Pyrolytic reactors, control

Optimal control for pyrolytic reactors (with A.P. Jackman). Paper presented at the Fourth European Symposium, Brussels, 1968. 

Jackman,A.P. and R.Aris."Optimal Control for Pyrolytic Reactors 4th Euro.SympoOn Chemical Reaction Engineering. (1968). 

Kutrieb Corporation (Chetek, Wisconsin) operates a pyrolator process for converting tires into oil, pyrolytic filler, gas, and steel. Nu-Tech (Bensenvike, Illinois) employs the Pyro-Matic resource recovery system for tire pyrolysis, which consists of a shredding operation, storage hopper, char-coUection chambers, furnace box with a 61-cm reactor chamber, material-feed conveyor, control-feed inlet, and oil collection system. It is rated to produce 272.5 L oil and 363 kg carbon black from 907 kg of shredded tires. TecSon Corporation (Janesville, Wisconsin) has a Pyro-Mass recovery system that pyroly2es chopped tire particles into char, oil, and gas. The system can process up to 1000 kg/h and produce 1.25 MW/h (16). 

Chlorination of Hydrocarbons or Chlorinated Hydrocarbons. Chlorination at pyrolytic temperatures is often referred to as chlorinolysis because it involves a simultaneous breakdown of the organics and chlorination of the molecular fragments. A number of processes have been described for the production of carbon tetrachloride by the chlorinolysis of various hydrocarbon or chlorinated hydrocarbon waste streams (22—24), but most hterature reports the use of methane as the primary feed. The quantity of carbon tetrachloride produced depends somewhat on the nature of the hydrocarbon starting material but more on the conditions of chlorination. The principal by-product is perchloroethylene with small amounts of hexachloroethane, hexachlorobutadiene, and hexachloroben2ene. In the Hbls process, a 5 1 mixture by volume of chlorine and methane reacts at 650°C the temperature is maintained by control of the gas flow rate. A heat exchanger cools the exit gas to 450°C, and more methane is added to the gas stream in a second reactor. The use of a fluidi2ed-bed-type reactor is known (25,26). Carbon can be chlorinated to carbon tetrachloride in a fluidi2ed bed (27). 

Carbonaceous compounds can also form in the absence of a catalyst by free-radical, gas-phase condensation reactions. The formation of this pyrolytic carbon is known in steam-reforming reactors where it can be controlled to some extent by minimizing the free volume within the reactor chamber. This type of carbon does not form readily with methane but can be severe with larger hydrocarbons. The compounds formed by free-radical reactions tend to be quite different from the graphitic carbon formed by metal catalysts. For example, Lee et al. showed that the compounds formed by passing pure, undi-... 

Preliminary results show it should be possible to operate the MHR with a coolant outlet temperature of up to 1 000°C using nuclear-grade graphite fuel blocks, carbon-carbon composite materials for control rods and other internal reactor components, and existing coated-particle fuel technology with silicon carbide (SiC) and pyrolytic carbon coatings. 

The char is separated by cyclones, liquid is separated with a quench fluid and the gas is recycled or purified. The residence time in the reactor again is very short. The temperature of pyrolysis found effective is 850 F to 1050 F. Quench fluids are chosen for their immiscibility, low vapor pressure and rapid phase disengagement, A desirable fluidity in the product oil may be achieved by varying the moisture content. The moisture content of the pyrolytic oil is controlled by the quench oil temperature, A moisture content of 14-18% gives a suitable viscosity for handling municipal solid waste oil. 

A simple laboratory type reactor for pyrolytic-graphite deposition is shown in Fig. 7.2.PI The substrate is a molded-graphite disk which is rotated to improve deposition uniformity. It is heated by a high-frequency (450 kHz) induction coil and deposition occurs at low pressure (500 Pa). Temperature is monitored and controlled by a sheathed thermocouple and corroborated by an optical pyrometer. 

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