermetallic alloy,  a porous composite filtering sleeve comprising a composite material, or  a porous ceramic filtering sleeve comprising a ceramic material. The system of claim 8, wherein the filter bag is doped with metal catalysts. The system of claim 9, wherein the filter bag is doped with metal catalysts in post-sintering by transition metal grafting. 11. System according to any one of claims 8 to 10, wherein the filter bag has at least one of the following features:  a pore diameter of between 1 and 10 micrometers;  a porosity of filter materials greater than 60%, a specific surface greater than 1 m ² / g,  a thickness of the order of 1 to 10 millimeters, and a diameter of 50 to 200 millimeters. 12. System according to any one of claims 8 to 11, wherein the filter bag comprises metal fibers having an apparent diameter of 0.1 to 100 micrometers and a length of 5 to 50 millimeters. 13. System according to any one of claims 5 to 12, further comprising a post-combustion zone (120) wherein are introduced the fumes (1) of the furnace (110) for performing post-combustion at a temperature of post ^¬ higher combustion temperature incineration if the Incineration temperature is below a threshold temperature. The system of any one of claims 5 to 13, wherein the injected reagent (141) is limestone or lime, and wherein the catalytic filter (131) comprises an alloy of FeCrAl, NiCrFe, CrNiSi, CrNi , NiCrFeAl, FeCrAlY, AlCuFe, AlCoNi, AlMoNi, Ni3Al, Fe3Al, A112W or A112Mo.