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
  • A62D3/34—Dehalogenation using reactive chemical agents able to degrade
• • 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
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S588/00—Hazardous or toxic waste destruction or containment
  • Y10S588/901—Compositions

Definitions

• the invention relates to a process for the chemical-thermal decomposition of halogenated hydrocarbons in an inert gas atmosphere, in particular of higher halogenated hydrocarbons, by reaction with a stoichiometric amount of alkaline solid substances at elevated temperatures in a reactor.
• halogenated hydrocarbons are very often used 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.
• DE-OS 30 28 193 describes a process for the pyrolytic decomposition of halogens and / or phosphorus-containing organic substances, which are reacted with calcium oxide / calcium hydroxide in a superstoichiometric ratio at temperatures of 300 to 800 ° C. in a reactor.
• So-called island silicates such as Ca 2 Si0 4 , Ca s Si 2 0 7 and Ca 3 Si 3 0 9 , chain silicates such as CaSi0 3 , band silicates such as Ca 3 Si 4 0 11 are preferably used as calcium silicates or magnesium , or network silicates such as CaSi 2 0 5 are used.
• These silicates can be found as naturally occurring minerals such as e.g. B. wollastonite or tobororite used or manufactured synthetically. During production, however, care must be taken to ensure that the melting points of the silicates in question are not reached, in order to avoid that a glass-like solidified product with only a small surface area and porosity is formed.
• magnesium silicates can equally well be used, it being possible for some of the calcium or magnesium in the silicate to be substituted by other metal cations, such as iron.
• synthetic silicates or silicate hydrates of calcium or magnesium can be used, which contain free excess calcium oxide or magnesium oxide.
• the chemical reaction of the halogenated hydrocarbons with silicates is less exothermic than the comparable reaction with calcium oxide, so that a lower temperature increase in the reactor results at comparable metering rates. This can be important for the reactor because of the choice of material.
• halogenated hydrocarbons are reacted with the silicates in the presence of inert gas, preferably under normal pressure.
• silicates in the form of granules or in lumpy form has proven to be very cheap.
• Such granules can be produced by a simple pelletizing process, using commercially available cements or ground cement raw clinker and water as starting materials.
• the use of granules enables the reaction to be carried out in a wide variety of reactors.
• a cartridge can be filled with granules into which the halogenated hydrocarbon is metered in either liquid or gaseous after heating to a reaction temperature of 450-700 ° C.
• the chemical-thermal decomposition then takes place inside the bed, while the halogen-free exhaust gas flows unhindered through the granulate bed and can escape at the other end of the cartridge. After approximately 80-85% utilization of the granulate fill, it can then be renewed or, if the cartridge is designed accordingly, it can be completely replaced.
• cement clinker, sand-lime brick and / or gas concrete is used as the alkaline solid substance.
• a shaft furnace which contains a bed of calcium silicate granulate, which is designed as a moving bed, the halogenated hydrocarbon and the resulting exhaust gas flowing through the bed either in cocurrent or in countercurrent.
• porous calcium silicate in granulated form has proven to be very advantageous.
• Corresponding granules can be produced, for example, by crushing silicate-rich building materials, such as gas concrete blocks or sand-lime blocks. These materials are mechanically and thermally sufficiently stable to serve as a bed in a moving bed reactor and also have a very large surface area. This material can be converted almost stoichiometrically with the halogenated hydrocarbons based on the Ca content.
• the gaseous reaction products formed during the chemical-thermal decomposition of halogenated hydrocarbons with silicates are halogen-free.
• the exhaust gas contains corresponding amounts of hydrogen and methane and possibly other partly saturated partly unsaturated low hydrocarbons, as well as carbon monoxide and carbon dioxide.
• the exhaust gas still has a considerable calorific value and can be used accordingly or simply re-burned to carbon dioxide and water in an afterburning chamber.
• gas concrete which is in granular form with a main grain fraction of about 4 mm, are filled into a reaction tube made of aluminum oxide ceramic.
• the filled reaction tube is closed on both sides and vertically in a tube furnace. Fixed and heated to 700 ° C.
• a total of 70 g of polychlorinated biphenyls (PCB) with an average chlorine content of 60% by weight are then metered into the reaction tube from above via a capillary within 3 hours, and at the same time the reactor is preheated from top to bottom with nitrogen preheated to 650 ° C. at normal pressure flows through.
• the nitrogen volume flow is about 5 to 10 NI per hour. The nitrogen escapes together with the gaseous reaction products at the lower end of the reactor and is passed through a washing section.
• the exothermic reaction of the PCB with Ca silicate leads to a temperature increase in the reaction zone in the upper part of the bed.
• the approximately 820 to 850 ° C. hot reaction zone migrates downward, so that a temperature measurement can be used to determine at what point in time the capacity of the bed is exhausted.
• composition of the gas concrete used as the solid reactant was determined as a mixture of 58% by weight Ca 3 S! 2 0 7 . H 2 0 and 42 wt.% A-quartz determined.
• the chemical analysis of the implementation was based on the residue analysis of the washing solution and the analysis of the solid residue. With a detection limit of 20 p.g PCB in the wash solution, no PCB could be detected, from which a degree of conversion of> 99.99996% is calculated.
• the chemical-thermal decomposition of PCBs does not result in the formation of metabolites, such as chlorinated dibenzodioxins or dibenzofurans. The compounds mentioned could not be detected at a limit of quantification of 10 ng.
• the solid granules were free-flowing even after the reaction and showed no caking.
• the main components were Si02. and CaCl 2 .
• the solid residue also contained calcium silicate and small amounts of elemental carbon.
• the chlorine metered into the reactor in the form of PCB was quantitatively recovered as chloride after the chemical-thermal decomposition of the PCB in the solid residue.
• the exhaust gas was halogen-free and essentially contained CO and H 2 in addition to nitrogen.
• Example 2 Analogous to Example 1, but cement is used instead of gas concrete.
• a porous granulate was produced from the cement powder as follows: 300 g of Portland cement are mixed with 140 g of water. After a curing time of 24 hours, the test specimen is dried at 600 ° C, almost all of the mixing water being expelled from the test specimen. The cement body, broken up into small pieces after drying and cooling, serves as filling material for the reaction tube.
• test result is comparable to the results described in Examples 1 and 2.
• burnt lime 168 g are mixed with 60 g of quartz sand and finely ground. Then the mixture is mixed with water to a dough-like mass and mixed with 0.6 aluminum powder. The mass swells up within a short time. The sample is then heated to 200 ° C. in an autoclave in a steam atmosphere. A solid pore is created Product that is broken into granules with an average grain size of approx. 5 mm in a jaw crusher.

Landscapes

• 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)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Processing Of Solid Wastes (AREA)
• Silicates, Zeolites, And Molecular Sieves (AREA)

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• 1985
  • 1985-05-11 DE DE19853517019 patent/DE3517019A1/de active Granted
• 1986
  • 1986-03-29 DE DE8686104351T patent/DE3660412D1/de not_active Expired
  • 1986-03-29 EP EP86104351A patent/EP0204910B1/de not_active Expired
  • 1986-03-29 AT AT86104351T patent/ATE35910T1/de not_active IP Right Cessation
  • 1986-05-09 ES ES554801A patent/ES8802119A1/es not_active Expired
  • 1986-05-09 CA CA000508823A patent/CA1288441C/en not_active Expired - Fee Related
  • 1986-05-12 JP JP61106893A patent/JPS61259683A/ja active Granted
• 1988
  • 1988-12-06 US US07/281,934 patent/US4937065A/en not_active Expired - Fee Related

Non-Patent Citations (2)

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