EP0188718A1 - Process for the chemical-thermal decomposition of higher halogenated hydrocarbons - Google Patents

Process for the chemical-thermal decomposition of higher halogenated hydrocarbons Download PDF

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EP0188718A1
EP0188718A1 EP85115514A EP85115514A EP0188718A1 EP 0188718 A1 EP0188718 A1 EP 0188718A1 EP 85115514 A EP85115514 A EP 85115514A EP 85115514 A EP85115514 A EP 85115514A EP 0188718 A1 EP0188718 A1 EP 0188718A1
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Prior art keywords
calcium
halogenated hydrocarbons
oxide
chemical
iron oxide
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French (fr)
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EP0188718B1 (en
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Paul-Gerhard Dr. Dipl.-Chem. Maurer
Daniel Dr. Dipl.-Chem. Neupert
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Nukem GmbH
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Nukem GmbH
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    • A—HUMAN NECESSITIES
    • A62—LIFE-SAVING; FIRE-FIGHTING
    • A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
    • A62D3/00—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances
    • A62D3/40—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances by heating to effect chemical change, e.g. pyrolysis
    • A—HUMAN NECESSITIES
    • A62—LIFE-SAVING; FIRE-FIGHTING
    • A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
    • A62D3/00—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances
    • A62D3/30—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances by reacting with chemical agents
    • A62D3/36—Detoxification by using acid or alkaline reagents
    • A—HUMAN NECESSITIES
    • A62—LIFE-SAVING; FIRE-FIGHTING
    • A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
    • A62D2101/00—Harmful chemical substances made harmless, or less harmful, by effecting chemical change
    • A62D2101/04—Pesticides, e.g. insecticides, herbicides, fungicides or nematocides
    • A—HUMAN NECESSITIES
    • A62—LIFE-SAVING; FIRE-FIGHTING
    • A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
    • A62D2101/00—Harmful chemical substances made harmless, or less harmful, by effecting chemical change
    • A62D2101/06—Explosives, propellants or pyrotechnics, e.g. rocket fuel or napalm
    • A—HUMAN NECESSITIES
    • A62—LIFE-SAVING; FIRE-FIGHTING
    • A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
    • A62D2101/00—Harmful chemical substances made harmless, or less harmful, by effecting chemical change
    • A62D2101/20—Organic substances
    • A62D2101/22—Organic substances containing halogen
    • A—HUMAN NECESSITIES
    • A62—LIFE-SAVING; FIRE-FIGHTING
    • A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
    • A62D2203/00—Aspects of processes for making harmful chemical substances harmless, or less harmful, by effecting chemical change in the substances
    • A62D2203/04—Combined processes involving two or more non-distinct steps covered by groups A62D3/10 - A62D3/40

