Pre-treatment of the wastes (SVZ) : Thus the solid wastes are applicable in the gasifier they had to meet certain conditions regarding
Therefore most wastes had to been pre-treated accordingly. At the SVZ the appropriate facilities for this purpose exists. As examples should be mentioned:
Mixed scrap plastics:
chopping, metals remove, sieving
cutting, sieving, metal separation (magnet), air
cutting, metal separation, air separation, secondary cutting, pelletization
drying process, mixing with other wastes, forming of briquettes
4. Summary and Outlook
In Germany the deposit is forbidden by waste with organic portions in principle. The cause for it is the harmful environmental effects and the high land consumption of the dumps. The recycling of waste received – apart from the waste incineration – therefore a high value. For the certain wastes, also in large quantities result, the recycling ratios are legally determined.
At present she endeavours the disposal economy, to develop the appropriate techniques, in order to be able to use these wastes materially or energetically (raw material or energetic recycling).
In Germany, two methods for recycling of high amounts of hazardous waste have been established. Both methods have their own specific advantages. One method is the ConTherm-Technology with approximately 100,000 t of hazardous waste are treated per year. Pyrolysis at about 500 °C leads to a degasification of waste. The products, pyrolysis gas and pyrolysis coke, can be treated energetically with high energetic efficiency at a slag-tap plant by common combustion with coal. The slag-tap plant is usually located at the same factory premises and benefits from a 10% substitution of coal by waste material. Initially, slag-tap plants were not designed for waste combustion. For that reason, the input material of the ConTherm-plant should be of high quality, i.e. highly contaminated waste is not suitable for this type of processing.
Another technology is represented by the SVZ plant – “Schwarze Pumpe”. About 300,000 t of solid waste and 60,000 t of liquid and paste-like waste are degasified at approx. 1,600 °C. The synthesis gas is to be cleaned and transformed to methanol at a separate plant. This processing method can be regarded as “material recycling” since methanol is a demanded raw material in chemical industry.
The SVZ-Process is highly flexible towards type and composition of waste due to the process control and the installed flue gas purification. Nevertheless, in most cases waste pre-treatment is needed. The gasification plant contains a fixed bed, slagging and entrained flow gasification. Five fixed-bed gasifiers (capacity 15 t/h), one slagging gasifier by British Gas Lurgi (BGL) (capacity 35 t/h) and two flue stream gasifier (capacity 16 t/h) are available [SVZ].
Possible input materials for slagging and fixed-bed gasification are solid wastes such as old plastics, Shredder-Light-Fractions (SLF), clearing sludge, municipal waste, domestic-like industrial waste, old rubber, old wood, rests of lacquer and paint, high calorific residues from mechanical-biological waste treatment, waste pellets from mixtures of tar and clearing sludge as well as other waste materials with hydrocarbon content.
Liquid and paste-like waste such as waste oil, tar/water mixtures and hydrous slurry products with high solid content are to be treated in the flue gas reactor. With the SVZ using technology after long development in between worked satisfactorily. In the future however the older aggregates (fixed bad gasifier and air flow gasifier) must be replaced.