Wood tar

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Wood tar

In wood tar ( English wood tar ; as medicaments Pix liquids) is a brown-black, translucent, slightly granular, viscous liquid of a peculiar, strong odor and taste. The viscous, water-insoluble mixture of organic substances is created, in addition to charcoal , wood gas , wood vinegar and water , during the pyrolysis of wood . In the past, pitch and tar were not separated, nowadays the DIN 55946 standard defines the two terms.

history

Tar stove for charring wood (view of heating opening)

The charring of wood for the purpose of extracting charcoal is very old. The distillation products resulting from charring were already known in the Mesolithic , e.g. B. liquid wood tar and wood vinegar, which the Egyptians used to embalm their dead, wood tar was used as an adhesive and preservative . Tar and pitch made from wood are the oldest plastics in human history. So who won the same time as technological innovations in Teerherstellung pillaging the Vikings considerable momentum. The charring methods from prehistoric times have basically remained almost unchanged up to the present day. While it was known earlier how to utilize the wood tar → coal pile , the technical exploitation of the more volatile distillation products was not successful until the 19th century. Until the end of the 18th century, the charring of charcoal was often done in mine piles , coal piles or tar pit piles, whereby all valuable products except tar were lost. The brick kilns ( single-chamber kilns ) of the pitch furnaces brought a significant improvement ; they had been in use since the 17th century, and wood tar was also extracted on pitch oil stones and in brick piles . Around 1800 vinegar was made from wood vinegar , Johann Tobias Lowitz . After the investigations by Carl Reichenbach (1835) on the components of wood tar and by Philippe Lebon and Max von Pettenkofer on those of wood gas, more attention began to be paid to wood distillation products (e.g. creosote ). The next consequence of this endeavor was the use of cast iron ovens and retorts ( two-chamber ovens ) to char the wood. The wood tar distillates were later displaced by hard coal, lignite and petroleum distillates.

Manufacturing

If wood is heated, i.e. pyrolysed, in a closed container (kiln, furnace, retort) in a closed container (kilns, furnace, retort), i.e. pyrolysed, it begins to decompose into the substances charcoal , wood tar, wood vinegar and wood gas . With the exception of charcoal, all substances are gaseous at the high temperature. When it cools down to ambient temperature, wood tar and wood vinegar condense and only the wood gas remains gaseous. Wood vinegar consists of the water that is created during pyrolysis and the organic substances dissolved in it, such as methanol , formic acid , acetic acid and phenol . The wood tar contains the water-insoluble organic substances, the two liquids are immiscible; the wood vinegar floats on top.

If you don't want to heat from the outside, you can also let a little air flow into the container, so that the wood carbonizes . Under such conditions, which correspond to those of wood gasification , the oxygen reacts with the organic tar and wood vinegar substances. Their properties and composition are then different to pure pyrolysis and almost correspond to those of wood gas condensate .

One differentiates:

  • Sediment tar (slab tar, lignin tar), this separates from the wood vinegar due to its higher density.
  • Extraction tar (residue tar, bubble tar), this is dissolved in the raw wood vinegar and remains as bubble residue after the acetic acid has been distilled off.
  • Ester tar that contains sulfuric acid is precipitated in the production of methyl ester .

The raw wood tars are processed by fractional distillation on creosote with the simultaneous production of "wood tar oils ", in the case of coniferous wood tar, turpentine oil is also obtained. The remainder is wood tar pitch . In the past, wood tar was only boiled, the lighter fractions were lost, and then finer and coarser pitch (tar) and the residue, the pitch cake, were obtained .

The composition of the different wood tars depends heavily on the wood used and the charring process used. The best tar yields are hardwoods , tar from beech wood (creosote) is particularly valuable .

composition

Wood tars are composed of resin acids , fatty acids , phenols , terpenes , resins and aromatics ( benzene , toluene , xylene , styrene , benzo (a) pyrene , naphthalene , reten , chrysene , cumene , cymene , mesitylene , pseudocumene ), ketones and various others Substances creosol , cresols , phenol ethers , guaiacol , acetic acid and other organic acids , as well as high-boiling hydrocarbons , aliphatic alcohols , aldehydes , catechol , glycerides , paraffins , pyrogallol ethers . In contrast to coal tar , wood tar does not contain any tar bases (nitrogenous heterocycles).