Definitions

  • the invention relates to a process for the chemical-thermal decomposition of higher halogenated hydrocarbons by reaction with calcium oxide and / or calcium hydroxide in a superstoichiometric ratio at temperatures of 600 to 800 ° C in a reactor.
  • halogenated hydrocarbons are used very frequently in industry and research.
  • fluorocarbons serve as dough gas and refrigerants and are the starting materials for the production of chemically very resistant plastics.
  • Chlorinated hydrocarbons are used in large quantities as degreasing agents in metal processing plants. Other areas of application are chemical cleaning of all kinds.
  • chlorinated hydrocarbons are the starting materials for the production of polymers, pesticides and herbicides.
  • the polychlorinated hydrocarbons were used as heat transfer oils or hydraulic fluids due to their high chemical and thermal resistance.
  • the polychlorinated biphenyls (PCB) are typical representatives of this class of substances.
  • PCBs which in the past were mainly used as transformer oils and as dielectrics in capacitors. Simply by replacing these liquids with substitutes, the Federal Republic of Germany expects to dispose of around 6,000 t of polychlorinated biphenyls annually over the next ten years.
  • DE-OS 30 28 193 describes a process for the pyrolytic decomposition of halogens and / or phosphorus-containing ones described organic substances, which are mixed with calcium oxide / calcium hydroxide in a superstoichiometric ratio at temperatures of 300 to 800 ° C in a reactor.
  • a disadvantage of this process is that not all halogenated hydrocarbons can be decomposed without problems.
  • the temperatures required for the quantitative decomposition of the chemically and thermally very stable higher halogenated hydrocarbons, to which the polychlorinated biphenyls in particular must be counted, are above 600 ° C. Above this temperature, mixtures of Ca0 and Ca (OH) 2 form with the corresponding calcium chlorides, Melt. This fact presents considerable difficulties since the necessary continuous throughput of solids through the reactor is thereby hindered and may even become impossible. In addition to the process engineering difficulties, the formation of melts also leads to a considerable reduction in the decomposition rate of the halogenated hydrocarbons.
  • Developed hydrocarbons by reaction with calcium oxide and / or calcium hydroxide in an over-stoichiometric ratio at temperatures of 600 to 800 0 C in a reactor in which no melts form and in which the exhaust gases are halogen and especially dioxin-free.
  • a two to five-fold stoichiometric excess of calcium oxide and / or calcium hydroxide is preferably used, it being possible for some of the calcium compounds to be replaced by the corresponding magnesium compounds.
  • Iron oxide additives in the size of 3 to 25% by weight have proven successful, it being possible for the iron oxide to be present as such or in the form of substances containing iron oxide.
  • the red mud obtained in the production of aluminum can be used, but fly ash from combustion plants is advantageously used.
  • the added iron oxide also has a catalytic effect on the chemical-thermal decomposition of halogenated hydrocarbons.
  • the amount of calcium oxide and / or calcium hydroxide used, based on the halogen to be set, is used in twice the stoichiometric amount. Equally good results cannot be achieved without the addition of iron oxide.
  • the iron oxide can be replaced by cheaper iron oxide-containing substitutes.
  • fly ash has proven to be particularly advantageous. Fly ash accumulates in large quantities in the combustion of hard coal and lignite in power plants and must also be disposed of so that no further costs arise when using the fly ash. Typical levels of iron oxide in fly ash are 5 to 18% by weight. In addition, fly ash also sometimes contains considerable amounts of calcium oxide, so that calcium oxide can also be saved.
  • the resulting gaseous reaction products are halogen-free.
  • the exhaust gas contains corresponding amounts of hydrogen, methane and possibly other partly saturated partly unsaturated low hydrocarbons and small amounts of carbon monoxide.
  • the exhaust gas still has a considerable calorific value and can be used accordingly or simply post-burned to carbon dioxide and water in a post-combustion chamber.
  • the chemical-thermal decomposition according to the invention of higher halogenated hydrocarbons by reaction with calcium oxide and / or calcium hydroxide and iron oxide or substances containing iron oxide is a very environmentally friendly and inexpensive method of disposing of them Substances.
  • the formation of metabolites, such as polychlorinated dibenzodioxins or furans, does not occur in the process mentioned, so that there are no safety-related concerns from this point of view either.
  • the exhaust gases escaping from the reactor during the test are free of halogenated hydrocarbons and are afterburned in a post-combustion chamber with a slight excess of air.

Abstract

A halohydrocarbon is destroyed chemical-thermally by reacting at 600 DEG to 800 DEG C. with calcium oxide and/or calcium hydroxide. The process can be carried out problem-free by having the calcium oxide of hydroxide present in at least twice the stoichiometric excess based on the halogen to be bound and by having the composition contain 2-30 wt. % iron oxide.

Description

Die Erfindung betrifft ein Verfahren zur chemisch-thermischen Zersetzung von höher halogenierten Kohlenwasserstoffen durch Umsetzung mit Calciumoxid und/oder Calciumhydroxid in einem überstöchiometrischen Verhältnis bei Temperaturen von 600 bis 800° C in einem Reaktor.The invention relates to a process for the chemical-thermal decomposition of higher halogenated hydrocarbons by reaction with calcium oxide and / or calcium hydroxide in a superstoichiometric ratio at temperatures of 600 to 800 ° C in a reactor.

