Rotating kiln reactor

Li et al. [16] also stndied the influence of pyrolysis temperature on the pyrolysis products derived from solid waste in a rotary kiln reactor. They used an externally heated laboratory-scale rotary kiln pyrolyser (Figure 19.8). The length of the rotary kiln was 0.45 m with an internal diameter of 0.205 m. Kiln rotation speed can be adjusted from 0.5 to 10 rpm. The raw materials used in this study were polyethylene (PE), wood and waste tyres. The results obtained by Li et al. [16] reiterated that as the reaction temperature profile changes so does the product yield (Figure 19.9). 

As described previously pyrolysis is a process that thermally degrades organic waste at high temperatures in absence of air and oxygen. This process can be carried out in a rotary kiln reactor or in a fluidized bed. In a rotary kiln process the feed material is conveyed through a rotating drum (i.e. reactor) and is then pyrolysed in the hot atmosphere into gas and solid residues. The residence time of the reaction is dependent on the rotating... 

The majority of the scientific literatnre devoted to pyrolysis of plastics is focused on the development of equipment or processes having recycling as their ultimate goal. Many of these have been introdnced in previous chapters and include studies using fluidized beds [61-77], cycled-sphere reactors [78, 79], fixed-bed reactors [80, 81], rotary kilns [82], screw reactors [83] and rotating cone reactors [84]. In all these studies the chemical analysis of the pyrolysis prodncts has been an important goal in order to asses the behavionr of the pyrolysis of plastics. 

Other designs of kilns use static shells rather than rotating shells and rely on mechanical rakes to move solid material through the reactor. 

Beside continuous horizontal kilns, numerous other methods for dry pyrolysis of urea have been described, eg, use of stirred batch or continuous reactors, ribbon mixers, ball mills, etc (109), heated metal surfaces such as moving belts, screws, rotating dmms, etc (110), molten tin or its alloys (111), dielectric heating (112), and fluidized beds (with performed urea cyanurate) (113). AH of these modifications yield impure CA. 

Continuous sulphuric acid breakdown processes are possible in which the acid and ore are fed together at the top of a rotating, inclined, heated kiln. The reaction products and excess sulphuric acid can then be removed continuously from the lower end. It is necessary that the reactants and products shall not be sufficiently mobile for by-passing to take place when flowing down the reactor, otherwise residence times will vary widely about the mean value. A kiln of this type resembles that commonly used for the manufacture of hydrofluoric acid by the reaction of sulphuric acid with fluorspar (calcium fluoride). 

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