ENAMELING MACHINES VZ-6 AND HES–4 BURNT GAS CATALYTIC PURIFICATION DEVICE AS A BASIS OF ENSURED ECOLOGICAL SAFETY IN ENAMEL-WIRE PRODUCTION.
In enamel-wire production in the PC “Akvaton” we use enamels with solid substance content from 30% to 40%. The remaining part consists of solvent that evaporates during enamel solidification. As the practical tests carried out in our enterprise showed the most effective oxidation and solvent vapor burning is provided by application of all-metal catalysts made by the firm KATEC KATALISATOREN (Germany), (see picture 1) for catalytic purification. Application of two catalysts on enameling machine is enough to reach complete purification of burnt gases. In our enterprise the enameling machines are equipped exactly in such mode.
Gas mixture, discharged form the enameling machines mainly is a mixture of air and solvent vapors. Solvent vapors burning by all-metal catalysts not only exclude pollution of the environment but also allows eliminating condensate in the furnace ventilation system.
Picture 1. All-metal catalysts made by the firm KATEC KATALISATOREN
Those catalysts were especially designed for hydrocarbons splitting in industrial burnt gases and they are mainly used in cable-conductor industry.
The process of all-metal catalysts production is shown in the pictures 2, 3, 4, 5. All-metal catalyst consists of base material and “active” substance, applied on it. As an active catalyst coat carrier there is produced a flat wire of thermo-strengthened chromium-nickel steel (Ni-60%, Cr-15%), and the rest is iron and special additions.
Picture 2. Process of binding of catalytic surfaces
On this wire by the method of galvanization is applied platinum and palladium as activating components. It is possible to transform the wire with cross-section of 0.5x3 mm in any form and wind it in any direction.
Picture 3. Galvanic coating of surfaces.
Thus a large active surface of catalyst is obtained that looks like a mat metal filter which provides satisfactory solvents vapors flow and offers the resistance to gas flow 5-10 times smaller then other catalysts and those catalysts also have greater mechanical strength.
High heat-conductivity prevents all-metal catalysts overheating in exothermal processes of complete CO and organic compounds oxidation.
Those catalysts differ from others by their high thermo-stability (they bear overheating up to 700-750 0C), they have a long service-life and they provide deep oxidation.
During enamel-wire production solvent vapors on the certain temperature level (temperature of solvents vapors burning is 550-700 0C) reach the active coat of catalyst, oxidize, i.e. under the oxygen influence they burn up. The tests in the field of catalysts selection, carried out in our enterprise, proved that all-metal catalysts with platinum-palladium activating components are the most effective for rendering gas-medium harmless that is provided by platinum and palladium power to accelerate different reactions. In platinum and palladium presence take place oxidation, hydrogenation, dehydrogenation and other transformations.
Picture 4. Surfaces activation process
Those catalysts are able to work both in regeneration and oxidation mediums what is highly essential for deep oxidation.
The firm KATEC KATALISATOREN carried out investigation of benzene, toluene and xylene deep oxidation (85-100%). The catalysts with active components of three types: noble metals (1) (platinum, palladium), alloys (2) and oxide systems (3) were used for investigation.
Picture 5. Catalysts assembly
On the picture 6 is shown reagents transformation degree on catalyst surface depending from reaction temperature.
T – temperature of catalytic reaction
Ŋ – reagents transformation degree.
Picture 6. Dependence of reagents transformation degree ŋ on catalyst surface from reaction temperature T for catalysts of types 1-3.
As the results of investigations have shown, the catalysts with noble metals active components provide practically complete transformation of substance being oxidized into carbon dioxide, water, nitrogen and exclude formation of carbon oxide and incomplete oxidation toxic products. The oxidation process occurs via formation of surface compounds with atomic oxygen with further implantation of oxygen to it and disintegration up to CO and H2O. The presence of active components decreases the interaction temperature and the process of oxidation reaction of, for example, CO, begins under low temperatures according to uninterrupted cycle with participation of O2 radicals.
Thus, during investigation and quantifiable determination of burnt gas exhausts in the process of enamel-wire production by one enameling machine with capacity of 1000 t per year their qualitative quantitative content can be equated to vehicle exhaust gases.
As the world practice has shown, there are no chemical substances in their pure form in exhaust air mixture if in enamel-wire production on enameling machines made by the firm MAG were used all-metal catalysts made by the firm KATEC KATALISATOREN. For determination of exhaust air mixture pollution degree we used gas analyzers that determine exactly separate components of exhaust gases.
Controlled efficiency coefficient of all-metal catalyst active coat burning reaches 99% and ensures burning of solvent gas mixture in the range not less then 95-96%. It means that, for example if the content of solvents in air mixture before catalyst is 2 g/m3, after catalytic cleaning the level of elimination of contamination by hydrocarbon radicals will reach 40 mg/m3. The service life of those catalysts without replacement is some thousands of hours. But thermal, chemical and mechanical influences reduce efficiency.
Investigations carried out in our enterprise with universal gas-analyzer ГАНК-4 have shown that concentration of harmful substances in exhaust gases is 4x10-6 (ppm) if a new catalyst is applied and concentration of harmful substances in exhaust gases reaches 28x10-6 (ppm) after a year of this catalyst operation (1 ppm = 0.45x10-5 mg/m3). But all-metal catalysts can be reactivated. Reactivation is a chemical catalyst cleaning process in the result of which contaminated catalyst surface achieves its active initial condition. In our enterprise we carry out the test of catalyst efficiency not less than once per week and we also carry out the monitoring of:
- Exhaust air temperature before and after the catalyst;
- Smelt and color of burnt gas after catalyst (steam, fug);
- Pressure losses though the middle of catalyst (U-tube manometer).
Not less than once per half a year we carry out the monitoring of burnt gas mixture. The methods for direct determination of gas mixture separate components, known in the world are – gas chromatography and infrared spectrography, but those methods require too much time for every separate measuring and its evaluation. For the present moment there is more precise method of exhaust gas mixture investigation, which is used in our enterprise too – with gas-analyzer ГАНК-4, that allows carrying out express-analysis of exhaust air and ensuring precise results even in concentration zone less than 5 mg/m3.
For the case of necessity there exists a reserve of catalytic cleaning efficiency by applying platinum-palladium alloy of the type 25/75, where platinum content is 25% and palladium content is 75% as an activating coat; it is significantly more expensive but more efficient catalyst.