Höher halogenierte Kohlenwasserstoffe werden in Industrie und Forschung sehr häufig eingesetzt. So dienen Fluorkohlenwasserstoffe als Teibgas und Kältemittel und sind Ausgangsstoffe zur Herstellung von chemisch sehr beständigen Kunststoffen. Chlorkohlenwasserstoffe werden in großen Mengen als Entfettungsmittel in metallverarbeitenden Betrieben eingesetzt. Weitere Anwendungsgebiete sind chemisch Reinigungen aller Art. Darüber hinaus sind die Chlorkohlenwasserstoffe, Ausgangsstoffe zur Herstellung von Polymeren, Pestiziden und Herbiziden. Insbesondere die polychlorierten Kohlenwasserstoffe wurden aufgrund ihrer hohen chemischen und thermischen Beständigkeit als Wärmeträgeröle oder Hydraulikflüssigkeiten eingesetzt. Die polychlorierten Biphenyle (PCB) sind typische Vertreter dieser Stoffklasse.Highly halogenated hydrocarbons are used very frequently in industry and research. For example, fluorocarbons serve as dough gas and refrigerants and are the starting materials for the production of chemically very resistant plastics. Chlorinated hydrocarbons are used in large quantities as degreasing agents in metal processing plants. Other areas of application are chemical cleaning of all kinds. In addition, chlorinated hydrocarbons are the starting materials for the production of polymers, pesticides and herbicides. In particular, the polychlorinated hydrocarbons were used as heat transfer oils or hydraulic fluids due to their high chemical and thermal resistance. The polychlorinated biphenyls (PCB) are typical representatives of this class of substances.

Obwohl von der Möglichkeit der Rezyklierung gebrauchter Halogenkohlenwasserstoffe, soweit dies technisch möglich und wirtschaftlich vertretbar ist, Gebrauch gemacht wird, fallen in der Bundesrepublik Deutschland jährlich ca. 30.000 bis 40.000 t Chlorkohlenwasserstoffe mit Chlorgehalten> 20 % an, die entsorgt werden müssen.Although use is made of the possibility of recycling used halogenated hydrocarbons, insofar as this is technically possible and economically justifiable, approx. 30,000 to 40,000 t of chlorinated hydrocarbons with chlorine contents> 20% are generated in the Federal Republic of Germany every year, which have to be disposed of.

Bei diesen sogenannten Sonderabfällen handelt es sich neben Rückständen aus Rezyklierungsanlagen und Produktionsrückständen auch um Stoffe, deren Verwendung aus sicherheits-und umwelttechnischen Gesichtspunkten immer mehr eingeschränkt wird und die letztendlich einer Entsorgung zugeführt werden müssen. Das bekannteste Beispiel hierfür sind PCB, die in der Vergangenheit hauptsächlich als Trafoöle und als Dielektrika in Kondensatoren eingestzt wurden. Allein durch Austausch dieser Flüssigkeiten gegen Ersatzstoffe rechnet man in der Bundesrepublik in den nächsten zehn Jahren mit jährlich ca. 6.000 t zu entsorgenden polychlorierten Biphenylen.In addition to residues from recycling plants and production residues, these so-called special wastes are also substances whose use is being increasingly restricted for safety and environmental reasons and which ultimately have to be disposed of. The best-known example of this are PCBs, which in the past were mainly used as transformer oils and as dielectrics in capacitors. Simply by replacing these liquids with substitutes, the Federal Republic of Germany expects to dispose of around 6,000 t of polychlorinated biphenyls annually over the next ten years.

Als Möglichkeit zur Entsorgung von Halogenkohlenwasserstoffen wird derzeit nur die Verbrennung auf See angesehen. Internationale Abkommen (Osloer und Londoner Konvention) zielen jedoch darauf hin, die Verbrennung auf See bis Ende dieses Jahrzehnts gänzlich einzuschränken. Als Alternative dazu bleibt dann nur noch die Verbrennung an Land. Die Verbrennung von Halogenkohlenwasserstoffen, insbesondere fluorierten und höher chlorierten, in bestehenden Sonderabfallverbrennungsanlagen ist problematisch. Die wesentlichen Gründe für die Schwierigkeiten sind die Korrosionsgefahr für die Ausmauerung und die Abgasstrecke durch eine hohe Rohgasbeladung an Halogenwasserstoffen (HF und HC1), die Emissionssituation, insbesondere bei Verbrennung von fluorierten Kohlenwasserstoffen, und der hohe Einsatz an Energie.At present, only incineration at sea is considered to be an option for the disposal of halogenated hydrocarbons. However, international agreements (the Oslo and London Conventions) aim to limit combustion at sea entirely by the end of this decade. The only alternative then is incineration on land. The combustion of halogenated hydrocarbons, especially fluorinated and more chlorinated ones, in existing hazardous waste incineration plants is problematic. The main reasons for the difficulties are the risk of corrosion for the brick lining and the exhaust gas section due to a high raw gas load of hydrogen halide (HF and HC1), the emission situation, especially when burning fluorinated hydrocarbons, and the high use of energy.

