Catalyst – solid sorbent – or support therefor: product or process – Forming or treating a sphere – process only – Treating preformed sphere only
Reexamination Certificate
2000-03-15
2001-11-13
Hendrickson, Stuart L. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Forming or treating a sphere, process only
Treating preformed sphere only
C201S025000, C201S038000, C502S418000, C502S432000, C502S437000
Reexamination Certificate
active
06316378
ABSTRACT:
The invention relates to a process for the production of shaped activated carbon by steam activation in a continuously operating rotary tunnel kiln. The activated carbon has high quality and is versatile. It is used for gas and air purification, for solvent recovery, in particular for decolouring in the chemical and pharmaceutical industry and in water treatment.
DE 19 65 04 14 relates to the production of spherical adsorbents from ion exchangers, weakly acidic cation exchangers, precursors of ion exchangers and distillation residues. Anion exchangers, cation exchangers and the precursors of ion exchangers are carbonised under oxidising conditions at up to 750° C. and then activated. Styrene/divinylbenzenes in gel form are mixed with radical formers, pyrolized and activated. The spherical activated carbon from distillation residues is obtained by adding bitumen, extruding to form cylindrically shaped articles, pelletizing to form spheres, carbonising and activation. The said pyrolysis and activation conditions lead to an activated carbon of only medium quality with too low a yield. The mixing of styrene/divinylbenzenes in gel form with radical formers increases the production-engineering expenditure without leading to a substantial improvement in the activated carbon quality. The processing of distillation residues is only possible using high equipment expenditure. The quality level, especially abrasion resistance and hardness, of the activated carbon produced in this way is unsatisfactory.
The production of activated carbon beads from ion exchangers is described in DE 43 28 219. Granular organic ion exchangers of the gel type are carbonised in an inert atmosphere at 600-900° C. and activated at 800-900° C. in an oxidising atmosphere. The ion exchangers are pre-oxidised at temperatures of up to 400° C., the oxygen content being reduced as the temperature increases. The activation takes place by means of from 3 to 50 vol % of steam in a fluidised bed. In order to prevent agglomeration, the starting products are dusted with hard coal powder or activated carbon. The activated carbon beads which are produced have a pore distribution with a narrow spectrum of mesopores in the 100 to 300 Å range and only a few macropores. This narrow pore distribution and the low number of macropores significantly restrict the use of the activated carbon beads. A prerequisite for a broad application spectrum of activated carbon is an open pore distribution over the entire pore range, covering micro-, meso- and macropores. A large number of macropores is important for the diffusion of the molecules to be absorbed. The diffusion is the speed determining step when activated carbon is used. Another disadvantage is that, under the conditions according to the invention, it is not possible to produce a high-quality activated carbon with defined and variable pore size distribution and sufficient yield.
U.S. Pat. No. 3,533,961 describes a method for the production of spherical activated carbon from powdered carbon material such as soot, bituminous coal, anthracite, charcoal and pitch as binder. A spherical activated carbon is produced by agglomeration, drying, charring and activation.
Processes for the production of spherical activated carbon from pitch by solvent agglomeration and activation in an ammonia atmosphere at from 550 to 1000° C. and additional steam treatment are disclosed by U.S. Pat. Nos. 3,909,449 and 4,045,368.
U.S. Pat. No. 3,041,116 describes a process for the production of spherical carbonaceous material and spherical activated carbon from pitch and amorphous coal particles with a viscosity modifier.
These processes are expensive in terms of equipment and engineering, since the production of spherical starting materials requires additional process stages. The production of shaped activated carbon with very high absorption capacity and BET surface area is limited by the reduction in hardness and abrasion resistance as the degree of activation increases, this being due to the nature of the process.
The object of the invention is to produce high-quality, versatile shaped activated carbon on a continuous scale from various carbon-based materials. For production engineering reasons, the shaped activated carbon should be substantially free of adhering dust and, besides a high adsorption capacity, should also have a high packing density.
The shaped activated carbon is produced from spherical raw materials which contain at least 3% volatile components and at most 40% ash, both expressed in terms of solids content, such as polymer resins, acetylene coke and pearl cellulose, by steam activation in an indirectly heated, continuously operating rotary tunnel kiln.
According to the invention, the preformed spherical starting product is delivered to a rotary tunnel dryer pre-heated to from 880° C. to 900° C. up to a filling level of from 10% to 20% of the kiln volume, a product temperature of from 250° C. to 300° C. is set up in the dryer in the 50% to 80% kiln length range, calculated from the product input, and the material is dried continuously with 6-fold product turnover per kiln rotation by means of a hot gas in countercurrent with a residence time of from 30 to 60 minutes to a residual moisture content of at least 10%, then transferred to an indirectly heated rotary tunnel kiln, which is subdivided into a carbonising zone and activating zone, up to a filling volume of from 5 to 12%, and carbonised and activated continuously in an inert-gas flow with 8-fold product turnover per kiln rotation and a product temperature profile in the carbonising zone of from 850 to 900° C., the residence time being from 120 to 180 minutes, and a product temperature profile in the activating zone of from 910 to 920° C., with a residence time of from 480 to 720 minutes, with the addition of from 3 to 5 kg/h.kg of steam in the activating zone.
In the rotary tunnel dryer, the product is transported with a speed of from 6 to 17 cm/min. The flow rate of the hot gas, expressed in terms of the free cross-section of the kiln, is from 0.2 to 0.5 m/s, with a kiln length to kiln diameter ratio of from 5.5 to 10.
The carbonising and activation take place in a rotary tunnel kiln, the carbonising zone covering 20% and the activating zone covering 80% of the heated kiln length. In the carbonising zone, there is no addition of steam and the product temperature profile, calculated in terms of the heated kiln length from the product input, is 850° C. at the product input, 880° C. after 10% of the kiln length and 900° C. after 20% of the kiln length. The activation is carried out with a product temperature profile of 910° C. after 30% of the kiln length, 920° C. after from 40 to 70% of the kiln length, 915° C. after 80% of the kiln length and 910° C. at the product output. The transfer speed through the carbonising zone and the activating zone is from 10 to 30 cm/min, with a kiln length to kiln diameter ratio of from 10 to 30. The steam is passed through the kiln with a flow rate of from 0.1 to 0.4 m/s, with an allowable reduced pressure of from 0.5 to 2.0 mm water column on the flue-gas side.
The shaped activated carbon produced according to the invention from various carbon-based spherical materials also has, besides a very high adsorption capacity and a very good desorption capability, outstanding abrasion resistance. Because of the high packing density and the open-pore structure, the shaped activated carbon is suitable for a wide variety of fields of use, in particular gas and air purification, solvent recovery, decolouring and in water treatment. The extremely low adhering and free dust content of the shaped activated carbon and its repeated regenerability are of particular advantage for practical application. The low equipment expenditure and the high qualitative yield permit economical production of very high-quality shaped activated carbon on a continuous scale.
The invention will be explained in more detail with the aid of the following embodiment examples.
REFERENCES:
patent: 1505517 (1924-08-01), Woodruff et al.
pat
Giebelhausen Jann-Michael
Spieker Hubertus
CarboTex, GmbH
Hendrickson Stuart L.
Keusey, Tutunjian & Bitetto
LandOfFree
Process for the production of shaped activated carbon does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for the production of shaped activated carbon, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the production of shaped activated carbon will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2592519