Chemistry plays an important role in almost every area of our lives - and so naturally that we are rarely aware of it. It doesn't matter whether we use the car, relax at home, work on the computer, play sports or just make phone calls: chemical products are part of our daily lives.
Due to the increased awareness of the social responsibility of a sustainable society, the impact of production on the environment must be reduced to a minimum level. As a result, the requirements for the production of chemical products and the purity of the products are increasing, the further or reuse of partial product flows and the air and water emissions are subject to ever stricter limit values.
The use of activated carbon helps in many processes and areas of application. This ranges from the treatment of liquid product streams in the chemical processes to the recovery of valuable substances and the purification of exhaust air and waste water in order to avoid negative effects on the environment.
A topic that is certainly becoming more and more interesting is the closing of the cycle of by-products from chemical processes, which generates a lot of savings potential and conserves resources. Here, too, the activated carbon plays a central role in the treatment of the by-product streams and is usually in the last stage.
Selection of the right activated carbon qualities
The activated carbon qualities from Donau Carbon for the treatment of liquids, cleaning of exhaust air and waste water include a large selection, which are very different in their adsorption capacity and properties.
Both the manufacturing or activation process and the raw material have a decisive influence on the properties and performance of activated carbon. Hard coal, lignite, wood, coconut shells and many other fruit shells or seeds that are available in sufficient quantities can be used as raw materials. When it comes to activation, a distinction is made between the use of steam and chemical activation using phosphoric acid.
The selection of the appropriate types of activated carbon for the respective application depends heavily on the chemical and physical properties of the substance to be adsorbed and the medium. However, other process-specific factors also play an important role in the adsorption process.
A wide area of application in adsorption technology is the treatment of liquids of all kinds. In addition to pure decolorization, the activated carbon also has the task of removing other dissolved organic impurities as well as odors and flavors by adsorption. As a rule, powdered activated carbon from the "®Carbopal" series is used in the stirred-in or suspension process or in sheet filtration. When using powdered carbon, multiple use is sometimes possible through recirculation. When using the fixed-bed process, the so-called "percolation process", granular activated carbon from the "®Epibon" series is used, which is characterized by an open-pored structure and excellent filter properties. The filtration behavior of powdered carbon depends on the fineness of the grind on the one hand, and on the other particularly on the grain shape of the ground activator. In the production of powdered activated carbon, the degree of grinding is adjusted to optimal filtration properties, since accompanying substances in the solution (e.g. colloids) can lead to filtration difficulties. In such cases it is advisable to use filter aids such as kieselguhr, perlite or cellulose fibers. In this case, a basic precoating (precoat) of the filter aid is first applied to the filter element before the filter is charged with the solution containing activated carbon. In special cases, filter aids can be dosed in addition to the activated carbon suspension. This does not affect the adsorption capacity of the activated carbon. Filter presses, candle filters and rotary vacuum filters are suitable for separating the powdered activated carbon.
When using granular activated carbon, depending on the type and concentration of the substances to be adsorbed, a reactivation of the used activated carbon is necessary.
The selection of the suitable activated carbon quality for the many different applications is carried out together with the customer and his specific requirements in application technology advice, which is based on more than 100 years of experience in the production, refinement and characterization of activated carbon.
Activated carbon used in the production of chemicals
The requirements for use in the chemical industry on the activated carbon are very high. The products not only have to provide the desired performance efficiently and reliably, but also have to be of the appropriate purity and homogeneous quality due to the high demands placed on the end products. Depending on the task, Donau Carbon products offer the right activated carbon.
| Application/ to be treated media |
Task / substance to be removed |
Recommended activated carbon |
| Phosphoric acid |
Removal of humic acids |
Epibon Y 12 x 40 spezial |
| Hydrochloric acid |
Removal of chlorobenzene |
Hydraffin CC 12 x 40 spezial |
| Adipic acid |
Removal of cyclopentanone |
Epibon Y 12 x 40 spezial |
| Natural resins, e.g. shellac |
Decolourization by removal of erythromycin |
Epibon Y 12 x 40 |
| Amino acid, e.g. methionine & cysteine |
decolourization |
Epibon Y 12 x 40 LC
Carbopal PA 4 N |
| Glycerine |
decolourization and deodourization |
Epibon Y 12 x 40
Hydraffin CC 12 x 40 |
| Paraben |
decolourization |
Epibon Y 12 x 40 spezial |
| Pentaerythritol |
decolourization |
Hydraffin P800 C |
| Amine purification |
Removal of organic compounds |
Hydraffin 30 N |
| Diammonium hydrogen phosphate |
Removal of BTEX |
Epibon Y 8 x 30 spezial |
| Bates, caustic solutions and galvanic baths |
Reduction of COD-concentration |
Hydraffin 30 N
Hydraffin MB 6 |
Use of activated carbon in waste water from chemical production
Activated carbon is used in many industries to prevent contamination of the aquatic environment.
In Germany, the maximum permissible pollutant concentrations for industry are regulated by the Wastewater Tax Act. An important and frequently used parameter is the chemical oxygen demand (COD). In order to be able to comply with the limit values, e.g. in oil refineries or in the steel industry, open-pore, granulated activated carbon such as our Hydraffin 30N is used. This quality, based on hard coal, guarantees the best adsorption properties and a long service life for the customer. In addition, depending on the adsorbed substance and loading, our wage reactivation service can be used.
