Systems and Design

The Impact of granular segregation on heat transfer in rotary kilns, Cristine Beaulieu

Fluidized bed thermogravimetric analyzer, Said Samih

The Impact of granular segregation on heat transfer in rotary kilns
Rotary kilns are versatile equipment frequently used in the industry. They are particularly used in drying operations in the wood and mining industries, and during pyrolysis in waste management.  However, despite their popularity and widespread use, many problems still occur when it is time to heat granular matter in a rotary kiln. As a matter of fact, the state of the art on heat transfer for particulate systems within rotary kilns is still limited. For example, during tire pyrolysis in rotary kilns, the temperature remains low during the beginning of the operation. Once the size of the particles begins to change, small particles move differently in the tumbler, bringing with them a quantity of energy that drives up the temperature of the bulk unpredictably. This issue is at the heart of many problems in the industry and represents a topic on which there is a lot of ongoing research.

Personally, I am investigating this problematic by combining two approaches: numerical simulations and experiments. The discrete element method (DEM) will be used to simulate the segregation of particles of different sizes in the kiln, while radioactive particle tracking (RPT) will allow us to validate the numerical results. The variation of temperature of each particle will also be computed with DEM and validated by the use of thermocouples installed on a rotary kiln of lab scale available in our group. The comprehension of this phenomenon should help designing more efficient kilns and determining appropriate operational conditions to optimize heat transfer.


Fluidized bed thermogravimetric analyzer
The newly developed fluidized bed thermogravimetric analyzer (TGA) is the first equipment that combines both the fluidization and the weight measurement of the sample. The standard fluidized bed TGA consists of a quartz reactor with a diameter of 1 inch and a total height of 6 inch, a furnace and various measuring instruments. The measuring instruments include (1) a load cell for the weight measurement, (2) several thermocouples for temperature measurement of the bed, (3) pressure transducers for pressure drop measurement and (4) two mass flow controllers for gas flow rate adjustment.  The two mass flow controllers are linked to the thermocouple, which permits decreasing the gas flow rates when the temperature is increasing.  The apparatus is equipped with a software for the fluidized bed TGA in order to keep the system at approximately minimum fluidization at any temperature. The load cell measures the apparent weight of the reactor and the pressure transducers give the pressure drop across the distributor and the filter. The apparent weight, which is obtained from the load cell, is corrected by the model giving the pseudo variation of the reactor weight as a function of the pressure drop along the distributor. The exiting gases from the fluidized bed TGA are analyzed by means of a GC/FT-IR system.

The reactor can be fed by a wide range of solid samples, including solid fuels, biomass and solid waste. With different particle size and shapes, 5 g of the solid sample can be fluidized with different gas medium in the quartz reactor. The ambient reaction chamber can be heated up to 1100 °C with a 50 °C/min heating rate.

A schematic of the experimental setup can be found in our recent article, published in the American Institute of Chemical Engineers Journal, via the link below:

This project was financed by the Carbon Management Canada (CMC-NCE).