Energy utilization of plastics, rubber waste and tyres

Plastics, tyres and rubber wastes represent a serious problem in the whole world. As a result of a growing demand for plastics and the growing vehicle ownership, production of plastics, production and import of tyres and subsequent increase of wastes from these commodities rise in all European countries. These wastes are not bio-degradable! Ten million people get a share of about eighty thousand tons of tyres per year; this amount would provide energy to a town with 400,000 population. Thermal degradation of plastics and/or tyres produces two energy fractions, i.e. a gaseous and a liquid fraction. The solid phase is represented with carbon, which can be utilized in several ways; in case of tyres, the phase represents steel scrap, which is found in these tyres.

The gas and the oil are further processed. The gas is treated and stored in gas containers or directly incinerated in electric power generators or cogeneration units. Some of the gas is used for heating the retort, thus equalizing the energy balance of the actual process, which is endothermic. The produced oil is treated by fractional distillation and produces various types of oil from extra light fuel oil to modified mazut. Just like in the gas phase, these compounds have multiple utilization, but they are primarily used in production of electric power and heat. The daily amount of processed plastics and tyres depends on the size of the equipment, but it ranges between 5 tons to 216 tons per day; it does not regard a single segment of the technology (a single retort), but it can involve more segments. The equipment can thus be connected in a cascade.

The chemical composition of the gaseous and liquid phase depends on several factors. The recovery ratio of plastics and tyres is about 75 %.The technology is suitable for resolving waste management issues, particularly ecological disposal of plastics and tyres stacked on dump sites and in scrap yards, which contain 2 % of rubber, 9 % of plastics, tyres, spent oils and steel scrap, which is a material demanded by ironworks. It is estimated that about 15 million tons of worn-out tyres must be liquidated in the civilized world each year; the Czech Republic produces about 70 thousand tons of "new" discarded tyres and the amount rises by ca 4 % per year; our technology can generate 70 barrels of oil from 10 tons of used tyres.