|
The production of peat supplies approximately 4 % of the total energy consumption on Finland. Peat is produced in bogs, where the produced fuel is stored in stockpiles. Because of self-heating caused by microbe activities and chemical reactions there is an annual loss of about 5% of the energy content of stored peat. The supervision based on visual control combined with manual temperature measurements carried out on the peat bog is expensive, and furthermore a very unreliable method. Because the warm patterns in the peat stockpiles are not necessarily found. The damages can partly be avoided when self-heating is observed in time and the necessary actions are carried out. The Research Institute of Northern Finland, University of Oulu, started an experimentation of airborne thermal scanning supervision of peat stockpiles on initiative of A. Jalander Oy, a subsidiary of Kemira Oy, in 1987. The field studies have been made as a co-operate project of the Research Institute of Northern Finland and Building Laboratory, Technical Research Center of Finland (Oulu, Finland). During the experiment 2800 thermograms were taken of peat stockpiles, the inner temperature of 200 of the stockpiles being controlled on the bogs. On the basis of the studies it has been possible to define the criteria for thermal scanning of peat stockpiles. Depending on the weather conditions, even a difference of 2 degrees in the surface temperature of the stockpile can indicate a warmed pattern. In autumn 1990 a regular airborne supervision based on thermal scanning was started on the peat bogs of two producers, the peat bogs containing altogether approximately 1 million m3 of peat, the area supervised being about 3500 hectares. The flights were made three times an autumn with intervals of 4 weeks. The flights have been made on a four-seated airplane, the frame of which was equipped with a hole for the infrared scanner. The results were documented on videotape, and video printer shots of the suspected warmed stockpiles were sent to the producers. The supervision has proved to be quite reliable. The self-heating of the stockpiles has been observed at an early stage long before the ignition. The costs of airborne supervision have been covered with the amounts of the saved energy.
|
