WO1998025690A1 - Method of reducing the concentration of pcdd and/or pcdf in waste gases - Google Patents

Method of reducing the concentration of pcdd and/or pcdf in waste gases Download PDF

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Publication number
WO1998025690A1
WO1998025690A1 PCT/EP1997/005066 EP9705066W WO9825690A1 WO 1998025690 A1 WO1998025690 A1 WO 1998025690A1 EP 9705066 W EP9705066 W EP 9705066W WO 9825690 A1 WO9825690 A1 WO 9825690A1
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pcdd
pcdf
exhaust gas
concentration
reduced
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PCT/EP1997/005066
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German (de)
French (fr)
Inventor
Klaus Kersting
Wolfgang Kowalski
Rüdiger WEMHÖNER
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Thyssen Stahl Ag
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Publication of WO1998025690A1 publication Critical patent/WO1998025690A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
    • B03C3/01—Pretreatment of the gases prior to electrostatic precipitation
    • B03C3/011—Prefiltering; Flow controlling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8659—Removing halogens or halogen compounds
    • B01D53/8662—Organic halogen compounds

Definitions

  • the invention relates to a method for reducing the concentration of PCDD and PCDF (poly . Chlorinated dibenzo dioxins and poly chlorinated dibenzo furans) in the exhaust gas stream of a sintering plant, in particular iron ore sintering plant.
  • PCDD poly . Chlorinated dibenzo dioxins and poly chlorinated dibenzo furans
  • the aim is to economically comply with the legally prescribed (17th BImSchV) low dioxin and / or furan limit of 0.1 ng TE / Nm 3 exhaust gas.
  • TE toxic equivalents is the defined unit of measure, which makes the different toxic PCDD and PCDF isomers comparable in terms of toxicity
  • Nm 3 cubic meters of exhaust gas in the thermodynamic standard state).
  • DE 44 29 027 AI discloses a process for the adsorptive deposition of polycyclic and polyhalogenated hydrocarbons, in particular of dioxins and furans, from the flowing exhaust gas of a sintering process.
  • a large number of usable adsorbents are mentioned, such as finely powdered zeolites, finely powdered activated aluminum oxide, silica gel, diatomaceous earth, activated carbon, clay, layered silicates, diatomaceous earth or mixtures thereof in a gas-solid suspension.
  • the device disclosed in DE 44 29 027 AI for carrying out the entrained flow adsorption process comprises:
  • the solid deposited in the electrostatic filter is returned to the sintering process so that the PCDD and PCDF bound to the adsorbents are effectively thermally destroyed at the high process temperatures of the sintering process.
  • a reaction time dependent on the adsorbent concentration must be available. If the reaction time is to be shortened, the adsorption surface or the adsorbent concentration must be increased. At least in the case of flammable, in particular carbon-containing, adsorbents, such as activated carbon or hearth coke made of brown coal, the adsorbent concentration quickly reaches safety-related limits because of the risk of combustion or explosion in the electrostatic filter.
  • the maximum permissible concentration in the exhaust gas flow is relatively low (for hearth furnace coke, for example, it is approximately 300 mg / m 3 exhaust gas), the available adsorption surface may not be large enough to meet the limit value of 0.1 ng TE / Nm 3 exhaust gas must be observed.
  • the exhaust gas temperature behind the electrostatic precipitator is only around 130 ° C. Therefore, with an initial concentration in the untreated sintered exhaust gas of 3-4 ng TE / Nm 3 exhaust gas, depletion below the limit value of 0.1 ng TE / Nm 3 exhaust gas can only be achieved if the dwell time in the catalytic converter is very long. However, this would require a very large length and correspondingly large volume of the catalyst. The high specific catalyst costs would very quickly render the process inefficient. Heating the sintered exhaust gas to increase the catalyst temperature and the associated increase in the specific degradation capacity of the catalyst is also out of the question for economic reasons. Even small increases in process costs make the sintering process, which is characterized by low added value, uneconomical.
  • the invention is based on the object of specifying an exhaust gas purification method for reducing the PCCD and PCDF concentration in the exhaust gas of a sintering plant which, with minimal investment and operating costs, reliably falls below the legal PCDD and PCDF limit value of 0.1 ng TE / Nm 3 ensures exhaust gas at all times.
  • the PCDD and PCDF concentration of the pre-cleaned exhaust gas is reduced to a value below the legally prescribed limit value by catalytic conversion.
  • the initial PCDD / PCDF concentration in the exhaust gas can be reduced to 1/5 to 1/20, in particular to about 1/10, using the entrained flow adsorption process.