Besonders durch den Umstand, daß bei unzureichenden Verbrennungsbedingungen bei der Chlorkohlenwasserstoff-Verbrennung hochgiftige polychlorierte Dibenzodioxine und Dibenzofurane gebildet werden können, ist diese Entsorgungspraxis zunehmender Kritik ausgesetzt.This disposal practice is subject to increasing criticism, in particular due to the fact that highly toxic polychlorinated dibenzodioxins and dibenzofurans can be formed in the case of insufficient combustion conditions during the chlorinated hydrocarbon combustion.

In der DE-OS 30 28 193 ist ein Verfahren zur pyrolytischen Zersetzung von Halogene und/oder Phosphor enthaltenden organischen Substanzen beschrieben, wobei diese mit Calciumoxid/Calciumhydroxid in einem überstöchiometrischen Verhältnis gemischt bei Temperaturen von 300 bis 800° C in einem Reaktor umgesetzt werden.DE-OS 30 28 193 describes a process for the pyrolytic decomposition of halogens and / or phosphorus-containing ones described organic substances, which are mixed with calcium oxide / calcium hydroxide in a superstoichiometric ratio at temperatures of 300 to 800 ° C in a reactor.

Nachteilig bei diesem Verfahren ist es, daß nicht alle Halogenkohlenwasserstoffe problemlos zersetzt werden können. Die notwendigen Temperaturen zur quantitativen Zersetzung der chemisch und thermisch sehr stabilen höher halogenierten Kohlenwasserstoffe, zu denen insbesondere die polychlorierten Biphenyle gezählt werden müssen, liegen über 600° C. Oberhalb dieser Temperatur bilden Mischungen aus Ca0 und Ca (OH)2 mit den entsprechenden Calciumchloriden, Schmelzen. Diese Tatsache bereitet erhebliche Schwierigkeiten, da der notwendige kontinuierliche Feststoffdurchsatz durch den Reaktor dadurch behindert und unter Umständen sogar unmöglich wird. Neben den verfahrenstechnischen Schwierigkeiten führt die Bildung von Schmelzen gleichzeitig zu einer erheblichen Herabsetzung der Zersetzungsrate der halogenierten Kohlenwasserstoffe. Dies ist auf die starke Verringerung der Oberfläche der festen Reaktionspartner zurückzuführen, die bei Gas-Feststoffreaktionen einen wesentlichen Einfluß auf die Reaktion ausüben. Selbst ein starker Überschuß der genannten basischen Verbindungen vermag bei Temperaturen über 600° C eine Schmelzenbildung mit anschließender Verkrustung in der Abkühlphase nicht zu verhindern.A disadvantage of this process is that not all halogenated hydrocarbons can be decomposed without problems. The temperatures required for the quantitative decomposition of the chemically and thermally very stable higher halogenated hydrocarbons, to which the polychlorinated biphenyls in particular must be counted, are above 600 ° C. Above this temperature, mixtures of Ca0 and Ca (OH) 2 form with the corresponding calcium chlorides, Melt. This fact presents considerable difficulties since the necessary continuous throughput of solids through the reactor is thereby hindered and may even become impossible. In addition to the process engineering difficulties, the formation of melts also leads to a considerable reduction in the decomposition rate of the halogenated hydrocarbons. This is due to the large reduction in the surface area of the solid reactants, which have a significant influence on the reaction in gas-solid reactions. Even a strong excess of the basic compounds mentioned cannot prevent the formation of melts with subsequent incrustation in the cooling phase at temperatures above 600 ° C.

