Thermal treatment effect on NO reduction by potassium-containing coal-briquettes and coal-chars

This communication reports the NO reduction activity of potassium containin g coal-briquettes prepared at different pyrolysis temperatures. For compara tive purposes coal-chars prepared at the same temperatures have also been a nalyzed. NO reduction experiments were performed in a fix-bed flow reactor at atmospheric pressure using two types of experiment: (i) temperature prog rammed reaction in a NO/He mixture; and (ii) isothermal reactions at 600 de grees C. The reaction products were monitored in both cases, thus allowing detailed oxygen and nitrogen balances to be determined. It has to be pointe d out that a previous in situ heat treatment in He before reaction is neces sary for the low temperature activity of potassium containing coal-briquett es. For fresh briquettes, NO direct attack in addition to NO conversion by the catalytic action of potassium is observed at high temperatures. The NO direct attack, both in potassium containing samples and coal-chars, is clea rly manifested by a nitrogen imbalance. (C) 1999 Elsevier Science B.V. All rights reserved.