  • the resultant in the first step dioxi 'n- and / or furanbeladene adsorbent can be deposited in an electrostatic precipitator and recycled into the sintering process, for example.
  • the reduction of the PCDD and PCDF initial concentration in the exhaust gas from generally about 3 to 4 ng TE / Nm 3 exhaust gas preferably to about 1/10, that is to 0.3 to 0.4 ng TE / Nm 3 exhaust gas in the first Stage can be realized on an entrained-flow reactor length of less than 20 m.
  • the adsorption stage can be retrofitted in existing plants due to the small space requirement.
  • the first stage there are no restrictions with regard to the adsorbent to be used. Even when using, for example, flammable adsorbents, such as hearth coke made of brown coal, the PCDD and PCDF depletion intended in the first stage must be adhered to safely.
  • the PCDD and PCDF adsorbed on the adsorbent are preferably circulated within the sintering plant so that they do not leave the plant.
  • the PCDD and PCDF bound to the adsorbent are returned to the sintering belt and thermally decomposed there at temperatures above 1,000 ° C.
  • the adsorbed PCDD / PCDF can also be converted in a separate unit.
  • the separation of the solids, including adsorbent, in the electrostatic filter is so thorough that an additional filter, such as a fabric filter, does not have to be connected upstream or downstream of the electrostatic filter. This saves investment costs and operating costs in avoiding an additional pressure loss.
  • the exhaust gas line can be designed as an entrained flow reactor in which the adsorbent is injected upstream into the exhaust gas stream via nozzles, for example at an angle of 45 °. This makes the adsorbent good with the exhaust gas mixed and evenly distributed over the flow cross-section (homogeneous exhaust gas adsorbent suspension).
  • Inexpensive carbon-containing adsorbents the concentration of which in the exhaust gas must not exceed certain adsorbent-specific maximum concentrations for safety reasons, can also provide the required adsorption capacity in the first stage.
  • Fig. 1 shows a flow diagram of the method
  • a fine ore fuel mixture is agglomerated to sinter on a sintering belt.
  • the in this sintering process e.g. Iron ore sintering and waste gases flow through an adsorber in which adsorbents are loaded with PCDD and PCDF.
  • the adsorbents loaded with PCDD and PCDF are then separated in an electrostatic precipitator and returned to the sintering belt for thermal conversion via a return line.
  • the pre-cleaned exhaust gas flows from the electrostatic precipitator into a subsequent area in which the PCDD and PCDF concentration is reduced to a value below the legal limit by catalytic conversion.
  • this area can be equipped with any known catalysts.
  • powdered material is converted into a material via a sintering belt 1.
  • Sintering furnace 2 transport.
  • the exhaust gases discharged under the sintering belt 2 are collected in an exhaust pipe 3.
  • adsorbent is mixed with the exhaust gas via a metering station 5 with measurement and control technology through a blowing device 4.
  • the reaction section 7 the adsorbent with the. PCDD and PCDF loaded from the exhaust gas, in the following.
  • Electrofilter 9 separated from the pre-cleaned exhaust gas and returned to the sintering bath 2 via the return line 8.
  • the waste gas pre-cleaned in the electrostatic filter 9 is optionally heated to a higher temperature in a combustion chamber 11 by means of a blower 10 and is cleaned in the downstream oxidation catalytic converter 12 to a value below the legally prescribed PCDD and PCDF concentration.
  • the cleaned exhaust gas can then be passed outside via the chimney 13.

Abstract

The invention concerns a method of reducing the concentration of PCDD and PCDF (polychlorinated dibenzodioxins and polychlorinated dibenzofurans) in the flow of waste gases from a sintering plant, in particular an iron-ore sintering plant. The invention is characterized in that the initial PCDD/PCDF concentration in the waste gas is reduced adsorptively, preferably to approximately 1/10, and the PCDD/PCDF concentration of the pre-purified waste gas is then reduced by catalytic conversion to a value below the legal limit. The dioxin- and/or furan-charged adsorbent can be separated in an electrostatic filter and fed back to the sintering process.