Es war daher Aufgabe der vorliegenden Erfindung, ein Verfahren zur chemisch-thermischen Zersetzung von höher haloge-. nierten Kohlenwasserstoffen zu entwickeln, durch Umsetzung mit Calciumoxid und/oder Calciumhydroxid in einem überstöchiometrischen Verhältnis bei Temperaturen von 600 bis 8000 C in einem Reaktor, bei dem sich keine Schmelzen bilden und bei dem die Abgase halogen- und insbesondere dioxinfrei sind.It was therefore an object of the present invention to provide a process for the chemical-thermal decomposition of higher halogen. Developed hydrocarbons by reaction with calcium oxide and / or calcium hydroxide in an over-stoichiometric ratio at temperatures of 600 to 800 0 C in a reactor in which no melts form and in which the exhaust gases are halogen and especially dioxin-free.

Diese Aufgabe wurde erfindungsgemäß dadurch gelöst, daß das Calciumoxid und/oder Calciumhydroxid bezogen auf das abzubindende Halogen in mindestens zweifachem stöchiometrischen Überschuß vorliegt und 2 bis 30 Gew. % Eisenoxid enthält.This object was achieved in that the calcium oxide and / or calcium hydroxide, based on the halogen to be set, is present in at least a two-fold stoichiometric excess and contains 2 to 30% by weight of iron oxide.

Vorzugsweise verwendet man einen zwei- bis fünffachen stöchiometrischen Überschuß an Calciumoxid und/oder Calciumhydroxid, wobei ein Teil der Calciumverbindungen auch durch die entsprechenden Magnesiumverbindungen ersetzt sein kann. Bewährt haben sich Eisenoxidzusätze in der Größe von 3 bis 25 Gew. %, wobei das Eisenoxid als solches oder in Form von eisenoxidhaltigen Substanzen vorliegen kann. Als eisenoxidhaltige Substanz kann beispielsweise der bei der Aluminiumherstellung anfallende Rotschlamm eingesetzt werden, vorteilhafterweise verwendet man jedoch Flugasche aus Feuerungsanlagen.A two to five-fold stoichiometric excess of calcium oxide and / or calcium hydroxide is preferably used, it being possible for some of the calcium compounds to be replaced by the corresponding magnesium compounds. Iron oxide additives in the size of 3 to 25% by weight have proven successful, it being possible for the iron oxide to be present as such or in the form of substances containing iron oxide. As a substance containing iron oxide, for example, the red mud obtained in the production of aluminum can be used, but fly ash from combustion plants is advantageously used.

Es hat überraschenderweise gezeigt, daß schon bei einem Anteil von 2 Gew. % Eisenoxid im Calciumoxid oder Calciumhydroxid eine Schmelzenbildung durch entstehendes Calciumchlorid zuverlässig verhindert wird und die nach der Halogenkohlenwasserstoffzersetzung vorliegende Feststoffmischung selbst bei Temperaturen von 8000 C rieselfähig bleibt und beim Abkühlen auch nicht verkrustet.Surprisingly, it has been shown that even with a proportion of 2% by weight of iron oxide in calcium oxide or calcium hydroxide, melt formation by calcium chloride formed is reliably prevented and that the solid mixture present after the halogenated hydrocarbon decomposition remains free-flowing even at temperatures of 800 ° C. and does not become encrusted when it cools down .

Das zugesetzte Eisenoxid zeigt neben seiner Eigenschaft im vorliegenden Fall Verkrustungen zu verhindern auch katalytische Wirkung auf die chemisch-thermische Zersetzung von Halogenkohlenwasserstoffen. Für die vollständige Zersetzung von höher halogenierten Kohlenwasserstoffen reicht es aus, wenn die eingesetzte Menge an Calciumoxid und/oder Calciumhydroxid, bezogen auf das abzubindende Halogen, in zweifacher überstöchiemetrischer Menge eingesetzt wird. Gleich gute Ergebnisse lassen sich ohne Zusatz von Eisenoxid nicht erzielen.In addition to its property of preventing incrustations, the added iron oxide also has a catalytic effect on the chemical-thermal decomposition of halogenated hydrocarbons. For the complete decomposition of more highly halogenated hydrocarbons, it is sufficient if the amount of calcium oxide and / or calcium hydroxide used, based on the halogen to be set, is used in twice the stoichiometric amount. Equally good results cannot be achieved without the addition of iron oxide.

