Combustion furnace pyrolysers

Earlier pyrolysis equipment tended to be somewhat complex in design and operation. Thus, Cox and Ellis Mescribed a micro-reactor pyrolyser which they applied to large numbers of polymers. Temperatures increases of 700 - 1000°C were used in order to completely pyrolyse O.lg samples of the polymers. The pyrolysis products were collected for 15 min then swept onto a gas chromatographic column equipped with a flame ionization detector. This type of equipment has now been displaced by the more recently described equipment as discussed later. 

Two procedures have been described, (I) flash filament pyrolysis (Section 6.3.1) and (ii) heating the polymer in a micro-reactor and collecting the total volatiles produced, (Section 6.3.2). In yet another more recent approach, the pyrolyser probe method discussed below, the polymer is placed in a quartz tube which is then inserted into a platinum coil heater element. The coil heater is switched on to release the pyrolysis products which are then directly swept into the gas chromatograph. 

Chemical Data Systems UK supply a range of pyrolyser probes which are discussed in Method 107. These probes can be used in conjunction with any suitable gas chromatograph. 

In the chemical data systems - filament coil type pyrolyser, Pyro-probe 122.the polymer samples are held in a quartz tube that is inserted into the platinum coil. If pyrolyses are to be conducted at slow rates the pyrolyser is interfaced to a sample concentration (Model 320, Chemical Data Systems) which collected the pyrolysates on a Tenax filled trap. In this way polymer samples can be processed for minutes or hours at slow heating rates and the pyrolysates collected for a single gas chromatographic analysis. When the pyrolysis is complete, the trap is pulse heated and backflushed with the carrier gas. The desorbed pyrolysates are transferred to a gas chromatograph (Model 3700 Varian or equivalent) equipped with a 50 m x 0.25 mm i.d. SE-54 capillary column (Quadrex). 

A 6- 1 split was established at the injection port of the gas chromatograph and the column was programmed from 50 to 280° at a rate of 40°C min . A flame ionization detector is used and the area data obtained from a recording integrator. 

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Figure 1. Design of the Pyrolyser-6 Trio combustion furnace...

In industrial practice, however, the most widespread technique consists in passmg a mixture of hydrocarbons and steam through tubes placed in a furnace. The hydrocarbons, which are raised to high temperature, are pyrolysed and the resulting products are separated after a rapid quench. Coke deposits are periodically removed by controlled combustion. This is the technology of steam cracking, which is the main focus of this chapter. 

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