Description

Verfahren zur Verringerung der PCDD- und/oder PCDF- onzentration in AbgasenProcess for reducing the PCDD and / or PCDF concentration in exhaust gases
Die Erfindung betrifft ein Verfahren zur Verringerung der Konzentration von PCDD- und PCDF- (Poly .chlorierte Dibenzo Dioxine und Poly chlorierte Dibenzo Furane) im Abgasstrom einer Sinteranlage, insbesondere Eisenerz- Sinteranlage. Das Ziel ist, den gesetzlich vorgeschriebenen (17. BImSchV) niedrigen Dioxin- und/oder Furan-Grenz ert von 0 , 1 ng TE/Nm3 Abgas auf wirtschaftliche Weise einzuhalten. (TE = toxic equivalents ist die definierte Maßeinheit, v/elche die unterschiedlich toxischen PCDD- und PCDF-Isomere bzgl . der Toxizität miteinander vergleichbar macht; Nm3 = Kubikmeter Abgas im thermodynamischen Normzustand) .The invention relates to a method for reducing the concentration of PCDD and PCDF (poly . Chlorinated dibenzo dioxins and poly chlorinated dibenzo furans) in the exhaust gas stream of a sintering plant, in particular iron ore sintering plant. The aim is to economically comply with the legally prescribed (17th BImSchV) low dioxin and / or furan limit of 0.1 ng TE / Nm 3 exhaust gas. (TE = toxic equivalents is the defined unit of measure, which makes the different toxic PCDD and PCDF isomers comparable in terms of toxicity; Nm 3 = cubic meters of exhaust gas in the thermodynamic standard state).
Aus der DE 44 29 027 AI ist ein Verfahren zur adsorptiven Abscheidung von polycyclischen und polyhalogenierten Kohlenwassersto fen, insbesondere von Dioxinen und Furanen, aus dem strömenden Abgas eines Sinterprozesses bekannt. Es v/erden eine Vielzahl verwendbarer Adsorbentien genannt, wie feinpulvrige Zeolithe, feinpulvriges aktiviertes Aluminiumoxid, Kieselgel, Kieselgur, Aktivkohle, Ton, Schichtεilikate, Diatomeenerde oder Mischungen davon in einer Gas- Feststoff-Suspension.DE 44 29 027 AI discloses a process for the adsorptive deposition of polycyclic and polyhalogenated hydrocarbons, in particular of dioxins and furans, from the flowing exhaust gas of a sintering process. A large number of usable adsorbents are mentioned, such as finely powdered zeolites, finely powdered activated aluminum oxide, silica gel, diatomaceous earth, activated carbon, clay, layered silicates, diatomaceous earth or mixtures thereof in a gas-solid suspension.
Die in der DE 44 29 027 AI offenbarte Vorrichtung zur Durchführung des Flugstromadsorptionsverfahrens umfaßt:The device disclosed in DE 44 29 027 AI for carrying out the entrained flow adsorption process comprises:
eine als Flugstromreaktor gestaltete Abgasleitung einen dieser nachgeschalteten Elektrofilter und eine Feststoff-Rückführvorrichtung für den im Elektrofilter abgeschiedenen Feststoff.an exhaust pipe designed as entrained flow reactor one of these downstream electrostatic precipitators and a solids return device for the solids separated in the electrostatic precipitator.
Der im Elektrofilter abgeschiedene Feststoff wird in den Sinterprozeß zurückgeführt, damit die auf den Adsorbentien gebundenen PCDD und PCDF bei den hohen Prozeßtemperaturen des Sintervorgangs wirkungsvoll thermisch zerstört werden.The solid deposited in the electrostatic filter is returned to the sintering process so that the PCDD and PCDF bound to the adsorbents are effectively thermally destroyed at the high process temperatures of the sintering process.
Um mit dem Flugstromadsorptionsver ahren den PCDD- bzw. PCDF-Grenzwert von 0 , 1 ng TE/Nm3 Abgas einhalten zu können, muß eine von der Adsorbenskonzentration abhängige Reaktionszeit zur Verfügung stehen. Soll die Reaktionszeit verkürzt werden, muß die Adsorptions- Oberfläche bzw. die Adsorbens-Konzentration, erhöht werden. Zumindest bei brennbaren, insbesondere kohlenstoffhaltigen Adsorbentien, wie Aktivkohle oder Herdofenkoks aus Braunkohle, stößt die Adsorbenskonzentration aber wegen der Gefahr der Verbrennung oder Explosion im Elektrofilter sehr schnell an sicherheitstechnische Grenzen. Bei Verwendung solcher Adsorbentien, deren maximal zulässige Konzentration im Abgasstrom relativ niedrig ist (bei Herdofenkoks liegt sie z.B. bei ca. 300 mg/m3 Abgas), kann die zur Verfügung stehende Adsorptionsoberfläche u.U. nicht ausreichend groß sein, um den Grenzwert von 0 , 1 ng TE/Nm3 Abgas sicher einzuhalten. Auch einer Verlängerung der Adsorptionszeit durch die Vergrößerung der aktiven Länge des Flugstromreaktors bzw. durch eine anderweitige Vergrößerung des Reaktorvolumens sind technische und wirtschaftliche Grenzen gesetzt.In order to be able to comply with the PCDD or PCDF limit value of 0.1 ng TE / Nm 3 exhaust gas with the entrained flow adsorption process, a reaction time dependent on the adsorbent concentration must be available. If the reaction time is to be shortened, the adsorption surface or the adsorbent concentration must be increased. At least in the case of flammable, in particular carbon-containing, adsorbents, such as activated carbon or hearth coke made of brown coal, the adsorbent concentration quickly reaches safety-related limits because of the risk of combustion or explosion in the electrostatic filter. When using such adsorbents, the maximum permissible concentration in the exhaust gas flow is relatively low (for hearth furnace coke, for example, it is approximately 300 mg / m 3 exhaust gas), the available adsorption surface may not be large enough to meet the limit value of 0.1 ng TE / Nm 3 exhaust gas must be observed. There are also technical and economic limits to extending the adsorption time by increasing the active length of the entrained-flow reactor or by increasing the reactor volume in some other way.
