Patent Application
20130172167
CN101607780(A)-2009-12-23 Jihong Zhang Int. Cl. C02F1/24
JP2207098353(A) 2007-04-19 Ito Kimio Int. Cl. B01D17/00
U.S. Pat. No. 2,366,899 1945-09-01 E. L. Hall 252/346
U.S. Pat. No. 7,915,458 1997-04-28 Peter Bruckmayer 568/840
U.S. Pat. No. 4,206,186 1980-06-03 Heinz Holter 423/230
U.S. Pat. No. 4,282,096 1981-08-04 Burkert 210/182
U.S. Pat. No. 4,364,796 1982-12-21 Yoshiaki Ishii 201/4
U.S. Pat. No. 5,897,689 1998-04-08 Emil Wieser 95/152
U.S. Pat. No. 7,626,069 2008-02-12 Thomas Nissen 585/802
US20040220285 2002-08-22 Harold Boerrrigter 518/726
US20070007170 2005-07-08 Robert S track 208/106
The present invention relates to a method and a device for separating carbon, hydrogen and oxygen containing tars and/or char from syngas wet scrubber liquids such as those derived from gasification or pyrolysis of biomass containing feedstocks including municipal solid waste or agricultural wastes including wood wastes. The invention also relates to a method and device for removing resins from biomass derived resin containing liquids such as those derived from a coniferous source, for example, including spruce or pine. The solid discharges from the device can be used as such or pelletized for a variety of applications and markets.
It is known that waste to energy plants, for example biomass waste to energy plants, very often use the wet scrubber technique for cleaning the syngas of tar and/or char so that the syngas is more suitable for use as a fuel. The gas leaving the gas-making apparatus, e.g. gasifier or pyrolyzer, is usually brought into contact with liquid or a process derived liquid such as in a wet scrubber, for example an aqueous liquid i.e. containing water. Since a water containing scrubber solution is hydrophilic and the tar and/or char or resin are hydrophobic and semi-hydrophobic i.e. semi-hydrophilic, the scrubber liquid converts to a tarry suspension in water.
The resinous or tarry suspension of resin or tar and/or tar containing hydrophilic liquid such as water is extremely difficult to handle by prior art techniques including concentration, filtration, absorption, thickening, use of cyclones or dehydration. The product remains extremely hazardous if spilled into the environment. The resinous or tarry suspension may contain as much as 99.5% liquid or even higher. Alternatively, the resinous or tarry suspension may be in the form of a pasty, sticky, high viscosity resinous or tar/char greasy solid of up to 35% solids.
Untreated spent tar/char/liquid tarry suspensions derived from syngas wet scrubbers cannot be disposed of to the environment due to the content of tar, including mono-aromatic and poly-aromatic hydrocarbons and phenols. These components are toxic in bio-treatment systems and are possibly poisonous or carcinogenic.
According to a study published by the National Renewable Energy Laboratory, currently available technologies for tar removal do not meet the needs of the industry in terms of cost, performance, and environmental considerations (T. A. Milne, et. al., “Biomass Gasification Tars, Their Nature, Formation, and Conversion”, NRELITP 570-25357, November 1998). Devi et al further illustrate problems associated with handling tars derived from biomass processing (“A Review of the Primary Measures for Tar Elimination in Biomass Gasification Systems”, Biomass and Bioenergy, 2003. 24(2):125-140).
Accordingly, a need exists for a method of and a device for treating this waste stream in an effective and simple way.
The current invention is a method and apparatus for cleaning resin or tar/char or tar-bearing scrubber liquids including scrubber liquids containing tarry or resinous suspensions containing water and tars containing hydrocarbons for example mono-aromatic or poly-aromatic hydrocarbons and phenols, naphthalenes or resins. The tarry suspension is processed in a continuous feed horizontal axis centrifuge, to create tar/char or resin depleted liquid for recycle as syngas scrubber liquid or for treatment prior to discharge. The continuous feed centrifuge also produces a liquid depleted centrifuge cake (tarry or resinous solids) for use as fuel, recycle to the gasifier or pyrolysis process to generate additional syngas or in the case of resinous solids for further use e.g. varnish or lacquer raw material. The continuous feed centrifuge contains a slow moving scraper in its discharge section to prevent clogging or fouling by the cake tar/solids unlike a centrifuge such as the scraper-free horizontal-axis type described in U.S. Pat. No. 7,915,458 to Bruckmeyer or the decanter centrifuge described in U.S. Pat. No. 5,897,689 to Wieser-Linhart.
The following non-limiting example illustrates one use of the current invention:
The following 3 non-limiting examples describe the current invention:
Tarry suspension containing 0.5% solids by weight was input to the apparatus described in
Tarry suspension containing 20% solids by weight was input to the apparatus described in
In the drying process of coniferous biomass, e.g. spruce or pine, aromatics and resins go in the vapour phase, and are partially condensed by reducing the temperature. However much resin, especially resin molecules that condense at lower temperatures remain in the vapour stream. This vapour can be scrubbed with water to remove its contained resin and the resulting resinous water scrubber liquid can be fed into the horizontal axis centrifuge described in this invention to separate the contained resin in whole or part from the scrubber liquid. The scrubber liquid can then be recycled in whole or part or further treated in whole or part.
