Optimizing a thermal fluidized-bed tar-sands extraction process

The viability of a thermal fluidized-bed tar-sands extraction process, consisting of two fluidized beds operated in series and thermally coupled by heat pipes, has been previously demonstrated. To properly scale-up the reactor, both laboratory-scale and industrial-scale reactors should be operated in the same fluidization regime. A program was undertaken to examine the effects of heat pipes on fluidization regime. From studying the power spectrum of the pressure-drop fluctuations, it was concluded that the lab-scale unit is always operating in the bubbling regime. To identify the most economically optimal operating conditions and reactor configuration, a mathematical model of the coupled system has been developed, including a novel py-rolysis-reaction network. The model predicts trends in accord with those observed experimentally. Concern has previously been expressed that the casing of the heat pipes might fail, due to the highly erosive environment inside the fluidized beds. An experimental program concluded that this is not likely to happen within the expected life time of a plant, even though erosion and corrosion act synergistically to increase wear rate over that of the sum of both processes acting independently. The temperature control of the two thermally coupled fluidized beds is complicated by the nature of the thermal interaction between them. Using the internal model control tuning method, sufficiently good control performance was experimentally observed without lengthy on-line tuning.