Somit stellt sich das technische Problem, daß bei Vorliegen bestimmter technischer Voraussetzungen, z.B. einer zu geringen realisierbaren Maximallänge des Flugstromreaktors oder einer zu niedrigen Maximalkonzentration des Adsorbens, mit dem Flugstromadsorptionsverfahren der gesetzliche Grenzwert für PCCD und PCDF nicht eingehalten werden kann.The technical problem thus arises that if certain technical requirements are met, for example a maximum length of the entrained-flow reactor that is too short or too short Maximum concentration of the adsorbent with which entrained-flow adsorption cannot meet the legal limit for PCCD and PCDF.
In der DE 36 23 492 AI ist der katalytische Abbau halogenierter Aromaten, zu denen auch PCDD und PCDF gehören, in Anwesenheit eines Metalls, Metalloxids, Metallcarbonats, Silikats oder eines Gemisches davon in einem Temperaturbereich von 100 bis 800 °C beschrieben. Bei kurzen Verweilzeiten der Schadstoffe im Bereich der Katalysatoren werden aber wesentlich höhere Temperaturen erforderlich, die im Abgasstrom einer Sinteranlage hinter dem Elektrofilter nicht vorliegen. Untersuchungen an Sinteranlagen haben ergeben, daß ein beträchtlicher Teil der PCDD- und PCDF-Konzentration nicht an im Abgas vorhandenem Feststoff, der nicht Adsorbens ist, gebunden ist, sondern gasförmig vorliegt. Dieser Teil verweilt nur eine relativ kurze Zeit für den katalytischen Abbau der PCDD und PCDF im Reaktor. Zudem liegt die Abgastemperatur hinter dem Elektrofilter nur bei ca. 130 °C. Daher läßt sich bei einer Anfangskonzentration im unbehandelten Sinterabgas von 3 - 4 ng TE/Nm3 Abgas eine Abreicherung unter den Grenzwert von 0 , 1 ng TE/Nm3 Abgas nur dann realisieren, wenn die Verweilzeit im Katalysator sehr groß ist . Dies würde aber eine sehr große Baulänge und entsprechend großes Bauvolumen des Katalysators erfordern. Die hohen spezifischen Katalysatorkosten würden das Verfahren sehr schnell unwirtschaf lich machen. Auch ein Aufheizen des Sinterabgases zur Erhöhung der Katalysatortemperatur und damit einhergehender Steigerung der spezifischen Abbauleistung des Katalysators kommt aus wirtschaftlichen Gründen nicht in Betracht. Schon geringe Steigerungen der Prozeßkosten machen den durch eine niedrige Wertschöpfung gekennzeichneten Sinterprozeß unwirtschaftlich. Der Erfindung liegt nun die Aufgabe zugrunde, ein Abgasreinigungsverfahren zum Abbau der PCCD- und PCDF- Konzentration im Abgas einer Sinteranlage anzugeben, welches bei minimalen Investitions- und Betriebskosten eine sichere Unterschreitung des gesetzlichen PCDD- und PCDF-Grenzwertes von 0 , 1 ng TE/Nm3 Abgas jederzeit sicherstellt .DE 36 23 492 AI describes the catalytic decomposition of halogenated aromatics, which also include PCDD and PCDF, in the presence of a metal, metal oxide, metal carbonate, silicate or a mixture thereof in a temperature range from 100 to 800 ° C. With short dwell times of the pollutants in the area of the catalysts, however, significantly higher temperatures are required which are not present in the exhaust gas stream of a sintering plant behind the electrostatic precipitator. Studies on sintering plants have shown that a considerable part of the PCDD and PCDF concentration is not bound to the solid present in the exhaust gas, which is not adsorbent, but is instead in gaseous form. This part only remains for a relatively short time for the catalytic degradation of the PCDD and PCDF in the reactor. In addition, the exhaust gas temperature behind the electrostatic precipitator is only around 130 ° C. Therefore, with an initial concentration in the untreated sintered exhaust gas of 3-4 ng TE / Nm 3 exhaust gas, depletion below the limit value of 0.1 ng TE / Nm 3 exhaust gas can only be achieved if the dwell time in the catalytic converter is very long. However, this would require a very large length and correspondingly large volume of the catalyst. The high specific catalyst costs would very quickly render the process inefficient. Heating the sintered exhaust gas to increase the catalyst temperature and the associated increase in the specific degradation capacity of the catalyst is also out of the question for economic reasons. Even small increases in process costs make the sintering process, which is characterized by low added value, uneconomical. The invention is based on the object of specifying an exhaust gas purification method for reducing the PCCD and PCDF concentration in the exhaust gas of a sintering plant which, with minimal investment and operating costs, reliably falls below the legal PCDD and PCDF limit value of 0.1 ng TE / Nm 3 ensures exhaust gas at all times.
Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daßThis object is achieved in that
a) in einem ersten Verfahrensschritt die PCDD-/PCDF- Anfangskonzentration im Abgas adsorptiv verringert wird unda) in a first process step the PCDD / PCDF initial concentration in the exhaust gas is reduced by adsorption and
b) in einem zweiten Verfahrensschritt die PCDD- und PCDF-Konzentration des vorgereinigten Abgases auf einen unter dem gesetzlich vorgegebenen Grenzwert liegenden Wert durch katalytische Umsetzung gesenkt wird .b) in a second process step, the PCDD and PCDF concentration of the pre-cleaned exhaust gas is reduced to a value below the legally prescribed limit value by catalytic conversion.
Die PCDD- /PCDF-Anfangskonzentration im Abgas kann mit Hilfe des Flugstrom-Adsorptionsverfahrens auf 1/5 bis 1/20, insbesondere auf etwa 1/10 abgebaut werden.The initial PCDD / PCDF concentration in the exhaust gas can be reduced to 1/5 to 1/20, in particular to about 1/10, using the entrained flow adsorption process.
Das im ersten Verfahrensschritt entstehende dioxi'n- und/oder furanbeladene Adsorbens kann z.B. in einem Elektrofilter abgeschieden und in den Sinterprozeß zurückgeführt werden.The resultant in the first step dioxi 'n- and / or furanbeladene adsorbent can be deposited in an electrostatic precipitator and recycled into the sintering process, for example.
Die Verringerung der PCDD- und PCDF- Anfangskonzentration im Abgas von in der Regel etwa 3 bis 4 ng TE/Nm3 Abgas bevorzugt auf etwa 1/10, also auf 0,3 bis 0,4 ng TE/Nm3 Abgas in der ersten Stufe kann auf einer Flugstromreaktorlänge von unter 20 m realisiert werden. So kann die Adsorptionsstufe aufgrund des geringen Platzbedarfs in bestehenden Anlagen nachgerüstet werden. Ferner bestehen in der ersten Stufe keine Beschränkungen hinsichtlich des einzusetzenden Adsorbens. Auch bei Verwendung z.B. von brennbaren Adsorbentien, wie Herdofenkoks aus Braunkohle, ist die in der ersten Stufe beabsichtigte PCDD- und PCDF-Abreicherung sicher einzuhalten .The reduction of the PCDD and PCDF initial concentration in the exhaust gas from generally about 3 to 4 ng TE / Nm 3 exhaust gas preferably to about 1/10, that is to 0.3 to 0.4 ng TE / Nm 3 exhaust gas in the first Stage can be realized on an entrained-flow reactor length of less than 20 m. The adsorption stage can be retrofitted in existing plants due to the small space requirement. Furthermore, in the first stage there are no restrictions with regard to the adsorbent to be used. Even when using, for example, flammable adsorbents, such as hearth coke made of brown coal, the PCDD and PCDF depletion intended in the first stage must be adhered to safely.
Die auf dem Adsorbens adsorbierten PCDD und PCDF werden vorzugsweise innerhalb der Sinteranlage im Kreislauf geführt, so daß diese die Anlage nicht verlassen. Das an das Adsorbens gebundene PCDD und PCDF wird auf das Sinterband zurückgeführt und dort bei Temperaturen oberhalb 1.000 °C thermisch zersetzt. Alternativ zur Rückführung kann das adsorbierte PCDD/PCDF auch in einem separaten Aggregat umgewandelt werden.The PCDD and PCDF adsorbed on the adsorbent are preferably circulated within the sintering plant so that they do not leave the plant. The PCDD and PCDF bound to the adsorbent are returned to the sintering belt and thermally decomposed there at temperatures above 1,000 ° C. As an alternative to recycling, the adsorbed PCDD / PCDF can also be converted in a separate unit.
