Abstract: The presence of the oxides of nitrogen in the exhaust gas leaving a regenerator is limited by injecting water or water vapour into the regenerator 1 during its firing phase and causing the water or water vapour to reach the combustion chamber 26 of the regenerator 1 by way its heat storage bed 11 which has been preheated during a previous heat collecting phase.

Abstract: The presence of the oxides of nitrogen in the exhaust gas leaving a regenerator is limited by injecting water or water vapor into the regenerator 1 during its firing phase and causing the water or water vapor to reach the combustion chamber 26 of the regenerator 1 by way its heat storage bed 11 which has been preheated during a previous heat collecting phase.

Abstract: The presence of the oxides of nitrogen in the exhaust gas leaving a regenerator is limited by injecting water or water vapor into the regenerator 1 during its firing phase and causing the water or water vapor to reach the combustion chamber 26 of the regenerator 1 by way its heat storage bed 11 which has been preheated during a previous heat collecting phase.

Abstract: A pulse-fired burner is operated by modulating a fuel supply rate between a pilot level and a main level to provide a flame the level of which modulates respectively between a pilot level during a non-firing phase and a main flame level during a firing phase. Air supplied at a pilot rate is premixed with the fuel before ignition, the pilot air level being sufficient to support combustion of the fuel at the pilot rate but not at the main rate. The supply of fuel is terminated if no flame is sensed.

Abstract: The regenerative heating apparatus (FIG. 1) comprises a pair of regenerators 51a and 51b arranged so that in use while one is being heated by waste gas, the other is preheating air for the combustion of fuel. A reversing valve 58 is connected to each lower end 91a and 91b of the regenerators 51a and 51b, the valve 58 connecting the regenerators 51a and 51b to an inlet 99 for receiving air and an outlet 100 for discharge of the waste gas. The reversing valve 58 is reversible to connect one regenerator to the inlet and the other regenerator to the outlet. Each regenerator incorporates at its upper end a burner (B1 and B2) with as shown in FIG. 2 a body having a passage 2 formed with openings 3 and 4. The opening 4 serves to receive air for combustion when its regenerator is preheating air or to discharge waste gas to the regenerator while the opening 3 serves to supply combusted fuel and air to the furnace 90 or to receive waste gas from the furnace 90.