Da die Reaktion von höher halogenierten Kohlenwasserstoffen mit Caleiumoxid zu Calciumchlorid exotherm ist, kann bei entsprechend hoher Dosierrate der Reaktionspartner eine Wärmeabfuhr notwendig werden. Auf eine über die üblichen Wärmeverluste durch Abstrahlung und Wärmeleitung hinausgehende Wärmeabfuhr durch Kühlung des Reaktormantels kann aber dann verzichtet werden, wenn das Calciumoxid der Reaktionsmischung teilweise durch Calciumhydroxid ersetzt wird.Since the reaction of higher halogenated hydrocarbons with caleium oxide to calcium chloride is exothermic, heat removal may be necessary if the reactants are dosed accordingly. However, heat dissipation by cooling the reactor jacket, which goes beyond the usual heat losses due to radiation and heat conduction, can be dispensed with if the calcium oxide of the reaction mixture is partially replaced by calcium hydroxide.

Bei geeignetem Mischungsverhältnis, das bei kontinuierlicher Umsetzung experimentell einfach ermittelt und über geeignete Dosiereinrichtungen eingestellt werden kann, ist auf diese Weise sogar eine autotherme Reaktionsführung möglich. Mit diesem Verfahren ist damit eine kontinuierliche chemisch-thermische Zersetzung von höher halogenierten Kohlenwasserstoffen ohne zusätzlichen Energieeinsatz durchzuführen.With a suitable mixing ratio, which can be easily determined experimentally in the case of continuous implementation and adjusted using suitable metering devices, an autothermal reaction procedure is even possible in this way. With this process, a continuous chemical-thermal decomposition of higher halogenated hydrocarbons can be carried out without additional energy consumption.

Als zusätzliche Möglichkeit zur kostengünstigen Gestaltung des erfindungsgemäßen Verfahrens kann das Eisenoxid durch billigere eisenoxidhaltige Ersatzstoffe ersetzt werden. Als besonders vorteilhaft hat sich die Verwendung von Flugasche herausgestellt. Flugasche fällt in großen Mengen bei der Verbrennung von Steinkohle und Braunkohle in Kraftwerken an und muß ebenfalls einer Entsorgung zugeführt werden, so daß beim Einsatz der Flugasche keine weiteren Kosten entstehen. Typische Gehalte an Eisenoxid in Flugasche betragen 5 bis 18 Gew. %.Flugasche enthält darüber hinaus zum Teil auch noch erhebliche Mengen an Calciumoxid, so daß auch Calciumoxid eingespart werden kann.As an additional possibility for the inexpensive design of the method according to the invention, the iron oxide can be replaced by cheaper iron oxide-containing substitutes. The use of fly ash has proven to be particularly advantageous. Fly ash accumulates in large quantities in the combustion of hard coal and lignite in power plants and must also be disposed of so that no further costs arise when using the fly ash. Typical levels of iron oxide in fly ash are 5 to 18% by weight. In addition, fly ash also sometimes contains considerable amounts of calcium oxide, so that calcium oxide can also be saved.

Die entstehenden gasförmigen Reaktionsprodukte sind halogenfrei. Im Falle der Zersetzung von nicht perhalogenierten Kohlenwasserstoffen enthält das Abgas entsprechende Mengen an Wasserstoff, Methan und evtl. andere teils gesättigte teils ungesättigte niedrige Kohlenwasserstoffe sowie geringe Anteile Kohlenmonoxid. Das Abgas besitzt in diesem Falle noch einen erheblichen Heizwert und kann entsprechend genutzt werden oder auch einfach in einer Nachbrennkammer zu Kohlendioxid und Wasser nachverbrannt werden.The resulting gaseous reaction products are halogen-free. In the event of the decomposition of non-perhalogenated hydrocarbons, the exhaust gas contains corresponding amounts of hydrogen, methane and possibly other partly saturated partly unsaturated low hydrocarbons and small amounts of carbon monoxide. In this case, the exhaust gas still has a considerable calorific value and can be used accordingly or simply post-burned to carbon dioxide and water in a post-combustion chamber.