Die Abscheidung der Feststoffe, inklusive Adsorbens, im Elektrofilter ist so gründlich, daß ein zusätzlicher Filter, wie etwa ein Gewebefilter, dem Elektrofilter nicht vor- oder nachgeschaltet werden muß. Dadurch werden Investitionskosten und Betriebskosten in Vermeidung eines zusätzlichen Druckverlustes gespart.The separation of the solids, including adsorbent, in the electrostatic filter is so thorough that an additional filter, such as a fabric filter, does not have to be connected upstream or downstream of the electrostatic filter. This saves investment costs and operating costs in avoiding an additional pressure loss.
Aufgrund der niedrigen Eintrittskonzentration an PCDD/PCDF in die Katalysatorstrecke der zweiten Stufe kann die benötigte Katalysatormaεse gering gehalten werden. Durch eine der Katalysatorstufe vorgeschaltete Abgasaufheizung kann aufgrund der höheren Betriebstemperaturen eine verbesserte spezifische Abbauleistung erreicht werden.Due to the low entry concentration of PCDD / PCDF in the catalyst section of the second stage, the required catalyst mass can be kept low. By means of an exhaust gas heating upstream of the catalyst stage, an improved specific degradation performance can be achieved due to the higher operating temperatures.
Die Abgasleitung kann als Flugstromreaktor gestaltet sein, in dem das Adsorbens über Düsen, z.B. unter einem Winkel von 45 ° stromaufwärts in den Abgasstrom eingedüst wird. Dadurch wird das Adsorbens gut mit dem Abgas gemischt und gleichmäßig über den Strömungsquerschnitt verteilt (homogene Abgas-Adsorbens-Suspenεion) .The exhaust gas line can be designed as an entrained flow reactor in which the adsorbent is injected upstream into the exhaust gas stream via nozzles, for example at an angle of 45 °. This makes the adsorbent good with the exhaust gas mixed and evenly distributed over the flow cross-section (homogeneous exhaust gas adsorbent suspension).
Für die PCDD- /PCDF-Abreicherung in der ersten Stufe können alle für diese Anwendung geeigneten bekannten Adsorbentien eingesetzt werden.All known adsorbents suitable for this application can be used for the PCDD / PCDF depletion in the first stage.
Auch preiswerte kohlenstoffhaltige Adsorbentien, deren Konzentration im Abgas bestimmte adsorbensspezifische Maximalkonzentrationen aus sicherheitstechnischen Gründen nicht überschreiten darf, können die erforderliche Adsorptionsleistung in der ersten Stufe erbringen.Inexpensive carbon-containing adsorbents, the concentration of which in the exhaust gas must not exceed certain adsorbent-specific maximum concentrations for safety reasons, can also provide the required adsorption capacity in the first stage.
In der zweiten Stufe können ebenfalls alle bekannten Katalysatoren/Katalysatortypen eingesetzt v/erden. Allerdings sind solche Katalysatoren zu bevorzugen, die im Temperaturbereich zwischen 100 und 150 °C die größte spezifische Abbauleistung aufweisen, da in Sinteranlagen die Abgastemperatur hinter dem Elektroabscheider in diesem Temperaturbereich liegt. Bezüglich der Bauart des Katalysators bestehen keine Einschränkungen. Eine katalytische Anlage zur Dioxin-Minderung haben B. Frings und K. Werner in "Katalytische Dioxin- Minderung" BWK/TÜ/Umwelt-Special, März 1994 beschrieben.All known catalysts / catalyst types can also be used in the second stage. However, preference should be given to those catalysts which have the greatest specific degradation capacity in the temperature range between 100 and 150 ° C., since in sintering plants the exhaust gas temperature behind the electrostatic precipitator lies in this temperature range. There are no restrictions on the type of catalyst. B. Frings and K. Werner described a catalytic plant for dioxin reduction in "Catalytic Dioxin Reduction" BWK / TÜ / Umwelt-Special, March 1994.
Anhand der Zeichnung wird die Erfindung näher erläutert.The invention is explained in more detail with reference to the drawing.
Fig. 1 zeigt ein Fließschema des erfindungsgemäßen Verfahrens undFig. 1 shows a flow diagram of the method and
Fig. 2 eine zur Ausführung des erfindungsgemäßenFig. 2 one for executing the invention
Verfahrens geeignete Anlage in schematischer Darstellung.Process suitable plant in a schematic representation.
