Pyrolysis of 10 coals with carbon contents of less than 80 wt%(daf) has been studied with a fixed bed quartz reactor to examine mainly nitrogen release from char-N without volatile matters. When temperature is raised from 1000 to 1350 degreesC, N-2 yield increases but char-N decreases for all the coals used. There is a strong reverse correlation between N-2 and char-N-2 which points out that most of N-2 arises from char-N via solid phase reactions. NH3 is also formed from char-N at high temperatures of greater than or equal to 1000 degreesC. In the pyrolysis of low rank coals, demineralization by HCl washing increases yields of tar-N, HCN and char-N, but decreases NH3 and N-2. The addition of 3 wt% Ca to the demineralized coals shows almost the reverse effect. The XRD measurements after pyrolysis at 1000-1350 degreesC reveal that the Ca exists predominantly as CaO with the average crystallite size of 25-65 urn and promotes carbon crystallization. As the extent of crystallized carbon increases, N-2 yield increases remarkably. It is likely that the highly dispersed CaO catalyzes efficiently conversion reactions of char-N to N2 in the process of carbon crystallization. The reaction mechanism is discussed in term of interactions between CaO particles and char-N. (C) 2002 Elsevier Science Ltd. All rights reserved.