Die erfindungsgemäße chemisch-thermische Zersetzung von höher halogenierten Kohlenwasserstoffen durch Reaktion mit Calciumoxid und/oder Calciumhydroxid und Eisenoxid oder eisenoxidhaltigen Stoffen ist ein sehr umweltverträgliches und kostengünstiges Verfahren zur Entsorgung dieser Substanzen. Eine Bildung von Metaboliten, wie polychlorierten Dibenzodioxinen oder Furanen, erfolgt bei dem genannten Verfahren nicht, so daß auch aus dieser Sicht keine sicherheitstechnischen Bedenken bestehen.The chemical-thermal decomposition according to the invention of higher halogenated hydrocarbons by reaction with calcium oxide and / or calcium hydroxide and iron oxide or substances containing iron oxide is a very environmentally friendly and inexpensive method of disposing of them Substances. The formation of metabolites, such as polychlorinated dibenzodioxins or furans, does not occur in the process mentioned, so that there are no safety-related concerns from this point of view either.

Das erfindungsgemäße Verfahren soll am folgenden Beispiel näher erläutert werden:

  • Der Reaktor, in dem die chemisch-thermische Zersetzung der Halogenkohlenwasserstoffe durchgeführt wird, ist als Rührbettreaktor gemäß DE-OS 30 28 193 ausgeführt. In diesem Reaktor befinden sich ca. 10 kg einer Kugelschüttung, die auf einem für feinkörnige oder pulvrige Feststoffe durchlässigen Tragrost ruht. Die Kugelschüttung besteht aus Keramikkugeln mit Durchmessern von ca. 16 mm und wird mit einem Wendelrührer umgewälzt. Die Rührerdrehzahl beträgt ca. 2 Umdrehungen pro Minute. Vor Beginn der Halogenkohlenwasserstoff-Einspeisung wird das Rührbett elektrisch aufgeheizt. Nach Erreichen der Betriebstemperaturen von 700 C wird eine Mischung aus 40 % Ca0, 10 % Ca (OH)2 und 50 % Flugasche mit 8 % Eisenoxidgehalt in den Rührbettreaktor von oben mit einer Dosierrate von ca. 500 g/Stunde eindosiert. Nach einer Vorlaufzeit von etwa 10 Minuten wird eine Dosierpumpe eingeschaltet, die die zu zersetzenden Halogenkohlenwasserstoffe über eine getrennte Zuführung in den Reaktor einspeist. Die Abfallösung besteht aus etwa 40 % Dichlormethan und 60 % polychlorierten Biphenylen (PCB). Durch die Rührbewegung der Kugelschüttung werden die Reaktanden sowie die Reaktionsprodukte von oben nach unten durch das heiße Kugelbett hindurchtransportiert.
The process according to the invention will be explained in more detail using the following example:
  • The reactor in which the chemical-thermal decomposition of the halogenated hydrocarbons is carried out is designed as a stirred bed reactor according to DE-OS 30 28 193. This reactor contains approx. 10 kg of a ball bed, which rests on a supporting grate that is permeable to fine-grained or powdery solids. The ball bed consists of ceramic balls with a diameter of approx. 16 mm and is circulated with a spiral stirrer. The stirrer speed is approx. 2 revolutions per minute. The stirred bed is heated electrically before starting the hydrocarbon feed. After the operating temperatures of 700 C have been reached, a mixture of 40% Ca0, 10% Ca (OH) 2 and 50% fly ash with 8% iron oxide content is metered into the stirred bed reactor from above at a metering rate of approximately 500 g / hour. After a lead time of about 10 minutes, a metering pump is switched on, which feeds the halogenated hydrocarbons to be decomposed into the reactor via a separate feed. The waste solution consists of approximately 40% dichloromethane and 60% polychlorinated biphenylene (PCB). The reactants and the reaction products are transported through the hot ball bed from top to bottom by the stirring movement of the ball bed.