The calorific value is approx. 24 MJ per kg.

properties

Wood tar is a highly flammable mixture, and if substances with a comparatively low boiling point were obtained during production, the tar is liquid (not viscous), has a pungent smell of smoke and is brown in color. If the tar is left open, it becomes more and more viscous to solid due to evaporation and further chemical reactions of the organic substances in light and air. The tar is then almost black and firm, like plasticine . The aromatic smell of smoked sausage and meat products comes from these substances. Wood tar is heavier than water and tar from lignite , peat and slate .

use

Wood tar was used for a long time in wood shipbuilding for caulking and to preserve wood and ropes , textiles and leather → Creosote , as well as an adhesive, nets used in salt water were also impregnated with wood tar. It was also used as a lubricant (with additives: pine oil , lime , animal fats, beeswax), as a car lubricant and in hammer mills, etc. It was also used to produce inks and paints. It was also used as a bearer in Greek fire . Today it is used mainly in the form of beech wood - not to be confused with carrying tar - as an attractant for wild boar and deer at Wallowing use. When shoeing and the claws cutting wood tar is still today as disinfectants used. In medicine, wood tar is used to treat skin diseases. In the Middle Ages, linen and leather rags soaked in wood tar were used as plasters. The wood tar from various pine trees, pinaceae and conifers, abietineen, forms a thick, black liquid with the consistency of a thin extract (Pix liquida). The ingredients present in tars act alleviates itching , anti-inflammatory and antiseptic , the epidermal cell proliferation is inhibited. Wood tar is also used as a flotation agent in ore processing, and it can also be used as fuel .

See also

literature

  • W. Bleyberg, G. Meyerheim, W. Bachmann, J. Davidsohn, F. Frank, F. Fritz, J. Herzenberg, L. Jablonski, H. Kantorowicz, HP Kaufmann, EL Lederer, P. Levy, I. Lifschütz, H. Lindemann, H. Mallison: Hydrocarbon oils and fats: as well as the chemically and technically related substances. 7th edition, Springer-Verlag, 1933, ISBN 978-3-642-89045-1 , pp. 593-598.
  • Dieter Osteroth: From coal to biomass: chemical raw materials and energy sources in the course of time , Springer-Verlag, 1989, ISBN 978-3-642-88669-0 , pp. 86–91.

Web links

Individual evidence

  1. ^ A b c W. Brandt, A. Braun, R. Brieger, H. Dieterle, R. Dietzel, W. Moeser, PN Schürhoff, F. Stadlmayr, O. Wiegand: Commentary on the German Pharmacopoeia. 6th edition, 1926, 2nd volume, Springer Berlin Heidelberg, 1928, ISBN 978-3-642-88891-5 , p. 299.
  2. ↑ What made the Vikings feared seafarers. In: Spiegel Online . November 6, 2018, accessed November 6, 2018.
  3. ↑ Andreas HENNIUS: Viking Age tar production and outland exploitation. In: Antiquity. Volume 92, Issue 365, 2018, pp. 1349–1361, doi: 10.15184 / aqy.2018.22 .
  4. ↑ Grubenmeiler ( Memento from January 9, 2017 in the Internet Archive ).
  5. ↑ Teergrubenmeiler (PDF; 2.60 MB), on stadtentwicklung.berlin.de, accessed on February 6, 2017.
  6. ↑ Dieter Osteroth: Biomass: Return to the ecological balance. Springer, 1992, ISBN 978-3-642-77410-2 , p. 88.
  7. ^ A b H. M. Bunbury, W. Elsner: The dry distillation of wood. Springer Berlin Heidelberg, 1925, ISBN 978-3-642-91149-1 .
  8. ↑ a b Max Klar: Technology of charring. Springer-Verlag, 1903, ISBN 978-3-642-98495-2 .
  9. ^ Karl Winnacker , Leopold Küchler : Chemical Technology: Organic Technology I-II. Carl Hanser Verlag, 1952, p. 571.
  10. ↑ a b L. Schmitz, J. Follmann: The liquid fuels: their extraction, properties and investigation. 3rd edition, Springer, 1923, ISBN 978-3-642-89309-4 , p. 112 f.
  11. ^ J. Falbe, M. Regitz: RÖMPP Lexikon Chemie. Volume 3: H – L , 10th edition, Georg Thieme Verlag, 1997, ISBN 3-13-734810-2 .
  12. ^ Bleyberg: p. 594.
  13. ↑ Otto Anselmino, Ernst Gilg : Commentary on the German Pharmacopoeia: 3rd volume, 5th edition, Springer, 1911, ISBN 978-3-662-38918-8 , p. 57.
  14. ↑ P. H. List, L. Hörhammer: Chemicals and drugs. Volume 6: Part A: N-Q , Springer, 1977, ISBN 978-3-642-65036-9 , p. 538.
  15. ↑ a b Dieter Osteroth: Biomass: return to ecological balance. Springer-Verlag, 1992, ISBN 978-3-642-77409-6 , p. 85.
  16. ↑ Abietineen on zeno.org, accessed on August 5, 2016.
  17. ↑ Joseph Herzog, Adolf Hanner: The chemical and physical test methods of the German Pharmacopoeia. 5th edition, Springer-Verlag, 1924, ISBN 978-3-662-27585-6 , p. 359.
  18. ↑ Hans-Hasso Frey (Ed.), Felix R. Althaus: Textbook of Pharmacology and Toxicology for Veterinary Medicine: 3rd Edition, Enke Verlag, 2010, ISBN 978-3-8304-1079-9 , p. 415.
  19. ↑ Otto Lange: Metals and Minerals. Volume 1, 3rd edition, Springer-Verlag, 1923, ISBN 978-3-662-31451-7 (reprint), p. 10.