Screw pyrolyzers

The screw pyrolyzer, with its lower cost of construction and operation, has great prospects in the future. A screw pyrolysis conveyer is provided with internal and external heating modes. It has a special configuration for the removal of the coke formed during the process, which is a threat to heat transfer, and continuous operation. Figure 27.4 shows a screw pyrolyzer. 

Figure 27.4 Screw pyrolyzer [2]. 1 horizontal vessel 2 gearbox 3 screw shaft 4 hopper 5 mouth for balance 6 jacket heating 7 inlet of heating gas 8 outlet of heating gas 9-11 drain pipes 12 outlet of volatile gas 13 char discharge 14 baffle...

A schematic diagram of the entrained flow reactor is shown in Figure 1. At the top of the reactor, a screw feeder and semi-venturi system is used to entrain the ground coal particles in the cold primary gas stream. The coal is then injected into the reactor where it is entrained in, and heated by, the preheated secondary gas. The pyrolyzing coal particles fall in a thin stream through the reactor and are collected by a movable water-cooled collector probe. The time which the particles spend in the reactor is controlled by moving the collector probe up and down the reactor axis. The pyrolysis reactions are rapidly quenched in the collector probe, and the particles are separated from the gas stream by a cyclone in the collection system. 

Scraped surface heat exchangers (SSHE) have been used as tubular reactors for plastics pyrolysis. SSHE overcome coking and carbon deposits forming on heat exchanging surfaces when the plastic pyrolyzes to hot gases. A tubular reactor with a special internal screw mixer has been developed in Poland [5]. The purpose of the specially shaped internal mixer is to mix the molten plastic and to scrape coke from the internal surface... 

The indirectly heated screw conveyor developed by Herbold for pyrolyzing shredded tires has been tested on a 2.5 t/d pilot installation. The main products are oil and a carbonaceous residue. The research project seems to be inactive at this moment[35l ... 

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