SLUDGE COMBUSTOR USING SWIRL AND ACTIVE COMBUSTION CONTROL

摘要

A research program directed at developing technology for compact shipboard incinerators for sludges isrndescribed. The concept utilizes previously developed Vortex Confinement Combustor (VCC) as a primary unitrnwith an active combustion control afterburner (AB).rnThe overall power scale of the combined system is 0.15 MJoule/sec and has a target sludge processing rate ofrn0.75 liter/min. Tests were undertaken to evaluate the particulate suspension qualities of the VCC and the overallrnperformance of the combined VCC / active control AB processing intermediately levels of a surrogate ‘sludge’.rnThe VCC operates like a combusting cyclone separator. Air is introduced circumferentially to create swirl inrnthe combustion zone. This swirl suspends and traps particulate matter until it combusts or pyrolyzes to a size smallrnenough to escape. Particle suspension was enhanced with flow directors that created a net upward velocity componentrnnear the floor of the VCC to prevent formation of dunes in the boundary layer. Particles were found to havernvery long residence times in the combustion zone of the VCC: 43 μm particles had a 1/e lifetime of over 20 seconds.rnThe VCC was operated successfully both fuel lean and fuel rich. The VCC flame was found to be stable at arn‘surrogate sludge’ (water) flow rate of 0.35 liter/min. Tests at higher flow rates are pending.rnIn addition, mixing has been enhanced in a dump combustor configuration afterburner using active combustionrncontrol. The technology is based on injection of waste gases circumferentially into the shear layer of a centralrnair jet from which sheds an acoustically controlled coherent spanwise vortex. The waste is rapidly entrained intornthe air vortex and the good large and fine scale mixing allows compact high efficiency combustion with highrndestruction and removal efficiency (DRE) and low emissions.rnThe performance of the combined system was evaluated with and without ‘surrogate sludge’. It was found thatrnthe actively controlled AB efficiently combusts all of the pyrolysis gases and soot coming from the VCC: therernwas no visible soot emission and the carbon monoxide (CO) levels were below 50 ppm without sludge and belowrn70 ppm with a flow rate of 0.35 liter/min. In addition it was seen that the combined system efficiently destroysrnorganics introduced into the ‘surrogate sludge’: the CO levels were virtually unchanged when 5% ethanol wasrnadded to the water ‘surrogate sludge’. This implies greater than 99.9% destruction of the organic content in this yetrnto be optimized system.