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Show The DAZ registers employ two sets of indepentently adjustable louvers; core and annulus, which divide the combustion air into two counterrotating concentric streams. The principle of operation of the two counter-rotating streams is to promote highly turbulent mixing at a relatively low net swirl number. The resultant effect is a short, narrow flame body, which, for this application, was highly compatible with the closely spaced existing front wall throat cutouts. To accomodate the larger register throat size in the confined front wall available space, plastic re-" fractory was installed (in lieu of the normally used pre-fitted refractory tile). The packed throat served ~o adequately protect the front waterwall tubes without tube relocation. To avoid interference of the closely spaced flame fronts, the throats were shaped to be narrower on the horizontal center-line, and wider on the vertical center-line,producing an oval shape necessary for successful operation. Each of the four registers was equipped with automatic louver control, whereby core and annulus blade angles are positioned as a function of firing rate. The utilization of automatic louver control enables system operation at lower excess air levels throughout the firing range. A single power unit and associated linkages are provided for each burner to control the core and annulus blade angle settings. The burner guns used for this application were Coen #2-MVs (multiple venturi), single gun arrangement (four guns total). The atomizer is a twin fluid, internal mix type, designed to operate on either steam or compressed air. The atomizer utilizes an internally located multiple venturi mixer for initial liquid breakup. The mixed stream then exits the nozzle body via a multiple drilled orifice cap which, for this application, was designed to bias the oil spray in the direction of the available (tertiary) air stream. The atomizers are designed to operate with between .15 and .2 pounds of steam per pound of oil, depending on flowrate. Maximum supply pressures for this application are 150 PSIG for both steam and oil. Steam and oil piping trains were factory assembled onto brackets and were bolted or welded in place on the front of the windbox extension, minimizing field retrofit installation. The most Significant combustion modification to the boiler was the addition of floor ports; The selected design, which is discussed later in this report, utilizes two ports per burner for a total of eight NOx ports. For each burner, tertiary air is brought in from the common wind box via a 12 inch diameter header, which is then divided into two rectangular sleeves prior to penetrating the furnace floor. Port velocities are designed to utilize the maximum available windbox differential pressure. Each set of ports is equipped with an individual damper for tertiary air balancing and control. Figure 3: MV ATOMIZER |
