Black liquor
Black liquor (cooking liquor) is an energy- and lignin - rich by-product in cellulose production using the sulfate process in the paper industry . It arises when the lignin is separated from the pulp , which then forms the paper fibers.
Composition and proportion
Black liquor is a mixture of the lignin remaining after the pulp separation, water and chemicals that are used for the extraction. The dry matter content is about 15%, based on the dry matter, the amount of black liquor produced roughly corresponds to the mass of the cellulose produced.
Procedure
As soon as the wood fibers have been separated, the remaining black liquor is concentrated in the so-called liquor line to a dry content of 75 percent. In the recovery boiler the thickened black liquor (ie, essentially the energy lignin) burnt to the chemicals reduce and electricity to be generated. The melt that has formed on the bottom of the boiler flows through channels into the melt dissolving tank. Adding dilute white liquor creates green liquor, which is converted into white liquor in the causticizing system and can then be used again for fiber digestion . Up to 99 percent of the chemicals can be reused this way.
One problem with the process so far has been the sulfur content of the black liquor: Sulfur not only attacks technical equipment, it is also released into the atmosphere, where it is converted into harmful sulfur dioxide . In the meantime, fiberization processes are possible in which the black liquor produced is sulfur-free.
use
The combustion of black liquor in pulp production is used to generate electricity and process heat, which cover a significant part of the energy requirements in pulp and paper production. The generation of electricity from black liquor can under certain conditions according to the Renewable Energy Sources Act be sold to the energy supply companies at fixed, increased prices . In addition, the white liquor is recovered, which is used to break down the cellulose from wood fibers.
It is also possible to produce bio-hydrogen from black liquor using different processes ( gasification and steam reforming or conversion in supercritical water ). Black liquor can also be used to produce biogas , which is an alternative to fossil fuels . In Sweden, the biofuel dimethyl ether is experimentally extracted from the lignin-containing mass. In Germany, attempts are being made to extract and purify lignin from black liquor in order to produce biomaterials ( duromers and natural fiber composites ) from it.
Individual evidence
- ↑ Daniela Thrän, Frank Scholwin, Ina Körner: By-products, residues and waste. In: Martin Kaltschmitt, Hans Hartmann, Hermann Hofbauer (eds.), 2009: Energy from biomass. 2nd edition, Springer Verlag, p. 166. ISBN 978-3-540-85094-6 .
- ↑ Innovation report: Paper industry: green electricity from black liquor ( Memento from August 3, 2012 in the web archive archive.today ) Message from November 23, 2004, accessed on July 7, 2009.
- ↑ ORF: Black liquor as a new bio-fuel ( memento of the original from March 26, 2005 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. .
- ↑ Research Association Biopolymers - Bioplastics for the recycling of biomass. (Project description part 2a ( memento from September 3, 2012 in the web archive archive.today ) and part 2a ( memento from September 9, 2012 in the archive.today web archive )).