Auf einem Sinterband wird ein Feinerz-Brennstoffgemisch zu Sinter agglomeriert. Die bei diesem Sinterprozeß, z.B. Eisenerz-Sintern, anfallenden Abgase durchströmen einen Adsorber, in dem Adsorbentien mit PCDD und PCDF beladen werden. Anschließend werden die mit PCDD und PCDF beladenen Adsorbentien in einem Elektrofilter abgeschieden und über eine Rückführleitung dem Sinterband zur thermischen Umsetzung zurückgeführt. Das vorgereinigte Abgas strömt aus dem Elektrofilter in einen nachfolgenden Bereich, in dem die PCDD- und PCDF- Konzentration durch katalytische Umsetzung auf einen unter dem gesetzlichen Grenzwert liegenden Wert verringert wird. Dazu kann dieser Bereich mi beliebigen bekannten Katalysatoren bestückt sein.A fine ore fuel mixture is agglomerated to sinter on a sintering belt. The in this sintering process, e.g. Iron ore sintering and waste gases flow through an adsorber in which adsorbents are loaded with PCDD and PCDF. The adsorbents loaded with PCDD and PCDF are then separated in an electrostatic precipitator and returned to the sintering belt for thermal conversion via a return line. The pre-cleaned exhaust gas flows from the electrostatic precipitator into a subsequent area in which the PCDD and PCDF concentration is reduced to a value below the legal limit by catalytic conversion. For this purpose, this area can be equipped with any known catalysts.
Bei der in Fig. 2 dargestellten Anlage wird über ein Sinterband 1 pulverförmiges Material zu einer. Sinterofen 2 transportier . Die unter dem Sinterband 2 abgeführten Abgase werden in einer Abgasleitung 3 gesammelt. Aus einem Vorratssilo 6 wird Adsorbens über eine Dosierεtation 5 mit Meß- und Regeltechnik durch eine Einblasvorrichtung 4 mit dem Abgas gemischt . In der Reaktionsstrecke 7 wird das Adsorbens mit der. PCDD und PCDF aus dem Abgas beladen, im nachfolgender. Elektrofilter 9 aus dem vorgereinigten Abgas abgeschieden und über die Rückführleitung 8 dem Sinterbaπd 2 zurückgeführt .In the system shown in FIG. 2, powdered material is converted into a material via a sintering belt 1. Sintering furnace 2 transport. The exhaust gases discharged under the sintering belt 2 are collected in an exhaust pipe 3. From a storage silo 6, adsorbent is mixed with the exhaust gas via a metering station 5 with measurement and control technology through a blowing device 4. In the reaction section 7, the adsorbent with the. PCDD and PCDF loaded from the exhaust gas, in the following. Electrofilter 9 separated from the pre-cleaned exhaust gas and returned to the sintering bath 2 via the return line 8.
Das im Elektrofilter 9 vorgereinigte Abgaε wird mittels Gebläses 10 optional in einer Brennkammer 11 auf höhere Temperatur erhitzt und im nachgeschalteten Oxidationskatalysator 12 auf einen unterhalb der gesetzlich vorgeschriebenen PCDD- und PCDF-Kor.zentration liegenden Wert gereinigt. Das gereinigte Abgas kann dann über den Kamin 13 ins Freie geleitet werden. The waste gas pre-cleaned in the electrostatic filter 9 is optionally heated to a higher temperature in a combustion chamber 11 by means of a blower 10 and is cleaned in the downstream oxidation catalytic converter 12 to a value below the legally prescribed PCDD and PCDF concentration. The cleaned exhaust gas can then be passed outside via the chimney 13.

Claims

Patentansprüche claims
1. Verfahren zur Verringerung der Konzentration von PCDD und PCDF (Poly .chlorierte Dibenzo Dioxine und Poly .chlorierte Dibenzo Furane) im Abgasstrom einer Sinteranlage, insbesondere Eisenerz-Sinteranlage, d a d u r c h g e k e n n z e i c h n e t, daß1. A method for reducing the concentration of PCDD and PCDF (poly . Chlorinated dibenzo dioxins and poly . Chlorinated dibenzo furans) in the exhaust gas stream of a sintering plant, in particular iron ore sintering plant, characterized in that
a) in einem ersten Verfahrensschritt die PCDD-/PCDF- Anfangεkonzentration im Abgaε adεorptiv verringert wird unda) in a first process step, the initial PCDD / PCDF concentration in the exhaust is reduced adεorptively and
b) in einem zweiten Verfahrensschritt die PCDD- und PCDF-Konzentration des vorgereinigten Abgases auf einen unter dem gesetzlich vorgegebenen Grenzwert liegenden Wert durch katalytische Umsetzung gesenkt wird .b) in a second process step, the PCDD and PCDF concentration of the pre-cleaned exhaust gas is reduced to a value below the legally prescribed limit value by catalytic conversion.