Nach Beendigung des 2-stündigen Versuchs haben sich unterhalb des Tragrosts, über eine Schleuse abgezogen, ca. 1500 g eines pulvrigen Feststoffs in einem Behälter angesammelt. Diese Feststoffmischung enthält vornehmlich überschüssigen gebrannten Kalk und Flugasche sowie Calciumchlorid und Eisenverbindungen.Sie ist frei von organischen Stoffen.After the 2-hour test had ended, about 1500 g of a powdery solid had collected in a container below the supporting grate, drawn off via a lock. This mixture of solids mainly contains excess burnt lime and fly ash as well as calcium chloride and Iron compounds, it is free of organic substances.

Die während des Versuches aus dem Reaktor entweichenden Abgase sind frei von Halogenkohlenwasserstoffen und werden in einer Nachbrennkammer mit leichtem Luftüberschuß nachverbrannt.The exhaust gases escaping from the reactor during the test are free of halogenated hydrocarbons and are afterburned in a post-combustion chamber with a slight excess of air.

Claims (4)

1. Verfahren zur chemisch-thermischen Zersetzung von höher halogenierten Kohlenwasserstoffen durch Umsetzung mit Calciumoxid und/oder Calciumhydroxid in einem überstöchiometrischen Verhältnis bei Temperaturen von 600 bis 800° C in einem Reaktor,
dadurch gekennzeichnet,
daß das Calciumoxid und/oder Calciumhydroxid bezogen auf das abzubindende Halogen in mindestens zweifachem stöchiometrischen Überschuß vorliegt und 2 bis 30 Gew. % Eisenoxid enthält.1. Process for the chemical-thermal decomposition of higher halogenated hydrocarbons by reaction with calcium oxide and / or calcium hydroxide in a superstoichiometric ratio at temperatures of 600 to 800 ° C. in a reactor,
characterized,
that the calcium oxide and / or calcium hydroxide, based on the halogen to be set, is present in at least a two-fold stoichiometric excess and contains 2 to 30% by weight of iron oxide. 2. Verfahren nach Anspruch 1,
dadurch gekennzeichnet,
daß ein zwei- bis fünffacher stöchiometrischer Überschuß an Calciumoxid und/oder Calciumhydroxid verwendet wird.2. The method according to claim 1,
characterized,
that a two to five-fold stoichiometric excess of calcium oxide and / or calcium hydroxide is used. 3. Verfahren nach Anspruch 1 und 2,
dadurch gekennzeichnet,
daß das Calciumoxid und/oder Calciumhydroxid 3 bis 25 Gew. % Eisenoxid enthält.3. The method according to claim 1 and 2,
characterized,
that the calcium oxide and / or calcium hydroxide contains 3 to 25% by weight of iron oxide. 4. Verfahren nach Anspruch 1 bis 3,
dadurch gekennzeichnet,
daß das Eisenoxid in Form von Flugasche aus Feuerungsanlagen vorliegt.4. The method according to claim 1 to 3,
characterized,
that the iron oxide is in the form of fly ash from combustion plants.
EP85115514A 1984-12-24 1985-12-06 Process for the chemical-thermal decomposition of higher halogenated hydrocarbons Expired EP0188718B1 (en)

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AT85115514T ATE30120T1 (en) 1984-12-24 1985-12-06 PROCESS FOR THE CHEMICAL-THERMAL DECOMPOSITION OF HIGHER HALOGENATED HYDROCARBONS.

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DE3447337A DE3447337C2 (en) 1984-12-24 1984-12-24 Process for the chemical-thermal decomposition of higher halogenated hydrocarbons
DE3447337 1984-12-24

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EP0188718B1 EP0188718B1 (en) 1987-10-07

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EP (1) EP0188718B1 (en)
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EP0667180A1 (en) * 1994-02-11 1995-08-16 CS-GmbH Halbleiter- und Solartechnologie Process for the disposal of halogenated hydrocarbons
WO1996029118A1 (en) * 1995-03-22 1996-09-26 Nkt Research Center A/S A method for treatment of halogen-containing waste material

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Also Published As

Publication number Publication date
DE3447337A1 (en) 1986-07-03
US4654203A (en) 1987-03-31
ATE30120T1 (en) 1987-10-15
DE3560739D1 (en) 1987-11-12
DE3447337C2 (en) 1986-11-06
EP0188718B1 (en) 1987-10-07

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