GRAIN COMPOSITION AND CORROSIVE ACTIVITY OF ASH FROM CFB OIL SHALE BOILER
Tallinn Technical University
Thermal Engineering Department
SE Eesti Energia
| Burning of the Estonian oil shale in CFB test boilers of
Hans Ahlstrom Laboratory and LLB Lurgi Lentjes Babcock GmbH  showed very intensive
pulverizing of ash. The following laboratory investigations of ash properties showed the
incomplete decomposition of the oil shale carbonate part . Decomposition of minerals of the
sandy-clay part was at initial stage due to considerably low temperature (850 °C). Only carbonate
minerals decomposed. At such temperatures the formed free CaO is not over-burned and can be very
easily pulverized. In test devices the intensive pulve-
rizing of ash took place in the system reactor/recycling cyclone. Up to 50 % of the total ash was collected as fines.
Above-mentioned changes in oil shale ash properties and amounts may, compared to the traditional pulverized firing (PF), cause also the different behaviour of ash keeping in view the fouling and corrosion of heat transfer surfaces.