Heated Tube
Heated tube reactors include a family of reactors with fixed walls in a tube shape with the feedstock inside being transported via various driving modes. Tubular reactors are externally heated and so are often used for pyrolysis applications as this allows the introduction of heat without oxygen. This type of reactor takes different forms such as a screw pyrolyser, a tubular rectilinear reactor with solid driven forward by a vibro-fluidised transport, and a tube with an inner mixer. The advantages of these systems include:
- Continuous coke and gas removal from the reactor tubes free from leakage
- Larger heat transfer surface in a unit volume
- Convenience for syngas reforming[1]
Design
As a typical tubular reactor, the screw tube, with its lower construction and operation costs, has great future prospects. For this design, the screw speed can be varied within 0.5–25 rpm (rotations per minute), thereby changing the residence time of the materials in the tube reactor. Examples of tubular reactors used in pyrolysis systems include in the Thermoselect process, the Compact Power process and CNRS thermo-chemical convertor[2].
Feedstock
This reactor system has been found to be useful for both the thermal and catalytic cracking of waste plastics. However, tubular reactors have the same rigid requirements for MSW pre-treatment as the fluidised-bed reactors due to the small channel for passage of MSW. In addition, erosion caused by sand and other hard solids contained in the MSW can be a risk for this reactor, and heat transfer rates are not well defined for different waste types[1].