2. Verfahren nach Anspruch 1, d a d u r c h g e k e n n z e i c h n e t, daß in der ersten Verfahrensεtufe die PCDD-/PCDF- Anfangskonzentration im Abgaε mit Hilfe deε Flugstrom-Adsorptionsverfahrens auf 1/5 bis 1/20 verringert wird.2. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that the PCDD / PCDF initial concentration is reduced in the waste gas with the help of the entrained flow adsorption process to 1/5 to 1/20 in the first process step.
3. Verfahren nach Anspruch 2, d a d u r c h g e k e n n z e i c h n e t, daß in der ersten Verfahrensstufe die PCDD-/PCDF- Anfangskonzentration im Abgas auf etwa 1/10 verringert wird. 3. The method according to claim 2, characterized in that in the first process stage, the PCDD / PCDF initial concentration in the exhaust gas is reduced to about 1/10.
4. Verfahren nach Anspruch 1, d a d u r c h g e k e n n z e i c h n e t, daß das dioxin- und/oder furanbeladene Adsorbens in einem Elektrofilter abgeschieden und in den Sinterprozeß zurückgeführt wird.4. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that the dioxin and / or furan-laden adsorbent is separated in an electrostatic precipitator and returned to the sintering process.
5. Verfahren nach Anspruch 1, d a d u r c h g e k e n n z e i c h n e t, daß die Umsetzungstemperatur, d. h. die Temperatur, bei der die katalytische Umsetzung in der Katalysatorstufe stattfindet, geregelt wird.5. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that the reaction temperature, d. H. the temperature at which the catalytic conversion takes place in the catalyst stage is regulated.
6. Verfahren nach Anspruch 5, d a d u r c h g e k e n n z e i c h n e t, daß die Umsetzungstemperatur in dem Temperaturbereich liegt, in dem die spezifische Abbauleistung des Katalysators maximal ist .6. The method of claim 5, d a d u r c h g e k e n n z e i c h n e t that the reaction temperature is in the temperature range in which the specific degradation performance of the catalyst is maximum.
7. Verfahren nach Anspruch 5 , d a d u r c h g e k e n n z e i c h n e t, daß zur Regelung der Umsetzungstemperatur die Temperatur des vorgereinigten Abgases vor dessen Eincritt in die Katalysatorstufe gezielt, insbesondere geregelt verändert wird.7. The method according to claim 5, so that the temperature of the pre-cleaned exhaust gas is changed in a targeted manner, in particular in a controlled manner, before it enters the catalyst stage, in order to regulate the reaction temperature.
8. Verfahren nach Anspruch 6 , d a d u r c h g e k e n n z e i c h n e t, daß die Temperatur des vorgereinigten Abgases vor dessen8. The method of claim 6, d a d u r c h g e k e n n z e i c h n e t that the temperature of the pre-cleaned exhaust gas before it
Eintritt in die Katalysatorεtufe in einerEntry into the catalyst stage in one
Aufheizvorrichtung, z.B. einer Brennkammer, erhöht wird. Heating device, e.g. a combustion chamber, is increased.
PCT/EP1997/005066 1996-12-13 1997-09-16 Method of reducing the concentration of pcdd and/or pcdf in waste gases WO1998025690A1 (en)

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DE19651822.9 1996-12-13
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DE19856260C1 (en) * 1998-12-07 2000-03-16 Steinmueller Gmbh L & C Reduction of polychlorinated dibenzodioxin and dibenzofuran content in waste gas from sintering plant by adding adsorbent comprises agglomeration of adsorbent and dust from filter before recycling
AT501149B8 (en) * 2005-03-24 2007-02-15 Voest Alpine Ind Anlagen METHOD AND DEVICE FOR TREATING EXHAUST GASES FROM SINTERING EQUIPMENT
AT8227U3 (en) * 2005-12-13 2006-09-15 Voest Alpine Ind Anlagen METHOD AND DEVICE FOR TREATING EXHAUST GASES FROM SINTERING EQUIPMENT
AT502375B1 (en) * 2006-02-28 2007-03-15 Voest Alpine Ind Anlagen Treatment of waste gases from iron ore sintering and pelleting plant comprises adding sodium bicarbonate to gas in feed pipe upstream from fabric filter which then separates it out, at least some bicarbonate being recirculated to feed pipe

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JPH0775720A (en) * 1993-07-13 1995-03-20 Kawasaki Heavy Ind Ltd Treatment of waste gas and catalyst for removing nitrogen oxide and dioxin
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