Basic operations particle size reduction

Before MPW is fed into the process, a basic separation of the non-plastic fraction and size reduction is needed. This prepared feedstock is then introduced in the heated fluidised bed reactor which forms the core of the process. The reactor operates at approximately 500 °C in the absence of air. At this temperature, thermal cracking of the plastics occurs. The resulting hydrocarbons vapourise and leave the bed with the fluidising gas. Solid particles, mainly impurities formed from, e.g., stabilisers in plastics, as well as some coke formed in the process mainly accumulate in the bed. Another fraction is blown out with the hot gas and captured in a cyclone. 

Basic unit operations may be defined as those by which chemicals undergo physical change, such as a reduction in particle size, a change in crystal form, or the change of a liquid to vapour. Unit operations may be carried out on a batch basis (i.e. discontinuous production) or on a continuous basis. It is important to distinguish between unit operations as described, and unit processes such as esterification, nitration, or sulphonation, which are chemical changes by which new compounds are formed. They are, however, interrelated since no unit process can be carried out in the chemical factory without the application of one or more unit operations. The basic unit operations are listed in Table 2, showing the type of chemical plant used. 

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