The report describes a low-NOx burner design, presented for residual-oil-fired industrial boilers and boilers cofiring conventional fuels and nitrated hazardous wastes. The burner offers lower NOx emission levels for these applications than conventional commercial burners. The burner utilizes two-stage combustion in a deep staging mode in which a precombustor firing substoichiometrically is retrofitted to the front of the boiler. The completion of the combustion in the second stage is achieved through sidefire air ports to be retrofitted to the boiler. The precombustor is a cylindrical shell of 2.1 m internal diameter fabricated of lightweight refractory blocks with a Saffil based coating. This material gives a lightweight, non-regenerative precombustor which can adapt to the start-up, shutdown, and load following transients typical of industrial boilers. The precombustor is designed for the capacity range of 15-29 MW heat input. A modular design using annular spool sections adapts to different design loads within this range. For larger loads, a geometric scale-up is required. Design data are also given for 59 MW capacity.