Example: A waste water system with a capacity of 150 m³/h water with the following process run:
1. Collection basin (surface water + process water)
2. Flocculation
3. Gravel filter
4. Fixed bed reactor (biological stage)
5. Third cleaning stage with two activated carbon filters of 60 m³ each
6. Outfall
Service life of the activated carbon filter: 2-3 years
Another problem for many companies is the removal of residual product concentrations (pollutants from the WGK), which are usually present in significantly lower concentrations and have to be cleaned in a correspondingly complex manner. Donau Carbon recommends that customers either use powdered activated carbon if it is often a question of temporary production or low volume flows. Here, a dosage of 10-20 g of activated carbon per m3 of waste water must be assumed. In the case of regular waste water, the use of granulated activated carbon is an economically viable solution.
The decolorization of waste water is not only an important topic for the textile industry, as the removal of colorants is a key issue in waste water treatment and public perception. The use of very porous powdered activated carbon has proven to be the best product quality in large-scale technical tests. It turned out that the simultaneous dosing of coagulation aids (polymers) into the treatment tank is ideal for the desired goal in waste water treatment.
Use of activated carbon in the exhaust air from chemical production
Gaseous emissions are usually also problematic for the production companies, which, in addition to undesirable odors, can also have a health relevance. For this purpose, activated carbon from Donau Carbon is used in various processes. The abundance of different substances that impair human well-being or disrupt highly sensitive production processes can usually be separated by using special types of activated carbon. Both non-impregnated and chemisorptive activated carbons are used here. Therefore, Donau Carbon has its own impregnation capacities.
A contact time of 0.1 to 0.2 seconds in the fixed-bed adsorber can be used as a guideline for the separation of organic vapors and odorous substances. In the case of high, relative humidities and very high clean air requirements, higher contact times are also used. In general, fine-pored activated carbon with a high retention capacity is used for this task, which, depending on the substance adsorbed, is primarily reactivated or otherwise used. The adsorption isotherm of benzene from air at 20° C is used, for example, to characterize suitable activated carbons. Another standard method is the determination of the carbon tetrachloride or n-butane activity, which is determined according to ASTM. The relevant characteristics of the Desorex and Supersorbon types are listed in the data sheets of Donau Carbon.
In many exhaust air problems, in addition to low-molecular, mostly inorganic, poorly adsorbable substances, there are also organic vapors that are to be eliminated by adsorption (e.g. traces of hydrogen sulphide in addition to petrol vapours). In these cases, a combination of impregnated and purely adsorptive, non-impregnated activated carbon is optimal.
Extremely volatile pollutants such as chlorine, ammonia, sulfur dioxide, mercury and hydrogen sulfide can only be accumulated on activated carbon to a very small extent at normal pressure, so that pure adsorption processes cannot be used
By impregnating activated carbon with various substances, such as metal salts, iodine, sulphur, acids or bases, these substances are converted and fixed on the adsorbent via chemisorption. The impregnating substances act either as chemical reactants or as a catalyst.
In industry, solvents are often used, which then evaporate as the process progresses, e.g. B. in the printing industry, paint shops. A recovery of these solvents is both ecologically and economically desirable. The Donau Carbon (formerly Lurgi) Supersorbon® process is based on enriching the solvent with activated carbon, which is then desorbed again using superheated steam or hot inert gas and recovered by treating the condensate.
High-quality activated carbon with a balanced pore structure is used for this application. The solvents are retained in the micropores and the required exhaust air values are maintained. The existing access pores in the macro and mesopore range ensure that the solvent can be desorbed from the activated carbon with low steam consumption. The activated carbon is used in fixed-bed adsorbers and should have the lowest possible flow resistance. For this reason, mainly cylindrical activated carbons with a diameter of 4 mm are used. Depending on the type of solvent to be separated, activated carbon types based on different raw materials or with a low ash content are suitable.
Summarized
The chemical industry is one of the most important branches of industry, as it produces the educts required for many other branches of the economy, such as plastics, pharmaceutical products, adhesives, pigments, cleaning agents and personal care products. Important branches of industry that require these substances are the plastics industry, the food industry, the automotive industry, mechanical engineering, the glass industry and the building materials industry.
There are a variety of applications in which activated carbon is used for this central branch of the economy and many new ideas for closing material cycles or meeting the latest requirements for emissions from manufacturing companies and reducing the environmental impact.
Our mobile filter systems, which are flexible in every respect, are in great demand in many companies: the small and medium-sized filters are completely replaced after use. For larger filters there are facilities for changing the loaded activated carbon. Donau Carbon offers logistics and changeover concepts that are tailored to the needs of customers and reduce personnel and operating costs. Ready-to-use part or complete solutions (i.e. activated carbon filters including all necessary components) are available to those customers who do not have their own logistics or personnel for the maintenance of the filter systems. There is also the option of just renting the filters - for temporary needs or to test the extent to which an adsorption process can be used economically.
Author: Head of Activated Carbon Application Technology Marco Müller
Together with his team, he is constantly working on high-quality activated carbon qualities and innovative application solutions.