Classifications

• • 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
  • A62D2101/20—Organic substances
• • 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 halogenated hydrocarbons in the absence of air by reaction with a stoichiometric amount of calcium oxide and / or calcium hydroxide at temperatures of 600 to 800 ° C. in a reactor.
• Halogenated hydrocarbons are used very frequently in industry and research.
• fluorocarbons serve as propellants 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. Further areas of application are chemical cleaning of all kinds.
• the chlorinated hydrocarbons are raw 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.
• Halogenated hydrocarbons are currently mainly disposed of by incineration at sea.
• international agreements (the Oslo and London Conventions) aim to limit combustion at sea entirely by the end of this decade.
• the only alternative is incineration on land.
• the combustion of halogenated hydrocarbons, especially fluorinated ones and more chlorinated, 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 HCl), the emission situation, especially when burning fluorinated hydrocarbons, the high use of energy and the high halogen content in the exhaust gas limited throughput in connection with the available flue gas cleaning system.
• HF and HCl hydrogen halide
• DE-OS 30 28 193 describes a process for the pyrolytic decomposition of halogens and / or phosphorus-containing organic substances, these being mixed with calcium oxide / calcium hydroxide in a superstoichiometric ratio and reacted at temperatures of 300 to 800 ° C. in a reactor .
• the disadvantage of this process is that not all halogenated hydrocarbons can be easily decomposed.
• the temperatures required for the quantitative decomposition of the chemically and thermally very stable higher halogenated ones Hydrocarbons, to which polychlorinated biphenyls in particular must be counted, are above 600 o C. Above this temperature, mixtures of CaO and Ca (OH) 2 form with the corresponding calcium chlorides.
• 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.
• DE-OS 34 47 337 describes 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, in which the addition of Iron oxide the formation of melts in the temperature range of 600 to 800 o C is avoided.
• a disadvantage of this method is that the temperature must not exceed 800 ° C. if incrustations are to be reliably prevented. Avoiding incrustations in the reactor area is a necessary prerequisite for the success of this decomposition process.
• a temperature of 800 o C is sufficient for the implementation of the chemically and thermally extremely stable PCB, but the reaction of the highly halogenated hydrocarbons with CaO can be extremely exothermic. With a correspondingly high metering rate, there can thus be a sharp rise in temperature in the reactor, which must then be limited to 800 ° C. by appropriate measures, which in practice amounts to limiting the metering rate of halogenated hydrocarbons.
• both processes have the serious disadvantage that by adding stoichiometric amounts of reactants, a significantly larger amount of secondary waste compared to the throughput of halogenated hydrocarbons - reaction product (calcium halide) and excess reactants - also has to be disposed of as hazardous waste.
• This object is achieved in that 1 to 10 parts by weight of sand, based on one part of calcium oxide, are introduced into the reactor with the calcium oxide and / or calcium hydroxide in that the reaction product, which consists primarily of calcium halide and sand, with steam at temperatures of 150 to 800 o C is dehalogenated in another reactor, and that the mixture of calcium oxide and sand thus obtained is fed back to the first reactor.
• the resulting reaction product (Kalziumhalogenid with sand and excess calcium oxide) can be preferably from 500 to 800 o C to the originally used regenerate calcium oxide, or dehalogenate.
• the only secondary waste is acid - in the case of chlorinated hydrocarbons, for example hydrochloric acid - which can be recycled if necessary.
• a fluidized bed is preferably used to carry out the dehalogenation reaction because of its excellent heat and mass transfer properties.
• the process of chemical-thermal decomposition of halogenated hydrocarbons is essentially based on the fact that the halogen atoms contained in the HKW contribute to a solid reagent capable of reacting with the organic halides, such as powdered calcium oxide, with the exclusion of oxygen (inert gas atmosphere) 600 to 800 o C are bound.
• the reaction takes place according to the following reaction equation: The reaction accordingly creates gaseous reaction products that are burned, as well as solid reaction products consisting of CaCl2 and carbon as well as excess CaO.
• liquid halogenated hydrocarbons and the optionally preheated solid consisting of calcium oxide or calcium hydroxide and sand, are over in certain mass flow ratios
• Corresponding entry and metering devices under nitrogen (oxygen exclusion) are fed separately, for example, into a spherical stirred-bed reactor.
• a bed of ceramic balls in the reactor This lies on a bottom permeable to gas and fine solid particles, is slowly stirred (2 to 4 min ⁇ 1) and heated electrically via the reactor wall.
• the chemical-thermal decomposition takes place with the exclusion of oxygen (N2 atmosphere) on the spherical surfaces and within the spherical spaces.
• the solid reaction product that forms and the stoichiometrically used calcium oxide are discharged through the slow stirring movement over the bottom designed as a supporting grate downwards through a lock from the reactor.
• the added sand acts as a reliable abrasive.
• the low gas volume flow also leaves the reaction chamber via the supporting grate and is completely burned in a post-combustion chamber after a high-temperature dedusting with blow-back filter cartridges or fed to a special waste incineration plant.
• the flue gas is cleaned and released into the environment via a chimney.
• the resulting solid reaction product is continuously discharged and, for example, fluidized in a fluidized bed apparatus with water vapor and optionally nitrogen.
• the reaction product supplied does not need to be heated, since it emerges from the stirred bed at 600 - 800 o C and the dehalogenation preferably takes place in the same temperature range.

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• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Toxicology (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Business, Economics & Management (AREA)
• Emergency Management (AREA)
• Fire-Extinguishing Compositions (AREA)
• Processing Of Solid Wastes (AREA)

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• 1989
  • 1989-06-08 DE DE19893918716 patent/DE3918716C1/de not_active Expired - Fee Related
• 1990
  • 1990-06-07 EP EP90110755A patent/EP0401810A1/fr not_active Withdrawn
  • 1990-06-08 JP JP2148859A patent/JPH03103271A/ja active Pending

Patent Citations (2)

Non-Patent Citations (1)

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